228 research outputs found

    Geometric local epsilon factors

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    Inspired by the work of Laumon on ε\varepsilon-factors and by Deligne's 19741974 letter to Serre, we give an explicit cohomological definition of ε\varepsilon-factors for \ell-adic Galois representations over henselian discrete valuation fields of positive equicharacteristic pp \neq \ell, with (not necessarily finite) perfect residue fields. These geometric local ε\varepsilon-factors are completely characterized by an explicit list of purely local properties, such as an induction formula and the compatibility with geometric class field theory in rank 11, and satisfy a product formula for \ell-adic sheaves on a curve over a perfect field of characteristic pp.Comment: 92 page

    Orthogonal polynomial expansions for the Riemann xi function

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    We study infinite series expansions for the Riemann xi function Ξ(t)\Xi(t) in three specific families of orthogonal polynomials: (1) the Hermite polynomials; (2) the symmetric Meixner-Pollaczek polynomials Pn(3/4)(x;π/2)P_n^{(3/4)}(x;\pi/2); and (3) the continuous Hahn polynomials pn(x;34,34,34,34)p_n\left(x; \frac34,\frac34,\frac34,\frac34\right). The first expansion was discussed in earlier work by Tur\'an, and the other two expansions are new. For each of the three expansions, we derive formulas for the coefficients, show that they appear with alternating signs, derive formulas for their asymptotic behavior, and derive additional interesting properties and relationships. We also apply some of the same techniques to prove a new asymptotic formula for the Taylor coefficients of the Riemann xi function. Our results continue and expand the program of research initiated in the 1950s by Tur\'an, who proposed using the Hermite expansion of the Riemann xi function as a tool to gain insight into the location of the Riemann zeta zeros. We also uncover a connection between Tur\'an's ideas and the separate program of research involving the so-called De Bruijn-Newman constant. Most significantly, the phenomena associated with the new expansions in the Meixner-Pollaczek and continuous Hahn polynomial families suggest that those expansions may be even more natural tools than the Hermite expansion for approaching the Riemann hypothesis and related questions.Comment: Changes from previous version: typo corrections, added references and other minor improvements to Chapter 4, formattin

    Power Factor Enhancement in Solution‐Processed Organic n‐Type Thermoelectrics Through Molecular Design

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    A new class of high‐performance n‐type organic thermoelectric materials, self‐doping perylene diimide derivatives with modified side chains, is reported. These materials achieve the highest n‐type thermoelectric performance of solution‐processed organic materials reported to date, with power factors as high as 1.4 μW/mK^2. These results demonstrate that molecular design is a promising strategy for enhancing organic thermoelectric performance

    HIV Treatment as Prevention: Debate and Commentary-Will Early Infection Compromise Treatment-as-Prevention Strategies?

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    Universal HIV testing and immediate antiretroviral therapy for infected individuals has been proposed as a way of reducing the transmission of HIV and thereby bringing the HIV epidemic under control. It is unclear whether transmission during early HIV infection—before individuals are likely to have been diagnosed with HIV and started on antiretroviral therapy—will compromise the effectiveness of treatment as prevention. This article presents two opposing viewpoints by Powers, Miller, and Cohen, and Williams and Dye, followed by a commentary by Fraser

    Qualitative evaluation of mental health services for clients with limited English proficiency

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    BACKGROUND: To meet federal requirements under Title VI of the Civil Rights Act, the state of California instituted policies requiring that comprehensive mental health services in native languages be made available to limited English proficiency (LEP) populations when concentrations exceed “threshold” levels. METHODS: This paper builds on promising results from quantitative evaluations by reporting on qualitative interviews with Latino and Vietnamese LEP clients in mental health services (N = 20) to examine the awareness, impact, and implications of these threshold language policies. RESULTS: Results suggest that, while individuals are often not aware of the policies themselves, the language-related services they receive that are prompted by the policies are critical to treatment initiation and retention. Results also convey the complexities of using interpreters for sensitive psychological topics, and suggest that, for LEP individuals seeking mental health treatment, providers who speak their native languages are generally preferred. CONCLUSIONS: Access to language-appropriate services seems to be an important part of why LEP populations seek mental health treatment. However, there are multiple variables that factor into the usage and usefulness of such services

    Barriers to asymptomatic screening and other STD services for adolescents and young adults: focus group discussions

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    BACKGROUND: Sexually transmitted diseases (STDs) are a major public health problem among young people and can lead to the spread of HIV. Previous studies have primarily addressed barriers to STD care for symptomatic patients. The purpose of our study was to identify perceptions about existing barriers to and ideal services for STDs, especially asymptomatic screening, among young people in a southeastern community. METHODS: Eight focus group discussions including 53 White, African American, and Latino youth (age 14–24) were conducted. RESULTS: Perceived barriers to care included lack of knowledge of STDs and available services, cost, shame associated with seeking services, long clinic waiting times, discrimination, and urethral specimen collection methods. Perceived features of ideal STD services included locations close to familiar places, extended hours, and urine-based screening. Television was perceived as the most effective route of disseminating STD information. CONCLUSIONS: Further research is warranted to evaluate improving convenience, efficiency, and privacy of existing services; adding urine-based screening and new services closer to neighborhoods; and using mass media to disseminate STD information as strategies to increase STD screening

    A Novel G Protein-Coupled Receptor of Schistosoma mansoni (SmGPR-3) Is Activated by Dopamine and Is Widely Expressed in the Nervous System

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    Schistosomes have a well developed nervous system that coordinates virtually every activity of the parasite and therefore is considered to be a promising target for chemotherapeutic intervention. Neurotransmitter receptors, in particular those involved in neuromuscular control, are proven drug targets in other helminths but very few of these receptors have been identified in schistosomes and little is known about their roles in the biology of the worm. Here we describe a novel Schistosoma mansoni G protein-coupled receptor (named SmGPR-3) that was cloned, expressed heterologously and shown to be activated by dopamine, a well established neurotransmitter of the schistosome nervous system. SmGPR-3 belongs to a new clade of “orphan” amine-like receptors that exist in schistosomes but not the mammalian host. Further analysis of the recombinant protein showed that SmGPR-3 can also be activated by other catecholamines, including the dopamine metabolite, epinine, and it has an unusual antagonist profile when compared to mammalian receptors. Confocal immunofluorescence experiments using a specific peptide antibody showed that SmGPR-3 is abundantly expressed in the nervous system of schistosomes, particularly in the main nerve cords and the peripheral innervation of the body wall muscles. In addition, we show that dopamine, epinine and other dopaminergic agents have strong effects on the motility of larval schistosomes in culture. Together, the results suggest that SmGPR-3 is an important neuronal receptor and is probably involved in the control of motor activity in schistosomes. We have conducted a first analysis of the structure of SmGPR-3 by means of homology modeling and virtual ligand-docking simulations. This investigation has identified potentially important differences between SmGPR-3 and host dopamine receptors that could be exploited to develop new, parasite-selective anti-schistosomal drugs
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