1,833 research outputs found
Age and structure parameters of a remote M31 globular cluster B514 based on HST, 2MASS, GALEX and BATC observations
B514 is a remote M31 globular cluster which locating at a projected distance
of R_p~55 kpc. Deep observations with the Advanced Camera for Surveys (ACS) on
the Hubble Space Telescope (HST) are used to provide the accurate integrated
light and star counts of B514. By coupling analysis of the distribution of the
integrated light with star counts, we are able to reliably follow the profile
of the cluster out to ~40". Based on the combined profile, we study in detail
its surface brightness distribution in F606W and F814W filters, and determine
its structural parameters by fitting a single-mass isotropic King model. The
results showed that, the surface brightness distribution departs from the
best-fit King model for r>10". B514 is quite flatted in the inner region, and
has a larger half-light radius than majority of normal globular clusters of the
same luminosity. It is interesting that, in the M_V versus log R_h plane, B514
lies nearly on the threshold for ordinary globular clusters as defined by
Mackey & van den Bergh. In addition, B514 was observed as part of the
Beijing-Arizona-Taiwan-Connecticut (BATC) Multicolor Sky Survey, using 13
intermediate-band filters covering a wavelength range of 3000--8500 \AA. Based
on aperture photometry, we obtain its SEDs as defined by the 13 BATC filters.
We determine the cluster's age and mass by comparing its SEDs (from 2267 to
20000{\AA}, comprising photometric data in the near-ultraviolet of GALEX, 5
SDSS bands, 13 BATC intermediate-band, and 2MASS near-infrared JHKs} filters)
with theoretical stellar population synthesis models, resulting in age of
Gyr. This age confirms the previous suggestion that B514 is an old
GC in M31. B514 has a mass of , and is a
medium-mass globular cluster in M31.Comment: Accepted for Publication in AJ, 18 pages, 6 figures and 9 table
Deregulation of apoptosis mediators' p53 and bcl2 in lung tissue of COPD patients
Abnormal apoptotic events in chronic obstructive pulmonary disease (COPD) subvert cellular homeostasis and may play a primary role in its pathogenesis. However, studies in human subjects are limited
Reproductive competition triggers mass eviction in cooperative banded mongooses
In many vertebrate societies, forced eviction of group members is an important determinant of population structure, but little is known about what triggers eviction. Three main explanations are (1) the reproductive competition hypothesis; (2) the coercion of cooperation hypothesis; and (3) the adaptive forced dispersal hypothesis. The last hypothesis proposes that dominant individuals use eviction as an adaptive strategy to propagate copies of their alleles through a highly structured population. We tested these hypotheses as explanations for eviction in cooperatively breeding banded mongooses (Mungos mungo), using a 16-year dataset on life history, behaviour and relatedness. In this species, groups of females, or mixed-sex groups, are periodically evicted en masse. Our evidence suggests that reproductive competition is the main ultimate trigger for eviction for both sexes. We find little evidence that mass eviction is used to coerce helping, or as a mechanism to force dispersal of relatives into the population. Eviction of females changes the landscape of reproductive competition for remaining males, which may explain why males are evicted alongside females. Our results show that the consequences of resolving within-group conflict resonate through groups and populations to affect population structure, with important implications for social evolution
Female reproductive competition explains variation in prenatal investment in wild banded mongooses
Female intrasexual competition is intense in cooperatively breeding species where offspring compete locally for resources and helpers. In mammals, females have been proposed to adjust prenatal investment according to the intensity of competition in the postnatal environment (a form of ‘predictive adaptive response’; PAR). We carried out a test of this hypothesis using ultrasound scanning of wild female banded mongooses in Uganda. In this species multiple females give birth together to a communal litter, and all females breed regularly from one year old. Total prenatal investment (size times the number of fetuses) increased with the number of potential female breeders in the group. This relationship was driven by fetus size rather than number. The response to competition was particularly strong in low weight females and when ecological conditions were poor. Increased prenatal investment did not trade off against maternal survival. In fact we found the opposite relationship: females with greater levels of prenatal investment had elevated postnatal maternal survival. Our results support the hypothesis that mammalian prenatal development is responsive to the intensity of postnatal competition. Understanding whether these responses are adaptive requires information on the long-term consequences of prenatal investment for offspring fitness
Morphologic and Molecular Features of Hepatocellular Adenoma with Gadoxetic Acid-enhanced MR Imaging
Purpose To evaluate the diagnostic performance of imaging features of gadoxetic acid-enhanced magnetic resonance (MR) imaging to differentiate among hepatocellular adenoma (HCA) subtypes by using the histopathologic results of the new immunophenotype and genotype classification and to correlate the enhancement pattern on the hepatobiliary phase (HBP) with the degrees of expression of organic anion transporting polypeptide (OATP1B1/3), multidrug resistance-associated protein 2 (MRP) (MRP2), and MRP 3 (MRP3) transporters. Materials and Methods This retrospective study was approved by the institutional review board, and the requirement for informed consent waived. MR imaging findings of 29 patients with 43 HCAs were assessed by two radiologists independently then compared with the histopathologic analysis as the standard of reference. Receiver operating characteristic curves and Spearman rank correlation coefficient were used to test the diagnostic performance of gadoxetic acid-enhanced MR imaging features, which included the retention or washout at HBP and degree of transporter expression. Interreader agreement was assessed by using the κ statistic with 95% confidence interval. Results The area under the curve for the diagnosis of inflammatory HCA was 0.79 (95% confidence interval: 0.64, 0.90); for the steatotic type, it was 0.90 (95% confidence interval: 0.77, 0.97); and for the β-catenin type, it was 0.87 (95% confidence interval: 0.74, 0.95). There were no imaging features that showed a significant statistical correlation for the diagnosis of unclassified HCAs. On immunohistochemical staining, OATP1B1/3 expression was the main determinant for the retention, whereas MRP3 was the key determinant for washout of gadoxetic acid at HBP (P < .001). MRP2 appeared to have no role. Conclusion Gadoxetic acid-enhanced MR imaging features may suggest the subtype of HCA. The degree of OATP1B1/3 and MRP3 expression correlated statistically with gadoxetic acid retention and washout, respectively, in the HBP. (©) RSNA, 2015 Online supplemental material is available for this article
The Void Galaxy Survey
The Void Galaxy Survey (VGS) is a multi-wavelength program to study 60
void galaxies. Each has been selected from the deepest interior regions of
identified voids in the SDSS redshift survey on the basis of a unique geometric
technique, with no a prior selection of intrinsic properties of the void
galaxies. The project intends to study in detail the gas content, star
formation history and stellar content, as well as kinematics and dynamics of
void galaxies and their companions in a broad sample of void environments. It
involves the HI imaging of the gas distribution in each of the VGS galaxies.
Amongst its most tantalizing findings is the possible evidence for cold gas
accretion in some of the most interesting objects, amongst which are a polar
ring galaxy and a filamentary configuration of void galaxies. Here we shortly
describe the scope of the VGS and the results of the full analysis of the pilot
sample of 15 void galaxies.Comment: 9 pages, 6 figures. This is an extended version of a paper to appear
in "Environment and the Formation of Galaxies: 30 years later", Proceedings
of Symposium 2 of JENAM 2010, eds. I. Ferreras, A. Pasquali, ASSP, Springer.
Version with highres figures at
http://www.astro.rug.nl/~weygaert/vgs_jenam_weygaert.col.pd
Challenges to the development of antigen-specific breast cancer vaccines
Continued progress in the development of antigen-specific breast cancer vaccines depends on the identification of appropriate target antigens, the establishment of effective immunization strategies, and the ability to circumvent immune escape mechanisms. Methods such as T cell epitope cloning and serological expression cloning (SEREX) have led to the identification of a number target antigens expressed in breast cancer. Improved immunization strategies, such as using dendritic cells to present tumor-associated antigens to T lymphocytes, have been shown to induce antigen-specific T cell responses in vivo and, in some cases, objective clinical responses. An outcome of successful tumor immunity is the evolution of antigen-loss tumor variants. The development of a polyvalent breast cancer vaccine, directed against a panel of tumor-associated antigens, may counteract this form of immune escape
Relation Between the Thickness of Stellar Disks and the Relative Mass of Dark Halo in Galaxies
We consider a thickness of stellar disks of late-type galaxies by analyzing
the R and K_s band photometric profiles for two independent samples of edge-on
galaxies. The main goal is to verify a hypotesis that a thickness of old
stellar disks is related to the relative masses of the spherical and disk
components of galaxies. We confirm that the radial-to-vertical scale length
ratio for galactic disks increases (the disks become thinner) with the
increasing of total mass-to-light ratio of the galaxies, which characterize the
contribution of dark halo to the total mass, and with the decreasing of central
deprojected disk brightness (surface density). Our results are in good
agreement with numerical models of collisionless disks evolved from subcritical
velocity dispersion state to a marginally stable equilibrium state. This
suggests that in most galaxies the vertical stellar velocity dispersion, which
determine the equilibrium disk thickness, is close to the minimum value, that
ensures disk stability. The thinnest edge-on disks appear to be low brightness
galaxies (after deprojection) in which a dark halo mass far exceeds a mass of
the stellar disk.Comment: 13 pages. To be Published in Astronomy Letters, v.28(2002
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