473 research outputs found
Spectroscopic Observations of Convective Patterns in the Atmospheres of Metal-Poor Stars
Convective line asymmetries in the optical spectrum of two metal-poor stars,
Gmb1830 and HD140283, are compared to those observed for solar metallicity
stars. The line bisectors of the most metal-poor star, the subgiant HD140283,
show a significantly larger velocity span that the expectations for a
solar-metallicity star of the same spectral type and luminosity class. The
enhanced line asymmetries are interpreted as the signature of the lower metal
content, and therefore opacity, in the convective photospheric patterns. These
findings point out the importance of three-dimensional convective velocity
fields in the interpretation of the observed line asymmetries in metal-poor
stars, and in particular, urge for caution when deriving isotopic ratios from
observed line shapes and shifts using one-dimensional model atmospheres.
The mean line bisector of the photospheric atomic lines is compared with
those measured for the strong Mg I b1 and b2 features. The upper part of the
bisectors are similar, and assuming they overlap, the bottom end of the
stronger lines, which are formed higher in the atmosphere, goes much further to
the red. This is in agreement with the expected decreasing of the convective
blue-shifts in upper atmospheric layers, and compatible with the high velocity
redshifts observed in the chromosphere, transition region, and corona of
late-type stars.Comment: 27 pages, LaTeX; 10 Figures (14 PostScript files); to be published in
The Astrophysical Journa
Evidence for short-lived SN Ia progenitors
We use the VESPA algorithm and spectra from the Sloan Digital Sky Survey to
investigate the star formation history of the host galaxies of 257 Type Ia
supernovae. We find 5 evidence for a short-lived population of
progenitors with lifetimes of less than 180 Myr, indicating a Type Ia supernova
channel arising from stars in the mass range 3.5-8 . As
standardizeable candles, Type Ia supernovae play an important role in
determining the expansion history of the Universe, but to be useful for future
cosmological surveys, the peak luminosity needs to be free of uncorrected
systematic effects at the level of 1-2%. If the different progenitor routes
lead to supernovae with even moderately small differences in properties, then
these need to be corrected for separately, or they could lead to a systematic
bias in future supernovae surveys, as the prompt route is likely to increase in
importance at high redshift. VESPA analysis of hosts could be a valuable tool
in this, by identifying which progenitor route is most likely.Comment: Accepted version by the journal, no changes in the result
Completing the 3CR Chandra Snapshot Survey: Extragalactic Radio Sources at High Redshift
We present the analysis of nine radio sources belonging to the Third Cambridge Revised catalog (3CR) observed with Chandra during Cycle 20 in the redshift range between 1.5 and 2.5. This study completes the 3CR Chandra Snapshot Survey thus guaranteeing the X-ray coverage of all 3CR sources identified to date. This sample lists two compact steep spectrum sources, four radio galaxies, and three quasars. We detected X-ray emission from all nuclei, with the only exception of 3C 326.1 and 3C 454.1 and from radio lobes in six out of nine sources at a level of confidence larger than ∼5σ. We measured X-ray fluxes and luminosities for all nuclei and lobes in the soft (0.5-1 keV), medium (1-2 keV), and hard (2-7 keV) X-ray bands. Since the discovered X-ray extended emission is spatially coincident with the radio structure in all cases, its origin could be due to inverse Compton (IC) scattering of the cosmic microwave background (CMB) occurring in radio lobes
Biomimetic Magnetic Nanocarriers Drive Choline Kinase Alpha Inhibitor inside Cancer Cells for Combined Chemo-Hyperthermia Therapy
Choline kinase a1 (ChoKa1) has become an excellent antitumor target. Among all the
inhibitors synthetized, the new compound Ff35 shows an excellent capacity to inhibit ChoKa1 activity.
However, soluble Ff35 is also capable of inhibiting choline uptake, making the inhibitor not selective
for ChoKa1. In this study, we designed a new protocol with the aim of disentangling whether the
Ff35 biological action is due to the inhibition of the enzyme and/or to the choline uptake. Moreover,
we offer an alternative to avoid the inhibition of choline uptake caused by Ff35, since the coupling
of Ff35 to novel biomimetic magnetic nanoparticles (BMNPs) allows it to enter the cell through
endocytosis without interacting with the choline transporter. This opens the possibility of a clinical
use of Ff35. Our results indicate that Ff35-BMNPs nanoassemblies increase the selectivity of Ff35 and
have an antiproliferative effect. Also, we demonstrate the effectiveness of the tandem Ff35-BMNPs
and hyperthermia.This research was funded by the Ministerio de Economía y Competitividad (CGL2013-46612 and
CGL2016-76723 projects), Ramón y Cajal programme (RYC-2014-16901) and the Fondo Europeo de Desarrollo
Regional (FEDER). Also, this research was aided by the Andalusian regional government (CTS-236)
The cavity of 3CR 196.1: H emission spatially associated with an X-ray cavity
We present a multifrequency analysis of the radio galaxy 3CR 196.1 (), associated with the brightest galaxy of the cool core cluster
CIZAJ0815.4-0303. This nearby radio galaxy shows a hybrid radio morphology and
an X-ray cavity, all signatures of a turbulent past activity, potentially due
to merger events and AGN outbursts. We present results of the comparison
between and VLT/MUSE data for the inner region of the galaxy cluster,
on a scale of tens of kpc. We discovered H + [N II]
emission spatially associated with the X-ray cavity (at 10 kpc from the
galaxy nucleus) instead of with its rim. This result differs from previous
discoveries of ionized gas surrounding X-ray cavities in other radio galaxies
harbored in galaxy clusters and could represent the first reported case of
ionized gas filling an X-ray cavity, either due to different AGN outbursts or
to the cooling of warm ( K) AGN outflows. We also found that
the H, [N II] and [S
II] emission lines show an additional redward
component, at 1000 kms from rest frame, with no detection in
H or [O III]. We believe the most likely
explanation for this redward component is the presence of a background gas
cloud since there appears to be a discrete difference in velocities between
this component and the rest frame.Comment: 15 pages, 8 figures, ApJ accepted, pre-proof versio
Extended X-ray emission around FR II radio galaxies: Hot spots, lobes, and galaxy clusters
We present a systematic analysis of the extended X-ray emission discovered around 35 FR II radio galaxies from the revised Third Cambridge Catalog (3CR) Chandra Snapshot Survey with redshifts between 0.05 and 0.9. We aimed to (i) test for the presence of extended X-ray emission around FR II radio galaxies, (ii) investigate whether the extended emission origin is due to inverse Compton (IC) scattering of seed photons arising from the cosmic microwave background (CMB) or thermal emission from an intracluster medium (ICM), and (iii) test the impact of this extended emission on hot-spot detection. We investigated the nature of the extended X-ray emission by studying its morphology and compared our results with low-frequency radio observations (i.e., ~150 MHz) in the TGSS and LOFAR archives, as well as with optical images from Pan-STARRS. In addition, we optimized a search for X-ray counterparts of hot spots in 3CR FR II radio galaxies. We found statistically significant extended emission (>3s confidence level) along the radio axis of ~90% and in the perpendicular direction of ~60% of the galaxies in our sample. We confirmed the detection of seven hot spots in the 0.5-3 keV energy range. In the cases where the emission in the direction perpendicular to the radio axis is comparable to that along the radio axis, we suggest that the underlying radiative process is thermal emission from the ICM. Otherwise, the dominant radiative process is likely nonthermal IC/CMB emission from lobes. We found that nonthermal IC/CMB is the dominant process in ~70% of the sources in our sample, while thermal emission from the ICM dominates in ~15% of them
Gravitational Waves From Known Pulsars: Results From The Initial Detector Era
We present the results of searches for gravitational waves from a large selection of pulsars using data from the most recent science runs (S6, VSR2 and VSR4) of the initial generation of interferometric gravitational wave detectors LIGO (Laser Interferometric Gravitational-wave Observatory) and Virgo. We do not see evidence for gravitational wave emission from any of the targeted sources but produce upper limits on the emission amplitude. We highlight the results from seven young pulsars with large spin-down luminosities. We reach within a factor of five of the canonical spin-down limit for all seven of these, whilst for the Crab and Vela pulsars we further surpass their spin-down limits. We present new or updated limits for 172 other pulsars (including both young and millisecond pulsars). Now that the detectors are undergoing major upgrades, and, for completeness, we bring together all of the most up-to-date results from all pulsars searched for during the operations of the first-generation LIGO, Virgo and GEO600 detectors. This gives a total of 195 pulsars including the most recent results described in this paper.United States National Science FoundationScience and Technology Facilities Council of the United KingdomMax-Planck-SocietyState of Niedersachsen/GermanyAustralian Research CouncilInternational Science Linkages program of the Commonwealth of AustraliaCouncil of Scientific and Industrial Research of IndiaIstituto Nazionale di Fisica Nucleare of ItalySpanish Ministerio de Economia y CompetitividadConselleria d'Economia Hisenda i Innovacio of the Govern de les Illes BalearsNetherlands Organisation for Scientific ResearchPolish Ministry of Science and Higher EducationFOCUS Programme of Foundation for Polish ScienceRoyal SocietyScottish Funding CouncilScottish Universities Physics AllianceNational Aeronautics and Space AdministrationOTKA of HungaryLyon Institute of Origins (LIO)National Research Foundation of KoreaIndustry CanadaProvince of Ontario through the Ministry of Economic Development and InnovationNational Science and Engineering Research Council CanadaCarnegie TrustLeverhulme TrustDavid and Lucile Packard FoundationResearch CorporationAlfred P. Sloan FoundationAstronom
Comparison of next-generation sequencing (NGS) and next-generation flow (NGF) for minimal residual disease (MRD) assessment in multiple myeloma
Detecting persistent minimal residual disease (MRD) allows the identification of patients with an increased risk of relapse and death. In this study, we have evaluated MRD 3 months after transplantation in 106 myeloma patients using a commercial next-generation sequencing (NGS) strategy (LymphoTrack®), and compared the results with next-generation flow (NGF, EuroFlow). The use of different marrow pulls and the need of concentrating samples for NGS biased the applicability for MRD evaluation and favored NGF. Despite that, correlation between NGS and NGF was high (R = 0.905). The 3-year progression-free survival (PFS) rates by NGS and NGF were longer for undetectable vs. positive patients (NGS: 88.7% vs. 56.6%; NGF: 91.4% vs. 50%; p < 0.001 for both comparisons), which resulted in a 3-year overall survival (OS) advantage (NGS: 96.2% vs. 77.3%; NGF: 96.6% vs. 74.9%, p < 0.01 for both comparisons). In the Cox regression model, NGS and NGF negativity had similar results but favoring the latter in PFS (HR: 0.20, 95% CI: 0.09-0.45, p < 0.001) and OS (HR: 0.21, 95% CI: 0.06-0.75, p = 0.02). All these results reinforce the role of MRD detection by different strategies in patient prognosis and highlight the use of MRD as an endpoint for multiple myeloma treatment
Regional and large-scale patterns in Amazon forest structure and function are mediated by variations in soil physical and chemical properties
Forest structure and dynamics have been noted to vary across the Amazon Basin in an east-west gradient in a pattern which coincides with variations in soil fertility and geology. This has resulted in the hypothesis that soil fertility may play an important role in explaining Basin-wide variations in forest biomass, growth and stem turnover rates.
To test this hypothesis and assess the importance of edaphic properties in affect forest structure and dynamics, soil and plant samples were collected in a total of 59 different forest plots across the Amazon Basin. Samples were analysed for exchangeable cations, C, N, pH with various Pfractions also determined. Physical properties were also examined and an index of soil physical quality developed.
Overall, forest structure and dynamics were found to be strongly and quantitatively related to edaphic conditions. Tree turnover rates emerged to be mostly influenced by soil physical properties whereas forest growth rates were mainly related to a measure of available soil phosphorus, although also dependent on rainfall amount and distribution. On the other hand, large scale variations in forest biomass could not be explained by any of the edaphic properties measured, nor by variation in climate.
A new hypothesis of self-maintaining forest dynamic feedback mechanisms initiated by edaphic conditions is proposed. It is further suggested that this is a major factor determining forest disturbance levels, species composition and forest productivity on a Basin wide scale
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