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Search Results: 1 - 10 of 597 matches for " Sabino; "
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Fabrication and characterization of gold ultra and microelectrodes
Menolasina,Sabino;
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2004,
Abstract: gold disk ultramicroelectrodes of 10 μm and microelectrodes of 60 μm diameter were fabricated using gold wires. these ultra and microelectrodes were characterized by electrochemical measurements and using scanning electron microscopy (sem) for determining the real shape of the surface, and obtaining information about the quality of the seal at the electrode material-insulating material interface.
Electrochemical study of the underpotential deposition of PB on gold ultramicroelectrodes
Menolasina,Sabino;
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2004,
Abstract: gold disc electrodes of 10 mm diameter were fabricated using gold wires. the underpotential deposition (upd) of lead on gold ultramicrodisks was investigated by cyclic voltammetry and chronoamperometry, using dilute solutions of pb2+ in 0.2 mol dm-3 hclo4. the upd of pb(0) occurs between 0 v and -0.4 v vs. sce. the process of underpotential deposition is controlled by diffusion. the results of voltammetry experiments show that a monolayer of lead is formed in the upd region. the results of the chronoamperometry experiments demostrate that the formation of a complete monolayer can be related to the appearence of a nonmonotonic current-time transient.
Electrochemical studies of Fe(CN)6(4-)/Fe(CN)6(3-) on gold ultramicroelectrodes varying the concentrations of KF as supporting electrolyte
Menolasina,Sabino;
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2005,
Abstract: gold disk ultramicroelectrodes of 10 mm diameter were fabricated using gold wires. these ultramicroelectrodes were characterized by electrochemical measurements and scanning electron microscopy (sem). electrochemical behavior of the hexacyano ferrate couple using gold ultramicroelectrodes (10 mm diameter) was investigated in a range of different concentrations of kf as supporting electrolyte. the steady state response at a gold ultramicrodisc at different concentrations of hexacyanoferrate couple with high concentrations of electrolyte was utilised to determine the diffusion coefficients of both electroactive species. voltammetric experiments shown, that the oxidation and reduction of this couple is affected by the concentration of the supporting electrolyte. theoretical tafel plots were calculated considering double layer effects and comparisons with the experimental results indicated that determination of the heterogeneous rate constants for the free (unpaired) anions species seems to be imposible. even at lower concentrations and after correction for double layer effects, the reaction is still dominated by ion pair effects.
Application of Different Methods of Surface Analysis for the Early Diagnosis of Art-Stone (Calcarenite) Deterioration
Sabino Bufo
Karaelmas Science and Engineering Journal , 2011, DOI: http://dx.doi.org/10.7212/zkufbd.v1i2.53
Abstract: The deterioration process of historical building is progressive and irreversible, and the timing and mode of impact are different depending on the characteristics of building materials used, local microclimate, air pollution, presence of specific flora and fauna. The surface structural characterisation of building materials is mandatory in preventing and eventually recovering degradation effects. Ideally, the analysis of structural stones should be complete, efficient, rapid, and non destructive when dealing with a precious or unique construction.For this purpose a building sample (ca. 1m3) was constructed by using calcarenite stones (33x15cm), collected from a local quarry, and placed between the archaeological site of Lavello, a little town located in the Basilicata Region (Italy), and the industrial area surrounding this town.In this case study in progress on the degradation of stone materials, we set as an objective the characterization of the state of conservation of stone surfaces.The intact calcarenite stone was characterised by using different methods of surface analysis (XRD, XPS, SEM), and exposed to outdoor conditions. The analyses of the stone material were repeated after three and six months to early evaluate the progression of alterations and the forward modifications of calcarenite structure. Results obtained by using all the applied surface analysis methods were compared. Climatic parameters (temperature, light irradiation, wind intensity, humidity), and air pollutants (SO2, CO, NO2, NO, O3, and heavy metals) were determined. Biological attacks on the surface of calcarenite stones were also investigated.After only three months of the stone sample exposures, the adopted analytical methods were able to provide a series of data, which as in the arrangement of a simple jigsaw puzzle, allowed the assessment of the incipient modification of the stone surfaces confirmed by observations performed on six months replicates, given that climatic conditions and air pollution undermined the structure and the compactness of stones favouring the biological colonization especially in the South–East direction of prevailing winds.
Electrochemical studies of Fe(CN)6(4-)/Fe(CN)6(3-) on gold ultramicroelectrodes varying the concentrations of KF as supporting electrolyte
Sabino Menolasina
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2005,
Abstract: Gold disk ultramicroelectrodes of 10 mum diameter were fabricated using gold wires. These ultramicroelectrodes were characterized by electrochemical measurements and scanning electron microscopy (SEM). Electrochemical behavior of the hexacyano ferrate couple using gold ultramicroelectrodes (10 mum diameter) was investigated in a range of different concentrations of KF as supporting electrolyte. The steady state response at a gold ultramicrodisc at different concentrations of hexacyanoferrate couple with high concentrations of electrolyte was utilised to determine the diffusion coefficients of both electroactive species. Voltammetric experiments shown, that the oxidation and reduction of this couple is affected by the concentration of the supporting electrolyte. Theoretical Tafel plots were calculated considering double layer effects and comparisons with the experimental results indicated that determination of the heterogeneous rate constants for the free (unpaired) anions species seems to be imposible. Even at lower concentrations and after correction for double layer effects, the reaction is still dominated by ion pair effects. Ultramicroelectrodos de oro de 10 mym de diámetro fueron fabricados utilizando alambres de oro. Estos ultramicroelectrodos fueron caracterizados electroquimicamente y utilizando microscopía de barrido electrónico para determinar la forma real de la superficie y obtener información acerca de la calidad del sello entre la interface del metal y el material aislante utilidado en la construcción del electrodo. El comportamiento electroquímico de la pareja redox Fe(CN)6(4-)/Fe(CN)6(3-) fue investigado a diferentes concentraciones del electrolito de soporte KF. Los experimentos realizados por Voltamperometría mostraron que la oxidación y reducción de estas especies son afectadas por la concentración del electrolito de soporte. La velocidad de transferencia electrónica es favorecida al aumentar la concentración del electrolito de soporte. Cálculos teóricos de curvas Tafel tomando en cuenta los efectos de la doble capa fueron realizados y comparados con los resultados experimentales. Estos estudios mostraron que no se puede determinar las constantes de velocidad heterogénea para las especies iónicas no apareadas, debida a que aún a concentraciones muy bajas del electrolito de soporte, la reacción sigue siendo controlada por efectos de par iónico.
Fabrication and characterization of gold ultra and microelectrodes
Sabino Menolasina
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia , 2004,
Abstract: Microelectrodos de oro de 10 y 60 μm de diámetro fueron fabricados utilizando alambres de oro. Estos microelectrodos fueron caracterizados electroquímicamente y utilizando microscopía de barrido electrónico para determinar la forma real de la superficie y obtener información acerca de la calidad del sello entre la interfase del metal y el material aislante utilizado en la construcción del electrodo. Gold disk ultramicroelectrodes of 10 μm and microelectrodes of 60 μm diameter were fabricated using gold wires. These ultra and microelectrodes were characterized by electrochemical measurements and using scanning electron microscopy (SEM) for determining the real shape of the surface, and obtaining information about the quality of the seal at the electrode material-insulating material interface.
Relativistic Cosmology: from super--horizon to small scales
Sabino Matarrese
Physics , 1996,
Abstract: The general relativistic non--linear dynamics of a self--gravitating collisionless fluid with vanishing vorticity is studied in synchronous and comoving -- i.e. {\em Lagrangian} -- coordinates. Writing the equations in terms of the metric tensor of the spatial sections orthogonal to the fluid flow allows an unambiguous expansion in inverse powers of the speed of light. The Newtonian and post--Newtonian approximations are derived in Lagrangian form; the non--linear evolution of the system on super--horizon scales, leading to the so--called ``silent universe", is also briefly discussed. A general formula for the gravitational waves generated by the non--linear evolution of cosmological perturbations is given: a stochastic gravitational--wave background is shown to be produced by non--linear cosmic structures, with present--day closure density $\Omega_{gw} \sim 10^{-5}$ -- $10^{-6}$ on the scale of 1 -- 10 Mpc.
Non--Linear Evolution of Cosmological Perturbations
Sabino Matarrese
Physics , 1996, DOI: 10.1007/BFb0102584
Abstract: In these lecture notes I review the theory of the non--linear evolution of cosmological perturbations in a self--gravitating collisionless medium, with vanishing vorticity. The problem is first analyzed in the context of the Newtonian approximation, where the basic properties of the Zel'dovich, frozen--flow and adhesion algorithms are introduced. An exact general relativistic formalism is then presented and it is shown how the Newtonian limit, both in Lagrangian and Eulerian coordinates, can be recovered. A general discussion on the possible role of possible relativistic effects in the cosmological structure formation context is finally given.
Measurements of properties of the Higgs-like Particle at 125 GeV by the CMS collaboration
Sabino Meola
Physics , 2013,
Abstract: CMS results on the measurement of properties of the Higgs-like particle discovered last summer with a mass near 126 GeV are presented. The results are based on a data samples corresponding to an integrated luminosity of up to 5.1 fb-1 at 7 TeV and up to 19.6 fb-1 at 8 TeV in proton-proton collisions at the LHC. Five decay modes are studied: gamma-gamma, ZZ, WW, tau-tau and bb. The event yields obtained by different analyses targeting specific decay modes and production mechanisms are consistent with those expected for the Standard Model (SM) Higgs boson. The mass of the new boson is measured to be 125.7 +- 0.4 GeV. The best-fit signal strength for all channels combined, expressed in units of the SM Higgs boson cross section, is 0.80 +- 0.14 at the measured mass. A discussion on the consistency of the couplings and the spin-parity properties of the observed boson with those predicted for the SM Higgs boson is presented, updated with the most recent results. No significant deviations are found.
Implementing Quasi-Monte Carlo Simulations with Linear Transformations
Piergiacomo Sabino
Mathematics , 2007,
Abstract: Pricing exotic multi-asset path-dependent options requires extensive Monte Carlo simulations. In the recent years the interest to the Quasi-monte Carlo technique has been renewed and several results have been proposed in order to improve its efficiency with the notion of effective dimension. To this aim, Imai and Tan introduced a general variance reduction technique in order to minimize the nominal dimension of the Monte Carlo method. Taking into account these advantages, we investigate this approach in detail in order to make it faster from the computational point of view. Indeed, we realize the linear transformation decomposition relying on a fast ad hoc QR decomposition that considerably reduces the computational burden. This setting makes the linear transformation method even more convenient from the computational point of view. We implement a high-dimensional (2500) Quasi-Monte Carlo simulation combined with the linear transformation in order to price Asian basket options with same set of parameters published by Imai and Tan. For the simulation of the high-dimensional random sample, we use a 50-dimensional scrambled Sobol sequence for the first 50 components, determined by the linear transformation method, and pad the remaining ones out by the Latin Hypercube Sampling. The aim of this numerical setting is to investigate the accuracy of the estimation by giving a higher convergence rate only to those components selected by the linear transformation technique. We launch our simulation experiment also using the standard Cholesky and the principal component decomposition methods with pseudo-random and Latin Hypercube sampling generators. Finally, we compare our results and computational times, with those presented in Imai and Tan.
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