Nitrosyl Rhenium Complexes: Thiocyanato Derivatives

Fusion of K₂[Re(NO)Cl₅] with KSCN produces the ion [Re(NO)(SCN)₅]^2? which has been isolated as free acid and K⁺, Na⁺, NMe₄⁺, Pb²⁺, Hg²⁺, phen H⁺ and dipyH⁺ salts. A salt of composition Hg₂[Re(NO)(SCN)₇] has also been prepared. The species [Re(NO)Cl(SCN)₄]^2? has been obtained from the reaction of H₂[Re(NO)(SCN)₅] with HCl in aqueous medium and its NMe₄⁺ salt has been isolated. Hydrated Re(NO)Cl₃ reacts with KSCN in aqueous medium to produce the ion [Re(NO)Cl₂(SCN)₃]^2? which has been isolated as its phenH⁺ and dipyH⁺ salts. The complexes have been characterized through elemental analyses, spectral (u.v., vis., i.r.) properties, magnetic and conductance data. The structures of all those compounds have been proposed.     

On a theorem of Scott and Swarup

Let be an exact sequence of hyperbolic groups induced by an automorphism of the free group . Let be a finitely generated distorted subgroup of . Then there exist and a free factor of such that the conjugacy class of is preserved by and contains a finite index subgroup of a conjugate of . This is an analog of a theorem of Scott and Swarup for surfaces in hyperbolic 3-manifolds.

     

Interaction of bacterial acidic polysaccharide with cationic dyes

The interaction of acidic capsular polysaccharide isolated fromKlebsiella K26 with cationic dyes pinacyanol chloride, acridine orange and phenosafranin has been studied by spectral measurements. The polymer induces metachromasy in pinacyanol chloride dye, indicating a blue shift in the visibly absorption spectrum of the dye from 600 to 500 nm. The stoichiometry of polymer/dye in the metachromatic compound, thermodynamic parameters of interaction, and effects of different cosolvents on the stability of the complex have been studied. Spectrophotometric and spectrofluorometric properties of the interaction between the polymer and all three dyes are presented. The chromotropic property of the polymer has been established.     

Synthesis, spectroscopic, and structural aspects of two trinuclear cyano-bridged heterometallic complexes

Two new cyano-bridged trinuclear heterometallic complexes [Sr₂(Phen)₄(CF₃CO₂)(H₂O)₃Fe(CN)₆]·2H₂O (1) [Ca₂(Phen)₄(CF₃CO₂)(H₂O)Co(CN)₆]·2H₂O (2) (where Phen=1,10-phenanthroline) have been synthesized and their crystal structures have been determined. The structure of complex (1) features a central [Fe(CN)₆]³⁻ unit that links a monocation, [Sr(Phen)₂(OH₂)(OOCCF₃)]⁺ and a dication, [Sr(Phen)₂(OH₂)₂]²⁺ via two trans cyanide bridges. The complex (2) features a central [Co(CN)₆]³⁻ unit that links two monocations of [Ca(Phen)₂(OH₂)(OOCCF₃)]⁺ (the positions of the trifluoro acetate and water molecules are disordered over two positions) via two trans cyanide bridges. Each metal atom is seven coordinated and achieves pentagonal bipyramidal geometry. Two cocrystallized water molecules are present in both the complexes. The presence of an extensive network of hydrogen bonding imparts the overall stability to both the systems.     

A PM3 study of the critical distance factor in the activation/cyclization of selected Neocarzinostatin analogs

Semiempirical MOPAC RHF/PM 3 and BIRADICAL/PM 3 calculations are performed on several selected analogs of the Neocarzinostatin chromophore. The critical distance parameter, heat of formation, and pertinent bond orders are reported for each model compound. Heats of reaction are also reported for the cyclization of several model compounds to their corresponding diradical products. It is suggested that 3.49 ÅR represents an upper bound to the critical distance in the cyclization of compound related to Neocarzinostatin chromophore. © 1994 John Wiley & Sons, Inc.     

Studies on ZnS Nanoparticles Prepared in Aqueous Sodium Dodecylsulphate (SDS) Micellar Medium

ZnS, a large band gap material, is useful in electro-luminescence and optoelectronic devices. We herein report a method for preparation of nanosized ZnS particles in micellar medium of anionic surfactant sodium dodecylsulphate. The optical properties of the prepared ZnS nanoparticles have been studied by absorption and fluorescence methods. Electron microscopic characterization has evidenced triangular particles, an uncommon observation in the synthesis of nanomaterials. PVC membrane containing nano ZnS dispersions has been prepared and its response as Zn²⁺ ion-selective membrane has been reported.__________From Kolloidnyi Zhurnal, Vol. 67, No. 4, 2005, pp. 494–499.Original English Text Copyright © 2005 by Debolina Mitra, Indranil Chakraborty, Satya P. Moulik.The text was submitted by the authors in English.     

Wärmeübertragung durch freie Konvektion an waagerechten,zylindrischen Rohren bei konzentrischer und exzentrischer Anordnung in einem zylindrischen Behälter

Zusammenfassung Die vorliegende Arbeit beschäftigt sich mit experimentellen Untersuchungen zur Wärmeübertragung durch freie Konvektion an waagerechten, zylindrischen Rohren in zylindrischen Behältern. Die Messungen wurden bei einem Durchmesserverh ältnis D_a/D_i=11,4 sowohl bei konzentrischer als auch bei exzentrischer Anordnung von Innen- und Außenzylinder durchgeführt. Als Wärmeübertragungsmedium diente Wasser. Die Ergebnisse bei konzentrischer Anordnung wurden mit folgenden physikalischen Modellen verglichen: a) freie Konvektion um den Einzelzylinder im unendlichen Medium, b) freie Konvektion in zylindrischen Schichten. Der Vergleich mit vorhandenen Korrelationsgleichungen zu beiden Fällen zeigte, daß der Wärmeübergang dem Fall b) zugeordnet werden muß. Dies wurde durch die Ergebnisse bei exzentrischer Anordnung bestätigt. Es zeigte sich, daß die geometrische Anordnung von Innen- und Außenzylinder einen wesentlichen Einfluß auf die Wärmeübertragung und das Strömungsverhalten hat.

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Heat transfer by free convection from a horizontal tube in concentric and eccentric cylindrical annulus

Heat transfer by free convection from a horizontal cylindrical tube in a cylindrical water filled annulus was measured for concentric and eccentric configurations. The ratio of the diameters of the annulus and the tube is 11.4. Comparisons with available correlation equations show that even for concentric configuration, the heat transfer problem can not be analysed as that in an infinite medium. For the eccentric configuration, the location and eccentricity influence strongly the heat transfer.

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Bezeichungen c_p spez. Wärmekapazität bei konstantem Druck - D Durchmesser - g Fallbeschleunigung - Gr Grashofzahl, Gl. (9) - l charakteristische Länge - L Rohrlänge - m Massenstrom - Nu Nusseltzahl, Gl. (2) - Pr Prandtlzahl, Gl. (8) - Wärmestrom - r Radius - Ra Rayleighzahl,Pr·Gr - s Schichtdicke, r_a r_i - T Temperatur - V Volumenstrom - Differenz - Exzentrizität (Verschiebung des Innenzylinders aus der konzentrischen Position) - dynamische Viskosität - v kinematische Viskosität - Wärmeleitfähigkeit - Dichte - Neigungswinkel von der Vertikalen Indizes a Innenwand des äußeren Zylinders - i Außenwand des inneren Zylinders - E Rohreintritt - A Rohraustritt - m mittel - s Wert bezogen auf Schichtdicke - D Wert bezogen auf Durchmesser - kr kritisch - L Wärmeleitung     

Phase transformation studies on Mn−Al−C alloy,by DSC and electrical resistivity measurements

Phase transformation studies carried out on Mn?Al?C permanent magnet alloy employing DSC and electrical resistivity measurements, are reported and discussed. The transformation of the hexagonal Mn?Al phase (disordered and non-magnetic) to the ferromagnetic fct phase proceeds via the formation, in at least two stages, of the ordered orthorhombic phase. The activation energy for the formation of the fct phase is ≈34.65 kcal/mol. Microstructural changes occurring at various stages of the transformation are also studied.     

High-performance catalytic chromatography. The adapter approach

A sequence-specific DNA that binds EcoRI endonuclease was immobilized on glycidioloxypropyl-silica and Sepharose by cyanogen bromide (CNBr)-activated coupling. Elution of bound enzyme by conventional affinity strategies (increase of salt concentration) or by catalysis-induced elution (adding a Mg2+ cofactor required for catalysis) was compared. Greater yield and fold-purification was obtained with catalysis-induced elution for both DNA-silica and DNA-Sepharose columns, and silica gives higher performance than Sepharose. Sodium dodecylsulfate polyacrylamide gel electrophoresis showed primarily a single band for EcoRI endonuclease for catalysis-induced elution from DNA-silica columns. Since catalysis-induced elution decreases the lifetime of DNA affinity columns, an alternative approach for preparing re-usable DNA columns was also developed. In this approach, a single stranded adapter DNA sequence is first coupled to silica or Sepharose and then annealed with another DNA sequence that contains a complementary, single stranded tail and the duplex binding site for EcoRI endonuclease. After use, replacing the hydrolyzed DNA regenerates the column. For this adapter approach, Sepharose gives better purity than silica and comparable yields and catalytic based elution gave the highest purity and yield, regardless of support. Substrate DNA with either a tail (for annealing to the column) at one end or both ends were compared and the former gave higher purity. Finally, enzyme binding to the substrate in solution ("trapping") or on a pre-bound substrate column was compared and trapping gave higher yield and similar purity to the alternative. Thus, trapping with a single tailed substrate oligonucleotide on a Sepharose adapter column and using catalytic elution gave the highest performance.     

Synthesis,Characterization and Molecular Structure of a New Tetrameric Palladium(II) Complex Containing Schiff‐Bases Derived from AMTTO (AMTTO = 4‐amino‐6‐methyl‐1,2,4‐triazine‐thione‐5‐one)

The reactions of AMTTO = 4‐amino‐6‐methyl‐1,2,4‐triazine‐thione‐5‐one (AMTTO, 1 ) with 2‐hydroxybenzaldehyde (salicylaldehyde) and 4‐hydroxybenzaldehyde in methanol under reflux conditions led to the corresponding Schiff‐bases ( H₂L1 and H₂L2 ). The reaction of H₂L1 with palladium acetate in ethanol and additional recrystallization from toluene gave the tetrameric complex [Pd(L)]₄·2C₇H₈ ( 2 ). All compounds were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for H₂L1 at ?80 °C: space group P2₁/c with a = 1285.4(1), b = 707.7(1), c = 1348.2(1) pm, β = 109.32(1)°, Z = 4, R₁ = 0.0328, H₂L2 at ?80 °C: space group P4₃2₁2 with a = 762.5(1), b = 762.5(1), c = 4038.9(2) pm, Z = 8, R₁ = 0.025 and for 2 at ?103 °C: space group C2/c with a = 2862.5(6), b = 2847.6(6), c = 1727.8(4) pm, β = 105.18(3)°, Z = 8, R₁ = 0.0704.