Influence of surface tension, osmotic pressure and pores morphology on the densification of ice-templated ceramics

International audienceWe attempt here to clarify the influence of the nature of the solvent on the ice-templating process, based on literature experimental results of porosity and suspension concentration. In particular, we compare the relative influence of surface tension, osmotic pressure and the pore size and radius of curvature on the densification of the green bodies. Variations of the osmotic pressure when changing the solvent can yield significantly different behaviour during the freezing stage and therefore significantly affect the densification behaviour, an effect not apparent when using the Shanti model. In addition, and equally important, a modification of the macropores morphology is induced by the evolution of the solvent crystals morphology, and resulting in smaller and more intricate crystals and macropores which facilitates the densification. The radius of curvature is probably also an essential parameter controlling the densification of ice-templated ceramics

Deux mille musiciens et musiciennes d'Église en 1790

Accéder à la collection Muséfrem dans HAL-SHS http://hal.archives-ouvertes.fr/MUSEFREMAll over France, after 1790, a large number of church musicians found themselves without a job and without an income, because of the closure of chapters and abbeys. The documents they gathered, with a view to obtaining a pension or financial help provide a first rate documentation for the knowledge of this profession in the last years of the Ancien Régime. This rich corpus is now preserved both in the Archives Nationales in Paris (Comité ecclésiastique, série DXIX) and the Archives Départementales (série L). It is now the object of nation-wide research aiming at the establishment of a prosopographic data base managed by the Centre d'histoire "Espaces et Cultures" (CHEC, Université Blaise-Pascal, Clermont-Ferrand) within a project funded by the Agence Nationale de la Recherche, MUSÉFREM.Un grand nombre de musiciens d'Église, partout en France, perdent leur poste et leurs revenus à partir de 1790, en raison de la fermeture des chapitres et des abbayes. Les dossiers qu'ils rassemblent dans le but d'obtenir une pension ou un secours constituent une base documentaire de premier ordre pour connaître cette profession dans les dernières années de l'Ancien Régime. Ce riche corpus est aujourd'hui conservé aux Archives nationales à Paris (Comité ecclésiastique, série DXIX) et dans les dépôts départementaux (série L). Il fait l'objet d'une enquête nationale aboutissant à la mise en œuvre d'une base de données prosopographiques gérée par le Centre d'Histoire " Espaces et Cultures " (CHEC, Université Blaise-Pascal, Clermont-Ferrand), dans le cadre d'un projet soutenu par l'Agence nationale de la recherche, MUSÉFREM. Trois articles ont été publiés dans le cadre du programme de recherche Muséfrem, à l'issue du congrès du CTHS à Bordeaux (2009) : Bernard Dompnier, Sylvie Granger et Isabelle Langlois, "Deux mille musiciens et musiciennes d'Église en 1790" (http://halshs.archives-ouvertes.fr/docs/00/49/13/70/PDF/HAL_BORDEAUX_ENQUETE_2009.pdf), Marie-Claire Mussat, "L'itinérance dans la carrière des musiciens d'église" et Bastien Mailhot, Christophe Maillard et Françoise Talvard, "Musique et musiciens des églises de Guyenne en 1790 : bilan d'étape sur l'enquête collective et la base de données" (http://halshs.archives-ouvertes.fr/halshs-00877164)

Schelling dans la querelle de la méthode en France (1828-1840)

Peu étudiée, la querelle de la méthode, qui eut lieu entre 1828 et 1840 et mit en discussion trois nations philosophiques (Allemagne, Écosse, France) s’avère déterminante pour comprendre l’élaboration, via la réception de Schelling, d’une philosophie française. À partir de l’étude de cette querelle, ce travail propose d’identifier et d’analyser la fonction de Schelling dans l’élaboration d’une identité philosophique française, en particulier dans les spiritualismes concurrents de Victor Cousin et Félix Ravaisson. En retour, il nous ouvre de nouvelles perspectives sur la philosophie française du xixe siècle, mais aussi sur la philosophie schellingienne.The quarrel of the method (1828-1840), which is still rarely considered, connected three philosophical nations (Germany, Scotland, France) and is thus determining for the understanding of the elaboration, via the reception of Schelling, of a French philosophy. From the study of this quarrel, this work proposes to identify and analyze the function of Schelling in the elaboration of a French philosophical identity, particularly in the competing spiritualisms of Victor Cousin and Félix Ravaisson. Thus we can better understand French philosophy of the 19th century, as well as Schellingian philosophy

Présentation

Les études de réception en philosophie, notamment dans le cadre de l’étude des transferts culturels, recoupent aujourd’hui des enjeux qui vont bien au-delà de ce qu’on appelait autrefois les phénomènes d’« influence ». Il suffit, pour s’en convaincre, de relever quelques problématiques qui ressortent des recherches contemporaines (années 2000-2020).La question de la langue. La génération actuelle des traducteurs de Marx montre que les choix de traduction, déjà discutés du vivant de Marx, ont..

Phenomenological analysis of densification mechanism during spark plasma sintering of MgAl2O4

International audienceSpark plasma sintering (SPS) of MgAl2O4 powder was investigated at temperatures between 1200 and 1300°C. A significant grain growth was observed during densification. The densification rate always exhibits at least one strong minimum, and resumes after an incubation period. Transmission electron microscopy investigations performed on sintered samples never revealed extensive dislocation activity in the elemental grains. The densification mechanism involved during SPS was determined by anisothermal (investigation of the heating stage of a SPS run) and isothermal methods (investigation at given soak temperatures). Grain-boundary sliding, accommodated by an in-series {interface-reaction/lattice diffusion of the O 2-anions} mechanism controlled by the interface reaction step, governs densification. The zero-densification-rate period, detected for all soak temperatures, arise from the difficulty of annealing vacancies, necessary for the densification to proceed. The detection of atomic ledges at grain boundaries and the modification of the stoichiometry of spinel during SPS could be related to the difficulty to anneal vacancies at temperature soaks.

Influence of the amount of fine particles on rheological properties of uranium dioxide powders

International audienc

Performance of matrices developed to identify patients with early rheumatoid arthritis with rapid radiographic progression despite methotrexate therapy: an external validation study based on the ESPOIR cohort data

International audienceIntroduction Use of prediction matrices of risk or rapid radiographic progression (RRP) for early rheumatoid arthritis (RA) in clinical practice could help to better rationalise the first line of treatment. Before use, they must be validated in populations that have not participated in their construction. The main objective is to use the ESPOIR cohort to validate the performance of 3 matrices (ASPIRE, BEST and SONORA) to predict patients at high risk of RRP at 1 year of disease despite initial treatment with methotrexate (MTX).Methods We selected from the ESPOIR cohort 370 patients receiving MTX or leflunomide (LEF) for ≥3 months within the first year of follow-up. Patients were assessed clinically every 6 months, and structural damage progression seen on radiography was measured by the van der Heijde-modified Sharp score (vSHS) at 1 year. RRP was defined as an increase in the vSHS≥5 points during the first year.Results At 1 year, the mean vSHS score was 1.7±5.0 and 46 patients had RRP. The ASPIRE matrix had only moderate validity in the ESPOIR population, with area under the receiver operating characteristic curve (AUC) <0.7. The AUC for the BEST and SONORA matrices were 0.73 and 0.76. Presence of rheumatoid factor (RF)—or anti-citrullinated protein antibodies (ACPAs) and initial structural damage were always predictive of RRP at 1 year. Disease Activity Score in 28 joints (DAS28) and C reactive protein (ASPIRE threshold) were not associated with RRP.Conclusions Matrices to identify patients at risk of RRP tested in the ESPOIR cohort seem to perform moderately. There is no matrix that shows clearly superior performance

A four compartment epidemic model with retarded transition rates

We study an epidemic model for a constant population by taking into account four compartments of the individuals characterizing their states of health. Each individual is in one of the compartments susceptible (S); incubated - infected yet not infectious (C), infected and infectious (I), and recovered - immune (R). An infection is 'visible' only when an individual is in state I. Upon infection, an individual performs the transition pathway S to C to I to R to S remaining in each compartments C, I, and R for certain random waiting times, respectively. The waiting times for each compartment are independent and drawn from specific probability density functions (PDFs) introducing memory into the model. We derive memory evolution equations involving convolutions (time derivatives of general fractional type). We obtain formulae for the endemic equilibrium and a condition of its existence for cases when the waiting time PDFs have existing means. We analyze the stability of healthy and endemic equilibria and derive conditions for which the endemic state becomes oscillatory (Hopf) unstable. We implement a simple multiple random walker's approach (microscopic model of Brownian motion of Z independent walkers) with random SCIRS waiting times into computer simulations. Infections occur with a certain probability by collisions of walkers in compartments I and S. We compare the endemic states predicted in the macroscopic model with the numerical results of the simulations and find accordance of high accuracy. We conclude that a simple random walker's approach offers an appropriate microscopic description for the macroscopic model.Comment: 26 pages, 11 figure

Metastable and unstable cellular solidification of colloidal suspensions

International audienceColloidal particles are often seen as big atoms that can be directly observed in real space. They are therefore playing an increasingly important role as model systems to study processes of interest in condensed matter physics such as melting, freezing and glass transitions. The solidification of colloidal suspensions has long been a puzzling phenomenon with many unexplained features. Here we demonstrate and rationalize the existence of instability and metastability domains in cellular solidification of colloidal suspensions, by direct in situ high-resolution X-ray radiography and tomography observations. We explain such interface instabilities by a partial Brownian diffusion of the particles leading to constitutional supercooling situations. Processing under unstable conditions leads to localized and global kinetic instabilities of the solid/liquid interface , affecting the crystals morphology and particle redistribution behaviour