A COMPUTED TOMOGRAPHIC STUDY OF VOLUME AND X-RAY ATTENUATION OF THE LUNGS OF BEAGLES IN VARIOUS BODY POSITIONS

The influence of body position on volume and x-ray attenuation of the lungs of three Beagles was investigated with computed tomography. In left and right lateral recumbency, the dependent lung had decreased volume and increased x-ray attenuation compared with ventral recumbency. Volume and x-ray attenuation of the nondependent lung, however, were unchanged. In dorsal recumbency, there was a vertical gradient of x-ray attenuation being increased dorsally and decreased ventrally compared with ventral recumbency where regional differences in x-ray attenuation were not found. Results indicate a risk of overlooking a mass in the dependent pulmonary parenchyma of dogs in lateral and dorsal recumbency. Regional differences in x-ray attenuation of the lungs of dogs can be avoided if the radiographs are obtained with the dog in ventral recumbency.     

论蚕种场面临的困境与对策

目前蚕种场系统面临困境，本文就此进行了原因分析，并就茧量平衡，提高经营水平，综合开发，政策引导，科技改良等方提出了对策 。     

莲草直胸跳甲成虫产卵选择性及叶位与幼虫发育适合度的关系

采用室内自由选择法和发育测定法研究莲草直胸跳甲(Agasicles hygrophila)成虫对喜旱莲子草(Alternanthera philoxeroides)叶位的产卵选择性及后代发育与不同叶位叶片的适合度.结果表明:(1)莲草直胸跳甲成虫嗜好在中部叶片的叶背产卵,以在第2对叶上的选择系数最高,选择率为35.18%,与第1对叶上的28.03%差异不显著,但显著高于对其他叶位的选择系数;(2)相对于在叶表进行取食,初孵幼虫显著趋向在叶背,且这样取食的1龄幼虫存活率高、发育历期显著缩短,这与雌虫选择在叶背产卵的习性相符,说明其选择有一定生物学意义,即有利于后代发育;(3)叶龄对莲草直胸跳甲各龄幼虫发育有显著影响,叶位越低,各龄幼虫的发育历期越长,但存活率上以取食第1叶位的为最高.     

浅谈自然保护区在湖北生态建设中的地位与作用

随着全国野生动植物保护和自然保护区建设工程的实施 ,自然保护区在我省生态环境建设中的地位与作用越来越重要 ,运用生物多样性管护区的理论指导我省的自然保护区建设将是正确认识自然保护区地位与作用的关键所在。     

变形轴中心孔最佳位置的确定

以往生产中只能凭直观或用外圆打表测量方法来确定变形轴中心孔最佳位置，这既不方便又不准确．经分析与计算，得出变形轴中心孔最佳位置为０．３５Ｌ．     

Variation in infiltration with landscape position: Implications for forest productivity and surface water quality

Variation of infiltration rates with landscape position influences the amount, distribution, and routing of overland flow. Knowledge of runoff patterns gives land managers the opportunity to affect changes that optimize water use efficiency and reduce the risk of water quality impacts. The objective of this study was to assess the effect of landscape position and associated soil properties on infiltration in a small (147 ha) forest/pasture watershed in the Ozark Highlands. Three previously reported studies measured infiltration rates using double ring, sprinkling, single ring, and tension infiltrometers on soils at varying landscape positions. Although large variation in infiltration rates was observed among measurement techniques, upland and side slope soils (Nixa and Clarksville) had consistently lower infiltration rates compared to the soil in the valley bottom (Razort). A conceptual understanding of watershed runoff is developed from these data that includes infiltration excess runoff from the Nixa and Clarksville soils and saturation excess runoff on the Razort soil. Management of the soil water regime based on this understanding would focus on increasing infiltration in upland soils and maintaining the Razort soil areas in forest. Forest productivity would be enhanced by increasing plant-available water in upland soils and decreasing flooding on the Razort soil. Surface water quality would be improved by reducing the transport of potential water contaminants from animal manure applied to upland pastures.     

水杨酸对杏树花期抗寒性及坐果率的影响

以室温蒸馏水处理为对照,分别用浓度为0、2、10、20、40、80 m g.L-1的水杨酸溶液处理张公园杏初开花朵,放入0℃恒温培养箱4 h,取出后测定花朵的外渗电导率值、呼吸强度、雌蕊的超氧化物歧化酶和过氧化物酶的活性及丙二配醛的含量,结果表明:水杨酸可有效抑制由低温引起的细胞电解质外渗,提高呼吸速率,提高雌蕊超氧化物歧化酶和过氧化物酶的活性,减少丙二醛的积累。还在田间条件下,以7年生3个品种的杏树为试材,于初花期分别用浓度为0、2、10、20、40 m g.L-1的水杨酸溶液进行喷施,结果发现:浓度为10 m g.L-1的水杨酸能够极显著地提高骆驼黄、华县接杏品种的坐果率,但其对张公园品种的影响却并未达到显著水平。认为在杏树初花期喷施一定浓度的水杨酸可以起到预防低温伤害及提高产量的作用。     

卷荚相思在福建五台山林场的生长表现

在五台山林场引种卷荚相思3年试验结果表明,卷荚相思能适应林场的立地和气候条件,生长快且好,胸径和树高年生长量分别为3 cm,2.5 m;不同坡向,坡位,立地条件下卷荚相思生长差异显著,试验结果表明,五台山地区比较适合种植卷荚相思,尽管在冬季有严重的霜冻,但试验林未出现严重寒害。     

柑橘高接换种适宜嫁接部位探讨

以温州蜜柑为中间砧,对高林温州蜜柑、太田椪柑进行不同部位高接的适宜性研究.结果表明,不同部位高接对成活率的影响无显著性差异,但树冠的恢复程度与嫁接部位的高低成正比,即高接部位越高,树冠恢复越快;含糖量和糖酸比以腹接最高,侧枝次之;外观以腹接、侧枝高接为好,副主枝高接次之,主枝高接最差.柑桔高接最高高度应控制在1.0 ～ 1.3m,早投产,树冠恢复快,果实品质好,以侧枝高接,腹接为好,侧枝高接易引起内膛空虚,可采取内膛腹接弥补.     

Leaf-fall phenology along a topography-mediated environmental gradient in a cool–temperate deciduous broad-leaved forest in Japan

Leaf-fall phenology was studied in a cool–temperate deciduous broad-leaved forest in central Japan in relation to the topographic environmental gradients that occur along a short mountain slope. Leaf-fall phenology was described quantitatively using data from leaf litter collected along the slope. In autumn, leaf fall at the study site tended to occur slightly earlier on the upper slope than on the lower slope. This pattern was found at both the stand and the species levels. Our results suggest that leaf-fall phenology may be affected by difference in microclimatic conditions, because environmental conditions are thought to be more severe on the upper slope than on the lower slope. The less intensive methods used in this study, the litter trap method, and Dixon’s model succeeded in quantifying the phenological patterns of leaf fall within stands and within species along the short mountain slope.