93 research outputs found
Formation History of Metal-Poor Halo Stars with Hierarchical Model and the Effect of ISM accretion on the Most Metal-Poor Stars
We investigate the star formation and chemical evolution in the early
universe by considering the merging history of the Galaxy in the {\Lambda}CDM
scenario according to the extended Press-Schechter theory. We give some
possible constraints from comparisons with observation of extremely metal-poor
(EMP) stars. We demonstrate that (1) The hierarchical structure formation can
explain the characteristics of the observed metallicity distribution function
(MDF) including a break around [Fe/H]~-4. (2) A high mass IMF of peak mass
~10Msun with the contribution of binaries, derived from the statistics of
carbon enhanced EMP stars (Komiya et al. 2007), predicts the frequency of
low-mass survivors consistent with the number of EMP stars observed for
-4~<[Fe/H]~<-2.5. (3) The stars formed from primordial gas before the first
supernova explosions in their host mini-halos are assigned to the HMP stars
with [Fe/H]~-5. (4) There is no indication of significant changes in the IMF
and the binary contribution at metallicity -4~<[Fe/H]~<-2.5, or even larger as
long as the field stars of Galactic halo are concerned. We further study the
effects of the surface pollution through the accretion of ISM along the
chemical and dynamical evolution of the Galaxy for low-mass Pop.III and EMP
survivors. Because of shallower potential of smaller halos, the accretion of
ISM in the mini-halos in which these stars were born dominates the surface
metal pollution. This can account for the surface iron abundances as observed
for the HMP stars if the cooling and concentration of gas in their birth
mini-halos is taken into account. We also study the feedback effect from the
very massive Pop. III stars. The metal pre-pollution by PISNe is shown to be
compatible with the observed lack of their nucleosynthetic signatures when some
positive feedback on gas cooling works and changes IMF from being very massive
to being high mass.Comment: 20 pages, 14 figures. ApJ accepte
Early-Age Evolution of the Milky Way Related by Extremely Metal-Poor Stars
We exploit the recent observations of extremely metal-poor (EMP) stars in the
Galactic halo and investigate the constraints on the IMF of the stellar
population that left these low-mass survivors of [Fe/H]<-2.5 and the chemical
evolution that they took part in. A high-mass IMF with the typical mass~10Msun
and the overwhelming contribution of low-mass members of binaries to the EMP
survivors are derived from the statistics of carbon-enriched EMP stars with and
without the enhancement of s-process elements (Komiya et al. 2007). We first
examine the analysis to confirm their results for various assumptions on the
mass-ratio distribution function. As compared with the uniform distribution,
the increase or decrease function of the mass ratio gives a higher- or
lower-mass IMF, and a lower-mass IMF results for the independent distribution
with the both members in the same IMF, but the derived ranges of typical mass
differ less than by a factor of two and overlap for the extreme cases.
Furthermore, we prove that the same constraints are placed on the IMF from the
surface density of EMP stars estimated from the surveys and the chemical
evolution consistent with the metal yields of theoretical supernova models. We
then apply the derived high-mass IMF with the binary contribution to show that
the observed MDF of EMP stars can be reproduced not only for the shape but also
for the number of EMP stars. In particular, the scarcity of stars below
[Fe/H]<-4 is naturally explained in terms of the hierarchical structure
formation, and there is no indication of significant changes in the IMF for the
EMP Population. The present study indicates that 3 HMP stars of [Fe/H]<-4 are
the primordial stars that were born as the low-mass members of binaries before
the host clouds were polluted by their own supernovae.Comment: 19 pages, 9 figures, accepted in Ap
Relationship between cardiac allograft vasculopathy and left ventricular diastolic dysfunction assessed by cardiac magnetic resonance imaging in heart transplant recipients
POSTER PRESENTATION12th Annual SCMR Scientific Sessions – 2009 / Orlando, FL, USA / 29 January–1 February 200
Analysis of Expressed Sequence Tags from the Fungus Aspergillus oryzae Cultured Under Different Conditions
We performed random sequencing of cDNAs from nine biologically or industrially important cultures of the industrially valuable fungus Aspergillus oryzae to obtain expressed sequence tags (ESTs). Consequently, 21 446 raw ESTs were accumulated and subsequently assembled to 7589 non-redundant consensus sequences (contigs). Among all contigs, 5491 (72.4%) were derived from only a particular culture. These included 4735 (62.4%) singletons, i.e. lone ESTs overlapping with no others. These data showed that consideration of culture grown under various conditions as cDNA sources enabled efficient collection of ESTs. BLAST searches against the public databases showed that 2953 (38.9%) of the EST contigs showed significant similarities to deposited sequences with known functions, 793 (10.5%) were similar to hypothetical proteins, and the remaining 3843 (50.6%) showed no significant similarity to sequences in the databases. Culture-specific contigs were extracted on the basis of the EST frequency normalized by the total number for each culture condition. In addition, contig sequences were compared with sequence sets in eukaryotic orthologous groups (KOGs), and classified into the KOG functional categories
Efficacy of capillary pattern type IIIA/IIIB by magnifying narrow band imaging for estimating depth of invasion of early colorectal neoplasms
<p>Abstract</p> <p>Background</p> <p>Capillary patterns (CP) observed by magnifying Narrow Band Imaging (NBI) are useful for differentiating non-adenomatous from adenomatous colorectal polyps. However, there are few studies concerning the effectiveness of magnifying NBI for determining the depth of invasion in early colorectal neoplasms. We aimed to determine whether CP type IIIA/IIIB identified by magnifying NBI is effective for estimating the depth of invasion in early colorectal neoplasms.</p> <p>Methods</p> <p>A series of 127 consecutive patients with 130 colorectal lesions were evaluated from October 2005 to October 2007 at the National Cancer Center Hospital East, Chiba, Japan. Lesions were classified as CP type IIIA or type IIIB according to the NBI CP classification. Lesions were histopathologically evaluated. Inter and intraobserver variabilities were assessed by three colonoscopists experienced in NBI.</p> <p>Results</p> <p>There were 15 adenomas, 66 intramucosal cancers (pM) and 49 submucosal cancers (pSM): 16 pSM superficial (pSM1) and 33 pSM deep cancers (pSM2-3). Among lesions diagnosed as CP IIIA 86 out of 91 (94.5%) were adenomas, pM-ca, or pSM1; among lesions diagnosed as CP IIIB 28 out of 39 (72%) were pSM2-3. Sensitivity, specificity and diagnostic accuracy of the CP type III for differentiating pM-ca or pSM1 (<1000 μm) from pSM2-3 (≥1000 μm) were 84.8%, 88.7 % and 87.7%, respectively. Interobserver variability: κ = 0.68, 0.67, 0.72. Intraobserver agreement: κ = 0.79, 0.76, 0.75</p> <p>Conclusion</p> <p>Identification of CP type IIIA/IIIB by magnifying NBI is useful for estimating the depth of invasion of early colorectal neoplasms.</p
Usefulness of left ventricular peak filling rate measurement by cardiac MR imaging in heart transplant recipients with cardiac allograft vasculopathy
Oral presentation13th Annual SCMR Scientific Sessions / Phoenix, AZ, USA. / 21-24 January 201
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