5,729 research outputs found
K*{\Lambda}(1116) photoproduction and nucleon resonances
In this presentation, we report our recent studies on the
photoproduction off the proton target, using the tree-level Born approximation,
via the effective Lagrangian approach. In addition, we include the nine (three-
or four-star confirmed) nucleon resonances below the threshold
MeV, to interpret the discrepancy between the
experiment and previous theoretical studies, in the vicinity of the threshold
region. From the numerical studies, we observe that the and
play an important role for the cross-section enhancement near
the . It also turns out that, in order to reproduce the
data, we have the vector coupling constants
and
.Comment: 2 pages, 2 figures, talk given at International Conference on the
structure of baryons, BARYONS'10, Dec. 7-11, 2010, Osaka, Japa
Recommended from our members
Expression of Heterologous OsDHAR Gene Improves Glutathione (GSH)-Dependent Antioxidant System and Maintenance of Cellular Redox Status in Synechococcus elongatus PCC 7942.
An excess of reactive oxygen species (ROS) can cause severe oxidative damage to cellular components in photosynthetic cells. Antioxidant systems, such as the glutathione (GSH) pools, regulate redox status in cells to guard against such damage. Dehydroascorbate reductase (DHAR, EC 1.8.5.1) catalyzes the glutathione-dependent reduction of oxidized ascorbate (dehydroascorbate) and contains a redox active site and glutathione binding-site. The DHAR gene is important in biological and abiotic stress responses involving reduction of the oxidative damage caused by ROS. In this study, transgenic Synechococcus elongatus PCC 7942 (TA) was constructed by cloning the Oryza sativa L. japonica DHAR (OsDHAR) gene controlled by an isopropyl β-D-1-thiogalactopyranoside (IPTG)-inducible promoter (Ptrc) into the cyanobacterium to study the functional activities of OsDHAR under oxidative stress caused by hydrogen peroxide exposure. OsDHAR expression increased the growth of S. elongatus PCC 7942 under oxidative stress by reducing the levels of hydroperoxides and malondialdehyde (MDA) and mitigating the loss of chlorophyll. DHAR and glutathione S-transferase activity were higher than in the wild-type S. elongatus PCC 7942 (WT). Additionally, overexpression of OsDHAR in S. elongatus PCC 7942 greatly increased the glutathione (GSH)/glutathione disulfide (GSSG) ratio in the presence or absence of hydrogen peroxide. These results strongly suggest that DHAR attenuates deleterious oxidative effects via the glutathione (GSH)-dependent antioxidant system in cyanobacterial cells. The expression of heterologous OsDHAR in S. elongatus PCC 7942 protected cells from oxidative damage through a GSH-dependent antioxidant system via GSH-dependent reactions at the redox active site and GSH binding site residues during oxidative stress
J/psi hadron interaction in vacuum and in QGP
Motivated by the recent lattice data that will survive up to
1.6, we calculate the thermal width of at finite temperature in
perturbative QCD. The inputs of the calculation are the parton quarkonium
dissociation cross sections at the NLO in QCD, which were previously obtained
by Song and Lee, and a gaussian charmonium wave function, whose size were
fitted to an estimate by Wong by solving the schrodinger equation for
charmonium in a potential extracted from the lattice at finite temperature. We
find that the total thermal width above 1.4 becomes larger than 100 to 200
MeV, depending on the effective thermal masses of the quark and gluon, which we
take it to vary from 600 to 400 MeV.Comment: 4 pages, Talk at Quark Matter 200
Multiple Failure Survivability in WDM Mesh Networks
Coordinated Science Laboratory was formerly known as Control Systems LaboratoryNational Science Foundation (NSF) / ANI 01-21662 ITR and ACI 99-84492 CAREE
Observational Evidence for the Effect of Amplification Bias in Gravitational Microlensing Experiments
Recently Alard\markcite{alard1996} proposed to detect the shift of a star's
image centroid, , as a method to identify the lensed source among
blended stars. Goldberg & Wo\'zniak\markcite{goldberg1997} actually applied
this method to the OGLE-1 database and found that 7 out of 15 events showed
significant centroid shifts of arcsec. The amount of
centroid shift has been estimated theoretically by
Goldberg.\markcite{goldberg1997} However, he treated the problem in general and
did not apply it to a particular survey or field, and thus based his estimates
on simple toy model luminosity functions (i.e., power laws). In this paper, we
construct the expected distribution of for Galactic bulge events by
using the precise stellar LF observed by Holtzman et al.\markcite{holtzman1998}
using HST. Their LF is complete up to (),
corresponding to faint M-type stars. In our analysis we find that regular
blending cannot produce a large fraction of events with measurable centroid
shifts. By contrast, a significant fraction of events would have measurable
centroid shifts if they are affected by amplification-bias blending. Therefore,
Goldberg & Wo\'zniak's measurements of large centroid shifts for a large
fraction of microlensing events confirms the prediction of Han and Alard that a
large fraction of Galactic bulge events are affected by amplification-bias
blending.Comment: total 15 pages, including 6 figures, and no Table, submitted to ApJ
on Apr 26 1998, email [email protected]
Pion and Kaon Electromagnetic Form Factors in a Effective Lagrangian
A SU(2) effective lagrangian is extended to a by
including the vector and axial vector meson. With this effective lagrangian,
electromagnetic form factors of charged pion and kaon are calculated. The
pseudoscalar meson loops are taken into account. Good agreement with
experimental data is obtained for those form factors. Decay widths of and are also calculated and shown to agree with
experimental data very well.Comment: 19pages, 7figure
Local structures of polar wurtzites Zn_{1-x}Mg_{x}O studied by Raman and {67}Zn/{25}Mg NMR spectroscopies and by total neutron scattering
Local compositions and structures of Zn_{1-x}Mg_{x}O alloys have been
investigated by Raman and solid-state {67}Zn/{25}Mg nuclear magnetic resonance
(NMR) spectroscopies, and by neutron pair-distribution-function (PDF) analyses.
The E2(low) and E2(high) Raman modes of Zn_{1-x}Mg_{x}O display Gaussian- and
Lorentzian-type profiles, respectively. At higher Mg substitutions, both modes
become broader, while their peak positions shift in opposite directions. The
evolution of Raman spectra from Zn_{1-x}Mg_{x}O solid solutions are discussed
in terms of lattice deformation associated with the distinct coordination
preferences of Zn and Mg. Solid-state magic-angle-spinning (MAS) NMR studies
suggest that the local electronic environments of {67}Zn in ZnO are only weakly
modified by the 15% substitution of Mg for Zn. {25}Mg MAS spectra of
Zn_{0.85}Mg_{0.15}O show an unusual upfield shift, demonstrating the prominent
shielding ability of Zn in the nearby oxidic coordination sphere. Neutron PDF
analyses of Zn_{0.875}Mg_{0.125}O using a 2x2x1 supercell corresponding to
Zn_{7}MgO_{8} suggest that the mean local geometry of MgO_{4} fragments concurs
with previous density functional theory (DFT)-based structural relaxations of
hexagonal wurtzite MgO. MgO_{4} tetrahedra are markedly compressed along their
c-axes and are smaller in volume than ZnO_{4} units by ~6%. Mg atoms in
Zn_{1-x}Mg_{x}O have a shorter bond to the -axial oxygen atom than to the
three lateral oxygen atoms, which is distinct from the coordination of Zn. The
precise structure, both local and average, of Zn_{0.875}Mg_{0.125}O obtained
from time-of-flight total neutron scattering supports the view that
Mg-substitution in ZnO results in increased total spontaneous polarization.Comment: 12 pages, 14 figures, 2 table
The Globular Cluster System of M60 (NGC 4649). I. CFHT MOS Spectroscopy and Database
We present the measurement of radial velocities for globular clusters in M60,
giant elliptical galaxy in the Virgo cluster. Target globular cluster
candidates were selected using the Washington photometry based on the deep
16\arcmin \times 16\arcmin images taken at the KPNO 4m and using the
photometry derived from the HST/WFPC2 archive images. The spectra of the target
objects were obtained using the Multi-Object Spectrograph (MOS) at the
Canada-France-Hawaii Telescope (CFHT). We have measured the radial velocity for
111 objects in the field of M60: 93 globular clusters (72 blue globular
clusters with and 21 red globular clusters with
), 11 foreground stars, 6 small galaxies, and the nucleus of
M60. The measured velocities of the 93 globular clusters range from
km s to km s, with a mean value of
km s, which is in good agreement with the velocity of the nucleus of M60
( km s). Combining our results with data in the
literature, we present a master catalog of radial velocities for 121 globular
clusters in M60. The velocity dispersion of the globular clusters in the master
catalog is found to be km s for the entire sample,
km s for 83 blue globular clusters, and
km s for 38 red globular clusters.Comment: 29 pages, 8 figures. To appear in Ap
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