6,163 research outputs found
On the Existence of Configurations of Subspaces in a Hilbert Space with Fixed Angles
For a class of -algebras, where -algebra is generated
by projections associated with vertices of graph and depends on a
parameter , we study the sets of
values of such that the algebras have nontrivial
-representations, by using the theory of spectra of graphs. In other words,
we study such values of that the corresponding configurations of
subspaces in a Hilbert space exist.Comment: Published in SIGMA (Symmetry, Integrability and Geometry: Methods and
Applications) at http://www.emis.de/journals/SIGMA
Differential diagnostic of histological specimens as a practical tool for teaching histology inforeign medical students
МЕДИЦИНСКИЕ УЧЕБНЫЕ ЗАВЕДЕНИЯОБРАЗОВАНИЕ МЕДИЦИНСКОЕСТУДЕНТЫ МЕДИЦИНСКИХ УЧЕБНЫХ ЗАВЕДЕНИЙИНОСТРАННЫЕ СТУДЕНТЫГИСТОЛОГИЯ /ОБУЧГИСТОЛОГИЯ (ДИСЦИПЛИНА)МЕТОДИКА ОБУЧЕНИЯМЕТОДИКА ПРЕПОДАВАНИ
Thermal decomposition of a honeycomb-network sheet - A Molecular Dynamics simulation study
The thermal degradation of a graphene-like two-dimensional triangular
membrane with bonds undergoing temperature-induced scission is studied by means
of Molecular Dynamics simulation using Langevin thermostat. We demonstrate that
the probability distribution of breaking bonds is highly peaked at the rim of
the membrane sheet at lower temperature whereas at higher temperature bonds
break at random anywhere in the hexagonal flake. The mean breakage time
is found to decrease with the total number of network nodes by a power law
and reveals an Arrhenian dependence on temperature .
Scission times are themselves exponentially distributed. The fragmentation
kinetics of the average number of clusters can be described by first-order
chemical reactions between network nodes of different coordination. The
distribution of fragments sizes evolves with time elapsed from a
-function through a bimodal one into a single-peaked again at late
times. Our simulation results are complemented by a set of -order
kinetic differential equations for which can be solved exactly and
compared to data derived from the computer experiment, providing deeper insight
into the thermolysis mechanism.Comment: 21pages, 9 figures, LaTeX, revised versio
MULTIPLE CORRELATION MODEL FOR ESTABLISHING THE ASSOCIATION BETWEEN ATMOSPHERIC AIR POLLUTION AND MORBIDITY
A characteristics of atmospheric air pollution during the period from 1980 till 1992 in the town of Beloslav, a settlement located in the immediate proximity of Devnya industrial complex was prepared. The following parameters were examined: dust, sulphur dioxide, sulphuric acid, hydrogen sulphide, nitric oxides, ammonia, chlorine, and hydrogen fluoride. Annual indexes of pollution presented according to the Canadian Indexing System exceeded considerably the hygienic standards concerning most atmospheric air pollutants. During the whole period of observation the total index varied between 3,22 and 8,28 one unit being the standard. The morbidity rate of the population according to the registration files for children and adults was analyzed, too. Multiple correlation and step regression analyses were applied to follow-up the influence of the atmospheric air pollution on the morbidity. There were statistically reliable correlation dependences between the atmospheric air pollution and the diseases of the respiratory, nervous, alimentary and other systems
Inversionless light amplification and optical switching controlled by state-dependent alignment of molecules
We propose a method to achieve amplification without population inversion by
anisotropic molecules whose orientation by an external electric field is
state-dependent. It is based on decoupling of the lower-state molecules from
the resonant light while the excited ones remain emitting. The suitable class
of molecules is discussed, the equation for the gain factor is derived, and the
magnitude of the inversionless amplification is estimated for the typical
experimental conditions. Such switching of the sample from absorbing to
amplifying via transparent state is shown to be possible both with the aid of
dc and ac control electric fields.Comment: AMS-LaTeX v1.2, 4 pages with 4 figure
Inversionless gain in a three-level system driven by a strong field and collisions
Inversionless gain in a three-level system driven by a strong external field
and by collisions with a buffer gas is investigated. The mechanism of
populating of the upper laser level contributed by the collision transfer as
well as by relaxation caused by a buffer gas is discussed in detail. Explicit
formulae for analysis of optimal conditions are derived. The mechanism
developed here for the incoherent pump could be generalized to other systems.Comment: RevTeX, 9 pages, 4 eps figure
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