809 resultados para 887


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利用能量为161—175MeV的~(32)S束流,通过反应~(118)Sn(~(32)S,1p3n)~(146)Tb研究了双奇核~(146)Tb的高自旋态能级结构。实验进行了γ射线的激发函数、γ射线的各向异性度、X-γ和γ-γ-t符合测量。基于这些测量结果,建立了激发能达8390kev的~(146)Tb核的能级纲图,其中包括新发现的41条γ射线和新建立的27个能级,并指定了~(146)Tb新发现能级的自旋值。用一个h_(11/2)价质子和一个h_(11/2)~(-1)价中子空穴耦合、πh_(11/2)υh_(11/2)~(-1)与~(146)Gd核实激发态的耦合对~(146)Tb的能级结构进行了定性地讨论。

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本论文利用三剖面法和梯度法对HIRFL束流发射度进行了测量,并对这两种测量方法的系统误差,测量最佳条件和数据处理作了较详细地研究。通过测量,给出了HIRFL束流剖面。相图、横向密度分布和束流百分比-发射度特性曲线。对两种方法的测量结果作了比较,在误差范围内二者基本一致。测量结果如下:水平方向:束流百分比76%:EMH = 4.987 ± 0.287 mm mrad 90%:EMH = 9.887 ± 0.829 mm mrad垂直方向:束流百分比76%:EMV = 3.800 ± 0.254 mm mrad 90%:EMV = 7.554 ± 0.740 mm mrad

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采用田测法研究不同土壤水分条件下稻田需水规律 .试验采用淹灌、湿润灌和间歇灌 3种灌水处理 .结果表明 ,在整个生育期内由田测法测得的淹灌、湿润灌和间歇灌 3种处理的蒸散量分别为 889.1、6 35 .9和 775 .9mm ,蒸散速率分别为 6 .9、4 .9和 6 .0mm·d-1.与淹灌处理相比 ,湿润灌和间歇灌处理分别节水 2 8.5 %和 12 .7% .在充分供水的情况下 ,由Penman法计算的潜在蒸散值分别比田测法小 2 9.30 % .淹灌、湿润灌和间歇灌 3种处理的生物产量分别为 16 4 38.2 2、15 887.94和 15 75 7.88kg·hm-2 ,经济产量分别为 80 14 .0 1、782 8.91和 785 3.93kg·hm-2 .统计分析结果表明 ,3种处理间的产量差别不显著 .淹灌、湿润灌和间歇灌 3种处理的水分利用效率 (WUE)分别为 9.0 1、12 .31和 10 .12kg·hm-2 ·mm-1,淹灌的WUE分别比湿润灌和间歇灌减少 2 6 .8%和 11.0 % .对比分析结果表明 ,湿润灌的节水效果最好

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实地测定了黄土高原半干旱区固原不同生长年限苜蓿草地和连作8a苜蓿草地翻耕轮作不同年限粮食作物后深层土壤水分特征,分析了苜蓿草地土壤干燥化特征和粮草轮作对土壤水分的恢复效应。结果表明:(1)苜蓿连作1a、5a、8a和12a等4类苜蓿草地0~1000cm土层平均土壤湿度值为6.6%,平均土壤水分过耗量702.8mm,平均土壤干燥化速率147.1 mm/a,达到强烈干燥化程度,苜蓿连作5a土壤干层深度超过1000cm,苜蓿连作8a土壤干层深度超过1360cm,苜蓿草地合理利用年限为7a。(2)连作8a苜蓿草地翻耕并轮作4~7a和25a粮食作物等5类粮田0~1000cm土层土壤湿度介于6.74%~11.95%,土壤贮水量恢复值介于210.6~887.3mm,平均土壤水分恢复速率为80.8mm/a。轮作6a后粮田土壤干层轻度恢复程度以上深度达到1000cm。通过粮草轮作使苜蓿草地土壤湿度恢复到当地土壤稳定湿度需要13a以上。黄土高原半干旱区适宜的粮草轮作模式为:7a苜蓿→13a粮食作物。

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裂萼苔属Chiloscyphus,异萼苔属Heteroscyphus及齿萼苔属Lophocolea是地萼苔科(Geocaly-caceae)中亲缘关系非常接近的三个属,由于植物体特征变化极大,且缺乏足够的分类修订研究,长期以来它们的系统分类地位和属间关系存有很大争议,属及某些种的概念和界线极其模糊.亚洲为该类群的分布中心之一,目前对该类群的分类学研究也不够深入全面.故拟通过文献考证法、经典分类学方法并结合形态特征和数量分类,必要时利用分子系统学的方法对这一类群进行一次较为详尽的分类修订.

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目的研究气候变化与人间鼠疫流行之间的关系。方法选择内蒙古和福建省分别作为我国北方和南方鼠疫疫源地和历史鼠疫病区的典型省,采用对比分析和相关分析的方法,研究气候变化(降水变化以旱涝指数表示,气温变化以冷暖指数表示)与人间鼠疫发病强度之间的关系。结果在北方地区,人间鼠疫发病强度与前一年和当年的旱涝指数及冷暖指数呈显著负相关;而在南方地区,人间鼠疫的发病强度仅与当年秋季的冷暖指数有显著负相关性。结论气候变化与鼠疫流行之间的关系有明显的区域差异。降水丰富及气候温暖利于北方鼠疫的流行与传播;降水变化对南方鼠疫的流行没有明显的影响,秋冬季的气温与南方鼠疫的流行强度有一定的正相关关系。

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An aptamer-based label-free approach to hemin recognition and DNA assay using capillary electrophoresis with chemiluminescence detection is introduced here. Two guanine-rich DNA aptamers were used as the recognition element and target DNA, respectively. In the presence of potassium ions, the two aptamers folded into the G-quartet structures, binding hemin with high specificity and affinity. Based on the G-quartet-hemin interactions, the ligand molecule was specifically recognized with a K (d)approximate to 73 nM, and the target DNA could be detected at 0.1 mu M. In phosphate buffer of pH 11.0, hemin catalyzed the H2O2-mediated oxidation of luminol to generate strong chemiluminescence signal; thus the target molecule itself served as an indicator for the molecule-aptamer interaction, which made the labeling and/or modification of aptamers or target molecules unnecessary. This label-free method for molecular recognition and DNA detection is therefore simple, easy, and effective.

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Reactions of Zn(BF4)(2) and pyridine-2,4-dicarboxylic acid (2,4-pydcH(2)) in the presence of 1,2-bis( 4-pyridyl) ethylene or 1,3-bis(4-pyridyl) propane under hydro(solvo) thermal conditions yielded two polymorphic metal-organic coordination polymers formulated as Zn-2(OH)(2)(2,4-pydc) (1 and 2). Polymorph 1 features a two-dimensional (2-D) layer-like structure that is constructed by 2,4-pydc ligands bridging between the Zn-OH-Zn double-chain units. Each single Zn-OH-Zn chain is composed of mu(2)-OH groups connecting trigonal bipyramidal and tetrahedral Zn centers. Polymorph 2 is a 3-D coordination polymer containing 2-D Zn-OH-Zn sheets that consist of mu(2)- and mu(3)-OH groups and trigonal bipyramidal Zn centers. The sheets are pillared by 2,4-pydc ligands to form an acentric structural architecture. 1 and 2 are rare examples that the two polymorphs exhibit a centrosymmetric 2-D coordination network and an acentric 3-D coordination network, respectively. The different structures lead to differences in photoluminescent properties and thermal stabilities for 1 and 2.

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研究了La3+或Eu3+与微过氧化酶-8(MP-8)相互作用并比较了它们与MP-8相互作用的强弱.紫外-可见(UV-Vis)吸收光谱和电化学的结果表明,不论在不含NaCl或含NaCl的溶液中,一个La3+或Eu3+优先与MP-8分子中血红素上两个丙酸基中的羧基氧发生强的键合作用,而过量的La3+或Eu3+与肽链上的羰基氧发生弱的相互作用.实验结果还清楚地证明Eu3+与MP-8的相互作用要强于La3+与MP-8的相互作用.

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本文利用聚苯胺薄膜化学修饰电极对巯基化合物的促进作用进行了研究,结果表明,这种促进作用是对巯基乙醇在PAn薄膜表面的氧化还原过程的一种加强,而这种加强作用是通过-SH与PAn中的N以质子形式加成的。

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The complex [Nd(L)(CH3CN)(CF3SO3)3] has been synthesized. Where L = 1-methyl-1, 4, 7, 10-tetraazacycldodecane. The crystal structure of the complex has been determined by a four-circle X-ray diffractometer to a final deviation factor B value of 0.0370 and R(w) value of 0.0385 respectively. The crystal is triclinic system, space group P1BAR with a = 0.8738(2), b = 1.2870(3), c = 1.2900(3) nm, alpha = 85.63(2), beta = 87.25(2), gamma = 78.30(2)-degrees, V = 1.41571 (60) nm3, Z = 2, D(c) = 1.92 g/cm3. The neodymium ion is eight-coordinated to forming a distorted square antiprism.

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本文报道了三价钕与氮杂大环(简称L)配合物的合成和晶体结构.配合物组成为[Nd(L)-(CH_3CN)(CF_3SO_3)_3],晶体属于三斜晶系,空间群为PI,晶胞参数α=0.8738(2),b=1.2870(3),c=1.2900(3)nm;α=85.63(2),α=87.25(2),γ=78.30(2)°;最终偏差因子R=0.0370,R_w00385.配合物中钕为8配位,其配位多面体为扭曲的四方反棱柱体.