997 resultados para Equilibrium point


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Numerosos son ya los estudios que se han centrado en el llamado "cine serio" de Woody Allen y, entre ellos, cabe mencionar el que Pau Gilabert Barberà, autor de este artículo, escribió (2006) sobre lo que, en su opinión, es el legado sofístico subyacente en el guión de Crimes and Misdemeanors. En esta ocasión, su objetivo es analizar la trayectoria fluctuante del director americano en relación con la tragedia griega, desde la convicción de que, sólo así, es posible revelar su empatía con el espíritu trágico de los griegos y comprender su necesidad de presentar aquel género literario como un paradigma desde el cual entender las grandezas y miserias del mundo contemporáneo.

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A general and straightforward analytical expression for the defect-state-energy distribution of a-Si:H is obtained through a statistical-mechanical treatment of the hydrogen occupation for different sites. Broadening of available defect energy levels (defect pool) and their charge state, both in electronic equilibrium and nonequilibrium steady-state situations, are considered. The model gives quantitative results that reproduce different defect phenomena, such as the thermally activated spin density, the gap-state dependence on the Fermi level, and the intensity and temperature dependence of light-induced spin density. An interpretation of the Staebler-Wronski effect is proposed, based on the ''conversion'' of shallow charged centers to neutrals near the middle of the gap as a consequence of hydrogen redistribution.

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Background In patients presenting with acute cardiac symptoms, abnormal ECG and raised troponin, myocarditis may be suspected after normal angiography. Aims To analyse cardiac magnetic resonance (CMR) findings in patients with a provisional diagnosis of acute coronary syndrome (ACS) in whom acute myocarditis was subsequently considered more likely. Methods and results 79 patients referred for CMR following an admission with presumed ACS and raised serum troponin in whom no culprit lesion was detected were studied. 13% had unrecognised myocardial infarction and 6% takotsubo cardiomyopathy. The remainder (81%) were diagnosed with myocarditis. Mean age was 45615 years and 70% were male. Left ventricular ejection fraction (EF) was 58610%; myocardial oedema was detected in 58%. A myocarditic pattern of late gadolinium enhancement (LGE) was detected in 92%. Abnormalities were detected more frequently in scans performed within 2 weeks of symptom onset: oedema in 81% vs 11% (p<0.0005), and LGE in 100% vs 76% (p<0.005). In 20 patients with both an acute (<2 weeks) and convalescent scan (>3 weeks), oedema decreased from 84% to 39% (p<0.01) and LGE from 5.6 to 3.0 segments (p¼0.005). Three patients presented with sustained ventricular tachycardia, another died suddenly 4 days after admission and one resuscitated 7 weeks following presentation. All 5 patients had preserved EF. Conclusions Our study emphasises the importance of access to CMR for heart attack centres. If myocarditis is suspected, CMR scanning should be performed within 14 days. Myocarditis should not be regarded as benign, even when EF is preserved.

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The formation of coherently strained three-dimensional (3D) islands on top of the wetting layer in the Stranski-Krastanov mode of growth is considered in a model in 1 + 1 dimensions accounting for the anharmonicity and nonconvexity of the real interatomic forces. It is shown that coherent 3D islands can be expected to form in compressed rather than expanded overlayers beyond a critical lattice misfit. In expanded overlayers the classical Stranski-Krastanov growth is expected to occur because the misfit dislocations can become energetically favored at smaller island sizes. The thermodynamic reason for coherent 3D islanding is incomplete wetting owing to the weaker adhesion of the edge atoms. Monolayer height islands with a critical size appear as necessary precursors of the 3D islands. This explains the experimentally observed narrow size distribution of the 3D islands. The 2D-3D transformation takes place by consecutive rearrangements of mono- to bilayer, bi- to trilayer islands, etc., after the corresponding critical sizes have been exceeded. The rearrangements are initiated by nucleation events, each one needing to overcome a lower energetic barrier than the one before. The model is in good qualitative agreement with available experimental observations.

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Les POCT (point of care tests) ont un grand potentiel d'utilisation en médecine infectieuse ambulatoire grâce à leur rapidité d'exécution, leur impact sur l'administration d'antibiotiques et sur le diagnostic de certaines maladies transmissibles. Certains tests sont utilisés depuis plusieurs années (détection de Streptococcus pyogenes lors d'angine, anticorps anti-VIH, antigène urinaire de S. pneumoniae, antigène de Plasmodium falciparum). De nouvelles indications concernent les infections respiratoires, les diarrhées infantiles (rotavirus, E. coli entérohémorragique) et les infections sexuellement transmissibles. Des POCT, basés sur la détection d'acides nucléiques, viennent d'être introduits (streptocoque du groupe B chez la femme enceinte avant l'accouchement et la détection du portage de staphylocoque doré résistant à la méticilline). POCT have a great potential in ambulatory infectious diseases diagnosis, due to their impact on antibiotic administration and on communicable diseases prevention. Some are in use for long (S. pyogenes antigen, HIV antibodies) or short time (S. pneumoniae antigen, P. falciparum). The additional major indications will be community-acquired lower respiratory tract infections, infectious diarrhoea in children (rotavirus, enterotoxigenic E. coli), and hopefully sexually transmitted infections. Easy to use, these tests based on antigen-antibody reaction allow a rapid diagnosis in less than one hour; the new generation of POCT relying on nucleic acid detection are just introduced in practice (detection of GBS in pregnant women, carriage of MRSA), and will be extended to many pathogens

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The Organization of the Thesis The remainder of the thesis comprises five chapters and a conclusion. The next chapter formalizes the envisioned theory into a tractable model. Section 2.2 presents a formal description of the model economy: the individual heterogeneity, the individual objective, the UI setting, the population dynamics and the equilibrium. The welfare and efficiency criteria for qualifying various equilibrium outcomes are proposed in section 2.3. The fourth section shows how the model-generated information can be computed. Chapter 3 transposes the model from chapter 2 in conditions that enable its use in the analysis of individual labor market strategies and their implications for the labor market equilibrium. In section 3.2 the Swiss labor market data sets, stylized facts, and the UI system are presented. The third section outlines and motivates the parameterization method. In section 3.4 the model's replication ability is evaluated and some aspects of the parameter choice are discussed. Numerical solution issues can be found in the appendix. Chapter 4 examines the determinants of search-strategic behavior in the model economy and its implications for the labor market aggregates. In section 4.2, the unemployment duration distribution is examined and related to search strategies. Section 4.3 shows how the search- strategic behavior is influenced by the UI eligibility and section 4.4 how it is determined by individual heterogeneity. The composition effects generated by search strategies in labor market aggregates are examined in section 4.5. The last section evaluates the model's replication of empirical unemployment escape frequencies reported in Sheldon [67]. Chapter 5 applies the model economy to examine the effects on the labor market equilibrium of shocks to the labor market risk structure, to the deep underlying labor market structure and to the UI setting. Section 5.2 examines the effects of the labor market risk structure on the labor market equilibrium and the labor market strategic behavior. The effects of alterations in the labor market deep economic structural parameters, i.e. individual preferences and production technology, are shown in Section 5.3. Finally, the UI setting impacts on the labor market are studied in Section 5.4. This section also evaluates the role of the UI authority monitoring and the differences in the Way changes in the replacement rate and the UI benefit duration affect the labor market. In chapter 6 the model economy is applied in counterfactual experiments to assess several aspects of the Swiss labor market movements in the nineties. Section 6.2 examines the two equilibria characterizing the Swiss labor market in the nineties, the " growth" equilibrium with a "moderate" UI regime and the "recession" equilibrium with a more "generous" UI. Section 6.3 evaluates the isolated effects of the structural shocks, while the isolated effects of the UI reforms are analyzed in section 6.4. Particular dimensions of the UI reforms, the duration, replacement rate and the tax rate effects, are studied in section 6.5, while labor market equilibria without benefits are evaluated in section 6.6. In section 6.7 the structural and institutional interactions that may act as unemployment amplifiers are discussed in view of the obtained results. A welfare analysis based on individual welfare in different structural and UI settings is presented in the eighth section. Finally, the results are related to more favorable unemployment trends after 1997. The conclusion evaluates the features embodied in the model economy with respect to the resulting model dynamics to derive lessons from the model design." The thesis ends by proposing guidelines for future improvements of the model and directions for further research.

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We investigate the phase behavior of a single-component system in three dimensions with spherically-symmetric, pairwise-additive, soft-core interactions with an attractive well at a long distance, a repulsive soft-core shoulder at an intermediate distance, and a hard-core repulsion at a short distance, similar to potentials used to describe liquid systems such as colloids, protein solutions, or liquid metals. We showed [Nature (London) 409, 692 (2001)] that, even with no evidence of the density anomaly, the phase diagram has two first-order fluid-fluid phase transitions, one ending in a gas¿low-density-liquid (LDL) critical point, and the other in a gas¿high-density-liquid (HDL) critical point, with a LDL-HDL phase transition at low temperatures. Here we use integral equation calculations to explore the three-parameter space of the soft-core potential and perform molecular dynamics simulations in the interesting region of parameters. For the equilibrium phase diagram, we analyze the structure of the crystal phase and find that, within the considered range of densities, the structure is independent of the density. Then, we analyze in detail the fluid metastable phases and, by explicit thermodynamic calculation in the supercooled phase, we show the absence of the density anomaly. We suggest that this absence is related to the presence of only one stable crystal structure.

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We study the dynamics of density fluctuations in purely diffusive systems away from equilibrium. Under some conditions the static density correlation function becomes long ranged. We then analyze this behavior in the framework of nonequilibrium fluctuating hydrodynamics.

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We have shown that the mobility tensor for a particle moving through an arbitrary homogeneous stationary flow satisfies generalized Onsager symmetry relations in which the time-reversal transformation should also be applied to the external forces that keep the system in the stationary state. It is then found that the lift forces, responsible for the motion of the particle in a direction perpendicular to its velocity, have different parity than the drag forces.

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In a recent paper, [J. M. Porrà, J. Masoliver, and K. Lindenberg, Phys. Rev. E 48, 951 (1993)], we derived the equations for the mean first-passage time for systems driven by the coin-toss square wave, a particular type of dichotomous noisy signal, to reach either one of two boundaries. The coin-toss square wave, which we here call periodic-persistent dichotomous noise, is a random signal that can only change its value at specified time points, where it changes its value with probability q or retains its previous value with probability p=1-q. These time points occur periodically at time intervals t. Here we consider the stationary version of this signal, that is, equilibrium periodic-persistent noise. We show that the mean first-passage time for systems driven by this stationary noise does not show either the discontinuities or the oscillations found in the case of nonstationary noise. We also discuss the existence of discontinuities in the mean first-passage time for random one-dimensional stochastic maps.

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The front form and the point form of dynamics are studied in the framework of predictive relativistic mechanics. The non-interaction theorem is proved when a Poincar-invariant Hamiltonian formulation with canonical position coordinates is required.

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In this Contribution we show that a suitably defined nonequilibrium entropy of an N-body isolated system is not a constant of the motion, in general, and its variation is bounded, the bounds determined by the thermodynamic entropy, i.e., the equilibrium entropy. We define the nonequilibrium entropy as a convex functional of the set of n-particle reduced distribution functions (n ? N) generalizing the Gibbs fine-grained entropy formula. Additionally, as a consequence of our microscopic analysis we find that this nonequilibrium entropy behaves as a free entropic oscillator. In the approach to the equilibrium regime, we find relaxation equations of the Fokker-Planck type, particularly for the one-particle distribution function.

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The liquid-liquid critical point scenario of water hypothesizes the existence of two metastable liq- uid phases low-density liquid (LDL) and high-density liquid (HDL) deep within the supercooled region. The hypothesis originates from computer simulations of the ST2 water model, but the stabil- ity of the LDL phase with respect to the crystal is still being debated. We simulate supercooled ST2 water at constant pressure, constant temperature, and constant number of molecules N for N ≤ 729 and times up to 1 μs. We observe clear differences between the two liquids, both structural and dynamical. Using several methods, including finite-size scaling, we confirm the presence of a liquid-liquid phase transition ending in a critical point. We find that the LDL is stable with respect to the crystal in 98% of our runs (we perform 372 runs for LDL or LDL-like states), and in 100% of our runs for the two largest system sizes (N = 512 and 729, for which we perform 136 runs for LDL or LDL-like states). In all these runs, tiny crystallites grow and then melt within 1 μs. Only for N ≤ 343 we observe six events (over 236 runs for LDL or LDL-like states) of spontaneous crystal- lization after crystallites reach an estimated critical size of about 70 ± 10 molecules.

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Enfants de moins de 10 ans fumant passivement 14 cigarettes ! D'avril 2010 à avril 2011, l'exposition de 148 enfants (81 garçons et 67 filles) a été testée: 10 enfants de moins d'un an, 25 de 1 à 5 ans, 19 de 5 à 10 ans, 30 de 10 à 15 ans et 64 de 15 à 18 ans. 10 d'entre eux sont des fumeurs et la plus jeune de 14 ans fume 10 cigarettes par jour. Leurs parents, ou parfois des jeunes eux-mêmes, ont commandé de manière volontaire, via les sites Internet des CIPRET Valais, Vaud et Genève, un badge MoNIC gratuit. Les résultats quant à l'exposition de ces enfants interpellent et méritent l'attention.Pour l'ensemble des enfants, la concentration moyenne de nicotine dans leur environnement intérieur mesurée via les dispositifs MoNIC est de 0,5 mg/m3, avec des maximums pouvant aller jusqu'à 21 mg/m3. Pour le collectif d'enfants âgés de moins de 10 ans (26 garçons et 28 filles; tous non-fumeurs), la concentration de nicotine n'est pas négligeable (moyenne 0,069 mg/m3, min 0, max 0,583 mg/m3). En convertissant ce résultat en équivalent de cigarettes inhalées passivement, nous obtenons des chiffres allant de 0 à 14 cigarettes par jour* avec une moyenne se situant à 1.6 cig/j. Encore plus surprenant, les enfants de moins d'un an (4 garçons et 6 filles) inhalent passivement, dans le cadre familial, en moyenne 1 cigarette (min 0, max 2.2). Pour les deux autres collectifs: 10-15 ans et 15-18 ans, les valeurs maximales avoisinent les 22 cigarettes. Notons cependant que ce résultat est influencé, ce qui n'est pas le cas des enfants plus jeunes, par le fait que ces jeunes sont également parfois des fumeurs actifs.* Quand la durée d'exposition dépassait 1 jour (8 heures), le nombre d'heures a toujours été divisé par 8 heures. Le résultat obtenu donne l'équivalent de cigarettes fumées passivement en huit heures. Il s'agit de ce fait d'une moyenne, ce qui veut dire que durant cette période les enfants ont pu être exposés irrégulièrement à des valeurs supérieures ou inférieures à cette moyenne. [Auteurs]