198,662 research outputs found

    Viscosity and Thermal Relaxation for a resonantly interacting Fermi gas

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    The viscous and thermal relaxation rates of an interacting fermion gas are calculated as functions of temperature and scattering length, using a many-body scattering matrix which incorporates medium effects due to Fermi blocking of intermediate states. These effects are demonstrated to be large close to the transition temperature TcT_c to the superfluid state. For a homogeneous gas in the unitarity limit, the relaxation rates are increased by nearly an order of magnitude compared to their value obtained in the absence of medium effects due to the Cooper instability at TcT_c. For trapped gases the corresponding ratio is found to be about three due to the averaging over the inhomogeneous density distribution. The effect of superfluidity below TcT_c is considered to leading order in the ratio between the energy gap and the transition temperature.Comment: 7 pages, 3 figure

    Frequency and damping of the Scissors Mode of a Fermi gas

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    We calculate the frequency and damping of the scissors mode in a classical gas as a function of temperature and coupling strength. Our results show good agreement with the main features observed in recent measurements of the scissors mode in an ultracold gas of 6^6Li atoms. The comparison between theory and experiment involves no fitting parameters and thus allows an identification of non-classical effects at and near the unitarity limit.Comment: 4 pages, 2 figure

    Covalent bonding of antibodies of polystyrene latex beads: A concept

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    Technique facilitates purification of vaccines and production of immunoadsorption columns exhibiting relatively long stability. Information interests biochemists, medical researchers, and pharmaceutical manufacturers

    Viscous relaxation and collective oscillations in a trapped Fermi gas near the unitarity limit

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    The viscous relaxation time of a trapped two-component gas of fermions in its normal phase is calculated as a function of temperature and scattering length, with the collision probability being determined by an energy-dependent s-wave cross section. The result is used for calculating the temperature dependence of the frequency and damping of collective modes studied in recent experiments, starting from the kinetic equation for the fermion distribution function with mean-field effects included in the streaming terms.Comment: 10 pages, 9 figures; proof version, corrected typo in Eq. (23); accepted for publication in PR

    Pulse transit time: a new approach to haemodynamic monitoring in obstetric spinal anaesthesia

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    Part of the Portfolio Thesis by Geoffrey H. Sharwood-Smith: The inferior vena caval compression theory of hypotension in obstetric spinal anaesthesia: studies in normal and preeclamptic pregnancy, a literature review and revision of fundamental concepts, available at http://hdl.handle.net/10023/1815Original abstract presented at the Obstetric Anaesthetisits' Association congress 2002, Nottingham, 9-10 May.Postprin

    Molecular oxygen densities from rocket measurements of Lyman-alpha absorption profiles

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    Molecular oxygen density measurements in upper atmosphere by absorption spectroscopy using solar Lyman alpha radiatio

    Pulse transit time confirms altered response to spinal anaesthesia in pregnancy induced hypertension

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    Poster presented at the International Society for the Study of Hypertension in Pregnancy (ISSHP)Congress, Toronto 2002.Part of the Portfolio Thesis by Geoffrey H. Sharwood-Smith: The inferior vena caval compression theory of hypotension in obstetric spinal anaesthesia: studies in normal and preeclamptic pregnancy, a literature review and revision of fundamental concepts, available at http://hdl.handle.net/10023/1815Postprin
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