2,849 research outputs found

    On a new test of fit to the beta distribution

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    We propose a new L2-type goodness-of-fit test for the family of beta distributions based on a conditional moment characterization. The asymptotic null distribution is identified, and since it depends on the underlying parameters, a parametric bootstrap procedure is proposed. Consistency against all alternatives that satisfy a convergence criterion is shown, and a Monte Carlo simulation study indicates that the new procedure outperforms most of the classical tests. Finally, the procedure is applied to a real data set related to air humidity

    Developing a Web-Based Question-Driven Audience Response System Supporting BYOD

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    Question-driven Audience Response Systems (ARSs) are in the focus of research since the 1960s. Since then, the technology has changed and therefore systems have evolved too. This work is about conception and implementation of the web-based ARS RealFeedback which uses the principle of bring your own device (BYOD). A state-of-the-art analysis compares the features of existing web-based ARSs. The most important findings are used for the conception and the implementation of the system. Thinking-aloud tests, and the first usages during lectures confirm that the chosen requirements are very significant and valuable for lecturers

    Pd-catalyzed enantioselective aerobic oxidation of secondary alcohols: Applications to the total synthesis of alkaloids

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    Enantioselective syntheses of the alkaloids (-)-aurantioclavine, (+)-amurensinine, (-)-lobeline, and (-)- and (+)-sedamine are described. The syntheses demonstrate the effectiveness of the Pd-catalyzed asymmetric oxidation of secondary alcohols in diverse contexts and the ability of this methodology to set the absolute configuration of multiple stereocenters in a single operation. The utility of an aryne C-C insertion reaction in accessing complex polycyclic frameworks is also described

    Anisotropy in the helicity modulus of a 3D XY-model: application to YBCO

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    We present a Monte Carlo study of the helicity moduli of an anisotropic classical three-dimensional (3D) XY-model of YBCO in superconducting state. It is found that both the ab-plane and the c-axis helicity moduli, which are proportional to the inverse square of the corresponding magnetic field penetration depth, vary linearly with temperature at low temperatures. The result for the c-axis helicity modulus is in disagreement with the experiments on high quality samples of YBCO. Thus we conclude that purely classical phase fluctuations of the superconducting order parameter cannot account for the observed c-axis electrodynamics of YBCO.Comment: 7 pages, 1 figur

    Density-functional theory for classical fluids and solids

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    We formulate a density-functional theory that is capable of describing simultaneously the solid, liquid, and gas phases of a simple classical material. The formalism can be reduced to the Ebner-Saam-Stroud theory for the liquid-gas case and to a generalized version of the Ramakrishnan-Youssouff theory for the liquid-solid case. The theory requires as input the direct correlation functions of a uniform fluid. As an example we apply the formalism to the calculation of the phase diagram of a system with Lennard-Jones intermolecular interactions. We obtain the correlation functions from a closure scheme proposed by Zerah and Hansen [J. Chem. Phys. 84, 2336 (1986)]. The calculated density-temperature phase diagram compares favorably with those obtained from numerical simulations of the same model system. We also compute the equations of state in the solid and fluid phases

    Neural Mechanisms of Reading Facial Emotions in Young and Older Adults

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    The ability to read and appropriately respond to emotions in others is central for successful social interaction. Young and older adults are better at identifying positive than negative facial expressions and also expressions of young than older faces. Little, however, is known about the neural processes associated with reading different emotions, particularly in faces of different ages, in samples of young and older adults. During fMRI, young and older participants identified expressions in happy, neutral, and angry young and older faces. The results suggest a functional dissociation of ventromedial prefrontal cortex (vmPFC) and dorsomedial prefrontal cortex (dmPFC) in reading facial emotions that is largely comparable in young and older adults: Both age groups showed greater vmPFC activity to happy compared to angry or neutral faces, which was positively correlated with expression identification for happy compared to angry faces. In contrast, both age groups showed greater activity in dmPFC to neutral or angry than happy faces which was negatively correlated with expression identification for neutral compared to happy faces. A similar region of dmPFC showed greater activity for older than young faces, but no brain-behavior correlations. Greater vmPFC activity in the present study may reflect greater affective processing involved in reading happy compared to neutral or angry faces. Greater dmPFC activity may reflect more cognitive control involved in decoding and/or regulating negative emotions associated with neutral or angry than happy, and older than young, faces

    Proper English Usage : a sociolinguistic investigation of attitudes towards usage problems in British English

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    Focusing on the general public, an often-forgotten key player in the debate on correct and proper English usage, this dissertation provides a current perspective on attitudes towards fourteen usage problems, including literally as an intensifier and the notorious split infinitive, in British English. Proper English Usage investigates the impact of the social variables age, gender, language nativeness and level of education on attitudes towards the usage problems investigated. The results of various attitude elicitation tests, including an online questionnaire completed by 112 respondents, have shown that social variables such as age play a crucial role in the social stratification of usage attitudes. Using a mixture of different attitude elicitation techniques has shown that both subconsciously and consciously offered attitudes need to be taken into account in order to circumvent the issue of obtaining socially desirable answers. Besides applying a mixed-methods approach, qualitative and quantitative attitudinal data contribute further to a fuller picture of current usage attitudes. A historical dimension is added to the study by exploring the Hyper Usage Guide of English (HUGE) database, which allowed for a systematic assessment of percept data found in advice manuals spanning 240 years.Language Use in Past and Presen

    A Convergent and Enantioselective Synthesis of (+)-Amurensinine via Selective C−H and C−C Bond Insertion Reactions

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    A convergent and enantioselective synthesis of the natural product amurensinine is described. The synthetic strategy takes advantage of mild and selective C−H and C−C bond insertion reactions, in addition to the palladium-catalyzed aerobic oxidative kinetic resolution recently developed in these laboratories

    Molecular and immunological characterization of profilin from mugwort pollen

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    In late summer in Europe, pollen of mugwort is one of the major sources of atopic allergens. No information about the complete molecular structure of any mugwort allergen has been published so far. Here we report the isolation and characterization of mugwort pollen cDNA clones coding for two isoforms of the panallergen profilin. Thirtysix percent of the mugwort allergic patients tested displayed IgE antibodies against natural and recombinant profilin, and no significant differences were observed in the IgEbinding properties of the isoforms. One profilin isoform was purified to homogeneity and detailed structural analysis indicated that the protein exists in solution as dimers and tetramers stabilized by sulfydryl and/or ionic interactions. Profilin monomers were detectable only after exposure of multimers to harsh denaturing conditions. Dimers and tetramers did not significantly differ in their ability to bind serum IgE from mugwort pollenallergic patients. However, oligomeric forms might have a higher allergenic potential than monomers because larger molecules would have additional epitopes for IgEmediated histamine release. Profilin isolated from mugwort pollen also formed multimers. Thus, oligomerization is not an artifact resulting from the recombinant production of the allergen. Inhibition experiments showed extensive IgE crossreactivity of recombinant mugwort profilin and profilin from various pollen and food extracts
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