Possible use of provitamin D<Subscript>3</Subscript> photoisomerization for spectral dosimetry of bioactive antirachitic UV radiation

The possible use of a simplified UV absorption spectroscopic method for dosimetry of bioactive antirachitic UV radiation has been analyzed. The method is based on the observation of the phototransformation kinetics of the provitamin D₃ primary molecule in ethanol (in vitro vitamin D₃ synthesis model) by measuring the decrease in the optical density at a fixed wavelength during UV exposure. The method can be used successfully for artificial UV sources with a constant radiation spectrum. However, such a technique turns out to be inapplicable to solar UV dosimetry in view of the variability of the solar UV spectrum that results in a varying rate of formation of irreversible photoproducts. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 256–260, March–April, 2009.     

Synthesis and nonlinear optical properties of donor-acceptor dyes based on triphenylpyrazolines as a donor block and dicyanoisophorone as acceptor

A series of donor-acceptor dyes based on polyfluoro-substituted triarylpyrazolines (as a donor block) and a dicyanoisophorone group (as an acceptor) were synthesized using the Knoevenagel condensation. The dyes have an absorption in the region of 509–514 nm and intense luminescence at 648–663 nm in chloroform with a large Stokes shift (up to 4410 cm^–1). Based on the synthesized dyes, chromophore–polymer (guest–host) films were obtained in a polycarbonate matrix with a chromophore content up to 27 wt.%. Poling of chromophore–polymer films was carried out in an electric field of a corona discharge and the coefficient of nonlinear optical response d₃₃ was measured by the second-harmonic generation method of the fundamental frequency of a Nd-YAG laser (1064 nm). The obtained films have a high initial thermal stability and a nonlinear optical response up to 80 pm V^–1, which persists up to 115 °С.

     

Analyzing the orientation characteristics of <Superscript>12</Superscript>С(2<Superscript>+</Superscript>; 4.44 MeV) nuclei in the inelastic scattering of α particles on carbon at <Emphasis Type="Italic">E</Emphasis><Subscript>α</Subscript> = 16–25 MeV

All even components of the spin-tensors of a density matrix reconstructed by means of angular correlation for ¹²С nuclei in the 2⁺ state (4.44 MeV), produced during the inelastic scattering of α particles with energies of 16 to 25 MeV in scattering angle range θ_α(lab) = 20°–90°, are presented. The energy dependences of its orientation characteristics (i.e., the population of magnetic substates and the orientation tensors of multipole moments) are determined. Experimental results are compared to calculations using the coupledchannel method and the compound nucleus model.     

Accurate X-ray diffraction studies of KTiOPO<Subscript>4</Subscript> single crystals doped with niobium

Single crystals of potassium titanyl phosphate doped with 4% of niobium (КТР:4%Nb) and 6% of niobium (KTP:6%Nb) are studied by accurate X-ray diffraction at room temperature. The niobium atoms are localized near the Ti1 and Ti2 atomic positions, and their positions are for the first time refined independent of the titanium atomic positions. Maps of difference electron density in the vicinity of K1 and K2 atomic positions are analyzed. It is found that in the structure of crystal КТР:4%Nb, additional positions of K atoms are located farther from the main positions and from each other than in КТР and KTP:6%Nb crystals. The nonuniform distribution of electron density found in the channels of the КТР:4%Nb structure is responsible for ~20% increase in the signal of second harmonic generation.     

Conjugates of polyhedral boron compounds with carbohydrates. 1. New approach to the design of selective agents for boron neutron capture therapy of cancer

Russian Chemical Bulletin -     

A programming environment for large software projects

Translated from Sistemnoe Programmirovanie i Modeli Issledovaniya Operatsii, pp. 22–27, 1993.     

Sample Preparation and the Detection of α-Aminopropiophenone and Amphetamine in Narcotic Drugs Using IR Spectroscopy

A procedure was developed for the IR-spectroscopic detection of -aminopropiophenone and amphetamine in narcotic drugs prepared from phenylpropanolamine-containing medicines using sample preparation by liquid–liquid extraction. Extraction conditions were selected using the computation of physicochemical parameters of the analytes. The procedure is simple, inexpensive, and can be used in combination with other chemical and physicochemical methods for the expert analysis of narcotic drugs.