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Search Results: 1 - 10 of 808446 matches for " D. M. A.;Melo "
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Effects of anti-inflammatory drugs on fever and neutrophilia induced by Clostridium difficile toxin B
R. A. Cardoso,A. A. Melo Filho,M. C. C. Melo,D. M. Lyerly
Mediators of Inflammation , 1996, DOI: 10.1155/s0962935196000245
Abstract:
Caracteriza??o e usos de argilas bentonitas e vermiculitas para adsor??o de cobre (II) em solu??o
Santos, C. P. F. dos;Melo, D. M. A.;Melo, M. A. F.;V. Sobrinho, E.;
Ceramica , 2002, DOI: 10.1590/S0366-69132002000400002
Abstract: mineral clays have been extensively used for metal removal. the process involves precipitation, ion exchange and adsorption. the present investigation assessed the adsorption of cu (ii) solution by natural vermiculite and both natural and synthetic bentonite. tests were carried out at ambient temperature for the main parameters of the process, i.e., ph, contact time, and adsorbent content. atomic absorption was also carried out both for the floater and solid residue. all raw materials used herein, i.e., sodic bentonite from campina grande-pb, sodic bentonite from wyoming-usa, synthetic sodic bentonite and vermiculite from piaui, were characterized both before and after adsorption of cu (ii) solution by chemical analysis, tg, dta, bet surface area, infrared spectroscopy, x-ray diffraction, and ph determination. the results showed that clay minerals adsorb heavy metals by ionic exchange. vermiculite was the most efficient material studied adsorbing 40.9% of cu solution.
Caracteriza o e usos de argilas bentonitas e vermiculitas para adsor o de cobre (II) em solu o
Santos C. P. F. dos,Melo D. M. A.,Melo M. A. F.,V. Sobrinho E.
Ceramica , 2002,
Abstract: Vários trabalhos tratam da remo o de metais por argilas e argilominerais. O processo de remo o geralmente ocorre por precipita o, troca i nica e adsor o. Neste trabalho estudou-se a adsor o de solu o de Cu (II) em vermiculita, bentonitas sódica e cálcica, proveniente de Campina Grande-PB , tendo-se como variáveis pH, tempo de contato e concentra o do adsorvente. Os ensaios foram realizados à temperatura ambiente e as medidas de Absor o At mica foram feitas no sobrenadante e no resíduo sólido. As argilas bentonitas cálcicas, provenientes de Campina-Grande (PB), sódica de Wyoming (Wyoming-USA) e sódicas (preparadas em laboratório) e as vermiculitas (provenientes do Piauí) foram caracterizadas antes e após o processo de adsor o de Cu (II) em solu o através das técnicas, análise química, TG e DTA, área superficial (BET), espectroscopia na regi o de infravermelho, difra o de raios X e medidas de pH. Os resultados mostram que as argilas estudadas adsorvem metais pesados através da troca i nica e que a vermiculita foi mais eficaz no processo, adsorvendo 40,9% de cobre da solu o em estudo, em rela o às outras argilas envolvidas no processo.
Cor e propriedades mecanicas de algumas argilas do Rio Grande do Norte para uso em ceramica branca
Melo M. A. F.,G. Neto S.,Melo D. M. A.,Carvalho L. P.
Ceramica , 2002,
Abstract: O interesse crescente no uso de argilas para a produ o de ceramica no Rio Grande do Norte requer a caracteriza o técnica das matérias primas. Este trabalho mostra algumas propriedades de cinco argilas encontradas nesta regi o, tais como colora o após queima a 950 masculineC, 1250 masculineC e 1450 masculineC, retra o linear e resistência à flex o. A queima de argilas regionais resultaram em uma variedade de faixas de tonalidades do branco ao creme. As propriedades gerais dos produtos da queima s o melhores que as reportadas na literatura, demonstrando o potencial tecnológico das argilas da regi o estudada.
Otimiza??o de uma metodologia para análise mineralógica racional de argilominerais
Varela, M. L.;Nascimento, R. M. do;Martinelli, A. E.;Hotza, D.;Melo, D. M. A.;Melo, M. A. F.;
Ceramica , 2005, DOI: 10.1590/S0366-69132005000400013
Abstract: the method proposed herein for the rational mineralogical analysis of ceramics uses conventional results obtained by x-ray diffraction (xrd) and x-ray fluorescence (xrf) in addition to a free quartz content correction evaluated for different types of clays. all this information was collected and used to assemble matrix systems containing linear equations. each line of the system represents an element present in one of the crystallographic phases detected by xrd, and each column the phase itself. the solution of the equation systems is found from sub-routines such as a.x = b, whose output is the likely mineralogical composition of the constituents of a particular clay. the joint use of chemical and rational analyses provides a powerful tool to establish the detailed composition of raw materials used in the formulation of industrial ceramic mixtures.
Caracteriza??o e uso de xisto para adsor??o de chumbo (II) em solu??o
Pimentel, P. M.;Silva Jr., C. N.;Melo, D. M. A.;Melo, M. A. F.;Maldonado, G.;Henrique, D. M.;
Ceramica , 2006, DOI: 10.1590/S0366-69132006000300013
Abstract: there has been a growing interest in the use of cost-effective materials to remove heavy metals from wastewater. new processing techniques and adsorbents including natural clays, synthetic resins, peat and chitosan have been studied aiming at replacing activated coal. in the present investigation, retorted shale, a solid residue of the thermal transformation of oil shale, was characterized with the objective of preparing heavy metals adsorbents. in addition to the direct environmental benefits from the technology to wastewater, brazil has the second world reserve of oil shale. the fine residue was fully characterized by different techniques including particle size determination, thermogravimetric analyses, bet, ftir, x-ray diffraction, and sem/eds. the characteristics of the powder were appropriate for adsorption. batch adsorption studies in pb2+ synthetic solution were performed. the removal of pb 2+ ion was found to be above 85%.
Synthesis and characterization of lanthanum- and yttrium-doped Fe2O3 pigments
Melo, D. M. A.;Melo, M. A .F.;Martinelli, A. E.;Silva, Z. R.;Cunha, J. D.;Lima, A. C.;
Ceramica , 2007, DOI: 10.1590/S0366-69132007000100012
Abstract: iron oxide has been doped with rare earth ions (yttrium or lanthanum) aiming at producing ceramic pigments with hues that vary from orange to brown. the powders were synthesized from polymeric precursors using the pechini method and subsequently calcined between 900 and 1100 oc. the resulting pigments were characterized by bet, x ray diffraction, colorimetric analysis, uv-visible, infrared (ftir), particle size distribution and thermal analysis. the color depicted by la/fe powders changed as the calcination temperature increased from 900 oc to 1100 oc, as established by the corresponding changes in the values of the colorimetric coordinates from l* a* b* = 49.003, 10.541, 12.609 to l* a* b* = 31.279, 6.096, 6.877. on the other hand, y/fe powders were little affected by similar changes in the calcination temperature, revealing the effect of yttrium on the color stability of the powder. the values of the colorimetric coordinates in this case varied from l* a* b* = 45.230, 17.315, 28.750 to l* a* b* =51.631, 15.726, 25.825. structural changes were also noticed as a function of the size of the rare earth ion added to the structure. upon calcination at 900°c, lanthanum stabilized the abo3-type perovskite structure whereas the presence of yttrium resulted in a mixture of oxides.
Síntese e caracteriza??o de espinélios à base de ferritas com gelatina como agente direcionador
Costa, A. F.;Pimentel, P. M.;Melo, D. M. A.;Melo, M. A. F.;Aquino, F. M.;
Ceramica , 2011, DOI: 10.1590/S0366-69132011000300015
Abstract: the ferrites with spinel type structure comprise a group of magnetic materials very well established. however, improvements and innovations are still happening seeking new applications and optimization of preparation techniques. among the materials with spinel structure, the ferrite stand out because they have a broad technological importance in the area of materials, with applications in humidity and oxygen sensors, microwave materials, pigments, magnetic materials and electrical, catalytic hydrogenation, thin films ceramic tiles, among others. in this work spinel-type cufe2o4 and cufecr2o4 were synthesized using gelatin as directing agent with the purpose of producing nanosized homogeneous particles through a simple, fast and affordable method. the ferrites were characterized by thermal analysis, x-ray diffraction, infrared spectroscopy and scanning electron microscopy. the results confirmed the feasibility of the used synthesis route.
Preparation of Acetylated Guar Gum – Unsaturated Polyester Composites & Effect of Water on Their Properties
David DMelo,Anagha Sabnis,M. A. Shenoy,Mukesh Kathalewar
Current Chemistry Letters , 2012,
Abstract: Guar gum has seen extensive use in blends, however, its application as a filler in thermoset composites has as yet not been investigated. The effect of the addition of guar gum and its acetyl derivatives on the kinetics of water diffusion in unsaturated polyester composites was studied. The effect of water on the mechanical properties of the composites was studied with respect to the nature of filler, filler concentration and time of immersion. All the mechanical properties were observed to decrease on exposure to water. Further, it was observed that acetylated guar gum, with a degree of substitution of 0.21, showed the best mechanical properties, surpassing the other filled composites and that of the pure unsaturated polyester. Thus, acetylated guar gum showed promise as eco-friendly filler in composite formulation.
A correlation between Bogue's equations and Taylor's procedure for the evaluation of crystalline phases in special class Portland oilwell cement clinker
Bezerra, U. T.;Martinelli, A. E.;Melo, D. M. A.;Melo, M. A. F.;Lima, F. M.;
Ceramica , 2011, DOI: 10.1590/S0366-69132011000100016
Abstract: the crystalline composition of portland cement clinker is commonly established by bogue's equations, which are based on a series of assumptions that seldom apply to oilwell cements. this is probably due to the presence of additional oxides and phase reconversion upon cooling of the clinker from the calcination temperature. important differences are therefore observed between the numerical values yielded by the mathematical equations and image analysis quantification. in this study, the concentration of crystalline phases in oilwell cement was determined using taylor's procedure, which consists in a system of linear equations corresponding to each one of the four main clinker phases. the results revealed an adequate relationship between this method and phase quantification by optical micrography, especially concerning the contents of aluminate and ferrite.
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