Study of Polyphenolic Compounds in Extracts from Flowers and Leaves of Canadian Goldenrod and Dwarf Goldenrod (Solidago canadensis L. and Solidago nana Nitt.)

Moscow University Chemistry Bulletin - The results of qualitative and quantitative determination of polyphenolic compounds, in particular flavon glycosides and flavon aglycones, in...     

Limit of Detection in Test Methods of Analysis with Visual Indication: Affecting Factors

A statistical approach to evaluating the limit of detection (c_min) was used for studying 12 test systems with visual indication based on reagent indicator paper, polyurethane foam, gelatin films, powdered methylsilicic acid, and reagent solutions. It was proposed to characterize the quality of test systems by relative width of the region of an unreliable response. The dependence of the characteristics of test systems on the material of the support, the type of analytical reaction, the conditions of color observation in the test system, and the number of observations were discussed.     

Fast generation of an electron beam in a magnetron gun with a secondary-emission metallic cathode

The formation of an electron layer and the generation of an electron beam in magnetron guns where secondary emission is triggered by nanosecond pulses are studied. In the guns with small cross sizes, hollow electron beams with an outer diameter of 3–6 mm are generated. The beam current is 1–2 A, and the cathode voltage is 5–7 kV. Results obtained indicate that the generation of nanosecond beam-current pulses is a possibility.     

Electrically controlled surface diffraction gratings in nematic liquid crystals

Photorefractive diffraction gratings were studied in cells of homeotropically aligned pentyl-cyanobiphenyl liquid crystal. These holographic gratings were induced by the simultaneous and nonsimultaneous application of dc and coherent optical electric fields. The observed behavior was consistent with a predominantly surface-mediated photorefractive effect. Beam coupling was observed in all cases and led to a model involving screened and unscreened interfacial trapped charges driving a modulation of the easy axis. Holographic gratings could be switched on and off by the application of a small voltage.     

Determination of nitrite ions using test strips based on 3-hydroxy-7,8-benzo-1,2,3,4-terahydroquinoline

RIB-Nitrite-Test and Sorbfil-Nitrite-Test strips were developed for determining nitrite ions in water samples and foodstuffs by a reaction similar to the Griess reaction. Stable and noncarcinogenic 3-hydroxy-7,8-benzo-1,2,3,4-tetrahydroquinoline was used as an azo component adsorbed in the reagent paper zone on a polymeric support or on a Sorbfil plate sealed in a transparent polymeric film. Performance characteristics were evaluated by a statistical method for visual test procedures for the detection and determination of NO ₂ ^? using two different test strips. The determination limit was 0.54 and 0.09 mg/L, and the detection limit was 0.50 and 0.08 mg/L, respectively.     

Synthesis and structures of 3-hydroxy-6-(R-phenylazo)-7,8-benzo-1,2,3,4-tetrahydroquinolines as products of analytical test reactions for nitrite and nitrate anions

An improved procedure was proposed for the synthesis of 3-hydroxy-7,8-benzo-1,2,3,4-tetrahydroquinoline, which is used as a reagent for the analytical test reaction for nitrate and nitrite anions based on azo coupling with diazo compounds. 3-Hydroxy-6-(R-phenylazo)-7,8-benzo-1,2,3,4-tetrahydroquinolines (R = 2-COOH, 4-COOH, or 4-SO₃H) were synthesized by azo coupling reactions in 65–70% yields. The structures of these compounds were confirmed by elemental analysis, ¹H NMR and IR spectroscopy, and X-ray diffraction. Based on the X-ray data, the bathochromic shift in the UV spectrum of the o-carboxy isomer compared to the p-carboxy isomer (Δλ_max = 50 nm) is attributed to a strong intramolecular hydrogen bond. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1027–1031, June, 2006     

Model of impurity distribution in the atmosphere for a source above the Earth’s surface

Taking into account diffusion and wind transport processes, a model of the distribution of an impurity polluting the Earth’s atmosphere was constructed. On its basis, simple formulas were derived, which, using gas-correlation IR radiometry, allow the estimation of the power and position of impurity sources above the Earth’s surface.     

Comparative analysis of sensory rhodopsin II structures in complex with a transducer and without it

Sensory rhodopsin II (NpSRII) is a heptahelical transmembrane protein containing the retinal chromophore. In complex with another membrane protein, i.e., NpHtrII transducer, NpSRII transmits a signal into a cell, initiating negative phototaxis of Natronobacterium pharaonis. In the absence of a transducer, rhodopsin II can work as a proton pump similar to bacteriorhodopsin. The main objective of this study is to comparatively analyze receptor structures in complex with the transducer and without it to understand the mechanism of the protein switching function. Diffraction data for sensory rhodopsin II crystals grown in the lipidic cubic phase were obtained at the synchrotron x-ray source. In this paper, we present a new NpSRII structure with a resolution of 2.1 Å and the results of a comparative analysis of the obtained NpSRII structure with our previously published data on the NpSRII/NpHtrII complex structure and with two NpSRII structures without a transducer, previously published in the literature.     

Surface driven transition in a nematic liquid crystal cell

Surface driven reorientation effects in a nematic liquid crystal cell caused by light-induced changes of the anchoring parameters were studied. Theoretical consideration of one-dimensional flat distributions of the director has shown that the director can undergo threshold reorientation between hybrid, homeotropic, and planar alignments as the anchoring energy varies continuously. The threshold reorientation takes place when the reference and light-induced easy axes are perpendicular. In the one-elastic-constant approximation the light-induced transition was found to be of second order as shown by a critical increase of the director thermal fluctuations in the vicinity of the transition point. These effects were experimentally studied in the cells containing 5CB liquid crystal aligned by the photosensitive azo-containing polymer layer. Zh. éksp. Teor. Fiz. 112, 2045–2055 (December 1997) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.