Static Self-Forces in a Five-Dimensional Black Hole Spacetime

We obtain the electric field and scalar field for a static point charge in closed form in the 5D Schwarzschild-Tangherlini black hole spacetime. We then compute the static self-force in each of these cases by assuming that the appropriate singular field is a 4D Hadamard Green's function on the constant time Riemannian slice. It is well known that the Hadamard Green's function involves an arbitrary regular biscalar $W_{0}(x,x')$, whose coincidence limit $w(x)$ appears in the expression for the self-force. We develop an axiomatic approach to reduce this arbitrary function to a single arbitrary dimensionless coefficient. We show that in the context of this approach to regularization, the self-force does not depend on any undetermined length-scale and need not depend on the internal structure of the charge.Comment: Agrees with published versio

Self-forces in arbitrary dimensions

Bodies coupled to electromagnetic or other long-range fields are subject to radiation reaction and other effects in which their own fields can influence their motion. Self-force phenomena such as these have been poorly understood for spacetime dimensions not equal to four, despite the relevance of differing dimensionalities for holographic duals, effectively two-dimensional condensed matter and fluid systems, and so on. We remedy this by showing that forces and torques acting on extended electromagnetic charges in all dimensions $d \geq 3$ have the same functional form as the usual test body expressions, except that the electromagnetic field appearing in those expressions is not the physical one; it is an effective surrogate. For arbitrary even $d \geq 4$, our surrogate field locally satisfies the source-free field equations, and is conceptually very similar to what arises in the Detweiler-Whiting prescription previously established when $d=4$. The odd-dimensional case is different, involving effective fields which are not necessarily source-free. Moreover, we find a 1-parameter family of natural effective fields for each odd $d$, where the free parameter--a lengthscale--is degenerate with (finite) renormalizations of a body's stress-energy tensor. While different parameter choices can result in different forces, they do so without affecting physical observables. Having established these general results, explicit point-particle self-forces are derived in odd-dimensional Minkowski spacetimes. Simple examples are discussed for $d=3$ and $d=5$, one of which illustrates that the particularly slow decay of fields in three spacetime dimensions results in particles creating their own "preferred rest frames:" Initially-static charges which are later perturbed have a strong tendency to return to rest. Our results easily extend also to the scalar and gravitational self-force problems.Comment: 6 page

Quantitative Assessment of Children with Osteogenesis Imperfecta

Assessments of children with Osteogenesis Imperfecta (OI) are typically limited to a physical exam and observations from a clinician during a hospital visit. Often quantitative information such as bone mineral density and outcome questionnaires is obtained, but with the increasing prevalence of motion analysis and other performance type laboratories, there are many other tools available, which could be beneficial to this patient population. These laboratories can provide date supplementary to morphologic and radiographic data that is helpful in tracking changes in the patient’s functional abilities, recover from fracture, and treatment outcomes. This chapter will cover some useful evaluation methods for children with the most commonly seen types of OI and provide some examples of their test results

The Rationale of Autologously Prepared Bone Marrow Aspirate Concentrate for use in Regenerative Medicine Applications

Autologously prepared bone marrow aspirate concentrates, have the potential to play an adjunctive role in various patient pathologies that have not been able to heal with conventional treatment modalities. The use of bone marrow aspirate (BMA) and concentrates in regenerative medicine treatment plans and clinical applications is based on the fact that bone marrow cells, including progenitor and nucleated cells, platelets, and other cytokines, support in tissue healing and tissue regenerative processes. The use of concentrated BMA cells focuses primarily on mesenchymal stem cells (MSCs), with the ability to self-renew and differentiate into multiple cell types. Concentrated bone marrow cells can be retrieved from harvested BMA and ensuing minimal manipulative cell processing techniques, executed at point of care (POC). The application of bone marrow biological therapies may offer solutions in musculoskeletal pathologies, spinal disorders, chronic wound care, and critical limb ischemia (CLI), to effectively change the local microenvironment to support in tissue healing and facilitate tissue regeneration. This chapter will address the cellular content of bone marrow tissue, harvesting and preparation techniques, and discuss the biological characteristics of individual marrow cells, their inter-connectivity, and deliberate on the effects of BMA concentration

The Pole Behaviour of the Phase Derivative of the Short-Time Fourier Transform

The short-time Fourier transform (STFT) is a time-frequency representation widely used in applications, for example in audio signal processing. Recently it has been shown that not only the amplitude, but also the phase of this representation can be successfully exploited for improved analysis and processing. In this paper we describe a rather peculiar pole phenomenon in the phase derivative, a recurring pattern that appears in a characteristic way in the neighborhood around any of the zeros of the STFT, a negative peak followed by a positive one. We describe this phenomenon numerically and provide a complete analytical explanation.Comment: 15 pages, 4 figures; Applied and Computational Harmonic Analysis (in press), available online 22 October 201

Facilitators and Barriers to Prescribing PreExposure Prophylaxis (PrEP) for the Prevention of HIV

Background: What is PrEP and who gets it? PrEP is the use of medication by individuals to prevent HIV contraction, approved in 2012 after demonstrating safety and efficacy in the iPrEx study and Partners PrEP2 trials. HIV infection risk is 92% lower in patients using PrEP. Truvada®, a combination of tenofovir and emtricitabine taken orally daily, is the only approved PrEP regimen and is intended to compliment other prevention strategies such as condoms. HIV negative-individuals at risk for exposure to HIV have been identified as men who have sex with men (MSM), IV drug users, heterosexuals who have unprotected sex with partners of unknown HIV status, and those in serodiscordant relationships. Barriers to PrEP Implementation PrEP is effective when patients adhere; however, both the medical community and some high-risk populations have been slow to adopt it as an HIV prevention strategy. Surveys have shown clinicians perceived barriers to PrEP such as adverse side effects, viral drug resistance, increased high-risk behavior, cost, and training. HIV in Vermont New diagnoses of HIV among Vermont residents has remained relatively stable over the last twenty years. Vermont CARES, a non-profit, offers free and anonymous HIV tests and in-person risk-reduction counseling. Clients are increasingly asking about PrEP as a prevention strategy, but the response from the medical community is difficult to ascertain.https://scholarworks.uvm.edu/comphp_gallery/1235/thumbnail.jp