1,073 research outputs found
Pionic Atom Spectroscopy in the (d,3He) reaction at finite angles
We study the formation of deeply bound pionic atoms in the (d,3He) reactions
theoretically and show the energy spectra of the emitted 3He at finite angles,
which are expected to be observed experimentally. We find that the different
combinations of the pion-bound and neutron-hole states dominate the spectra at
different scattering angles because of the matching condition of the reaction.
We conclude that the observation of the (d,3He) reaction at finite angles will
provide the systematic information of the pionic bound states in each nucleus
and will help to develop the study of the pion properties and the partial
restoration of chiral symmetry in nuclei.Comment: 7 pages, 4 figures, 1 tabl
The 2006 Radio Outburst of a Microquasar Cyg X-3: Observation and Data
We present the results of the multi-frequency observations of radio outburst
of the microquasar Cyg X-3 in February and March 2006 with the Nobeyama 45-m
telescope, the Nobeyama Millimeter Array, and the Yamaguchi 32-m telescope.
Since the prediction of a flare by RATAN-600, the source has been monitored
from Jan 27 (UT) with these radio telescopes. At the eighteenth day after the
quench of the activity, successive flares exceeding 1 Jy were observed
successfully. The time scale of the variability in the active phase is
presumably shorter in higher frequency bands.
We also present the result of a follow-up VLBI observation at 8.4 GHz with
the Japanese VLBI Network (JVN) 2.6 days after the first rise. The VLBI image
exhibits a single core with a size of <8 mas (80 AU). The observed image was
almost stable, although the core showed rapid variation in flux density. No jet
structure was seen at a sensitivity of K.Comment: 17 pages,6 figures; accepted by PAS
Coupling biochemistry and mechanics in cell adhesion: a model for inhomogeneous stress fiber contraction
Biochemistry and mechanics are closely coupled in cell adhesion. At sites of
cell-matrix adhesion, mechanical force triggers signaling through the
Rho-pathway, which leads to structural reinforcement and increased
contractility in the actin cytoskeleton. The resulting force acts back to the
sites of adhesion, resulting in a positive feedback loop for mature adhesion.
Here we model this biochemical-mechanical feedback loop for the special case
when the actin cytoskeleton is organized in stress fibers, which are
contractile bundles of actin filaments. Activation of myosin II molecular
motors through the Rho-pathway is described by a system of reaction-diffusion
equations, which are coupled into a viscoelastic model for a contractile actin
bundle. We find strong spatial gradients in the activation of contractility and
in the corresponding deformation pattern of the stress fiber, in good agreement
with experimental findings.Comment: Revtex, 35 pages, 13 Postscript figures included, in press with New
Journal of Physics, Special Issue on The Physics of the Cytoskeleto
A radiation driven implosion model for the enhanced luminosity of protostars near HII regions
Context. Molecular clouds near the H II regions tend to harbor more luminous
protostars. Aims. Our aim in this paper is to investigate whether or not
radiation-driven implosion mechanism enhances luminosity of protostars near
regions of high-ionizing fluxes. Methods. We performed numerical simulations to
model collapse of cores exposed to UV radiation from O stars. We investigated
dependence of mass loss rates on the initial density profiles of cores and
variation of UV fluxes. We derived simple analytic estimates of accretion rates
and final masses of protostars. Results. Radiation-driven implosion mechanism
can increase accretion rates of protostars by 1-2 orders of magnitude. On the
other hand, mass loss due to photo-evaporation is not large enough to have a
significant impact on the luminosity. The increase of accretion rate makes
luminosity 1-2 orders higher than those of protostars that form without
external triggering. Conclusions. Radiation-driven implosion can help explain
the observed higher luminosity of protostars in molecular clouds near H II
regions.Comment: 9 pages, 6 figures, accepted for publication in Astronomy and
Astrophysic
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