23,120 research outputs found
Electrolytes between dielectric charged surfaces: Simulations and theory
We present a simulation method to study electrolyte solutions in a dielectric
slab geometry using a modified 3D Ewald summation. The method is fast and easy
to implement, allowing us to rapidly resum an infinite series of image charges.
In the weak coupling limit, we also develop a mean-field theory which allows us
to predict the ionic distribution between the dielectric charged plates. The
agreement between both approaches, theoretical and simulational, is very good,
validating both methods. Examples of ionic density profiles in the strong
electrostatic coupling limit are also presented. Finally, we explore the
confinement of charge asymmetric electrolytes between neutral surfaces
Effects of a CPT-even and Lorentz-violating nonminimal coupling on the electron-positron scattering
We propose a new \emph{CPT}-even and Lorentz-violating nonminimal coupling
between fermions and Abelian gauge fields involving the CPT-even tensor
of the standard model extension. We thus
investigate its effects on the cross section of the electron-positron
scattering by analyzing the process .
Such a study was performed for the parity-odd and parity-even nonbirefringent
components of the Lorentz-violating tensor.
Finally, by using experimental data available in the literature, we have
imposed upper bounds as tight as on the magnitude of the
CPT-even and Lorentz-violating parameters while nonminimally coupled.Comment: LaTeX2e, 06 pages, 01 figure
Radiative generation of the CPT-even gauge term of the SME from a dimension-five nonminimal coupling term
In this letter we show for the first time that the usual CPT-even gauge term
of the standard model extension (SME) can be radiatively generated, in a gauge
invariant level, in the context of a modified QED endowed with a dimension-five
nonminimal coupling term recently proposed in the literature. As a consequence,
the existing upper bounds on the coefficients of the tensor can be
used improve the bounds on the magnitude of the nonminimal coupling,
by the factors or The nonminimal coupling
also generates higher-order derivative contributions to the gauge field
effective action quadratic terms.Comment: Revtex style, two columns, 6 pages, revised final version to be
published in the Physics Letters B (2013
Supressão das anomalias de fase e batimentos laterais em espectros de RMN 13C obtidos com a sequência de precessão livre no estado estacionário.
Montagem do genoma de Spathaspora arborariae, uma levedura fermentadora de xilose, para a produção de biocombustÃveis.
O presente trabalho visou montar o genoma de S. arborariae a partir de dados de sequenciamento genômico
Study of vanadium doped ZnO films prepared by dc reactive magnetron sputtering at different substrate temperatures
ZnO films doped with vanadium (ZnO:V) have been prepared by dc reactive magnetron sputtering technique at different substrate temperatures (RT–500 C). The effects of the substrate temperature on ZnO:V films properties have been studied. XRD measurements show that only ZnO polycrystalline structure has been obtained, no V2O5 or VO2 crystal phase can be observed. It has been found that the film prepared at low substrate temperature has a preferred orientation along the (002)
direction. As the substrate temperature is increased, the (002) peak intensity decreases. When the substrate temperature reaches the 500 ºC, the film shows a random orientation. SEM measurements
show a clear formation of the nano-grains in the sample surface when the substrate
temperature is higher than 400 º C. The optical properties of the films have been studied by measuring the specular transmittance. The refractive index has been calculated by fitting the transmittance
spectra using OJL model combined with harmonic oscillator
Effect of the deposition rate on ITO thin films properties prepared by ion beam assisted deposition (IBAD) technique
Indium tin oxide (ITO) thin films have been deposited onto glass substrates at room temperature by ion beam assisted deposition technique at different deposition rates (0.1 -- 0.3 nm/s). The effects of the deposition rate on the structural, optical and electrical properties of the deposited films have been studied. The optical constants of the deposited films were calculated by fitting the transmittance spectra using the semi-quantum model. Considering the application for the electromagnetic wave shielding which needs a high IR reflectance, the optimising deposition rate is 0.2 nm/s. The films prepared at this deposition rate shows a relative high IR reflectance (60%), a good electrical conductivity (5 x 10-3 -cm), and a reasonable transmittance in the visible region (over 80%)
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