Theoretical Studies of CO Adsorption on Si(100)-2 × 1 Surface

Ab initio molecular orbital and density functional calculations have been carried out to investigate the adsorption of CO on the Si(100)-2 × 1 surface using the Si 9 H 12 and Si 13 H 20 cluster models of the surface. It was found that B3LYP/6-31G(d) is a reasonable level of theory for calculation of the geometries of the clusters and adsorbates, as well as energetics of the adsorbates of the CO/Si(100)-2 × 1 surface. The addition of a doubly contracted polarizarion d-function for the non-hydrogen atoms changes the calculated CO desorption energy by 1 kcal/mol. Increasing the size of the cluster from Si 9 H 12 to Si 13 H 20 , in general, increases the CO desorption energy by 1-2 kcal/mol, while it does not change the Si d -Si d , Si d -Si sub , and Si sub -Si sub bond distances, which suggests that the Si 9 H 12 cluster is a good model for the single-dimer cluster. Interaction of the CO molecule with the surface dramatically changes the Si d -Si d and Si d -Si sub bond distances corresponding to the silicon dimer on the surface and that between the first-and second-layer atoms, respectively. These results suggest that the geometry relaxation of the cluster upon interaction with gas molecules should be taken into account. Different adsorption geometries of CO on the silicon surface dimer have been studied. The adsorbed CO is most stable when bonded perpendicularly to the surface dimer with the C atom attached to one of the Si atoms. The calculated CO desorption energy at the B3LYP/6-311G(2d) level, 10.5 kcal/mol, is in good agreement with the experimental value, 11.4 kcal/mol. Vibrational frequencies of the different CO adsorption isomers have been analyzed. For the OC-normal adsorption process, an extensive search for its transition state failed to locate it; this suggests that the adsorption reaction is a nonactivated process with zero barrier

The 100th anniversary of the Federal Scientific Vegetable Center, the leader of Russian scientific vegetable growing

This year, the staff of the Federal Scientific Vegetable Center (FSVC) celebrates their 100th anniversary. Prof. S. I. Zhegalov was the recognized founder of the institution, which was reorganized from Gribovo Vegetable Experimental Station. Its team started with 14 employees, and the experimental crop area was slightly less than 4 hectares. In a short period of time (1920 to 1927), 74 cultivars of the most popular vegetable crops and a number of flower crop varieties were developed and improved. The second period of the Station’s development (1937 to 1966) was associated with the name of Acad. E. I. Ushakova. During this period, a pleiad of talented scientific plant breeders emerged and thrived: A. V. Alpatyev, S. P. Agapova, E. M. Popova, A. D. Plinka, Yu. A. Kobyakova, and others. In 1971, Gribovo Experimental Station was transformed into the All-Union Scientific Research Institute for Breeding and Seed Production of Vegetable Crops (VNIISSOK). The Institute was headed by Acad. P. F. Sokol. Under his leadership, capacity building and logistic support of the Institute were promoted: new facilities were built, and the experimental production network was expanded. Despite the difficulties associated with the reorganization and the financial and political situation in the country in 1992–2017, the staff achieved significant results during the years of the directorship by Acad. V. F. Pivovarov. New cultivars were developed to meet the demand; they occupied more than 50% of the crop area under vegetables across the country. Each year, the Institute produced 200–300 tons of elite and cultivar seeds. In 2017, the Institute was merged into the Federal Scientific Vege table Center as the keystone element. The Center also incorporated the All-Russian Research Institute of Vegetable Production and seven experiment stations throughout the Russian Federation. The Institute has been successfully cooperating with the N.I. Vavilov Institute of Plant Genetic Resources (VIR) for many years, exchanging germplasm materials and experience, and jointly developing vegetable cultivars

Comments on QED with background electric fields

It is well known that there is a total cancellation of the \emph{factorizable} IR divergences in unitary interacting field theories, such as QED and quantum gravity. In this note we show that such a cancellation does not happen in QED with background electric fields which can produce pairs. There is no factorization of the IR divergences.Comment: 14 pages, 1 figur

Exotic branes in Exceptional Field Theory: the SL(5) duality group

© 2018, The Author(s). We study how exotic branes, i.e. branes whose tensions are proportional to gs− α, with α > 2, are realised in Exceptional Field Theory (EFT). The generalised torsion of the Weitzenböck connection of the SL(5) EFT which, in the language of gauged supergravity describes the embedding tensor, is shown to classify the exotic branes whose magnetic fluxes can fit into four internal dimensions. By analysing the weight diagrams of the corresponding representations of SL(5) we determine the U-duality orbits relating geometric and non-geometric fluxes. As a further application of the formalism we consider the Kaluza-Klein monopole of 11D supergravity and rotate it into the exotic 6(3,1)-brane

The effect of seed fractions and nutrition on the physiological changes and productivity of spring barley grown in the south of Uzbekistan

The influence of physiological changes on the grain yield of spring barley sown in optimal fractions and fed with mineral fertilizers in optimal norms in irrigated light gray-meadow soils with unfavorable conditions (subject to wind erosion) of the steppe zones of the Kashkadarya region was studied

Duality Invariant M-theory: Gauged supergravities and Scherk-Schwarz reductions

We consider the reduction of the duality invariant approach to M-theory by a U-duality group valued Scherk-Schwarz twist. The result is to produce potentials for gauged supergravities that are normally associated with non-geometric compactifications. The local symmetry reduces to gauge transformations with the gaugings exactly matching those of the embedding tensor approach to gauged supergravity. Importantly, this approach now includes a nontrivial dependence of the fields on the extra coordinates of the extended space.Comment: 22 pages Latex; v2: typos corrected and references adde

Observational Constraints on Potassium Synthesis during the Formation of Stars of the Galactic Disk

The non-LTE potassium abundances in the atmospheres of 33 Galactic-disk stars are derived and the parameters of the atmospheres of 23 of the stars are determined. Neglecting departures from LTE results in a systematic overestimation of the potassium abundances and an increase in their dispersion, even for differential analyses relative to the Sun. The non-LTE corrections are significant ((-0.2)-(-0.6) dex) and depend on the surface gravities and effective temperatures of the stars. The mean potassium abundance for a sample of ten stars with [Fe/H] ∼ 0.0 is in agreement with the solar and meteoritic abundances (log ε ⊙ (K) = 5.12). As the stellar metallicity increases from [Fe/H] = (-1.0) to (0.2) dex, the [K/Fe] ratio decreases systematically from 0.3 dex to -0.1 dex. The derived dependence [K/Fe]-[Fe/H] is in agreement with the results of published model calculations of the chemical evolution of the Galaxy. This indicates the dominance of explosive oxygen burning in massive type II supernovae during the synthesis of potassium in the Galactic disk. © 2003 MAIK "Nauka/Interperiodica"