110 research outputs found

    Casimir interaction between two concentric cylinders: exact versus semiclassical results

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    The Casimir interaction between two perfectly conducting, infinite, concentric cylinders is computed using a semiclassical approximation that takes into account families of classical periodic orbits that reflect off both cylinders. It is then compared with the exact result obtained by the mode-by-mode summation technique. We analyze the validity of the semiclassical approximation and show that it improves the results obtained through the proximity theorem.Comment: 28 pages, 5 figures include

    The Relational Power of Education: The immeasurability of knowledge, value and meaning

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    Recognizing the challenge of adequate evaluation in higher education, this essay introduces some of the critical, alternative-seeking conversation about educational measurement. The thesis is that knowledge, value, and meaning emerge in the relational dynamics of education, thus requiring complex approaches to evaluation, utilizing relational criteria. The method of the essay is to analyse two educational case studies à à à ¢ a travel seminar and a classroom course à à à ¢ in dialogue with educational literature and a process-relational philosophy of education. Building from this analysis, the essay concludes with proposals for relational criteria of evaluation: relations with self, community and culture, difference, earth, and social structures

    Employment as HIV Prevention: An Employment Support Intervention for Adolescent Men Who Have Sex With Men and Adolescent Transgender Women of Color

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    BACKGROUND: The purpose of this study was to adapt and pilot-test an employment support, primary HIV intervention tailored to the needs of adolescent men who have sex with men and adolescent transgender women of color. SETTING: The intervention was implemented in 2 settings: controlled environment (Phase 1) and real-world community-based (Phase 2) setting in Chicago, IL. METHODS: Eighty-seven adolescent men who have sex with men and adolescent transgender women of color ages 16-24 participated in Work2Prevent , a 4-session employment and HIV prevention intervention, designed to increase job-readiness and reduce HIV risk. Intervention sessions consisted of group activities: educational games, roleplaying/modeling behavior, and self-regulation exercises. Participants were assessed at baseline, postintervention, and 8-month (Phase 1) or 3-month follow-up (Phase 2). RESULTS: Participants evaluated Work2Prevent as feasible and acceptable, rating intervention quality, usefulness, and satisfaction highly. Overall, 59.6% (Phase 1) and 85.0% (Phase 2) participants attended 2 or more sessions. At 8 months, Phase 1 participants reported a mean increase of 11.4 hours worked per week. Phase 2 participants reported a mean increase of 5.2 hours worked per week and an increase in job-seeking self-efficacy. Phase 2 participants also reported a decrease in transactional sex work. CONCLUSION: Work2Prevent is one of the first structural primary HIV interventions to specifically focus on adolescent employment readiness. Findings suggest Work2Prevent is feasible and acceptable, improved adolescent employment outcomes, and reduced HIV risk associated with transactional sex work. Our study underscores the need for alternative pathways, such as addressing socioeconomic determinants, to prevent adolescent HIV infection

    Lattice gauge theory with baryons at strong coupling

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    We study the effective Hamiltonian for strong-coupling lattice QCD in the case of non-zero baryon density. In leading order the effective Hamiltonian is a generalized antiferromagnet. For naive fermions, the symmetry is U(4N_f) and the spins belong to a representation that depends on the local baryon number. Next-nearest-neighbor (nnn) terms in the Hamiltonian break the symmetry to U(N_f) x U(N_f). We transform the quantum problem to a Euclidean sigma model which we analyze in a 1/N_c expansion. In the vacuum sector we recover spontaneous breaking of chiral symmetry for the nearest-neighbor and nnn theories. For non-zero baryon density we study the nearest-neighbor theory only, and show that the pattern of spontaneous symmetry breaking depends on the baryon density.Comment: 31 pages, 5 EPS figures. Corrected Eq. (6.1

    Optical Light Curves of Supernovae

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    Photometry is the most easily acquired information about supernovae. The light curves constructed from regular imaging provide signatures not only for the energy input, the radiation escape, the local environment and the progenitor stars, but also for the intervening dust. They are the main tool for the use of supernovae as distance indicators through the determination of the luminosity. The light curve of SN 1987A still is the richest and longest observed example for a core-collapse supernova. Despite the peculiar nature of this object, as explosion of a blue supergiant, it displayed all the characteristics of Type II supernovae. The light curves of Type Ib/c supernovae are more homogeneous, but still display the signatures of explosions in massive stars, among them early interaction with their circumstellar material. Wrinkles in the near-uniform appearance of thermonuclear (Type Ia) supernovae have emerged during the past decade. Subtle differences have been observed especially at near-infrared wavelengths. Interestingly, the light curve shapes appear to correlate with a variety of other characteristics of these supernovae. The construction of bolometric light curves provides the most direct link to theoretical predictions and can yield sorely needed constraints for the models. First steps in this direction have been already made.Comment: To be published in:"Supernovae and Gamma Ray Bursters", Lecture Notes in Physics (http://link.springer.de/series/lnpp

    Recommendations for reporting ion mobility Mass Spectrometry measurements

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    Here we present a guide to ion mobility mass spectrometry experiments, which covers both linear and nonlinear methods: what is measured, how the measurements are done, and how to report the results, including the uncertainties of mobility and collision cross section values. The guide aims to clarify some possibly confusing concepts, and the reporting recommendations should help researchers, authors and reviewers to contribute comprehensive reports, so that the ion mobility data can be reused more confidently. Starting from the concept of the definition of the measurand, we emphasize that (i) mobility values (K0) depend intrinsically on ion structure, the nature of the bath gas, temperature, and E/N; (ii) ion mobility does not measure molecular surfaces directly, but collision cross section (CCS) values are derived from mobility values using a physical model; (iii) methods relying on calibration are empirical (and thus may provide method‐dependent results) only if the gas nature, temperature or E/N cannot match those of the primary method. Our analysis highlights the urgency of a community effort toward establishing primary standards and reference materials for ion mobility, and provides recommendations to do so. © 2019 The Authors. Mass Spectrometry Reviews Published by Wiley Periodicals, Inc

    New insights into the genetic etiology of Alzheimer's disease and related dementias

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    Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele
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