2,530 research outputs found

    Developmental and comparative aspects of brine shrimp tubulin

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    4-[(E)-2-Ferrocenylethen­yl]-1,8-naphthalic anhydride

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    In the structure of the title compound, [Fe(C5H5)(C19H11O3)], the plane of the substituted ferrocene ring is tilted by 14.17 (6)° with respect to the mean plane through the naphthalene ring system. In the crystal structure, centrosymmetric dimers are formed through π–π inter­actions [centroid–centroid distance = 3.624 (2) Å] between the substituted ferrocene ring and the three fused rings of the naphthalic anhydride unit. Pairs of dimers are held together by further naphthalene–naphthalene π–π interactions [distance between parallel mean planes 3.45 (3) Å]. Each dimer inter­acts with four neighbouring dimers in a herringbone fashion through C—H⋯π inter­actions, so forming a two-dimensional sheet-like structure

    Spontaneous Gender Categorization in Masking and Priming Studies: Key for Distinguishing Jane from John Doe but Not Madonna from Sinatra

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    Facial recognition is key to social interaction, however with unfamiliar faces only generic information, in the form of facial stereotypes such as gender and age is available. Therefore is generic information more prominent in unfamiliar versus familiar face processing? In order to address the question we tapped into two relatively disparate stages of face processing. At the early stages of encoding, we employed perceptual masking to reveal that only perception of unfamiliar face targets is affected by the gender of the facial masks. At the semantic end; using a priming paradigm, we found that while to-be-ignored unfamiliar faces prime lexical decisions to gender congruent stereotypic words, familiar faces do not. Our findings indicate that gender is a more salient dimension in unfamiliar relative to familiar face processing, both in early perceptual stages as well as later semantic stages of person construal

    Impact of age norms and stereotypes on managers' hiring decisions of retirees

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    Purpose -Our study investigates the role of managers in the re-employment of early retirees and asks what the effect is of managers’ age norms and stereotypes on managers’ employment decisions. Design/methodology/approach- A combination of a factorial study and a survey was conducted. First, information on the age norms and stereotypes was collected. Secondly, profiles of hypothetical retired job applicants were presented to the employers, who were asked to make a specific hiring decision. The information collected during both studies was combined in the analysis and multilevel models were estimated. Findings -The results indicate that higher age norms result in a higher propensity to hire an early retiree. Stereotypes, by contrast, do not influence managers’ decisions. Early retirees’ chances for re-employment are also related to their own circumstances (physical appearance and relevant experience) and organisational forces, as they are hired when organisations face labour force shortages. Research limitation / implications – with the use of vignettes study we deal with hypothetical hiring situation. Originality value- Although the effect of age norms and age stereotypes has been often suggested, not much empirical evidence was presented to support this notion. Our study estimates the effect of age norms and stereotypes on hiring decision. key words: bridge employment; early retirees; age norms; age stereotypes; multilevel models.

    From wormhole to time machine: Comments on Hawking's Chronology Protection Conjecture

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    The recent interest in ``time machines'' has been largely fueled by the apparent ease with which such systems may be formed in general relativity, given relatively benign initial conditions such as the existence of traversable wormholes or of infinite cosmic strings. This rather disturbing state of affairs has led Hawking to formulate his Chronology Protection Conjecture, whereby the formation of ``time machines'' is forbidden. This paper will use several simple examples to argue that the universe appears to exhibit a ``defense in depth'' strategy in this regard. For appropriate parameter regimes Casimir effects, wormhole disruption effects, and gravitational back reaction effects all contribute to the fight against time travel. Particular attention is paid to the role of the quantum gravity cutoff. For the class of model problems considered it is shown that the gravitational back reaction becomes large before the Planck scale quantum gravity cutoff is reached, thus supporting Hawking's conjecture.Comment: 43 pages,ReV_TeX,major revision

    Regularizing Portfolio Optimization

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    The optimization of large portfolios displays an inherent instability to estimation error. This poses a fundamental problem, because solutions that are not stable under sample fluctuations may look optimal for a given sample, but are, in effect, very far from optimal with respect to the average risk. In this paper, we approach the problem from the point of view of statistical learning theory. The occurrence of the instability is intimately related to over-fitting which can be avoided using known regularization methods. We show how regularized portfolio optimization with the expected shortfall as a risk measure is related to support vector regression. The budget constraint dictates a modification. We present the resulting optimization problem and discuss the solution. The L2 norm of the weight vector is used as a regularizer, which corresponds to a diversification "pressure". This means that diversification, besides counteracting downward fluctuations in some assets by upward fluctuations in others, is also crucial because it improves the stability of the solution. The approach we provide here allows for the simultaneous treatment of optimization and diversification in one framework that enables the investor to trade-off between the two, depending on the size of the available data set

    2-Bromo-N-(4-chloro­phen­yl)-2-methyl­propanamide

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    In the title mol­ecule, C10H11BrClNO, there is a twist between the mean plane of the amide group and the benzene ring [C(=O)—N—C—C torsion angle = −27.1 (3)°]. In the crystal, inter­molecular N—H⋯O and weak C—H⋯O hydrogen bonds link the mol­ecules into chains along [010]

    2-Bromo-2-methyl-N-p-tolyl­propanamide

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    In the title mol­ecule, C11H14BrNO, there is twist between the mean plane of the amide group and the benzene ring [C(=O)—N—C C torsion angle = −31.2 (5)°]. In the crystal, inter­molecular N—H⋯O and weak C—H⋯O hydrogen bonds link mol­ecules into chains along [100]. The methyl group H atoms are disordered over two sets of sites with equal occupancy
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