Effect of thermo‐solutal stratification on recirculation flow patterns in a backward‐facing step channel flow

This paper presents results on the combined effect of thermo‐solutal buoyancy forces on the recirculatory flow behavior in a horizontal channel with backward‐facing step and the ensuing impact on heat and mass transfer phenomena. The governing equations for double diffusive mixed convection are represented in velocity–vorticity form of momentum equations, velocity Poisson equations, energy and concentration equations. Galerkin's finite‐element method has been employed to solve the governing equations. Recirculatory flow fields with heat and mass transfer are simulated for opposing and aiding thermo‐solutal buoyancy forces by assuming suitable boundary conditions for energy and concentration equations. The effect of Richardson number (0.1?Ri?10) and buoyancy ratio (?10?N?10) on the recirculation bubble and Nusselt and Sherwood numbers are studied in detail. For Richardson number greater than unity, distinct variations in the gradients of Nusselt number and Sherwood number with buoyancy ratio are observed for flow regimes with opposing and aiding buoyancy forces. Copyright © 2009 John Wiley & Sons, Ltd.     

FTIR study of 11 interacting vibrational states of CH2DI

Rotational level structure of 12 vibrational states of CH₂DI with energies in the 1000-1800 cm⁻¹ region has been retrieved from high resolution (0.001-0.003 cm⁻¹) FTIR spectra. Eleven vibrational states, namely, 2¹, 3¹6¹(A′), 5¹(A′′), 3¹6¹(A′′), 6²(A′), 5¹(A′), 6¹(A′) 6¹(A′′), 2¹3¹, 6²(A′′), 3²6¹(A′) and 3¹5¹(A′′) have been found to interact. A total of 27 919 transitions belonging to diverse fundamental, combination and hot bands were assigned and used in the combined nonlinear root mean square fit to give the band centers, rotational, centrifugal distortion and coupling parameters of the states under investigation. The RMS deviation of the fit has been demonstrated to be 0.000218 cm⁻¹. The number of the coupling parameters required to reproduce the observed spectra with the experimental uncertainty appeared to be 46.     

Graph-theoretic conditions for injectivity of functions on rectangular domains

This paper presents sufficient graph-theoretic conditions for injectivity of collections of differentiable functions on rectangular subsets of Rn. The results have implications for the possibility of multiple fixed points of maps and flows. Well-known results on systems with signed Jacobians are shown to be easy corollaries of more general results presented here.     

Fluorimetric study of interaction of benzidine with trypsin

The interaction of benzidine (BEN) with trypsin was studied by fluorescence spectrum. It was shown that BEN has quenched the fluorescence launching from trypsin by reacting with it and forming a certain kind of new complex. The quenching and energy transfer mechanisms were discussed. The binding constants and thermodynamic parameters at three different temperatures, the binding locality, and the binding power were obtained. The conformation of trypsin was discussed by synchronous and three-dimensional fluorescence techniques.     

Volumetric and Viscometric Properties of Aqueous Solutions of N-Methylformamide, 1,2-Diaminopropane and 2-Methylpropane-2-ol

Density and viscosity of aqueous solutions of N-methylformamide (NMF), 1,2-diaminopropane (DAP) and 2-methylpropane-2-ol (MPL) have been measured precisely over the entire composition range (i.e., 1 ≥ x ₂ ≥ 0) at five equidistant temperatures ranging from 298.15 to 318.15 K. Excess molar volume (V^E _m ) and excess viscosity (η ^E ) have been calculated from measured density and viscosity data, respectively. Excess molar volume and excess viscosity have been fitted by the least squares method to the four parameters Redlich-Kister equation. The results have been interpreted on the basis of (i) interstitial incorporation, (ii) breakdown of the structure of pure liquids, (iii) hydrophobic hydration, (iv) hydrophobic interaction and (v) association between dissimilar liquids.     

Syntheses,structures, and properties of transition metal complexes with 2-( n -pyridyl)benzimidazole ( n = 2, 3, and 4)

Three pyridylbenzimidazoles (2-PBIM, 3-PBIM, and 4-PBIM) have been prepared (2-PBIM: 2-(2-pyridyl)-benzimidazole, 3-PBIM: 2-(3-pyridyl)-benzimidazole, 4-PBIM: 2-(4-pyridyl)-benzimidazole). Reactions of several transition metals (Cd²⁺, Cu²⁺, Fe²⁺) with the three ligands gave four new coordination complexes, [(Cd)₂(2-PBIM)₂(CH₃COO)₄] (1), [Cu(3-PBIM)₂(CH₃COO)₂]?·?2H₂O (2), [Cu(4-PBIM)₂(CH₃COO)₂(H₂O)]?·?H₂O (3), and [Fe(4-PBIM)₂(Cl)₂(H₂O)₂] (4), respectively. These four complexes have been characterized by X-ray crystallography, IR spectroscopy, and UV absorption spectroscopy. Thermogravimetric properties of 2 and 4 were also measured. X-ray crystallographic studies reveal that these four complexes are very different, although the ligands are similar in structure. The role of hydrogen-bonding and π–π interactions in extending dimensionality of simple complexes has been discussed.     

Crystal structure,interaction with DNA,and bovine serum albumin of the cobalt(II) complex of demethylcantharate and 2,2′-bipyridine

A new cobalt(II) complex [Co(DCA)(bipy)(H₂O)] (DCA?=?demethylcantharate, 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylate, C₈H₈O₅; bipy?=?2,2′-bipyridine, C₁₀H₈N₂) was synthesized from cobalt acetate, demethylcantharidin, and bipy. This complex was characterized by elemental analysis, molar conductance, infrared spectra, and X-ray single-crystal diffraction. It crystallized in orthorhombic crystal system and Pbca space group. The DNA binding of the complex was investigated by electronic absorption spectra and viscosity measurements. The complex binds to DNA via partial intercalation with binding constant K _b of 4.02?×?10⁴?L?M^?1. The complex could quench the intrinsic fluorescence of bovine serum albumin through static quenching. The binding constant K _A was 7.28?×?10⁶?L?M^?1 and binding site was one.     

Ruthenium(II) complexes of pyrrol-azo ligands: cytotoxicity,interaction with calf thymus DNA and bovine serum albumin

Two ruthenium(II) complexes of newly designed pyrrol-azo ligands(L) and bipyridine(bpy) formulated as [Ru(L)(bpy)₂]ClO₄, where HL^1?=?(4-chloro-phenyl)-(1H-pyrrol-2-yl)-diazene (1) complex 1 and HL^2?=?(4-nitro-phenyl)-(1H-pyrrol-2-yl)-diazene for 2, were isolated in pure form. The complexes were characterized by physicochemical and spectroscopic methods. The electrochemical behavior of the complexes showed the Ru(III)/Ru(II) couple at different potentials with quasi-reversible voltammograms. The study of cytotoxicity effects of 1 and 2 on human breast cancer cells (MCF 7, MDA-MB 231) and cervical cancer cell (HeLa) taking Cisplatin as a positive reference showed that 1 exhibited higher cytotoxicity against cancer cell lines than 2, but less activity than Cisplatin. The interaction of 1 with calf thymus DNA (CT-DNA) using absorption, emission spectral studies, viscosity-measurement, and electrochemical techniques has been used to determine the binding constant K _b and the linear Stern–Volmer quenching constant K _SV. The results indicate that 1 strongly interacts with CT-DNA in groove binding mode. The interaction of bovine serum albumin (BSA) with 1 was also investigated with the help of spectroscopic tools. Absorption spectroscopy proved the formation of a BSA-[Ru(L¹)(bpy)₂]ClO₄ complex.