Photoelectric properties of magnetically sensitive MOS structures

The photoelectric properties of MOS structures having compensation regions near the field electrode have been studied experimentally. It is shown that the presence of such regions can lead to the appearance of a number of features in the integrated photoelectric properties: the presence of a large photovoltage signal in enhancement, dependence of the form of the photovoltage frequency dependence on the intensity of the light flux, and distortion of the shape of the photovoltage signal in inversion. The presence of compensation regions can be established using measurements of the distribution of the photovoltage over the area of the structure and measurements of the voltage dependence of the phase of the integrated photovoltage signal. The increase or decrease of the photovoltage signal in enhancement after exposure to a weak magnetic field is due to the rearrangement of the impurity-defect structure in the near-surface layer of the semiconductor, leading to the appearance of compensated semiconductor regions near the field electrode. Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 82–87, May, 1998.     

Convergence properties of multiple reflection expansions

The convergence properties of the multiple reflection expansion for massless scalar and Dirac propagators in a general convex cavity are studied. A sufficient condition for convergence is arrived at and the regions in the complex frequency plane are examined where this condition is satisfied. For the case of a spherical cavity, a necessary and sufficient condition for convergence is obtained by making use of a partial wave expansion for the propagator. The corresponding convergence regions in the complex frequency plane are also determined in more detail.     

石髓的光学性质分析

对石髓样品进行了化学成份、物理结构、透射光谱及散射退偏振能力等方面的分析,结论是:此材料有极强的散射退偏振能力;又由于它本身为固体材料,硬度高,不易被损伤,非常适合于制作紫外,可见及近红外探测器的退偏振窗口.     

Experimental investigation on transmission properties of lossy single-negative metamaterials

We studied the ground state of alkaline-earth-metal atoms confined in one-dimensional optical lattices modeled by the Kondo lattice model plus a quadratic confining potential. We considered the half-filling case and both ferromagnetic and antiferromagnetic interaction between the localized and delocalized atoms. We found Kondo insulator domains that always coexist with metallic and/or band insulator regions. We observed that the on-site delocalized-localized spin correlation remains constant in the insulating regions and used it to determine the state diagrams. Metallic regions were found for both ferromagnetic and antiferromagnetic couplings.     

Bandgap properties of Kagomé photonic crystal fibers

Photonic crystal fibers (PCFs) can guide light by the photonic bandgap (PBG) effect created by the periodically arranged air holes in the cladding. In this paper, the bandgap properties of Kagomé photonic crystal fibers (KPCFs) are investigated in detail. First, the bandgap properties of PCFs based on the basic Kagomé lattice are analyzed and compared with the PBGs of PCFs based on honeycomb and triangular lattices. We highlight the similarities between KPCFs and honeycomb PCFs in their PBGs, both having air-guiding regions only at very large air filling fractions (AIFs), whereas the PBGs of triangular PCFs can have large air-guiding regions at smaller AIFs due to the difference in the gap structure. In the second half of this paper, we show how the PBGs of KPCFs can be modified by introducing an extra air hole into the vacant space of the original lattice. In particular, KPCFs with medium-sized air holes can be designed to guide air by introducing extra air holes of a larger size. The air-guiding regions of KPCFs with very large air holes can also be greatly extended by the extra air holes. These air-guiding regions occur at higher normalized frequencies, resulting in larger air hole pitches favorable for fabrication. PACS 42.70.Qs; 42.25.Bs; 42.81.Qb     

Statistical properties of thermodynamically predicted RNA secondary structures in viral genomes

By performing a comprehensive study on 1832 segments of 1212 complete genomes of viruses, we show that in viral genomes the hairpin structures of thermodynamically predicted RNA secondary structures are more abundant than expected under a simple random null hypothesis. The detected hairpin structures of RNA secondary structures are present both in coding and in noncoding regions for the four groups of viruses categorized as dsDNA, dsRNA, ssDNA and ssRNA. For all groups, hairpin structures of RNA secondary structures are detected more frequently than expected for a random null hypothesis in noncoding rather than in coding regions. However, potential RNA secondary structures are also present in coding regions of dsDNA group. In fact, we detect evolutionary conserved RNA secondary structures in conserved coding and noncoding regions of a large set of complete genomes of dsDNA herpesviruses.     

Photoelastic properties of graphenes

The components of the elastooptic tensor of graphenes with the sp ² hybridization of atomic orbitals for the visible and near infrared spectral regions are calculated. These components are shown to be comparable with those of lithium niobate.

     

Kink properties on curved manifold

In the framework of the two-dimensional field model the influence of the curvature on kink width is discussed. Breading of the kink width in a curved region of the manifold is observed. Examples of kinks on curved manifolds are studied analytically and numerically as well. The deformation of the kink front in the form of the travelling waves propagating along the curved surfaces are found. Enlarging of the travelling wave speed in a curved regions of the manifold is predicted.     

Dielectric properties of perovskite ferroelectrics at the nonequilibrium concentrations of point defects

Dielectric properties of ceramic barium titanate modified by the addition of aluminum oxide are studied via impedance spectroscopy in weak electric fields in frequency range of 0.3–10³ kHz. For better separation of the properties of the inner regions of crystallites and the boundary regions by quenching, an excess concentration of point defects is created, leading to the formation of bulk charge. The experimental results are performed using the Maxwell-Wagner capacitor model and the Schottky barrier model.     

Scaling properties of universal conductance fluctuations in quasi ballistic narrow wires

We study the scaling properties of universal conductance fluctuations, observed in the magneto-resistance of quasi ballistic, split gate wires. In such devices the correlation field analysis is not simply determined by theoretical predictions for corresponding diffusive systems, and we discuss this breakdown in terms of a spreading of phase coherent electron interference, into the ungated regions of the devices. In order to characterise this effect we develop a simple model, in which the degree of spreading is represented by a single parameter γ. Performing this analysis we find that γ scales as a simple function of the wire length and width, enabling us to characterise the interplay of interference from the different regions of the split gate wire.     

Entanglement witnesses and characterizing entanglement properties of some PPT states

On the basis of linear programming, new sets of entanglement witnesses (EWs) for 3⊗3 and 4⊗4 systems are constructed. In both cases, the constructed EWs correspond to the hyper-planes contacting, without intersecting, the related feasible regions at line segments and restricted planes respectively. Due to the special property of the contacting area between the hyper-planes and the feasible regions, the corresponding hyper-planes can be turned around the contacting area throughout a bounded interval and hence create an infinite number of EWs. As these EWs are able to detect entanglement of some PPT states, they are non-decomposable (nd-EWs).     

Localization properties of bulk-dead and comb magnetostatic modes in Brillouin light scattering spectrum

We show that magnetostatic modes with amplitude localized in different regions of the sample along the direction of the magnetic field occur in ferromagnetic stripes: bulk-dead modes, with amplitude localized in two regions and comb modes localized in its central part. We also demonstrate these localization properties can be studied by Brillouin light scattering techniques and applied in practice. Having established that the localization of these modes varies with their frequency, we use this finding as the basis of a trial reinterpretation of experimental results obtained by Demidov et al. [Appl. Phys. Lett. 92 (2008) 232503].     

Strain-induced bond buckling and its role in insulating properties of Cr-doped V2O3

Structural transformations around both V and Cr atoms in (V1-xCrx)2O3 across its metal-insulator transition (MIT) at x approximately 0.01 are studied by extended x-ray absorption fine-structure technique. Our new results for Cr made possible by the use of a novel x-ray analyzer that we developed reveal the substitutional mechanism of Cr doping. We find that this system has a buckled structure with short Cr-V and long V-V bonds. This system of bonds is disordered around the average trigonal lattice ascertained by x-ray diffraction. Such local distortions can result in a long range strain field that sets in around dilute Cr atoms in microscopic regions. We suggest that such locally strained regions should be insulating even at small x. The possibility of local insulating regions within a metallic phase, first suggested by Rice and Brinkman in 1972, remains unaccounted for in modern MIT theories.     

Dispersion properties of two-dimensional plasma photonic crystals with periodically external magnetic field

Dispersion properties of two types of two-dimensional periodically magnetized plasma array structures with square lattices have been investigated by using plane wave expansion method. It is found that two different regions of flatbands and photonic band gaps occur in the TE polarization due to the external magnetic field. The two types of system can be seen as a kind of unusual plasma photonic crystals. The results show that not only the location of flatbands but also the position and bandwidth of photonic band gaps can be tuned by external magnetic field. The cutoff frequency decreases as external magnetic field increases. The edge of two different of flatbands regions and cutoff frequency shift downward to lower frequencies obviously with increasing plasma collision frequency, while they shift upward to higher frequencies notably with increasing plasma frequency. The filling factor has little effect on the location of flatbands regions. The width of flatbands regions and photonic band gaps are almost unchanged by increasing filling factor, but the number of ominidirectional photonic band gap for type-1 structure plasma photonic crystals can be effectively controlled by adjusting filling factor. It is worth to be noted that the first band gaps above the cutoff frequencies in Г–X and Г–M direction for two types of PPCs can be modulated by the parameters as mentioned above, and the relative bandwidth of band gap in Г–X direction is wider than the one in Г–M direction. The results may provide theoretical instructions to design new tunable photonic crystals devices.     

High-frequency vibrational properties of metallic nanocrystalline grain boundaries

The high-frequency phonon properties of a computer generated nanocrystalline (nc) fcc Ni with a mean grain size of 5 nm are investigated by directly calculating the on-site phonon Green's function using a recursion technique based on a continued fraction representation. It is found that the high-frequency tail, observed in both experiment and previous simulation work, arises primarily from spatially confined vibrational modes forming within the nc grain boundary regions.     

Phase diagrams properties of the mixed traffic flow on a crossroad

Based on the Ishibashi and Fukui crossroad traffic flow model [Y. Ishibashi and M. Fukui. J. Phys. Soc. Japan. 70 (2001) 2793], mixed traffic flow (i.e., the fast and slow vehicles with different maximum velocities are mixed) is investigated in this work. According to the numerical simulation results and the principle for constructing the phase diagram, phase diagrams for mixed traffic flow are constructed. It is noted that the topology of these phase diagrams is similar to that of phase diagrams for homogeneous vehicles (which refers to slow vehicles only). From the phase diagrams, it is evident that mixed traffic flow is influenced by the mixing rate f (fraction of slow and fast vehicles) in regions II and V, but not in other regions. Although a mixture of fast and slow vehicles is introduced in the crossroad traffic flow model, the separation between phases in the phase diagrams remains linear. For a given q (the vehicle density on the northbound road), one flow plateau appears in regions IIx or IVy, while two maximum flow plateaus appear in region V in each of the phase diagrams. The maximum flow values in region V reflect the maximum traffic capacity for the traffic system as defined in this work. Since mixed traffic flow is a common phenomenon in real traffic, this work may offer help in real traffic simulations and traffic management.     

Dicke模型的量子混沌和单粒子相干动力学特性

量子化的Dicke模型在非旋波近似条件下表现为量子混沌动力学特征.利用单粒子一阶时间关联函数,通过数值计算详细考察了Dicke模型中单粒子相干动力学特性.结果表明:当初始相干态处在混沌区域时,一阶时间关联函数曲线衰减较快,而当初始相干态处在规则区域时,一阶时间关联函数曲线衰减较慢,单粒子相干动力学对初态具有较强的敏感性,经典混沌抑制量子相干.考察单粒子相干动力学在相空间的平均演化性质,得到一种较好的量子经典对应关系.最后研究了相空间单粒子相干的整体动力学性质,更好地揭示了相空间的混沌和规则结构.     

Architectonics and optical properties of dentin and dental enamel

The optical polarization method is used to study the distribution of tubules in human dentin. Horizontal sections of molars display circular local regions 1 mm in diameter and inclined with respect to the section surface, which are continuations of the pulp horns towards the crown cusps. They exhibit specific optical effects resembling conoscopic patterns, revealing the highly hierarchical structure of the crown dentin.     

Photoelectric properties ofp-CuInSe2 crystals

Spectra of the photoelectromotive force of p-CuInSe₂ single crystals obtained by directional crystallization of a stoichiometric-composition melt in an upright ampoule have been investigated by the method of phase-sensitive detection. A difference in the phase shifts between the exciting light and the arising photoelectromotive force in the extrinsic (impurity) and intrinsic regions of optical absorption is determined. The lifetime in the region of optical self-absorption is found to equal τ=15·10⁻⁶ at T=77 K. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 129–131, January–February, 1997.     

Alterations in diffusion properties of white matter in Williams syndrome

Diffusion tensor imaging (DTI) was used to investigate the involvement of brain white matter in Williams syndrome (WS), a genetic neurodevelopmental disorder. Whole-brain DTIs were obtained from 16 young adults with WS and 16 normal controls. A voxel-based analysis was performed to compare fractional anisotropy (FA) values between the two groups. A tract-based analysis was also performed to compare FA values between the two groups along two major white matter tracts that pass through the external capsule: the uncinate and inferior fronto-occipital fasciculi. Several regions of both increased and decreased FA were found within major white matter tracts that connect functional regions that have previously been implicated in the cognitive and neurological symptoms of the syndrome. The tract-based analysis provided additional insight into the involvement of specific white matter tracts implicated in the voxel-based analysis within the external capsule. The results from this study support previously reported changes in white matter diffusion properties in WS and demonstrate the potential usefulness for tract-based analysis in future studies of the disorder.