Identification and characterization of a new zirconium hydride.

Zirconium alloys are currently used in nuclear power plants where they are susceptible to hydrogen pick-up. Hydride precipitation may occur when the hydrogen solubility limit is reached. Various Zr hydride phases, gamma, delta and epsilon have been identified since the 1950s. Combining electron precession microdiffraction, electron energy loss spectroscopy and ab initio electronic calculations, a new Zr hydride named zeta has been identified and characterized. It belongs to the trigonal crystal system with space group P3 m1 and it is fully coherent with the alphaZr matrix.

Density functional calculations on structural materials for nuclear energy applications and functional materials for photovoltaic energy applications (abstract only).

Ab initio density functional theory calculations are carried out in order to predict the evolution of structural materials under aggressive working conditions such as cases with exposure to corrosion and irradiation, as well as to predict and investigate the properties of functional materials for photovoltaic energy applications. Structural metallic materials used in nuclear facilities are subjected to irradiation which induces the creation of large amounts of point defects. These defects interact with each other as well as with the different elements constituting the alloys, which leads to modifications of the microstructure and the mechanical properties. VASP (Vienna Ab initio Simulation Package) has been used to determine the properties of point defect clusters and also those of extended defects such as dislocations. The resulting quantities, such as interaction energies and migration energies, are used in larger scale simulation methods in order to build predictive tools. For photovoltaic energy applications, ab initio calculations are used in order to search for new semiconductors and possible element substitutions for existing ones in order to improve their efficiency.

Prognostic factors of epiretinal membranes: A systematic review.

INTRODUCTION: Epiretinal membranes (ERM) have been increasingly characterized with the advent of new optical coherence tomographies (OCTs). We intended to perform a systematic review regarding prognostic factors (PF) of ERM after surgery. MATERIALS AND METHODS: Systematic review of electronic databases was performed (last date of search was 10 August 2015): Medline, Scopus, Google Scholar, clinicaltrials.gov and current controlled trials. Search queries included: "membrane", "pucker", "prognosis", "prognostic", "epiretinal", "épirétinienne". Inclusion criteria were: (1) primary purpose was to identify a PF of ERM; (2) prospective or retrospective study, case series (more than 10 patients), or clinical trials; (3) follow-up of at least 3 months; (4) complete ophthalmological evaluation in each patient with visual acuity and OCT, preoperative and≥3months after surgery; (5) vitrectomy with ERM peeling performed in each patient. Eligibility criteria verification, data extraction and evaluation of risk of bias were performed according to Cochrane's recommendations. RESULTS: From 817 studies found, 21 were included (9 prospective, 12 retrospective, 0 trials). In all studies, there was significant visual acuity improvement after surgery. The majority of the studies included pars plana vitrectomy (PPV) combined with phacoemulsification. DISCUSSION AND CONCLUSION: PF for visual acuity (VA) improvement after ERM surgery included: shorter duration of symptoms before surgery, lesser central foveal thickness at baseline identified by the OCT, good integrity of the inter segment/outer segment photoreceptor junction at baseline, and thinner ganglion cell inner plexiform layer at baseline. To avoid bias, studies should analyze VA separately if phacoemulsification is also performed. The knowledge of these PF may assist in planning surgery.

Interfacial properties of hydrides in α-Zr: a theoretical study.

In order to better understand hydride formation in zirconium alloys, heterophase interfaces between α-Zr and γ-ZrH are investigated by means of ab initio atomic-scale simulations of multilayers coupled with continuous elasticity. Our approach allows us to separate out the elastic contribution, leading to basal and prismatic [Formula: see text] interface energies around 200 [Formula: see text] and 750 [Formula: see text] respectively, i.e. values noticeably higher than previously found for coherent particles such as ζ-Zr2H. By considering interfacial changes of H contents, the possibility of competing elasticity and chemistry effects for interface stability is analyzed. The effects of the strong anisotropy evident in [Formula: see text] interface energies on the important practical issue of preferential habit planes are discussed, allowing us to propose a plausible explanation for the experimental results.

[Retinal vascular occlusion and primary antiphospholipid syndrome. Report of 2 cases]. / Occlusion vasculaire rétinienne et syndrome primaire des antiphospholipides. A propos de 2 cas.

INTRODUCTION: The antiphospholipid syndrome is characterized by the association of antiphospholipid antibodies and occlusive vascular events. The ocular vascular damage is described in the literature and may reveal the syndrome. It's diagnosis is important because this disease, which generally affects young people, may endanger ocular and vital prognosis. Two cases are reported. PATIENTS: Two young people aged 22 and 32 presented with a sudden unilateral loss of vision. In both cases, fundus examination and fluorescein angiography revealed a severe retinal vascular occlusion. For one patient, an antiphospholipid syndrome was discovered during etiological check-up. for the second one, it was associated with a heterozygote state mutation of Leiden V factor. In both cases the visual function of the affected eye was lost. DISCUSSION: In most cases central artery or vein occlusion means atherosclerosis. However, other etiologies must be studied in young patients. According to several studies: antiphospholipid syndrome has been detected in 5% to 33% of the patients showing a major vascular retinal obstruction. The association of thrombophilia must be considered because it increases the risk of thrombotic recurrence. CONCLUSION: The antiphospholipid syndrome must be studied in cases of numerous and severe retinal vascular obstruction occurring in young patients, even if vascular risks exist. This diagnosis is important because it may imply a long-lasting anticoagulative or an antiaggregative treatment to significantly reduce the risk of recurrent thrombotic events.

Comprehensive ab initio thermodynamic treatment of impurities in ordered alloys: application to boron in B2 Fe-Al.

A rigorous description of impurities in nearly stoichiometric ordered systems, relying on independent-point-defect thermodynamics and density-functional-theory ab initio calculations, is presented and applied to the study of the equilibrium point defect structure of Fe-Al-B alloys in the B2 composition domain (x(Al) approximately 50 at. %, x(B) approximately 0), including the influences of (i) magnetism and (ii) the local density approximation (LDA) or generalized gradient approximation (GGA) exchange-correlation functionals. Whatever the alloy composition, B substitutes for Al, except in the nonmagnetic GGA scheme predicting a switch towards interstitial occupancy for sufficient Al contents.

Characterization of malate dehydrogenase isozymes in wheat germ.

Malate dehydrogenase of wheat germ exists in multiple molecular forms (isozymes). Comparisons of some physical properties such as Stoke's radii, sedimentation constants, electrophoretic mobilities on polyacrylamide gel, chromatographic behaviors on DEAE-cellulose, stabilities to heat and iodacetamide inactivation, as well as kinetic parameters were described. When all these properties are considered together, at least five isozymes were found to associate with cytoplasm, mitochondria, glyoxysomes and proplastids of wheat germ. Wheat germ malate dehydrogenases are specific for the reduction of oxaloacetate and its monoesters. At least one carboxylic group of oxaloacetate must be free, in order to exhibit substrate activity, and maximum binding of oxaloacetate is achieved when both carboxylic groups are free. Soluble malate dehydrogenase and organelle-associated malate dehydrogenase can be differentiated readily in that the former can not utilize 4-ethyl oxaloaceode of ATP inhibition.