Journal of Physics B: Atomic, Molecular and Optical Physics, 2016
In this work we examine a nonlinear version of the Jaynes-Cummings model for two identical two-le... more In this work we examine a nonlinear version of the Jaynes-Cummings model for two identical two-level atoms allowing for Ising-like and dipole-dipole interplays between them. The model is said to be nonlinear in the sense that it can incorporate both a general intensity-dependent interaction between the atomic system and the cavity field and/or the presence of a nonlinear medium inside the cavity. As an example, we consider a particular type of atom-field coupling based upon the so-called Buck-Sukumar model and a lossless Kerr-like cavity. We describe the possible effects of such features on the evolution of some quantities of current interest, such as atomic excitation, purity, concurrence, the entropy of the field and the evolution of the latter in phase space.
Camellia sinensis (Green Tea) has been reported to have numerous health benefits. The present stu... more Camellia sinensis (Green Tea) has been reported to have numerous health benefits. The present study investigated the lipid-lowering effect and the antioxidant activity of the leaf of Camellia sinensis (CS). Palm oil (PO) and groundnut oil (GO) (ratio 2:1; 8 mL/kg) were administered to Sprague-Dawley rats orally for 5 wk to induce hyperlipidemia. Rats, which showed high plasma levels of total cholesterol (TC), triglyceride (TG) and low-density lipoprotein (LDL-C) were selected for the study. Rats in the treatment groups received CS (250 and 500 mg/kg) while the control groups received distilled water and atorvastatin (10 mg/kg). All animals were treated for 7 wk and blood samples were collected after 10 h fast. Antioxidant activity was evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging and ferric-reducing antioxidant power (FRAP) assays. The extract significantly (p ≤ 0.05) attenuated the elevated plasma TC, TG and LDL-cholesterol, while the plasma level of HDL-cholesterol was significantly (p ≤ 0.05) increased. The atherogenic index and plasma level of malondialdehyde (MDA) was also attenuated by the extract. The extract showed effective antioxidant properties by its ability to scavenge free radical of DPPH and conversion of Fe 3+ to Fe 2+ in the FRAP assay. Direct correlation was observed between DPPH and FRAP. Similarly, there were positive correlations between MDA and lipid profiles except HDL-cholesterol which showed a negative correlation. This study suggests that Camellia sinensis may be effective in lowering blood lipid level through the regulation of cholesterol and inhibition of lipid peroxidation.
Abstract The energy transfer between vibrational and translational degrees of freedom during an i... more Abstract The energy transfer between vibrational and translational degrees of freedom during an inelastic collision between two molecules induces quantum squeezing in the vibrational molecular coordinate under very diverse circumstances. In this chapter, we present the relevant calculation for the very simple case of an atom–diatomic collinear transition, the Landau–Teller model. Both the uncertainty of the vibrational coordinate and the Husimi function show clear evidence of quantum squeezing. Our model treats the relative translation of the colliding species as a classical variable. The vibrational motion of the diatomic molecule is treated quantum mechanically in terms of the evolution operator and coherent states. The corresponding classical and quantum equations of motion are coupled. We first consider the squeezing of a coherent vibrational state where we include the dynamic evolution of the Husimi function. The second case corresponds to an initial thermal distribution of vibrational states where we plot the position uncertainty for the squeezed vibrational state.
A harmonic oscillator may display a nonlinear behavior when forced by an inhomogeneous field. We ... more A harmonic oscillator may display a nonlinear behavior when forced by an inhomogeneous field. We calculate the response of harmonic molecules adsorbed on a surface to a monochromatic electric field employing algebraic methods. The field inhomogeneity, due to image effects, produces harmonics which we evaluate non-perturbatively as a function of the intensity and frequency of the field and the distance
We study the evolution of coherent and Schröautdinger cat states in radio-frequency traps, which ... more We study the evolution of coherent and Schröautdinger cat states in radio-frequency traps, which were used to bound Hg+ ions. The quantum confinement is determined by evaluating the expectation values and dispersions of the position and momentum operators, together with the probability densities in coordinate and momenta representations. Also the Wigner functions associated to this nonstationary quantum system, a parametric
We extend a formalism for the calculation of the surface-induced infrared anisotropy spectra of c... more We extend a formalism for the calculation of the surface-induced infrared anisotropy spectra of cubic polar crystals, in order to incorporate surface relaxation, reconstruction, and in general, surface modifications to the dynamic matrix. We calculate the reflectance anisotropy of a model (110) GaAs surface. The spectra have a rich structure which can be related to critical points of the phonon dispersion relation, and to coupling to surface states and surface resonances. The results display a very large sensitivity to the surface parameters, indicating that the surface induced anisotropy can be employed as an optical surface probe in the far IR.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2012
The Jaynes-Cummings Hamiltonian with deformed operators of the field is considered; as a particul... more The Jaynes-Cummings Hamiltonian with deformed operators of the field is considered; as a particular case the Kerr-like medium is obtained via an appropriate deformation function. We find that, for an appropriate choice of the parameter of the deformation function, states of the uncoupled basis with a selected fixed number of quanta are in resonance, providing a maximum probability of transition of the atom for these states. Under this condition one may find an appropriate value of the coupling constant such that complete revivals are obtained.
Using the Optical Stochastic Bloch equations (OSBE), and considering a two-level molecular system... more Using the Optical Stochastic Bloch equations (OSBE), and considering a two-level molecular system interacting with a thermal reservoir (modeled as an Ornstein–Uhlenbeck process) in four-wave mixing spectroscopy, we derive analytical expressions for the nonlinear optical properties (absorptive and dispersive processes). Here, we have widened the previous formalism [(J.L. Paz et al., Phys. Lett. A 226 (1997) 365)] to consider the
Journal of Physics B Atomic Molecular and Optical Physics
The Jaynes–Cummings Hamiltonian with deformed operators of the field is considered; as a particul... more The Jaynes–Cummings Hamiltonian with deformed operators of the field is considered; as a particular case the Kerr-like medium is obtained via an appropriate deformation function. We find that, for an appropriate choice of the parameter of the deformation function, states of the uncoupled basis with a selected fixed number of quanta are in resonance, providing a maximum probability of transition of the atom for these states. Under this condition one may find an appropriate value of the coupling constant such that complete revivals are obtained.
ABSTRACT We consider the effect of a time-dependent perturbation on an anharmonic oscillator. By ... more ABSTRACT We consider the effect of a time-dependent perturbation on an anharmonic oscillator. By expressing the anharmonic oscillator in terms of deformed ladder operators, we obtain the energy spectrum of the unperturbed problem in terms of the quanta of the number operator and an anharmonicity parameter. The combined presence of quadratic terms in the unperturbed Hamiltonian and of the time-dependent perturbation does not lead to a closed algebra and an exact solution. Introducing the mean field in the unperturbed term allows us to obtain a closed algebra with a time-dependent frequency in the unperturbed term. Through factorization of the corresponding evolution operator, the dynamical problem is reduced to a self-consistent system of first-order differential equations. We can now examine this system for transition probabilities, expectation values, phase-space trajectories, and criteria for chaotic behavior in the case of a dipole pulse perturbation.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2016
In this work we examine a nonlinear version of the Jaynes-Cummings model for two identical two-le... more In this work we examine a nonlinear version of the Jaynes-Cummings model for two identical two-level atoms allowing for Ising-like and dipole-dipole interplays between them. The model is said to be nonlinear in the sense that it can incorporate both a general intensity-dependent interaction between the atomic system and the cavity field and/or the presence of a nonlinear medium inside the cavity. As an example, we consider a particular type of atom-field coupling based upon the so-called Buck-Sukumar model and a lossless Kerr-like cavity. We describe the possible effects of such features on the evolution of some quantities of current interest, such as atomic excitation, purity, concurrence, the entropy of the field and the evolution of the latter in phase space.
Camellia sinensis (Green Tea) has been reported to have numerous health benefits. The present stu... more Camellia sinensis (Green Tea) has been reported to have numerous health benefits. The present study investigated the lipid-lowering effect and the antioxidant activity of the leaf of Camellia sinensis (CS). Palm oil (PO) and groundnut oil (GO) (ratio 2:1; 8 mL/kg) were administered to Sprague-Dawley rats orally for 5 wk to induce hyperlipidemia. Rats, which showed high plasma levels of total cholesterol (TC), triglyceride (TG) and low-density lipoprotein (LDL-C) were selected for the study. Rats in the treatment groups received CS (250 and 500 mg/kg) while the control groups received distilled water and atorvastatin (10 mg/kg). All animals were treated for 7 wk and blood samples were collected after 10 h fast. Antioxidant activity was evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging and ferric-reducing antioxidant power (FRAP) assays. The extract significantly (p ≤ 0.05) attenuated the elevated plasma TC, TG and LDL-cholesterol, while the plasma level of HDL-cholesterol was significantly (p ≤ 0.05) increased. The atherogenic index and plasma level of malondialdehyde (MDA) was also attenuated by the extract. The extract showed effective antioxidant properties by its ability to scavenge free radical of DPPH and conversion of Fe 3+ to Fe 2+ in the FRAP assay. Direct correlation was observed between DPPH and FRAP. Similarly, there were positive correlations between MDA and lipid profiles except HDL-cholesterol which showed a negative correlation. This study suggests that Camellia sinensis may be effective in lowering blood lipid level through the regulation of cholesterol and inhibition of lipid peroxidation.
Abstract The energy transfer between vibrational and translational degrees of freedom during an i... more Abstract The energy transfer between vibrational and translational degrees of freedom during an inelastic collision between two molecules induces quantum squeezing in the vibrational molecular coordinate under very diverse circumstances. In this chapter, we present the relevant calculation for the very simple case of an atom–diatomic collinear transition, the Landau–Teller model. Both the uncertainty of the vibrational coordinate and the Husimi function show clear evidence of quantum squeezing. Our model treats the relative translation of the colliding species as a classical variable. The vibrational motion of the diatomic molecule is treated quantum mechanically in terms of the evolution operator and coherent states. The corresponding classical and quantum equations of motion are coupled. We first consider the squeezing of a coherent vibrational state where we include the dynamic evolution of the Husimi function. The second case corresponds to an initial thermal distribution of vibrational states where we plot the position uncertainty for the squeezed vibrational state.
A harmonic oscillator may display a nonlinear behavior when forced by an inhomogeneous field. We ... more A harmonic oscillator may display a nonlinear behavior when forced by an inhomogeneous field. We calculate the response of harmonic molecules adsorbed on a surface to a monochromatic electric field employing algebraic methods. The field inhomogeneity, due to image effects, produces harmonics which we evaluate non-perturbatively as a function of the intensity and frequency of the field and the distance
We study the evolution of coherent and Schröautdinger cat states in radio-frequency traps, which ... more We study the evolution of coherent and Schröautdinger cat states in radio-frequency traps, which were used to bound Hg+ ions. The quantum confinement is determined by evaluating the expectation values and dispersions of the position and momentum operators, together with the probability densities in coordinate and momenta representations. Also the Wigner functions associated to this nonstationary quantum system, a parametric
We extend a formalism for the calculation of the surface-induced infrared anisotropy spectra of c... more We extend a formalism for the calculation of the surface-induced infrared anisotropy spectra of cubic polar crystals, in order to incorporate surface relaxation, reconstruction, and in general, surface modifications to the dynamic matrix. We calculate the reflectance anisotropy of a model (110) GaAs surface. The spectra have a rich structure which can be related to critical points of the phonon dispersion relation, and to coupling to surface states and surface resonances. The results display a very large sensitivity to the surface parameters, indicating that the surface induced anisotropy can be employed as an optical surface probe in the far IR.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2012
The Jaynes-Cummings Hamiltonian with deformed operators of the field is considered; as a particul... more The Jaynes-Cummings Hamiltonian with deformed operators of the field is considered; as a particular case the Kerr-like medium is obtained via an appropriate deformation function. We find that, for an appropriate choice of the parameter of the deformation function, states of the uncoupled basis with a selected fixed number of quanta are in resonance, providing a maximum probability of transition of the atom for these states. Under this condition one may find an appropriate value of the coupling constant such that complete revivals are obtained.
Using the Optical Stochastic Bloch equations (OSBE), and considering a two-level molecular system... more Using the Optical Stochastic Bloch equations (OSBE), and considering a two-level molecular system interacting with a thermal reservoir (modeled as an Ornstein–Uhlenbeck process) in four-wave mixing spectroscopy, we derive analytical expressions for the nonlinear optical properties (absorptive and dispersive processes). Here, we have widened the previous formalism [(J.L. Paz et al., Phys. Lett. A 226 (1997) 365)] to consider the
Journal of Physics B Atomic Molecular and Optical Physics
The Jaynes–Cummings Hamiltonian with deformed operators of the field is considered; as a particul... more The Jaynes–Cummings Hamiltonian with deformed operators of the field is considered; as a particular case the Kerr-like medium is obtained via an appropriate deformation function. We find that, for an appropriate choice of the parameter of the deformation function, states of the uncoupled basis with a selected fixed number of quanta are in resonance, providing a maximum probability of transition of the atom for these states. Under this condition one may find an appropriate value of the coupling constant such that complete revivals are obtained.
ABSTRACT We consider the effect of a time-dependent perturbation on an anharmonic oscillator. By ... more ABSTRACT We consider the effect of a time-dependent perturbation on an anharmonic oscillator. By expressing the anharmonic oscillator in terms of deformed ladder operators, we obtain the energy spectrum of the unperturbed problem in terms of the quanta of the number operator and an anharmonicity parameter. The combined presence of quadratic terms in the unperturbed Hamiltonian and of the time-dependent perturbation does not lead to a closed algebra and an exact solution. Introducing the mean field in the unperturbed term allows us to obtain a closed algebra with a time-dependent frequency in the unperturbed term. Through factorization of the corresponding evolution operator, the dynamical problem is reduced to a self-consistent system of first-order differential equations. We can now examine this system for transition probabilities, expectation values, phase-space trajectories, and criteria for chaotic behavior in the case of a dipole pulse perturbation.
Uploads
Papers by J. Recamier