474 research outputs found
Lambda(1405) as a Resonance in the Baryon-Meson Scattering Coupled to the q^3 State in a Quark Model
In order to describe Lambda(1405) as a resonance in the baryon-meson
scattering, we have investigated q^3-q qbar scattering system with the
flavor-singlet q^3 (0s)^2(0p) state (the Lambda^1 pole). The scattering is
treated by the quark cluster model (QCM). The Lambda^1 pole is treated as a
bound state embedded in the continuum. We found that the peak appears below the
N Kbar threshold in the spin one half, isospin 0 channel even if the mass of
the Lambda^1 pole is above the threshold. This peak disappears when the
coupling to the Lambda^1 pole is switched off. To use the observed hadron mass
in the kinetic part of QCM is also found to be important to reproduce a peak
just below the N Kbar threshold.Comment: 16 pages and 7 figure
P-wave Pentaquark and its Decay in the Quark Model with Instanton Induced Interaction
P-wave pentaquarks with strangeness +1, I=0 and J^P=1/2^+ are studied in the
non-relativistic quark model with instanton induced interaction (III). We
present their mass splittings and orbital-spin-isospin-color structures. It is
found that decompositions of the wave functions are sensitive to III, while the
mass splittings are insensitive. The decay of the lowest energy pentaquark,
\Theta^+, is found to be suppressed when the contribution of III is increased.
Its wave function is dominated by Jaffe-Wilczek-type configuration at large
III.Comment: 9 pages, 5 figure
Effects of Instanton Induced Interaction on the Pentaquarks
Roles of instanton induced interactions (III) in the masses of pentaquark
baryons, Theta^+ (J=1/2 and 3/2) and Xi^{--}, and a dibaryon, H, are discussed
using the MIT bag model in the negative parity case. It is shown that the
two-body terms in III give a strong attraction mainly due to the increase of
the number of pairs in multi-quark systems. In contrast, the three-body u-d-s
interaction is repulsive. It is found that III lowers the mass of Theta^+ as
much as 100 MeV from the mass predicted by the bag model without III.Comment: 11 pages, 3 figure
Adaptability of Maize--Italian Ryegrass Cropping to Variable Sowing Dates by Life Cycle Assessment in Southern Kyushu, Japan
Charmonium and meson-molecule hybrid tetraquarks - Vector meson width and the isospin breaking in the X(3872) decay
In the X(3872) decay, both of the J/\psi\pi\pi\ and J/\psi\pi\pi\pi\
branching fractions are observed experimentally, and their sizes are comparable
to each other. In order to clarify the mechanism to cause such a large isospin
violation, we investigate X(3872) employing a model of coupled-channel
two-meson scattering with a ccbar core. The two-meson states consist of
D0Dbar*0, D+Dbar*-, J/\psi\rho, and J/\psi\omega. The effects of the \rho\ and
\omega\ meson width are also taken into account.
We calculate the transfer strength from the ccbar core to the final two-meson
states. It is found that very narrow J/\psi\rho\ and J/\psi\omega\ peaks appear
very close to the D0Dbar*0 threshold for a wide range of variation in the
parameter sets. The size of the J/\psi\rho\ peak is almost the same as that of
J/\psi\omega, which is consistent with the experiments. The large width of the
\rho\ meson makes the originally small isospin violation by about five times
larger.Comment: 4 pages, 5figures, proceedings of APFB201
Formation of a Massive Black Hole at the Center of the Superbubble in M82
We performed 12CO(1-0), 13CO(1-0), and HCN(1-0) interferometric observations
of the central region (about 450 pc in radius) of M82 with the Nobeyama
Millimeter Array, and have successfully imaged a molecular superbubble and
spurs. The center of the superbubble is clearly shifted from the nucleus by 140
pc. This position is close to that of the massive black hole (BH) of >460 Mo
and the 2.2 micron secondary peak (a luminous supergiant dominated cluster),
which strongly suggests that these objects may be related to the formation of
the superbubble. Consideration of star formation in the cluster based on the
infrared data indicates that (1) energy release from supernovae can account for
the kinetic energy of the superbubble, (2) the total mass of stellar-mass BHs
available for building-up the massive BH may be much higher than 460 Mo, and
(3) it is possible to form the middle-mass BH of 100-1000 Mo within the
timescale of the superbubble. We suggest that the massive BH was produced and
is growing in the intense starburst region.Comment: 9 pages, 3 figures, to appear in ApJ Lette
Mapping candidate QTLs related to plant persistency in red clover
Red clover (Trifolium pratense L.) is a diploid (2n = 14), self-incompatible legume that is widely cultivated as a forage legume in cold geographical regions. Because it is a short-lived perennial species, improvement of plant persistency is the most important objective for red clover breeding. To develop a marker-assisted selection (MAS) approach for red clover, we identified candidate QTLs related to plant persistency. Two full-sib mapping populations, 272 × WF1680 and HR × R130, were used for QTL identification. Resistance to Sclerotinia trifoliorum and Fusarium species, as well as to winter hardiness, was investigated in the laboratory and in field experiments in Moscow region (Russia), and Sapporo (Japan). With the genotype data derived from microsatellite and other DNA markers, candidate QTLs were identified by simple interval mapping (SIM), Kruskal–Wallis analysis (KW analysis) and genotype matrix mapping (GMM). A total of 10 and 23 candidate QTL regions for plant persistency were identified in the 272 × WF1680 and the HR × R130 mapping populations, respectively. The QTLs identified by multiple mapping approaches were mapped on linkage group (LG) 3 and LG6. The significant QTL interactions identified by GMM explained the higher phenotypic variation than single effect QTLs. Identification of haplotypes having positive effect QTLs in each parent were first demonstrated in this study for pseudo-testcross mapping populations in plant species using experimental data. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00122-009-1253-5) contains supplementary material, which is available to authorized users
Role of Heat Shock Protein 70 in Induction of Stress Fiber Formation in Rat Arterial Endothelial Cells in Response to Stretch Stress
We investigated the mechanism by which endothelial cells (ECs) resist various forms of physical stress using an experimental system consisting of rat arterial EC sheets. Formation of actin stress fibers (SFs) and expression of endothelial heat-shock stress proteins (HSPs) in response to mechanical stretch stress were assessed by immunofluorescence microscopy. Stretch stimulation increased expression of HSPs 25 and 70, but not that of HSP 90. Treatment with SB203580, a p38 MAP kinase inhibitor that acts upstream of the HSP 25 activation cascade, or with geldanamycin, an inhibitor of HSP 90, had no effect on the SF formation response to mechanical stretch stress. In contrast, treatment with quercetin, an HSP 70 inhibitor, inhibited both upregulation of endothelial HSP 70 and formation of SFs in response to tensile stress. In addition, treatment of stretched ECs with cytochalasin D, which disrupts SF formation, did not adversely affect stretch-induced upregulation of endothelial HSP 70. Our data suggest that endothelial HSP 70 plays an important role in inducing SF formation in response to tensile stress
Tungsten isotopic compositions in stardust SiC grains from the Murchison meteorite: Constraints on the s-process in the Hf-Ta-W-Re-Os region
We report the first tungsten isotopic measurements in stardust silicon
carbide (SiC) grains recovered from the Murchison carbonaceous chondrite. The
isotopes 182W, 183W, 184W, 186W and 179Hf, 180Hf were measured on both an
aggregate (KJB fraction) and single stardust SiC grains (LS+LU fraction)
believed to have condensed in the outflows of low-mass carbon-rich asymptotic
giant branch (AGB) stars with close-to-solar metallicity. The SiC aggregate
shows small deviations from terrestrial (=solar) composition in the 182W/184W
and 183W/184W ratios, with deficits in 182W and 183W with respect to 184W. The
186W/184W ratio, however, shows no apparent deviation from the solar value.
Tungsten isotopic measurements in single mainstream stardust SiC grains
revealed lower than solar 182W/184W, 183W/184W, and 186W/184W ratios. We have
compared the SiC data with theoretical predictions of the evolution of W
isotopic ratios in the envelopes of AGB stars. These ratios are affected by the
slow neutron-capture process and match the SiC data regarding their 182W/184W,
183W/184W, and 179Hf/180Hf isotopic compositions, although a small adjustment
in the s-process production of 183W is needed in order to have a better
agreement between the SiC data and model predictions. The models cannot explain
the 186W/184W ratios observed in the SiC grains, even when the current 185W
neutron-capture cross section is increased by a factor of two. Further study is
required to better assess how model uncertainties (e.g., the formation of the
13C neutron source, the mass-loss law, the modelling of the third dredge-up,
and the efficiency of the 22Ne neutron source) may affect current s-process
predictions.Comment: Accepted for Publication on The Astrophysical Journal 43 pages, 2
tables, 7 figure
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