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排序方式: 共有512条查询结果,搜索用时 15 毫秒
51.
52.
Hakho Lee Yong Liu Westervelt R.M. Ham D. 《Solid-State Circuits, IEEE Journal of》2006,41(6):1471-1480
This paper introduces an integrated circuit (IC)/microfluidic hybrid system for magnetic manipulation of biological cells. The hybrid system consists of an IC and a microfluidic system fabricated on top. Biological cells attached to magnetic beads are suspended inside the microfluidic system that maintains biocompatibility. The IC contains a microcoil array circuit that produces spatially-patterned microscopic magnetic fields. Programmable, rapid reconfiguration of the field pattern made possible by the IC allows an efficient simultaneous manipulation of multiple individual bead-bound cells with precise position control. Two prototypes, SiGe/microfluidic and CMOS/microfluidic hybrid systems, validate the proposed approach. 相似文献
53.
A new method for detecting fluctuations in the fundamental frequency component of a power system, by relating it to a leakage coefficient in the FFT, is presented. The phenomenon of leakage in the FFT is used advantageously to increase spectral resolution. The leakage coefficient is a quantitative measure of the deviation from the fundamental frequency component with respect to the sampling frequency. Theoretical aspects are considered along with a method for on-line implementation. 相似文献
54.
This bibliography is compiled to assist in locating papers related to the application of scanning electron microscopy (SEM) to cerebrospinal-fluid-contacting surfaces in vertebrates. The use of SEM by neuroscientists has continued apace since the publication of the first bibliography in 1980. SEM studies now include more than 50 species of vertebrates and range from cyclostomes to humans; they encompass development from embryo to senescence and concern both normal and pathologic morphology. Although remarkable strides have been made toward a greater understanding of many aspects of the structure and function of cerebrospinal-fluid-contacting surfaces, many significant problems await the judicious application of scanning electron microscopy. 相似文献
55.
The melt polymerization of nylon 4, I was studied, starting with nylon-salt and nylon prepolymers (ηinh=0.25). With nylon-salt only low molecular polymers were obtained, while with prepolymers the inherent viscosity could be raised to 0.77 (3h, 270°, vac.). The cyclization of tetra methylene diamine to pyrrolidine seem to be the major disturbing factor. The polymer is glassy and could easily be melt pressed. The torsion modulus of the material at 20°C was high (1.8 109 Pa) and remained high to near its Tg (138°C). 相似文献
56.
The aim of this study was to assess the reproducibility of a number of simplified clearance methods using chromium-51 ethylenediamine tetraacetic acid (51Cr-EDTA) and to compare these with the multiple blood sample technique. Twenty-four healthy volunteers were enrolled into the study. The test was performed twice, 1 week apart and under similar physiological conditions. After intravenous injection of the tracer, 13 blood samples were taken between 5 and 240 min. The reference clearance was calculated after adapting a bi-exponential fit on the whole plasma disappearance curve. Simplified methods included the slope intercept method using different combinations of blood samples (2 and 4 h; 2, 3 and 4 h; 1.5, 2, 3 and 4 h; 1.5, 2 and 3 h) and several single clearance methods (Constable 3 h; Groth 3 h; Groth 4 h). The standard deviation of the differences between the first and second measurements were similar for all methods, confirming the comparable reproducibility of these methods. 相似文献
57.
三端双向晶闸管用于控制AC电源负载。在大多数应用中,三端双向晶闸管会消耗大量电能,因而需要考虑散热。同时必须计算散热器的大小并预测最高结点温度Tjmax。散热设计和分析是设计和开发过程的基本部分。散热设计需要几个计算阶段,涉及到功率、热阻和温度升高。本文介绍的便是这些计算。 相似文献
58.
H Kim EK Ham YI Kim JG Chi HS Lee SH Park YM Jung NK Myung MJ Lee JJ Jang 《Canadian Metallurgical Quarterly》1998,131(2):177-183
We have shown previously that normal B cells share, with Epstein-Barr virus-transformed and malignant B cells, the ability to activate the alternative pathway (AP) of complement in vitro, resulting in the deposition of C3 fragments on the cell surface. Complement receptor type 2 (CR2, CD21) has been implicated directly as the site for formation of an AP convertase, which provides nascent C3b for deposition at secondary sites on the B-cell surface. In the present study, we have examined C3 fragment deposition in vitro in more detail by (1) assessing the importance of locally generated C3b for the deposition process, (2) investigating whether CR2 is the sole requirement for conferring AP activation capacity on a cell, and (3) determining whether CR2's function, as an AP activator, has different structural requirements from ligand binding. Increasing the availability of native C3, by increasing the serum (NHS) concentration, resulted in enhanced C3 fragment deposition on the B cells, whereas use of factor 1-depleted NHS, which showed massive fluid phase C3 conversion during the incubation, diminished the deposition. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting of untreated and hydroxylamine-treated lysates from B cells, after in vitro activation, revealed that the majority of C3 fragments (primarily iC3b and C3dg) had been covalently bound to the cell surface. Transfection of COS cells with wild-type CR2 or a deletion mutant lacking 11 of the molecule's 15 homologous domains, but retaining the ligand-binding site, revealed that expression of intact CR2 conferred a 12-fold increase in AP-activating capacity on these cells, while no increase in AP activity was apparent on cells transfected with the mutant CR2. 相似文献
59.
Cord blood was obtained from 164 neonates at birth and investigated for the presence of aflatoxins. 14 of the samples were neonates without jaundice and 150 from neonates with jaundice. There was significant reduction (P > 0.05) in birth weight of jaundiced neonates with aflatoxin. Neonates with jaundice have high mean concentration of aflatoxin B1 (32.3 ng/ml and 35.6 ng/ml). Aflatoxin G1 was not detected in any of the groups. The rate of detection was higher in wet (81.8%) than dry season (50.0%). These findings show that neonates are exposed to aflatoxin prenatally and that high incidence of jaundice occurred in the wet warm months. 相似文献
60.
The theory that adolescence is universally a time of emotional turmoil has been disproved, yet research indicates higher rates of negative affect among adolescents than preadolescents. This study evaluates the relationship of distressed affect in early adolescence to the experience of stressful life events. 483 5th–9th graders provided experience sampling reports on their daily emotional states; data on recent major events in the child's life were obtained from the child and a parent. Findings indicate that older students in this age range encountered more negative events than younger ones, including more peer, school, and family events, and that experience of multiple negative events had a stronger association with daily negative affect among the older students. These findings suggest that the higher rates of daily distress experienced in adolescence may be partly attributable to the greater number of negative life events encountered by some youths. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献