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排序方式: 共有105条查询结果,搜索用时 15 毫秒
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2.
Quenched phosphorescence detection is a sensitive detection method recently introduced in capillary zone electrophoresis. It is based on the dynamic quenching interaction of the analytes (quenchers) with a phosphorophore, 1-bromo-4-naphthalenesulfonate (BrNS), present in the separation buffer. In this study, it is shown that this detection method can also be used in cyclodextrin-based electrokinetic chromatography (CD-EKC) despite the presence in the buffer solution of cyclodextrins, which are known to reduce the luminescence quenching rate constants. Experiments indicate that BrNS mainly resides in the aqueous phase, while the analytes are distributed between both phases. In principle, the observed quenching might arise from the interaction of BrNS with uncomplexed as well as complexed analytes. However, from the dependence of the fractional quenching on the capacity factor (the normalized fractional quenching was found to be equal to the fraction of analyte in the aqueous phase), it was concluded that only aqueous-phase quenching contributes significantly to the observed quenching. Nevertheless, separation and detection can be regarded as fully compatible, because the capacity factors encountered in CD-EKC are generally low (in this study they ranged from about 0.1 to 2.5). Indeed, with nitroaromatic compounds as the target analytes, limits of detection in the 10(-8) M range were achieved. 相似文献
3.
Gelinck GH Huitema HE van Veenendaal E Cantatore E Schrijnemakers L van der Putten JB Geuns TC Beenhakkers M Giesbers JB Huisman BH Meijer EJ Benito EM Touwslager FJ Marsman AW van Rens BJ de Leeuw DM 《Nature materials》2004,3(2):106-110
At present, flexible displays are an important focus of research. Further development of large, flexible displays requires a cost-effective manufacturing process for the active-matrix backplane, which contains one transistor per pixel. One way to further reduce costs is to integrate (part of) the display drive circuitry, such as row shift registers, directly on the display substrate. Here, we demonstrate flexible active-matrix monochrome electrophoretic displays based on solution-processed organic transistors on 25-microm-thick polyimide substrates. The displays can be bent to a radius of 1 cm without significant loss in performance. Using the same process flow we prepared row shift registers. With 1,888 transistors, these are the largest organic integrated circuits reported to date. More importantly, the operating frequency of 5 kHz is sufficiently high to allow integration with the display operating at video speed. This work therefore represents a major step towards 'system-on-plastic'. 相似文献
4.
Interpretation of a non-conventional reverse-current curve of a depletion-type gate-controlled diode
This work deals with the reverse-current characteristics of an nMOS gate-controlled diode with an implanted N type layer at the surface of the channel. Two possible forms of the characteristics curve, which can be obtained depending on the final material quality (lifetime and surface generation velocity) and on the silicon surface doping level, are discussed. An experimental nonconventional curve and its interpretation are presented. An estimated surface generation velocity was calculated by means of Pierret's correction procedure and a value of approx. 1 cm/sec was obtained. 相似文献
5.
Van Wyk Jacobus D. Swart Pieter L. Olivier Daniel N. Van Niekerk John D. 《Industry Applications, IEEE Transactions on》1983,(6):932-939
Microprocessor-based signal processing equipment for frequencies up to 20 kHz have become compact and fast enough to allow direct on-line real-time analysis on power systems to determine behavior. A case study is presented for a small steelworks operating a 25-MVA open arc furnace, installing 6.5 MVA of thyristor control equipment and further power factor correcting equipment and harmonic filters on a system with ill-defined parameters, low short- circuit capacity, and already containing power factor correcting capacitors tuned at the third harmonic. Discrete spectrum analysis equipment, microprocessor-based and coupled via IEEE-bus to a microcomputer system, was used to do on-line analysis at various points in the system. The high-speed system enabled sophisticated signal processing to yield even and uneven harmonics, stochastic components, system parameters and resonances and mutual interference. It is shown how this is used to rectify problems in the system, adapt equipment, and design power factor and filter equipment. 相似文献
6.
Boneschans B Wessels A van Staden J Zovko M Zorc B Bergh J 《Drug development and industrial pharmacy》2003,29(2):155-160
An improved method of piroxicam benzoate synthesis was described, and an isocratic reversed-phase high-performance liquid chromatography method for its determination was developed and fully validated. The method was found to be specific, precise (relative standard deviation 0.3%), accurate (mean recovery 99.9%), and robust. Limit of detection was estimated at 0.055 µg mL-1 and limit of quantification at 0.185 µg mL-1. The kinetics of piroxicam benzoate hydrolysis in aqueous buffer solutions (pH 1.1 and 10), simulated gastric and intestinal fluids was studied. The hydrolysis followed first-order kinetics. The following rate constants were obtained at pH 10: k = 1.8 × 10-3 hr-1 at 37°C and k = 3.4 × 10-2 hr-1 at 60°C. In acidic media, no significant hydrolysis was observed after 24 hr. During the 24-hr period in simulated intestinal fluid, only 10.9% of the starting ester was hydrolyzed. 相似文献
7.
Recent reports document that α‐tetralone (3,4‐dihydro‐2H‐naphthalen‐1‐one) is an appropriate scaffold for the design of high‐potency monoamine oxidase (MAO) inhibitors. Based on the structural similarity between α‐tetralone and 1‐indanone, the present study involved synthesis of 34 1‐indanone and related indane derivatives as potential inhibitors of recombinant human MAO‐A and MAO‐B. The results show that C6‐substituted indanones are particularly potent and selective MAO‐B inhibitors, with IC50 values ranging from 0.001 to 0.030 μM . C5‐Substituted indanone and indane derivatives are comparatively weaker MAO‐B inhibitors. Although the 1‐indanone and indane derivatives are selective inhibitors of the MAO‐B isoform, a number of homologues are also potent MAO‐A inhibitors, with three homologues possessing IC50 values <0.1 μM . Dialysis of enzyme–inhibitor mixtures further established a selected 1‐indanone as a reversible MAO inhibitor with a competitive mode of inhibition. It may be concluded that 1‐indanones are promising leads for the design of therapies for neurodegenerative and neuropsychiatric disorders such as Parkinson’s disease and depression. 相似文献
8.
The standardization data for the California Verbal Learning Test-Second Edition (CVLT-II; D. C. Delis, J. H. Kramer, E. Kaplan, & B. A. Ober, 2000) were used to evaluate the base rate of 6 specific discrepancies between various key variables. The results indicated that CVLT-II performance discrepancies should equal or exceed 1 or 1.5 z score points (depending on the individual comparison) in the hypothesized direction to be considered potentially unusual. However, because about 1 in 3 persons in the standardization sample displayed at least 1 such large discrepancy, it is concluded that these base rates should be viewed only as a starting point for interpretation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
Mancini SA Lacrampe-Couloume G Jonker H van Breukelen BM Groen J Volkering F Lollar BS 《Environmental science & technology》2002,36(11):2464-2470
Compound-specific carbon and hydrogen isotope analysis was used to investigate biodegradation of benzene and ethylbenzene in contaminated groundwater at Dow Benelux BV industrial site. delta13C values for dissolved benzene and ethylbenzene in downgradient samples were enriched by up to 2+/-0.5 per thousand, in 13C, compared to the delta13C value of the source area samples. delta2H values for dissolved benzene and ethylbenzene in downgradient samples exhibited larger isotopic enrichments of up to 27+/-5 per thousand for benzene and up to 50+/-5 per thousand for ethylbenzene relative to the source area. The observed carbon and hydrogen isotopic fractionation in downgradient samples provides evidence of biodegradation of both benzene and ethylbenzene within the study area at Dow Benelux BV. The estimated extents of biodegradation of benzene derived from carbon and hydrogen isotopic compositions for each sample are in agreement, supporting the conclusion that biodegradation is the primary control on the observed differences in carbon and hydrogen isotope values. Combined carbon and hydrogen isotope analyses provides the ability to compare biodegradation in the field based on two different parameters, and hence provides a stronger basis for assessment of biodegradation of petroleum hydrocarbon contaminants. 相似文献
10.
Johannes Jacobus Laas 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》1998,13(1):23
A project was initiated from hypotheses that the use of longer and different types of tendon support could lead to improved control of tunnel deformation in changing stress fields. An extensive literature study was conducted. Subsequently a tunnel was supported with various lengths and types of cable tendons. The tunnel was subjected to mining-induced stress changes. Tunnel deformations were measured using instrumentation. Results from the literature study and tunnel deformation measurements indicated within context that: (1) long tendons or other support systems cannot substitute for good tunnel layout; (2) long tendons effect a retain-and-hold function while shorter tendons strengthen and reinforce highly fractured tunnel walls; (3) larger boreholes or weakergrout reduce support system stiffness; (4) cable tendons have high shear resistance and debonding tendency; (5) long tendons are beneficial in sidewalls but not the hangingwall, (6) long tendons induce a more stable sidewall deformation distribution; (7) the updip sidewall deformed less than downdip; (8) more deformation occurred with stress decrease than with stress increase. 相似文献