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Search Results: 1 - 10 of 450178 matches for " José W. J. Silva "
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Corrosion Resistance of Zn and Zn-Ni Electrodeposits: Morphological Characterization and Phases Identification  [PDF]
Concei??o A. M. Dutra, José W. J. Silva, Roberto Z. Nakazato
Materials Sciences and Applications (MSA) , 2013, DOI: 10.4236/msa.2013.410079

Zinc alloys coatings formed with elements of group VIIIB are promising because they display similar properties and protect steel by galvanic action. The Zn-Ni alloy is remarkable by showing improved mechanical properties and better corrosion resistance when compared to zinc coatings of similar thickness, also can be applied at higher temperatures. In this work, electrodeposits of Zn, Zn-12%Ni, obtained upon SAE 1010 steel from commercial alkali baths, were treated by blue chromatization and characterized according to mechanical properties and morphology. Studies were carried out by using measures of hardness, roughness, SEM, EDS and XRD. Among the studied electrodeposits, alloys treated by chromatization showed higher corrosion resistance and Zn-Ni electrodeposits showed higher value of roughness and hardness, while zinc coating had results similar to the steel substrate By means of XRD, it was found that electrodeposits are crystalline, being identified in Zn-Ni alloy the presence of the phases g(Ni5Zn21) and d(Ni3Zn22), which are responsible for its higher corrosion resistance.

Electrochemical and Microstructural Study of Ni-Cr-Mo Alloys Used in Dental Prostheses  [PDF]
José W. J. Silva, Lucíola L. Sousa, Roberto Z. Nakazato, Eduardo N. Codaro, Hamilton de Felipe
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.21006
Abstract: Ni-Cr-Mo alloys have been widely used as fixed dental prostheses. Recast process influence on corrosion behavior of Ni-Cr-Mo dental alloy in simulated physiological serum has been investigated using chemical and electrochemical techniques. Ni-Cr-Mo alloy recast by induction (induction) or by blowtorch (torch) has exhibited similar dendritic structures with wide and precipitate grains in their boundaries. The torch alloy has presented good corrosion resistance in physiological serum. Passivation process provides this corrosion resistance. Passivation of Ni-Cr-Mo alloy is often attributed to the formation of a thin and compact layer of chromium oxide (Cr2O3). This film is self-limiting because it acts as a barrier to the oxygen transport and metal ions. This film stability will depend on its solubility to the working temperature. Different recast procedures change electrochemical parameters as stabilizing potential in open circuit, current density and passivation interval.
Influence of Ni and Cr Content on Corrosion Resistance of Ni-Cr-Mo Alloys for Fixed Dental Prostheses in 0.05% NaF Aqueous Solution  [PDF]
Nilo A. S. Sampaio, José W. J. Silva, Heloisa A. Acciari, Roberto Z. Nakazato, Eduardo N. Codaro, Hamilton de Felipe
Materials Sciences and Applications (MSA) , 2010, DOI: 10.4236/msa.2010.16053
Abstract: The Ni-Cr-Mo alloys have been used as dental prostheses because they own a good mechanical strength, high corrosion resistance and even to be economically viable. These alloys corrosion protection against in salt solutions typical of physiological media is due to passivation phenomenon with an oxide surface layer formation, mainly chromium oxides. This protective film, subjected to a mechanical stress in a corrosive environment, can partially dissolve by releasing ions, which have deleterious effects in a human body. Fluoride ions, existing in hygiene products, change the buccal environment and their presence may enable a localized corrosion process initiation. The aim of this work has been to investigate the chemical composition influence of three alloys in corrosion resistance to: A (Ni-73% Cr-14% Mo-8.5% Be-1.8% Al-1.8%), B (Ni-61% Cr-25% Mo-10.5% Si-1.5%) and C (Ni-65% Cr-22.5% Mo-9.5%) in media containing fluorides that simulate mouthwashes solution. The study has been done in a 0.05% NaF solution, pH 6, at 37°C using electrochemical techniques. The alloy with the highest nickel and the lowest chromium content is not passive in the middle studied, showing a continuous increase in current density with the potential increasing, while the other alloys show passivation range of 600 mV and passive current density of about 10-6 A/cm2.
Morphology Characterization and Kinetics Evaluation of Pitting Corrosion of Commercially Pure Aluminium by Digital Image Analysis  [PDF]
Marinalda C. Pereira, José W. J. Silva, Heloisa A. Acciari, Eduardo N. Codaro, Luis R. O. Hein
Materials Sciences and Applications (MSA) , 2012, DOI: 10.4236/msa.2012.35042
Abstract: The pit morphology and growth kinetics of commercially pure aluminium in naturally aerated NaCl solutions were studied using an image processing method based on reflected light microscopy. In order to distinguish between pits and pre-existing cavities, metallographic examination and statistical analysis were carried out before and after corrosion testing. The results show that the pit shapes and sizes are more dependent on the immersion time than the chloride concentration. Pits are predominantly hemispherical, but they undergo reasonable geometric transitions associated with increased immersion time and occur without significant depth variation. The role of chloride ions is more closely associated with the pit nucleation phenomenon.
Response of young 'Tahiti' lime trees to different irrigation levels
Alves Júnior, José;Folegatti, Marcos V.;Silva, Cláudio R. da;Silva, Tonny J. A. da;Evangelista, Ad?o W. P.;
Engenharia Agrícola , 2011, DOI: 10.1590/S0100-69162011000200010
Abstract: the aim of this study was to evaluate the effect of different irrigation levels on canopy and root growth, productivity, and fruit quality of young ‘tahiti’ acid lime trees. the experiment was installed in piracicaba, brazil in a 1.0-ha orchard plot with ‘tahiti’ acid lime trees, grafted on ‘swingle’ citrumelo rootstock and carried out from august of 2002 to may 2005. each treatment was assigned to a drip irrigation level, based on etc as follows: t1) non-irrigated, t2) 25%, t3) 50%, t4) 75% and t5) 100% of etc determined by weighing lysimeter presented in the orchard plot. trunk diameter and tree height were evaluated monthly. the roots were evaluated when the trees were 30 and 48 months old. the yield and fruit quality was evaluated in 2004 and 2005. the results showed that irrigation did not influence root distribution in depth, and trees irrigated with 75% and 100% etc showed horizontal root distribution concentrated until 0.6 m from the trunk. irrigation did not improve the quality of fruit. yield increased in all irrigated treatment, but the most efficient yield mean per unit of water applied was the 25% etc treatment.
Altera??es físicas e químicas de um Argissolo amarelo sob diferentes sistemas de uso e manejo
Silva, Apolino J. N. da;Cabeda, Mário S. V.;Carvalho, Fabíola G. de;Lima, José F. W. F.;
Revista Brasileira de Engenharia Agrícola e Ambiental , 2006, DOI: 10.1590/S1415-43662006000100012
Abstract: alterations in the chemical conditions of the soil due to different soil management systems with sugarcane can cause modifications in clay dispersion and in the state of aggregation of the soil. the effects of different soil management systems with sugarcane on the physical and chemical properties of a cohesive yellow argisol were studied, being selected four different use and management systems, constituted of a site with irrigated cultivation, a site with not irrigated cultivation, a site with vinasse application and a site under native forest as original condition. samples of each site were collected at 0-0,2, 0,2-0,4 and 0,4-0,8 m depths to determine the alterations in the chemical and physical properties of soil. the management systems with sugarcane affected the chemical properties of the soil, resulting in reduction of cation exchange capacity and increase of the electrical conductivity, ph in water and critical flocculation concentration. these chemical alterations resulted in larger clay dispersion in the soil cultivated with sugarcane, reducing the stability of the aggregates in water.
Impacto do beneficiamento sobre o número de neps e quantidade de impurezas da fibra do algod?o
Silva, Odilon R. R. F. da;Sofiatti, Valdinei;Santana, Jo?o C. F. de;Wanderley, Maurício J. R.;Santos, José W. dos;
Revista Brasileira de Engenharia Agrícola e Ambiental , 2010, DOI: 10.1590/S1415-43662010000100015
Abstract: the purpose of this work was to study the ginning effect on the amount of cotton contaminants, dust and neps in cotton fiber, in 12 industries in the mato grosso state. the experiment consisted of a factorial combination over five stages of ginning and 12 cotton industries using a randomized design with four replications. some samples of cotton were collected in the following phases: a) in the bale dismantling; b) before the ginning; c) right after ginning; d) into the covered lint slide not using the saw lint cleaner; and e) into the covered lint slide, after cleaning process using the saw lint cleaner system. over all stages four standard samples of lint with 350 g were collected to be analyzed by the afis instrument (advanced fiber information system), for determining the content of trash, dust and the number of neps in the cotton fiber. the results indicate that the processes of cotton pre-cleaning and fiber cleaning reduced significantly the amount of cotton trash and dust, while that jointly with the ginning, these processes increased the number of neps in cotton fiber. the use of the saw lint cleaner system increases the efficiency of fiber cleaning, but causes considerable rise in the number of neps.
Características tecnológicas da Prosopis juliflora (Sw.) DC. e alternativas para o uso racional
Gomes, Juáres J.;Toledo Filho, Romildo D.;Nascimento, José W. B. do;Silva, Valneide R. da;Nóbrega, Marcilene V. da;
Revista Brasileira de Engenharia Agrícola e Ambiental , 2007, DOI: 10.1590/S1415-43662007000500015
Abstract: this work was carried out with the objective of increasing the knowledge on the existing wild trees species in north-eastern brazil. the main purpose was to determine the technological characteristics of the prosopis juliflora (sw.) dc and to indicate alternative use of its wood for agricultural constructions. the procedures adapted for the characterization of the species were in agreement with the brazilian norm 7190 of brasilian association of technical norms referring to the standard conditions moisture content of 12%. tests of basic and apparent densities were carried out, moisture content and parallel fibers resistance to compression, traction and shear, were measured. the results were analyzed through the comparison of the values obtained with those found in literature for other kinds of wood. in agreement with the results, it was concluded that the prosopis juliflora's wood can be compared with other traditional kinds of wood used in brazil.
Epicarp and mesocarp of babassu (Orbignya speciosa): characterization and application in copper phtalocyanine dye removal
Vieira, Adriana P.;Santana, Sirlane A. A.;Bezerra, Cícero W. B.;Silva, Hildo A. S.;Chaves, José A. P.;Melo, Júlio C. P. de;Silva Filho, Edson C. da;Airoldi, Claudio;
Journal of the Brazilian Chemical Society , 2011, DOI: 10.1590/S0103-50532011000100003
Abstract: the mesocarp and epicarp components of the babassu palm tree were applied as novel alternative biosorbents for copper phtalocyanine textile dye removal from aqueous solutions. the natural biopolymers were characterized by elemental analyses, solid state 13c nmr, infrared spectroscopy, thermogravimetric analysis and x-ray diffractometry. results demonstrated that the compositions of the mesocarp and epicarp are similar to those of other lignocellulosic materials, and that they were very effective for removal of the textile dye turquoise remazol. a pseudo second-order kinetic model resulted in the best fit with experimental data for both epicarp and mesocarp (r2 = 0.999), providing rate constants of sorption, k2, of 0.31 and 1.43 g mg-1 min-1, respectively. the langmuir and freundlich isotherm models were employed for adsorption analysis of the experimental data in their linearized forms. the second model resulted in the better fit for turquoise remazol dye, which presented maximum adsorption of 1.44 and 2.38 mg g-1 at ph 6.0 for mesocarp and epicarp, respectively.
Hemoglobinúria paroxística noturna: relato de dois casos
Araújo, Carlos J.;Soares, Francisca V.M.;Rocha, Francisco D.;Silva, Herivaldo F.;Nogueira, José O.L.;Correia, José W.;Guimar?es, Manoel P.G.;
Revista Brasileira de Hematologia e Hemoterapia , 2002, DOI: 10.1590/S1516-84842002000400006
Abstract: paroxysmal nocturnal hemoglobinuria (pnh) is an acquired hematopoietic stem cell disease characterized by chronic hemolytic anemia, thrombotic episodes and often pancytopenia. it is a chronic disorder caused by a somatic mutation of the x-linked gene pig-a, which is required for formation of the glycosylphosphatidylinositols (gpi) - anchor structure. deficiency of the gpi-anchored protein cd59 explains intravascular hemolysis in pnh, which results from the inability of erythrocytes to inactivate the surface complement. a very strong clinical relationship exists between aplastic anemia (aa) and pnh. absence of gpi-anchored proteins is easily detected by flow cytometric methods applied to both erythrocytes and leukocytes; the ham and sucrose tests are now obsolete. treatment with glucocorticoids and / or androgen is sometimes helpful. allogeneic hematopoietic cell transplantation is curative. the aim of this work is to relate two cases of pnh with review emphasizing the pathophysiological, clinical and diagnostic features and therapy for pnh.
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