G. Barbero
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View article: Relaxation phenomenon in electrolytic cells limited by Ohmic electrodes
Relaxation phenomenon in electrolytic cells limited by Ohmic electrodes Open
The electric response of an electrolytic cell submitted to an external electric field is investigated. It is assumed that the cell is limited by Ohmic electrodes, in which the conduction current at the electrodes is proportional to the sur…
View article: Influence of Ion Generation–Recombination on Dielectric Relaxation Time in Electrolytes
Influence of Ion Generation–Recombination on Dielectric Relaxation Time in Electrolytes Open
The well-known Poisson–Nernst–Planck model is a classical approach usedto describe ion transport in liquids. Extended versions of this model account for thegeneration–recombination of ions at equilibrium. In this paper, we investigate the …
View article: Electrical conductivity in kerosene-based ferrofluid under DC potential
Electrical conductivity in kerosene-based ferrofluid under DC potential Open
This study investigates the direct current behavior of a kerosene-based ferrofluid. Experimental data reveal linear current–voltage (I–V) characteristics, measured using slab-shaped cells with platinum electrodes. A polarization voltage of…
View article: Influence of the Generation-Recombination Term on the Dielectric Relaxation in an Electrolytic Cell
Influence of the Generation-Recombination Term on the Dielectric Relaxation in an Electrolytic Cell Open
We investigate the influence of the generation-recombination term on dielectric relaxation in an electrolytic cell shaped like a slab, bounded by two parallel blocking electrodes. We show that, in the adiabatic limit, valid when the reacti…
View article: A splay-twist phase stabilized by the interaction between the nematic and torsional fields in nematics
A splay-twist phase stabilized by the interaction between the nematic and torsional fields in nematics Open
The transition from the uniform nematic state to the splay-twist nematic state occurs when the magnitude of the coupling elastic constant, η r , between the nematic and torsional fields exceeds a critical value, η c .
View article: Impedance measurements on kerosene-based ferrofluids
Impedance measurements on kerosene-based ferrofluids Open
We study the impedance behavior of two ferrofluids, of a similar magnetic material, one constituted by spherical nanoparticles and the other constituted by cubes, both suspended in kerosene. The ferrofluid constituted by cubic nanoparticle…
View article: A Brief Review of Fractional Calculus as a Tool for Applications in Physics: Adsorption Phenomena and Electrical Impedance in Complex Fluids
A Brief Review of Fractional Calculus as a Tool for Applications in Physics: Adsorption Phenomena and Electrical Impedance in Complex Fluids Open
Many fundamental physical problems are modeled using differential equations, describing time- and space-dependent variables from conservation laws. Practical problems, such as surface morphology, particle interactions, and memory effects, …
View article: Analytical description of the ionic relaxation in the presence of surface adsorption
Analytical description of the ionic relaxation in the presence of surface adsorption Open
The temporal evolution of the surface electric field in a cell in the presence of ionic adsorption is investigated. The analysis is performed in the framework of the Poisson–Nernst–Planck model, based on the conservation of particles and t…
View article: The Kinetics of Sorption–Desorption Phenomena: Local and Non-Local Kinetic Equations
The Kinetics of Sorption–Desorption Phenomena: Local and Non-Local Kinetic Equations Open
The kinetics of adsorption phenomena are investigated in terms of local and non-local kinetic equations of the Langmuir type. The sample is assumed in the shape of a slab, limited by two homogeneous planar-parallel surfaces, in such a mann…
View article: Anomalous Diffusion and Surface Effects on the Electric Response of Electrolytic Cells
Anomalous Diffusion and Surface Effects on the Electric Response of Electrolytic Cells Open
We propose an anomalous diffusion approach to analyze the electrical impedance response of electrolytic cells using time-fractional derivatives. We establish, in general terms, the conservation laws connected to a modified displacement cur…
View article: Fountain fringe field switching (FFFS) for wide viewing angle LCDs
Fountain fringe field switching (FFFS) for wide viewing angle LCDs Open
To reduce or completely remove the viewing angle dependence of liquid crystal (LC) displays and devices, we have recently introduced a new electrode structure for LC displays. This electrode structure has openings (holes) in the pixel elec…
View article: Ions, adsorption and electric response of a ferrofluid cell
Ions, adsorption and electric response of a ferrofluid cell Open
We show that the electric response of a cell in the shape of a slab containing a ferrofluid (magnetic particles in kerosene) can be interpreted by means of a model based on the adsorption of ions from limiting surfaces.
View article: Nonlinear behavior of the impedance spectrum of a kerosene based ferrofluid
Nonlinear behavior of the impedance spectrum of a kerosene based ferrofluid Open
We investigate the nonlinear behavior of the electric impedance of a kerosene-based ferrofluid (FF) sample subjected to an ac electric voltage of amplitude ranging from 10 mV to 3 V in the frequency range 6.3 mHz, 100 kHz.
View article: A Model for Bias Potential Effects on the Effective Langmuir Adsorption–Desorption Processes
A Model for Bias Potential Effects on the Effective Langmuir Adsorption–Desorption Processes Open
We discuss the foundations of a model based on an extension of the Langmuir approximation for the adsorption–desorption phenomena, in which the phenomenological coefficients depend on the bias potential, in addition to their dependence on …
View article: Free ions in kerosene-based ferrofluid detected by impedance spectroscopy
Free ions in kerosene-based ferrofluid detected by impedance spectroscopy Open
The influence of the free ions on the electric response of cells filled with kerosene-based ferrofluids in the low-frequency region is explored.
View article: Random Energy Barrier Model for AC Electrode Conductivity
Random Energy Barrier Model for AC Electrode Conductivity Open
We investigate the electric response of an electrolytic cell of water and KCl, limited by gold electrodes, to derive information on the role of the electrodes in the spectra of the real and imaginary parts of the electric impedance of the …
View article: Nonlinear curvature elasticity of nematic liquid crystals
Nonlinear curvature elasticity of nematic liquid crystals Open
The nonlinear elastic properties of nematic liquid crystals have acquired new interest with the recent experimental observation of bulk modulated nematic phases which are composed by achiral molecules. We extend the Oseen-Zocher-Frank's el…
View article: Fourth order nematic elasticity and modulated nematic phases: a poor man's approach
Fourth order nematic elasticity and modulated nematic phases: a poor man's approach Open
We propose an extension of Frank-Oseen's elastic energy for bulk nematic liquid crystals which is based on the hypothesis that the fundamental deformations allowed in nematic liquid crystals are splay, twist and bend. The extended elastic …
View article: Nanometric pitch in modulated structures of twist-bend nematic liquid crystals
Nanometric pitch in modulated structures of twist-bend nematic liquid crystals Open
The extended Frank elastic energy density is used to investigate the existence of a stable periodically modulate structure that appears as a ground state exhibiting a twist-bend molecular arrangement. For an unbounded sample, we show that …
View article: Unwinding of the twist-bend nematic structure under an external field
Unwinding of the twist-bend nematic structure under an external field Open
The recently discovered twist-bend nematic phase, $\rm N_{tb}$, is a non-uniform equilibrium nematic phase that presents a spontaneous bend with a precession of the nematic director, $\textbf{n}$, on a conical helix with a tilt angle $θ$ a…
View article: Elastic continuum theory: Towards understanding of the twist-bend nematic phases
Elastic continuum theory: Towards understanding of the twist-bend nematic phases Open
The twist-bend nematic phase, N_{TB}, may be viewed as a heliconical molecular arrangement in which the director n precesses uniformly about an extra director field, t. It corresponds to a nematic ground state exhibiting nanoscale periodic…