Synthesis and nonlinear light scattering of microemulsions and nanoparticle suspensions

Microemulsions composed of normal or inverse micellar solutions and aqueous suspensions of pristine (uncoated) or silica-coated iron oxide nanoparticles, mainly γ-Fe₂O₃, were synthesised and their optical limiting properties investigated. The microemulsions are colorless solutions with high transparency for visible wavelengths while the aqueous suspensions of iron oxide are of pale yellow colour. Optical limiting experiments performed in 2 mm cells using a f/5 optical system with a frequency doubled Nd:YAG laser delivering 5 ns pulses with 10 Hz repetition rate, showed clamping levels of ∼3 μJ for the suspensions of both pristine and silica-coated iron oxide nanoparticles. A strong photoinduced nonlinear light scattering was observed for the water-in-oil microemulsion and the aqueous suspensions of nanoparticles while oil-in-water microemulsions did not show a significant nonlinear effect. Measurements carried out using an integrating sphere further verified that the photoinduced nonlinear light scattering is the dominating nonlinear mechanism while the nonlinear absorption of iron oxide nanoparticles is negligible at 532 nm.     

An approximate global solution of Einstein’s equations for a rotating finite body

We obtain an approximate global stationary and axisymmetric solution of Einstein’s equations which can be considered as a simple star model: a self-gravitating perfect fluid ball with constant mass density rotating in rigid motion. Using the post-Minkowskian formalism (weak-field approximation) and considering rotation as a perturbation (slow-rotation approximation), we find second-order approximate interior and exterior (asymptotically flat) solutions to this problem in harmonic and quo-harmonic coordinates. In both cases, interior and exterior solutions are matched, in the sense of Lichnerowicz, on the surface of zero pressure to obtain a global solution. The resulting metric depends on three arbitrary constants: mass density, rotational velocity and the star radius at the non-rotation limit. The mass, angular momentum, quadrupole moment and other constants of the exterior metric are determined by these three parameters. It is easy to check that Kerr’s metric cannot be the exterior part of that metric.     

Isomerization of monohydroperfluoroalkenes

Isomerization of monohydroperfluoro-1-alkenes HC(CF₂)_nCF=CF₂ (n = 2 to 8) catalyzed by Lewis bases or acids (CsF, KHF₂, and SbF₅) under conditions of thermodynamic control affords equilibrium mixtures of all of the possible isomers resulting from migration of the double bond along the carbon chain. Under conditions of kinetic control, isomerization through the action of SbF₅ gives -H-perfluoro-2-alkenes. The substantially higher proportion ofcis-isomers in the resulting monohydroperfluoroalkenes than in their perfluorinated analogs has been attributed to the effect of an intramolecular hydrogen bond.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1614–1619, September, 1994.     

Lamellar graphite compounds with metallic potassium as catalysts for deuterium-hydrogen exchange in hydrocarbons

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1935–1936, August, 1991. March 13, 1991.     

Reaction of internal fluoroolefin oxides with fluorosulfonic acid

Conclusions Internal perfluoroolefin oxides react with fluorosulfonic acid to give perfluoroketones that contain a fluorosulfate group in the-position.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1878–1879, August, 1979.     

S-anions from 2,2,4,4-tetrakis(Trifluoromethyl)-1,3-dithietane and their reactions

Russian Chemical Bulletin -     

Ionic medium effects on equilibrium constants Part I. Proton, copper(II), cadmium(II), lead(II) and acetate activity coefficients in aqueous solution

The molar single ion activity coefficients associated with hydrogen, copper(II), cadmium(II) and lead(II) ions were determined at 25 degrees C and ionic strengths between 0.100 and 3.00 M (NaClO4), whereas for acetate the ionic strengths were fixed between 0.300 and 2.00 M, held with the same inert electrolyte. The investigation was carried out potentiometrically by using proton-sensitive glass, copper, cadmium and lead ion-selective electrodes and a second-class Hg|Hg2(CH3COO)2 electrode. It was found that the activity coefficients of these ions (y(i)) can be assessed through the following empirical equations: log y(H) = -0.542I(0.5) + 0.451I; log y(Cu) = -1.249I(0.5) + 0.912I; log y(Cd) = -0.829I(0.5) + 0.448I(1.5); log y(Pb) = -0.404I(0.5) + 0.117I(2); and log y(Ac) = 0.0370I     

Determination of nafcillin and methicillin by different spectrofluorimetric techniques

In order to explore the possibilities of combining synchronous fluorescence and derivative spectrometry and to establish a methodology for this type of technique, nafcillin and methicillin were determined using these techniques. Several methods for resolving binary mixtures of these penicillins using first derivative spectrofluorimetry, first derivative constant wavelength synchronous luminescence spectrometry and constant energy synchronous luminescence spectrometry are described. The analyses were performed in aqueous medium at pH 6.20 provided by the addition of phosphate buffer solution. A complete and exhaustive statistical analysis of the experimental data was performed to demonstrate the validity of these methods, which obtained good results when applied for determining nafcillin and methicillin synthetic and real mixtures.