Electrochemical synthesis of perfluoropolyethers by the Kolbe method

Electrochemical dimerization of hexafluoropropylene oxide dimer and trimer acids on SU-2000 glassy carbon, bulk platinum, and SU-2000 electrodes modified with platinum-group metals in acetonitrile in the presence of water was studied at various concentrations of the starting substance and different degrees of neutralization of the starting acid. Also, the possibility was examined of obtaining some perfluoropolyethers in a single process by cross-condensation of several starting perfluorocarboxylic acids, followed by separation of the products by physicochemical methods.     

The smooth classification of coarse vector fields on a circumference

Translated from Teoriya Funktsii, Funktsional'nyi Analiz i Ikh Prilozheniya, No. 52, pp. 110–113, 1989.     

Shock compression of liquid nitrogen at a pressure of 320 GPa

The experimental data on the shock compression of liquid nitrogen in the megabar pressure range are reported. The experiments have been performed with a spherical measuring setup in which pressure is created by the impact of a steel shell accelerated to a velocity of 23 km/s on the samples. The density of shock-compressed nitrogen at a pressure of about 320 GPa is about 3.4 g/cm³ (compression degree of about 4.2). The experimental data are described using a model equation of state.     

Matrix and vector models in the strong coupling limit

We consider matrix and vector models in the large-N limit: we study N × N matrices and vectors with N² components. In the case of a zero-dimensional model (D = 0), we prove that in the strong coupling limit (g → ∞), the partition functions of the two models coincide up to a coefficient. This also holds for D = 1. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 155, No. 2, pp. 236–243, May, 2008.     

Comparative analysis of Reaction-Diffusion Manifold based reduced models for Head-On- and Side-Wall-Quenching flames

In this study, multi-dimensional molecular transport phenomena during Flame-Wall-Interactions (FWI) and their effects on model reduction strategies are investigated. In order to access the problem, the standard configurations of a two-dimensional Side-Wall Quenching (SWQ) flame and a one-dimensional Head-On Quenching (HOQ) flame are used and compared. In the case of the SWQ configuration it is shown that the gradients of the species scatter significantly both in the physical space and in the state space. Moreover, the gradient vector of the specific enthalpy describing energy losses towards the wall is not aligned with the gradient vectors of the species, which can be considered as a typical case while a flame in application might approach to the wall at any arbitrary transversal direction. This observation motivates to take the gradients’ scattering and multi-dimensional transport phenomena into account during model reduction to describe reliably the quenching process.The Reaction-Diffusion Manifold (REDIM) method is applied in this work. The method allows to take into account multi-dimensional transport in a very generic way. In order to generate the REDIM, gradient estimates are approximated by using a Singular-Value Decomposition (SVD) of SWQ detailed gradients fields. Two-dimensional REDIMs for both cases are constructed and compared to each other. Different transport (diffusion) models are implemented to compare quantitatively the manifolds with HOQ and SOQ gradients estimates. The comparison shows that the differences between reduced models with varying transport models is significantly larger than the differences for varying configurations (multidimensional gradient estimates). This justifies the use of a relatively simple REDIM for more complicated geometries and configurations. This simplifies the treatment and model reduction procedure significantly for such complicated transient phenomena.     

A sorbent based on phosphorylated lignin

A procedure was developed for preparing an effective sorbent based on lignin phosphorylated in the presence of urea. The phosphorus content was 16.6 wt %. The total exchange capacity was 0.86 mmol g⁻¹ for Cu²⁺ ions and 0.23 mmol g⁻¹ for UO₂²⁺ ions. The effect of urea on the lignin phosphorylation was examined by IR spectroscopy.     

Experimental study of the multiple scattering effect on the flow velocity profiles measured in Intralipid phantoms by DOCT

Time domain Doppler Optical Coherence Tomography (DOCT) technique was applied to measure flow velocity profiles in highly scattering media. We analyzed the distortions of the measured velocity profiles of the 1% Intralipid solution flow embedded into the scattering medium at different embedding depths. For this purpose a tissue phantom consisting of a plain glass capillary (inner diameter 0.3 mm) embedded into a slab of Intralipid solution mimicking human skin was designed. The measured flow velocity profiles and behavior of distortions caused by multiple scattering are shown.     

Temporal differentiation of optical signals using resonant gratings

We study theoretically the possibility of performing temporal differentiation of optical signals using a resonant diffraction grating. We demonstrate that the resonant grating allows the calculation of the first-order derivative of an optical signal envelope in the vicinity of waveguide resonant frequencies in the zeroth transmitted diffraction order. The grating is shown to allow the calculation of the fractional derivative of order 1/2 in the vicinity of Rayleigh-Wood anomalies. Numerical simulations based on the rigorous coupled-wave analysis of Maxwell's equations demonstrate the high-quality differentiation of optical signals with temporal features in the picosecond range.     

Synthesis of 2-hetaryl-3-(indol-1-yl)-and -(3-pyrrol-1-yl)maleimides and study of their conversions under the action of protic acids*

A series of 3-(indol-1-yl)maleimides has been synthesized, substituted at position 2 by residues of amines or various nitrogenous heterocycles. The possibility of obtaining new polycondensed heterocyclic structures from them has been studied. Experimental investigations confirmed theoretical predictions made on the basis of results of quantum-chemical calculations.