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31.
DM Nathan 《Canadian Metallurgical Quarterly》1993,328(23):1676-1685
32.
Robert Keller James Karki 《电子产品世界》2003,(12):30-31
第三代移动电话主要依靠宽带码分多址(WCDMA)技术,信号处理技术的发展、体系结构的进步以及新开发的高速数据转换器和运算放大器正在使无线基础结构的设计师们降低成本,更好地实现第三代无线通信系统的目标。 相似文献
33.
Hydrogenated amorphous silicon (a-Si:H) active matrix organic light-emitting diode (AMOLED) displays are attractive given the potentially low manufacturing cost and ultimately low-temperature fabrication enabling using flexible substrates. Although the conventional two thin-film transistor (2-TFT) AMOLED voltage-programmed pixel circuit (VPPC) can provide high resolution and high yield, the 2-TFT VPPC is prone to image retention over time due to shift in the threshold voltage (VT-shift) of a-Si:H TFTs. This paper presents a new driving scheme that not only preserves the simplicity of the 2-TFT VPPC, but also demonstrates high uniformity. Experimental results indicate that the current drop in the new driving scheme is less than 11% after 15 days of operation whereas it is over 50% for the conventional driving scheme. Moreover, the new driving scheme is less sensitive to temperature variations due to an internal feedback mechanism. After a 70% change in the temperature, the current in the conventional driving scheme increases by as much as 300%. However, the current in the driving scheme presented here is approximately constant 相似文献
34.
Microhardness measurements have been performed on untreated (virgin) and electrically stressed, solvent‐cast laboratory‐prepared samples of pure poly(phenylene oxide) (PPO), pure polystyrene (PS), and PPO : PS polyblends with different weight proportions. Results of such measurement on untreated polyblend sample show that microhardness (Hv) increases with increase in the content of PS up to 10 wt %, which attributed to the existence of homogeneous phase morphology. However, this feature is not observable in samples containing higher content of PS. Electrical stress is found to modify considerably the mechanical property of polymer. The effect of electric field on the microhardness of such samples (PPO : PS :: 90 : 10) has been characterized by the existence of a peak. Trapping of charge carriers in electrically stressed samples imparts hardening to the polyblend up to an applied step field of 190 kV/cm. However, the excessive charging beyond this step field value destroys this characteristic. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
35.
NA Nathan 《Canadian Metallurgical Quarterly》1993,99(6):721-725
The application of fine-needle aspiration cytology for the diagnosis of solid lesions is well-established. Its sensitivity as a diagnostic tool for both benign and malignant lesions can vary significantly, however, and depends on the quality of the smears submitted. In particular, air-drying artifact can render wet alcohol-fixed smears unsatisfactory for diagnosis. This study examines the basic cause of air-drying artifacts, which is directly related to the moisture of the aspirate that varies among tissues and specimens from any tumor type. A simple modification to the standard smearing technique incorporating precoated slides that introduces moisture into the aspirate is recommended. The technique is applicable to aspirates from all sites without compromising accepted diagnostic cytologic criteria, and offers excellent cytologic clarity with routine stains as well as being flexible enough for other investigative staining methods. 相似文献
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N Weiss V Gudnasson P Ostwald S Humphries H Schuster C Keller 《Canadian Metallurgical Quarterly》1997,13(3):141-151
The DNA adduct 8-hydroxy-2'-deoxyguanosine (8-OHdG) has been widely used as a biomarker for oxidative stress. Bulky DNA adducts, which are detectable by the 32P-postlabelling method, provide evidence for exposure to and metabolic activation of large, mainly apolar compounds, e.g. polycyclic aromatic hydrocarbons. We determined both types of adducts in placental tissues of 30 term pregnancies and related the adduct levels to the exposure to tobacco smoke and the plasma antioxidant status. Urine and plasma continine concentrations were used to select 10 nonsmokers, 9 nonsmokers exposed to environmental tobacco smoke (ETS) and 11 smoking women. Placental levels of 8-OHdG were 0.84 +/- 0.11, 0.90 +/- 0.21 and 0.83 +/- 0.20/10(5) deoxyguanosine bases (dG) for nonsmokers, nonsmokers exposed to ETS and smokers, respectively. The differences between the groups were not significant. Smoking women had significantly lower plasma vitamin C and beta-carotene concentrations than nonsmoking women or nonsmoking women exposed to environmental tobacco smoke. The 8-OHdG adduct level in placental DNA was inversely correlated with the plasma vitamin E concentration (r = -0.47, P < 0.05). There was no association between placental 8-OHdG adducts and vitamin A, C and beta-carotene in plasma. In total, 15 different adducts could be identified in the 30 placenta samples by the 32P-postlabelling method. There was a strong inter-individual variation in both the number of adducts and adduct intensities. No smoking-related or vitamin-related effects on adduct patterns or intensities were found. Our findings suggests that, within the limits of the methods used, tobacco smoke exposure during pregnancy does not lead to a measurable increase in placental DNA adduct levels and that vitamin E appears to have a protective effect on placental 8-OHdG formation. 相似文献
39.
Androgens repress expression of many genes, yet the mechanism of this activity has remained elusive. The cytokine, interleukin-6, is active in a variety of biological systems, and its expression is repressed by androgens. Accordingly we dissected the mechanism of androgen's ability to inhibit interleukin-6 expression at the molecular level. In a series of co-transfection assays, we found that 5alpha-dihydrotestosterone, through the androgen receptor, repressed activation of the interleukin-6 promoter, in part, by inhibiting NFkappaB activity. It did not appear that 5alpha-dihydrotestosterone inhibited NFkappaB by activating the androgen receptor to compete for the NFkappaB response element as we could not detect androgen receptor binding to the IL-6 promoter by DNase I footprinting assay. However, by electrophoretic mobility shift assay we found that 5alpha-dihydrotestosterone repressed formation of NFkappaB middle dotNFkappaB response element complex formation. In LNCaP prostate carcinoma cells, 5alpha-dihydrotestosterone achieved this effect through maintenance of IkappaBalpha protein levels in the face of phorbol ester, a stimulus that results in IkappaBalpha degradation. Finally, we confirmed that IkappaBalpha inhibits NFkappaB-mediated activation of the interleukin-6 promoter. These data suggest that maintenance of IkappaBalpha levels may represent the first identified mechanism for androgen-mediated repression of a natural androgen-regulated gene. 相似文献
40.