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Vivas L.,Venezuelan Institute for Scientific Research | Delgado G.E.,University of Los Andes, Venezuela | Leret P.,CSIC - Institute of Ceramics and Glass | Fernandez J.F.,CSIC - Institute of Ceramics and Glass | And 2 more authors.
Journal of Alloys and Compounds | Year: 2017

Electron Paramagnetic Resonance (EPR) is used to study the transport properties in CaCu3Ti4O12 (CCTO) and its mixtures with TiO2. The temperature dependence of the peak to peak linewidth of the EPR spectra in the temperature range 430 ≤ T ≤ 660 K, is studied for the powders of CCTO, 5% CCTO + 95% TiO2 and 1% CCTO + 99% TiO2. All the samples show a behavior predicted by the Small Polaron Hopping model. This behavior is studied as a function of the TiO2 content, finding an activation energy that decreases with increasing TiO2 concentration. We found that two mechanisms govern the conductivity in these system one, intrinsic to the CCTO, via oxygen vacancies and the other one, which improve the conductivity, related to the polarizability of the Ti-ions at the surface of the grains and mediated by the oxygen vacancies at the surface of the CCTO. © 2016 Elsevier B.V.


Bodega G.,University of Alcalá | Suarez I.,University of Alcalá | Lopez-Fernandez L.A.,Hospital General Universitario Gregorio Maranon | Garcia M.I.,Hospital General Universitario Gregorio Maranon | And 8 more authors.
Neurochemistry International | Year: 2012

Aquaporin-4 (AQP4) is a water channel protein mainly located in the astroglial plasma membrane, the precise function of which in the brain edema that accompanies hepatic encephalopathy (HE) is unclear. Since ammonia is the main pathogenic agent in HE, its effect on AQP4 expression and distribution in confluent primary astroglial cultures was examined via their exposure to ammonium chloride (1, 3 and 5 mM) for 5 and 10 days. Ammonia induced the general inhibition of AQP4 mRNA synthesis except in the 1 mM/5 day treatment. However, the AQP4 protein content measured was dependent on the method of analysis; an apparent increase was recorded in treated cells in in-cell Western assays, while an apparent reduction was seen with the classic Western blot method, perhaps due to differences in AQP4 aggregation. Ammonia might therefore induce the formation of insoluble AQP4 aggregates in the astroglial plasma membrane. The finding of AQP4 in the pellet of classic Western blot samples, plus data obtained via confocal microscopy, atomic force microscopy (using immunolabeled cells with gold nanoparticles) and scanning electron microscopy, all corroborate this hypothesis. The effect of ammonia on AQP4 seems not to be due to any osmotic effect; identical osmotic stress induced by glutamine and salt had no significant effect on the AQP4 content. AQP4 functional analysis (subjecting astrocytes to a hypo-osmotic medium and using flow cytometry to measure cell size) demonstrated a smaller water influx in ammonia-treated astrocytes suggesting that AQP4 aggregates are representative of an inactive status; however, more confirmatory studies are required to fully understand the functional status of AQP4 aggregates. The present results suggest that ammonia affects AQP4 expression and distribution, and that astrocytes change their expression of AQP4 mRNA as well as the aggregation status of the ensuing protein depending on the ammonia concentration and duration of exposure. © 2012 Elsevier Ltd. All rights reserved.


Gonzalez-Arrabal R.,Technical University of Madrid | Redondo-Cubero A.,Autonomous University of Madrid | Redondo-Cubero A.,Technical University of Madrid | Gonzalez Y.,Institute Microelectronica Of Madrid Csic | And 2 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2011

The lattice order degree and the strain in as-grown, Mn-implanted and post-implanted annealed InAs thin films were investigated with depth resolution by means of Rutherford backscattering spectrometry in channeling conditions (RBS/C). Three main crystallographic axes were analyzed for both In and As sublattices. The behaviour of the induced defects was evaluated in two regions with different native defects: the interface and the surface. The results show that Mn implantation and post-implantation annealing are anisotropic processes, affecting in a different way the In and As sublattices. The mechanisms influencing the enhancement and deterioration of the crystal quality during the implantation are discussed in relation to the as-grown defects and the segregation of the elements. © 2011 Elsevier B.V. All rights reserved.


Lorenzoni M.,Institute Microelectronica Of Barcelona Imb Cnm | Evangelio L.,Institute Microelectronica Of Barcelona Imb Cnm | Nicolet C.,Arkema | Navarro C.,Arkema | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

The nanomechanical properties of solvent cast polymer thin films have been investigated using PeakForce™ quantitative nanomechanical mapping. The samples consisted in films of polystyrene and poly(methyl methacrylate) obtained after dewetting of toluene solution on a polymeric brush layer. As a second step, we have probed the mechanical properties of Poly(styrenen- methilmethacrylate) (PS-b-PMMA) block co-polymers (BCP) thin films randomly oriented. The measured films has a critical thickness below 50 nm and present features to be resolved of less than 42 nm. Measured surface elastic modulus obtained present a good agreement with previous literature and show how PeakForce technique could be crucial to BCP investigation predicting the mechanical stability of the different phases. © 2015 SPIE.


Lorenzoni M.,Institute Microelectronica Of Barcelona Imb Cnm | Evangelio L.,Institute Microelectronica Of Barcelona Imb Cnm | Nicolet C.,Arkema | Navarro C.,Arkema | And 3 more authors.
Journal of Micro/ Nanolithography, MEMS, and MOEMS | Year: 2015

The nanomechanical properties of solvent-cast polymer thin films have been investigated using PeakForce™ Quantitative Nanomechanical Mapping. The samples consisted of films of polystyrene (PS) and poly(methyl methacrylate) (PMMA) obtained after the dewetting of toluene solution on a polymeric brush layer. Additionally, we have probed the mechanical properties of poly(styrene-b-methyl methacrylate) block copolymers (BCP) as randomly oriented thin films. The probed films have a critical thickness <50 nm and present features to be resolved <42 nm. The Young's modulus values obtained through several nanoindentation experiments present a good agreement with previous literature, suggesting that the PeakForce™ technique could be crucial for BCP investigations, e.g., as a predictor of the mechanical stability of the different phases. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE).


Losilla N.S.,Institute Microelectronica Of Madrid Csic | Martinez J.,Institute Microelectronica Of Madrid Csic | Bystrenova E.,CNR Institute of Nanostructured Materials | Greco P.,CNR Institute of Nanostructured Materials | And 2 more authors.
Ultramicroscopy | Year: 2010

Sequential and parallel local oxidation nanolithographies have been applied to pattern pentacene samples by creating a variety of nanostructures. The sequential local oxidation process is performed with an atomic force microscope and requires the application of a sequence of voltage pulses of 36V for 1ms. The parallel local oxidation process is performed by using a conductive and patterned stamp. Then, a voltage pulse is applied between the stamp and the pentacene surface. Patterns formed by arrays of parallel lines covering 1mm2 regions and with a periodicity of less than 1γm have been generated in a few seconds. We also show that the patterns can be used as templates for the deposition of antibodies. © 2010 Elsevier B.V.


Parra-Borderias M.,CSIC - National Institute of Aerospace Technology | Fernandez-Martinez I.,Institute Microelectronica Of Madrid Csic | Fernandez-Martinez I.,Technical University of Madrid | Fabrega L.,CSIC - Institute of Materials Science | And 7 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2013

The first dark characterization of a thermometer fabricated with our Mo/Au bilayers to be used as a transition edge sensor is presented. High-quality, stress-free Mo layers, whose thickness is used to tune the critical temperature (TC) down to 100 mK, are deposited by sputtering at room temperature (RT) on Si3N4 bulk and membranes, and protected from degradation with a 15-nm sputtered Au layer. An extra layer of high-quality Au is deposited by ex situ e-beam to ensure low residual resistance. The thermometer is patterned on a membrane using standard photolithographic techniques and wet etching processes, and is contacted through Mo paths, displaying a sharp superconducting transition (α 600). Results show a good coupling between Mo and Au layers and excellent TC reproducibility, allowing to accurately correlate dMo and TC. Since d Au is bigger than \xiM for all analyzed samples, bilayer residual resistance can be modified without affecting TC. Finally, first current to voltage measurements at different temperatures are measured and analyzed, obtaining the corresponding characterization parameters © 2011 IEEE.


Rojo M.M.,Institute Microelectronica Of Madrid Csic | Calero O.C.,Institute Microelectronica Of Madrid Csic | Lopeandia A.F.,Autonomous University of Barcelona | Rodriguez-Viejo J.,Autonomous University of Barcelona | Martin-Gonzalez M.,Institute Microelectronica Of Madrid Csic
Nanoscale | Year: 2013

Physical properties at the nanoscale are novel and different from those in bulk materials. Over the last few decades, there has been an ever growing interest in the fabrication of nanowire structures for a wide variety of applications including energy generation purposes. Nevertheless, the study of their transport properties, such as thermal conductivity, electrical conductivity or Seebeck coefficient, remains an experimental challenge. For instance, in the particular case of nanostructured thermoelectrics, theoretical calculations have shown that nanowires offer a promising way of enhancing the hitherto low efficiency of these materials in the conversion of temperature differences into electricity. Therefore, within the thermoelectrical community there has been a great experimental effort in the measurement of these quantities in actual nanowires. The measurements of these properties at the nanoscale are also of interest in fields other than energy, such as electrical components for microchips, field effect transistors, sensors, and other low scale devices. For all these applications, knowing the transport properties is mandatory. This review deals with the latest techniques developed to perform the measurement of these transport properties in nanowires. A thorough overview of the most important and modern techniques used for the characterization of different kinds of nanowires will be shown. © 2013 The Royal Society of Chemistry.


PubMed | Institute Microelectronica Of Madrid Csic
Type: Evaluation Studies | Journal: Ultramicroscopy | Year: 2010

Sequential and parallel local oxidation nanolithographies have been applied to pattern pentacene samples by creating a variety of nanostructures. The sequential local oxidation process is performed with an atomic force microscope and requires the application of a sequence of voltage pulses of 36V for 1ms. The parallel local oxidation process is performed by using a conductive and patterned stamp. Then, a voltage pulse is applied between the stamp and the pentacene surface. Patterns formed by arrays of parallel lines covering 1mm(2) regions and with a periodicity of less than 1microm have been generated in a few seconds. We also show that the patterns can be used as templates for the deposition of antibodies.


PubMed | Institute Microelectronica Of Madrid Csic
Type: Journal Article | Journal: Nanoscale | Year: 2013

Physical properties at the nanoscale are novel and different from those in bulk materials. Over the last few decades, there has been an ever growing interest in the fabrication of nanowire structures for a wide variety of applications including energy generation purposes. Nevertheless, the study of their transport properties, such as thermal conductivity, electrical conductivity or Seebeck coefficient, remains an experimental challenge. For instance, in the particular case of nanostructured thermoelectrics, theoretical calculations have shown that nanowires offer a promising way of enhancing the hitherto low efficiency of these materials in the conversion of temperature differences into electricity. Therefore, within the thermoelectrical community there has been a great experimental effort in the measurement of these quantities in actual nanowires. The measurements of these properties at the nanoscale are also of interest in fields other than energy, such as electrical components for microchips, field effect transistors, sensors, and other low scale devices. For all these applications, knowing the transport properties is mandatory. This review deals with the latest techniques developed to perform the measurement of these transport properties in nanowires. A thorough overview of the most important and modern techniques used for the characterization of different kinds of nanowires will be shown.

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