Wavelength-selectable light sources fabricated using advanced microarray-selective epitaxy

An advanced microarray-selective epitaxy with wider open-stripes has been developed for simple fabrication of distributed-feedback laser diode array-based high-power wavelength-selectable light sources. More than 40-mW fiber-coupled power and 50-dB sidemode suppression ratio over 9.2-nm wavelength were achieved.     

A new modification method of exploded lignin for the preparation of a carbon fiber precursor

A lignin-pitch for carbon fiber was prepared in a high yield from exploded lignin on phenolysis followed by heat treatment under a vacuum. The lignin-pitch had an excellent spinnability in the melt state to form a fine filament. The green fibers were easily made infusible when heated in air at a relatively high heating rate (15-60°C/h). The lignin-based carbon fiber was produced in 43.7% of yield based on a starting material. The tensile strength was more than 400 MPa, indicating that the lignin-based carbon fiber is classified into a general purpose grade. © 1993 John Wiley & Sons, Inc.     

Dispersion of pure GeO2 glass core and f-doped GeO2 glass cladding single-mode optical fibre

The letter investigates the dispersion of GeO2 glass core and F-doped GeO2 glass cladding single-mode optical fibre. It is estimated that the total dispersion goes to zero at about ? = 1.77 ?m. The material dispersions of these glasses are also measured. Material dispersion of GeO2 glass, which contains fluorine of 0.41 wt%, vanished at ? = 1.722?m. This occurs at ? = 1.734 ?m for pure GeO2 glass.     

Ultra-High speed InGaAsP/InP DFB lasers emitting at 1.3 µm wavelength

A bandwidth of 13 GHz has been attained in a 1.3 μm DFB laser at 25 °C. A mesa structure was introduced to reduce the parasitic capacitance and the lasing wavelength was detuned from the gain peak to increase the differential gain. This bandwidth is the widest so far reported in 1.3 μm DFB lasers.     

The variation of greenhouse gas emissions from soils of various land-use/cover types in Jambi province,Indonesia

We measured fluxes of three greenhouse gases (N₂O, CO₂O and CH₄) from soils of six different land-use types at 27 temporary field sites in Jambi Province, Sumatra, Indonesia. Study sites included natural and logged-over forests; rubber plantation; oil palm plantation; cinnamon plantation; and grassland field. The ranges of N₂O, CO₂ and CH₄ fluxes were 0.13–55.8 gN m-2h-1; 1.38–5.16 g C m-2d-1; –1.27–1.18 mg C m-2d-1, respectively. The averages of N₂O, CO₂ and CH₄ fluxes at 27 sites were 9.4 gN m-2h-1,3.65 g C m-2d-1, –0.45 mg C m-2d-1, respectively. The values of CO₂ and CH₄ fluxes were comparable with those in the reports regarding other humid tropical forests, while the N₂O flux was relatively lower than those of previous reports. The N₂O fluxes in each soil type were correlated with the nitrification rates of soils of 0–5 cm depth. In Andisols, the ratio of the N₂O emission rate to the nitrification rate was possibly smaller than that of the other soil types. There was no clear relationship between N₂O flux and the soil water condition, such as water-filled pore space. Seventeen percent of CH₄ fluxes were positive; according to these positive fluxes, we did not find a good correlation between CH₄ uptake rate and soil properties. Although we performed a chronosequence analysis to produce some hypotheses about the effect of land-use change by a limited amount of sampling at one point in time, further tests are required for the future.     

Electron Temperature Distribution Measurements in Clouds of Polystyrene Pellets Ablating in LHD Heliotron Plasma

Two methods for measuring the spatial distribution of the temperature of electrons in a cloud near a polystyrene pellet that ablates in LHD heliotron plasma are described. The first method is based on measuring the ratio of the local emission-coefficient values at wavelengths of 486 ± 5 nm (the H_β line) and 630 ± 5 nm (continuum). The second (new) method is based on the measurement of radiation distributions of the H_β line in the direction along the magnetic field. Both the methods use an assumption about the partial local thermodynamic equilibrium in the cloud and show close results. It is shown for the first time that the temperature of cloud electrons increases from 0.8 eV in the immediate vicinity of the pellet surface to 6.0–7.0 eV at a distance of 6–8 mm from the pellet in the direction along the magnetic field, which agrees with the experimentally observed longitudinal distribution of the H_β radiation in the cloud.     

Effects of Mobile-Phase Composition and Temperature on the Selectivity of Poly(N-isopropylacrylamide)-Bonded Silica Gel in Reversed-Phase Liquid Chromatography

We developed a simple preparation method for poly(N-isopropylacrylamide) (poly(NIPAM))-bonded silica using a water-organic two-phase system to directly copolymerize N-isopropylacrylamide with 3-(methacryloxy)propyl moieties on the silica surfaces. The stationary phase showed a phase transition with the change in temperature or in methanol content, resulting in notable changes in selectivity which cannot be expected with alkyl-type stationary phases. The packing material showed an increase in retention and column efficiency with the increase in temperature between 30 and 40 °C or in methanol content between 10 and 20%. The temperature-responsive properties were reduced with the increase in methanol content of the mobile phase and lost at 40% or higher. Significant changes in retention selectivity by the addition of methanol were observed for benzene derivatives below the transition temperature of poly(NIPAM). The preferential retention of hydrogen bond acceptors was observed at low temperatures in the mobile phase of low methanol content, while dominant contribution of the hydrophobic interaction to the retention of solutes was observed at the higher temperature in aqueous mobile phase or at the higher methanol concentration. The temperature increase brought about similar changes in retention behavior of the poly(NIPAM)-bonded silica packing materials to the addition of methanol to the mobile phase.     

Epoxy curing process with small shrinkage based on binary nucleophilic reagent system consisting of amine and carboxylic acid

A curing process of bisphenol‐A diglycidyl ether using amine‐carboxylic acid salts was studied with focusing on its small‐volume shrinkage. The characteristic point of the curing process was the initial high‐density created by strong interactions between the ionic species such as electro‐statistic one and hydrogen‐bonding, which disappeared on the consumption of these species by their reactions with the epoxide to give the low‐density neutral polymers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Weathering of low‐density polyethylene grafted with itaconic acid in laboratory tests

Polyethylene grafted with itaconic acid was subjected to weathering under laboratory accelerated conditions. The course of the photo‐oxidative degradation process of that material was studied by FTIR spectroscopy both through quantitative measurements of changes in absorbance values at selected wave numbers and through measurements of surface area values for absorption bands which were separated by means of deconvolution. The use of both those procedures of quantitative determinations resulted in a general conclusion that the oxidation process was initiated from the very first moment of irradiation, and it produced ketones, acids, esters (intramolecular and of acetate type), peracids, peresters, hydroperoxides, and alcohols. The molecular weight values and gel number values, which were established as well, pointed out that oxidation was accompanied by cracking of polymer macromolecules, and also by polymer crosslinking to a limited degree. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Evaluation of an air-cleaning unit having photocatalytic sheets to remove acetaldehyde from indoor air

A photocatalytic oxidation (PCO) reactor to which newly developed photocatalytic sheets were applied to decontaminate indoor air was considered in this study. Firstly, the PCO reactor was designed to achieve efficient ultraviolet (UV) irradiation. Then the rate at which acetaldehyde, as a representative indoor air contaminant, was removed by the PCO reactor was calculated using a computational fluid dynamics (CFD) simulation. In this process, some alternatives that achieved higher removal performance using obstacles at the inlet and outlet openings were introduced. The results of the CFD simulation showed that the obstacles installed in the middle of the inlet and outlet openings helped to improve the removal performance of the PCO reactor as the degree of contact by the acetaldehyde on the PCO sheets was increased. Furthermore, the results of these experiments also showed some improvement in removal performance when obstacles were installed. However, the overall experimental performances were far lower than as had been suggested by the CFD simulation, which inferred that the oxidation rate on the surface of the PCO sheets was not 100%, as had been assumed in the CFD simulation. Nevertheless, CFD simulations are assumed to be a good method for selecting the optimal option from many alternative PCO reactors.