The role of hematite in aluminosilicate gels based on metakaolin

International audienceThis paper investigates the role of iron oxide in natural clay and its contribution to polycondensation reactions. Iron oxide was added to pure kaolin in the same proportion as Medenine clay with different amounts of potassium hydroxide. The physicochemical and structural properties of these materials were determined by infrared spectroscopy, scanning electron microscopy, thermal analyses (DTA-TG) and X-ray diffraction. The amorphous character seen in the diffractograms obtained from the materials and the displacement of the IR wavenumber are indicative of a polycondensation reaction. The representative characterization of the microstructure of different samples using electron microscopy highlights the nonreactivity of iron exhibited during consolidation. In general, the contribution of iron oxide seems to be small under the conditions described here

EFFECT OF CALCINATION TEMPERATURE OF TUNISIAN CLAYS ON THE PROPERTIES OF GEOPOLYMERS

Geopolymers are amorphous three dimensional aluminosilicate materials that may be synthesized at room or slightly higher temperature by alkaline activation of aluminosilicates obtained from industrial wastes, calcined clays and natural minerals. Among the different family of geopolymers, two Tunisian clays (a kaolinite clay from Tabarka and illito/kaolinitic clay from Medenine) are tested for their feasibility of geopolymers at low temperature. The unfired and calcined clays were dissolved in strongly alkaline solution in order to produce consolidated materials whose pastes were characterized by their compressive strength. Hardened geopolymer samples were also submitted to X-Ray diffraction, FTIR spectroscopy and scanning electron microscopy analyses. The geopolymer strength is related to the structure and reactivity of the clay generated by thermal treatment and to the role of associated minerals in clays. The amorphous character of obtained geopolymers and the displacement of the IR wavenumber are signature of geopolymerisation reaction

Myasthenie - spondylarthropathies: association fortuite ? A propos d’un cas et revue de la littérature

Propos Nous rapportons le cas d’un patient atteint d’une myasthénie associée à une spondylarthropathie. Cette observation est originale de part sa rareté, six cas seulement on été rapportés dans la littérature et le problème que pose cette association : est ce qu’elle est fortuite ou impliquerait-elle d’autres facteurs génétiques qui restent à prouver ?Observation Monsieur J.H. âgé de 32 ans, aux antécédents de myasthénie depuis 2002, était hospitalisé en avril 2004 pour polyarthrite chronique bilatérale et asymétrique évoluant depuis un an, touchant le poignet gauche, les inter phalangiennes proximales des 3ème et 5ème doigts droits et le genou droit associées à des talalgiesbilatérales et une douleur des articulations sacro-iliaques. La biologie montrait un syndrome inflammatoire modéré, des facteurs rhumatoïdes faiblement positifs et un typage HLA B7 et B17. Le bilan radiologiquemontrait une arthrite des mains, une enthésite calcanéenne et permettait de suspecter une sacro-iliite bilatérale qui était confirmée par un scanner. L’évolution était bonne sous anti- inflammatoires nonstéroïdiens pendant 6 mois. Il consulte en janvier 2006 pour le même tableau associé à une sècheresse buccale et oculaire. Le bilan trouvait une VS à 20, des facteurs rhumatoïdes faiblement positifs mais desAAN positifs à un taux 1/160 homogènes avec des anti SSA. Les radiographies standard montraient une carpite stade II gauche. L’examen ophtalmologique a confirmé le syndrome sec oculaire. La biopsie des glandes salivaires accessoires a montré un syndrome de Gougerot Sjögren grade 2 de Shisholm

Defending with Errors: Approximate Computing for Robustness of Deep Neural Networks

Machine-learning architectures, such as Convolutional Neural Networks (CNNs) are vulnerable to adversarial attacks: inputs crafted carefully to force the system output to a wrong label. Since machine-learning is being deployed in safety-critical and security-sensitive domains, such attacks may have catastrophic security and safety consequences. In this paper, we propose for the first time to use hardware-supported approximate computing to improve the robustness of machine-learning classifiers. We show that successful adversarial attacks against the exact classifier have poor transferability to the approximate implementation. Surprisingly, the robustness advantages also apply to white-box attacks where the attacker has unrestricted access to the approximate classifier implementation: in this case, we show that substantially higher levels of adversarial noise are needed to produce adversarial examples. Furthermore, our approximate computing model maintains the same level in terms of classification accuracy, does not require retraining, and reduces resource utilization and energy consumption of the CNN. We conducted extensive experiments on a set of strong adversarial attacks; We empirically show that the proposed implementation increases the robustness of a LeNet-5, Alexnet and VGG-11 CNNs considerably with up to 50% by-product saving in energy consumption due to the simpler nature of the approximate logic.Comment: arXiv admin note: substantial text overlap with arXiv:2006.0770

Ultracarbonaceous Antarctic micrometeorites recovered from snow at the Dome C - CONCORDIA station.

第6回極域科学シンポジウム[OA] 南極隕石11月17日（火）　国立国語研究所 2階 講

Formation and Alteration of Complex Organics Induced by Energetic Processing

The frozen surface of small bodies in the outer Solar System are exposed to energetic charged particles that alter their chemical composition. Laboratory experiments allow to simulate the interaction between cosmic rays and solar particles with frozen surfaces, showing the formation of complex organic compounds. However, irradiation also determines the destruction of both simple and complex molecules. We here report about recent laboratory experiments to simulate the irradiation and heating of surfaces in the outer Solar System and the detection of complex organics. We also present experiments that will be held on the International Space Station (OREOCube and Exocube) and a new facility to study the alteration induced on such complex organics, as well as on prebiotic species and biosignatures

Financing micro-entrepreneurs for poverty alleviation: a performance analysis of microfinance services offered by BRAC, ASA, and Proshika from Bangladesh

Microfinance services have emerged as an effective tool for financing microentrepreneurs to alleviate poverty. Since the 1970s, development theorists have considered non-governmental microfinance institutions (MFIs) as the leading practitioners of sustainable development through financing micro-entrepreneurial activities. This study evaluates the impact of micro-finance services provided by MFIs on poverty alleviation. In this vein, we examine whether microfinance services contribute to poverty alleviation, and also identify bottlenecks in micro-finance programs and operations. The results indicate that the micro-loans have a statistically significant positive impact on the poverty alleviation index and consequently improve the living standard of borrowers by increasing their level of income

Corrosion atmosphérique en entreposage

Certains déchets nucléaires et combustibles usagés sont conditionnés en conteneurs métalliques. Ces derniers peuvent être entreposés, de manière non définitive, dans des entrepôts. Les phénomènes de condensation pouvant éventuellement survenir sur les colis les plus froids, il n'est pas possible d'exclure les risques d'endommagement des colis du fait des phénomènes de corrosion atmosphérique. Le travail présenté entre dans le cadre d'un projet visant à élaborer un modèle prédictif du comportement à long terme des colis de déchets entreposés vis à vis de la corrosion atmosphérique. On s'est attaché dans un premier temps à évaluer la corrosivité atmosphérique dans un entrepôt à l'intérieur duquel les conditions environnementales sont supposées assez proches de celles à l'extérieur, exceptions faites des précipitations, qui ne pourront atteindre la surface des conteneurs. Nous avons pour ce faire simulé la thermique d'un colis bien défini, entreposé et soumis aux fluctuations thermohygrométriques de 2 environnements choisis. La corrosivité atmosphérique est ensuite exprimée dans les termes de la norme ISO/DIS 9223 c'est à dire en considérant notamment la durée d'humidification du conteneur. On présente enfin les perspectives de ce travail de modélisation