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Hernandez-Martinez A.R.,University of the Basque Country | Bucio E.,Institute Ciencias Nucleares
Journal of Radioanalytical and Nuclear Chemistry | Year: 2010

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.


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 | Year: 2014

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.


Ballen-Daza D.A.,Industrial University of Santander | Gonzalez G.A.,Industrial University of Santander | Gutierrez-Pineres A.C.,Institute Ciencias Nucleares
Astrophysics and Space Science Proceedings | Year: 2014

A new family of exact solutions of the Einstein-Maxwell equations is presented, which describes an infinitely axially symmetric thin disk surrounded by a spheroidal halo with magnetic field. The models are obtained from axisymmetric solutions of Einstein-Maxwell equations for conformastatic spacetimes in which the metric and the magnetic potential present a discontinuity in its normal first derivative through a thin disk. The energy-momentum tensor and the current density are found and expressed in terms of the magnetic potential and the metric function and the system satisfies all the energy conditions and the total mass it is finite. Finally, we consider a particular case of Kuzmin-Toomre disks, by showing the behavior of the four-vector current and energy density profile for the halo as well as for disk. © Springer International Publishing Switzerland 2014.


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 | Year: 2014

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.


Contreras-Garcia A.,Institute Ciencias Nucleares | Contreras-Garcia A.,University of Santiago de Compostela | Bucio E.,Institute Ciencias Nucleares | Concheiro A.,University of Santiago de Compostela | Alvarez-Lorenzo C.,University of Santiago de Compostela
Journal of Bioactive and Compatible Polymers | Year: 2011

To improve the hemocompatibility and elution of antimicrobial agents for medical devices, N,N′-dimethylacrylamide (DMAAm) and N-isopropylacrylamide (NIPAAm) were sequentially grafted onto polypropylene (PP) films. Various (PP-g-DMAAm)-g-NIPAAm grafts were prepared using different time periods of irradiation while keeping the radiation dose constant. The hydrogel layer that formed on the surface of the PP was temperature-responsive (shifted from 32°C for NIPAAm to 37°C for the copolymer). The (PP-g-DMAAm)-g-NIPAAm films adsorbed serum albumin but not fibrinogen and had significantly lower hemolytic and thrombogenic activity. The DMAAm promoted the loading of norfloxacin (13.3 μg cm -2) when the hydrogel layer was swollen; as the NIPAAm shrank, a sustained delivery (∼6 h) occurred at body temperature. These functionalized PP films have potential as hemo- and cyto-compatible materials for medical devices and drug delivery products. © 2011 The Author(s).


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 | Year: 2010

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.


Contreras-Garcia A.,Institute Ciencias Nucleares | Contreras-Garcia A.,University of Santiago de Compostela | Bucio E.,Institute Ciencias Nucleares | Concheiro A.,University of Santiago de Compostela | Alvarez-Lorenzo C.,University of Santiago de Compostela
Reactive and Functional Polymers | Year: 2010

Polypropylene (PP) films grafted with N-isopropylacrylamide (NIPAAm) and N-(3-aminopropyl) methacrylamide hydrochloride (APMA) were tested as components of medical devices able to load and to sustain the release of the antimicrobial agent nalidixic acid. A pre-irradiation method was applied for grafting PP films with two NIPAAm:APMA weight ratios and to various extents. The grafting composition was analyzed recording FTIR-ATR spectra. PP-g-(1NIPAAm-r-0.5APMA) exhibited the temperature-responsiveness of PNIPAAm, while the grafting with a greater content in APMA led to that PP-g-(1NIPAAm-r-1APMA) remained highly swollen at 37 °C. The greater the content in APMA on the PP surface, the higher the amount of nalidixic acid loaded (up to 0.036 mg/cm2) and the slower the release rate in phosphate buffer pH 7.4. Coating with carboxymethyl-dextran (CM-dextran) of some drug-loaded films led to minor drug unloading while remarkably high amounts of dextran were deposited (up to 0.50 mg/cm2). This coating did not significantly modify the drug release rate neither the hemocompatibility of the PP-g-(NIPAAm-r-APMA) films, which was per se very good. Drug-loaded films remarkably inhibited the growth of Escherichia coli in in vitro microbiological tests. © 2010 Elsevier Ltd. All rights reserved.


Aguilar-Arevalo A.A.,Institute Ciencias Nucleares
AIP Conference Proceedings | Year: 2013

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.


Contreras-Garcia A.,Institute Ciencias Nucleares | Contreras-Garcia A.,University of Santiago de Compostela | Alvarez-Lorenzo C.,University of Santiago de Compostela | Taboada C.,University of Santiago de Compostela | And 2 more authors.
Acta Biomaterialia | Year: 2011

Co-polymers of N-isopropyl acrylamide (NIPAAm) and N-(3-aminopropyl) methacrylamide hydrochloride (APMA) were grafted on polypropylene (PP) films by means of a γ-ray pre-irradiation method, with the aim of developing medical devices able to load non-steroidal anti-inflammatory drugs (NSAIDs) and to control their release under physiological conditions. The NIPAAm/APMA molar ratios in the grafts, estimated by Fourier transform infrared attenuated total reflection spectroscopy and X-ray photoelectron spectroscopy analysis, were 4.76 and 1.23 for PP-g-(1 M NIPAAm-r-0.5 M APMA) and PP-g-(1 M NIPAAm-r-1 M APMA), respectively. By varying the reaction time, different degrees of grafting were achieved, while the monomer ratio was kept constant. PP-g-(NIPAAm-r-APMA) films showed temperature-responsive swelling, smaller friction coefficients, hemolysis and thrombogenicity and higher cell compatibility, did not elicit secretion of cytokines, and took up remarkable amounts of diclofenac and ibuprofen and sustained delivery for several hours in phosphate buffer, pH 7.4. Coating with carboxymethyl dextran of diclofenac-loaded PP-g-(NIPAAm-r-APMA) films caused a minor discharge of the drug but did not alter the drug release rate. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


Vazquez-Gonzalez B.,Institute Ciencias Nucleares | Melendez-Ortiz H.I.,Institute Ciencias Nucleares | Diaz-Gomez L.,University of Santiago de Compostela | Alvarez-Lorenzo C.,University of Santiago de Compostela | And 2 more authors.
Macromolecular Materials and Engineering | Year: 2014

Silicone rubber (SR) was γ-ray grafted with poly(methacrylic acid) (PMAA) to improve its ability to host antimicrobial drugs. Dependence of grafting yield on monomer concentration, pre-irradiation dose, temperature and reaction time was evaluated. Modified SR films were characterized by means of FT-IR, DSC, TGA, SEM, contact angle measurements, and swelling studies. SR-g-MAA showed pH sensitivity (critical pH ∼6) and good cytocompatibility. Soaking of SR-g-MAA in benzalkonium chloride and vancomycin aqueous solutions led to high loadings; up to 5.8 and 15.2 mg cm-2, respectively. SR-g-MAA released 100% vancomycin after 24 h in buffer pH 7.4 at 37 8C, but only 20% benzalkonium chloride due to strong ionic interactions. Drug-loaded SR-g-MAA prevented in vitro growth of Staphylococcus aureus. Overall, grafting of PMAA may improve the performance of SR for biomedical applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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