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41.
对四种植被类型下土壤微生物量碳、氮、土壤呼吸速率以及代谢熵的研究,结果表明,土壤微生物量碳、氮以及土壤呼吸在四种植被类型间差异显著,而土壤微生物代谢熵之间差异不明显.且不同植被演替阶段土壤微生物量碳、氮从初级阶段到次生林阶段逐步增大,从次生林到成熟林阶段明显减小;土壤呼吸随着植被的正向演替,呼吸速率逐渐增强;四种植被类型间土壤微生物代谢熵在次生林中最低,为0.44 mgg-1 h-1,万熟林地中最高,为1.01 mgg-1 h-1,表明土壤微生物对土壤碳的利用效率次生林较高,成熟林地较低. 相似文献
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Cigarette smoking and the colorectal adenoma-carcinoma sequence: a hypothesis to explain the paradox
As recognized precursor lesions to colorectal cancer, colorectal adenomatous polyps have been studied to enhance knowledge of colorectal cancer etiology. Although most of the known risk factors for colorectal cancer are also associated with the occurrence of colorectal adenomas, cigarette smoking has had a strong, consistent relationship with colorectal adenomas but is generally not associated with colorectal cancer. The explanation for this paradox is unknown. With data collected in 1986-1988 during a large case-control study based on colonoscopy results in New York City, New York, the authors investigated the possibility that the paradox may arise because subjects with colorectal adenomas were included in the control group of cancer case-control studies. The authors found a statistically significant increased risk between heavy cigarette smoking (smokers with > or = 40 pack-years of smoking) and risk of adenoma (odds ratio (OR) = 1.61, 95% confidence interval (CI) 1.06-2.44). They saw no increased colorectal cancer risk from heavy cigarette smoking (OR = 1.02, 95% CI 0.52-1.99) using a "manufactured" control group to simulate a typical unscreened, population-based control group. When the authors compared these colorectal cancer cases with an adenoma-free control group examined by colonoscopy in a polytomous model with several case groups (newly diagnosed adenomas, carcinoma in situ, intramucosal carcinoma, and colorectal cancer), they found that the risk for 20-39 pack-years of smoking was elevated, although not statistically significant, and was similar for all four case groups. The risk for the highest smoking category (> or = 40 pack-years) was more strongly elevated in all four case groups, although it was statistically significant for only the newly diagnosed adenoma and the carcinoma in situ cases (adenomas, OR = 1.59, 95% CI 1.05-2.42; carcinoma in situ, OR = 2.05, 95% CI 1.01-4.15; intramucosal carcinoma, OR = 1.30, 95% CI 0.61-2.77; and colorectal cancer, OR = 1.30, 95% CI 0.64-2.65). While the authors' study is weakened by the lack of statistical significance concerning risk for colorectal cancer, these data offer some support for the hypothesis that the association between cigarette smoking and risk of colorectal cancer may have been masked by inclusion in the control group of subjects with adenomas. They also suggest that the major effect of smoking on the colorectal adenoma-carcinoma sequence occurs in the earlier stages of the formation of adenoma and the development of carcinoma in situ. 相似文献
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研究基于计算机视觉的实时动态手势识别技术,并利用OpenCV计算机视觉库在VS2010平台上设计一个基于该技术在多媒体教学中PPT演示控制方面的应用。首先,利用背景差分法进行手势检测,在背景更新的基础上,通过背景差分图和颜色直方图的反投影图来检测运动手势区域,可以达到较为满意的实时运动手势检测效果;其次,采用基于颜色直方图的粒子跟踪算法进行手势跟踪,基本能满足跟踪的实时性;最后,在手势识别阶段,采用基于Hu不变矩的轮廓匹配算法,得到较好的手势识别效果;使用六种手势,来实现演示文稿中的控制应用。 相似文献
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Two bacteriophages were isolated from field collected samples representing two different mosquito breeding places. The phage AB-1 (isolated from Abheit village, Faiyoum Governorate "seepage water") and the phage GA-2 (isolated from El-Gabal El-Asfer Qualyobia Governorate "sewage drain water") were purified. Both bacteriophages were ultrastructurally described with respect to their morphology, dimensions, phases of bacterial attack and lysogeny. No major differences were observed between both isolated phages in relation to specificity, however; they were isolated from two different types of breeding places and two different geographic areas as well. This study may assume a wide host range of the isolated phages and reflect how bacterial insecticides used for mosquito larval control could be inhibited by such bacteriophage. 相似文献
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HW Klafki AI Pick I Pardowitz T Cole LA Awni HU Barnikol F Mayer HD Kratzin N Hilschmann 《Canadian Metallurgical Quarterly》1993,374(12):1117-1122
Motivated by the finding that the amino acid sequence of the Bence Jones protein BJP-DIA was identical to that of the main protein component of the amyloid fibrils obtained from the same patient with AL-amyloidosis, (Klafki, H.-W., Kratzin, H.-D., Pick, A.-I., Eckart, K., Karas, M. & Hilschmann, N. (1992) Biochemistry 31, 3265-3272.), we attempted to create "amyloid-like" fibrils from the Bence Jones protein in vitro, without addition of proteolytic enzymes. Reduction of BJP-DIA, solubilized in PBS, pH 7.4, overnight at 37 degrees C resulted in the formation of a precipitate which had affinity for the dye Congo red. Electron microscopy of negatively stained samples of the reduced protein revealed aggregates of linear unbranched fibrils. SDS-polyacrylamide gel electrophoresis demonstrated that the precipitate consisted almost exclusively of intact light chain molecules. This result makes it possible to deduce a molecular model of these amyloid fibrils generated in vitro. 相似文献
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本文针对农村水电站管理特点,结合水电站数量多、分布广、管理要素杂、管理手段落后的客观情况,提出了信息系统建设应从"看的清、搞的懂、有办法、能落实"四个层面入手构建技术体系、功能体系和应用体系。并结合广西农村水电站信息化建设过程,探讨了农村水电站信息化建设思路。 相似文献