3,704 research outputs found
Obtención por vía SHS-AE de compuesto cerámico αSiC-αAl2O3-CaAl4O7
El presente trabajo muestra los resultados experimentales de la obtención del compuesto cerámico SiC-Al2O3-CaAl 4O7 mediante el proceso SHS-AE (síntesis auto-sostenida de alta temperatura combinada con arco eléctrico) a partir del sistema vidrio sódico-cálcico-Al-C. Se utilizó horno de arco eléctrico con atmósfera de argón para la reducción del contenido de sílice presente en el vidrio con aluminio.La combinación de la energía de la reacción de formación del Al2O3 con la del arco eléctrico provee suficiente energía térmica para superar las barreras cinéticas asociadas con la reacción de formación de los componentes cerámicos.A partir de las relaciones estequiométricas de las materias primas, (polvos que se compactan en forma de pastilla) se efectúa la síntesis alcanzando una temperatura superior a los 2500 K formándose el compuesto SiC-Al2O3-CaAl 4O7. Las muestras obtenidas se caracterizaron por DRX y MEB-EDX confirmando la obtención simultánea de αSiC-αAl2O3-CaAl4O7
Plasma Molecular Signatures in Hypertensive Patients With Renin-Angiotensin System Suppression: New Predictors of Renal Damage and De Novo Albuminuria Indicators
Albuminuria is a risk factor strongly associated with cardiovascular disease, the first cause of death in the general population. It is well established that renin-angiotensin system suppressors prevent the development of new-onset albuminuria in naïf hypertensive patients and diminish its excretion, but we cannot forget the percentage of hypertensive patients who develop de novo albuminuria. Here, we applied multiple proteomic strategy with the purpose to elucidate specific molecular pathways involved in the pathogenesis and provide predictors and chronic organ damage indicators. Briefly, 1143 patients were followed up for a minimum period of 3 years. One hundred and twenty-nine hypertensive patients chronically renin-angiotensin system suppressed were recruited, classified in 3 different groups depending on their albuminuria levels (normoalbuminuria, de novo albuminuria, and sustained albuminuria), and investigated by multiple proteomic strategies. Our strategy allowed us to perform one of the deepest plasma proteomic analysis to date, which has shown 2 proteomic signatures: (1) with predictive value of de novo albuminuria and (2) sustained albuminuria indicator proteins. These proteins are involved in inflammation, immune as well as in the proteasome activation occurring in situations of endoplasmic reticulum stress. Furthermore, these results open the possibility of a future strategy based on anti-immune therapy to treat hypertension which could help to prevent the development of albuminuria and, hence, the progression of kidney damage.N
P-P Total Cross Sections at VHE from Accelerator Data
Comparison of P-P total cross-sections estimations at very high energies -
from accelerators and cosmic rays - shows a disagreement amounting to more than
10 %, a discrepancy which is beyond statistical errors. Here we use a
phenomenological model based on the Multiple-Diffraction approach to
successfully describe data at accelerator energies. The predictions of the
model are compared with data On the basis of regression analysis we determine
confident error bands, analyzing the sensitivity of our predictions to the
employed data for extrapolation. : using data at 546 and 1.8 TeV, our
extrapolations for p-p total cross-sections are only compatible with the Akeno
cosmic ray data, predicting a slower rise with energy than other cosmic ray
results and other extrapolation methods. We discuss our results within the
context of constraints in the light of future accelerator and cosmic ray
experimental results.Comment: 26 pages aqnd 11 figure
Long-lasting defence priming by β-aminobutyric acid in tomato is marked by genome-wide changes in DNA methylation
Exposure of plants to stress conditions or to certain chemical elicitors can establish a primed state, whereby responses to future stress encounters are enhanced. Stress priming can be long-lasting and likely involves epigenetic regulation of stress-responsive gene expression. However, the molecular events underlying priming are not well understood. Here, we characterise epigenetic changes in tomato plants primed for pathogen resistance by treatment with β-aminobutyric acid (BABA). We used whole genome bisulphite sequencing to construct tomato methylomes from control plants and plants treated with BABA at the seedling stage, and a parallel transcriptome analysis to identify genes primed for the response to inoculation by the fungal pathogen, Botrytis cinerea. Genomes of plants treated with BABA showed a significant reduction in global cytosine methylation, especially in CHH sequence contexts. Analysis of differentially methylated regions (DMRs) revealed that CHH DMRs were almost exclusively hypomethylated and were enriched in gene promoters and in DNA transposons located in the chromosome arms. Genes overlapping CHH DMRs were enriched for a small number of stress response-related gene ontology terms. In addition, there was significant enrichment of DMRs in the promoters of genes that are differentially expressed in response to infection with B. cinerea. However, the majority of genes that demonstrated priming did not contain DMRs, and nor was the overall distribution of methylated cytosines in primed genes altered by BABA treatment. Hence, we conclude that whilst BABA treatment of tomato seedlings results in characteristic changes in genome-wide DNA methylation, CHH hypomethylation appears only to target a minority of genes showing primed responses to pathogen infection. Instead, methylation may confer priming via in-trans regulation, acting at a distance from defence genes, and/or by targeting a smaller group of regulatory genes controlling stress responses
PROCESOS BIOESTRATINÓMICOS ACTUANTES EN KATEPENSAURUS GOICOECHEAI: ANÁLISIS DE FACTORES INTRÍNSECOS Y EXTRÍNSECOS. FORMACIÓN BAJO BARREAL (CRETÁCICO SUPERIOR), PATAGONIA, ARGENTINA
Se analizan los factores intrínsecos y extrínsecos que controlaron la preservación del saurópodo rebaquisáurido Katepensaurus goicoecheai, procedente de la Formación Bajo Barreal (Grupo Chubut-Cretácico Superior) en el centro-sur de Chubut, cuenca del Golfo San Jorge, Patagonia central, Argentina. Los restos se preservaron en un depósito de desbordamiento no canalizado, de geometría lobulada, de 30 cm de potencia y vinculado a canales fluviales arenosos. Litológicamente está integrado por areniscas gruesas con abundante matriz pelítica y tobácea,
que permiten caracterizarlo como un flujo hiperconcentrado. Los elementos recuperados, que corresponden principalmente al esqueleto axial, yacían sobre depósitos pelíticos de una planicie de inundación distal mal drenada y fueron parcialmente cubiertos por el lóbulo de desbordamiento, quedando estructuras expuestas que fueron intensamente erosionadas. Los restos se encontraron incompletos, desarticulados y exhibiendo evidencias de una exposición subaérea prolongada. Fueron poco movilizados por procesos hidráulicos y reorientados de forma normal a la dirección del desbordamiento. La dispersión lateral muestra grupos de huesos producto de entrampamientos hidráulicos causados por los restos de mayor tamaño en la parte central del lóbulo y los más pequeños hacia los laterales acorde a la distribución de energía del depósito. La escasa potencia del desbordamiento no sepultó completamente los restos. Finalmente, un nuevo desbordamiento cubrió completamente los materiales. La acumulación de huesos de Katepensaurus sería una concentración ósea residual y representa una acumulación parautóctona de origen sedimentológico
Elucidating the neuropathologic mechanisms of SARS-CoV-2 infection
Acknowledgements We want to express our gratitude to the Union Medical University Clinic, Dominican Republic, for their support and collaboration in the development of this research project. We also want to express our gratitude to the Mexican families who have donated the brain of their loved ones affected with Alzheimer's disease and made our research possible. This work is dedicated to the memory of Professor Dr. José Raúl Mena López†.Peer reviewedPublisher PD
Constraining the Ratio in TeV Cosmic Rays with Observations of the Moon Shadow by HAWC
An indirect measurement of the antiproton flux in cosmic rays is possible as
the particles undergo deflection by the geomagnetic field. This effect can be
measured by studying the deficit in the flux, or shadow, created by the Moon as
it absorbs cosmic rays that are headed towards the Earth. The shadow is
displaced from the actual position of the Moon due to geomagnetic deflection,
which is a function of the energy and charge of the cosmic rays. The
displacement provides a natural tool for momentum/charge discrimination that
can be used to study the composition of cosmic rays. Using 33 months of data
comprising more than 80 billion cosmic rays measured by the High Altitude Water
Cherenkov (HAWC) observatory, we have analyzed the Moon shadow to search for
TeV antiprotons in cosmic rays. We present our first upper limits on the
fraction, which in the absence of any direct measurements, provide
the tightest available constraints of on the antiproton fraction for
energies between 1 and 10 TeV.Comment: 10 pages, 5 figures. Accepted by Physical Review
The 2HWC HAWC Observatory Gamma Ray Catalog
We present the first catalog of TeV gamma-ray sources realized with the
recently completed High Altitude Water Cherenkov Observatory (HAWC). It is the
most sensitive wide field-of-view TeV telescope currently in operation, with a
1-year survey sensitivity of ~5-10% of the flux of the Crab Nebula. With an
instantaneous field of view >1.5 sr and >90% duty cycle, it continuously
surveys and monitors the sky for gamma ray energies between hundreds GeV and
tens of TeV.
HAWC is located in Mexico at a latitude of 19 degree North and was completed
in March 2015. Here, we present the 2HWC catalog, which is the result of the
first source search realized with the complete HAWC detector. Realized with 507
days of data and represents the most sensitive TeV survey to date for such a
large fraction of the sky. A total of 39 sources were detected, with an
expected contamination of 0.5 due to background fluctuation. Out of these
sources, 16 are more than one degree away from any previously reported TeV
source. The source list, including the position measurement, spectrum
measurement, and uncertainties, is reported. Seven of the detected sources may
be associated with pulsar wind nebulae, two with supernova remnants, two with
blazars, and the remaining 23 have no firm identification yet.Comment: Submitted 2017/02/09 to the Astrophysical Journa
The Sensitivity of HAWC to High-Mass Dark Matter Annihilations
The High Altitude Water Cherenkov (HAWC) observatory is a wide field-of-view
detector sensitive to gamma rays of 100 GeV to a few hundred TeV. Located in
central Mexico at 19 degrees North latitude and 4100 m above sea level, HAWC
will observe gamma rays and cosmic rays with an array of water Cherenkov
detectors. The full HAWC array is scheduled to be operational in Spring 2015.
In this paper, we study the HAWC sensitivity to the gamma-ray signatures of
high-mass (multi- TeV) dark matter annihilation. The HAWC observatory will be
sensitive to diverse searches for dark matter annihilation, including
annihilation from extended dark matter sources, the diffuse gamma-ray emission
from dark matter annihilation, and gamma-ray emission from non-luminous dark
matter subhalos. Here we consider the HAWC sensitivity to a subset of these
sources, including dwarf galaxies, the M31 galaxy, the Virgo cluster, and the
Galactic center. We simulate the HAWC response to gamma rays from these sources
in several well-motivated dark matter annihilation channels. If no gamma-ray
excess is observed, we show the limits HAWC can place on the dark matter
cross-section from these sources. In particular, in the case of dark matter
annihilation into gauge bosons, HAWC will be able to detect a narrow range of
dark matter masses to cross-sections below thermal. HAWC should also be
sensitive to non-thermal cross-sections for masses up to nearly 1000 TeV. The
constraints placed by HAWC on the dark matter cross-section from known sources
should be competitive with current limits in the mass range where HAWC has
similar sensitivity. HAWC can additionally explore higher dark matter masses
than are currently constrained.Comment: 15 pages, 4 figures, version to be published in PR
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