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Digital.CSIC (162.855 recursos)

Repositorio institucional del Consejo Superior de Investigaciones Científicas. Digital.CSIC es un depósito de documentos digitales, cuyo objetivo es organizar, archivar, preservar y difundir en modo de acceso abierto la producción intelectual resultante de la actividad investigadora del CSIC.

(IQFR) Artículos post-print

Mostrando recursos 1 - 20 de 59

  1. Laser induced fluorescence and FT-Raman spectroscopy for characterizing patinas on stone substrates

    Oujja, M.; Vázquez Calvo, M. Carmen; Sanz, M.; Álvarez de Buergo, Mónica; Fort González, Rafael; Castillejo, Marta
    This article reports on a compositional investigation of stone patinas: thin colored layers applied for protective and/or aesthetic purposes on architectural or sculptural substrates of cultural heritage. The analysis and classification of patinas provide important information of historic and artistic interest, as their composition reflects local practices, the availabilities of different materials, and the development of technological knowledge during specific historical periods. Model patinas fabricated according to traditional procedures and applied onto limestone, and a historic patina sample from the main façade of the San Blas Monastery in Lerma (a village in the province of Burgos, Spain), were analyzed by...

  2. UV laser removal of varnish on tempera paints with nanosecond and femtosecond pulses

    Oujja, M.; García, Ana; Romero, Carolina; Vázquez de Aldana, Javier R.; Moreno, Pablo; Castillejo, Marta
    Two laser cleaning approaches based on ablation by ultraviolet laser pulses of femtosecond (fs) and nanosecond (ns) durations for the removal of shellac varnish from egg-yolk based tempera paints are investigated. Laser irradiation effects, induced on the varnish layer and on the underlying temperas by multiple pulses in the fs domain at 398 and 265 nm and single pulses in the ns domain at 213 nm, were examined following a spectroanalytical approach. By using optical microscopy, colorimetry and laser induced fluorescence it was found that irradiation of the varnished temperas with fs pulses changes the texture of the varnish surface...

  3. Laser cleaning of 19th century Congo rattan mats

    Carmona, N.; Oujja, M.; Roemich, H.; Castillejo, Marta
    There is a growing interest by art conservators for laser cleaning of organic materials, such as wooden artworks, paper and textiles, since traditional cleaning with solvents can be a source of further decay and mechanical cleaning may be too abrasive for sensitive fibers. In this work we present a successful laser cleaning approach for 19th century rattan mats from the Brooklyn Museum collection of African Art, now part of the study collection at the Conservation Center in New York. Tests were carried out using the fundamental (1064 nm) and second harmonic (532 nm) wavelength of a Q-switched Nd:YAG laser to...

  4. Assessing thermal interactions during laser cleaning by means of infrared thermal imaging

    Gómez-Heras, Miguel; Sanz, Mikel; Álvarez de Buergo, Mónica; Oujja, M.; Fort González, Rafael; Speranza, Mariela; Ríos, Asunción de los; Ascaso, Carmen; Pérez Ortega, Sergio; Castillejo, Marta
    Peer reviewed

  5. Characterization of laser-induced plasmas of nucleobases: Uracil and thymine

    Lopez-Quintas, Ignacio; Oujja, M.; Sanz, M.; Benitez-Cañete, A.; Hutchison, C.; de Nalda, R.; Martín Muñoz, Margarita; Ganeev, R.A.; Marangos, J.P.; Castillejo, Marta
    In this work, nanosecond laser ablation plasmas generated at 266 and 1064 nm of the two pyrimidine nucleobases uracil and thymine were characterized using time-of-flight mass spectrometry, optical emission spectroscopy and temporally resolved third harmonic generation of a probe laser. This multiple technique approach provides insight into the role played by the irradiation wavelength on the composition and dynamics of plasma species and on the differences between the laser plasmas of the two nucleobases.

  6. Micrometric rods grown by nanosecond pulsed laser deposition ofboron carbide

    Lopez-Quintas, Ignacio; Oujja, M.; Sanz, M.; Benitez-Cañete, A.; Chater, R.J.; Cañamares, María Vega; Marco, J.F.; Castillejo, Marta; Castillejo, Marta
    Micrometric size rods have been fabricated via pulsed laser deposition in vacuum from boron carbidetargets using nanosecond pulses of 1064 and 266 nm and room temperature Si (1 0 0) substrates. Mor-phological, structural and chemical characterization of the microrods was made by applying scanningelectron microscopy, focussed ion beam microscopy coupled to secondary ion mass spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy and micro-Raman spectroscopy. Ablation at 1064 nmfavours the formation of microrods with high aspect ratio, sharp edges and pyramidal tips, typically 10 mlong with a cross section of around 2 m × 2 m. Differently, at 266 nm the microrods...

  7. Synthesis and surface modification of uniform MFe2O4 (M = Fe, Mn, and Co) nanoparticles with tunable sizes and functionalities

    Cabrera-Lara, Lourdes I.; Somoza, Álvaro; Marco, J.F.; Serna Pereda, Carlos J.; Morales, M. P.
    Cubic monodisperse MFe 2O 4 ferrite nanoparticles (M = Fe, Co, and Mn) with tunable sizes between 7 and 20 nm and a narrow size distribution have been achieved in a one step synthesis by thermal decomposition of Fe(III), Co (II), and Mn(II) oleates. These nanoparticles have been functionalized with dimercaptosuccinic acid (DMSA), 11-mercaptoundecanoic acid (MUA), and bis(carboxymethyl)(2-maleimidylethyl)ammonium 4-toluenesulfonate (MATS) to grant them aqueous stability and the possibility for further functionalization with different biomolecules. Their structural, magnetic, and colloidal properties have also been studied to determine their chemical and physical properties and the degree of stability under physiological conditions that...

  8. Electrooxidation of 2,4,6-trichlorophenol on glassy carbon electrodes modified with composite Ni(oh)2-co(oh)2 films

    González, T.; Salazar, R.; Marco, J.F.; Gutiérrez de la Fe, Claudio; Soledadureta-Zañartu, M.
    Glassy carbon electrodes coated with a film of electrodeposited cobalt and nickel hydroxides were prepared in order to determine its activity to the 2,4,6-trichlorophenol (TCP) oxidation. The modified electrodes were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy and Scan Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS). The results indicate that both hydroxides are homogeneously distributed in the electrode surface. From the viewpoint of electrochemical oxidation of TCP, the presence of cobalt and nickel hydroxides on the electrode surface (i) promotes a more complete oxidation of TCP and (ii) decreases the fouling of the...

  9. Low temperature study of micrometric powder of melted Fe50Mn10Al40 alloy

    Zamora Alfonso, Ligia Edith; Pérez Alcázar, G. A.; Tabares, J. A.; Romero Fanego, Juan José; Martínez, A.; González Fernández, Jesús María; Palomares, F. Javier; Marco, J.F.
    Melted Fe 50Mn 10Al 40 alloy powder with particle size less than 40 μm was characterized at room temperature by XRD, SEM and XPS; and at low temperatures by Mössbauer spectrometry, ac susceptibility, and magnetization analysis. The results show that the sample is BCC ferromagnetic but with a big contribution of paramagnetic sites, and presents super-paramagnetic and re-entrant spin-glass phases with critical temperatures of 265 and 35 K, respectively. The presence of the different phases detected is due to the disordered character of the sample and the competitive magnetic interactions. The obtained values of the saturation magnetization and the coercive...

  10. Low temperature study of mechanically alloyed Fe67.5Ni32.5 Invar sample

    Valenzuela, J. L.; Valderruten, J.F.; Pérez Alcázar, G. A.; Colorado, H. D.; Romero Fanego, Juan José; González, J. M.; Greneche, J. M.; Marco, J.F.
    © 2015 Elsevier B.V. All rights reserved. The study at low temperatures of powder of the Invar alloy, Fe67.5Ni32.5, produced by mechanical alloying, shows that the sample presents two structural phases, the Fe-Ni BCC and the Fe-Ni FCC. The 57Fe Mössbauer spectra obtained in this sample at different temperatures were fitted considering two hyperfine magnetic field distributions. The first one having the larger mean field and only one peak (at ca. 35 T, varying with T), is associated with the BCC phase, and the second one, presenting several broad peaks (distributed between 10 and 35 T), is associated to the...

  11. Physicochemical modifications accompanying UV laser induced surface structures on poly(ethylene terephthalate) and their effect on adhesion of mesenchymal cells

    Rebollar, Esther; Pérez, Susana; Hernández, Margarita; Domingo, Concepción; Martín, Margarita; Ezquerra, Tiberio A.; García-Ruiz, Josefa P.; Castillejo, Marta
    This work reports on the formation of different types of structures on the surface of polymer films upon UV laser irradiation. Poly(ethylene terephthalate) was irradiated with nanosecond UV pulses at 193 and 266 nm. The polarization of the laser beam and the irradiation angle of incidence were varied, giving rise to laser induced surface structures with different shapes and periodicities. The irradiated surfaces were topographically characterized by atomic force microscopy and the chemical modifications induced by laser irradiation were inspected via micro-Raman and fluorescence spectroscopies. Contact angle measurements were performed with different liquids, and the results evaluated in terms of...

  12. Platinum Nanoparticles as Photoactive Substrates for Mass Spectrometry and Spectroscopy Sensors

    Cueto, Maite; Piedrahita, Mauricio; Caro Salazar, Carlos Alberto; Martínez-Haya, Bruno; Sanz, Mikel; Oujja, M.; Castillejo, Marta
    8 pags. ; 6 figs.

  13. Synthesis of 6-kestose using an efficient β-fructofuranosidase engineered by directed evolution

    Abreu, J. M. de; Álvaro-Benito, Miguel; Sanz-Aparicio, J.; Plou Gasca, Francisco José; Fernández Lobato, María; Alcalde Galeote, Miguel
    The β-fructofuranosidase (Ffase) from Schwanniomyces occidentalis (Ffase-Leu196 variant) was subjected to four cycles of directed evolution to enhance the transglycosylation activity for the synthesis of β-(2→6) linked fructooligosaccharides (FOS). With a 5.5-fold improvement in fructose transferase activity over the parental type and greater selectivity for the synthesis of 6-kestose (up to 73% of the total FOS), the mutants doubled FOS synthesis to 168 g L.-1 Whilst the F523V and H510P mutations were located at the C-terminus of the protein, mutations Q78L and I203L were associated with the acidic catalytic triad where they modified its interactions with the surrounding residues, in...

  14. On the origin of the eukaryotic chromosome: the role of noncanonical DNA structures in telomere evolution.

    Garavís, M.; González, Carlos; Villasante, Alfredo
    The transition of an ancestral circular genome to multiple linear chromosomes was crucial for eukaryogenesis because it allowed rapid adaptive evolution through aneuploidy. Here, we propose that the ends of nascent linear chromosomes should have had a dual function in chromosome end protection (capping) and chromosome segregation to give rise to the >proto-telomeres.> Later on, proper centromeres evolved at subtelomeric regions. We also propose that both noncanonical structures based on guanine-guanine interactions and the end-protection proteins recruited by the emergent telomeric heterochromatin have been required for telomere maintenance through evolution. We further suggest that the origin of Drosophila telomeres may...

  15. Stoichiometric magnetite grown by infrared nanosecond pulsed laser deposition

    Sanz, Mikel; Oujja, M.; Rebollar, Esther; Marco, J.F.; de la Figuera, Juan; Monti, Matteo; Bollero, A.; Camarero, Jesús Julio; Pedrosa, Francisco J.; García-Hernández, M.; Castillejo, Marta
    Pulsed laser deposition (PLD) is a versatile technique for the fabrication of nanostructures due to the possibilities it offers to control size and shape of nanostructured deposits by varying the laser parameters. Magnetite nanostructures are currently promising materials to be used in computing, electronic devices and spintronic applications. For all these uses the fabrication of uniform nanostructured pure magnetite thin films is highly advantageous. In PLD of magnetite, the laser irradiation wavelength and substrate temperature crucially affect the composition, crystallinity, surface structure and the magnetic properties of the grown samples. This work shows that the use of nanosecond IR laser...

  16. Room temperature in-plane 〈100〉 magnetic easy axis for Fe3O4/SrTiO3(001):Nb grown by infrared pulsed laser deposition

    Monti, Matteo; Sanz, Mikel; Oujja, M.; Rebollar, Esther; Castillejo, Marta; Bollero, A.; Camarero, Jesús Julio; Nemes, N. M.; Mompean, F. J.; García-Hernández, M.; McCarty, K. F.; Marco, J.F.; de la Figuera, Juan
    5 páginas, 3 figuras.-- et al.

  17. Order-disorder phase transition on the (100) surface of magnetite

    Bartelt, Norman C.; Bernal-Villamil, Iván; Gallego, Silvia; Vergara, L.; McCarty, K. F.; de la Figuera, Juan
    et al.

  18. Near UV multiphoton dissociation of organosilanes with picosecond and nanosecond laser pulses

    Nalda, R. de; Silva, Diego; Siegel, Jan; Solís Céspedes, Javier; Castillejo, Marta
    Multiphoton dissociation undergone by the organosilanes 2-chloroethenylsilane and phenylsilane upon irradiation with laser pulses of 20 ps and 4ns duration at 290 nm has been studied through detection of their spontaneous fluorescence. Atomic Si (4s 1S0 1) emissions are reported, together with the Swan bands of C2. Additionally, SiH2 formed in a two-photon process was observed by laser-induced fluorescence techniques in the photolysis of 2-chloroethenylsilane. The results show a strong selectivity when compared to those obtained previously for far UV irradiation around 200 nm and provide insight into the nature of the photodissociation mechanisms, where the SiH2 fragment plays a...

  19. Crystal structure of rat liver betaine homocysteine S-methyltransferase reveals new oligomerization features and conformational changes upon substrate binding

    González, Beatriz; Pajares, María A.; Martínez-Ripoll, Martín; Blundell, Tom L.; Sanz-Aparicio, J.
    Betaine homocysteine S-methyltransferase (BHMT) is one of the two enzymes known to methylate homocysteine to generate methionine in the liver. It presents a Zn2+ atom linked to three essential Cys residues. The crystal structure of rat liver BHMT has been solved at 2.5Å resolution, using crystals with P21 symmetry and 45% solvent content in the cell. The asymmetric unit contains the whole functional tetramer showing point symmetry 222. The overall fold of the subunit consists mostly of a (α/β) 8 barrel, as for human BHMT. From the end of the barrel, the polypeptide chain extends away and makes many interactions...

  20. Cu2+ binding triggers αBoPrP assembly into insoluble laminar polymers

    González-Iglesias, Reinerio; Elvira, Gema; Rodríguez-Navarro, José A.; Pajares, María A.; Gasset, M.
    Cu2+ binding is so far the best characterized property of the prion protein. This interaction has been mapped to the N-terminal domain of the prion protein where multiple His residues occur largely embedded within the repetitive PHGGGWGQ sequence known as octarepeats. When Cu2+ interaction is studied using a solution of full-length bovine prion protein containing six octarepeats at protein concentrations above 25 μM, a drastic increase in solution turbidity is observed due to the formation of insoluble cation-protein complexes that appear as bidimensional polymer meshes. These bidimensional meshes consist of a single layer of protein molecules crosslinked by Cu2+ cations....

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