Permutation sampling in Path Integral Monte Carlo

A simple algorithm is described to sample permutations of identical particles in Path Integral Monte Carlo (PIMC) simulations of continuum many-body systems. The sampling strategy illustrated here is fairly general, and can be easily incorporated in any PIMC implementation based on the staging algorithm. Although it is similar in spirit to an existing prescription, it differs from it in some key aspects. It allows one to sample permutations efficiently, even if long paths (e.g., hundreds, or thousands of slices) are needed. We illustrate its effectiveness by presenting results of a PIMC calculation of thermodynamic properties of superfluid Helium-four, in which a very simple approximation for the high-temperature density matrix was utilized

Selecting and implementing overview methods: implications from five exemplar overviews

This is the final version of the article. Available from BioMed Central via the DOI in this record.Background Overviews of systematic reviews are an increasingly popular method of evidence synthesis; there is a lack of clear guidance for completing overviews and a number of methodological challenges. At the UK Cochrane Symposium 2016, methodological challenges of five overviews were explored. Using data from these five overviews, practical implications to support methodological decision making of authors writing protocols for future overviews are proposed. Methods Methods, and their justification, from the five exemplar overviews were tabulated and compared with areas of debate identified within current literature. Key methodological challenges and implications for development of overview protocols were generated and synthesised into a list, discussed and refined until there was consensus. Results Methodological features of three Cochrane overviews, one overview of diagnostic test accuracy and one mixed methods overview have been summarised. Methods of selection of reviews and data extraction were similar. Either the AMSTAR or ROBIS tool was used to assess quality of included reviews. The GRADE approach was most commonly used to assess quality of evidence within the reviews. Eight key methodological challenges were identified from the exemplar overviews. There was good agreement between our findings and emerging areas of debate within a recent published synthesis. Implications for development of protocols for future overviews were identified. Conclusions Overviews are a relatively new methodological innovation, and there are currently substantial variations in the methodological approaches used within different overviews. There are considerable methodological challenges for which optimal solutions are not necessarily yet known. Lessons learnt from five exemplar overviews highlight a number of methodological decisions which may be beneficial to consider during the development of an overview protocol.The overview conducted by Pollock [19] was supported by a project grant from the Chief Scientist Office of the Scottish Government. The overview conducted by McClurg [21] was supported by a project grant by the Physiotherapy Research Foundation. The overview by Hunt [22] was supported as part of doctoral programme funding by the National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care South West Peninsula (PenCLAHRC). The overview conducted by Estcourt [20] was supported by an NIHR Cochrane Programme Grant for the Safe and Appropriate Use of Blood Components. The overview conducted by Brunton [23] was commissioned by the Department of Health as part of an ongoing programme of work on health policy research synthesis. Alex Pollock is employed by the Nursing, Midwifery and Allied Health Professions (NMAHP) Research Unit, which is supported by the Chief Scientist Office of the Scottish Government. Pauline Campbell is supported by the Chief Nurses Office of the Scottish Government

Performance and Implementation Evaluation of the Abbott BinaxNOW Rapid Antigen Test in a High-throughput Drive-through Community Testing Site in Massachusetts

Background: Rapid diagnostic tests (RDTs) for SARS-CoV-2 antigens (Ag) that can be performed at point-of-care (POC) can supplement molecular testing and help mitigate the COVID-19 pandemic. Deployment of an Ag RDT requires an understanding of its operational and performance characteristics under real-world conditions and in relevant subpopulations. We evaluated the Abbott BinaxNOW COVID-19 Ag Card in a high-throughput, drive-through, free community testing site in Massachusetts (MA) using anterior nasal (AN) swab RT-PCR for clinical testing. Methods: Individuals presenting for molecular testing in two of seven lanes were offered the opportunity to also receive BinaxNOW testing. Dual AN swabs were collected from symptomatic and asymptomatic children ( \u3c /= 18 years) and adults. BinaxNOW testing was performed in a testing pod with temperature/humidity monitoring. One individual performed testing and official result reporting for each test, but most tests had a second independent reading to assess inter-operator agreement. Positive BinaxNOW results were scored as faint, medium, or strong. Positive BinaxNOW results were reported to patients by phone and they were instructed to isolate pending RT-PCR results. The paired RT-PCR result was the reference for sensitivity and specificity calculations. Results: Of 2482 participants, 1380 adults and 928 children had paired RT-PCR/BinaxNOW results and complete symptom data. 974/1380 (71%) adults and 829/928 (89%) children were asymptomatic. BinaxNOW had 96.5% (95% confidence interval [CI] 90.0- 99.3) sensitivity and 100% (98.6-100.0) specificity in adults within 7 days of symptoms, and 84.6% (65.1-95.6) sensitivity and 100% (94.5-100.0) specificity in children within 7 days of symptoms. Sensitivity and specificity in asymptomatic adults were 70.2% (56.6-81.6) and 99.6% (98.9-99.9), respectively, and in asymptomatic children were 65.4% (55.6-74.4) and 99.0% (98.0-99.6), respectively. By cycle threshold (Ct) value cutoff, sensitivity in all subgroups combined (n=292 RT-PCR-positive individuals) was 99.3% with Ct \u3c /=25, 95.8% with \u3c /=30, and 81.2% with \u3c /=35. Twelve false positive BinaxNOW results (out of 2308 tests) were observed; in all twelve, the test bands were faint but otherwise normal, and were noted by both readers. One invalid BinaxNOW result was identified. Inter-operator agreement (positive versus negative BinaxNOW result) was 100% (n = 2230/2230 double reads). Each operator was able to process 20 RDTs per hour. In a separate set of 30 specimens (from individuals with symptoms \u3c /=7 days) run at temperatures below the manufacturer\u27s recommended range (46-58.5 degrees F), sensitivity was 66.7% and specificity 95.2%. Conclusions: BinaxNOW had very high specificity in both adults and children and very high sensitivity in newly symptomatic adults. Overall, 95.8% sensitivity was observed with Ct \u3c /= 30. These data support public health recommendations for use of the BinaxNOW test in adults with symptoms for \u3c /=7 days without RT-PCR confirmation. Excellent inter-operator agreement indicates that an individual can perform and read the BinaxNOW test alone. A skilled laboratorian can perform and read 20 tests per hour. Careful attention to temperature is critical

Sustaining Educational Reforms in Introductory Physics

While it is well known which curricular practices can improve student performance on measures of conceptual understanding, the sustaining of these practices and the role of faculty members in implementing these practices are less well understood. We present a study of the hand-off of Tutorials in Introductory Physics from initial adopters to other instructors at the University of Colorado, including traditional faculty not involved in physics education research. The study examines the impact of implementation of Tutorials on student conceptual learning across eight first-semester, and seven second-semester courses, for fifteen faculty over twelve semesters, and includes roughly 4000 students. It is possible to demonstrate consistently high, and statistically indistinguishable, student learning gains for different faculty members; however, such results are not the norm, and appear to rely on a variety of factors. Student performance varies by faculty background - faculty involved in, or informed by physics education research, consistently post higher student learning gains than less-informed faculty. Student performance in these courses also varies by curricula used - all semesters in which the research-based Tutorials and Learning Assistants are used have higher student learning gains than those semesters that rely on non-research based materials and do not employ Learning Assistants.Comment: 21 pages, 4 figures, and other essential inf

Storage monitoring systems for the year 2000

In September 1993, President Clinton stated the US would ensure that its fissile material meet the highest standards of safety, security, and international accountability. Frequent human inspection of the material could be used to ensure these standards. However, it may be more effective and less expensive to replace these manual inspections with virtual inspections via remote monitoring technologies. To prepare for this future, Sandia National Laboratories has developed several monitoring systems, including the Modular Integrated Monitoring System (MIMS) and Project Straight-Line. The purpose of this paper is to describe a Sandia effort that merges remote monitoring technologies into a comprehensive storage monitoring system that will meet the near-term as well as the long-term requirements for these types of systems. Topics discussed include: motivations for storage monitoring systems to include remote monitoring; an overview of the needs and challenges of providing a storage monitoring system for the year 2000; an overview of how the MIMS and Straight-Line can be enhanced so that together they create an integrated and synergistic information system by the end of 1997; and suggested milestones for 1998 and 1999 to assure steady progress in preparing for the needs of 2000

Tomographic imaging and scanning thermal microscopy: thermal impedance tomography

The application of tomographic imaging techniques developed for medical applications to the data provided by the scanning thermal microscope will give access to true three-dimensional information on the thermal properties of materials on a mm length scale. In principle, the technique involves calculating and inverting a sensitivity matrix for a uniform isotropic material, collecting ordered data at several modulation frequencies, and multiplying the inverse of the matrix with the data vector. In practice, inversion of the matrix in impractical, and a novel iterative technique is used. Examples from both simulated and real data are given

Investigating student interpretations of the differences between classical and quantum computers: Are quantum computers just analog classical computers?

Significant attention in the PER community has been paid to student cognition and reasoning processes in undergraduate quantum mechanics. Until recently, however, these same topics have remained largely unexplored in the context of emerging interdisciplinary quantum information science (QIS) courses. We conducted exploratory interviews with 22 students in an upper-division quantum computing course at a large R1 university crosslisted in physics and computer science, as well as 6 graduate students in a similar graduate-level QIS course offered in physics. We classify and analyze students' responses to a pair of questions regarding the fundamental differences between classical and quantum computers. We specifically note two key themes of importance to educators: (1) when reasoning about computational power, students often struggled to distinguish between the relative effects of exponential and linear scaling, resulting in students frequently focusing on distinctions that are arguably better understood as analog-digital than classical-quantum, and (2) introducing the thought experiment of analog classical computers was a powerful tool for helping students develop a more expertlike perspective on the differences between classical and quantum computers.Comment: Submitted to Proceedings of the 2022 Physics Education Research Conference, Grand Rapids, MI, US 7/13-7/14/2