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Search Results: 1 - 10 of 215006 matches for " Emmanuel Mendoza-López "
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Incidencia de Candida albicans en pacientes estudiadas en la Ciudad de Puebla, México
José Antonio Sánchez-Hernández, José Antonio Rivera-Tapia, Laura Lizeth Coyotécatl-García, Emmanuel Mendoza-López
Acta Cientifica Estudiantil , 2009,
Characterization and Modelling of Circular Piezoelectric Micro Speakers for Audio Acoustic Actuation
J. Mendoza-López,S. Sánchez-Solano,J. L. Huertas-Díaz
ISRN Mechanical Engineering , 2012, DOI: 10.5402/2012/635268
Abstract: A study of circular piezoelectric micro speakers is presented for applications in the audio frequency range, including values for impedance, admittance, noise figures, transducer gain, and acoustic frequency responses. The micro speakers were modelled based on piezoelectric micro ultrasonic transducer (pMUT) design techniques and principles. In order to reach the audio frequency range, transducer radii were increased to the order of one centimetre, whilst piezoelectric layer thicknesses ranged the order of several μm. The micro actuators presented might be used for a variety of electroacoustic applications including noise control, hearing aids, earphones, sonar, and medical diagnostic ultrasound. This work main contribution is the characterization of the design space and transducer performance as a function of transducer radius, piezoelectric layer thickness, and frequency range, looking towards an optimized fabrication process. 1. Introduction Multimedia systems and components such as micro speakers are elements of great interest for the research community, driven by the needs of mobile phone, entertainment, laptop, tablets, and computer industries. It has been long time since “full range” multimedia micro speakers are trying to be developed, often finding design conflicts limited by fundamental physics. For example, the concept of miniaturization is in conflict with the idea of full-range: the smaller the radiating source, the higher the operating frequency range. Low frequencies and therefore large wavelengths require big source sizes which mean large loudspeaker diaphragms and piston excursion. There are usually many more conflicting requirements and tradeoffs found in the design of high sound pressure level output, low noise and distortion, full audio range, omnidirectional, and minimum size transducers. Some studies concerning micro speakers of the moving coil type have been reported in [1–4]. Within this type of speakers, performance was improved after modifying magnetic characteristics [2], optimizing diaphragm pattern design via a finite element approach [5] or introducing a combined permanent magnet [4]. Although moving-coil is a well-matured technology, and probably best for mid- or low-frequency range loudspeaker units, the voice coil and the magnet do produce coupling interactions and nonlinearities difficult to deal with [6, 7], introducing complexity in the design. A different approach to micro speaker development is the piezoelectric type, as reported amongst others in [8–12]. Driven not only by applications in the audio field but most
Evaluation of Positive Inotropic Activity Induced bya Danazol Derivative in Isolated Rat Heart Model  [PDF]
L. Figueroa-Valverde, F. Díaz-Cedillo, E. García-Cervera, E. Pool Gómez, M. López-Ramos, M. Rosas-Nexticapa, R. Mendoza-López, I. May-Gil, A. Sarao
Pharmacology & Pharmacy (PP) , 2013, DOI: 10.4236/pp.2013.44058
Abstract: There is scarce information about the effects of danazol and its derivatives at cardiovascular level. In addition, to date the cellular site and mechanism of action of danazol at the cardiovascular level is very confusing. In order to clarify those phenomena in this study, a danazol derivative was synthesized with the objective of evaluating its activity on perfusion pressure and coronary resistance and comparing this phenomenon with the effect exerted by danazol. The Langendorff technique was used to measure changes on perfusion pressure and coronary resistance in an isolated rat heart model in the absence or presence of danazol and its derivative. Additionally, to characterize the molecular mechanism involved in the inotropic activity induced by danazol derivative was evaluated by measuring left ventricular pressure in the absence or presence of following compounds; flutamide, prazosin, metoprolol, indomethacin and nifedipine. The results showed that danazol derivative significantly increased the perfusion pressure and coronary resistance in comparison with the control conditions and danazol. Additionally, other data indicate that the
Characterization and Modelling of Circular Piezoelectric Micro Speakers for Audio Acoustic Actuation
J. Mendoza-López,S. Sánchez-Solano,J. L. Huertas-Díaz
ISRN Mechanical Engineering , 2012, DOI: 10.5402/2012/635268
Juan Francisco Aguirre-Medina,Daniela Montserrat Moroyoqui-Ovilla,Alexander Mendoza-López,Jorge Cadena-I?iguez
Agronomía Mesoamericana , 2011,
Abstract: Con el objetivo de determinar el efecto de la inoculación con Azospirillum brasilense y Glomus intraradice en café, se estableció la presente investigación en un vivero en el Campo Experimental Rosario Izapa, Chiapas, México de septiembre de 2005 a abril de 2006. Se utilizó un suelo Andosol mólico típico de la región cafetalera del Soconusco Chiapas, México. El A. brasilense tuvo una concentración de 100 x 106 bacterias por gramo de turba y el hongo micorrízico, cuarenta esporas por gramo de suelo con infección de 95% en el sistema radical de cebolla. Los tratamientos utilizados fueron los microorganismos solos, la combinación de ambos y el testigo sin inocular que se distribuyeron en un dise o de bloques completos al azar. Se evaluaron variables morfológicas y fisiológicas del rendimiento cada treinta días a partir del segundo mes de siembra durante siete meses y se determinó el contenido de N, P y Ca en el tejido vegetal. Los resultados se analizaron estadísticamente y las diferencias entre tratamientos se compararon de acuerdo a Tukey 5%. Los resultados indican una respuesta diferencial entre los microorganismos. A. brasilense indujo mayor desarrollo radical y la simbiosis doble G. intraradices + A. brasilense mejoró el desarrollo del tallo y lámina foliar. El contenido de N, P y Ca se presentó de forma consistente con G. intraradices.
Tolerancia y capacidad de fitorremediación de combustóleo en el suelo por seis especies vegetales
Wendy Sangabriel,Ronald Ferrera-Cerrato,Dora Trejo-Aguilar,María Remedios Mendoza-López
Revista internacional de contaminación ambiental , 2006,
Abstract: Se hizo un estudio en invernadero para evaluar la tolerancia y el crecimiento de tres especies de leguminosas (Clitoria ternatea, Phaseolus coccineus, Cicer arietinum) y tres gramíneas (Brachiaria híbrido, Brachiaria brizantha y Panicum maximum) en suelo contaminado con combustóleo, así como su capacidad de reducir el contenido de hidrocarburos provenientes del mismo. Se sembraron semillas en el suelo no contaminado y en el suelo colectado de la comunidad Frijol Colorado, Veracruz, que fue contaminada por un derrame accidental de combustóleo (50,000 mg kg-1). A los 90 días, se evaluó la tolerancia, crecimiento, la población microbiana en la rizósfera y la degradación de combustóleo. Phaseolus coccineus fue la única leguminosa con tolerancia y crecimiento en suelo contaminado; mientras que las tres gramíneas no fueron afectadas negativamente por la presencia del contaminante, aunque el híbrido de Brachiaria mostró mayor crecimiento. La población rizosférica de bacterias y hongos fue diferencialmente afectada por la presencia del contaminante en combinación con la planta. Sin embargo, la rizósfera de P. coccineus presentó mayor población microbiana en el suelo contaminado en comparación con las plantas restantes. La degradación de combustóleo evaluada cualitativamente por GC-MS, fue mayor en la rizósfera de B. brizantha y P. maximum. En contraste P. coccineus presentó una degradación similar a la observada en suelo contaminado sin planta.
A Qualitative Assessment of Lontra longicaudis annectens Aquatic Habitats in Alvarado, Mexico
Gilberto Silva-López,,María Remedios Mendoza-López,Jesús Samuel Cruz-Sánchez,Oscar García-Barradas
IUCN Otter Specialist Group Bulletin , 2012,
Abstract: A laboratory screening study following USEPA SW-846 test methods allowed the detection of organic compounds in the aquatic habitat of the Neotropical river otter (Lontra longicaudis annectens), in the Alvarado Lagoon System, Veracruz, Mexico. The compounds detected included 2-chlorocyclohexanol, phenylethylene glycol, benzophenone, ethanol-2-butoxyphosphate, styrene, p-xylene, ethylbenzene, trans-1,2- cyclohexanediol, di-2-ethylhexyl phthalate, benzeneacetaldehyde, hexadecane, tetracosane, docosane, triacontane, sitosterol, hexadecanoic acid, 1-eicosanol, chlorobenzene, and phosphorothioic acid trimethyl ester. Literature review showed a lack of data on the compounds′ potential effects on wildlife, although some of them could be considered harmful to the otters and their prey. The different compounds detected needs follow-up.
Efecto de la biofertilización en vivero del cacao (Theobroma cacao L) con Azospirillum brasilense Tarrand, Krieg et d?bereiner y Glomus intraradices Schenk et Smith
Aguirre-Medina,Juan F.; Mendoza-López,Alexander; Cadena-I?iguez,Jorge; Avenda?o-Arrazate,Carlos H.;
Interciencia , 2007,
Abstract: theobroma cacao l. originated in america and has been associated with the development of various indian cultures in the tropical forest. its beans are used for the production of food, beverages and sweets. the demand of cocoa cultivated without agrochemical products has increased. plant nutrition with microbial fertilizers is an alternative for increasing its organic production. in this experiment the contribution of two micro organisms to the development and nutritive characteristics of cocoa was determined under two soil conditions, treated with methyl bromide or untreated, in the soconusco region, chiapas, mexico. the cocoa beans were inoculated with azospirillum brasilense and glomus intraradices, alone or in combination at sowing. morphological and physiological characters, and the n2, p and ca2+ content in the vegetal tissue were recorded every 30 days for six months. the results indicate a differential response for soil condition and micro organisms in the production of dry matter. root and foliar lamina were the most affected organs. the inoculated plants showed a higher n2 concentration. g. intraradices translocated more p in the untreated soil and more ca2+ under either soil conditions.
Hongo endomicorrízico y bacteria fijadora de nitrógeno inoculadas a Coffea arabica en vivero
Aguirre-Medina,Juan Francisco; Moroyoqui-Ovilla,Daniela Montserrat; Mendoza-López,Alexander; Cadena-I?iguez,Jorge; Avenda?o-Arrazate,Carlos Hugo; Aguirre-Cadena,Juan Francisco;
Agronomía Mesoamericana , 2011,
Abstract: endomycorrhizic fungi and nitrogen-fixing bacteria inoculated in coffee nurseries. in order to study the effect of bio-fertilization of coffea arabica l. with azospirillum brasilense and glomus intraradice a trial was established in a nursery at the experimental station rosario izapa, chiapas, mexico from september 2005 to april 2006. we used a andosol-mollic soil typical of the soconusco coffee region of chiapas, mexico. a. brasilense had a concentration of 100 x 106 bacteria per gram of peat and the mycorrhizal fungi of 40 spores per gram of soil with 95% infection of the root system of onion. the treatments were the microorganisms alone, the combination of both, and the control without microorganism, which were arranged in a randomized complete block design. morphological and physiological yield components were evaluated every 30 days from the second month to seven months. the content of n, p and ca in plant tissue was determined. the results were analyzed statistically and differences between treatments were compared according to tukey 5%. the results indicate a differential response of microorganisms. a. brasilense induced greater root development and the double symbiosis g. intraradices + a. brasilense enhanced the development of stems and leaf blades. the content of n, p and ca are presented in a manner consistent with g. intraradices.
Aplicación de Celda Fotoacústica Diferencial en la Determinación de la Permeabilidad de Agua en Hueso Descalcificado
Cortés-Ibarra,María de Lourdes; Urriolagoitia-Calderón,Guillermo M.; Hernández-Gómez,Luis Héctor; Mendoza-López,María Luisa; Rodríguez-García,Mario Enrique; Urriolagoitia Sosa,Guillermo;
Revista Colombiana de Biotecnología , 2008,
Abstract: differential photoacoustic cell (dpc) spectroscopy is able to measure the development of several dynamic processes in situ, such as water diffusion through a membrane. this technique was used for studying water permeation in healthy and decalcified wistar rat bones. decalcified bones were given electromagnetic stimulation to evaluate cell activity in bone and attempt to detain decalcification. it was possible to determine the viability of applying dpc for indirectly evaluating bone density in situ, as well as the amount of water retained within bone structure.
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