Enumeration of one-nodal rational curves in projective spaces

We give a formula computing the number of one-nodal rational curves that pass through an appropriate collection of constraints in a complex projective space. The formula involves intersections of tautological classes on moduli spaces of stable rational maps. We combine the methods and results from three different papers.     

Distinctive features of time-resolved photoluminescence of porous silicon coated with a layer of diamondlike carbon

Time-resolved photoluminescence from porous silicon coated with a diamondlike carbon film is investigated. The intensity of the photoluminescence from the carbon film is obserd to increase after deposition, and there is an accompanying change in the intensity and a shortwavelength shift of the photoluminescence band of porous silicon that depends on the porosity of its original layers. These changes are explained by the formation of carbon nanoclusters on the surface of the silicon filaments. Zh. Tekh. Fiz. 68, 83–87 (April 1998)     

Thin-Layer Chromatography with an Isolated Support and Forced Flow of the Mobile Phase

JPC – Journal of Planar Chromatography – Modern TLC -     

On the ultraviolet photodissociation of H(2)Te

The photodissociation of H(2)Te through excitation in the first absorption band is investigated by means of multireference spin-orbit configuration interaction (CI) calculations. Bending potentials for low-lying electronic states of H(2)Te are obtained in C(2v) symmetry for Te-H distances fixed at the ground state equilibrium value of 3.14a(0), as well as for the minimum energy path constrained to R(1)=R(2). Asymmetric cuts of potential energy surfaces for excited states (at R(1)=3.14a(0) and theta;=90.3 degrees ) are obtained for the first time. It is shown that vibrational structure in the 380-400 nm region of the long wavelength absorption tail is due to transitions to 3A('), which has a shallow minimum at large HTe-H separations. Transitions to this state are polarized in the molecular plane, and this state converges to the excited TeH((2)Pi(1/2))+H((2)S) limit. These theoretical data are in accord with the selectivity toward TeH((2)Pi(1/2)) relative to TeH((2)Pi(3/2)) that has been found experimentally for 355 nm H(2)Te photodissociation. The calculated 3A(')<--XA(') transition dipole moment increases rapidly with HTe-H distance; this explains the observation of 3A(') vibrational structure for low vibrational levels, despite unfavorable Franck-Condon factors. According to the calculated vertical energies and transition moment data, the maximum in the first absorption band at approximately 245 nm is caused by excitation to 4A("), which has predominantly 2(1)A(") ((1)B(1) in C(2v) symmetry) character.     

Titrimetric microdetermination of sulfur in compounds containing alkali or alkaline earth

Summary The titrimetric dry combustion method can be employed for micro-determination of sulfur in organic compounds containing both alkali metal or alkaline earth metal and sulfur.The residue of alkali or alkaline earth sulfate in the boat, formed during the combustion, is fused with 3 to 4 times its weight of boron trioxide, whereby sulfur trioxide is displaced by the boron trioxide.

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Zusammenfassung Die Bestimmung des Schwefels durch Verbrennung und Titration der gebildeten Schwefelsäure kann mit organischen Verbindungen ausgeführt werden, die Alkalien oder alkalische Erden enthalten.Der Metallsulfate enthaltende Verbrennungsrückstand wird im Schiffchen mit der 3- bis 4fachen Menge Bortrioxyd versetzt. Beim darauffolgenden Erhitzen wird das Schwefeltrioxyd in Freiheit gesetzt.

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Résumé On peut employer la méthode par combustion à sec et titrage pour le dosage du soufre dans des composés organiques contenant un métal alcalin ou un métal alcalino-terreux.Le résidu de sulfate alcalin ou alcalino -terreux formés pendant la combustion dans la nacelle est fondu avec trois ou quatre fois son poids de trioxyde de bore; l'anhydride sulfurique est déplacé par le trioxyde de bore.

     

Size and Shape Effects in Optical Spectra of Silver and Gold Nanoparticles

Journal of Russian Laser Research - We report some theoretical results on the extinction, absorption, and scattering of light by individual silver and gold nanoparticles of different sizes and...     

Time-resolved photoluminescence study of excited states in nanostructured melanin

Abstract

Time resolved emission spectra (TRES), 3D maps of photoluminescence excitation-emission (PLE maps), 3D maps of TRES, and kinetics of photoluminescence (PL) spectra of natural and synthetic melanin, as well as melanin composites with surfactant, sodium dodecyl benzenesulfonate, have been studied. The kinetics of PL and TRES for the melanin and the composites were investigated at low temperatures that allowed to discuss melanin’s intermolecular complexation, nano-aggregation and formation of charge transfer states. Particularly, the radiation of Frenkel excitons from fragments of different degrees of conjugation that are the parts of molecular nanodisks of melanin is observed. Furthermore, charge transfer excitons (CT-excitons) can be formed and observed at both room and helium temperatures. Some bands in the PL spectra of melanin, depending on temperature, behave like excimer radiation. The studies are aiming to understand the electronic properties of various melanins, particularly natural ones.     

Nanocrystalline aerogel VOx/MgO as a catalyst for oxidative dehydrogenation of propane

Nanocrystalline aerogel VO_x/MgO catalysts for the oxidative dehydrogenation of propane with high surface area and uniform vanadium distribution were synthesized by co-gelation followed by supercritical drying. The catalysts were shown to have superior performance compared to nanocrystalline VO_x/MgO catalysts prepared by impregnation.