22 research outputs found

    Dielectric signature of charge order in lanthanum nickelates

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    Three charge-ordering lanthanum nickelates La2-xAxNiO4, substituted with specific amounts of A = Sr, Ca, and Ba to achieve commensurate charge order, are investigated using broadband dielectric spectroscopy up to GHz frequencies. The transition temperatures of the samples are characterized by additional specific heat and magnetic susceptibility measurements. We find colossal magnitudes of the dielectric constant for all three compounds and strong relaxation features, which partly are of Maxwell-Wagner type arising from electrode polarization. Quite unexpectedly, the temperature-dependent colossal dielectric constants of these materials exhibit distinct anomalies at the charge-order transitions.Comment: 7 pages, 6 figure

    Hipervitaminose D em animais

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    Aspects of pituitary and adrenal disease

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    SIGLEAvailable from British Library Document Supply Centre-DSC:DXN004074 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

    Structural requirements for the modulatory effect of 6-substituted pterins on interleukin 2 receptor binding.

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    (6R)-5,6,7,8-Tetrahydrobiopterin is produced by stimulated human T lymphocytes, and is known to affect various aspects of interleukin-2-directed T cell proliferation. Using an increased apparent affinity of interleukin 2 receptor to interleukin 2 as a measure of activity, this study explores whether other 6-substituted pterins might have the same effect, and what structural features are necessary for activity. Of the compounds tested, only the T-lymphocyte-derived (6R)-5,6,7,8-tetrahydrobiopterin was active. The diastereomeric (6S)-5,6,7,8-tetrahydrobiopterin was inactive, as were 7,8-dihydrobiopterin, sepiapterin, 5,6,7,8-tetrahydroneopterin, 6,7-dimethyl-5,6,7,8-tetrahydropterin and 6-hydroxymethylpterin. 7,8-Dihydroneopterin and neopterin were also found to be inactive. It follows that neither of these compounds participates in the feedback modulation of IL-2 receptor affinity, although both of them can be detected upon IFN-γ stimulation of human monocytes/macrophages. A computer-based molecular modelling study of (6R)-5,6,7,8-tetrahydrobiopterin and (6R)-5,6,7,8-tetrahydroneopterin revealed substantial differences in overall shape between the two molecules, with certain features figuring prominently in the low-energy conformers of (6R)-5,6,7,8-tetrahydrobiopterin

    Underwater Soundscape and Modeling Metadata Standard

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    A lack of globally applied standards for underwater acoustic measurements (soundscapes) means that different researchers make different choices for frequency ranges and time averaging windows, often referring to the resulting plethora of different quantities with identical names, making it difficult, and sometimes impossible, to compare like with like.<div><br></div><div>This document, the ADEON Underwater Soundscape and Modeling Metadata Standard, is the first of five standardization products. Its purpose is to specify a minimum metadata standard for measured and predicted OCS soundscapes in the US EEZ. It is intended to be used as a tool to facilitate direct comparisons between soundscapes reported by different projects. Compliance with this standard in no way precludes calculation of metrics not specified by the standard or of the same metrics in different frequency bands or averaging intervals.<br></div
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