科技解构“非典”——加拿大医学杂志发表药物疗法论文     

《中国科技信息》2003,(9):30-30

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用图象法分析“测定电源电动势和内阻”实验中的E、r误差     

顾春杰 《数理化解题研究》2007,(6):49-49,F0004

高中物理电学实验“测定电源电动势和内阻”中为了减小实验误差,我们采用图象法描绘出U-Ⅰ图线,通过求图线的截距和斜率,根据外电压和电流的关系式：U=E-rⅠ,从而得到电源的电动势E和内阻r,但是由于电流表和电压表内阻会引起实验误差,具体分析如下。  相似文献   

Potential production simulation and optimal nutrient management of two hybrid rice varieties in Jinhua,Zhejiang Province,China     

Xie WX  Wang GH  Zhang QC 《Journal of Zhejiang University. Science. B》2007,8(7):486-492

Potential growth of two widely-grown hybrid rice varieties in the Jinhua district of Zhejiang Province, Shanyou63 for mid-rice and Xieyou46 for late rice, was simulated using a crop growth model of WOFOST. Parameters of the rice growth in WOFOST were calibrated through field experiments from 1999 to 2002 in Jinhua. The potential yield simulated with WOFOST was about 12 t/ha for Shanyou63 and 10 t/ha for Xieyou46, which are in good agreement with the highest recorded yield obtained in this area. Under farmers practice, current yield is about 7.5 t/ha for Shanyou63 and 6.5 t/ha for Xieyou46. There is a gap between the actual rice yield and the potential yield for these two hybrid rice varieties grown in this area. The attainable target yields were set to 70% to 75% of their potential yields for the two varieties. A recently developed software ＂Nutrient Decision Support System （NuDSS）＂ for irrigated rice was used to optimize nutrient management for these two rice varieties. According to NuDSS, the optimal fertilizer N requirement for the target yields was about 150 kg/ha for Shanyou63 and about 120 kg/ha for Xieyou46, which were only about 70% of the fertilizer N application under current farmers＇ practice. Comparing with farmers＇ practice, there is great potential to increase actual rice yields and to reduce fertilizer N use rates by improving rice crop management practice in Jinhua.  相似文献   

A rapid and accurate 3-（4,5-dimethyl thiazol-2-yl）-2,5-diphenyl tetrazolium bromide colorimetric assay for quantification of bacteriocins with nisin as an example     

Wang F  Cao LT  Hu SH 《Journal of Zhejiang University. Science. B》2007,8(8):549-554

The objective of this study is to propose a more accurate and faster MTT 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide colorimetric assay (MCA) for quantitative measurement of polypeptide bacteriocins in solutions with nisin as an example. After an initial incubation of nisin and indicator bacterium Micrococcus luteus NCIB 8166 in tubes, MTT was added for another incubation period. After that, nisin was quantified by estimating the number of viable bacteria based on measuring the amount of purple formazan produced by cleavage of yellow tetrazolium salt MTT. Then MCA was compared to a standard agar diffusion assay (ADA). The results suggested a high correlation coefficient (r2=0.975±0.004) between optical density (OD) and the inhibitory effect of nisin on a bacterial strain Micrococcus luteus NCIB 8166 at a range of 0.125～32 IU/ml. The MCA described in this study was very quick. Quantification of nisin took only 7～8 h and the detection limit was at the level of 0.125 IU/ml when compared to 12 IU/ml and 24～28 h for ADA. The MCA provides an accurate and rapid method for quantifi-cation of nisin in solutions and is expected to be used for quantification of other antimicrobial substances.  相似文献   

粉花月见草中总黄酮含量的分析测定     

杨再波  张炜 《黔南民族师范学院学报》2011,(6):1-3

目的：测定粉花月见草中总黄酮的含量。方法：以无水乙醇作为回流提取溶剂,在375nm处用紫外可见分光光度法测定粉花月见草中总黄酮的含量。结果：测得粉花月见草中总黄酮的含量为1.4435mg/g,精密度RSD=0.14%（n=5）,回收率为90.87%～98.98%。结论：该方法操作简便、准确、可靠,可用于植物中总黄酮的含量测定。  相似文献   

阿里红中提取总黄酮的含量测定     

阿布来提·阿布都热西提 《喀什师范学院学报》2011,32(6):43-45

用乙醇热回流提取法对阿里红中总黄酮进行了提取,通过分光光度法,以芦丁为对照品,测定了阿里红中总黄酮含量.本法简便,快速,可用于阿里红生药及其制剂总黄酮含量测定.  相似文献   

维管束：植物的“桥梁”     

史军 《中学生阅读(初中版)》2011,(3):52-53

面对一棵大树,人们经常会赞美阳光下勤勤恳恳的绿叶,它们是充满工作热情的榜样：也会大力讴歌居于地下默默无闻的树根,那可是无私奉献的楷模。可是很少有人会去深究：根吸收的水分和氮、磷、钾等如何被送上枝头,绿叶制成的＂面包＂又是怎样被运到根部的。  相似文献   

“测定空气中氧气体积含量”的新方法     

马逸群 《中国现代教育装备》2011,(16):57-57

一、教科书实验的不足 1.燃烧匙从伸进集气瓶到塞紧橡皮塞这段时间里,免不了会有部分空气受热而逸出,这会使测量的结果偏大。 2.没有考虑导气管里的空气。弹簧夹之前的导气管内的空气很难参与燃烧反应,而弹簧夹之后的导气管内的空气则不能参与燃烧反应。  相似文献   

一种新型光学纯胡椒醛基氮杂环丙基羧酸酯的合成与表征   总被引：2，自引：2，他引：0  

赵文献  李高伟  张锟  陈东丽  刘念  雷晓明 《商丘师范学院学报》2011,27(6):38-40

为发展新型手性配体,降低手性催化剂的合成成本,检验由芳醛与手性氨基酸酯缩合、还原反应的普适性,以L-丝氨酸为手性源,经酯化,缩合,还原氨化,关环等反应,设计合成了一种新的胡椒醛基氮杂环丙基羧酸酯5,其结构通过IR,1H NMR,13C NMR,HRMS进行了表征.发展了一条高效便捷合成这类具有光学活性化合物的方法.  相似文献   

探研氮素对返魂草生长的影响     

刘丽娟  李海燕  孙聪 《通化师范学院学报》2011,32(4):42-43

以采自通化县兴林镇朝阳林场修正返魂草生产基地的返魂草实生苗为试材,采用砂培法对返魂草进行缺氮培养,并检测有缺素表现时植株内氮含量.结果表明,返魂草缺氮时,植株生长受阻,老叶首先出现黄斑,黄斑逐渐扩增至整个叶片,至叶片全部枯黄,并且生长点干枯,严重时死亡;随着缺氮培养时间的增加返魂草体内氮含量逐渐降低.  相似文献