杨树低产林成因及对策——以宿州市踊桥区祁县镇为例

通过设立固定标准地对杨树的中幼林龄期和近熟林龄期生长情况进行调查分析，了解踊桥区祁县镇不同立地条件下杨树长势，判断林分立地条件对生长量影响的关键因子，并进行了标准地土壤剖面结构、理化性质和土壤养分含量对比，结论如下：影响杨树生长的关键因素是林地土层厚度，分析了杨树低产林形成原因是：土壤层浅、瘠薄、空隙度小、质地粘重。并提出相应对策：杨树低产林改造；加强中幼林抚育、进行土壤改良；发展林下经济改善土壤结构理化性质；营造复层林、间接改良土壤，提高林地综合利用率。     

基于Fluent的甘蔗收割机排杂装置气流场的模拟

采用商用计算流体力学(CFD)软件Fluent,对华南农业大学研制的HN4GDL-91型切段式甘蔗收割机排杂装置内部流场进行模拟。利用Pro/E建立三维实体模型,Gambit软件对模型进行网格划分,使用Fluent软件进行数值模拟,在TECPLOT中完成分析。根据实际条件需要设置边界条件,对排杂装置在不同转速下的速度场和压力场进行模拟,并对比模拟数据与实验数据,为甘蔗联合收割机排杂装置结构的设计和优化,以及提高排杂装置效率提供参考。     

农用运输车用液力缓速器的设计与仿真分析

为解决农用运输车长时间制动造成的热衰退问题,参考THB40液力缓速器,基于相似理论设计了一款液力缓速器。计算确定了其设计制动力矩值和定转子叶轮参数,运用Pro/E构建了其三维结构,并在CFX14.5平台上以SST-kω湍流模型进行仿真计算。结果表明:制动力矩符合设计要求,流场的特征与THB40流场特征高度一致,为设计适合农用车用液力缓速器提供了借鉴。     

冯契对毛泽东哲学思想的理性解读

冯契对毛泽东哲学思想的理性解读主要体现在 :充分肯定了毛泽东对中国近代哲学革命的历史总结 ,扬弃了毛泽东的辩证法思想 ,基本上肯定了毛泽东对社会理想的探索 ,坚持了毛泽东的义利观、完善了毛泽东的群己观     

长输管道水力瞬变仿真

根据各种管道边界的瞬变方程和管道水击的连锁Ａｌｌｉｅｖｉ方法，针对具有实际元器件和边界的长输管道的不稳定流动，设计了基于特征线差分解法的分析流程和仿真计算程序。利用长输管道水击数值计算所得线路上各节点的瞬态值进行Ｂ样条曲线拟合，实现了水力瞬变过程中线路水力坡降线及某些水力参数变化情况的图形输出 。     

CerealBeta-Amylases

Cerealbeta-amylases are perhaps best known in terms of the vital role they play in releasing easily fermentable sugars from cereal grain starch to fuel the production of alcohol by yeast in brewing. The extent to which they have been investigated is indeed largely due to their significance in this economically important industry. However, cerealbeta-amylases are also, or could be, employed in many other aspects of the food industry and the analysis of starch, and they constitute valuable markers in cereal assessment and breeding studies. Quite apart from their practical significance, they are rewarding objects of biochemical and physiological research. They are interesting models for the study of enzyme polymorphism, post-translational modification and the differential expression of isoenzymes. In spite of their often high activitiesin situand all that is known about their generation, they are an enigma in that their physiological function, or even necessity, remains unclear. It has been recently recognised that there are two different categories of cerealbeta-amylases which exhibit different tissue and taxonomic specificities and physiological developmental patterns. The «classical»beta-amylases present at high activities in cereal seeds appear to be limited to the endosperm of the species of the Triticeae tribe of the Festucoideae subfamily of the Gramineae (wheat, barley and rye), whereas all cereals exhibit a different, tissue-«ubiquitous» form of the enzyme which is present at much lower activity levels. The physiological phenomenology and the usage of cerealbeta-amylases are discussed in relation to these two categories of enzyme.     

光照对棉花胚珠纤维离体发育的影响

分析了光照和黑暗条件下，对培养棉花胚珠纤维离体发育的影响。表明在其它条件相同时，纤维离体发育在基因型之间有很大的差异，光照对纤维的发育起了明显的抑制作用。无论受精胚珠还是未受精胚珠，在光照条件下其胚珠成活率、纤维诱导率、纤维生长量、胚珠鲜重均低于在黑暗条件。尤其是未受精胚珠，在光照条件下珂３１２ 与ＴＭ－ １虽能诱导产生纤维，但纤维诱导率很低，仅有８．１９％ 和４．９６％ ，纤维生长量为０．１６３７和０．１１３２，而浙５０６、罗甸铁子和徐州１４２无絮突变体均不能产生纤维。本试验表明：只有在黑暗条件下才适合纤维离体发育。     

日粮钙水平对泌乳水牛生产性能的影响

为了探讨日粮钙水平对泌乳水牛生产性能的影响,本试验选用12头胎次、泌乳时间、泌乳量相近的水牛,随机分成4组,每组3头水牛。采用4×4拉丁方试验方法,4组水牛基础日粮中钙含量分别占基础日粮干物质的0.47%、0.62%、0.78%、0.93%,其他营养成分均相同,其中磷占采食干物质比例为0.50%;共4期试验,每一试验期21 d,其中预饲期7 d,正饲期14 d。试验结果表明:1、不同钙水平日粮对泌乳水牛的产奶性能影响不显著(P>0.05),但0.78%钙水平日粮组水牛的产奶量分别比其他3组提高5.4%、5.5%、3.9%,不同钙水平对水牛奶营养成分影响不显著(P>0.05)。2、不同钙水平日粮对水牛血浆中钙含量影响差异显著(P<0.05);随着日粮钙水平的上升,水牛血液甲状旁腺素和1,25二羟基维生素D呈显著下降趋势(P<0.05)。综合各指标,日粮钙占采食干物质的比例为0.78%能进一步提高泌乳水牛产奶量。     

Splenectomy enhances sensitivity of islets to STZ in mice

AIM: To explore the protective role of spleen in damage of islet beta cells induced by streptozotocin (STZ).METHODS: Splenectomy in mice was performed by surgery. Sixty splenectomy mice were divided into 3 groups as the mice were intraperitoneally injected with STZ at doses of 80 mg/kg or 160 mg/kg, and saline, respectively. Sixty normal mice (without splenectomy) were also grouped and treated as above for controls. One week later, fasting blood glucose and serum insulin were monitored,and beta cell mass and the apoptosis of islet cells were analyzed by the methods of immunohistochemistry and ELISA, respectively. The content of reactive oxygen species was determined by the method of luminol-enhanced chemiluminescence.RESULTS: Compared to the normal control mice, the concentrations of fasting blood glucose significantly increased, and serum insulin reduced in splenectomy mice treated with STZ at the dose of 80 mg/kg. Moreover, beta cell mass decreased, enrichment factor of nucleosomes of islet apoptotic cells and reactive oxygen species produced in pancreas tissues significantly increased in splenectomy mice treated with STZ at the dose of 80 mg/kg.CONCLUSION: Splenectomy increases the sensitivity of islets to STZ in mice by increasing the production of reactive oxygen species in pancreas.     

Development of stump suckers by betula pubescens at different light intensities

Young trees (4–5 year old) of Betula pubescens Ehrh. growing in a stand in the middle of Sweden (lat. 60°15'N) were cut in early June to stump heights of 0 and 10 cm. The birch stumps were exposed to different relative light intensities (100, 50, 25 and 10%) for 100 days until mid September. Five stumps per treatment were used in a randomized complete block with seven blocks on mesic dwarf‐shrub type with low herbs and three blocks on moist dwarf‐shrub type. The number of sprouting stumps was correlated with relative light intensity and forest type. 2.5 % of the stumps of mesic and 14 % of moist forest type did not produce suckers. On mesic forest type, 7% of the stumps exposed to 10% light did not sprout compared with 1.4, 3.0 and 0% at 25, 50 and 100% light, respectively. At stump height 0 cm fewer sprouting stumps were produced than at 10 cm. The mean height of suckers was significantly lower at 10% light intensity than at other levels. The number of suckers per sprouting stump was not related to light intensity but to forest type. More suckers were produced on mesic than on moist forest type. The dry weight of suckers was significantly lower at 10 and 25% relative light intensity than at 50 and 100%. On moist forest type, the dry weight of suckers was lower than on mesic forest type.