Synthesis and characterization of Al 20 3 -YAG composite and Al 20 3-YAG and Al 20 3 with Nb 20 5 additives [Síntese e caracterização do compósito A1 20 3-YAG e do A1 20 3-YAG e A1 20 3 aditivados com Nb 2O s]
Cabral R.F.,Instituto Militar Of Engineering Ime |
Cabral R.F.,Centro Universitario Estadual da Zona Oeste |
Louro L.H.L.,Instituto Militar Of Engineering Ime |
Prado Da Silva M.H.,Instituto Militar Of Engineering Ime |
And 2 more authors.
Ceramica | Year: 2012
The Al 20 3-YAG composite exhibits high corrosion and creep resistance in aggressive environments, which provides quite glimpse attractive applications such as jet engine vanes and as gas turbines. This composite also shows high hardness and wear resistance allowing its use in ballistic armor. In this study, precursor powders of Al 20 3, Y 20 3 and Nb 2O 5 were homogeneously mixed in a planetary ball mill for 4 h, dried in an oven at 120 °C for 48 h, sieved and deagglomerated. The Al 20 3-YAG composite was produced from mixtures of Al 2O 3-YO at 1300 °C for 2 h. Samples of Al 2O 3-YAG, Al 2O 3 -YAG with Nb 2O 5 and Al 2O 3 with Nb 2O 5 were produced. Each powder composition was uniaxially pressed at 70 MPa. Sintering was performed at 1400 and 1450 °C. The powders as received and as processed were characterized for specific surface area and particle size. The sintered materials were characterized by apparent density and porosity by the Archimedes method and evaluated for shrinkage and loss of mass. The obtained results showed that further adjustments are needed in the sintering conditions of Al 20 3-YAG composition with Nb 2O s in order to improve the densification and shrinkage, which were low, 60% and 3%, respectively. The Al 20 3 with Nb 2O 5 addition, on the other hand, presented a satisfactory densification of 96% and shrinkage around 15%.
Rodrigues G.C.,Instituto Militar Of Engineering Ime |
Aguiar A.P.,Instituto Militar Of Engineering Ime |
da Silva Goncalves Vianez Jr. J.L.,Federal University of Rio de Janeiro |
Macrae A.,Federal University of Rio de Janeiro |
And 2 more authors.
Current Enzyme Inhibition | Year: 2010
Chagas disease, caused by Trypanosoma cruzi, is one of the neglected parasitic tropical diseases affecting thirteen million people annually. At present, there are only two compounds used in the clinical treatment to this disease and they were introduced in the 1960s and 1970s. Nifurtimox and Benznidazole have limited effectiveness and serious side effects. New strategies and targets for an effective chemotherapy for American trypanosomiasis need to be developed. Within this framework, the peptidases have aroused great interest as a chemotherapeutic target against Chagas disease. This is because some T. cruzi peptidases have been implicated, among other processes, in host-parasite interactions and parasitic survival in their hosts like cruzipain (cysteine peptidase) and prolyl oligopeptidase (serine peptidase). Besides, some of these peptidases are expressed in all life cycle stages of the parasite and it is essential for replication of the intracellular forms. The inhibition of these enzymes has shown high anti-T. cruzi activity in vitro and in vivo. In this review, we describe some peptidase inhibitors that have potential in the fight against T. cruzi. Emphasis is given to cruzipain inhibitors and the inhibition mechanism proposed for some them. Among these inhibitors are peptidyl irreversible (halomethyl ketone, diazomethane ketones and vinyl sulfones derivatives) and reversible (aryl ureas and oxadiazoles derivatives) inhibitors, besides non-peptidyl inhibitors (thiosemicarbazones, triazole, triazine nitriles and vinyl sulfones derivatives). Some serine peptidase inhibitors are also described (tic-based peptides, prolylprolylisoxazoles and prolylprolylisoxazolines). Other peptidases, including the metallo-, aspartic and threonine (proteosome) peptidases are discussed and along with blocking cruzipain are targets for future therapeutic strategies. © 2010 Bentham Science Publishers Ltd.
Hermano C.L.,Federal University of Campina Grande |
Lima A.M.N.,Federal University of Campina Grande |
Almeida L.A.L.,Federal University of ABC |
Ferreira C.L.,Instituto Militar Of Engineering Ime |
Neff H.,Federal University of Campina Grande
Conference Record - IEEE Instrumentation and Measurement Technology Conference | Year: 2014
The pronounced variation of the optical reflectance R of nanometer thin VO2 films with temperature T at the phase transition recently has triggered interest in the development of compact thermo-optical sensors that utilize optical fiber technology. Its immunity against electromagnetic interference effects makes this approach suited for an optical detection of local areas with increased temperature, i.e. so called hot spots, inside of high power transformers. Optical reflectance of thin VO2-films as function of T throughout the hysteretic phase transition is reported in this work. A modified version of the Preisach hysteresis model is utilized, and combined with experimental optical data. Suited VO2 film thickness values and wavelengths range for optimum sensor operation can be extracted. The achievable temperature range, as confirmed by experimental observations, is consistent with requirements that apply for power transformers of the first group, according to NBR 5416 (ABNT). © 2014 IEEE.
Vermelho A.B.,Federal University of Rio de Janeiro |
Nogueira de Melo A.C.,Federal University of Rio de Janeiro |
Soares R.A.,Federal University of Rio de Janeiro |
Alviano D.S.,Federal University of Rio de Janeiro |
And 9 more authors.
Open Parasitology Journal | Year: 2010
Peptidases are a group of enzymes which have a catalytic function that is to hydrolyze peptide bonds of proteins. The enzymes that hydrolyze peptide bonds at the amino- or carboxy- terminus are classified as exopeptidases, and those that cleave peptide bonds inside the polypeptide are endopeptidases. Endopeptidases, such as cysteine-, metalo-, serine-and threonine peptidases as well as some exopeptidases, have been characterized in Trypanosoma cruzi. Understanding the pathogenesis of T. cruzi requires the identification of functional properties of those peptidases, as they are implied in virulence, are important for host-parasite interactions and are critical for successful survival in their hosts. Here we examine the main T. cruzi peptidases, focusing on their biological roles, especially concerning the parasite-mammalian host relations. © Vermelho et al.
Rangel I.R.,Federal University of Fluminense |
Rangel I.R.,Instituto Militar Of Engineering Ime |
Thompson R.L.,Federal University of Fluminense |
Pereira R.G.,Federal University of Fluminense |
De Abreu F.L.B.,National Institute of Metrology of Brazil
Journal of the Brazilian Society of Mechanical Sciences and Engineering | Year: 2012
Enhanced oil recovery methods are becoming an important source of oil production of wells that have already been explored and, by these methods, of increase of the total volume of oil extracted. An important example is the injection of polymeric solutions after the injected water has reached the breakthrough point. In the present work an experimental apparatus was built in order to test the ability of enhanced oil recovery of polymeric solutions, composed by Xanthan Gum (XG) dissolved in distilled water. This apparatus consists of an idealized porous media made with small spheres inserted in a cylindrical cell and then filled with oil with the same viscosity as the petroleum found in Campos Basin (Rio de Janeiro, Brazil). As displacing fluid, we tested polymeric solutions of different concentrations of Xanthan Gum and these non-Newtonian fluids were characterized using a rotational rheometer. The resulting characterization has shown that increasing the concentration, not only the level of viscosity, but also the elasticity of the fluid increases. The shear-thinning behavior of the solution can be well captured by a power-law model. For higher concentrations the shear-thinning feature of the Xanthan Gum solution is more pronounced. We conducted an experimental procedure to mimic enhanced oil recovery process by first injecting water until the breakthrough point. Increasing the polymer concentration, the extra amount of oil recovered also increase. Theoretical and heuristic analyses show that in the shear dominated regions, the Xanthan Gum polymeric solutions do not increase pore efficiency, but increase sweep efficiency, while the extensional character of the polymeric solution seems to indicate that in extensional dominated regions the polymeric solutions play an important role on the oil recovery efficiency from both perspectives: pore and sweep efficiencies. Copyright © 2012 by ABCM.
De Moraes I.G.,Federal University of Minas Gerais |
Silva A.O.,Federal University of Minas Gerais |
Martinez M.A.G.,Federal University of Minas Gerais |
Giraldi M.T.M.R.,Instituto Militar Of Engineering Ime
Progress in Electromagnetics Research Symposium | Year: 2015
Nonorthogonal coupled mode theory is used to analyze the impact of iron nano-inclusion in the TE mode coupling between two integrated optical waveguides structures. In the first case, the nano-inclusion fractions are included in an identical manner in both waveguides, and in the second the nano-inclusion are added only in one of the waveguides. The structures beating lengths strongly depends on the inclusion filling factor and the thickness of the cladding layer. They reduce with increasing inclusion-filling factors, reaching a 70% and a 56% reduction with respect to the lossless case, for the identical and non-identical cases, respectively. Cladding thickness increases the beating length reducing the structure total power as filling factor increases, for the identical case, and depicting a inflection point for the non-identical case where the total power increases.
De Mendonca R.R.,Federal University of Rio de Janeiro |
Da Cruz S.M.S.,Federal Rural University of Rio de Janeiro |
De La Cerda J.F.S.M.,Instituto Militar Of Engineering Ime |
Cavalcanti M.C.,Instituto Militar Of Engineering Ime |
And 2 more authors.
Proceedings of the 5th Workshop on Semantic Web Information Management, SWIM 2013 | Year: 2013
The Web of Data has emerged as a means to expose, share, reuse, and connect information on the Web identified by URIs using RDF as a data model, following Linked Data Principles. However, the reuse of third party data can be compromised without proper data quality assessments. In this context, important questions emerge: how can one trust on published data and links? Which manipulation, modification and integration operations have been applied to the data before its publication? What is the nature of comparisons or transformations applied to data during the interlinking process? In this scenario, provenance becomes a fundamental element. In this paper, we describe an approach for generating and capturing Linked Open Provenance (LOP) to support data quality and trustworthiness assessments, which covers preparation and format transformation of traditional data sources, up to dataset publication and interlinking. The proposed architecture takes advantage of provenance agents, orchestrated by an ETL workflow approach, to collect provenance at any specified level and also link it with its corresponding data. We also describe a real use case scenario where the architecture was implemented to evaluate the proposal.
Loureiro F.A.M.,Federal University of Rio de Janeiro |
De Marins E.S.,Federal University of Rio de Janeiro |
Dos Anjos G.D.C.,Federal University of Rio de Janeiro |
Rocco A.M.,Federal University of Rio de Janeiro |
Pereira R.P.,Instituto Militar Of Engineering Ime
Polimeros | Year: 2014
The optimization of fuel cell materials, particularly polymer membranes, for PEMFC has driven the development of methods and alternatives to achieve systems with more adequate properties to this application. The sulfonation of poly(styrene-co-allyl alcohol) (PSAA), using sulfonating agent:styrene ratios of 2:1, 1:1, 1:2, 1:4, 1:6, 1:8 and 1:10, was previously performed to obtain proton conductive polymer membranes. Most of those membranes exhibited solubility in water with increasing temperature and showed conductivity of approximately 10-5 S cm-1. In order to optimize the PSAA properties, especially decreasing its solubility, semi-IPN (SIPN) membranes are proposed in the present study. These membranes were obtained from the diglycidyl ether of bisphenol A (DGEBA), curing reactions in presence of DDS (4,4-diaminodiphenyl sulfone) and PSAA. Different DGEBA/PSAA weight ratios were employed, varying the PSAA concentration between 9 and 50% and keeping the mass ratio of DGEBA:DDS as 1:1. The samples were characterized by FTIR and by electrochemical impedance spectroscopy. Unperturbed bands of PSAA were observed in the FTIR spectra of membranes, suggesting that chemical integrity of the polymer is maintained during the synthesis. In particular, bands involving C-C stretching (1450 cm-1), C=C (aromatic, ∼ 3030 cm-1) and C-H (2818 and 2928 cm-1) were observed, unchanged after the synthesis. The disappearance or reduction of the intensity of the band at 916 cm-1, attributed to the DGEBA epoxy ring, is evidenced for all samples, indicating the epoxy ring opening and the DGEBA crosslinking. Conductivity of H3PO4 doped membranes increases with temperature, reaching 10-4 S cm-1.
Poubel W.M.,Federal University of Rio de Janeiro |
Silva C.E.F.C.,Engineering Simulation and Scientific Software ESSS |
Souza E.N.,Instituto Militar Of Engineering Ime |
Pinto J.C.,Federal University of Rio de Janeiro
Macromolecular Reaction Engineering | Year: 2014
This work analyzes the possible influence of the inevitable temperature and concentration fluctuations that take place inside typical stirred tank heterogeneous polymerization reactors on the evolution of kinetic variables. Preliminary analyses regarding the characteristic time constants for heat and mass transfer inside polymer particles that are suspended in a continuous phase are performed in order to evaluate how fast particles respond to perturbations along a dynamic trajectory inside the reactor. It is concluded that particles of typical heterogeneous systems can respond almost immediately to operation changes. For this reason, simulations are performed to evaluate the influence of the varying temperature and concentration fields on the evolution of kinetic variables. It is concluded that the effects caused by the inevitable fluctuations of temperature and concentration inside the vessel can be neglected in usual conditions of reaction of heterogeneous polymerization systems. The evolution of kinetic variables is regarded in light of possible impacts of inevitable temperature and concentration fluctuations inside typical stirred tank heterogeneous polymerization. Elaborations of responding time constants of particles on perturbations inside the reactor are performed. Simulations disclose the effects of varying temperature and concentration fields inside the vessel. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.