999 resultados para accident causation theory
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The classical wave-of-advance model of the neolithic transition (i.e., the shift from hunter-gatherer to agricultural economies) is based on Fisher's reaction-diffusion equation. Here we present an extension of Einstein's approach to Fickian diffusion, incorporating reaction terms. On this basis we show that second-order terms in the reaction-diffusion equation, which have been neglected up to now, are not in fact negligible but can lead to important corrections. The resulting time-delayed model agrees quite well with observations
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State Agency Audit Report
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The performance of the SAOP potential for the calculation of NMR chemical shifts was evaluated. SAOP results show considerable improvement with respect to previous potentials, like VWN or BP86, at least for the carbon, nitrogen, oxygen, and fluorine chemical shifts. Furthermore, a few NMR calculations carried out on third period atoms (S, P, and Cl) improved when using the SAOP potential
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The basis set superposition error-free second-order MØller-Plesset perturbation theory of intermolecular interactions was studied. The difficulties of the counterpoise (CP) correction in open-shell systems were also discussed. The calculations were performed by a program which was used for testing the new variants of the theory. It was shown that the CP correction for the diabatic surfaces should be preferred to the adiabatic ones
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A comparative systematic study of the CrO2F2 compound has been performed using different conventional ab initio methodologies and density functional procedures. Two points have been analyzed: first, the accuracy of results yielded by each method under study, and second, the computational cost required to reach such results. Weighing up both aspects, density functional theory has been found to be more appropriate than the Hartree-Fock (HF) and the analyzed post-HF methods. Hence, the structural characterization and spectroscopic elucidation of the full CrO2X2 series (X=F,Cl,Br,I) has been done at this level of theory. Emphasis has been given to the unknown CrO2I2 species, and specially to the UV/visible spectra of all four compounds. Furthermore, a topological analysis in terms of charge density distributions has revealed why the valence shell electron pair repulsion model fails in predicting the molecular shape of such CrO2X2 complexes
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A conceptually new approach is introduced for the decomposition of the molecular energy calculated at the density functional theory level of theory into sum of one- and two-atomic energy components, and is realized in the "fuzzy atoms" framework. (Fuzzy atoms mean that the three-dimensional physical space is divided into atomic regions having no sharp boundaries but exhibiting a continuous transition from one to another.) The new scheme uses the new concept of "bond order density" to calculate the diatomic exchange energy components and gives them unexpectedly close to the values calculated by the exact (Hartree-Fock) exchange for the same Kohn-Sham orbitals
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Bimodal dispersal probability distributions with characteristic distances differing by several orders of magnitude have been derived and favorably compared to observations by Nathan [Nature (London) 418, 409 (2002)]. For such bimodal kernels, we show that two-dimensional molecular dynamics computer simulations are unable to yield accurate front speeds. Analytically, the usual continuous-space random walks (CSRWs) are applied to two dimensions. We also introduce discrete-space random walks and use them to check the CSRW results (because of the inefficiency of the numerical simulations). The physical results reported are shown to predict front speeds high enough to possibly explain Reid's paradox of rapid tree migration. We also show that, for a time-ordered evolution equation, fronts are always slower in two dimensions than in one dimension and that this difference is important both for unimodal and for bimodal kernels
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The empirical evidence testing the validity of the rational partisan theory (RPT) has been mixed. In this article, we argue that the inclusion of other macroeconomic policies and the presence of an independent central bank can partly contribute to explain this inconclusiveness. This article expands Alesina s (1987) RPT model to include an extra policy and an independent central bank. With these extensions, the implications of RPT are altered signi ficantly. In particular, when the central bank is more concerned about output than public spending (an assumption made by many papers in this literature), then the direct relationship between in flation and output derived in Alesina (1987) never holds. Keywords: central bank, conservativeness, political uncertainty. JEL Classi fication: E58, E63.
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State Agency Audit Report
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RÉSUMÉ Introduction. Les hémopathies représentent une cause rare d'accident vasculaire cérébral (AVC), faisant l'objet de peu de publications, mais sont très fréquemment recherchées après un AVC par de coûteux bilans dont la rentabilité reste à définir. Matériel et Méthodes. Dans le registre lausannois des AVC, nous nous sommes intéressés de façon rétrospective aux dossiers des patients hospitalisés entre 1979 et 2001 pour un premier AVC ischémique artériel, dont la cause a été attribuée à une pathologie hématologique. Sur 4 697 patients, 22 (0,47 p. 100) ont vu leur AVC imputé à l'une des causes hématologiques suivantes : maladie de Vaquez , polyglobulie secondaire , thrombocytémie essentielle , thrombocytose secondaire , myélome multiple , MD , déficit en protéine S , syndrome anticorps antiphospholipides , hyperhomocystéinémie . Chaque hémopathie retrouvée a donné lieu à une revue de la littérature. Conclusion. À la lumière de ces données, nous concluons qu'une formule sanguine représente un bilan hématologique de dépistage suffisant pour l'immense majorité des patients hospitalisés pour un premier AVC artériel ischémique. Les recherches d'anticorps antiphospholipides, de thrombophilies héréditaires et d'hyperhomocystéinémie peuvent être limitées à des cas sélectionnés. SUMMARY Cerebral infarction of arterial origin and haematological causation: the Lausanne experience and a review of the literature. Introduction. Hematological diseases are seldom found as the etiology of ischemic strokes, but are frequently investigated by expensive laboratory tests after a first cerebral vascular event. Methods. In the Lausanne Stroke Registry, we retrospectively reviewed the cases of patients hospitalized between 1979 and 2001 for a first ischemic arterial stroke which was attributed to a hematological etiology. Of 4697 patients, 22 (0.47 per cent) had a stroke due to one of the following hematological pathology: polycythemia vera, secondary polycythemia, essential thrombocytemia, secondary thrombocytosis, multiple myeloma, CIVD, protein S deficiency, antiphospholipid antibody syndrome, moderate homocysteinemia. A literature review was undertaken for each hemopathy. Conclusion. In light of the results of these data, we concluded that a complete blood count provides sufficient hematological screening for the majority of patients hospitalized for an arterial stroke. The antiphospholipid antibody syndrome is a rare cause of cerebral infarction, which needs to be investigated in young patients, in cases of multiple or recurring stroke or in the presence of a typical history. Inherited thrombophilias are not a significant risk factor for arterial cerebral infarction and their investigation is only warranted for a sub-group of young patients with a cryptogenic stroke, in which group the prevalence is slightly increased. Moderate homocysteinemia must be considered as a cerebrovascular risk factor of minor importance, but potentially treatable by a substitution of vitamin B12, B 6 and folates. The efficacy of this substitution in the prevention of cardiovascular events needs yet to be demonstrated.