Modern Physics Letters B

We discuss possibility of using time-dependent inhomogeneous magnetic field to decrease the speed of particles in a molecular/atomic beam. This includes deceleration via traveling magnetic field gradient. We also discuss possible implementations of the magnetic decelerator.

For a two-dimensional electron gas with equal Rashba and Dresselhaus spin-orbit coupling strength (ReD model), and the Dresselhaus [110] model, the influence of an external magnetic field on the lifetime of the Spin Helix (SH) has been considered. A perpendicular magnetic field has no influence on the lifetime of the SH for the Dresselhaus [110] model, independent of the strength of the magnetic field. But for the ReD model, when the magnetic field is weak, and we only take the linear term of the magnetic field B into account, the conclusion is still so. In addition, if the external magnetic field is in-plane with a suitable angle between the x and y component, the lifetime of the SH will also be infinite.

We derive the shape equations in terms of Euler angles for a uniform elastic rod with isotropic bending rigidity and spontaneous curvature, and study within this model the elasticity and stability of a helical filament under uniaxial force and torque. We find that due to the special requirements on the boundary conditions, a static slightly distorted helix cannot exist in this system except in some special cases. We show analytically that the extension of a helix may undergo a one-step sharp transition. This agrees quantitatively with experimental observations for a stretched helix in a chemically-defined lipid concentrate (CDLC). We predict further that under twisting, the extension of a helix in CDLC may also exhibit similar behavior. We find that a negative twist tends to destabilize a helix.

We investigated the motion of two-head Brownian motors by introducing a model in which the two heads coupled through an elastic spring is subjected to a stochastic flashing potential. The ratchet potential felt by the individual head is anti-correlated. The mean velocity was calculated based on Langevin equations. It turns out that we can obtain a unidirectional current. The current is sensitive to the transition rates and neck length and other parameters. The coupling of transition rate and neck length leads to variations both in the values and directions of currency. With a larger neck length, the bi-particle system has a larger velocity in one direction, while with a smaller neck length, it has a smaller velocity in the other direction. This is very likely the case of myosins with a larger neck length and larger velocity in the positive direction of filaments and kinesins with a smaller neck length and smaller velocity in the negative direction of microtubules. We also further investigated how current reversal depended on the neck length and the transition rates.

The five-dimensional Ising model with nearest-neighbor pair interactions is simulated on the Creutz cellular automaton by using finite-size lattices with the linear dimensions L=4, 6, 8, 10, 12, 14, and 16. The temperature variations and the finite-size scaling plots of the specific heat and Binder parameter verify the theoretically-predicted expression near the infinite-lattice critical temperature. The approximate values for the critical temperature of the infinite-lattice, T_c=8.8063, T_c=8.7825 and T_c=8.7572, are obtained from the intersection points of specific heat curves, Binder parameter curves and the straight line fit of specific heat maxima, respectively. These results are in agreement with the more precise value of T_c=8.7787. The value obtained for the critical exponent of the specific heat, i.e. α=0.009, is also in agreement with α=0 predicted by the theory.

The main aim of this paper is to fabricate and characterize silver oxide thin films and to investigate the effect of processing parameters on the microstructure of deposited films. Radio frequency (RF) magnetron sputtering was used under oxygen-argon mixed gas atmosphere for fabrication. Oxide phase evolution and stability were investigated by X-ray diffraction (XRD) of as-deposited and post deposition annealed films. In all cases, the hexagonal phase was initially observed which then got transformed to the cubic phase upon annealing films. The hexagonal–cubic "transition" temperature decreases initially upon increase of oxygen content, which is corroborated by optical spectra. The evolution of optical absorption edge was monitored by a spectrophotometer. A bandgap energy of 3.5 eV was deduced for Ag₂O at 300 K. Atomic force microscopy (AFM) has revealed the influence of deposition conditions on the surface morphology of the films.

Cu-doped Cadmium sulfide (CdS) films were prepared by chemical bath deposition method. Various quantities of Cu were used for mixing. Surface characterization, structure, morphology and defect structures of the films were studied. The structure of all Cu-doped CdS films was a unique CdS cubic phase. The grain size of CdS was decreased when doped with Cu. The F-type defect in the undoped CdS is clearly confirmed by an ESR signal arising from the hyperfine interaction of electron spin (S=1/2) trapped in sulfur vacancies and neighboring cadmium nuclear spin (I=1/2). In the Cu-doped CdS films, the ESR peaks shift towards low fields as the copper concentration is increased. This is due to the change in crystal field experience by Cu²⁺ (3d⁹) ions while the Cd²⁺ signal disappears. The Cu²⁺ ions in the Cd_1-xCu_xS itself are ESR silent due to a very short relaxation time. The dark resistance increased with increasing amount of Cu concentrations up to about 0.03 M. This 0.03 M Cu-doped CdS sample also possesses the maximum photosensitivity.