Saponins of dioscorea XV. Caucasosaponin and caucasoprosapogenin fromD. caucasica

Summary Two new saponins have been isolated from the rhizomes ofD. caucasica: the water-soluble caucasosaponin—a rhamnosotriglucoside of 25 D-22-spirost-22-en-3-ol—and the water insoluble caucasoprosapogenin—a glucosotrioside of 25 D-22-spirost-5-en-3-ol-, and also the previously known rhamnosidodiglucoside of 25 D-22-spirost-5-en-3-ol—gracillin.Khimiya Prirodnykh Soedinenii, Vol. 3, No. 4, pp. 237–241, 1967     

Effect of modification of the MF-4SC membranes in the potassium form with acid salts of heteropolyacids on membrane properties and characteristics of dp sensors based on them

Hybrid materials based on perfluorinated sulfo cation-exchange MF-4SC membrane and nanoparticles of cesium hydrogen phosphotungstate and silicotungstate heteropolyanions were obtained. These membranes with a gradual dopant distribution along the length were used to develop potentiometric sensors for determination of amino-containing organic cations in aqueous solutions at pH < 7. A relationship between the membrane transport characteristics and sensing properties was elucidated.     

Low-energy electron-induced reactions in thin films of glucose and N-acetyl-glucosamine

Reactions induced in thin films of α-d-glucose and N-acetylglucosamine by low-energy electron exposure at incident electron energies (E₀) between 5 eV and 15 eV have been investigated by high-resolution electron energy loss spectroscopy (HREELS). The reactions of α-d-glucose upon electron exposure were also studied in the presence of molecular oxygen. Electron exposure leads to characteristic changes of the vibrational spectra indicating that OH groups are lost with the formation of CC double bonds taking place preferentially above the ionisation threshold of the investigated molecules. At lower E₀, OH groups are equally decomposed suggesting that dissociative electron attachment contributes to the reactions but formation of double bonds is not observed. The results show that different reaction channels are effective depending on E₀ and that the outcome of electron-driven chemistry in saccharides may be controlled by changing from the subionisation regime to E₀ above the ionisation threshold. Generally, low-energy electron exposure in the absence of O₂ produces a material with lower oxygen content, i.e. leads to a reduction of the saccharide. In the case of N-acetylglucosamine, removal of the amide group from the sugar is also important at subionisation energies. In contrast, as shown for α-d-glucose, low-energy electron exposure in the presence of O₂ leads to oxidation of the sugar even at cryogenic temperature.     

Theory of concentrational profile at the surface of a decomposing binary alloy

In the self-consistent-field approximation, a statistical theory is constructed for the atomic distribution in the near-surface region of a binary alloy which is able to disintegrate from the atomically smooth free surface of the crystal. The form of the surface-segregation functions of the components is found, in closed form, taking the relaxation of the coordination energies and the atomicinteraction energies at the surface into account. The possibility of the existence of metastable nonmonotonic concentrational profiles at the crystal surface is demonstrated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 51–56, December, 1981.     

Ordering of ternary alloys in the self-consistent field approximation

In the self-consistent field approximation, without allowance for correlation, a static theory of the ordering of ternary alloys is constructed which makes it possible to take into account the long-range nature of the interatomic interaction forces in substitutional and interstitial alloys. The theory enables one to take into account the possible existence in the alloy of two subsets of points differing by the species of atoms that occupy them. The stability of the disordered state in such alloys is analyzed and an expression obtained for the temperature at which the disordered state loses stability.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 61–64, November, 1980.     

Distribution of atoms in a ternary alloy with a free surface in the self-consistent field approximation

Analytical form for the functions describing atomic distribution of the components in the subsurface layer of a ternary alloy has been found in a closed form in the self-consistent field approximation, without taking correlation into account. The functions obtained allow one to construct concentration profiles of the components near the surface, to calculate the component surface concentration, and to investigate the dependence of the composition on the surface of the alloy crystal on temperature, and surface relaxation of coordination numbers and energies of the nearest neighbor interatomic interaction in an alloy. An analysis of the character of temperature dependencies of the composition on the surface has been performed for various alloys.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 47–52, August, 1982.     

Control of two-dimensional motion of microparticles in nematic liquid crystal

The possibility of controlling two-dimensional motion of dielectric microparticles in the channel filledwith nematic liquid crystalwas experimentally shown. It was found that particle motion along the electric field occurs by means of the electrophoresis phenomenon. Particle motion along electrodes perpendicularly to the electric field is caused by the combination of two effects, i.e., the backflow and Quincke rotation.     

First example of the cascade acylation/IMDAV/ene reaction sequence,leading to N-arylbenzo[f]isoindole-4-carboxylic acids possessing anti-viral activity

The reaction between readily accessible N-aryl-3-phenylallylamines and maleic anhydride led to unexpected products – polysubstituted hydrogenated benzo[f]isoindole-4-carboxylic acids. This transformation proceeds through a previously unknown sequence of steps: N-acylation of the allylamine with maleic anhydride, intramolecular Diels-Alder reaction of the vinylarene in the intermediate N-maleamide, and Alder-ene reaction of the products of the previous two steps. Selected benzo[f]isoindoles displayed antiviral activity.