513 research outputs found
Photometric Properties of Six Local Volume Dwarf Galaxies from Deep Near-Infrared Observations
We have obtained deep near-infrared - (1.25 m), - (1.65m)
and -band (2.15 m) imaging for a sample of six dwarf galaxies
(M_B\ga-17 mag) in the Local Volume (LV, D\la10 Mpc). The sample consists
mainly of early-type dwarf galaxies found in various environments in the LV.
Two galaxies (LEDA 166099 and UGCA 200) in the sample are detected in the
near-infrared for the first time. The deep near-infrared images allow for a
detailed study of the photometric and structural properties of each galaxy. The
surface brightness profiles of the galaxies are detected down to the ~ isophote in the - and -bands, and in
the -band. The total magnitudes of the galaxies are derived in the three
wavelength bands. For the brightest galaxies (M_B\la-15.5 mag) in the sample,
we find that the Two Micron All Sky Survey (2MASS) underestimates the total
magnitudes of these systems by up to \la0.5 mag. The radial surface
brightness profiles of the galaxies are fitted with an exponential (for those
galaxies having a stellar disk) or S\'ersic law to derive the structure of the
underlying stellar component. In particular, the effective surface brightness
() and effective radius () are determined from the analytic fits to
the surface brightness profile. The - colours for the galaxies have
been measured to explore the luminosity-metallicity relation for early-type
dwarfs. In addition, the - colours of the galaxies are used to assess
their evolutionary state relative to other galaxy morphologies. The total
stellar masses of the dwarf galaxies are derived from the -band photometric
measurements. These will later be compared to the dynamical mass estimates for
the galaxies to determine their dark matter content.Comment: 14 pages, 8 figures, submitted to MNRA
Tip of the Red Giant Branch Distance for the Sculptor Group Dwarf ESO 540-032
We present the first VI CCD photometry for the Sculptor group galaxy ESO
540-032 obtained at the Very Large Telescope UT1+FORS1. The (I, V-I)
colour-magnitude diagram indicates that this intermediate-type dwarf galaxy is
dominated by old, metal-poor ([Fe/H]~-1.7 dex) stars, with a small population
of slightly more metal-rich ([Fe/H]~-1.3 dex), young (age 150-500 Myr) stars. A
discontinuity in the I-band luminosity function is detected at I_0 = 23.44 \pm
0.09 mag. Interpreting this feature as the tip of the red giant branch and
adopting M_I=-4.20\pm 0.10 mag for its absolute magnitude, we have determined a
Population II distance modulus of (m - M)_0=27.64 \pm 0.14 mag (3.4 \pm 0.2
Mpc). This distance confirms ESO 540-032 as a member of the nearby Sculptor
group but is significantly larger than a previously reported value based on the
Surface Brightness Fluctuation (SBF) method. The results from stellar
population synthesis models suggest that the application of the SBF technique
on dwarf galaxies with mixed morphology requires a detailed knowledge of the
underlying stellar composition and thus offers no advantage over a direct
distance measurement using the tip of the red giant branch as distance
indicator. We produce the surface brightness profiles for ESO 540-032 and
derive the photometric and structural parameters. The global properties follow
closely the relations between metallicity and both absolute magnitude and
central surface brightness defined by dwarf elliptical galaxies in the Local
Group. Finally, we identify and discuss a non-stellar object near the galaxy
center which may resemble a globular cluster.Comment: 10 pages, 10 figures; Astronomy and Astrophysics in pres
Too Big to Fail: Motives, Countermeasures, and the Dodd-Frank Response
Government forbearance, support, and bailouts of banks and other financial institutions deemed 'too big to fail' (TBTF) are widely recognized as encouraging large companies to take excessive risk, placing smaller ones at a competitive disadvantage and influencing banks in general to grow inefficiently to a 'protected' size and complexity. During periods of financial stress, with bailouts under way, government officials have promised 'never again'. During periods of financial stability and economic growth, they have sanctioned large-bank growth by merger and ignored the ongoing competitive imbalance. Repeated efforts to do away with TBTF practices over the last several decades have been unsuccessful. Congress has typically found the underlying problem to be inadequate regulation and/or supervision that has permitted important financial companies to undertake excessive risk. It has responded by strengthening regulation and supervision. Others have located the underlying problem in inadequate regulators, suggesting the need for modifying the incentives that motivate their behavior. A third explanation is that TBTF practices reflect the governmentâs perception that large financial firms serve a public interest - they constitute a 'national resource' to be preserved. In this case, a structural solution would be necessary. Breakups of the largest financial firms would distribute the 'public interest' among a larger group than the handful that currently hold a disproportionate concentration of financial resources. The Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010 constitutes the most recent effort to eliminate TBTF practices. Its principal focus is on the extension and augmentation of regulation and supervision, which it envisions as preventing excessive risk taking by large financial companies; Congress has again found the cause for TBTF practices in the inadequacy of regulation and supervision. There is no indication that Congress has given any credence to the contention that regulatory motivations have been at fault. Finally, Dodd-Frank eschews a structural solution, leaving the largest financial companies intact and bank regulatory agencies still with extensive discretion in passing on large bank mergers. As a result, the elimination of TBTF will remain problematic for years to come
Pharmacological Effects of Asiatic acid in Glioblastoma Cells under Hypoxia
Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumor in adults. Despite current treatment options including surgery followed by radiation and chemotherapy with temozolomide (TMZ) and cisplatin, the median survival rate remains low (<16 months). Combined with increasing drug resistance and the inability of some compounds to cross the blood brain barrier (BBB), novel compounds are being sought for the treatment of this disease. Here, we aimed to examine the pharmacological effect of Asiatic acid (AA) in glioblastoma under hypoxia.
To investigate the effects of AA on cell viability, proliferation, apoptosis and wound healing, SVG p12 fetal glia and U87-MG grade IV glioblastoma cells were cultured under normoxic (21% O2) and hypoxic (1% O2) conditions.
In normoxia, AA reduced cell viability in U87-MG cells in a time and concentration-dependent manner. A significant decrease in viability, compared to cisplatin, was observed following 2hrs of AA treatment with no significant changes in cell proliferation or cell cycle progression observed. Under hypoxia, a significantly greater number of cells underwent apoptosis in comparison to cisplatin. While cisplatin showed a reduction in wound healing in normoxia, a significantly greater reduction was observed following AA treatment. An overall reduction in wound healing was observed under hypoxia.
The results of this study show that AA has cytotoxic effects on glioma cell lines and has the potential to become an alternative treatment for glioblastoma
Effective Rheology of Bubbles Moving in a Capillary Tube
We calculate the average volumetric flux versus pressure drop of bubbles
moving in a single capillary tube with varying diameter, finding a square-root
relation from mapping the flow equations onto that of a driven overdamped
pendulum. The calculation is based on a derivation of the equation of motion of
a bubble train from considering the capillary forces and the entropy production
associated with the viscous flow. We also calculate the configurational
probability of the positions of the bubbles.Comment: 4 pages, 1 figur
The Imprinted Gene DIO3 Is a Candidate Gene for Litter Size in Pigs
Genomic imprinting is an important epigenetic phenomenon, which on the phenotypic level can be detected by the difference between the two heterozygote classes of a gene. Imprinted genes are important in both the development of the placenta and the embryo, and we hypothesized that imprinted genes might be involved in female fertility traits. We therefore performed an association study for imprinted genes related to female fertility traits in two commercial pig populations. For this purpose, 309 SNPs in fifteen evolutionary conserved imprinted regions were genotyped on 689 and 1050 pigs from the two pig populations. A single SNP association study was used to detect additive, dominant and imprinting effects related to four reproduction traits; total number of piglets born, the number of piglets born alive, the total weight of the piglets born and the total weight of the piglets born alive. Several SNPs showed significant () additive and dominant effects and one SNP showed a significant imprinting effect. The SNP with a significant imprinting effect is closely linked to DIO3, a gene involved in thyroid metabolism. The imprinting effect of this SNP explained approximately 1.6% of the phenotypic variance, which corresponded to approximately 15.5% of the additive genetic variance. In the other population, the imprinting effect of this QTL was not significant (), but had a similar effect as in the first population. The results of this study indicate a possible association between the imprinted gene DIO3 and female fertility traits in pigs
Hypoxia and Prostaglandin E Receptor 4 Signalling Pathways Synergise to Promote Endometrial Adenocarcinoma Cell Proliferation and Tumour Growth
The prostaglandin endoperoxide synthase (PTGS) pathway is a potent driver of tumour development in humans by enhancing the biosynthesis and signalling of prostaglandin (PG) E2. PTGS2 expression and PGE2 biosynthesis is elevated in endometrial adenocarcinoma, however the mechanism whereby PTGS and PGE2 regulate endometrial tumour growth is unknown. Here we investigated (a) the expression profile of the PGE synthase enzymes (PTGES, PTGES-2, PTGES-3) and PGE receptors (PTGER1â4) in endometrial adenocarcinomas compared with normal endometrium and (b) the role of PTGER4 in endometrial tumorigenesis in vivo. We found elevated expression of PTGES2 and PTGER4 and suppression of PTGER1 and PTGER3 in endometrial adenocarcinomas compared with normal endometrium. Using WT Ishikawa endometrial adenocarcinoma cells and Ishikawa cells stably transfected with the full length PTGER4 cDNA (PTGER4 cells) xenografted in the dorsal flanks of nude mice, we show that PTGER4 rapidly and significantly enhances tumour growth rate. Coincident with enhanced PTGER4-mediated tumour growth we found elevated expression of PTGS2 in PTGER4 xenografts compared with WT xenografts. Furthermore we found that the augmented growth rate of the PTGER4 xenografts was not due to enhanced angiogenesis, but regulated by an increased proliferation index and hypoxia. In vitro, we found that PGE2 and hypoxia independently induce expression of PTGER4 indicating two independent pathways regulating prostanoid receptor expression. Finally we have shown that PGE2 and hypoxia synergise to promote cellular proliferation of endometrial adenocarcinoma cells
Distinct Behaviour of the Homeodomain Derived Cell Penetrating Peptide Penetratin in Interaction with Different Phospholipids
Penetratin is a protein transduction domain derived from the homeoprotein Antennapedia. Thereby it is currently used as a cell penetrating peptide to introduce diverse molecules into eukaryotic cells, and it could also be involved in the cellular export of transcription factors. Moreover, it has been shown that it is able to act as an antimicrobial agent. The mechanisms involved in all these processes are quite controversial.In this article, we report spectroscopic, calorimetric and biochemical data on the penetratin interaction with three different phospholipids: phosphatidylcholine (PC) and phosphatidylethanolamine (PE) to mimic respectively the outer and the inner leaflets of the eukaryotic plasma membrane and phosphatidylglycerol (PG) to mimic the bacterial membrane. We demonstrate that with PC, penetratin is able to form vesicle aggregates with no major change in membrane fluidity and presents no well defined secondary structure organization. With PE, penetratin aggregates vesicles, increases membrane rigidity and acquires an α-helical structure. With PG membranes, penetratin does not aggregate vesicles but decreases membrane fluidity and acquires a structure with both α-helical and ÎČâsheet contributions.These data from membrane models suggest that the different penetratin actions in eukaryotic cells (membrane translocation during export and import) and on prokaryotes may result from different peptide and lipid structural arrangements. The data suggest that, for eukaryotic cell penetration, penetratin does not acquire classical secondary structure but requires a different conformation compared to that in solution
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