514 research outputs found
Electron mass operator in a strong magnetic field
The electron mass operator in a strong magnetic field is calculated by
summation of the leading log contributions in all orders of the perturbation
theory. An influence of the strong field on the virtual photon polarization
operator is taken into account. The contribution of higher Landau levels of
virtual electrons, along with the ground Landau level, is shown to be essential
in the leading log approximation.Comment: 7 pages, LATEX, 1 PS figure, submitted to Modern Physics Letters
Prospects for Establishment of Technological Complexes in Machine Building Industry on The Basis of Electromechatronic Propulsion Systems
The authors consider prospects for technological complex establishment in machine building industry on the basis of electromechatronic propulsion systems for production of innovative products with different novelty levels: world, state, brunch, region, etc
Spiral attractors as the root of a new type of "bursting activity" in the Rosenzweig-MacArthur model
We study the peculiarities of spiral attractors in the Rosenzweig-MacArthur
model, that describes dynamics in a food chain "prey-predator-superpredator".
It is well-known that spiral attractors having a "teacup" geometry are typical
for this model at certain values of parameters for which the system can be
considered as slow-fast system. We show that these attractors appear due to the
Shilnikov scenario, the first step in which is associated with a supercritical
Andronov-Hopf bifurcation and the last step leads to the appearance of a
homoclinic attractor containing a homoclinic loop to a saddle-focus equilibrium
with two-dimension unstable manifold. It is shown that the homoclinic spiral
attractors together with the slow-fast behavior give rise to a new type of
bursting activity in this system. Intervals of fast oscillations for such type
of bursting alternate with slow motions of two types: small amplitude
oscillations near a saddle-focus equilibrium and motions near a stable slow
manifold of a fast subsystem. We demonstrate that such type of bursting
activity can be either chaotic or regular
Charge transfer and weak bonding between molecular oxygen and graphene zigzag edges at low temperatures
Electron paramagnetic resonance (EPR) study of air-physisorbed defective
carbon nano-onions evidences in favor of microwave assisted formation of
weakly-bound paramagnetic complexes comprising negatively-charged O2- ions and
edge carbon atoms carrying pi-electronic spins. These complexes being located
on the graphene edges are stable at low temperatures but irreversibly
dissociate at temperatures above 50-60 K. These EPR findings are justified by
density functional theory (DFT) calculations demonstrating transfer of an
electron from the zigzag edge of graphene-like material to oxygen molecule
physisorbed on the graphene sheet edge. This charge transfer causes changing
the spin state of the adsorbed oxygen molecule from S = 1 to S = 1/2 one. DFT
calculations show significant changes of adsorption energy of oxygen molecule
and robustness of the charge transfer to variations of the graphene-like
substrate morphology (flat and corrugated mono- and bi-layered graphene) as
well as edges passivation. The presence of H- and COOH- terminated edge carbon
sites with such corrugated substrate morphology allows formation of ZE-O2-
paramagnetic complexes characterized by small (<50 meV) binding energies and
also explains their irreversible dissociation as revealed by EPR.Comment: 28 pages, 8 figures, 2 tables, accepted in Carbon journa
Tools for evaluating the competitiveness of innovative clusters
Federal programmes to support regional clusters in Russia were introduced several years ago. Today, they need updating and revision. A promising starting point for effective support for hi-tech and innovative clusters may be an evaluation of cluster performance aimed to understand whether further development and financing of cluster projects are required and whether the list of supported clusters should be extended or reduced. This article analyses the case of the Silicon Saxony innovation cluster (Germany), using the World Bank’s methodology for cluster competitiveness evaluation. Each analysis tool is provided with concrete data obtained for Germany and the Silicon Saxony cluster over the past ten years. Competitive clusters considered in the analysis are Minalogic in Grenoble (France) and Micro- and nanosystems in Catania (Italy). The results of employing the methodology are examined from the perspective of its possible use in evaluating the competitiveness of innovative clusters in the Russian Federation. Early recommendations on adapting the methodology are produced
Dirac fermions on a disclinated flexible surface
A self-consisting gauge-theory approach to describe Dirac fermions on
flexible surfaces with a disclination is formulated. The elastic surfaces are
considered as embeddings into R^3 and a disclination is incorporated through a
topologically nontrivial gauge field of the local SO(3) group which generates
the metric with conical singularity. A smoothing of the conical singularity on
flexible surfaces is naturally accounted for by regarding the upper half of
two-sheet hyperboloid as an elasticity-induced embedding. The availability of
the zero-mode solution to the Dirac equation is analyzed.Comment: 6 page
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