67 resultados para C ... f, B ... n.
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中国是受沙漠化影响最严重的国家之一。梭梭(Haloxylon ammodendronBunge) 1<0.5m( 0,5-lm)AB、D(>1m)也呈聚集分布，样地c中的成熟个体呈随机分布，从整个种群来看，所有梭梭种群均呈聚集分布。种群的龄级结构图表明样地AcD中的种群幼苗和幼树数量较少，但这种现象是暂时的，种群仍具有持续更新的能力，样地B 2;另一个可能的解释是在种群更新和发展过程中，由于种内竞争的增强而发生了自疏现象。 3ISSR标记对新疆和内蒙古境内共98219184(84%)AMOVA分析表明大部分遗传多样性分布在种群内，区域间、种群间的遗传变异均很小。梭梭种群较高的遗传多样性水平可能源于对异质、高胁迫环境的长期适应，而种群间遗传分异低的主要原因是种群间存在强大的基因流。 45个梭梭种群的地面植被和种子库的遗传结构进行了比较分析，并调查了其中3( 0-10 m) 5
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光合放氧研究近十年来已有重要进展，但在该领域仍有很多重要问题待研究。本论文工作主要是对光系统氧化侧与光合放氧密切相关的组分的结构和性能进行理论和模拟研究，工作可概括如下： () 1Mn202H2OCl等结合方式的理论研究显示：(a)、组氨酸和H20分子均可能与Mn202Mn;(b)2个H2O分子可能结合在不同Mn202 2Mn簇核心骨架的理论研究显示有必要引入新的CaCl结合方式，以防止因两个Mn2022个H2O分子结合位点远离。 ()Tyr_zTyr_D的结构与功能。 对次级电子给体Tyr_zTyr_D(a)Tyr_D和Tyr_z;(b)、当失去电子后，结构发生明显变化，导致正电荷主要集中在组氨酸上，自由基主要集中在Tyr上;(c)(H_20分子或羧基等);(d)Tyr_D~+和Tyr_z~+ () 1P_(870)的理论研究显示：(a)、双分子结构比单分子结构稳定;(b)P870C3P870+•的总能量和化学活性明显降低。推测这种构型转变对于防止原初反应过程中的电荷重组、维持光能的高效转化有重要意义。提出了原初反应过程中结构动态变化的新观点，利用这一观点可对光合细菌原初反应动力学研究所观测到的慢过程及蛋白质微环境对原初电子给体和原初反应都有重要影响等实验现象给予较好的解释。 2IIP680a分子平面间夹角为50.0±2.5° 3N-(C4H6N2)模拟生物体内的组氨酸，通过观测CCL4Chla与C4H6N2CDMCD(a)CCL4Chla处于5ChlaChla通过不等价的2Mg-O(OC131C17C=O)连接为紧密双体结构;(b)C4H6N2Chla = 0.51时，其吸收、CDMCDChlaC4H6N2Mg-O酯键，进而取代Mg-OChlaMgOP_(680)的结构相似。 TyrZ2个H2O分子不对称地结合于“C”形结构开口端两个低价的Mn1IIMn4III;两个组氨酸的咪唑环通过NMn2IV、Mn3IV;ClMB4TM，并与Ca;CaOCOO-相连使两个Mn202TyrZ通过组氨酸(D1-His190)MnO(包括TyrZTyrD)整体处于中性状态。 Ca在维持放氧中心的结构方面担负重要作用，C1Mn离子之间的亲核作用变化是放氧中心结构变化的关键。
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渤海湾沿岸人口密集，工农、航运发达，渤海自身净化能力非常有限。因此，渤海湾 环境污染的压力越来越大，主要污染物包括重金属和持久性有机污染物的。四角蛤蜊广泛 分布于渤海湾海域，是一种重要的经济贝类，对污染物具有较强的富集能力。为了研究不 同站点渤海湾四角蛤蜊软体部重金属含量，选择大港油田、高沙岭码头、涧河村三个断面 进行研究，对不同站点四角蛤蜊软体部重金属含量进行了分析和讨论，最后对水生动物的 POPs 1. 通过比较渤海不同站点四角蛤蜊软体部重金属含量分布特征和方差分析，发现四 角蛤蜊软体部必需重金属元素含量较高，而非必需重金属元素含量较低，这是由于必需重 金属元素具有重要的生理功能作用。侧重比较AB 两个断面各站位间四角蛤蜊软体部重 金属含量，发现虽然各站位间分布规律不明显，但各站位间差异显著。 2. 利用简单相关回归分析金属元素间及其与生物学性状间的关系，发现Mn 与Zn 之 间，Cu Zn Se AsCd A 断面，BL 与Cd Y（Cd=1395.97＋88.34BLR=0.633B 断面，利用BW 和BH 分别与Cd As BW 和Cd Y（Cd=1968.80＋220.72（BWR=0.656。BH 和As 的回归方 程为：YAs）=1496.86227.82BHR=0.656 3. 利用PLS（偏最小二乘分析）方法分析，发现五个生物学性状都与CoAs 关，而与CrPb、Se 呈负相关，而与必须重金属元素相关不明显。进一步分析表明表明 渤海湾海域中CoAs Cr、PbSe 四角蛤蜊正常生长发育所需的量。最后，通过PLS-DA C 站点样品能与A B A、B 况。 4. 四角蛤蜊软体部重金属含量进行风险评价，首先，利用单因子污染指数法比较分析， 发现从1997 -2008 Cd 已低于《海洋生物质量标准》（第二类）标准。而CrAs 然后，利用金属污染指数法进行比较研究，发现B A C 断面。最后，利用《人 体消费卫生标准》进行比较分析，发现CdNi 控制。 5. 渤海湾污染物除了重金属外，还存在一些典型持久性有机污染物。为进一步揭示 二者间协同毒理机制，利用分子系统学方法，对芳香烃受体通道进行了探索性研究，发现 水生动物AhR通道基因在进化过程中发生了适应性进化，对进一步研究重金属和POPs 壳贝类的毒理机制具有参考价值。
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测定了白腹锦鸡C. amherstiae两个个体部分细胞色素b,861bpC. pictus的同源序列相比,21个位点上出现变异,2.5%b基因核苷酸替换的速率约为每百万年0.5%-0.7%,1.7(C. amherstiae)(C. pictus)是两个独立种。
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The early life-history of Chinese rock carp Procypris rabaudi was investigated during a 56-day rearing period: 318 artificially propagated P. rabaudi larvae were reared throughout metamorphosis in a small-scale recirculation system (345 L water volume, 10 x 18 L rearing tanks, 150 L storage and filter compartment with bioballs, 20-30 larvae L-1) at the Institute of Hydrobiology, Wuhan, Hubei Province, China. The newly hatched larvae had an initial total length of 8.93 +/- 0.35 mm SD (n = 10) at 3 days post-hatch and reached an average total length of 33.29 mm (+/- 1.88 mm SD, n = 10) 56 days after hatching. Length increment averaged 0.45 mm day(-1), resulting in a mean growth of 24.4 mm within the 56-day period. High mortality rates of up to 92% derived from an introduced fungus infection and subsequent treatment stress with malachite green. Our results indicate that Chinese rock carp can be raised successfully from artificially fertilized eggs. We therefore assume this species to be a candidate for commercial aquaculture.
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In the present paper, sorption, persistence, and leaching behavior of three microcystin variants in Chinese agriculture soils were examined. Based on this study, the values of capacity factor and slope for three MCs variants in three soils ranged from 0.69 to 6.00, and 1.01 to 1.54, respectively. The adsorption of MCs in the soils decreased in the following order: RR > Dha(7) LR > LR. Furthermore, for each MC variant in the three soils, the adsorption rate in the soils decreased in the following order: soil A > soil C > soil B. The calculated half-time ranged between 7.9 and 17.8 days for MC-RR, 6.0-17.1 days for MC-LR, and 7.1-10.2 days for MC-Dha(7) LR. Results from leaching experiments demonstrated that recoveries of toxins in leachates ranged from 0-16.7% for RR, 73.2-88.9% for LR, and 8.9-73.1% for Dha 7 LR. The GUS value ranged from 1.48 to 2.06 for RR, 1.82-2.88 for LR, and 1.76-2.09 for Dha(7) LR. Results demonstrated the use of cyanobacterial collections as plant fertilizer is likely to be unsafe in soils. (c) 2006 Elsevier Ltd. All rights reserved.
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A novel method for positioning of InAs islands on GaAs (110) by cleaved edge overgrowth is reported. The first growth sample contains strained InxGa1-xAs/GaAs superlattice (SL) of varying indium fraction, which acts as a strain nanopattern for the cleaved-edge overgrowth. Atoms incident on the cleaved edge will preferentially migrate to InGaAs regions where favorable bonding sites are available. By this method InAs island chains with lateral periodicity defined by the thickness of InGaAs and GaAs of SL have been realized by molecular beam epitaxy (MBE). They are observed by means of atomic force microscopy (AFM). The strain nanopattern's effect is studied by the different indium fraction of SL and MBE growth conditions. (c) 2005 Elsevier B.V. All rights reserved.
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A new two-dimensional structure modulation along c- and b-axes has been discovered in superconducting single crystals of Bi2.13Sr1.87CuO6+delta (Bi2201) by x-ray scattering. Such modulation structure does not exist in non-superconducting Bi2201 single crystals, but instead lattice distortions are observed in the a-b-plane. This phenomenon may indicate that both strain relaxation and charge modulation in the a-b-plane are important to the occurrence of superconductivity in the copper oxides.
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We report on high-frequency (300-700 GHz) ferromagnetic resonance (HF-FMR) measurements on cobalt superparamagnetic particles with strong uniaxial effective anisotropy. We derive the dynamical susceptibility of the system on the basis of an independent-grain model by using a rectangular approach. Numerical simulations give typical line shapes depending on the anisotropy, the gyromagnetic ratio, and the damping constant. HF-FMR experiments have been performed on two systems of ultrafine cobalt particles of different sizes with a mean number of atoms per particles of 150 +/- 20 and 310 +/- 20. In both systems, the magnetic anisotropy is found to be enhanced compared to the bulk value, and increases as the particle size decreases, in accordance with previous determinations from magnetization measurements. Although no size effect has been observed on the gyromagnetic ratio, the transverse relaxation time is two orders of magnitude smaller than the bulk value indicating strong damping effects, possibly originating from surface spin disorders.
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We investigate high-field ferromagnetic resonance of superparamagnetic particles with uniaxial anisotropy, In this case, since the field is large enough to saturate the magnetization, the thermal orientational fluctuations of the magnetic moment of the particle are negligible. Thus, we derive the dynamic susceptibility of the system on the basis of an independent particle model. High-field ferromagnetic resonance has been performed on fine cobalt particles, The analysis of the spectra obtained at different frequencies allows us to estimate the effective magnetic anisotropy, the gyromagnetic ratio, and the transverse relaxation time. (C) 1998 Elsevier Science B.V. All rights reserved.
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Pseudomorphic Iny2Al1-y2As/In0.73Ga0.27As/Iny1Al1-y1As (y1 greater than or equal to 0.52) modulation-doped heterostructures with an intentional nonlattice-matched buffer layer were successfully grown by molecular beam epitaxy on (100)InP substrates. Fourier transform photoluminescence and double crystal x-ray diffraction measurements show a superior crystalline quality in the high In content channel, when In mole fraction increases from y1=0.52 to 0.55 in the Iny1Al1-y1As buffer layer. In this case, an increasing of 16.3% and 23.5% for conductivity (mu xn(s)) and mobility, related to the strain compensation in the In0.73Ga0.27As channel, was achieved, respectively, comparing to the structure containing a well-lattice matched buffer layer. With increasing the mismatch further (y1=0.58), a morphology with cross-hatched pattern was observed due to the onset of a large amount of misfit dislocations, and the electronic characterization is not able to be improved continuously. Because we can realize high quality strained P-HEMTs in a relative wide range of equivalent beam flux (EBF) ratios, the stringent control over the constant EBF is not indispensable on this In-based material system. (C) 1997 American Vacuum Society.
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提出了一种新的钟控密钥流生成器,3:两个被钟控的线性反馈移位寄存器AB,一个提供钟控信息的非线性反馈移位寄存器C。设ABC的长度分别为l1l2l3。移位寄存器ABC选取的两个比特串提供,k,分析了这种密钥流生成器的安全性。
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本试验结果表明:(1).PHC/N.(2)B组最好，ACC/NB组的C/N.本试验研究提出了一个以稻草为原料，沼气发酵为基础，蚯蚓为中心环节的良性生态循环..
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C2-1,1-联萘-2-酚(BINOL) 本论文以天然的手性酮(-)-(+)-(-)-薄荷酮为原料合成两个系列的手性吡啶醇类化合物2a-c，12a-b3-3,3-(硼酸嚬呐醇酯)- 2,2’-()-1,1--2-Suzuki3,3-位引入手性吡啶醇取代基，合成了两个系列手性联萘酚衍生物，十对非对映异构体8a-c，9a-c，19a-b20a-b1H NMR13C NMRIR和ESI-MS表征和验证结构。 探讨了两个系列手性配体在芳香醛不对称ZnEt28a-c，9a-c在芳香醛的不对称ZnEt296% e.e.51％e.e.19a-b，20a-bZnEt2(91% e.e.)e.e.值最高可达71 同时，将部分配体与金属钼()
