380 research outputs found
Effect of light polarization on plasma distribution and filament formation
We show that, for 200 fs light pulses at 790 nm, the formation of filaments
is strongly affected by the laser light polarization . Filamentation does not
exist for a pure circularly polarized light, propagating in vacuum before
focusing in air, while there is no difference for focusing the light in air or
vacuum for linearly polarized light.Comment: 4pages 2 figure
High resolution studies of low-energy electron attachment to SF5Cl: Product anions and absolute cross sections
Low energy electron attachment to SFCl was studied at high energy resolution by mass spectrometric detection of the product anions. Two variants of the laser photoelectron attachment (LPA) technique (Kaiserslautern) were used for determining the threshold behaviour of the yield for SF formation at about 1 meV resolution, and to investigate the relative cross sections for Cl, FCl, and SF formation towards higher energies (up to 1 eV) at about 20 meV resolution. Thermal swarm measurements (Birmingham) were used to place the relative LPA cross sections on an absolute scale. A trochoidal electron monochromator (Innsbruck) was used for survey measurements of the relative cross sections for the different product anions over the energy range of 0-14 eV with a resolution of 0.30 eV. Combined with earlier beam data (taken at Berlin, J. Chem. Phys. 88 (1988) 149), the present experimental results provide a detailed set of partial cross sections for anion formation in low-energy electron collisions with SFCl
Spreading Dynamics of Polymer Nanodroplets
The spreading of polymer droplets is studied using molecular dynamics
simulations. To study the dynamics of both the precursor foot and the bulk
droplet, large drops of ~200,000 monomers are simulated using a bead-spring
model for polymers of chain length 10, 20, and 40 monomers per chain. We
compare spreading on flat and atomistic surfaces, chain length effects, and
different applications of the Langevin and dissipative particle dynamics
thermostats. We find diffusive behavior for the precursor foot and good
agreement with the molecular kinetic model of droplet spreading using both flat
and atomistic surfaces. Despite the large system size and long simulation time
relative to previous simulations, we find no evidence of hydrodynamic behavior
in the spreading droplet.Comment: Physical Review E 11 pages 10 figure
Thyroid dysfunction caused by second-generation tyrosine kinase inhibitors in Philadelphia chromosome-positive chronic myeloid leukemia
BACKGROUND: Thyroid dysfunction is a well-known adverse effect of first-generation tyrosine kinase inhibitors (TKIs), like sunitinib. The aim of this study was to investigate the effect of second-generation TKIs on thyroid function. METHODS: We retrospectively assessed the effect of the first-generation TKI imatinib and the second-generation TKI nilotinib and dasatinib on thyroid function tests in 73 Philadelphia chromosome-positive (Ph-positive) chronic myeloid leukemia patients. RESULTS: Overall, 33 of 73 (45%) had one or more thyroid function test abnormalities during follow-up. Hypothyroidism or hyperthyroidism were found in 18 of 73 (25%) and 21 of 73 (29%) cases after a median of 6 and 22 weeks, respectively. In most patients (29 of 39, 74%) thyroid dysfunction was transient without clinical symptoms. Therapy of hypo-/hyperthyroidism was required in three patients. Thyroid dysfunction never resulted in the discontinuation of TKI therapy. Under treatment with imatinib, nilotinib, and dasatinib, thyroid abnormalities were detected in 25%, 55%, and 70%, respectively. Four of 55 patients (7%) treated with nilotinib had evidence for an autoimmune thyroiditis (antibody positive in 3 of 4 patients) with an episode of hyperthyroidism preceding hypothyroidism. CONCLUSIONS: Thyroid dysfunction is a common adverse event with second-generation TKI therapy in patients with Ph-positive chronic myeloid leukemia. Although the mechanism is still unclear, the high frequency of thyroid abnormalities, including autoimmune thyroiditis, warrants regular and long-term monitoring of thyroid function in these patients
Magnetic Moment of The Pentaquark State
We have calculated the magnetic moment of the recently observed
pentaquark in the framework of the light cone QCD sum rules using the photon
distribution amplitudes. We find that ,
which is quite small. We also compare our result with predictions of other
groups.Comment: 1 eps figure, 13 page
Learning Automata Based Algorithms for Mapping of a Class of Independent Tasks over Highly Heterogeneous Grids
Abstract. The computational grid provides a platform for exploiting various computational resources over wide area networks. One of the concerns in implementing computational grid environment is how to effectively map tasks onto resources in order to gain high utilization in the highly heterogeneous environment of the grid. In this paper, three algorithms for task mapping based on learning automata are introduced. To show the effectiveness of the proposed algorithms, computer simulations have been conducted. The results of experiments show that the proposed algorithms outperform two best existing mapping algorithms when the heterogeneity of the environment is very high. 1
Baryon Tri-local Interpolating Fields
We systematically investigate tri-local (non-local) three-quark baryon fields
with U_L(2)*U_R(2) chiral symmetry, according to their Lorentz and isospin
(flavor) group representations. We note that they can also be called as
"nucleon wave functions" due to this full non-locality. We study their chiral
transformation properties and find all the possible chiral multiplets
consisting J=1/2 and J=3/2 baryon fields. We find that the axial coupling
constant |g_A| = 5/3 is only for nucleon fields belonging to the chiral
representation (1/2,1)+(1,1/2) which contains both nucleon fields and Delta
fields. Moreover, all the nucleon fields belonging to this representation have
|g_A| = 5/3.Comment: 8 pages, 3 tables, accepted by EPJ
Realistic Equations of State for the Primeval Universe
Early universe equations of state including realistic interactions between
constituents are built up. Under certain reasonable assumptions, these
equations are able to generate an inflationary regime prior to the
nucleosynthesis period. The resulting accelerated expansion is intense enough
to solve the flatness and horizon problems. In the cases of curvature parameter
\kappa equal to 0 or +1, the model is able to avoid the initial singularity and
offers a natural explanation for why the universe is in expansion.Comment: 32 pages, 5 figures. Citations added in this version. Accepted EPJ
Infrared exponents and the strong-coupling limit in lattice Landau gauge
We study the gluon and ghost propagators of lattice Landau gauge in the
strong-coupling limit beta=0 in pure SU(2) lattice gauge theory to find
evidence of the conformal infrared behavior of these propagators as predicted
by a variety of functional continuum methods for asymptotically small momenta
. In the strong-coupling limit, this same
behavior is obtained for the larger values of a^2q^2 (in units of the lattice
spacing a), where it is otherwise swamped by the gauge field dynamics.
Deviations for a^2q^2 < 1 are well parameterized by a transverse gluon mass
. Perhaps unexpectedly, these deviations are thus no finite-volume
effect but persist in the infinite-volume limit. They furthermore depend on the
definition of gauge fields on the lattice, while the asymptotic conformal
behavior does not. We also comment on a misinterpretation of our results by
Cucchieri and Mendes in Phys. Rev. D81 (2010) 016005.Comment: 17 pages, 12 figures. Revised version (mainly sections I and II);
references and comments on subsequent work on the subject added
Strong-coupling study of the Gribov ambiguity in lattice Landau gauge
We study the strong-coupling limit beta=0 of lattice SU(2) Landau gauge
Yang-Mills theory. In this limit the lattice spacing is infinite, and thus all
momenta in physical units are infinitesimally small. Hence, the infrared
behavior can be assessed at sufficiently large lattice momenta. Our results
show that at the lattice volumes used here, the Gribov ambiguity has an
enormous effect on the ghost propagator in all dimensions. This underlines the
severity of the Gribov problem and calls for refined studies also at finite
beta. In turn, the gluon propagator only mildly depends on the Gribov
ambiguity.Comment: 14 pages, 22 figures; minor changes, matches version to appear in
Eur. Phys. J.
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