1,519 research outputs found

    Pricing Multi-Unit Markets

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    We study the power and limitations of posted prices in multi-unit markets, where agents arrive sequentially in an arbitrary order. We prove upper and lower bounds on the largest fraction of the optimal social welfare that can be guaranteed with posted prices, under a range of assumptions about the designer's information and agents' valuations. Our results provide insights about the relative power of uniform and non-uniform prices, the relative difficulty of different valuation classes, and the implications of different informational assumptions. Among other results, we prove constant-factor guarantees for agents with (symmetric) subadditive valuations, even in an incomplete-information setting and with uniform prices

    Transmission tree of the highly pathogenic avian influenza (H5N1) epidemic in Israel, 2015

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    The transmission tree of the Israeli 2015 epidemic of highly pathogenic avian influenza (H5N1) was modelled by combining the spatio-temporal distribution of the outbreaks and the genetic distance between virus isolates. The most likely successions of transmission events were determined and transmission parameters were estimated. It was found that the median infectious pressure exerted at 1 km was 1.59 times (95% CI 1.04, 6.01) and 3.54 times (95% CI 1.09, 131.75) higher than that exerted at 2 and 5 km, respectively, and that three farms were responsible for all seven transmission events. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13567-016-0393-2) contains supplementary material, which is available to authorized users

    Viral adaptation to host: a proteome-based analysis of codon usage and amino acid preferences

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    Viruses differ markedly in their specificity toward host organisms. Here, we test the level of general sequence adaptation that viruses display toward their hosts. We compiled a representative data set of viruses that infect hosts ranging from bacteria to humans. We consider their respective amino acid and codon usages and compare them among the viruses and their hosts. We show that bacteria-infecting viruses are strongly adapted to their specific hosts, but that they differ from other unrelated bacterial hosts. Viruses that infect humans, but not those that infect other mammals or aves, show a strong resemblance to most mammalian and avian hosts, in terms of both amino acid and codon preferences. In groups of viruses that infect humans or other mammals, the highest observed level of adaptation of viral proteins to host codon usages is for those proteins that appear abundantly in the virion. In contrast, proteins that are known to participate in host-specific recognition do not necessarily adapt to their respective hosts. The implication for the potential of viral infectivity is discussed

    Nagaoka ferromagnetism observed in a quantum dot plaquette

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    Engineered, highly-controllable quantum systems hold promise as simulators of emergent physics beyond the capabilities of classical computers. An important problem in many-body physics is itinerant magnetism, which originates purely from long-range interactions of free electrons and whose existence in real systems has been subject to debate for decades. Here we use a quantum simulator consisting of a four-site square plaquette of quantum dots to demonstrate Nagaoka ferromagnetism. This form of itinerant magnetism has been rigorously studied theoretically but has remained unattainable in experiment. We load the plaquette with three electrons and demonstrate the predicted emergence of spontaneous ferromagnetic correlations through pairwise measurements of spin. We find the ferromagnetic ground state is remarkably robust to engineered disorder in the on-site potentials and can induce a transition to the low-spin state by changing the plaquette topology to an open chain. This demonstration of Nagaoka ferromagnetism highlights that quantum simulators can be used to study physical phenomena that have not yet been observed in any system before. The work also constitutes an important step towards large-scale quantum dot simulators of correlated electron systems

    NNLO corrections to top-pair production at hadron colliders: the all-fermionic scattering channels

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    This is a second paper in our ongoing calculation of the next-to-next-to-leading order (NNLO) QCD correction to the total inclusive top-pair production cross-section at hadron colliders. In this paper we calculate the reaction qqˉ→ttˉ+qqˉq\bar q \to t\bar t + q\bar q which was not considered in our previous work on qqˉ→ttˉ+Xq\bar q \to t\bar t +X due to its phenomenologically negligible size. We also calculate all remaining fermion-pair-initiated partonic channels qqâ€Č,qqˉâ€Čqq', q\bar q' and qqqq that contribute to top-pair production starting from NNLO. The contributions of these reactions to the total cross-section for top-pair production at the Tevatron and LHC are small, at the permil level. The most interesting feature of these reactions is their characteristic logarithmic rise in the high energy limit. We compute the constant term in the leading power behavior in this limit, and achieve precision that is an order of magnitude better than the precision of a recent theoretical prediction for this constant. All four partonic reactions computed in this paper are included in our numerical program Top++. The calculation of the NNLO corrections to the two remaining partonic reactions, qg→ttˉ+Xqg\to t\bar t+X and gg→ttˉ+Xgg\to t\bar t+X, is ongoing.Comment: 1+16 pages; 3 figure

    Chemically controlled interfacial nanoparticle assembly into nanoporous gold films for electrochemical applications

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    Nanoporous gold (NPG) is an effective material for electrocatalysis and can be made by self-assembly of gold nanoparticles at liquid–air interface.</p

    Transfer of manualized Short Term Psychodynamic Psychotherapy (STPP) for social phobia into clinical practice: study protocol for a cluster-randomised controlled trial

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    <p>Abstract</p> <p>Background</p> <p>Psychodynamic psychotherapy is frequently applied in the treatment of social phobia. Nevertheless, there has been a lack of studies on the transfer of manualized treatments to routine psychodynamic practice. Our study is the first one to examine the effects of additional training in a manualized Short Term Psychodynamic Psychotherapy (STPP) procedure on outcome in routine psychotherapy for social phobia. This study is an extension to a large multi-site RCT (N = 512) comparing the efficacy of STPP to Cognitive-Behavioral Therapy (CBT) of Social Phobia.</p> <p>Methods/Design</p> <p>The manualized treatment is designed for a time limited approach with 25 individual sessions of STPP over 6 months. Private practitioners will be randomized to training in manualized STPP vs. treatment as usual without a specific training (control condition). We plan to enrol a total of 105 patients (84 completers). Assessments will be conducted before treatment starts, after 8 and 15 weeks, after 25 treatment sessions, at the end of treatment, 6 months and 12 months after termination of treatment. The primary outcome measure is the Liebowitz Social Anxiety Scale. Remission from social phobia is defined scoring with 30 or less points on this scale.</p> <p>Discussion</p> <p>We will investigate how the treatment can be transferred from a controlled trial into the less structured setting of routine clinical care. This question represents Phase IV of psychotherapy research. It combines the benefits of randomized controlled and naturalistic research. The study is genuinely designed to promote faster and more widespread dissemination of effective interventions. It will answer the questions whether manualized STPP can be implemented into routine outpatient care, whether the new methods improve treatment courses and outcomes and whether treatment effects reached in routine psychotherapeutic treatments are comparable to those of the controlled, strictly manualized treatment of the main study.</p> <p>Trial Registration</p> <p>German Clinical Trials Register (DRKS) DRKS00000570</p
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