设施桃对硒的吸收运转及积累特性的初步研究

本试验以设施栽培的4年生春雪毛桃（砧木为青州冬雪蜜桃）为试材,研究硒元素在桃中的吸收运转及积累特性,为设施桃富硒果品生产技术的提出提供理论依据。结果表明：从花后40d至80d,设施桃不同部位硒元素含量的变化趋势不同,其中叶片呈‘升-降-升（土施氨基酸硒）’与‘持续上升（叶面喷施氨基酸硒）’、果肉呈‘升-降’、果皮呈‘升-降（土施氨基酸硒）’和‘降-升-降（叶面喷施氨基酸硒）’、果核呈下降的变化趋势;设施桃从果实硬核至转色阶段是设施桃可食部分-果肉对硒元素吸收的活跃期;硒肥的施用方式不仅影响硒元素在果皮、果肉和果核及果肉和叶片等各部位的累积顺序,而且显著影响硒元素的利用效率,叶面喷硒的硒元素利用率远高于土壤根际施硒的硒元素利用率。综上,设施桃从坐果到果实成熟,采用叶面喷硒,尤其是加强果实硬核至果实转色阶段的施用,是设施桃富硒果品生产的关键措施。此外,抑制设施桃果实成熟前后新梢的补偿性生长是减轻或避免果实中硒元素外流的重要措施。     

Effects of different sources of carbohydrates on intake,digestibility, chewing,and performance of Holstein dairy cows

To investigate the effects of different sources of carbohydrates on intake, digestibility, chewing, and performance, nine lactating Holstein dairy cows (day in milk= 100±21 d; body weight=645.7 ± 26.5 kg) were allotted to a 3 × 3 Latin square design at three 23-d periods. The three treatments included 34.91% (B), 18.87% (BC), and 18.86% (BB) barley that in treatment B was partially replaced with only corn or corn plus beet pulp in treatments BC and BB, respectively. The concentration of starch and neutral detergent soluble carbohydrate varied (22.2, 20.2, and 14.5; 13.6, 15.9, and 20.1% of DM in treatments B, BC, and BB, respectively). Cows in treatment BB showed a higher DMI and improved digestibility of DM, NDF, and EE compared with treatments B or BC. Ruminal pH was higher in cows fed on BB (6.83) compared with those that received B or BC treatments (6.62 and 6.73, respectively). A lower proportion of propionate accompanied the higher pH in the BB group; however, a greater proportion of acetate and acetate: propionate ratio was observed compared with cows fed either on the B or BC diet. Moreover, cows fed on the BB diet showed the lowest ruminal passage rate and longest ruminal and total retention time. Eating time did not differ among treatments, rumination time was greater among cows fed on the BB diet compared with the others, whereas total chewing activity was greater than those fed on BC, but similar to those fed on B. The treatments showed no effect on milk yield. Partially replacing barley with corn or beet pulp resulted in an increase in milk fat and a lower protein concentration. Changing dietary NFC with that of a different degradability thus altered intake, chewing activity, ruminal environment, retention time or passage rate, and lactation performance. The results of this study showed that beet pulp with a higher NDF and a detergent-soluble carbohydrate or pectin established a more consistent ruminal mat than barley and corn, thus resulting in higher mean retention time and chewing activity, whereas no changes in 3.5% FCM and milk fat were observed.     

对虾白斑综合征病毒研究概况

对虾白斑综合征病毒(WSSV)引起世界范围内养殖对虾的急性、致死性传染病,造成对虾养殖业的巨大损失,在我国这种情况尤为严重。WSSV是同一类紧密相关的无包埋体类杆状病毒,与杆状病毒并无同源性。2001年,中国和荷兰科学家分别报道了WSSV的全基因组DNA序列,启动了WSSV后基因组研究。已有多种检测方法用于WSSV的检测和致病机理的研究。WSSV感染宿主谱广,以多种传播途径感染宿主,目前还没有用于病毒增殖的细胞系,但已有成熟的动物模型,从而方便了对WSSV的研究。本文就该病毒的命名、病毒特性、检测方法、病毒感染增殖、感染宿主、传播途径及感染动物模型等方面的研究现状和进展作一综述。     

五种西方蜜蜂品种形态指标差异性比较

采集吉林的东北黑蜂×意蜂、云南景洪的浙大蜜浆蜜胶、云南景洪的白山6号、云南个旧蛮耗的本地王和云南蒙自草坝的浙大蜜浆高产5种西方蜜蜂子代工蜂共8群样本,每群测定分析15只,测定每只工蜂38个形态指标。结果表明不同生产性能的西方蜜蜂在形态特征上都表现出差异性(P≤0.01,或0.01P≤0.05,或P0.05),通过实验,为蜜蜂生产上培育杂种优势西方蜜蜂品种提供有力的理论依据。     

空肠弯曲杆菌生物学特性及分型技术研究新进展

Campylobacter jejuni (C.jejuni) is a major pathogen of human campylobacteriosis, as well as one of the major food-borne pathogen. It can not only cause human diarrhea, but also cause many systemic diseases such as endocarditis, arthritis, septisis. The most serious complication it can cause is the Guillain Barre syndrome. In developed countries, C.jejuni even has a trend to excess Salmonella and be reported as next Salmonella, which has caused a worldwide concern. Analysis of biological characteristics for C.jejuni can help us to distinguish it with other pathogens. Typing methods play important roles in the identification, monitoring and prevention of C.jejuni. It can also help us to understand its virulence and resistance mechanisms to C.jejuni. This paper reviews advances of C.jejuni in biological characteristics, serotyping and genotyping methods so as to help us further understand its new progress in these areas.     

旋壳转速对腔内液体流动特性的效应

为研究旋壳转速对腔内液体流动特性的影响,以试验旋喷泵为研究对象,在高度验证叶轮与旋壳同步旋转试验与模拟结果准确性的基础上,对叶轮转速相同、旋壳转速不同的5个模型采用RNG k-ε湍流模型进行数值计算,分析腔内液体流动特性的变化情况,研究泵的性能.结果表明:旋壳转速增大,液体圆周速度和旋转系数均增大,圆周速度曲线沿径向逐渐形成同心圆,腔内液体做非刚性旋转.腔内液体径向压力梯度增大,压力低于624 kPa时,旋壳转速越高,压力越小;压力高于624 kPa时,旋壳转速越高,压力越大.集流管迎流区涡分布在进口附近,尾迹区涡集中在扩散段结尾处,整体呈增大趋势.旋壳转速增大,泵的扬程升高,但效率降低,通过改变集流管进口直径发现集流管并非效率降低的主要原因,而是由圆盘摩擦损失的增大导致的,圆盘摩擦损失随旋壳转速增加呈3次幂函数式增大,文中最优进口直径为13 mm.     

运用强夯法加固油罐深层回填地基

加固回填地基的方法主要有分层回填碾压、桩基和强夯加固3种方法。而强夯加固法是一种适用范围较广的地基处理方法,具有效果显著、施工方便、节材省时等优点。其主要技术指标是影响深度、单击夯击能、夯击次数、夯击遍数及夯点间距。以秦皇岛首站5号10×10~4m~3油罐深层回填地基处理实践为例,着重介绍了运用强夯加固法回填地基的处理方法,根据初步确定的强夯参数,提出强夯试验方案,在具有代表性的场地中选取一个或几个试验区,进行现场试夯,再根据不同土质条件,待试夯结束一至数周后,对试夯区进行测试,并与夯前测试数据进行对比,用以检验强夯效果、确定工程采用的各项强夯参数。强调了在强夯施工中应注意的事项。     

Calculation Method of Hydraulic Characteristics for Direct-Return Chilled Water System

In order to optimize design and operation, it is necessary to calculate accurately hydraulic characteristics large central air-conditioning systems. Simplified Model can not be applied to hydraulic calculation of large pipe network topological structure for its large calculation error. Taking into account the regulating characteristics of terminal branch temperature regulating valve, a direct-return chilled water system is studied, an accurate mathematical model of pipe network hydraulic characteristics has been established and a computer logic algorithm with virtual flow has been given. A direct-return pipe network with ten AHU branches is used as simulation calculation object, the pipe network supply-return water pressure difference is calculated, and also the temperature regulating valve opening and actual flow of each branch are calculated in the condition of different supply-return water pressure difference. The calculated results accord with the natural characteristics of high pressure difference unbalanced for direct-return pipe network. The calculation method can ensure calculation convergence.     

Factors affecting the adoption of agroforestry practices by farmers in Cameroon

This paper presents empirical evidence on the impact of socio-economic factors on the adoption of agroforestry practices in Cameroon. The analysis uses primary farm-level data collected from June to December 1996. Three major provinces of the country were covered, namely Centre, Southwest and Northwest Several agroforestry technologies have been promoted among farmers in the zone, including alley farming, improved fallow, live fencing, cut-and-carry fodder and apiculture. The status of adoption of each agroforestry practice is described and factors that affect adoption identified. These are gender of farmer, household family size, level of education, farmer’s experience, membership within farmers’ associations, contact with research and extension, security of land tenure, agroecological zone, distance of the village from nearest town, village accessibility and income from livestock. Research findings indicate that since factors affecting farmers’ adoption of agroforestry practices differ across techniques, generalisation is to be avoided.     

不同泡桐品种(种源)埋根苗生长与光合特性分析

为进一步研究泡桐埋根苗生长发育动态与光合特性之间的关系,以在郑州地区生长良好的4个泡桐品种(种源)埋根苗为研究材料,对1年生埋根苗生长期的苗高、地径、净光合速率、气孔导度、胞间CO2浓度、蒸腾速率等指标变化动态进行分析。结果表明:不同泡桐品种(种源)埋根苗的苗高生长和地径生长的季节变化趋势基本一致,苗高生长的快速生长期在7月中旬到8月下旬,9月为生长缓慢期,10月初到10月中旬苗高生长基本停止;地径生长的快速生长期从7月中旬到9月初,9月中下旬到10月为缓慢生长期,但10月下旬地径仍然还在缓慢生长,即泡桐地径生长比苗高生长延长10~15 d。不同泡桐品种(种源)埋根苗净光合速率、胞间CO2浓度、气孔导度、蒸腾速率4个光合指标在不同月份的日变化规律比较一致,胞间CO2浓度的日变化均呈现出先下降后上升的单谷曲线特征;净光合速率、蒸腾速率、气孔导度均在6、8、10月份出现双峰现象,且峰值出现时间较为一致,说明几个指标呈正相关;毛白33、9502的净光合速率相对较高,郑州白花的值相对较小,与生长量的表现一致;总体来看,5、10月份各泡桐品种(种源)无性系埋根苗的净光合速率偏低,6、7、8、9月份则相对较高,显示了泡桐在不同月份光合能力大小的差异。