Analysis and design of a flat central finned-tube radiator

Computer program based on fixed conductance parameter yields minimum weight design. Second program employs variable conductance parameter and variable ratio of fin length to tube outside radius, and is used for radiator designs with geometric limitations. Major outputs of the two programs are given

Quantum Gauge Equivalence in QED

We discuss gauge transformations in QED coupled to a charged spinor field, and examine whether we can gauge-transform the entire formulation of the theory from one gauge to another, so that not only the gauge and spinor fields, but also the forms of the operator-valued Hamiltonians are transformed. The discussion includes the covariant gauge, in which the gauge condition and Gauss's law are not primary constraints on operator-valued quantities; it also includes the Coulomb gauge, and the spatial axial gauge, in which the constraints are imposed on operator-valued fields by applying the Dirac-Bergmann procedure. We show how to transform the covariant, Coulomb and spatial axial gauges to what we call ``common form,'' in which all particle excitation modes have identical properties. We also show that, once that common form has been reached, QED in different gauges has a common time-evolution operator that defines time-translation for states that represent systems of electrons and photons. By combining gauge transformations with changes of representation from standard to common form, the entire apparatus of a gauge theory can be transformed from one gauge to another.Comment: Contribution for a special issue of Foundations of Physics honoring Fritz Rohrlich; edited by Larry P. Horwitz, Tel-Aviv University, and Alwyn van der Merwe, University of Denver (Plenum Publishing, New York); 40 pages, REVTEX, Preprint UCONN-93-3, 1 figure available upon request from author

Precision Measurements of Stretching and Compression in Fluid Mixing

The mixing of an impurity into a flowing fluid is an important process in many areas of science, including geophysical processes, chemical reactors, and microfluidic devices. In some cases, for example periodic flows, the concepts of nonlinear dynamics provide a deep theoretical basis for understanding mixing. Unfortunately, the building blocks of this theory, i.e. the fixed points and invariant manifolds of the associated Poincare map, have remained inaccessible to direct experimental study, thus limiting the insight that could be obtained. Using precision measurements of tracer particle trajectories in a two-dimensional fluid flow producing chaotic mixing, we directly measure the time-dependent stretching and compression fields. These quantities, previously available only numerically, attain local maxima along lines coinciding with the stable and unstable manifolds, thus revealing the dynamical structures that control mixing. Contours or level sets of a passive impurity field are found to be aligned parallel to the lines of large compression (unstable manifolds) at each instant. This connection appears to persist as the onset of turbulence is approached.Comment: 5 pages, 5 figure

Basic research on the biology of meta-tetra(hydroxyphenyl) chlorin for photodynamic therapy in gynaecology: Somatic genotoxicity assayed with Drosophila melanogaster

The well-established SMART test, a somatic mutation and recombination assay of Drosophila, was applied to assess the possible genotoxicity of sublethal meta-tetra(hydroxyphenyl) chlorin (mTHPC) photodynamic therapy (PDT) to clonogenic cells in situ. The SMART assay monitors the loss of heterozygosity (LOH) at selected cell-marker loci in clonogenic cells of the larval wing primordia. No evidence of genotoxicity was observed under conditions that killed between 38 and 86% of the exposed test larvae. Since the SMART assay is based on the oral uptake of the suspected genotoxic agent, the uptake kinetics of mTHPC by the assay's specific target cells must be known. Therefore, relevant studies are being carried out at present in order to draw final conclusions from this negative test result for genotoxicit

Experimental Measurements of Stretching Fields in Fluid Mixing

The mixing of an impurity into a flowing fluid is an important process in many areas of science, including geophysical processes, chemical reactors, and microfluidic devices. In some cases, for example periodic flows, the concepts of nonlinear dynamics provide a deep theoretical basis for understanding mixing. Unfortunately, the building blocks of this theory, i.e. the fixed points and invariant manifolds of the associated Poincaré map, have remained inaccessible to direct experimental study, thus limiting the insight that could be obtained. Using precision measurements of tracer particle trajectories in a two-dimensional fluid flow producing chaotic mixing, we directly measure the time-dependent stretching fields. These quantities, previously available only numerically, attain local maxima along lines coinciding with the stable and unstable manifolds, thus revealing the dynamical structures that control mixing. Contours or level sets of a passive impurity field are found to be aligned parallel to the lines of large stretching at each instant, thus explaining what happens as one stirs milk into coffee. --author-supplied descriptio

Comparative efficacy of different exercise interventions in chronic non-specific low back pain: protocol of a systematic review and network meta-analysis.

INTRODUCTION:Chronic non-specific low back pain is a major public health problem. Evidence supports the effectiveness of exercise as an intervention. Due to a paucity of direct comparisons of different exercise categories, medical guidelines were unable to make specific recommendations regarding the type of exercise working best in improving chronic low back pain. This network meta-analysis (NMA) of randomised controlled trials aims to investigate the comparative efficacy of different exercise interventions in patients with chronic non-specific low back pain. METHODS AND ANALYSIS:MEDLINE, Scopus, Cochrane Central Register of Controlled Trials, Physiotherapy Evidence Database, SPORTDiscus, Clinicaltrials.gov and the WHO International Clinical Trials Registry Platform search portal were searched on November 2019 and without language restrictions. The search will be updated after data analysis. Studies on adults with non-specific low back pain of at least 12 weeks duration comparing exercise to either no specific intervention (ie, no treatment, wait-list or usual care at the treating physician's discretion) and/or functionally inert interventions (ie, sham or attention control interventions) will be eligible. Pain intensity and back-specific disability are defined as primary outcomes. Secondary outcomes will include health-related physical and mental quality of life, work disability, frequency of analgesic use and adverse events. All outcomes will be analysed short-term, intermediate-term and long-term. Data will be extracted independently by two review authors. Risk of bias will be assessed using the recommendations by the Cochrane Back and Neck Group and be based on an adaptation of the Cochrane Risk of Bias tool. ETHICS AND DISSEMINATION:This NMA will be reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses_NMA checklist. The results will be presented in peer-reviewed journals, implemented in existing national and international guidelines and will be presented to health care providers and decision makers. The planned completion date of the study is 1 July 2021. PROSPERO REGISTRATION NUMBER:CRD42020151472

Clinical factors associated with the non-utilization of an anaesthesia incident reporting system

Background Incident reporting is a widely recommended method to measure undesirable events in anaesthesia. Under-utilization is a major weakness of voluntary incident reporting systems. Little is known about factors influencing reporting practices, particularly the clinical environment, anaesthesia team composition, severity of the incident, and perceived risk of litigation. The purpose of this study was to assess each of these, using an existing anaesthesia database. Methods We performed a retrospective cohort study and analysed 46 207 surgical patients. We used multivariate analysis to identify factors associated with the non-utilization of the reporting system. Results We found that in 7022 (15.1%) of the procedures performed, the incident reporting system was not used. Factors associated with the non-use of the system were regional anaesthesia/local anaesthesia, odds ratio (OR) 1.64 [95% confidence interval (CI) 1.03-2.62], emergency procedures OR 1.15 (95% CI: 1.05-1.27), and a consultant anaesthetist working without a trainee, OR 1.71 (95% CI: 1.03-2.82). In contrast, factors such as longer duration of surgery, OR 0.85 (95% CI: 0.76-0.94), the presence of a senior anaesthesia trainee, OR 0.86 (95% CI: 0.81-0.92), and the occurrence of severe complications with a high risk of litigation (i.e. death, nerve injuries) were less associated with a non-use of the reporting system, OR 0.65 (95% CI: 0.44-0.97). Team composition and time of day had no measurable impact on reporting practices. Conclusions Clinical factors play a significant role in the utilization of an anaesthesia incident reporting system and more particularly, severity of complications and higher liability risks which appear more as incentives than barriers to incident reportin

General practitioners' views and preferences about quality improvement feedback in preventive care: a cross-sectional study in Switzerland and France.

Feedback is widely used as a strategy to improve the quality of care in primary care settings. As part of a study conducted to explore the quality of preventive care, we investigated general practitioners' (GPs) views on the usefulness of feedback and their preferences regarding how feedback is provided. This cross-sectional study was conducted in 2015 among randomly selected community-based GPs in two regions of Switzerland and France. GPs were asked to complete an anonymous questionnaire about how often they provided 12 measures of preventive care: blood pressure, weight and height measurements, screening for dyslipidemia, at-risk drinking (and advice to reduce for at-risk drinkers), smoking (and advice to stop for smokers), colon and prostate cancer, and influenza immunization for patients >65 years and at-risk patients. They were also asked to estimate the usefulness of a feedback regarding their preventive care practice, reason(s) for which a feedback could be useful, and finally, to state which type of feedback they would like to receive. Chi-square tests were used to compare frequencies. Multivariate logistic regression was used to identify factors associated with GPs considering feedback as useful. Five hundred eighteen of 1100 GPs (47.1%) returned the questionnaire. They were predominantly men (62.5%) and most (40.1%) were aged between 55 and 64 years old. Overall, 44.3% stated that a feedback would be useful. Younger GPs and those carrying out more measures of preventive care were more likely to consider feedback useful. The two main reasons for being interested in feedback were to receive knowledge about the study results and to modify or improve practice. The two preferred feedback interventions were a brief report and a report with specific information regarding prevention best practice, whereas less than 1% would like to discuss the results face-to-face with the study investigators. These findings suggest that GPs have preferences regarding the types of feedback they would like to receive. Because the implementation of guidelines is highly related to the acceptance of feedback, we strongly encourage decision makers to take GPs' preferences into account when developing strategies to implement guidelines, in order to improve the quality of primary care