Differential Equation for the Transfer Matrix

An electron propagating through a crystal toward an interface can either reflect or transmit. The determination of its transmission and reflection probabilities represents an actual task in such fields as nanoelectronics, magnetoelectronics, or spin electronics. Within the framework of the effective mass approximation the problem can be reduced to the tunneling of the quantum particle through one-dimensional potential barrier. The tunneling process can be described by means of the transfer matrix, which contains all the information about the energetic dependence of the transmission and reflection coefficients. In the present work the differential equation for the transfer matrix of the arbitrary potential barrier is derived. The method proposed represents an alternative way of the calculation of the transfer matrix.     

Quantum-chemical study on the electronic structure and ligand-receptor binding mechanisms of some pyridin-4(1<Emphasis Type="Italic">H</Emphasis>)-one and pyran-4-one derivatives

Molecular structure optimization of a series of pyridin-4-one and pyran-4-one derivatives, namely 5-hydroxy-2-hydroxymethylpyridin-4(1H)-one, 5-hydroxy-1-methyl-4-oxo-1H-pyridine-2-carboxylic acid, and 5-hydroxy-2-hydroxymethylpyran-4-one (kojic acid) as free acids, the corresponding anions, calcium salts, calcium chelates, and calcium chelate calcium salts, was performed ab initio in terms of the restricted Hartree-Fock method with 6-31G* basis set using GAMESS program. The effects of salt and complex formation on the geometric and electronic structure of these molecules were analyzed. The solvation effects were examined by complete geometry optimization of all substrates in terms of the polarized continuum model (PCM) with dielectric constants ? of 10 and 78.3. The energies of formation of the salts and complexes were estimated. A set of geometric parameters responsible for the possibility of ligand-receptor binding with participation of pyran-4-ones and pyridin-4(1H)-ones and probable mechanism of binding of the latter to opioid receptors were proposed on the basis of the calculation data.     

Spin rings in semiconductor microcavities

New effects of self-organization and polarization pattern formation in semiconductor microcavities, operating in the nonlinear regime, are predicted and theoretically analyzed. We show that a spatially inhomogeneous elliptically polarized optical cw pump leads to the formation of a strongly circularly polarized ring in real space. This effect is due to the polarization multistability of cavity polaritons which was recently predicted. The possible switching between different stable configurations allows the realization of a localized spin memory element, suitable for an optical data storage device.     

Optical circuits based on polariton neurons in semiconductor microcavities

By exploiting the polarization multistability of polaritons, we show that polarized signals can be conducted in the plane of a semiconductor microcavity along controlled channels or "neurons." Furthermore, because of the interaction of polaritons with opposite spins it is possible to realize binary logic gates operating on the polarization degree of freedom. Multiple gates can be integrated together to form an optical circuit contained in a single semiconductor microcavity.     

Quantum theory of spin dynamics of exciton-polaritons in microcavities

We present the quantum theory of momentum and spin relaxation of exciton-polaritons in microcavities. We show that giant longitudinal-transverse splitting of the polaritons mixes their spin states, which results in beats between right- and left-circularly polarized photoluminescence of microcavities, as was recently experimentally observed [Phys. Rev. Lett. 89, 077402 (2002)]]. This effect is strongly sensitive to the bosonic stimulation of polariton scattering.     

火焰原子吸收光谱法测定鱼腥草、西洋参和茯苓中的铜含量

用硝酸-高氯酸混合酸(4∶1)消化鱼腥草、西洋参和茯苓,在波长324.8nm处,利用火焰原子吸收光谱法测定鱼腥草、西洋参和茯苓中铜的含量。线性回归方程为A=0.1708C 0.0004,相关系数r=0.9997,线性范围为0—5μg/mL,检出限为0.0035μg/mL,测定结果的相对标准偏差为0.09%,加标回收率为98.0%—104.2%。     

Electromagnetic Dressing of Graphene

We present a theory to describe the interaction of electrons in gapped and gapless graphene with a strong off-resonant electromagnetic field (dressing field). This interaction (electromagnetic dressing) is shown to renormalize substantially electron velocities and the band gap in gapped graphene. Particularly, renormalized electronic parameters depend strongly on the field polarization: linearly polarized fields always reduce the gap, while circularly polarized fields break the equivalence of the valleys at various points of the Brillouin zone and can increase or decrease the corresponding band gaps. Moreover, a linearly polarized dressing field induces anisotropy of electron dispersion in the graphene plane. Consequently, dressing fields can be an effective tool to control electronic properties of graphene and be prospectively used in various optoelectronic devices.     

Optical anisotropy and pinning of the linear polarization of light in semiconductor microcavities

We report strong experimental evidence of the optical anisotropy in a CdTe-based microcavity: the polarization of light is pinned to one of the crystallographic axes independently of the polarization of the excitation. The polarization degree depends strongly on the excitation power, reaching almost 100% in the stimulated regime. The relaxation time of the polarization is about 1 ns. We argue that all of this is an effect of a splitting of the polariton doublet at k=0. We consider different sources for the splitting and conclude that the most likely one is optical birefringence in the mirrors and/or the cavity.