Asymmetric lateral inhibitory neural activity in the auditory system: a magnetoencephalographic study

Background  

Decrements of auditory evoked responses elicited by repeatedly presented sounds with similar frequencies have been well investigated by means of electroencephalography and magnetoencephalography (MEG). However the possible inhibitory interactions between different neuronal populations remains poorly understood. In the present study, we investigated the effect of proceeding notch-filtered noises (NFNs) with different frequency spectra on a following test tone using MEG.     

Optical interconnection between different spatial modes using double phase conjugate mirror with polarization alignment system

We propose a fundamental interconnection method using a polarization alignment system for waveguides having different spatial modes. In addition, as an example for the verification of the fundamental operation, we demonstrate an interconnection between a photonic crystal fiber and a laser that have obviously different spatial modes. The polarization alignment system operates synergistically with a self-written waveguide formed with a double phaseconjugate mirror. This technique enables us to interconnect a photonic crystal fiber with a laser source without complicated and time-consuming optical alignment. In this method, although it is not necessary to perform an external control for interconnection, the waveguide most suitable for connection is formed autonomously in a Sn₂P₂S₆:Sb crystal developed for this purpose. There was a marked reduction in the polarization dependence of coupling efficiency, compared with that observed using a stand-alone double phase-conjugate mirror.     

Quantum Nernst effect

It is theoretically predicted that the Nernst coefficient is strongly suppressed and the thermal conductance is quantized in the quantum Hall regime of the two-dimensional electron gas. The Nernst effect is the induction of a thermomagnetic electromotive force in the y-direction under a temperature bias in the x-direction and a magnetic field in the z-direction. The quantum nature of the Nernst effect is analyzed with the use of a circulating edge current and is demonstrated numerically. The present system is a physical realization of the non-equilibrium steady state.     

Adjacency Effect in the Atmospheric Correction of Satellite Remote Sensing Data: Evaluation of the Influence of Aerosol Extinction Profiles

In the atmospheric correction of satellite data in the visible and near-infrared bands, it is necessary to remove the adjacency effect due to the reflection from contiguous pixels. Evaluation of the influence of aerosol vertical distributions on the adjacency effect is done by calculating the single-scattering light intensity which, after the reflection at the ground surface, reaches the satellite sensor via a single scattering with a molecule or an aerosol particle. In the simulation, we assume aerosol vertical profiles similar to those used in the MODTRAN radiation transfer code, and those having a mixed layer with a uniform value of the aerosol extinction coefficient. We assume for the ground surface a simple model representing a border of land/sea surfaces. In spite of the single scattering approximation, it is confirmed that even if the optical thickness is the same, we have a larger adjacency effect when the extinction coefficient is large at higher altitudes. We also discuss the dependence of the adjacency effect on the aerosol optical thickness and that on the difference in the reflectances of the land and sea surfaces along the border.     

Estimating the amplitude of measurement noise present in chaotic time series

We propose a method for estimating the amplitude of measurement noise present in chaotic time series. This method is based on the evaluation of initial errors for a given time series and for a new one synthesized by adding an adequate amount of noise to the given one. The method is valid over a much wider range of noise levels than the previous methods are because it is not based on the detail of dynamical structure which generates the data. In addition, it is possible to check if the method is valid for the given data prior to its application. To confirm the effectiveness of the method we show the results of numerical experiments and apply the method to chaotic data obtained from an electrochemical experiment. (c) 1999 American Institute of Physics.     

The effect of oxygen vacancy on the oxide ion mobility in LaAlO3-based oxides

The electrical property of (La_1−xSr_x)_1−z(Al_1−yMg_y)O_3−δ (LSAM; x≤0.3, y≤0.15 and z≤0.1) was measured using the DC four-probe method as a function of temperature (500–1000°C) and oxygen partial pressure (1–10⁻²² atm). Among LSAMs, (La_0.9Sr_0.1)AlO_3−δ showed the highest ionic conductivity, σ_i=1.3×10⁻² S cm⁻¹ at 900°C. A simultaneous substitution at A and B sites or A site deficiency is expected to create larger oxygen vacancy and higher ionic conductivity. However, it showed a negative effect. The effect of the vacancy increase did not effect monotonously the ionic conductivity. It was found that the concentration of oxygen vacancy, [V_O], influences not only the oxide ion conductivity, σ_i, but also the mobility, μ_v, of [V_O]. These properties exhibit a maximum at around [V_O]=0.05. With the increase in [V_O], the activation energy, E_a, of the ionic conduction dropped from 1.8 to ca. 1.0 eV at [V_O]=0.05 and became almost constant at [V_O]>0.05. The dependency of the pre-exponential term, μ⁰_v, and E_a on [V_O] was analyzed and their effect on μ_v and σ_i was discussed with respect to crystal structure and defect association. It was estimated that the crystal structure mainly governs these properties. The effect of defect association could not be ignored but is considered to be a complicated correlation.     

WIDE RANGE DETECTOR USING PARABOLIC CYLINDRICAL MIRROR FOR THz APPLICATIONS

A new, wide-band, high-speed and high-sensitivity THz detector has been developed. The prototype detector consists of a parabolic cylindrical mirror, a long wire antenna and a Schottky barrier diode. Direct detection measurements have shown a stable sensitivity of 150 ± 50 V/W for 1–2 THz without any adjustments. The long wire antenna was fixed at the focus of parabolic cylindrical mirror then it has been realized less operation steps, easy coupling to the external THz signals and a dramatic enhancement in the practicality of this system. The optically polished mirror and frosted surface one showed comparable sensitivities, thus easy polishing and less cost mirror fabrication can be applied for this system. The radiation pattern showed a maximum radiation angle of approximately 23° with its dominant main lobe, which was attributed to the wire antenna character and confirmed good agreements with classical antenna theory.     

Correlation of fluctuation field and temperature coefficient of coercivity in a CoCrPtB thin film

The effect of the ratio of fluctuation field (H_f) to coercivity (H_c) on the temperature coefficient of coercivity [α(H_c)] was investigated for Co₅₅Cr_15.5Pt₂₈B_1.5/Co₆₃Cr₃₇/Cr, Co₆₉Cr₁₉Pt₉Ta₃/Cr, and Co₈₆Cr₁₀Ta₄/Cr thin films (longitudinal recording media) with very small average grain volume (V_phy). α(H_c) increases markedly with increase in temperature between near 250 and 350 K for Co₅₅Cr_15.5Pt₂₈B_1.5/Co₆₃Cr₃₇/Cr thin films. α(H_c) is approximately proportional to the ratio H_f/H_c for all thin films, as in the case of advanced data backup tapes prepared from ultrafine particles. α(H_c) and the ratio H_f/H_c increase as V_phy decreases. Smaller H_f/H_c values are necessary for small α(H_c) values, which is very important for the thermal stability of high-density recording media with very small V_phy.     

Reinvestigation of the thermoelectric properties of Ag8GeTe6

High‐density polycrystalline samples (above 98% of the theoretical density) of Ag₈GeTe₆ were prepared by solid‐state reactions of Ag₂Te, GeTe, and Te, followed by hot‐pressing. The thermoelectric properties were measured at temperatures ranging from room temperature to around 700 K. The thermal conductivity values were extremely low (0.25 Wm^–1 K^–1 at room temperature), and consequently Ag₈GeTe₆ exhibited a relatively high thermoelectric figure of merit, ZT = 0.48 at 703 K. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)