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361.
白忠玉 《太原师范学院学报(自然科学版)》2013,(3):4-7
运用黎曼流形和希尔伯特唯一性方法,研究一类常系数波动方程的精确控制问题,计算出了具体的时间T和系数k的范围. 相似文献
362.
WU Qiong BAI LinQuan LIU WeiCheng LI YingYing LU CaiGe LI YaQian LIN ZhenYa WANG Meng XUE ChunSheng CHEN Jie 《科学通报(英文版)》2013,58(26):3266-3273
Streptomyces lydicus A01 resists many plant pathogens (including Fusarium spp.) by producing the antifungal agent natamycin, which binds to the ergosterol of fungal cell membranes and inhibits the growth of pathogens. Trichoderma harzianum CECT2413 is a widely-distributed soil fungus that antagonizes several plant fungal pathogens (including Fusarium spp.) by producing chi-tinase and degrading chitin, a major component of the fungal cell wall. This study attempted to enhance the biocontrol effect of S. lydicus A01 on Fusarium spp. by transforming the chitinase gene of Trichoderma. Chitinase and natamycin could act synergisti-cally on both the cell walls and cell membranes of pathogens. The 33-kD chitinase-encoding gene (chit33) was cloned and conju-gal-transformed from T. harzianum CECT2413 to S. lydicus A01, and then confirmed via polymerase chain reaction (PCR) assays. Subsequent analyses using the 3,5-dinitrosalicylic acid (DNS) method and ultraviolet spectrophotometry showed that compared with its wild type strain (WT), the S. lydicus A01 conjugal transformant (CT) with chit33 gene exhibited substantially higher chi-tinase activity and natamycin production. The resistance of S. lydicus A01-chit33 CT and WT to four Fusaria in crops and vegetables was tested via the cup-plate method. Compared with the WT, the conjugal transformant of S. lydicus A01 with chit33 gene from T. harzianum CECT2413 showed greatly increased biocontrol effect on fusarium disease. This study would be beneficial to the development of high-quality antifungal bio-agents for agricultural applications via the synergy between the previously non-existent and pre-existing functions achieved through heterogeneous gene transformation. 相似文献
363.
LU XiuPing GUI YiJie XIAO BingGuang LI YongPing TONG ZhiJun LIU Yun BAI XueFei WU WeiRen XIA Ling HUTTNER Eric KILIAN Adrzej FAN LongJiang 《科学通报(英文版)》2013,58(6):641-648
Tobacco(Nicotiana tabacum) is one of the most economically important nonfood crops,and flue-cured tobacco accounts for approximately 80% of world tobacco production.An extremely narrow genetic diversity in the tobacco pool has led to a low efficiency of PCR-based molecular markers(such as AFLP and SSR).Diversity Arrays Technology(DArT) is a high-throughput hybridisation-based marker system that has been developed in many plants including wheat,which,like tobacco,has a complex genome.In this study,we developed a tobacco DArT chip that included 7680 representative sequence tags based on typical tobacco accessions.The 1076 DArT markers of flue-cured tobacco were identified and most(82.1%) of their polymorphism information contents(PICs) were greater than 0.4.An integrated linkage map that included 851 markers(238 DArT and 613 SSR),which is the highest density map of flue-cured tobacco to date,was constructed.This chip-based DArT system provides an alternative in high-throughput marker genotyping for tobacco. 相似文献
364.
通过对光伏电池特性的分析以及对电导增量法和模糊控制技术两种最大功率点跟踪(MPPT)方法的研究,提出了组合两种算法的MPPT技术.仿真结果和实验数据均表明,组合算法能使光伏发电系统快速、准确地跟踪最大功率点,提升了系统总体性能,具有良好的动态和稳态特性. 相似文献
365.
1932年,安德森通过对宇宙射线的仔细研究,发现了第一个反物质粒子——正电子,并因此获得1936年诺贝尔物理学奖.2012年恰逢正电子发现80周年,现在回顾正电子发现的历程以及对正电子发现做出贡献的科学家是很有意义的.本文围绕正电子的发现这一历史过程简要介绍安德森的生平以及狄拉克关于正电子存在的预言,并介绍了中国物理学家赵忠尧所做的工作. 相似文献
366.
367.
Magnetoelectric (ME) voltage coefficient of plate layered magnetostricUve-piezoelectric composites was always considered independent of the in-plane size due to the oversimplification in ME theoretical models. Here we report that the ME voltage coefficient depends on the in-plane size owing to shape demagnetization effect on magnetostriction. Both theoretical analysis and experimental results indicate that ME voltage coefficient of layered ME composites changes with the variation in in-plane sizes (length and width). ME coefficient increases with a rise in in-plane sizes, and different aspect ratio also results in different ME coefficients. Proper design of in-plane shape will greatly promote the development of ME devices. 相似文献
368.
小鼠采用非暴露式气管内注人法注入不同浓度多壁碳纳米管(MWNT)颗粒物悬液,在第10 d处死小鼠,并进行肺泡灌洗,测定肺泡灌洗液(BALF)中各项指标、肺脏器系数,并进行病理形态学观察.MWNT 10mg·kg-1bw-1组以上各指标均高于对照组和纳米1 mg·kg-1bw-1组,差异显著(P<0.01或P<0.05);病理形态学观察结果表明,MWNT 10 mg·kg-1bw-1组小鼠肺部损伤最重.在实验条件下,MWNT对小鼠肺造成急性损伤作用,对生物体健康构成潜在威胁,为研究MWNT对人体及环境的潜在性影响奠定实验基础. 相似文献
369.
目的 以德惠市为黑土区代表,研究其农业生态景观格局及其动态,为黑土区农业生态建设提供依据.方法 根据影像解译的土地利用图上各类斑块的分布特点,应用地理信息系统方法和景观生态学方法进行研究.结果 德惠市的农业景观主要以旱地和水田构成,形成以旱地为基质,水田为斑块镶嵌于其上的格局.水田较多沿松花江分布在东北部分,居民地基本上呈东北一西南走向且平行排列.其土地利用变化主要体现为各类用地向水田转化.结论 自然和社会因素共同作用形成了德惠市的农业生态景观格局.德惠市农业属于扩大耕地面积的"外延式"发展,甚至仍然存在开垦林、草地为耕地的现象,很大程度上影响了德惠市土地可持续利用.发展生态农业,在耕地资源总量减少的情况下,提高农村收入,促进黑土区农村社会经济的全面发展是今后农村生态建设的重点问题. 相似文献
370.
The inherent noise in positron emission tomography (PET) leads to the instability of quantitative indicators, which may affct the diagnostic accuracy for diffrentiating malignant and benign lesions in the management of lung cancer. In this paper, the reliability of retention index (RI) is systematically investigated by using computer simulation for the dual-time-point imaging protocol. The area under the receiver operating characteristic (ROC) curve is used to evaluate the optimal protocol. Results demonstrate that the reliability of RI is a?ected by several factors including noise level, lesion type, and imaging schedule. The RIs with small absolute values su?er from worse reliability than those larger ones. The results of ROC curves show that over delayed second scan cannot help to improve the diagnostic performance further, while an early ?rst scan is expected. The method of optimization based on ROC analysis can be easily extended to comprise as many lesions as possible. 相似文献