Silicium et siliciures de structure clathrate (d'une architecture 3D vers des formes fullerènes dépolymérisées)

Ce travail concerne les composés de type clathrate du silicium, qui présentent les mêmes structures nanoporeuses que celles de certaines formes de glace (hydrates de gaz ou de liquide). D’abord, nous avons désintercalé le sodium (taux résiduel de Na :37 ppm) du siliciure NaxSi136, et obtenu ainsi une nouvelle variété allotropique du silicium élémentaire. Ensuite, en vue d’obtenir des clusters isolés Si20 (le plus petit des clusters de type fullerène), nous avons synthétisé sous haute pression deux nouvelles phases de type clathrate du système siliciumtellure, dans lesquelles le tellure s’organise progressivement en une nouvelle charpente d’ions tellurures, dont le réseau est analogue à celui des atomes Al/Si dans un silicate de type sodalite. Enfin, à l’aide d’atomes d’or occupant des postions cristallographiques articulières, nous avons isolé les clusters Si20 dans le composé Ba8Au6Si40 (i.e. Ba8Au6(Si20)2) et montré l’existence d’une concentration en or critique (5,33%) séparant deux états métalliques n et p.This work concerns clathrate type compounds of silicon which exhibit the same nanoporous structures as those of some forms of ice (gaz hydrates or liquid hydrates). First, we have deintercalated sodium atoms (residual concentration of Na: 37 ppm) from NaxSi136, and obtained a new allotropic form of elemental silicon. Second, in the way to obtain some isolated Si20 clusters (the smallest fullerene-like cluster), we have synthesized under high pressure, two new clathrate-like phases of the silicon-tellurium system, in which tellurium atoms are progressively organised in a new framework of tellurium ions, which is similar to the Al/Si network in a silicate of the sodalite type. Finally, by means of gold atoms occupying special positions, we have isolated Si20 clusters in Ba8Au6Si40 (i.e., Ba8Au6(Si20)2) and proved the existence of a critical gold concentration (5.33%) separating two metallic n and p states.BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Réintervention pour dysfonction de bioprothèse aortique

AIX-MARSEILLE2-BU Méd/Odontol. (130552103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Cryoglobulinémies, expérience clinique et biologique : à propos de 96 cas

REIMS-BU Santé (514542104) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Open-heart transcatheter aortic valve replacement in complex aortic valve reoperation: about a case series

International audienc

Letter: Reintervention for a failed surgical aortic bioprosthesis. Percutaneous or surgical treatment: should we look at the short- or long-term perspective?

International audienc

High pressure synthesis and structure of a novel clathrate-type compound: Te7+xSi20−x (x ~ 2.5)

A novel clathrate-type compound, Te7+xSi20+x (x ~ 2.5), has been synthesized from the elements under high pressure and high temperature conditions. Its structure has been solved by Rietveld analysis of the XRD powder patterns combined with the results of an electron diffraction study. This structure is closely related to that of a type I clathrate, but with a different unit-cell parameter (a ~ 2 ×a0) and space group (Fd-3c instead of Pm-3n). Its main feature is that it corresponds to a double clathration of a Te atom enclosed in a partially Te substituted (12.5%) Si20 pentagonal dodecahedra, which is itself enclosed in a large Te24 polyhedron, in form of a truncated octahedron..

High pressure synthesis and crystal structure of two forms of a new tellurium-silicon clathrate related to the classical type I

Two new clathrate-type structures have been identified in the samples obtained by high pressure–high temperature treatment of appropriate mixtures of elemental silicon and tellurium at 5 GPa and 1200 °C for 60 min reaction time..

Structural trends and chemical bonding in Te-doped silicon clathrates

The recently discovered tellurium-doped silicon clathrates, Te7+xSi20-x and Te16Si38, both low- and high-temperature forms (cubic and rhombohedral, respectively), exhibit original structures that are all derived from the parent type I clathrate G8Si46 (G = guest atom). The similarities and differences between the structures of these compounds and that of the parent one are analyzed and discussed on the basis of charge distribution and chemical bonding considerations. Because of the particular character of the Te atom, these compounds appear to be at the border between the clathrate and polytelluride families

Cross-Reactivity Between Heparin and Danaparoid Antibodies in Cardiac Surgery

International audienceManagement of heparin-induced thrombocytopenia (HIT) entails cessation of heparin and initiation of a nonheparin parenteral anticoagulant such as danaparoid. Danaparoid cross-reactivity with HIT antibodies is an uncommon complication of treatment of HIT. We report the case of confirmed HIT and in vivo cross-reactivity with danaparoid, complicating severe sepsis due to an infectious endocarditis treated by cardiac surgery. (C) 2017 by The Society of Thoracic Surgeon

Long-Term Evolution of Malnutrition and Loss of Muscle Strength after COVID-19: A Major and Neglected Component of Long COVID-19

Post-acute consequences of COVID-19, also termed long COVID, include signs and symptoms persisting for more than 12 weeks with prolonged multisystem involvement; most often, however, malnutrition is ignored. Method: The objective was to analyze persistent symptoms, nutritional status, the evolution of muscle strength and performance status (PS) at 6 months post-discharge in a cohort of COVID-19 survivors. Results: Of 549 consecutive patients hospitalized for COVID-19 between 1 March and 29 April 2020, 23.7% died and 288 patients were at home at D30 post-discharge. At this date, 136 of them (47.2%) presented persistent malnutrition, a significant decrease in muscle strength or a PS ≥ 2. These patients received dietary counseling, nutritional supplementation, adapted physical activity guidance or physiotherapy assistance, or were admitted to post-care facilities. At 6 months post-discharge, 91.0% of the 136 patients (n = 119) were evaluated and 36.0% had persistent malnutrition, 14.3% complained of a significant decrease in muscle strength and 14.9% had a performance status > 2. Obesity was more frequent in patients with impairment than in those without (52.8% vs. 31.0%; p = 0.0071), with these patients being admitted more frequently to ICUs (50.9% vs. 31.3%; p = 0.010). Among those with persistent symptoms, 10% had psychiatric co-morbidities (mood disorders, anxiety, or post-traumatic stress syndrome), 7.6% had prolonged pneumological symptoms and 4.2% had neurological symptoms. Conclusions: Obese subjects as well as patients who have stayed in intensive care have a higher risk of functional loss or undernutrition 6 months after a severe COVID infection. Malnutrition and loss of muscle strength should be considered in the clinical assessment of these patients