Driving forces for the weathering and alteration of silica in the regolith: implications for studies of prehistoric flint tools.

International audienceA range of geochemical and mineralogical factors trigger the weathering and influence the stability of various silica phases under near-surface temperatures and pressures. Based on the current knowledge of the crystallochemical basis of silica behaviour in near-surface environments, the mineralogical and petrographical transformations of silica under weathering conditions in the regolith are reviewed using data from wide-ranging and detailed investigations of siliceous materials. Some of the investigations are of siliceous materials that evolved in near-surface environments over geological time and thus the weathering and alteration features are relatively clear and well expressed. Examples include weathering of tightly cemented sandstones, the formation of silica duricrusts (pedogenetic silcretes), and the weathering of flints. The various micromorphological and mineralogical forms of silica as determined by high resolution petrographic and electron-optical techniques can be related to geochemical and hydrological conditions in particular microenvironments. However, new studies have demonstrated that silica alteration and transformation mechanisms can also occur within prehistoric and historic time intervals. These are also described but are more difficult to observe, principally because of the microcrystalline character of the alteration phases and the infra-millimetric scale on which they develop.Of many potential applications of knowledge about the near-surface alteration of silica in regolith materials and the environmental conditions under which it occurs, our studies can be used as a basis determining the provenance and post-discard history of prehistoric flint tools and artefacts, in part to determine the source of the primary raw material. We suggest that the mineralogical and petrographical characteristics of the weathering rind (cortex) of the flint (specifically the recrystallization, dissolution and deposition of the silica phases, and the spatial arrangement of surfaces that have undergone successive transformations) are related to specific and identifiable weathering environments

Near-collisions and their Impact on Biometric Security

Biometric recognition encompasses two operating modes. The first one is biometric identification which consists in determining the identity of an individual based on her biometrics and requires browsing the entire database (i.e., a 1:N search). The other one is biometric authentication which corresponds to verifying claimed biometrics of an individual (i.e., a 1:1 search) to authenticate her, or grant her access to some services. The matching process is based on the similarities between a fresh and an enrolled biometric template. Considering the case of binary templates, we investigate how a highly populated database yields near-collisions, impacting the security of both the operating modes. Insight into the security of binary templates is given by establishing a lower bound on the size of templates and an upper bound on the size of a template database depending on security parameters. We provide efficient algorithms for partitioning a leaked template database in order to improve the generation of a master-template-set that can impersonates any enrolled user and possibly some future users. Practical impacts of proposed algorithms are finally emphasized with experimental studies

On the Leakage of Fuzzy Matchers

In a biometric recognition system, the matcher compares an old and a fresh template to decide if it is a match or not. Beyond the binary output (`yes' or `no'), more information is computed. This paper provides an in-depth analysis of information leakage during distance evaluation, with an emphasis on threshold-based obfuscated distance (\textit{i.e.}, Fuzzy Matcher). Leakage can occur due to a malware infection or the use of a weakly privacy-preserving matcher, exemplified by side channel attacks or partially obfuscated designs. We provide an exhaustive catalog of information leakage scenarios as well as their impacts on the security concerning data privacy. Each of the scenarios leads to generic attacks whose impacts are expressed in terms of computational costs, hence allowing the establishment of upper bounds on the security level.Comment: Minor correction

Flint in its diverse natural occurrences: geo-­‐tools for a better definition of the sourcing of secondary outcrops

International audiencePrecise identification of siliceous geo-resources used during prehistory still poses many problems, and archaeologists make ever-increasing demands for this data. The purpose is to provide a database containing an exact and descriptive identity for each different type of geological flint found within a region. The parameters we have chosen to characterize are the mineralogical composition (by optical microscopy, SEM, microprobe, cathodo-luminescence), microfacies characteristics (identified during microscopy and SEM image analysis), porosity measurements (by image analysis and porosimeter), and the presence and distribution of major and trace elements (using ICP, LA-ICP-MS, XRF, PIXE, Raman and SEM-EDS) at the surface or in the cracks in the matrix

Myoferlin: an indispensable component in VEGFA secretion by pancreas cancer cells

In this poster, our laboratory showed the importance of myoferlin, a biomarker of pancreas cancer, in the controle of VEGF-A mediated angiogenesis. Our laboratory showed that silencing myoferlin in pancreas cancer cells, BxPC-3, provoques a decrease in cell prolifération in vitro and a decrease in tumor volumes in animal model. Myoferlin silencing also provokes a decrease in VEGF-A secretion in the conditioned medium and that decrease was abserved in the animal model as a decrease in microvessels dencity. It appeared that this decrease in secretion is due to a a blockage in the exocytosis. Our data also showed a significate correlation between myoferlin expression and microvessels density in patients section

La moral universal ó los deberes del hombre fundados en su naturaleza

Contiene: t. 1º. Teoría de la moral--t, 2º. Practica de la moral. t. 3º. Práctica de la moralEncabezamiento tomado de Palau. Según Palau el traductor es Manuel Díaz MorenoPie de imp. tomado del t. 1º. Impresor del t. 2º: En la Imprenta de los Señores García y Compañía. Impresor del t. 3º: Mateo RepullesLa h. de lám. calc. : "J. Altarriba delint. B. Ametller sct