External Synchronization of 160-GHz Optical Beat Signal by Optical Phase-Locked Loop Technique

We have synchronized a 160-GHz optical beat signal with a 40-GHz reference optical pulse train by using an optical phase-locked loop (OPLL). The OPLL consists of an optical beat signal source, comprising a pair of three-electrode distributed feedback laser diodes that works as a voltage controlled oscillator, and an all-optical phase detector based on the two-photon absorption in a silicon avalanche photodiode. Phase-locking operation is confirmed through phase-error measurement and cross-correlation trace measurement. The residual timing jitter of the 160-GHz optical beat signal relative to the reference pulse train, in the bandwidth of 80 MHz, is measured to be as small as 126 fs     

Fabrication of blue-light emission fused-silica substrates by using Si-ion implantation and high-temperature annealing

We fabricated fused-silica substrates which emit blue light by using Si-ion implantation and high-temperature annealing. Photoluminescence peak wavelengths are around 400 nm, and the peak intensities can be remarkable after annealing above 1150 °C.     

Challenges of Raman Amplification

Raman amplifiers are often regarded as a typical example of technologies rapidly developed in the midst of turmoil created by the so-called wavelength division multiplexing (WDM) bubble. Indeed, Raman amplifiers turned out to be technically very attractive in all the aspects of capacity, reach, and bit rate. Even though Raman amplifiers are actually being deployed into systems in commercial service, the practical issues, such as cost, reliability and safety, are yet to be further discussed, particularly for the configuration of distributed amplification. After summarizing the advantages of Raman amplification and reviewing pump laser technologies, this paper will highlight ongoing efforts on practical issues, which include reliability and safety issues of fiber under high-power operations. Finally, it is concluded that by overcoming the above-mentioned practical issues, Raman amplification will stay as a key technology for future optical communications because of its compelling unique advantages.     

Optical pulse compression based on stationary rescaled pulse propagation in a comblike profiled fiber

In this paper, optical pulse compression using a comblike profiled fiber (CPF) is theoretically and experimentally studied, in which highly nonlinear fibers and single-mode fibers are alternately concatenated. Stationary rescaled pulse (SRP), is the main focus, which is a recently discovered nonlinear stationary pulse in CPF. The fundamental characteristics of SRP are investigated, and SRP propagation is applied to the design of the CPF pulse compressor. Using the proposed design method, the specifications of the CPF can easily be controlled, such as the compression ratio per step of the CPF or the pedestal of the output pulse. Two experimental results of pulse compression using the CPF based on the proposed design method are shown: 1) pulse compression with a large compression ratio per step of the CPF and 2) low-pedestal and wideband wavelength-tunable compression. A parametric noise-amplification phenomenon occurring in a compression process for an optical pulse sequence is also numerically analyzed.     

Oxidative Degradation of β-Cyclodextrin Induced by Lipid Peroxidation

The oxidative degradation of β-cyclodextrin (β-CD) induced by autoxidation of linoleate has been investigated in the solid system composed of β-CD and linoleate. β-CD was oxidized with a propagative oxidation of linoleate to induce the cleavage of its glucosidic linkage and this degradation proceeded proportionally with the moisture content in the solid system. The oxidative cleavage of β-CD gave several kinds of oligosaccharides which were composed of D -erythrose, D -arabinose, D -erythropentosulose, D -xylopentdial-dose, D -glucose and deoxyunsaturated hexose as their reducing terminals. These degradation of β-CD seemed to be initiated by certain radical species formed from the peroxidation of linoleate.     

Transformation of epithelial Madin-Darby canine kidney cells with p60(v-src) induces expression of membrane-type 1 matrix metalloproteinase and invasiveness

Membrane-type 1 matrix metalloproteinase (MT1-MMP) is expressed both in carcinoma cells and in surrounding stromal fibroblasts. MT1-MMP localizes to the surface of tumor cells and is thought to play an important role in tumor invasion. To analyze the mechanism of MT1-MMP gene expression in epithelial tumor cells, the dog kidney epithelial cell line Madin-Darby canine kidney (MDCK) was transformed by oncogenes, including v-src, and expression of MT1-MMP was examined. Transformation of MDCK cells with v-src resulted in loss of cell-to-cell contacts and morphological change. Expression of MT1-MMP in v-src-transformed cells was identified by Northern and Western blotting. Gelatin zymography analysis showed that progelatinase A in the culture medium was processed from latent to activated form by MDCK cells transformed with v-src. The MDCK cells transformed by v-src were tumorigenic in the subcutis (ectopic) and kidney (orthotopic) of nude mice and spontaneously metastasized to the lung after orthotopic implantation. These results suggest that MT1-MMP induced by v-src transformation may promote invasiveness of transformed cells.     

Hypertonicity regulates the function of human neutrophils by modulating chemoattractant receptor signaling and activating mitogen-activated protein kinase p38

Excessive neutrophil activation causes posttraumatic complications, which may be reduced with hypertonic saline (HS) resuscitation. We tested if this is because of modulated neutrophil function by HS. Clinically relevant hypertonicity (10-25 mM) suppressed degranulation and superoxide formation in response to fMLP and blocked the activation of the mitogen activated protein kinases (MAPK) ERK1/2 and p38, but did not affect Ca2+ mobilization. HS did not suppress oxidative burst in response to phorbol myristate acetate (PMA). This indicates that HS suppresses neutrophil function by intercepting signal pathways upstream of or apart from PKC. HS activated p38 by itself and enhanced degranulation in response to PKC activation. This enhancement was reduced by inhibition of p38 with SB203580, suggesting that p38 up-regulation participates in HS-induced enhancements of degranulation. HS had similar effects on the degranulation of cells that were previously stimulated with fMLP, but had no effect on its own, suggesting that HS enhancement of degranulation requires another signal. We conclude that depending on other stimuli, HS can suppress neutrophil activation by intercepting multiple receptor signals or augment degranulation by enhancing p38 signaling. In patients HS resuscitation may reduce posttraumatic complications by preventing neutrophil activation via chemotactic factors released during reperfusion.     

Initial Collection Performance of Resin Wool Filters and Estimation of Charge Density

Abstract

A new type of resin wool filter (RWF) that persists the load with oil droplets was developed by Kimura and colleagues. In the present work, the initial collection performances of RWF (A and C) are measured for various particle sizes (0.03, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3 μm) with different charging states at various filtration velocities (0.05, 0.1, 0.15, and 0.3 m/s). As a result, it is shown that the present RWF impregnated with PTBP resin can attain high collection efficiency (99.999% at filtration velocity of 0.05 m/s) with a pressure drop of less than 30 Pa. The charge density is estimated by applying prediction equations of single-fiber collection efficiencies of electret filters with a dipolar charge distribution because no other prediction equation for RWF are available at present. The experimental single-fiber efficiencies for uncharged particles are successfully predicted by assigning a single value of charge density in the prediction equations for dipolar fibers. The estimated charge density on RWF fibers is 2.1 × 10^{? 4} C/m², which is much higher than those of conventional electret filter media. Therefore, RWF studied in the present work is suitable for the application to respirators as well as room air cleaners.     

Hydrogen behavior in gasochromic tungsten oxide films investigated by elastic recoil detection analysis

Changes in the composition and crystalline structure of gasochromic tungsten oxide films resulting from the incorporation of hydrogen were investigated; the oxide films were prepared by reactive RF magnetron sputtering on SiO₂ and glassy carbon substrates simultaneously. X-ray diffraction analysis of the deposited films at 600 °C showed a uniaxial oriented structure in the (0 1 0) plane of monoclinic WO₃ for both substrates. The elastic recoil detection analysis (ERDA) and Rutherford backscattering spectroscopy (RBS) for the films on glassy carbon revealed that the hydrogen impurity was uniformly distributed up to a concentration of 0.24 H/W. The Pd-coated films on SiO₂ turned blue when they were exposed to a mixture of Ar and 5% H₂ gases. When the sample became colored, the hydrogen concentration in the film increased to 0.47 H/W and the crystalline structure of the film changed from monoclinic to tetragonal. These results indicated that the gasochromic coloration of the tungsten oxide films coincided with incorporation of hydrogen atoms into the crystalline lattice, corresponding to the formation of hydrogen tungsten bronze (H_xWO₃).