产蛋鸡对夏季高温环境的应激反应及其缓解剂应用的效果

应用化学和放射免疫分析法。研究了27—44周龄哈可产蛋鸡在夏季高温环境中血液生化指标及某些内分泌激素的变化.结果表明在高温时,血糖、血钙、血钠、血钾、抗坏血酸和甲状腺素的含量与适温时比较差异极显著(P<0.01),血浆碱储差异显著(P<0.05),皮质醇略有升高,A/G 比伉降低.提示了热应激对机体的能量代谢和水盐代谢的影响很大,气温越高对鸡群的产蛋率和抗病力的影响越明显,危害越大.     

Evaluation of the soil penetration resistance along a transect to determine the loosening depth

The objective of this study was to evaluate the distribution of soil strength (measured as cone index, CI) along a 600 m transect and to determine the soil loosening depth necessary to eliminate zones with soil strengths exceeding a threshold value down to a depth of 0.6 m. The transect was located at a site in a glacial drift area which was characterised by sandy deposits overlying boulder clay. A tractor-mounted multi-penetrometer array consisting of four hydraulically driven single vertical penetrometers was used to determine CI at 1-m sampling intervals as a measure of penetration resistance. The spatial fluctuation of the CI readings in general and that of repeatedly averaged readings along the transect was examined. Furthermore, the relationships between the penetration resistance of several soil layers and the relationships between the CI of single penetrometers were identified. Averaged CI values over 5-m intervals were used to determine the depth of soil loosening required. By using various data sub-sets based on the averaged data of the four array mounted penetrometers and simulating several different sampling intervals, treatment intervals and threshold values of soil strength, a sampling interval of about 10 m proved to be sufficiently accurate to determine the loosening depth required.Special Issue: Papers from the 5th European Conference on Precision Agriculture (5ECPA), Uppasala, Sweden, 2005.     

Surface morphologies and internal fine structures of bast fibers

Fiber surface morphologies and associated internal structures are closely related to its properties. Unlike other fibers including cotton, bast fibers possess transverse nodes and fissures in cross-sectional and longitudinal directions. Their morphologies and associated internal structures were anatomically examined under the scanning electron microscope. The results showed that the morphologies of the nodes and the fissures of bast fibers varied depending on the construction of the inner fibril cellular layers. The transverse nodes and fissures were formed by the folding and spiralling of the cellular layers during plant growth. The dimensions of nodes and fissures were determined by the dislocations of the cellular layers. There were also many longitudinal fissures in bast fibers. Some deep longitudinal fissures even opened the fiber lumen for a short way along the fiber. In addition, the lumen channel of the bast fibers could be disturbed or disrupted by the nodes and the spirals of the internal cellular layers. The existence of the transverse nodes and fissures in the bast fibers could degrade the fiber mechanical properties, whereas the longitudinal fissures may contribute to the very rapid moisture absorption and desorption.     

可变电荷土壤中特殊化学现象及其微观机制的研究进展

综述了近年来可变电荷土壤化学研究的进展,着重总结了可变电荷土壤中的盐吸附、铁铝氧化物对土壤自然酸化的抑制作用和离子强度对离子专性吸附的影响等特殊化学现象及其微观机制的研究进展。用颗粒表面扩散层重叠导致有效电荷数量减小的原理解释了盐吸附现象和铁铝氧化物对土壤自然酸化的抑制作用。阐明了可变电荷土壤和矿物中介质离子强度影响离子专性吸附的机制,用四层吸附模型解释了离子专性吸附随离子强度增大而增加的现象,并根据胶体zeta电位随离子强度改变而变化的趋势进一步证明了离子强度增大使胶体专性吸附面上静电电位的绝对值减小,是离子专性吸附随离子强度增大而增加的主要原因。带电颗粒表面双电层结构和双电层相互作用的深入研究,有助于阐明可变电荷土壤中一些特殊化学现象的微观机理,从而进一步完善土壤化学理论。     

铜水平对蛋鸡铜铁锌代谢及淋巴组织的影响

选择体重及产蛋率相近的海兰褐23周龄蛋鸡216只,随机分成6个处理,每个处理4个重复,每个重复9只鸡,以玉米--杂粕型日粮为基础日粮,硫酸铜添加水平分别为0、6、15、30、60、125mg/kg,预试期1周后进入8周试验期.试验结果表明:随着日粮铜添加水平的增加,肝脏、血液、肌肉中铜含量都有所增加,尤以肝铜含量增加显著,各处理组间差异极显著(P<0.01);当铜添加水平在6、15、30、60、125mg/kg范围时,随铜的增加,蛋鸡体组织中的锌、铁含量呈下降趋势,以6mg/kg添加量时血液、肌肉组织的锌、铁含量最高,与其余铜添加组差异显著(P<0.05);从所测血液生理生化指标也说明蛋鸡体内铜、铁、锌代谢受日粮铜添加水平的影响.此外日粮添加15mg/kg铜,盲肠淋巴小结平均直径最大,添加30mg/kg铜,盲肠淋巴小结数目最多,脾淋巴小结平均直径最大.     

Mechanical properties of outer layers from near-isogenic lines of common wheat differing in hardness

The mechanical properties of the combined outer layers from near-isogenic wheats differing by hardness were determined. Results from traction tests showed significant differences between the isogenic lines, outer layers from grains of the soft type showing higher extensibility. Determination of the mechanical properties of the corresponding component tissues revealed significant differences between the isolated tissues from soft or hard wheat grains. It also allowed analysis of their respective contribution to the properties of the combined peripheral tissues using a simulation of their rupture as unseparated tissues. According to the results, if the component layers displayed similar maximum lineic force to rupture, the rupture of combined outer layers occurs when the least extensible individual tissue breaks. The major cell wall biochemical components of the combined outer layers and of their component tissues were analysed. The phenolic acid composition of soft wheat pericarp contained more ferulic acid in either monomeric or polymeric forms than the pericarp from hard wheat. Arabinoxylans in walls of the soft wheat pericarp appeared 1.6 times more cross-linked by ferulic acid dehydrodimers than walls of hard wheat. These differences in arabinoxylan cross-linking may explain the observed differences in pericarp mechanical properties.     

口服BSA免疫对鸡盲肠扁桃体组织结构变化的影响

为了观察T细胞依赖性抗原对鸡盲肠扁桃体组织结构变化的影响,将雏鸡分为免疫组和对照组,每组50只,免疫组雏鸡定时进行空腹口服免疫1mL浓度为10mg/mL牛血清白蛋白(BSA),连续口服免疫6d。在最后一次免疫后的1、4、7、10、13、16、19、22、25、28d分别随机选取4只鸡,取其盲肠扁桃体。对照组也在各免疫组取材相同的日龄时取相同部位的组织,用HE染色法结合图像分析软件和数据统计软件对其进行观察。结果显示,免疫组鸡的盲肠扁桃体的肠绒毛长度、皱褶高度、肠腺深度﹑生发中心的数量和直径均比对照组鸡盲肠扁桃体的肠绒毛长、皱褶高﹑肠腺深﹑生发中心的数量多和直径大。说明口服免疫T细胞依赖性抗原对鸡盲肠扁桃体组织结构变化存在影响。