El draa Cerro Medanoso (Atacama, Chile) y su importancia en el estudio de geomorfología de desierto

This work presents a morphological analysis of the Cerro Medanoso draa (Atacama Marginal Desert) and the type of contact with the desert pavements of neighboring glacis and piedmont. This study is based on an analysis of aerial photos, and a digital elevation model. Aster GDEM was used as a basis for the survey. Fieldwork observations covered two principal zones: the nucleus and the envelope. Following fieldwork, analysis of satellite imagery was conducted. It was possible to identify the following phases of formation: construction of a stellate nucleus, merging of the eastern envelope, merging of the southern envelope and merging of a complex western envelope. The southeastern facing envelope is much bigger than the northwestern facing one. Consequently, the construction of the complex draa is asymmetric. The correlation of this megadune with similar star and compound draas to other deserts in the world indicates that the closest analogue exists in Namibia, but without merging signals between the envelope and the nucleus. Star draas observed in other deserts exhibit a lack of this envelope. With reference to the neighboring piedmont, the beginning of its deflation must be necessarily correlative to the initial construction of the nuclear twin star draa. The later deflation could be responsible for the pulses, which formed the envelope. Therefore, the neighboring desert pavement and the draa are correlative landforms, which represent a very long time formation, in an important part of the desert history, as evidenced by the cited and referenced research works.Se muestra un análisis del draa Cerro medanoso (Desierto Marginal de Atacama) y su tipo de contacto con el pavimento de desierto del glacis y piedmont vecinos. El trabajo previo se apoyó en fotos aéreas. El modelo de elevación digital Aster Gdem sustentó el levantamiento topográfico. La observación de terreno cubrió dos zonas principales: el núcleo y la envoltura. Después del trabajo de campo se usó imágenes de satélite. Se deduce las siguientes fases en la formación de este draa: construcción de un núcleo estrellado, fusión de la envoltura oriental, fusión de la envoltura sur y fusión de la envoltura occidental compleja. La envoltura de exposición suroeste es más maciza que la de exposición noroeste. Consecuentemente, la construcción del draa complejo es asimétrica. La correlación de esta megaduna con draas estrellados y compuestos similares de otros desiertos del mundo, indica que el tipo más cercano existe en Namibia, pero sin señales de fusión entre la envoltura y el núcleo. Draas estrellados observados en otros desiertos carecen de envoltura. En relación con el piedmont y glacis vecinos, el comienzo de su deflación debe ser necesariamente correlativo a la construcción inicial del draa nuclear doblemente estrellado. La deflación tardía puede ser responsable de los pulsos que formaron la envoltura. Luego, el pavimento de desierto vecino y el draa son formas correlativas, que representan un tiempo muy largo de formación, en una parte importante de la historia del desierto, como se evidencia en los trabajos de investigación citados y referenciados

The TRPV4 channel links calcium influx to DDX3X activity and viral infectivity

Ion channels are well placed to transduce environmental cues into signals used by cells to generate a wide range of responses, but little is known about their role in the regulation of RNA metabolism. Here we show that the TRPV4 cation channel binds the DEAD-box RNA helicase DDX3X and regulates its function. TRPV4-mediated Ca2+ influx releases DDX3X from the channel and drives DDX3X nuclear translocation, a process that involves calmodulin (CaM) and the CaM-dependent kinase II. Genetic depletion or pharmacological inhibition of TRPV4 diminishes DDX3X-dependent functions, including nuclear viral export and translation. Furthermore, TRPV4 mediates Ca2+ influx and nuclear accumulation of DDX3X in cells exposed to the Zika virus or the purified viral envelope protein. Consequently, targeting of TRPV4 reduces infectivity of dengue, hepatitis C and Zika viruses. Together, our results highlight the role of TRPV4 in the regulation of DDX3X-dependent control of RNA metabolism and viral infectivity

Formation of a Massive Black Hole at the Center of the Superbubble in M82

We performed 12CO(1-0), 13CO(1-0), and HCN(1-0) interferometric observations of the central region (about 450 pc in radius) of M82 with the Nobeyama Millimeter Array, and have successfully imaged a molecular superbubble and spurs. The center of the superbubble is clearly shifted from the nucleus by 140 pc. This position is close to that of the massive black hole (BH) of >460 Mo and the 2.2 micron secondary peak (a luminous supergiant dominated cluster), which strongly suggests that these objects may be related to the formation of the superbubble. Consideration of star formation in the cluster based on the infrared data indicates that (1) energy release from supernovae can account for the kinetic energy of the superbubble, (2) the total mass of stellar-mass BHs available for building-up the massive BH may be much higher than 460 Mo, and (3) it is possible to form the middle-mass BH of 100-1000 Mo within the timescale of the superbubble. We suggest that the massive BH was produced and is growing in the intense starburst region.Comment: 9 pages, 3 figures, to appear in ApJ Lette

Molecular Gas in NUclei of GAlaxies (NUGA) I.The counter-rotating LINER NGC4826

We present new high-resolution observations of the nucleus of the counter-rotating LINER NGC4826, made in the J=1-0 and J=2-1 lines of 12CO with the IRAM Plateau de Bure mm-interferometer(PdBI).The CO maps, which achieve 0.8''(16pc) resolution in the 2-1 line, fully resolve an inner molecular gas disk which is truncated at an outer radius of 700pc. The total molecular gas mass is distributed in a lopsided nuclear disk of 40pc radius and two one-arm spirals, which develop at different radii in the disk. The distribution and kinematics of molecular gas in the inner 1kpc of NGC4826 show the prevalence of different types of m=1 perturbations in the gas. Although dominated by rotation, the gas kinematics are perturbed by streaming motions related to the m=1 instabilities. The non-circular motions associated with the inner m=1 perturbations agree qualitatively with the pattern expected for a trailing wave developed outside corotation ('fast' wave). In contrast, the streaming motions in the outer m=1 spiral are better explained by a 'slow' wave. A paradoxical consequence is that the inner m=1 perturbations would not favour AGN feeding. An independent confirmation that the AGN is not being generously fueled at present is found in the low values of the gravitational torques exerted by the stellar potential for R<530pc. The distribution of star formation in the disk of NGC4826 is also strongly asymmetrical. Massive star formation is still vigorous, fed by the significant molecular gas reservoir at R<700pc. There is supporting evidence for a recent large mass inflow episode in NGC4826. These observations have been made in the context of the NUclei of GAlaxies (NUGA) project, aimed at the study of the different mechanisms for gas fueling of AGN.Comment: A&A, 2003, Paper accepted (04/06/03). For a full-resolution version of this paper see http://www.oan.es/preprint

Heterologous expression screens in Nicotiana benthamiana identify a candidate effector of the wheat Yellow Rust Pathogen that associates with processing bodies

Rust fungal pathogens of wheat (Triticum spp.) affect crop yields worldwide. The molecular mechanisms underlying the virulence of these pathogens remain elusive, due to the limited availability of suitable molecular genetic research tools. Notably, the inability to perform high-throughput analyses of candidate virulence proteins (also known as effectors) impairs progress. We previously established a pipeline for the fast-forward screens of rust fungal candidate effectors in the model plant Nicotiana benthamiana. This pipeline involves selecting candidate effectors in silico and performing cell biology and protein-protein interaction assays in planta to gain insight into the putative functions of candidate effectors. In this study, we used this pipeline to identify and characterize sixteen candidate effectors from the wheat yellow rust fungal pathogen Puccinia striiformis f sp tritici. Nine candidate effectors targeted a specific plant subcellular compartment or protein complex, providing valuable information on their putative functions in plant cells. One candidate effector, PST02549, accumulated in processing bodies (P-bodies), protein complexes involved in mRNA decapping, degradation, and storage. PST02549 also associates with the P-body-resident ENHANCER OF mRNA DECAPPING PROTEIN 4 (EDC4) from N. benthamiana and wheat. We propose that P-bodies are a novel plant cell compartment targeted by pathogen effectors

Mid-infrared spectroscopy of infrared-luminous galaxies at z~0.5-3

We present results on low-resolution mid-infrared (MIR) spectra of 70 infrared-luminous galaxies obtained with the Infrared Spectrograph (IRS) onboard Spitzer. We selected sources from the European Large Area Infrared Survey (ELAIS) with S15 > 0.8 mJy and photometric or spectroscopic z > 1. About half of the sample are QSOs in the optical, while the remaining sources are galaxies, comprising both obscured AGN and starbursts. We classify the spectra using well-known infrared diagnostics, as well as a new one that we propose, into three types of source: those dominated by an unobscured AGN (QSOs), obscured AGN, and starburst-dominated sources. Starbursts concentrate at z ~ 0.6-1.0 favored by the shift of the 7.7-micron PAH band into the selection 15 micron band, while AGN spread over the 0.5 < z < 3.1 range. Star formation rates (SFR) are estimated for individual sources from the luminosity of the PAH features. An estimate of the average PAH luminosity in QSOs and obscured AGN is obtained from the composite spectrum of all sources with reliable redshifts. The estimated mean SFR in the QSOs is 50-100 Mo yr^-1, but the implied FIR luminosity is 3-10 times lower than that obtained from stacking analysis of the FIR photometry, suggesting destruction of the PAH carriers by energetic photons from the AGN. The SFR estimated in obscured AGN is 2-3 times higher than in QSOs of similar MIR luminosity. This discrepancy might not be due to luminosity effects or selection bias alone, but could instead indicate a connection between obscuration and star formation. However, the observed correlation between silicate absorption and the slope of the near- to mid-infrared spectrum is compatible with the obscuration of the AGN emission in these sources being produced in a dust torus.Comment: 32 pages, 24 figures, 15 tables, accepted for publication in MNRA

Bacteriosis foliares del cultivo de maíz en Argentina

En Argentina hay detectadas enfermedades de origen bacteriano que atacan las hojas del maíz. Algunas producen síntomas característicos y fácilmente distinguibles, mientras otras se confunden con enfermedades fúngicas o lesiones por factores abióticos. En cultivos extensivos las enfermedades bacterianas tienen estrategias de manejo variadas, pero no cuentan con opciones de control químico. Por esto, es importantereconocer estas enfermedades y evitar decisiones que podrían agravar más la condición del cultivo. En los últimos años se han registrado, diagnosticado e identificado mediante el análisis de perfil proteico con Maldi-Tof, las siguientes: Estría Bacteriana causada por Xanthomonas vasicola pv vasculorum1. Es la más frecuente en el cultivo. Produce lesiones internervales finas, alargadas, de bordes irregulares en hojas, coloración amarilla a pardas que alcanzan toda la lámina. Produce zoogleas. Las condiciones ambientales favorables de desarrollo de síntomas son temperaturas moderadas y tormentas con vientos fuertes. Los híbridos disponibles en general desarrollan síntomas, presentando sensibilidad variada de acuerdo a su genotipo. Rayado foliar y Podredumbre del ápice por Acidovorax avenae2. El rayado foliar se presenta a lo largo de la hoja, más ancho que la Estría Bacteriana y el tejido dentro de la lesión de color blanquecino. En estados vegetativos puede producir necrosis en el ápice. Origina retraso del desarrollo de la planta y detención del crecimiento. Con lluvias prolongadas puede alcanzar tallo y necrosar haces vasculares, produciendo estrangulamientos. Mancha Bacteriana por Burkholderia andropogonis3. La mancha bacteriana tiene forma rectangular color marrón claro, frecuentemente rodeada de halo clorótico. Estas lesiones se extienden internervalmente hasta alcanzar unos 5 mm de ancho y 10-15 cm de largo, pueden coalescer. El tejido necrótico se torna claro y translúcido, con líneas evidentes a trasluz. La presencia de variada sintomatología sobre las hojas hace necesario un diagnóstico preciso de las enfermedades para poder discriminar la problemática adecuar su manejo

Molecular Gas in NUclei of GAlaxies (NUGA): II. The Ringed LINER NGC7217

We present CO(1-0) and CO(2-1) maps of the LINER galaxy NGC7217, obtained with the IRAM interferometer, at 2.4"x1.9" and 1.2"x0.8" resolution respectively. The nuclear ring (at r=12"=0.8kpc) dominates the CO maps, and has a remarkable sharp surface density gradient at its inner edge. The latter is the site of the stellar/Halpha ring, while the CO emission ring extends farther or is broader (500-600pc). This means that the star formation has been more intense toward the inner edge of the CO ring, in a thin layer, just at the location of the high gas density gradient. In the CO(2-1) map, a central concentration inside 3" coincides with a spiral dust lane, clearly seen in the HST V-I color image. N-body simulations including gas dissipation and star formation are performed to better understand the nature of the nuclear ring observed. In the best model, the gas content was higher in the recent past (having been consumed via star formation), and the oval/spiral formed were more self-gravitating (abridged).Comment: 16 pages, 23 figures, accepted in Astronomy and Astrophysic

Projeto SIENHA – Rede europeia estratégica e inovadora para a educação no envelhecimento saudável

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