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The influence of the static magnetic field on the edge states of finite zig-zag nanotubes has been explored theoretically by the tight-binding approximation. It was found that the magnetic field removes the degeneracy of the energy levels of the edge states. Investigation of the formation of new edge states by the magnetic field indicated the dependence of the number of these states on the length of a nanotube. 相似文献
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Zuzana Barbieriková Mária Mihalíková Vlasta Brezová 《Photochemistry and photobiology》2012,88(6):1442-1454
The reactions of sterically hindered amines (SHA) were investigated in acetonitrile solutions and TiO2 suspensions upon exposure to monochromatic radiation, λ = 365 nm, by means of in situ EPR spectroscopy. The formation of singlet oxygen, as one of the possible oxidation agents for SHA, in these systems is affected significantly by solvent used and the experimental conditions. Experiments in homogeneous media evidenced alternative pathways for the SHA oxidation with a variety reactive oxygen species involved. In anhydrous acetonitrile solutions containing KO2, the SHA oxidation was negligible not only in the dark but also on continuous exposure. However, the presence of water, even at low concentrations, led to the transformation of O2?? to singlet oxygen and hydrogen peroxide, which served as a source of hydroxyl radicals. These species participated in oxidation of SHA resulting in the generation of nitroxide radicals. To investigate the influence of different competitive reactions of SHA with other ROS formed upon TiO2 photoexcitation, a series of experiments using different additives (e.g. KO2, H2O2, NaN3, dimethylsulfoxide, methanol as organic cosolvents) under air or argon were performed. The detailed analysis of paramagnetic intermediates formed upon the irradiation of the studied systems was accomplished using EPR spin trapping technique. 相似文献
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V. A. Osipov E. A. Kochetov M. Pudlak 《Journal of Experimental and Theoretical Physics》2003,96(1):140-149
The electronic structure of graphitic nanoparticles is investigated within a gauge field-theory model. The local and total densities of states (DOS) near the pentagonal defects (disclinations) are calculated for three geometries: sphere, cone, and hyperboloid. It is found that the low-energy electron states have a rather specific dependence on both the energy and the distance from a disclination line. In particular, the low-energy total DOS has a cusp that drops to zero at the Fermi energy for disclinations with the Frank index v<1/2, while a region of a nonzero DOS across the Fermi level is formed for v=1/2. The true zero-mode fermion state is found for the graphitic hyperboloid. The appearance of an enhanced charge density near the Fermi level for nanocones with a 60° opening angle (180° disclination) is predicted. 相似文献
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Konstantin Nikolaevich Pichugin Mihal Pudlak Rashid Giyasovich Nazmitdinov 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(6):1-10
We report a study of the normal and superconducting state properties of the Ti x V1?x alloys for x = 0.4, 0.6, 0.7 and 0.8 with the help of dc magnetization, electrical resistivity and heat capacity measurements along with the electronic structure calculation. The superconducting transition temperature T c of these alloys is higher than that of elemental Ti and is also higher than elemental V for x ≤ 0.7. The roles of electron density of states, electron-phonon coupling and spin fluctuations in the normal and superconducting state properties of these alloys have been investigated in detail. The experimentally observed value of T c is found to be considerably lower than that estimated on the basis of electron density of states and electron-phonon coupling in the x = 0.4, 0.6 and 0.7 alloys. There is some evidence as well for the preformed Cooper pair in all these Ti-V alloys in the temperature regime well above T c . Similar to x = 0.6 [Md. Matin, L.S. Sharath Chandra, R.K. Meena, M.K. Chattopadhyay, A.K. Sinha, M.N. Singh, S.B. Roy, Physica B 436, 20 (2014)], the normal state properties of the x = 0.4 alloy showed the signature of the presence of spin fluctuations. The difference between the experimentally observed T c and that estimated by considering electron density of states and electron-phonon coupling in the x = 0.4, 0.6 and 0.7 alloys is attributed to the possible influence of these spin fluctuations. We show that the non-monotonous variation of T c as a function of x in the Ti x V1?x alloys is due to the combined effects of the electron-phonon coupling and the spin fluctuations. 相似文献
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The effect of an electric field on the electron transfer in the bacterial reaction centers is investigated. The rate constants
and quantum yields affected by the electric field for wild type (WT) and reaction center (RC) mutant of Rhodobacter capsulatus were computed. The dependence of the asymmetry of electron transfer in electric field on the temperature was evaluated. We
found stable electron transfer for WT of the reaction center towards an electric field in comparison with the F(L121)D mutant
of RC. We found quantum yields sensitive to the variation of the medium reorganization energy at low temperatures and strong
electric fields. The quantum yields for unoriented RC samples were also calculated. 相似文献
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Michal?Pudlak Richard?PincakEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2013,86(3):107
The electronic structure of the zig-zag bilayer strip is analyzed. The electronic spectraof the bilayer strip is computed. The dependence of the edge state band flatness on thebilayer width is found. The density of states at the Fermi level is analytically computed.It is shown that it has the singularity which depends on the width of the bilayer strip.There is also asymmetry in the density of states below and above the Fermi energy. 相似文献
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M. Pudlak R. Pincak 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(4):565-576
The electronic spectra for double-wall zigzag and armchair
nanotubes are found. The influence of nanotube curvatures on the
electronic spectra is also calculated. Our finding that the outer
shell is hole doped by the inner shell is in the difference
between Fermi levels of individual shells which originate from the
different hybridization of π orbital. The shift and rotation
of the inner nanotube with respect to the outer nanotube are
investigated. We found stable semimetal characteristics of the
armchair DWNTs in regard of the shift and rotation of the inner
nanotube. We predict the shift of kF towards the bigger wave
vectors with decreasing of the radius of the armchair nanotube. 相似文献
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R J Krueger T R Hobbs K A Mihal J Tehrani M G Zeece 《Journal of chromatography. A》1991,543(2):451-461
The specificity and rate of cleavage of adrenocorticotrophic hormone (ACTH) peptide bonds by endoproteinase Arg C were analyzed using capillary electrophoresis (CE) and reversed-phase (C18) high-performance liquid chromatography (HPLC). Acidic cleavage products were readily resolved by CE in uncoated capillaries using low ionic strength electrolytes. However, products predicted to have a net positive charge greater than 2 or more than 4 positively charged groups per peptide did not migrate out from the capillary at low ionic strength. Addition of salts and zwitterions to the electrolyte decreased capillary-peptide interactions such that all of the ACTH peptides examined were eluted with high efficiency separation by CE. Commercially obtained endoproteinase Arg C preparations exhibited peptidase activity at Lys-15-Lys16 and at Lys16-Arg17 in addition to the expected cleavage at Arg-X bonds. ACTH peptide bond cleavage rates for Arg8-Trp9, Arg17-Arg-18, Lys15-Lys16, and Lys16-Arg17 were 1.46, 0.096, 0.57, and 0.029 mumol min-1 mg-1 respectively. CE separations generally exhibited better resolution and were accomplished in shorter times than C18 HPLC separations. These properties make CE a particularly appropriate method for kinetic analysis of proteolytic enzyme action on peptide substrates. 相似文献