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An innovative hydrogenation method to investigate the hydrogen embrittlement of metals and alloys is hereby presented. The benefits of electroplating samples with copper and nickel prior to gaseous hydrogenation at mid-range temperatures are quantified. It is showed that these electrodeposited layers allow to control the hydrogen desorption rate occurring after hydrogenation, during the cooling of the hydrogenated specimen. The present study demonstrates the capability of the method to control the introduced total hydrogen concentration within a margin of 0.2 wt.ppm. The applicability of the described method to further investigations into hydrogen concentrations effects on hydrogen embrittlement of ferritic alloys by the means of mechanical tests is evaluated. 相似文献
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It is shown that the performance of heterodyne Doppler lidar (HDL) can be improved by (i) at least one good realization for every single shot or (ii) several simultaneous good realizations for accumulation. Until now, several simultaneous independent realizations at high carrier-to-noise ratio (CNR) have been considered. At low CNR, noise may have a detrimental effect on the accumulation techniques. We determine the chances of getting "heavy" speckles in HDL signals from many receiver-detector units on a single-shot basis and several good realizations on a single-shot basis, which is required for an effective accumulation. The use of multiple receiver-detector units at low CNR is worthwhile in contexts such as space lidar, where optimized treatment is at a premium. We conclude on the effectiveness of many receiver-detector units in parallel in order to achieve simultaneous independent realizations at low CNR to improve the performance of HDL on a statistical basis. 相似文献
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The objective of this study is to develop a technique to remove ammonium ion from water intended for potable purposes. An ion exchange method is used with a selective ion exchanger, a natural cation zeolite, clinoptilolite. Glass columns (Fig. 1) are used for laboratory experiments. These experiments show that the NH4+ exchange capacity is very small compared to its total capacity 2.17 meq g?1; its value depends essentially on the NH4+ initial concentration and less on the Ca2+ concentration in the influent water. Figure 3 illustrates the practical exchange capacity relative to the initial concentration of ammonium ion for a soft water (Ca2+ = 35–50 mg l?1). We were particularly interested in waters weak in ammonium ion concentration (NH4+ = 1–3 mg l?1). In this case and for ~1 and 2 mg l?1 NH4+ concentration in water, the practical capacity is only 0.06 and 0.108 meq g?1 respectively. The leakage is smaller than the ECC limit (European Community Council) for drinking waters (NH4+ ? 0.5 mg l?1) and the treated volume of water to breakthrough, defined at 0.5 mg l?1 of NH4+, is ?720 BV (BV = bed volume) in both cases.In another way Fig. 6 shows that hard waters (due to Ca2+ ions) are more difficult to treat than soft waters. The practical capacity is smaller than before and the NH4+-leakage is greater. To lessen NH4+-leakage to less than 0.5 mg l?1 for soft waters down-flow and up-flow, regeneration is used. Figure 7 shows that up-flow regeneration is more attractive than down-flow regeneration.Cycle reproducibility (Figs 4 and 5) shows that the regeneration conditions satisfied our requirements: in this case, the salt consumption is 180 eq of salt per eq of NH4+ eliminated. This prompted us to try to reuse the regenerant (with NH4+ ion). An increase of NH4+-leakage is noticed in the presence of an NH4+-residual in the regenerant. This increase is more significant with down-flow regeneration.After these laboratory experiments, we carried out a semi-industrial pilot-plant. Our objective was first to verify the laboratory results and secondly to study clinoptilolite behaviour relative to the time it was used. Two plexiglass columns comprise the pilot-plant shown in Fig. 9; soft water is used for these experiments. The first column is regenerated with fresh salt solution. The cycles obtained, considering their initial NH4+-concentration, are reproduced in Fig. 10. For 2 mg l?1 NH4+ in the influent water, the leakage is about 0.2 mg l?1 and the treated volume to breakthrough (0.5 mg l?1 of NH4+) is about 750 BV. The second column is regenerated with a recycled solution. The quality of the cycles decreases with the number of reuse of the regenerant as shown in Fig. 11. Nevertheless, it is interesting to note that after 3 reuses, the performance decrease is only 25% and the leakage, although it increases is smaller than 0.5 mg l?1.Pilot results allowed us to propose a treatment of 30,000 m3 day?1; the cost per cubic meter water treated, relative to NH4+-removal, is about 0.165 FF (0.033 US $) for a plant and 0.77 FF (0.014 US $) for the same plant at the seaside. Using two serial columns decreased the cost by about 40–50%. 相似文献
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Vial J.C. Herino R. Billat S. Bsiesy A. Gaspard F. Ligeon M. Mihalcescu I. Muller F. Romestain R. 《IEEE transactions on nuclear science》1992,39(4):563-569
The authors discuss progress in the control of the luminescent properties of porous silicon and in the understanding of the basic mechanisms which govern the light emission. The main features of porous silicon formation and properties are briefly recalled. The photoluminescence characteristics are reported. It is shown that anodic oxidation of porous silicon is a technique which provides photoluminescent layers with good mechanical properties and enhanced emission efficiency. A model accounting for the quite long measured carrier lifetimes is outlined. The electroluminescence which appears during the anodic oxidation of porous silicon in pure water was studied 相似文献
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Gaspard Gerschenfeld Rachida Aid Teresa Simon-Yarza Soraya Lanouar Patrick Charnay Didier Letourneur Piotr Topilko 《International journal of molecular sciences》2021,22(23)
Central nervous system (CNS) lesions are a leading cause of death and disability worldwide. Three-dimensional neural cultures in biomaterials offer more physiologically relevant models for disease studies, toxicity screenings or in vivo transplantations. Herein, we describe the development and use of pullulan/dextran polysaccharide-based scaffolds for 3D neuronal culture. We first assessed scaffolding properties upon variation of the concentration (1%, 1.5%, 3% w/w) of the cross-linking agent, sodium trimetaphosphate (STMP). The lower STMP concentration (1%) allowed us to generate scaffolds with higher porosity (59.9 ± 4.6%), faster degradation rate (5.11 ± 0.14 mg/min) and lower elastic modulus (384 ± 26 Pa) compared with 3% STMP scaffolds (47 ± 2.1%, 1.39 ± 0.03 mg/min, 916 ± 44 Pa, respectively). Using primary cultures of embryonic neurons from PGKCre, Rosa26tdTomato embryos, we observed that in 3D culture, embryonic neurons remained in aggregates within the scaffolds and did not attach, spread or differentiate. To enhance neuronal adhesion and neurite outgrowth, we then functionalized the 1% STMP scaffolds with laminin. We found that treatment of the scaffold with a 100 μg/mL solution of laminin, combined with a subsequent freeze-drying step, created a laminin mesh network that significantly enhanced embryonic neuron adhesion, neurite outgrowth and survival. Such scaffold therefore constitutes a promising neuron-compatible and biodegradable biomaterial. 相似文献
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Berthault P Huber G Ha PT Dubois L Desvaux H Guittet E 《Chembiochem : a European journal of chemical biology》2006,7(1):59-64
The interaction of xenon with beta-cryptogein, a basic 10 kDa protein belonging to the elicitin family, has been studied by using dissolved thermal and laser-polarized gas in liquid-state NMR. 13C and 1H chemical-shift-mapping experiments were unfruitful, the proton lines only experienced a slight narrowing but no significant frequency variation when the xenon concentration was increased. Nevertheless magnetization transfer from hyperpolarized xenon to protons of the protein demonstrates an undoubted interaction and enables localization of the noble-gas-binding site. Due to the proton-proton cross-relaxation efficiency, however, this experiment is subjected to important spin-diffusion. An automatic procedure that takes spin-diffusion into account when assigning the protons that interact with xenon is then used. The binding site, as defined by 30 Xe--H interactions, is situated in the inner core of the protein. The protons that interact with xenon border the channel by which sterols are known to enter into the cavity. These results support the idea that xenon is a good probe for hydrophobic protein regions. 相似文献