153 resultados para Isidro Labrador, Santo, ca. 1070-1130
em Chinese Academy of Sciences Institutional Repositories Grid Portal
Resumo:
Er3+ doped multicomponent fluoride based glass was prepared. These precursor fluoride glass samples were then heated using different schedules. Crystalline phase particles were successfully precipitated in the multicomponent fluoride glass samples after heat treatment. The influence of heat treatment on the spectroscopic properties of Er3+ in multicomponent fluoride based glass samples were discussed. Small changes of the Judd-Ofelt parameters Omega(i) (i = 2,4,6) were found in multicomponent fluoride glass samples before and after heat treatment compared to oxyfluoride telluride glass. Preparation conditions used to produce transparent multicomponent fluoride glass ceramics doped with rare-earth ions are discussed. (c) 2007 Elsevier B.V. All rights reserved.
Resumo:
通过实验我们证明Ca2+对叶绿体膜的流动性,对PS I和PS II叶绿素蛋白质复合物的相对含量,以及PS I和PS II的多肽均有影响。 Ca2+对叶绿体膜表层的流动性影响不大,但降低了叶绿体膜深层脂质分子的流动性。从另一个角度阐明了Ca2+抑制光能从PS II向PS I传递的机制。 Ca2+可使PS I的21,23,110KD的多肽转移至PS II,LHCP1和LHCP2中的CF1的两个亚基(55,60KD)转至CPa和LHCP3,从而增加了PS II的捕光截面,引起激发能在两个系统之间的分配的改变。 用免疫学方法可以证明CPIa2和LHCP2的Ab为复合抗体,CPIa1的Ab为单抗,我们可以推测向日葵的不同叶绿素蛋白质复合物具有同源性。
Resumo:
Ca~(++)离子能极大地激活五步蛇蛇毒PLA_2的酶活力,Na离子只能在一定程度上激活,作者推测在测定PLA_2酶活力的底物溶液中可以不加Na~+离子。
Resumo:
以鱼腥藻为材料 ,研究了外源Ca2 +对模拟微重力环境中微藻细胞膜透性的影响。实验结果表明 :提高培养基中的Ca2 +浓度可减轻由模拟微重力造成的膜透性增大 ,有助于稳定细胞膜结构和功能。同时 ,外源Ca2 +降低了藻细胞光系统Ⅱ (PSⅡ )的光化学效率 (以荧光参数Fv/Fm表示 )下降的幅度 ,表明外源Ca2 +对模拟微重力环境下鱼腥藻细胞光合作用的损伤 ,有良好的防护效应。
Resumo:
5种水生植物对所用4种放射性同位素都有一定的清除能力,其清除能力的大小不仅取决于生物的种类,而且还取决于生物本身代谢率的高低。试验结果:去污率高的可达80%,积累系数最高可达1,500;水体中含Ca的多少对生物吸收积累放射性物质的多少有一定的影响;生物在积累放射性物质之后,转移到无放射性物质的水体中将释放出原积累的一部分放射性物质。
Resumo:
The luminescence from Eu2+ ions in MF2 (M = Ca, Sr, Ba) fluorides has been investigated under the pressure range of 0-8 GPa. The emission band originating from the 4f(6)5d(1) -> 4f(7) transition of Eu2+ ions in CaF2 and SrF2 shows the red-shift as increasing pressure with pressure coefficients of -17 meV/GPa for CaF2 and -18 meV/GPa for SrF2. At atmospheric pressure, the emission spectrum of BaF2:Eu2+ comprises two peaks at 2.20 and 2.75 eV from the impurity trapped exciton (ITE) and the self-trapped exciton (STE), respectively. As the pressure is increased, both emission peaks shift to higher energies, and the shifting rate is slowed by the phase transition from the cubic to orthorhombic phase at 4 GPa. Due to the phase transition at 4-5 GPa pressure, the ITE emission disappears gradually, and the STE emission is gradually replaced by the 4f(6)5d(1) -> 4f(7) transition of Eu2+. Above 5 GPa, the pressure behavior of the 4f(6)5d(1) -> 4f(7) transition of EU2+ in BaF2: EU2+ is the same as the normal emission of Eu2+ in CaF2 and SrF2 phosphors.
Resumo:
A systematic investigation of crystallographic and magnetic properties of nitride R3Fe29-xCrxN4 (R=Y, Ce, Nd, Sm, Gd, Tb, and Dy) has been performed. The lattice constants and unit cell volume decrease with increasing rare earth atomic number from Nd to Dy, reflecting the lanthanide contraction. After nitrogenation the relative volume expansion of each nitride is around between 5% and 7%. The nitrogenation results in a good improvement in the Curie temperature, the saturation magnetization and anisotropy fields at 4.2 K, and room temperature for R3Fe29-xCrxN4. Magnetohistory effects of R3Fe29-xCrxN4 and R3Fe29-xCrx (R=Nd and Sm) are observed in a low field of 0.04 T. First order magnetization process occurs in Sm3Fe24.0Cr5.0N4 in magnetic fields of 2.8 T at 4.2 K. After nitrogenation, the easy magnetization direction of Sm3Fe24.0Cr5.0 is changed from the easy-cone structure to the uniaxial. The good intrinsic magnetic properties of Sm3Fe24.0Cr5.0N4 make this compound a hopeful candidate for new high-performance hard magnets. (C) 1998 American Institute of Physics.
Resumo:
CA(certificate authority)是PKI中的关键设施.CA私有密钥一旦泄露,该CA发的所有证书就只能全部作废.保护在线服务CA私钥也就成为一个非常重要的课题.不是从保护系统或检测入侵出发来保证CA安全,而是确保当少数部件被攻击或占领后,CA统的机密信息并没有暴露.通过将私钥分发给不同的部件,并保证任何一个在线的部件无法恢复CA私钥,从而保护了CA钥的保密性.
Resumo:
弹性CA一种使用入侵容忍技术保护CA钥的CA统,它采用了新的私钥分割方法加强了系统的安全性,但其使用的密钥分发中心却不利于CA钥安全.分布式密钥产生方案就是在传统的弹性CA案的基础上取消了密钥分发中心,使用分布式的密钥产生和分割机制,从而保证了在CA始化和整个运行过程中,任意t-1(t为门限值)台服务器都不可能窃得CA钥,大大加强了CA统安全.
Resumo:
随着萃取技术的不断发展,人们日益要求更加深入的了解萃取过程的机制及其动力学特性。以便有效地控制和强化萃取过程,提高萃取效率,或者利用萃取动力学的差异来实现某些分离嘴过程。尽管许多萃取过程进行得很快,但是人们也发现不少的金属鳌合物萃取体系,其萃取过程相当缓慢。因而这类体系的萃取机制和萃取动力学问题已日益引人注目。除此而外,在设计,放大或改进萃取设备时,研究和掌握有关萃取过程的动力学规律也有十分重要意义。在本文中主要对稀土萃取动力学进行了研究,得到主要结果如下:1.研究了硫代有机磷酸Cyan.ex302萃取饵的动力学。通过测定各种萃取条件对萃取速率的影响,获得了萃取速率方程,并讨论了萃取的控制过程。实验发现萃取剂中的杂质对萃取具有较大的加速作用,这对工业生产具有一定的实际意义。2.用两相滴定法测定了两种新合成的J梭酸萃取剂CA-12和CA-100的某些重要的物理常数。这将有助于深入研究它们的萃取性质及机理。3.用层流恒界面池研究了CA-12萃取La, Gd,Er, Yb和Y的动力学。考察了各种因素对萃取速率的影响,获得了它们的萃取速率方程,实验发现了它们的萃取控速步骤并推测了其萃取机理。4.研究了HEHEHP对CA-12萃取Yb和Y的动力学的影响。实验发现在CA12中加入少量的HEHEHP后,萃取活化能显著降低,萃取速率明显加快。由于加入HEHEHP后,萃取Yb的活化能的降低要比萃取Y的活化能降低的程度大',所以使Yb和Y的萃取分离因素加大。5.用两相滴定法研究了HEHEHP萃取铭的机理,CA-12萃取稀土及其相关离子的机理。并计算了它们相应的平衡常数。