13 research outputs found
ALMA Observations toward the starburst dwarf galaxy NGC 5253: I. Molecular cloud properties and scaling relations
We present high-spatial-resolution (\sim 0\farcs2, or 3\,pc) CO(2--1)
observations of the nearest young starburst dwarf galaxy, NGC\,5253, taken with
the Atacama Large Millimeter/submillimeter Array. We have identified 118
molecular clouds with average values of 4.3\,pc in radius and 2.2\,\kms\, in
velocity dispersion, which comprise the molecular cloud complexes observed
previously with 100\,pc resolution. We derive for the first time in this
galaxy the --(H) conversion factor, =
\,cm(K\,\kms), based on the
virial method. The line-width and mass-to-size relations of the resolved
molecular clouds present an offset on average toward higher line-widths and
masses with respect to quiescent regions in other nearby spiral galaxies and
our Galaxy. The offset in the scaling relation reaches its maximum in regions
close to the central starburst, where velocity dispersions are 0.5 dex
higher and gas mass surface densities are as high as =
10\,\Msol\,pc . These central clouds are gravitationally bound
despite the high internal pressure. A spatial comparison with star clusters
found in the literature enables us to identify six clouds that are associated
with young star clusters. Furthermore, the star formation efficiencies (SFEs)
of some of these clouds exceed those found in star-cluster-forming clouds
within our Galaxy. We conclude that once a super star cluster is formed, the
parent molecular clouds are rapidly dispersed by the destructive stellar
feedback, which results in such a high SFE in the central starburst of
NGC\,5253.Comment: 18 pages, 11 figures, accepted to Ap
Deficiency of Senescence Marker Protein 30 Exacerbates Cardiac Injury after Ischemia/Reperfusion
Early myocardial reperfusion is an effective therapy but ischemia/reperfusion (I/R) causes lethal myocardial injury. The aging heart was reported to show greater cardiac damage after I/R injury than that observed in young hearts. Senescence marker protein 30 (SMP30), whose expression decreases with age, plays a role in reducing oxidative stress and apoptosis. However, the impact of SMP30 on myocardial I/R injury remains to be determined. In this study, the left anterior descending coronary artery was occluded for 30 min, followed by reperfusion in wild-type (WT) and SMP30 knockout (KO) mice. After I/R, cardiomyocyte apoptosis and the ratio of infarct area/area at risk were higher, left ventricular fractional shortening was lower, and reactive oxygen species (ROS) generation was enhanced in SMP30 KO mice. Moreover, the previously increased phosphorylation of GSK-3β and Akt was lower in SMP30 KO mice than in WT mice. In cardiomyocytes, silencing of SMP30 expression attenuated Akt and GSK-3β phosphorylation, and increased Bax to Bcl-2 ratio and cardiomyocyte apoptosis induced by hydrogen peroxide. These results suggested that SMP30 deficiency augments myocardial I/R injury through ROS generation and attenuation of Akt activation
Non-strange dibaryons studied in coherent double neutral-meson photoproduction on the deuteron
The B = 2 bound/resonance state (dibaryon) is an interesting object, which can be a molecule consisting of two baryons or a spatially compact hexaquark hadron object. The yd ^ n°n°d reaction has been experimentally investigated at incident energies ranging from 0.58 to 1.15 GeV to study non-strange dibaryons. The angular distributions of deuteron emission in the yd center-of-mass energy cannot be reproduced by quasi-free production of two neutral pions followed by deuteron coalescence. Additionally a 2.14-GeV peak is observed in the n°d invariant mass distribution. These suggest a sequential process such as yd ^ RIS ^ n°RIV ^ n°n°d with an isoscalar dibaryon RIS and an isovector dibaryon RIV. Since the mass of the observed isoscalar dibaryons are close to the sum of the nucleon (N) and nucleon resonance (N*) masses, an S-wave NN* molecule may play a role as a doorway to a dibaryon