Principal infinity-bundles - Presentations

We discuss two aspects of the presentation of the theory of principal infinity-bundles in an infinity-topos, introduced in [NSSa], in terms of categories of simplicial (pre)sheaves. First we show that over a cohesive site C and for G a presheaf of simplicial groups which is C-acyclic, G-principal infinity-bundles over any object in the infinity-topos over C are classified by hyper-Cech-cohomology with coefficients in G. Then we show that over a site C with enough points, principal infinity-bundles in the infinity-topos are presented by ordinary simplicial bundles in the sheaf topos that satisfy principality by stalkwise weak equivalences. Finally we discuss explicit details of these presentations for the discrete site (in discrete infinity-groupoids) and the smooth site (in smooth infinity-groupoids, generalizing Lie groupoids and differentiable stacks). In the companion article [NSSc] we use these presentations for constructing classes of examples of (twisted) principal infinity-bundles and for the discussion of various applications.Comment: 55 page

Angular and Polarization Response of Multimode Sensors with Resistive-Grid Absorbers

High sensitivity receiver systems with near ideal polarization sensitivity are highly desirable for development of millimeter and sub-millimeter radio astronomy. Multimoded bolometers provide a unique solution to achieve such sensitivity, for which hundreds of single-mode sensors would otherwise be required. The primary concern in employing such multimoded sensors for polarimetery is the control of the polarization systematics. In this paper, we examine the angular- and polarization- dependent absorption pattern of a thin resistive grid or membrane, which models an absorber used for a multimoded bolometer. The result shows that a freestanding thin resistive absorber with a surface resistivity of \eta/2, where \eta\ is the impedance of free space, attains a beam pattern with equal E- and H-plane responses, leading to zero cross polarization. For a resistive-grid absorber, the condition is met when a pair of grids is positioned orthogonal to each other and both have a resistivity of \eta/2. When a reflective backshort termination is employed to improve absorption efficiency, the cross-polar level can be suppressed below -30 dB if acceptance angle of the sensor is limited to <60degrees. The small cross-polar systematics have even-parity patterns and do not contaminate the measurements of odd-parity polarization patterns, for which many of recent instruments for cosmic microwave background are designed. Underlying symmetry that suppresses these cross-polar systematics is discussed in detail. The estimates and formalism provided in this paper offer key tools in the design consideration of the instruments using the multimoded polarimeters.Comment: 22 pages, 15 figure

Interviews With Transgender Students: Academic And Environmental Factors

Although research on gay and lesbian students has taken off in recent years, there is a serious lack of research devoted solely to the transgender population, and even less specifically focused on transgender students. The research that has been conducted on transgender individuals is often focused on discrimination that they experience, and the effects of that discrimination. College is a period of personal growth and discovery for all students, but perhaps especially for transgender students. This study, therefore, aims to better understand how being transgender affects the college experience. This qualitative study interviewed self-identified transgender students within the University of Maine system. Data was collected via interviews focused on the academic and environmental experiences of these students. The aim of this exploratory study was to gain further understanding of the unique needs of this student population, with the hope that it may inform future research on the trans community, as well as influence University of Maine policy to better suit the particular needs of these students. Results revealed a number of of concerns regarding academic, residential, transgender-specific resources, health, and safety. Implications and recommendations for future research are discussed

Corneal ulcers and opacities

The principal points in connection with my Thesis are: 1. That Ulcers of the Cornea are an extremely common occurrence. 2. Ulcer of the Cornea must not be locked upon as a Simple Condition. 3. On account of the complications which can he set up, there is always the danger of impaired vision and even of complete loss of sight. 4. Treatment must be adopted at once. 5. As soon as possible put your patients to bed and keep them there. 6. Kerotomy is one of the simplest and at the same time one of the most efficacious remedies we have. 7. If doubtful cf the case, take Cultures at once. 8. In the case of Opacities, if not of too long standing and if other remedies fail try Pericausis. 9. Don't expect to get rapid cures. Treatment lasts sometimes for many months: therefore persevere

Space shuttle main engine fault detection using neural networks

A method for on-line Space Shuttle Main Engine (SSME) anomaly detection and fault typing using a feedback neural network is described. The method involves the computation of features representing time-variance of SSME sensor parameters, using historical test case data. The network is trained, using backpropagation, to recognize a set of fault cases. The network is then able to diagnose new fault cases correctly. An essential element of the training technique is the inclusion of randomly generated data along with the real data, in order to span the entire input space of potential non-nominal data

Four Decades Of African American Portrayals In Magazine Advertising

This paper examines the frequency of black portrayals as well as the occupations and racial compositions employed in ads depicting blacks in four mass circulation consumer magazines over four decades The portrayal of African Americans in advertising has been of interest to marketers for more than half a century. However, few studies have spanned multiple decades and very few have been extended into the 21st century. This study extends a previous paper (Stevenson 1999) addressing the portrayal of blacks in the consumer print media. Through the use of content analysis, more than 1500 ads were analyzed in these magazines for the years 1975, 1985, 1995, and 2005.&nbsp; Findings indicate that there were significant increases in the numbers of blacks portrayed in the magazines analyzed in this study. It was also determined that where blacks were portrayed in occupational roles, most depictions were &ldquo;above skilled labor&rdquo; and that most portrayals utilized mixed peer rather than non-mixed peer depictions. Findings are compared to previous studies, managerial implications are considered, and suggestions for future research are offered

Degradation of Polymers Based on Styrene and Butadiene

This discussion is concerned with the preparation, characterisation and subsequent degradation of some high polymers based on styrene and butadiene. It also considers some refinements to existing high vacuum techniques of thermal analysis and in addition, the development of a set of techniques able to identify and manipulate quantitatively the noncondensable product fraction associated with thermal degradation under open pumping conditions of polymer systems