Aggregation and photoisomerization of amphiphilic crown-ether styryl dye in monolayers at the interface

The molecules oftrans-isomer of styryl dye1a, containing the benzo-18-crown-6 moiety and the methoxybenzothiazole residue with theN-octadecyl substituent, were shown to form stable, highly ordered monolayers at the water/air interface. Increasing the surface pressure of the monolayer results in the formation of the H-aggregated molecules of compound1a. The H-aggregates tend to dissociate to the monomerictrans-form, when the monolayer forms in the Langmuir-Blodgett film (LB film). The light irradiation of the LB films leads to the partially reversibletrans-cis-photoisomerization of compound1a, whose efficiency is much lower than that observed in an acetonitrile solution of1a. The aggregation of cis-1a isomers in the LB film is suggested to hamper the reversecis-trans-isomerization. The aggregation oftrans-1a molecules in the LB films does not occur in air, but, after dipping in an aqueous solution, molecules of the LB film slowly form J-aggregates. A model of the structural organization oftrans-1a molecules in the LB films was proposed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2490–2496, October, 1996.     

Structure of the steroid alkaloid radpetine from Petilium raddeana

A new base with the composition C₂₉H₄₅NO₃ has been isolated from the plantPetilium raddeana and has been called radpetine. Its structure has been established as 3-hydroxy-23,28-epoxy-23-ethyl-^22(N)-22,26-iminocholestan-y-one-by the x-ray structural method (diffractometer, CuK, 1046 reflections, direct method, MLS in the anisotropic approximation, R = 0.118). Radpetine belongs to a new type of steroid alkaloids with a spiro-methyloxirane grouping at C-23 in the azomethine ring F.Deceased.Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 384–388, May–June, 1991.     

MOVPE-grown high CW power InGaAs/InGaAsP/InGaP diode lasers

Al-free InGaAs/InGaAsP/InGaP laser structures grown by MOVPE have yielded new records in performance. CW front-facet-emitted powers of 5.8 W are achieved from optimized double-quantum-well lasers with 100 μm wide stripes and 1 mm long cavity lengths. Devices with a 0.5 mm cavity length exhibit total power conversion efficiencies as high as 59%. A novel facet passivation technique, consisting of laser-assisted deposition of ZnSe, is shown to increase the COD level by 50%. Single-mode, CW output powers of 400 mW are obtained from triple-core ARROW lasers fabricated by a two-step MOVPE growth process.     

Photoluminescence Properties of Thin-Film Nanohybrid Material Based on Quantum Dots and Gold Nanorods

The dynamics of coherent propagation of a unipolar subcycle pulse of a large electric-field area (the integral of the electric-field strength with respect to time) in a nonlinear two-level resonant medium is studied theoretically. The propagating pulse is shown to be capable of splitting into a pair of individual components, each of which behaves like a pulse of self-induced transparency. This phenomenon is similar to the well-known phenomenon of splitting of a 4π or 6π pulse into a pair of 2π pulses of self-induced transparency, which occurs in the case of propagation of long pulses, when the notion of the pulse area is applicable and the area theorem holds.     

Field-emission diodes based on semiconductor—polycrystalline diamond heterojunctions

A complex of electrophysical and technological studies of solid-state field-emission diodes is carried out. Emission comes from an array of nanometer objects near the semiconductor—polycrystalline diamond interface. The process route of the diode heterostructures includes the fabrication of nanometer masks and nanometer cone (tip) arrays, as well as plasma-assisted growth of polycrystalline diamond films on the surface of structures with nanometer cone arrays. In field-emission diodes thus formed, a current density as high as 20 A/cm² is achieved at a threshold of field emission from the nanotip arrays into the diamond of about 0.5 V.     

Imperialine esters and their M2-choline-blocking activity

Four new imperialine esters, with butyric, isovaleric, pyromucic, and benzoic acids, have been synthesized, and their M₂-choline-blocking activity has been studied. Deceased