小麦持久抗条锈病品种的定量判别研究

对甘肃省陇南地区多年种植没有丧失抗病性和已丧失抗病性的9个品种进行了田间成株期条锈病发生情况及特点的比较研究,测定了潜育期、普遍率、严重度、病情指数和侵染机率等抗性组分。结果表明,持久抗性品种与感病品种的抗性组分大不相同。运用DPS统计软件依上述抗性组分对试验材料进行了聚类分析,初步建立了判断小麦持久抗条锈性品种的判别函数,其回判结果符合率100%,表明利用抗性组分在成株期进行持久抗性品种的鉴定是可行的。     

我国玉米单产与全要素生产率贡献分解测算及动态特征考察

基于索洛余值法和随机前沿法测算2003～2019年间玉米的全要素生产率,并将单产增长率和全要素生产率进行贡献分解,分析长期以来我国玉米单产增长和全要素生产率变化的原因。结果表明,2003～2019年间,中国玉米单产累计增长28%,其中劳动投入量、机械费用、种子用量、化肥施用量及全要素生产率增长的贡献率分别为-0.8%、22.5%、-3.8%、6.1%和75.9%。2003～2019年间,中国玉米生产全要素生产率波动性增长,余值法和随机前沿生产函数法计算累计涨幅达13.7%和18.7%,技术进步和技术效率提升在玉米全要素生产率增长中起到决定性的贡献作用,贡献率分别为68.8%和32.3%。在全要素生产率的强有力拉动作用下,我国玉米单产增长已从投入型转向效率型增长,要素投入趋于饱和,但全要素生产率提升仍有空间,分别表现在种子创新力提高、机械转型升级以及通过服务规模化提升规模效率等方面。     

重庆市植烟区不同肥力植烟土壤氮素矿化特性研究

通过室内培养试验研究了重庆市植烟区不同肥力植烟土壤氮素矿化规律,求得土壤氮素矿化参数,并探讨了氮素矿化潜势（N0）、有机质、全氮、pH、碱解氮之间的关系。结果表明,在35℃条件下培养,一级动力学方程能够很好的拟合氮素的矿化过程,相关系数均达到显著水平（r高肥力土=0.976、r中肥力土=0.986、r低肥力土=0.996）,不同肥力土壤氮素矿化量存在显著差异。矿化潜势(N0)为：高肥力土（25.0mg?kg-1±0.60）﹥中肥力土（21.5mg?kg-1±0.61）﹥低肥力土（19.7mg?kg-1±1.14）;矿化速率（k）为：低肥力土（0.1596mg?kg-1?d-1±0.0104）﹥中肥力土（0.1492mg?kg-1?d-1±0.0155）﹥高肥力土（0.1029mg?kg-1?d-1±0.0071）。矿化潜势(N0)与全氮、有机质呈正相关,相关系数分别为0.9799和0.9788,与pH之间呈负相关（R=-0.9784）。表明不同肥力植烟土壤的供氮能力存在差异,在肥料管理上要因土、因时施肥。     

凝结芽孢杆菌对感染产气荚膜梭菌肉鸡生长性能、肠道病变及免疫器官指数的影响

本试验旨在研究日粮中添加凝结芽孢杆菌对感染产气荚膜梭菌肉鸡生长性能、肠道病变及免疫器官指数的影响。选用312只1日龄科宝500肉鸡公雏,随机分成4个处理,每个处理6个重复,每个重复13只鸡。采用2×2双因子完全随机设计,产气荚膜梭菌分为无感染产气荚膜梭菌组和感染产气荚膜梭菌组,日粮中凝结芽孢杆菌水平分别为0和400mg/kg。试验期35d。结果表明,感染产气荚膜梭菌后15~35日龄肉鸡平均日增重显著降低(P0.05),28日龄肠道病变严重(P0.01),35日龄法氏囊指数极显著降低(P0.01);日粮中添加凝结芽孢杆菌可显著提高15~35日龄肉鸡平均日增重(P0.05),显著降低料重比(P0.05),能缓解感染导致的肠道损伤(P0.05),28日龄肉鸡胸腺指数极显著提高(P0.01),35日龄法氏囊指数极显著提高(P0.01)。肠道病变结果分析表明,日粮中添加凝结芽孢杆菌与感染产气荚膜梭菌有显著交互作用(P0.05)。综上所述,日粮中添加凝结芽孢杆菌能够提高感染产气荚膜梭菌肉鸡生长性能及免疫器官指数,增强动物免疫能力,并能缓解由于产气荚膜梭菌感染而导致的不利影响。     

全沟硬蜱围食膜初步观察研究

本工作用光镜和电镜技术对全沟硬蜱的围食膜进行了初步观察研究。结果表明，饥饿幼虫、若虫、成虫以及吸血期雄性成虫不具围食膜。吸血期幼虫、若虫及雌性成虫最晚分别于吸血开始后20、20及18小时出现了单层结构的围食膜；缓慢吸血期围食膜的厚度持续增加，而在快速吸血期其厚度却会显著减小。饱血后发育期围食膜不断增厚，愈来愈拱曲，与肠壁的距离不断扩大，并形成多层结构；至少分别于饱血后12、25及11天，仍能在幼虫、若虫及雌性成虫肠腔观察到完好状态的围食膜。全沟硬蜱是我国北方地区多种血液传播病原体的重要媒介，其围食膜的发现及围食膜形态变化的初步描述，对进一步认识这些病原体在全沟硬蜱体内迁移扩散规律、发育动态以及向宿主的传播途径，可提供有益的启示。     

Carbon nanotubes with temperature-invariant viscoelasticity from -196 degrees to 1000 degrees C

Viscoelasticity describes the ability of a material to possess both elasticity and viscosity. Viscoelastic materials, such as rubbers, possess a limited operational temperature range (for example, for silicone rubber it is -55° to 300°C), above which the material breaks down and below which the material undergoes a glass transition and hardens. We created a viscoelastic material composed from a random network of long interconnected carbon nanotubes that exhibited an operational temperature range from -196° to 1000°C. The storage and loss moduli, frequency stability, reversible deformation level, and fatigue resistance were invariant from -140° to 600°C. We interpret that the thermal stability stems from energy dissipation through the zipping and unzipping of carbon nanotubes at contacts.     

双表达H9N2禽流感病毒HA基因的假型重组杆状病毒系统的构建

以含有H9N2禽流感病毒HA基因的重组质粒pMD18-H9HA为模板,扩增HA基因,将其亚克隆入杆状病毒表面展示质粒pBACsurf-1中,再次将含有H9HA及gp64的基因片段克隆到质粒pcDNA3.1(+),获得重组质粒pcDNA-H9-HA.然后将含有CMV启动子、H9HA及gp64的基因片段克隆到杆状病毒转移质...     

Rice <Emphasis Type="Italic">terpene synthase 18</Emphasis> (<Emphasis Type="Italic">OsTPS18</Emphasis>) encodes a sesquiterpene synthase that produces an antibacterial (<Emphasis Type="Italic">E</Emphasis>)-nerolidol against a bacterial pathogen of rice

Plant volatile compounds, including terpenes, are known to be involved in the rice defense system. In the present analysis of a terpene synthase, OsTPS18, in rice, we found that OsTPS18 was localized in the cytoplasm and synthesized the sesquiterpenes (E)-nerolidol and (E)-β-farnesene. The amounts of (E)-nerolidol and (E)-β-farnesene increased after jasmonic acid (JA) treatment. (E)-Nerolidol had significant antibacterial activity against Xanthomonas oryzae pv. oryzae (Xoo). These results suggest that (E)-nerolidol plays an important role in JA-induced resistance against Xoo and that it functions as an antibacterial compound in rice.     

Partitioning the multi-scale effects of human activity on the occurrence of riparian forest birds

Conservationists, managers, and land planners are faced with the difficult task of balancing many issues regarding humans impacts on natural systems. Many of these potential impacts arise from local-scale and landscape-scale changes, but such changes often covary, which makes it difficult to isolate and compare independent effects arising from humans. We partition multi-scale impacts on riparian forest bird distribution in 105 patches along approximately 500 km of the Madison and Missouri Rivers, Montana, USA. To do so, we coupled environmental information from local (within-patch), patch, and landscape scales reflecting potential human impacts from grazing, invasive plant species, habitat loss and fragmentation, and human development with the distribution of 28 terrestrial breeding bird species in 2004 and 2005. Variation partitioning of the influence of different spatial scales suggested that local-scale vegetation gradients explained more unique variation in bird distribution than did information from patch and landscape scales. Partitioning potential human impacts revealed, however, that riparian habitat loss and fragmentation at the patch and landscape scales explained more unique variation than did local disturbances or landscape-scale development (i.e., building density in the surrounding landscape). When distribution was correlated with human disturbance, local-scale disturbance had more consistent impacts than other scales, with species showing consistent negative correlations with grazing but positive correlations with invasives. We conclude that while local vegetation structure best explains bird distribution, managers concerned with ongoing human influences in this system need to focus more on mitigating the effects of large-scale disturbances than on more local land use issues. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

卵黄离心及精液透析预处理对猪精子冷冻效果的影响

从卵黄离心处理和精液透析两方面对现有猪精子冷冻方法进行优化。分别采用两种离心方案除去卵黄中大颗粒物质,研究卵黄离心处理对猪精子冷冻效果的影响;在精液冷冻预处理的第一阶段降温平衡中,将包含精浆的猪精液在大体积稀释液中进行透析,研究透析方法对猪精子冷冻效果的影响。结果发现,对卵黄进行离心以及对包含精浆的精液采用透析处理均能明显改善猪精子冷冻效果(P0.05)。