Identifier les «préférences sociales»: une étude expérimentale en jeu d’ultimatum

Partant du constat que des préférences sociales très différentes peuvent conduire, assez paradoxalement, à des comportements assez similaires en jeu d’ultimatum, ce papier a pour ambition de proposer une méthode d’identification de ces préférences. Nous proposons une modélisation théorique en incertitude du comportement de trois types de joueurs : les égoïstes, les compétiteurs et les averses à l’inégalité et testons, lors d’une session expérimentale, son pouvoir prédictif des préférences sociales. Nous montrons alors que celles-ci peuvent être identifiées avec précision : lors d’un questionnaire post-expérimental, plus de 80% des joueurs valident notre prédiction sur leur préférence.Jeu d’ultimatum, préférences sociales

The effect of an organic pentasulfide EP additive in turning and milling operations

Coopération avec Ecole Centrale LyonBecause a cutting fluid could be equally used for different cutting operations, this study proposed to investigate the behavior of a well-known extreme-pressure additive (pentasulfide) in both turning and milling operations of a steel workpiece. The experimental approach is based on the coupling of mechanical tests (turning, milling, and tribological tests) with physico-chemical characterizations (Auger Electron Spectroscopy and X-Ray Photoelectron Spectroscopy) of the friction surfaces (chip and tool). In the case of milling, it was shown that the presence of a pentasulfide additive has a beneficial effect on the specific cutting energy (kc) and flank wear (Vb). These results are correlated with the presence of iron sulfides (FeS and FeS2) on the flank face of the cutter mill and on the chip face in contact with the mill. No such additive effects are found in case of turning. A lubrication model is proposed for the case of milling based on an indirect lubrication of the tool/workpiece and tool/chip contacts due to the transfer of iron and its reaction with sulfur compounds to produce iron sulfides. Because milling is a discontinuous cutting process, this lubrication mechanism is much more efficient than that observed in turning. Indeed, the tool faces are re-fed iron sulfides each time they leave the workpiece

Tribological aspect of lubrication in form tapping of high strength steel

Collaboration avec le LTDSThis study aims at analyzing the tribochemical mechanisms of lubrication during the process of form tapping and consequently optimizing the formulation of the lubricant. In order to correlate the tribochemical reactions with the performance of a lubricant, we measure the alteration of tapping torque according to ASTM D5619 standard. The objective of the study also relates to the identification of the additives and the association of their properties to the performance of lubrication. The goal is to characterize the nature of the tribofilm created at the bottom of the threads which is the zone the most severely affected by the working tool. X-ray Photoelectron Spectroscopy (XPS) is used to characterize the surface of formed threads. This study demonstrates a link between the sulphur reactions on the metallic surface and the friction reducing performance of lubricant during form tapping.Thèse CIFRE TOTA

Entre santé et contraintes organisationnelles: le rôle du manager

absentéisme, exemplarité, managers

Tribological aspect of lubrication in form tapping of high strength steel

Collaboration avec le LTDSThis study aims at analyzing the tribochemical mechanisms of lubrication during the process of form tapping and consequently optimizing the formulation of the lubricant. In order to correlate the tribochemical reactions with the performance of a lubricant, we measure the alteration of tapping torque according to ASTM D5619 standard. The objective of the study also relates to the identification of the additives and the association of their properties to the performance of lubrication. The goal is to characterize the nature of the tribofilm created at the bottom of the threads which is the zone the most severely affected by the working tool. X-ray Photoelectron Spectroscopy (XPS) is used to characterize the surface of formed threads. This study demonstrates a link between the sulphur reactions on the metallic surface and the friction reducing performance of lubricant during form tapping.Thèse CIFRE TOTA

Detection and characterization of biogenic selenium nanoparticles in selenium-rich yeast by single particle ICPMS

A method based on single particle inductively coupled plasma mass spectrometry (SP-ICPMS) was developed for the analysis of commercial Se-rich yeasts, to confirm the occurrence of selenium nanoparticles in these food supplements. A considerable reduction of background levels was achieved by combining data acquisition at microsecond dwell times and the use of a H2 reaction cell, improving by a factor of 10 the current state-of-the-art methodology, and bringing size detection limits down to 18 nm for selenium nanoparticles. The presence of nanoparticulate selenium was revealed by size-exclusion chromatography ICPMS, with detection of a selenium peak at the exclusion volume of the column showing absorption at a wavelength corresponding to selenium nanoparticles. SP-ICPMS allowed us to confirm the presence of Se-nanoparticles, as well as to calculate the nanoparticle size distribution, from information about the shape and elemental composition of the nanoparticles obtained by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS), respectively. These results reveal the significance of nanoparticles in the speciation of metals and metalloids in biological samples and the capability of SP-ICPMS in combination with TEM-EDS to carry out these analyses

Evaluation of Lubricant Viscosity and Base Oil Effects by Form Tapping Test

In order to correlate the effect of lubricant viscosity and base oil on the efficiency of a lubricant, we measure the variation of tapping torque according to ASTM D5619 standard. Three fully formulated lubricants containing the same additive package but having different viscosities are tested in the first part of the experiment. The effect of chemically active and chemically non-active paraffinic base oils combined with a sulphur additive is studied in the second part. The nature of the tribofilm created at the bottom of the threads formed during the second part of the study is characterized by X-ray Photoelectron Spectroscopy (XPS). The aim is to associate the surface analysis results with the efficiency obtained during the form tapping tests. The results show that the lubricant viscosity does not have any influence on the tapping torque values whereas physico-chemical interactions between different base oils and a sulphur additive can modify importantly the overall efficiency of lubricant

The role of iron and copper on the oligomerization dynamics of DR_2577, the main S-layer protein of deinococcus radiodurans

Surface (S)-layers are cryptic structures that coat the external surface of the bacterial cell in many species. The paracrystalline regularity of the S-layer is due to the self-assembling of one or more protein units. The property of self-assembling seems to be mediated by specific topologies of the S-layer proteins as well as the presence of specific ions that provide support in building and stabilizing the bi-dimensional S-layer organization. In the present study, we have investigated the self-assembling mechanism of the main S-layer protein of Deinococcus radiodurans (DR_2577) finding an unusual role played by Fe3+ and Cu2+ in the oligomerization of this protein. These findings may trace a structural and functional metallo-mediated convergence between the role of these metals in the assembling of the S-layer and their well-known roles in protecting against oxidative stress in D. radiodurans

Selenium biochemistry and its role for human health

Despite its very low level in humans, selenium plays an important and unique role among the (semi)metal trace essential elements because it is the only one for which incorporation into proteins is genetically encoded, as the constitutive part of the 21st amino acid, selenocysteine. Twenty-five selenoproteins have been identified so far in the human proteome. The biological functions of some of them are still unknown, whereas for others there is evidence for a role in antioxidant defence, redox state regulation and a wide variety of specific metabolic pathways. In relation to these functions, the selenoproteins emerged in recent years as possible biomarkers of several diseases such as diabetes and several forms of cancer. Comprehension of the selenium biochemical pathways under normal physiological conditions is therefore an important requisite to elucidate its preventing/therapeutic effect for human diseases. This review summarizes the most recent findings on the biochemistry of active selenium species in humans, and addresses the latest evidence on the link between selenium intake, selenoproteins functionality and beneficial health effects. Primary emphasis is given to the interpretation of biochemical mechanisms rather than epidemiological/observational data. In this context, the review includes the following sections: (1) brief introduction; (2) general nutritional aspects of selenium; (3) global view of selenium metabolic routes; (4) detailed characterization of all human selenoproteins; (5) detailed discussion of the relation between selenoproteins and a variety of human diseases

An experimental study on the effects of lubrication in form tapping

This paper presents the results of a study of lubrication in form tapping and aims at a better understanding of its effect. It appears that lubrication is of paramount importance. Oil with efficient high pressure additives can reduce considerably the torque necessary to form the thread. Lubricants reduce the tool / work material friction during the forming process and, as a consequence, the resulting strain distribution and the strain hardening of the thread are affected. This investigation includes an analysis on the effects of additives in lubricants on the temperature during tapping, enabling correlation with the appearance of chemical elements of the oil which react with the thread material and contribute to lubrication.These AMN these CIFR