oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 234 )

2018 ( 272 )

2017 ( 242 )

2016 ( 330 )

Custom range...

Search Results: 1 - 10 of 118335 matches for " Edwin O. Ortiz-Quiles "
All listed articles are free for downloading (OA Articles)
Page 1 /118335
Display every page Item
Enhanced Structural Integrity and Electrochemical Performance of AlPO4-Coated MoO2 Anode Material for Lithium-Ion Batteries
José I. López-Pérez,Edwin O. Ortiz-Quiles,Khaled Habiba,Mariel Jiménez-Rodríguez,Brad R. Weiner,Gerardo Morell
ISRN Electrochemistry , 2014, DOI: 10.1155/2014/359019
Abstract: AlPO4 nanoparticles were synthesized via chemical deposition method and used for the surface modification of MoO2 to improve its structural stability and electrochemical performance. Structure and surface morphology of pristine and AlPO4-coated MoO2 anode material were characterized by electron microscopy imaging (SEM and TEM) and X-ray diffraction (XRD). AlPO4 nanoparticles were observed, covering the surface of MoO2. Surface analyses show that the synthesized AlPO4 is amorphous, and the surface modification with AlPO4 does not result in a distortion of the lattice structure of MoO2. The electrochemical properties of pristine and AlPO4-coated MoO2 were characterized in the voltage range of 0.01–2.5?V versus Li/Li+. Cyclic voltammetry studies indicate that the improvement in electrochemical performance of the AlPO4-coated anode material was attributed to the stabilization of the lattice structure during lithiation. Galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) studies reveal that the AlPO4 nanoparticle coating improves the rate capability and cycle stability and contributes toward decreasing surface layer and charge-transfer resistances. These results suggest that surface modification with AlPO4 nanoparticles suppresses the elimination of oxygen vacancies in the lattice structure during cycling, leading to a better rate performance and cycle life. 1. Introduction Lithium ion batteries are extensively used in a variety of portable electronic devices due to their high power density and long cycle life [1]. As reported, they are critically important for electric/hybrid vehicles as the power storage of the future [2]. Therefore, lithium ion batteries have attracted much interest in the field of fundamental study and applied research. Most commercialized lithium ion batteries use graphite as an anode material due to its accessibility and low cost; but its theoretical capacity is only 372?mAh g?1 calculated by forming the compound of LiC6 and cannot meet the ever-increasing demands for high capacity lithium ion technology [3]. By replacing graphite with transition metal oxides as anode materials, the capacity is enhanced. This is due to their close packed oxygen array, providing a framework structure and specific site for topotactic insertion and removal of lithium ions during charge/discharge process. A number of transition metal oxides have been studied and reported so far, including Mn3O4, Co3O4, MnO, TiO2, NiO, MoO2, and SnO2, because of their possibility of various oxidation states and the search of new materials for
Electrochemical Capacitance DNA Sensing at Hairpin-Modified Au Electrodes
Joel Rivera-Gandía,Maria del Mar Maldonado,Yarimar De La Torre-Meléndez,Edwin O. Ortiz-Quiles,Nella M. Vargas-Barbosa,Carlos R. Cabrera
Journal of Sensors , 2011, DOI: 10.1155/2011/735279
Abstract: An interfacial capacitance measurement electrochemical technique has been used for the sensing of self-assembled DNA hairpin probes (M. tuberculosis and B. anthracis) attached to Au electrodes. The double-layer capacitance ( ) was determined with electrochemical perturbations from 0.2?V to 0.5?V versus Ag/AgCl at a Au/M. tuberculosis DNA hairpin probe at surface coverage Au electrodes. The capacitance study was done at pH 7, which was necessary to maintain the M. tuberculosis and B. anthracis DNA probes closed during the electrochemical perturbation. Detailed experimental analysis carried out by repetitively switching the electrochemical potential between 0.2 and 0.5?V (versus Ag/AgCl) strongly supports the use of capacitance measurements as a tool to detect the hybridization of DNA targets. A large change in the capacitance deference between 0.2 and 0.5?V was observed in the DNA hybridization process. Therefore, no fluorophores or secondary transducers were necessary to sense a DNA target for both DNA hairpins. 1. Introduction The behavior of DNA attached onto metallic and nonmetallic surfaces via self-assembly with various chemistries (e.g., Au-S) may have applications in biomedical devices. For example, single-stranded DNA (ssDNA) self-assembled on a metallic interface such as gold [1, 2] or on nonmetals such as carbon nanotubes [3] and diamond [4–6] has potential use in DNA microarrays [7]. In addition, detection of DNA hybridization has been possible with techniques using different types of reporting, including fluorescence [8–11], chronocoulometry [12–14], surface plasmon resonance (SPR) [15, 16], colloidal labeling [17–19], and polarization modulation infrared reflection absorption spectroscopy [20]. Electroactive molecules can also be used to monitor the electron transfer mechanism during the hybridization process [21]. Here, we present a nonfaradaic electrochemical method based on capacitive measurement to sense DNA hairpin modification and hybridization. A nucleic acid probe has been developed to recognize specific DNA targets in solution [22]. These probes, called molecular beacons, are DNA hairpins with a fluorophore-quencher pair, which is completely unable to fluoresce when the two components are in close proximity (i.e., closed molecular beacon). When the molecular beacon spontaneously changes its conformation (like during hybridization), the fluorophore attached to one end of the molecule is no longer quenched as the quencher moves away. The capacity of this DNA hairpin has shown to discriminate between alleles with high specificity when
Arquitectura Contestataria y la Construcción de Utopías
Edwin Quiles
Revista Umbral , 2010,
Abstract: Si bien es cierto que las condiciones de desigualdad llevan a una pérdida de autonomía y de capacidad para decidir sobre sus vidas, no es menos cierto que cuando las condiciones de dificultad extrema amenazan la subsistencia, los seres humanos utilizamos nuestros recursos con más creatividad. Lejos de sumirse en la desesperanza y la aceptación de las condiciones desfavorables que les han sido impuestas, la humanidad en todos los rincones del planeta se encuentra en lucha franca para reinventar este mundo. La sociedad civil, como se ha venido a llamar esta muchedumbre llena de esperanza, está creando alternativas de gobierno y de gestión, de comunidad, programas de salud, economía, transportación, manejo del ambiente, producción agro-ecológica, alimentación, alojamiento, desarrollo social y maneras de hacer cultura. Pretende construir un mundo más equitativo donde vivir, a partir de conceptos de solidaridad e inclusión, utilizando las tecnologías de formas más humanas. No puedo dejar de consignar aquí la gran influencia de las culturas indígenas ancestrales que, basadas en el respeto hacia los seres vivientes, han ayudado a ver y reencontrar otras maneras posibles de convivencia con la madre tierra, la pacha mama, y todas las manifestaciones de la vida. A nivel internacional, reconociendo que la desigualdad tiene una base económica, el llamado movimiento altermundista trabaja por una nueva regulación democrática del sistema financiero y comercial internacional y el perdón de la deuda externa de los países del Sur. Todo lo anterior viene acompa ado, no puede ser de otra manera, de nuevos espacios y nuevos usos para viejos espacios. Con y sin nosotros la gente está reinventando la Ciudad, creando lugares, construyendo sus propias estructuras desde donde incidir en las estructuras del poder. Cómo podemos los arquitectos colaborar en esos procesos y ser parte de esos nuevos proyectos donde se está construyendo ese “otro mundo posible”? Estoy convencido de que en este momento de cambio los arquitectos y dise adores ambientales tenemos la capacidad, y por eso mismo la responsabilidad, de dar forma a estas nuevas construcciones sociales, de representarlas adecuadamente. Esto, como acompa antes solidarios y como líderes. Para ello necesitamos un cambio de mirada, o como sugiere el urbanista en la novela Texaco del martiniquense Patrick Chamoiseau (Editorial Anagrama), un aprender de nuevo a leer para reinventar la ciudad, (Pp.277). Esto requiere unir fuerzas con otros profesionales como los científicos sociales, economistas, ambientalistas, entre otros y por su
ADQPCI: Placa de Adquisición de Datos con Fines Docentes
Quiles,Francisco J; Ortiz,Manuel A; Moreno,Carlos D; Brox,María;
Formación universitaria , 2009, DOI: 10.4067/S0718-50062009000300005
Abstract: in this work a data acquisition board developed for educational use in subjects related to real-time systems and industrial computing, is presented. the main advantages and disadvantages of using these boards versus the use of commercial boards are discussed. the hardware design described along this work emphasizes the facility of programming the board, which is one of the main advantages versus the commercial boards. in these practices it is essential that student comprehend the importance of the hardware-software interface in order to obtain a reliable system which exploits in a maximum way the characteristics of the hardware. the development of a data acquisition board allows to obtain a system that the students can use in several course during his university career which are related to the development and programming of embedded systems.
CAN2PCI: Placa con Interfaz al Bus CAN y PCI con Finalidad Docente
Ortiz,Manuel A; Quiles,Francisco J; Moreno,Carlos D; Brox,María;
Formación universitaria , 2009, DOI: 10.4067/S0718-50062009000300006
Abstract: in this work the development of a board with interface to the can and pci bus for its use in lab courses related to control networks, is presented. this board has high benefits and advantages and has been implemented for educational purposes due to its programming facility. the board has two independent can channels and it allows direct access to the registers of the can controller. the objective of the lab experiments is to study the control networks in the physical and link levels and to develop a middleware that performs the interface between these layers and the user application. the experiments done in one of the courses, which includes control networks, are briefly described. in these practical labs it is very important the use of a known hardware that allows programming the basic functions which directly operate with the can bus controller.
Protected cerrado fragments grow up and lose even metapopulational birds in central S?o Paulo, Brazil
Willis, Edwin O.;
Brazilian Journal of Biology , 2006, DOI: 10.1590/S1519-69842006000500008
Abstract: moderately dense woodland (cerrad?o) grew in two isolated patches of bushy savanna (cerrado) in central s?o paulo over 23 years of bird censuses. various uncommon birds were lost and some forest species were permanently gained. fall and winter fruits attract long and short-distance migrants. woodpeckers and some birds that nest in their holes seem to disappear during tree growth. some birds in weedy areas nearby disappeared when the pastures replaced these areas, however sugar cane reduced the numbers of birds even more up to the point when some areas became pastures once more. even travel-prone species disappear with vegetation growth in cerrado protected fragments, and therefore "metapopulations" may not survive over time, only in space.
Myrmeciza and related antbirds (Aves, Formicariidae) as army ant followers
Willis, Edwin O.;
Revista Brasileira de Zoologia , 1984, DOI: 10.1590/S0101-81751984000300005
Abstract: antbirds of the genera myrmeciza (including sipia and myrmoborus), gymnocichla, and sclateria hop near or on the ground in fairly dense vegetation, "pounding" their tails downward. where dense understory vegetation is widespread and ants move in it for long distances, certain of these antbirds become regular ant followers: m. immaculata and m. fortis in cluttered moist foothill forest from costa rica to upper amazonia; gymnocichla nudiceps in moist cluttered second growth of central america to colombia. where the forest understory is more open, myrmeciza species follow ants mainly in cluttered patches: m. exsul in lowland forest west of the andes, m. myotherina east of the andes. myrmeciza or relatives that specialize on water-edge or very dense zones rarely follow ants.
Cercomacra and related antbirds (Aves, Formicariidae) as army ant followers
Willis, Edwin O.;
Revista Brasileira de Zoologia , 1984, DOI: 10.1590/S0101-81751984000300005
Abstract: cercomacra and schistocichla antbirds (formicariidae) favor dense foliage and seldom follow army ants for flushed prey, since the ants move through open forest understory as well as through dense zones. two other lineages, the drymophila-hypocnemis lineage (of dense woodland understory) and the formicivora lineage (of dense bushes in dry or semiopen zones), also cannot follow ants regularly through open forest understory.
Antthrushes, antpittas, and gnateaters (Aves, Formicariidae) as army ant followers
Willis, Edwin O.;
Revista Brasileira de Zoologia , 1984, DOI: 10.1590/S0101-81751984000300005
Abstract: antthrushes (formicarius, chamaeza) sometimes walk around swarms of army ants and capture ground prey, but do not follow ants regularly. among antpittas, only fast-leaping pittasoma michleri and p. rufopileatum regularly follow ants. gnateaters (conopophaga) follow ants little. all these ground-foraging genera are poorly adapted for rapid flying, and failure to follow ants is perhaps due to inability to evade predators or out fly competitors near groups of birds attracted by ants.
Hypophylax, Hypocnemoides and Myrmoderus (Aves, Formicariidae) as army ant followers
Willis, Edwin O.;
Revista Brasileira de Zoologia , 1983, DOI: 10.1590/S0101-81751983000300007
Abstract: hylophylax naevia of moderately dense forest undergrowth and h. punctulata of open swamp undergrowth tend to sally for arthropods in low foliage rather than sally to the ground among large ant-following antbirds. they and related hypocnemoides melanopogon of swamp understory edges are also limited by their microhabitat niches in following ants. myrmoderus ferrugineus and m. loricatus, ground-walking small antbirds seemingly derived from hylophylax, follow ants infrequently, probably because ants, large ant-following birds, and predators would attack them if they did so.
Page 1 /118335
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.