Inflationary Brans-Dicke universe andG

In a recent paper, Mathiazhagan and Johri reduced the field equations for an isotropic, homogeneous, and almost flat universe with a constant vacuum-energy density by Brans-Dicke theory to a pair of coupled differential equations. They also obtained a particular solution of these equations. Further, they used this particular solution of the equations to estimate the value of the gravitational constant. Here we obtain the complete set of solutions of the above-mentioned coupled differential equations and improved the estimate of Mathiazhagan and Johri of the gravitational constant.     

Chemistry of a family of semiquinone monochelates of carbonyl ruthenium(II) generated by reacting quinones with hydridic species

The reactions of [Ru(H)(Cl)(CO)(PPh₃)₃] with 3,5-di-tert-butyl-o-benzoquinone (dbq) and 3,4,5,6-tetrachloro-o-benzoquinone (tcq) have afforded the corresponding semiquinone complexes [Ru^II(dbsq)(Cl)(CO)(PPh₃)₂] and [Ru^II(tcsq)(Cl)(CO)(PPh₃)₂], respectively. The reaction of [Ru(H)₂(CO)(PPh₃)₃] with tcq has furnished [Ru^II(tcsq)(H)(CO)(PPh₃)₂]. Structure determination of [Ru(dbsq)(Cl)(CO)(PPh₃)₂] has revealed that it is a model semiquinonoid chelate with two equal C---O lengths ( 1.291(6) and 1.296(6) Å). The complexes are one-electron paramagnetic (1.85μ_B) and their EPR spectra in fluid media display a triplet structure (g2.00) due to superhyperfine coupling with two trans-³¹P atoms (A_iso17 G). The stretching frequency of the CO ligand increases by 20 cm⁻¹ in going from [Ru(dbsq)(Cl)(CO)(PPh₃)₂] to [Ru(tcsq)(Cl)(CO)(PPh₃)₂] consistent with electron withdrawal by chloro substituents. For the same reason the E_1/2 values of the cyclic voltammetric quinone/semiquinone and semiquinone/catechol couples undergo a shift of 500 mV to higher potentials between [Ru(dbsq)(Cl)(CO)(PPh₃)₂] and [Ru(tcsq)(Cl)(CO)(PPh₃)₂].     

Chemistry of metal-bound anion radicals. A family of mono- and bis(azopyridine) chelates of bivalent ruthenium

The reaction of the dihydride [RuII(H)2(CO)(PPh3)3], 3, with excess azo-2,2'-bipyridine (abp) in boiling dry benzene has afforded the diradical bischelate [RuII(abp.-)2(CO)(PPh3)], 4, and the hydridic monochelate monoradical [RuII(abp.-)(H)(CO)(PPh3)2], 5. A similar reaction between 3 and 2-(p-chlorophenylazo)pyridine (Clpap) did not yield a bischelate, but the hydridic monoradical [RuII(Clpap.-)(H)(CO)(PPh3)2], 6, has been isolated. Upon treatment of 4-6 with NH4PF6 in a wet dichloromethane-acetonitrile medium, the one-electron-oxidized salts 4+PF6-, 5+PF6-, and 6+PF6- are isolated, H+ being the oxidizing agent. The X-ray structures of 4+PF6-.CH2Cl2, 5+PF6-.H2O, and 6+PF6- have been determined. In the monoradical 4+ the azo N-N bond lengths in the two chelate rings are 1.284(6) and 1.336(6) A, showing that the radical electron is localized in the latter ring. The half-filled extended Hückel HOMO is indeed found to be so localized, and it has a large azo character. Complexes 4-6 display radical redox couples with E1/2 in the range -0.5 to +0.10 V vs SCE. The E1/2 values qualitatively correlate with corresponding vco values (1900-2000 cm-1). The monoradicals (S = 1/2) 4+, 5, and 6 uniformly display a strong EPR signal near g = 2.00. Metal-mediated magnetic interaction makes the EPR-silent diradical 4 strongly antiferromagnetic with J = -299 cm-1. Crystal data are as follows: (4+PF6-.CH2Cl2, C40H33Cl2F6N8-OP2Ru) monoclinic, space group P2(1)/c (no. 14), a = 14.174(6) A, b = 16.451(4) A, c = 18.381(4) A, beta = 98.00(3) degrees, Z = 4; (5+PF6-.H2O, C47H41F6N4O2P3Ru) monoclinic, space group P2(1)/n (no. 14), a = 9.433(2) A, b = 38.914(17) A, c = 13.084(3) A, beta = 103.47(2) degrees, Z = 4; (6+PF6-, C48H39ClF6N3OP3Ru) monoclinic, space group P2(1)/n (no. 14), a = 10.496(5) A, b = 22.389(8) A, c = 19.720(6) A, beta = 90.53(3) degrees, Z = 4.     

Solution of the five-dimensional vacuum Einstein equations in Kaluza-Klein theory

In a recent paper Ross obtained the five-dimensional vacuum Einstein equations in Kaluza-Klein theory with energy-momentum tensor equal to zero and solved the equations for a particular case. Here we obtain the complete set of solutions of these equations.     

Ab initio calculations, electronegativity equalisation and group electronegativity

A correspondence betweenab initio calculations, the principle of electronegativity equalisation and group electronegativity has been established within the framework of Mulliken population analysis. Using this we have calculated electronegativities of some 37 groups/atoms. These electronegativities show excellent linear correlation with¹ J _CC coupling constants in monosubstituted benzenes and Inamoto’si scale and a satisfactory one with Wells’ group electronegativity data. The correspondence however required a scaling of charge (obtained byab initio calculations) and a proportionality between the electronegativity of the neutral group and its hardness. It is shown that using these electronegativity values it is possible to calculate group charges in molecules where groups under consideration interact with each other through σ bond only.     

Determination of trace metals in natural waters at nanogram per liter levesls by electrothermal atomic absorption spectrometry after extraction with sodium diethyldithiocarbamate

The determination of trace metals (Cd, Co, Cu, Fe, Ni and Pb) at concentrations found in fresh and sea waters is described. The metals are extracted as diethyldithiocarbamates from 500-ml samples into carbon tetrachloride, the extracts are evaporated to dryness and the residues are mineralized with 0.1 ml of concentrated nitric acid. This solution is used for graphite-furnace atomic absorption spectrometry after appropriate dilution. The detection limits are 10 pg Cd, 150 pg Co, 125 pg Cu, 100 pg Fe, 250 pg Ni and 100 pg Pb. The extraction/mineralization method is almost free from interferences, e.g., from trace elements at 500-fold and Na, K, Ca and Mg at million-fold amounts. The procedure is successfully applied to the determination of the above metals in deionized water, and river and sea waters.     

Electroosmotic transport of immiscible binary system with a layer of non‐conducting fluid under interfacial slip: The role applied pressure gradient

We investigate the transport of immiscible binary fluid layers, constituted by one conducting (top layer fluid) and another non‐conducting (bottom layer fluid) fluids in a microfluidic channel under the combined influences of an applied pressure gradient and imposed electric field. We solve the transport equation governing the flow dynamics analytically and obtain the closed‐form expressions of the velocity fields. We bring out the alteration in the flow dynamics, mainly attributable to the non‐linear interaction between interfacial slip and the electrical double layer effect over small scales as modulated by the applied pressure gradient. In particular, we show the augmentation in the net volume transport rate through the channel, emerging from an intricate competition among electrical forcing, applied pressure gradient and the viscous resistance as modulated by the interfacial slip. We believe that the results of this study may be of immense consequence for the design of various microfluidic devises, which are often used for the manipulation of two immiscible fluids in different biomedical/biochemical processes.     

Occurrence of monoalkyllead species during the speciation of organolead

When tri-levels are determined in environmental samples by a method based on Grignard derivatization and subsequent gas chromatography/atomic absorption spectrometry, monoalkyllead species are sometimes detected. A rearrangement process during or following Grignard derivatization explains this occurrence at least partly. The accuracy of the determination does not suffer significantly from this limited-scale reaction but the detection of a monoalkyltributyllead species does not necessarily mean that the sample contains monoalkyllead compounds.