355 research outputs found

    Newton-Cartan Gravity and Torsion

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    We compare the gauging of the Bargmann algebra, for the case of arbitrary torsion, with the result that one obtains from a null-reduction of General Relativity. Whereas the two procedures lead to the same result for Newton-Cartan geometry with arbitrary torsion, the null-reduction of the Einstein equations necessarily leads to Newton-Cartan gravity with zero torsion. We show, for three space-time dimensions, how Newton-Cartan gravity with arbitrary torsion can be obtained by starting from a Schroedinger field theory with dynamical exponent z=2 for a complex compensating scalar and next coupling this field theory to a z=2 Schroedinger geometry with arbitrary torsion. The latter theory can be obtained from either a gauging of the Schroedinger algebra, for arbitrary torsion, or from a null-reduction of conformal gravity.Comment: 21 page

    Facile synthesis of TEG-substituted 4-(<i>N</i>-methyl-<i>N</i>-<i>Boc</i>-amino)styrylpyridine and PET imaging agent [F]florbetapir ([F]AV-45)

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    <p>Triethylene glycol-substituted 4-(<i>N</i>-methyl-<i>N-Boc</i>-amino)styrylpyridine which can serve as key precursor for many monodentate and multidentate imaging agents for Aβ plaques in human brain has been readily synthesized with cost-effective starting materials. The important non-radioactive monodentate positron emission tomography agent [F]florbetapir ([F]AV-45) has also been prepared by our new method.</p

    Experiment and Calculation Method of the Dynamic Response of Deep Water Bridge in Earthquake

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    <div><p>Abstract For deep-water long span bridges under earthquakes, the interaction between water and structure will inevitably induce the hydrodynamic force on the structures. Based on the Morison potential fluid theory, a simplified calculation method of hydrodynamic force was proposed. Taken the 3rd Nanjing Yangtze River Bridge in China as the prototype, the shaking table test for the elevated pile caps was performed. And the results from the experiment and the proposed simplified calculation method were analyzed and compared. The main conclusions include: the natural vibration frequency of the bridge in deep water is decreased, and the predominant frequency is reduced by 8.24% due to the water-structure interaction. In earthquake, the effect of hydrodynamic force on the dynamic response of the deep water bridge is significant that the bending moment of the main girder is increased 7.73% and the bottom bending moment of the most adverse pile is increased 14.22%. In the seismic design of deep-water bridges, the effect of water-structure interaction should not be ignored.</p></div

    The whole dataset for this study.

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    Estimation results in different major occupational categories.

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    Estimation results in different major occupational categories.</p

    Estimation results of moderation effects.

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    Estimation results of moderation effects.</p

    Descriptive statistics of the variables.

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    Descriptive statistics of the variables.</p

    The full list of alternative measurements.

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    The alternative measurement of displacement risk by sectors.

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    The alternative measurement of displacement risk by sectors.</p

    Estimation results of robustness tests.

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    Estimation results of robustness tests.</p