Both TGF-β1 and Smad4 regulate type I collagen expression in the muscle of grass carp,Ctenopharyngodon idella

Fish Physiology and Biochemistry - Type I collagen is proven to make an important contribution to fish muscle quality. Our previous study has shown the Smad4-dependent regulation of type I collagen...     

西宁市林木植物检疫对象及防治

本文根据西宁市林木植物检疫对象普查结果,对其发生情况进行了综合分析提出相应的防治措施.     

福建省油茶林主要传粉昆虫种类及访花行为

对福建省福州、泉州、龙岩、南平、宁德等地油茶林传粉昆虫及其访花行为进行了调查,结果表明:福建省油茶林中主要传粉昆虫有24种,分属于3目11科17属,其中膜翅目的昆虫种类最多,有11种;大分舌蜂是油茶最重要的传粉昆虫,其数量多,传粉效率高;传粉昆虫日活动时间在12∶00—14∶30出现高峰,昆虫个体数量平均占全天总数的70%左右;油茶传粉昆虫的访花行为因昆虫的访花目的不同而有较大差异,温度和光照是影响传粉昆虫数量、行为和频率的主要因素。     

苹果苗断根施肥机的设计与试验

苹果苗倒栽作业是苗圃园艺生产作业中将矮化中间砧半成品苗倒栽进行嫁接果树穗种的一项准备工作,工作强度大.为此,根据苹果苗苗圃园艺作业要求,设计了L型断根铲的断根施肥机.田间试验表明:作业参数为断根深度178mm,工作幅宽450mm,施肥量300kg/hm2,配套动力22kW以上轮式拖拉机能够实现对苹果苗的断根和施肥联合作业,可提高效率和减轻工作强度.     

叶片出口角对离心泵性能曲线形状的影响

采用FLUENT,在多重参考坐标系下,利用有限体积法对雷诺时均Navier-Stokes方程进行数值离散,选用标准k-ε湍流模型和SIMPLEC方法求解,对4台不同比转速离心泵在不同叶片出口角下的内部流场进行了叶轮和蜗壳的多工况耦合数值模拟,研究了叶片出口角对离心泵扬程曲线和效率曲线的影响并进行了实验验证.研究给出了性能曲线随叶片出口角变化的规律并指出叶片出口角的改变对高比转速泵的扬程和效率曲线形状影响最为明显.研究结果对离心泵的选型和性能改进具有一定的指导意义.     

河北省山区土壤养分与玉米产量的相关性研究

在时间和空间上对河北省山区的土壤养分及玉米的产量进行了定量分析和相关性研究.2007年3月在河北省37个山区县进行土壤和玉米采样,并在室内化验,运用统计分析、地统计分析、克立格插值法、时序分析法方法对数据进行统计分析,得出河北省山区土壤中全钾含量大大提高,其次有机质含量也有较大程度提高.目前,土壤中全钾含量地区间差异较大,冀西北土石山区和太行山土石山区土壤养分提高幅度较大,坝上高原草原区基础最好;玉米籽养分含量空间差异不大,冀西北玉米籽养分含量略优于其它区域;河北省山区玉米产量整体大大提高,其中太行山土石山区玉米产量提高最快;土壤中全磷和速效钾的含量是影响玉米的产量主要因素,应加强钾肥中有效钾肥的使用.     

大网目底拖网在稳定流场中的数值模拟

通过有限单元法构建大网目底拖网渔具的数学模型,以计算在定常流条件下底拖网渔具的受力情况、网口扩张和渔具的形态变化.为了提高计算效率,提出了适用于拖网的网目群化方法.群化后的拖网模型为单元数6513的model-1模型和单元数1787的model-2模型两种规格,分别进行数值计算,并与水槽物理模型试验结果进行比较.结果表...     

中国鱿鱼钓机装备研究现状及展望

鱿鱼钓机是远洋鱿钓渔业的重要生产工具。目前鱿鱼钓机装备发展面临的主要问题是机钓产量低。本文介绍了我国鱿鱼钓机装备的研究现状,对钓机运转速度、作业水深控制、抖动模式设置及结构设计等方面的研究趋势进行了探讨。最后,提出了我国鱿鱼钓机发展对策,研究指出需重点解决钓机结构优化设计、控制系统性能优化、运行参数优化等问题,为远洋鱿钓渔业的可持续发展提供参考依据。     

Cytoplasmic diversity of the cotton genus as revealed by chloroplast microsatellite markers

The diversity of chloroplast genomes has played an important role, as have those of nuclear and mitochondrial genomes, in the evolution of plants. The sequences of the chloroplast genome supply unsubstituted information for genome analysis. In order to understand the genetic differentiation and relationship of cotton species, we investigated the cytoplasmic diversity of chloroplast genomes in 41 Gossypium accessions with 75 chloroplast simple sequence repeat (cpSSR) markers. The markers were developed from reference sequences of the chloroplast genomes of G. hirsutum and G. barbadense and covered approximately 12.6 kb. Among the 75 markers, 50 were polymorphic, with polymorphism information content values ranging from 0.11 to 0.88. Analyses of the dataset demonstrated that single copy regions were much more informative than inverted repeat regions. The non-coding sequences were well differentiated among these species. For some common cpDNA haplotypes, the E-genome species that may be the oldest of the extant cotton species was deduced. The differentiation of A-genome species lagged behind that of AD-genome species. Neither G. herbaceum nor G. arboreum was the cytoplasmic donor of tetraploid species, strongly suggesting that AD genomes originated from an extinct ancestor of modern A-genome species. We speculate that the genetic differentiation of the chloroplast genome of each cotton species resulted from the dispersal of that species and its adaptations to local ecological conditions. These cpSSR markers provided valuable information to reveal the diversity and differentiation of cotton during evolution.     

番茄品种耐弱光性的综合评价

研究了苗期弱光条件对幼苗素质，开花，果实大小及产量的影响，采用模糊数学的隶属法对品种的耐弱光性进行评价，并探讨了番茄耐弱光性状的鉴定方法，结果表明，苗期弱光对幼苗素质影响最大，其次影响开花，果实大小和产量，春雷２号和春雷１号属于耐弱光惭弱的品种，白果强丰属不耐弱光品种。