451 research outputs found
The Persistence of Memory, or How the X-Ray Spectrum of SNR 0509-67.5 Reveals the Brightness of its Parent Type Ia Supernova
We examine the dynamics and X-ray spectrum of the young Type Ia supernova
remnant 0509-67.5 in the context of the recent results obtained from the
optical spectroscopy of its light echo. Our goal is to estimate the kinetic
energy of the supernova explosion using Chandra and XMM-Newton observations of
the supernova remnant, thus placing the birth event of 0509-67.5 in the
sequence of dim to bright Type Ia supernovae. We base our analysis on a
standard grid of one-dimensional delayed detonation explosion models, together
with hydrodynamic and X-ray spectral calculations of the supernova remnant
evolution. From the remnant dynamics and the properties of the O, Si, S, and Fe
emission in its X-ray spectrum we conclude that 0509-67.5 was originated ~400
years ago by a bright, highly energetic Type Ia explosion similar to SN 1991T.
Our best model has a kinetic energy of 1.4x10E51 erg and synthesizes 0.97 Msun
of 56Ni. These results are in excellent agreement with the age estimate and
spectroscopy from the light echo. We have thus established the first connection
between a Type Ia supernova and its supernova remnant based on a detailed
quantitative analysis of both objects.Comment: 10 pages, 9 figures, plus an exclusive astro-ph-only Appendix; ApJ in
press, companion paper to Rest et al. 0
White dwarf dynamical interactions and fast optical transients
This is the author accepted manuscript. The final version is available from OUP via the DOI in this record.Recent advances in time-domain astronomy have uncovered a new class of optical
transients with timescales shorter than typical supernovae and a wide range of peak
luminosities. Several subtypes have been identi ed within this broad class, including
Ca-rich transients, .Ia supernovae, and fast/bright transients. We examine the predic-
tions from a state-of-the-art grid of three-dimensional simulations of dynamical white
dwarf interactions in the context of these fast optical transients. We nd that for colli-
sions involving carbon-oxygen or oxygen-neon white dwarfs the peak luminosities and
durations of the light curves in our models are in good agreement with the properties
of fast/bright transients. When one of the colliding white dwarfs is made of helium
the properties of the light curves are similar to those of Ca-rich gap transients. The
model lightcurves from our white dwarf collisions are too slow to reproduce those of
.Ia SNe, and too fast to match any normal or peculiar Type Ia supernova.This work was partially funded by the MINECO
grant AYA2014-59084-P and by the AGAUR (EG-B).
CB acknowledges support from grants NASA ADAP
NNX15AM03G S01 and NSF/AST-1412980. We acknowl-
edge the useful comments of our referee, which helped in
improving the original version of the paper
Application of genomic technologies to the breeding of trees
The recent introduction of next generation sequencing (NGS) technologies represents a major revolution in providing new tools for identifying the genes and/or genomic intervals controlling important traits for selection in breeding programs. In perennial fruit trees with long generation times and large sizes of adult plants, the impact of these techniques is even more important. High-throughput DNA sequencing technologies have provided complete annotated sequences in many important tree species. Most of the high-throughput genotyping platforms described are being used for studies of genetic diversity and population structure. Dissection of complex traits became possible through the availability of genome sequences along with phenotypic variation data, which allow to elucidate the causative genetic differences that give rise to observed phenotypic variation. Association mapping facilitates the association between genetic markers and phenotype in unstructured and complex populations, identifying molecular markers for assisted selection and breeding. Also, genomic data provide in silico identification and characterization of genes and gene families related to important traits, enabling new tools for molecular marker assisted selection in tree breeding. Deep sequencing of transcriptomes is also a powerful tool for the analysis of precise expression levels of each gene in a sample. It consists in quantifying short cDNA reads, obtained by NGS technologies, in order to compare the entire transcriptomes between genotypes and environmental conditions. The miRNAs are non-coding short RNAs involved in the regulation of different physiological processes, which can be identified by high-throughput sequencing of RNA libraries obtained by reverse transcription of purified short RNAs, and by in silico comparison with known miRNAs from other species. All together, NGS techniques and their applications have increased the resources for plant breeding in tree species, closing the former gap of genetic tools between trees and annual species
Are the Models for Type Ia Supernova Progenitors Consistent with the Properties of Supernova Remnants?
We explore the relationship between the models for progenitor systems of Type
Ia supernovae and the properties of the supernova remnants that evolve after
the explosion. Most models for Type Ia progenitors in the single degenerate
scenario predict substantial outflows during the presupernova evolution.
Expanding on previous work, we estimate the imprint of these outflows on the
structure of the circumstellar medium at the time of the supernova explosion,
and the effect that this modified circumstellar medium has on the evolution of
the ensuing supernova remnant. We compare our simulations with the
observational properties of known Type Ia supernova remnants in the Galaxy
(Kepler, Tycho, SN 1006), the Large Magellanic Cloud (0509-67.5, 0519-69.0,
N103B), and M31 (SN 1885). We find that optically thick outflows from the white
dwarf surface (sometimes known as accretion winds) with velocities above 200
km/s excavate large low-density cavities around the progenitors. Such large
cavities are incompatible with the dynamics of the forward shock and the X-ray
emission from the shocked ejecta in all the Type Ia remnants that we have
examined.Comment: To appear in ApJ. 17 pages, 10 figures, emulateap
Editorial: Breeding Innovations in Underutilized Temperate Fruit Trees
The recent growing interest in minor species (i.e., fig, pomegranate, feijoa, etc.) has recently driven new research on breeding and genetics to address producer and consumer traits. Since these species have received little attention from the scientific community, they were less improved via conventional breeding, and lacked detailed genomic information on important traits. This lack of data, together with a general poor genetic knowledge of these species, has limited a wider cultivation of varieties with improved characteristics
Hemoglobin concentrations and RBC transfusion thresholds in patients with acute brain injury: an international survey.
The optimal hemoglobin (Hb) threshold at which to initiate red blood cell (RBC) transfusion in patients with acute brain injury is unknown. The aim of this survey was to investigate RBC transfusion practices used with these patients.
We conducted a web-based survey within various societies of critical care medicine for intensive care unit (ICU) physicians who currently manage patients with primary acute brain injury.
A total of 868 responses were obtained from around the world, half of which (n = 485) were from European centers; 204 (24%) respondents had a specific certificate in neurocritical care, and most were specialists in anesthesiology or intensive care and had less than 15 years of practice experience. Four hundred sixty-six respondents (54%) said they used an Hb threshold of 7-8 g/dl to initiate RBC transfusion after acute brain injury, although half of these respondents used a different threshold (closer to 9 g/dl) in patients with traumatic brain injury, subarachnoid hemorrhage, or ischemic stroke. Systemic and cerebral factors were reported as influencing the need for higher Hb thresholds. Most respondents agreed that a randomized clinical trial was needed to compare two different Hb thresholds for RBC transfusion, particularly in patients with traumatic brain injury, subarachnoid hemorrhage, and ischemic stroke.
The Hb threshold used for RBC transfusion after acute brain injury was less than 8 g/dl in half of the ICU clinicians who responded to our survey. However, more than 50% of these physicians used higher Hb thresholds in certain conditions
Structure and Expression of Bud Dormancy-Associated MADS-Box Genes (DAM) in European Plum
Bud dormancy in temperate perennials ensures the survival of growing meristems under the harsh environmental conditions of autumn and winter, and facilitates an optimal growth and development resumption in the spring. Although the molecular pathways controlling the dormancy process are still unclear, DORMANCY-ASSOCIATED MADS-BOX genes (DAM) have emerged as key regulators of the dormancy cycle in different species. In the present study, we have characterized the orthologs of DAM genes in European plum (Prunus domestica L.). Their expression patterns together with sequence similarities are consistent with a role of PdoDAMs in dormancy maintenance mechanisms in European plum. Furthermore, other genes related to dormancy, flowering, and stress response have been identified in order to obtain a molecular framework of these three different processes taking place within the dormant flower bud in this species. This research provides a set of candidate genes to be genetically modified in future research, in order to better understand dormancy regulation in perennial species
School adjustment in children who stutter: The quality of the student-teacher relationship, peer relationships, and children's academic and behavioral competence
Increased conductivity of a hole transport layer due to oxidation by a molecular nanomagnet
Thin film transistors based on polyarylamine poly(N,N′-diphenyl-N,N′bis(4-hexylphenyl)-[1,1′biphenyl]-4,4′-diamine (pTPD) were fabricated using spin coating in order to measure the mobility of pTPD upon oxidation. Partially oxidized pTPD with a molecular magnetic cluster showed an increase in mobility of over two orders of magnitude. A transition in the mobility of pTPD upon doping could also be observed by the presence of a maximum obtained for a given oxidant ratio and subsequent decrease for a higher ratio. Such result agrees well with a previously reported model based on the combined effect of dipolar broadening of the density of states and transport manifold [email protected] [email protected]
The metal contents of two groups of galaxies
The hot gas in clusters and groups of galaxies is continuously being enriched
with metals from supernovae and stars. It is well established that the
enrichment of the gas with elements from oxygen to iron is mainly caused by
supernova explosions. The origins of nitrogen and carbon are still being
debated. Possible candidates include massive, metal-rich stars, early
generations of massive stars, intermediate or low mass stars and Asymptotic
Giant Branch (AGB) stars. In this paper we accurately determine the metal
abundances of the gas in the groups of galaxies NGC 5044 and NGC 5813, and
discuss the nature of the objects that create these metals.
We mainly focus on carbon and nitrogen. We use spatially-resolved
high-resolution X-ray spectroscopy from XMM-Newton. For the spectral fitting,
multi-temperature hot gas models are used. The abundance ratios of carbon over
oxygen and nitrogen over oxygen that we find are high compared to the ratios in
the stars in the disk of our Galaxy. The oxygen and nitrogen abundances we
derive are similar to what was found in earlier work on other giant ellipticals
in comparable environments. We show that the iron abundances in both our
sources have a gradient along the cross-dispersion direction of the Reflection
Grating Spectrometer (RGS). We conclude that it is unlikely that the creation
of nitrogen and carbon takes place in massive stars, which end their lives as
core-collapse supernovae, enriching the medium with oxygen because oxygen
should then also be enhanced. Therefore we favour low-and intermediate mass
stars as sources of these elements. The abundances in the hot gas can best be
explained by a 30-40% contribution of type Ia supernovae based on the measured
oxygen and iron abundances and under the assumption of a Salpeter Initial Mass
Function (IMF).Comment: Accepted for publication in A&A, 12 pages, 10 figures. Data points on
which figs 4,5,8 and 9 are based are present as comment in the source fil
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