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We theoretically study the valley aspect of lateral tunneling transport in valleytronic materials, using AB-stacked (Bernal-stacked) bilayer graphene as a material example. A lateral structure with multiple well/barrier interfaces is considered. A full-zone tight-binding method is employed, allowing for the study of intervalley mixing in electron states. We study the degree of tunneling current valley contrast under the condition of a source-drain bias or barrier asymmetry. For a single-barrier structure, it is found that the intervalley mixing is negligible, and the contrast is positively correlated with the barrier width and height. For a double-barrier structure, the effect of resonant tunneling is investigated. The intervalley mixing is shown to be significantly enhanced at resonant tunneling. In addition, the resonant levels are found valley split, and a proposal is given which exploits the splitting for the generation of a sizable tunneling current valley polarization. Based on a simple model using momentum-shifted thermal distribution for obliquely incident electrons, the temperature dependence of tunneling current valley polarization is also examined. An interesting crossover from the valley-orbit interaction-dominant polarization to the warping-dominant polarization is found to occur as the temperature is increased. [ABSTRACT FROM AUTHOR]

Whole-cell recordings from optic tectal neurons in Xenopus tadpoles were used to study the maturation of a glutamatergic synapse. The first glutamatergic transmission is mediated only by N-methyl-D-aspartate (NMDA) receptors and is silent at resting potentials. More mature synapses acquire transmission by [Alpha]-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors. This maturational program is mimicked by postsynaptic expression of constitutively active calcium-calmodulin-dependent protein kinase II (CaMKII). Newly formed synapses may be silent unless sufficient depolarization is provided by coincident activity that could activate postsynaptic CaMKII, resulting in the appearance of AMPA responses., Most excitatory synapses in the vertebrate central nervous system use glutamate to mediate synaptic transmission[1] through two types of ionotropic receptors, the AMPA and NMDA receptors. AMPA and NMDA receptors [...]

OBJECTIVE: To investigate the effects of dexmedetomidine (Dex) treatment administered at various times on acute lung injury (ALI). MATERIALS AND METHODS: Thirty Wistar rats were randomly divided into five groups (n = 6/group). Lipopolysaccharide (LPS) was intraperitoneally injected into the rats in the LPS, Dex1, Dex2, and Dex3 groups to induce ALI, while the control group (C) was left untreated. Rats in the Dex1 group were intraperitoneally administered with 50 µg/kg Dex 30 minutes before modeling. Rats in the Dex2 group were injected with 25 µg/kg Dex 30 minutes before modeling and two hours after. Rats in the Dex3 group received 50 µg/kg Dex two hours after modeling. The animals in the C and LPS groups were given an equal volume of saline. The wet-to-dry (W/D) weight ratio of the rats' lungs was calculated, and pathological alterations in lung tissues were observed. The concentrations of inflammation-related factors and the expression of Janus kinase 1 (JAK1), signal transducer and activator of transcription 3 (STAT3), and matrix metallopeptidase 9 (MMP9) were measured. RESULTS: The W/D ratio, expression of inflammatory factors, and expression of JAK1, STAT3, and MMP9 were significantly increased in the ALI rats (p < 0.05) compared with the C group. The level of anti-inflammatory factors in the Dex-treated groups was also significantly increased compared with the LPS group (p < 0.05). The concentration of anti-inflammatory factors in the Dex2 group was significantly higher than that recorded in the Dex1 and Dex3 groups (p < 0.05). CONCLUSIONS: Dex treatment administered at different times protects rats against LPS-induced ALI to varying degrees. The protective effects of Dex were most robust when administered both before and after LPS stimulation. [ABSTRACT FROM AUTHOR]

We include the effect of band non-parabolicity on photonic defect states within the Wannier theory, which improves the quadratic approximation adopted by Painter et al. [Phys. Rev. B 68, 035214 (2003)] for large-size defects, as well as extends the theory to a wider range of defect size. A 2D hexagonal photonic crystal is considered, and analyzed for the origin and degree of non-parabolicity in the 1st TE band around J-point, and for the effect of non-parabolicity on acceptor type cavity modes. The non-parabolicity is shown to derive primarily from the inherent anisotropy of band dispersion around the point. Overall, with the inclusion of non-parabolicity, (i) mode degeneracy is lowered, (ii) the 'binding energy' of a cavity mode is increased, and (iii) the cut-off of defect size for a given cavity mode is reduced, by as much as 35% in certain cases, in comparison with that calculated without the non-parabolicity. A simple 'overall effective mass' picture is provided for the understanding of non-parabolicity effects. [ABSTRACT FROM AUTHOR]

In this work, we study Si-based three-dimensional photonic crystals infiltrated with liquid crystal (LC), within a one-dimensional effective medium model. Two specific systems of diamond crystal structure compatible with the mature Si technology are considered, namely, (i) diamond-1 which is composed of LC spheres embedded in the Si background, and (ii) diamond-2 which is the inverse of the foregoing structure, with Si spheres immersed in the LC background. For each system, the study is carried out with the LC being in the isotropic/nematic phase. The one-dimensional effective medium model employed in the study is an improved version of the conventional mean field theory (MFT). While retaining partially the typical advantage of MFT, e.g., physical transparency, analytical capability, and computational efficiency, it goes beyond the conventional MFT by taking into account the modulation of dielectric constant in the direction of wave propagation. As such, it improves greatly the poor numerical accuracy inherent in the MFT. We find a partial gap between the 2nd and 3rd bands, with the gap-to-midgap ratio being a few percents. Moreover, the edge of partial gap may be shifted by about 1% (in relative unit) when optical, thermal, or electrical means are applied to alter the phase of LC or rotate the axis of nematic molecules. [ABSTRACT FROM AUTHOR]

We propose a mean field band structure theory for low-lying two-dimensional photonic states based on the principle of plane wave expansion. Our theory reduces the complexities of a two-dimensional problem into that of an effective one-dimensional crystal, which provides two key advantages: (a) simplification of dimensions assists in the ease of calculation and (b) delineation of the photonic state physics leads to a gain in its physical insights. Our method distinguishes itself from previous known mean field theories in its capability to include more than one Fourier component of EM fields decomposed along the direction perpendicular to propagation. Furthermore, the method applies to virtually any crystal structure and direction of propagation, and it was discovered to function well for both E-polarization and H-polarization modes of states. We also attempt to demonstrate a systematic improvement of the calculation with the increasing number of Fourier components. Satisfactory numerical accuracy is obtained particularly for the states of the two lowest bands. [ABSTRACT FROM AUTHOR]

Making use of the effective medium theory, we reduce the two-dimensional photonic crystals to an effective one-dimensional model. This one-dimensional model not only predicts correctly the dispersion in the long-wavelength limit (where the wavelength is much larger than the period of material) but also gives a good approximation for shorter wavelength. We further use the perturbation theory to improve the calculation of dispersion up to medium wavelength (which is of the order of space period of the material). Our work gives an insight into the modes of electromagnetic field propagating in photonic crystals. [ABSTRACT FROM AUTHOR]

Presents a theoretical study of electron transport in the resonant-tunneling diode under the effects of an in-plane magnetic field. Description of the theoretical model; Results; Conclusions.

We generalize the Wigner formalism to include effects of an in-plane magnetic field and present theoretical study of effects of a transverse magnetic field on tunneling dynamics for resonant-tunneling diodes. We solve transport equation for the steady-state Wigner distribution function. Particle trajectories are determined in phase space as contour lines of the distribution function. From trajectories we estimate tunneling times. Discussions of magnetic field dependence and transverse momentum dependence of tunneling times are presented. [ABSTRACT FROM AUTHOR]

[Sm.sub.2][Co.sub.17], thin films were deposited on a Cr underlayer by dc magnetron sputtering. [Sm.sub.2][Co.sub.17] (300) in-plane texture was observed as the thicknes of the Cr underlayer was in the range of 100-300 nm. The exchange coupling effect of the [Sm.sub.2][Co.sub.17] films was investigated from [Delta] M plots. The Cr underlayer was found to play an important role in decreasing the intergranular interactions in the [Sm.sub.2][Co.sub.17] films because of the formation of granular structure. TEM micrographs indicate that the magnetic decoupling can be due to isolated [Sm.sub.2][Co.sub.17] magnetic clusters which is induced by a Cr(110) textured underlayer. Index Terms--Exchange coupling, intergranular interaction, magnetic decoupling, magnetron sputtering.

Presents information on a study which examined the effect of variation in the band offset on the band gap and optical properties of the HgTe-CdTe superlattices. Role of strain in the HgTe layers in HgTe-CdTe superlattices grown on CdTe substrates; Conclusions.