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Search Results: 1 - 10 of 490316 matches for " R. S.;Nascimento "
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Compartimenta??o fisiográfica para análise ambiental do potencial erosivo a partir das propriedades da rede de drenagem
Nascimento, Paulo S. R.;Garcia, Gilberto J.;
Engenharia Agrícola , 2005, DOI: 10.1590/S0100-69162005000100026
Abstract: the present work had as objective to divide the sub-basin of the low piracicaba river (sp, brazil) in homogeneous units in order to evaluate the erosion potential aiming to subsidize the environmental management. the importance of this research is due to the intense development of the erosive processes in the area, and its socio-economic importance. the adopted procedure was the analysis of the drainage network and the lineaments obtained from tm/landsat-5 images. the result was the division of the area in four compartments considering potentiality to the erosion: very high; high; medium and low. it was concluded that the studied area is heterogeneous, with regions presenting different intensities of erosive processes and that the adopted methodology was enough to characterize the landscape compartimentation of the erosive potentiality and these can and must be used as inputs for the environmental management under the principles of the sustainable development.
Gauge Invariant Effective Potential for Abelian Maxwell-Chern-Simons Systems
D. Bazeia,J. R. S. Nascimento
Physics , 1996, DOI: 10.1103/PhysRevD.55.1105
Abstract: We investigate the effective potential for Abelian Maxwell--Chern--Simons systems. The calculations follow an alternate approach, recently proposed as a gauge invariant formulation of the effective potential, constructed in terms of a gauge invariant order parameter. We compare the results with another investigation, obtained within a standard route of calculating the effective potential.
Self-Dual Model Coupled to Bosons
M. A. Anacleto,J. R. S. Nascimento,R. F. Ribeiro
Physics , 2000, DOI: 10.1103/PhysRevD.62.067701
Abstract: In this paper we investigated the dynamics, at the quantum level, of the self-dual field minimally coupled to bosons. In this investigation we use the Dirac bracket quantization procedure to quantize the model. Also, the relativistic invariance is tested in connection with the elastic boson-boson scattering amplitudes.
Radiatively Induced Lorentz and CPT Violation in QED at Finite Temperature
J. R. S. Nascimento,R. F. Ribeiro,N. F. Svaiter
Physics , 2000,
Abstract: In this paper we evaluate the induced Lorentz and CPT violating Chern-Simons term in the QED action at finite temperature. We do this using the method of derivative expansion of fermion determinants. Also, we use the imaginary-time formalism to calculate the temperature dependence of the Chern-Simons term
Palladium(0)-catalyzed efficient synthesis of allylic N- and S-benzoheterocycles linked to unsaturated carbohydrate derivatives
Ronaldo Nascimento de Oliveira,Wilson S. do Nascimento,Girliane R. da Silva,Tania Maria S. Silva
Orbital : the Electronic Journal of Chemistry , 2012,
Abstract: An efficient strategy was developed to envisage the synthesis of new N- and S-benzoheterocycles attached to the C-4 position of pseudo-carbohydrates. The reaction was performed with unsaturated carbohydrates and benzoheterocycles as nucleophiles in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium(0) and chelating bidentate ligand dppb. This strategy allowed easy access to benzoheterocyclic sugars in moderate-to-good yields. A preliminary study for antioxidant activities of O-glycosides 2,3-unsaturated was evaluated based on the 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging and 2,2-azinobis 3-ethylbenzothiozoline-6-sulfonic acid (ABTS) radical cation decolorization assay, and showed low-to-moderate activities.
S. M. Nascimento,R. I. J. P. Dutra,S. Numazawa
Holos Environment , 2006,
Abstract: The objective of this study was to characterize waste residues from the lumber industry, their consequences for the environment, and possible alternative uses. A field survey was carried out to quantify the volume of residues, with data collected from a sawmill located in the city of Mojú-Pará. Physical analyses of these residues were conducted in the Laboratory of Technology of Forest Products - LTPF - UFRA to determine their uses. Findings indicated that the industry employs rudimentary logistics; in other words, the production system resulted in low yields and generated a great amount of residues of wood that could be used to fabricate workmanship. = O estudo teve como objetivo caracterizar os resíduos de indústria madeireira, as conseqüências que os mesmos podem causar ao meio ambiente e quais as alternativas de uso. Para tal, foi realizada um levantamento de campo para quantificar o volume de resíduos, com dados coletados a partir de uma serraria localizada no município de Mojú - PA, possibilitando a análise física dos mesmos no Laboratório de Tecnologia de Produtos Florestais -LTPF – UFRA para determina o de seus usos. Verificou-se que a indústria possui uma logística rudimentar, ou seja, seu sistema de produ o apresentou baixo rendimento, gerando grande quantidade de resíduos, sugerindo que os mesmos fossem utilizados para confec o de artefatos.
Modulated phases and devil's staircases in a layered mean-field version of the ANNNI model
E. S. Nascimento,J. P. de Lima,S. R. Salinas
Physics , 2013, DOI: 10.1016/j.physa.2014.04.045
Abstract: We investigate the phase diagram of a spin-$1/2$ Ising model on a cubic lattice, with competing interactions between nearest and next-nearest neighbors along an axial direction, and fully connected spins on the sites of each perpendicular layer. The problem is formulated in terms of a set of noninteracting Ising chains in a position-dependent field. At low temperatures, as in the standard mean-feild version of the Axial-Next-Nearest-Neighbor Ising (ANNNI) model, there are many distinct spatially commensurate phases that spring from a multiphase point of infinitely degenerate ground states. As temperature increases, we confirm the existence of a branching mechanism associated with the onset of higher-order commensurate phases. We check that the ferromagnetic phase undergoes a first-order transition to the modulated phases. Depending on a parameter of competition, the wave number of the striped patterns locks in rational values, giving rise to a devil's staircase. We numerically calculate the Hausdorff dimension $D_{0}$ associated with these fractal structures, and show that $D_{0}$ increases with temperature but seems to reach a limiting value smaller than $D_{0}=1$.
On the Existence of Solutions of a Nonlocal Elliptic Equation with a -Kirchhoff-Type Term
Francisco Julio S. A. Corrêa,Rúbia G. Nascimento
International Journal of Mathematics and Mathematical Sciences , 2008, DOI: 10.1155/2008/364085
Abstract: Questions on the existence of positive solutions for the following class of elliptic problems are studied: ?[(‖‖1,)]1,Δ=(,), in Ω, =0, on Ω, where Ω?? is a bounded smooth domain, ∶Ω×?
Volatile substances from male Anastrepha fraterculus wied. (Diptera: Tephritidae): identification and behavioural activity
Lima, Ivanildo S.;House, Philip E.;Nascimento, Ruth R. do;
Journal of the Brazilian Chemical Society , 2001, DOI: 10.1590/S0103-50532001000200012
Abstract: volatile compounds produced by calling males of anastrepha species have previously been reported from a. ludens and a. suspensa. both species mate in the afternoon, release a similar range of compounds in different proportions, and only differ in the production of monoterpenes. when calling, male a. fraterculus releases two isomers of the sesquiterpene a-farnesene, three lactones (anastrephin, epianastrephin and (e,e)-suspensolide), and two monoterpenes (limonene and (z)-b-ocimene). the dimorphic male salivary glands produce and/or store the same isomers of a-farnesene and suspensolide, and four pyrazines. two of these compounds have been previously reported from male a. ludens and a. suspensa. salivary glands from virgin calling male a. fraterculus showed behavioural activity when bioassayed with virgin mature female flies, but immature females were not attracted.
Compara??o de técnicas de determina??o de ésteres em cacha?a
Nascimento, Eduardo S. P.;Cardoso, Daniel R.;Franco, Douglas W.;
Química Nova , 2009, DOI: 10.1590/S0100-40422009000900016
Abstract: an analytical comparison of three different techniques for quantitative profile of esters in cacha?a is reported. the ministério da agricultura pecuária e abastecimento (mapa) recommends the use of gc/fid or volumetry. despite being laborious and lacking in chemical speciation, the volumetric technique for total ester content shows to be appropriate, reproducible, and accurate for the analysis of cacha?a. however, the gc/fid suggested by mapa, considering only ethyl acetate, shows inaccuracy, underestimating the total ester content by a median factor of 72%, mainly due to the absence of ethyl lactate analysis. on the other hand, the gc/ms technique that comprises the analysis and speciation of nine esters, including ethyl lactate, proved to be reproducible, simple, fast and accurate for the analysis of total ester content in cacha?a. thus, the total ester content results obtained using gc/fid must be considered with precaution.
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