Semi-batch crystallization of gypsum from calcite and sulfuric acid

International audienceOne of the most important environmental issues for decades to come is the treatment of industrial wastewaters containing salts (sulfates, chlorides, sodium, magnesium ...) which can lead to strong perturbations affecting the fauna and flora when highly concentrated at the discharge point. Different processes used to separate the dissolved salts from the liquid matrix may be encountered depending on the nature and the composition of the effluent. One major objective in the R&D sectors of water and environment is to optimize such processes, while another is to promote the treated wastewaters by recycling the cleared liquid phase or reusing some compounds they contain in other production processes. The latter is of great interest, both to limit the amount of waste and to save natural resources including rare metals but also less noble materials whose amount consumed each year is very important, but the one available not unlimited. Gypsum, the most important raw material of plaster's industry, is a rather interesting example from this point of view as world's known resources are estimated at 2.34 billion tons, which roughly represents 25 years of operation. The industry of plaster will therefore meet in the coming decades a decrease in resources for the commodity, especially in some countries where gypsum deposits will eventually become out of reach or completely depleted

Dense suspension of solid particles as a new heat transfer fluid for concentrated solar thermal plants: on-sun proof of concept

This paper demonstrates the capacity of dense suspensions of solid particles to transfer concentrated solar power from a tubular receiver to an energy conversion process by acting as a heat transfer fluid. Contrary to a circulating fluidized bed, the dense suspension of particles’ flows operates at low gas velocity and large solid fraction. A single-tube solar receiver was tested with 64 µm mean diameter silicon carbide particles for solar flux densities in the range 200–250 kW/m2, resulting in a solid particle temperature increase ranging between 50 °C and 150 °C. The mean wall-to-suspension heat transfer coefficient was calculated from experimental data. It is very sensitive to the particle volume fraction of the suspension, which was varied from 26 to 35%, and to the mean particle velocity. Heat transfer coefficients ranging from 140 W/m2 K to 500 W/m2 K have been obtained, thus corresponding to a 400 W/m2 K mean value for standard operating conditions (high solid fraction) at low temperature. A higher heat transfer coefficient may be expected at high temperatures because the wall-to-suspension heat transfer coefficient increases drastically with temperature. The suspension has a heat capacity similar to a liquid heat transfer fluid, with no temperature limitation but the working temperature limit of the receiver tube. Suspension temperatures of up to 750 °C are expected for metallic tubes, thus opening new opportunities for high efficiency thermodynamic cycles such as supercritical steam and supercritical carbon dioxide

Characterization of Desulfovibrio giganteus sp. nov., a sulfate-reducing bacterium isolated from a brackish coastal lagoon

In the course of ecological studies in Berre Lagoon, a mediterranean brackish coastal lagoon (Marseille, France), a new slightly halophilic sulfate-reducing bacterium was isolated from anoxic sediments enriched with lactate plus sulfate, and cysteine-HCL as reductant. Because of its morphology and the incomplete oxidation of organic substrates, the isolated strain 8601 was assigned to the genus #Desulfovibrio, resembling #Desulfovibrio gigas. However, it differed from this species in some morphological and physiological characteristics : only one polar flagellum the utilization of methanol, isopropanol, glycerol and cysteine as energy source. Therefore a new species #Desulfovibrio giganteus$ is described. (Résumé d'auteur

Le syndrome de Pinocchio ou la question du départ / Pinocchio's syndrome or the question of departure

Le syndrome de Pinocchio ou la question du dépar

A natureza ama esconder-se: o objeto do encontro

À plusieurs reprises Lacan a insisté, en particulier dans son séminaire sur l'Éthique de la psychanalyse, sur l'importance de retourner aux textes aristotéliciens. Dans Les Quatre concepts fondamentaux de la psychanalyse, il consacre une leçon au commentaire des notions physiques, tuchè et automaton. Essayons donc de questionner Lacan à partir d'Aristote, même si le risque serait de dresser un inventaire de ce qui fait sens pour une lecture analytique. L'originalité d'Aristote tient entre autres dans sa manière d'appréhender le réel en examinant le particulier qui résiste et dysfonctionne pour définir une norme universelle. Tuchè et automaton sont des phénomènes résiduels qui proviennent de l'observation de la physis, et Aristote se fonde sur les travaux préaristotéliciens pour lire entre les lignes ce qui a été passé sous silence bien qu'utilisé avant d'en faire un couple conceptuel au sein du système causal.À plusieurs reprises Lacan a insisté, en particulier dans son séminaire sur l'Éthique de la psychanalyse, sur l'importance de retourner aux textes aristotéliciens. Dans Les Quatre concepts fondamentaux de la psychanalyse, il consacre une leçon au commentaire des notions physiques, tuchè et automaton. Essayons donc de questionner Lacan à partir d'Aristote, même si le risque serait de dresser un inventaire de ce qui fait sens pour une lecture analytique. L'originalité d'Aristote tient entre autres dans sa manière d'appréhender le réel en examinant le particulier qui résiste et dysfonctionne pour définir une norme universelle. Tuchè et automaton sont des phénomènes résiduels qui proviennent de l'observation de la physis, et Aristote se fonde sur les travaux préaristotéliciens pour lire entre les lignes ce qui a été passé sous silence bien qu'utilisé avant d'en faire un couple conceptuel au sein du système causal.RESUMO:Por diversas vezes Lacan insistiu, em particular no seu seminário sobre a Ética da psicanálise, sobre a importância de retornar aos textos aristotélicos. Na obra Os quatro conceitos fundamentais da psicanálise, ele dedica uma aula ao comentário das noções físicas tyche e automaton. Tentemos, pois, questionar Lacan a partir de Aristóteles, mesmo com o risco de erguer um inventário do que faz sentido para uma leitura analítica. A originalidade de Aristóteles consiste, entre outras coisas, em sua maneira de apreender o real através da análise do particular que resiste e disfunciona, para definir uma norma universal. Tyche e automaton são fenômenos residuais que provêm da observação da physis, e Aristóteles se baseia nos trabalhos pré-aristotélicos para ler nas entrelinhas o que foi passado em silêncio, embora utilizado, antes de formar um par conceitual no seio do sistema causal. RÉSUMÉ:À plusieurs reprises Lacan a insisté, en particulier dans son séminaire sur l'Éthique de la psychanalyse, sur l'importance de retourner aux textes aristotéliciens. Dans Les Quatre concepts fondamentaux de la psychanalyse, il consacre une leçon au commentaire des notions physiques, tuchè et automaton. Essayons donc de questionner Lacan à partir d'Aristote, même si le risque serait de dresser un inventaire de ce qui fait sens pour une lecture analytique. L'originalité d'Aristote tient entre autres dans sa manière d'appréhender le réel en examinant le particulier qui résiste et dysfonctionne pour définir une norme universelle. Tuchè et automaton sont des phénomènes résiduels qui proviennent de l'observation de la physis, et Aristote se fonde sur les travaux préaristotéliciens pour lire entre les lignes ce qui a été passé sous silence bien qu'utilisé avant d'en faire un couple conceptuel au sein du système causal

Placental malaria : decreased transfer of maternal antibodies directed to Plasmodium falciparum and impact on the incidence of febrile infections in infants

The efficacy of mother-to-child placental transfer of antibodies specific to malaria blood stage antigens was investigated in the context of placental malaria infection, taking into account IgG specificity and maternal hypergammaglobulinemia. The impact of the resulting maternal antibody transfer on infections in infants up to the age of 6 months was also explored. This study showed that i) placental malaria was associated with a reduced placental transfer of total and specific IgG, ii) antibody placental transfer varied according to IgG specificity and iii) cord blood malaria IgG levels were similar in infants born to mothers with or without placental malaria. The number of malaria infections was negatively associated with maternal age, whereas it was not associated with the transfer of any malaria-specific IgG from the mother to the fetus. These results suggest that i) malaria-specific IgG may serve as a marker of maternal exposure but not as a useful marker of infant protection from malaria and ii) increasing maternal age contributes to diminishing febrile infections diagnosed in infants, perhaps by means of the transmission of an effective antibody response

Chromosomal location of a gene that controls sterol esterification in Triticum aestivum L.

A previously described D genome locus (Pln) that controls sterol esterification in the wheat kernel has been assigned to the short arm of chromosome 7 D by comparison of the steryl ester phenotype of euploid kernels of Triticum aestivum variety Chinese Spring with those of the compensated nulli-tetrasomic lines and the 7 D S ditelosomic. Palmitate is the predominant ester in all but the 7 D nullisomic combinations, which have linoleate as the main ester. These lines also show a marked decrease in sterol esterification and a two-fold increase in free sterol, indicating that chromosomes 7 A and 7 B do not compensate for the loss of esterification capacity associated with 7 D

On the relevance of APIs facing fairwashed audits

Recent legislation required AI platforms to provide APIs for regulators to assess their compliance with the law. Research has nevertheless shown that platforms can manipulate their API answers through fairwashing. Facing this threat for reliable auditing, this paper studies the benefits of the joint use of platform scraping and of APIs. In this setup, we elaborate on the use of scraping to detect manipulated answers: since fairwashing only manipulates API answers, exploiting scraps may reveal a manipulation. To abstract the wide range of specific API-scrap situations, we introduce a notion of proxy that captures the consistency an auditor might expect between both data sources. If the regulator has a good proxy of the consistency, then she can easily detect manipulation and even bypass the API to conduct her audit. On the other hand, without a good proxy, relying on the API is necessary, and the auditor cannot defend against fairwashing. We then simulate practical scenarios in which the auditor may mostly rely on the API to conveniently conduct the audit task, while maintaining her chances to detect a potential manipulation. To highlight the tension between the audit task and the API fairwashing detection task, we identify Pareto-optimal strategies in a practical audit scenario. We believe this research sets the stage for reliable audits in practical and manipulation-prone setups.Comment: 18 pages, 7 figure

Fluorite's precipitation in KOH solutions in view of removing fluorides from wastewaters

International audienceThe process under study aims at removing dissolved fluorides from effluent waters through the addition of calcium and the precipitation of fluorite in a fluidized bed. In the concept developed at COMURHEX, the effluent is a highly concentrated KOH solution and the calcium is provided as a suspension of portlandite with calcite as an impurity. COMURHEX's target is to achieve an efficient defluorination of KOH solutions prior to recycling and to control the growth of the fluorite grains. Since building a fluorite crystallisation model requires a thermodynamic basis, we started exploring portlandite, calcite and fluorite solubility in concentrated KOH solutions. We are primarily concerned with equilibria in the system Ca(OH)2-CaCO3-CaF2-KOHH2O at temperatures 15 - 35°C in KOH solutions up to 6M (340g/kg). Suspensions and mixtures are prepared in a 3 L stirred reactor under N2 atmosphere and the temperature is varied. Liquid samples are taken from the reactor, filtered, diluted, and analysed by ICP-AES for cations and ionic chromatography for anions, while the solids are washed in ethanol and observed by SEM. In order to choose materials and improve techniques, this work was started with the Ca(OH)2-CaCO3-KOH-H2O subsystem, where solubility data and speciation models are already available from the literature. In this subsystem we experienced the analytical and kinetic difficulties already quoted by other authors. Albeit ICP-AES is very sensitive, Ca analysis is difficult in KOH solutions, because portlandite solubility is low and a matrix effect of potassium weakens the Ca signal, so that its calibration must be performed using KOH solutions rather than conventional (dilute) standards. This problem was overcome by using the standard addition method where the calibrating solutions are prepared at the same KOH concentration as the unknown samples and spiked with increasing amounts of calcium. This method enables the absolute calcium variations to be calibrated and the calcium present as impurities in the KOH parent solution (and thus in the standards) to be evaluated by regression

VITRUV - Science Cases

VITRUV is a second generation spectro-imager for the PRIMA enabled Very Large Telescope Interferometer. By combining simultaneously up to 8 telescopes VITRUV makes the VLTI up to 6 times more efficient. This operational gain allows two novel scientific methodologies: 1) massive surveys of sizes; 2) routine interferometric imaging. The science cases presented concentrate on the qualitatively new routine interferometric imaging methodology. The science cases are not exhaustive but complementary to the PRIMA reference mission. The focus is on: a) the close environment of young stars probing for the initial conditions of planet formation and disk evolution; b) the surfaces of stars tackling dynamos, activity, pulsation, mass-loss and evolution; c) revealing the origin of the extraordinary morphologies of Planetary Nebulae and related stars; d) studying the accretion-ejection structures of stellar black-holes (microquasars) in our galaxy; e) unveiling the different interacting components (torus, jets, BLRs) of Active Galactic Nuclei; and f) probing the environment of nearby supermassive black-holes and relativistic effects in the Galactic Center black-hole.Comment: 15 pages. The Power of Optical/IR Interferometry: Recent Scientific Results and 2nd Generation VLTI Instrumentation, Allemagne (2005) in pres