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排序方式: 共有542条查询结果,搜索用时 15 毫秒
501.
Jean-Louis Vignes Claude Frappart Thomas Di Costanzo Jean-Claude Rouchaud Leo Mazerolles Daniel Michel 《Journal of Materials Science》2008,43(4):1234-1240
The oxidation of aluminium through a mercury film usually leads to unorganized filaments or fibrous powders of hydrated alumina.
Here, we show that the addition of a small amount of silver in the mercury considerably modifies the growth process, and that
large sized monoliths can be obtained through a new process. Regular growth can be maintained at a typical rate of 2.1 μm s−1 (∼0.75 cm/h) for several hours. The samples consist of tangled nanometric fibres and have an open porosity of 99%. The influence
of various parameters has been studied and optimal conditions for regular growth have been determined. Anhydrous alumina monoliths
with a nanometric microstructure and a high-specific area are obtained after thermal treatments that remove water. 相似文献
502.
Myoung Youp Song Sung Hwan Baek Jean-Louis Bobet Sung Nam Kwon Seong-Hyeon Hong 《Journal of Materials Science》2009,44(18):4827-4833
The 71.5%Mg–23.5%Ni–5%Fe alloy prepared by reactive mechanical grinding for 4 h does not need activation. The activated sample
has the hydriding rate of 0.494 wt%/min for 5 min and absorbs 3.32 wt% for 60 min at 593 K under 1.2 MPa H2. It has the dehydriding rate of 0.330 wt%/min for 5 min and desorbs 2.42 wt%H for 20 min at 593 K 0.1 MPa H2. The XRD pattern of 71.5 wt%Mg–23.5 wt%Ni–5 wt%Fe after reactive mechanical grinding exhibits MgH2 in addition to starting elements Mg, Ni, and Fe. 71.5 wt%Mg–23.5 wt%Ni–5 wt%Fe after hydriding–dehydriding cycling contains
Mg, Mg2Ni, MgO, and Fe. The reactive mechanical grinding of Mg with Ni and Fe is considered to facilitate nucleation by creating
many defects on the surface and in the interior of Mg, by the additive acting as active sites for the nucleation and shorten
diffusion distances of hydrogen atoms by reducing the particle size of Mg. The MgH2 formed in the as-milled 71.5 wt%Mg–23.5 wt%Ni–5 wt%Fe alloy is considered to lead to the creation of more defects and finer
particle size. 相似文献
503.
Madathil PK Heinrich B Donnio B Mathevet F Fave JL Guillon D Attias AJ Lee C Kim TD Lee KS 《Journal of nanoscience and nanotechnology》2010,10(10):6800-6804
We report here the synthesis and characterization of novel diethynylbenzene-based liquid crystalline semiconductor (P1) for organic thin-film transistors (OTFTs). Compound P1 was synthesized by the Sonogashira coupling reaction between 2-bromo-5-(4-hexylthiophen-2-yl)thieno[3,2-b]thiophene and 1,4-bis(dodecyloxy)-2,5-diethynylbenzene. Top contact OTFTs were fabricated by spin casting with 2 wt% solution of P1 in chloroform and their best performance, which exhibited a hole mobility of 4.5 x 10(-5) cm2/Vs, was showed after annealing of the films at liquid crystalline temperature. Time-of-flight (TOF) mobility measured at liquid crystalline phase was observed to be 1.5 x 10(-6) cm2/Vs for both positive and negative carriers. These results indicate that the liquid crystallinity helps to improve the molecular packing and enhance charge mobility for P1. These advantages can be applicable to design and construct solution-processable OTFT materials for electronic applications. 相似文献
504.
This paper overviews the biophysical methods developed to gain access to meat structure information. The meat industry needs reliable meat quality information throughout the production process in order to guarantee high-quality meat products for consumers. Fast and non-invasive sensors will shortly be deployed, based on the development of biophysical methods for assessing meat structure. Reliable meat quality information (tenderness, flavour, juiciness, colour) can be provided by a number of different meat structure assessment either by means of mechanical (i.e., Warner-Bratzler shear force), optical (colour measurements, fluorescence) electrical probing or using ultrasonic measurements, electromagnetic waves, NMR, NIR, and so on. These measurements are often used to construct meat structure images that are fusioned and then processed via multi-image analysis, which needs appropriate processing methods. Quality traits related to mechanical properties are often better assessed by methods that take into account the natural anisotropy of meat due to its relatively linear myofibrillar structure. Biophysical methods of assessment can either measure meat component properties directly, or calculate them indirectly by using obvious correlations between one or several biophysical measurements and meat component properties. Taking these calculations and modelling the main relevant biophysical properties involved can help to improve our understanding of meat properties and thus of eating quality. 相似文献
505.
Sarradin P Melo S Barc C Lecomte C Andréoletti O Lantier F Dacheux JL Gatti JL 《Reproduction (Cambridge, England)》2008,135(3):415-418
Scrapie is the most common transmissible spongiform encephalopathy (TSE) in livestock. Natural contamination in sheep flocks is presumed to occur by maternal transmission to offspring. However, horizontal prion transmission from animal to animal exists and may be significant in sustaining and spreading contagion in the field. Artificial insemination is widely used in modern farming, and as large amounts of prion protein have been found in sheep sperm membrane, epididymal fluid and seminal plasma, horizontal transmission by this route was hypothesized since no clear information has been obtained on possible sexual transmission of TSE. We therefore tested the contamination levels of semen from scrapie-infected rams at different stages of incubation, including the clinical phase of the disease. We report here that under our experimental conditions ram semen did not transmit infectivity to scrapie-susceptible transgenic mice overexpressing the V(136)R(154)Q(171) allele of the sheep prion (PRNP) gene. These results suggest that artificial insemination and natural mating have a very low or negligible potential for the transmission of scrapie in sheep flocks. 相似文献
506.
综述膜的设计及结构,以及膜技术在乳品工业中应用的研究进展。随着膜技术的发展以及人们对乳成分知识的深入了解,膜技术在液态乳的除菌、乳蛋白的分离、干酪的加工、乳清的处理、初乳的处理,乃至干酪盐水及废水处理与纯化等方面的应用日益广泛。膜技术将为提高乳制品质量、新产品开发、提高生产效率及增加产品利润提供新的途径,成为在不破坏乳成分的前提下保证乳制品安全的强有力的加工手段。 相似文献
507.
Jeffree RA Warnau M Teyssié JL Markich SJ 《The Science of the total environment》2006,368(2-3):839-852
The bioaccumulation of selected heavy metals and radionuclides ((241)Am, (109)Cd, (57)Co, (51)Cr, (134)Cs, (54)Mn and (65)Zn) from seawater was experimentally compared in the Chondrichthyan Scyliorhinus canicula (spotted dogfish) and the Actinopterygian Teleost Psetta maxima (turbot), of comparable size, age and benthic feeding habits. The speciation of these elements in seawater (salinity 38 per thousand, pH 8.1, temperature 16.5 degrees C) was also calculated to determine their potential bioavailability. The uptake rates, measured over 14 days, varied greatly among isotopes and between species. Concentration factors (CFs) in P. maxima varied 5-fold between ca. 0.2 for (51)Cr and 2.5 for (65)Zn and (134)Cs, whereas in S. canicula they varied by a much greater factor of 350, with CFs for (51)Cr and (241)Am ranging from ca. 0.4 to 140, respectively. With the exception of (134)Cs, all radiotracers were accumulated at a faster rate in S. canicula than in P. maxima, particularly for (241)Am and (65)Zn where the CFs attained during the uptake phase were, two and one order of magnitude greater in S. canicula, respectively. In contrast, (134)Cs reached a CF of about 2.5 in P. maxima, which was 5-fold greater than in S. canicula. Patterns of loss from the experimental depuration phase over 29 days showed greater similarities between species, compared to the uptake phase that highlighted the greater differences between elements. The distributions of these seven radioisotopes among six body components indicated that between the two species the skin of the dogfish displayed a greater bioaccumulation potential, particularly for (241)Am, (57)Co and (65)Zn. However (65)Zn was also distinctive from (241)Am and (57)Co in its pattern of bioaccumulation in dogfish, with its other body components attaining concentrations of (65)Zn that were comparable to the levels found in its skin. The heightened uptake of (134)Cs in turbot was characterised by a more even percentage distribution among its tissues compared to (241)Am and (57)Co, but every tissue of turbot had a higher concentration of (134)Cs, compared to dogfish, particularly the muscle and liver. The elevated uptake rates and higher CFs for most radioisotopes indicate that S. canicula is more susceptible than P. maxima to exposure and contamination by these metals and radionuclides in seawater. These experimentally-determined differences between dogfish and turbot in their bioaccumulation characteristics were assessed against a set of criteria erected to evaluate the working hypothesis that they were taxonomically based. The outcomes of this initial assessment were supportive of this hypothesis that warrants further investigation. 相似文献
508.
Lanet Jean-Louis Le Bouder Hélène Benattou Mohammed Legay Axel 《International Journal of Information Security》2018,17(4):395-409
International Journal of Information Security - One of the main challenges in system’s development is to give a proof of evidence that its functionalities are correctly implemented. This... 相似文献
509.
Federico Sanjuan Gwenaël Gaborit Jean-Louis Coutaz 《Journal of Infrared, Millimeter and Terahertz Waves》2018,39(4):378-386
We report for the first time on the observation of an angular anisotropy of the THz signal generated by optical rectification in a < 111 > ZnTe crystal. This cubic (zinc-blende) crystal in the <?111 > orientation exhibits both transverse isotropy for optical effects involving the linear χ(1) and nonlinear χ(2) susceptibilities. Thus, the observed anisotropy can only be related to χ(3) effect, namely two-photon absorption, which leads to the photo-generation of free carriers that absorb the generated THz signal. Two-photon absorption in zinc-blende crystals is known to be due to a spin-orbit interaction between the valence and higher-conduction bands. We perform a couple of measurements that confirm our hypothesis, as well as we fit the recorded data with a simple model. This two-photon absorption effect makes difficult an efficient generation, through optical rectification in <?111 > zinc-blende crystals, of THz beams of any given polarization state by only monitoring the laser pump polarization. 相似文献
510.
A high-throughput enzyme assay is described that uses 1 microL or less of enzyme solution for each test. Enzyme solutions are deposited by robotic handling in a throughput of over 1000 tests/h on the surface of silica gel plates that have been preimpregnated with fluorogenic substrates. The reaction is quantitated by fluorescence. The method is compatible with water-insoluble substrates (lipases), water-soluble substrates (glycosidases), whole-protein substrates (proteases), and enzyme inhibition measurements. Hydrolytically labile umbelliferyl esters can be used to assay lipases in this format without background hydrolysis. High throughput and reproducibility were tested by fingerprint analysis of lipases and esterases against 37 different fluorogenic ester substrates. A set of eight fluorogenic unbelliferyl esters was selected for optimal activity screening of lipases and esterases on silica gel plates. 相似文献