Nanoporous Ge thin film production combining Ge sputtering and dopant implantation

In this work a novel process allowing for the production of nanoporous Ge thin films is presented. This process uses the combination of two techniques: Ge sputtering on SiO2 and dopant ion implantation. The process entails four successive steps: (i) Ge sputtering on SiO2, (ii) implantation preannealing, (iii) high-dose dopant implantation, and (iv) implantation postannealing. Scanning electron microscopy and transmission electron microscopy were used to characterize the morphology of the Ge film at different process steps under different postannealing conditions. For the same postannealing conditions, the Ge film topology was shown to be similar for different implantation doses and different dopants. However, the film topology can be controlled by adjusting the postannealing conditions

Genome sequence of the stramenopile Blastocystis, a human anaerobic parasite

International audienceABSTRACT: BACKGROUND: Blastocystis is a highly prevalent anaerobic eukaryotic parasite of humans and animals that is associated with various gastrointestinal and extraintestinal disorders. Epidemiological studies have identified different subtypes but no one subtype has been definitively correlated with disease. RESULTS: Here we report the 18.8 Mb genome sequence of a Blastocystis subtype 7 isolate, which is the smallest stramenopile genome sequenced to date. The genome is highly compact and contains intriguing rearrangements. Comparisons with other available stramenopile genomes (plant pathogenic oomycete and diatom genomes) revealed effector proteins potentially involved in the adaptation to the intestinal environment, which were likely acquired via horizontal gene transfer. Moreover, Blastocystis living in anaerobic conditions harbors mitochondria-like organelles. An incomplete oxidative phosphorylation chain, a partial Krebs cycle, amino acid and fatty acid metabolisms and an iron-sulfur cluster assembly are all predicted to occur in these organelles. Predicted secretory proteins possess putative activities that may alter host physiology, such as proteases, protease-inhibitors, immunophilins and glycosyltransferases. This parasite also possesses the enzymatic machinery to tolerate oxidative bursts resulting from its own metabolism or induced by the host immune system. CONCLUSIONS: This study provides insights into the genome architecture of this unusual stramenopile. It also proposes candidate genes with which to study the physiopathology of this parasite and thus may lead to further investigations into Blastocystis-host interactions

Places de Paris XIXe-XXe siècles

International audiencePeu nombreuses au Moyen Age, rares et chamarrées à l'époque classique, les places de Paris se multiplient aux XIXème et XXème siècles. 400 nouvelles places forgent alors le paysage urbain. Par leur nombre, leur forme et leur signification, elles sculptent la capitale. (.) Tour à tour minérales ou végétales, elles sont la clé de voûte du système urbain, le cadre majestueux, modeste ou secret de l'histoire nationale ou locale. Mémoire des Parisiens, elles inspirent les artistes, les écrivains, les peintres, les sculpteurs et les fontainiers. Béatrice de Andia. Publié à l'occasion d'une exposition présentée par les Mairies des 8ème et 20ème arrondissements en 2004. Avec 400 illustrations dont 76 en couleur

Microstructures et mécanismes de déformation des alliages quasicristallins Al-Cu-Fe et Al-Pd-Mn déformés aux hautes et basses températures

En plus de leurs structures étonnantes, les alliages quasicristallins présentent des propriétés physiques remarquables en regard de leurs compositions chimiques. Notamment, leurs propriétés mécaniques sont caractérisées par une très grande dureté et une extrême fragilité à basse température. Au delà de 70 % de leur température de fusion, ces alliages présentent un caractère ductile et leur comportement plastique fait apparaître un stade d'adoucissement au cours de la déformation. Ces caractéristiques suggèrent une influence importante de la diffusion sur les mécanismes de déformation dans ces alliages. Au cours de ce travail, l'étude du comportement mécanique des alliages Al-Cu-Fe et Al-Pd-Mn a été effectuée par la réalisation d'essais mécaniques et par l'analyse microstructurale d'échantillons déformés, afin d'identifier les mécanismes de déformation contrôlant la plasticité de ces alliages. Différents mécanismes microscopiques sont proposés pour rendre compte de leur comportement plastique macroscopique.As well as their surprising structures, quasicrystalline alloys present peculiar physical properties. In particular, their mechanical properties combine very high hardness with extreme brittleness at low temperatures. Beyond 70 % of their melting temperature, they become ductile and their plastic behaviour shows a characteristic softening stage during the deformation test. These features suggest that the influence of diffusion processes on deformation mechanisms is significant and plays an important role during plastic deformation. In the course of this work, a study of the plastic behaviour of Al-Cu-Fe and Al-Pd-Mn alloys has been carried out. Various mechanical tests and TEM observations of deformed specimens were produced in order to identify the microscopic mechanisms that control the plasticity of icosahedral quasicrystalline alloys. Different microscopic mechanisms are proposed so as to explain the atypical mechanical behaviour of these alloys.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Thermomechanic behavior of epitaxial GeTe ferroelectric films on Si(111)

International audienceA key development toward new electronic devices integrating memory and processing capabilities could be based on the electric control of the spin texture of charge carriers in semiconductors. In that respect, GeTe has been recently recognized as a promising ferroelectric Rashba semiconductor, with giant spin splitting of the band structure, due to the inversion symmetry breaking arising from ferroelectric polarization. Here, we address the temperature dependence of the ferroelectric structure of GeTe thin films grown on Si(111). We demonstrate the hysteretic behavior of the ferroelectric domain density upon heating/cooling cycles by low energy electron microscopy. This behavior is associated with an abnormal evolution of the GeTe lattice parameter as shown by x-ray diffraction. We explain these thermomechanical phenomena by a large difference of thermal expansion coefficients between the film and the substrate and to the pinning of the GeTe/Si interface. The accumulated elastic energy by the GeTe thin film during sample cooling is released by the formation of a-nanodomains with in-plane ferroelectric polarization components

Blastocystis Legumain Is Localized on the Cell Surface, and Specific Inhibition of Its Activity Implicates a Pro-survival Role for the Enzyme*

Programmed cell death (PCD) is crucial for cellular growth and development in multicellular organisms. Although distinct PCD features have been described for unicellular eukaryotes, homology searches have failed to reveal clear PCD-related orthologues among these organisms. Our previous studies revealed that a surface-reactive monoclonal antibody (mAb) 1D5 could induce multiple PCD pathways in the protozoan Blastocystis. In this study, we identified, by two-dimensional gel electrophoresis and mass spectrometry, the target of mAb 1D5 as a surface-localized legumain, an asparagine endopeptidase that is usually found in lysosomal/acidic compartments of other organisms. Recombinant Blastocystis legumain displayed biphasic pH optima in substrate assays, with peaks at pH 4 and 7.5. Activity of Blastocystis legumain was greatly inhibited by the legumain-specific inhibitor carbobenzyloxy-Ala-Ala-AAsn-epoxycarboxylate ethyl ester (APE-RR) (where AAsn is aza-asparagine) and moderately inhibited by mAb 1D5, cystatin, and caspase-1 inhibitor. Interestingly, inhibition of legumain activity induced PCD in Blastocystis, observed by increased externalization of phosphatidylserine residues and in situ DNA fragmentation. In contrast to plants, in which legumains have been shown to play a pro-death role, legumain appears to display a pro-survival role in Blastocystis

Complete circular DNA in the mitochondria-like organelles of Blastocystis hominis.

International audienceBlastocystis hominis is an anaerobic parasite of the human intestinal tract belonging to the Stramenopile group. Using genome sequencing project data, we describe here the complete sequence of a 29,270-bp circular DNA molecule that presents mitochondrial features (such as oxidative phosphorylation complex I subunits) but lacks complexes III, IV and V. Transmission electron microscopy analyses reveal that this molecule, as well as mitochondrial (NADH:ubiquinone oxidoreductase subunit 7 (NAD7), beta-succinyl-CoA synthetase (beta-SCS)) and hydrogenosomal (pyruvate ferredoxin oxido-reductase (PFOR), iron-hydrogenase) proteins, are located within double-membrane surrounded-compartments known as mitochondria-like organelles (MLOs). As there is no evidence for hydrogen production by this organism, we suggest that MLOs are more likely anaerobic mitochondria

Ferroelectric nanodomains in epitaxial GeTe thin lms

International audienceIn the quest for materials for ferroelectrics-based spintronics with a large spin-orbit coupling, it is essential to carefully control the ferroelectric domains structure, their spatial organization and the domain wall type. Here, we perform the growth of GeTe thin lms on Si by molecular beam epitaxy in a large thickness range. We show that the volume fraction along with the size of the ferroelectric nanodomains can be controlled by nely adjusting the deposition thickness and temperature. We evidence the formation of 71 •-type domain walls and in situ measurements during thermal cycling show the hysteretic appearance and decay of ferroelectric domains. In combination with a detailed analysis of the GeTe/Si interface, we demonstrate that the interfacial mist dislocations formed during the growth plays a key role in the stability of the ferroelectric nanodomains

Anomalous Glide Plane in Platinum Nano- and Microcrystals

International audienceAt the nanoscale, the properties of materials depend critically on the presence of crystal defects. However, imaging and characterising the structure of defects in three dimensions inside a crystal remain a challenge. Here, by using Bragg coherent diffraction imaging, we observe an unexpected anomalous {110} glide plane in two Pt sub-micrometer crystals grown by very different processes and having very different morphologies. The structure of the defects (type, associated glide plane and lattice displacement) is imaged in these faceted Pt crystals. Using this non-invasive technique both plasticity and unusual defect behaviour can be probed at the nanoscale