Study of the parameters affecting contact performance of high reliability relays

Parameters affecting contact performance of high reliability relay

Magnetic Flux Braiding: Force-Free Equilibria and Current Sheets

We use a numerical nonlinear multigrid magnetic relaxation technique to investigate the generation of current sheets in three-dimensional magnetic flux braiding experiments. We are able to catalogue the relaxed nonlinear force-free equilibria resulting from the application of deformations to an initially undisturbed region of plasma containing a uniform, vertical magnetic field. The deformations are manifested by imposing motions on the bounding planes to which the magnetic field is anchored. Once imposed the new distribution of magnetic footpoints are then taken to be fixed, so that the rest of the plasma must then relax to a new equilibrium configuration. For the class of footpoint motions we have examined, we find that singular and nonsingular equilibria can be generated. By singular we mean that within the limits imposed by numerical resolution we find that there is no convergence to a well-defined equilibrium as the number of grid points in the numerical domain is increased. These singular equilibria contain current "sheets" of ever-increasing current intensity and decreasing width; they occur when the footpoint motions exceed a certain threshold, and must include both twist and shear to be effective. On the basis of these results we contend that flux braiding will indeed result in significant current generation. We discuss the implications of our results for coronal heating.Comment: 13 pages, 12 figure

Understanding sperm quality for improved reproductive performance

The assessment of semen quality is used to identify factors that influence sperm performance and diagnose male infertility [...

Utilizing the American Board of Surgery in-training exam in a Rwandan surgical residency program: Alignment of exam topics with the University of Rwanda general surgery curriculum

Background: University of Rwanda (UR) increased postgraduate surgery training and assessment strategies are needed. We compared American Board of Surgery In-Training Exam (ABSITE) topics with UR surgery curriculum to determine the applicability of ABSITE in Rwanda.Methods: Topics are outlined in the Surgical Council on Resident Education (SCORE) curriculum whereas the UR utilizes a modular system. Diseases and conditions in SCORE were compared with UR surgery module content. Operation and procedures in SCORE were compared with operative procedures in UR surgery curriculum.Results: Overall, 72% of diseases and conditions from SCORE were covered in UR curriculum. Of this, 76% of medical knowledge and 71% of patient care content was covered in UR curriculum. 41% of operations and procedures from SCORE were identified in UR curriculum. 55% of core operations and 16% of advanced operations from SCORE were included in UR general surgery curriculum. Content identified in UR curriculum and not SCORE included infectious and tropical diseases, orthopedics, urology and neurosurgery.Conclusions: There is alignment between ABSITE topics and UR general surgery curriculum suggesting that the ABSITE can be used as an in-training examination for Rwandan residents. Understanding the limitations of the ABSITE exam can help utilization of this examination.Keywords: internship and residency, curriculum, Rwanda, global healt

Scaling up a surgical residency program in Rwanda

Background: Beginning in 2012, the Government of Rwanda implemented the Human Resources for Health (HRH) program to enhance capacity building in the Rwandan health education sector. Through this program, surgical training at University of Rwanda (UR) has expanded. The aim of this presentation is to describe the scaling up of the UR surgical residency programMethods: We performed a descriptive analysis of the UR surgical residency program after initiation of the Rwanda HRH Program.Results: Through the HRH Program, faculty from US institutions supplements the existing Rwandan educational infrastructure to increase the teaching capacity in Rwanda. Intake of surgical trainees more than doubled within the first year of the program. Service-based surgical training has changed to competency-based training through curriculum development, dedicated academic days and surgical education within firms. Lectures remain a dominant feature of the educational program, but more focus is placed on bedside teaching and peer-education. Shortage of operative space and a tremendous number of emergency patients overwhelm public teaching hospitals posing a challenge towards providing residents with a broad spectrum of operative experiences, especially elective surgical cases.Conclusion: Through this program, the ursurgical residency program has greatly expanded. Over time, the quantity and quality of surgical residents is expected to increase

Gastrointestinal Strongyles in Wild Ruminants

Parasitologists have long studied helminth infections in wildlife species and have documented the existence of many organisms from a diversity of mammalian hosts. With this accumulation of information has come improved understanding of the significance of these organisms and the diseases they produce in their mammalian hosts. Some of the most notable examples include the metastrongyloid lungworms, Trichinella spiralis, and Elaeophora schneideri, which are covered separately in this volume. It is, however, for the group of parasites referred to as gastrointestinal nematodes that we have accumulated the most data. Only recently has progress been made in determining the significance of these strongylate nematodes with respect to their potential impact on the morbidity and mortality of the ruminants that they infect. The accumulation of information on diseases of wild animals into a single combined volume has been slow, but progress has coincided with the proliferation of data for host and parasite interactions. Numerous references including Alaskan Wildlife Diseases (Dieterich 1981), Manual of Common Wildlife Diseases in Colorado (Adrian 1981), Field Manual of Wildlife Diseases in the Southeastern United States (Davidson and Nettles 1988), Zoo and Wildlife Medicine (Fowler 1993), and the previous editions of Parasitic Diseases of Wild Mammals (Davis and Anderson 1971) have all made significant contributions to our knowledge. Beyond North America, Dunn (1969) and Govorka et al. (1988) provided excellent compilations on the helminths in wild ruminants. In the 1971 printing of Parasitic Diseases of Mammals, however, there was no general coverage of gastrointestinal nematodes, and only T. spiralis was addressed. Herein, we present the first synoptic review of the strongylate nematodes that occur in the gastrointestinal system of wild ruminants from North America

The homotopy theory of dg-categories and derived Morita theory

The main purpose of this work is the study of the homotopy theory of dg-categories up to quasi-equivalences. Our main result provides a natural description of the mapping spaces between two dg-categories $C$ and $D$ in terms of the nerve of a certain category of $(C,D)$-bimodules. We also prove that the homotopy category $Ho(dg-Cat)$ is cartesian closed (i.e. possesses internal Hom's relative to the tensor product). We use these two results in order to prove a derived version of Morita theory, describing the morphisms between dg-categories of modules over two dg-categories $C$ and $D$ as the dg-category of $(C,D)$-bi-modules. Finally, we give three applications of our results. The first one expresses Hochschild cohomology as endomorphisms of the identity functor, as well as higher homotopy groups of the \emph{classifying space of dg-categories} (i.e. the nerve of the category of dg-categories and quasi-equivalences between them). The second application is the existence of a good theory of localization for dg-categories, defined in terms of a natural universal property. Our last application states that the dg-category of (continuous) morphisms between the dg-categories of quasi-coherent (resp. perfect) complexes on two schemes (resp. smooth and proper schemes) is quasi-equivalent to the dg-category of quasi-coherent complexes (resp. perfect) on their product.Comment: 50 pages. Few mistakes corrected, and some references added. Thm. 8.15 is new. Minor corrections. Final version, to appear in Inventione