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排序方式: 共有3759条查询结果,搜索用时 31 毫秒
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Neural Computing and Applications - With an increase in online longitudinal users’ interactions, capturing users’ precise preferences and giving accurate recommendations have become an... 相似文献
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Microstrip stepped impedance resonator bandpass filter with an extended optimal rejection bandwidth 总被引:2,自引:0,他引:2
Bandpass filters with an optimal rejection bandwidth are designed using parallel-coupled stepped impedance resonators (SIRs). The fundamental (f/sub o/) and higher order resonant harmonics of an SIR are analyzed against the length ratio of the high-Z and low-Z segments. It is found that an optimal length ratio can be obtained for each high-Z to low-Z impedance ratio to maximize the upper rejection bandwidth. A tapped-line input/output structure is exploited to create two extra transmission zeros in the stopband. The singly loaded Q(Q/sub si/) of a tapped SIR is derived. With the aid of Q/sub si/, the two zeros can be independently tuned over a wide frequency range. When the positions of the two zeros are purposely located at the two leading higher order harmonics, the upper rejection band can be greatly extended. Chebyshev bandpass filters with spurious resonances up to 4.4f/sub o/, 6.5f/sub o/, and 8.2f/sub o/ are fabricated and measured to demonstrate the idea. 相似文献
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Cell cycle-dependent tumor necrosis factor apoptosis 总被引:1,自引:0,他引:1
To determine if tumor necrosis factor (TNF)-mediated apoptosis affects cells at defined stages of the cell cycle, WEHI-164/2F (WEHI) cells were synchronized at G0-G1 after 3-day cultures in medium containing RPMI 1640 and 0.5% FCS (RPMI-0.5% FCS). The arrested WEHI cells (60-75% in G0-G1) showed increased sensitivity to TNF killing, measured as 48-h 3-(5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assays, and 15-h apoptosis by propidium iodide staining and flow cytometry analysis. The TNF killing kinetics of G0-G1-arrested cells was similar to controls, and TNF did not accelerate or retard cell cycle progression of the arrested cells after feeding with fresh RPMI-0.5% FCS. However, TNF inhibited WEHI DNA synthesis as early as 1 h after treatment, and inhibition was proportionate to sensitivity to TNF-induced apoptosis. WEHI cells treated with TNF showed a higher percentage of cells in S phase with concomitant decrease in G0-G1 and G2-M. When cultured for 3-18 h in fresh RPMI-0.5% FCS to allow progression of the G0-G1-arrested cells toward the G1-S boundary, WEHI cells became more sensitive to TNF killing, especially at the 3-9 h time points. Moreover, TNF did not degrade [125I]5-iodo-2'-deoxyuridine-labeled WEHI DNA if the labeled cells were precultured for 9 h in fresh RPMI-0.5% FCS to allow them to pass S phase before the addition of TNF. These results show that TNF-induced apoptosis of WEHI cells is connected to cell cycle events; WEHI targets receive the TNF cytotoxic signal mainly at the G1-S boundary and begin to die by apoptosis as they exit from S phase. 相似文献
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AG Niessen JG Bollemeijer RJ de Keizer PH de Meijer 《Canadian Metallurgical Quarterly》1994,138(15):770-775
OBJECTIVE: To assess how often the aetiology is established in patients with uveitis, what systemic disease are found and what is the contribution of the internist to the diagnostic process. DESIGN: Retrospective study. SETTING: University Hospital Leiden, the Netherlands. METHOD: From January 1987 to April 1992, 342 patients presented with uveitis. All patients underwent a standard ophthalmological examination. Referral to an internist and individualised laboratory screening followed in patients with recurrent, chronic, bilateral or panuveitis. Recorded were: ophthalmological data, results of laboratory screening, results of analysis by the internist, final diagnosis and presence of systemic disease. RESULTS: 149 (44%) patients were examined by the internist, 18 (5.2%) were seen by another specialist. In 169 (49%) patients a specific diagnosis was made. 74 (22%) had a systemic disease, 74 a primary ocular disease. In 28 (8%) a systemic disease was presumed (5% were HLA-B27 positive, 3% had abnormal laboratory results); 5 (1%) patients had endophthalmitis as a complication of a septic process. CONCLUSION: In approximately 1/3 of the patients with uveitis a systemic disease was found. Examination by the internist tailored to the individual patient is essential in the evaluation of uveitis patients. 相似文献
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A. Vahid Shahidi I. Shih T. Araki C. H. Champness 《Journal of Electronic Materials》1985,14(3):297-310
Structural investigation on monocrystalline CuInSe2 samples has been made. From the single crystal results, the space group of CuInSe2 was confirmed to be Iˉ42d and the crystal solidification direction was investigated. Compositional uniformity of the ingots
was established by EPMA and it was found that the indium concentration was greater than that for copper. Systematic annealing
experiments were carried out in vacuum at different temperatures (as low as 160° C) and for different times. Large variation
in resistivity was observed after the annealing treatment. P-type samples were found to convert to n-type after the heat-treatments. 相似文献
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MD Goldberg JR Canvin P Freestone C Andersen D Laoudj PH Williams IB Holland V Norris 《Canadian Metallurgical Quarterly》1997,79(6):315-322
In the bacterium Escherichia coli, H-NS-(H1, H1a) is a heat-stable protein with a molecular mass of 15.5 kDa involved in nucleoid organisation and gene regulation linked to certain signal transduction pathways. We have shown that, following addition of preparations of everted inner membrane vesicles, heat-stable cleavage products of approximately 10 kDa of H-NS are formed in vitro from newly synthesised, radio-labelled H-NS and from purified H-NS. The 15.5 kDa protein and its cleavage products were also recovered from a minicell system. These results raised the possibility that cleavage of H-NS is physiologically significant. However, the cleavage of H-NS observed appears to occur during cell breakage and to depend on the method of protein extraction and the presence of the outer membrane protease, OmpT. Nevertheless, the results indicate that H-NS may contain at least two separate domains with cleavage occurring between these domains at a preferred OmpT site. Failure to take account of H-NS cleavage in sample preparation and analysis can lead to serious underestimation of H-NS levels. 相似文献
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Acute and chronic antidepressant drug treatments respectively decrease and increase the aggressive behaviour of resident rats during encounters with unfamiliar conspecifics. We have now examined the effect of the 5-hydroxytryptamine1A receptor antagonist, WAY-100635, on fluoxetine-, paroxetine- or venlafaxine-induced changes in aggression. WAY-100635 (0.1 mg/kg), which did not modify behaviour when given alone, potentiated the venlafaxine (5.54 mg/kg)-induced reduction in aggression after acute treatment and, during chronic treatment, accelerated the fluoxetine (0.34 mg/kg/day)-induced increase in aggression, from day 5 to day 2. A similar change in time course was seen with paroxetine (0.33 mg/kg/day), although the increase in aggression was smaller. Venlafaxine (5.54 mg/kg/day, alone or co-administered with WAY-100635) increased aggression by day 2. During chronic treatment, therefore, venlafaxine, at the dose used, had a more rapid onset of action than either fluoxetine or paroxetine, whereas the fluoxetine- and paroxetine-, but not the venlafaxine-, induced increase in aggression was accelerated by WAY-100635. These studies further support the hypothesis that selective blockade of the 5-hydroxytryptamine1A receptor augments the effects of antidepressant drugs in an animal model predictive of antidepressant activity, presumably by concomitant blockade of the somatodendritic 5-hydroxytryptamine1A autoreceptor-mediated negative feedback system of serotonergic neurones. 相似文献
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