1,552 research outputs found

    Hamiltonian domain wall fermions at strong coupling

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    We apply strong-coupling perturbation theory to gauge theories containing domain-wall fermions in Shamir's surface version. We construct the effective Hamiltonian for the color-singlet degrees of freedom that constitute the low-lying spectrum at strong coupling. We show that the effective theory is identical to that derived from naive, doubled fermions with a mass term, and hence that domain-wall fermions at strong coupling suffer both doubling and explicit breaking of chiral symmetry. Since we employ a continuous fifth dimension whose extent tends to infinity, our result applies to overlap fermions as well.Comment: Revtex, 21 pp. Some changes in Introduction, dealing with consistency with previous wor

    Airy Distribution Function: From the Area Under a Brownian Excursion to the Maximal Height of Fluctuating Interfaces

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    The Airy distribution function describes the probability distribution of the area under a Brownian excursion over a unit interval. Surprisingly, this function has appeared in a number of seemingly unrelated problems, mostly in computer science and graph theory. In this paper, we show that this distribution also appears in a rather well studied physical system, namely the fluctuating interfaces. We present an exact solution for the distribution P(h_m,L) of the maximal height h_m (measured with respect to the average spatial height) in the steady state of a fluctuating interface in a one dimensional system of size L with both periodic and free boundary conditions. For the periodic case, we show that P(h_m,L)=L^{-1/2}f(h_m L^{-1/2}) for all L where the function f(x) is the Airy distribution function. This result is valid for both the Edwards-Wilkinson and the Kardar-Parisi-Zhang interfaces. For the free boundary case, the same scaling holds P(h_m,L)=L^{-1/2}F(h_m L^{-1/2}), but the scaling function F(x) is different from that of the periodic case. We compute this scaling function explicitly for the Edwards-Wilkinson interface and call it the F-Airy distribution function. Numerical simulations are in excellent agreement with our analytical results. Our results provide a rather rare exactly solvable case for the distribution of extremum of a set of strongly correlated random variables. Some of these results were announced in a recent Letter [ S.N. Majumdar and A. Comtet, Phys. Rev. Lett., 92, 225501 (2004)].Comment: 27 pages, 10 .eps figures included. Two figures improved, new discussion and references adde

    The literacy practices for assessment in the vocational curriculum - the case of Hospitality

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    This article explores two case studies of the literacy practices of assessment in the vocational curriculum. Previous studies have identified learning in the vocational curriculum as being assessment-driven and that subjects often associated with limited levels of literacy actually require multiple literacy practices from students. Drawing upon studies of the literacy practices of assessment in the teaching of Hospitality, the study explores the academic and occupational forms of reading and writing required of students. These literacy practices are often invisible to both students and staff and yet are central to the success of students in relation to attainment. The article suggests that vocational subjects may actually be more demanding in the range of literacies required for assessment than is often considered to be the case

    Wannier-function description of the electronic polarization and infrared absorption of high-pressure hydrogen

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    We have constructed maximally-localized Wannier functions for prototype structures of solid molecular hydrogen under pressure, starting from LDA and tight-binding Bloch wave functions. Each occupied Wannier function can be associated with two paired protons, defining a ``Wannier molecule''. The sum of the dipole moments of these ``molecules'' always gives the correct macroscopic polarization, even under strong compression, when the overlap between nearby Wannier functions becomes significant. We find that at megabar pressures the contributions to the dipoles arising from the overlapping tails of the Wannier functions is very large. The strong vibron infrared absorption experimentally observed in phase III, above ~ 150 GPa, is analyzed in terms of the vibron-induced fluctuations of the Wannier dipoles. We decompose these fluctuations into ``static'' and ``dynamical'' contributions, and find that at such high densities the latter term, which increases much more steeply with pressure, is dominant.Comment: 17 pages, two-column style with 14 postscript figures embedded. Uses REVTEX and epsf macro

    Smart homes and their users:a systematic analysis and key challenges

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    Published research on smart homes and their users is growing exponentially, yet a clear understanding of who these users are and how they might use smart home technologies is missing from a field being overwhelmingly pushed by technology developers. Through a systematic analysis of peer-reviewed literature on smart homes and their users, this paper takes stock of the dominant research themes and the linkages and disconnects between them. Key findings within each of nine themes are analysed, grouped into three: (1) views of the smart home-functional, instrumental, socio-technical; (2) users and the use of the smart home-prospective users, interactions and decisions, using technologies in the home; and (3) challenges for realising the smart home-hardware and software, design, domestication. These themes are integrated into an organising framework for future research that identifies the presence or absence of cross-cutting relationships between different understandings of smart homes and their users. The usefulness of the organising framework is illustrated in relation to two major concerns-privacy and control-that have been narrowly interpreted to date, precluding deeper insights and potential solutions. Future research on smart homes and their users can benefit by exploring and developing cross-cutting relationships between the research themes identified

    Optimal designs for rational function regression

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    We consider optimal non-sequential designs for a large class of (linear and nonlinear) regression models involving polynomials and rational functions with heteroscedastic noise also given by a polynomial or rational weight function. The proposed method treats D-, E-, A-, and Φp\Phi_p-optimal designs in a unified manner, and generates a polynomial whose zeros are the support points of the optimal approximate design, generalizing a number of previously known results of the same flavor. The method is based on a mathematical optimization model that can incorporate various criteria of optimality and can be solved efficiently by well established numerical optimization methods. In contrast to previous optimization-based methods proposed for similar design problems, it also has theoretical guarantee of its algorithmic efficiency; in fact, the running times of all numerical examples considered in the paper are negligible. The stability of the method is demonstrated in an example involving high degree polynomials. After discussing linear models, applications for finding locally optimal designs for nonlinear regression models involving rational functions are presented, then extensions to robust regression designs, and trigonometric regression are shown. As a corollary, an upper bound on the size of the support set of the minimally-supported optimal designs is also found. The method is of considerable practical importance, with the potential for instance to impact design software development. Further study of the optimality conditions of the main optimization model might also yield new theoretical insights.Comment: 25 pages. Previous version updated with more details in the theory and additional example

    'To live and die [for] Dixie': Irish civilians and the Confederate States of America

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    Around 20,000 Irishmen served in the Confederate army in the Civil War. As a result, they left behind, in various Southern towns and cities, large numbers of friends, family, and community leaders. As with native-born Confederates, Irish civilian support was crucial to Irish participation in the Confederate military effort. Also, Irish civilians served in various supporting roles: in factories and hospitals, on railroads and diplomatic missions, and as boosters for the cause. They also, however, suffered in bombardments, sieges, and the blockade. Usually poorer than their native neighbours, they could not afford to become 'refugees' and move away from the centres of conflict. This essay, based on research from manuscript collections, contemporary newspapers, British Consular records, and Federal military records, will examine the role of Irish civilians in the Confederacy, and assess the role this activity had on their integration into Southern communities. It will also look at Irish civilians in the defeat of the Confederacy, particularly when they came under Union occupation. Initial research shows that Irish civilians were not as upset as other whites in the South about Union victory. They welcomed a return to normalcy, and often 'collaborated' with Union authorities. Also, Irish desertion rates in the Confederate army were particularly high, and I will attempt to gauge whether Irish civilians played a role in this. All of the research in this paper will thus be put in the context of the Drew Gilpin Faust/Gary Gallagher debate on the influence of the Confederate homefront on military performance. By studying the Irish civilian experience one can assess how strong the Confederate national experiment was. Was it a nation without a nationalism

    Unsettling boundaries in making a space for research

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    In engaging in research we draw upon and develop meanings and concepts that help to frame what we do, how we do it and the meaning we make of it. In the process of framing, we exclude other possibilities from our research practices. To do research then is to engage in the fashioning of conceptual boundaries. This article explores the dilemmas of boundary-making in the context of a research project aimed at exploring the border literacy practices of students in UK further education, those boundary crossing practices which relate to the everyday and more formal demands of the curriculum. This discussion is related to wider debates in the social sciences on the significance of boundaries and borders and their powerful effects on identities and actions

    Levels and equivalence in credit and qualifications frameworks: Contrasting the prescribed and enacted curriculum in school and college

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    Drawing on data from an empirical study of three matched subjects in upper secondary school and further education college in Scotland, this article explores some of the factors that result in differences emerging from the translation of the prescribed curriculum into the enacted curriculum. We argue that these differences raise important questions about equivalences which are being promoted through the development of credit and qualifications frameworks. The article suggests that the standardisation associated with the development of a rational credit and qualifications framework and an outcomes-based prescribed curriculum cannot be achieved precisely because of the multiplicity that emerges from the practices of translation

    The angiotensin type 1 receptor antagonist, eprosartan, attenuates the progression of renal disease in spontaneously hypertensive stroke-prone rats with accelerated hypertension

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    ABSTRACT The effects of the angiotensin type 1 (AT 1 ) receptor antagonist, eprosartan, were studied in a model of severe, chronic hypertension. Treatment of male spontaneously hypertensive stroke prone rats (SHR-SP) fed a high-fat, high-salt diet with eprosartan (60 mg/kg/day i.p.) for 12 weeks resulted in a lowering of blood pressure (250 Ϯ 9 versus 284 Ϯ 8 mm Hg), renal expression of transforming growth factor-␤ mRNA (1.5 Ϯ 0.2 versus 5.4 Ϯ 1.4) and the matrix components: plasminogen activator inhibitor-1 (5.2 Ϯ 1.4 versus 31.4 Ϯ 10.7), fibronectin (2.2 Ϯ 0.6 versus 8.2 Ϯ 2.2), collagen I-␣1 (5.6 Ϯ 2.0 versus 23.8 Ϯ 7.3), and collagen III (2.7 Ϯ 0.9 versus 7.6 Ϯ 2.1). Data were corrected for rpL32 mRNA expression and expressed relative to Wistar Kyoto (WKY) rats [ϭ1.0]. Expression of fibronectin protein was also lowered by eprosartan (0.8 Ϯ 0.1 versus 1.9 Ϯ 0.5), relative to WKY rats. Eprosartan provided significant renoprotection to SHR-SP rats as measured by decreased proteinuria (22 Ϯ 2 versus 127 Ϯ 13 mg/day) and histological evidence of active renal damage (5 Ϯ 2 versus 195 Ϯ 6) and renal fibrosis (5.9 Ϯ 0.7 versus 16.4 Ϯ 1.9) in vehicle-versus eprosartantreated rats, respectively. Our results demonstrated that AT 1 receptor blockade with eprosartan can reduce blood pressure and preserve renal structure and function in this model of severe, chronic hypertension. These effects were accompanied by a decreased renal expression of transforming growth factor-␤1, plasminogen activator inhibitor-1, and several other extracellular matrix proteins compared with vehicle-treated SHR-SP. The renin-angiotensin system is a major regulator of blood pressure within the body, through the maintenance of vascular tone and sodium homeostasis. The renin-angiotensin system has, however, also been implicated in a number of diseases, characterized by remodeling and fibrosis, including forms of progressive renal disease. The generation of angiotensin II can lead to organ damage through both mitogenic activity and profibrotic remodeling. Eprosartan is a potent (K i ϭ 1.4 nM) angiotensin II receptor antagonist selective for the AT 1 subtype. AT 1 receptor antagonists have been shown to attenuate the effects of exogenous angiotensin II Materials and Methods Experimental Design. Male SHR-SP rats, progeny from the strain developed b
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