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Search Results: 1 - 10 of 42046 matches for " Luiz Roberto Evangelista "
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A Poisson-Boltzmann Description for the Double-Layer Capacitance of an Electolytic Cell
Roberta Rarumy Ribeiro de Almeida,Luiz Roberto Evangelista,Giovanni Barbero
Physics , 2012,
Abstract: A Poisson-Boltzmann approach is used to determine the double-layer integral and differential capacitances in a finite-length situation for an electrolytic cell. By means of simple analytical calculations, it is shown how these quantities exhibit the bell-like and the camel-like shapes as a function of the applied voltage, when the thickness of the sample or the surface charge are varied. The problem is formulated treating the bulk liquid as a member of a grand canonical ensemble in contact with blocking electrodes. As a consequence, an applied voltage dependent Debye's screening length arises as a fundamental length governing the electrical behavior of the system.
The Kramers-Kronig relations for usual and anomalous Poisson-Nernst-Planck models
Luiz Roberto Evangelista,Ervin Kaminski Lenzi,Giovanni Barbero
Physics , 2013, DOI: 10.1088/0953-8984/25/46/465104
Abstract: The consistency of the frequency response predicted by a class of electrochemical impedance expressions is analytically checked by invoking the Kramers-Kronig (KK) relations. These expressions are obtained in the context of Poisson-Nernst-Planck usual (PNP) or anomalous (PNPA) diffusional models that satisfy Poisson's equation in a finite-length situation. The theoretical results, besides being successful in interpreting experimental data, are also shown to obey the KK relations when these relations are modified accordingly
Comparison of diversity indices applied to macrophyte incidence-based data
Evangelista, Heloísa Beatriz Antoniazi;Thomaz, Sidinei Magela;Evangelista, Luiz Roberto;
Brazilian Archives of Biology and Technology , 2012, DOI: 10.1590/S1516-89132012000200014
Abstract: in this work, a recently proposed diversity index based on patil and taillie parametric diversity measure (or tsallis entropy), sq*, was applied to samples (presence-absence data) of macrophytes from the itaipu reservoir, brazil. this new index was the value of the family of indices sq for a specific evenness of a sample. results demonstrated that the shannon index and species richness showed expressively high correlation with the sq*; however, the evenness had low correlation coefficients with the index sq*, indicating that sq* was particularly sensitive to rarity and species richness. on the other hand, the weak correlations of this index with evenness demonstrated that it was less sensitive to species relative abundances.
Curvas de crescimento de ovinos Bergamácia criados no Distrito Federal
McManus Concepta,Evangelista Cibele,Fernandes Luiz Augusto Costa,Miranda Roberto Meirelles de
Revista Brasileira de Zootecnia , 2003,
Abstract: A análise de um banco de dados de crescimento em ovinos Bergamácia (pesos até dois anos de idade de 1982 a 1996) foi feita usando-se métodos n o-lineares para determinar parametros de três curvas (Brody, Richards e Logística) de crescimento. Os parametros das curvas foram analisados pelo Statistical Analysis System (SAS) usando o procedimento GLM e CORR para determinar fatores que influenciaram os parametros e as correla es entre os parametros e pesos dos animais. O sistema de manejo foi semi-extensivo com os ovinos ao pasto durante o dia e presos à noite para proteger dos predadores. Os fatores fixos incluídos foram ordem do parto, sexo do cordeiro, tipo de nascimento, mês e ano. As médias dos parametros das curvas foram: Richards - A = 50,024, B = 0,647, k = 0,003, M = 17,771 e R2 = 0,838; Brody - A= 52,763, B=0,885, k =0,003, R2= 0,842; Logístico - A=47,894, B=-3,895, k=0,007 e R2= 0,840. O meio ambiente influenciou o crescimento e a reprodu o de ovinos na regi o de Brasília. A correla o negativa entre k e A indica que animais que amadurecem mais cedo têm menos probabilidade de atingir pesos adultos mais altos que animais que amadurecem tardiamente. A curva Logística estimou o peso adulto dos animais com média inferior às das outras curvas. Os pesos atuais est o, contudo, mais bem correlacionados com os estimados pela Logística. N o houve diferen a entre os três tipos de curvas em termos de R2. O quadrado médio do resíduo foi maior para a curva de Richards. A curva recomendada para ajustar dados de crescimento de ovinos da ra a Bergamácia é Logística.
Immittance response of an electrolytic cell in the presence of adsorption, generation, and recombination of ions
Jamile Lorena de Paula,José Adauto da Cruz,Ervin Kaminski Lenzi,Luiz Roberto Evangelista
Physics , 2012,
Abstract: Effects of the adsorption-desorption process on the immittance response of an electrolytic cell are theoretically investigated in the framework of the diffusional Poisson-Nernst-Planck (PNP) continuum model, when the generation and recombination of ions is taken into account. The analysis is carried out by searching solutions for the drift-diffusion equation coupled to the Poisson's equation relating the effective electric field to the net charge density. The effect of different ion mobilities on the immittance, i.e., situations with equal and different diffusion coefficients for positive and negative ions, are considered. A general exact expression for the admittance in the context of the linear approximation is obtained.
Elastic continuum theory: Fully understanding of the twist-bend nematic phases
Giovanni Barbero,Luiz Roberto Evangelista,Michely Patrícia Rosseto,Rafael Soares Zola,Ioannis Lelidis
Physics , 2015, DOI: 10.1103/PhysRevE.92.030501
Abstract: The twist-bend nematic phase, $N_{\rm TB}$, may be viewed as a heliconical molecular arrangement in which the director $\bf n$ precesses uniformly about an extra director field, $\bf t$. It corresponds to a nematic ground state exhibiting nanoscale periodic modulation. To demonstrate the stability of this phase from the elastic point of view, a natural extension of the Frank elastic energy density is proposed. The elastic energy density is built in terms of the elements of symmetry of the new phase in which intervene the components of these director fields together with the usual Cartesian tensors. It is shown that the ground state corresponds to a deformed state for which $K_{22} > K_{33}$. When the elastic free energy is interpreted in analogy with the Landau theory, it is demonstrated the existence of a second order phase transition between the usual and the twist-bend nematic phase, driven by a new elastic parameter playing a role similar to the one of the main dielectric anisotropy of classical nematics and being closely related to the bulk compression modulus representing the pseudo-layers of twist-bend nematic phases. A phase transition and the value of the nanoscale pitch are predicted in accordance to experimental results.
A connection between anomalous Poisson-Nernst-Planck models and equivalent circuits with constant--phase elements
Ervin Kaminski Lenzi,Jamile Lorena de Paula,Fernanda R. G. B. Silva,Luiz Roberto Evangelista
Physics , 2013,
Abstract: A connection between the impedance spectroscopy response of anomalous Poisson-Nernst-Planck (PNPA) diffusional models and of equivalent circuits containing constant phase elements (CPE) is established for a typical electrolytic cell. The analysis is carried out in the limit of low frequency in order to highlight the surface effects and to explore how they can be connected to the presence of CPE in the circuit. It is shown that, depending on the choice of the equivalent circuit, the action of these elements can be the same as the one obtained by using integro-differential boundary conditions to describe anomalous diffusive processes in the framework of PNPA models. The predictions are also compared with an experimental data obtained from an electrolytic solution.
"Imperium in imperio". Il rapporto uomo-natura in Spinoza
Evangelista, Roberto
Laboratorio dell'ISPF , 2010,
Abstract: The relationship between man and nature denotes many problems in Spinoza’s context, where necessity plays an essential role. This essay tries to define the status of the possibility and its relationship to the natural necessity. The man-nature relationship reveals itself as conflictual space, where the human being faces the possibility of death and looks for the possibility of survival. The political action and the constitution of community offer an answer to the uncertainty of human position. Community is not an artificial monster; it is rather the adequate place where the human right and the human power express themselves. Nature and culture are not dissociated, since the society affirms the natural potentia of the human being and that of the multitude.
Che cos'è la cultura? Presenza, crisi e trascendimento in Ernesto de Martino
Roberto Evangelista
S&F_scienzaefilosofia.it , 2010,
Avalia??o físico-química de filés de tilápia (Oreochromis niloticus) submetidos à sanitiza??o
Oliveira, Nelma de Mello Silva;Oliveira, Wilson Roberto Mesquita;Nascimento, Luiz Carlos;Silva, José Mauricio Schneedorf Ferreira da;Vicente, Eduardo;Fiorini, Jo?o Evangelista;Bressan, Maria Cristina;
Ciência e Tecnologia de Alimentos , 2008, DOI: 10.1590/S0101-20612008000100013
Abstract: the present research had as objectives to study the effects of chlorinated water (sodium dichloroisocyanurate - 3 to 3.5 mg.l-1) (t1); chlorinated water associated to ultrasound (t2); ozonated water (3 to 3.5 mg.l-1) (t3); ozonated water associated to ultrasound (t4), and control (t5) on the centesimal composition, fatty acid profile, cholesterol content and peroxide value in "tilápia" fillets. the fillets were treated by immersion in the solutions, at ph 6.0, 5 °c, for 20 minutes. the treatments affected the centesimal composition. sanitizers caused a loss of water and increased the concentration of protein in the fillets, more strongly in t3 (77.16% moisture and 19.73% protein), when compared to t5 (78.60% moisture and 18.71% protein). significant differences were observed for saturated fatty acids (sfa), monounsaturated fatty acids (mufa) and polyunsaturated fatty acids (pufa). sfa presented differences in t3, t4 and t5, with the respective averages of 37, 33.50 and 36.30%. t1 and t2 (34.90 and 34.80%) did not present differences, but were different from t3, t4 and t5 (39.30, 36.30 and 39.10%) for mufa. t3 preserved more fractions of mufa. pufa did not differ in t1 and t2 (23 and 22.50%) and t3, t4 and t5 (18.30, 20.40 and 17.70%) differed from eachother, with t1 presenting the highest averages. there was a marked reduction in the level of cholesterol in t2 (43.94 mg.100 g-1), when compared to t5 (54.77 mg.100 g-1). there was no statistical difference in peroxide level among the treatments.
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