Singularities in spherically symmetric black holes in the Einstein-Yang-Mills and the Einstein-Yang-Mills with dilaton theories
for the SU(2) group are investigated. Analytical formulas describing the exponentially oscillating and power-law behavior of the metric
near a space-like singularity in a solution of the general form are presented.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 12, 855–860 (25 June 1997) 相似文献
The morphological features of carbon nanotube (CNT) polymer composites and their influence on the effective modulus are evaluated. The considered features include bundle formation from the helical sub‐bundles made of individual CNTs. The formation of bundles is considered as a result of agglomeration of individual nanotubes above and below onset of percolation and is related to electrical conductivity. The proposed geometrical model yields a bundle diameter that agrees closely with that of the experimentally measured by voltage‐contrast method and scanning electron microscopy analysis of polyimide nanocomposites. The proposed micromechanical analytical model includes the helical structure of a bundle and provides close agreement of the effective Young's modulus of nanocomposite over a wide range of CNT content. It is shown that considering the helical structure of CNT bundles and its effect on bundle modulus is vital for predicting the effective modulus of CNT‐polymer nanocomposite.
Metal‐catalyzed functionalizations at the ortho position of a directing group have become an efficient bond‐forming strategy. A wide range of transformations that employ Cp*RhIII catalysts have been described, but despite their synthetic potential, enantioselective variants that use chiral versions of the Cp* ligand remain scarce (Cp*=pentamethyl cyclopentadienyl). Cyclopentadienyl compounds with an atropchiral biaryl backbone are shown to be suitable ligands for the efficient intramolecular enantioselective hydroarylation of aryl hydroxamates. Dihydrofurans that bear methyl‐substituted quaternary stereocenters are thus obtained by C? H functionalization under mild conditions. 相似文献
Graphitic carbon nitride (g‐CN) films are important components of optoelectronic devices, but current techniques for their production, such as drop casting and spin coating, fail to deliver uniform and pinhole‐free g‐CN films on solid substrates. Here, versatile, cost‐effective, and large‐area growth of uniform and pinhole‐free g‐CN films is achieved by using a thermal vapor condensation method under atmospheric pressure. A comparison of the X‐ray diffraction and Fourier transform infrared data with the calculated infrared spectrum confirmed the graphitic build‐up of films composed of tri‐s‐triazine units. These g‐CN films possess multiple active energy states including π*, π, and lone‐pair states, which facilitate their efficient (6 % quantum yield in the solid state) photoluminescence, as confirmed by both experimental measurements and theoretical calculations. 相似文献
A facile synthetic approach for the synthesis of 1,8-naphthyridine-4(1H)-one derivatives via a catalyst free and Pd-supported tandem amination sequence is developed and described. In a case of aliphatic amines reaction proceeds in a catalyst free mode, however anilines demand Pd-supported reaction conditions. 相似文献
We report the scanning tunnelling microscopy (STM) observation of a self-organization of 4-cyano-4′-n-decylbiphenyl (10CB) molecules on the reconstructed Au(111) surface. The self-organized monolayers were obtained by the deposition from a liquid. We revealed a row-like dimer structure with regularly arranged kinks within each dimer row. The separation between neighbor kinks is equal to 4 or 5 intermolecular distances. STM-images with intramolecular resolution showed that the association of molecules in dimers is due to the interaction between cyano groups. The obtained results are discussed in terms of the balance between the molecule-molecule and molecule-substrate interactions and are supported by the results of DFT calculations. 相似文献
Ternary oxides of Li-Fe-Mn-O system with overstoichiometric spinel structure Li1+xMn1-yFeyO4, have been synthesized. The effect of composition and synthesis temperature on the electrochemical performance of the oxides as a material of positive electrodes of Li-ion batteries has been studied. The optimal temperature of synthesis was found to be 850 °C for the composition Li1.2Mn1.6Fe0.4O4. This oxide shows good reversibility at acceptable level of capacity near 105 mAh/g.Presented at the 3rd International Meeting "Advanced Batteries and Accumulators", June 16th–20th 2002, Brno, Czech Republic 相似文献