REMGa3Ge and RE3Ni3Ga8Ge3 (M = Ni, Co; RE = rare-earth element): new intermetallics synthesized in liquid gallium. X-ray, electron, and neutron structure determination and magnetism

New quaternary intermetallic phases REMGa(3)Ge (1) (RE = Y, Sm, Tb, Gd, Er, Tm; M = Ni, Co) and RE(3)Ni(3)Ga(8)Ge(3) (2) (RE = Sm, Gd) were obtained from exploratory reactions involving rare-earth elements (RE), transition metal (M), Ge, and excess liquid Ga the reactive solvent. The crystal structures were solved with single-crystal X-ray and electron diffraction. The crystals of 1 and 2 are tetragonal. Single-crystal X-ray data: YNiGa(3)Ge, a = 4.1748(10) A, c = 23.710(8) A, V = 413.24(2) A(3), I4/mmm, Z = 4; Gd(3)Ni(3)Ga(8)Ge(3), a = 4.1809(18) A, c = 17.035(11) A, V = 297.8(3) A(3), P4/mmm, Z = 1. Both compounds feature square nets of Ga atoms. The distribution of Ga and Ge atoms in the REMGa(3)Ge was determined with neutron diffraction. The neutron experiments revealed that in 1 the Ge atoms are specifically located at the 4e crystallographic site, while Ga atoms are at 4d and 8g. The crystal structures of these compounds are related and could be derived from the consecutive stacking of disordered [MGa](2) puckered layers, monatomic RE-Ge planes and [MGa(4)Ge(2)] slabs. Complex superstructures with modulations occurring in the ab-plane and believed to be associated with the square nets of Ga atoms were found by electron diffraction. The magnetic measurements show antiferromagnetic ordering of the moments located on the RE atoms at low temperature, and Curie-Weiss behavior at higher temperatures with the values of mu(eff) close to those expected for RE(3+) free ions.     

Kinetics and mechanism of the wet oxidation of propene to acetone in the presence of Pd2+ ions and Mo-V-phosphoric heteropoly acids ?

Summary Oxidation of propene to acetone in water solutions in the presence of homogeneous catalysts (Pd²⁺ + HPA-x, where HPA-x = H_3+xPV_xMo_12-xO₄₀, x = 1-4) is studied. This reaction is shown to be of the 1st order with respect to C₃H₆ and of the 0.5th order with respect to Pd. The reaction rate does not depend on the concentration of HPA-x and acidity of the catalyst solution. The apparent activation energy of the reaction is 21 kJ/mol. A reaction mechanism is proposed.     

Solubility Behavior in Ternary Water-Salt Systems under Sub- and Supercritical Conditions

Summary.  Two main types of binary systems with distinctive solubility behavior under sub- and supercritical conditions were used to subdivide ternary water-salt systems into three classes. Characteristic features of solubility behavior and phase equilibria in ternary water-salt systems of each class at temperatures above 200°C are discussed on the basis of available experimental data and some conclusions obtained as a result of theoretical derivation of fluid and complete phase diagrams. Corresponding author. E-mail: Valyashko@IGIC.RAS.RU Received September 25, 2002; accepted (revised) November 28, 2002 Published online April 24, 2003 RID="a" ID="a" Dedicated to Prof. Dr. H. Gamsjaeger on the occasion of his 70^th birthday anniversary     

Hexaaquacobalt(II) bis(hypophosphite) and hexaaquacobalt(II)/nickel(II) bis(hypophosphite)

The title compounds, hexa­aqua­cobalt(II) bis­(hypophosphite), [Co(H₂O)₆](H₂­PO₂)₂, and hexa­aqua­cobalt(II)/nickel(II) bis(hypophosphite), [Co_0.5Ni_0.5(H₂O)₆](H₂PO₂)₂, are shown to adopt the same structure as hexa­aqua­magnesium(II) bis­(hypophosphite). The packing of the Co(Ni) and P atoms is the same as in the structure of CaF₂. The Co^II(Ni^II) atoms have a pseudo‐face‐centred cubic cell, with a = b～ 10.3 Å, and the P atoms occupy the tetrahedral cavities. The central metal cation has a slightly distorted octahedral coordination sphere. The geometry of the hypophosphite anion in the structure is very close to ideal, with point symmetry mm2. Each O atom of the hypophosphite anion is hydrogen bonded to three water mol­ecules from different cation complexes, and each H atom of the hypophosphite anion is surrounded by three water mol­ecules from further different cation complexes.     

Sulfonated and sulfoacylated poly(styrene-divinylbenzene) copolymers as packing materials for cation chromatography

Three different types of cation exchangers were produced from four basic poly(styrene-divinylbenzene) substrates with different properties. Porous PS-DVB resin beads were functionalized by sulfonation and sulfoacylation under various conditions to produce sulfonated resins with exchange capacities of 0.03-1.80 mM g(-1). The matrix with 50% of cross-linking is most suitable for updating by the proposed technique. Sulfuric and chlorosulfonic acids were used as the reagents for sulfonation. The sulfonating conditions, capacities, and the technique of the synthesis are given. The effects of parameters of the sulfonation reaction and the composition of the reactionary mixture on ion-exchange capacity of the sorbents were investigated. Selectivity and efficiency of the separation of some inorganic cations and derivatives of amines and hydrazines on the resins obtained are compared by ion chromatography with conductometric detection. As a result, the sulfoacylated resin was proved more efficient for the separation of these analytes. The resolution of the analytes strongly depends on the degree of functionalization. The best performance about 19,000 plates m(-1) was obtained using the sulfopropionylated beads with an ion-exchange capacity of 0.3 mM g(-1). The prepared sulfoacylated cation exchanger was compared with the commercially available Dionex CS-12 packing material. It was found that the separation of alkaline ions and 1,1-dimethylhydrazine (UDMH) were much better that those for the commercial material.     

Kinetics of swelling of polyether-modified poly(acrylic acid) microgels with permanent and degradable cross-links

Spherical particles of 50-100 mum size composed of poly(acrylic acid) networks covalently bonded to Pluronic polyether copolymers were tested for swelling in aqueous media. The microgels were cross-linked either by permanent ethylene glycol dimethacrylate (EGDMA) cross-links alone or by EDGMA together with reversible disulfide or biodegradable azoaromatic cross-links. Optimum conditions for a rapid, diffusion-limited swelling of the pH- and temperature-sensitive microgels with nondegradable cross-links were found. The microgels cross-linked by disulfide groups and equilibrium-swollen in the buffer solution exhibited degradation-limited kinetics of swelling under physiological conditions, with a first-order reaction constant, k(1), linearly proportional to the concentration of reducing agents such as dithiotreitol and tris(2-carboxyethyl)phosphine (TCEP). A severalfold faster swelling in the presence of more powerful reducing agent, TCEP, was observed, indicating the chemical specificity of the microgel swelling. The reoxidation of the thiol groups into disulfide cross-links by sodium hypochlorite led to the restoration of the microgels' diameter measured prior to the reduction-reoxidation cycle, which confirms the shape memory of the microgels. Enzymatically degradable azoaromatic cross-links enabled slow microgel swelling due to degradation of the cross-links by azoreductases from the rat intestinal cecum. The low rate of swelling of the Pluronic-containing microgels can enable sustained drug release in colon-specific drug delivery.     

Spectroscopic characterization of human and mouse primary cells,cell lines and malignant cells

Fourier transform infrared (FTIR) spectroscopy is currently being developed as a new optical approach to the diagnosis and characterization of cell or tissue pathology. The advantage of FTIR microspectroscopy over conventional FTIR spectroscopy in the diagnosis of malignancies is that it facilitates inspection of restricted regions of the cell culture or tissue. In this study, we set out to evaluate FTIR microspectroscopy as a diagnostic tool for identifying retrovirus-induced malignancies. Our study showed significant and consistent differences between cultures of different types of cells of both mouse and human origin, i.e. primary fibroblast cells (one to two passages in cell culture), fibroblast cell lines and malignant cells transformed by murine sarcoma virus. An impressive decrease in the levels of phosphate and other metabolites was seen in malignant cells compared with primary cells. The levels of these metabolites in the cell lines were significantly lower than in the primary cells but higher than in the malignant cells. In addition, the peak attributed to the PO2- symmetric stretching mode at 1082 cm(-1) in primary cells shifted significantly to 1085 cm(-1) for the cell line and to 1087 cm(-1) for the malignant cells. These differences taken together with differences in the shapes of various bands throughout the spectrum strongly support the possibility of developing FTIR microspectroscopy for the detection and study of malignant--and possibly premalignant--cells.     

Factor probabilistic distance clustering (FPDC): a new clustering method

Factor clustering methods have been developed in recent years thanks to improvements in computational power. These methods perform a linear transformation of data and a clustering of the transformed data, optimizing a common criterion. Probabilistic distance (PD)-clustering is an iterative, distribution free, probabilistic clustering method. Factor PD-clustering (FPDC) is based on PD-clustering and involves a linear transformation of the original variables into a reduced number of orthogonal ones using a common criterion with PD-clustering. This paper demonstrates that Tucker3 decomposition can be used to accomplish this transformation. Factor PD-clustering alternatingly exploits Tucker3 decomposition and PD-clustering on transformed data until convergence is achieved. This method can significantly improve the PD-clustering algorithm performance; large data sets can thus be partitioned into clusters with increasing stability and robustness of the results. Real and simulated data sets are used to compare FPDC with its main competitors, where it performs equally well when clusters are elliptically shaped but outperforms its competitors with non-Gaussian shaped clusters or noisy data.