Value of tracheal bifurcation angle measurement as a radiographic sign of left atrial enlargement in dogs

An increased tracheal bifurcation angle on the dorsoventral projection is described as a sign of left atrium enlargement in dogs, with a normal range of 60-90 degrees reported. However in people, this angle is a poor indicator of left atrial size. Our purpose was to evaluate the value of the tracheal bifurcation angle for differentiating normal from enlarged left atrium in dogs. Dorsoventral radiographs and echocardiograms of 33 healthy and 73 dogs with confirmed degenerative myxomatous mitral valve disease were evaluated. Left atrial size was classified according to the echocardiographic left atrium to aorta ratio, as normal, mildly, moderately, or severely enlarged. Independent samples t-tests were used to compare the bifurcation angle between groups. A significant difference was observed between the angle of dogs with normal left atrium (68.1 +/- 8.5 degrees, range: 51.3-92.4 degrees) and dogs with enlarged left atrium (75.8 +/- 8.2 degrees, range: 57.3-91.7 degrees). A significant difference was also noted between the angle of normal dogs and those with moderate (75.5 +/- 6.8 degrees, range: 62.8-88.7 degrees) and severe (80.4 +/- 7.7 degrees, range: 64.7-91.7 degrees) left atrial enlargement, as well as between dogs with mild (70.7 +/- 7.2 degrees, range: 57.3-89.9 degrees) and severe enlargement. Using two discriminators, 85.1 degrees and 76.6 degrees, the bifurcation angle had a specificity of 92.6% and 88.9%, respectively, for identifying left atrial enlargement, and a sensitivity of 15.4% and 40.4%. Although significant differences were observed between dogs with normal and increased left atrial size, the large degree of overlap in the range of bifurcation angles and its poor sensitivity make the measurement of this angle of little value for diagnosing left atrial enlargement.     

冻融作用对黑土力学性质的影响研究

反复的冻融循环会通过改变土壤黏聚力、内摩擦角等土壤力学性质而使其侵蚀加剧。探讨了冻融循环作用对土壤黏聚力及内摩擦角的影响,从冻融机理上分析了冻融作用对土壤抗蚀性的影响机制。以黑土为试验对象,考虑冻融循环周期和土壤含水率2个影响因素,通过室内冻融试验研究了黑土黏聚力c和内摩擦角ψ的变化规律。结果表明,冻融作用对黑土黏聚力影响较大,而对内摩擦角影响较小。随着冻融循环次数的增加,同一含水率下,黑土黏聚力c呈减小趋势,3次冻融循环以后,c值趋于稳定。在冻融循环次数一定时,随着土壤含水率的增加,黑土黏聚力c呈先减小后增大的趋势。在冻结温度一定时,1次冻融循环对土壤黏聚力c的扰乱较大,其后扰动程度则基本不变。与土壤黏聚力不同,土壤内摩擦角在整个冻融循环过程中没有明显变化。     

胶棒滚筒棉花采摘头的设计与试验

为确定胶棒滚筒棉花采摘头运动参数对新疆机采棉种植模式下的棉花采摘质量的影响,该文阐述了胶棒滚筒棉花采摘头的工作原理及其关键部件、总体结构。基于运动学分析,建立了采摘速比K值与采棉工艺速度、采摘工作角、滚筒转速之间的相应的函数关系,分析了其对棉花采摘性能影响规律。田间试验表明,当采棉机作业速度0.83 m/s,滚筒转速在450 r/min时,棉花采净率达95%以上,含杂率小于15%,落地棉小于2%,达到了棉花收获机械作业的技术要求。     

Evaluation of the distance between Schwalbe’s line and the anterior lens capsule as a parameter for the correction of ultrasound biomicroscopic values of the canine iridocorneal angle

Objective To determine whether the distance between Schwalbe’s line (the peripheral termination of Descemet’s membrane, i.e., the borderline between the cornea and sclera) and the anterior lens capsule (SLD) is an applicable parameter for correcting raw ultrasound biomicroscopic values of the canine iridocorneal angle (ICA) and to establish a comparative system for the ICA values in different canine breeds with varied body sizes/weights. Animal studied The dogs were divided into four groups based on body weight (BW): <4 kg, 4–8 kg, 8–20 kg, and >20 kg, and 180 normotensive eyes were studied. Procedures The ICA microstructure was examined by ultrasound biomicroscopy (UBM) using 40‐MHz probes in dogs with or without anesthesia/sedation. Linear regression analysis and correlation coefficients were evaluated between SLD or SLD² and UBM measurements; subsequently, noncorrected and SLD‐corrected UBM values were statistically assessed. Results Significant linear correlations were detected between SLD and the ciliary cleft width, the minimum distance between the angle recess and the scleral venous plexus, and the scleral thickness. Positive linear correlations were also demonstrated between SLD² and the ciliary cleft area as well as the scleral venous plexus area. Raw UBM measurements were corrected by using a ratio with SLD on the distance or SLD² on the area. Although noncorrected UBM measurements increased with canine BW, SLD‐corrected UBM values remained similar with no significant statistical differences in any of the dogs. Conclusions Correction with SLD would be clinically useful for comparing UBM measurements of the ICA in dogs with different body sizes/weights.     

Development and Distribution of Root System in Two GrainSorghum Cultivars Originated from Sudan under Drought Stress

Abstract

The difference in rooting pattern between two grain sorghum cultivars differing in drought tolerance was investigated under drought stress. The cultivars, Gadambalia (drought-tolerant) and Tabat (droughtsusceptible), were grown in bottomless wooden or acrylic root boxes to examine root parameters. Gadambalia consistently exhibited higher dry matter production and leaf water potential than Tabat under drought stress in both root boxes. In the experiment with wooden root boxes, under a drought condition, Gadambalia extracted more water from deep soil layers (1.1-1.5 m), which was estimated from the reduction in soil water content, than Tabat. This was because Gadambalia had a significantly higher root length density in these soil layers. The high root length density was due to enhanced lateral root development in Gadambalia. In the other experiment with acrylic root boxes, though total root length in the upper soil layer (0-0.5 m) was declined by limited irrigation in both cultivars, the reduction in Gadambalia was moderate compared with that in Tabat owing to the maintenance of fine root growth. Unlike Tabat, Gadambalia had an ability to produce the nodal roots from higher internodes even under drought, which resulted in the high nodal root length of Gadambalia. The growth angle of nodal roots was significantly correlated with root diameter, and the nodal roots from the higher internodes had large diameters and penetrated into the soil more vertically. These results indicate that the responses of roots (i.e. branching and/or growth of lateral root, and nodal root emergence from higher internodes) to soil dryness could be associated with the drought tolerance of Gadambalia.     

基于高光谱影像的高寒牧区土地覆盖分类与草地生物量监测模型

利用环境减灾卫星HJ 1A高光谱图像数据,分析了研究区不同土地覆盖类型的波谱曲线特征,比较了监督分类和光谱角分类方法对高光谱影像的分类精度,研究了高寒牧区草地生物量超光谱遥感监测模型。结果表明,1）不同地物波谱曲线的吸收位置和吸收深度等波谱特征在可见光波段具有较大差异,在近红外波段吸收特征相似。在可见光波段,云和植被的吸收位置最少,都只有1处,但云的吸收深度小于植被;裸地吸收位置有5处;水域吸收位置最多,有6处。2）光谱角与监督分类均适于高光谱影像分类,但光谱角分类方法的总精度可达85.9%,远高于监督分类法。3）依据草地生物量与9种植被指数间的回归分析结果,选出了适合研究区草地植被生物量动态监测的两种植被指数,即归一化植被指数和比值植被指数。     

云南不同类型烟叶表面自由能及其分量的研究

【目的】采用接触角法测量不同类型烟叶的表面自由能,为烟叶表面润湿性的量化表征和加香加料生产工艺的改进提供理论依据。【方法】以2010年云南产的白肋烟、烤烟和香料烟为试验对象,利用视频光学接触角测量仪测定不同探测液与3种云南烟叶表面的接触角,计算烟叶的表面自由能及其分量。【结果】云南产的白肋烟、烤烟和香料烟的表面自由能比较接近,分别为25.21,25.77和27.15mN/m;极性分量和色散分量所占比例差别显著,对色散分量而言,香料烟高达92.3%,而烤烟仅为41.1%,白肋烟居中,为65.5%。【结论】3种云南烟叶的表面自由能较低,属于低能表面,较难被水润湿,较易被一些特定表面张力的液体润湿。     

平模成型机压辊的特性分析

在运动学和动力学分析的基础上,就平模成型机压辊产生的滑动作用进行讨论分析,研究产生最大动压力所需要的条件,为平模成型机的优化设计提供理论依据。结果表明：平模成型机压辊的滑动作用是有利于物料压缩成型的,在一定程度上增加物料的预压缩行程。数学模型的建立有利于平模成型机精确控制压辊的运动状态,提高成型机的工作效率。     

湿地松木材管胞长度微纤丝角的变异及其相关性分析

研究了３个不同立地条件上１５株１７年生湿地松木材管胞长度,微纤丝角的变异及二性状间的相关性。结果表明立地指数对管胞长度,微纤丝角有着较大的影响。株内径向管胞长度由髓心向外递增,纤丝角递减,二性状间呈显著的线性负相关。