大电流电流源实现方法     

卢玉宇 《福建农林大学学报(自然科学版)》2008,37(3):329-333

提出2种大电流可控电流源方法:对于输出中小电流电流源,对通用的串联式线性调整可控电流源进行改进,降低调整管的温升;对于输出大电流的电流源,采用PWM控制方法,使调整管工作处于开关状态,调整管的功耗很小,温升低.根据上述方法,分别制作1台样机并进行性能测试,实践证明这2种方法是可行的.  相似文献   

人工林UHF频段电波传播场强预测模型   总被引：1，自引：0，他引：1  

李文彬  张俊梅  撒潮  王德明  高凯 《北京林业大学学报》2007,29(4):15-18

人工林无线电波传播场强模型是合理设计人工林环境无线电遥测遥控等通信电路的理论依据.该文在分析无线电波传播机理的基础上确定了人工林UHF频段传播损耗的三大组成部分及相应的计算方法,提出了人工林中某接收点处电场强度的预测模型.经过对北京西山人工侧柏林中不同参数的场强测试数据进行分析,校验了所建模型具有很高的精度.   相似文献   

甘蓝杂种致死材料的鉴定与遗传分析     

薛玉前  张扬勇  杨丽梅  方智远  刘玉梅  李占省  吕红豪  庄木 《中国蔬菜》2015,1(1):24-27

杂种致死是一种生殖隔离类型,致死材料的鉴定及遗传分析不仅有助于了解杂种致死的遗传机制,还可以为致死基因的定位和克隆奠定基础。利用已知携带杂种致死基因的甘蓝自交系09-211、09-222、10-260和其他自交系配制的杂交组合为试材,鉴定携带致死基因的新材料,并对甘蓝杂种致死性状进行了遗传分析。结果表明:11-204和11-176是2个新的甘蓝致死材料;11-176与09-222及10-260具有遗传等效性,而11-204与09-211具有遗传等效性;甘蓝杂种致死性状是由2个显性基因互补控制的,其中1个致死基因来自09-211或11-204,另1个致死基因来自09-222或10-260或11-176,其遗传模式符合Dobzhansky-Muller(DM)模式。  相似文献   

Integration of transgenes into sexual polyploidization schemes for potato (Solanum tuberosum L.)     

Alexander A.T. Johnson  Richard E. Veilleux 《Euphytica》2003,133(1):125-138

Most potato transgenic research has focused on development of resistance to pathogens and modification of potato physiology. Many transgenes, particularly those conferring pathogen resistance, could substantially lower potato production costs in developing countries. However, transgenes have not been reported in sexually propagated 4x-2x potato hybrids commonly grown in developing countries. Two transgenes,the Bacillus thuringiensis cry3Aa endotoxin protein gene and the PVY°coat protein gene, were engineered intodiploid and tetraploid potato using Agrobacterium tumefaciens-mediated transformation. Cry3Aa was produced at high levels in several lines while the PVY° coat protein was not expressed. Diplandroid and tetraploid genotypes were crossed to produce transgenic 4x-2x hybrids. Genetic transformation had no discernable effect on fertility ofthe primary transformants, germination of4x-2x seed derived from the transformants and agronomic performance(tuber set, average tuber weight and total tuber yield) of the 4x-2xhybrids. The transgenic 4x-2xhybrids produced non-viable pollen and could only be crossed as female parents. Results suggest that transgenes, such ascry3Aa, could be expressed in 4x-2x hybrids to lower costs of production with no significant effect on plant phenotype. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

小菜蛾对杀螟丹抗性相关序列的代表性差异分析   总被引：1，自引：0，他引：1  

程罗根  陈之浩  张晓飞  李忠英 《华北农学报》2003,18(2):14-16

采用代表性差异分析方法，以小菜峨的敏感品系作为驱赶扩增子，抗杀螟丹近等基因系作为检测扩增子，通过3轮消减杂交得到大小为150—300bp的差异片段，经亚克隆测序并与GenBank等数据库同源比较，发现其中一个亚克隆序列与P450基因有部分同源性，其余亚克隆与已知基因序列的同源性较低，判断这些序列可能是新基因的片段。  相似文献   

大豆吡哆醇生物合成蛋白基因(PDX)的电子克隆和进化分析   总被引：3，自引：0，他引：3  

李蕊  孟宪萍  胡英考  蔡民华  李雅轩 《华北农学报》2007,22(1):64-68

电子克隆(In silicocloning)是随着基因组计划和EST计划实施而发展起来的利用生物信息学手段进行基因克隆的新方法。根据物种间同源基因相对保守的特点,以拟南芥(Arabidopsis thaliana)吡哆醇生物合成蛋白cDNA序列为信息探针,对大豆(Glycine max)EST数据库进行同源搜索和序列拼接,获得了1 280 bp长的大豆吡哆醇生物合成蛋白的基因序列(GenBank登陆号为DQ139265)。经过RT-PCR扩增、基因组PCR扩增、分子克隆和序列分析验证,结果表明与电子克隆序列完全一致。该基因具有完整的开放阅读框架(ORF,20~955 bp),编码311个氨基酸。通过与水稻、日本百脉根、烟草、截形苜蓿等物种的吡哆醇生物合成蛋白序列比对,发现该基因具有高度的保守性。表明根据物种间同源基因序列,对跨物种间EST数据库进行同源检索、筛选、拼接,是克隆基因的有效途径。  相似文献   

The global adaptation of bread wheat at high latitudes     

R. M. Trethowan  Alexei Morgunov  Zhonghu He  R. De Pauw  J. Crossa  M. Warburton  Arman Baytasov  Chunli Zhang  M. Mergoum  G. Alvarado 《Euphytica》2006,152(3):303-316

Spring sown bread wheat is grown at high latitudes in Europe, Asia and North America. However, it is not clear what the associations are among environments, particularly in Asia and North America, and whether or not cultivars developed in one region may adapt in another. A yield trial comprised of cultivars developed in northern Kazakhstan, western Siberia, the Canadian Prairies, northern USA, northeastern China and broadly adapted genotypes bred by CIMMYT in Mexico was planted in all the above mentioned environments in 2002–2004. In general, cultivars performed best within the regions they were developed. However, cultivars developed in northern Kazakhstan/western Siberia were the most broadly adapted at high latitudes; they were not significantly different for grain yield from the locally developed cultivars in both China and Canada. Stronger photoperiod response, greater plant height and larger seed weight appeared to be key adaptive features of these materials. At lower latitudes, the Kazakh/Siberian cultivars were significantly lower yielding than all other materials. When low latitude Mexican sites were removed from the analysis, the Chinese locations tended to associate, whereas most Canadian and Kazak/Siberian locations were negatively associated with those from China. SSR analysis of the cultivars from each region split the materials into two general groups, one based on North American cultivars and one comprised of Kazakh/Siberian and Chinese cultivars. Lines developed in Mexico were spread across these two groupings. Evidence suggests that considerable scope exists to improve bread wheat adaptation at high latitudes globally through intercrossing materials originating from Asia and North America.  相似文献   

不同水(陆)稻品种(系)干旱胁迫效应分析评价     

王士梅  沈国霞  陈秀晨  朱启升  王海娟  王申 《中国农学通报》2015,31(6):7-14

为了扩大水稻抗旱资源的应用,提高水稻抗旱育种效率,对来自17个不同国家105份水(陆)稻品种(系)进行干旱胁迫效应评价。采用了同异分析法,在干旱胁迫下,株高、单株有效穗、穗长、每穗实粒数、每穗总粒数、结实率、千粒重、单株谷重8项农艺及经济性状,进行了综合评价分析。结果表明:105份水(陆)稻品种(系),分析评语"差"的有60个品种,占57.1%;"一般"的评语共有22个品种,占21%;"较好"和"好"的评语各有10个品种,占9.5%;"优良"的只有4个品种,占3.8%,分别为IR77298-14-1-2-13、IR77298-5-6-18、CACHO PRETO、IR77298-5-6-11,均为籼稻品种。由此得出,籼稻品种抗旱性明显高于粳稻品种,抗旱同异评语的级别与每穗实粒数、结实率、单株谷重3个性状密切相关。  相似文献   

10个紫花苜蓿品种耐盐性的比较研究   总被引：15，自引：2，他引：15  

马春平  崔国文 《种子》2006,25(7):50-53

对10个紫花苜蓿品种种子分别用0%、0.3%、0.7%和1.0%的NaC l溶液进行处理,通过种子发芽率、相对发芽势、幼苗重和幼苗高对各品种种子萌发期耐盐性进行了研究。结果表明:用0.7%或1.0%NaC l溶液性鉴定较为合理;0.7%NaC l溶液处理苜蓿种子,其幼苗重和幼苗高可作为苜蓿品种耐盐的鉴定指标。0.7%、1.0%NaC l溶液处理下,通过测定第3天和第5天各品种种子的发芽势,可以鉴定耐盐性大小。对10个苜蓿品种耐盐性综合研究结果是:龙牧801和巨人201的耐盐性最强,其次是肇东、龙牧803和CW 200;新疆大叶和爱菲尼特的耐盐性最弱。  相似文献   

褐潮土长期定位不同施肥制度土壤生产功能演化研究   总被引：16，自引：1，他引：16  

李秀英  李燕婷  赵秉强  李小平  王丽霞  张振山 《作物学报》2006,32(5):683-689

通过14年长期定位试验研究了褐潮土不同施肥制度对土壤生产功能、产量可持续性指数及农学效率的影响。结果表明，N、P为褐潮土作物高产的主要限制因子，14年产量平均，NPK比CK、N、NK、PK分别增产459%、386%、280%、205%（小麦）和154%、108%、87%、78%（玉米）；NPK+M(NPK配施厩肥)比NPK平均增产12%，NPK+S(NPK加秸秆)与NPK产量相当。NPK及NPK配施有机肥（包括厩肥和秸秆）处理的小麦、玉米产量可持续性指数高于N、P不均衡施用处理。化肥肥效因作物种类、施肥组合而不同，N肥单施时小麦和玉米N的农学效率降低，而NPK配施时N的农学效率有上升趋势，平均分别为16 kg/kg N（小麦）和14 kg/kg N（玉米）；磷肥肥效具有短期的叠加效应，P的农学效率小麦大于玉米，种植10年后P的农学效率最高可达最初的4.5～7倍；K的农学效率在试验进行十年后NK处理平均为负值，同期NPK处理中小麦K的农学效率却急剧增加，K成为作物高产的限制因素；有机肥对小麦和玉米的农学效率分别为21 kg/t和25 kg/t，秸秆对小麦和玉米的农学效率分别为负值和37 kg/t。NPK均衡施肥能提高土壤有机质、全N、全P、速效N、速效P等肥力指标；NPK配施有机肥能加快土壤有机质和N、P、K养分的积累；NPK不均衡施肥导致土壤中此种营养元素的耗竭。  相似文献