3,800 research outputs found

    Treatment of Scarlatina.

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    Theoretical Study of Fluid Membranes of Spherical Topology with Internal Degrees of Freedom

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    A theoretical study of vesicles of topological genus zero is presented. The bilayer membranes forming the vesicles have various degrees of intrinsic (tangent-plane) orientational order, ranging from smectic to hexatic, frustrated by curvature and topology. The field-theoretical model for these `nn-atic' surfaces has been studied before in the low temperature (mean-field) limit. Work presented here includes the effects of thermal fluctuations. Using the lowest Landau level approximation, the coupling between order and shape is cast in a simple form, facilitating insights into the behaviour of vesicles. The order parameter contains vortices, whose effective interaction potential is found, and renormalized by membrane fluctuations. The shape of the phase space has a counter-intuitive influence on this potential. A criterion is established whereby a vesicle of finite rigidity may be burst by its own in-plane order, and an analogy is drawn with flux exclusion from a type-I superconductor.Comment: 34 pages + 4 Postscript figures. Uses RevTe

    Observing the spin of a free electron

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    Long ago, Bohr, Pauli, and Mott argued that it is not, in principle, possible to measure the spin components of a free electron. One can try to use a Stern-Gerlach type of device, but the finite size of the beam results in an uncertainty of the splitting force that is comparable with the gradient force. The result is that no definite spin measurement can be made. Recently there has been a revival of interest in this problem, and we will present our own analysis and quantum-mechanical wave-packet calculations which suggest that a spin measurement is possible for a careful choice of initial conditions

    'Reclaiming the criminal' : the role and training of prison officers in England, 1877-1914

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    This article examines the role and training of prison officers in England, between 1877 and 1914. It is concerned with the changing penal philosophies and practices of this period and how these were implemented in local prisons, and the duties of the prison officer. More broadly, this article argues that the role of the prison officer and their training (from 1896) reflect wider ambiguities in prison policy and practice during this period

    Relativistic precession and spin dynamics of an elliptic Rydberg wave packet

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    Time evolution of wave packets built from the eigenstates of the Dirac equation for a hydrogenic system is considered. We investigate the space and spin motion of wave packets which, in the non-relativistic limit, are stationary states with a probability density distributed uniformly along the classical, elliptical orbit (elliptic WP). We show that the precession of such a WP, due to relativistic corrections to the energy eigenvalues, is strongly correlated with the spin motion. We show also that the motion is universal for all hydrogenic systems with an arbitrary value of the atomic number Z.Comment: Latex2e, uses IOP style files (included), 10 pages, 5 jpg figures, 1 postscript figure. Relation between precession time and radiative liftime added (eq.(12)). Accepted for publication in J. Phys.

    Light Hadron Masses from Lattice QCD

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    This article reviews lattice QCD results for the light hadron spectrum. We give an overview of different formulations of lattice QCD, with discussions on the fermion doubling problem and improvement programs. We summarize recent developments in algorithms and analysis techniques, that render calculations with light, dynamical quarks feasible on present day computer resources. Finally, we summarize spectrum results for ground state hadrons and resonances using various actions.Comment: 53 pages, 24 figures, one table; Rev.Mod.Phys. (published version); v2: corrected typ

    Radioactive decays at limits of nuclear stability

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    The last decades brought an impressive progress in synthesizing and studying properties of nuclides located very far from the beta stability line. Among the most fundamental properties of such exotic nuclides, usually established first, is the half-life, possible radioactive decay modes, and their relative probabilities. When approaching limits of nuclear stability, new decay modes set in. First, beta decays become accompanied by emission of nucleons from highly excited states of daughter nuclei. Second, when the nucleon separation energy becomes negative, nucleons start to be emitted from the ground state. Here, we present a review of the decay modes occurring close to the limits of stability. The experimental methods used to produce, identify and detect new species and their radiation are discussed. The current theoretical understanding of these decay processes is overviewed. The theoretical description of the most recently discovered and most complex radioactive process - the two-proton radioactivity - is discussed in more detail.Comment: Review, 68 pages, 39 figure

    Photography as an act of collaboration

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    The camera is usually considered to be a passive tool under the control of the operator. This definition implicitly constrains how we use the medium, as well as how we look at – and what we see in – its interpretations of scenes, objects, events and ‘moments’. This text will suggest another way of thinking about – and using – the photographic medium. Based on the evidence of photographic practice (mine and others’), I will suggest that, as a result of the ways in which the medium interprets, juxtaposes and renders the elements in front of the lens, the camera is capable of depicting scenes, events and moments that did not exist and could not have existed until brought into being by the act of photographing them. Accordingly, I will propose that the affective power of many photographs is inseparable from their ‘photographicness’ – and that the photographic medium should therefore be considered as an active collaborator in the creation of uniquely photographic images

    Sampling a Littoral Fish Assemblage: Comparison of Small-Mesh Fyke Netting and Boat Electrofishing

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    We compared small-mesh (4-mm) fyke netting and boat electrofishing for sampling a littoral fish assemblage in Muskegon Lake, Michigan. We hypothesized that fyke netting selects for small-bodied fishes and electrofishing selects for large-bodied fishes. Three sites were sampled during May (2004 and 2005), July (2005 only), and September (2004 and 2005). We found that the species composition of captured fish differed considerably between fyke netting and electrofishing based on nonmetric multidimensional scaling (NMDS). Species strongly associated with fyke netting (based on NMDS and relative abundance) included the brook silverside Labidesthes sicculus, banded killifish Fundulus diaphanus, round goby Neogobius melanostomus, mimic shiner Notropis volucellus, and bluntnose minnow Pimephales notatus, whereas species associated with electrofishing included the Chinook salmon Oncorhynchus tshawytscha, catostomids (Moxostoma spp. and Catostomus spp.), freshwater drum Aplodinotus grunniens, walleye Sander vitreus, gizzard shad Dorosoma cepedianum, and common carp Cyprinus carpio. The total length of fish captured by electrofishing was 12.8 cm (95% confidence interval ¼ 5.5– 17.2 cm) greater than that of fish captured by fyke netting. Size selectivity of the gears contributed to differences in species composition of the fish captured, supporting our initial hypothesis. Thus, small-mesh fyke nets and boat electrofishers provided complementary information on a littoral fish assemblage. Our results support use of multiple gear types in monitoring and research surveys of fish assemblages. Copyright by the American Fisheries Society 2007, Originally published in the North American Journal of Fisheries Management 27: 825-831, 2007

    Jekyll and Hyde: men's constructions of feminism and feminists

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    Research and commentary on men's responses to feminism has demonstrated the range of ways in which men have mobilised both against and for feminist principles. This paper argues that further analyses of men's responses require a sophisticated theory of discourse acknowledging the fragmented and contradictory nature of representation. A corpus of men's talk on feminism and feminists was studied to identify the pervasive patterns in men's accounting and regularities in rhetorical organisation. Material from two samples of men was included: a sample of white middle-class 17-18 year old school students and a sample of 60 interviews with a more diverse sample of older men aged 20 to 64. Two interpretative repertoires of feminism and feminists were identified. These set up a 'Jekyll and Hyde' binary and positioned feminism along with feminists very differently as reasonable versus extreme and monstrous. Both repertoires tended to be deployed together and the paper explores the ideological and interactional consequences of typical deployments along with the identity work accomplished by the men as they positioned themselves in relation to these
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