Spanish National Research Council

About: Spanish National Research Council is a government organization based out in Madrid, Spain. It is known for research contribution in the topics: Population & Galaxy. The organization has 79563 authors who have published 220470 publications receiving 7698991 citations. The organization is also known as: CSIC & Consejo Superior de Investigaciones Científicas.

Evolution of the Solar Activity over Time and Effects on Planetary Atmospheres: I. High-energy Irradiances (1-1700 A)

Abstract: We report on the results of the Sun in Time multi-wavelength program (X-rays to the UV) of solar analogs with ages covering ~0.1-7 Gyr. The chief science goals are to study the solar magnetic dynamo and to determine the radiative and magnetic properties of the Sun during its evolution across the main sequence. The present paper focuses on the latter goal, which has the ultimate purpose of providing the spectral irradiance evolution of solar-type stars to be used in the study and modeling of planetary atmospheres. The results from the Sun in Time program suggest that the coronal X-ray-EUV emissions of the young main-sequence Sun were ~100-1000 times stronger than those of the present Sun. Similarly, the transition region and chromospheric FUV-UV emissions of the young Sun are expected to be 20-60 and 10-20 times stronger, respectively, than at present. When considering the integrated high-energy emission from 1 to 1200 A, the resulting relationship indicates that the solar high-energy flux was about 2.5 times the present value 2.5 Gyr ago and about 6 times the present value about 3.5 Gyr ago (when life supposedly arose on Earth). The strong radiation emissions inferred should have had major influences on the thermal structure, photochemistry, and photoionization of planetary atmospheres and also played an important role in the development of primitive life in the Solar System. Some examples of the application of the Sun in Time results on exoplanets and on early Solar System planets are discussed.

1,2,3-Triazole-[2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D- ribofuranosyl]-3'-spiro-5"-(4"-amino-1",2"-oxathiole 2",2"-dioxide) (TSAO) analogues: synthesis and anti-HIV-1 activity.

Abstract: Several 4- or 5-monosubsituted and 4,5-disubstituted 1,2,3-triazole analogues of the anti-HIV-1 lead compound [1-[2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D- ribofuranosyl]thymine]-3'-spiro-5"-(4"-amino-1",2"-oxathiole 2",2"-dioxide) (TSAO-T) have been prepared and evaluated as inhibitors of HIV-1-induced cytopathicity. These analogues have been prepared by 1,3-diplar cycloaddition of [2,5-bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]- 3-spiro-5'-(4'-amino- and 4'-(N-acetylamino)-1',2'-oxathiole 2',2'-dioxide) (TSAO) azides to various substituted acetylenes. Several 4- and 5-substituted 1,2,3-triazole-TSAO analogues proved superior to the unsubstituted derivative by 1-2 orders of magnitude. In particular the 5-substituted amido-, (methylamido)-, and (dimethylamido)-1,2,3-triazole derivatives of TSAO were endowed with potent anti-HIV-1 activity (50% effective concentration: 0.056-0.52 microM). They show a similar resistance spectrum as previously noted for TSAO-T and related derivatives.

Cadmium-induced subcellular accumulation of O2·− and H2O2 in pea leaves

Abstract: Cadmium is a toxic metal that produces disturbances in plant antioxidant defences giving rise to oxidative stress. The effect of this metal on H2O2 and O2·− production was studied in leaves from pea plants growth for 2 weeks with 50 µm Cd, by histochemistry with diaminobenzidine (DAB) and nitroblue tetrazolium (NBT), respectively. The subcellular localization of these reactive oxygen species (ROS) was studied by cytochemistry with CeCl3 and Mn/DAB staining for H2O2 and O2·−, respectively, followed by electron microscopy observation. In leaves from pea plants grown with 50 µm CdCl2 a rise of six times in the H2O2 content took place in comparison with control plants, and the accumulation of H2O2 was observed mainly in the plasma membrane of transfer, mesophyll and epidermal cells, as well as in the tonoplast of bundle sheath cells. In mesophyll cells a small accumulation of H2O2 was observed in mitochondria and peroxisomes. Experiments with inhibitors suggested that the main source of H2O2 could be a NADPH oxidase. The subcellular localization of O2·− production was demonstrated in the tonoplast of bundle sheath cells, and plasma membrane from mesophyll cells. The Cd-induced production of the ROS, H2O2 and O2·−, could be attributed to the phytotoxic effect of Cd, but lower levels of ROS could function as signal molecules in the induction of defence genes against Cd toxicity. Treatment of leaves from Cd-grown plants with different effectors and inhibitors showed that ROS production was regulated by different processes involving protein phosphatases, Ca2+ channels, and cGMP.

A γ-ray burst at a redshift of z ≈ 8.2

Abstract: Long-duration gamma-ray bursts (GRBs) are thought to result from the explosions of certain massive stars(1), and some are bright enough that they should be observable out to redshifts of z > 20 using current technology(2-4). Hitherto, the highest redshift measured for any object was z = 6.96, for a Lyman-alpha emitting galaxy(5). Here we report that GRB 090423 lies at a redshift of z approximate to 8.2, implying that massive stars were being produced and dying as GRBs similar to 630 Myr after the Big Bang. The burst also pinpoints the location of its host galaxy.

Determining Star Formation Rates for Infrared Galaxies

Abstract: We show that measures of star formation rates (SFRs) for infrared galaxies using either single-band 24 μm or extinction-corrected Paα luminosities are consistent in the total infrared luminosity = L(TIR) ~ 1010 L ☉ range. MIPS 24 μm photometry can yield SFRs accurately from this luminosity upward: SFR(M ☉ yr–1) = 7.8 × 10–10 L(24 μm, L ☉) from L(TIR) = 5× 109 L ☉ to 1011 L ☉ and SFR = 7.8 × 10–10 L(24 μm, L ☉)(7.76 × 10–11 L(24))0.048 for higher L(TIR). For galaxies with L(TIR) ≥ 1010 L ☉, these new expressions should provide SFRs to within 0.2 dex. For L(TIR) ≥ 1011 L ☉, we find that the SFR of infrared galaxies is significantly underestimated using extinction-corrected Paα (and presumably using any other optical or near-infrared recombination lines). As a part of this work, we constructed spectral energy distribution templates for eleven luminous and ultraluminous purely star forming infrared galaxies and over the spectral range 0.4 μm to 30 cm. We use these templates and the SINGS data to construct average templates from 5 μm to 30 cm for infrared galaxies with L(TIR) = 5× 109 to 1013 L ☉. All of these templates are made available online.