1,536 research outputs found

    Derivation of revised formulae for eddy viscous forces used in the ocean general circulation model

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    Presented is a re-derivation of the eddy viscous dissipation tensor commonly used in present oceanographic general circulation models. When isotropy is imposed, the currently-used form of the tensor fails to return to the laplacian operator. In this paper, the source of this error is identified in a consistent derivation of the tensor in both rectangular and earth spherical coordinates, and the correct form of the eddy viscous tensor is presented

    Modeling left-truncated and right-censored survival data with longitudinal covariates

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    There is a surge in medical follow-up studies that include longitudinal covariates in the modeling of survival data. So far, the focus has been largely on right-censored survival data. We consider survival data that are subject to both left truncation and right censoring. Left truncation is well known to produce biased sample. The sampling bias issue has been resolved in the literature for the case which involves baseline or time-varying covariates that are observable. The problem remains open, however, for the important case where longitudinal covariates are present in survival models. A joint likelihood approach has been shown in the literature to provide an effective way to overcome those difficulties for right-censored data, but this approach faces substantial additional challenges in the presence of left truncation. Here we thus propose an alternative likelihood to overcome these difficulties and show that the regression coefficient in the survival component can be estimated unbiasedly and efficiently. Issues about the bias for the longitudinal component are discussed. The new approach is illustrated numerically through simulations and data from a multi-center AIDS cohort study.Comment: Published in at http://dx.doi.org/10.1214/12-AOS996 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

    1992 Visit of Bonnie TuSmith, East Asian / International Studies

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    Communications regarding Bonnie Tu-Smith visit, 1992. Asian Studies / International Studie

    Propane-1,2-diaminium bis­(4-meth­oxy­benzoate)

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    The asymmetric unit of the title salt, C3H12N2 2+·2C8H7O3 −, contains two 4-meth­oxy­benzoate anions and one propane-1,2-diaminium cation. All the amino H atoms of the cation are involved in N—H⋯O hydrogen bonds with the carboxyl­ate O atoms of the anions

    Bis(2-amino­benzonitrile)tetra­aqua­cobalt(II) dichloride

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    In the crystal structure of the title compound, [Co(C7H6N2)2(H2O)4]Cl2, the CoII cation lies on an inversion center and is coordinated by two 2-amino­benzonitrile ligands and four water mol­ecules in a distorted octa­hedral geometry. The Cl− counter-anion links with the complex cations via O—H⋯Cl and N—H⋯Cl hydrogen bonding. Inter­molecular O—H⋯N hydrogen bonding links the complex cations, forming supra­molecular chains running along the b axis

    Methyl 1-bromo-2-naphthoate

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    In the mol­ecular structure of the title compound, C12H9BrO2, the methoxy­carbonyl group is twisted by a dihedral angle of 29.8 (3)°with respect to the naphthalene ring system. An overlapped arrangement is observed between parallel naphthalene ring systems of adjacent mol­ecules, and the face-to-face distance of 3.590 (9) Å suggests there is π–π stacking in the crystal structure

    3,5-Dichloro-N-(2-methyl­but-3-yn-2-yl)benzamide

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    In the title compound, C12H11Cl2NO, the amide group is twisted by a dihedral angle of 31.98 (2)° with respect to the benzene ring. In the crystal structure, mol­ecules are linked via N—H⋯O hydrogen bonds, forming one-dimensional supra­molecular chains

    Nanostructured Indium Tin Oxides and Other Transparent Conducting Oxides: Characteristics and Applications in the THz Frequency Range

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    Transparent conductors are essential for optoelectronic components operating in the far-infrared or terahertz (THz) frequency range. Indium tin oxide (ITO), extensively used in the visible, is semi-transparent in the far-infrared frequency range. Other types of bulk transparent conducting oxides (TCOs), such as aluminum-doped zinc oxide (AZO) and aluminum and ytterbium-doped zinc oxide (AYZO), have not yet been explored for THz applications. Recently, biomimic nanomaterials have been shown to exhibit exotic optical properties, e.g., broadband, omnidirectional antireflective properties. Indeed, nanostructured ITO was found to exhibit the above desirable characteristics. In this chapter, we describe the fabrication and characterization of several TCOs, including ITO nanomaterials and several types of bulk TCO thin films, e.g., AZO and AYZO. Performance of THz phase shifters with ITO nanomaterials as transparent electrodes and liquid crystals for functionalities is presented

    Diet Shapes Mortality Response to Trauma in Old Tephritid Fruit Flies.

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    Despite the importance of trauma in healthspan and lifespan in humans as well as in non-human species, with one important exception the literature in both gerontology and ecology contains virtually no experimental demographic studies concerned with trauma in any species. We used dietary manipulation [full diet (F) versus sugar-only (S)] to produce four levels of frailty in 55-day old tephritid fruit flies (Anastrepha ludens) that were then subject to the trauma of cage transfer stress (n = 900/sex in each of the 4 treatments). The key results included the following: (1) there is a trauma effect caused by the transfer that depends on previous diet before transfer, new diet after transfer and gender of the fly; (2) males are more vulnerable than females; (3) if initial diet was F, flies are relatively immune against the trauma, and the subsequent diet (F or S) does not matter; (4) however if initial diet was S, then the effect of the trauma depends largely on the diet after the transfer; (5) flies transferred from S to F diets do very well in terms of remaining longevity (i.e. greatest remaining longevity), while flies transferred from S to S diet do poorly (i.e. shortest remaining longevity). We discuss both the strengths and weaknesses of this study and implications of the results
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