The influence of topography on vertical velocity of air in relation to severe storms near the Southern Andes Mountains

On the basis of 180 storms which took place between 2004 and 2011 over the province of Mendoza (Argentina) near to the Andes Range at southern mid-latitudes, we consider those registered in the northern and central crop areas (oases). The regions affected by these storms are currently protected by an operational hail mitigation project. Differences with previously reported storms detected in the southern oasis are highlighted. Mendoza is a semiarid region situated roughly between 32S and 37S at the east of the highest Andes top. It forms a natural laboratory where different sources of gravity waves, mainly mountain waves, occur. In this work, we analyze the effects of flow over topography generating mountain waves and favoring deep convection. The joint occurrence of storms with hail production and mountain waves is determined from mesoscale numerical simulations, radar and radiosounding data. In particular, two case studies that properly represent diverse structures observed in the region are considered in detail. A continuous wavelet transform is applied to each variable and profile to detect the main oscillation modes present. Simulated temperature profiles are validated and compared with radiosounding data. Each first radar echo, time and location are determined. The necessary energy to lift a parcel to its level of free convection is tested from the Convective Available Potential Energy and Convection Inhibition. This last parameter is compared against the mountain waves' vertical kinetic energy. The time evolution and vertical structure of vertical velocity and equivalent potential temperature suggest in both cases that the detected mountain wave amplitudes are able to provide the necessary energy to lift the air parcel and trigger convection. A simple conceptual scheme linking the dynamical factors taking place before and during storm development is proposed.Fil: de la Torre, Alejandro. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pessano, H.. Universidad Tecnologica Nacional. Facultad Regional San Rafael; ArgentinaFil: Hierro, Rodrigo Federico. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Santos, J. R.. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Llamedo Soria, Pablo Martin. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alexander, Pedro Manfredo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Protective effect of Melissa officinalis aqueous extract against Mn-induced oxidative stress in chronically exposed mice

AbstractManganese (Mn) is an essential element for biological systems; however occupational exposure to high levels of this metal may lead to neurodegenerative disorders, resembling Parkinson's disease (PD). While its mechanisms of neurotoxicity have yet to be fully understood, oxidative stress plays a critical role. Thus, the main goal of this study was to investigate the efficacy of aqueous extract of Melissa officinalis in attenuating Mn-induced brain oxidative stress in mice. Sixteen male mice were randomly divided into two groups and treated for 3 months: the first group consumed tap water (control group) and the second group was treated with Mn (50mg/kg/day for habituation during the first 15 days followed by 100mg/kg/day for additional 75 days) in the drinking water. After 3 months both groups were sub divided (n=4 per group) and treated for additional 3 months with Mn and/or M. officinalis in the drinking water. The first group (control) was treated with water and served as control; the second group (M. officinalis) was treated with M. officinalis (100mg/kg/day); the third group was treated with Mn (100mg/kg/day); the fourth group (Mn+M. officinalis) was treated with both Mn and M. officinalis (100mg/kg/day each). Mn-treated mice showed a significant increase in thiobarbituric acid reactive species (TBARS) levels (a marker of oxidative stress) in both the hippocampus and striatum. These changes were accompanied by a decrease in total thiol content in the hippocampus and a significant increase in antioxidant enzyme activity (superoxide dismutase and catalase) in the hippocampus, striatum, cortex and cerebellum. Co-treatment with M. officinalis aqueous extract in Mn-treated mice significantly inhibited the antioxidant enzyme activities and attenuated the oxidative damage (TBARS and decreased total thiol levels). These results establish that M. officinalis aqueous extract possesses potent antioxidative properties, validating its efficacy in attenuating Mn-induced oxidative stress in the mouse brain

Target antigen of monoclonal reagent S5.7: comparison with T3 antigen

S5.7 recognizes a 20 kD cell surface protein which is present on T lymphocytes. S5.7 binds to a nonglycosylated protein, which can be labeled by cell-surface radioiodination and by a hydrophobic reagent [125I]-iodo-5-naphthyl-1-azide (INA). As the T-lymphocyte-specific T3 complex was found to contain a nonglycosylated 20 kD species, and since this 20 kD T3 form can be labeled preferentially by INA, a comparison between T3 and S5.7 was made. Isoelectric focusing experiments showed, however, that the two proteins are different. Moreover, the S5.7 monoclonal antibody does not block CML, is not mitogenic, reacts with immature cells of several hemopoietic lineages, and differs in that respect from anti-T3 monoclonal antibodie

Alguna aplicaciones recientes de la técnica de radio ocultamiento satelital en el estudio de procesos atmósfericos

In the last years, the use of radio occultation (RO) technique to observe the terrestrial atmosphere and the climate takes advantage of the occultation of the Sun, the Moon, the stars and principally of artificial satellites of low height (LEO). In the latter case, crossed signs between LEO and GPS satellites are used. The application of RO's technology using transmitters of the GPS system in high orbits and recipients on board of low orbit satellites, has provided profiles of atmospheric refractivity very precise. The basic idea of a RO is to observe how waves emitted by a GPS are propagated in the atmosphere. The ray trajectory associated to a radio wave between a GPS and a LEO, while these are hiding themselves mutually due to the interposition of the Earth, is deviated due to refractivity gradients. The ray bending angle is obtained from a change in the phase (Doppler shift) of the signal received by the LEO. Assuming spherical symmetry, the deviation information may be inverted by an Abel transformation to obtain a vertical profile of the index of refraction. From atmospheric profiles of refractivity and an atmospheric model, several parameters are obtained: from temperature (T), pressure, geopotential height and water vapor to minor species as aerosols, cloud liquid water and ionospheric electron density. The enormous advantage offered by the coverage in the whole planet, above the continental and oceanic territories, the 1K T resolution, the long term stability and mainly the absence of any restriction imposed by climatic conditions, makes the GPS RO technique unique among different remote sensing atmospheric systems. Up to now, hundreds of thousands of soundings have been processed, from the first satellites to recent (SAC-C, CHAMP, GRACE, COSMIC, TerraSAR-X, MetOp). In the present work, examples of global and regional water vapor and atmospheric wave energy distributions will be shown. It will be put on special emphasis on the mountainous regions of the Andes Range at middle latitudes and the Antarctic Peninsula and case studies will be analyzed. This analysis will be complemented by WRF model simulations and with measured T profiles in the regions of interest. In particular it will be shown: i) the spatial distribution of stationary gravity waves, ii) their propagation in the lower and middle atmospheres, and iii) the possible relevance of mountain waves as a triggering mechanism of seep convection processes with hail production. Key words: satellite radio occultation, gravity waves.En los últimos años, el uso del principio de radio ocultamiento (RO) satelital para observar la atmósfera terrestre y el clima aprovecha los ocultamientos bajo el horizonte del sol, de la luna, de las estrellas y principalmente de satélites artificiales de baja altura (LEO). En este último caso, se utilizan señales cruzadas entre satélites LEO y satélites de gran altura GPS. La aplicación de la técnica de RO usando transmisores del sistema de GPS en órbitas altas y receptores a bordo de satélites de baja órbita, ha provisto perfiles de refractividad atmosférica muy precisos. La idea básica de un RO es observar como las ondas de radio emitidas por los GPS se propagan en la atmósfera. La trayectoria del rayo asociado a una onda de radio entre un LEO y un satélite GPS, mientras se están ocultando mutuamente por interponerse la Tierra entre ambos, atraviesa la atmósfera desviándose debido a gradientes de refractividad. El ángulo de desviación del rayo se obtiene a partir de un cambio en el retraso de la fase (corrimiento Doppler) de la señal GPS recibida por el LEO. Suponiendo simetría esférica, la información de la desviación puede ser invertida mediante una transformación de Abel, y así obtener un perfil vertical del índice de refracción. A partir de perfiles atmosféricos verticales de refractividad y de un modelo atmosférico, se obtienen diversos parámetros indirectamente: desde temperatura (T), presión, altura geopotencial y vapor de agua, hasta especies minoritarias como aerosoles, agua líquida de las nubes y densidad electrónica ionosférica. La enorme ventaja ofrecida por la cobertura en todo el planeta, tanto sobre los territorios continentales como oceánicos, la resolución en T menor que 1 K, la estabilidad a largo plazo y fundamentalmente la ausencia de cualquier limitación impuesta por posibles condiciones climáticas, hace a la técnica de RO GPS única dentro de los diferentes sistemas de sensado remoto de la atmósfera. Hasta la actualidad ha sido obtenida y procesada una base de datos con varios cientos de miles de sondeos de este tipo, recogidos por los primeros satélites LEO y posteriores (SAC-C, CHAMP, GRACE, COSMIC, TerraSAR-X, MetOp). En el presente trabajo, se mostrarán ejemplos de resultados, a escala global y regional de la distribución de vapor de agua y de energía asociada a ondas atmosféricas, mediante datos de RO GPS. Se pondrá especial énfasis sobre las regiones montañosas de la cordillera de los Andes a latitudes medias y de la península antártica, para lo cual se analizarán individualmente eventos de RO de interés, a partir de las excepcionales características observables de OIG en dicha región. Dicho análisis será complementado con simulaciones numéricas con el modelo de mesoescala WRF, versión 3.2. y con perfiles de T de RO disponibles en las regiones de interés. En particular, se mostrará: la distribución espacial de ondas internas de gravedad (OIG) estacionarias, n su propagación en las atmósferas baja y media y la posible importancia relativa de las ondas de montaña como mecanismo de detonación de procesos de convección profunda con generación de granizo. Palabras clave: radio ocultamiento satelital, ondas de gravedad

Orographic effects related to deep convection events over the Andes region

In this work, we analyze a set of 39 storms which took place between 2006 and 2011 over the South of Mendoza, Argentina. This is a semiarid region situated at mid-latitudes (roughly between 32S and 36S) at the east of the highest Andes tops which constitutes a natural laboratory where diverse sources of gravity waves usually take place. We consider a cultivated subregion near San Rafael district, where every summer a systematic generation of deep convection events is registered. We propose that the lift mechanism required to raise a parcel to its level of free convection is partially supplied by mountain waves (MWs). From Weather Research and Forecasting (WRF) mesoscale model simulations and radar network data, we calculate the evolution of convective available potential energy and convective inhibition indices during the development of each storm. Global Final Analysis is used to construct initial and boundary conditions. Convective inhibition indices are compared with the vertical kinetic energy capable of being supplied by the MWs, in order to provide a rough estimation of this possible triggering mechanism. Vertical velocity is chosen as an appropriate dynamical variable to evidence the presence of MWs in the vicinity of each detected first radar echo. After establishing a criterion based on a previous work to represent MWs, the 39 storms are split into two subsets: with and without the presence of MWs. 12 cases with considerable MWs amplitude are retained and considered. Radar data differences between the two samples are analyzed and the simulated MWs are characterized.Fil: Hierro, Rodrigo Federico. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería; ArgentinaFil: Pessano, H.. Universidad Tecnologica Nacional. Facultad Regional San Rafael; ArgentinaFil: Llamedo Soria, Pablo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería; ArgentinaFil: de la Torre, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería; ArgentinaFil: Alexander, Pedro Manfredo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: Odiard, A.. Dirección de Agricultura y Contingencias Climáticas; Argentin