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排序方式: 共有211条查询结果,搜索用时 62 毫秒
21.
A method is presented for near-Earth spacecraft or aviation vehicle‘s attiude rate cstimation by using relative Doppler frequency shift of the Global Positioning System(GPS)carrier.It comprises two GPS receiving antennas,a signal processing circuit and an algorithm.The whole system is relatvely simple,the cost and weight,as well power consumption,are very low. 相似文献
22.
Stephen Ridout Milos Dusek Chris Bailey Chris Hunt 《Microelectronics Reliability》2006,46(12):2122-2130
This paper presents both modelling and experimental test data to characterise the performance of four non-destructive tests. The focus is on determining the presence and rough magnitude of thermal fatigue cracks within the solder joints for a surface mount resistor on a strip of FR4 PCB. The tests all operate by applying mechanical loads to the PCB and monitoring the strain response at the top of the resistor. The modelling results show that of the four tests investigated, three are sensitive to the presence of a crack in the joint and its magnitude. Hence these tests show promise in being able to detect cracking caused by accelerated testing. The experimental data supports these results although more validation is required. 相似文献
23.
Lenka Monincová Dr. Milos Buděšínský Sabina Čujová Dr. Václav Čeřovský Dr. Václav Veverka 《Chembiochem : a European journal of chemical biology》2014,15(2):301-308
Lasiocepsin is a unique 27‐residue antimicrobial peptide, isolated from Lasioglossum laticeps (wild bee) venom, with substantial antibacterial and antifungal activity. It adopts a welldefined structure consisting of two α‐helices linked by a structured loop. Its basic residues form two distinct positively charged regions on the surface whereas aliphatic side chains contribute to solvent‐accessible hydrophobic areas, thus emphasising the amphipathic character of the molecule. Lasiocepsin structurally belongs to the ShK family and shows a strong preference for anionic phospholipids; this is further augmented by increasing concentrations of cardiolipin, such as those found at the poles of bacterial cells. The membrane‐permeabilising activity of the peptide is not limited to outer membranes of Gram‐negative bacteria. The peptide interacts with phospholipids initially through its N terminus, and its degree of penetration is strongly dependent on the presence of cardiolipin. 相似文献
24.
Tetiana Borzda Christoph Gadermaier Natasa Vujicic Peter Topolovsek Milos Borovsak Tomaz Mertelj Daniele Viola Cristian Manzoni Eva A. A. Pogna Daniele Brida Maria Rosa Antognazza Francesco Scotognella Guglielmo Lanzani Giulio Cerullo Dragan Mihailovic 《Advanced functional materials》2015,25(22):3351-3358
The 2D semiconductor MoS2 in its mono‐ and few‐layer form is expected to have a significant exciton binding energy of several 100 meV, suggesting excitons as the primary photoexcited species. Nevertheless, even single layers show a strong photovoltaic effect and work as the active material in high sensitivity photodetectors, thus indicating efficient charge carrier photogeneration. Here, modulation spectroscopy in the sub‐ps and ms time scales is used to study the photoexcitation dynamics in few‐layer MoS2. The results suggest that the primary photoexcitations are excitons that efficiently dissociate into charges with a characteristic time of 700 fs. Based on these findings, simple suggestions for the design of efficient MoS2 photovoltaic and photodetector devices are made. 相似文献
25.
Milos S. Bil 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1972,22(7):853-856
4-Fluoro-3-nitroaniline has become of significant importance in the U.S.A. as a novel dye intermediate. Its use for pharmaceuticals, insecticides, and more dyes might soon be extended. Preparations of its various N-substituted derivatives are briefly reviewed in this article. 相似文献
26.
27.
Silica-based lectin microcolumns are described in this study together with the chemical procedures necessary for their preparation. The analytical merits of Canavalia ensiformis and Sambucus nigra lectins, [immobilized on activated macroporous silica], such as binding capacity, trapping reproducibility, and substrate selectivity, have been evaluated using model glycoproteins. The described microcolumns are applicable to high-pressure analytical schemes utilizing microvalving procedures, washing steps, and quantitative desorption for LC/MS analysis. The described analytical systems are amenable to the applications aiming at fractionation of complex glycopeptide mixtures and determination of the sites of glycosylation. 相似文献
28.
The Fischer-Tropsch Synthesis in the Liquid Phase 总被引:3,自引:0,他引:3
The hydrogenation of carbon monoxide by the Fischer-Tropsch (F-T) process [1] forms saturated and unsaturated compounds of the homologous hydrocarbon series. It permits the synthesis of hydrocarbons ranging from methane to high-melting paraffins with molecular weights above 20,000, depending on the catalyst, temperature, and type of process employed. By-products such as alcohols, aldehydes, ketones, acids, and esters are formed on a smaller scale. Small amounts of aromatic compounds are formed at high temperatures by secondary dehydrocyclization reactions from the primary hydrocarbons formed. 相似文献
29.
Helena A. Soini Donald Wiesler Sachiko Koyama Christophe Féron Claude Baudoin Milos V. Novotny 《Journal of chemical ecology》2009,35(5):580-589
Whereas the house mouse (Mus domesticus) has been studied extensively in terms of physiology/behavior and pheromonal attributes, the evolutionarily related mound-building
mouse (Mus spicilegus) has received attention only recently due to its divergent behavioral traits related to olfaction. To date, no chemical studies
on urinary volatile compounds have been performed on M. spicilegus. The rationale for our investigations was to determine if there are differences in urinary volatiles of intact and castrated
M. spicilegus males and to explore further whether this species could utilize the same or structurally similar pheromones as the male house
mouse, M. domesticus. The use of capillary gas chromatography/mass spectrometry (GC-MS) together with sorptive stir bar extraction sampling enabled
quantitative comparisons between the intact and castrated M. spicilegus urinary profiles. Additionally, through GC-MS and atomic emission (sulfur-selective) detection, we identified qualitative
molecular differences between intact M. spicilegus and M. domesticus. A series of volatile and odoriferous lactones and the presence of coumarin were the unique features of M. spicilegus, as was the notable absence of 2-sec-butyl-4,5-dihydrothiazole (a prominent M. domesticus male pheromone) and other sulfur-containing compounds. Castration of M. spicilegus males eliminated several substances, including δ-hexalactone and γ-octalactone, and substantially decreased additional compounds,
suggesting their possible role in chemical communication. Some other M. domesticus pheromone components were also found in M. spicilegus urine. These comparative chemical analyses support the notion of metabolic similarities as well as the uniqueness of some
volatiles for M. spicilegus, which may have a distinct physiological function in reproduction and behavior. 相似文献
30.
A new analytical approach has been developed for simultaneous measurements of endogenous salsolinol and major catecholamines in brain tissue of experimental animals. This procedure involves a combination of on-line phenyl boronate affinity preconcentration and microcolumn liquid chromatography, followed by mass spectrometry equipped with an atmospheric pressure photoionization (APPI) source. Flow conditions of the APPI source were optimized for detection sensitivity while different dopants were evaluated. The on-line preconcentration was found essential for the sensitivity requirements of salsolinol measurements in the brain tissue from alcohol-preferring rats subjected to different levels of alcohol exposure. 相似文献