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31.
Conventional cancer therapies, the second leading cause of death worldwide, result in serious side effects and, at best, merely extend the patient''s lifespan by a few years. Searching for effective prevention is of high priority in both basic and clinical sciences. In recent decades natural products have been considered to be an important source of cancer chemopreventive agents. Red wine polyphenols, which consisted of various powerful antioxidants such as flavonoids and stilbenes, have been implicated in cancer prevention and that promote human health without recognizable side effects. Since resveratrol, a major component of red wine polyphenols, has been studied and reviewed extensively for its chemopreventive activity to interfere with the multi-stage carcinogenesis, this review focuses on recent progress in studies on cancer chemopreventive activities of red wine polyphenol extracts and fractions as well as other red wine polyphenols, like procyanidin B5 analogues and myricetin. 相似文献
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金能煤业公司矿井为老矿井,随着矿井的延伸,通风能力已不能满足矿井安全生产的需要,为此对矿井主通风机进行了改造并对其运行效果进行分析. 相似文献
34.
In this study, a single unit of planar micro-solid-oxide fuel cell (μSOFC) is investigated numerically to evaluate the influences of flow channel design, oxygen composition, and thermal operating conditions on cell performance. Four flow channel designs are examined under the co-flow configuration: serpentine, double serpentine, rod bundle, and oblique rib. For all designs, the contacts areas of interconnect to electrodes are kept consistent to maintain the ohmic losses at the same level. To characterize the mass transport effects, there are three different compositions, 100% O2, 50% O2/50% N2 and air, fed to the cathode inlet. Different thermal conditions, adiabatic and isothermal, are applied to the outer boundary of the μSOFC and the results are compared. The outcomes suggest that both thermal conditions and oxidant composition show remarkable influences on μSOFC performance. Under adiabatic conditions, the rise of cell temperature causes a decrease in reversible voltage, deteriorating the overall cell competence. When oxygen is diluted with nitrogen, local gas diffusion becomes dominant to the cathode reaction. Bulk flow, on the other hand, plays a minor role in cell performance since there is little deviation in the polarization curves for all flow channel designs, even at high current densities. For comparison, the flow visualization technique is employed to observe the transport phenomena in various flow channel designs. The flow patterns are found to resemble the concentration distribution, providing a useful tool to design μSOFCs. 相似文献
35.
校长是一所学校的指挥者,一名好的校长,可以带出一批训练有素的教师队伍,可以推进学校教育改革的不断发展.抓好校长队伍建设是贯彻党的教育方针,全面推进素质教育,办好学校的头等大事.那么,如何加强校长队伍建设就显得尤为重要了. 相似文献
36.
管内覆丝网强化对流换热及阻力特性的实验研究 总被引:1,自引:1,他引:0
通过实验对管内覆丝网管进行了强迫对流换热和阻力特性研究。结果表明:管内覆丝网使换热明显增强,阻力也相应增长。菱形丝网对角线距离与平行边距离之比对换热效果有决定作用,丝网厚度对换热的影响比较小,而丝网网格的大小对换热几乎没有影响,在相同的泵功率和几何条件下,换热系数最大增加21%。 相似文献
37.
北京谱仪(BESⅡ)顶点探测器数据获取系统是北京谱仪数据获取系统的一部分,该子系统电子学采用快总线标准,本文描述了该系统的硬件结构和软件系统,软件包括快总线系统的微码软件和上层控制软件,该系统的死时间为1.5ns,对BESⅡ系统总死时间的贡献小于0.5ms。 相似文献
38.
Complements in serum and middle ear effusion were determined in 20 patients with secretory otitis media, and compared with those in the normal controls. The C5 and C1-INH in serum of the patients were significantly higher. On the contrary, C9 and B factor (Bf) were significantly lower, and the circulatory immunocomplex was also higher. In patients with secretory otitis media, the middle ear effusion levels of C3, C4 and C5 were significantly lower, and Bf and immunocomplex were significantly higher than those in serum. The results suggest that the ability of complements in clearing immunocomplex is low. Therefore, the immunocomplex may deposit in the mucosa of the middle ear. Thus the permeability of capillary will be increased, and the middle ear effusion occurs. 相似文献
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对不同能量、不同质量数、不同初始条件的入射束和有无空间电荷效应的离子束流在高梯度加速管中的传输进行了计算,并讨论了一些影响加速管聚焦作用的主要因素,计算结果与实际情况相符。 相似文献