玉米果穗轴截面在籽粒产量预测中的应用

玉米杂交种田间测产是玉米育种和栽培科技成果评价的一项必要工作。研究了用果穗轴截面预测单株籽粒产量的方法,结果表明:(1)果穗轴截面承载力为2.02 g/cm2左右,是一个比较稳定的参数;(2)单株籽粒产量大约是果穗轴截面积的2.02倍;(3)单株籽粒产量的预测平均值与实际平均值十分接近,误差较少;(4)单株籽粒产量的预测平均值与种植密度的乘积能较准确地估计出单位面积籽粒产量,是一种简单易行、准确可靠的测产方法。     

空间斜平面弯管轴线几何参数的矢量计算法

提出用矢量法计算空间斜平面弯管轴线几何参数的简捷方法，推导出计算管轴线参数、弯管段设计参数和施工放线参数的所有公式。并给出一实用设计例。     

大尺寸轴类零件测控系统设计

大尺寸轴类零件的检测基本是通过人工完成的，其检测手段已远远不能满足实际生产的需要。基于此，开发出了大尺寸轴类零件智能检测系统。该系统可以完成相关轴颈的尺寸和形位误差的检测，测量系统分辨率可达0.1μm，对不合格产品可修复性判断的准确率在97％以上。     

脂多糖刺激对仔猪下丘脑-垂体-肾上腺轴Toll样受体4信号通路关键基因表达的影响

本试验旨在研究脂多糖(LPS)刺激对仔猪下丘脑-垂体-肾上腺(HPA)轴Toll样受体4(TLR4)信号通路关键基因表达的影响。选取12头断奶仔猪,分成2个组,每个组6个重复。试验组注射100μg/kg体重的LPS,对照组注射等量的生理盐水。注射LPS或生理盐水4 h后采血,测定血浆中与应激相关激素的含量;采血后屠宰仔猪,取下丘脑、垂体、肾上腺,测定TLR4信号通路关键基因的mRNA表达水平,包括TLR4、髓样分化因子88(My D88)、白细胞介素-1受体相关激酶1(IRAK1)、肿瘤坏死因子受体相关因子6(TRAF6)和核转录因子-κB(NF-κB)mRNA表达水平。结果表明:与对照组相比,1)LPS刺激导致血浆肿瘤坏死因子-α、皮质醇和促肾上腺皮质激素含量显著上升(P<0.05)。2)LPS刺激导致TLR4信号通路关键基因TLR4在下丘脑、垂体、肾上腺中mRNA表达水平显著升高(P<0.05);My D88在垂体、肾上腺中mRNA表达水平显著升高(P<0.05),在下丘脑中mRNA表达水平有升高的趋势(P<0.10);IRAK1在垂体、肾上腺中mRNA表达水平有升高的趋势(P<0.10);TRAF6在下丘脑、垂体、肾上腺中mRNA表达水平显著升高(P<0.05);NF-κB在垂体中mRNA表达水平显著升高(P<0.05)。试验结果表明LPS刺激激活了HPA轴,诱导了HPA轴的TLR4信号通路关键基因的表达。     

大功率拖拉机传动系试验技术研究

针对大功率拖拉机传动系室内试验的特点和难点,提出了可行的解决方案。基于NI LabVIEW虚拟仪器平台建立了传动系仿真试验系统,找到了实现差速器"电轴"连锁的控制方法,并通过试验进行了技术验证。     

Stress responses and disease resistance in salmonid fish: Effects of chronic elevation of plasma cortisol

Basal levels of plasma cortisol in unstressed salmonid fish are normally in the range 0–5 ng ml⁻¹. An acute stress such as handling or 1 h confinement caused a temporary elevation of the plasma cortisol levels of both brown trout,Salmo trutta L., and rainbow trout,Salmo gairdneri Richardson, in the range 40–200 ng ml⁻¹ with a return to basal levels within 24–48 h. The extent of the cortisol elevation in response to an acute stress was dependent upon both the species and strain of trout. Chronic stresses, such as prolonged confinement or crowding, resulted in an elevation of plasma cortisol levels to approximately 10 ng ml⁻¹. Under these circumstances, blood cortisol levels remained elevated for periods of up to 4 weeks before acclimation finally occurred. It is shown, by means of intraperitoneal implantation of cortisol, that chronic elevation of plasma cortisol levels in the brown trout results in a dose-dependent increase in mortality due to common bacterial and fungal diseases. This effect is apparent at plasma cortisol levels as low as 10 ng ml⁻¹, levels below those often reported as being representative of ‘unstressed’ fish. These findings are discussed in relation to the known immunosuppressive effects of corticosteroids in teleost fish.     

几种促生长剂对反刍动物的研究与开发前景

本文简要介绍了近年来我们对三种促生长剂(CS87、β—受体激动剂、苯二氮卓类F89)在反刍动物的实验研究情况。CS87主要通过耗竭体内生长抑素 ,提高生长激素、IGF—I和其他代谢激素水平 ;同时加强消化代谢机能 ,从而促进动物生长和提高饲料转化率。β—受体激动剂对反刍动物的效果比单胃动物更为显著 ,可能是由于瘤胃微生物存在 β—受体 ,改善了蛋白质代谢。但应使用规范化 ,防止残留量超标 ,以利保证肉品卫生。初步研究表明 ,F89可提高动物采食量和养分消化量。上述三种生理调节剂都有良好的开发前景     

RADIOGRAPHIC MEASUREMENTS OF HOOF BALANCE ARE SIGNIFICANTLY INFLUENCED BY A HORSE'S STANCE

Hoof balance radiographs are commonly used as the basis for corrective farriery decision‐making in horses, however there are limited published data quantifying effects of the stance of the horse or the horizontal radiographic beam angle. In this analytical study, the influence of variation of the horse's stance in the craniocaudal and lateromodial plane on hoof balance measurements as well as the influence of variation of the horizontal radiographic beam angle on dorsopalmar hoof balance measurements was examined. Distal left thoracic limb lateromedial radiographs were acquired using a standardized protocol while varying the craniocaudal stance of five horses, each selected to be sound and conformationally normal. Dorsopalmar foot radiographs were acquired while varying the lateromedial stance; and variable angle horizontal beam dorsopalmar foot radiographs were acquired while keeping the limb position constant. Analyses of measurements demonstrated that hoof pastern angle had a linear relationship (R² = 0.89, P < 0.001) with craniocaudal stance of the horse. The relationship of joint angle and stance was greater for the distal interphalangeal joint angle (R² = 0.89, P < 0.001) than the proximal interphalangeal joint angle (R² = 0.65, P = 0.001). The distal phalanx angle did not change with craniocaudal stance variation. The proximal interphalangeal joint width, distal interphalangeal joint width, or distal phalanx height did not change with lateromedial stance variation, nor within a 15 degree dorsolateral to caudomedial and dorsomedial to caudolateral variation from the dorsopalmar axis. Findings indicated that positioning of the thoracic limb needs to be considered during radiographic interpretation and decision‐making for corrective farriery.