Resumo em Inglês:

Temperature and doping dependencies of electron mobility in InAs, AlAs and AlGaAs structures have been calculated using an ensemble Monte Carlo simulation. Electronic states within the conduction band valleys at the Γ, L and X are represented by non-parabolic ellipsoidal valleys centred on important symmetry points of the Brillouin zone. The simulation shows that intervalley electron transfer plays a dominant role in high electric fields leading to a strongly inverted electron distribution and to a large negative differential conductance. Our simulation results have also shown that the electron velocity in InAs and AlAs is less sensitive to temperature than in other III-V semiconductors like GaAs and AlGaAs. So InAs and AlAs devices are expected be more tolerant to self-heating and high ambient temperature device modeling. Our steady-state velocity-field characteristics are in fair agreement with other recent calculations.

Resumo em Inglês:

A kinetic approach to the problem of wave propagation in dusty plasmas, which takes into account the variation of the charge of the dust particles due to inelastic collisions with electrons and ions, is utilized as a starting point for the development of a new formulation, which writes the components of the dielectric tensor in terms of a finite and an infinite series, containing all effects of harmonics and Larmor radius. The formulation is quite general and valid for the whole range of frequencies above the plasma frequency of the dust particles, which were assumed motionless. The formulation is employed to the study of electrostatic waves propagating along the direction of the ambient magnetic field, in the case for which ions and electrons are described by Maxwellian distributions. The results obtained in a numerical analysis corroborate previous analysis, about the important role played by the inelastic collisions between electrons and ions and the dust particles, particularly on the imaginary part of the dispersion relation. The numerical analysis also show that additional terms in the components of the dielectric tensor, which are entirely due these inelastic collisions, play a very minor role in the case of electrostatic waves, under the conditions considered in the present analysis.

Resumo em Inglês:

A DEPT pulse sequence is well-known 13C-detected, edited-pulse and cross polarization transfer NMR experiment which offers to selective detection capability of CH, CH2 and CH3 groups from each other. The product operator theory is widely used for analytical descriptions of the cross polarization transfer NMR experiments for weakly coupled spin systems. In this study, analytical descriptions of the DEPT NMR experiment have been presented for ISn(I = 1,S = 1; n = 1, 2, 3, 4) spin systems by using product operator theory. Then a theoretical discussion and experimental suggestions were made. It has been investigated that this experiment can be used to edit 14N sub-spectra of partly or full deuterated 14NDn (n=1, 2, 3, 4) groups.

Resumo em Inglês:

The entanglement dynamics in a system of the interaction of an atom with a single-mode cavity field in the presence of noise is studied by the Jaynes-Cummings model. Random phase telegraph noise is considered as the noise in the interaction and an exact solution to the model under this noise is obtained. The obtained solution is used to investigate the entanglement dynamics of the atom-field interaction. The mutual entropy is adopted for the quantification of the entanglement in the interaction. It is found that the entanglement is a non monotonic function of the intensity of the noise. The degree of the entanglement decreases to a minimum value for an optimal intensity of the noise and then increases for a sufficiently large intensity.

Resumo em Inglês:

Aluminum-doped zinc oxide (AZO) films were prepared on glass substrate by mid-frequency direct current reactive magnetron sputtering (MF-DC-MS). The influence of surface texture by NH4Cl aqueous solution on the surface morphology, electrical and optical properties of the AZO films was systematically investigated by scanning electron microscope, four-point probe and ultraviolet-visible-near infrared spectrophotometer, respectively. The results indicate that textured AZO film obtains a better texture surface for light trapping. The reflectivity for textured AZO film decreases drastically in visible light region and the electrical resistivity increases, which can be explained by the textured surface morphology of AZO film. The results above prove that NH4Cl aqueous solution is an appropriate candidate for AZO wet etching because of its easy control and relatively low cost.

Resumo em Inglês:

In the present work we report the mechanical properties of ca(b)-planes of Ag-doped top-seeded melt-grown YBaCuO (YBCO) pellets at different concentrations. Hardness and elastic modulus were obtained by instrumented indentation and fracture toughness by conventional Vickers indentation. Hardness profiles for both planes indicated values between 7-8 GPa at deep tip penetration. Significant differences in elastic modulus were observed as a function of Ag content for the ab-plane while no difference were seen for the ca(b)-plane. Doping with 5 wt. % Ag2O increases the hardness and elastic modulus for the ab-plane in relation to the undoped sample due to Ag solid-solution hardening. Indentation fracture toughness rises with Ag doping for the ab-plane. Intensive plastic deformation was observed in ca(b) plane for conventional Vickers indentation.

Resumo em Inglês:

The present paper describes a radiography technique to inspect low thickness samples, on the order of micra. The penetrating radiation are charged particles generated by a lithium fluoride screen irradiated by thermal neutrons. The film used to register the images is a solid state nuclear track detector and the experimental conditions to obtain the best radiography are provided. A digital system for data acquisition and image processing was also used.

Resumo em Inglês:

We study the robustness and stability of the yeast cell regulatory network by using a general inhomogeneous discrete model. We find that inhomogeneity, on average, enhances the stability of the biggest attractor of the dynamics and that the large size of the basin of attraction is robust against changes in the parameters of inhomogeneity. We find that the most frequent orbit, which represents the cell-cycle pathway, has a better biological meaning than the one exhibited by the homogeneous model.

Resumo em Inglês:

We present some essential results for the Hamiltonian of a particle in a box. We discuss the invariance of this operator under time-reversal T, the possibility of choosing real eigenfunctions for it and the degeneracy of its energy eigenvalues. Once these results have been presented, we introduce the usual nondegeneracy theorem and discuss some issues surrounding it. We find that the nondegeneracy theorem is true if the boundary conditions are T-invariant but "confining" (i.e., the particle is in a real impenetrable box). If the boundary conditions are not T-invariant (belonging to a family of so-called "not confining" boundary conditions), the respective eigenfunctions are strictly complex and there is no degeneracy. Consistently, we verify the validity of the theorem also in this case. Finally, if the boundary conditions are also T-invariant, but "not confining", then we can have degeneracy in the energy levels only if the respective eigenfunctions can be specifically written as complex. We find that the nondegeneracy theorem fails in these cases. If the respective eigenfunctions can be written as only real, then we do not have degeneracy and the nondegeneracy theorem is true.

Resumo em Inglês:

We investigate an extension of the Perard and Bishop (PB) model. In the studied model we get a harmonic one dimensional lattice chain with an additional Morse potential on site. The rotation and vibration motion of each component of the lattice are considered and the coupling for these motions is introduced by a resonance condition. Thermodynamics and structural properties of the system are explored.

Resumo em Inglês:

It is proven that the field equations of a previously studied metric nonsymmetric theory of gravitation do not admit any non-singular stationary solution which represents a field of non-vanishing total mass and non-vanishing total fermionic charge.