Anomalies of the partition coefficient and properties of crystals in the region of low concentrations of an isomorphous admixture. 1. Unusual decomposition of solid solutions of the NaCl—CdCl2 system

Solid solutions NaCl—CdCl₂ were studied in an interval of CdCl₂ concentrations of 0.05—3 mol.% by Raman spectroscopy. The molecular form Na₂CdCl₄ decomposes: Na₂CdCl₄ 2Na⁺ + Cd²⁺ + 2Cl₂ ^– + 2e^–; 2Na + 2e^– 2Na⁰. Free sodium atoms form color centers of crystal (F centers) in the region of jumpwise changing the partition coefficient of CdCl₂ in NaCl (K jump).     

2-Trif luoromethyl-4H-thiochromen-4-one and 2-trif luoromethyl-4H-thiochromene-4-thione: Synthesis and reactivities

2-Trifluoromethyl-4H-thiochromene-4-thione obtained from 2-trifluoromethyl-4H-thiochromen-4-one and P₂S₅ reacts with aromatic amines, hydrazine hydrate, phenylhydrazine, and hydroxylamine at the C(4) atom of the chromene ring to give the corresponding anils, azine, hydrazones, and oxime of thiochromone. 2-Trifluoromethyl-4H-thiochromen-4-one is oxidized by hydrogen peroxide in AcOH into 4-oxo-2-trifluoromethyl-4H-thiochromene 1,1-dioxide and reduced by NaBH₄ to 2-trifluoromethyl-4H-thiochromen-4-ol or cis-2-(trifluoromethyl)thiochroman-4-ol. When treated with hydrazine hydrate, thiochromen-4-one gives 3(5)-(2-mercaptophenyl)-5(3)-trifluoromethylpyrazole. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 504–509, March, 2006.     

XPS characterization of wood chemical composition after heat‐treatment

XPS was used to characterize the chemical changes occurring after drying or applying a heat‐treatment to beech wood samples. Our results indicate that the surface of this air‐exposed material could be strongly affected either by the ambient atmosphere during storage or by the complex atmosphere in the oven during drying or heat‐treatment. However, the O/C ratio measured after removal of a thin slice of a few millimetres of an untreated sample is in reasonable agreement with that calculated from the well‐established chemical composition of beech. Through this methodology (equivalent to scraping for hard materials) it is expected to get a realistic characterization of the wood. The reliability and repeatability of the XPS measurements have been checked and the method applied to the study of the chemical changes of the beech samples subjected to heat‐treatment. Heating at 240 °C induces a significant decrease of the O/C ratio from 0.55 before to 0.44 after the treatment. Heat‐treatment induces also a decrease of the C₂ carbon contribution (carbon atom bound to a single non‐carbonyl oxygen) associated with an increase of the C₁ carbon contribution (carbon atoms bound only to carbon or hydrogen atoms), in agreement with chemical modifications reported previously in the literature. Thanks to the small analysed area of the equipment used in this study, different spots were analysed to demonstrate the presence or absence of a gradient of chemical composition due to thermal degradation or migration of extractives from within the wood structure to its surface. At the scale of our observations, the different wood samples investigated (dried or heat treated) appear to be homogeneous. Copyright © 2006 John Wiley & Sons, Ltd.     

Use of a Dual-Marker Form of Analysis to Estimate Binding Constants Between Receptors and Ligands by Affinity Capillary Electrophoresis

This work describes the use of a dual-standard analysis approach termed the time-average ratio (TAR) in affinity capillary electrophoresis (ACE) to estimate binding constants of receptors to ligands. In this form of analysis the TAR is the migration time of the receptor divided by the average of the sum of the migration times of two non-interacting standards. This change in TAR as a function of the concentration of ligand yields a value for the binding constant. This concept is demonstrated using three model systems: carbonic anhydrase B (CAB, EC 4.2.1.1) and arylsulfonamides, vancomycin (Van) and ristocetin (Rist) from Streptomyces orientalis and Nocardia lurida, respectively, and d-Ala- d-Ala terminus peptides. Three ACE techniques are used to examine the three systems: standard ACE, flow-through partial-filling ACE (FTPFACE), and on-column derivatization coupled to ACE. The findings described here demonstrate that ACE data analyzed using the TAR form of analysis yield binding constants between receptors and ligands comparable to those estimated using other ACE forms of analysis. A comparison to three other forms of analysis is described.     

Effect of solvent composition on free release static coating of capillary columns

Summary Three aspects with respect to the selection of solvents for static coating of capillary columns, i.e. coating speed, occurrence of bumping and solubility of stationary phases are discussed. Hypotheses are proposed in an attempt to explain the observed facts that mixed solvents result in much higher coating speeds than those obtained from pure solvents, that a proper choice of solvents together with a good and uniform deactivitation of the column inner wall is needed to prevent bumping. Stationary phase solubility vs. solvent composition is also briefly discussed.     

Conformational studies of soluble and immobilized frog epidermis tyrosinase by fluorescence

Fluorescence spectra and soluble quenching of intrinsic protein fluorescence were used as indexes of conformational changes suffered by frog epidermis tyrosinase. The activation process and the immobilization of the enzyme involving either free amino groups or its carbohydrate moiety were studied. The conformational changes resulting from denaturation of each one of the protein derivatives, as well as the effect of active center copper extraction, were followed by fluorescence studies. The results showed that: (a) both activation and immobilization were accompanied by conformational changes of the protein leading to more unfolded states; (b) neither enzyme nor immobilized enzyme were fully unfolded upon denaturation although enzymic activity was lost; (c) the enzyme immobilized through its carbohydrate moiety was more unfolded upon denaturation than the enzyme immobilized through amino groups, thus pointing to a higher conformational stabilization in the last situation; and (d), that tryptophyl residues moved to a localization near the active site upon activation.     

Phosphaniminato-Trichloroselenate(II): Synthese und Kristallstrukturen von [SeCl(NPPh3)2]+SeCl3− und [Me3SiN(H)PMe3]2+[Se2Cl6]2−

Phosphorane Iminato-Trichloroselenates(II): Syntheses and Crystal Structures of [SeCl(NPPh₃)₂]⁺SeCl₃^? and [Me₃SiN(H)PMe₃]₂⁺[Se₂Cl₆]^2? [SeCl(NPPh₃)₂]⁺SeCl₃^? has been synthesized by the reaction of Se₂Cl₂ with Me₃SiNPPh₃ in acetonitrile solution, forming orangered crystals, whereas red crystals of [Me₃SiN(H)PMe₃]₂⁺[Se₂Cl₆]^2? were obtained by the reaction of Me₃SiNPMe₃ with SeOCl₂ in acetonitrile solution. Both complexes were characterized by X-ray structure determinations. [SeCl(NPPh₃)₂]⁺SeCl₃^?: Space group P2₁/n, Z = 4, structure solution with 7 489 observed unique reflections, R = 0.057. Lattice dimensions at ?60°C: a = 1 117.0; b = 2 241, c = 1 407.5 pm, β = 95.61°. In the cation [SeCl(NPPh₃)₂]⁺ the selenium atom is φ-tetrahedrally coordinated by the chlorine atom and by the nitrogen atoms of the phosphorane iminato ligands, whereas the anion SeCl₃^? has a T-shaped structure with φ-trigonal-bipyramidale surrounding of the selenium atom. [Me₃SiN(H)PMe₃]₂⁺[Se₂Cl₆]^2?: Space group P2₁/c, Z = 4, structure solution with 2 093 observed unique reflections, R = 0.080. Lattice dimensions at ?70°C: a = 956, b = 828, c = 1 973 pm, β = 93.80°. The structure consists of [Me₃SiN(H)PMe₃]⁺ ions and planar [Se₂Cl₆]^2? anions, in which the selenium atoms are bridged nearly symmetrically by two chlorine atoms.     

The Studies of the Heterogeneous Properties of Solid Surfaces by Means of the Derivatograph Q-1500 D

A simple method has been adopted to obtain an important information on the heterogeneous properties of materials studied, adsorbed liquid films and liquid-solid interactions. The method utilizes Q-TG mass loss and the first derivative Q-DTG mass loss curves with respect to temperature and time obtained during programmed liquid thermodesorption in quasi-isothermal conditions. The values of the adsorption capacity, total porosity of material, the value of active centers, desorption energy distribution and mesopore-size distribution functions obtained by this method are in good agreement with those estimated on the basis of independent methods. The theoretical and experimental results provided novel and unique data on the heterogeneity of solid surfaces, properties of liquid adsorbed films and thermal stability of the liquid/solid interfaces. This paper presents the more important results obtained so far in the studies the liquid/solid systems by means of the Paulik's classical and quasi-isothermal techniques. This revised version was published online in July 2006 with corrections to the Cover Date.     

腔长失调对光腔衰荡法测量精度的影响

 只考虑腔长失调因素下建立了反射率模拟测量的理论模型。根据高斯光束传输规律分析了腔长失调对衰荡腔模式耦合的影响，推导了腔长失调与谐振腔输出脉冲信号、衰荡信号与反射率之间的关系，模拟了腔长失调在±10mm范围内的光脉冲衰荡现象。结果表明：对于光敏面直径为0.2mm的高速探测器，为了保证10^-6的测量精度，腔长的失调量应控制在±1mm之间。在光路调节中采用具有对数变换功能的示波器和动态范围较大的探测器，可以提高测量精度。     

神光-Ⅱ装置三倍频实验中靶场单元技术的改进

 主要介绍为了满足神光-Ⅱ高功率激光装置三倍频光（351nm，3ω）的物理实验要求，靶场三倍频模拟光源和瞄准监视系统两个主要单元技术的改进，即三倍频模拟光源由基频光（1 053nm，3ω）通过腔外的KTP+BBO晶体倍频获得，再经八路分光系统和主激光耦合；瞄准监视系统由透射式光学系统改进为反射式光学系统，避免原系统存在较大的色差，提高瞄准精度。