563 research outputs found

    A month in Switzerland

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    A strongly-interacting phase of the Minimal Supersymmetric Model

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    We argue that in the minimal supersymmetric extension of the Standard Model with a large trilinear coupling both the fundamental Higgs boson and a bound state of squarks (formed via strong scalar interaction) can have a non-zero VEV. This alters drastically the pattern of electroweak-symmetry breaking and the Higgs phenomenology. In particular, the upper bound on the supersymmetric Higgs-boson mass may be relaxed. Also, the Higgs boson can be produced at hadron colliders through a direct coupling to gluons.Comment: 14 pages; 1 figure; epsf; replaced with published version (a comment and an acknowledgement added

    Bound-State Variational Wave Equation For Fermion Systems In QED

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    We present a formulation of the Hamiltonian variational method for QED which enables the derivation of relativistic few-fermion wave equation that can account, at least in principle, for interactions to any order of the coupling constant. We derive a relativistic two-fermion wave equation using this approach. The interaction kernel of the equation is shown to be the generalized invariant M-matrix including all orders of Feynman diagrams. The result is obtained rigorously from the underlying QFT for arbitrary mass ratio of the two fermions. Our approach is based on three key points: a reformulation of QED, the variational method, and adiabatic hypothesis. As an application we calculate the one-loop contribution of radiative corrections to the two-fermion binding energy for singlet states with arbitrary principal quantum number nn, and l=J=0l =J=0. Our calculations are carried out in the explicitly covariant Feynman gauge.Comment: 26 page

    Spectroscopic properties and optoelectronic parameters of ternary composites incorporating poly(L-Tryptophane):P(TER-CO-TRI) and Sudan dye

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    In this study, the spectroscopic properties and optoelectronic parameters of a ternary composite containing poly(L-Tryptophane): P(TER-CO-TRI) and Sudan dye were thoroughly investigated. Poly(L-Tryptophane) and P (TER-CO-TRI), the electron acceptor and donor, were solution processed and doped with different ratios of Sudan dye to form ternary composite systems. The FTIR technique, UV-Vis spectroscopy, and cyclic voltammetry (CV) were utilized to study the broad properties of the samples. Results showed that with the help of dye doping, the non-dispersive refractive index and energy gap of the ternary system were increased to 2.00 and decreased to 2.11 eV, respectively. The optical band gap, refractive index, dielectric constant, and optical conductivity of the samples were elaborated. The nature of the electronic transition in the studied samples was found to be a direct allowed transition, which was derived from the application of Tauc’s equation. The combination of CV test and absorption spectroscopy was successfully used to determine the molecular energy levels, HOMO and LUMO of the polymer samples

    Measurement Based Resource Allocation for Multimedia Applications

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    Modern networks are now capable of guaranteeing a consistent Quality of Service (QoS) to multimedia traffic streams. A number of major operating system vendors are also working hard to extend these guarantees into the end-system. In both cases, however, there remains the problem of determining a service rate sufficient to ensure the desired Quality of Service. Source modelling is not a sustainable approach in the network case and it is even less feasible to model the demands of multimedia applications. The ESPRIT Measure project is successfully using online measurement and estimation to perform resource allocation for bursty traffic in ATM networks. In this paper we consider the applicability of the same theory to resource allocation in a multimedia operating system which offers QoS guarantees to its applications

    Bayesian inference reveals positive but subtle effects of experimental fishery closures on marine predator demographics

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    Global forage-fish landings are increasing, with potentially grave consequences for marine ecosystems. Predators of forage fish may be influenced by this harvest, but the nature of these effects is contentious. Experimental fishery manipulations offer the best solution to quantify population-level impacts, but are rare. We used Bayesian inference to examine changes in chick survival, body condition and population growth rate of endangered African penguins Spheniscus demersus in response to 8 years of alternating time–area closures around two pairs of colonies. Our results demonstrate that fishing closures improved chick survival and condition, after controlling for changing prey availability. However, this effect was inconsistent across sites and years, highlighting the difficultly of assessing management interventions in marine ecosystems. Nevertheless, modelled increases in population growth rates exceeded 1% at one colony; i.e. the threshold considered biologically meaningful by fisheries management in South Africa. Fishing closures evidently can improve the population trend of a forage-fish-dependent predator—we therefore recommend they continue in South Africa and support their application elsewhere. However, detecting demographic gains for mobile marine predators from small no-take zones requires experimental time frames and scales that will often exceed those desired by decision makers

    Optical and Optoelectronic Studies of Binary and Ternary Films of Poly(L-Tryptophane), Poly(5-hydroxy-L-tryptophane), and P(TER-CO-TRI) Doped with Sudan Dye

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    In this work, the optical properties and optoelectronics parameters of binary and ternary composite films made of two electron acceptors, poly(L-Tryptophane) and poly(5-hydroxy-L-Tryptophane), with an electron donor, P(TER-CO-TRI), doped with Sudan dyes, are comprehensively investigated. The films with different volumetric ratios of the components were deposited onto the glass substrates using spin coating technique. Results showed that with the help of dye doping into the binary systems of poly(L-Tryptophane):P(TRI-co-TER) (1:2) and poly(5-hydroxy-L-Tryptophane):P(TRI-co-TER)(1:2), the refractive index was increased from 2.01 to 2.32. The nature of the electronic transition in the studied films was found to be a direct allowed transition, which was derived from Tauc’s equation. The combination of Cyclic voltammetry (CV) technique and absorption spectroscopy was used to determine the molecular energy levels, HOMO and LUMO of the polymer samples. It was seen that the mixture of poly(L-Tryptophane):P(TRI-co-TER):Sudan dye (1:2:2) has led to increase the energy gap to 2.95 eV and the real optical conductivity ( ) to about 433.11 S.cm-1. According to the findings, the investigated polymers can have a great potential for semitransparent organic solar cells

    Small farmers, NGOs, and a Walmart World: Welfare effects of supermarkets operating in Nicaragua

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    Despite more than a decade of NGO and government activities promoting developing world farmer participation in high-value agricultural markets, evidence regarding the household welfare effects of such initiatives is limited. This paper analyzes the geographic placement of supermarket supply chains in Nicaragua between 2000 and 2008 and uses a difference-in-difference specification on measures of supplier and non-supplier assets to estimate the welfare effects of small farmer participation. Though results indicate that selling to supermarkets increases household productive asset holdings, they also suggest that only farmers with advantageous endowments of geography and water are likely to participate

    Lithic technological responses to Late Pleistocene glacial cycling at Pinnacle Point Site 5-6, South Africa

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    There are multiple hypotheses for human responses to glacial cycling in the Late Pleistocene, including changes in population size, interconnectedness, and mobility. Lithic technological analysis informs us of human responses to environmental change because lithic assemblage characteristics are a reflection of raw material transport, reduction, and discard behaviors that depend on hunter-gatherer social and economic decisions. Pinnacle Point Site 5-6 (PP5-6), Western Cape, South Africa is an ideal locality for examining the influence of glacial cycling on early modern human behaviors because it preserves a long sequence spanning marine isotope stages (MIS) 5, 4, and 3 and is associated with robust records of paleoenvironmental change. The analysis presented here addresses the question, what, if any, lithic assemblage traits at PP5-6 represent changing behavioral responses to the MIS 5-4-3 interglacial-glacial cycle? It statistically evaluates changes in 93 traits with no a priori assumptions about which traits may significantly associate with MIS. In contrast to other studies that claim that there is little relationship between broad-scale patterns of climate change and lithic technology, we identified the following characteristics that are associated with MIS 4: increased use of quartz, increased evidence for outcrop sources of quartzite and silcrete, increased evidence for earlier stages of reduction in silcrete, evidence for increased flaking efficiency in all raw material types, and changes in tool types and function for silcrete. Based on these results, we suggest that foragers responded to MIS 4 glacial environmental conditions at PP5-6 with increased population or group sizes, 'place provisioning', longer and/or more intense site occupations, and decreased residential mobility. Several other traits, including silcrete frequency, do not exhibit an association with MIS. Backed pieces, once they appear in the PP5-6 record during MIS 4, persist through MIS 3. Changing paleoenvironments explain some, but not all temporal technological variability at PP5-6.Social Science and Humanities Research Council of Canada; NORAM; American-Scandinavian Foundation; Fundacao para a Ciencia e Tecnologia [SFRH/BPD/73598/2010]; IGERT [DGE 0801634]; Hyde Family Foundations; Institute of Human Origins; National Science Foundation [BCS-9912465, BCS-0130713, BCS-0524087, BCS-1138073]; John Templeton Foundation to the Institute of Human Origins at Arizona State Universit
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