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Search Results: 1 - 10 of 217749 matches for " E. Hernández-Rodríguez "
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Efecto de la temperatura de substrato en las propiedades estructurales, ópticas y ferroelóctricas de películas delgadas de BaTiO3 depositadas por RF sputtering
A. Márquez-Herrera,E. Hernández-Rodríguez,O. Calzadilla-Amaya,M. Meléndez-Lira
Revista mexicana de física , 2012,
Abstract: Se crecieron películas delgadas de Titanato de Bario (BaTiO3) sobre substratos de cuarzo y nicromel, utilizando un blanco de BaTiO3 mediante la técnica erosión catódica por radiofrecuencia. Variamos la temperatura de substrato con el fin de determinar su efecto sobre las propiedades estructurales, ópticas y ferroeléctricas de las muestras. Los resultados de la difracción de Rayos-X indicaron que las muestras tuvieron una estructura tetragonal, aumentando su cristalinidad conforme se aumentó la temperatura de substrato. El ancho de banda prohibida disminuyo con el aumento en la temperatura de substrato, mostrando un decremento abrupto a 494.8±C. Las propiedades ferroeléctricas de las películas mostraron una dependencia con la temperatura de substrato, obteniéndose la mejor respuesta a 494.8±C.
Electrical properties of resistive switches based on Ba1-xSr xTiO3 thin films prepared by RF co-sputtering
A. Márquez-Herrera,E. Hernández-Rodríguez,M.P. Cruz,O. Calzadilla-Amaya
Revista mexicana de física , 2010,
Abstract: En este trabajo, se propone el uso de películas delgadas de Ba1-xSr xTiO3 (0 < x < 1) para la construcción de heteroestructuras metal-aislante-metal (MIM por sus siglas en inglés) y se muestra el gran potencial que poseen para el desarrollo de memorias no volátiles resistivas (ReRAM). El depósito de las películas de Ba1-xSr xTiO3 se hizo mediante de la técnica de rf-sputtering usando dos ca ones tipo magnetrón con blancos de BaTiO3 y SrTiO3, respectivamente. La composición química de las películas (parámetro x) fue variado a través de la potencia aplicada a cada uno de los blancos. Las heteroestructuras depositadas fueron Al/Ba1-xSr xTiO3/nicromel. Las pruebas I-V de las heteroestructuras mostraron que es posible cambiar su comportamiento eléctrico mediante la variación de la proporción Ba/Sr presente la película de Ba1-xSr xTiO3; la proporción Ba/Sr fue determinada por espectroscopia de energía dispersada. Las micrografías obtenidas mediante un microscopio electrónico de barrido mostraron que las películas son uniformes y no presentan fracturas ni huecos. Por otra parte, la caracterización de las películas por difracción de rayos x mostró la incorporación sustitucional del Sr en la red del BaTiO3 y la obtención de películas cristalinas para todo el intervalo de valores de x.
Aplicación foliar de quelatos de zinc en nogal pecanero
D. L., Ojeda-Barrios;Hernández-Rodríguez, O. A.;Martínez-Téllez, J.;Nú?ez-Barrios, A.;Perea-Portillo, E.;
Revista Chapingo. Serie horticultura , 2009,
Abstract: during 2007, a study was carried on pecan trees 8-years age applying zinc. orchard soil conditions were to a xerosol calcic, loam texture, alkaline ph and organic matter and caco3 contents of 1.09 and 12.84% respectively. the experiment consisted on different applications of zn products supplied from sprung leaf to maturity: treatments were as followed: t1) control, t2) nzn 100 mg·kg-1 zn, t3) edta-zn 150 mg·kg-1 zn, t4) edta-zn 100 mg·kg-1 zn, t5) edta-zn 50 mg·kg-1 zn, t6) dtpa-zn 100 mg·kg-1 zn. although none of the treatments significantly improved the concentration of zinc in the leaves, zn-dtpa was a 34.84% better than the other treatments. the values of chlorophyll in this study were 39,445 spad units, which is equivalent to 43 mg·litro-1 extractable chlorophyll, consistent with values of zn deficiency, 20 mg·kg-1. the same applies to the leaf area index which is reduced by 30% in conditions of deficiency. results are preliminary due to that pecan trees present alternancy.
Calentador de sustratos compacto y de bajo costo para tratamiento térmico in situ de películas delgadas depositadas por rf-sputtering
Márquez-Herrera, A.;Hernández-Rodríguez, E.;Cruz-Jáuregui, M.P.;Zapata-Torres, M.;Zapata-Navarro, A.;
Revista mexicana de física , 2010,
Abstract: in this work we present the design, construction and the evaluation of a low cost substrate heater for working at high vacuum. its use concentrates in providing in-situ annealing during the growth of thin films under conditions of controlled pressure and corrosive atmosphere. the heater was constructed mainly of stainless steel, ceramic and a resistance of khantal-al. the body of the heater is cooled using a system of fins and cooling liquid which is isolated completely of the vacuum chamber. the design of the heater also incorporates a rotation system that allows that the substrate turns during the process of growth providing uniformity to the film. temperature of the substrate is recorded by a type "k" thermocouple which feeds back a temperature controller that provides a modulated voltage to the heating resistance. in order to evaluate the functionality of the heating system, this was mounted in a rf-sputtering equipment and thin films of batio3 were grown under different substrate temperatures in an off-axis geometry. the heating system is able to provide an uniform temperature to the substrate as well as to operate by long periods of times.
Calentador de sustratos compacto y de bajo costo para tratamiento térmico in situ de películas delgadas depositadas por rf-sputtering
A. Márquez-Herrera,E. Hernández-Rodríguez,M.P. Cruz-Jáuregui,M. Zapata-Torres
Revista mexicana de física , 2010,
Abstract: En este trabajo se presenta el dise o y construcción de un calentador de sustratos de bajo costo, el cual es capaz de operar en sistemas de alto vacío. Su utilización se centra en proporcionar tratamiento térmico in-situ durante el crecimiento de películas delgadas bajo condiciones de presión controlada y atmósfera corrosiva. El calentador fue construido principalmente de acero inoxidable, cerámica y una resistencia comercial de khantal-A1. El cuerpo del horno es enfriado usando un sistema de aletas y líquido refrigerante, el cual se encuentra completamente aislado de la cámara de depósito. El dise o del calentador también incorpora un sistema de rotación que permite que el sustrato gire durante el proceso de crecimiento proporcionando uniformidad a la película. La temperatura del sustrato es monitoreada mediante un termopar tipo "K" que retroalimenta a un controlador de temperatura, el cual modula una fuente de poder variable que suministra el voltaje a la resistencia. Con el propósito de evaluar la funcionalidad del sistema de calentamiento, éste se montó en un equipo de rf-sputtering y se crecieron películas delgadas de BaTiO3 con distintas temperaturas de sustrato en una geometría off-axis. El sistema de tratamientos térmicos in-situ es capaz de proveer una temperatura uniforme al sustrato así como de operar por largos periodos de tiempos.
Identification of ompL1 and lipL32 Genes to Diagnosis of Pathogenic Leptospira spp. Isolated from Cattle  [PDF]
Hernández-Rodríguez Patricia, Gomez Ramirez Arlen, Baquero Mónica, Quintero Gladys
Open Journal of Veterinary Medicine (OJVM) , 2014, DOI: 10.4236/ojvm.2014.45012
Abstract:

Diagnosis of leptospirosis in Colombia is based on clinical history and serological testing. However, disease symptoms are nonspecific and there is no uniform criteria regarding the qualifications considered positive. Therefore, it is important to identify and characterize genes associated with pathogenicity in native strains for the development of new diagnostic tests and vaccine production. The aim of this study was to identify the ompL1 and lipL32 genes in Leptospira strains isolated from urine samples of cattle. Sixteen strains were obtained from urine samples and, DNA was isolated to perform two Polymerase Chain Reaction (PCR) tests which identified lipL32 and ompL1 genes. As positive control, a reference strain of L. interrogans was used. L. biflexa and Escherichia coli strains were used as a negative control. In 100% of the samples were identified amplicons of 960 bp and 423 bp corresponding to ompL1 and lipL32 genes respectively. Thus, the pathogenic property and conservation of genes in the isolated strains were confirmed. This study is presented as a contribution to the diagnosis of leptospirosis to use these genes as molecular markers of infection. The results of this study might provide clues for future clinical, epidemiological and molecular research leading to implement new diagnostic strategies and to expand knowledge of the pathophysiology of a disease of public health impact on human and

Electrical properties of resistive switches based on Ba1-xSr xTiO3 thin films prepared by RF co-sputtering
Márquez-Herrera, A.;Hernández-Rodríguez, E.;Cruz, M.P.;Calzadilla-Amaya, O.;Meléndez-Lira, M.;Guillén-Rodríguez, J.;Zapata-Torres, M.;
Revista mexicana de física , 2010,
Abstract: in this work, we propose the use of ba1-xsrxtio3(0 ≤ x ≤ 1) thin films for the construction of mim (metal-insulator-metal) heterostructures; and their great potential for the development of non-volatile resistance memories (reram) is shown. the deposition of ba1-xsrxtio3 thin films was done by the rf co-sputtering technique using two magnetron sputtering cathodes with batio3 and srtio3 targets. the chemical composition (x parameter) in the deposited ba1-xsrxtio3 thin films was varied through the rf power applied to the targets. the constructed mim heterostructures were al/ba1-xsrxtio3/nichrome. the i-v measurements of the heterostructures showed that their hysteretic characteristics change depending on the ba/sr ratio of the ba1-xsrxtio3 thin films; the ba/sr ratio was determined by employing the energy dispersive spectroscopy; sem micrographs showed that ba1-xsrxtio3 thin films were uniform without cracks or pinholes. additionally, the analysis of the x-ray diffraction results indicated the substitutional incorporation of sr into the batio3 lattice and the obtainment of crystalline films for the entire range of the x values.
Ultra Structural Comparison of Trophi in Species of the Genus Brachionus Pallas, 1766 in Aguascalientes State, Mexico  [PDF]
Gerardo Guerrero-Jiménez, Marcelo Silva-Briano, Araceli Adabache-Ortiz, Sandra Hernández-Rodríguez
Natural Science (NS) , 2015, DOI: 10.4236/ns.2015.79045
Abstract: Trophi is only found in rotifers. The trophi has been used as a tool to identify species as well as an instrument for reconstructing the phylogeny of the organism, morphometric analysis, etc. Twelve species of rotifers of the genus Brachionus Pallas, 1766 were collected from different regions of the state of Aguascalientes, Mexico. An ultra-structure analysis was performed to examine the structural composition of the trophi of each species using scanning electron microscopy (SEM). The SEM observations show significant differences in the structural composition of each species, with the most considerable differences found in the trophi of B. budapestinensis.
16S rRNA gene-based identification of bacteria in postoperative endophthalmitis by PCR- Denaturing Gradient Gel Electrophoresis (PCR-DGGE) fingerprinting
Navarro-Noya, Yendi;Hernández-Rodríguez, César;Zenteno, Juan C;Buentello-Volante, Beatriz;Cancino-Díaz, Mario E;Jan-Roblero, Janet;Cancino-Díaz, Juan C;
Brazilian Journal of Microbiology , 2012, DOI: 10.1590/S1517-83822012000100033
Abstract: conventional microbiological culture techniques are frequently insufficient to confirm endophthalmitis clinical cases which could require urgent medical attention because it could lead to permanent vision loss. we are proposing pcr-dgge and 16s rrna gene libraries as an alternative to improve the detection and identification rate of bacterial species from endophthalmitis cases.
Importancia química de Jatropha curcas y sus aplicaciones biológicas, farmacológicas e industriales
Pabón,Ludy C; Hernández-Rodríguez,Patricia;
Revista Cubana de Plantas Medicinales , 2012,
Abstract: introduction: jatropha curcas (euforbiaceae) is a multipurpose tree, an alternative source for biodiesel production, food, feed, fertilizers and in traditional medicine. in recent years, the increasing prevalence of multidrug resistant bacteria and the emergence of strains with reduced susceptibility to antibiotics have led to the search for natural active ingredients to control pests and minimize infections and side effects caused by synthetic substances. objective: to ascertain the chemical importance and the biological, pharmacological and industrial applications of jatropha curcas as well as its toxic effects. methods: a thorough updated review of various studies was conducted to identify the most relevant traits of the main chemical compounds in every part of the plant. additionally, the biological application, the medical benefits, the toxicity and the industrial importance of jatropha curcas were determined. results: jatropha curcas is traditionally used to treat bacterial and fungal infections or febrile diseases, muscle pain or jaundice. it is also used for obtaining new drugs through the identification of active ingredients to eliminate pathogens or inhibit signs and symptoms of human and veterinary diseases. conclusions: among the species with diverse medicinal applications jatropha curcas is one having wide recognition due to its utility for obtaining useful products in the pharmaceutical, agricultural, cosmetic and food industries.
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