羊长久性双筒T形瘘管及其安装的手术方法

本文介绍一种我们自己设计制作的双筒T形痿管,它兼有经典十二指肠区体外吻合瘘管与普通T形痿管的功能和优点,不需切断小肠,对肠壁上的血管及神经损伤较小;能定时计量,而且制作方便,成本低廉。这种痿管安装在胰胆管入口处之前,可以研究皱胃食糜排空规律及其组成变化。我们已在14头绵羊及山羊上经过试验,均获得良好的结果。     

基于近红外漫反射光谱技术的芒果糖度无损检测方法研究

近红外光谱分析技术是近年迅速发展的一门绿色分析技术,具有快速、准确、无损伤检测的特点,正越来越广泛地应用于水果内部品质的无损检测。为此,应用近红外漫反射光谱技术无损检测芒果糖度,光谱数据经一阶微分和Savitzk-Golay预处理后,分别采用主成分回归法(PCR)和偏最小二乘法(PLS)建立芒果糖度近红外分析模型,当主成分数为10时,预测相关系数R分别为0.838 69,0.976 59,RMSEC分别为1.628 4,0.205 8,MEP为1.235 0,0.738 3;采用BP神经网络对70个样品光谱进行训练,建模集相关系数达到0.983 3,而对36个预测样品集的相关系数只有0.663 9;调整建模集和预测集样品,相关系数增大到0.683 6,平均相对误差由10.336 9%降到8.057 6%。研究结果表明,利用近红外漫反射光谱技术对芒果糖度进行无损检测是可行的。     

陇东绒山羊周岁母羊主要经济性状遗传力估测

试验测定周岁陇东绒山羊的主要经济性状,采用父系半同胞相关法估测了遗传力。结果表明,陇东绒山羊周岁母羊产绒量、体重、体高、体长、胸围、管围、羊绒直径、绒层高度、羊绒伸直长度的遗传力分别为0.4129、0.3871、0.3732、0.3128、0.3468、0.2873、0.4013、0.3916、0.3908,为陇东绒山羊的科研育种提供了一定的科学依据。     

Zonal lacunarity analysis: a new spatial analysis tool for geographic information systems

Landscape Ecology - Lacunarity as a scale-dependent measure of spatial heterogeneity has received great attention in landscape ecology. Most lacunarity measures have been obtained from greyscale or...     

Determination of nuclear magnetic resonance T2 cutoff in remoulded loess by the freezing point

Proton nuclear magnetic resonance (NMR) is widely applied to characterize the microscopic properties of hydrogen-containing porous media. The transverse relaxation time cutoff (T_2c) value is the crucial parameter for the quantitative analysis of NMR data. Currently, there is no universal method for the determination of the T_2c in clayey soils. This study aimed to develop a laboratory method for determining the T_2c of remoulded loess by the freezing point of loosely bound water. Malan loess, a kind of typical clayey silt, was used as test material. Based on the soil freezing characteristic, NMR measurements were performed on remoulded loess with different macro-parameter controls during the cooling process to obtain the T₂ spectrum at each target temperature. By analysing the variation of unfrozen water content with temperature reduction, the freezing point of loosely bound water and the T_2c value within the freezing-point range was determined. The freezing point of loosely bound water in remoulded loess is about −3 to −5°C and that of firmly bound water is less than −5°C. Accordingly, the T_2c value of remoulded loess is determined to be 1.5–1.8 ms. The assessment of heating and cooling process and different methods for determining the T_2c shows that the laboratory method by the freezing point is effective and reliable, and the T_2c determined by statistical methods is worthy of further study and improvement. The saturated permeability of remoulded loess is evaluated according to the determined T_2c, and two NMR-based permeability equations can well reflect pore water distribution in remoulded loess, but to a certain extent, both equations ignore soil microstructure, pore connectivity and chemical effects of pore solution. The laboratory method by the freezing point and the determined T_2c value of remoulded loess fill the gap of NMR measurement in loess analysis and are of great significance for low-plastic clays and clay types.