Person: Fernández Castillo, Jesús
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First Name
Jesús
Last Name
Fernández Castillo
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Química Física
Area
Química Física
Identifiers
20 results
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Item Structural and cathodoluminiscent properties of Zr0.95Ce0.05O2 nanopowders prepared by sol–gel and template methods(Journal of Luminescence, 2011) Fernández Castillo, Jesús; Isasi Marín, Josefa; Pérez Estébanez, Marta; Aldama, Iván; Arévalo, Pablo; Díaz-Guerra Viejo, CarlosNanopowders of Zr0.95Ce0.05O2 composition have been prepared by a standard Pechini-type sol–gel process and by means of a colloidal crystal template approach. In the latter method, inverse opal Zr0.95Ce0.05O2 powders were fabricated employing poly(methylmethacrylate) (PMMA) colloidal crystals as a template.The effects of the two different synthesis routes on the structure and microstructural characteristics of the prepared nanopowders were evaluated by X-ray diffraction and scanning electron microscopy. For both preparation routes, the X-ray diffraction analysis has shown that a tetragonal fluorite structure is formed with a crystallite size of 35–40 nm. The scanning electron microscopy measurements indicate that the powder obtained by the sol–gel Pechini-type process is comprised of nanoparticles that are arranged in agglomerates with shape and size relatively uniform whereas the inverse opal Zr0.95Ce0.05O2 nanopowders exhibit the formation of macropores with a mean size of 100 nm. The cathodoluminescence spectra of the prepared Zr0.95Ce0.05O2 nanomaterials have been measured in the 300–800 nm wavelength range. The powder prepared by sol–gel method yields a broad emission band centered at 482nm whereas the emission from the inverse opal preparation is considerably less intense.Item Structural, magnetic and luminescent characteristics of Pr3+-doped ZrO2 powders synthesized by a sol–gel method(Journal of Physics D: Applied physics, 2009) Isasi Marín, Josefa; Pérez Estébanez, Marta; Díaz-Guerra Viejo, Carlos; Fernández Castillo, Jesús; Correcher, Virgilio; Cuervo Rodríguez, María RocíoThe structural, magnetic and luminescence properties of praseodymium-doped zirconia powders of compositions Pr0.03Zr0.97O2 and Pr0.05Zr0.95O2 synthesized by a sol–gel process have been investigated. X-ray diffraction patterns indicate that these materials crystallize in a tetragonal fluorite-type structure. Scanning electron microscopy shows that the powders exhibit an agglomerated microcrystalline structure and the grain size may be in the order of 5–20μm. The study of the magnetic properties of these doped metal oxides indicates a Curie–Weiss behaviour in the temperature range (100–300)K that allow us to estimate an effective magnetic moment of 3.51μB, which indicates the presence of Pr3+ in the grown samples. Cathodoluminescence spectra recorded at temperatures between 85 and 295K show emission peaks that can be attributed to transitions between different states within the 4f2 configuration of Pr3+ ions incorporated in the zirconia crystal lattice. Thermoluminescence measured at temperatures ranging from 373 to 773K and at 550 nm wavelength show an intense and broad peak around 653K for the Pr-doped zirconia which is not observed in the undoped material.Item Structural and luminescence characterization of synthetic Cr-doped Ni3(PO4)2(Journal of Physics and Chemistry of solids, 2013) Correcher, Virgilio; Isasi Marín, Josefa; Cubero, Ágata; Pérez Estébanez, Marta; Aldama, Iván; Arévalo, Pablo; Fernández Castillo, Jesús; García Guinea, JavierNi3–xCr2x/3(PO4)2 (x¼0 and 0.02) microcrystalline powders were obtained as single phases via a modified sol–gel Pechini-type in situ polymerizable complex method. The samples were characterized using scanning electron microscopy, X-ray diffraction, cathodoluminescence (CL), and thermoluminescence (TL) techniques. We found that Cr3+ doping modified the average particle and distribution. The mean particle size was 0.441 μm for Ni3(PO4)2 and 0.267 μm for Ni2.98Cr0.013(PO4)2. The results also reveal that Cr3+ doping notably enhanced the CL and TL UV-blue emission.Item Preparation and characterization of Ce0.95Zr0.05O2 nanopowders obtained by solegel and template methods(Materials Chemistry and Physics, 2012) Isasi Marín, Josefa; Pérez Estébanez, Marta; Fernández Castillo, Jesús; Correcher, Virgilio; Aldama, Iván; Arévalo, Pablo; Carbajo, María CarmenCe0.95Zr0.05O2 nanopowders have been prepared by a standard Pechini-type solegel process and by using polymethyl methacrylate (PMMA) colloidal crystals as template. The effects of these different synthesis routes, on the structure and microstructural features of the nanopowders, were evaluated by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and specific surface area measurements. For both preparation routes, the XRD analysis has shown that a cubic fluorite structure is formed with a crystallite size of w45e50 nm. The SEM images indicate that the powder obtained by the solegel Pechini-type process, is constituted by aggregated nanoparticles with relatively uniform shape and size, whereas the powder synthesized as inverse opal exhibits the formation of macropores with a mean size of w130 nm. The specific surface areas of the powder samples obtained by the Pechini-type solegel and inverse opal methods are w56 m2 g 1 and w90 m2 g 1 respectively. Additionally, the thermoluminescence (TL) signal of the synthetized samples has been measured in order to examine its potential application in the field of dosimetry of ionizing radiations.Item A diet based on cured acorn-fed ham with oleic acid content promotes antiinflammatory gut microbiota and prevents ulcerative colitis in an animal model(Lipids in Health and Disease, 2020) Fernández Castillo, Jesús; García de la Fuente, V.; Fernández García, M. T.; Gómez Sánchez, J.; Isabel Redondo, Beatriz; Villar, C. J.; Lombó, F.; Springer NatureBackground: Diets based on meat products are not recommended in the case of ulcerative colitis (UC). The objective here is to test if some traditional cured meat products, as acorn-fed ham (high levels of oleic acid), may be useful for controlling inflammatory diseases as UC in animal models, which could represent a new dietary complementary intervention in the prevention of this inflammatory disease in humans. Methods: Two rat cohorts have been used: conventional vegetable rat feed and acorn-fed ham. UC was induced with DSS in drinking water ad libitum for 1 week. Short-chain fatty acids (SCFAs) and 16S rRNA metagenomics from bacterial populations were analyzed in cecum samples. Colon samples were analyzed for histological parameters. Results: Acorn-fed ham diet induced changes in gut microbiota composition, with pronounced enrichments in anti-inflammatory bacterial genera (Alistipes, Blautia, Dorea, Parabacteroides). The animals with this diet showed a strong reduction in most parameters associated to ulcerative colitis: disease activity index, macroscopic score of colitis, epitelium alteration in colon mucosa, inflammatory cell density in colon, myeloperoxidase titers in colon, proinflammatory cytokines (IL-17, IFN-γ). Also, acorn-fed ham diet animals showed increased total antioxidant activity an oleic acid levels in plasma, as well as higher short-chain fatty acid concentrations in cecum (isobutyric, isovaleric and valeric). Conclusions: In the acorn-fed ham cohort, as a result of the dietary intake of oleic acid and low intake of omega-6 fatty acids, a strong preventive effect against UC symptoms was observed. Keywords: Oleic acid, Acorn-fed ham, Gut microbiota, Ulcerative colitis, AntiiflammatoryItem A historical account of types of fuzzy sets and their relationships(IEEE Transactions on Fuzzy Systems, 2016) Bustince, H.; Barrenechea, Edurne; Fernández Castillo, Jesús; Pagola, M.; Xu, Z.; Bedregal, B.; Montero, Javier; Hagras, H.; Herrera, F.; De Baets, B.In this paper, we review the definition and basic properties of the different types of fuzzy sets that have appeared up to now in the literature. We also analyze the relationships between them and enumerate some of the applications in which they have been used.Item Geometric form of volcanoes with a limited based(XXI Congreso de Ecuaciones Diferenciales y Aplicaciones XI Congreso de Matematica Aplicada, 2009) Arjona, Alicia; Díaz Díaz, Jesús Ildefonso; Fernández Castillo, JesúsMany volcanic constructs have geometric different shapes depending on different phenomena as parasitic cones, erosion or coral growth. In Lacey, Ockendon and Turcotte [11] the authors proposed a nonlinear model proving that the shape of volcanoes is determined by the hydraulic resistance to the flow of magma, from a line source, through the porous edifice. This model was later extended in Angevine, Turcotte and Ockendon [2] to include the shape of aseismic, submarine ridges. In this communication we propose a modification of the above mentioned models in order to simulate the more realistic case of volcanoes with a limited base.Item Geodetic and Structural Research in La Palma, Canary Islands, Spain: 1992-2007 Results(Pure and Applied Geophysics, 2008) Prieto, J. F.; Gónzalez, P. J.; Seco, A.; Rodríguez Velasco, Gema; Tunini, L.; Perlock, P.A.; Arjona, Alicia; Aparicio, A.; Camacho, A. G.; Rundle, J.B.; Tiampo, K.F.; Pallero, J. L. G.; Pospiech, S.; Fernández Castillo, JesúsWe review the results of the geodetic and structural studies carried out on La Palma Island using geodetic and geophysical data during the period 1992-2007. InSAR and GPS observation techniques were applied to study the existence of deformation on the island and gravity observations were carried out for structural studies. Gravity data were inverted using a nonlinear three-dimensional gravity inversion approach to obtain the geometry of the anomalous bodies constructed in a random growth process with respect to an exponentially stratified background. The main structural feature is a large central body (under the Caldera de Taburiente) with high density, which was interpreted as the Pliocene-age uplifted seamount and a relatively dense intrusive plutonic complex/magma body. The Cumbre Vieja series is characterized by elongated minima distributed according to the rift structure. InSAR results show a clear subsidence located on the Teneguia volcano, where the last eruption took place in 1971. A thermal source is the most probable origin for this deformation. A GPS network composed of 26 stations covering the total island surface was set up. Vertical displacements determined comparing the GPS coordinates obtained in 2007 with coordinates determined in 1994 are consistent with the InSAR results obtained in the southern part of the island. This is not the case for the northern part. From the comparison of 2006 and 2007 coordinates it is clear that more time is needed to obtain significant displacements, but observed trends are also consistent with InSAR results. All the observed significant displacements are in stations located outside of the large high-density central body.Item Contrast of a fuzzy relation.(Information Sciences, 2010) Bustince, H.; Barrenechea, E.; Fernández Castillo, Jesús; Pagola, M.; Montero, Javier; Guerra, C.In this paper we address a key problem in many fields: how a structured data set can be analyzed in order to take into account the neighborhood of each individual datum. We propose representing the dataset as a fuzzy relation, associating a membership degree with each element of the relation. We then introduce the concept of interval-contrast, a means of aggregating information contained in the immediate neighborhood of each element of the fuzzy relation. The interval-contrast measures the range of membership degrees present in each neighborhood. We use interval-contrasts to define the necessary properties of a contrast measure, construct several different local contrast and total contrast measures that satisfy these properties, and compare our expressions to other definitions of contrast appearing in the literature. Our theoretical results can be applied to several different fields. In an Appendix A, we apply our contrast expressions to photographic images.Item Generation of Interval-Valued Fuzzy Negations from Trillas’ Theorem. The Case of Interval Type-2 Fuzzy Sets(Enric Trillas: A Passion for Fuzzy Sets. A Collection of Recent Works on Fuzzy Logic, 2015) Bustince, H.; Barrenechea, E.; Fernández Castillo, Jesús; Pagola, M.; Montero, Javier; Magdalena, Luis; Verdegay, José Luis; Esteva, FrancescIn this work we introduce a method for building interval-valued negations using the characterization theorem for strong negations which was proposed by Trillas in 1979. We also show that interval type-2 fuzzy sets are a three dimensional representation of interval-valued fuzzy sets and we analyze the problems to build complementation for such interval type-2 fuzzy sets. We finally propose a method to construct this complementation.