Professor Clive Beggs

The high world-wide prevalence of tuberculosis (TB) and the increase in multi-drug resistant strains (MDRTB) have prompted increased interest in engineering control solutions such as ventilation system design and the use of ultraviolet germicidal irradiation (UVGI). This study considers the contribution of the ventilation airflow to the transmission of TB, and uses computational fluid dynamics (CFD) simulations to examine how changes in the design of a ward, in Hospital Nacional Dos de Mayo, Lima, Peru may reduce the transmission of TB from patients to health-care workers, visitors and other patients. The results of this study were used to advise the architects and engineers in the remodelling of the ward.

Purpose: To characterize the intracranial volumetric changes that influence the cerebrospinal fluid (CSF) pulse in the Aqueduct of Sylvius (AoS). Materials and Methods: Neck MRI data were acquired from 12 healthy adults (8 female and 4 males; mean age=30.9 years), using a 1.5 Tesla scanner. The intracranial arterial, venous and CSF volumes changes, together with the aqueductal CSF (aCSF) volume, were estimated from flow rate data acquired at C2/C3 level and in the AoS. The correlations and temporal relationships among these volumes were computed. Results: The aCSF volumetric changes were strongly correlated (r = 0.967, p<0.001) with the changes in intracranial venous volume, whose peak occurred 7.0% of cardiac cycle (p = 0.023) before peak aCSF volume, but less correlated with the intracranial arterial and CSF volume changes (r=-0.664 and 0.676 respectively, p<0.001). The intracranial CSF volume change was correlated with the intracranial venous volume change (r=0.820, p<0.001), whose peak occurred slightly before (4.2% of CC, p=0.059). Conclusion: The aCSF pulse is strongly correlated with intracranial venous volume, with expansion of the cortical veins occurring prior to aCSF flow towards the third ventricle. Both caudal-cranial aCSF flow and venous blood retention occur when arterial blood volume is at a minimum.

The desiccant cooling cycle is a novel open heat-driven cycle which can be used both to cool and to dehumidify air. Although desiccant cooling systems have been used in Scandinavian buildings for over 20 years, they have only relatively recently been used in the United Kingdom (UK). This paper describes the operation of a desiccant cooling system at the University of Lincoln, which was among the first facilities in the UK to install such a system. The desiccant system at the University of Lincoln was monitored for the period September 1998 to August 1999. The results of this monitoring programme reveal the system to be an effective low-energy solution.

The desiccant cooling cycle is a novel open heat driven cycle which can be used both to cool and dehumidify air. Being a heat driven cycle, desiccant cooling affords an opportunity to utilise heat which might otherwise be wasted. It can therefore be coupled to solar collectors to produce a cooling system which, in theory, should be environmentally friendly. This paper discusses the feasibility of using solar energy to power the desiccant cooling cycle and also presents a study, in which a solar desiccant cooling model is used to evaluate installations located in the southeast and east midlands of England, and in central Scotland. The paper demonstrates that solar powered desiccant cooling is a feasible solution for cooling and heating buildings in the United Kingdom. © 2002 Elsevier Science Ltd. All rights reserved.

Desiccant cooling is an environmentally friendly technology which can be used to condition the internal environment of buildings. Unlike conventional air conditioning systems, which rely on electrical energy to drive the cooling cycle, desiccant cooling is a heat driven cycle. Desiccant cooling systems have been used successfully in northern Europe and a number of studies have demonstrated that solar energy can be used to drive the system in this region. However, to date, desiccant cooling has not been used in southern European. This paper presents the results of a study, in which a solar desiccant cooling model was used to evaluate the potential for using solar power to drive a single-stage desiccant cooling system in various locations in southern Europe. The study demonstrates that solar desiccant cooling is feasible in parts of southern Europe, provided that the latent heat gains experienced are not excessive. However, if the relative humidities experienced are too high then desiccant cooling becomes impracticable simply because the regeneration temperatures required are excessive. © 2002 Elsevier Science Ltd. All rights reserved.

As the world economies get out of the lockdown imposed by the COVID-19 pandemic, there is an urgent need to assess the suitability of known technologies to mitigate COVID-19 transmission in confined spaces such as buildings. This feasibility study looks at the method of upper-room ultraviolet (UV) air disinfection that has already proven its efficacy in preventing the transmission of airborne diseases such as measles and tuberculosis. Using published data from various sources it is shown that the SARS-CoV-2 virus, which causes COVID-19, is highly likely to be susceptible to UV damage while suspended in air irradiated by UV-C at levels that are acceptable and safe for upper-room applications. This is while humans are present in the room. Both the expected and worst-case scenarios are investigated to show the efficacy of the upper-room UV-C approach to reduce COVID-19 air transmission in a confined space with moderate but sufficient height. Discussion is given on the methods of analysis and the differences between virus susceptibility to UV-C when aerosolised or in liquid or on a surface.

As the world’s economies come out of the lockdown imposed by the COVID-19 pandemic, there is an urgent need for technologies to mitigate COVID-19 transmission in confined spaces such as buildings. This feasibility study looks at one such technology, upper-room ultraviolet (UV) air disinfection, that can be safely used while humans are present in the room space, and which has already proven its efficacy as an intervention to inhibit the transmission of airborne diseases such as measles and tuberculosis. Using published data from various sources, it is shown that the SARS-CoV-2 virus, the causative agent of COVID-19, is highly likely to be susceptible to UV-C damage when suspended in air, with a UV susceptibility constant likely to be in the region 0.377–0.590 m2/J, similar to that for other aerosolised coronaviruses. As such, the UV-C flux required to disinfect the virus is expected to be acceptable and safe for upper-room applications. Through analysis of expected and worst-case scenarios, the efficacy of the upper-room UV-C approach for reducing COVID-19 transmission in confined spaces (with moderate but sufficient ceiling height) is demonstrated. Furthermore, it is shown that with SARS-CoV-2, it should be possible to achieve high equivalent air change rates using upper-room UV air disinfection, suggesting that the technology might be particularly applicable to poorly ventilated spaces.

The year 2020 has seen the emergence of a global pandemic as a result of the disease COVID-19. This report reviews knowledge of the transmission of COVID-19 indoors, examines the evidence for mitigating measures, and considers the implications for wintertime with a focus on ventilation.

There is increasing evidence that the 2020 COVID-19 pandemic has been influenced by variations in air temperature and humidity. However, the impact that these environmental parameters have on survival of the SARS-CoV-2 virus has not been fully characterised. Therefore, an analytical study was undertaken using published data to develop a psychrometric model to assess the biological decay rate of the virus in aerosols. This revealed that it is possible to describe with reasonable accuracy (R2 = 0.718, p < 0.001) the biological decay constant for the SARS-CoV-2 virus using a regression model with enthalpy, vapour pressure and specific volume as predictors. Applying this to historical meteorological data from London, Paris and Milan over the pandemic period, produced results which indicate that the average half-life of the virus in aerosols outdoors was in the region 13-22 times longer in March 2020, when the outbreak was accelerating, than it was in August 2020 when epidemic in Europe was at its nadir. However, indoors, this variation is likely to be much less. As such, this suggests that changes in virus survivability due the variations in the psychrometric qualities of the air might influence the transmission of SARS-CoV-2.

Biological decontamination using a nonthermal gas discharge at atmospheric pressure in air is the subject of significant research effort at this time. The mechanism for bacterial deactivation undergoes a lot of speculation, particularly with regard to the role of ions and reactive gas species. Two mechanisms have been proposed: electrostatic disruption of cell membranes and lethal oxidation of membrane or cytoplasmic components. Results show that death is accompanied by cell lysis and fragmentation in Gram-negative bacteria but not Gram-positive species, although cytoplasmic leakage is generally observed. Gas discharges can be a source of charged particles, ions, reactive gas species, radicals, and radiation (ultraviolet, infrared, and visible), many of which have documented biocidal properties. The individual roles played by these in decontamination are not well understood or quantified. However, the reactions of some species with biomolecules are documented otherwise in the literature. Oxidative stress is relatively well studied, and it is likely that exposure to gas discharges in air causes extreme oxidative challenge. In this paper, a review is presented of the major reactive species generated by nonthermal plasma at atmospheric pressure and the known reactions of these with biological molecules. Understanding these mechanisms becomes increasingly important as plasma-based decontamination and sterilization devices come closer to a wide-scale application in medical, healthcare, food processing, and air purification applications. Approaches are proposed to elucidate the relative importance of reactive species. © 2006 IEEE.

Venous abnormalities contribute to the pathophysiology of several neurological conditions. This paper reviews the literature regarding venous abnormalities in multiple sclerosis (MS), leukoaraiosis, and normal-pressure hydrocephalus (NPH). The review is supplemented with hydrodynamic analysis to assess the effects on cerebrospinal fluid (CSF) dynamics and cerebral blood flow (CBF) of venous hypertension in general, and chronic cerebrospinal venous insufficiency (CCSVI) in particular.CCSVI-like venous anomalies seem unlikely to account for reduced CBF in patients with MS, thus other mechanisms must be at work, which increase the hydraulic resistance of the cerebral vascular bed in MS. Similarly, hydrodynamic changes appear to be responsible for reduced CBF in leukoaraiosis. The hydrodynamic properties of the periventricular veins make these vessels particularly vulnerable to ischemia and plaque formation.Venous hypertension in the dural sinuses can alter intracranial compliance. Consequently, venous hypertension may change the CSF dynamics, affecting the intracranial windkessel mechanism. MS and NPH appear to share some similar characteristics, with both conditions exhibiting increased CSF pulsatility in the aqueduct of Sylvius.CCSVI appears to be a real phenomenon associated with MS, which causes venous hypertension in the dural sinuses. However, the role of CCSVI in the pathophysiology of MS remains unclear.

In this work, a novel concept in freeze desalination (FD) was introduced. Nowadays the total liquefied natural gas (LNG) production capacity has reached 290. Mt/year. Its enormous cold energy released from re-gasification can be used in the freeze desalination process to minimize the overall energy consumption. A process of FD on flake ice maker utilizing LNG cold energy was designed and simulated by HYSYS software. An ice bucket on flake ice maker was chosen as seawater crystallizer mainly due to its continuous ice making and removing ice without heat source. A dynamic model of the freezing section has been developed and simulated through gPROMS software. The results show that the consumption of 1. kg equivalent LNG cold energy can obtain about 2. kg of ice melt water. In addition, it is shown that the power consumption of this LNG/FD hybrid process is negligible.

BACKGROUND: The nosocomial transmission of respiratory viruses causes significant disruption to hospital care, but the spatial dynamics of transmission on hospital wards are poorly understood. METHODS: We developed a model integrating computational fluid dynamics (CFD) simulations into an epidemiological reconstruction of virus transmission to quantify the relationship between SARS-CoV-2 transmission and the location of beds in medicine for the elderly wards. FINDINGS: Data from CFD simulations described a pattern in which exposure to an infected host decreased by approximately 40% for each additional metre of distance, with a further four-fold reduction when patients were in separate rooms. However, statistical inference suggested that only 72% (95% confidence interval 45%-96%) of the transmission events identified on wards could be explained by this model. Other cases of transmission occurred at distances too great to be consistent with the simulation model, suggesting that distance-independent mechanisms such as shared facilities or staff-mediated transmission had an important role in nosocomial transmission. CONCLUSION: Our results suggest that while spatial separation reduces transmission risk, infection prevention and control strategies such as the use of single-bed rooms may be insufficient to prevent outbreaks. Comprehensive approaches to preventing nosocomial transmission, addressing multiple potential viral transmission pathways, are necessary.

BACKGROUND: To determine whether or not jugular venous reflux (JVR) is associated with structural brain parenchyma changes in individuals with mild cognitive impairment (MCI) and Alzheimer's disease (AD). METHODS: 16 AD patients (mean (SD): 81.9 (5.8) years), 33 MCI patients (mean (SD): 81.4 (6.1) years) and 18 healthy elderly controls (mean (SD): 81.5 (3.4) years) underwent duplex ultrasonography and magnetic resonance imaging scans to quantify structural brain parenchyma changes. Normalized whole brain (WB), gray matter (GM) and white matter (WM) volumes were collected, together with CSF volume. RESULTS: JVR was strongly associated with increased normalized WB (p = 0.014) and GM (p = 0.002) volumes across all three subject groups. There was a trend towards increased WB and GM volumes, which was accompanied by decreased CSF volume, in the JVR-positive subjects in both the MCI and AD groups. When the MCI and AD subjects were aggregated together significant increases were observed in both normalized WB (p = 0.009) and GM (p = 0.003) volumes for the JVR-positive group. No corresponding increases were observed for the JVR-positive subjects in the control group. Through receiver operating characteristic analysis of the brain volumetric data it was possible to discriminate between the JVR-positive and negative AD subjects with reasonable accuracy (sensitivity = 71.4%; specificity = 88.9%; p = 0.007). CONCLUSIONS: JVR is associated with intracranial structural changes in MCI and AD patients, which result in increased WB and GM volumes. The neuropathology of this unexpected and counterintuitive finding requires further investigation, but may suggest that JVR retrogradely transmits venous hypertension into the brain and leads to brain tissues swelling due to vasogenic edema.

OBJECTIVES: Acquiring central venous pressure (CVP), an important clinical parameter, requires an invasive procedure, which poses risk to patients. The aim of the study was to develop a non-invasive methodology for determining mean-CVP from ultrasound assessment of the jugular venous pulse. METHODS: In thirty-four adult patients (age = 60 ± 12 years; 10 males), CVP was measured using a central venous catheter, with internal jugular vein (IJV) cross-sectional area (CSA) variation along the cardiac beat acquired using ultrasound. The resultant CVP and IJV-CSA signals were synchronized with electrocardiogram (ECG) signals acquired from the patients. Autocorrelation signals were derived from the IJV-CSA signals using algorithms in R (open-source statistical software). The correlation r-values for successive lag intervals were extracted and used to build a linear regression model in which mean-CVP was the response variable and the lagging autocorrelation r-values and mean IJV-CSA, were the predictor variables. The optimum model was identified using the minimum AIC value and validated using 10-fold cross-validation. RESULTS: While the CVP and IJV-CSA signals were poorly correlated (mean r = -0.018, SD = 0.357) due to the IJV-CSA signal lagging behind the CVP signal, their autocorrelation counterparts were highly positively correlated (mean r = 0.725, SD = 0.215). Using the lagging autocorrelation r-values as predictors, mean-CVP was predicted with reasonable accuracy (r2 = 0.612), with a mean-absolute-error of 1.455 cmH2O, which rose to 2.436 cmH2O when cross-validation was performed. CONCLUSIONS: Mean-CVP can be estimated non-invasively by using the lagged autocorrelation r-values of the IJV-CSA signal. This new methodology may have considerable potential as a clinical monitoring and diagnostic tool.

Objectives: To determine the sensitivity and specificity of decreased venous vasculature visibility (VVV) on susceptibility-weighted imaging (SWI) venography in multiple sclerosis (MS) patients versus controls, and to compare this with assessment of whole brain atrophy. Methods: Forty MS patients and 22 controls without known central nervous system (CNS) disease who had non-specific white-matter (WM) lesions were imaged on a 3T GE scanner using SWI venography. Apparent total venous volume (ATVV) and increased average distance from vein (DFV) were calculated for various vein mean diameter categories: <0.3, 0.3-0.6, 0.6-0.9, and >0.9 mm. Principal component analysis (PCA) was used to identify potential discriminatory metrics. Receiver operating characteristics (ROC) of these metrics, along with normalized brain volume (NBV), were calculated to determine sensitivity and specificity values between the groups. The efficacy of the metrics was validated against blinded data from 14 MS patients and 8 controls who had non-specific WM lesions. Results: PCA identified 0.3-0.6 mm venous relative fraction (VRF) and DFV as useful metrics. ROC analysis results in initial sample of 40 MS patients and 22 controls were (sensitivity, specificity): 0.3-0.6 mm VRF (95.0%, 100.0%); DFV (100.0%, 100.0%); and NBV (82.5%, 68.2%). The results in validation sample were: 0.3-0.6 mm VRF (92.9%, 75.0%); DFV (100.0%, 100.0%); and NBV (78.6%, 75.0%). Discussion: Altered VVV indices on SWI venography showed high sensitivity and specificity for MS. The value of SWI venography for diagnosis of MS has to be further tested at early disease stages and against patients with other neurologic diseases. © W. S. Maney & Son Ltd 2012.

Purpose: To investigate characteristics of cine phase contrast-calculated cerebrospinal fluid (CSF) flow and velocity measures in patients with relapsing-remitting (RR) multiple sclerosis (MS) receiving standard medical treatment who had been diagnosed with chronic cerebrospinal venous insufficiency (CCSVI) and underwent percutaneous transluminal angioplasty (PTA). Materials and Methods: This case-controlled, magnetic resonance (MR) imaging-blinded study included 15 patients with RR MS who presented with significant stenoses (≥50% lumen reduction on catheter venography) in the azygous or internal jugular veins. Eight patients underwent PTA in addition to medical therapy immediately following baseline assessments (case group) and seven had delayed PTA after 6 months of medical therapy alone (control group). CSF flow and velocity measures were quantified over 32 phases of the cardiac cycle by a semiautomated method. Outcomes were compared between groups at baseline and at 6 and 12 months of the study by mixed-effect model analysis. Results: At baseline, no significant differences in CSF flow or velocity measures were detected between groups. At month 6, significant improvement in flow (P<.001) and velocity (P =.013) outcomes were detected in the immediate versus the delayed group, and persisted to month 12 (P =.001 and P =.021, respectively). Within-group flow comparisons from baseline to follow-up showed a significant increase in the immediate group (P =.033) but a decrease in the delayed group (P =.024). Altered CSF flow and velocity measures were associated with worsening of clinical and MR outcomes in the delayed group. Conclusions: PTA in patients with MS with CCSVI increased CSF flow and decreased CSF velocity, which are indicative of improved venous parenchyma drainage. © 2013 SIR.

To determine whether jugular venous reflux (JVR) is associated with cerebral white matter changes (WMCs) in individuals with Alzheimer's disease (AD), we studied 12 AD patients 24 mild cognitive impairment (MCI) patients, and 17 elderly age- and gender-matched controls. Duplex ultrasonography and 1.5T MRI scanning was applied to quantify cerebral WMCs [T2 white matter (WM) lesion and dirty-appearing-white-matter (DAWM)]. Subjects with severe JVR had more frequently hypertension (p = 0.044), more severe WMC, including increased total (p = 0.047) and periventricular DAWM volumes (p = 0.008), and a trend for increased cerebrospinal fluid volumes (p = 0.067) compared with the other groups. A significantly decreased (65.8%) periventricular DAWM volume (p = 0.01) in the JVR-positive AD individuals compared with their JVR-negative counterparts was detected. There was a trend for increased periventricular and subcortical T2 WMC lesion volumes in the JVR-positive AD individuals compared with their JVR-negative counterparts (p = 0.073). This phenomenon was not observed in either the control or MCI groups. In multiple regression analysis, the increased periventricular WMC lesion volume and decreased DAWM volume resulted in 85.7% sensitivity and 80% specificity for distinguishing between JVR-positive and JVR-negative AD patients. These JVR-WMC association patterns were not seen in the control and MCI groups. Therefore, this pilot study suggests that there may be an association between JVR and WMCs in AD patients, implying that cerebral venous outflow impairment might play a role in the dynamics of WMCs formation in AD patients, particularly in the periventricular regions. Further longitudinal studies are needed to confirm and validate our findings.

To investigate cerebrospinal fluid (CSF) dynamics in the aqueduct of Sylvius (AoS) in chronic cerebrospinal venous insufficiency (CCSVI)-positive and -negative healthy individuals using cine phase contrast imaging.Fifty-one healthy individuals (32 CCSVI-negative and 19 age-matched CCSVI-positive subjects) were examined using Doppler sonography (DS). Diagnosis of CCSVI was established if subjects fulfilled ≥2 venous hemodynamic criteria on DS. CSF flow and velocity measures were quantified using a semiautomated method and compared with clinical and routine 3T MRI outcomes.CCSVI was associated with increased CSF pulsatility in the AoS. Net positive CSF flow was 32% greater in the CCSVI-positive group compared with the CCSVI-negative group (P = 0.008). This was accompanied by a 28% increase in the mean aqueductal characteristic signal (ie, the AoS cross-sectional area over the cardiac cycle) in the CCSVI-positive group compared with the CCSVI-negative group (P = 0.021).CSF dynamics are altered in CCSVI-positive healthy individuals, as demonstrated by increased pulsatility. This is accompanied by enlargement of the AoS, suggesting that structural changes may be occurring in the brain parenchyma of CCSVI-positive healthy individuals.

Existing indoor closed ultraviolet-C (UVC) air purifiers (UVC in a box) have faced technological challenges during the COVID-19 breakout, owing to demands of low energy consumption, high flow rates, and high kill rates at the same time. A new conceptual design of a novel UVC-LED (light-emitting diode) air purifier for a low-cost solution to mitigate airborne diseases is proposed. The concept focuses on performance and robustness. It contains a dust-filter assembly, an innovative UVC chamber, and a fan. The low-cost dust filter aims to suppress dust accumulation in the UVC chamber to ensure durability and is conceptually shown to be easily replaced while mitigating any possible contamination. The chamber includes novel turbulence-generating grids and a novel LED arrangement. The turbulent generator promotes air mixing, while the LEDs inactivate the pathogens at a high flow rate and sufficient kill rate. The conceptual design is portable and can fit into ventilation ducts. Computational fluid dynamics and UVC ray methods were used for analysis. The design produces a kill rate above 97% for COVID and tuberculosis and above 92% for influenza A at a flow rate of 100 L/s and power consumption of less than 300 W. An analysis of the dust-filter performance yields the irradiation and flow fields.

The cerebrospinal fluid (CSF) pulse in the Aqueduct of Sylvius (aCSF pulse) is often used to evaluate structural changes in the brain. Here we present a novel application of the general linear model (GLM) to predict the motion of the aCSF pulse. MR venography was performed on 13 healthy adults (9 female and 4 males—mean age = 33.2 years). Flow data was acquired from the arterial, venous and CSF vessels in the neck (C2/C3 level) and from the AoS. Regression analysis was undertaken to predict the motion of the aCSF pulse using the cervical flow rates as predictor variables. The relative contribution of these variables to predicting aCSF flow rate was assessed using a relative weights method, coupled with an ANOVA. Analysis revealed that the aCSF pulse could be accurately predicted (mean (SD) adjusted r2 = 0.794 (0.184)) using the GLM (p < 0.01). Venous flow rate in the neck was the strongest predictor of aCSF pulse (p = 0.001). In healthy individuals, the motion of the aCSF pulse can be predicted using the GLM. This indicates that the intracranial fluidic system has broadly linear characteristics. Venous flow in the neck is the strongest predictor of the aCSF pulse.

Purpose: To assess early and midterm outcomes of iliac branch device (IBD) implantation without an aortic stent-graft for the treatment of isolated common iliac artery aneurysm (CIAA). Methods: From December 2006 to June 2016, 49 isolated CIAAs in 46 patients were treated solely with an IBD at 7 vascular centers. Five patients were lost to follow-up, leaving 41 male patients (mean age 72.5±7.8 years) for analysis. Mean CIAA diameter was 39.1±10.5 mm (range 25–65). Thirty-two patients (2 with bilateral CIAAs) were treated with a Cook Zenith iliac branch device; 9 patients (1 bilateral) received a Gore Excluder iliac branch endoprosthesis. Primary endpoints were technical success, survival, aneurysm exclusion, device patency, and freedom from reintervention at 1 and 5 years. Freedom from major adverse events and aneurysm shrinkage at 1 year were also assessed. Results: Thirty-day mortality and the IBD occlusion rate were 2.4% and 2.3%, respectively. At a mean follow-up of 40.2±33.9 months, no patient presented buttock claudication, erectile dysfunction, or bowel or spinal cord ischemia. Three patients died within 6 months after the procedure. Estimates of cumulative survival, device patency, and freedom from reintervention were 90.2%, 95.2%, and 95.7%, respectively, at 1 and 5 years. At 1 year, CIAA shrinkage ≥5 mm was recorded in 21 of 38 survivors. No evidence of endoleak, device migration, or disconnection was found on imaging follow-up. Conclusion: The use of IBDs without an aortic stent-graft for isolated CIAAs resulted in excellent patency, with low morbidity and mortality. This, in conjunction with no endoleak or migration and a low reintervention rate, supports the use of isolated IBDs as a stable and durable means of endovascular reconstruction in cases with suitable anatomy. Longer follow-up and a larger cohort are needed to validate these results.

The transmission bottleneck describes the number of viral particles that initiate an infection in a new host. Previous studies have used genome sequence data to suggest that transmission bottlenecks for influenza and SARS-CoV-2 involve few viral particles, but the general principles of virus transmission are not fully understood. Here we show that, across a broad range of circumstances, tight transmission bottlenecks are a simple consequence of the physical process of airborne viral transmission. We use mathematical modelling to describe the physical process of the emission and inhalation of infectious particles, deriving the result that that the great majority of transmission bottlenecks involve few viral particles. While exceptions to this rule exist, the circumstances needed to create these exceptions are likely very rare. We thus provide a physical explanation for previous inferences of bottleneck size, while predicting that tight transmission bottlenecks prevail more generally in respiratory virus transmission.

Abstract

The transmission bottleneck describes the number of viral particles that found an infection in a new host. Previous studies have used genome sequence data to suggest that transmission bottlenecks for influenza and SARS-CoV-2 involve few viral particles, but the general principles underlying these bottlenecks are not fully understood. Here we show that, across a broad range of circumstances, tight transmission bottlenecks arise as a consequence of the physical process underlying airborne viral transmission. We use a mathematical model to describe the process of infectious particles being emitted by an infected individual and inhaled by others nearby. The extent to which exposure to particles translates into infection is determined by an effective viral load, which is calculated as a function of the epidemiological parameter R 0 . Across multiple scenarios, including those present at a superspreading event, our model suggests that the great majority of transmission bottlenecks involve few viral particles, with a high proportion of infections being caused by a single viral particle. Our results provide a physical explanation for previous inferences of bottleneck size and predict that tight transmission bottlenecks prevail more generally in respiratory virus transmission.

With the general increase in the worldwide incidence of tuberculosis there is increasing interest in the use of upper room ultraviolet germicidal irradiation (UVGI) systems to disinfect air. A number of researchers have demonstrated experimentally the ability of such systems to inactivate airborne microorganisms. However, relatively little theoretical work has been done to explain the results observed and few models exist to describe the performance of upper room UVGI systems. This paper presents a new model, which can be used both to design such systems and to evaluate their germicidal effectiveness. A theoretical study is undertaken, which indicates that although upper room UVGI systems work well at lower ventilation rates, they are of limited benefit in highly ventilated applications. The paper also demonstrates and quantifies the relationship between inter-zonal air velocity and room ventilation rate. In particular, the paper shows that under steady-state conditions the number of passes made by bioaerosol particles through an upper room UV field is independent of the ventilation rate. © 2002 Elsevier Science Ltd. All rights reserved.

Abstract

The effectiveness of any ultraviolet germicidal irradiation (UVGI) system is governed by the passage of airborne microorganisms through the UV field. This paper describes a new method for evaluating the performance of UVGI devices using computational fluid dynamic (CFD) simulations. A microorganism inactivation equation is combined with a scalar transport equation to describe the concentration of airborne microorganisms in the presence of a UV field. The solution of this equation, in conjunction with the momentum and turbulent energy equations, allows the effect of both the airflow and the UV field on the microorganism distribution to be examined. Solutions are shown for the airflow and microorganism concentration through a bench scale flow apparatus, at five different UV intensities. The results from the CFD model are validated against the experimental data, obtained from the flow apparatus, for aerosolised Pseudomonas aeruginosa microorganisms. Good comparisons are seen, giving confidence in the application of the technique to other situations. © 2003 Elsevier Ltd. All rights reserved.

The lethal effect of ultraviolet (UV) light on microorganisms is well known and many studies have been undertaken into the effects of UV induced damage. Most of this work has been experimental; by comparison relatively little theoretical work has been undertaken to analyse the kinetics of the UV inactivation process, or to develop quantitative methodologies to support the experimental work. This paper presents a new and simple model for quantifying the photolysis rate. A theoretical study is also presented in this paper which quantifies photolysis rates for E. coli O26 and E. coli O157:H7. This study uses experimental data collected by Tosa and Hirata, and reveals the photolysis rate for E. coli O26 during the UV irradiation process to be 4.69 × 10

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To investigate the potential usefulness of u.v. germicidal irradiation (UVGI) in preventing the spread of Burkholderia cepacia, an important pathogen in cystic fibrosis (CF), the in-vitro susceptibility of B. cepacia to UVGI was determined. Five strains were exposed to UVGI from a 7.2-W source. Burkholderia cepacia was less susceptible to UVGI than other important CF-related pathogens, namely Staphylococcus aureus and Pseudomonas aeruginosa, but was more susceptible than Stenotrophomonas maltophilia. No strain of B. cepacia survived longer than an 8 s exposure to UVGI, with doses required to achieve 1 log reduction in bacterial numbers ranging from 28.3 to 57.5 J m

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Background Aerosol spread of SARS-CoV-2 is a major problem in hospitals, leading to an increase in supplementary HEPA filtration aimed at reducing nosocomial transmission. We report a natural experiment that occurred when an air-cleaning unit (ACU) on a medicine for older people ward was accidentally switched off while being commissioned. Aim To assess aerosol transport within the ward and determine whether the ACU reduced airborne particulate matter (PM) levels. Methods An ACU was placed in a ward comprising two 6-bedded bays plus three single-bed isolation rooms, which had previously experienced several COVID-19 outbreaks. During commissioning, real-time measurements of key indoor air quality parameters (PM1-10, CO2, temperature and humidity) were collected from multiple sensors over two days. During this period, the ACU was accidentally switched off for approximately 7 hours, allowing the impact of the intervention on PM to be assessed. Findings The ACU greatly reduced PM counts (e.g. PM1: 65.5 – 78.2%) throughout the ward (p<0.001 all sizes), with all PM fractions and CO2 positively correlated (r = 0.343 – 0.817; all p<0.001). PM counts rose/fell simultaneously when ACU was off, with PM signals from multiple locations correlated (e.g., r = 0.343 – 0.868 (all p<0.001) for particulates <1μm). Conclusion Aerosols rapidly migrated between the various ward sub-compartments, suggesting that social distancing alone cannot prevent nosocomial transmission of SARS-CoV-2, as it fails to mitigate longer-range (>2m) transmission. The ACU greatly reduced PM levels throughout the ward space indicating its potential as an effective intervention to reduce the risk posed by infectious airborne particles.

The book addresses this issue via a practical route one approach designed to show readers how to successfully tackle a range of soccer related problems using the easy-to-learn computer language R. Through a series of easy-to-follow examples ...

Background: Nosocomial infections are costly, and airborne transmission is increasingly recognized as important for spread. Air cleaning units (ACUs) may reduce transmission, but little research has focused on their effectiveness on open wards. Aim: To assess whether ACUs reduce nosocomial severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), or other, infections on older adult inpatient wards. Methods: This was a quasi-experimental before-and-after study on two intervention–control ward pairs in a UK teaching hospital. Infections were identified using routinely collected electronic health record data during 1 year of ACU implementation and the preceding year (‘core study period’). Extended analyses included 6 months of additional data from one ward pair following ACU removal. Hazard ratios (HRs) were estimated through Cox regression controlling for age, sex, ward and background infection risk. The time that the ACUs were switched on was also recorded for Intervention Ward 2. Findings: ACUs were initially feasible, but compliance reduced towards the end of the study (average operation in first vs second half of ACU time on Intervention Ward 2: 77% vs 53%). In total, 8171 admissions for >48 h (6112 patients, median age 85 years) were included. Overall, the incidence of ward-acquired SARS-CoV-2 was 3.8%. ACU implementation was associated with a non-significant trend of lower hazard for SARS-CoV-2 infection [HR core study period 0.90, 95% confidence interval (CI) 0.53–1.52; HR extended study period 0.78, 95% CI 0.53–1.14]. Only 1.5% of admissions resulted in other notable ward-acquired infections. Conclusion: ACUs may reduce SARS-CoV-2 infection to a clinically meaningfully degree. Larger studies could reduce uncertainty, perhaps using a crossover design, and factors influencing acceptability to staff and patients should be explored further.

The use of electroencephalograms (EEGs) to diagnose and analyses Alzheimer’s disease (AD) has received much attention in recent years. The sample entropy (SE) has been widely applied to the diagnosis of AD. In our study, nine EEGs from 21 scalp electrodes in 3 AD patients and 9 EEGs from 3 age-matched controls are recorded. The calculations show that the kurtoses of the AD patients’ EEG are positive and much higher than that of the controls. This finding encourages us to introduce a kurtosis-based de-noising method. The 21-electrode EEG is first decomposed using independent component analysis (ICA), and second sort them using their kurtoses in ascending order. Finally, the subspace of EEG signal using back projection of only the last five components is reconstructed. SE will be calculated after the above de-noising preprocess. The classifications show that this method can significantly improve the accuracy of SE-based diagnosis. The kurtosis analysis of EEG may contribute to increasing the understanding of brain dysfunction in AD in a statistical way.

Internal jugular vein (IJV) narrowing has been implicated in central nervous system pathologies, however normal physiological age- and gender-related IJV variance in healthy individuals (HIs) has not been adequately assessed.We assessed the relationship between IJV cross-sectional area (CSA) and aging.This study involved 193 HIs (63 males and 130 females) who received 2-dimensional magnetic resonance venography at 3T. The minimum CSA of the IJVs at cervical levels C2/C3, C4, C5/C6, and C7/T1 was obtained using a semi-automated contouring-thresholding technique. Subjects were grouped by decade. Pearson and partial correlation (controlled for cardiovascular risk factors, including hypertension, heart disease, smoking and body mass index) and analysis of variance analyses were used, with paired t-tests comparing side differences.Mean right IJV CSA ranges were: in males, 41.6 mm2 (C2/C3) to 82.0 mm2 (C7/T1); in females, 38.0 mm2 (C2/C3) to 62.3 mm2 (C7/T1), while the equivalent left side ranges were: in males, 28.0 mm2 (C2/C3) to 52.2 mm2 (C7/T1); in females, 27.2 mm2 (C2/C3) to 47.8 mm2 (C7/T1). The CSA of the right IJVs was significantly larger (p<0.001) than the left at all cervical levels. Controlling for cardiovascular risk factors, the correlation between age and IJV CSA was more robust in males than in the females for all cervical levels.In HIs age, gender, hand side and cervical location all affect IJV CSA. These findings suggest that any definition of IJV stenosis needs to account for these factors.

Chronic cerebrospinal venous insufficiency (CCSVI) is a syndrome characterized by stenoses or obstructions of the internal jugular and/or azygos veins with disturbed flow and formation of collateral venous channels. Studies using ultrasound in patients with multiple sclerosis (MS) have demonstrated a high prevalence of CCSVI (mean 70%; range 0-100%; N.=1496), whereas, in normal controls and patients without MS the prevalence was much lower (mean 10%; range 0-36%; N.=635). Ultrasound uses a combination of physiological measurements as well as anatomical imaging and has been used for the detection of CCSVI by different centers with variable results. A high prevalence ranging from 62% to 100% of obstructive lesions has been found by some teams in patients with MS compared with a lower prevalence of 0-25% in controls. However, absence of such lesions or a lower prevalence (16-52%) has been reported by others. This variability could be the result of differences in technique, training, experience or criteria used. The current lack of a methodology shared among experts is a confounding element in epidemiologic studies, and does not permit further Bayesan or other kind of analysis. In order to ensure a high reproducibility of Duplex scanning with comparable accuracy between centers, a detailed protocol with standard methodology and criteria is proposed. This is also necessary for training. It has been shown that inter-rater variability increases post-training (from k=0.47 to k=0.80), while within-rater reproducibility in trained operators was k=0.75. Finally, the consensus document proposes a reporting standard of Duplex measurements, and future research to answer areas of uncertainty.

Objectives Multiple sclerosis (MS) patients frequently suffer from headaches and fatigue, and many reports have linked headaches with intracranial and/or extracranial venous obstruction. We therefore designed a study involving MS patients diagnosed with obstructive disease of internal jugular veins (IJVs), with the aim of evaluating the impact of percutaneous transluminal angioplasty (PTA) on headache and fatigue indicators. Methods 286 MS patients (175 relapsing remitting (RR), 75 secondary progressive (SP), and 36 primary progressive (PP)), diagnosed with obstructive disease of IJVs, underwent PTA of IJVs during the period 2011–2015. This included 113 headache positive patients (82 RR, 22 SP, and 9 PP) and 277 fatigue positive patients (167 RR, 74 SP, and 36 PP). Migraine Disability Assessment (MIDAS), and the Fatigue Severity Scale (FSS) were evaluated: before PTA; 3-months after PTA; and at final follow-up in 2017. Patients were evaluated with Doppler sonography of the IJVs at 1, 6 and 12 months after PTA and yearly thereafter. Non-parametric statistical analysis was performed using a combination of the Friedman test and Spearman correlation analysis. Results With the exception of the PP patients there were significant reductions (all p < 0.001) in the MIDAS and FSS scores in the 3-month following PTA. The improvement in MIDAS score following PTA was maintained throughout the follow-up period in both the RR (p < 0.001; mean of 3.55 years) and SP (p = 0.002; mean of 3.52 years) MS cohorts. With FSS, significant improvement was only observed at 2017 follow-up in the RR patients (p < 0.001; mean of 3.37 years). In the headache-positive patients, post-PTA MIDAS score was significantly negatively correlated with the change in the blood flow score in the left (r = -0.238, p = 0.031) and right (r = -0.250, p = 0.023) IJVs in the RR patients and left IJV (r = -0.727, p = 0.026) in the PP patients. In the fatigue-positive cohort, post-PTA FSS score was also significantly negatively correlated with the change in blood flow in the right IJV in the PP patients (r = -0.423, p = 0.010). In addition, the pre and post-PTA FSS scores were significantly positively correlated in the fatigue-positive RR (r = 0.249, p = 0.001) and SP patients (r = 0.272, p = 0.019). Conclusions The intervention of PTA was associated with a large and sustained (>3 years) reduction in MIDAS score in both RR and SP MS patients. While a similar initial post-PTA reduction in FSS score was also observed, this was not maintained in the SP and PP patients, although it remained significant at follow-up (>3 years) in the RR MS patients. This suggests that venoplasty might be a useful intervention for treating patients with persistent headaches and selected concomitant obstructive disease of the IJVs.

Objectives Constricted cerebral venous outflow has been linked with increased cerebrospinal fluid (CSF) pulsatility in the aqueduct of Sylvius in multiple sclerosis (MS) patients and healthy individuals. This study investigates the relationship between CSF pulsatility and internal jugular vein (IJV) cross-sectional area (CSA) in these two groups, something previously unknown. Methods 65 relapsing-remitting MS patients (50.8% female; mean age = 43.8 years) and 74 healthy controls (HCs) (54.1% female; mean age = 43.9 years) were investigated. CSF flow quantification was performed on cine phase-contrast MRI, while IJV-CSA was calculated using magnetic resonance venography. Statistical analysis involved correlation, and partial least squares correlation analysis (PLSCA). Results PLSCA revealed a significant difference (p<0.001; effect size = 1.072) between MS patients and HCs in the positive relationship between CSF pulsatility and IJV-CSA at C5-T1, something not detected at C2-C4. Controlling for age and cardiovascular risk factors, statistical trends were identified in HCs between: increased net positive CSF flow (NPF) and increased IJV-CSA at C5-C6 (left: r = 0.374, p = 0.016; right: r = 0.364, p = 0.019) and C4 (left: r = 0.361, p = 0.020); and increased net negative CSF flow and increased left IJV-CSA at C5-C6 (r = -0.348, p = 0.026) and C4 (r = -0.324, p = 0.039), whereas in MS patients a trend was only identified between increased NPF and increased left IJV-CSA at C5-C6 (r = 0.351, p = 0.021). Overall, correlations were weaker in MS patients (p = 0.015). Conclusions In healthy adults, increased CSF pulsatility is associated with increased IJV-CSA in the lower cervix (independent of age and cardiovascular risk factors), suggesting a biomechanical link between the two. This relationship is altered in MS patients.

Clive Beggs, Senior Lecturer at Nene College, Northampton, UK, presents four main types of ice storage system commonly used in the air‐conditioning industry and illustrates further aspects of the technology in case studies, including that there are significant benefits to the building user, the electricity generating company, and to the environment.

Energy - its source, security, price, and the efficiency of its use, are increasingly important issues for a diverse range of people. ‘Energy: Management, Supply and Conservation’ is a comprehensive text dealing with the theory and practice of the supply of energy, energy management and auditing, and the design of sustainable energy facilities. It considers the systems needed to create low-energy, sustainable buildings, including passive solar design, energy-efficient heating and air-conditioning, and combined heat and power. In addition the book includes substantial sections on renewable energy, transport energy, and energy economics. This new edition includes the latest in alternate-energy technology, for example wind turbines and solar panels as well as updating important energy values and statistics. The book’s readable style, along with its many figures, tables and worked examples make it an ideal text for courses on energy management, environmental engineering, architectural engineering and building services engineering. It will also be useful as a definitive handbook for professionals in the environmental, construction, utilities and facilities management sectors, as well as being of interest to those involved in sustainability economics and environmental policy making. Clive Beggs is Professor of Medical Technology at the University of Bradford. He is both a mechanical engineer and a biomedical scientist, who for many years has had an interest in ways in which energy is utilized and consumed. He is an expert in the fields of energy management and low energy building design, with many years experience of the design and installation of mechanical services within the construction industry. He is a well known international speaker and is author of many scientific papers on low energy and environmentally friendly building design. He is a holder of the CIBSE Carter Bronze Medal for his work on desiccant cooling.

Objective Percutaneous transluminal angioplasty (PTA) of the internal jugular veins (IJVs) has been proposed in recent years to treat chronic cerebrovascular venous insufficiency, with discordant results. Moreover, very little is known about the efficacy of PTA in restoring a normal cerebral venous outflow. The aim of this study was to investigate the anatomic factors and patient characteristics that might influence the efficacy of PTA of the IJV. Methods There were 797 consecutive patients with venous outflow anomalies who underwent standardized, operator-independent catheter venography and PTA of the IJVs. Before and after PTA, morphologic and hemodynamic anomalies of the IJVs were documented. The primary end point of the study was to evaluate the morphologic factors influencing the efficacy of angioplasty in improving IJV outflow. Results PTA resulted in an increased outflow through the IJVs in most patients. However, younger individuals with transverse endoluminal defects and higher pre-PTA flows are more likely to respond well to PTA compared with those who exhibit hypoplasia, stenosis, or longitudinal endoluminal defects. Conclusions This study identified the factors that influence and could predict the efficacy of PTA in the treatment of IJV anomalies.

Negative air ionisers have seen increasing use as devices for improving indoor air quality, including some success in clinical environments for reducing the transmission of infection. This study uses a ventilation model and a CFD model to examine the physical effects of negative ionisers in indoor environments. The results demonstrate how the negative ion distribution and electric field due to an ioniser are influenced by both the room airflow and the ion generation rate. It is shown that ion concentrations greater than 1010 ions/m3 are necessary for the electrical effects to be significant. The effect on particles is also considered, with the results demonstrating that the ioniser will only increase the deposition of particles when the particle concentration is high enough to contribute to the space charge in the room.

The classical deterministic susceptible-infectious-recovered (SIR) model has played an important role in the analysis of epidemic systems with large populations. However, when population numbers become small e.g. in a hospital ward, a stochastic analysis will be vital. The stochastic Petri-Nets using Gillespie algorithm for modeling the transmission of airborne infections in enclosed spaces is present to be incorporated into an SIR epidemic model with a short incubation period to simulate the transmission dynamics of airborne infectious diseases in indoor environments. The stochastic model not only allows the long-term impact of infection control measures and enables the evaluation of environmental factors, but also depicts the probability of an outbreak of an airborne infection. A quantitative performance study was carried out to demonstrate how to limit the probability rate of outbreak of infection.

Cutting-edge and authoritative, this volume offers practitioners a valuable resource for research and clinical practice. This thoroughly updated edition covers all clinical aspects of neuroinflammation.

There is evidence that both the herb Sanicle and the cytokine TGF- β3 can be beneficial in enhancing wound repair. In this study 3T3 fibroblast cells were cultured and the confluent monolayers were wounded (scarred) using a disposable plastic pipette. Various amounts of TGF-β3 (a growth factor) and Sanicle extract were applied to the cell monolayers. TGF-β3 was applied at concentrations of 50ng/ml, 5ng/ml, 500pg/ml, 50pg/ml and 5pg/ml to five different culture flasks with one additional flask acting as control. Sanicle was applied at concentrations of 100μg/ml, 10μg/ml, 1μg/ml, 100ng/ml and 10ng/ml with one additional flask as a control. The cells were imaged over a period of 20 hours with or without presence of TGF-β3 and Sanicle. The results indicated that although there were no significant increases in the rate of wound closure in relation to application of TGF-β3, there is an indication that TGF-β3 may enhance model wound closure at optimum working concentration between 5ng/ml and 50ng/ml. However, the sanicle extract did not stimulate enhanced repair of the model in vitro wound, but instead seemed to promote cell death along the wound margin. These results indicate that sanicle may be used in the care of wounds, but not as a growth promoter, but because it acts as an antibiotic agent, and possibly because it aids wound debridement.

Magnetic resonance imaging and echo color Doppler (ECD) scan techniques do not accurately assess the cerebral venous return. This generated considerable scientific controversy linked with the diagnosis of a vascular syndrome known as chronic cerebrospinal venous insufficiency (CCSVI) characterized by restricted venous outflow from the brain. The purpose of this study was to assess the cerebral venous return in relation to the change in position by means of a novel cervical plethysmography method. This was a single-center, cross-sectional, blinded case-control study conducted at the Vascular Diseases Center, University of Ferrara, Italy. The study involved 40 healthy controls (HCs; 18 women and 22 men) with a mean age of 41.5 ± 14.4 years, and 44 patients with multiple sclerosis (MS; 25 women and 19 men) with a mean age of 41.0 ± 12.1 years. All participants were previously scanned using ECD sonography, and further subset in HC (CCSVI negative at ECD) and CCSVI groups. Subjects blindly underwent cervical plethysmography, tipping them from the upright (90°) to supine position (0°) in a chair. Once the blood volume stabilized, they were returned to the upright position, allowing blood to drain from the neck. We measured venous volume (VV), filling time (FT), filling gradient (FG) required to achieve 90% of VV, residual volume (RV), emptying time (ET), and emptying gradient (EG) required to achieve 90% of emptying volume (EV) where EV = VV - RV, also analyzing the considered parameters by receiver operating characteristic (ROC) curves and principal component mathematical analysis. The rate at which venous blood discharged in the vertical position (EG) was significantly faster in the controls (2.73 mL/second ± 1.63) compared with the patients with CCSVI (1.73 mL/second ± 0.94; P = .001). In addition, respectively, in controls and in patients with CCSVI, the following parameters were highly significantly different: FT 5.81 ± 1.99 seconds vs 4.45 ± 2.16 seconds (P = .003); FG 0.92 ± 0.45 mL/second vs 1.50 ± 0.85 mL/second (P < .001); RV 0.54 ± 1.31 mL vs 1.37 ± 1.34 mL (P = .005); ET 1.84 ± 0.54 seconds vs 2.66 ± 0.95 seconds (P < .001). Mathematical analysis demonstrated a higher variability of the dynamic process of cerebral venous return in CCSVI. Finally, ROC analysis demonstrated a good sensitivity of the proposed test with a percent concordant 83.8, discordant 16.0, tied 0.2 (C = 0.839). Cerebral venous return characteristics of the patients with CCSVI were markedly different from those of the controls. In addition, our results suggest that cervical plethysmography has great potential as an inexpensive screening device and as a postoperative monitoring tool. © 2012 Society for Vascular Surgery.

Background: Although the merits of ventilating operating theatres and isolation rooms are well known, the clinical benefits derived from ventilating hospital wards and patient rooms are unclear. This is because relatively little research work has been done in the ventilation of these areas compared with that done in operating theatres and isolation rooms. Consequently, there is a paucity of good quality data from which to make important decisions regarding hospital infrastructure. This review evaluates the role of general ward ventilation to assess whether or not it affects the transmission of infection. Methods: A critical review was undertaken of guidelines in the United Kingdom and United States governing the design of ventilation systems for hospital wards and other multibed rooms. In addition, an analytical computational fluid dynamics (CFD) study was performed to evaluate the effectiveness of various ventilation strategies in removing airborne pathogens from ward spaces. Results: The CFD simulation showed the bioaerosol concentration in the study room to be substantially lower (2467 cfu/m

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This paper examines the feasibility of desiccant cooling in UK climates, using gas-solar hybrid technology for regeneration. Desiccant cooling is a heat driven system. It has potential to reduce energy costs and environmental pollution, when compared with conventional vapour compression systems. The regeneration of the desiccant can be provided by any low temperature warm air or water source including waste heat, CHP, gas or solar. Heat recovery is also available. Gaia Research worked with Napier University to develop computer codes for the simulation of solar energy collection and hot water delivery to drive the desiccant cooling system, based on real meteorological data. A solar desiccant computer model was developed with the University of Leeds which analysed the energy consumption and costs associated with desiccant cooling using meteorological data for an inner London site in 1994. The study demonstrates that coupling the desiccant system to solar collectors produces significant savings in both running cost and CO2 emissions. The existing models of solar contribution and desiccant cooling will be refined. This will enable an assessment to be made of the UK opportunities for energy conservation and CO2 emission reduction in relation to latitude, internal design conditions, and real loads.

BACKGROUND: In recent years there has been renewed interest in the use of air ionisers to control of the spread of airborne infection. One characteristic of air ions which has been widely reported is their apparent biocidal action. However, whilst the body of evidence suggests a biocidal effect in the presence of air ions the physical and biological mechanisms involved remain unclear. In particular, it is not clear which of several possible mechanisms of electrical origin (i.e. the action of the ions, the production of ozone, or the action of the electric field) are responsible for cell death. A study was therefore undertaken to clarify this issue and to determine the physical mechanisms associated with microbial cell death. RESULTS: In the study seven bacterial species (Staphylococcus aureus, Mycobacterium parafortuitum, Pseudomonas aeruginosa, Acinetobacter baumanii, Burkholderia cenocepacia, Bacillus subtilis and Serratia marcescens) were exposed to both positive and negative ions in the presence of air. In order to distinguish between effects arising from: (i) the action of the air ions; (ii) the action of the electric field, and (iii) the action of ozone, two interventions were made. The first intervention involved placing a thin mica sheet between the ionisation source and the bacteria, directly over the agar plates. This intervention, while leaving the electric field unaltered, prevented the air ions from reaching the microbial samples. In addition, the mica plate prevented ozone produced from reaching the bacteria. The second intervention involved placing an earthed wire mesh directly above the agar plates. This prevented both the electric field and the air ions from impacting on the bacteria, while allowing any ozone present to reach the agar plate. With the exception of Mycobacterium parafortuitum, the principal cause of cell death amongst the bacteria studied was exposure to ozone, with electroporation playing a secondary role. However in the case of Mycobacterium parafortuitum, electroporation resulting from exposure to the electric field appears to have been the principal cause of cell inactivation. CONCLUSION: The results of the study suggest that the bactericidal action attributed to negative air ions by previous researchers may have been overestimated.

Whilst a number of researchers have demonstrated the disinfection effectiveness of upper-room UV irradiation devices against a range of airborne microorganisms, it is technically difficult to determine the performance of such systems because the biological and physical processes involved can be complex. In particular, most of the quantitative data on the susceptibility of airborne microorganisms to UV irradiation is obtained from single-pass experiments which are not representative of the fragmented UV exposure experienced by airborne microorganisms in real rooms. This paper presents complete and partial mixing models for predicting an effective UV susceptibility constant, Zeff, that is appropriate for quantifying the behaviour of airborne microorganisms when irradiated using an upper-room system. The use of both decay and continuous contamination experimental techniques are discussed and related to the models presented. Experimental results are presented which indicate that Zeff for Serratia marcescens is up to an order of magnitude lower than the susceptibility constants derived from single-pass experiments, suggesting that using these data to design upper-room UV systems may lead to a lower than expected performance. © 2005 Elsevier Ltd. All rights reserved.

BACKGROUND: Clostridium difficile-associated diarrhoea (CDAD) is a frequently occurring healthcare-associated infection, which is responsible for significant morbidity and mortality amongst elderly patients in healthcare facilities. Environmental contamination is known to play an important contributory role in the spread of CDAD and it is suspected that contamination might be occurring as a result of aerial dissemination of C. difficile spores. However previous studies have failed to isolate C. difficile from air in hospitals. In an attempt to clarify this issue we undertook a short controlled pilot study in an elderly care ward with the aim of culturing C. difficile from the air. METHODS: In a survey undertaken during February (two days) 2006 and March (two days) 2007, air samples were collected using a portable cyclone sampler and surface samples collected using contact plates in a UK hospital. Sampling took place in a six bedded elderly care bay (Study) during February 2006 and in March 2007 both the study bay and a four bedded orthopaedic bay (Control). Particulate material from the air was collected in Ringer's solution, alcohol shocked and plated out in triplicate onto Brazier's CCEY agar without egg yolk, but supplemented with 5 mg/L of lysozyme. After incubation, the identity of isolates was confirmed by standard techniques. Ribotyping and REP-PCR fingerprinting were used to further characterise isolates. RESULTS: On both days in February 2006, C. difficile was cultured from the air with 23 samples yielding the bacterium (mean counts 53 - 426 cfu/m3 of air). One representative isolate from each of these was characterized further. Of the 23 isolates, 22 were ribotype 001 and were indistinguishable on REP-PCR typing. C. difficile was not cultured from the air or surfaces of either hospital bay during the two days in March 2007. CONCLUSION: This pilot study produced clear evidence of sporadic aerial dissemination of spores of a clone of C. difficile, a finding which may help to explain why CDAD is so persistent within hospitals and difficult to eradicate. Although preliminary, the findings reinforce concerns that current C. difficile control measures may be inadequate and suggest that improved ward ventilation may help to reduce the spread of CDAD in healthcare facilities.

BACKGROUND: Although many infections that are transmissible from person to person are acquired through direct contact between individuals, a minority, notably pulmonary tuberculosis (TB), measles and influenza are known to be spread by the airborne route. Airborne infections pose a particular threat to susceptible individuals whenever they are placed together with the index case in confined spaces. With this in mind, waiting areas of healthcare facilities present a particular challenge, since large numbers of people, some of whom may have underlying conditions which predispose them to infection, congregate in such spaces and can be exposed to an individual who may be shedding potentially pathogenic microorganisms. It is therefore important to understand the risks posed by infectious individuals in waiting areas, so that interventions can be developed to minimise the spread of airborne infections. METHOD: A stochastic Monte Carlo model was constructed to analyse the transmission of airborne infection in a hypothetical 132 m3 hospital waiting area in which occupancy levels, waiting times and ventilation rate can all be varied. In the model the Gammaitoni-Nucci equation was utilized to predict probability of susceptible individuals becoming infected. The model was used to assess the risk of transmission of three infectious diseases, TB, influenza and measles. In order to allow for stochasticity a random number generator was applied to the variables in the model and a total of 10000 individual simulations were undertaken. The mean quanta production rates used in the study were 12.7, 100 and 570 per hour for TB, influenza and measles, respectively. RESULTS: The results of the study revealed the mean probability of acquiring a TB infection during a 30-minute stay in the waiting area to be negligible (i.e. 0.0034), while that for influenza was an order of magnitude higher at 0.0262. By comparison the mean probability of acquiring a measles infection during the same period was 0.1349. If the duration of the stay was increased to 60 minutes then these values increased to 0.0087, 0.0662 and 0.3094, respectively. CONCLUSION: Under normal circumstances the risk of acquiring a TB infection during a visit to a hospital waiting area is minimal. Likewise the risks associated with the transmission of influenza, although an order of magnitude greater than those for TB, are relatively small. By comparison, the risks associated with measles are high. While the installation of air disinfection may be beneficial, when seeking to prevent the transmission of airborne viral infection it is important to first minimize waiting times and the number of susceptible individuals present before turning to expensive technological solutions.

BACKGROUND: Cystic fibrosis (CF) is an inherited multi-system disorder characterised by chronic airway infection with pathogens such as Pseudomonas aeruginosa. Acquisition of P. aeruginosa by patients with CF is usually from the environment, but recent studies have demonstrated patient to patient transmission of certain epidemic strains, possibly via an airborne route. This study was designed to examine the survival of P. aeruginosa within artificially generated aerosols. RESULTS: Survival was effected by the solution used for aerosol generation. Within the aerosols it was adversely affected by an increase in air temperature. Both epidemic and non-epidemic strains of P. aeruginosa were able to survive within the aerosols, but strains expressing a mucoid phenotype had a survival advantage. CONCLUSION: This would suggest that segregating individuals free of P. aeruginosa from those with chronic P. aeruginosa infection who are more likely to be infected with mucoid strains may help reduce the risk of cross-infection. Environmental factors also appear to influence bacterial survival. Warming and drying the air within clinical areas and avoidance of humidification devices may also be beneficial in reducing the risk of cross-infection.

Background: We describe a novel analytical technique for determining instantaneous trends in body temperature data, which may assist clinicians in optimizing antimicrobial therapy in patients with febrile neutropenia. The paper presents a new algorithm, based on a modified second backward difference (M2BD) matrix filter for monitoring temperature response to anti-microbial chemotherapies in neutropenic patients and develops techniques for extracting accurate, instantaneous trend data from clinical time series data. Such an algorithm is needed because it is difficult to assess patient wellbeing in those who are neutropenic. Temperature data, a key indicator of response to antimicrobial therapy, are typically very noisy, with many fluctuations, making it very difficult to identify underlying trends in real time. Clinicians are therefore forced to make important decisions concerning drug therapy on imperfect data. Methods: In order to determine the underlying temperature trend, analysis of synthetic time series data (with a known underlying trend) was undertaken using both the CUSUM technique and the M2BD matrix filter. The CUSUM analysis was undertaken using four reference temperatures, 37.5°C, 38.0°C, 38.5°C and 39.0°C. A validation study was also undertaken using four sets of noisy synthetic temperature data to evaluate the performance of the M2BD filter. The M2BD filter was then used to analyse anonymized serial temperature data from a neutropenic patient undergoing chemotherapy. Results: For all four reference temperatures the CUSUM analysis failed to predict the underlying temperature trend. By comparison, the M2BD filter extracted, in real time, the underlying temperature trend with great accuracy and no time lag. In the validation study, the M2BD filter accurately extracted the underlying temperature trend for all four of the synthetic datasets. With regard to the anonymized patient data, the M2BD filter again performed well, accurately determining the underlying trend. Conclusion: The study demonstrated that the M2BD filter is capable of instantaneously extracting underlying trends from clinical time series data. This finding suggests that this algorithm has great potential as a tool for assisting clinicians in the management of patients with febrile neutropenia. © 2009 Informa Healthcare USA, Inc.

AIMS: To compare an ultra-rapid hand dryer against warm air dryers, with regard to: (A) bacterial transfer after drying and (B) the impact on bacterial numbers of rubbing hands during dryer use. METHODS AND RESULTS: The Airblade™ dryer (Dyson Ltd) uses two air 'knives' to strip water from still hands, whereas conventional dryers use warm air to evaporate moisture whilst hands are rubbed together. These approaches were compared using 14 volunteers; the Airblade™ and two types of warm air dryer. In study (A), hands were contaminated by handling meat and then washed in a standardized manner. After dryer use, fingers were pressed onto foil and transfer of residual bacteria enumerated. Transfers of 0-10(7) CFU per five fingers were observed. For a drying time of 10 s, the Airblade™ led to significantly less bacterial transfer than the other dryers (P < 0·05; range 0·0003-0·0015). When the latter were used for 30-35 s, the trend was for the Airblade to still perform better, but differences were not significant (P > 0·05, range 0·1317-0·4099). In study (B), drying was performed ± hand rubbing. Contact plates enumerated bacteria transferred from palms, fingers and fingertips before and after drying. When keeping hands still, there was no statistical difference between dryers, and reduction in the numbers released was almost as high as with paper towels. Rubbing when using the warm air dryers inhibited an overall reduction in bacterial numbers on the skin (P < 0·05). CONCLUSIONS: Effective hand drying is important for reducing transfer of commensals or remaining contaminants to surfaces. Rubbing hands during warm air drying can counteract the reduction in bacterial numbers accrued during handwashing. SIGNIFICANCE AND IMPACT OF THE STUDY: The Airblade™ was superior to the warm air dryers for reducing bacterial transfer. Its short, 10 s drying time should encourage greater compliance with hand drying and thus help reduce the spread of infectious agents via hands.

BACKGROUND: In recent years there has been renewed interest in the use of air ionizers to control the spread of infection in hospitals and a number of researchers have investigated the biocidal action of ions in both air and nitrogen. By comparison, the physical action of air ions on bacterial dissemination and deposition has largely been ignored. However, there is clinical evidence that air ions might play an important role in preventing the transmission of Acinetobacter infection. Although the reasons for this are unclear, it is hypothesized that a physical effect may be responsible: the production of air ions may negatively charge items of plastic medical equipment so that they repel, rather than attract, airborne bacteria. By negatively charging both particles in the air and items of plastic equipment, the ionizers minimize electrostatic deposition on these items. In so doing they may help to interrupt the transmission of Acinetobacter infection in certain healthcare settings such as intensive care units. METHODS: A study was undertaken in a mechanically ventilated room under ambient conditions to accurately measure changes in surface potential exhibited by items of plastic medical equipment in the presence of negative air ions. Plastic items were suspended on nylon threads, either in free space or in contact with a table surface, and exposed to negative ions produced by an air ionizer. The charge build-up on the specimens was measured using an electric field mill while the ion concentration in the room air was recorded using a portable ion counter. RESULTS: The results of the study demonstrated that common items of equipment such as ventilator tubes rapidly developed a large negative charge (i.e. generally >-100V) in the presence of a negative air ionizer. While most items of equipment tested behaved in a similar manner to this, one item, a box from a urological collection and monitoring system (the only item made from styrene acrylonitrile), did however develop a positive charge in the presence of the ionizer. CONCLUSION: The findings of the study suggest that the action of negative air ionizers significantly alters the electrostatic landscape of the clinical environment, and that this has the potential to cause any Acinetobacter-bearing particles in the air to be strongly repelled from some plastic surfaces and attracted to others. In so doing, this may prevent critical items of equipment from becoming contaminated with the bacterium.

Bone repair has been studied in order to understand the complex phases involved that result in full conformity of the original bone. Our body has the unique ability to heal a bone fracture without scarring. Bone repair is modulated by different stimulus including growth factors. Transforming Growth Factor-beta (TGF-β) super-family have been studied with strong evidence in vitro and in vivo that TGF-β has significant effects on bone construction and resorption by regulating the duplication and differentiation of chondrocytes, osteoblasts and osteoclasts. Dosage carriers of TGF-β1, 2 or 3 namely HCl was used in vitro to see the effects it has on closure rates using a model wound in cultured monolayers of MG63 bone cells. The wound healing time was investigated using 6.25μl, 12.5μl, 25μl and 50μl concentrations of HCl compared against control. The model wound was made on fully confluent monolayers of MG63 bone cells with an average wound width of 300μm ± 10-30μm. For each concentration of HCl and control after wounding, the wound width was measured over a 30hr period. The results showed that after the 30hr period, the 25μl and 50μl concentrations of HCI enhanced the speed of wound closure in vitro as compared to the control. The culture treated with 25μl concentration of HCI was fully confluent at 25hrs and the 50μl concentration of HCl showed the highest percentage of wound closure but taking the full 30hrs to become confluent. The 6.25μ; and 12.5μl concentrations of HCl had slower closure rates than that of the higher concentrations with confluency not achieved at 30hrs. Results from un-treated flasks (control) showed slowest wound closure compared to treated flasks with HCl.

Increased awareness of airborne disease transmission has renewed interest in the use of upper-room ultraviolet germicidal irradiation (UVGI) systems to disinfect air. A number of researchers have demonstrated experimentally the ability of such systems to inactivate airborne microorganisms. However, relatively little work has been done on the effect of room air mixing and ventilation strategy on the performance of upper-room UV systems. This paper presents a parametric study of a hypothetical upper-room UV system using a two-zone mixing model to evaluate the effect of four ventilation regimes on air disinfection performance. The results of the study indicate that upper-room UVGI systems are most effective in applications where ventilation rates are low, being only of limited benefit in highly ventilated spaces. The paper also demonstrates that upper-room UVGI systems are best suited to applications that have good room air mixing. © 2004 ASHRAE.

The airborne route of transmission has long been considered as being of only limited importance in the epidemiology of nosocomial infection. Despite accumulating evidence that significant nosocomial pathogens such as Staphylococcus aureus are transmitted in this manner, there is much skepticism about the overall contribution of airborne microorganisms to nosocomial infection. This skepticism reflects the lack of data on the airborne microflora in hospitals - a topic that has received scant attention in recent years. This paper presents the results of a short study undertaken in a respiratory medicine ward at St James's University Hospital, Leeds, in the United Kingdom. The study found Acinetobacter spp., Haemophilus spp., and Moraxella spp. in the ward air, as well as Streptococcus spp. and Staphylococcus spp. Over 50% of all the microorganisms isolated during the study were found in the high dependency area of the ward. © 2004 ASHRAE.

BACKGROUND: In this paper we use multivariate statistical techniques to gain insights into how adaptive gait involving obstacle crossing is regulated in lower-limb amputees compared to able-bodied controls, with the aim of identifying underlying characteristics that differ between the two groups and consequently highlighting gait deficits in the amputees. METHODS: Eight unilateral trans-tibial amputees and twelve able-bodied controls completed adaptive gait trials involving negotiating various height obstacles; with amputees leading with their prosthetic limb. Spatiotemporal variables that are regularly used to quantify how gait is adapted when crossing obstacles were determined and subsequently analysed using multivariate statistical techniques. RESULTS AND DISCUSSION: There were fundamental differences in the adaptive gait between the two groups. Compared to controls, amputees had a reduced approach velocity, reduced foot placement distance before and after the obstacle and reduced foot clearance over it, and reduced lead-limb knee flexion during the step following crossing. Logistic regression analysis highlighted the variables that best distinguished between the gait of the two groups and multiple regression analysis (with approach velocity as a controlling factor) helped identify what gait adaptations were driving the differences seen in these variables. Getting closer to the obstacle before crossing it appeared to be a strategy to ensure the heel of the lead-limb foot passed over the obstacle prior to the foot being lowered to the ground. Despite adopting such a heel clearance strategy, the lead-foot was positioned closer to the obstacle following crossing, which was likely a result of a desire to attain a limb/foot angle and orientation at instant of landing that minimised loads on the residuum (as evidenced by the reduced lead-limb knee flexion during the step following crossing). These changes in foot placement meant the foot was in a different part of swing at point of crossing and this explains why foot clearance was considerably reduced in amputees. CONCLUSIONS: These results highlight that trans-tibial amputees use quite different gait adaptations to cross obstacles compared with controls (at least when leading with their prosthetic limb), indicating they are governed by different constraints; seemingly related to how they land on/load their prosthesis after crossing the obstacle.

Tuberculosis (TB) is a disease that is closely associated with poverty, with transmission occurring in situations where infected persons are in close contact with others in confined spaces. While it is well recognised that overcrowding increases the risk of transmission, this increased risk has not been quantified and the relationship between overcrowding and duration of exposure is not well understood. This paper analyses three epidemiological models that have been used to predict the transmission of airborne disease in confined spaces: the Mass Action model, Riley, Murphy and Riley's model and Gammaitoni and Nucci's model. A study is presented to demonstrate the range of applicability of each model and show how they can be applied to the transmission of both TB and diseases with short incubation periods such as measles. Gammiatoni and Nucci's generalised formulation is shown to be the most suitable for modelling airborne transmission in ventilated spaces, and it is subsequently used in a parametric study to evaluate the effect of physical and environmental factors on the rate of disease transmission. The paper also presents reported quanta production data for several TB outbreaks and demonstrates that the greatest risk of TB infection is during clinical procedures that produce large quantities of aerosol, such as bronchoscopy or intubation.

The Wells–Riley equation for modelling airborne infection in indoor environments is incorporated into an SEIR epidemic model with a short incubation period to simulate the transmission dynamics of airborne infectious diseases in ventilated rooms. The model enables the effect of environmental factors such as the ventilation rate and the room occupancy to be examined, and allows the long-term impact of infection control measures to be assessed. A theoretical parametric study is carried out to demonstrate how changes to both the physical environment and infection control procedures may potentially limit the spread of short-incubation-period airborne infections in indoor environments such as hospitals.

The world-wide occurrence of tuberculosis (TB) is very high, and in many parts of the world prevalence has reached epidemic proportions. While the WHO's global 'directly observed therapy short-course' (DOTS) programme has yielded some notable successes, it has reached only 12% of the world's TB cases. This suggests that the use of drug therapy alone is not enough to solve the global TB problem and that prevention using public health engineering techniques may provide a complementary solution. There are a number of engineering control strategies, such as the use of ultraviolet germicidal irradiation (UVGI) and advanced ventilation techniques, which can be used to combat the spread of Mycobacterium tuberculosis and other airborne pathogens. This paper describes a pilot study currently being undertaken at the Leeds General Infirmary in the UK, which is investigating the use of UVGI to disinfect air in ward spaces.

Bateman et al. (2021) shows that multiple sclerosis (MS) is strongly associated with raised pressure in the superior sagittal sinus (SSS) and increased jugular bulb height above the sigmoid sinus. These findings are consistent with an increased aqueductal CSF pulse, as previously described in MS. They reinforce the hypothesis that intracranial compliance is reduced in MS and that internal jugular vein abnormalities contribute to SSS hypertension. However, the contribution of this to the pathophysiology of MS has not been established. Further investigation is therefore needed to determine what role, if any, these changes play in the complex puzzle of MS.

Background: Direct contact between health care staff and patients is generally considered to be the primary route by which most exogenously-acquired infections spread within and between wards. Handwashing is therefore perceived to be the single most important infection control measure that can be adopted, with the continuing high infection rates generally attributed to poor hand hygiene compliance. Methods: Through the use of simple mathematical models, this paper demonstrates that under conditions of high patient occupancy or understaffing, handwashing alone is unlikely to prevent the transmission of infection. Conclusions: The study demonstrates that applying strict nurse cohorting in combination with good hygiene practice is likely to be a more effective method of reducing transmission of infection in hospitals. © 2006 Association for Professionals in Infection Control and Epidemiology, Inc.

The human body employs a sophisticated windkessel mechanism to dampen the arterial pulse entering the brain, thus ensuring the smooth flow of blood through the cerebral capillary bed. The energy from the arterial pulse is transferred to the cerebrospinal fluid (CSF), which pulses backwards and forwards across the foramen magnum. The dynamics associated with this system are complex and poorly understood. In an attempt to better understand the physiology, a number of researchers have constructed electrical analogue circuits to simulate the hydrodynamic behaviour of the brain. These generally consist of several low-pass filters. While such models have great potential, to date, they have met with only limited success. We suspect that this is in part due to a failure to identify the . order of the model required to successfully capture the hydrodynamics of the brain. Here, we advance the hypothesis that the cerebral hydrodynamic system is at most a third order system, using evidence collected from the spectral eigensystem of the arterial, venous and CSF flows. Using . singular spectrum analysis we computed the singular vectors for the measured arterial, venous and CSF flows from an individual. This revealed that the first singular vector contributes 67% of the observed variance; the first plus the second singular vectors contribute 96% of the variance; and sum of the first three singular vectors contribute more than 99.5% of the observed variance. © 2011 Elsevier Ltd.

Nosocomial infections are a major problem in many hospital buildings, with approximately 10% of patients acquiring such an infection during a hospital stay. Airborne transmission is one of the important routes for a number of nosocomial pathogens. To combat this problem there are a number of engineering control strategies, such as the use of ultraviolet germicidal irradiation and advanced ventilation techniques, which can be used. This paper outlines the 'state of the art' in air disinfection, and reviews recent research work in this field. Copyright (C) 2000 S. Karger AG, Basel.

Objective: To determine effect of negative air ions on colonisation/ infection with methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter species in an intensive care unit. Design: Prospective single-centre cross-over study in an adult general intensive care unit. Patients: 201 patients whose stay on the unit exceeded 48 hour's duration. Intervention: Six negative air ionisers were installed on the unit but not operational for the first 5 months of the study (control period). Devices were then operational for the following 5.5 months. Measurements and results: 30 and 13 patients were colonised/infected with MRSA and Acinetobacter spp., respectively, over 10.5 months. No change in MRSA colonisation/infection was observed compared with the 5 month control period. Acinetobacter cases were reduced from 11 to 2 (p = 0.007). Conclusion: Ionisers may have a role in the prevention of Acinetobacter infections. © Springer-Verlag 2005.

BACKGROUND: The potential pathogenesis between the presence and severity of chronic cerebrospinal venous insufficiency (CCSVI) and its relation to clinical and imaging outcomes in brain parenchyma of multiple sclerosis (MS) patients has not yet been elucidated. The aim of the study was to investigate the relationship between CCSVI, and altered brain parenchyma venous vasculature visibility (VVV) on susceptibility-weighted imaging (SWI) in patients with MS and in sex- and age-matched healthy controls (HC). METHODS: 59 MS patients, 41 relapsing-remitting and 18 secondary-progressive, and 33 HC were imaged on a 3T GE scanner using pre- and post-contrast SWI venography. The presence and severity of CCSVI was determined using extra-cranial and trans-cranial Doppler criteria. Apparent total venous volume (ATVV), venous intracranial fraction (VIF) and average distance-from-vein (DFV) were calculated for various vein mean diameter categories: < .3 mm, .3-.6 mm, .6-.9 mm and > .9 mm. RESULTS: CCSVI criteria were fulfilled in 79.7% of MS patients and 18.2% of HC (p < .0001). Patients with MS showed decreased overall ATVV, ATVV of veins with a diameter < .3 mm, and increased DFV compared to HC (all p < .0001). Subjects diagnosed with CCSVI had significantly increased DFV (p < .0001), decreased overall ATVV and ATVV of veins with a diameter < .3 mm (p < .003) compared to subjects without CCSVI. The severity of CCSVI was significantly related to decreased VVV in MS (p < .0001) on pre- and post-contrast SWI, but not in HC. CONCLUSIONS: MS patients with higher number of venous stenoses, indicative of CCSVI severity, showed significantly decreased venous vasculature in the brain parenchyma. The pathogenesis of these findings has to be further investigated, but they suggest that reduced metabolism and morphological changes of venous vasculature may be taking place in patients with MS.

Abstract

The TermoDeck hollow core slab system is a versatile energy storage technique for controlling the environment within large and medium sized buildings. It utilises the hollow cores within pre-cast concrete floor slabs as ventilation ducts to produce an environment which is thermally stable. Although many TermoDeck systems have successfully been installed in Scandinavia, the United Kingdom and in other northern European countries, the thermal performance of the system is not fully understood. This paper presents the results of a theoretical study, using a numerical model, into the thermal performance of the TermoDeck system. In particular, the role of the bends in the system is investigated and the conclusion reached that their impact on overall heat transfer is minimal. It is also concluded that greater thermal attenuation is achieved by using a five-core pass system in comparison with a three-core system. © 2002 Elsevier Science Ltd. All rights reserved.

BACKGROUND: Good hand hygiene has for many years been considered to be the most important measure that can be applied to prevent the spread of healthcare-associated infection (HAI). Continuous emphasis on this intervention has lead to the widespread opinion that HAI rates can be greatly reduced by increased hand hygiene compliance alone. However, this assumes that the effectiveness of hand hygiene is not constrained by other factors and that improved compliance in excess of a given level, in itself, will result in a commensurate reduction in the incidence of HAI. However, there is evidence that the law of diminishing returns applies to hand hygiene, with the greatest benefits occurring in the first 20% or so of compliance. While this raises intriguing questions about the extent to which increasing compliance alone can further reduce rates of HAI, analysis of this subject has been hampered by a lack of quantifiable data relating to the risk of transmission between patients on wards. METHODS: In order to gain a greater understanding of the transmission of infection between patients via the hands of healthcare workers (HCWs), we constructed a stochastic Monte Carlo model to simulate the spread of methicillin-resistant Staphylococcus aureus (MRSA) between patients. We used the model to calculate the risk of transmission occurring, firstly between two patients in adjacent beds, and then between patients in a four-bedded bay. The aim of the study was to quantify the probability of transmission under a variety of conditions and thus to gain an understanding of the contribution made by the various factors which influence transmission. RESULTS: The study revealed that on a four-bedded bay, the average probability of transmitting an infection by the handborne route is generally low (i.e. in the region 0.002 - 0.013 depending on the hand hygiene behaviour of HCWs and other factors). However, because transmission is strongly influenced by stochastic events, it is the frequency with which 'high-risk events' occur, rather than average probability, that governs whether or not transmission will take place. The study revealed that increased hand hygiene compliance has a dramatic impact on the frequency with which 'high-risk events' occur. As compliance increases, so the rate at which 'high-risk events' occur, rapidly decreases, until a point is reached, beyond which, further hand hygiene is unlikely to yield any greater benefit. CONCLUSION: The findings of the study confirm those of other researchers and suggest that the greatest benefits derived from hand hygiene occur as a result of the first tranche of compliance, with higher levels (>50%) of hand hygiene events yielding only marginal benefits. This suggests that in most situations relatively little benefit is accrued from seeking to achieve very high levels of hand hygiene compliance.

In this proof-of-concept study the impact of central venous pressure (CVP) on internal jugular veins cross-sectional area (CSA) and blood flow time-average velocity (TAV) was evaluated in eight subjects, with the aim of understanding the drivers of the jugular venous pulse. CVP was measured using a central venous catheter while CSA variation and TAV along a cardiac cycle were acquired using ultrasound. Analysis of CVP, CSA and TAV time-series signals revealed TAV and CSA to lag behind CVP by on average 0.129 s and 0.138 s, with an inverse correlation between CSA and TAV (r= –0.316). The respective autocorrelation signals were strongly correlated (mean r=0.729-0.764), with mean CSA periodicity being 1.062 Hz. Fourier analysis revealed the frequency spectrums of CVP, TAV and CSA signals to be dominated by frequencies at approximately 1 and 2 Hz, with those >1 Hz greatly attenuated in the CSA signal. Because the autocorrelograms and periodograms of the respective signals were aligned and dominated by the same underlying frequencies, this suggested that they are more easily interpreted in the frequency domain rather than the time domain.

Catheter venography has been considered to be the "gold standard" in the evaluation of venous occlusive disease. Venography provides valuable information regarding stenotic areas, flow patterns, reflux, and the presence of collaterals. Many attempts have been made to evaluate the cerebral outflow and patients who may benefit from a treatment of internal jugular vein stenosis. The evidence that emptying time of contrast medium may correlate with stenotic segments gave a new chance for studies evaluating the venous outflow. The increased prevalence of extra-cranial venous flow anomalies has encouraged the use of angioplasty to treat the internal jugular vein (IJV) stenosis, with the aim of producing a clinical benefit. The need for careful evaluation of cerebral venous outflow was also driven by the increasing demand for the evaluation of percutaneous transluminal angioplasty (PTA) success both hemodynamic and clinical. In recent years there has been considerable interest in the use of PTA of the IJV to treat chronic cerebrospinal venous insufficiency. The present review provides a brief overview on the main techniques for the evaluation of cerebral venous outflow.

There is an ongoing debate about the reasons for and factors contributing to healthcare-associated infection (HAI). Different solutions have been proposed over time to control the spread of HAI, with more focus on hand hygiene than on other aspects such as preventing the aerial dissemination of bacteria. Yet, it emerges that there is a need for a more pluralistic approach to infection control; one that reflects the complexity of the systems associated with HAI and involves multidisciplinary teams including hospital doctors, infection control nurses, microbiologists, architects, and engineers with expertise in building design and facilities management. This study reviews the knowledge base on the role that environmental contamination plays in the transmission of HAI, with the aim of raising awareness regarding infection control issues that are frequently overlooked. From the discussion presented in the study, it is clear that many unknowns persist regarding aerial dissemination of bacteria, and its control via cleaning and disinfection of the clinical environment. There is a paucity of good-quality epidemiological data, making it difficult for healthcare authorities to develop evidence-based policies. Consequently, there is a strong need for carefully designed studies to determine the impact of environmental contamination on the spread of HAI.

Covid-19 is an airborne disease, with the vast majority of infections occurring indoors. By comparison, little transmission occurs outdoors. Here, we investigate the airborne transmission pathways that differentiate the indoors from outdoors, and conclude that profound differences exist, which help to explain why SARS-CoV-2 transmission is much more prevalent indoors. Near and far-field transmission pathways are discussed along with factors that affect infection risk, with aerosol concentration, air entrainment, thermal plumes, and occupancy duration all identified as being influential. In particular, we present the fundamental equations that underpin the Wells-Riley model, and show the mathematical relationship between inhaled virus particles and quanta of infection. A simple model is also presented for assessing infection risk in spaces with incomplete air mixing. Transmission risk is assessed in terms of aerosol concentration using simple 1D equations, followed by a description of thermal plume-ceiling interactions. With respect to this, we present new experimental results using Schlieren-visualisation and Computational Fluid Dynamics (CFD) based on the Eulerian-Lagrangian approach. Pathways of airborne infection are discussed, with the key differences identified between indoors and outdoors. In particular, the contribution of thermal and exhalation plumes is evaluated, and the presence of near-field/far-field feedback loop postulated, which is absent outdoors.

COVID-19 is an airborne disease, with the vast majority of infections occurring indoors. In comparison, little transmission occurs outdoors. Here, we investigate the airborne transmission pathways that differentiate the indoors from outdoors and conclude that profound differences exist, which help to explain why SARS-CoV-2 transmission is much more prevalent indoors. Near- and far-field transmission pathways are discussed along with factors that affect infection risk, with aerosol concentration, air entrainment, thermal plumes, and occupancy duration all identified as being influential. In particular, we present the fundamental equations that underpin the Wells–Riley model and show the mathematical relationship between inhaled virus particles and quanta of infection. A simple model is also presented for assessing infection risk in spaces with incomplete air mixing. Transmission risk is assessed in terms of aerosol concentration using simple 1D equations, followed by a description of thermal plume–ceiling interactions. With respect to this, we present new experimental results using Schlieren visualisation and computational fluid dynamics (CFD) based on the Eulerian–Lagrangian approach. Pathways of airborne infection are discussed, with the key differences identified between indoors and outdoors. In particular, the contribution of thermal and exhalation plumes is evaluated, and the presence of a near-field/far-field feedback loop is postulated, which is absent outdoors.

Objectives To assess the relationship between cross-sectional area of internal jugular veins and brain volumes in healthy individuals without neurologic disease. Methods A total of 193 healthy individuals without neurologic disease (63 male and 130 female; age > 20 to < 70 years) received magnetic resonance venography and structural brain magnetic resonance imaging at 3T. The internal jugular vein cross-sectional area was assessed at C2–C3, C4, C5–C6, and C7–T1. Normalized whole brain volume was assessed. Partial correlation analyses were used to determine associations. Results There was an inverse relationship between normalized whole brain volume and total internal jugular vein cross-sectional area (C7–T1: males r = −0.346, p = 0.029; females r = −0.301, p = 0.002). After age adjustment, association of normalized whole brain volume and normalized gray matter volume with internal jugular vein cross-sectional area became positive in males (normalized whole brain volume and right internal jugular vein cross-sectional area (C2–C3) changed from r = −0.163 to r = 0.384, p = 0.002), but not in the females. Conclusion Sex differences exist in the relationship between brain volume and internal jugular vein cross-sectional area in healthy individuals without neurologic disease.

Designers are being encouraged towards passive cooling and natural ventilation in buildings. This will promote heavyweight buildings which utilise both fabric thermal storage and night venting techniques. In terms of energy consumption and carbon dioxide emissions, the new build sector is of relatively minor importance compared with the existing stock of high energy consumption buildings, many of which already contain air conditioning. This paper describes a new technique whereby new and existing buildings can be fitted with a low energy air movement system, which significantly increases the fabric thermal storage capacity of the building. This should eliminate the need for air conditioning whilst still enabling occupants to remain comfortable in summer.

The paper investigates the use of ice storage technology as a demand side management tool. A theoretical study of a dairy application is described in which the costs of running an ice storage installation under a traditional maximum demand tariff are compared with those under a pool-based contract. The paper also describes a new dynamic ice slurry system currently under development.

Air conditioning makes a significant contribution to UK carbon dioxide emissions. This paper investigates the impact that ice thermal storage might make on carbon dioxide emissions. Carbon dioxide emissions from English and Welsh generating plant are also analysed in detail.

The extent to which ice thermal storage is adopted depends very much on its commercial viability. To establish fully the economic viability of such systems, it is necessary to examine the factors which affect their operation over a complete cooling season. This paper examines the factors affecting the economic performance of ice storage systems, and investigates the impact of variations within these factors on ice storage systems. An investigation is made of systems controlled by both chiller priority and store priority operating strategies. The figures quoted in the text are the results of an ice storage computer program developed by the authors.

The forthcoming expansion of the electricity contract market in England and Wales in April 1994 will have far-reaching consequences on energy usage in buildings. This paper examines the effect of the expansion on the utilisation of ice thermal storage within the England and Wales. Electricity pool selling prices are analysed, and a cost study is carried out to compare ice storage operating costs under a pool based contract with those incurred while running under a maximum-demand tariff.

Desiccants have been used in many applications to provide dehumidification. This paper describes an application of desiccants which provides both dehumidification and sensible cooling, with little or no use of conventional vapour-compression refrigeration plant. Through a parametric study, the energy consumption and costs of a desiccant cooling system are compared with those of a conventional vapour-compression refrigeration-based air-conditioning system.

Desiccant cooling is a potentially environmentally friendly technology that can be used to condition the internal environment of buildings. Unlike conventional air conditioning systems, which rely on electrical energy to drive the cooling cycle, desiccam cooling is a heat-driven cycle. This paper follows on from an initial study by Halliday and Beggs, and uses real meteorological data to evaluate the potential in the United Kingdom of using solar energy to drive the desiccant cooling cycle. Through the use of parametric studies, the paper investigates the energy consumption and costs associated with desiccant cooling

The privatisation of the etectricity supply industry in the UK has had far reaching environmental consequences. This paper discusses the environmental impact of the changes that have taken place in the generating sector, and presents a model for the prediction of carbon dioxide emissions per kWh of delivered electrical energy in England and Wales, on a time of day basis.

The installation of upper-room ultraviolet germicidal irradiation (UVGI) devices in ventilated rooms has the potential to reduce transmission of infections by an airborne route. However, the performance of such devices is dependant on several factors including the location of the lamp and the ventilation airflow in the room. This study uses a CFD model to evaluate the performance of UVGI devices by considering the cumulative UV-C dose received by the bulk room air in a ventilated room. By evaluating the UV dose rather than the resulting micro-organism inactivation the methodology can be used to optimise UVGI systems at the design stage, particularly when the source location of bioaerosol contaminants is not known. The study investigates the relationships between the lamp location, lamp power, ventilation system and room heating in a small, ventilated room. The results show that with ventilation air supplied at low level and extracted at high level the UVGI system performs better than with the air supplied at high level and extracted close to the floor. In addition the results show the presence of a heater in the room is unlikely to have a detrimental effect on performance and may promote mixing to increase the extent of disinfection.

Infections associated with Acinetobacter spp. are an increasing problem in hospitals around the world, with many infections being multiply resistant to antibiotics. Acinetobacter spp. are particularly hardy and can survive on dry surfaces for long periods of time. They have also been cultured from the air on hospital wards. While it is known that environmental factors can contribute to the spread of infections caused by Acinetobacter spp., the precise role of the clinical environment in this process remains unclear. This review paper investigates this issue and seeks to identify environmental factors which may influence the spread of infections associated with Acinetobacter spp.

AbstractNosocomial infections are a major problem in many hos pital buildings, with approximately 10% of patients ac quiring such an infection during a hospital stay. Airborne transmission is one of the important routes for a number of nosocomial pathogens. To combat this problem there are a number of engineering control strategies, such as the use of ultraviolet germicidal irradiation and ad vanced ventilation techniques, which can be used. This paper outlines the'state of the art' in air disinfection, and reviews recent research work in this field.

Objective Percutaneous transluminal angioplasty (PTA) of the internal jugular veins (IJVs) has been proposed in recent years to treat chronic cerebrovascular venous insufficiency, with discordant results. Moreover, very little is known about the efficacy of PTA in restoring a normal cerebral venous outflow. The aim of this study was to investigate the anatomic factors and patient characteristics that might influence the efficacy of PTA of the IJV. Methods There were 797 consecutive patients with venous outflow anomalies who underwent standardized, operator-independent catheter venography and PTA of the IJVs. Before and after PTA, morphologic and hemodynamic anomalies of the IJVs were documented. The primary end point of the study was to evaluate the morphologic factors influencing the efficacy of angioplasty in improving IJV outflow. Results PTA resulted in an increased outflow through the IJVs in most patients. However, younger individuals with transverse endoluminal defects and higher pre-PTA flows are more likely to respond well to PTA compared with those who exhibit hypoplasia, stenosis, or longitudinal endoluminal defects. Conclusions This study identified the factors that influence and could predict the efficacy of PTA in the treatment of IJV anomalies.

The use of electrocardiograms (ECGs) to diagnose and analyse atrial fibrillation (AF) has received much attention recently. When studying AF, it is important to isolate the atrial activity (AA) component of the ECG plot. We present a new autoregressive (AR) model for semiblind source extraction of the AA signal. Previous researchers showed that one could extract a signal with the smallest normalized mean square prediction error (MSPE) as the first output from linear mixtures by minimizing the MSPE. However the extracted signal will be not always the desired one even if the AR model parameters of one source signal are known. We introduce a new cost function, which caters for the specific AR model parameters, to extract the desired source. Through theoretical analysis and simulation we demonstrate that this algorithm can extract any desired signal from mixtures provided that its AR parameters are first obtained. We use this approach to extract the AA signal from 12-lead surface ECG signals for hearts undergoing AF. In our methodology we roughly estimated the AR parameters from the fibrillatory wave segment in the V1 lead, and then used this algorithm to extract the AA signal. We validate our approach using real-world ECG data. Copyright © 2008 Gang Wang et al.

This paper presents a new Fiedler vector model for categorising amino acids, which is based on the Miyazawa-Jernigan matrix. The model splits the amino acid residues into two hydrophobic groups (LFI) and (MVWCY) and two polar groups (HATGP) and (RQSNEDK). In so doing, it independently confirms the findings of Wang and Wang and Cieplak et al. and demonstrates the validity of using eigenvectors to partition amino acid groups. © 2007 EBSA.

Aging of the healthy brain is characterized by focal or nonfocal white matter (WM) signal abnormality (SA) changes, which are typically detected as leukoaraiosis (LA). Hypertension is a risk factor for WM lesion formation. This study investigated whether LA might be associated with increased cerebrospinal fluid (CSF) pulsatility linked to arterial hypertension.A total of 101 individuals without neurologic diseases (53 females and 48 males) aged between 18 and 75 years underwent 3T brain MRI with cine phase contrast imaging for CSF flow estimation, after providing their informed consent. LA was defined as the presence of focal T2 WM SA changes and/or nonfocal uniform areas of signal increase termed dirty appearing white matter (DAWM). Relevant information relating to cardiovascular risk factors was also collected.When controlled for age and hypertension, significant partial correlations were observed between: DAWM volume and: net negative flow (r = -.294, P = .014); net positive flow (NPF) (r = .406, P = .001); and peak positive velocity (r = .342, P = .004). Multiple linear regression analysis revealed DAWM volume to be significantly correlated with CSF NPF (P = .019) and hypertension (P = .007), whereas T2 WM SA volume was only significantly correlated with age (P = .002). Combined DAWM and T2 WM SA volumes were significantly related with age (P = .001) and CSF peak negative velocity (P = .041).Rarefaction of WM leading to LA is a multifactorial process, in which formation of DAWM induced by hypertension and increased aqueductal CSF pulsatility, may play a contributory role. These two factors appear to act independently of each other in a process that is independent of age.

The trend in facilities management towards outsourcing is in conflict with the current trend towards holistic low energy building design. Designers are busily “designing out” building services, in favour of new passive/low energy technologies which are integrated into the building envelope. A lack of understanding of each other’s discipline allows designers to produce “passively” controlled buildings which are difficult for facilities managers to manage. Examines the nature of the conflict between holistic “passive” building design and facilities management. Includes a case study based on ten recently constructed passive/mixed‐mode buildings. The case study appraises each building with respect to facilities management, and identifies specific problem areas that could be improved and which are in need of further investigation.

In this review, the impact of restricted cere- bral venous outflow on the biomechanics of the intracranial fluid system is investigated. The cerebral venous drainage system is often viewed simply as a series of collecting vessels channeling blood back to the heart. However there is growing evidence that it plays an important role in regulating the intracranial fluid system. In particular, there appears to be a link between increased cerebrospinal fluid (CSF) pulsatility in the Aqueduct of Sylvius and constricted venous outflow. Constricted venous outflow also appears to inhibit absorp- tion of CSF into the superior sagittal sinus. The compliance of the cortical bridging veins appears to be critical to the behaviour of the intracranial fluid system, with abnormalities at this location implicated in normal pressure hydrocephalus. The compliance associated with these vessels appears to be functional in nature and dependent on the free egress of blood out of the cranium via the extracranial venous drainage pathways. Because constrict- ed venous outflow appears to be linked with increased aqueductal CSF pulsatility, it sug- gests that inhibited venous blood outflow may be altering the compliance of the cortical bridging veins.

BACKGROUND: Hand hygiene is generally considered to be the most important measure that can be applied to prevent the spread of healthcare-associated infection (HAI). Continuous emphasis on this intervention has lead to the widespread opinion that HAI rates can be greatly reduced by increased hand hygiene compliance alone. However, this assumes that the effectiveness of hand hygiene is not constrained by other factors and that improved compliance in excess of a given level, in itself, will result in a commensurate reduction in the incidence of HAI. However, several researchers have found the law of diminishing returns to apply to hand hygiene, with the greatest benefits occurring in the first 20% or so of compliance, and others have demonstrated that poor cohorting of nursing staff profoundly influences the effectiveness of hand hygiene measures. Collectively, these findings raise intriguing questions about the extent to which increasing compliance alone can further reduce rates of HAI. METHODS: In order to investigate these issues further, we constructed a deterministic Ross-Macdonald model and applied it to a hypothetical general medical ward. In this model the transmission of staphylococcal infection was assumed to occur after contact with the transiently colonized hands of HCWs, who, in turn, acquire contamination only by touching colonized patients. The aim of the study was to evaluate the impact of imperfect hand cleansing on the transmission of staphylococcal infection and to identify, whether there is a limit, above which further hand hygiene compliance is unlikely to be of benefit. RESULTS: The model demonstrated that if transmission is solely via the hands of HCWs, it should, under most circumstances, be possible to prevent outbreaks of staphylococcal infection from occurring at a hand cleansing frequencies < 50%, even with imperfect hand hygiene. The analysis also indicated that the relationship between hand cleansing efficacy and frequency is not linear--as efficacy decreases, so the hand cleansing frequency required to ensure R0 < 1 increases disproportionately. CONCLUSION: Although our study confirmed hand hygiene to be an effective control measure, it demonstrated that the law of diminishing returns applies, with the greatest benefit derived from the first 20% or so of compliance. Indeed, our analysis suggests that there is little benefit to be accrued from very high levels of hand cleansing and that in most situations compliance > 40% should be enough to prevent outbreaks of staphylococcal infection occurring, if transmission is solely via the hands of HCWs. Furthermore we identified a non-linear relationship between hand cleansing efficacy and frequency, suggesting that it is important to maximise the efficacy of the hand cleansing process.

Although much hospital acquired infection is associated with person-to-person contact, there is increasing evidence that some nosocomial infections may be transmitted via the airborne route. However, the knowledge base concerning airborne microflora in hospitals is poor. In particular, there is a need for good quality data relating bioaerosol production to clinical activity in hospital wards. A short aerobiological survey was therefore undertaken by the authors on a respiratory ward at St James’s University Hospital in Leeds in order to gain an understanding of the relationship between activity and bioaerosol production. This survey involved regular microbiological and particulate (0.3–5 m) sampling of the ward air, together with an observational study of ward activity. Two identical four-bed ward bays were surveyed, one containing high dependency patients who regularly used noninvasive ventilators (NIVs), and the other containing patients who did not require mechanical ventilation. The survey found a correlation between activity and aerosol production.

Airborne transmission is known to be the route of infection for diseases such as tuberculosis and aspergillosis. It has also been implicated in nosocomial outbreaks of MRSA, Acinetobacter spp. and Pseudomonas spp. Despite this there is much scepticism about the role that airborne transmission plays in nosocomial outbreaks. This paper investigates the airborne spread of infection in hospital buildings, and evaluates the extent to which it is a problem. It is concluded that although contact-spread is the principle route of transmission for most infections, the contribution of airborne micro-organisms to the spread of infection is likely to be greater than is currently recognised. This is partly because many airborne micro-organisms remain viable while being non-culturable, with the result that they are not detected, and also because some infections arising from contact transmission involve the airborne transportation of micro-organisms onto inanimate surfaces.

Models to evaluate upper room ultraviolet germicidal irradiation (UVGI) devices can be used to improve the understanding of the behaviour of UV devices in ventilated rooms and so enable more confident predictions to be made of their performance. This paper presents two- and three-zone mixing models for investigating the effect of upper room UVGI devices in a typical ventilated room. The results from these analytical models are compared to a CFD simulation of the same room that incorporates the biological inactivation of micro-organisms in the presence of an ultraviolet field. The study demonstrates that analytical mixing models give reasonably good average zone concentrations and are therefore useful in estimating overall performance. However, the CFD simulations are necessary to fully examine the interaction of the room airflow with the inactivation of micro-organisms due to the UV field.

This paper is the last of three dealing with 'real time' electricity use and ice storage. The paper investigates the ability of ice thermal storage to reduce carbon dioxide emissions through the use of night-time electrical power. Time-related carbon dioxide emission data are used to analyse the potential environmental benefits of ice thermal storage.

OBJECTIVE: While chronic cerebrospinal venous insufficiency (CCSVI) can be characterized using cervical plethysmography, much remains unknown about the haemodynamics associated with this procedure. The aim of the study was therefore to gain a deeper understanding of the observed haemodynamics. METHOD: Forty healthy controls and 44 CCSVI patients underwent cervical plethysmography, which involved placing a strain-gauge collar around their necks and tipping them from the upright (90(o)) to supine position (0(o)) in a chair. Once stabilized, they were returned to the upright position, allowing blood to drain from the neck. A mathematical model was used to calculate the hydraulic resistance of the extracranial venous system for each subject in the study. RESULTS: The mean hydraulic resistance of the extracranial venous system was 10.28 (standard deviation [SD] 5.14) mmHg.s/mL in the healthy controls and 16.81 (SD 9.22) in the CCSVI patients (P < 0.001). CONCLUSIONS: The haemodynamics of the extracranial venous system are greatly altered in CCSVI patients.

Pseudomonas aeruginosa is a common and important pathogen in people with cystic fibrosis (CF). Recently epidemic strains of P. aeruginosa associated with increased morbidity, have been identified. The method of transmission is not clear, but there is evidence of a potential airborne route. The aim of this study was to determine whether different strains of P. aeruginosa isolated from people with CF were able to survive within artificially generated aerosols in an aerobiological chamber. Viable P. aeruginosa could still be detected up to 45 min after halting generation of the aerosols. All of the strains of P. aeruginosa expressing a non-mucoid phenotype isolated from people with CF had a reduced ability to survive within aerosols compared to an environmental strain. Expression of a mucoid phenotype by the strains of P. aeruginosa isolated from people with CF promoted survival in the aerosol model compared to strains expressing a non-mucoid phenotype. © 2009 European Cystic Fibrosis Society.

Air ionizers have seen increasing use as devices for improving indoor air quality, including applications designed to reduce the transmission of infection in healthcare environments. However, little attention has been given to understanding and quantifying the physical behavior of ions in indoor air. This study presents experimental data and a theoretical model to examine the factors that influence the concentration of ions in a ventilated room. The results demonstrate how, with an ionizer in operation, the ion concentration is governed by ion—ion interactions and electrical deposition at the walls, with the ventilation rate having a minimal influence. The results also demonstrate that an ion concentration > 1010 ions · m ×3 is necessary for these electrical effects to be significant, which has implications for the suitability of an ionizer for a particular location.

Background: Falls are a significant public health concern for older adults, and are associated with many detrimental physical, psychological and economic consequences. The aim of this thesis was to identify which functional variables (i.e. balance, gait and clinical measures) and physical characteristics (i.e. strength and body composition) could best distinguish between older female fallers and non-fallers, using a novel machine learning approach. Methods: 60 community-dwelling older women (≥65 years), classified as fallers and non-fallers based on falls history, attended three data collection sessions. Centre of pressure data were collected during five static posturography protocols. Ground reaction force (GRF) and kinematic data were measured during walking trials at two gait speeds. Participants completed five clinical measures, and strength assessments were performed at the trunk, knee and ankle for both limbs using an isokinetic dynamometer. Dual energy X-ray absorptiometry scans were conducted to assess body composition, bone mineral density and hip structure. The data (281 variables) were partitioned into five data packages (balance, gait, clinical measures, strength and body composition) and a uniform analysis strategy was applied to each in the single-domain analyses. Random forest and leave-one-variable-out partial least squares correlation analysis were employed to assess variable importance. The important variables selected were combined into two refined datasets, and classification models were constructed to differentiate between fallers and non-fallers. Subsequently, the strongest discriminators from each data package were compiled and analysed in the multi-domain analyses using the same strategy. Findings: Overall, this thesis demonstrates that it is possible to distinguish between fallers and non-fallers with a high degree of accuracy, using a refined set of variables and a sophisticated multivariate approach, in both a single- and multi-domain context. Important balance, gait, clinical measures, strength, and body composition variables were identified for discriminating between groups, alongside redundant factors. In the balance data package, multiple variables measured during the limits of stability, unilateral stance, and Modified Clinical Test of Sensory Interaction on Balance were identified as important discriminators. In the gait data package, a combination of spatiotemporal, kinematic, GRF, and variability variables were selected as important. In the clinical measures data package, several variables measured during the Timed Up and Go, Tinetti Performance Oriented Mobility Assessment, and gait speed protocols appeared useful when differentiating between groups. In the strength data package, a combination of peak torque variables, namely knee flexion, dorsiflexion and plantar flexion, alongside three asymmetry variables were identified as important. In the body composition data package, several muscle quality indices were selected as important. In the multi-domain data package, a combination of gait, clinical measures, strength, and body composition variables appeared to be the most important discriminators between fallers and non-fallers. This study is one of the few comprehensive analyses to include important variables from multiple domains with a sophisticated machine learning approach. The findings can be used to inform the design of optimal falls screening and prevention methods. Furthermore, this work highlights the applicability of machine learning techniques when investigating falls in older women.

Falls are a significant ongoing public health concern for older adults. At present, few studies have concurrently explored the influence of multiple measures when seeking to determine which variables are most predictive of fall risks. As such, this cross-sectional study aimed to identify those functional variables (i.e. balance, gait and clinical measures) and physical characteristics (i.e. strength and body composition) that could best distinguish between older female fallers and non-fallers, using a machine learning approach. Overall, 60 community-dwelling older women (≥65 years), retrospectively classified as fallers (n = 21) or non-fallers (n = 39), attended three data collection sessions. Data (281 variables) collected from tests in five separate domains (balance, gait, clinical measures, strength and body composition) were analysed using random forest (RF) and leave-one-variable-out partial least squares correlation analysis (LOVO PLSCA) to assess variable importance. The strongest discriminators from each domain were then aggregated into a multi-domain dataset, and RF, LOVO PLSCA, and logistic regression models were constructed to identify the important variables in distinguishing between fallers and non-fallers. These models were used to classify participants as either fallers or non-fallers, with their performance evaluated using receiver operating characteristic (ROC) analysis. The study found that it is possible to classify fallers and non-fallers with a high degree of accuracy (e.g. logistic regression: sensitivity = 90%; specificity = 87%; AUC = 0.92; leave-one-out cross-validation accuracy = 63%) using a combination of 18 variables from four domains, with the gait and strength domains being particularly informative for screening programmes aimed at assessing falls risk.

The coronavirus disease 2019 (COVID-19) pandemic has caused disruption to professional and recreational sports across the world. The SARS-CoV-2 virus can be transmitted by relatively large respiratory droplets that behave ballistically, and exhaled aerosol droplets, which potentially pose a greater risk. This review provides a summary of end-to-end SARS-CoV-2 transmission risk factors for sport and an overview of transmission mechanisms to be considered by all stakeholders. The risk of SARS-CoV-2 transmission is greatest indoors, and primarily influenced by the ventilation of the environment and the close proximity of individuals. The SARS-CoV-2 transmission risks outdoors, e.g. via water, and from fomites, appear less than initially thought. Mitigation strategies include good end-to-end scenario planning of activities to optimise physical distancing, face mask wearing and hygiene practice of individuals, the environment and equipment. The identification and removal of infectious individuals should be undertaken by means of the taking of temperature and COVID-19 symptom screening, and the use of diagnostic monitoring tests to identify asymptomatic individuals. Using adequate video footage, data from proximity technology and subject interviews, the identification and isolation of ‘close contacts’ should also be undertaken to limit SARS-CoV-2 transmission within sporting environments and into the wider community. Sports should aim to undertake activities outdoors where possible, given the lower SARS-CoV-2 transmission risk, in comparison to indoor environments.

Purpose Despite being a widely used management technique, cumulative sum (CUSUM) analysis remains almost unheard of in professional sport. To address this, CUSUM analysis of soccer match data from the English Premier League (EPL) was performed. The primary objective of the study was to evaluate CUSUM as a tool for assessing ‘on-field’ team performance. As a secondary objective, the association between managerial change and team performance was evaluated. Design/methodology/approach CUSUM was applied retrospectively to goal difference data for six EPL teams (Arsenal, Chelsea, Everton, Liverpool, Manchester United, and Tottenham) over 23 consecutive seasons from 1995-2018. This was supplemented with change point analysis to identify structural changes in mean goal difference. Succession was evaluated by mapping historical managerial changes onto the CUSUM plots for the respective clubs. Findings CUSUM analysis revealed the presence of structural changes in four clubs. Two structural change points were identified for both Chelsea and Everton, one for Manchester United and Tottenham, and none for Arsenal and Liverpool. Relatively few managerial changes coincided temporally with structural changes in ‘on-field’ performance, with most appointments having minimal impact on long-term team performance. Other factors (e.g. changes in ownership) appear to have been influential. Research limitations/implications The study was limited by the fact that only successful teams were investigated. Practical implications CUSUM analysis appears to have potential as a tool for executive decision-makers to evaluate performance outcomes in professional soccer. Originality/value The study is the first of its kind to use CUSUM analysis to evaluate team performance in professional soccer.

BACKGROUND AND AIM:Age-related declines in muscle strength have been associated with reduced functional capacity, postural instability and increased risk of falls in older adults. Studies have generally focussed on the significance of lower limb strength, however more recently the importance of trunk muscle strength has been explored, which may have been previously overlooked (Granacher et al., 2013). A limited number of studies have investigated the relationship between trunk strength and function, but this was tested under isometric contractions(Shahtahmassebi et al., 2017). Therefore, the purpose of this study was to investigate the relationship between dynamic (concentric) trunk strength and functional mobility in older women. METHODS:A sample of 40 older women (age: 68.9±3.73 years) participated in this study. To assess functional mobility, participants completed the timed up and go (TUG), 30 second chair stand test (CST), and a timed stair climb task (ascent and descent). Both self-selected normal and fast gait speed (GS) were also recorded. Concentric trunk flexion and extension strength data were collected using an isokinetic dynamometer (Biodex, USA). Measurements were conducted in the seated-compressed position in line with the manufacturer's guidelines. Following five sub-maximal trials, peak torque was recorded during three maximal flexion and extension trials at two testing speeds (20°/s and 45°/s). Peak torque was then normalised to body mass. Pearson's correlations were performed to investigate relationships between trunk strength and functional mobility measures. The level of significance was set at p≤0.05. RESULTS:A number of associations between trunk strength and functional mobility measures were revealed. Greater trunk extension strength was correlated with superior performance in the CST (45°/s: r=0.33, p=0.037), stair ascent (20°/s: r=-0.32, p=0.043; 45°/s: r=-0.56, p=<.001) and stair descent tasks (45°/s: r=-0.47, p=0.002). Trunk extension strength was also associated with GS during normal (20°/s: r=0.37, p=0.019; 45°/s: r=0.48, p=0.004) and fast trials (45°/s: r=0.34, p=0.034). Trunk flexion strength was correlated with TUG (45°/s: r=-0.42, p=0.007), stair ascent (20°/s: r=-0.41, p=0.008; 45°/s: r=-0.47, p=0.002) and stair descent times (20°/s: r=-0.44, p=0.005; 45°/s: r=-0.42, p=0.007). Trunk flexion strength was also associated with normal (20°/s: r=0.55, p=<.001; 45°/s: r=0.56, p=<.001) and fast GS (20°/s: r=0.32, p=0.047; 45°/s: r=0.34, p=0.031). CONCLUSIONS: These findings suggest that there is a moderate-strong relationship between muscle strength in the trunk area and a range of functional mobility measures in older women. These results have important practical implications which could be used to inform the inclusion of trunk exercises in interventions targeting functional mobility for older adults.

Purpose: The purpose of this invited commentary is to discuss the use of principal component analysis (PCA) as a dimension reduction and visualisation tool to assist in decision making and communication when analysing complex multivariate data sets associated with the training of athletes. Conclusions: Using PCA it is possible to transform a data matrix into a set of orthogonal composite variables called principal components (PC), with each PC being a linear weighted combination of the observed variables and with all PCs uncorrelated to each other. The benefit of transforming the data using PCA is that the first few PCs generally capture the majority of the information (i.e. variance) contained in the observed data, with the first PC accounting for the highest amount of variance and each subsequent PC capturing less of the total information. Consequently, through PCA it is possible to visualise complex data sets, containing multiple variables on simple 2D scatterplots without any great loss of information, thereby making it much easier to convey complex information to coaches. In the future, athlete monitoring companies should integrate PCA into their client packages to better support practitioners trying to overcome the challenges associated with multivariate data analysis and interpretation. In the interim, we present here an overview of PCA and associated R code to assist practitioners working within the field to integrate PCA into their athlete monitoring process.

Establishing dose-response relationships between training load and fatigue can help the planning of training. The aim was to establish the relative importance of external training load measurements to relate to the musculoskeletal response on a group and individual player level. Sixteen elite male rugby league players were monitored across three seasons. Two to seven day exponential weighted averages (EWMA) were calculated for total distance, and individualised speed thresholds (via 30-15 Intermittent Fitness Test) derived from global positioning systems. The sit and reach, dorsiflexion lunge, and adductor squeeze tests represented the musculoskeletal response. Partial least squares and repeated measures correlation analyses established the relative importance of training load measures and then investigated their relationship to the collective musculoskeletal response for individual players through the construction of latent variables. On a group level, 2 and 3 day EWMA total distance had the highest relative importance to the collective musculoskeletal response (p < 0.0001). However, the magnitude of relationships on a group (r value = 0.20) and individual (r value = 0.06) level were trivial to small. The lack of variability in the musculoskeletal response over time suggest practitioners adopting such measures to understand acute musculoskeletal fatigue responses should do so with caution.

Ranking enables coaches, sporting authorities, and pundits to determine the relative performance of individual athletes and teams in comparison to their peers. While ranking is relatively straightforward in sports that employ traditional leagues, it is more difficult in sports where competition is fragmented (e.g. athletics, boxing, etc.), with not all competitors competing against each other. In such situations, complex points systems are often employed to rank athletes. However, these systems have the inherent weakness that they frequently rely on subjective assessments in order to gauge the calibre of the competitors involved. Here we show how two Internet derived algorithms, the PageRank (PR) and user preference (UP) algorithms, when utilised with a simple ‘who beat who’ matrix, can be used to accurately rank track athletes, avoiding the need for subjective assessment. We applied the PR and UP algorithms to the 2015 IAAF Diamond League men’s 100m competition and compared their performance with the Keener, Colley and Massey ranking algorithms. The top five places computed by the PR and UP algorithms, and the Diamond League ‘2016’ points system were all identical, with the Kendall’s tau distance between the PR standings and ‘2016’ points system standings being just 15, indicating that only 5.9% of pairs differed in their order between these two lists. By comparison, the UP and ‘2016’ standings displayed a less strong relationship, with a tau distance of 95, indicating that 37.6% of the pairs differed in their order. When compared with the standings produced using the Keener, Colley and Massey algorithms, the PR standings appeared to be closest to the Keener standings (tau distance = 67, 26.5% pair order disagreement), whereas the UP standings were more similar to the Colley and Massey standings, with the tau distances between these ranking lists being only 48 (19.0% pair order disagreement) and 59 (23.3% pair order disagreement) respectively. In particular, the UP algorithm ranked ‘one-off’ victors more highly than the PR algorithm, suggesting that the UP algorithm captures alternative characteristics to the PR algorithm, which may more suitable for predicting future performance in say knockout tournaments, rather than for use in competitions such as the Diamond League. As such, these Internet derived algorithms appear to have considerable potential for objectively assessing the relative performance of track athletes, without the need for complicated points equivalence tables. Importantly, because both algorithms utilise a ‘who beat who’ model, they automatically adjust for the strength of the competition, thus avoiding the need for subjective decision making.

Clive Beggs is professor of medical technology at the University of Bradford. He argues that medical engineering's life-saving contribution to healthcare is being largely ignored, and that the discipline is suffering as a result. If you walk into a hospital anywhere in the Western world, you'll see engineering devices all over the place. Patients who are incredibly ill are housed in intensive-care units, kept alive by life-support systems, and cardiologists rely on the signal given out by an electrocardiogram (ECG) to tell whether the heart is behaving normally or abnormally. Complex medical engineering is involved with everything from brain scanners to X-rays, but people just think of them as part of the furniture of a hospital. The same is true of artificial hip joints and pacemakers: all of these are engineered devices. The problem is that most of these things were developed before medical engineering was officially recognised as a discipline, and few realise the huge importance they have. The general public assumes that doctors and nurses treat people, and that pharmaceutical companies manufacture drugs, but they're just not aware of the role of engineering in healthcare. Hospital doctors do three things: diagnose, prescribe therapies and sometimes carry out technical procedures. But if you didn't have an ECG to diagnose cardiovascular problems, where would you be? If we didn't have X-rays, it would be like going back to the Dark Ages. These machines make huge differences to people's quality of life, and if you took them away, many more people would die. But as engineering devices, they remain unrecognised. Doctors use an armoury of tools to treat patients. This is vital to those patients, but individual doctors rarely influence the lives of populations. But medical engineers have the chance to improve the lives of millions – few doctors can do that. Engineers have the opportunity to create and develop new medical devices, which doctors can use to revolutionise the treatment of populations. While the next generation of tools are waiting to be developed, there is a shortage of medical engineers, and we need to raise awareness of the subject so people will enter the profession. Today, the big medical advances are often not made by clinicians; rather they are developed by scientists and engineers. Medical engineering is a cutting-edge discipline, and it's going to be a big growth area in the 21st century, but as yet the public don't realise this. A lot of school leavers who want to work with science in medicine aren't even aware that the subject exists: many will go into biomedical science instead, even though they might have found medical engineering more fulfilling. We need to publicise medical engineering, so they know how influential and interesting it can be.

The role of the venous circulation has long been underestimated in clinical practice and in research into neurological diseases. In this review, we present an overview of the existing evidence that venous abnormalities can play a key role in the development and manifestation of neurological and neurodegenerative diseases. We review the history behind the role of venous diseases in multiple sclerosis and their connections with the disease landmarks, the links of chronic venous hypertension to cerebral hydrodynamics and the role of iron in MS. In addition, we highlight the role of venous abnormalities in other diseases including jugular venous reflux, developmental anomalies, hydrocephalus and cerebrospinal fluid flow. Finally, and based on the information presented throughout the whole review, we conclude with the link between chronic cerebrospinal venous insufficiency and MS and the role and power of magnetic resonance imaging in diagnosing venous anomalies. © 2012 Bentham Science Publishers.

INTRODUCTION Research within Rugby league (RL) tackle investigations using video analysis has often used two sources of variables. The exception being King et al (2010) who described the characteristics of the RL tackle event such as number of tacklers and tackle height of the first tackler. However, the majority of investigations have either adopted technical variables from rugby union (RU) tackle variables (Sperenza et al., 2017) or technical criteria from coaching cues (Gabbett, 2008). In doing so, content validity and relevance to RL could be questioned (O’Donoghue, 2014). The aim of this study was to adopt a 5 stage process to determine tackle variables which are valid and reliable for RL research METHODS A 5 stage process was undertaken based upon recommendations by O’Donoghue (2014). STAGE 1 involved a synthesis of literature and examined phases of the tackle, variables describing the tackle descriptions of these variables research. A draft variable list was then developed before the start of STAGE 2. To achieve content validity and relevancy, STAGE 2 formed an expert group of practitioners to critique the previously formed draft variable list and develop new phases, variables and descriptors. STAGE 3 refined the variable list based upon the practitioner consultation. STAGE 4 established an expert group agreement in the refined variable list. Finally, STAGE 5 tested intra and inter-reliability of the list using Kappa statistics (McHugh, 2012). RESULTS The agreed variable list comprised of 6 phases including defensive start point, pre-contact, initial contact, post-contact and play the ball phases. Within the phases 66 variables were determined. The intra- and inter-reliability testing resulted in at least moderate agreement (>0.7) (McHugh, 2012) of all phases. DISCUSSION Due to possessing both strong relevance to an RL tackle and demonstrating good levels of reliability, researchers can be confident that the variables within the list are valid for research purposes (O’Donoghue, 2014). In addition, the rigorous 5 stage process of validating the content of the variable list should be used when determining different variables within different sports and actions for research purposes. In doing so, researchers can be confident that they are valid in use and thus can be used consistently for research purposes. Furthermore, the findings show that although there are similarities between a RU and RL tackle, clear differences exist and therefore justifies the need for specific RL variables during tackle research.

Objectives Soccer leagues reflect the partial standings of the teams involved after each round of competition. However, the ability of partial league standings to predict end-of-season position has largely been ignored. Here we analyze historical partial standings from English soccer to understand the mathematics underpinning league performance and evaluate the predictive ‘power’ of partial standings. Methods Match data (1995-2017) from the four senior English leagues was analyzed, together with random match scores generated for hypothetical leagues of equivalent size. For each season the partial standings were computed and Kendall’s normalized tau-distance and Spearman r-values determined. Best-fit power-law and logarithmic functions were applied to the respective tau-distance and Spearman curves, with the ‘goodness-of-fit’ assessed using the R2 value. The predictive ability of the partial standings was evaluated by computing the transition probabilities between the standings at rounds 10, 20 and 30 and the final end-of-season standings for the 22 seasons. The impact of reordering match fixtures was also evaluated. Results All four English leagues behaved similarly, irrespective of the teams involved, with the tau-distance conforming closely to a power law (R2>0.80) and the Spearman r-value obeying a logarithmic function (R2>0.87). The randomized leagues also conformed to a power-law, but had a different shape. In the English leagues, team position relative to end-of-season standing became ‘fixed’ much earlier in the season than was the case with the randomized leagues. In the Premier League, 76.9% of the variance in the final standings was explained by round-10, 87.0% by round-20, and 93.9% by round-30. Reordering of match fixtures appeared to alter the shape of the tau-distance curves. Conclusions All soccer leagues appear to conform to mathematical laws, which constrain the league standings as the season progresses. This means that partial standings can be used to predict end-of-season league position with reasonable accuracy.

PURPOSE: Adductor longus injuries are complex. The conflict between views in the recent literature and various nineteenth-century anatomy books regarding symphyseal and perisymphyseal anatomy can lead to difficulties in MRI interpretation and treatment decisions. The aim of the study is to systematically investigate the pyramidalis muscle and its anatomical connections with adductor longus and rectus abdominis, to elucidate injury patterns occurring with adductor avulsions. METHODS: A layered dissection of the soft tissues of the anterior symphyseal area was performed on seven fresh-frozen male cadavers. The dimensions of the pyramidalis muscle were measured and anatomical connections with adductor longus, rectus abdominis and aponeuroses examined. RESULTS: The pyramidalis is the only abdominal muscle anterior to the pubic bone and was found bilaterally in all specimens. It arises from the pubic crest and anterior pubic ligament and attaches to the linea alba on the medial border. The proximal adductor longus attaches to the pubic crest and anterior pubic ligament. The anterior pubic ligament is also a fascial anchor point connecting the lower anterior abdominal aponeurosis and fascia lata. The rectus abdominis, however, is not attached to the adductor longus; its lateral tendon attaches to the cranial border of the pubis; and its slender internal tendon attaches inferiorly to the symphysis with fascia lata and gracilis. CONCLUSION: The study demonstrates a strong direct connection between the pyramidalis muscle and adductor longus tendon via the anterior pubic ligament, and it introduces the new anatomical concept of the pyramidalis-anterior pubic ligament-adductor longus complex (PLAC). Knowledge of these anatomical relationships should be employed to aid in image interpretation and treatment planning with proximal adductor avulsions. In particular, MRI imaging should be employed for all proximal adductor longus avulsions to assess the integrity of the PLAC.

This study examined the relationship between accelerometer metrics and both collisions and running demands during rugby union match-play. Twelve under-18 forwards and 14 under-18 backs were recruited from a professional rugby union club. Six competitive matches were filmed during which players wore micro-technological units (Optimeye S5, Catapult Innovations, Melbourne, Australia). Video footage was analysed for total collisions, while GPS data was analysed for total distance. Accelerometer metrics analysed were Player loadTM (PL), Player LoadTM 2D (PL2D), and Player LoadTM slow (PLslow). A total of 81 player observations were included in the final analysis. Data were analysed using ordinary least squares regression. A 10-fold cross validation analysis was used to validate the findings. All PL variables demonstrated very large relationships with collisions in the forwards, while PLslow demonstrated the largest relationship (large) with collisions in the backs. Therefore, based on the strong relationship in both forwards and backs, PLslow may provide the most useful metric for measuring collision-based activity in both positional groups during match-play. Additionally, nearly perfect and very large relationships were observed between PL and total distance for forwards and backs respectively, suggesting that PL can be successfully used to quantify running demands when other methods are unavailable, for example during indoor training.

This systematic review aimed to identify and summarise associations between currently identified contextual factors and match running in senior male professional rugby league. Eligible articles included at least one contextual factor and used GPS to measure at least one displacement variable within competitive senior, male, professional rugby league matches. Of the 15 included studies, the identified contextual factors were grouped into factors related to individual characteristics (n = 3), match result (n = 4), team strength (n = 2), opposition strength (n = 3), match conditions (n = 6), technical and tactical demands (n = 6), spatial and temporal characteristics (n = 7), and nutrition (n = 1). Speed was the most commonly reported measure of match running (100%), followed by distance (47%), and acceleration (20%). Inconsistencies were found between studies for most contextual factors on match running. Higher speeds were generally associated with higher fitness, encountered earlier in the match and whilst defending. All 15 studies utilised a univariate approach to quantify associations of a contextual factor. The inconsistencies found in the associations of given contextual factors highlight the complex and multi-faceted nature of match running. Therefore, practitioners should consider contextual factors when analysing and interpreting GPS data.

Rugby league (RL) carries a high injury incidence with 61% of injuries occurring at tackles. The ball carrier has a higher injury incidence than the defender, therefore understanding mechanisms occurring during injurious tackles are important. Given the dynamic, open nature of tackling, characteristics influencing tackle outcome likely encompass complex networks of dependencies. This study aims to identify important classifying characteristics of the tackle related to ball carrier injurious and non-injurious events in RL and identify the characteristics capability to correctly classify those events. Forty-one ball carrier injuries were identified and 205 matched non-injurious tackles were identified as controls. Each case and control were analysed retrospectively through video analysis. Random forest models were built to 1.) filter tackle characteristics possessing relative importance for classifying tackles resulting in injurious/non-injurious outcomes and 2.) determine sensitivity and specificity of tackle characteristics to classify injurious and non-injurious events. Six characteristics were identified to possess relative importance to classify injurious tackles. This included ‘tackler twisted ball carrier’s legs when legs were planted on ground’, ‘the tackler and ball carrier collide heads’, ‘the tackler used body weight to tackle ball carrier, ‘the tackler has obvious control of the ball carrier’ ‘the tackler was approaching tackle sub-maximally’ and ‘tackler's arms were below shoulder level, elbows were flexed’. The study identified tackle characteristics that can be modified in attempt to reduce injury. Additional injury data are needed to establish relationship networks of characteristics and analyse specific injuries. Sensitivity and specificity results of the random forest were 0.995 and 0.525.

This study aimed to identify which physical and technical-tactical performance indicators (PI) can classify between levels of rugby league match-play. Data were collected from 46 European Super League (ESL) and 36 under-19 Academy (Academy) level matches over two seasons. Thirty-one ESL players and 41 Academy players participated. Microtechnology units were used to analyse the physical PI and matches were videoed and coded for individual technical-tactical PI, resulting in 157 predictor variables. Data were split into training and testing datasets. Random forests (RF) were built to reduce the dimensionality of the data, identify variables of importance and build classification models. To aid practical interpretation, conditional inference (CI) trees were built. Nine variables were identified as most important for backs, classifying between levels with 83% (RF) and 78% (CI tree) accuracy. The combination of variables with the highest classification rate was PlayerLoad2D, PlayerLoadSLOW per Kg body mass and high-speed running distance. Four variables were identified as most important for forwards, classifying with 68% (RF) and 64% (CI tree) accuracy. Defensive play-the-ball losses alone had the highest classification rate for forwards. The identified PI and their unique combinations can be developed during training to aid in progression through the rugby league playing pathway.

Understanding the most demanding passages of European Super League competition can optimise training prescription. We established positional and match half differences in peak relative distances (m·min-1) across durations, and the number of collisions, high-speed- and very-high-speed-distance completed in the peak 10 min period. Moving-averages (10 s, 30 s, 1 min, 5 min, 10 min) of instantaneous speed (m·s-1) were calculated from 25 professional rugby league players during 25 matches via microtechnology. Maximal m·min-1 was taken for each duration for each half. Concurrently, collisions (n), high-speed- (5 to 7 m·s-1; m) and very-high-speed-distance (> 7 m·s-1; m) were coded during each peak 10 min. Mixed-effects models determined differences between positions and halves. Aside from peak 10 s, trivial differences were observed in peak m·min-1 between positions or halves across durations. During peak 10 min periods, adjustables, full- and outside-backs ran more at high-speed and very-high-speed whilst middle- and edge-forwards completed more collisions. Peak m·min-1 is similar between positional groups across a range of durations and are maintained between halves of the match. Practitioners should consider that whilst the overall peak locomotor "intensity" is similar, how they achieve this differs between positions with forwards also exposed to additional collision bouts.

This study aimed to determine the similarity between and within positions in professional rugby league in terms of technical performance and match displacement. Here, the analyses were repeated on 3 different datasets which consisted of technical features only, displacement features only, and a combined dataset including both. Each dataset contained 7617 observations from the 2018 and 2019 Super League seasons, including 366 players from 11 teams. For each dataset, feature selection was initially used to rank features regarding their importance for predicting a player's position for each match. Subsets of 12, 11, and 27 features were retained for technical, displacement, and combined datasets for subsequent analyses. Hierarchical cluster analyses were then carried out on the positional means to find logical groupings. For the technical dataset, 3 clusters were found: (1) props, loose forwards, second-row, hooker; (2) halves; (3) wings, centres, fullback. For displacement, 4 clusters were found: (1) second-rows, halves; (2) wings, centres; (3) fullback; (4) props, loose forward, hooker. For the combined dataset, 3 clusters were found: (1) halves, fullback; (2) wings and centres; (3) props, loose forward, hooker, second-rows. These positional clusters can be used to standardise positional groups in research investigating either technical, displacement, or both constructs within rugby league.

Introduction Research within Rugby league (RL) tackle investigations using video analysis has often used two sources of variables. The exception being King et al (2010) who described the characteristics of the RL tackle event such as number of tacklers and tackle height of the first tackler. However, the majority of investigations have either adopted technical variables from rugby union (RU) tackle variables (Sperenza et al., 2017) or technical criteria from coaching cues (Gabbett, 2008). In doing so, content validity and relevance to RL could be questioned (O’Donoghue, 2014). The aim of this study was to adopt a 5 stage process to determine tackle variables which are valid and reliable for RL research. Method A 5 stage process was undertaken based upon recommendations by O’Donoghue (2014). STAGE 1 involved a synthesis of literature and examined phases of the tackle, variables describing the tackle descriptions of these variables research. A draft variable list was then developed before the start of STAGE 2. To achieve content validity and relevancy, STAGE 2 formed an expert group of practitioners to critique the previously formed draft variable list and develop new phases, variables and descriptors. STAGE 3 refined the variable list based upon the practitioner consultation. STAGE 4 established an expert group agreement in the refined variable list. Finally, STAGE 5 tested intra and inter-reliability of the list using Kappa statistics (McHugh, 2012). Results The agreed variable list comprised of 6 phases including defensive start point, pre-contact, initial contact, post-contact and play the ball phases. Within the phases 66 variables were determined. The intra- and inter-reliability testing resulted in at least moderate agreement (>0.7) (McHugh, 2012) of all phases. Discussion Due to possessing both strong relevance to an RL tackle and demonstrating good levels of reliability, researchers can be confident that the variables within the list are valid for research purposes (O’Donoghue, 2014). In addition, the rigorous 5 stage process of validating the content of the variable list should be used when determining different variables within different sports and actions for research purposes. In doing so, researchers can be confident that they are valid in use and thus can be used consistently for research purposes. Furthermore, the findings show that although there are similarities between a RU and RL tackle, clear differences exist and therefore justifies the need for specific RL variables during tackle research.

The purpose of this study was to determine the importance of physical qualities for speed and change of direction (CoD) ability in female soccer players. Data were collected on 10 female soccer players who were part of a professional English Women’s Super League team. Player assessments included anthropometric (stature and body mass), body composition (dual-energy X-ray absorptiometry), speed (10m, 30m sprint), CoD ability (505 agility), aerobic (Yo-Yo Intermittent Recovery Test), lower-body strength (bilateral knee extensions) and power (countermovement jump [CMJ], squat jump [SJ], 30cm drop jump [DJ]) measures). The relationships between the variables were evaluated using eigenvector analysis and Pearson correlation analysis. Multiple linear regression revealed that the performance variables (10 and 20m speed, mean 505, and CoD deficit mean) can be predicted with almost 100% accuracy (i.e. adjusted R2 > 0.999) using various combinations of the predictor variables (DJ height, CMJ height, SJ height, lean body mass). An increase of one standard deviation (SD) in DJ height was associated with reductions of -5.636 and 9.082 SD in 10 m and 20 m sprint times. A one SD increase in CMJ also results in a reduction of -3.317 and -0.922 SD respectively in mean 505 and CoD deficit mean values. This study provides comparative data for professional English female soccer players that can be used by strength and conditioning coaches when monitoring player development and assessing the effectiveness of training programmes. Findings highlight the importance of developing reactive strength to improve speed and CoD ability in female soccer players.

Purpose: To evaluate the relative importance and predictive ability of salivary immunoglobulin A (s-IgA) measures with regards to upper respiratory illness (URI) in youth athletes. Methods: Over a 38-week period, 22 youth athletes (age = 16.8 [0.5] y) provided daily symptoms of URI and 15 fortnightly passive drool saliva samples, from which s-IgA concentration and secretion rate were measured. Kernel-smoothed bootstrapping generated a balanced data set with simulated data points. The random forest algorithm was used to evaluate the relative importance (RI) and predictive ability of s-IgA concentration and secretion rate with regards to URI symptoms present on the day of saliva sampling (URIday), within 2 weeks of sampling (URI2wk), and within 4 weeks of sampling (URI4wk). Results: The percentage deviation from average healthy s-IgA concentration was the most important feature for URIday (median RI 1.74, interquartile range 1.41–2.07). The average healthy s-IgA secretion rate was the most important feature for URI4wk (median RI 0.94, interquartile range 0.79–1.13). No feature was clearly more important than any other when URI symptoms were identified within 2 weeks of sampling. The values for median area under the curve were 0.68, 0.63, and 0.65 for URIday, URI2wk, and URI4wk, respectively. Conclusions: The RI values suggest that the percentage deviation from average healthy s-IgA concentration may be used to evaluate the short-term risk of URI, while the average healthy s-IgA secretion rate may be used to evaluate the long-term risk. However, the results show that neither s-IgA concentration nor secretion rate can be used to accurately predict URI onset within a 4-week window in youth athletes.

Video analysis research into the rugby league tackle typically uses technical criteria from coaching cues or tackle variables from rugby union. As such, the content validity and relevance could be questioned. A video analysis framework which establishes appropriate variables for rugby league is therefore required. The aim of this study was to adopt a 5-stage process to establish a video analysis framework for the rugby league tackle, which was content valid, relevant and reliable. The 5-stage process included 1) creation of draft variable list (video analysis framework), using available rugby tackle research, 2) expert group recruitment and critique, 3) refinement of video analysis framework to establish content validity, 4) response process validity task and agreement within expert group, 5) intra- and inter-reliability testing using Kappa statistics. The agreed video analysis framework comprised 6 phases including; tackle event, defensive start point, pre-contact, initial contact, post-contact and play the ball. Within the identified phases, 63 variables were established. The intra- and inter-reliability testing resulted in strong agreement (>0.81-1.0) within all phases. The 5-stage process allowed for the creation of a valid, relevant and reliable video analysis framework. The video analysis framework can be used in rugby league tackle research, categorising complex tackle events such as injurious or optimal tackles, improving both player welfare and performance. Furthermore, the application of the video analysis framework to future rugby league research will increase the coherence and usefulness of research findings.

This study investigated sources of variability in the overall and phase-specific running match characteristics in elite rugby league. Microtechnology data were collected from 11 Super League (SL) teams, across 322 competitive matches within the 2018 and 2019 seasons. Total distance, high-speed running (HSR) distance (>5·5 m·s−1), average speed, and average acceleration were assessed. Variability was determined using linear mixed models, with random intercepts specified for player, position, match, and club. Large within-player coefficients of variation (CV) were found across whole match, ball-in-play, attack and defence for total distance (CV range = 24% to 35%) and HSR distance (37% to 96%), whereas small to moderate CVs (≤10%) were found for average speed and average acceleration. Similarly, there was higher between-player, -position, and -match variability in total distance and HSR distance when compared with average speed and average acceleration across all periods. All metrics were stable between-teams (≤5%), except HSR distance (16% to 18%). The transition period displayed the largest variability of all phases, especially for distance (up to 42%) and HSR distance (up to 165%). Absolute measures of displacement display large within-player and between-player, -position, and -match variability, yet average acceleration and average speed remain relatively stable across all match-periods.

The skeleton of a cricket fast bowler is exposed to a unique combination of gravitational and torsional loading in the form of substantial ground reaction forces delivered through the front landing foot, and anterior-posterior shear forces mediated by regional muscle contractions across the lumbo-pelvic region. The objectives of this study were to compare the hip structural characteristics of elite fast bowlers with recreationally-active age-matched controls, and to examine unilateral bone properties in fast bowlers. Dual-energy X-ray absorptiometry (DXA) of the proximal femur was performed in 26 elite male fast bowlers and 26 normally-active controls. Hip structural analysis (GE Lunar; enCORE version 15.0) determined areal bone mineral density (BMD) of the proximal femur, and cross-sectional area (CSA), section modulus (Z), cross-sectional moment of inertia (CSMI) and femoral strength index (FSI) at the narrow region of the femoral neck. Mean femoral neck and trochanter BMD were greater in fast bowlers than controls (p < 0.001). All bone geometry properties except for CSMI were superior in fast bowlers (p < 0.05) following adjustment for height and lean mass. There were no asymmetries in BMD or bone geometry when considering leg dominance of the fast bowlers (p > 0.05). Elite fast bowlers have superior bone characteristics of the proximal femur, with results inferring enhanced resistance to axial compression (CSA), and bending (Z) forces, and enhanced strength to withstand a fall impact as indicated by their higher FSI. No asymmetries in hip bone properties were identified, suggesting that both torsional and gravitational loading offer significant osteogenic potential.

This study examined the relative contribution of exercise duration and intensity to team-sport athlete’s training load. Male, professional rugby league (n = 10) and union (n = 22) players were monitored over 6- and 52-week training periods, respectively. Whole-session (load) and per-minute (intensity) metrics were monitored (league: session rating of perceived exertion training load [sRPE-TL], individualised training impulse, total distance, BodyLoad™; union: sRPE-TL, total distance, high-speed running distance, PlayerLoad™). Separate principal component analyses were conducted on the load and intensity measures to consolidate raw data into principal components (PC, k = 4). The first load PC captured 70% and 74% of the total variance in the rugby league and rugby union datasets, respectively.. Multiple linear regression subsequently revealed that session duration explained 73% and 57% of the variance in first load PC, respectively, while the four intensity PCs explained an additional 24% and 34%, respectively. Across two professional rugby training programmes, the majority of the variability in training load measures was explained by session duration (~60–70%), while a smaller proportion was explained by session intensity (~30%). When modelling the training load, training intensity and duration should be disaggregated to better account for their between-session variability.

Objectives Professional sporting organisations invest considerable resources collecting and analysing data in order to better understand the factors that influence performance. Recent advances in non-invasive technologies, such as global positioning systems (GPS), mean that large volumes of data are now readily available to coaches and sport scientists. However analysing such data can be challenging, particularly when sample sizes are small and data sets contain multiple highly correlated variables, as is often the case in a sporting context.

Identifying the external training load variables which influence subjective internal response will help reduce the mismatch between coach-intended and athlete-perceived training intensity. Therefore, this study aimed to reduce external training load measures into distinct principal components (PCs), plot internal training response (quantified via session Rating of Perceived Exertion [sRPE]) against the identified PCs and investigate how the prescription of PCs influences subjective internal training response. Twenty-nine school to international level youth athletes wore microtechnology units for field-based training sessions. SRPE was collected post-session and assigned to the microtechnology unit data for the corresponding training session. 198 rugby union, 145 field hockey and 142 soccer observations were analysed. The external training variables were reduced to two PCs for each sport cumulatively explaining 91%, 96% and 91% of sRPE variance in rugby union, field hockey and soccer, respectively. However, when internal response was plotted against the PCs, the lack of separation between low-, moderate- and high-intensity training sessions precluded further analysis as the prescription of the PCs do not appear to distinguish subjective session intensity. A coach may therefore wish to consider the multitude of physiological, psychological and environmental factors which influence sRPE alongside external training load prescription.

Ranking sports teams generally relies on supervised techniques, requiring either prior knowledge or arbitrary metrics. In this paper, we offer a purely unsupervised technique. We apply this to operational decision-making, specifically, the controversial European Super League for associa-tion football, demonstrating how this approach can select dominant teams to form the new league. We first use random forest regression to select important variables predicting goal difference, which we use to calculate the Euclidian distances between teams. Creating a Laplacian eigenmap, we bisect the Fiedler vector to identify the natural clusters in five major European football leagues. Our results show how an unsupervised approach could identify four clusters based on five basic performance metrics: shots, shots on target, shots conceded, possession, and pass success. The top two clusters identify teams that dominate their respective leagues and are the best candidates to create the most competitive elite super league.

Prediction of adult performance from early age talent identification in sport remains difficult. Talent identification research has generally been performed using univariate analysis, which ignores multivariate relationships. To address this issue, this study used a novel higher-dimensional model to orthogonalize multivariate anthropometric and fitness data from junior rugby league players, with the aim of differentiating future career attainment. Anthropometric and fitness data from 257 Under-15 rugby league players was collected. Players were grouped retrospectively according to their future career attainment (i.e., amateur, academy, professional). Players were blindly and randomly divided into an exploratory (n = 165) and validation dataset (n = 92). The exploratory dataset was used to develop and optimize a novel higher-dimensional model, which combined singular value decomposition (SVD) with receiver operating characteristic analysis. Once optimized, the model was tested using the validation dataset. SVD analysis revealed 60 m sprint and agility 505 performance were the most influential characteristics in distinguishing future professional players from amateur and academy players. The exploratory dataset model was able to distinguish between future amateur and professional players with a high degree of accuracy (sensitivity = 85.7%, specificity = 71.1%; p<0.001), although it could not distinguish between future professional and academy players. The validation dataset model was able to distinguish future professionals from the rest with reasonable accuracy (sensitivity = 83.3%, specificity = 63.8%; p = 0.003). Through the use of SVD analysis it was possible to objectively identify criteria to distinguish future career attainment with a sensitivity over 80% using anthropometric and fitness data alone. As such, this suggests that SVD analysis may be a useful analysis tool for research and practice within talent identification.

Objectives: To retrospectively compare the longitudinal physical development of junior rugby league players between the Under 13 and 15 age categories in relation to their adult career attainment outcome.Design: Retrospective longitudinal design.Methods: Fifty-one former junior rugby league players were retrospectively grouped according to their career attainment outcome as adults (i.e., amateur, academy or professional). As juniors, players under-took a physical testing battery on three consecutive annual occasions (Under 13s, 14s, 15s) including height, body mass, sum of four skinfolds, maturation, vertical jump, medicine ball chest throw, 10–60 msprint, agility 505 and estimated VO2max. Results: Future professional players were younger than academy players with a greater estimated˙VO2max compared to amateur players. Between Under 13s and 15s, professional players (5.8 ± 2.5 cm) increased sitting height more than amateur (4.4 ± 2.1 cm) and academy (4.1 ± 1.4 cm) players. Logistic regression analyses demonstrated improvements in sitting height, 60 m sprint, agility 505 and estimated˙VO2max between amateur and professional players with a high degree of accuracy (sensitivity = 86.7%, specificity = 91.7%). Conclusions: Findings demonstrate that the development of anthropometric, maturational and physical qualities in junior rugby league players aged between 13 and 15 years contributed to adulthood career attainment outcomes. Results suggest that age, maturity and size advantages, commonly observed in adolescent focused talent identification research and practice, may not be sensitive to changes in later stages of development in order to correctly identify career attainment. Practitioners should identify, monitor and develop physical qualities of adolescent rugby league players with long-term athlete development in mind.

Due to the focus of research within athletic populations, little is known about the hydration strategies of rugby league referees. We observed all 8 full-time professional referees, during 31 Super League matches to investigate the drinking strategies and magnitude of dehydration (body mass loss) experienced by referees during match play. Referees arrived and remained euhydrated (urine osmolality; pre and post-match 558 ± 310 and 466 ± 283 mOsmol•kg-1). Mean body mass change was -0.7 ± 0.8%, fluid loss was 890 ± 435 g and fluid intake was 444 ± 167, 438 ± 190, 254 ± 108 and 471 ± 221 g during pre-match, first-half, half-time and second-half. This study suggests elite referees adopt appropriate hydration strategies during match-play to prevent large reductions in body mass, although individual variability was observed. Future research should investigate dehydration in referees from other sports and the effects on refereeing performance.