Composite black holes in external fields

The properties of composite black holes in the background of electric or magnetic flux tubes are analyzed, both when the black holes remain in static equilibrium and when they accelerate under a net external force. To this effect, we present a number of exact solutions (generalizing the Melvin, C and Ernst solutions) describing these configurations in a theory that admits composite black holes with an arbitrary number of constituents. The compositeness property is argued to be independent of supersymmetry. Even if, in general, the shape of the horizon is distorted by the fields, the dependence of the extreme black hole area on the charges is shown to remain unchanged by either the external fields or the acceleration. We also discuss pair creation of composite black holes. In particular, we extend a previous analysis of pair creation of massless holes. Finally, we give the generalization of our solutions to include non-extreme black holes.Comment: 27 pages, LaTe

Developing the next generation of dissemination and implementation researchers: Insights from initial trainees

BACKGROUND: Dissemination and implementation (D&I) research is a relatively young discipline, underscoring the importance of training and career development in building and sustaining the field. As such, D&I research faces several challenges in designing formal training programs and guidance for career development. A cohort of early-stage investigators (ESI) recently involved in an implementation research training program provided a resource for formative data in identifying needs and solutions around career development. RESULTS: Responses outlined fellows’ perspectives on the perceived usefulness and importance of, as well as barriers to, developing practice linkages, acquiring additional methods training, academic advancement, and identifying institutional supports. Mentorship was a cross-cutting issue and was further discussed in terms of ways it could foster career advancement in the context of D&I research. CONCLUSIONS: Advancing an emerging field while simultaneously developing an academic career offers a unique challenge to ESIs in D&I research. This article summarizes findings from the formative data that outlines some directions for ESIs and provides linkages to the literature and other resources on key points

Electromechanical Robotic Platform for Patient Motion Management in Radiotherapy

Head and neck cancer is often treated with radiation therapy. During this treatment, patient movement causes healthy cells to receive excessive radiological dose. We have designed an electromechanical robotic platform that enables compensation of patient movement during treatment. This project includes analysis of materials and motion of the system, design of the control system and model, and the functional prototype. The design of the robotic platform will be compatible with pre-existing head and mouth harnesses in order to keep a patient’s head steady while the patient’s headrest in motion. For radiotherapy, this system requires radio-compatible materials. Through the use of computer-aided engineering technology and technical calculations, the project team demonstrated the feasibility of the design. Finite element analysis was used to determine which specific materials were best suited for the project, taking into consideration the difficulty in obtaining certain materials. The development of a prototype device was established with electrical motors to allow for precise controls and movements of the device. Overall, this project will benefit patients by ensuring the optimal treatment delivery. The project will lead to advancement in patient motion management systems and radiation therapy, and will serve as a foundation for future radiotherapy systems.https://scholarscompass.vcu.edu/capstone/1131/thumbnail.jp

Understanding the Tibial-Pedal Arterial Anatomy: Practical Points for Current Clinical Presentations

peer reviewedThe lower extremity arterial vasculature encompasses a balanced, tapering distribution closely related to the muscular compartments of the leg and foot. From the main ilio-femoral inflow to further remote capillary vessels, a harmonious pyramid of gradually tapering limb perfusion is created. This impressive vascular system is structured into several ranks of tapering vessels that correspond with angiosomes in the lower extremities. Each of these levels expresses unique anatomic features when threatened by atherosclerotic ischemic disease. As atherosclerosis progressively worsens, the vascular anatomy, including the tibio-pedal trunks, foot arches, and collateral distributions, continuously provides coordinated support and dynamic adaptations in regional perfusion of the foot, in accordance with various endogenous and exogenous factors. Critical limb ischemia (CLI) involves characteristic infragenicular patterns of arterial disease and related compensatory flow paths that are useful for interventionists to acknowledge and understand. The present article briefly reviews the main anatomical features describing infra-popliteal arterial vasculature with, and without, ischemic impairment, in accordance with practical clinical issues encountered in daily practice

Duality between Electric and Magnetic Black Holes

A number of attempts have recently been made to extend the conjectured $S$ duality of Yang Mills theory to gravity. Central to these speculations has been the belief that electrically and magnetically charged black holes, the solitons of quantum gravity, have identical quantum properties. This is not obvious, because although duality is a symmetry of the classical equations of motion, it changes the sign of the Maxwell action. Nevertheless, we show that the chemical potential and charge projection that one has to introduce for electric but not magnetic black holes exactly compensate for the difference in action in the semi-classical approximation. In particular, we show that the pair production of electric black holes is not a runaway process, as one might think if one just went by the action of the relevant instanton. We also comment on the definition of the entropy in cosmological situations, and show that we need to be more careful when defining the entropy than we are in an asymptotically-flat case.Comment: 23 pages, revtex, no figures. Major revision: two sections on the electric Ernst solution adde

Black Hole Pair Creation and the Entropy Factor

It is shown that in the instanton approximation the rate of creation of black holes is always enhanced by a factor of the exponential of the black hole entropy relative to the rate of creation of compact matter distributions (stars). This result holds for any generally covariant theory of gravitational and matter fields that can be expressed in Hamiltonian form. It generalizes the result obtained previously for the pair creation of magnetically charged black holes by a magnetic field in Einstein--Maxwell theory. The particular example of pair creation of electrically charged black holes by an electric field in Einstein--Maxwell theory is discussed in detail.Comment: (12 pages, ReVTeX) Revised version of "Pair Creation of Electrically Charged Black Holes". New section shows that the BH pair creation rate is enhanced by a factor $\exp(BH entropy)$ for any Hamiltonian gravity + matter theor

A novel patient engagement platform using accessible text messages and calls (Epharmix): Feasibility study

BACKGROUND: Patient noncompliance with therapy, treatments, and appointments represents a significant barrier to improving health care delivery and reducing the cost of care. One method to improve therapeutic adherence is to improve feedback loops in getting clinically acute events and issues to the relevant clinical providers as necessary (ranging from detecting hypoglycemic events for patients with diabetes to notifying the provider when patients are out of medications). Patients often don\u27t know which information should prompt a call to their physician and proactive checks by the clinics themselves can be very resource intensive. We hypothesized that a two-way SMS system combined with a platform web service for providers would enable both high patient engagement but also the ability to detect relevant clinical alerts. OBJECTIVE: The objectives of this study are to develop a feasible two-way automated SMS/phone call + web service platform for patient-provider communication, and then study the feasibility and acceptability of the Epharmix platform. First, we report utilization rates over the course of the first 18 months of operation including total identified clinically significant events, and second, review results of patient user-satisfaction surveys for interventions for patients with diabetes, COPD, congestive heart failure, hypertension, surgical site infections, and breastfeeding difficulties. METHODS: To test this question, we developed a web service + SMS/phone infrastructure ( Epharmix ). Utilization results were measured based on the total number of text messages or calls sent and received, with percentage engagement defined as a patient responding to a text message at least once in a given week, including the number of clinically significant alerts generated. User satisfaction surveys were sent once per month over the 18 months to measure satisfaction with the system, frequency and degree of communication. Descriptive statistics were used to describe the above information. RESULTS: In total, 28,386 text messages and 24,017 calls were sent to 929 patients over 9 months. Patients responded to 80% to 90% of messages allowing the system to detect 1164 clinically significant events. Patients reported increased satisfaction and communication with their provider. Epharmix increased the number of patient-provider interactions to over 10 on average in any given month for patients with diabetes, COPD, congestive heart failure, hypertension, surgical site infections, and breastfeeding difficulties. CONCLUSIONS: Engaging high-risk patients remains a difficult process that may be improved through novel, digital health interventions. The Epharmix platform enables increased patient engagement with very low risk to improve clinical outcomes. We demonstrated that engagement among high-risk populations is possible when health care comes conveniently to where they are

Synergistic Ca^(2+) Responses by Gα_i- and Gα_q-coupled G-protein-coupled Receptors Require a Single PLCβ Isoform That Is Sensitive to Both Gβ_γ and Gα_q

Cross-talk between Gα_i- and Gα_q-linked G-protein-coupled receptors yields synergistic Ca^(2+) responses in a variety of cell types. Prior studies have shown that synergistic Ca^(2+) responses from macrophage G-protein-coupled receptors are primarily dependent on phospholipase Cβ3 (PLCβ3), with a possible contribution of PLCβ2, whereas signaling through PLCβ4 interferes with synergy. We here show that synergy can be induced by the combination of Gβγ and Gαq activation of a single PLCβ isoform. Synergy was absent in macrophages lacking both PLCβ2 and PLCβ3, but it was fully reconstituted following transduction with PLCβ3 alone. Mechanisms of PLCβ-mediated synergy were further explored in NIH-3T3 cells, which express little if any PLCβ2. RNAi-mediated knockdown of endogenous PLCβs demonstrated that synergy in these cells was dependent on PLCβ3, but PLCβ1 and PLCβ4 did not contribute, and overexpression of either isoform inhibited Ca^(2+) synergy. When synergy was blocked by RNAi of endogenous PLCβ3, it could be reconstituted by expression of either human PLCβ3 or mouse PLCβ2. In contrast, it could not be reconstituted by human PLCβ3 with a mutation of the Y box, which disrupted activation by Gβγ, and it was only partially restored by human PLCβ3 with a mutation of the C terminus, which partly disrupted activation by Gα_q. Thus, both Gβγ and Gα_q contribute to activation of PLCβ3 in cells for Ca^(2+) synergy. We conclude that Ca^(2+) synergy between Gα_i-coupled and Gα_q-coupled receptors requires the direct action of both Gβγ and Gαq on PLCβ and is mediated primarily by PLCβ3, although PLCβ2 is also competent

The Allen Telescope Array: The First Widefield, Panchromatic, Snapshot Radio Camera for Radio Astronomy and SETI

The first 42 elements of the Allen Telescope Array (ATA-42) are beginning to deliver data at the Hat Creek Radio Observatory in Northern California. Scientists and engineers are actively exploiting all of the flexibility designed into this innovative instrument for simultaneously conducting surveys of the astrophysical sky and conducting searches for distant technological civilizations. This paper summarizes the design elements of the ATA, the cost savings made possible by the use of COTS components, and the cost/performance trades that eventually enabled this first snapshot radio camera. The fundamental scientific program of this new telescope is varied and exciting; some of the first astronomical results will be discussed.Comment: Special Issue of Proceedings of the IEEE: "Advances in Radio Telescopes", Baars,J. Thompson,R., D'Addario, L., eds, 2009, in pres