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61.
重齿小蠹对人工合成聚集信息素的昼夜反应节律发生在白天7:00~21:00,反应高峰在14:00-19:00,反应模式为"单峰式—白天型";利用人工合成的聚集信息素对重齿小蠹成虫发生期监测表明,成虫扬飞的开始时间为5月20日左右,扬飞高峰期为6月下旬和7月上旬,扬飞末期为8月26日,成虫扬飞的持续期为98 d。2007-2009年大量诱杀防治的试验前、后重齿小蠹致死木平均分别为3.39株/hm2和0.76株/hm2,致死木减少了77.58%,而对照区试验前、后致死木平均分别为15.89株/hm2和18.11株/hm2,致死木增加了13.97%,3 a大量诱杀试验的防治效果显著。 相似文献
62.
为寻求根据汽车尾气参数来诊断汽车故障的方法,利用径向基函数(RBF)神经网络,对丰田雷克萨斯(LEXUS)400电控发动机进行故障诊断研究。研究结果表明,径向基函数神经网络对发动机故障的诊断是迅速、准确的。 相似文献
63.
Oberstrass FC Auweter SD Erat M Hargous Y Henning A Wenter P Reymond L Amir-Ahmady B Pitsch S Black DL Allain FH 《Science (New York, N.Y.)》2005,309(5743):2054-2057
The polypyrimidine tract binding protein (PTB) is a 58-kilodalton RNA binding protein involved in multiple aspects of messenger RNA metabolism, including the repression of alternative exons. We have determined the solution structures of the four RNA binding domains (RBDs) of PTB, each bound to a CUCUCU oligonucleotide. Each RBD binds RNA with a different binding specificity. RBD3 and RBD4 interact, resulting in an antiparallel orientation of their bound RNAs. Thus, PTB will induce RNA looping when bound to two separated pyrimidine tracts within the same RNA. This leads to structural models for how PTB functions as an alternative-splicing repressor. 相似文献
64.
J Black 《Science (New York, N.Y.)》1989,245(4917):486-493
This lecture illustrates the early stages in the planning and discovery of propranolol, an adrenaline beta-adrenergic receptor antagonist, and cimetidine, a histamine H2-receptor antagonist--the first examples of clinically useful drugs from each of these classes. The significance of selective agonists, partial agonists, and syntopic antagonists and the importance of the bioassay and the use of molar models in the drug discovery process are discussed. For the future, an outline of potential developments in hormone-receptor concepts is offered leading to the conclusion that progress may depend on improvements in bioassays and related molar modeling. 相似文献
65.
Comparisons are made between the volatile inventories of the terrestrial planets, including Pioneer Venus data, and the predictions of three classes of theories for the origin of planetary atmospheres. Serious difficulties arise for the primary atmosphere and external source hypotheses. The grain accretion hypothesis can account for the trends in the volatile inventory from Venus to Earth to Mars, if volatiles were incorporated into planet-forming grains at nearly the same temperature for all of these planets, but at systematically lower pressures in the regions of planet formation farther from the center of the solar nebula. 相似文献
66.
Ultrahigh-density nanowire arrays grown in self-assembled diblock copolymer templates 总被引:1,自引:0,他引:1
Thurn-Albrecht T Schotter J Kästle GA Emley N Shibauchi T Krusin-Elbaum L Guarini K Black CT Tuominen MT Russell TP 《Science (New York, N.Y.)》2000,290(5499):2126-2129
We show a simple, robust, chemical route to the fabrication of ultrahigh-density arrays of nanopores with high aspect ratios using the equilibrium self-assembled morphology of asymmetric diblock copolymers. The dimensions and lateral density of the array are determined by segmental interactions and the copolymer molecular weight. Through direct current electrodeposition, we fabricated vertical arrays of nanowires with densities in excess of 1.9 x 10(11) wires per square centimeter. We found markedly enhanced coercivities with ferromagnetic cobalt nanowires that point toward a route to ultrahigh-density storage media. The copolymer approach described is practical, parallel, compatible with current lithographic processes, and amenable to multilayered device fabrication. 相似文献
67.
冬枣溃疡病病原初步鉴定 总被引:3,自引:0,他引:3
2003~2004年在山东省滨州市沾化县、无棣县等冬枣产区调查发现,冬枣生长前期在枣吊和叶片上发生了一种细菌性新病害。通过对典型病害样本进行病原菌分离、纯化获得20个菌株。从中选出4个菌株进行致病性测定,同时对其细菌形态、培养性状、染色反应、生理生化测定及血清学反应等性状进行了较为系统研究。结果表明,该地区冬枣溃疡病是由油菜黄单胞Xanthom onas campestrisPamm e(Dowson,1939)侵染引起的。 相似文献
68.
Murine leukemia: a virus-induced autoimmune disease? 总被引:1,自引:0,他引:1
Thymocytes from mice carrying Moloney murine leukemia virus since birth are cytotoxic for normal syngeneic fibroblasts; they are much less cytotoxic for the same cells infected with this virus. The cytotoxic thymocytes appear to increase in number with age of the carrier mice and are present both during preleukemic and leukemic periods. These results suggest that lymphomas in carrier mice result from a sequence of events initiated by intrathymic destruction of normal cells by virus-infected cells, and culminating in the unrestricted proliferation of autoaggressive clones in the thymic cortex. 相似文献
69.
The local effects of isolated magnetic adatoms on the electronic properties of the surface of a superconductor were studied with a low-temperature scanning tunneling microscope. Tunneling spectra obtained near magnetic adsorbates reveal the presence of excitations within the superconductor's energy gap that can be detected over a few atomic diameters around the impurity at the surface. These excitations are locally asymmetric with respect to tunneling of electrons and holes. A model calculation based on the Bogoliubov-de Gennes equations can be used to understand the details of the local tunneling spectra. 相似文献
70.