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We study the influence of a membrane filter's internal pore structure on its flow and adsorptive fouling behaviour. Membrane performance is measured via (1) comparison between volumetric flow rate and throughput during filtration and (2) control of concentration of foulants at membrane pore outlets. Taking both measures into account, we address the merits and drawbacks of selected membrane pore structures. We first model layered planar membrane structures with intra-layer pore connections, and present comparisons between non-connected and connected structures. Our model predicts that membrane filters with connected pore structures lead to higher total volumetric throughput than those with non-connected structures, over the filter lifetime. We also provide a sufficient criterion for the concentration of particles escaping the filter to achieve a maximum in time (indicative of a membrane filter whose particle retention capability can deteriorate). Additionally, we find that the influence of intra-layer heterogeneity in pore-size distribution on filter performance depends on the connectivity properties of the pores.
In this work we consider a new class of oscillatory instabilities that pertain to thermocapillary destabilization of a liquid film heated by a solid substrate. We assume the substrate thickness and substrate–film thermal conductivity ratio are large so that the effect of substrate thermal diffusion is retained at leading order in the long-wave approximation. As a result, the system dynamics is described by a nonlinear partial differential equation for the film thickness that is non-locally coupled to the full substrate heat equation. Perturbing about a steady quiescent state, we find that its stability is described by a non-self-adjoint eigenvalue problem. We show that, under appropriate model parameters, the linearized eigenvalue problem admits complex eigenvalues that physically correspond to oscillatory (in time) instabilities of the thin-film height. As the principal results of our work, we provide a complete picture of the susceptibility to oscillatory instabilities for different model parameters. Using this description, we conclude that oscillatory instabilities are more relevant experimentally for films heated by insulating substrates. Furthermore, we show that oscillatory instability where the fastest-growing (most unstable) wavenumber is complex, arises only for systems with sufficiently large substrate thicknesses. Finally, we discuss adaptation of our model to a practical setting and make predictions of conditions at which the reported instabilities can be observed.
Introduction: Patients with concussion often present to the emergency department (ED). Current guidelines recommend graded return to work and physical activity (i.e., sport, recreation and exercise activities); however, whether emergency physicians target this advice based on patient-reported activities is unknown. This study aimed to assess mismatches between physicians’ rest and return-to-activity advice and self-reported pre-injury work and physical activity of adult concussion patients. Methods: Adults (>17 years) presenting with a concussion from April 2013 to April 2015 to a study ED with Glasgow coma scale score ≥13 were recruited by on-site research assistants. Data on patient characteristics (i.e., age, sex, employment, and physical activity level) and activity leading to injury were collected from structured patient interviews. A structured questionnaire collected data from the treating physician about discharge advice provided. “Working” was defined as employed or enrolled in any level of school at the time of injury. “Physically active” was defined by reporting regular exercise (≥2 times a week) or concussed during a sports-related activity. Proportions or medians (interquartile range [IQR]) are reported, as appropriate. Results: Physician questionnaires were completed for 198/248 enrolled patients (median age: 37 years [IQR: 23, 49]; 46% male). Overall, 89% (177/198) were working; 110/177 (62%) received return-to-work advice, while 10/21 (48%) patients also received return-to-work advice, despite not working. Mentally strenuous work/school duties were reported by 143 patients, of which 85 (60%) were recommended cognitive rest. Overall, 148 patients were physically active and 115 (78%) of these were recommended physical rest while 124 (82%) were advised on safe return to physical activity. On the other hand, 35/50 (70%) patients who were not physically active received advice on safe return to physical activity. Sustaining a sports-related injury significantly increased the likelihood of safe return to physical activity advice among physically active patients (Fisher's exact p = 0.001). Conclusion: There is a mismatch between concussed patients’ pre-injury activities, and the rest and return-to-activity (i.e., work and physical activity) advice provided by emergency physicians. The possible effect of this mismatch on patient outcomes should be assessed in future research, as should strategies to improve emergency physician-patient communications around concussion management.
Introduction: Patients with concussion often present to the emergency department (ED). Although sports and recreation (SR) activities account for less than half of all adult concussions, guidelines developed for management of SR-related concussions (SRC) are widely used for all concussion patients. This study aimed to identify whether there are clinically relevant differences in patient and injury characteristics between SRC and those occurring outside of SR activities. Methods: Adults ( >17 years) presenting from April 2013 to April 2015 with a concussion to one of three EDs with Glasgow coma scale score ≥13 were recruited by on-site research assistants. Data on patient characteristics (i.e., age, sex, employment, lifestyle, relevant medical history), ED presentation (i.e., EMS arrival, hours since injury, CTAS, Glasgow Coma Scale score) and injury characteristics (i.e., activity leading to injury, loss of consciousness [LOC], signs and symptoms [scored using the Rivermead Post-Concussion Questionnaire], and health-related quality of life [from the 12-Item Short Form Health Survey [SF-12]) were collected from structured interviews and the ED chart. Dichotomous and categorical variables were compared using Fisher's exact test; continuous variables were compared using t-tests or Mann-Whitney tests, as appropriate. Results: In total, 248 patients were enrolled (47% male, median [IQR] age: 35 [23, 49]). Patients with SRC were younger (median: 23.5 years vs 35 years; p < 0.001), more likely to be a student (31% vs 8%; p > 0.001), and more likely to exercise regularly (89% vs 66%; p = 0.001). Patients with SRC were less likely to present during the daytime (66% vs. 77%; p = 0.022), less likely to have a history of mental health issues (18% vs 33%; p = 0.011) and had significantly higher median SF-12 physical components scores (55.5 [IQR: 51.4 to 57.8] vs. 53.5 [IQR: 45.5 to 56.7]; p = 0.025). All other characteristics were similar between the two groups. Conclusion: Although differences in demographics and lifestyle have been identified between patients sustaining a SRC and those concussed during other activities, injury characteristics, such as presentation acuity, proxies for severity, and signs and symptoms, were similar in both groups. Further analysis to assess whether the demographic and lifestyle differences affect clinical outcomes, such as time to symptom resolution, between these two groups is required to assess if sport-based treatment guidelines are appropriate for all patients.
Introduction: Continued smoking by cancer patients causes adverse cancer treatment outcomes, but few patients receive evidence-based smoking cessation as a standard of care.
Aim: To evaluate practical strategies to promote wide-scale dissemination and implementation of evidence-based tobacco cessation services within state cancer centers.
Methods: A Collaborative Learning Model (CLM) for Quality Improvement was evaluated with three community oncology practices to identify barriers and facilitate practice change to deliver evidence-based smoking cessation treatments to cancer patients using standardized assessments and referrals to statewide smoking cessation resources. Patients were enrolled and tracked through an automated data system and received follow-up cessation support post-enrollment. Monthly quantitative reports and qualitative data gathered through interviews and collaborative learning sessions were used to evaluate meaningful quality improvement changes in each cancer center.
Results: Baseline practice evaluation for the CLM identified the lack of tobacco use documentation, awareness of cessation guidelines, and awareness of services for patients as common barriers. Implementation of a structured assessment and referral process demonstrated that of 1,632 newly registered cancer patients,1,581 (97%) were screened for tobacco use. Among those screened, 283 (18%) were found to be tobacco users. Of identified tobacco users, 207 (73%) were advised to quit. Referral of new patients who reported using tobacco to an evidence-based cessation program increased from 0% at baseline across all three cancer centers to 64% (range = 30%–89%) during the project period.
Conclusions: Implementation of quality improvement learning collaborative models can dramatically improve delivery of guideline-based tobacco cessation treatments to cancer patients.
Introduction: Patients with concussion frequently present to the emergency department (ED). Studies of athletes and children indicate that concussion symptoms are often more severe and prolonged in females compared with males. To-date, study of sex-based concussion differences in general adult populations have been limited. This study examined sex-based differences in concussion outcomes. Methods: Adult (>17 years) patients presenting to one of three urban EDs in Edmonton, Alberta with Glasgow coma scale score 13 within 72 hours of a concussive event were recruited by on-site research assistants. Follow-up calls at 30 and 90 days post ED discharge captured extent of PCS using the Rivermead Post-Concussion questionnaire (RPQ), effect on daily living activities measured by the Rivermead Head Injury Questionnaire (RHIQ), and overall health-related quality of life using the 12-item Short Form Health Survey (SF-12). Dichotomous and categorical variables were compared using Fishers exact test; continuous variables were compared using t-tests or Mann-Whitney tests, as appropriate. Results: Overall, 130/250 enrolled patients were female. The median age was 35 years; men trended towards being younger (median=32 years; IQR: 23, 45) than women (median=40 years; IQR: 22, 52). Compared to women, more men were single (56% vs 38% (p=0.007) and employed (82% vs 71% (p=0.055). Men and women experienced different injury mechanisms (p=0.007) with more women reporting injury due to a fall (44% vs 26%), while more men were injured at work (16% vs 7%) or due to an assault (11% vs. 3%). Men had a higher return to ED rate (13% vs. 5%; p=0.015). Women had higher RPQ scores at baseline (p<0.001) and 30-day follow-up (p=0.001); this difference was not significant by 90 days (p=0.099). While women reported on the RHIQ at 30 days that their injury affected their usual activities significantly more than men (Median=5, IQR: 0, 11 vs. median=0.5, IQR: 0.5, 7; p=0.004), both groups had similar scores on the SF-12 physical composite and mental composite scales at all three measurement points. Conclusion: In a general ED concussion population, demographic differences exist between men and women. Based on self-reported and objective outcomes, womens usual activities may be more affected by concussion and PCS than men. Further analysis of these differences is required in order to identify different treatment options and ensure adequate care and treatment of injury.
To determine the effect of mandatory and nonmandatory influenza vaccination policies on vaccination rates and symptomatic absenteeism among healthcare personnel (HCP).
Retrospective observational cohort study.
This study took place at 3 university medical centers with mandatory influenza vaccination policies and 4 Veterans Affairs (VA) healthcare systems with nonmandatory influenza vaccination policies.
The study included 2,304 outpatient HCP at mandatory vaccination sites and 1,759 outpatient HCP at nonmandatory vaccination sites.
To determine the incidence and duration of absenteeism in outpatient settings, HCP participating in the Respiratory Protection Effectiveness Clinical Trial at both mandatory and nonmandatory vaccination sites over 3 viral respiratory illness (VRI) seasons (2012–2015) reported their influenza vaccination status and symptomatic days absent from work weekly throughout a 12-week period during the peak VRI season each year. The adjusted effects of vaccination and other modulating factors on absenteeism rates were estimated using multivariable regression models.
The proportion of participants who received influenza vaccination was lower each year at nonmandatory than at mandatory vaccination sites (odds ratio [OR], 0.09; 95% confidence interval [CI], 0.07–0.11). Among HCP who reported at least 1 sick day, vaccinated HCP had lower symptomatic days absent compared to unvaccinated HCP (OR for 2012–2013 and 2013–2014, 0.82; 95% CI, 0.72–0.93; OR for 2014–2015, 0.81; 95% CI, 0.69–0.95).
These data suggest that mandatory HCP influenza vaccination policies increase influenza vaccination rates and that HCP symptomatic absenteeism diminishes as rates of influenza vaccination increase. These findings should be considered in formulating HCP influenza vaccination policies.
Introduction: Patients with mild traumatic brain injury (mTBI) frequently present to the emergency department (ED); however, wide variation in diagnosis and management has been demonstrated in this setting. Sub-optimal mTBI management can contribute to post-concussion syndrome (PCS), affecting vocational outcomes like return to work. This study documented the work-related events, ED management, discharge advice, and outcomes for employed patients presenting to the ED with mTBI. Methods: Adult (>17 years) patients presenting to one of three urban EDs in Edmonton, Alberta with Glasgow coma scale score ≥13 within 72 hours of a concussive event were recruited by on-site research assistants. Follow-up calls ascertained outcomes, including symptoms and their severity, advice received in the ED, and adherence to discharge instructions, at 30 and 90 days after ED discharge. Dichotomous variables were analyzed using chi-square testing; continuous variables were compared using t-tests or Mann-Whitney tests, as appropriate. Work-related injury and return to work outcomes were modelled using logistic or linear regression, as appropriate. Results: Overall, 250 patents were enrolled; 172 (69%) were employed at the time of their injury and completed at least one follow-up. The median age was 37 years (interquartile range [IQR]: 24, 49.5), both sexes were equally represented (48% male), and work-related concussions were uncommon (16%). Work-related concussion was related to manual labor jobs and self-reported history of attention deficit disorder. Patients often received advice to avoid sports (81%) and/or work (71%); however, the duration of recommended time off varied. Most employed patients (80%) missed at least one day of work (median=7 days; IQR: 3, 14); 91% of employees returned to work by 90 days, despite 41% reporting persistent symptoms. Increased days of missed work were linked to divorce, history of sleep disorder, and physician’s advice to avoid work. Conclusion: While work-related concussions are uncommon, most employees who sustain a mTBI at any time miss some work. Many patients experience mTBI symptoms past 90 days, which has serious implications for workers’ abilities to fulfill their work duties and risk of subsequent injury. Workers, employers, and the workers compensation system should take the necessary precautions to ensure that workers return to work safely and successfully following a concussion.
Introduction: Patients with mild traumatic brain injury (mTBI) often present to the emergency department (ED). Incorrect diagnosis may delay appropriate treatment and recommendations for these patients, prolonging recovery. Notable proportions of missed mTBI diagnosis have been documented in children and athletes, while diagnosis of mTBI has not been examined in the general adult population. Methods: A prospective cohort study was conducted in one academic (site 1) and two non-academic (sites 2 and 3) EDs in Edmonton, Canada. On-site research assistants enrolled adult (>17 years) patients presenting within 72 hours of the injury event with clinical signs of mTBI and Glasgow comma scale score ≥13. Patient demographics, injury characteristics, and ED flow information were collected by chart review. Physician-administered questionnaires and patient interviews documented the recommendations given by emergency physicians at discharge. Bi-variable comparisons are reported using Pearson’s chi-square tests, Student’s t-tests or Mann-Whitney tests, as appropriate. Multivariate analyses were performed using logistic regression methods. Results: Overall, 130/250 enrolled patients were female, and the median age was 35. Proportions of successfully diagnosed mTBI varied significantly across study sites (Site 1: 89%; Site 2: 73%, Site 3: 53%; p>0.001). Patients without a diagnosis were less likely to receive a recommendation to follow-up with their family physician (OR=0.08; 95% CI: 0.03, 0.21) or advice about return to work (OR=0.17; 95% CI: 0.08, 0.04) or physical activity (OR=0.08; 95% CI: 0.04, 0.17). Patients with missed diagnoses had longer ED stays (median=5.0 hours; IQR: 3.8, 7.0) compared with diagnosed mTBI patients (median=3.9 hours; IQR: 3.0, 5.3). In the adjusted model, patients presenting to non-academic centers had reduced likelihood of mTBI diagnosis (Site 2: OR=0.21; 95% CI: 0.08, 0.58; Site 3: OR=0.07; 95% CI: 0.02, 0.24). Conclusion: The diagnostic accuracy of physicians assessing patients presenting with symptoms of mTBIs to these three EDs is suboptimal. The rates of missed diagnosis vary among EDs and were associated with length of ED stay. Closer examination of institutional factors, including diagnosis processes and personnel factors such as physician training, is needed to identify effective strategies to heighten the awareness of mTBI presentations.
Membrane filters are used extensively in microfiltration applications. The type of membrane used can vary widely depending on the particular application, but broadly speaking the requirements are to achieve fine control of separation, with low power consumption. The solution to this challenge might seem obvious: select the membrane with the largest pore size and void fraction consistent with the separation requirements. However, membrane fouling (an inevitable consequence of successful filtration) is a complicated process, which depends on many parameters other than membrane-pore size and void fraction; and which itself greatly affects the filtration process and membrane functionality. In this work we formulate mathematical models that can (i) account for the membrane internal morphology (internal structure, pore size and shape, etc.); (ii) describe fouling of membranes with specific morphology; and (iii) make some predictions as to what type of membrane morphology might offer optimum filtration performance.
The reader might get the impression that the four projects described in this Special Section proceeded in a systematic and predictable way. Of course, those of us engaged in each research project encountered pitfalls and challenges along the way. A main goal of this Special Section is to provide pathways and encouragement for those who may be interested in advancing high-quality research on this topic. In this paper, we describe a set of practical and ethical challenges that we encountered in conducting our longitudinal, process-oriented, and translational research with conflict-affected youth, and we illustrate how problems can be solved with the goal of maintaining the internal and external validity of the research designs. We are hopeful that by describing the challenges of our work, and how we overcame them, which are seldom treated in this or any other literature on research on child development in high-risk contexts, we can offer a realistic and encouraging picture of conducting methodologically sound research in conflict-affected contexts.
This study examined the transactional interplay among dimensions of destructive interparental conflict (i.e., hostility and dysphoria), children's emotional insecurity, and their psychological problems from middle childhood and adolescence. Participants were 232 families, with the first of five measurement occasions occurring when children were in first grade (M age = 7 years). Cross-lagged, autoregressive models were conducted with a multiple-method, multiple-informant measurement approach to identify developmental cascades of interparental and child cascades. Results indicated that emotional insecurity was a particularly powerful mediator of prospective associations between interparental conflict (i.e., dysphoria and hostility) and child adjustment during adolescence rather than childhood. In reflecting bidirectionality in relationships between interparental and child functioning, children's psychological problems predicted increases in interparental dysphoria during childhood and adolescence. Although emotional insecurity was not identified as a proximal predictor of interparental difficulties, an indirect cascade was identified whereby insecurity in early adolescence was associated with increases in teen psychological problems, which in turn predicted greater interparental dysphoria over time. Results are interpreted in the context of how they advance transactional formulation of emotional security theory and its resulting translational implications for clinical initiatives.
Pleated membrane filters are widely used in many applications, and offer significantly better surface area to volume ratios than equal-area unpleated membrane filters. However, their filtration characteristics are markedly inferior to those of equivalent unpleated membrane filters in dead-end filtration. While several hypotheses have been advanced for this, one possibility is that the flow field induced by the pleating leads to spatially non-uniform fouling of the filter, which in turn degrades performance. In this paper we investigate this hypothesis by developing a simplified model for the flow and fouling within a pleated membrane filter. Our model accounts for the pleated membrane geometry (which affects the flow), for porous support layers surrounding the membrane, and for two membrane fouling mechanisms: (i) adsorption of very small particles within membrane pores; and (ii) blocking of entire pores by large particles. We use asymptotic techniques based on the small pleat aspect ratio to solve the model, and we compare solutions to those for the closest-equivalent unpleated filter.
Peer drinking norms are arguably one of the strongest correlates of adolescent drinking. Prospective studies indicate that adolescents tend to select peers based on drinking (peer selection) and their peers' drinking is associated with changes in adolescent drinking over time (peer socialization). The present study investigated whether the peer selection and socialization processes in adolescent drinking differed as a function of the dopamine receptor D4 (DRD4) variable number tandem repeat genotype in two independent prospective data sets. The first sample was 174 high school students drawn from a two-wave 6-month prospective study. The second sample was 237 college students drawn from a three-wave annual prospective study. Multigroup cross-lagged panel analyses of the high school student sample indicated stronger socialization via peer drinking norms among carriers, whereas analyses of the college student sample indicated stronger drinking-based peer selection in the junior year among carriers, compared to noncarriers. Although replication and meta-analytic synthesis are needed, these findings suggest that in part genetically determined peer selection (carriers of the DRD4 seven-repeat allele tend to associate with peers who have more favorable attitudes toward drinking and greater alcohol use) and peer socialization (carriers' subsequent drinking behaviors are more strongly associated with their peer drinking norms) may differ across adolescent developmental stages.
Although cattle movement and commingling play an important role in the inter-herd transmission of pathogens, little is known about the effect of commingling of heifers at raising operations. The objective of this study was to compare the resistance of E. coli and prevalence of Salmonella from pooled faecal pats of heifers raised off-farm at multi-source raisers (MULTI) that raised heifers from at least two farms compared with on-farm raisers (HOME), with heifers from only that farm. MULTI faecal pat samples were collected from pens with animals that had arrived at the farm within the previous 2 months (AP) and from animals that would be departing the heifer raiser in 2–3 months (DP). Corresponding age sampling was conducted at HOME raisers. Odds of ampicillin resistance were 3·0 times greater in E. coli collected from MULTI compared to HOME raisers. E. coli from AP pens had significantly (P < 0·05) higher odds of resistance to ampicillin, neomycin, streptomycin, and tetracycline compared to DP pens. Salmonella recovery was not significantly different between heifer-raising systems (P = 0·3). Heifer-raising system did not have a major overall impact on selection of resistant E. coli, which was strongly affected by the age of the animals sampled.
We consider a coating flow of nematic liquid crystal (NLC) fluid film on an inclined substrate. Exploiting the small aspect ratio in the geometry of interest, a fourth-order nonlinear partial differential equation is used to model the free surface evolution. Particular attention is paid to the interplay between the bulk elasticity and the anchoring conditions at the substrate and free surface. Previous results have shown that there exist two-dimensional travelling wave solutions that translate down the substrate. In contrast to the analogous Newtonian flow, such solutions may be unstable to streamwise perturbations. Extending well-known results for Newtonian flow, we analyse the stability of the front with respect to transverse perturbations. Using full numerical simulations, we validate the linear stability theory and present examples of downslope flow of nematic liquid crystal in the presence of both transverse and streamwise instabilities.
This retrospective, descriptive case-series reviews the clinical presentations and significant laboratory findings of patients diagnosed with and treated for injectional anthrax (IA) since December 2009 at Monklands Hospital in Central Scotland and represents the largest series of IA cases to be described from a single location. Twenty-one patients who fulfilled National Anthrax Control Team standardized case definitions of confirmed, probable or possible IA are reported. All cases survived and none required limb amputation in contrast to an overall mortality of 28% being experienced for this condition in Scotland. We document the spectrum of presentations of soft tissue infection ranging from mild cases which were managed predominantly with oral antibiotics to severe cases with significant oedema, organ failure and coagulopathy. We describe the surgical management, intensive care management and antibiotic management including the first description of daptomycin being used to treat human anthrax. It is noted that some people who had injected heroin infected with Bacillus anthracis did not develop evidence of IA. Also highlighted are biochemical and haematological parameters which proved useful in identifying deteriorating patients who required greater levels of support and surgical debridement.
Impairments in learning and recall have been well established in amnestic mild cognitive impairment (aMCI). However, a relative dearth of studies has examined the profiles of memory strategy use in persons with aMCI relative to those with Alzheimer's disease (AD). Participants with aMCI, nonamnestic MCI, AD, and healthy older adults were administered the California Verbal Learning Test-II (CVLT-II). Measures of semantic clustering and recall were obtained across learning and delayed recall trials. In addition, we investigated whether deficits in semantic clustering were related to progression from healthy aging to aMCI and from aMCI to AD. The aMCI group displayed similar semantic clustering performance as the AD participants, whereas the AD group showed greater impairments on recall relative to the aMCI participants. Control participants who progressed to aMCI showed reduced semantic clustering at the short delay at baseline compared to individuals who remained diagnostically stable across follow-up visits. These findings show that the ability to engage in an effective memory strategy is compromised in aMCI, before AD has developed, suggesting that disruptions in semantic networks are an early marker of the disease. (JINS, 2014, 20, 1–11)
Systematic asymptotic methods are used to formulate a model for the extensional flow of a thin sheet of nematic liquid crystal. With no external body forces applied, the model is found to be equivalent to the so-called Trouton model for Newtonian sheets (and fibres), albeit with a modified ‘Trouton ratio’. However, with a symmetry-breaking electric field gradient applied, behaviour deviates from the Newtonian case, and the sheet can undergo finite-time breakup if a suitable destabilizing field is applied. Some simple exact solutions are presented to illustrate the results in certain idealized limits, as well as sample numerical results to the full model equations.
We study spreading dynamics of nematic liquid crystal droplets within the framework of the long-wave approximation. A fourth-order nonlinear parabolic partial differential equation governing the free surface evolution is derived. The influence of elastic distortion energy and of imposed anchoring variations at the substrate are explored through linear stability analysis and scaling arguments, which yield useful insight and predictions for the behaviour of spreading droplets. This behaviour is captured by fully nonlinear time-dependent simulations of three-dimensional droplets spreading in the presence of anchoring variations that model simple defects in the nematic orientation at the substrate.