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

TECHNOLOGICAL PARADIGMS: A JUMP TO THE SIXTH OR A SLIP DOWN TO THE FOURTH

The aim of this article is to analyse approaches to emphasizing the essence of the sixth technological paradigm (wave of innovation). The author uses the historical research method. By examining ideas on the technological paradigms (wave, cycle, paradigm, formation, etc.), the author shows the limitation of the purely economic approach to solving technological paradigms issues. The attention is paid also on the periodization of paradigms and there is an absence of a single logical basis in it. paradigms change. This circumstance does not allow us to speak about a really theoretical description of the process of changing paradigms. The situation is being considered from a wider historical perspective of the humankind existence (as a species), as a subject not only on a planetary scale. From this point of view, the essence of the sixth paradigm and the prospects for the evolution of paradigms are more clearly identified

A comparative study of density functional and density functional tight binding calculations of defects in graphene

The density functional tight binding approach (DFTB) is well adapted for the study of point and line defects in graphene based systems. After briefly reviewing the use of DFTB in this area, we present a comparative study of defect structures, energies and dynamics between DFTB results obtained using the dftb+ code, and density functional results using the localised Gaussian orbital code, AIMPRO. DFTB accurately reproduces structures and energies for a range of point defect structures such as vacancies and Stone-Wales defects in graphene, as well as various unfunctionalised and hydroxylated graphene sheet edges. Migration barriers for the vacancy and Stone-Wales defect formation barriers are accurately reproduced using a nudged elastic band approach. Finally we explore the potential for dynamic defect simulations using DFTB, taking as an example electron irradiation damage in graphene

Graphene edge structures: Folding, scrolling, tubing, rippling and twisting

Conventional three-dimensional crystal lattices are terminated by surfaces, which can demonstrate complex rebonding and rehybridisation, localised strain and dislocation formation. Two dimensional crystal lattices, of which graphene is the archetype, are terminated by lines. The additional available dimension at such interfaces opens up a range of new topological interface possibilities. We show that graphene sheet edges can adopt a range of topological distortions depending on their nature. Rehybridisation, local bond reordering, chemical functionalisation with bulky, charged, or multi-functional groups can lead to edge buckling to relieve strain, folding, rolling and even tube formation. We discuss the topological possibilities at a 2D graphene edge, and under what circumstances we expect different edge topologies to occur. Density functional calculations are used to explore in more depth different graphene edge types.Comment: Additional figure in published versio

Mechanical properties of nanosheets and nanotubes investigated using a new geometry independent volume definition

Cross-sectional area and volume become difficult to define as material dimensions approach the atomic scale. This limits the transferability of macroscopic concepts such as Young's modulus. We propose a new volume definition where the enclosed nanosheet or nanotube average electron density matches that of the parent layered bulk material. We calculate the Young's moduli for various nanosheets (including graphene, BN and MoS2) and nanotubes. Further implications of this new volume definition such as a Fermi level dependent Young's modulus and out-of-plane Poisson's ratio are shown

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

Ripple edge engineering of graphene nanoribbons

It is now possible to produce graphene nanoribbons (GNRs) with atomically defined widths. GNRs offer many opportunities for electronic devices and composites, if it is possible to establish the link between edge structure and functionalisation, and resultant GNR properties. Switching hydrogen edge termination to larger more complex functional groups such as hydroxyls or thiols induces strain at the ribbon edge. However we show that this strain is then relieved via the formation of static out-of-plane ripples. The resultant ribbons have a significantly reduced Young's Modulus which varies as a function of ribbon width, modified band gaps, as well as heterogeneous chemical reactivity along the edge. Rather than being the exception, such static edge ripples are likely on the majority of functionalized graphene ribbon edges.Comment: Supplementary Materials availabl

Low energy graphene edge termination via small diameter nanotube formation

We demonstrate that free graphene sheet edges can curl back on themselves,reconstructing as nanotubes. This results in lower formation energies than any other non-functionalised edge structure reported to date in the literature. We determine the critical tube size and formation barrier and compare with density functional simulations of other edge terminations including a new reconstructed Klein edge. Simulated high resolution electron microscopy images show why such rolled edges may be difficult to detect. Rolled zigzag edges serve as metallic conduction channels, separated from the neighbouring bulk graphene by a chain of insulating sp$^3$-carbon atoms, and introduce Van Hove singularities into the graphene density of states.Comment: To appear in Phys. Rev. Let