306 research outputs found
An analogue of the Magnus problem for associative algebras
We prove an analogue of the Magnus theorem for associative algebras without
unity over arbitrary fields. Namely, if an algebra is given by n+k generators
and k relations and has an n-element system of generators, then this algebra is
a free algebra of rank n
OPO-laser system for atmospheric sounding in the MID-IR range
A laser system is designed that provides for tunable generation of nanosecond radiation pulses in the 3–4 μm range. Optical block-diagram and specifications of the system are presented. The laser system as a part of a differential absorption lidar designed can be used for remote control of pollutant concentrations along surface atmospheric path
Non-contact infrared temperature measurements in dry permafrost boreholes
While planning the COAST Expedition to the Siberian Laptev Sea in 2005, the question of how to make a short equilibrium temperature measurement in a dry borehole arose. As a result, an infrared borehole tool was developed and used in three dry boreholes (up to 60.2 m deep) in the coastal transition zone from terrestrial to sub-sea permafrost near Mamontovy Klyk in the western Laptev Sea. A depth versus temperature profile was acquired with equilibration times of 50 × 10−3 s at each depth interval. Comparison with a common resistor string revealed an offset due to limitations of accuracy of the infrared technique and the influence of the probe's massive steel housing. Therefore it was necessary to calibrate the infrared sensor with a high precision temperature logger in each borehole. The results of the temperature measurements show a highly dynamic transition zone with temperature gradients up to −0.092°C/m and heat flow of −218 mW/m. A period of submergence of only 600 years the drilled sub-sea permafrost is approaching the overlying seawater temperature at −1.61°C with a temperature gradient of 0.021°C/m and heat flow of 49 mW/m. Further offshore, 11 km from the coastline, a temperature gradient of 0.006°C/m and heat flow of 14 mW/m occur. Thus the sub-sea permafrost in the Mamontovy Klyk region has reached a critical temperature for the presence of interstitial ice. The aim of this article is to give a brief feasibility study of infrared downhole temperature measurements and to present experiences and results of its successful application
Class preserving automorphisms of unitriangular groups
Let be a unitriangular group over a field and
, where
denotes the -th term of the lower central
series of , . We prove that the group of all
class preserving automorphisms of is equal to
\Inn(\Gamma_{n,k}) if and only if is a prime field. Let .
We calculate the group of all class preserving automorphisms and class
preserving outer automorphisms of .Comment: 19 pages, accepted for publication in International Journal of
Algebra and Computatio
Correlated theory of triplet photoinduced absorption in phenylene-vinylene chains
In this paper we present results of large-scale correlated calculations of
triplet photoinduced absorption (PA) spectrum of oligomers of
poly-(para)phenylenevinylene (PPV) containing up to five phenyl rings. In
particular, the high-energy features in the triplet PA spectrum of oligo-PPVs
are the focus of this study, which, so far, have not been investigated
theoretically, or experimentally. The calculations were performed using the
Pariser-Parr-Pople (PPP) model Hamiltonian, and many-body effects were taken
into account by means of multi-reference singles-doubles configuration
interaction procedure (MRSDCI), without neglecting any molecular orbitals. The
computed triplet PA spectrum of oligo-PPVs exhibits rich structure consisting
of alternating peaks of high and low intensities. The predicted higher energy
features of the triplet spectrum can be tested in future experiments.
Additionally, theoretical estimates of exciton binding energy are also
presented.Comment: To appear in Phys. Rev.
Electron correlation effects in electron-hole recombination in organic light-emitting diodes
We develop a general theory of electron--hole recombination in organic light
emitting diodes that leads to formation of emissive singlet excitons and
nonemissive triplet excitons. We briefly review other existing theories and
show how our approach is substantively different from these theories. Using an
exact time-dependent approach to the interchain/intermolecular charge-transfer
within a long-range interacting model we find that, (i) the relative yield of
the singlet exciton in polymers is considerably larger than the 25% predicted
from statistical considerations, (ii) the singlet exciton yield increases with
chain length in oligomers, and, (iii) in small molecules containing nitrogen
heteroatoms, the relative yield of the singlet exciton is considerably smaller
and may be even close to 25%. The above results are independent of whether or
not the bond-charge repulsion, X_perp, is included in the interchain part of
the Hamiltonian for the two-chain system. The larger (smaller) yield of the
singlet (triplet) exciton in carbon-based long-chain polymers is a consequence
of both its ionic (covalent) nature and smaller (larger) binding energy. In
nitrogen containing monomers, wavefunctions are closer to the noninteracting
limit, and this decreases (increases) the relative yield of the singlet
(triplet) exciton. Our results are in qualitative agreement with
electroluminescence experiments involving both molecular and polymeric light
emitters. The time-dependent approach developed here for describing
intermolecular charge-transfer processes is completely general and may be
applied to many other such processes.Comment: 19 pages, 11 figure
The First Director: Academician A. M. Rumiantsev
Romanovskii N. V. The First Director: Academician A. M. Rumiantsev [Электронный ресурс] / N. V. Romanovskii// Sociological Research. - 2009. - Vol. 48, № 5 : The History of Sociology in Russia and the Soviet Union (I). - P. 55-64
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