On homogeneous statistical distributions exoplanets for their dynamic parameters

Correct distributions of extrasolar systems for their orbital parameters (semi-major axes, period, eccentricity) and physical characteristics (mass, spectral type of parent star) are received. Orbital resonances in extrasolar systems are considered. It is shown, that the account of more thin effects, including with use of wavelet methods, in obviously incorrectly reduced distributions it is not justified, to what the homogeneous statistical distributions for dynamic parameters of exoplanets, received in the present work, testify.Comment: 9 pages, 15 figures; International Conference "100 years since Tunguska phenomenon: Past, present and future", (June 26-28, 2008. Russia, Moscow), Lomonosov readings 2009 (Moscow State University

Structural distinctions of Fe2O3-In2O3 composites obtained by various sol-gel procedures, and their gas-sensing features

New and various approaches to the sol–gel synthesis of advanced gas-sensing materials based on nanosized Fe2O3–In2O3 (9:1 mol) mixed oxides, which differ in phase composition and grain size, have been considered in this paper. The correlation between the structural features of the composites and their gas-sensing behavior has been established. It was found that multi-phase Fe2O3–In2O3 composites containing metastable -Fe2O3 structure are characterized by the greatest sensitivity to both reducing (C2H5OH) and oxidizing (NO2) gases tested in this paper. The influence of synthesis conditions on the structural peculiarities of the Fe2O3–In2O3 composites was studied in detail and the possibility to adjust fine structure of the materials was demonstrated

Gas-sensitive properties of oxide systems based on ln203 and Sn02 obtained by sol-gel technology

The influence of structural features of ln203, Sn02, Mo03 and Fe203 simple oxides and their composites on the properties of the corresponding semiconductor gas sensors with regards to different gases (CO, CH4, NH3, C2H5OH, CH3OH, NO, N02, 03) have been studied. Structural peculiarities of oxide systems obtained by sol-gel technology have been considered. It was shown the possibility to control the sensor sensitivity to the mentioned above gases by varying chemical composition of sensitive materials and adjusting their structure, as well as by regulat-ing of detecting temperatur

Gas-sensitive properties of thin film heterojunction structures based on Fe2O3-In2O3 nanocomposites

This paper reports an investigation of the gas-sensitive properties of thin film based on the double-layers Fe2O3/In2O3 and Fe2O3-In2O3/In2O3 towards gases with different chemical nature (C2H5OH, CH4, CO, NH3, NO2, O3). As it was found, the -Fe2O3-In2O3 composite (Fe:In = 9:1) is more sensitive to O3; on the contrary, the -Fe2O3-In2O3 system (9:1), possesses an higher sensitivity to NO2. The optimal temperature for detecting both gases is in the range 70 - 100C. Sensors based on the -Fe2O3/In2O3 heterostructure show the maximum response to C2H5OH at considerably higher temperatures (250-300C), but this layer is practically insensitive to other reducing gases like CH4, CO and NH3 in the same temperature range. An explanation of the different gas-sensitive behavior for the these samples resulted from the particular features of their structure and phase stat

Catalysts for Alkylbenzene and Alkylpyridine Ammoxidation

An increase of effectivity of binary and ternary vanadium containing oxide catalysts can be achieved by a regulation of chemical and phase catalyst composition during their preparation. Activity and selectivity of V-Ti catalysts depend on the ratio of V2O5 to VO2 in the succession of substitutional solid solutions VO2-TiO2, as well as on the crystal modification of TiO2. It was investigated the influence of vanadium oxides over the rate of the polymorfous conversion from anatase to rutile and the kind of TiO2 crystal modification over V2O5 reduction degree during the thermal treatment of V-Ti catalysts. The synthesized catalysts offered producing nicotinonitrile from 3-methylpyridine with 93-95% mol. yield. Modifying of V-Ti catalysts by SnO2 increased their activity. The reason is V=O bond weakening under the influence of SnO2. That was verified by increasing of V2O5 dissociation rate almost by an order in comparison with V-Ti catalysts. SnO2 in the ternary catalysts exists as individual phase and acts as a donor of oxygen for the lower vanadium oxides. It provides the high stability of V-Ti-Sn catalysts and possibility of obtaining isonicotinonitrile with 95-97% mol. yield from 4-methylpyridine. The investigation of the mutual influence of starting components in the ternary V-Ti-Zr catalysts showed that ZrO2 prevented the polymorphous transformation from anatase into rutile. In its turn, anatase stabilized baddeleyite, which has a higher catalytic activity than ruffite. Taking into account the mutual influence of the components, it was able to prepare the selective V-Ti-Zr catalyst. It offered obtaining nicotininitrile from 3-methylpyridine with 92-96% mol. yield

Characterization of surface species on mesoporous TiO2 prepared by TiC oxidation

Surface species responsible for low pH values of zero charge point and high sorption capacity of mesoporous TiO2 powder obtained by TiC oxidation with nitric acid were studied by FTIR, EPR and XPS methods. It was found that during the titania synthesis the oxide surface was modified by nitrate-nitrite, carboxylic groups, NOx and ·С≡ radicals which determined adsorption properties of the TiO2 powder.publishe

Stable hydrogenated graphene edge types: Normal and reconstructed Klein edges

Hydrogenated graphene edges are assumed to be either armchair, zigzag or a combination of the two. We show that the zigzag is not the most stable fully hydrogenated structure along the direction. Instead hydrogenated Klein and reconstructed Klein based edges are found to be energetically more favourable, with stabilities approaching that of armchair edges. These new structures "unify" graphene edge topology, the most stable flat hydrogenated graphene edges always consisting of pairwise bonded C2H4 edge groups, irrespective the edge orientation. When edge rippling is included, CH3 edge groups are most stable. These new fundamental hydrogen terminated edges have important implications for graphene edge imaging and spectroscopy, as well as mechanisms for graphene growth, nanotube cutting, and nanoribbon formation and behaviour.Fundação para a Ciência e a Tecnologia (FCT

Ab initio study of bilateral doping within the MoS2-NbS2 system

We present a systematic study on the stability and the structural and electronic properties of mixed molybdenum-niobium disulphides. Using density functional theory we investigate bilateral doping with up to 25 % of MoS2 (NbS2) by Nb (Mo) atoms, focusing on the precise arrangement of dopants within the host lattices. We find that over the whole range of considered concentrations, Nb doping of MoS2 occurs through a substitutional mechanism. For Mo in NbS2 both interstitial and substitutional doping can co-exist, depending upon the particular synthesis conditions. The analysis of the structural and electronic modifications of the perfect bulk systems due to the doping is presented. We show that substitutional Nb atoms introduce electron holes to the MoS2, leading to a semiconductor-metal transition. On the other hand, the Mo doping of Nb2, does not alter the metallic behavior of the initial system. The results of the present study are compared with available experimental data on mixed MoS2-NbS2 (bulk and nanoparticles).Comment: 7 pages, 6 figure