Isolation and biological properties of virulent subpopulations from lentogenic Newcastle disease virus strains

From each of two lentogenic Newcastle disease virus (NDV) strains of the type LaSota and Hitchner B1 a virulent subpopulation could be obtained. The two subpopulations were—in comparison to the two parent viruses—more resistant to the lipid solvent chloroform and more stable against thermal degradation. Also, the glycoproteins haemagglutinin and F (fusion) were more stable against thermal inactivation. Electron microscopic observations revealed in terms of size and morphology all of the characteristics of NDV. Both subpopulations possessed, however, the same elution kinetics as their respective parent strains. The intracerebral and intravenous pathogenicity indices as well as the mean death times of the two subpopulations allow to classify these viruses as virulent Newcastle disease viruses.     

抗虫杨北抗一号在宁夏地区育苗技术初探

通过1年的育苗试验,总结出抗虫杨北抗一号在宁夏地区圃地选择、整地、种条处理、插穗剪截、扦插、圃地管理等育苗关键技术,为在该地区推广北抗一号提供依据。     

油菜菌核病轻发生条件下的空间分布格局与抽样技术

通过田间调查,应用聚集度指标法、Iwao法和Taylor幂函数法,研究油菜菌核病的田间空间分布格局和抽样技术.结果表明,油菜菌核病空间分布型总体上呈聚集分布,但聚集程度不高,少量田块呈随机、均匀分布.轻发生时油菜菌核病的空问分布型倾向随机和均匀分布.抽样数量随着发病程度的加重而递减,最适理论抽样模型为n2=103.33/m-0.86,在茎株发病率为轻发生的10％时,每田的理论抽样样方数为103,即1030株.     

De nosing method based on multiscale morphological filter optimized by particle swarm optimization algorithm

The traditional morphological filter is difficult to remove the noise of the vibration signal,because the signal has the characteristics of shocking and nonlinear. A new method based on multiscale morphological filter optimized by particle swarm optimization algorithm is proposed. The multiscale morphological filter is constructed according to the character of morphological algorithm. The particle swarm optimization algorithm is used to select the adaptive structure element,which plays an important role in morphological filter,achieving to get the optimal morphological filter. The signal is filtered through different scales of morphological filters and the noise removed signal is gotten through weight algorithm. The simulated signal and the bearing fault signal are analyzed,and the results show that the optimal morphological filter works better in removing noise and can effectively reduce the noise of the mechanical equipment.     

家禽脂肪酸代谢及其在禽蛋中的沉积和营养调控

在肝脏中载脂蛋白作用下,内源合成或外源获取的脂肪酸以甘油三酯的形式同胆固醇及其他脂类组装形成极低密度脂蛋白(VLDL)。VLDL经血液循环到达卵巢,穿过卵母细胞外层屏障后,经卵母细胞受体介导的内吞作用进入卵母细胞发生沉积。而机体的营养状况或饲粮中营养成分的改变可通过影响脂肪酸的从头合成或VLDL结构直接或间接影响禽蛋中脂肪酸的最终沉积。本文阐述了家禽体内脂肪酸的来源、转运与沉积过程,并探讨了脂肪酸代谢及其在禽蛋中沉积的营养调控。     

大花萱草‘金娃娃’的花器结构和繁育系统观察

通过观察,运用杂交指数、花粉/胚珠、花粉及柱头活力、坐果率等指标对大花萱草‘金娃娃’(Hemerocallis hybridus cv.‘Stella de oro’)的花部特征、开花动态及授粉特性等进行研究。在人工栽培条件下,金娃娃萱草5-9月开花,花苔分3～4次抽生,首次开花群体花期32 d,单苔花期9～16 d,单花花期1 d。雄蕊短于花柱,花药与柱头相差2.71 cm,在花朵开放的整个过程中雌、雄蕊的相对位置始终不变。开花前1 d的花粉活力最强,开花前1 d和开花当天的柱头具有较强的可授性。杂交指数为4,花粉/胚珠值为1 164,结合坐果率,可以判断其繁育系统属于兼性异交,部分自交亲和,需要传粉者。特殊的花部结构、缺少传粉者和花期短可能是金娃娃萱草结实率较低的原因。     

双酶分步水解制备棉籽多肽工艺条件优化

为高效制备棉籽多肽,采用Alcalase酶和Flavourzyme酶对棉籽蛋白进行双酶分步水解.在前期单因素试验的基础上,通过Plackett-Burrman设计对影响其多肽得率的相关因素进行评估并筛选出具有显著效应的3个因素,然后通过三因素三水平的 Box-Behnken 响应面分析法确定双酶分步水解棉籽蛋白的最优操作条件为:底物浓度(w/v)8.36%,先用Alcalase 酶在温度59.9℃、pH值8.0、酶用量25000 U/g的条件下水解150 min,再用Flavourzyme酶在温度50℃、pH值6.0、酶用量27430 U/g的条件下水解120 min,多肽得率可达到65.07%.     

Defining and Measuring Forest Health

If forest health is to be approached scientifically, it must be defined and measured. Forest health is a condition of forest ecosystems that sustains their complexity while providing for human needs. We developed this broad definition becaue a wisely acceptable definition is lacking, and forest health is a focal point in discussions of how to sustain forest ecosystems in the United States. Steps for measuring forest health are: (1) select a representative set of indicators for a particular ecosystem; (2) establish baseline data, such as a historical range of variability; (3) develop standards against which to compare current conditions; and (4) establish a monitoring program to assess current conditions and modify baseline data as new trends develop.     

Growth and mortality of the narrowbarred Spanish Mackerel, Scomberomorus commerson (Lacepède), in Omani waters

Length composition data from quarterly catches of Omani narrowband Spanish mackerel, Scomberomorus commerson (Lacepède), landed between 1987 and 1995 were used to estimate the growth, mortality and exploitation parameters of the stock. Non-linear least square fitting provided a complete set of von Bertalanffy growth estimates: L _∞ = 173.6 cm fork length; K  = 0.28; and t ₀ = −0.86 years. There were no seasonal differences among the growth estimates. The instantaneous natural mortalities determined by three independent methods based on life-history parameters were 0.35, 0.64 and 0.77. Seasonal total mortalities were calculated by the length converted catch curve method for evaluating seasonal exploitation ratios ( E ). The E -values exceeded 0.4, indicating overexploitation during almost all the seasons studied. This was supported by the large reduction in the total landings of S . commerson from 27 762 t in 1988 to 3265 t in 1993.