297 research outputs found

    Discrete charging of metallic grains: Statistics of addition spectra

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    We analyze the statistics of electrostatic energies (and their differences) for a quantum dot system composed of a finite number KK of electron islands (metallic grains) with random capacitance-inductance matrix CC, for which the total charge is discrete, Q=NeQ=Ne (where ee is the charge of an electron and NN is an integer). The analysis is based on a generalized charging model, where the electrons are distributed among the grains such that the electrostatic energy E(N) is minimal. Its second difference (inverse compressibility) χN=E(N+1)2E(N)+E(N1)\chi_{N}=E(N+1)-2 E(N)+E(N-1) represents the spacing between adjacent Coulomb blockade peaks appearing when the conductance of the quantum dot is plotted against gate voltage. The statistics of this quantity has been the focus of experimental and theoretical investigations during the last two decades. We provide an algorithm for calculating the distribution function corresponding to χN\chi_{N} and show that this function is piecewise polynomial.Comment: 21 pages, no figures, mathematical nomenclature (except for Abstract and Introduction

    Hepatitis C services at harm reduction centres in the European Union: a 28-country survey

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    Background: In the context of the WHO’s 2016 Viral Hepatitis Strategy and the introduction of treatment that can cure more than 95% of cases with hepatitis C virus (HCV) infection, the European Joint Action on HIV and Co-infection Prevention and Harm Reduction (HA-REACT) undertook a study in the member states of the European Union (EU). It aimed to determine service providers’ understanding of the current services in their respective countries and the barriers experienced by PWID in accessing HCV testing, care and treatment services in their country. Methods: In 2017, 38 purposively selected harm reduction service providers completed a 26-item Englishlanguage online survey addressing the availability, accessibility and funding of HCV services at harm reduction centres. HCV-related data and reported findings were extracted by country or by responding organization. Results: Responses were received from all EU member states. Respondents from 23 countries reported that HCV tests are offered by harm reduction services in their countries, and eight countries reported that addiction specialists in their countries are able to prescribe HCV therapy. Almost half of the respondents (45%) said that their respective organizations had established referral systems with centres providing HCV treatment. Conclusions: Not all EU member states have harm reduction services that provide HCV tests, and many do not have established referral systems with treatment providers. Moreover, the inability of addiction specialists to prescribe HCV treatment points to missed opportunities to make treatment more accessible. Further, discrepancies were noted between the available HCV services and stakeholders’ knowledge about their availability

    Health Outcomes for Clients of Needle and Syringe Programs in Prisons

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    High levels of drug dependence have been observed in the prison population globally, and the sharing of injecting drug equipment in prisons has contributed to higher prevalence of bloodborne diseases in prisoners than in the general population. Few prison needle and syringe programs (PNSPs) exist. We conducted a systematic review to assess evidence regarding health outcomes of PNSPs. We searched peer-reviewed databases for data relating to needle and syringe programs in prisons. The search methodology was conducted in accordance with accepted guidelines. Five studies met review inclusion criteria, and all presented evidence associating PNSPs with one or more health benefits, but the strength of the evidence was low. The outcomes for which the studies collectively demonstrated the strongest evidence were prevention of human immunodeficiency virus and viral hepatitis. Few negative consequences from PNSPs were observed, consistent with previous evidence assessments. More research is needed on PNSP effectiveness, and innovative study designs are needed to overcome methodological limitations of previous research. Until stronger evidence becomes available, policymakers are urged to recognize that not implementing PNSPs has the potential to cause considerable harm, in light of what is currently known about the risks and benefits of needle and syringe programs and PNSPs and about the high prevalence of human immunodeficiency virus and viral hepatitis in prisons

    Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s}=1.96 TeV using Lepton + Jets Events with Secondary Vertex b-tagging

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    We present a measurement of the ttbar production cross section using events with one charged lepton and jets from ppbar collisions at a center-of-mass energy of 1.96 TeV. In these events, heavy flavor quarks from top quark decay are identified with a secondary vertex tagging algorithm. From 162 pb-1 of data collected by the Collider Detector at Fermilab, a total of 48 candidate events are selected, where 13.5 +- 1.8 events are expected from background contributions. We measure a ttbar production cross section of 5.6^{+1.2}_{-1.1} (stat.) ^{+0.9}_{0.6} (syst.) pb.Comment: 28 pages, 20 figures. Published in Physical Review

    The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe

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    The preponderance of matter over antimatter in the early Universe, the dynamics of the supernova bursts that produced the heavy elements necessary for life and whether protons eventually decay --- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our Universe, its current state and its eventual fate. The Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed plan for a world-class experiment dedicated to addressing these questions. LBNE is conceived around three central components: (1) a new, high-intensity neutrino source generated from a megawatt-class proton accelerator at Fermi National Accelerator Laboratory, (2) a near neutrino detector just downstream of the source, and (3) a massive liquid argon time-projection chamber deployed as a far detector deep underground at the Sanford Underground Research Facility. This facility, located at the site of the former Homestake Mine in Lead, South Dakota, is approximately 1,300 km from the neutrino source at Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino charge-parity symmetry violation and mass ordering effects. This ambitious yet cost-effective design incorporates scalability and flexibility and can accommodate a variety of upgrades and contributions. With its exceptional combination of experimental configuration, technical capabilities, and potential for transformative discoveries, LBNE promises to be a vital facility for the field of particle physics worldwide, providing physicists from around the globe with opportunities to collaborate in a twenty to thirty year program of exciting science. In this document we provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess.Comment: Major update of previous version. This is the reference document for LBNE science program and current status. Chapters 1, 3, and 9 provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess. 288 pages, 116 figure

    Mesopontine rostromedial tegmental nucleus neurons projecting to the dorsal raphe and pedunculopontine tegmental nucleus: psychostimulant-elicited Fos expression and collateralization

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    The mesopontine rostromedial tegmental nucleus (RMTg) is a GABAergic structure in the ventral midbrain and rostral pons that, when activated, inhibits dopaminergic neurons in the ventral tegmental area and substantia nigra compacta. Additional strong outputs from the RMTg to the pedunculopontine tegmental nucleus pars dissipata, dorsal raphe nucleus, and the pontomedullary gigantocellular reticular formation were identified by anterograde tracing. RMTg neurons projecting to the ventral tegmental area express the immediate early gene Fos upon psychostimulant administration. The present study was undertaken to determine if neurons in the RMTg that project to the additional structures listed above also express Fos upon psychostimulant administration and, if so, whether single neurons in the RMTg project to more than one of these structures. We found that about 50% of RMTg neurons exhibiting retrograde labeling after injections of retrograde tracer in the dorsal raphe or pars dissipata of the pedunculopontine tegmental nucleus express Fos after acute methamphetamine exposure. Also, we observed that a significant number of RMTg neurons project both to the ventral tegmental area and one of these structures. In contrast, methamphetamine-elicited Fos expression was not observed in RMTg neurons labeled with retrograde tracer following injections into the pontomedullary reticular formation. The findings suggest that the RMTg is an integrative modulator of multiple rostrally projecting structures

    Nomenclature for kidney function and disease: report of a Kidney Disease:Improving Global Outcomes (KDIGO) Consensus Conference

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    The worldwide burden of kidney disease is rising, but public awareness remains limited, underscoring the need for more effective communication by stakeholders in the kidney health community. Despite this need for clarity, the nomenclature for describing kidney function and disease lacks uniformity. In June 2019, Kidney Disease: Improving Global Outcomes (KDIGO) convened a Consensus Conference with the goal of standardizing and refining the nomenclature used in the English language to describe kidney function and disease, and of developing a glossary that could be used in scientific publications. Guiding principles of the conference were that the revised nomenclature should be patient-centered, precise, and consistent with nomenclature used in the KDIGO guidelines. Conference attendees reached general consensus on the following recommendations: (i) to use "kidney" rather than "renal" or "nephro-" when referring to kidney disease and kidney function; (ii) to use "kidney failure" with appropriate descriptions of presence or absence of symptoms, signs, and treatment, rather than "end-stage kidney disease"; (iii) to use the KDIGO definition and classification of acute kidney diseases and disorders (AKD) and acute kidney injury (AKI), rather than alternative descriptions, to define and classify severity of AKD and AKI; (iv) to use the KDIGO definition and classification of chronic kidney disease (CKD) rather than alternative descriptions to define and classify severity of CKD; and (v) to use specific kidney measures, such as albuminuria or decreased glomerular filtration rate (GFR), rather than "abnormal" or "reduced" kidney function to describe alterations in kidney structure and function. A proposed 5-part glossary contains specific items for which there was general agreement. Conference attendees acknowledged limitations of the recommendations and glossary, but they considered standardization of scientific nomenclature to be essential for improving communication

    The genetic architecture of the human cerebral cortex

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    The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder
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