789 research outputs found
Determination of the Hubble Constant Using a Two-Parameter Luminosity Correction for Type Ia Supernovae
In this paper, we make a comprehensive determination of the Hubble constant
by using two parameters - the B-V color and the rate of decline - to simultaneously standardize the luminosities of all nearby
Cepheid-calibrated type Ia supernovae (SNe Ia) and those of a larger, more
distant sample of 29 SNe Ia. Each group is treated in as similar a manner as
possible in order to avoid systematic effects. A simultaneous
minimization yields a standardized absolute luminosity of the
Cepheid-calibrated supernovae as well as the Hubble constant obtained from the
more distant sample. We find and a standardized
absolute magnitude of -19.46. The sensitivity of to a metallicity
dependence of the Cepheid-determined distances is investigated. The total
uncertainty , dominated by uncertainties in the primary Cepheid
distance indicator, is estimated to be 5 km/s Mpc^{-1}.Comment: To appear in Ap
The Baryonic and Dark Matter Distributions in Abell 401
We combine spatially resolved ASCA temperature data with ROSAT imaging data
to constrain the total mass distribution in the cluster A401, assuming that the
cluster is in hydrostatic equilibrium. We obtain a total mass within the X-ray
core (290/h_50 kpc) of 1.2[+0.1,-0.5] 10^14 /h_50 Msun at the 90% confidence
level, 1.3 times larger than the isothermal estimate. The total mass within
r_500 (1.7/h_50 Mpc) is M_500 = 0.9[+0.3,-0.2] 10^15/ h_50 Msun at 90%
confidence, in agreement with the optical virial mass estimate, and 1.2 times
smaller than the isothermal estimate. Our M_500 value is 1.7 times smaller than
that estimated using the mass-temperature scaling law predicted by simulations.
The best fit dark matter density profile scales as r^{-3.1} at large radii,
which is consistent with the Navarro, Frenk & White (NFW) ``universal profile''
as well as the King profile of the galaxy density in A401. From the imaging
data, the gas density profile is shallower than the dark matter profile,
scaling as r^{-2.1} at large radii, leading to a monotonically increasing gas
mass fraction with radius. Within r_500 the gas mass fraction reaches a value
of f_gas = 0.21[+0.06,-0.05] h_50^{-3/2} (90% confidence errors). Assuming that
f_gas (plus an estimate of the stellar mass) is the universal value of the
baryon fraction, we estimate the 90% confidence upper limit of the cosmological
matter density to be Omega_m < 0.31.Comment: 17 pages, 6 figures, accepted by Ap
XMM-Newton discovery of O VII emission from warm gas in clusters of galaxies
XMM-Newton recently discovered O VII line emission from ~2 million K gas near
the outer parts of several clusters of galaxies. This emission is attributed to
the Warm-Hot Intergalactic Medium. The original sample of clusters studied for
this purpose has been extended and two more clusters with a soft X-ray excess
have been found. We discuss the physical properties of the warm gas, in
particular the density, spatial extent, abundances and temperature.Comment: 8 pages, 3 figures, conference "Soft X-ray emission from clusters of
galaxies and related phenomena", ed. R. Lieu, Kluwer, in pres
Exosome-mediated Transfer of αvβ3 Integrin from Tumorigenic to Nontumorigenic Cells Promotes a Migratory Phenotype.
The αvβ3 integrin is known to be highly upregulated during cancer progression and promotes a migratory and metastatic phenotype in many types of tumors. We hypothesized that the αvβ3 integrin is transferred through exosomes and, upon transfer, has the ability to support functional aberrations in recipient cells. Here, for the first time, it is demonstrated that αvβ3 is present in exosomes released from metastatic PC3 and CWR22Pc prostate cancer cells. Exosomal β3 is transferred as a protein from donor to nontumorigenic and tumorigenic cells as β3 protein or mRNA levels remain unaffected upon transcription or translation inhibition in recipient cells. Furthermore, it is shown that upon exosome uptake, de novo expression of an αvβ3 increases adhesion and migration of recipient cells on an αvβ3 ligand, vitronectin. To evaluate the relevance of these findings, exosomes were purified from the blood of TRAMP mice carrying tumors where the expression of αvβ3 is found higher than in exosomes from wild-type mice. In addition, it is demonstrated that αvβ3 is coexpressed with synaptophysin, a biomarker for aggressive neuroendocrine prostate cancer.
IMPLICATIONS: Overall this study reveals that the αvβ3 integrin is transferred from tumorigenic to nontumorigenic cells via exosomes, and its de novo expression in recipient cells promotes cell migration on its ligand. The increased expression of αvβ3 in exosomes from mice bearing tumors points to its clinical relevance and potential use as a biomarker. Mol Cancer Res; 14(11); 1136-46. ©2016 AACR
The cluster M-T relation from temperature profiles observed with ASCA and ROSAT
We calibrate the galaxy cluster mass - temperature relation using the
temperature profiles of intracluster gas observed with ASCA (for hot clusters)
and ROSAT (for cool groups). Our sample consists of apparently relaxed clusters
for which the total masses are derived assuming hydrostatic equilibrium. The
sample provides data on cluster X-ray emission-weighted cooling flow-corrected
temperatures and total masses up to r_1000. The resulting M-T scaling in the
1-10 keV temperature range is M_1000 = (1.23 +- 0.20)/h_50 10^15 Msun (T/10
keV)^{1.79 +- 0.14} with 90% confidence errors, or significantly (99.99%
confidence) steeper than the self-similar relation M propto T^{3/2}. For any
given temperature, our measured mass values are significantly smaller compared
to the simulation results of Evrard et al. (1996) that are frequently used for
mass-temperature scaling. The higher-temperature subsample (kT > 4 keV) is
consistent with M propto T^{3/2}, allowing the possibility that the
self-similar scaling breaks down at low temperatures, perhaps due to heating by
supernovae that is more important for low-temperature groups and galaxies as
suggested by earlier works.Comment: 8 pages, 2 figures, accepted by Ap
The Effect of Forage Legumes on Mineral Nitrogen Content in Soil
The cultivation of forage legumes is often suggested as a possibility to improve nitrogen (N) utilisation in farming. However, previous studies have indicated examples in which the cultivation of legumes such as white clover has led to accumulation of large amounts of N in soil (Adams & Pattison, 1985). In this study the potential risks of N leaching were estimated by determining amount of mineral N in the soil
Fungal proteins with mannanase activity identified directly from a Congo Red stained zymogram by mass spectrometry
Secreted fungal proteins with mannanase activity were identified by mass spectrometry of bands excised from a Congo Red stained zymogram containing locust bean gum as substrate. This technique circumvents the need to locate corresponding bands on a parallel gel without substrate and provides good accuracy in targeting proteins for identification. © 2009 Elsevier B.V. All rights reserved
Soft X-ray excess emission in clusters of galaxies observed with XMM-Newton
We present results on the spectroscopic analysis of XMM-Newton EPIC data of
the central 0.5/h_50 Mpc regions of the clusters of galaxies Coma, A1795 and
A3112. The temperature of the hot intracluster gas as determined by modeling
the 2 - 7 keV PN and MOS data is consistent with that inferred from the
FeXXV-FeXXVI line ratio. A significant warm emission component at a level above
the systematic uncertainties is evident in the data and confirmed by ROSAT PSPC
data for Coma and A1795. The non-thermal origin of the phenomenon cannot be
ruled out at the current level of calibration accuracy, but the thermal model
fits the data significantly better, with temperatures in the range of 0.6 --
1.3 keV and electron densities of the order of 10^{-4} -- 10^{-3} cm^{-3}. In
the outer parts of the clusters the properties of the warm component are
marginally consistent with the results of recent cosmological simulations,
which predict a large fraction of the current epoch's bayons located in a
warm-hot intergalactic medium (WHIM). However, the derived densities are too
high in the cluster cores, compared to WHIM simulations, and thus more
theoretical work is needed to fully understand the origin of the observed soft
X-ray excess.Comment: ApJ in press, 14 pages, 4 color figures WHIM discussion modifie
The Productivity of Coastal Meadows in Finland
The coastal meadows of Finland have gained a new interest as a summer pasture for cattle. These habitats have great historical, aesthetic and biological value (Pessa & Anttila, 2000). Typical features of the coastal meadows are the varying vegetation zones and wet, sometimes waterlogged, soils. The meadows are important nesting and feeding habitats for many water birds. When grazing ceases, reeds, trees and shrubs take over and the area loses its openness. Lately the amount of grasslands and pastures has drastically declined all over Europe. In Finland, the area of semi-natural biotopes has decreased to 1% of what it had been at the beginning of the twentieth century (Pitkänen & Tiainen, 2001). The goal of this study was to determine the yield and nutritional value of grass herbage in the meadows
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