Real-time enhancement of defects in periodic patterns by use of a bacteriorhodopsin film

We present a real-time optical system to enhance defects in periodic patterns by use of nonlinear spatial filtering by real-time holography. A straight and equispaced grating written in a bacteriorhodopsin film is read by the Fourier transform of a periodic pattern to be inspected. Because the diffraction efficiency of the grating depends on the intensity of the reading beam, only the defect component can be selectively diffracted and imaged. This system is applicable even to moving objects. We present experimental results that show enhancement of defects as small as 10 microm in a photomask with a pixel pitch of 150 microm used for a liquid-crystal display.     

Red electroluminescent process excited by hot holes in SrGa2S4:Ce, Mn thin film

This paper reports the first observation of red electroluminescence (EL) in SrGa₂S₄:Ce, Mn thin film. The EL spectrum consists of single broad emission band having a peak wavelength of 665 nm. The dominant EL decay time was 31 μs. The relationship between the applied voltage and the EL waveform was measured in single insulating thin film electroluminescent (TFEL) devices. An asymmetric EL waveform was observed in SrGa₂S₄:Ce, Mn TFEL devices under a rectangular applied voltage. The polarity of the EL waveform in these devices was different from the waveform in manganese-activated zinc sulfide ZnS:Mn devices. This indicates that hot holes excite the Mn²⁺ ions to cause the red EL.     

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.     

Influence of Zn Diffusion on Bandwidth and Extinction in MQW Electroabsorption Modulators Buried with Semi-Insulating InP

A comprehensive analysis of multi-quantum-well electroabsorption modulators buried with semi-insulating (SI)-InP is presented. We quantitatively demonstrate that suppression of Zn diffusion into the burying and optical core layers plays a key role in high-speed and high-extinction operation.     

5-Aza-2′-deoxycytidine reactivates the CDH1 gene without influencing methylation of the entire CpG island or histone modification in a human cancer cell line

It is well-recognized that DNA methylation and histone modifications play critical roles in epigenetic regulation of gene activity through the alteration of chromatin structure. Recent studies have shown that in a subset of cancer cells, the silencing of the human E-cadherin (CDH1) gene is associated with hypermethylation of the CpG island. However, the associated molecular mechanism remains unclear. To understand the mechanism, we have investigated the alteration of CpG island methylation and histone modifications during the reactivation of the CDH1 gene by treatment with 5-aza-2′-deoxycytidine (5-aza-dC). Although the CDH1 gene expression was recovered by treatment with 5-aza-dC in a liver cancer cell line Li21, the methylation status of the entire CpG island and acetylation and methylation status of associated histones were not significantly altered. These results demonstrate that the silenced CDH1 gene can be reactivated without apparent alteration of histone modification or CpG island methylation.     

Classical in-plane negative magnetoresistance and quantum positive magnetoresistance in undoped InSb thin films on GaAs (1 0 0) substrates

Magnetoresistance (MR) effects have been investigated in perpendicular and parallel magnetic fields at 300, 80 K and liquid He temperatures for undoped InSb thin films 0.1–2.3 μm thick grown on GaAs(1 0 0) substrates by MBE. At high temperatures, the intrinsic carriers show the parabolic negative MR observable only in magnetic fields parallel to the film. The skipping-orbit effect due to surface boundary scattering in the classical orbits in the plane vertical to the film has been argued to be responsible for the negative MR. At low temperatures (T=80 K), the transport is dominated by the two-dimensional (2D) electrons in the accumulation layers at the InSb/GaAs(1 0 0) hetero interface; MR is positive and shows a logarithmic increase with anisotropy between parallel and perpendicular field orientation, arising from the 2D weak anti-localization (WAL) that reflects the interplay between the spin-Zeeman effect and strong spin–orbit interaction caused by the asymmetric potential at the interface (Rashba term). The zero-field spin splitting energy of Δ₀13 meV, the electron effective mass of m^*0.10m₀ seven times of the band edge mass in bulk InSb and the effective g-factor of |g^*|15 in the accumulation layer have been inferred from fits of MR for the 0.1 μm thick film to the 2D WL theory.     

Direct observation of excitons and a continuum of one-dimensional Mott insulators: a reflection-type third-harmonic-generation study of Ni-halogen chain compounds

The third-harmonic-generation (THG) spectrum was measured for a NiBr-chain compound, which is a one-dimensional Mott insulator, in a reflection configuration. A sharp peak and a shoulder structure in the THG spectrum are attributed to three-photon resonance to an exciton and a continuum, respectively. The band-edge energy, the exciton binding energy, and the spectral weights for the exciton and the continuum were determined from comparative studies of linear absorption, THG, and electroreflectance spectra. The excitonic effect is more pronounced in the NiCl chain than in the NiBr chain.     

4T split TEM volume head and knee coils for improved sensitivity and patient accessibility

Split RF coils offer improved patient access by eliminating the need for the coil to be slid over the region of interest. For unshielded birdcage coils, the presence of end ring currents necessitates a direct electrical connection between two halves of the coil. For high-field (>3T) shielded birdcage coils, both the shield and the coil must be split and reliably connected electrically. This problem can be circumvented by the use of split TEM volume coils. Since the elements of a TEM coil are coupled inductively, no direct electrical connection between the halves is necessary. In this work we demonstrate that the effects of splitting the shield for head and knee TEMs can be compensated for, and performance retained. For the knee, the improved access allowed the coil diameter to be reduced, enhancing the sensitivity by 15-20%.     

Diffractive multi-beam surface micro-processing using 10 ps laser pulses

A high repetition rate picosecond laser system is combined with a spatial light modulator (SLM) for diffractive multiple beam processing. The effect of the zero order beam is eliminated by adding a Fresnel zone lens (FZL) to defocus the un-diffracted beam at the processing plane. Chromatic dispersion, which is evident with a large bandwidth femtosecond pulses leading to the problem of distorted hole shape is eliminated due to the much narrower spectral bandwidth, 0.1 nm at 10 ps pulselength, resulting in highly uniform intensity spots, independent of diffraction angle. In addition, high-throughput processing is demonstrated by combining the high power laser output, 2.5 W at λ ≈ 1064 nm and fast repetition rate, f ≈ 20 kHz with P > 1.2 W diffracted into 25 parallel beams. This has the effect of creating an “effective” repetition rate of 500 kHz without restrictive scan speeds.