36 resultados para Turân determinants


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The celebrated Turân inequalities P 2 n(x)-P n-x(x)P n+1(x) ≥ 0, x ε[-1,1], n ≥ 1, where P n(x) denotes the Legendre polynomial of degree n, are extended to inequalities for sums of products of four classical orthogonal polynomials. The proof is based on an extension of the inequalities γ 2 n - γ n-1γ n+1 ≥ 0, n ≥ 1, which hold for the Maclaurin coefficients of the real entire function ψ in the Laguerre-Pölya class, ψ(x) = ∑ ∞ n=0 γ nx n / n!. ©1998 American Mathematical Society.

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The isolate AF199 of Lettuce mosaic virus (LMV, genus Potyvirus) causes local lesions followed by systemic wilting and plant death in the lettuce cultivars Ithaca and Vanguard 75. Analysis of the phenotype of virus chimeras revealed that a region within the PI protein coding region (nucleotides 112-386 in the viral genome) and/or another one within the CI protein coding region (nucleoticles 5496-5855) are sufficient together to cause the lethal wilting in Ithaca, but not in Vanguard 75. This indicates that the determinants of this particular symptom are different in these two lettuce cultivars. The wilting phenotype was not directly correlated with differences in the deduced amino acid sequence of these two regions. Furthermore, transient expression of the LMV-AF 199 proteins, separately or in combination, did not induce local necrosis or any other visible reaction in the plants. Together, these results Suggest that the systemic wilting reaction might be Clue to RNA rather than protein sequences. (c) 2004 Elsevier B.V. All rights reserved.

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The concept of information is analyzed starting from Adams' hypothesis in The Informational Turn in Philosophy, according to which there has been a far-reaching turn in Philosophy following the publication of Turing's article "Computing Machinery and Intelligence". Adams maintains that new guidelines are being indicated in philosophical research, having the concept of "information" as the basis for treatment of classical problems, such as the relationships between mind-body, perception-action, and the nature of knowledge, amongst others. Partially agreeing with Adams, we believe, however, that his hypothesis faces difficulties, the most fundamental of which concerns the different meanings given to the concept of information. We argue that even though the concept of information underlying the mechanicist proposal of Turing, according to which "to think is to compute", is indeed being employed in Philosophy, this is not because of its mechanistic nature, but mainly due to the representationist presupposition dominant in this area. From this point of view, the informational turn in philosophy would not provide any great novelty, given that since the earliest days philosophical approaches to the nature of mind have always been mainly representationist. The novelty would not lie specifically in the Turing thesis, but in reflections on the nature of information, especially ecological information, and its relation to action.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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The mammalian scapula is a complex morphological structure, composed of two ossification plates that fuse into a single structure. Most studies on morphological differentiation in the scapula have considered it to be a simple, spatially integrated structure, primarily influenced by the important locomotor function presented by this element. We used recently developed geometric morphometric techniques to test and quantify functional and phylogenetic influences on scapular shape variation in fossil and extant xenarthran mammals. The order Xenarthra is well represented in the fossil record and presents a stable phylogenetic hypothesis for its genealogical history. In addition, its species present a large variety of locomotor habits. Our results show that approximately half of the shape variation in the scapula is due to phylogenetic heritage. This is contrary to the view that the scapula is influenced only by functional demands. There are large-scale shape transformations that provide biomechanical adaptation for the several habits (arboreality, terrestriality, and digging), and small scale-shape transformations (mostly related to the coracoid process) that are not influenced by function. A nonlinear relationship between morphometric and phylogenetic distances indicates the presence of a complex mixture of evolutionary processes acting on shape differentiation of the scapula. J. Morphol. 241,251-263, 1999. (C) 1999 Wiley-Liss, Inc.

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,,,,,INTRODUCTION:,,,,, While the incidence of HIV infection and AIDS is increasing in small Brazilian cities, epidemiological studies are often conducted in large urban centers. ,,,,,,,,,,,,,METHODS: ,,,,, Our group conducted a retrospective analysis of survival determinants among 358 patients who attended a reference unit in a small city.,,,,,,,,,,,,,,,,,,RESULTS: ,,,,,Death risk was lower among men that had sex with men, patients with an HIV-seropositive partner, and those admitted after highly active antiretroviral therapy (HAART) was available. ,,,,,,,,,,,,,CONCLUSIONS:,,,,, The study documents the striking beneficial effect of HAART. The finding of other groups with improved survival may aid in the development of programmatic strategies.,,,,

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The structural specificity of alpha-PMTX, a novel peptide toxin derived from wasp venom has been studied on the neuromuscular synapse in the walking leg of the lobster. alpha-PMTX is known to induce repetitive action potentials in the presynaptic axon due to sodium channel inactivation. We synthesized 29 analogs of alpha-PMTX by substituting one or two amino acids and compared threshold concentrations of these mutant toxins for inducing repetitive action potentials. In 13 amino acid residues of alpha-PMTX, Arg-1, Lys-3 and Lys-12 regulate the toxic activity because substitution of these basic amino acid residues with other amino acid residues greatly changed the potency. Determining the structure-activity relationships of PMTXs will help clarifying the molecular mechanism of sodium channel inactivation. (C) 2000 Elsevier B.V. Ireland Ltd. All rights reserved.

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This article examines the interplay between legitimacy and context as key determinants of public sector reform outcomes. Despite the importance of variables Such as legitimacy of public institutions, levels of civic morality and socio-economic realities, reform strategies often fail to take such contextual factors into account. The article examines, first, relevant literature both conceptual and empirical, including data from the World Values Survey project. It is argued that developing countries have distinctive characteristics which require particular reform strategies. The data analysed shows that in Latin American countries, there is no clear Correlation between confidence in public institutions and civic morality. Other empirical studies show that unemployment has a negative impact on the level of civic morality, while inequality engenders corruption. This suggests that poorer and socio-economically stratified countries face greater reform challenges owing to the lack of legitimacy of public institutions. The article concludes that reforms should focus on areas of governance that impact on poverty. This will in turn help produce more stable outcomes. Copyright (C) 2008 John Wiley & Sons, Ltd.