Examinando por Autor "Diaz, Susana Beatriz"

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Acceso Abierto
The September 2002 Antarctic vortex major warming as observed by visible spectroscopy and ozone soundings
(Taylor & Francis Ltd, 2005-08) Yela González, Margarita; Parrondo, María Concepción; Gil Moulet, Manuel; Rodríguez, S.; Araujo, J.; Ochoa, H.; Deferrari, Guillermo Alejandro; Diaz, Susana Beatriz
The record of O3 total column and NO2 obtained by visible spectroscopy at Ushuaia (55° S), Marambio (64° S) and Belgrano (78° S) and vertical ozone profiles from the latter station provide insight into the unprecedented major warming observed above Antarctica in the last week of September 2002. From 18 September to 25 September the temperature increased 54°C at the isentropic level of 700 K. The temperature anomaly was observed down to the level of 300 K in which a well-defined tropopause was established. From comparison of the ozone profiles before and during the event, it can be seen that a fast increase in O3 took place basically above 500 K, but the layer where the ozone hole occurs was barely affected. Low potential vorticity values above Belgrano occurred only at levels above 500 K, confirming that the vortex split was confined to heights above the layer of the Antarctic spring depletion. The signature of poleward-transported air is clearly visible from the NO2 column departure from the envelope of the previous years in all three stations. NO2 columns larger than typical for ozone hole conditions by 400% were observed at Belgrano. Diurnal variations provide evidence of non-denitrified extra-vortex air.
Acceso Abierto
Toxicity, Physiological, and Ultrastructural Effects of Arsenic and Cadmium on the Extremophilic Microalga Chlamydomonas acidophila
(Multidisciplinary Digital Publishing Institute (MDPI), 2020-03-03) Díaz, S.; De Francisco, P.; Olsson, S.; Aguilera, Á.; González Toril, Elena; Martín González, A.; Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Olsson, S. [https://orcid.org/0000-0002-1199-4499]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The cytotoxicity of cadmium (Cd), arsenate (As(V)), and arsenite (As(III)) on a strain of Chlamydomonas acidophila, isolated from the Rio Tinto, an acidic environment containing high metal(l)oid concentrations, was analyzed. We used a broad array of methods to produce complementary information: cell viability and reactive oxygen species (ROS) generation measures, ultrastructural observations, transmission electron microscopy energy dispersive x-ray microanalysis (TEM-XEDS), and gene expression. This acidophilic microorganism was affected differently by the tested metal/metalloid: It showed high resistance to arsenic while Cd was the most toxic heavy metal, showing an LC50 = 1.94 mu M. Arsenite was almost four-fold more toxic (LC50= 10.91 mM) than arsenate (LC50 = 41.63 mM). Assessment of ROS generation indicated that both arsenic oxidation states generate superoxide anions. Ultrastructural analysis of exposed cells revealed that stigma, chloroplast, nucleus, and mitochondria were the main toxicity targets. Intense vacuolization and accumulation of energy reserves (starch deposits and lipid droplets) were observed after treatments. Electron-dense intracellular nanoparticle-like formation appeared in two cellular locations: inside cytoplasmic vacuoles and entrapped into the capsule, around each cell. The chemical nature (Cd or As) of these intracellular deposits was confirmed by TEM-XEDS. Additionally, they also contained an unexpected high content in phosphorous, which might support an essential role of poly-phosphates in metal resistance.