Engineering of Low-Loss Metal for Nanoplasmonic and Metamaterials Applications

We have shown that alloying a noble metal (gold) with another metal (cadmium), which can contribute two electrons per atom to a free electron gas, can significantly improve the metals optical properties in certain wavelength ranges and make them worse in the other parts of the spectrum. In particular, in the gold-cadmium alloy we have demonstrated a significant expansion of the spectral range of metallic reflectance to shorter wavelengths. The experimental results and the predictions of the first principles theory demonstrate an opportunity for the improvement and optimization of low-loss metals for nanoplasmonic and metamaterials applications.Comment: 14 Pages, 4 figure

Interspecific hybridization of potato: theoretical and applied aspects

The common potato Solanum tuberosum is the fourth most important crop in the world and like many other cultivated plants is characterized by low level of genetic diversity. The most effective approach to broaden genetic diversity of breeding varieties is based on the introgression of genetic material of wild and cultivated species belonging to section Petota Dumort. of the genus Solanum L. This section, according to estimates by different taxonomists, includes from 112 to 235 species. At the same time, because of the barriers of prezygotic and postzygotic incompatibility, only about 10 % of wild potato species have been actively involved into the breeding process and their genetic material has been introgressed into the gene pool of varieties. To date, molecular genetics, genomics, and biotechnology have accumulated a large amount of information, allowing the problems of extension of the genetic diversity of common potato to be addressed. The article presents a review of modern data about the genetic factors determining prezygotic and postzygotic incompatibility, about the features of involvement in the hybridization process of the self-compatible and self-incompatible species of section Petota and species with different values of the endosperm balance number (EBN), as well as possible mechanisms of interaction between the parental genomes during the formation of the endosperm of the hybrid seed. Data are provided on the value of the theory of EBN for the further development of applied research aimed at increasing the genetic diversity of the breeding gene pool. This review discusses the traditional and modern approaches and methods of overcoming interspecific incompatibility and gives examples of successful studies on introgressive hybridization of potato. The article is preceded by information about the genetic diversity of potato species belonging to section Petota of the genus Solanum

Excitonic effects in solids described by time-dependent density functional theory

Starting from the many-body Bethe-Salpeter equation we derive an exchange-correlation kernel $f_{xc}$ that reproduces excitonic effects in bulk materials within time-dependent density functional theory. The resulting $f_{xc}$ accounts for both self-energy corrections and the electron-hole interaction. It is {\em static}, {\em non-local} and has a long-range Coulomb tail. Taking the example of bulk silicon, we show that the $- \alpha / q^2$ divergency is crucial and can, in the case of continuum excitons, even be sufficient for reproducing the excitonic effects and yielding excellent agreement between the calculated and the experimental absorption spectrum.Comment: 6 pages, 1 figur

Complexing of Sulfur(IV) Oxide with Hexamethylenetetramine and Hexamethylenediamine in Aqueous Solutions

Interaction in the sulfur(IV) oxide–hexamethylenetetramine (hexamethylenediamine)–water systems was studied by pH-, redox-, and conductometric titration techniques. The structure and stability of the resulting molecular and ionic complexes were examined in relation to the nature and concentration of the components in solution, as well as to temperature

Bottom Production

We review the prospects for bottom production physics at the LHC.Comment: 74 pages, Latex, 71 figures, to appear in the Report of the ``1999 CERN Workshop on SM physics (and more) at the LHC'', P. Nason, G. Ridolfi, O. Schneider G.F. Tartarelli, P. Vikas (conveners

Second harmonic generation in SiC polytypes

LMTO calculations are presented for the frequency dependent second harmonic generation (SHG) in the polytypes 2H, 4H, 6H, 15R and 3C of SiC. All independent tensor components are calculated. The spectral features and the ratios of the 333 to 311 tensorial components are studied as a function of the degree of hexagonality. The relationship to the linear optical response and the underlying band structure are investigated. SHG is suggested to be a sensitive tool for investigating the near band edge interband excitations.Comment: 12 pages, 10 figure

Ab initio optical properties of Si(100)

We compute the linear optical properties of different reconstructions of the clean and hydrogenated Si(100) surface within DFT-LDA, using norm-conserving pseudopotentials. The equilibrium atomic geometries of the surfaces, determined from self-consistent total energy calculations within the Car-Parrinello scheme, strongly influence Reflectance Anisotropy Spectra (RAS), showing differences between the p(2x2) and c(4x2)reconstructions. The Differential Reflectivity spectrum for the c(4x2) reconstruction shows a positive peak at energies < 1 eV, in agreement with experimental results.Comment: fig. 2 correcte