Mixed ligand cobalt(III) complexes of tetradentate N,N′-ethylenebis(acetylacetonimine) and flexidentate isonitroso-β-diketones and isonitrosomonoketones

A series of mixed ligand cobalt(III) complexes having the general formula Co(EA)X [where EA = dianion of N,N′-ethylenebis(acetylacetonimine) and X = anion of isonitroso-acetylacetone, IAA; isonitrosobenzoylacetone, IBA; isonitrosodibenzoylmethane, IDBM; isonitrosoethylacetoacetate, IEA; isonitrosoacetoacetanillide, IAN; isonitrosoethylmethylketone, IEMK; isonitrosobenzylmethylketone, IBMK and isonitrosopropiophenone, IPP] have been synthesised and characterised. A facial-cis-β structure (cis with respect to the coordinated two oxygen atoms of EA) with N,N,N,O,O,O ligational environment has been assigned for the complexes. The characterisation of the complexes has been based upon chemical analysis, electrical conductivity, magnetic moment, IR, PMR and electronic spectra.

Nonsimilar boundary layers for non-Darcy mixed convection flow about a horizontal surface in a saturated porous medium

The nonsimilar non-Darcy mixed convection flow about a heated horizontal surface in a saturated porous medium has been studied when the surface temperature is a power function of distance (Tw = T∞ ± Axλ). The analysis is performed for the cases of parallel and stagnation flows with favourable induced pressure gradient. The partial differential equations governing the flow have been solved numerically using the Keller box method. The heat transfer is enhanced due to the buoyancy parameter and wall temperature, but the non-Darcy parameter reduces it. For non-Darcy flow, the similarity solution exists only for the case of parallel flow.

Molecular Mechanics Studies of Homopolymeric and Mixed Sequence Py.Pu*Pu Triple Helices,

DNA triple helices containing two purine strands and one pyrimidine strand (C.G*G and T.A*A) have been studied, using model building followed by energy minimisation, for different orientations of the third strand resulting from variation in the hydrogen bonding between the Watson-Crick duplex and the third strand and the glycosidic torsion angle in the third strand. Our results show that in the C.G*G case the structure with a parallel orientation of the third strand, resulting from Hoogsteen hydrogen bonds between the third strand and the Watson-Crick duplex, is energetically the most favourable while in the T.A*A case the antiparallel orientation of the third strand, resulting from reverse Hoogsteen hydrogen bonds, is energetically the most favourable. These studies when extended to the mixed sequence triplexes, in which the second strand is a mixture of G and A, correspondingly the third strand is a mixture of G and APT, show that though the parallel orientation is still energetically more favourable, the antiparallel orientation becomes energetically comparable with an increasing number of thymines in the third strand. Structurally, for the mixed triplexes containing G and T in the third strand, it is seen that the basepair non-isomorphism between the C.G*G and the T.A*T triplets can be overcome with some changes in the base pair parameters without much distortion of either the backbone or the hydrogen bonds.

A Convenient High-Yield Room-Temerature Synthesis of Mixed Tri(Amino) Silanes by Transmination of Tris(Dicyclohexylamino) Silane And-Their Characterization

Tris(dicyclohexylamino)silane. (DCA)3SiH. is prepared by the reaction of trichlorosilane with dicyclohexylamine. This is found to undergo transamination reactions with other secondary amines (R2NH). such as pyrrolidine, piperidine, hexamethyleneimine. morpholine. N-methylpiperazine and diethylamine to yield mixed tri(amino)silanes of the formula (DCA)(R2N)2SiH in quantitative yields. These new derivatives are found to be moisture sensitive and hydrolyze to yield their respective amines, hydrogen and silica. They are found to be stable in an inert atmosphere. They have been characterized by IR, NMR (H-1, Si-29), mass spectroscopy and CHN analysis. N-15 NMR for one of the compounds has been done.

Fe-57 Mössbauer and Mo K-EXAFS Investigations of MoxFe3-xO4, an Interesting Mixed-Valent Oxide System

Ferrites of the formula MoxFe3-xO4, prepared by a soft-chemistry route, show mixed valence states of both iron and molybdenum cations. Mössbauer studies show that Fe2+ and Fe3+ ions are present on both the A and B sites, giving Fe an average oxidation state between 2+ and 3+. Molybdenum is present in the 3+ and the 4+ states on the B sites. The presence of Mo in the 3+ state has been established by determining the Mo3+-O distance (2.2 Å), for the first time, by Mo K-EXAFS. The mixed valence of Fe on both the A and B sites and of Mo on the B sites is responsible for the fast electron transfer between the cations. All the Mössbauer parameters including the line width show a marked change at a composition (x ? 0.3) above which the concentration of Fe2+A increases rapidly.

Non-Darcy mixed convection flow with thermal dispersion on a vertical cylinder in a saturated porous medium

The non-Darcy mixed convection flow on a vertical cylinder embedded in a saturated porous medium has been studied taking into account the effect of thermal dispersion. Both forced flow and buoyancy force dominated cases with constant wall temperature condition have been considered. The governing partial differential equations have been solved numerically using the Keller box method. The results are presented for the buoyancy parameter which cover the entire regime of mixed convection flow ranging from pure forced convection to pure free convection. The effect of thermal dispersion is found to be more pronounced on the heat transfer than on the skin friction and it enhances the heat transfer but reduces the skin friction.

Reduction behaviour of Fe3+/Al2O3 obtained from the mixed oxalate precursor and the formation of the Fe0-Al2O3 metal-ceramic composite

Reduction behaviour of Fe3+/Al2O3 obtained by the decomposition of the oxalate precursor has been investigated by employing X-ray diffraction (XRD), Mössbauer spectroscopy and electron paramagnetic resonance (EPR) spectroscopy. Calcination of Fe3+/Al2O3 at or below 1070 K yields mainly a poorly ordered, fine particulate form of ?-Al2�xFexO3. Calcination at or above 1220 K yields ?-Al2�xFexO3. Reduction of Fe3+/Al2O3 samples calcined at or below 1070 K gives the FeAl2O4 spinel on reduction at 870 K; samples calcined at or above 1220 K give Al2-xFexO3 with a very small proportion of metallic iron. Fe3+/Al2O3 samples calcined at 1220 K or above yield metallic iron and a very small proportion of the spinel on reduction below 1270 K. In the samples reduced at or above 1270 K, the main product is metallic iron in both ferromagnetic and superparamagnetic forms. The oxalate precursor route yields more metallic iron than the sol�gel route.

Simultaneous heat and mass transfer under unsteady mixed convection along a vertical slender cylinder embedded in a porous medium

Unsteady laminar mixed convection flow (combined free and forced convection flow) along a vertical slender cylinder embedded in a porous medium under the combined buoyancy effect of thermal and species diffusion has been studied. The effect of the permeability of the medium as well as the magnetic field has been included in the analysis. The partial differential equations with three independent variables governing the flow have been solved numerically using a implicit finite difference scheme in combination with the quasilinearization technique. Computations have been carried out for accelerating, decelerating and oscillatory free stream velocity distributions. The effects of the permeability of the medium, buoyancy forces, transverse curvature and magnetic field on skin friction, heat transfer and mass transfer have been studied. It is found that the effect of free stream velocity distribution is more pronounced on the skin friction than on the heat and mass transfer. The permeability and magnetic parameters increase the skin friction, but reduce the heat and mass transfer. The skin friction, heat transfer and mass transfer are enhanced due to the buoyancy forces and curvature parameter. The heat transfer is strongly dependent on the viscous dissipation parameter and the Prandtl number, and the mass transfer on the Schmidt number. Untersucht wurde die instationäre laminare Mischkonvektion längs eines vertikalen, in einem porösen Medium eingebetteten Zylinders unter kombinierten Auftriebseffekten von thermischer und spezieller Diffusion. Der Einfluß der Permeabilität des Mediums sowie des magnetischen Feldes wurden in die Betrachtung einbezogen. Die partiellen Differentialgleichungen mit drei unabhängigen Variablen, welche die Strömung beschreiben, wurde numerisch anhand des Schemas der endlichen Differenzen in Verbindung mit der Technik der Quasilinearisation gelöst. Berechnungen für die beschleunigte, verzögerte und oszillierende Geschwindigkeitsverteilung der freien Strömung sind durchgeführt worden. Untersucht wurden ebenfalls die Effekte der Permeabilität des Mediums, der Auftriebskräfte, der transversalen Krümmung, des magnetischen Feldes auf die Oberflächenreibung sowie die Wärmeund Stoffübertragung. Es wurde festgestellt, daß die Geschwindigkeit mehr Einfluß auf die Oberflächenreibung als auf die Wärmeund Stoffübertragung hat. Die Oberflächenreibung sowie die Wärme- und Stoffübertragung werden durch die Auftriebskräfte und die Krümmungsparameter verbessert. Die Wärmeübertragung ist stark abhängig von den Parametern der viskosen Dissipation und der Prandtl-Zahl; die Stoffübertragung von der Schmidt-Zahl.

Thermodynamic Study of Mixed Anionic Solid Solutions Using Gradient Solid Electrolytes System K2CO3 - K2SO4

The thermodynamic properties of K2CO3 -KSO, solid solutions with hexagonal structure have been measured using a solid-state cell, incorporating a composite solid electrolyte with step-changes in composition. The cell with the configuration Pt, CO2' + O2' || K2CO3 | K2(CO3)x(SO4)1-x || CO2'' + O2'' + Pt X =1 X=X was investigated in the temperature range of 925 to 1165 K. The composite gradient solid electrolyte consisted of pure K2CO3 at one extremity and the solid solution under study at the other. The Nernstian response of the cell to changes in partial pressures of CO2 and O2 at the electrodes and temperature was demonstrated. The activity of K2CO3 in the solid solution was measured by three techniques. All three methods gave identical results, indicating unit transport number for K+ ions and negligible diffusion potential due to concentration gradients of carbonate and sulfate ions. The activity of K2CO3 exhibits positive deviation from Raoult's law. The excess Gibbs energy of mixing of the solid solution can be represented using a subregular solution model DELTAG(E) = X(1 - X)[5030X + 4715(1 - X)] J mol-1 By combining this information with the phase diagram, mixing properties of the liquid phase were obtained.