969 resultados para mechanical stability
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On December 4th 2007, a 3-Mm3 landslide occurred along the northwestern shore of Chehalis Lake. The initiation zone is located at the intersection of the main valley slope and the northern sidewall of a prominent gully. The slope failure caused a displacement wave that ran up to 38 m on the opposite shore of the lake. The landslide is temporally associated with a rain-on-snow meteorological event which is thought to have triggered it. This paper describes the Chehalis Lake landslide and presents a comparison of discontinuity orientation datasets obtained using three techniques: field measurements, terrestrial photogrammetric 3D models and an airborne LiDAR digital elevation model to describe the orientation and characteristics of the five discontinuity sets present. The discontinuity orientation data are used to perform kinematic, surface wedge limit equilibrium and three-dimensional distinct element analyses. The kinematic and surface wedge analyses suggest that the location of the slope failure (intersection of the valley slope and a gully wall) has facilitated the development of the unstable rock mass which initiated as a planar sliding failure. Results from the three-dimensional distinct element analyses suggest that the presence, orientation and high persistence of a discontinuity set dipping obliquely to the slope were critical to the development of the landslide and led to a failure mechanism dominated by planar sliding. The three-dimensional distinct element modelling also suggests that the presence of a steeply dipping discontinuity set striking perpendicular to the slope and associated with a fault exerted a significant control on the volume and extent of the failed rock mass but not on the overall stability of the slope.
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Despite the long tradition for asking about the negative social and health consequences of alcohol consumption in surveys, little is known about the dimensionality of these consequences. Analysing cross-sectional and longitudinal data from the Nordic Taxation Study collected for Sweden, Finland, and Denmark in two waves in 2003 and 2004 by means of an explorative principal component analysis for categorical data (CATPCA), it is tested whether consequences have a single underlying dimension across cultures. It further tests the reliability, replicability, concurrent and predictive validity of the consequence scales. A one-dimensional solution was commonly preferable. Whereas the two-dimensional solution was unable to distinguish clearly between different concepts of consequences, the one-dimensional solution resulted in interpretable, generally very stable scales within countries across different samples and time.
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This article analyses stability and volatility of party preferences using data from the Swiss Household-Panel (SHP), which, for the first time, allow studying transitions and stability of voters over several years in Switzerland. Analyses cover the years 1999- 2007 and systematically distinguish changes between party blocks and changes within party blocks. The first part looks at different patterns of change, which show relatively high volatility. The second part tests several theories on causes of such changes applying a multinomial random-effects model. Results show that party preferences stabilise with their duration and with age and that the electoral cycle, political sophistication, socio-structural predispositions, the household-context as well as party size and the number of parties each explain part of electoral volatility. Different results for withinand between party-block changes underlie the importance of that differentiation.
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The present review will briefly summarize the interplay between coagulation and inflammation, highlighting possible effects of direct inhibition of factor Xa and thrombin beyond anticoagulation. Additionally, the rationale for the use of the new direct oral anticoagulants (DOACs) for indications such as cancer-associated venous thromboembolism (CAT), mechanical heart valves, thrombotic anti-phospholipid syndrome (APS), and heparin-induced thrombocytopenia (HIT) will be explored. Published data on patients with cancer or mechanical heart valves treated with DOAC will be discussed, as well as planned studies in APS and HIT. Although at the present time published evidence is insufficient for recommending DOAC in the above-mentioned indications, there are good arguments in favor of clinical trials investigating their efficacy in these contexts. Direct inhibition of factor Xa or thrombin may reveal interesting effects beyond anticoagulation as well.
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For several decades mechanical properties of shallow formations (soil) obtained by sonic to ultrasonic wave testing were reported to be greater than those based on mechanical tests. The present article relying on a statistical analysis of more than 300 tests shows that elastic moduli of the soil can indeed be obtained from (ultra)sonic tests and that they are identical to those resulting from mechanical tests.
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The evolution of a quantitative phenotype is often envisioned as a trait substitution sequence where mutant alleles repeatedly replace resident ones. In infinite populations, the invasion fitness of a mutant in this two-allele representation of the evolutionary process is used to characterize features about long-term phenotypic evolution, such as singular points, convergence stability (established from first-order effects of selection), branching points, and evolutionary stability (established from second-order effects of selection). Here, we try to characterize long-term phenotypic evolution in finite populations from this two-allele representation of the evolutionary process. We construct a stochastic model describing evolutionary dynamics at non-rare mutant allele frequency. We then derive stability conditions based on stationary average mutant frequencies in the presence of vanishing mutation rates. We find that the second-order stability condition obtained from second-order effects of selection is identical to convergence stability. Thus, in two-allele systems in finite populations, convergence stability is enough to characterize long-term evolution under the trait substitution sequence assumption. We perform individual-based simulations to confirm our analytic results.
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"Vegeu el resum a l'inici del document del fitxer adjunt."
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The paper develops a stability theory for the optimal value and the optimal set mapping of optimization problems posed in a Banach space. The problems considered in this paper have an arbitrary number of inequality constraints involving lower semicontinuous (not necessarily convex) functions and one closed abstract constraint set. The considered perturbations lead to problems of the same type as the nominal one (with the same space of variables and the same number of constraints), where the abstract constraint set can also be perturbed. The spaces of functions involved in the problems (objective and constraints) are equipped with the metric of the uniform convergence on the bounded sets, meanwhile in the space of closed sets we consider, coherently, the Attouch-Wets topology. The paper examines, in a unified way, the lower and upper semicontinuity of the optimal value function, and the closedness, lower and upper semicontinuity (in the sense of Berge) of the optimal set mapping. This paper can be seen as a second part of the stability theory presented in [17], where we studied the stability of the feasible set mapping (completed here with the analysis of the Lipschitz-like property).
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Joint-stability in interindustry models relates to the mutual simultaneous consistency of the demand-driven and supply-driven models of Leontief and Ghosh, respectively. Previous work has claimed joint-stability to be an acceptable assumption from the empirical viewpoint, provided only small changes in exogenous variables are considered. We show in this note, however, that the issue has deeper theoretical roots and offer an analytical demonstration that shows the impossibility of consistency between demand-driven and supply-driven models.
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The Stability and Growth Pact (SGP) was established to govern discretionary fiscal policy in the European Monetary Union. This article studies the effects created when there is uncertainty about the members’ commitment to respecting the established deficit limits in the SGP. We will show that, even if countries respect the SGP deficit ceiling, the presence of uncertainty about their compliance will bring about higher volatility in key economic variables, which could, in turn, affect unemployment and growth negatively. This finding shows that it is important to reduce uncertainty about the members’ commitment towards the SGP. Keywords: fiscal policy rules, monetary union, Stability and Growth Pact, uncertainty, commitment. JEL No.: E63, F55, H62, H87
Resumo:
BACKGROUND: Persisting metallic intraocular foreign bodies (IOFB) with a ferrous content have been associated with ocular siderosis and retinal degeneration. We describe two patients in whom a metallic IOFB containing iron was left embedded for many years in the choroid and sclera after having penetrated through the vitreous and the retina. HISTORY AND SIGNS: Two male patients, aged 41 and 48 years, presented with a metallic IOFB sustained during a work accident involving metal tools. THERAPY AND OUTCOME: For the first patient it was deemed unwise to operate, as the IOFB was also lodged very deeply in the choroid and sclera in the inferior temporal quadrant. The second patient underwent pars plana vitrectomy, but the IOFB could not be removed surgically as it was too deeply embedded in the sclera and choroid. After a period of 6 years (Case 1) and 4 years (Case 2) of follow-up, visual acuity remained at 1.0 and the IOFB was encased in a fibrotic capsule in both cases. Full-field and multifocal electroretinograms showed an inter-ocular asymmetry at baseline, which remained stable during the follow-up. CONCLUSIONS: Ocular siderosis may not develop in patients with a deeply embedded metallic IOFB. Regular monitoring of both visual function and the electroretinogram is mandatory when the IOFB is left inside the eye.
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Rrésumé: La première description dans une publication médicale des douleurs neuropathiques remonte à 1872, le Dr S.W. Mitchell les résumant ainsi [...]" la causalgie est la plus terrible des tortures qu'une lésion nerveuse puisse entraîner "[...]. Par définition, la douleur neuropathique est une douleur chronique faisant suite à une lésion ou dysfonction du système nerveux. Malgré les progrès faits dans la compréhension de ce syndrome, le détail des mécanismes impliqués nous échappe encore et son traitement reste insuffisant car moins de 50% des patients sont soulagés par les thérapies actuelles. Différents modèles expérimentaux ont été élaborés chez l'animal de laboratoire, en particulier des modèles de lésion de nerfs périphériques chez le rat, permettant des investigations tant moléculaires que fonctionnelles des mécanismes impliqués dans le développement de ces douleurs. En revanche, peu de modèles existent chez la souris, alors que cet animal, grâce à la transgénèse, est très fréquemment utilisé pour l'approche fonctionnelle ciblée sur un gène. Dans l'étude présentée ici, nous avons évalué chez la souris C57BL/6 l'adaptation d'un modèle neuropathique, proposé une nouvelle modalité de mesure de la sensibilité douloureuse adaptée à la souris et défini une méthode d'analyse performante des résultats. Ce modèle, dit de lésion avec épargne nerveuse (spared Werve injury, SNI), consiste en la lésion de deux des trois branches du nerf sciatique, soit les nerfs peronier commun et tibial. La troisième branche, le nerf sural est laissé intact et c'est dans le territoire cutané de ce dernier que la sensibilité douloureuse à des stimulations mécaniques est enregistrée. Des filaments calibrés de force croissante sont appliqués sur la surface de la patte impliquée et la fréquence relative de retrait de la patte a été modélisée mathématiquement et analysée par un modèle statistique intégrant tous les paramètres de l'expérience (mixed-effects model). Des variantes chirurgicales lésant séquentiellement les trois branches du nerf sciatique ainsi que la réponse en fonction du sexe de l'animal ont également été évaluées. La lésion SNI entraîne une hypersensibilité mécanique marquée comparativement aux souris avec chirurgie contrôle; cet effet est constant entre les animaux et persiste durant les quatre semaines de l'étude. De subtiles différences entre les variables, y compris une divergence de sensibilité mécanique entre les sexes, ont été démontrées. La nécessité de léser le nerf tibial pour le développement des symptômes a également été documentée par notre méthode d'évaluation et d'analyse. En conclusion, nous avons validé le modèle SNI chez la souris par l'apparition d'un symptôme reproductible et apparenté à l'allodynie mécanique décrite par les patients souffrant de douleurs neuropathiques. Nous avons développé des méthodes d'enregistrement et d'analyse de la sensibilité douloureuse sensibles qui permettent la mise en évidence de facteurs intrinsèques et extrinsèques de variation de la réponse. Le modèle SNI utilisé chez des souris génétiquement modifiées, de par sa précision et reproductibilité, pourra permettre la discrimination de facteurs génétiques et épigénétiques contribuant au développement et à la persistance de douleurs neuropathiques.