An over 2200-km coherent transmission experiment at 2.5 Gb/s usingerbium-doped-fiber in-line amplifiers

A 2223 km transmission distance was achieved with a 2.5-Gb/s heterodyne detection system that used erbium-doped-fiber in-line amplifiers and dispersion-shifted single-mode fibers. Twenty-five amplifiers, placed at approximately 80-km intervals, offered a total gain of more than 440 dB. Receiver sensitivity was -42.0 dBm, with only a 4.2-dB penalty from the initial sensitivity achieved by the back-to-back configuration     

Surface characterization and catalytic properties of La1−x -Sr x CoO3

The surface chemical states of the perovskite-type compounds, strontium doped lanthanum cobalt oxides (La_1?x Sr _x CoO₃), have been investigated using X-ray photoelectron spectroscopy (XPS). Catalytic oxidations of both methane and CO have also been investigated using flow methods. The chemical composition of the surface of La_1?x Sr _x CoO₃ was very different from that in the bulk, which was measured by X-ray fluorescence spectroscopy (XRFS). The catalytic activity of La_1?x Sr _x CoO₃ increased with an increase in the quantity of cobalt atoms on the surface.     

High-reliability GaAs-AlGaAs HBTs by MBE with Be base doping andInGaAs emitter contacts

The authors have developed a modified MBE growth process to produce high-gain n-p-n GaAs-AlGaAs heterojunction bipolar transistors (HBTs) with a mean time to failure (MTTF) of 1.5×10⁸ h at 125°C. Beryllium incorporation and diffusion are controlled through a combination of reduced substrate temperature and increased As/Ga flux ratio during MBE growth, resulting in extremely stable HBT profiles. The authors also demonstrate graded InGaAs surface layers with nonalloyed refractory metal contacts that significantly improve ohmic reliability compared to alloyed AuGe contacts. The ability to produce robust HBTs by MBE is critically important to this technology     

Metabolism of tetramethrin isomers in rat: IV. Tissues responsible for formation of reduced and hydrated metabolites

1. To identify the sites of formation of the reduced metabolites, 3-hydroxy-cyclohexane-1,2-dicarboximide (3-OH-HPI-1 and -2), 1,2-cyclohexanedicarboxylic acid (TCDA) and 1-hydroxy-1,2-cyclohexanedicarboxylic acid (1-OH-HPA), in rat treated with 14C-labelled (1RS, trans)-tetramethrin, [3,4,5,6-tetrahydrophthalimidomethyl (1RS, trans)-chrysanthemate], bile-duct cannulated animals were orally or intravenously administered 14C-labelled 3,4,5,6-tetrahydrophthalimide (TPI) or 3,4,5,6-tetrahydrophthalic acid (THPA), precursors of these metabolites, and bile, urine and faeces were collected for analysis. 2. 3-OH-HPI-1 and 3-OH-HPI-2, which are cis-form reduced metabolites, and 1-OH-HPA were detected in bile and urine samples of the bile-cannulated rat treated intravenously and orally with 14C-labelled TPI, indicating their formation in tissues or blood. TCDA, a trans-form reduced metabolite, was not detected in bile, urine or faeces of the bile-cannulated rat treated intravenously with 14C-THPA, but was found in the faeces after oral application, indicating formation in the gastrointestinal tract. 3. To clarify whether 1-OH-HPA is produced from THPA via TCDA (hydroxylation via reduction) or by direct addition of H2O to its double bond (hydration), rats were orally administered 14C-labelled TCDA, and metabolites in urine and faeces were analysed. The observed lack of 1-OH-HPA indicated formation by direct addition of H2O to the double-bond of THPA. 4. To specify which tissues form reduced and hydrated metabolites, in vitro metabolism studies were carried out. Reduction to the cis-form was found to take place in blood cells, reduction to the trans-form took place in the gastrointestinal tract contents, and hydration took place in the liver and the intestinal tract contents.     

Far-Infrared Reflection Spectra of Dielectric Ceramics for Microwave Applications

Far-infrared reflection spectra of dielectric ceramics, BaSm₂Ti₅O₁₄, BaTi₄O₉, and some pcrovskites such as Ba(Zn_1/3Nb_2/3)O₃, have been measured at room temperature using a Fourier transform infrared spectrometer in order to investigate the effect of the crystal structure on the dielectric properties. As for perovskites, Sr(Zn_1/3Nb_2/3)O₃ and Sr(Mg_1/3Nb_2/3)O₃, in which B site ions are ordered, were also measured. Reflectance data were analyzed by means of a factorized form of dielectric functions instead of the classical dispersion theory, and all of the spectra were well fitted. The values of dielectric constants and tan δ calculated from the reflectance data were in good agreement with resonant cavity measurements at 5 GHz. Furthermore, results of this study have shown that the main contribution to the microwave dielectric properties is caused by low-frequency optically active modes located at 50 to about 300 cm⁻¹, and for perovskite structures it is suggested that the ordering of B site ions is significant in obtaining low dielectric losses.     

The structure and maximal gain of CW-pumped GaP-AlGaP semiconductor Raman amplifier with tapers on both sides

GaP-AlGaP waveguide semiconductor Raman amplifiers (SRAs) tapered on both sides were fabricated by high-quality GaP-AlGaP liquid phase epitaxial growth using the temperature difference method with controlled vapor pressure (TDM-CVP), photolithography patterning, and reactive ion etching with PCl/sub 3/ gas. Although the finesse of the both-sides-tapered waveguide SRA is lower than previous values for straight or one-side-tapered waveguides, the CW-pumped gain was maximized, and a maximal gain of 4.2 dB was obtained. This letter presents the effect of tapered structures in SRA with CW pumping amplification.     

Characterization of temporal response, spectral responsivity and its spatial uniformity in photoconductive diamond detectors

Three photoconductive diamond detectors with highly oriented diamond (HOD) films fabricated by the same process were characterized with respect to temporal response, spectral responsivity and its spatial uniformity over the wavelength range from 190 to 250 nm. Temporal measurements showed a drift in the baseline, suggesting the presence of deep level carrier traps. The responsivity of specimen No. 2 was more than twice those of the other two specimens, but it showed an unpredictable current fluctuation. It was found that the spatial uniformities of all the specimens were too low for radiometric purposes. A prominent peak, thought to be due to photoemission, was found in the responsivity spatial distribution of specimen No. 3 under a negative applied voltage.     

High-performance polymer alloys of polybenzoxazine and bismaleimide

Two series of high-performance polymer alloys were prepared by mixing typical benzoxine monomers, 3-phenyl-3,4-dihydro-2H-1,3-benzoxazine (P-a) or 6,6-(1-methylethyliden)-bis-(3,4-dihydro-3-phenyl-2H-1,3-benzoxazine) (B-a), with a typical bismaleimide, 4,4-bismaleimidodiphenyl methane by various ratios followed by thermal treatment up to 240 °C. DSC and IR of the alloys were examined to follow the curing reaction. These analyses showed that the obtained polymer alloys are AB co-cross-linked polymer networks through the formation of ether linkage between the hydroxyl group of polybenoxazine and the double bond of bismaleimide. Viscoelastic analysis and softening temperature measurement revealed that the polymer alloys have much higher glass transition temperatures than those of each homopolymer. The thermal stability also increased with the increase of bismaleimide content as evidenced by TGA.     

A reconfigurable VLSI-based double-lens tracking camera

Watching and tracking an object while seeing a much wider view is one of advantages of the eye system. We proposed and developed a tracking camera system that mimics the eyes by using double-lens modules. In the system, a wide view is captured through the wide-lens module, while the target in it is tracked and magnified through the telescopic lens module. Electronic circuits for tracking control are implemented onto the reconfigurable VLSI or FPGA in order to embed the parallelism in the tracking algorithm into the hardware. A successfully developed FPGA-based prototype performs high-speed tracking at the video-rate. This work was present in part at the 12th International Symposium on Artificial Life and Robotics, Oita, Japan, January 25–27, 2007     

Young’s modulus of crystalline C60 nanotubes studied by in situ transmission electron microscopy

Bending tests of crystalline nanotubes composed of fullerene C₆₀ molecules are performed inside a high-resolution transmission electron microscope. We fixed one side of a C₆₀ nanotube with a body-centered tetragonal structure with typical inner and outer diameters, i.e., 180 nm and 510 nm, respectively, and then applied concentrated forces on the other side using piezomanipulation of a silicon nanotip. The bending process was observed in situ by transmission electron microscopy with simultaneous measurements of the forces by an optical deflection method. It was found that the Young’s modulus of the nanotube was estimated to be 62–107 GPa, which was 1.1–3.3 times larger than that of C₆₀ nanowhiskers. The result concerning the increase in the Young’s modulus of the C₆₀ nanotube provided an experimental evidence for the structural model composed of an inner core and a surface shell for C₆₀ nanowhiskers.