Effect of span loss increase on the optically amplifiedcommunication system

In optical fiber communication systems using Er³⁺ doped fiber amplifiers operating in their compression region, the optical signal power is known to be restored by the self-healing effect in the case of the span loss increase. In this paper, the influence of such excess loss on the system transmission performance is experimentally and numerically investigated from the point of view of the system signal-to-noise ratio and Q-factor. The results show that the system SNR is not completely recovered although the signal power is restored after several stages of amplifiers and that there exists the residual degradation of the system SNR. Through a 5.3 Gb/s data transmission experiment over 3000 km, the transmission penalty due to the excess span loss is confirmed to be decided by this residual degradation of the system SNR. The obtained results can be used for system design and a plan of maintenance for the optical amplifier communication system     

Photoacoustic spectra of Sb-doped ZnSe

Photoacoustic (PA) spectra were made on Sb-doped ZnSe samples grown by metalorganic vapor phase epitaxy (MOVPE). The samples deposited at a low temperature under irradiation show the PA spectrum with a sharp edge near the band gap and with three distinct peaks. From the Sb flow rate dependence of PA peaks, two of them seem to be related to Sb impurities. Non-doped sample shows only one peak, which is tentatively ascribed to the deep level associated with Se defects.     

2 Tbit/s (200×10 Gbit/s) over 9240 km transmission experimentwith 0.15 nm channel spacing using VSB format

2 Tbit/s (200 WDM×10 Gbit/s) transmission over 9240 km using only a C-band erbium-doped fibre amplifier is demonstrated. A vestigial sideband modulation scheme was adopted to realise 0.15 nm channel separation. Ultra-high spectral efficiency of 53% was achieved. All channels showed better than 9 dB Q-factor, which can be corrected to less than 10^-9 BER after OSW Super forward error correction     

Durability Characteristics of Some Assorted Rocks

Durability characteristics of some argillaceous clastic rocks from cold regions are investigated. Two sets of experiments, namely slake durability (wet-dry) and freeze-thaw tests, were conducted on welded tuff, carbonates (limestone and dolomite), sandstone, and schist samples collected from northern parts of Japan and from the higher Himalayas of Nepal. The slaking tests were performed in pure water and seawater as well as in aqueous solution of different salinity. A tendency to decrease in slake durability with an increase in porosity is observed. The results reveal that the slake durability of a rock increases with an increase in the concentration of salt in water. Freeze-thaw experiments conducted on welded tuff and schist reveal that crack initiates earlier but extends slower in schist than in welded tuff and that the tuff deteriorates and wears faster than the schist.     

Fabrication of flat silicon surfaces using ion-exchange particles in ultrapure water

A silicon etching process using an ultrafine particle dispersion is proposed. The ultrafine particles contain quaternary ammonium hydroxide groups as ion-exchange groups, giving an alkaline dispersion. In the etching process, the fine particles and impurity ions can be easily separated by filtration or dialysis. Dialysis led to a decrease in the concentration of impurities in the dispersion, which included heavy metal ions and alkali metal ions known to result in a rough etched surface and affect the electronic properties of the semiconductor. Our proposed method is applicable to the surface planarization of silicon single crystals, manufacture of semiconductor devices, and fabrication of MEMS (micro-electro and mechanical systems). In addition, the etching waste can be reused after removal of the impurity ions by dialysis. Thus, the method has low environmental burden. Using the proposed alkaline etching dispersion, cathodic electrochemical etching of a silicon single crystal was demonstrated. The etching characteristics, properties of the etched surface, and effects of particle size were evaluated. The roughness of a 2 μm × 2 μm etched p-Si(0 0 1) surface was measured to be 0.1228 nm Ra (center line average roughness) by AFM.     

Accurate contour control of mechatronic servo systems without parameter adjustment by use of modified input data method

This paper describes a technique of accurate contour control by a modified input data method for industrial mechatronic servo systems with unadjusted servo parameters. Adjustment of the servo parameters in order to achieve high‐performance contour control in mechatronic servo systems is a tedious task. The modified input data method can realize satisfactory contour control performance accuracy within rather large tolerances for servo parameter errors. The effectiveness of the proposed method has been verified by simulation and experimental studies of contour control of an actual mechatronic servo system. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(4): 60–69, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20322     

LIGAND database for enzymes, compounds and reactions

LIGAND is a composite database consisting of three sections and containing the information of chemical substances, chemical reactions and enzymes that catalyze reactions. The COMPOUND section is a collection of metabolic compounds, as well as macromolecules, chemical elements and other chemical substances in a living cell. The ENZYME section is a collection of all known enzymatic reactions, together with the information of enzyme molecules, classified according to the EC (Enzyme Commission) numbers. The REACTION section is a new addition to the database containing metabolic reactions that appear in the pathway diagrams of the KEGG/PATHWAY database and/or in the ENZYME section. The LIGAND database can be accessed through the WWW (http://www.genome.ad.jp/dbget/ligand.html) or may be downloaded by anonymous FTP (ftp://kegg.genome.ad. jp/molecules/ligand).     

Computational Models of Similarity for Drum Samples

In this paper, we optimize and evaluate computational models of similarity for sounds from the same instrument class. We investigate four instrument classes: bass drums, snare drums, high-pitched toms, and low-pitched toms. We evaluate two similarity models: one is defined in the ISO/IEC MPEG-7 standard, and the other is based on auditory images. For the second model, we study the impact of various parameters. We use data from listening tests, and instrument class labels to evaluate the models. Our results show that the model based on auditory images yields a very high average correlation with human similarity ratings and clearly outperforms the MPEG-7 recommendation. The average correlations range from 0.89-0.96 depending on the instrument class. Furthermore, our results indicate that instrument class data can be used as alternative to data from listening tests to evaluate sound similarity models.     

Functional analyses of a variety of chimeric dioxygenases constructed from two biphenyl dioxygenases that are similar structurally but different functionally

The biphenyl dioxygenases (BP Dox) of strains Pseudomonas pseudoalcaligenes KF707 and Pseudomonas cepacia LB400 exhibit a distinct difference in substrate ranges of polychlorinated biphenyls (PCB) despite nearly identical amino acid sequences. The range of congeners oxidized by LB400 BP Dox is much wider than that oxidized by KF707 BP Dox. The PCB degradation abilities of these BP Dox were highly dependent on the recognition of the chlorinated rings and the sites of oxygen activation. The KF707 BP Dox recognized primarily the 4'-chlorinated ring (97%) of 2,5,4'-trichlorobiphenyl and introduced molecular oxygen at the 2',3' position. The LB400 BP Dox recognized primarily the 2,5-dichlorinated ring (95%) of the same compound and introduced O2 at the 3,4 position. It was confirmed that the BphA1 subunit (iron-sulfur protein of terminal dioxygenase encoded by bphA1) plays a crucial role in determining the substrate selectivity. We constructed a variety of chimeric bphA1 genes by exchanging four common restriction fragments between the KF707 bphA1 and the LB400 bphA1. Observation of Escherichia coli cells expressing various chimeric BP Dox revealed that a relatively small number of amino acids in the carboxy-terminal half (among 20 different amino acids in total) are involved in the recognition of the chlorinated ring and the sites of dioxygenation and thereby are responsible for the degradation of PCB. The site-directed mutagenesis of Thr-376 (KF707) to Asn-376 (LB400) in KF707 BP Dox resulted in the expansion of the range of biodegradable PCB congeners.