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Hernandez-Martinez A.R.,University of the Basque Country | Bucio E.,Institute Ciencias Nucleares
Journal of Radioanalytical and Nuclear Chemistry

Both poly[2-(dimethylamino) ethyl methacrylate] (PDMAEMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) were radiation grafted onto polypropylene films (PP) using gamma radiation from a 60Co source. PP was pre-irradiated by gamma ray for modification following by grafted PDMAEMA and PEGMEMA by a one step method. Grafting was studied as a function of the pre-irradiation dose between 20 and 180 kGy, dose rate of 10.4 kGy/h, and monomer concentration 50% of PDMAEMA/PEGMEMA (1/1) in different solvents (toluene, acetone, and methanol). FTIR-ATR, TGA, and DSC were carried out in the characterization of the graft copolymer obtained. Stimuli-responsive behavior and critical pH point were studied by swelling in water. pH and thermo-responsive films of PE-g-(DMAEMA/PEGMEMA) presented a lower critical solution temperature (LCST) of 50 °C and critical pH point around 8.7. © 2009 Akadémiai Kiadó, Budapest, Hungary. Source

Archer Jr. P.D.,NASA | Franz H.B.,NASA | Sutter B.,NASA | Arevalo Jr. R.D.,NASA | And 17 more authors.
Journal of Geophysical Research E: Planets

The Sample Analysis at Mars (SAM) instrument on the Mars Science Laboratory (MSL) rover Curiosity detected evolved gases during thermal analysis of soil samples from the Rocknest aeolian deposit in Gale Crater. Major species detected (in order of decreasing molar abundance) were H2O, SO2, CO2, and O2, all at the μmol level, with HCl, H 2S, NH3, NO, and HCN present at the tens to hundreds of nmol level. We compute weight % numbers for the major gases evolved by assuming a likely source and calculate abundances between 0.5 and 3 wt.%. The evolution of these gases implies the presence of both oxidized (perchlorates) and reduced (sulfides or H-bearing) species as well as minerals formed under alkaline (carbonates) and possibly acidic (sulfates) conditions. Possible source phases in the Rocknest material are hydrated amorphous material, minor clay minerals, and hydrated perchlorate salts (all potential H2O sources), carbonates (CO2), perchlorates (O2 and HCl), and potential N-bearing materials (e.g., Martian nitrates, terrestrial or Martian nitrogenated organics, ammonium salts) that evolve NH3, NO, and/or HCN. We conclude that Rocknest materials are a physical mixture in chemical disequilibrium, consistent with aeolian mixing, and that although weathering is not extensive, it may be ongoing even under current Martian surface conditions. Key Points Major volatiles detected by SAM were H2O, SO2, CO2, and O2 Minor volatiles include HCl, H2S, NH3, NO, and HCN Calculating abundances from counts per second is explained ©2013. American Geophysical Union. All Rights Reserved. Source

Aguilar-Arevalo A.A.,Institute Ciencias Nucleares
AIP Conference Proceedings

This report attempts to give a brief bibliographical sketch of the academic life of Juan Carlos D'Olivo, researcher and teacher at the Instituto de Ciencias Nucleares of UNAM, devoted to advancing the fields of High Energy Physics and Astroparticle Physics in Mexico and Latin America. © 2013 AIP Publishing LLC. Source

Munoz-Munoz F.,National Autonomous University of Mexico | Bucio E.,Institute Ciencias Nucleares | Magarinos B.,University of Santiago de Compostela | Concheiro A.,University of Santiago de Compostela | Alvarez-Lorenzo C.,University of Santiago de Compostela
Journal of Applied Polymer Science

Temperature- and pH-sensitive interpenetrating polymer networks (IPNs) and semi-interpenetrating polymer networks (s-IPNs) were γ-ray grafted onto polyurethane (Tecoflex®; TFX) to obtain vancomycin-eluting implantable medical devices with minimized risk of infections. N-isopropylacrylamide (NIPAAm) was grafted onto TFX catheters and films via a preirradiation oxidative method (method P) or via a direct method (method D). The PNIPAAm network facilitated acrylic acid (AAc) inclusion and subsequent polymerization/crosslinking, under specific reaction conditions. IPNs and s-IPNs systems were characterized regarding the amount of grafted polymers, surface properties (FTIR-ATR, ESEM, EDX), thermal behavior (DSC), and their temperature- and pH-responsiveness. Loading and release of vancomycin for preventing in vitro growth of Staphylococcus aureus were also evaluated. Antimicrobial activity tests and hemo- (hemolysis, protein adsorption, thrombogenicity) and cyto-compatibility (cell viability and production of cytokines and NO) assays indicated that the modification of TFX by γ-radiation may improve the performance of polyurethanes for biomedical applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39992. Copyright © 2014 Wiley Periodicals, Inc. Source

Navarro-Gonzalez R.,Institute Ciencias Nucleares | Vargas E.,Institute Ciencias Nucleares | De La Rosa J.,Institute Ciencias Nucleares | Raga A.C.,Institute Ciencias Nucleares | McKay C.P.,NASA
Journal of Geophysical Research E: Planets

The most comprehensive search for organics in the Martian soil was performed by the Viking Landers. Martian soil was subjected to a thermal volatilization process to vaporize and break organic molecules, and the resultant gases and volatiles were analyzed by gas chromatography-mass spectrometry. Only water at 0.1-1.0 wt% was detected, with traces of chloromethane at 15 ppb, at Viking landing site 1, and water at 0.05-1.0 wt% and carbon dioxide at 50-700 ppm, with traces of dichloromethane at 0.04-40 ppb, at Viking landing site 2. These chlorohydrocarbons were considered to be terrestrial contaminants, although they had not been detected at those levels in the blank runs. Recently, perchlorate was discovered in the Martian Arctic soil by the Phoenix Lander. Here we show that when Mars-like soils from the Atacama Desert containing 32 ± 6 ppm of organic carbon are mixed with 1 wt% magnesium perchlorate and heated, nearly all the organics present are decomposed to water and carbon dioxide, but a small amount is chlorinated, forming 1.6 ppm of chloromethane and 0.02 ppm of dichloromethane at 500C. A chemical kinetics model was developed to predict the degree of oxidation and chlorination of organics in the Viking oven. Reinterpretation of the Viking results therefore suggests ≤0.1% perchlorate and 1.5-6.5 ppm organic carbon at landing site 1 and ≤0.1% perchlorate and 0.7-2.6 ppm organic carbon at landing site 2. The detection of organics on Mars is important to assess locations for future experiments to detect life itself. Copyright 2010 by the American Geophysical Union. Source

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