oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2020 ( 8 )

2019 ( 482 )

2018 ( 675 )

2017 ( 720 )

Custom range...

Search Results: 1 - 10 of 538633 matches for " F. J. Rodríguez-Gómez "
All listed articles are free for downloading (OA Articles)
Page 1 /538633
Display every page Item
Radio emission variability and proper motions of WR 112
J. O. Yam,S. A. Dzib,L. F. Rodríguez,V. Rodríguez-Gómez
Physics , 2014,
Abstract: We analyzed 64 radio observations at the frequency of 8.4 GHz of the Wolf-Rayet star WR 112, taken from the Very Large Array archive. These observations cover a time baseline of 13 years, from June 2000 to July 2013. The radio structure of WR 112 is consistent with it being a point source in all the epochs and with its flux density varying from 0.6 mJy to 2.1 mJy. We tried to search for periodicities in these variations but our results were not conclusive. We also looked for extended emission from the infrared nebula that surrounds WR 112, settimg upper limits of 50 $\mu$Jy. Finally, we used the highest angular resolution images to measure the proper motions of WR 112, obtaining $\mu_\alpha\cos \delta = -2.6 \pm 1.1 \mbox{ mas yr$^{-1}$}$, and $\mu_\delta = -5.4 \pm 1.4 \mbox{ mas yr$^{-1}$}$. These proper motions are smaller than those previously reported, but still suggest significant peculiar motions for WR 112.
Estudio del comportamiento de películas delgadas de Ni y óxido de Ni obtenidas por espurreo catódico frente a un medio amargo
C. R. Maga?a-Zavala,F. J. Rodríguez-Gómez,D. R. Acosta,J. Genescá
Revista mexicana de física , 2006,
Abstract: En este trabajo se presenta el estudio del comportamiento de películas delgadas de níquel y un óxido superior de níquel obtenidas por espurreo catódico sobre acero AISI 1018 (UNS G 10180), con el propósito de disminuir la velocidad de corrosión del acero al carbón cuando se expone a un medio amargo (presencia de ácido sulfhídrico y cloruros) y obtener una protección anticorrosiva eficaz. La caracterización de las superficies se realizó a través de técnicas electroquímicas[l] (curvas de polarización y espectroscopia de impedancia electroquímica).
Boric Acid as an Accelerator of Cerium Surface Treatment on Aluminum
K. Cruz-Hernández,S. López-Leon,F. J. Rodríguez-Gómez
International Journal of Corrosion , 2014, DOI: 10.1155/2014/128720
Abstract: Aluminum pieces are often used in various industrial processes like automotive and aerospace manufacturing, as well as in ornamental applications, so it is necessary to develop processes to protect these materials, processes that can be industrialized to protect the aluminum as well or better than chromate treatments. The purpose of this research is to evaluate boric acid as an accelerator by optimizing its concentration in cerium conversion coatings (CeCC) with 10-minute immersion time with a concentration of 0.1?g?L?1 over aluminum to protect it. The evaluation will be carried out by measuring anticorrosion properties with electrochemical techniques (polarization resistance, , polarization curves, PC, and electrochemical impedance spectroscopy, EIS) in NaCl 3.5% wt. aqueous solution and surface characterization with scanning electron microscopy (SEM). 1. Introduction Among the most striking characteristics of aluminum is its versatility, and the range of physical and mechanical properties that can be developed is remarkable. The properties of aluminum that make this metal and its alloys the most economical and attractive options for a wide variety of uses are appearance, light weight, manufacturing versatility, physical properties, mechanical properties, and corrosion resistance [1]. Aluminum and its alloys are widely used in automotive and aerospace devices. Sometimes pieces of an aircraft are submitted to aggressive environments and changes of temperature as well as condensation, resulting in corrosion attack on them. For many years, research for alternatives to chromatizing in order to diminish the damage to the environment has been carried out. Treatments that led to the development of other nontoxic coating processes with comparable adhesion properties and corrosion protection, such as conversion pretreatments formed by immersion in solutions containing phosphates, or cerium chloride, or other rare earth metal chlorides such as yttrium and lanthanum have been studied [2–5]. Approaches to cerium conversion coatings include different salts, variation on immersion temperature, anodizing, applying many layers, variation in concentration, surface activation, and use of accelerators like hydrogen peroxide [6–19]. The aim of this work is to improve understanding of accelerators on cerium conversion coatings, by studying the effect of different concentrations of boric acid as an accelerator added to CeCC at 0.1?g?L?1 at 60°C, and the role played by the substrate composition. The corrosion performance of treated aluminum surfaces that immersed 10 minutes
Estudio del comportamiento de películas delgadas de Ni y óxido de Ni obtenidas por espurreo catódico frente a un medio amargo
Maga?a-Zavala, C. R;Rodríguez-Gómez, F. J;Acosta, D. R;Genescá, J;ávila-Godoy, R;
Revista mexicana de física , 2006,
Abstract: the aim of this work is to study the behavior of nickel and nickel oxide thin films obtained by cathodic sputtering on steel aisi 1018 (uns g 10180), with the purpose of diminishing the corrosion rate of low carbon steel, when it is exposed to a sour medium, and to obtain an efficient anticorrosive protection. the characterization of the surfaces was carried out by electrochemical techniques, such polarization curves and electrochemical impedance spectroscopy.
Estudio del comportamiento de películas delgadas de Ni y óxido de Ni obtenidas por espurreo catódico frente a un medio amargo
C.R. Maga?a-Zavala,F.J. Rodríguez-Gómez,D.R. Acosta,J. Genescá
Revista mexicana de física , 2006,
Abstract: The aim of this work is to study the behavior of nickel and nickel oxide thin films obtained by cathodic sputtering on steel AISI 1018 (UNS G 10180), with the purpose of diminishing the corrosion rate of low carbon steel, when it is exposed to a sour medium, and to obtain an efficient anticorrosive protection. The characterization of the surfaces was carried out by electrochemical techniques, such polarization curves and electrochemical impedance spectroscopy.
Estudio del comportamiento ante la corrosión de películas delgadas de Ni y óxido de Ni obtenidas por espurreo catódico frente a un medio amargo
C.R. Maga?a-Zavala,F.J. Rodríguez-Gómez,D.R. Acosta,R. ávila-Godoy
Revista mexicana de física , 2005,
Abstract: En este trabajo se presenta el estudio del comportamiento de pel′ culas delgadas de n′ quel y un ′oxido superior de n′ quel obtenidas por espurreo cat′odico sobre acero AISI 1018 (UNS G 10180), con el prop′osito de disminuir la velocidad de corrosi′on del acero al carbono cuando se expone a un medio amargo (presencia de ′acido sulfh′ drico y cloruros) y alargar la vida ′util de las estructuras petroqu′ micas met′alicas, con lo que se ahorrar′ a una importante cantidad de recursos monetarios y humanos. La caracterizaci ′on de las superficies se realiz′o utilizando las t′ecnicas electroqu′ micas[1] (curvas de polarizaci′on y espectroscopia de impedancia electroqu′ mica).
Exponential Convergence of Multiquadric Collocation Method: a Numerical Study
Mu?oz-Gómez, J.A.;González-Casanova, P.;Rodríguez-Gómez, G.;
Ingeniería, investigación y tecnología , 2009,
Abstract: recent numerical studies have proved that multiquadric collocation methods can achieve exponential rate of convergence for elliptic problems. although some investigations has been performed for time dependent problems, the influence of the shape parameter of the multiquadric kernel on the convergence rate of these schemes has not been studied. in this article, we investigate this issue and the influence of the péclet number on the rate of convergence for a convection diffusion problem by using both an explicit and implicit multiquadric collocation techniques. we found that for low to moderate péclet number an exponential rate of convergence can be attained. in addition, we found that increasing the value of the péclet number produces a value reduction of the coefficient that determines the exponential rate of convergence. more over, we numerically showed that the optimal value of the shape parameter decreases monotonically when the diffusive coefficient is reduced.
Preconditioning with Triiodothyronine Improves the Clinical Signs and Acute Tubular Necrosis Induced by Ischemia/Reperfusion in Rats
Carla Ferreyra, Félix Vargas, Isabel Rodríguez-Gómez, Rocío Pérez-Abud, Francisco O'Valle, Antonio Osuna
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0074960
Abstract: Background Renal ischemia/reperfusion (I/R) injury is manifested by acute renal failure (ARF) and acute tubular necrosis (ATN). The aim of this study was to evaluate the effectiveness of preconditioning with 3, 3, 5 triiodothyronine (T3) to prevent I/R renal injury. Methodology/Principal Findings The rats were divided into four groups: sham-operated, placebo-treated (SO-P), sham-operated T3- treated (SO- T3), I/R-injured placebo-treated (IR-P), and I/R-injured T3-treated (IR- T3) groups. At 24 h before ischemia, the animals received a single dose of T3 (100 μg/kg). Renal function and plasma, urinary, and tissue variables were studied at 4, 24, and 48 h of reperfusion, including biochemical, oxidative stress, and inflammation variables, PARP-1 immunohistochemical expression, and ATN morphology. In comparison to the SO groups, the IR-P groups had higher plasma urea and creatinine levels and greater proteinuria (at all reperfusion times) and also showed: increased oxidative stress-related plasma, urinary, and tissue variables; higher plasma levels of IL6 (proinflammatory cytokine); increased glomerular and tubular nuclear PARP-1 expression; and a greater degree of ATN. The IR-T3 group showed a marked reduction in all of these variables, especially at 48 h of reperfusion. No significant differences were observed between SO-P and SO-T3 groups. Conclusions This study demonstrates that preconditioning rats with a single dose of T3 improves the clinical signs and ATN of renal I/R injury. These beneficial effects are accompanied by reductions in oxidative stress, inflammation, and renal PARP-1 expression, indicating that this sequence of factors plays an important role in the ATN induced by I/R injury.
Morphology and Corrosion Performance of Chromate Conversion Coatings on Different Substrates
Domínguez-Crespo, Miguel Antonio;Onofre-Bustamante, Edgar;Torres-Huerta, Aidé Minerva;Rodríguez-Gómez, Francisco J.;
Journal of the Mexican Chemical Society , 2008,
Abstract: the aqueous corrosion resistances of galvalume (fe-al+zn) and steel galvanized (fe-zn) alloys, passivated by immersion in chromating solution with different immersion times (0, 10, 30 y 60 s) are compared. the electrochemical behaviour of various chromated and non-chromated coatings was investigated in 3 wt-% nacl solution using polarization techniques. for comparison, aisi 1010 carbon steel substrates were also analyzed. the characterization measurements and polarization curves revealed that textural properties of fe alloys influence the growth of the films and both the cathodic and anodic reactions. an optimum anticorrosive protection was obtained at 30 s. cccs treatments inhibited the corrosion of zinc to a significant degree, but less effectively than coatings formed with aluminium-zinc alloys. the difference in the corrosion protection given by the two substrates types was attributed to the structural properties, thickness coating, grain size and roughness observed, which affect oxygen diffusion.
Hormone-induced spawning of wild and captive-grown spotted rose snapper Lutjanus guttatus using carp pituitary suspension and human chorionic gonadotropin
Boza-Abarca, J;Valverde-Chavarría, S;Calvo-Vargas, E;Ramírez-Alvarado, M;Rodríguez-Gómez, E;
Ciencias marinas , 2011,
Abstract: hormone-induced spawning of the spotted rose snapper lutjanus guttatus was studied using wild and cage-grown fish. carp pituitary suspension (cps) and human chorionic gonadotropin (hcg) were assessed. wild females (0.7-2.1 kg body weight (bw), n = 18) were collected by hook and line in the gulf of nicoya, costa rica, to induce final maturation and ovulation in the laboratory. in the first experiment, five doses of cps were evaluated and spawning was only observed at the higher doses (4.0 and 4.5 mg cps kg-1 bw); the doses used were lower than for other species under similar conditions. in the second experiment, cps and hcg protocols were compared using cage-grown broodstock (n = 30 females, 462-995 g; n = 60 males, 400-600 g); egg production was more consistent for the hcg protocol. in the third experiment, cage-grown fish (n = 12 females, 368-977 g; n = 24 males, 400-600 g) were used to assess the female response to hcg and the fertility of the spawned eggs; two successive injections of different hcg doses were tested. the results confirm that two successive doses of 900 and 700 iu hcg kg-1 bw result in the highest number of eggs spawned and the best fertilization rates.
Page 1 /538633
Display every page Item


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