Points of General Relativisitic Shock Wave Interaction are "Regularity Singularities" where Spacetime is Not Locally Flat

We show that the regularity of the gravitational metric tensor in spherically symmetric spacetimes cannot be lifted from $C^{0,1}$ to $C^{1,1}$ within the class of $C^{1,1}$ coordinate transformations in a neighborhood of a point of shock wave interaction in General Relativity, without forcing the determinant of the metric tensor to vanish at the point of interaction. This is in contrast to Israel's Theorem which states that such coordinate transformations always exist in a neighborhood of a point on a smooth single shock surface. The results thus imply that points of shock wave interaction represent a new kind of singularity for perfect fluids evolving in spacetime, singularities that make perfectly good sense physically, that can form from the evolution of smooth initial data, but at which the spacetime is not locally Minkowskian under any coordinate transformation. In particular, at such singularities, delta function sources in the second derivatives of the gravitational metric tensor exist in all coordinate systems of the $C^{1,1}$ atlas, but due to cancelation, the curvature tensor remains uniformly bounded.Comment: This article has been withdrawn since the main result is wrong due to an computational error. See arXiv:1506.04081 and arXiv:1409.5060 for a correction of this error and a proof of the opposite statemen

Modification of integrated partial payload lifting assembly

The Integrated Partial Payload Lifting Assembly (IPPLA) is currently used to transport and load experimental payloads into the cargo bay of the Space Shuttle. It is unable to carry the astronaut/passenger tunnel without a structural modification. The purpose of this design is to create a removalbe modification that will allow the IPPLA to lift and carry the passenger tunnel. Modifications evaluated were full-length insert beams which would extend through the existing strongback arms. These beam proposals were eliminated because of high cost and weight. Other proposals evaluated were attachments of cantilever beams to the existing strongback areas. The cantilever proposals reduced cost and weight compared to the full-length modifications. A third method evaluated was to simply make modifications to one side of the IPPLA therefore reducing the materials of the cantilever proposals by 40 percent. The design of the modification selected was completed with two channel beams jointly welded to a centered steel plate. The extension arm modification is inserted into the existing strongback channel beams and bolted into place. Two extension arms are added to one side of the IPPLA to provide the extra length needed to accommodate the passenger tunnel. The center counterbalance will then be offset about 20 inches to center gravity and therefore maintain horizontal status. The extension arm modification was selected because of minimum cost, low weight, and minimal installation time

The Numerical Simulation of General Relativistic Shock Waves by a Locally Inertial Godunov Method Featuring Dynamical Time Dilation

We introduce what we call a locally inertial Godunov method with dynamical time dilation, and use it to simulate a new one parameter family of general relativistic shock wave solutions of the Einstein equations for a perfect fluid. The forward time solutions resolve the secondary reflected wave (an incoming shock wave) in the Smoller-Temple shock wave model for an explosion into a static singular isothermal sphere. The backward time solutions indicate black hole formation from a smooth underlying solution via collapse associated with an incoming rarefaction wave. As far as we know, this is the first numerical simulation of a fluid dynamical shock wave in general relativity

The effectiveness and satisfaction of web-based physiotherapy in people with spinal cord injury: a pilot randomised controlled trial

Study Design: Pilot randomised controlled trial. Objectives: The aims of this study were to evaluate the effectiveness and participant satisfaction of web-based physiotherapy for people with Spinal Cord Injury (SCI). Setting: Community patients of a national spinal injury unit in a university teaching hospital, Scotland, UK. Methods: Twenty-four participants were recruited and randomised to receive eight weeks of web-based physiotherapy (intervention), twice per week, or usual care (control). Individual exercise programmes were prescribed based upon participant’s abilities. The intervention was delivered via a website (www.webbasedphysio.com) and monitored and progressed remotely by the physiotherapist. Results: Participants logged on to the website an average of 1.4±0.8 times per week. Between-group differences, although not significant were more pronounced for the 6 minute walk test. Participants were positive about using web-based physiotherapy and stated they would be happy to use it again and would recommend it to others. Overall it was rated as either good or excellent. Conclusions: Web-based physiotherapy was feasible and acceptable for people with SCI. Participants achieved good compliance with the intervention, rated the programme highly and beneficial for health and well-being at various states post injury. The results of this study warrant further work with a more homogenous sample

The SCI Exercise Self-Efficacy Scale (ESES): development and psychometric properties

<p>Abstract</p> <p>Background</p> <p>Rising prevalence of secondary conditions among persons with spinal cord injury (SCI) has focused recent attention to potential health promotion programs designed to reduce such adverse health conditions. A healthy lifestyle for people with SCI, including and specifically, the adoption of a vigorous exercise routine, has been shown to produce an array of health benefits, prompting many providers to recommend the implementation of such activity to those with SCI. Successfully adopting such an exercise regimen however, requires confidence in one's ability to engage in exercise or exercise self-efficacy. Exercise self-efficacy has not been assessed adequately for people with SCI due to a lack of validated and reliable scales, despite self efficacy's status as one of the most widely researched concepts and despite its broad application in health promotion studies. Exercise self efficacy supporting interventions for people with SCI are only meaningful if appropriate measurement tools exist. The objective of our study was to develop a psychometrically sound exercise self-efficacy self-report measure for people with SCI.</p> <p>Methods</p> <p>Based on literature reviews, expert comments and cognitive testing, 10 items were included and made up the 4-point Likert SCI Exercise Self-Efficacy Scale (ESES) in its current form. The ESES was administered as part of the first wave of a nationwide survey (n = 368) on exercise behavior and was also tested separately for validity in four groups of individuals with SCI. Reliability and validity testing was performed using SPSS 12.0.</p> <p>Results</p> <p>Cronbach's alpha was .9269 for the ESES. High internal consistency was confirmed in split-half (EQ Length Spearman Brown = .8836). Construct validity was determined using principal component factor analysis by correlating the aggregated ESES items with the Generalised Self Efficacy Scale (GSE). We found that all items loaded on one factor only and that there was a statistically significant correlation between Exercise Self-Efficacy Scale (ESES) and Generalised Self Efficacy Scale (GSE) (Spearman RHO = .316; p < .05; n = 53, 2-sided).</p> <p>Conclusion</p> <p>Preliminary findings indicate that the ESES is a reliable instrument with high internal consistency and scale integrity. Content validity both in terms of face and construct validity is satisfactory.</p

Intermittent Catheter Reimbursement in the United States: The Experience of Nine Stakeholders Through the Lens of Actor-Network Theory

A narrow interpretation of “medical necessity” can result in poorer health as well as a more restricted life for people with disabilities. We examined the impact of US policy on reimbursement of intermittent catheters (ICs) on the lives of people with neurogenic bladder (NB) who require catheters to urinate. We conducted in-depth, longitudinal interviews with nine stakeholders. Actor-Network Theory was used to describe interactions among human agents, IC products, and policies in the reimbursement arena. Restrictions on the type and quantities of ICs reimbursed emerged as the most potent inhibitor to health and wellbeing among consumers with NB. IC suppliers, due to the large number of other stakeholders with whom they interact in the reimbursement process, emerged as strong enablers of preferred IC use among people with NB. Lack of an impartial central clearinghouse on IC products and coverage impeded consumers’ ability to make informed decisions