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排序方式: 共有119条查询结果,搜索用时 15 毫秒
81.
张忠德 《西安邮电学院学报》2005,10(4):44-48
对公平与效率关系问题的探讨,研究者一般以两者是一对矛盾展开,这是片面的。实际上,公平与效率是完全可以统一的。本文在分析传统片面认识的基础上,从长远的、整体的、辩证的视角探讨了公平与效率的问题。 相似文献
82.
We examined the interaction between host trees and fungi associated with a tree-killing bark beetle, Dendroctonus frontalis. We evaluated (1) the response of four Pinus species to fungal invasion and (2) the effects of plant secondary metabolites on primary growth of and secondary colonization of three consistent fungal associates. Two of these fungi, Entomocorticium sp. A and Ophiostoma ranaculosum, are obligate mutualists with D. frontalis, and the third associate is a blue-staining fungus, O. minus, that is commonly introduced by beetles and phoretic mites. O. minus negatively affects beetle larvae and in high abundance can impact D. frontalispopulation dynamics. Size of lesions formed and quantity of secondary metabolites produced in response to fungal inoculations varied significantly among Pinus species. However, monoterpene composition within infected tissue did not significantly vary across treatments. While all eight tested metabolites negatively affected the growth rate of O. minus, only 4-allylanisole, p-cymene, and terpinene reduced the growth of the mycangial fungi. Surprisingly, growth rates of mycangial fungi increased in the presence of several secondary metabolite volatiles. O. minus out-competed both mycangial fungi, but the presence of secondary metabolites altered the outcome slightly. O. ranaculosum out-performed E. sp. A in the presence of dominant conifer monoterpenes, such as - and -pinene. Volatiles from the mycangial fungi, particularly E. sp. A, had a negative effect on O. minus growth. In general, phloem phytochemistry of particular Pinus species appeared to alter the relative growth and competitiveness of mutualistic and non-mutualistic fungi associated with D. frontalis. The outcome of interactions among these fungi likely has important consequences for the population dynamics of D. frontalis. 相似文献
83.
The preoptic area (POA) is critical for maternal behavior in rats but little is known about what neurotransmitters released here influence maternal responding. POA infusion of 10 μg (but not 2 μg) of the dopamine D1 receptor antagonist SCH-23390 greatly impaired retrieval and licking of pups but not other maternal or nonmaternal behaviors in lactating rats. In contrast, POA infusion of 10 μg (but not 2 μg) of the D2 receptor antagonist raclopride facilitated nursing but did not affect oral maternal behaviors. SCH-23390 in the medial hypothalamus tended to impair licking but not retrieval. Raclopride in the medial hypothalamus had no effects. Therefore, D1 and D2 receptor activity, particularly in the POA, is important for regulating different maternal behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
84.
85.
铈对黄绿木霉菌拮抗大豆菌核病菌能力的影响 总被引:1,自引:0,他引:1
利用室内菌落生长速度测定与对峙试验的方法研究了铈对拮抗菌黄绿木霉菌(T richoderm aaureov iride)拮抗大豆菌核病菌能力的影响,同时测定了添加铈后黄绿木霉菌发酵液抑菌能力的变化。实验结果表明:对黄绿木霉菌敏感的硝酸铈含量为240μg/mL,高于1200μg/mL的硝酸铈含量可完全抑制黄绿木霉菌的生长,低于390μg/mL的硝酸铈浓度可刺激黄绿木霉菌的生长;而大豆核盘菌对硝酸铈的敏感浓度高于黄绿木霉菌,为420μg/mL,在1200μg/mL的浓度下还未完全抑菌。硝酸铈的添加对黄绿木霉菌拮抗大豆菌核病菌(Sclerotin ia sclerotiorum)无影响,对峙培养抑菌率可达100%;不同硝酸铈浓度的发酵液抑制菌核菌的中浓度不同,低浓度下可促进抑菌作用的发挥。 相似文献
86.
87.
M.?N.?Peyrat-MaillardEmail author M.?E.?Cuvelier C.?Berset 《Journal of the American Oil Chemists' Society》2003,80(10):1007-1012
Interactions between phenolic antioxidants in binary systems were determined by adding two antioxidants simultaneously in
equimolar proportions to an aqueous dispersion of linoleic acid that was then subjected to 2,2′-azobis (2-amidinopropane)
dihydrochloride-induced oxidation and by evaluating the protective effect of the antioxidant mixture. The antioxidant power
of the mixture was then compared with the expected antioxidant activity calculated by the sum of efficiencies of each compound
separately, relative to their proportions in the mixture. If it was higher, a synergy was pointed out whereas a lower value
was representative of an antagonism. Thus, synergistic effects were observed between rosmarinic acid and quercetin, or rosmarinic
acid and caffeic acid, whereas antagonistic effects were obtained with the following mixtures: α-tocopherol/caffeic acid;
α-tocopherol/rosmarinic acid; (+)-catechin/caffeic acid; and caffeic acid/quercetin. These mixture effects are partly explained
by regeneration mechanisms between antioxidants, depending on the chemical structure of molecules and on the possible formation
of stable intermolecular complexes. 相似文献
88.
采用盆栽实验研究了土壤重金属Cd(20 mg/kg)污染下,外源镧(0、10、20 mg/L LaCl3)对‘燕白’和‘津优1号’2 个品种黄瓜(Cucumis satiuus L.)生长、丙二醛含量、抗氧化酶活性及果实中的总Cd含量和形态的影响。结果表明:La提高了2 个品种叶和根的抗氧化酶(过氧化氢酶、超氧化物歧化酶和过氧化物酶)的活性,增加了2 个品种的叶、茎、根、果实干质量及植株总干质量。La对‘津优1号’植株干物质量的影响大于‘燕白’。外源La使黄瓜叶和根抗氧化酶活性升高可能是植株对Cd的抗性增强、干质量增加的生理机制之一。La减少了2 个品种果实中总Cd含量和不同形态Cd含量,但随着La质量浓度的增加,2 个品种果实总Cd含量和残渣态Cd(FR)含量表现为先降后升的趋势。外源La使黄瓜叶、茎、根和果实中的Cd含量分别降低了6.0%~10.2%、8.9%~23.5%、4.0%~29.2%和32.0%~49.8%。喷La后,单株果实的Cd含量和Cd积累量、植株Cd全量均以‘津优1号’>‘燕白’。 相似文献
89.
90.
Dong Guo Lizi Xia Jacobus P. D. van Veldhoven Marc Hazeu Tamara Mocking Dr. Johannes Brussee Prof. Adriaan P. IJzerman Dr. Laura H. Heitman 《ChemMedChem》2014,9(4):752-761
Classical drug design and development rely mostly on affinity‐ or potency‐driven structure–activity relationships (SAR). Thus far, a given compound’s binding kinetics have been largely ignored, the importance of which is now being increasingly recognized. In the present study, we performed an extensive structure–kinetics relationship (SKR) study in addition to a traditional SAR analysis at the adenosine A2A receptor (A2AR). The ensemble of 24 A2AR compounds, all triazolotriazine derivatives resembling the prototypic antagonist ZM241385 (4‐(2‐((7‐amino‐2‐(furan‐2‐yl)‐[1,2,4]triazolo[1,5‐a][1,3,5]triazin‐5‐yl)amino)ethyl)phenol), displayed only minor differences in affinity, although they varied substantially in their dissociation rates from the receptor. We believe that such a combination of SKR and SAR analyses, as we have done with the A2AR, will have general importance for the superfamily of G protein‐coupled receptors, as it can serve as a new strategy to tailor the interaction between ligand and receptor. 相似文献