124 research outputs found
Magnetooptical Study of Zeeman Effect in Mn modulation-doped InAs/InGaAs/InAlAs Quantum Well Structures
We report on a magneto-photoluminescence (PL) study of Mn modulation-doped
InAs/InGaAs/InAlAs quantum wells. Two PL lines corresponding to the radiative
recombination of photoelectrons with free and bound-on-Mn holes have been
observed. In the presence of a magnetic field applied in the Faraday geometry
both lines split into two circularly polarized components. While temperature
and magnetic field dependences of the splitting are well described by the
Brillouin function, providing an evidence for exchange interaction with spin
polarized manganese ions, the value of the splitting exceeds the expected value
of the giant Zeeman splitting by two orders of magnitude for a given Mn
density. Possible reasons of this striking observation are discussed
Cyclic peroxides and related initiating systems for radical polymerization of methyl methacrylate
Cyclic peroxides as initiators for the radical polymerization of methyl methacrylate were proposed. The initial rates, initiation rates, and effective activation energies of polymerization initiated by cyclic peroxides and cyclic peroxide-1-pyridyl-2-ferrocene systems were determined. The radical yields to the volume upon the thermal decomposition of cyclic peroxides and their catalytic decomposition in the presence of 1-pyridyl-2-ferrocene were determined. In combination with 1-pyridyl-2-ferrocene cyclic peroxides form efficient initiating systems favoring an increase in the polymerization rate, a decrease in the molecular weights, and an increase in syndiotacticity of the synthesized poly(methyl methacrylate). © 2013 Springer Science+Business Media New York
Exchange current contributions in null-plane quantum models of elastic electron deuteron scattering
We investigate exchange current contributions to elastic electron-deuteron
scattering using exactly Poincar\'e invariant quantum mechanics with a
null-plane kinematic symmetry. Our model exchange current is motivated by
one-pion-exchange physics. Exact current conservation and current covariance
are satisfied by using this current to compute a linearly independent set of
current matrix elements. The remaining current matrix elements are generated
from the independent matrix elements using the covariance and current
conservation constraints. The presence of the exchange current increases the
sensitivity to the choice of independent current matrix elements. Two choices
of independent matrix elements that have distinct motivations lead to a good
description of all of the elastic scattering observables for momentum transfers
below 8 (GeV).Comment: 49 Pages, 24 figure
Weak Decays in the light--front Quark Model
We study the form factors of heavy--to--heavy and heavy--to--light weak
decays using the light--front relativistic quark model. For the
heavy--to--heavy B \ra D^{(\ast)} semileptonic decays we calculate the
corresponding Isgur--Wise function for the whole kinematic region. For the
heavy--to--light B\ra P and B\ra V semileptonic decays we calculate the
form factors at ; in particular, we have derived the dependence of the
form factors on the --quark mass in the m_b \ra \infty limit. This
dependence can not be produced by extrapolating the scaling behavior of the
form factors at using the single--pole assumption. This shows that
the dependence of the form factors in regions far away from the
zero--recoil could be much more complicated than that predicted by the
single--pole assumption.Comment: 24 pages, Latex, Postscript figure included at the en
Identification and localization of transitional hepatoblasts in liver development
The article deals with the origin of liver mesenchymal cells, one of the sources of which is the epithelial-mesenchymal transition. We have determined the presence and localization of hybrid cells with incomplete epithelial-mesenchymal transition at the stages of hepatogenesis in ratsВ статье рассмотрен вопрос происхождения мезенхимальных клеток печени, одним из источников которых является эпителиально-мезенхимальный переход. Определили наличие и особенности расположения гибридных клеток с неполных эпителиально-мезенхимальным переходом на этапах гепатогенеза у кры
Deuteron Magnetic and Quadrupole Moments with a Poincar\'e Covariant Current Operator in the Front-Form Dynamics
The deuteron magnetic and quadrupole moments are unambiguosly determined
within the front-form Hamiltonian dynamics, by using a new current operator
which fulfills Poincar\'e, parity and time reversal covariance, together with
hermiticity and the continuity equation. For both quantities the usual
disagreement between theoretical and experimental results is largely removed.Comment: To appear in Phys. Rev. Let
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