共查询到20条相似文献,搜索用时 93 毫秒
1.
本文以XL-200型超导NMR谱仪对镧系离子与L-组氨酸配合物进行了一系列的研究,测得微酸性条件下的顺磁诱导位移,对这些诱导位移进行分析计算,得到了各磁性核的配合物生成位移、接触位移和准接触位移,同时以准接触位移为依据,对配合物结构进行模拟,获得了有关的结构参数.并对镧系离子在磁学性质上的特征进行了讨论. 相似文献
2.
镝—镧—钛试剂荧光体系的协同发光效应及其分析应用 总被引:3,自引:0,他引:3
王磊 《光谱学与光谱分析》1999,19(3):463-465
发现了镧对镝-钛铁试剂荧光体系的协同发光效应,详细研究了镝-镧-钛铁试剂协同发光体系的荧光光谱特性,确定了各种试验条件对体系荧光强度的影响。 相似文献
3.
王磊 《光谱学与光谱分析》1999,19(3)
发现了镧对镝-钛铁试剂荧光体系的协同发光效应,详细研究了镝-镧-钛铁试剂协同发光体系的荧光光谱特性,确定了各种试验条件对体系荧光强度的影响。在镝-钛铁试剂荧光体系中引入适量的镧可使体系的荧光强度提高40倍,体系的荧光强度同镝的浓度在5.0×10-8~9.0×10-6mol/L范围内成线性关系,检测限可达1.0×10-10mol/L。采用标准加入法测定稀土样品中痕量的镝可获得满意结果。 相似文献
4.
G群链球菌G蛋白的B1结构域——GB1蛋白,常被用作发展体外及体内基于顺磁核磁共振(NMR)的蛋白质结构测定方法的研究模型.为确保赝接触化学位移(PCS)、顺磁弛豫增强(PRE)等顺磁约束数据的准确性,了解GB1和金属离子,尤其是顺磁离子的相互作用非常必要.然而GB1和二价金属离子以及镧系金属离子的相互作用并不十分清楚.本文利用NMR波谱研究了GB1和镧系金属离子以及多种二价金属离子的相互作用.我们发现GB1和镧系金属离子之间存在弱特异性相互作用,和Mn~(2+)、Cu~(2+)以及Co~(2+)等顺磁二价离子弱结合,但不与Ca~(2+)、Mg~(2+)以及Zn~(2+)等抗磁二价离子结合.该研究表明在GB1上链接顺磁探针时,应使用与固有位点结合常数差异明显的顺磁标签以获取正确的PRE数据. 相似文献
5.
针对锆钛酸铅镧(PLZT)电光陶瓷在光调制器应用中存在工作电压偏高、场致滞后明显等不足,以镧系镝(Dy)元素对锆钛酸铅镧(Pb0.88La0.12)(Zr0.4Ti0.6)0.96O3 [PLZT(12/40/60)]线性电光材料进行掺杂改性.采用热压技术研制镝掺杂锆钛酸铅镧[Pb0.88(La1-xDyx)0.12](Zr0.40Ti0.60)0.96O3](PLDZT)(x=0.1~0.5)透明电光陶瓷.系统考察了PLDZT透明陶瓷的光学性能和电光特性及其与材料结构的相关性.研究表明,Dy掺杂导致材料晶格畸变,微量Dy掺杂有效提高了 PLZT(12/40/60)透明陶瓷的光学透过率,并且使典型的线性电光材料呈现二次电光效应特征,二次电光系数R约为5.59×10-15m2/V2;同时掺杂改性的PLDZT(x=0.1)透明陶瓷的驱动电压较未改性PLZT材料明显降低. 相似文献
6.
本文从朗道二级相变理论出发,讨论了A-15结构化合物的M点相变模型,并得到了二级结构相变的相交方向。 相似文献
7.
G群链球菌G蛋白的B1结构域——GB1蛋白,常被用作发展体外及体内基于顺磁核磁共振(NMR)的蛋白质结构测定方法的研究模型.为确保赝接触化学位移(PCS)、顺磁弛豫增强(PRE)等顺磁约束数据的准确性,了解GB1和金属离子,尤其是顺磁离子的相互作用非常必要.然而GB1和二价金属离子以及镧系金属离子的相互作用并不十分清楚.本文利用NMR波谱研究了GB1和镧系金属离子以及多种二价金属离子的相互作用.我们发现GB1和镧系金属离子之间存在弱特异性相互作用,和Mn2+、Cu2+以及Co2+等顺磁二价离子弱结合,但不与Ca2+、Mg2+以及Zn2+等抗磁二价离子结合.该研究表明在GB1上链接顺磁探针时,应使用与固有位点结合常数差异明显的顺磁标签以获取正确的PRE数据. 相似文献
8.
9.
镧系金属因其具有较窄的发射光谱带,较大的斯托克斯位移以及毫秒级的荧光寿命,而被广泛应用于荧光检测中,其中Tb~(3+)、Eu~(3+)最为常用.镧系金属结合标签(Lanthanide Binding Tag,LBT)可以与蛋白质融合表达,并且一般不会影响蛋白的结构和功能,这些特点使LBT被广泛应用于蛋白质结构与功能研究中.LBT能够特异性地结合镧系金属离子,并利用LBT上色氨酸的吲哚环作为"天线"吸收外部能量,再将能量传递给镧系金属离子,进而激发镧系金属离子产生荧光.该文以经典模式蛋白泛素(Ubiquitin,Ub)作为媒介,将LBT引入到Ub的碳端,采用定点突变的方法增加LBT上吲哚环的数量,观察Ub-LBT[结合铽离子(Tb~(3+))]荧光量子产率的变化.结果表明在LBT结构中增加吲哚环的数量能够提高LBT(结合Tb~(3+))的荧光量子产率. 相似文献
10.
11.
The quantum theory of the transverse transport of charged particle systems in a strong, uniform magnetic field is reinvestigated in this article. All such previous theories, based on the Kubo formula in the Landau representation, only considered the second-order term of the collisional expansion series. However, if other high-order terms, especially the so-called reducible diagonal parts, are also considered, another second-order contribution is found, which exactly cancels the one derived prebiously. Hence, within the fxamwork of the usual theory, all the transverse transport coefficients would be identically zero. phis consequence is directly related to the local nature of the Landau eigen states.Only because previous calculations were incomplete did they obtain finite results. 相似文献
12.
SCREENING EFFECT OF THE SPIN DISTRIBUTION IN THE ATOMS OF HYDROGEN AND ALKALI METALS UNDER THE DISTURBANCE OF A STRONG PERIODIC MAGNETIC FIELD
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Using the path integral method, we calculated all the distribution probability ratios for the spin projection of the electron in a hydrogen atom under the disturbance of a strong periodic magnetic field, and studied the screening effect of the coupling of spin with the periodic magnetic field B(t) on the ratios of the spin distributions. It is found that the screening exists not only in the usual direction along the magnetic field (not affected by initial conditions) but also other directions affected by the initial conditions. For the valence electron in the alkali metals, such as 3/sup>Li, 11Na, 19K, 37Ru, and 55Ce, etc., a similar conclusion can be drawn. 相似文献
13.
14.
15.
F. W. Nijhoff 《Physica A》1985,130(3):375-411
In this paper we derive the Landau expansion for the ordered phases of liquid 3He in the presence of a magnetic field starting from a model hamiltonian which contains an l = 1 pairing interaction of the BCS type and a contact term of the Hubbard type. In the derivation use is made of an exact theorem in the theory of separable interactions and the contribution from the Hubbard interaction is evaluated in second order perturbation calculation. Some typical differences with the results based on a spin fluctuation theory are mentioned. 相似文献
16.
MnSi is an itinerant magnet which at low temperatures develops a helical spin-density wave. Under pressure it undergoes a transition into an unusual partially ordered state whose nature is debated. Here we propose that the helical spin crystal (the magnetic analog of a solid) is a useful starting point to understand partial order in MnSi. We consider different helical spin crystals and determine conditions under which they may be energetically favored. The most promising candidate has bcc structure and is reminiscent of the blue phase of liquid crystals in that it has line nodes of magnetization protected by symmetry. We introduce a Landau theory to study the properties of these states, in particular, the effect of crystal anisotropy, magnetic field, and disorder. These results compare favorably with existing data on MnSi from neutron scattering and magnetic field studies. Future experiments to test this scenario are also proposed. 相似文献
17.
We calculate the basic parameters of the Fermi liquid: the scattering vertex, the Landau interaction function, the effective mass, and physical susceptibilities for a model of two-dimensional (2D) fermions with a short-ranged interaction at nonzero temperature. The leading temperature dependences of the spin components of the scattering vertex, the Landau function, and the spin susceptibility are found to be linear. T-linear terms in the effective mass and in the "charge-sector" quantities are found to cancel to second order in the interaction, but the cancellation is argued not to be generic. The connection with previous studies of the 2D Fermi-liquid parameters is discussed. 相似文献
18.
19.
We have introduced a novel Majorana representation of S=1/2 spins using the Jordan-Wigner transformation and have shown that a generalized spin model of Kitaev defined on a brick-wall lattice is equivalent to a model of noninteracting Majorana fermions with Z2 gauge fields without redundant degrees of freedom. The quantum phase transitions of the system at zero temperature are found to be of topological type and can be characterized by nonlocal string order parameters (SOP). In appropriate dual representations, these SOP become local order parameters and the basic concept of Landau theory of continuous phase transition can be applied. 相似文献