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谯仕彦 《农业生物技术学报》2003,11(1):93-93
经实验证实,植物多糖可大大提高有益微生物的作用效果,是一种有效的益生协同剂。本项目在国内首次采用微生物学鉴定、微量快速生化反应和离子色谱分析法等手段,开展了猪和家禽肠道不同部位无芽孢厌氧菌的定位、定性和定量研究,从猪、家禽和鱼的消化道中分离筛选出地衣芽孢杆菌、蜡状芽孢杆菌、凝集芽孢杆菌、环状芽孢杆 相似文献
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Martínez-González MA López-Fontana C Varo JJ Sánchez-Villegas A Martinez JA 《Public health nutrition》2005,8(7):920-927
OBJECTIVE: The objective of this analysis was to test the validity of the estimates of energy expenditure and sedentary lifestyle obtained through a self-administered questionnaire of physical activity for Spanish-speaking people adapted from US questionnaires (Nurses' Health Study and Health Professionals' Follow-up Study) using a triaxial accelerometer (RT3 Triaxial Research Tracker) as the reference. DESIGN AND SETTING: Validation study, calculating the non-parametric correlation coefficients between the level of physical activity and sedentary lifestyle collected by the self-administered questionnaire and the triaxial accelerometer measurements. Percentage of misclassification and kappa coefficients were also calculated. SUBJECTS: The study population consisted of a sample of 40 obese women who were participants of the SUN (Seguimiento Universidad de Navarra) project (a prospective cohort study among Spanish university alumni). They were selected because of their peculiar metabolic characteristics, in the search for a sub-optimal scenario for validity. RESULTS: Physical activity during leisure time (estimated as MET-h week(-1)) derived from the self-administered questionnaire moderately correlated with kcal day(-1) assessed through the accelerometer (Spearman's rho = 0.507, 95% confidence interval (CI) 0.232, 0.707). The Spearman correlation between the ratio of sedentary lifestyle to physical activity obtained through the questionnaire and the direct estimation (RT3) was -0.578 (95% CI -0.754, -0.325). The kappa index was 0.25 (P = 0.002) when assessing the cross-classification into quintiles and 0.41 for the dichotomous estimation of a sedentary lifestyle. Only 2.5% of participants were misclassified by the questionnaire more than two quintiles apart from the estimates of the RT3. CONCLUSIONS: The moderate values obtained for correlation in a sub-optimal scenario for validity and the low percentage of extreme misclassification suggest the validity of the questionnaire to assess physical activity in Spanish-speaking women aged 20-50 years. 相似文献
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Qingxiang Z Wenying L Guoguang L Xiuling X 《Journal of agricultural and food chemistry》2000,48(6):2572-2575
It is reported that 2-chlorobenzamide, one of the chief degradation products of CCU (1-(2-chlorobenzoyl)-3-(4-chlorophenyl) urea), a new insect growth regulator, is a potential carcinogen, but few studies about its environmental stability have been found. This paper is concerned with the hydrolysis of 2-chlorobenzamide as part of the environmental study of CCU. The results showed that 2-chlorobenzamide is relatively stable in solutions of pH = 6 and 8, for which the rate constants are 0.00286 h(-)(1) (R = 99.13%, SD = 0. 0095) and 0.00109 h(-)(1) (R = 96.70%, SD = 0.0072), respectively. Hydrolysis was more rapid in acidic (pH = 5), alkaline (pH = 10), and neutral (pH = 7) environments, with hydrolytic rate constants of 0.00417h(-)(1) (R = 95.76%, SD = 0.0390), 0.00411h(-)(1) (R = 99.89%, SD = 0.0162) and 0.00408h(-)(1) (R = 98.29%, SD = 0.0237), respectively. The change of the rate of hydrolysis with pH showed two minima at 25 degrees C. Temperature has some impact on the hydrolysis, showing at higher temperature the larger rate of reaction. 相似文献
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农村信息化是我国信息化进程中的一个重要组成部分,也是实现农业现代化和社会主义新农村的必要途径。本文首先阐述了我国农村信息化发展的现状,然后指出了信息化进程中存在的问题,并分析了问题成因,最后,提出了若干加快我国农村信息化发展进程的政策建议。 相似文献
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防风效果的评估在防风工程中有非常重要的地位,本研究探讨在台湾防风研究常用两种指标之适用性和代表性。并考虑二维风向速度及改善背风面常出现回流等之问题而建立风阻指标(Windbreak Index,WBI)。以数值计算来模拟一地表直立墙附近之空气流场,期能对于防风工程提供较实际、客观的防风效果评估方式。 相似文献
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分析测定了野生菊(Mantianxing),药用菊(Hangbaiju),栽培菊(Huangjingqiu),三个菊花品种的还原糖、总糖、维生素C,氨基酸及钙,磷、铁、铜、锌、锰等矿质元素的含量。结果表明:野生菊的维生素C、总糖、还原糖、氨基酸总量分别比药用菊和栽培菊高,药用菊的铁、锌、铜、锰的含量分别比野生菊和栽培菊高。栽培菊的钙、磷则分别比野生菊和药用菊高。从而为进一步开发利用我国丰富的菊花资源提供了依据。 相似文献
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滑坡灾害复杂性特征研究 总被引:1,自引:0,他引:1
从系统论的角度出发,将滑坡灾害作为一个复杂的巨系统来进行研究,详细分析了滑坡灾害在存在意义和演化意义两个方面的复杂性特征。同时,从协同理论、分形分维、突变理论、人工神经网络与免疫系统以及空间信息技术综合集成等方面探讨了多学科在滑坡灾害复杂性方面的研究。滑坡灾害的复杂性研究可以在一定程度上促进人类对滑坡灾害整体行为和发展演化过程的研究与探索,同时也可以为滑坡灾害的防治评价和预测预报提供科学依据和辅助决策支持,在滑坡灾害及其相关地质灾害的防治中具有积极的作用,在滑坡灾害的防灾减灾中有着广泛的应用前景。 相似文献
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下层土壤反硝化作用的研究 总被引:10,自引:0,他引:10
在夏玉米生长期间 ,采用乙炔抑制 -原状土柱培养方法研究了北京褐土下层 (15~ 6 0cm)土壤的反硝化作用 ,并探讨影响该层土壤反硝化作用的主要因素。试验结果表明 ,施氮量越高 ,反硝化量越大。随着土壤层次的加深 ,反硝化量呈直线下降 ,但在亚表层土壤 (15~ 30cm)反硝化值仍保持了较高的量 ,约相当于表层的 10 .7%~ 33.5 % ;下层土壤 (15~ 6 0cm)的总反硝化量约相当于表层土壤的 14%~ 51%。加入碳源无论对表层土壤还是下层土壤 ,其反硝化损失氮量大大增加 ,尤其是对下层土壤增加的趋势更为明显。在计算夏玉米季土壤反硝化损失氮量时 ,如果忽略下层土壤的反硝化作用 ,肯定会低估其数值 相似文献
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免耕播种机单体工作性能试验研究 总被引:10,自引:4,他引:6
分析了免耕播种机单体的受力,在土槽上对四杆悬挂机构的免耕播种机单体的工作性能进行了试验研究,建立了开沟器牵引阻力和入土阻力回归的数学模型。以此对水平阻力和垂直方向阻力进行了分析。结果表明在土壤坚实度为16×105~26×105Pa范围内,开沟器入土阻力为686~980N,牵引阻力为441~784N;随工作速度和附加配重的增加,入土阻力和牵引阻力均增大。在受力特征研究的基础上,对影响开沟深度稳定性的结构参数及作业条件进行了分析,建立了播种机单体开沟深度稳定性数学模型,为免耕播种机合理设计提供参考 相似文献
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坡面流流速计算的研究 总被引:13,自引:0,他引:13
有降雨影响下的坡面流,多为三维非均匀沿程变量水流,其流速的计算是一个比较复杂的问题,也是研究土壤侵蚀力学机理的关键。本文根据室内人工降雨水槽模拟实验对影响坡面流速诸因子的研究结果,首先从理论上将流速表示为含有达西—维斯巴赫(Darcy—Weisbach)阻力系数f的函数,再根据实验资料建立起不同流态的计算式,进而可计算坡面任一处不同流态的径流速度。 相似文献
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使用各种便携式光合仪测定植物单叶平均光合速率的总误差是由仪器误差、观测误差和叶片本身产生的某些光合反应综合而成。简析了因CO2 、流量、温度、气压等参数测量所用传感器的精度引起的仪器误差 ,且该误差因测量方式 (开路或闭路 )及叶片光合速率水平而异 ,光合强度越强其误差越小 ,误差变幅为 8%~ 2 0 % (开路 )或2 5%~ 15% (闭路 )。并分析了各测量参数误差对光合速率综合误差的贡献 ,指出仪器误差主要是由CO2 分析器和流量计误差所致 相似文献