Design, fabrication, and structural testing of a lightweight shadow shield for deep-space application

Two full-scale, lightweight, double-sheeted shadow shields were developed as the primary element of a deep-space thermal protection system for liquid-hydrogen propellant tankage. The thermal and mechanical considerations used in s, the method of fabrication, and the environmental testing results on a prototype shield are discussed. Testing consisted of a transient cooldown period, a prolonged cold soak, and a transient warmup. The mechanical and thermal analyses used in the shield design are sufficient to produce a lightweight rugged shadow shield assembly that is structurally adequate for its intended application

The Fermion Self-Energy during Inflation

We compute the one loop fermion self-energy for massless Dirac + Einstein in the presence of a locally de Sitter background. We employ dimensional regularization and obtain a fully renormalized result by absorbing all divergences with BPHZ counterterms. An interesting technical aspect of this computation is the need for a noninvariant counterterm owing to the breaking of de Sitter invariance by our gauge condition. Our result can be used in the quantum-corrected Dirac equation to search for inflation-enhanced quantum effects from gravitons, analogous to those which have been found for massless, minimally coupled scalars.Comment: 63 pages, 3 figures (uses axodraw.sty), LaTeX 2epsilon. Revised version (to appear in Classical and Quantum Gravity) corrects some typoes and contains some new reference

Considerations on the Unruh Effect: Causality and Regularization

This article is motivated by the observation, that calculations of the Unruh effect based on idealized particle detectors are usually made in a way that involves integrations along the {\em entire} detector trajectory up to the infinitely remote {\em future}. We derive an expression which allows time-dependence of the detector response in the case of a non-stationary trajectory and conforms more explicitely to the principle of causality, namely that the response at a given instant of time depends only on the detectors {\em past} movements. On trying to reproduce the thermal Unruh spectrum we are led to an unphysical result, which we trace down to the use of the standard regularization t\to t-i\eps of the correlation function. By consistently employing a rigid detector of finite extension, we are led to a different regularization which works fine with our causal response function.Comment: 19 pages, 2 figures, v2: some minor change

Lorentz Symmetry Breaking in Abelian Vector-Field Models with Wess-Zumino Interaction

We consider the abelian vector-field models in the presence of the Wess-Zumino interaction with the pseudoscalar matter. The occurence of the dynamic breaking of Lorentz symmetry at classical and one-loop level is described for massless and massive vector fields. This phenomenon appears to be the non-perturbative counterpart of the perturbative renormalizability and/or unitarity breaking in the chiral gauge theories.Comment: 11 pages,LaTeX, Preprint DFUB/94 - 1

Representations of p-brane topological charge algebras

The known extended algebras associated with p-branes are shown to be generated as topological charge algebras of the standard p-brane actions. A representation of the charges in terms of superspace forms is constructed. The charges are shown to be the same in standard/extended superspace formulations of the action.Comment: 22 pages. Typos fixed, refs added. Minor additions to comments sectio

Effect of medical student preference on rural clinical school experience and rural career intentions

Introduction: The key parameter for rural clinical schools (RCSs) is to provide at least 1 year of clinical training in rural areas for 25% of Australian Commonwealth supported medical students with the intent to influence future rural medical workforce outcomes. The objective of this study was to describe the association between a medical student’s selection preference and their RCS experience and rural career intent. Methods: Medical students completing an RCS placement in 2012 and 2013 were encouraged to complete a survey regarding their experience and future career intent. Data were analysed to compare medical students for whom the RCS was their first choice with students who described the RCS as other than their first preference. Results: Students for whom RCS was their first choice (724/1092) were significantly more likely to be female, come from a rural background and be from an undergraduate program. These students reported more positive experiences of all aspects of the RCS program (costs, access, support and networks, safety) and were 2.36 times more likely to report intentions to practice in a non-metropolitan area (odds ratio(OR)=2.36 (95% confidence interval(CI)=1.82–3.06), p\u3c0.001). This was true for students of rural (OR=3.11 (95%CI=1.93–5.02), p\u3c0.001) and metropolitan backgrounds (OR=2.07 (95%CI=1.48–2.89), p\u3c0.001). More students in the first-choice group (68.8%) intended to practice in a regional area (not a capital or major city), significantly higher than the 48.4% of participants in the other-preference group (χ2 (1) 42.79, p\u3c0.001). Conclusions: The decision to choose an RCS placement is a marker of rural career intention and a positive rural training experience for students of both rural and metropolitan backgrounds. It may be important to identify other-preference students and their specific social support needs to ensure a positive perception of a future rural career

Energetic cost of breathing, body composition, and pulmonary function in horses with recurrent airway obstruction

This study was conducted to determine whether horses with naturally occurring, severe chronic recurrent airway obstruction (RAO) 1) have a greater resting energy expenditure (REE) than control horses, 2) suffer body mass depletion, and 3) have significantly decreased REE after bronchodilation and, therefore, also 4) whether increased work of breathing contributes to the cachexia seen in some horses with RAO. Six RAO horses and six control horses underwent indirect calorimetric measures of REE and pulmonary function testing using the esophageal balloon-pneumotachograph method before and after treatment with ipratropium bromide, a parasympatholytic bronchodilator agent, at 4-h intervals for a 24-h period. Body condition scoring was performed, and an estimate of fat mass was determined via B-mode ultrasonography. O2 and CO2 fractions, respiratory airflow, respiratory rate, and pleural pressure changes were recorded, and O2 consumption, CO2 production, REE, pulmonary resistance, dynamic elastance, and tidal volume were calculated. In addition, we performed lung function testing and calorimetry both before and after sedation in two control horses. RAO horses had significantly lower body condition scores (2.8 ± 1.0 vs. 6.4 ± 1.2) and significantly greater O2 consumption than controls (4.93 ± 1.30 vs. 2.93 ± 0.70 ml·kg−1·min−1). After bronchodilation, there was no significant difference in O2 consumption between RAO horses and controls, although there remained evidence of residual airway obstruction. There was a strong correlation between O2 consumption and indexes of airway obstruction. Xylazine sedation was not associated with changes in pulmonary function but did result in markedly decreased REE in controls

Semiclassical approximation to supersymmetric quantum gravity

We develop a semiclassical approximation scheme for the constraint equations of supersymmetric canonical quantum gravity. This is achieved by a Born-Oppenheimer type of expansion, in analogy to the case of the usual Wheeler-DeWitt equation. The formalism is only consistent if the states at each order depend on the gravitino field. We recover at consecutive orders the Hamilton-Jacobi equation, the functional Schrodinger equation, and quantum gravitational correction terms to this Schrodinger equation. In particular, the following consequences are found: (i) the Hamilton-Jacobi equation and therefore the background spacetime must involve the gravitino, (ii) a (many fingered) local time parameter has to be present on $SuperRiem \Sigma$ (the space of all possible tetrad and gravitino fields), (iii) quantum supersymmetric gravitational corrections affect the evolution of the very early universe. The physical meaning of these equations and results, in particular the similarities to and differences from the pure bosonic case, are discussed.Comment: 34 pages, clarifications added, typos correcte

Experiences in the Integration of Design Across the Mechanical Engineering Curriculum

The Faculty of the School of Mechanical Engineering at Purdue University have effected a major change in the Purdue Mechanical Engineering program by integrating design throughout the curriculum. In doing so, a significant level of faculty interaction has been achieved as well. The goals of the curriculum revision are: (1) to improve student skills in how to solve open-ended design problems, (2) to reduce the core of the curriculum to allow flexibility in course selection, and allow time for solving design problems, (3) to improve student skills in team work and communications, and (4) to improve student skills in using computers as tools for solving engineering problems. Reduction of the core allowed the addition of a sophomore cornerstone design course. This cornerstone course teaches students how to solve open-ended problems, bridging the gap between solution strategies that are effective for the science and mathematics courses, and those needed to solve open-ended engineering problems. The design fundamentals taught in the cornerstone course are applied in the core courses, such as heat transfer, thermodynamics, instrumentation, and machine design. The senior design experience comes primarily from a design elective and the capstone design course. This paper presents an overview of the curriculum revision process, and the changes which resulted from it. It also discusses the issues associated with infusing design projects into core courses which have traditionally focused on teaching engineering science fundamentals. Plans for the future evolution of the curriculum are also discussed