220 research outputs found
Is the metallicity of their hosts a good measure of the metallicity of Type Ia supernovae?
The efficient use of Type Ia supernovae (SNIa) for cosmological studies
requires knowledge of any parameter that can affect their luminosity in either
systematic or statistical ways. Observational samples of SNIa commonly use the
metallicity of the host galaxy, Z_host, as an estimator of the supernova
progenitor metallicity, Z_Ia, that is one of the primary factors affecting SNIa
magnitude. Here, we present a theoretical study of the relationship between
Z_Ia and Z_host. We follow the chemical evolution of homogeneous galaxy models
together with the evolution of the supernova rates in order to evaluate the
metallicity distribution function, MDF(Delta Z), i.e. the probability that the
logarithm of the metallicity of a SNIa exploding now differs in less than Delta
Z from that of its host. We analyse several model galaxies aimed to represent
from active to passive galaxies, including dwarf galaxies prone to experience
supernova driven outflows. We analyse the sensitivity of the MDF to uncertain
ingredients: IMF, star-formation law, stellar lifetime, stellar yields, and
SNIa delay-time distribution. There is a remarkable degree of agreement between
the mean Z_Ia in a galaxy and its Z_host when they both are measured as the CNO
abundance, especially if the DTD peaks at small time delays, while the average
Fe abundance of host and SNIa may differ up to 0.4-0.6 dex in passive galaxies.
The dispersion of Z_Ia in active galaxy models is quite small, meaning that
Z_host is a quite good estimator of the supernova metallicity. Passive galaxies
present a larger dispersion, which is more pronounced in low mass galaxies. We
discuss the use of different metallicity indicators: Fe vs. O, and gas-phase
metallicity vs. stellar metallicity. The results of the application of our
formalism to a galactic catalogue (VESPA) are roughly consistent with our
theoretical estimates. (abridged)Comment: 15 pages, 10 figures, 1 table, accepted for MNRA
Early Spectra of the Gravitational Wave Source GW170817: Evolution of a Neutron Star Merger
On 2017 August 17, Swope Supernova Survey 2017a (SSS17a) was discovered as
the optical counterpart of the binary neutron star gravitational wave event
GW170817. We report time-series spectroscopy of SSS17a from 11.75 hours until
8.5 days after merger. Over the first hour of observations the ejecta rapidly
expanded and cooled. Applying blackbody fits to the spectra, we measure the
photosphere cooling from K to K,
and determine a photospheric velocity of roughly 30% of the speed of light. The
spectra of SSS17a begin displaying broad features after 1.46 days, and evolve
qualitatively over each subsequent day, with distinct blue (early-time) and red
(late-time) components. The late-time component is consistent with theoretical
models of r-process-enriched neutron star ejecta, whereas the blue component
requires high velocity, lanthanide-free material.Comment: 33 pages, 5 figures, 2 tables, Accepted to Scienc
The correlation between C/O ratio, metallicity and the initial WD mass for SNe Ia
In this paper, we want to check whether or not the carbon abundance can be
affected by initial metallicity. We calculated a series of stellar evolution.
We found that when , the carbon abundance is almost independent of
metallicity if it is plotted against the initial WD mass. However, when
, the carbon abundance is not only a function of the initial WD mass,
but also metallicity, i.e. for a given initial WD mass, the higher the
metallicity, the lower the carbon abundance. Based on some previous studies,
i.e. both a high metallicity and a low carbon abundance lead to a lower
production of Ni formed during SN Ia explosion, the effects of the
carbon abundance and the metallicity on the amount of Ni are
enhanced by each other, which may account for the variation of maximum
luminosity of SNe Ia, at least qualitatively. Considering that the central
density of WD before supernova explosion may also play a role on the production
of Ni and the carbon abundance, the metallicity and the central
density are all determined by the initial parameters of progenitor system, i.e.
the initial WD mass, metallicity, orbital period and secondary mass, the amount
of Ni might be a function of the initial parameters. Then, our
results might construct a bridge linking the progenitor model and the explosion
model of SNe Ia.Comment: 7pages, 4 figures, accepted for publication in A&
Light Curves of the Neutron Star Merger GW170817/SSS17a: Implications for R-Process Nucleosynthesis
On 2017 August 17, gravitational waves were detected from a binary neutron
star merger, GW170817, along with a coincident short gamma-ray burst,
GRB170817A. An optical transient source, Swope Supernova Survey 17a (SSS17a),
was subsequently identified as the counterpart of this event. We present
ultraviolet, optical and infrared light curves of SSS17a extending from 10.9
hours to 18 days post-merger. We constrain the radioactively-powered transient
resulting from the ejection of neutron-rich material. The fast rise of the
light curves, subsequent decay, and rapid color evolution are consistent with
multiple ejecta components of differing lanthanide abundance. The late-time
light curve indicates that SSS17a produced at least ~0.05 solar masses of heavy
elements, demonstrating that neutron star mergers play a role in r-process
nucleosynthesis in the Universe.Comment: Accepted to Scienc
Hidden MHC genetic diversity in the Iberian ibex (Capra pyrenaica)
[EN]Background: Defining hidden genetic diversity within species is of great significance when attempting to maintain the evolutionary potential of natural populations and conduct appropriate management. Our hypothesis is that isolated (and eventually small) wild animal populations hide unexpected genetic diversity due to their maintenance of ancient polymorphisms or introgressions. Results: We tested this hypothesis using the Iberian ibex (Capra pyrenaica) as an example. Previous studies based on large sample sizes taken from its principal populations have revealed that the Iberian ibex has a remarkably small MHC DRB1 diversity (only six remnant alleles) as a result of recent population bottlenecks and a marked demographic decline that has led to the extinction of two recognized subspecies. Extending on the geographic range to include non-studied isolated Iberian ibex populations, we sequenced a new MHC DRB1 in what seemed three small isolated populations in Southern Spain (n=132). The findings indicate a higher genetic diversity than previously reported in this important gene. The newly discovered allele, MHC DRB1*7, is identical to one reported in the domestic goat C. aegagrus hircus. Whether or not this is the result of ancient polymorphisms maintained by balancing selection or, alternatively, introgressions from domestic goats through hybridization needs to be clarified in future studies. However, hybridization between Iberian ibex and domestic goats has been reported in Spain and the fact that the newly discovered allele is only present in one of the small isolated populations and not in the others suggests introgression. The new discovered allele is not expected to increase fitness in C. pyrenaica since it generates the same protein as the existing MHC DRB1*6. Analysis of a microsatellite locus (OLADRB1) near the new MHC DRB1*7 gene reveals a linkage disequilibrium between these two loci. The allele OLADRB1, 187 bp in length, was unambiguously linked to the MHC DRB1*7 allele. This enabled us to perform a DRB-STR matching method for the recently discovered MHC allele. Conclusions: This finding is critical for the conservation of the Iberian ibex since it directly affects the identification of the units of this species that should be managed and conserved separately (Evolutionarily Significant Units).SIThis study was partially funded by the Consejería de Medio Ambiente of the Junta de Andalucía (projects 173/2009/M/00 and 03/15/M/00) and the Ministerio de Economía y Competitividad of the Spanish Government (projects CGL2012-40043-C02-01, CGL2012-40043-C02-02 and CGL2016-80543-P). The funding bodies did not contribute to the design of the study or collection, analysis and interpretation of data, or to the writing of the manuscript
Medical imaging: Foundations and scope
Indexación: Scopus; Radalyc.En la actualidad es innegable la utilidad de las diversas modalidades
de imagenología médica como apoyo clínico tanto en
la generación de diagnósticos de un buen número de enfermedades
como en la planeación de tratamientos tendientes a
proporcionar una alternativa de solución a las personas que,
por una u otra razón, manifiestan algún desequilibrio en su
salud. Entre las modalidades imagenológicas que, frecuentemente,
se utilizan en el ámbito médico se pueden mencionar:
Ultrasonido (US), Resonancia Magnética (MRI), Tomografía
Computarizada sencilla (CT) y multicapa (MSCT), Tomografía
Computarizada por Emisión de Positrones (PET) y Tomografía
Computarizada por Emisión de Fotones simples (SPECT).
En este sentido, este artículo tiene como finalidad presentar
una descripción ordenada, coherente y sistemática de cada
una de las mencionadas modalidades y establecer la vinculación
de la MSCT con situaciones clínicas íntimamente relacionadas
con la anatomía cardiaca y procesos de hipertensión.
La razón por la cual se hace énfasis en la MSCT es debido a
que, por una parte, se cuenta con un número importante de
bases de datos tanto de sujetos fisiológicos como de sujetos
patológicos y, por la otra, que se tiene previsto presentar un
conjunto de técnicas computacionales que serán exploradas
en el desarrollo de futuras investigaciones en el contexto de
aspectos anatómico-cardiológicos que influyen directa o indirectamente
en la aparición, desarrollo y prevalencia de procesos
hipertensivos.Nowdays, several forms of medical imaging are usefulness in
clinical support for both diagnostics diseases generation and
treatment planning designed to provide an alternative solution
to people who, for one or another reason, manifest an
imbalance in your health. Among the imaging modalities that
frequently are used in the medical field may include: Ultrasound
(US), magnetic resonance imaging (MRI), simple computed
tomography (CT) and multilayer computed tomography
(MSCT), CT positron emission tomography (PET) Computed
tomography and single photon emission (SPECT). In this sense,
this article presents an orderly, coherent and systematic
description of these modalities and it establishes relationship
with the MSCT modality and clinical situations closely related
to cardiac anatomy and hypertension processes. The reason
emphasis on MSCT is done is because, on the one hand, we
have a large number of databases both physiological subjects
and pathological subjects and, on the other, we plan to
present a set of computational techniques that will be explored
in future research, in the context of cardiologic anatomical
aspects, with directly or indirectly influence in the emergence,
development and prevalence of hypertensive processes.http://www.redalyc.org/articulo.oa?id=5594990700
Diseases of Iberian ibex (Capra pyrenaica)
Iberian ibex (Capra pyrenaica) is an ecologically and economically relevant medium-sized emblematic mountain ungulate. Diseases participate in the population dynamics of the species as a regulating agent, but can also threaten the conservation and viability of vulnerable population units. Moreover, Iberian ibex can also be a carrier or even a reservoir of pathogens shared with domestic animals and/or humans, being therefore a concern for livestock and public health. The objective of this review is to compile the currently available knowledge on (1) diseases of Iberian ibex, presented according to their relevance on the health and demography of free-ranging populations; (2) diseases subjected to heath surveillance plans; (3) other diseases reported in the species; and (4) diseases with particular relevance in captive Iberian ibex populations. The systematic review of all the information on diseases affecting the species unveils unpublished reports, scientific communications in meetings, and scientific articles, allowing the first comprehensive compilation of Iberian ibex diseases. This review identifies the gaps in knowledge regarding pathogenesis, immune response, diagnostic methods, treatment, and management of diseases in Iberian ibex, providing a base for future research. Moreover, this challenges wildlife and livestock disease and wildlife population managers to assess the priorities and policies currently implemented in Iberian ibex health surveillance and monitoring and disease management
PPARGC1A gene promoter methylation as a biomarker of insulin secretion and sensitivity in response to glucose challenges
Methylation in CpG sites of the PPARGC1A gene (encoding PGC1-α) has been associated
with adiposity, insulin secretion/sensitivity indexes and type 2 diabetes. We assessed the association
between the methylation profile of the PPARGC1A gene promoter gene in leukocytes with insulin
secretion/sensitivity indexes in normoglycemic women. A standard oral glucose tolerance test (OGTT)
and an abbreviated version of the intravenous glucose tolerance test (IVGTT) were carried out in
n = 57 Chilean nondiabetic women with measurements of plasma glucose, insulin, and C-peptide.
Bisulfite-treated DNA from leukocytes was evaluated for methylation levels in six CpG sites of the
proximal promoter of the PPARGC1A gene by pyrosequencing (positions -816, -783, -652, -617, -521
and -515). A strong correlation between the DNA methylation percentage of different CpG sites of the
PPARGC1A promoter in leukocytes was found, suggesting an integrated epigenetic control of this
region. We found a positive association between the methylation levels of the CpG site -783 with the
insulin sensitivity Matsuda composite index (rho = 0.31; p = 0.02) derived from the OGTT. The CpG
hypomethylation in the promoter position -783 of the PPARGC1A gene in leukocytes may represent a
biomarker of reduced insulin sensitivity after the ingestion of glucose
Discovery and Follow-up of ASASSN-19dj: An X-ray and UV Luminous TDE in an Extreme Post-Starburst Galaxy
We present observations of ASASSN-19dj, a nearby tidal disruption event (TDE)
discovered in the post-starburst galaxy KUG 0810+227 by the All-Sky Automated
Survey for Supernovae (ASAS-SN) at a distance of d 98 Mpc. We observed
ASASSN-19dj from 21 to 392 days relative to peak UV/optical emission using
high-cadence, multi-wavelength spectroscopy and photometry. From the ASAS-SN
-band data, we determine that the TDE began to brighten on 2019 February 6.8
and for the first 25 days the rise was consistent with a flux
power-law. ASASSN-19dj peaked in the UV/optical on 2019 March 6.5 (MJD =
58548.5) at a bolometric luminosity of . Initially remaining roughly constant in X-rays and slowly fading
in the UV/optical, the X-ray flux increased by over an order of magnitude
225 days after peak, resulting from the expansion of the X-ray emitting
surface. The late-time X-ray emission is well-fit by a blackbody with an
effective radius of and a temperature of
. Analysis of Catalina Real-Time Transient
Survey images reveals a nuclear outburst roughly 14.5 years earlier with a
smooth decline and a luminosity of erg
s, although the nature of the flare is unknown. ASASSN-19dj occurred in
the most extreme post-starburst galaxy yet to host a TDE, with Lick
H = \AA.Comment: 25 pages, 14 figures. Will be submitted to MNRAS. For a short video
description please see https://youtu.be/WjTZwO7vcF
Enhanced therapeutic effect using sequential administration of antigenically distinct oncolytic viruses expressing oncostatin M in a Syrian hamster orthotopic pancreatic cancer model
The limited efficacy of current treatments against pancreatic cancer has prompted the search of new
alternatives such as virotherapy. Activation of the immune response against cancer cells is emerging as one of the
main mechanisms of action of oncolytic viruses (OV). Direct oncolysis releases tumor antigens, and viral replication
within the tumor microenvironment is a potent danger signal. Arming OV with immunostimulatory transgenes
further enhances their therapeutic effect. However, standard virotherapy protocols do not take full advantage of OV
as cancer vaccines because repeated viral administrations may polarize immune responses against strong viral
antigens, and the rapid onset of neutralizing antibodies limits the efficacy of redosing. An alternative paradigm
based on sequential combination of antigenically distinct OV has been recently proposed
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