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51.
Steric structures of dysprosium(III) aminobenzoate complexes with the 11 and 12 molar ratio in aqueous solutions were determined on the basis of pH-metric and paramagnetic birefringence data. An increase in conjugation observed for the series of the acids,viz., benzoic,meta-, ortho-, andpara-aminobenzoic acids, results in the increased stability of the complexes with the 11 and 12 composition. In the case ofpara-aminobenzoic acid, the polyhedra [DyL(H2O)6]2+ and [DyL2(H2O)4]+ are cubes with the ligands coordinated to one and two edges, respectively. In the case ofmeta-aminobenzoic acid, the polyhedra [DyL(H2O)6]2+ and [DyL2(H2O)4]+ are a dodecahedron with the ligand coordinated to one edge and a square anti-prism with the ligands coordinated to two edges, respectively. In the case ofortho-aminobenzoic acid, both the 11 and 12 complexes have structures that are intermediate between the structures ofmeta- andpara-aminobenzoic acids.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1767–1770, October, 1994. 相似文献
52.
Alexei A. Belik Shinya Uji Eiji Takayama-Muromachi 《Journal of solid state chemistry》2005,178(11):3461-3463
Magnetic properties of quasi-one-dimensional S=1/2 Heisenberg antiferromagnet Sr2Cu(PO4)2 were investigated by temperature and field dependence of AC susceptibility down to 0.03 K. A sharp peak was observed at on the temperature dependence of AC susceptibility indicating long-range magnetic ordering. Taking into account the exchange constant, (Hamiltonian =J∑SiSi+1), the ratio kBTN/J is 0.06%. Sr2Cu(PO4)2 is, therefore, one of the best one-dimensional Heisenberg antiferromagnet known so far. 相似文献
53.
The cubic inverse Perovskites (Eu3O)In and (Eu3O)Sn were prepared from the metals and Eu2O3 or SnO2, respectively. For (Eu3O)In the crystal structure analysis was performed on single crystal X‐ray diffraction data (space group , a = 512.79(3) pm, Z = 1, Rgt(F) = 0.022, wR(F2) = 0.044). The data indicated full occupancy on all sites and a fully ordered structure. According to magnetic susceptibility measurements and X‐ray absorption spectroscopic data at the Eu LIII edge both compounds contain europium in the 4f7 (Eu2+) electronic state. (Eu3O)In orders ferromagnetically at 185(5) K, (Eu3O)Sn shows antiferromagnetic order at 31.4(2) K. Both compounds behave as metallic conductors in electrical resistivity measurements. However, (Eu3O)In may be classified a metal, while (Eu3O)Sn is more likely a heavily doped degenerated semiconductor or semimetal according to the absolute values of the resistivity. 相似文献
54.
A single crystal of a new sodium calcium iron (III) phosphate, Na4CaFe4(PO4)6, has been synthesized by a flux method and characterized by X-ray diffraction, Mössbauer spectroscopy and magnetic susceptibility measurements. The compound crystallizes in the monoclinic space group C2/c(a=12.099(5) Å, b=12.480(5) Å, c=6.404(2) Å, β=113.77(3)°, Z=2, R1=0.022, Rw2=0.066). The crystal structure belongs to the alluaudite type, characterized by the X(2)X(1)M(1)M(2)2(PO4)3 general formula. The open framework results from Fe2O10 units of edge-sharing FeO6 octahedra, which alternate with M(1)O6 octahedra (M(1)=Na+Ca) that form infinite chains. These chains are linked together through the common corners of PO4 tetrahedra yielding two distinct tunnels of sodium cation occupation. This compound is antiferromagnetic with a Néel temperature of 35 K. Mössbauer parameters are consistent with the structural results. 相似文献
55.
The high-resolution 1H and 13C NMR spectra of 1-vinylimidazole complexes with iron group metals were recorded. The contact coupling in these systems was
established in the 1H and 13C NMR spectra. The applicability of the NMR spectra transformed by long-range hyperfine coupling for elucidating the molecular
structure of the ligand was shown.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1430–1433, June, 2005. 相似文献
56.
《Arabian Journal of Chemistry》2020,13(1):1198-1228
Vanadate and vanadium compounds exist in many environmental, biological and clinical matrices, and despite the need only limited progress has been made on the analysis of vanadium compounds. The vanadium coordination chemistry of different oxidation states is known, and the result of the characterization and speciation analysis depends on the subsequent chemistry and the methods of analysis. Many studies have used a range of methods for the characterization and determination of metal ions in a variety of materials. One successful technique is high performance liquid chromatography (HPLC) that has been used mainly for measuring total vanadium level and metal speciation. Some cases have been reported where complexes of different oxidation states of vanadium have been separated by HPLC. Specifically reversed phase (RP) HPLC has frequently been used for the measurement of vanadium. Other HPLC methods such as normal phase, anion-exchange, cation-exchange, size exclusion and other RP-HPLC modes such as, ion-pair and micellar have been used to separate selected vanadium compounds. We will present a review that summarizes and critically analyzes the reported methods for analysis of vanadium salts and vanadium compounds in different sample matrices. We will compare various HPLC methods and modes including sample preparation, chelating reagents, mobile phase and detection methods. The comparison will allow us to identify the best analytical HPLC method and mode for measuring vanadium levels and what information such methods provide with regard to speciation and quantitation of the vanadium compounds. 相似文献
57.
D.Allan Butterfield Joshua ColvinJiangling Liu Jianquan WangLeonidas Bachas Dibakar Bhattacharrya 《Analytica chimica acta》2002,470(1):29-36
The immobilization of biological molecules onto polymeric membranes to produce biofunctional membranes is used for selective catalysis, separation, analysis, and artificial organs. Normally, random immobilization of enzymes onto polymeric membranes leads to dramatic reduction in activity due to chemical reactions involved in enzyme immobilization, multiple-point binding, etc., and the extent of activity reduction is a function of membrane hydrophilicity (e.g. activity in cellulosic membrane?polysulfone membrane). We have used molecular biology to effect site-specific immobilization of enzymes in a manner that orients the active site away from the polymeric membrane surface, thus resulting in higher enzyme activity that approaches that in solution and in increased stability of the enzyme relative to the enzyme in solution. A prediction of this site-specific method of enzyme immobilization, which in this study with subtilisin and organophosphorus hydrolase consists of a fusion tag genetically added to these enzymes and subsequent immobilization via the anti-tag antibody and membrane-bound protein A, is that the active site conformation will more closely resemble that of the enzyme in solution than is the case for random immobilization. This hypothesis was confirmed using a new electron paramagnetic resonance (EPR) spin label active site titration method that determines the amount of spin label bound to the active site of the immobilized enzyme. This value nearly perfectly matched the enzyme activity, and the results suggested: (a) a spectroscopic method for measuring activity and thus the extent of active enzyme immobilization in membrane, which may have advantages in cases where optical methods can not be used due to light scattering interference; (b) higher spin label incorporation (and hence activity) in enzymes that had been site-specifically immobilized versus random immobilization; (c) higher spin label incorporation in enzymes immobilized onto hydrophilic bacterial cellulose membranes versus hydrophobic modified poly(ether)sulfone membranes. These results are discussed with reference to analysis and utilization of biofunctional membranes. 相似文献
58.
59.
从约化BCS哈密顿量出发,考虑随机矩阵理论中高斯正交系综和高斯辛系综所对应的电子能级分布,用配分函数的静态路径积分表示方法,计算了常规超导金属纳米粒子正常-超导相变临界区域附近的磁化率,得到了量子效应、奇偶效应、小尺寸效应导致超导金属纳米粒子的磁化率偏离块状超导体的磁化率的性质曲线。 相似文献
60.
求出了铁磁颗粒膜的自旋波激发谱和自旋极化激发谱随颗粒粒径和温度的变化规律,以及膜的磁化强度、磁化率、热容量.以(α-C:H)1-xCox颗粒膜为例作具体计算.结果表明:颗粒膜的自旋波激发谱的频率随颗粒粒径增大而减小,与温度无关;而颗粒膜的自旋极化激发谱与温度有关,表现出与铁磁块状晶体自旋波谱不同的变化特征.在零级近似下,由颗粒膜自旋波激发谱引起的磁化强度、热容量随温度变化规律与块状晶体相同,而一级近似下表现出颗粒膜与块状晶体的偏离. 相似文献