A new limit for the NW Río de la Plata Craton Border at about 24ºS (Argentina) detected by Magnetotellurics

Old South American structures constitute a puzzle where the Río de la Plata craton is the most important clue in the assembly of SW Gondwana. The present study was performed to improve the knowledge resulting from all the previous magnetotelluric (MT) studies focused particularly on characterizing the western border of the Rio de la Plata Craton. MT data were acquired along an approximately NW-SE 750 km profile at about 24ºS, from the Sub Andean Ranges in the province of Salta (NW) to the boundary Formosa Province frontier (SE) next to Paraguay River. Distortion and structure dimensionality analysis indicates that MT responses are two-dimensional with a NS strike orientation, consistent with the regional geological strike. A 2D inversion of the data provided a model showing a sharp lateral discontinuity, possibly associated with cratonic structures. The high resistivity (> 5000 ohm-m) observed, from about the middle of the profile toward its eastern end, may be interpreted as the terranes accreted to the Río de la Plata Craton during Neoproterozoic to Cambrian times, or even as the Río de la Plata Craton itself. Along the profile from the surface to a depth of about 10 km the resistivity model shows a significant resistivity variation in the structure. The resistive block identified at the western end of the profile represents the Sub Andean system. The markedly enhanced low-resistivity structure (~ 1 to 10 ohm-m) corresponds to a sedimentary pile whose thickness decreases from NW to SE

A new limit for the NW Río de la Plata Craton Border at about 24ºS (Argentina) detected by Magnetotellurics

Old South American structures constitute a puzzle where the Río de la Plata Craton is the most important clue in the assembly of SW Gondwana. The present study is aimed at characterizing the western border of the Río de la Plata Craton on the basis of magnetotelluric studies. Magnetotelluric (MT) data were acquired along an approximately NW-SE 750km profile at about 24ºS, from the Sub-Andean Ranges in the province of Salta (NW) to the Formosa Province frontier (SE) next to Paraguay River. Distortion and structure dimensionality analysis indicates that MT responses are two-dimensional with a NS strike orientation, consistent with the regional geological strike. A 2-D inversion of the data provided a model showing a lateral discontinuity, possibly associated with cratonic structures. The high resistivity observed (>5000ohm·m), from about the middle of the profile toward its eastern end, may be interpreted as the terranes accreted to the Río de la Plata Craton during Neoproterozoic to Cambrian times, or as the Río de la Plata Craton itself. Along the profile from the surface to a depth of about 10km the resistivity model shows a significant resistivity variation in the structure. The resistive block identified at the western end of the profile represents the Sub-Andean system. The markedly enhanced low-resistivity structure (~1 to 10ohm·m) corresponds to a sedimentary pile whose thickness decreases from NW to SE

Actividad, composición y distribución de tamaño de partículas de aerosol producidas por mezclas pirotécnicas que contienen I2Pb y I2Pb+IK

El objeto de este trabajo fue estudiar la dependencia de la actividad glaceógena de núcleos artificiales respecto al sobreenfriamiento del sistema (-6°C a -20°C) para mezclas pirotécnicas que contienen I2Pb y I2pb + IK. Se determinó, para las mismas, la distribución de tamaños usando un microscopio electrónico de transmisión comprobándose que las partículas del aerosol son submicrónicas (ø<200Á). Además se identificó la composición de las partículas por medio del análisis de difracción de electrones y de rayos-X.The purpose of this research work was to study the dependence of freezing activity of artificial nuclei in relation to the supercooling of the system (-6°C to -20°C) for pyrotechnic mixtures that contain l2Pb and I2pb + IK. Their size distribution was determined using a transmission electronic microscope. The aerosol particles proved to be submicronic (ø<200Á). Besides, the composition of the particles was analysed through electronic diffraction and X-rays.Asociación Argentina de Geofísicos y Geodesta

From acute injury to chronic disease: pathophysiological hypothesis of an epithelial/mesenchymal crosstalk alteration in CKD

Observational clinical studies link acute kidney injury to chronic kidney disease (CKD) progression. The pathophysiological mechanisms that underlie this process are currently unknown but recently published papers suggest that tubular epithelial cells and interstitial mesenchymal cells emerge as a single unit, and their integrity alteration as a whole might lead to renal fibrosis and CKD. The present article reviews the biological findings supporting the hypothesis of an altered epithelial/mesenchymal crosstalk in fibrosis development and progression toward CK

Estudios magnetotelúricos en la cuenca del mar de Wedell, cálculo de la matriz de inducción electromagnética terrestre

En este trabajo se revisaron datos magnetotelúricos obtenidos en campañas antárticas, en sitios aledaños a las bases argentinas Marambio y Matienzo, cuya interpretación preliminar ya era conocida. El análisis complementario que aquí se presenta pone énfasis en el cálculo detallado de los elementos del tensor impedancia, la forma de descripción mas general de la inducción en la tierra. Del análisis surgen las siguientes conclusiones: 1) un acuerdo general aceptable con los resultados preliminares, 2) argumentos para considerar válida la hipótesis de una estructura con simetría bidimensional en Marambio, 3) evidencias de una estructura de mayor complejidad en Matienz .In this paper antarctic magnetotelluric data obtained near the argentine bases Marambio and Matienzo were analyzed. Previous preliminary interpretation had been already published. The here presented complementary analysis put emphasis on the calculus of the elements of the impedance tensor, the more general description of the induction in earth phenomena. The conclusions of this analysis are: 1) There is a general agreement with preliminary results, 2) arguments in favour of the two dimensional structure hipothesis are obtained in the Marambio site, 3) there are evidencies of a more complex structure in the Matienzo sounding site.Asociación Argentina de Geofísicos y Geodesta

Sobre la calibración de medidores de impacto

En este trabajo los autores proponen una metodología para el tratamiento de la información obtenida a partir de los medidores de impacto, con el fin de dar pautas para la evaluación físico-estadística de la experiencia de lucha antigranizo encarada en la provincia de Mendoza por la Comisión Nacional de investigaciones Espaciales (C.N.I.E.). Se abordan los aspectos teóricos y prácticos de la calibración de los medidores de impacto. Además, se discuten los problemas emergentes de la curva de calibración que relacionan los diámetros reales con los medidos. Mediante experiencias basadas en la caída de esferas de acero, se obtuvo una función lineal entre el tamaño real y el diámetro medido mediante el ajuste por mínimos cuadrados. El diámetro real es mayor que el diámetro medido y se nota la imposibilidad de medir granizos con un diámetro menor de 0,5 cm. Se encontró que la distribución de frecuencias de los tamaños reales del granizo se ajusta mejor a la función gamma.In this paper the authors propose a methodology to treat the information which has been collected from the hailpads aimed to establish some points for the physical-statistical evaluation of the anti-hail experience which is being conducted in the province of Mendoza. Theoretical and empirical aspects related to the hailpads calibration are examined. Besides, the problems resulting from the use of the calibration curve which relates real and measured diameters are discussed. By means of experiences based on fallings of steel balls, it was obtained a linear function real and mesured diameters, by the minimwn square method. The real diameters is always longer than the mesured one, and untill now it is impossible to detect hail diameters less than 0,5 cm. It was found that frequency distribution of real sizes is almost well fitted by the gamma distribution.Asociación Argentina de Geofísicos y Geodesta

Preliminary data on the structure and potential of the Tocomar geothermal field (Puna plateau, Argentina).

AbstractThis study presents new stratigraphic, structural and hydrogeological data on the Tocomar geothermal volcanic area (Puna plateau, Central Andes, NW Argentina), together with preliminary geochemical and magnetotelluric data.The main geothermal reservoir is located within the fractured Pre-Palaeozoic–Ordovician units. The reservoir is recharged by meteoric waters. Geothermal fluids upwell where main regional structures intersect secondary structures associated with the development of the Tocomar basin. Preliminary data indicate a reservoir temperature of ∼ 200° C and a local geothermal gradient of ∼ 130° C/km associated with the Quaternary volcanic activity in the Tocomar area

The Promoter of Rv0560c Is Induced by Salicylate and Structurally-Related Compounds in Mycobacterium tuberculosis

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), is a major global health threat. During infection, bacteria are believed to encounter adverse conditions such as iron depletion. Mycobacteria synthesize iron-sequestering mycobactins, which are essential for survival in the host, via the intermediate salicylate. Salicylate is a ubiquitous compound which is known to induce a mild antibiotic resistance phenotype. In M. tuberculosis salicylate highly induces the expression of Rv0560c, a putative methyltransferase. We identified and characterized the promoter and regulatory elements of Rv0560c. PRv0560c activity was highly inducible by salicylate in a dose-dependent manner. The induction kinetics of PRv0560c were slow, taking several days to reach maximal activity, which was sustained over several weeks. Promoter activity could also be induced by compounds structurally related to salicylate, such as aspirin or para-aminosalicylic acid, but not by benzoate, indicating that induction is specific to a structural motif. The −10 and −35 promoter elements were identified and residues involved in regulation of promoter activity were identified in close proximity to an inverted repeat spanning the −35 promoter element. We conclude that Rv0560c expression is controlled by a yet unknown repressor via a highly-inducible promoter

Glucose-6-Phosphate Dehydrogenase Protects Escherichia coli from Tellurite-Mediated Oxidative Stress

The tellurium oxyanion tellurite induces oxidative stress in most microorganisms. In Escherichia coli, tellurite exposure results in high levels of oxidized proteins and membrane lipid peroxides, inactivation of oxidation-sensitive enzymes and reduced glutathione content. In this work, we show that tellurite-exposed E. coli exhibits transcriptional activation of the zwf gene, encoding glucose 6-phosphate dehydrogenase (G6PDH), which in turn results in augmented synthesis of reduced nicotinamide adenine dinucleotide phosphate (NADPH). Increased zwf transcription under tellurite stress results mainly from reactive oxygen species (ROS) generation and not from a depletion of cellular glutathione. In addition, the observed increase of G6PDH activity was paralleled by accumulation of glucose-6-phosphate (G6P), suggesting a metabolic flux shift toward the pentose phosphate shunt. Upon zwf overexpression, bacterial cells also show increased levels of antioxidant molecules (NADPH, GSH), better-protected oxidation-sensitive enzymes and decreased amounts of oxidized proteins and membrane lipids. These results suggest that by increasing NADPH content, G6PDH plays an important role in E. coli survival under tellurite stress