195 research outputs found
The formation of globular clusters with top-heavy initial mass functions
We study the formation of globular clusters in massive compact clouds with
the low-metallicity of by performing three-dimensional
radiative-hydrodynamics simulations. Considering the uncertainty of the initial
mass function (IMF) of stars formed in low-metallicity and high-density clouds,
we investigate the impacts of the IMF on the cloud condition for the GC
formation with the range of the power-law index of IMF as . We
find that the threshold surface density () for the GC
formation increases from at to
at in the cases of clouds with
because the emissivity of ionizing photons per
stellar mass increases as decreases. For , saturates with that is quite rare
and observed only in local starburst galaxies due to e.g., merger processes.
Thus, we suggest that formation sites of low-metallicity GCs could be limited
only in the very high-surface density regions. We also find that can be modelled by a power-law function with the cloud mass () and the emissivity of ionizing photons () as . Based on the relation between the power-law slope of
IMF and , future observations with e.g., the James Webb Space
Telescope can allow us to constrain the IMF of GCs.Comment: 9 pages, 6 figures, accepted for publication in MNRA
Generation of high circular polarization of interstellar Lyman radiation triggering biological homochirality
The homochirality of biological molecules on the Earth is a long-standing
mystery regarding the origin of life. Circularly polarized ultraviolet (UV)
light could induce the enantiomeric excess of biological molecules in the
interstellar medium, leading to the homochirality on the earth. By performing
3D radiation transfer simulations with multiple scattering processes in
interstellar dusty slabs, we study the generation of circular polarization (CP)
of ultraviolet light at Lyman () as well
as in the near-infrared (NIR, ) wavelengths. Our
simulations show that the distributions of CP exhibit a symmetric quadrupole
pattern, regardless of wavelength and viewing angle. The CP degree of scattered
light from a dusty slab composed of aligned grains is percent for
Ly and percent at NIR wavelengths in the case of oblate grains
with an MRN size distribution. We find that the CP degree of Ly is well
correlated with that in the NIR regardless of viewing angles, whilst being a
factor of higher. Thus, high CP of Ly is expected in sites
where NIR CP is detected. We suggest that such circularly polarized Ly
may initiate the enantiomeric excess of biological molecules in space.Comment: 10 pages, 11 figures, accepted for publication in MNRA
Differential Expression of Survivin in Mammary Gland Diseases
Objective: Unlike other inhibitors of apoptosis proteins (IAP), survivin is expressed during fetal development, cannot be detected in normal adult tissues, and is re-expressed in most of the common human cancers. However, the clinicopathological significance of the expression of survivin in human breast carcinoma has not been fully elucidated. Therefore, we examined the accumulation of survivin in pathological specimens of mammary gland diseases to identify new protein markers that may lead to improvements in patient management.Methods: We investigated the expression of survivin using immunohistochemistry in 180 cases of breast disease accessioned in the Department of Pathology, International University of Health and Welfare Hospital and Nissan Tamagawa Hospital between 2003 and 2013.Results: Ninety-eight out of 141 malignant tumor cases (69.5%) stained positive for survivin, with no significant staining being detected in the remaining cases. Staining for survivin was completely absent in the epithelial cells of 34 of 39 cases of benign disease. No correlation was observed between the expression of survivin and major prognostic factors in breast carcinomas including patient age, tumor size, histological grade, axillary lymph node metastasis, local recurrence, and visceral metastasis status. However, a significant difference was observed in the expression of survivin between malignant and benign tumors and other benign diseases.Conclusion: The results of the present study suggest that the expression of survivin is strongly selective for cancer cells and may be useful for identifying and quantifying human breast cancer
Huge right ventricle–right coronary artery fistula compromising right ventricular function in a patient with pulmonary atresia and intact ventricular septum: A case report
AbstractJ Thorac Cardiovasc Surg 2001;122:1030-
Observational signatures of forming young massive clusters: continuum emission from dense HII regions
Young massive clusters (YMCs) are the most massive star clusters forming in
nearby galaxies and are thought to be a young analogue to the globular
clusters. Understanding the formation process of YMCs leads to looking into
very efficient star formation in high-redshift galaxies suggested by recent
JWST observations. We investigate possible observational signatures of their
formation stage, particularly when the mass of a cluster is increasing via
accretion from a natal molecular cloud. To this end, we study the broad-band
continuum emission from ionized gas and dust enshrouding YMCs, whose formation
is followed by recent radiation-hydrodynamics simulations. We perform
post-process radiative transfer calculations using simulation snapshots and
find characteristic spectral features at radio and far-infrared frequencies. We
show that a striking feature is long-lasting, strong free-free emission from a
10pc-scale HII region with a large emission measure of , corresponding to the mean electron density of
. There is a turnover feature below 10
GHz, a signature of the optically-thick free-free emission, often found in
Galactic ultra-compact HII regions. These features come from the peculiar YMC
formation process, where the cluster's gravity effectively traps photoionized
gas for a long duration and enables continuous star formation within the
cluster. Such large and dense HII regions show distinct distribution on the
density-size diagram, apart from the standard sequence of Galactic HII regions.
This is consistent with the observational trend inferred for extragalactic HII
regions associated with YMCs.Comment: 12 pages, 10 figures, accepted for publication in MNRA
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