Fe-C and Fe-H systems at pressures of the Earth's inner core

The solid inner core of the Earth is predominantly composed of iron alloyed with several percent Ni and some lighter elements, Si, S, O, H, and C being the prime candidates. There have been a growing number of papers investigating C and H as possible light elements in the core, but the results are contradictory. Here, using ab initio simulations, we study the Fe-C and Fe-H systems at inner core pressures (330-364 GPa). Using the evolutionary structure prediction algorithm USPEX, we have determined the lowest-enthalpy structures of possible carbides (FeC, Fe2C, Fe3C, Fe4C, FeC2, FeC3, FeC4 and Fe7C3) and hydrides (Fe4H, Fe3H, Fe2H, FeH, FeH2, FeH3, FeH4) and have found that Fe2C (Pnma) is the most stable iron carbide at pressures of the inner core, while FeH, FeH3 and FeH4 are stable iron hydrides at these conditions. For Fe3C, the cementite structure (Pnma) and the Cmcm structure recently found by random sampling are less stable than the I-4 and C2/m structures found here. We found that FeH3 and FeH4 adopt chemically interesting thermodynamically stable structures, in both compounds containing trivalent iron. The density of the inner core can be matched with a reasonable concentration of carbon, 11-15 mol.percent (2.6-3.7 wt.percent) at relevant pressures and temperatures. This concentration matches that in CI carbonaceous chondrites and corresponds to the average atomic mass in the range 49.3-51.0, in close agreement with inferences from the Birch's law for the inner core. Similarly made estimates for the maximum hydrogen content are unrealistically high, 17-22 mol.percent (0.4-0.5 wt.percent), which corresponds to the average atomic mass in the range 43.8-46.5. We conclude that carbon is a better candidate light alloying element than hydrogen.Comment: Published in Physics-Uspekhi: full text will soon appear at http://ufn.ru/en/articles/2012/5/c/ (currently, only abstract is available

La charte du moniteur d'atelier à Brico-CES-services : droits et devoirs envers l'usager

Ce travail est adapté au contexte institutionnel du centre d'ergo-sociothérapie (CES) de Prilly. Dans une première partie, l'auteur présente le centre d'ergo-sociothérapie où travaille le moniteur d'atelier. Puis, il définit la profession de moniteur d'atelier, ainsi que les tâches qui lui sont propres. Cette analyse permet de préciser le modus operandi du moniteur d'atelier dans le cadre de la constitution de la chartre du moniteur d'atelier à Brico-CES-Services. L'exposé sur les droits des patients psychiques aide à réglementer les droits et devoirs du moniteur d'atelier envers l'usager inscrit aux ateliers. Ce travail s'achève par les dispositions qui constitueront la chartre du moniteur d'atelier à Brico-CES-Services

Elastic strain engineering of charge and thermal transport in semiconductor nanostructures: the role of heterogeneity

A variety of emergent phenomena in mechanical behavior, heat conduction, and electronic charge transport arise in materials when length scales associated with the physical dimensions or intrinsic structure approach the nanoscale. For instance, defect ensemble interactions and poor mechanical strength give way to discrete plasticity and ultra high strength in elemental nanostructures; facile thermal transport gives way to abundant phonon scattering in nanomaterials; and electronic band structure becomes altered in quantum-confined systems. Despite novel structural and transport physics discovered in many inorganic nanostructures, the interconnections between these various fields to exploit further property enhancements have received only recent attention. In this discussion, we describe the combination of a large dynamic range of elastic strain available in nanostructures with unique transport physics to enable tunable functional response via elastic strain engineering. In particular, the effect of strain heterogeneity on thermal and charge transport will be addressed by way of two examples on Si nanostructures. First, we report experimental measurements of the effect of tensile stress on thermal conductivity of an individual suspended Si nanowire using in situ Raman piezothermography. Our results show that, whereas phononic transport in undoped Si nanowires is only marginally affected by uniform elastic tensile strain, point defects introduced via ion bombardment that disrupt the pristine lattice reduces the thermal conductivity by over 70%. The second example furthers the study of inhomogeneous strains by showing tunable electrical conductivity and Seebeck coefficients in strained silicon nanomeshes with architected porosity. Using batch fabrication of freestanding nanomesh films from silicon-on-insulator wafers, we present a unique platform for exploring the effects of both changes in nanomesh geometry and strain state on charge transport. Experimental results are analyzed by combining analytical models for electron mobility in uniformly stressed silicon with finite element analysis of strained silicon nanomeshes. Our results show that the nonuniform and multiaxial strain fields defined by the nanomesh geometry give rise to spatially varying band shifts and warping, which in aggregate accelerate electron transport along directions of high stress. This allows for global electrical conductivity and Seebeck enhancements beyond those of homogenous samples under equivalent far-field stresses, ultimately increasing thermoelectric power factor over unstrained samples

Fit bur idle or frail but active? Estimating latent health-related work capacity among elderly Italians

This paper estimates if and to what extend older Italians could work, given their health status. It does so by comparing actual labour force participation rates to counterfactual participation rates. One participation rate is constructed through a non-parametric method, comparing actual rates with past ones, holding death rate, a proxy for health, constant. The other method creates a counterfactual rate by comparing younger and older individuals with the same health status. The results of both analyses point towards spare work capacity among the Italian male and female workforce of 5.97 years or 57% in terms of additional participation rate (for males) depending on the method, years and age. Results are in line with ndings for developed countries following the same approach

Estimation of genetic merit from bivariate « all or none » responses

A method of analysis of bivariate « all or none » categorical responses arising in animal breeding is presented. Conceptual bivariate normal variates following a mixed linear model are mapped onto a discrete scale via fixed thresholds. Parameters of the underlying scale are estimated in a Bayesian framework by finding the mode of a joint posterior distribution. The method requires iterative implementation and evaluation of bivariate normal integrals ; estimation equations are presented. An application of the method to data on calf viability and calving ease is presented.Cet article présente une méthode d’analyse bidimensionnelle de caractères tout-ou-rien intervenant en sélection animale. La modélisation des réponses tout-ou-rien postule l’existence d’une distribution binormale de variables sous-jacentes à seuils qui suivent un modèle linéaire mixte. Les paramètres sur l’échelle sous-jacente sont estimés selon une procédure bayesienne à partir du mode de la distribution a posteriori. La méthode implique une résolution itérative et le calcul d’intégrales normales à 2 dimensions. Le système correspondant d’équations est décrit. La méthode est illustrée par une application à des données de viabilité et conditions de naissance de veaux

Changing Jurisdiction in Chancery Court

Commen