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Search Results: 1 - 10 of 481599 matches for " S. López-Leon "
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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
Major Existing Classification Matrices and Future Directions for Internet of Things  [PDF]
Kedir Mamo Basher, Juan-Ivan Nieto-Hipolito, Maria De Los Angeles Cosio Leon, Mabel Vazquez-Briseno, Juan de Dios Sánchez López, Raymundo Buenrostro Mariscal
Advances in Internet of Things (AIT) , 2017, DOI: 10.4236/ait.2017.74008
Abstract: Classification method is a formula, logical description generalizing characteristics of objects of related area. Nowadays, billions of smart objects are immersed in the environment, sensing, interacting, and cooperating with each other to enable efficient services. When we think about IoT, classification is a major challenge particularly if our technology is international level applicable. So, this limitation needs clear and deep analysis of the existing classification matrixes and gives some future directions depending on the different researches in the area. The paper surveys the current state-of-art in the classification of IoT. First, we try to explain commonly existing classification matrixes; Second, cooperation of different methods defending on classification matrixes used. Then analyses challenges that IoT faced from classification angle and finally we give some direction for future IoT classification.
Selección de variables morfológicas para la caracterización del tejocote (Crataegus spp.)
López-Santiago, J.;Nieto-ángel, R.;Barrientos-Priego, A. F.;Rodríguez-Pérez, E.;Colinas-Leon, M. T.;Borys, M. W.;González-Andrés, F.;
Revista Chapingo. Serie horticultura , 2008,
Abstract: considering plant characterization as the set of characteristics for taxonomical differentiation, in the present research the selection of reliable and discriminating morphological variables was established as objective, using the analysis of variance, coefficient of variation, lineal correlation, stepwise selection analysis and mean component analysis. hawthorn (crataegus spp.) leaf, flower and fruit set characteristics from the chapingo autonomous university gene bank collection were selected. the statistical methods that contributed more in the selection of these morphologic characteristics and descriptors definition were: the coefficient of variation, the mean components analysis and their analysis of correlation, in addition to the researcher criterion, obtaining 35 characters that contributed more in the morphologic characterization, of a total of 76 variables. the discriminating variables were: from reproducrive shoots leaves: perimeter, major and minor axis lenght, elongation index, feret diameter, compaction index, basal angle and veins number; from short vegetative shoots leaves: perimeter, major and minor axis lenght, elongation index, feret diameter, compaction index, apical and basal angle, veins number; from long vegetative shoots leaves: perimeter, major and minor axis lenght, elongation index, feret diameter, compaction index, apical and basal angle; from reproductive leaves stomata: stomata frequency and stomata lenght; and from flowers: pedicel length, floral receptacle lenght, perimeter and feret petals diameter, style lenght, perimeter, major axis lenght, and feret anther filaments diameter.
A Decreased Expression and Functionality of Muscarinic Cholinergic Receptor in Acute Chagas Myocarditis  [PDF]
M. Labrador-Hernández, L. Jiménez, G. Leon, R. López, W. Mendoza, C. Bonfante-Rodriguez, J. Torres-Peraza, R. Bonfante-Cabarcas
World Journal of Cardiovascular Diseases (WJCD) , 2014, DOI: 10.4236/wjcd.2014.46040
Abstract: Background: Chagas disease is still a public health problem because of the remaining high prevalence, the expansion of the disease into developed countries and the re-emergences by oral transmission outbreaks. Chagas cardiomyopathy evolves as a consequence of an autonomic un-balance where the parasympathetic tone is undermined. Objective: To determine the functionality and expression of muscarinic cholinergic receptors in acute Chagas disease. Methodology: 62 male, 3-week-old Sprague Dawley rats were assayed; 32 were infected with Trypanosoma cruzi trypo-mastigotes and 30 were healthy controls. Electrocardiographic studies were conducted in the absence or presence of direct muscarinic (oxotremorine and McN-A-343) or indirect agonists (phenylephrine) or antagonist (pirenzepine). Muscarinic M1 and M2 receptor expression was determined by radioligand [3H]-QNB binding assay and immunoblot. Results: Chagasic acute myocarditis was sustained by electrocardiographic signs and histopathological findings. Bradycardia induced by oxotremorine was significantly higher in healthy rats (HR) and the differences were enhanced by CsCl. In the absence of the agonist, CsCl induced a greater bradycardia in chagasic rats (ChR). In HR McN-A-343 induced tachycardia, however it induces bradycardia in the presence of a acetylcholinesterase inhibitor (neostigmine); no effects were observed in ChR. Pirenzepine induced a higher tachycardia in HR. Phenylephrine in the presence of pirenzepine induced a similar bradycardia in both groups, but recovery was faster in ChR. Muscarinic M1 and M2 receptor density was higher in HR. Conclusion: Muscarinic receptor expression and functionality are decreased in the acute Chagas disease that could impact the evolution and prognosis of the disease.

Eutrophication Levels through San Pedro-Mezquital River Basin  [PDF]
María Elena Pérez López, Maria Guadalupe Sanchez-Martinez, Maria Guadalupe Vicencio de la Rosa, Margarita Teutli Leon
Journal of Environmental Protection (JEP) , 2013, DOI: 10.4236/jep.2013.411A006
Abstract:

This paper presents an eutrophication diagnosis for the San Pedro-Mezquital basin at Mexico; procedure accounted to set up 10 sampling points distributed along the river pathway, sample collection was done at two extreme conditions: rainy season and dry season. Five parameters were analyzed in this work: pH, % Dissolved Oxygen, reactive phosphorus, and nitrogen species as nitrate and ammonia compounds. Obtained concentrations were statistically analyzed to establish if there were significant differences among sites and between seasons; being the dry season the one with higher nutrient content, ammonia can be considered statistical significance due to the total values found for each season. Calculation of the Karydis eutrophication index for each parameter showed that more damaged sites were those nearby the cities, and most of the sampled sites belonged to the eutrophic category.

Effect of TNF-α genetic variants and CCR5Δ32 on the vulnerability to HIV-1 infection and disease progression in Caucasian Spaniards
Sergi Veloso, Montserrat Olona, Felipe García, Pere Domingo, Carlos Alonso-Villaverde, Montserrat Broch, Joaquim Peraire, Consuelo Viladés, Montserrat Plana, Enric Pedrol, Miguel López-Dupla, Carmen Aguilar, Mar Gutiérrez, Agathe Leon, Mariona Tasias, Josep Ma Gatell, Cristóbal Richart, Francesc Vidal
BMC Medical Genetics , 2010, DOI: 10.1186/1471-2350-11-63
Abstract: We aimed to determine whether carriage of the TNF-α-238G>A, -308G>A and -863 C>A gene promoter single nucleotide polymorphisms (SNP) and the CCR5Δ32 variant allele influence the risk of HIV-1 infection and disease progression in Caucasian Spaniards. The study group consisted of 423 individuals. Of these, 239 were uninfected (36 heavily exposed but uninfected [EU] and 203 healthy controls [HC]) and 184 were HIV-1-infected (109 typical progressors [TP] and 75 long-term nonprogressors [LTNP] of over 16 years' duration). TNF-α SNP and the CCR5Δ32 allele were assessed using PCR-RFLP and automatic sequencing analysis methods on white blood cell DNA. Genotype and allele frequencies were compared using the χ 2 test and the Fisher exact test. Haplotypes were compared by logistic regression analysis.The distribution of TNF-α-238G>A, -308G>A and -863 C>A genetic variants was non-significantly different in HIV-1-infected patients compared with uninfected individuals: -238G>A, p = 0.7 and p = 0.3; -308G>A, p = 0.05 and p = 0.07; -863 C>A, p = 0.7 and p = 0.4, for genotype and allele comparisons, respectively. Haplotype analyses, however, indicated that carriers of the haplotype H3 were significantly more common among uninfected subjects (p = 0.04). Among the infected patients, the distribution of the three TNF-α genetic variants assessed was non-significantly different between TP and LTNP: -238G>A, p = 0.35 and p = 0.7; -308G>A, p = 0.7 and p = 0.6: -863 C>A, p = 0.2 and p = 0.2, for genotype and allele comparisons, respectively. Haplotype analyses also indicated non-significant associations. Subanalyses in the LTNP subset indicated that the TNF-α-238A variant allele was significantly overrepresented in patients who spontaneously controlled plasma viremia compared with those who had a detectable plasma viral load (genotype comparisons, p = 0.02; allele comparisons, p = 0.03). The CCR5Δ32 distribution was non-significantly different in HIV-1-infected patients with respect to the
Sesto, Carmen. 2005. La vanguardia ganadera bonaerense, 1856-1990. Tomo II: "Historia del capitalismo agrario pampeano". Buenos Aires: UB; Siglo XXI
Andrés López
Mundo agrario , 2006,
Abstract:
Maestros de la medicina interna chilena Masters of Internal Medicine, in Chile
Gloria López S
Revista médica de Chile , 2011,
Abstract:
Formación en planificación para la pluralidad
JESúS LóPEZ
Cuadernos del Cendes , 2006,
Abstract:
Sedation/analgesia guidelines for endoscopy Directrices "guidelines" de sedación/analgesia en endoscopia
L. López Rosés
Revista Espa?ola de Enfermedades Digestivas , 2006,
Abstract:
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