5,247 research outputs found

    Subclinical salmonella infection in Danish finishing herds - prevalence of S. enterica measured by bacteriological and serological examination

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    Subclinically salmonella infected herds may represent a contamination risk for pork products although no clinical signs are present. In the nation-wide Salmonella enterica surveillance and control programme in Danish slaughter pig herds (Mousing et al. 1997) the salmonella prevalence in Danish pig herds is being monitored. The monitoring is based on serological examination of meat juice (Nielsen et al. 1997). Serological examination of blood samples and bacteriological examination of pen samples is used as follow-up

    Observation of a pairing pseudogap in a two-dimensional Fermi gas

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    Pairing of fermions is ubiquitous in nature and it is responsible for a large variety of fascinating phenomena like superconductivity, superfluidity of 3^3He, the anomalous rotation of neutron stars, and the BEC-BCS crossover in strongly interacting Fermi gases. When confined to two dimensions, interacting many-body systems bear even more subtle effects, many of which lack understanding at a fundamental level. Most striking is the, yet unexplained, effect of high-temperature superconductivity in cuprates, which is intimately related to the two-dimensional geometry of the crystal structure. In particular, the questions how many-body pairing is established at high temperature and whether it precedes superconductivity are crucial to be answered. Here, we report on the observation of pairing in a harmonically trapped two-dimensional atomic Fermi gas in the regime of strong coupling. We perform momentum-resolved photoemission spectroscopy, analogous to ARPES in the solid state, to measure the spectral function of the gas and we detect a many-body pairing gap above the superfluid transition temperature. Our observations mark a significant step in the emulation of layered two-dimensional strongly correlated superconductors using ultracold atomic gases

    Subclinical salmonella infection in Danish finishing herds - association between serological and bacteriological testing

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    As part of the salmonella surveillance programme in Danish slaughter pig herds (Mousing et a!. 1997), the occurrence of subclinical salmonella infection in pigs is monitored serologically at slaughter by examination of meat juice samples, using a mix-ELISA (Nielsen eta!. 1997). Subsequently blood samples and pen (faecal) samples are used as diagnostic tests in infected herds. The association between the serological and the bacteriological testing therefore needs assessment. The objective of the present study was to assess the association between serological and bacteriological testing

    Communities and patterns of scientific collaboration in Business and Management

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    This is the author's accepted version of this article deposited at arXiv (arXiv:1006.1788v2 [physics.soc-ph]) and subsequently published in Scientometrics October 2011, Volume 89, Issue 1, pp 381-396. The final publication is available at link.springer.com http://link.springer.com/article/10.1007%2Fs11192-011-0439-1Author's note: 17 pages. To appear in special edition of Scientometrics. Abstract on arXiv meta-data a shorter version of abstract on actual paper (both in journal and arXiv full pape

    Community structure and patterns of scientific collaboration in Business and Management

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    This is the author's accepted version of this article deposited at arXiv (arXiv:1006.1788v2 [physics.soc-ph]) and subsequently published in Scientometrics October 2011, Volume 89, Issue 1, pp 381-396. The final publication is available at link.springer.com http://link.springer.com/article/10.1007%2Fs11192-011-0439-1Author's note: 17 pages. To appear in special edition of Scientometrics. Abstract on arXiv meta-data a shorter version of abstract on actual paper (both in journal and arXiv full pape

    Variational Monte Carlo Study of Spin-Gapped Normal State and BCS-BEC Crossover in Two-Dimensional Attractive Hubbard Model

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    We study properties of normal, superconducting (SC) and CDW states for an attractive Hubbard model on the square lattice, using a variational Monte Carlo method. In trial wave functions, we introduce an interspinon binding factor, indispensable to induce a spin-gap transition in the normal state, in addition to the onsite attractive and intersite repulsive factors. It is found that, in the normal state, as the interaction strength U/t|U|/t increases, a first-order spin-gap transition arises at UcW|U_{\rm c}|\sim W (WW: band width) from a Fermi liquid to a spin-gapped state, which is conductive through hopping of doublons. In the SC state, we confirm by analysis of various quantities that the mechanism of superconductivity undergoes a smooth crossover at around |U_{\ma{co}}|\sim |U_{\rm c}| from a BCS type to a Bose-Einstein condensation (BEC) type, as U/t|U|/t increases. For |U|<|U_{\ma{co}}|, quantities such as the condensation energy, a SC correlation function and the condensate fraction of onsite pairs exhibit behavior of exp(t/U)\sim \exp(-t/|U|), as expected from the BCS theory. For |U|>|U_{\ma{co}}|, quantities such as the energy gain in the SC transition and superfluid stiffness, which is related to the cost of phase coherence, behave as t2/UTc\sim t^2/|U|\propto T_{\rm c}, as expected in a bosonic scheme. In this regime, the SC transition is induced by a gain in kinetic energy, in contrast with the BCS theory. We refer to the relevance to the pseudogap in cuprate superconductors.Comment: 14 pages, 22 figures, submitted to Journal of the Physical Society of Japa

    Radio-Frequency Spectroscopy

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    Contains reports on four research projects
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