Acyl derivatives of N,N′-diaminodibenzo-18-crown-6 ether,their complexing and catalytic properties

Conclusions Complex compounds of bisacyl derivatives of diaminodibenzo-18-crown-6 ether are active catalysts of the two stages of the synthesis of poly(ethylene terephthalate).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2544–2547, November. 1987.     

Alkylation of 2,3,6,11-tetrahydroanthra[2,1-d]isothiazole-3,6,11-trione and its S-oxide

The reactions of 2,3,6,11-tetrahydroanthra[2,1-d]isothiazole-3,6,11-trione with dimethyl sulfate, benzyl chloride, and allyl bromide afforded the corresponding 2-alkyl-2,3,6,11-tetrahydroanthra[2,1-d]isothiazole-3,6,11-triones and 3-(alkoxy)-6,11-dihydroanthra[2,1-d]isothiazole-6,11-diones. The reactions of 2,3,6,11-tetrahydroanthra[2,1-d]isothiazole-3,6,11-trione and its S-oxide with a formaldehyde—secondary amine system yielded 2-[(alkylamino)methyl]-2,3,6,11-tetrahydroanthra[2,1-d]isothiazole-3,6,11-triones and 2-[(alkylamino)methyl]-3,6,11-trioxo-2,3,6,11-tetrahydroanthra[2,1-d]isothiazole 1-oxides, respectively.     

New insights on amorphous silicon-nitride microcavities

All amorphous silicon-nitride planar optical microcavities operating in the visible range have been grown by plasma enhanced chemical vapor deposition. The luminescence intensity of the N-rich silicon-nitride layer from a microcavity with 6 period distributed Bragg reflectors (DBRs) is two order of magnitude higher than that of the luminescent layer without the cavity. Moreover, a strong directionality of the microcavities emission can be observed. Such results can be ascribed to the anisotropic optical density of states induced in the Fabry–Perot structure. The quality factors of the resonators are strictly correlated to the number of periods of the DBRs.     

Study of removal processes of <Superscript>7</Superscript>Be and <Superscript>137</Superscript>Cs from the atmosphere

In order to understand better the way in which radioactive contamination may be transferred from the atmosphere to other ecological compartments it is necessary to obtain information of the deposition mechanisms of radionuclides. Concentration and speciation of ¹³⁷Cs and ⁷Be in the atmospheric aerosol and deposition were studied. The mixed deposition velocities of water-soluble and insoluble ¹³⁷Cs and ⁷Be were determined. The relation between activity concentrations of insoluble ⁷Be in the atmosphere and its amount in deposition was observed. It is supposed that in the deposition process of radiocesium the precipitation plays an important role in scavenging of water-soluble radiocesium by falling raindrops, in contrast to insoluble ¹³⁷Cs where the dry deposition becomes predominant.     

A tight-binding study of LUMO states in ellipsoidal silicon nanocrystals

In this paper we report on tight-binding calculations of lowest unoccupied molecular orbitals states for silicon ellipsoidal nanocrystals. The electronic structure has been calculated for different nanocrystal shapes either keeping constant or varying the number of silicon atoms. We have found that changing the ellipsoid aspect ratio a non-obvious energy level structure is obtained. The implications for the infrared optical transitions and their relationship with the polarization of the radiation involved are discussed.     

Semiempirical calculation of the fine structure of the indium ion

The fine-structure parameters of a series of configurations of the first ion of indium and the gyromagnetic ratios in intermediate coupling are calculated by a semiempirical method in the single-configuration approximation.     

Rotational analysis ofA 1Π-X 1Σ+ bands of P14N and P15N: Perturbatio studies in theA 1Π state

The ultraviolet band systemsA ¹Π-X ¹Σ⁺ of P¹⁴N and P¹⁵N were excited in an electrodeless tube containing traces of phosphorus specpure nitrogen and neon using a microwave discharge (2450 MHz). Bands of the isotopic species, P¹⁵N, were obtained using¹⁵N₂ enriched to 95.5%. Rotational analyses of eleven bands of P¹⁴N and sixteen bands of P¹⁵N were carried out. Three perturbing statese ³Σ⁻,d ³Δ andb ³Π, arising from the lower valence configurations were identified from the observed perturbations in thev′=0–4 levels of theA ¹Π state. Deperturbation studies led to the determination of molecular constants of the perturbing states. Vibrational assignments of the perturbing states were made from isotope shift studies.     

Pattern formation on a nonlinear periodic electrical network

It is observed experimentally that a periodic array of resistively coupled LC-oscillators with ans-shaped nonlinearity exhibits stable non-uniform voltage and current distributions. The dependence of the resulting structure on the coupling resistance and the boundary conditions is investigated. The structure is rather insensitive to variations of the boundary values. The experiments are well described by a two-variable reaction-diffusion equation.