Light scattering by a 2D electron system with spin-orbit interaction in a strong magnetic field

We theoretically investigate light scattering by electrons of a 2D system in a strong magnetic field perpendicular to the plane of the system (the filling factor is smaller than two, i.e., only the states of the zeroth Landau level are filled). Analysis is carried out in the resonance approximation, in which the frequencies of the incident and scattered light are close to the effective separation between the conduction band and one of the branches of the valence band of the semiconductor. Spin splitting of the Landau level in the conduction band associated with Zeeman and the spin-orbit interactions is taken into account. The dynamic screening effects are considered in the random phase approximation (RPA).     

Thin film flowing down a curved surface

The film flow down a curved surface is analysed by an orthogonal curvilinear system and a perturbation in the small ratio of film thickness to minimum radius of curvature. General solutions are obtained to second order. The results are applied to plates with exponential curvature and sinusoidal curvature. Separation is most likely to occur on the upstream sides of a wavy plate.

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Zusammenfassung Es wird die Strömung einer dünnen Schicht entlang einer gekrümmten Fläche untersucht, mit Hilfe eines krummlinigen orthogonalen Koordinatensystems und einer Entwicklung, bei dem das Verhältnis von Schichtdicke zu (minimalem) Krümmungsradius als kleiner Parameter dient. Es werden allgemeine Lösungen bis zur zweiten Ordnung angegeben. Die Ergebnisse werden auf Platten mit exponentieller und sinusförmiger Krümmung angewendet. Ablösung wird am wahrscheinlichsten an Stellen stromaufwärts an einer gewellten Platte auftreten.

     

On the stability of continuous quadrature rules for differential equations with several constant delays

The aim of the present paper is to study the stability propertiesof the numerical methods for pure delay differential equations.The methods we consider are based on a quadrature rule and aninterpolant (NCE) to get an approximation of the retarded part(continuous quadrature rule). As a test equation we consider and we give sufficient conditions for the boundedness of thesolutions. The same behaviour is preserved by the continuousquadrature rule under some restriction on the parameters. Asa conclusion we give some examples. This work was supported by CNR and M.U.R.S.T.     

Structural,Optical, and Electrical Characteristics of Zinc Oxide and Copper Oxide Films and Their Heterojunctions

In this paper, n-Zinc oxide/p-copper oxide heterojunctions were fabricated by RF-sputtering on indium tin oxide-covered glass substrates. The structural and optical properties of the copper oxide and zinc oxide films were analyzed by X-ray diffraction, Fourier transform infrared, scanning electronic microscopy and ultraviolet-visible spectroscopy. The electrical junction properties were investigated by current–voltage (I–V) characteristics. Additionally, both capacitance (C) and conductance (G) versus frequency (f) measurements were realized at room temperature. The junctions showed a rectifying behavior, and C and G varied with both voltage and frequency.     

Direct Form I Realization of Active Photonic Filters

Abstract

An integrated photonic architecture is introduced and used to realize an optical filter with direct form I realization. The architecture offers gain from semiconductor optical amplifiers, and this gain results in an active optical filter whose filter response depends on the individual gains. The presence of gain provides advantages in filter performance, and tunable and adaptive functionality. The optical filter is modeled as a discrete time system and the z-transform is used in its analysis and design. A low-pass filter design example is presented and the filter coefficients are derived in terms of gains and coupler splitting ratios. The region of stable operations is derived by applying the Schur-Cohn stability test.     

Periodic antiphase boundary spinel-based structures in aluminates,gallates, aluminium oxynitrides and transition aluminas

The crystallographic structures of several transition aluminas possessing a face-centred cubic packing of oxygen anions can be considered as deriving from that of a non-stoichiometric spinel. However, they are not yet known in detail owing to the poor crystallinity of most of the samples studied by X-ray or electron diffraction. Conversely, relatively large crystals have been produced in the case of non-stoichiometric spinels in the alumina-rich (or Ga₂O₃-rich) parts of the Al₂O₃–AlN, Al₂O₃–MgO, Al₂O₃–NiO, Al₂O₃–Li₂O and Ga₂O₃–MgO systems. Detailed studies of their diffraction patterns have shown that all these phases possess periodic antiphase boundary (PAPB) structures based on the spinel structure. In the case of the so-called δ-transition aluminas, various structural models have been previously proposed and in this paper we are focusing on the striking similarities between their diffraction patterns and those of several metastable PAPB aluminate structures. This makes it possible to show that at least three distinct PAPB structures must be taken into account in the case of δ-transition aluminas. APB planes are either {100} or {110} whereas APB vectors are either 1/2??001? or 1/4??110? when referring to the spinel structure. Neighbouring octahedral and tetrahedral incompatible sites are observed in the vicinity of each APB and cation vacancies are shown to occupy these octahedral sites.     

Ultrasonic attenuation in dirty two-band superconductors with persistent currents

The ultrasonic attenuation in two-band superconductors with non-magnetic and paramagnetic impurities in the presence of persistent currents is studied. The case of high impurity concentrations is considered. Assuming space-independent sound waves, the absorption energy in the case of relatively low frequencies at low and zero temperatures is calculated.