Effect of surfactants on phenol removal by the method of polymerization and precipitation catalysed by Coprinus cinereus peroxidase

The removal of phenol by peroxidase‐catalysed polymerization was examined using Coprinus cinereus peroxidase in the presence of surfactants. The non‐ionic surfactants with poly(oxyethene) residues, Triton X‐100, Triton X‐405 and Tween 20, enhanced the phenol removal efficiency at a level similar to high relative molecular mass poly(ethylene glycol) (relative molecular mass 3000). Although the improvement in the removal efficiency was less than that of Triton X‐100, Span 20, sodium lauryl sulfate (SDS) and lauryl trimethylammonium bromide (DTAB) also enhanced the removal efficiency. The requirement of the enzyme for almost 100% removal of 100 mg dm^?3 phenol decreased to one‐fourth by the addition of 30 mg dm^?3 Triton X‐100. Triton X‐100, Triton X‐405, Tween 20 and DTAB could reactivate the enzyme precipitated with the phenol polymer, leading to the restarting of the phenol removal reaction. Copyright © 2003 Society of Chemical Industry     

Identification of stress-induced leakage current components and thecorresponding trap models in SiO2 films [MOStransistors]

Time-decay stress-induced leakage current (SILC) has been systematically investigated for the cases of both Fowler-Nordheim (FN) stress and substrate hot-hole stress. From the three viewpoints of the reproducibility of the current component for the gate voltage scan, the change of oxide charge during the gate voltage scan, and the resistance of the current component to thermal annealing, it has been found that time-decay stress-induced leakage current is composed of five current components, regardless of stress type. Trap models corresponding to each current component have been proposed. In addition, it has also been proven that holes generate the electron traps related to one of those current components     

Insolation forecasting by a multi-stage neural network

A single-stage neural network has been proposed to forecast next day insolation. In this paper, a multi-stage neural network is developed to reduce forecasting error further. A first-stage neural network forecasts average atmospheric pressure for the next day from atmospheric pressure data of the previous day. A second-stage neural network forecasts insolation level for the next day from the average atmospheric pressure and weather data of the previous day. A third-stage neural network forecasts next day insolation from the insolation level and weather data of the previous day. Meteorological data of Omaezaki, Shizuoka at April 1994 were chosen as input data. The insolation values forecasted by the multi-stage and the single-stage neural networks are compared with the measurement values. The results show that the forecasting error is reduced to 24% (by the multi-stage) from 33% (by the single-stage). © 1998 Scripta Technica, Electr Eng Jpn, 125(4): 26–33, 1998     

Extremely narrow spectral linewidth and low chirping of theMQW-DFB-PPIBH laser diode

The low threshold current of 9 mA, the high side-mode suppression ratio of more than 45 dB, the extremely narrow spectral linewidth of 1.1 MHz, and the low chirping of 2.8 Å at -20 dB at 2 Gb/s nonreturn to zero (NRZ) modulation have been achieved in the multiple quantum well (MQW) distributed feedback (DFB) p-substrate partially inverted buried heterostructure (PPIBH) laser diode. The spectral linewidth of 1.1 MHz is the narrowest value among 300-μm-length solitary laser diodes. These results suggest that the MQW-DFB laser diodes are a promising light source for longer distance and higher bit-rate optical communication systems and coherent optical communication systems     

Dynamically reducing retransmission control forslow-frequency-hopped communication systems

A dynamically reducing retransmission control scheme is proposed for slow-frequency-hopped communication systems. In the proposed scheme a transmitter defers transmission of a new packet until all the other transmitters receive positive acknowledgments, so that the number of active transmitters are dynamically reduced. The performance of the proposed scheme is compared with the conventional scheme, in which a transmitter is permitted to transmit a new packet in any slot, in terms of the normalized throughput and the 98% packet transmission delay. The numerical results show that the proposed scheme outperforms the conventional scheme, although for some values of the number of transmitters the conventional scheme has higher normalized throughput     

Reusable Floating Beads with Immobilized Xylose-Fermenting Yeast Cells for Simultaneous Saccharification and Fermentation of Lime-Pretreated Rice Straw

Novel bioreactor beads for simultaneous saccharification and fermentation (SSF) of lime-pretreated rice straw (RS) into ethanol were prepared. Genetically modified Saccharomyces cerevisiae cells expressing genes encoding xylose reductase, xylitol dehydrogenase, and xylulokinase were immobilized in calcium alginate beads containing inorganic lightweight filler particles to reduce specific gravity. For SSF experiments, the beads were floated in slurry composed of lime-pretreated RS and enzymes and incubated under CO₂ atmosphere to reduce the pH for saccharification and fermentation. Following this reaction, beads were readily picked up from the upper part of the slurry and were directly transferred to the next vessel with slurry. After 240 h of incubation, ethanol production by the beads was equivalent to that by free cells, a trend that was repeated in nine additional runs, with slightly improved ethanol yields. Slurry with pre-saccharified lime-pretreated RS was subjected to SSF with floating beads for 168 h. Although higher cell concentrations in beads resulted in more rapid initial ethanol production rates, with negligible diauxic behavior for glucose and xylose utilization, no improvement in the ethanol yield was observed. A fermentor-scale SSF experiment with floating beads was successfully performed twice, with repeated use of the beads, resulting in the production of 40.0 and 39.7 g/L ethanol. There was no decomposition of the beads during agitation at 60 rpm. Thus, this bioreactor enables reuse of yeast cells for efficient ethanol production by SSF of lignocellulosic feedstock, without the need for instruments for centrifugation or filtration of whole slurry.     

Removal of lignin in a liquid system by an isolated fungus

The screening of a strain which could perform lignin removal was carried out. Based on taxonomic study the isolated strain (LM‐2) was identified as Penicillium sp. LM‐2 could decolorize 0.6 g dm^?3 lignin within 4 days in a shaking culture at 25 °C. The efficiency of decolorization of the lignin was over 80% in the pH range of 4.0–6.0, but was low above pH 6.2. The rise of temperature had a slight adverse effect on the lignin decolorization in the range of 25–35 °C. Lignolytic enzymes such as lignin peroxidase, manganese peroxidase and laccase were not detected in the culture broth or within the fungal cells. The lignin was removed from the high molecular weight fraction mainly by adsorption and accumulation inside the cells. © 2001 Society of Chemical Industry     

Preparation and properties of transparent cellulose hydrogels

Highly transparent cellulose hydrogels with physical crosslinkage were prepared from nonaqueous organic cellulose solutions and viscose by coagulating and regenerating cellulose in an aqueous solution containing a water‐miscible organic solvent. Nonaqueous organic cellulose solutions used were LiCl/dimethylacetamide, paraformaldehyde/dimethyl sulfoxide, and triethylammonium chloride/dimethyl sulfoxide. Preparation conditions and physical properties of the transparent cellulose hydrogels were studied. The transparency of the cellulose hydrogels depended on the composition of the aqueous solution containing the organic solvent. Furthermore, transparent cellulose hydrogels from viscose showed high tensile strength. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3020–3025, 2003     

Proton-conducting electrolyte membranes based on hyperbranched polymer with a sulfonic acid group for high-temperature fuel cells

The hyperbranched polymers (HBP-SA-Acs) with both a sulfonic acid group as a functional group and an acryloyl group as a cross-linker at terminals in different ratios of sulfonic acid group/acryloyl group (SO₃H/Ac) were successfully synthesized as a new thermally stable proton-conducting electrolyte. The cross-linked hyperbranched polymer electrolyte membranes (CL-HBP-SAs) were prepared by thermal polymerizations of the HBP-SA-Acs using benzoyl peroxide, and their ionic conductivities under dry condition and thermal properties were investigated. The ionic conductivities of the CL-HBP-SAs were found to be in the range of 2.2 × 10⁻⁴ to 3.3 × 10⁻⁶ S/cm, depending upon the SO₃H unit contents, at 150 °C under dry condition, and showed the Vogel-Tamman-Fulcher (VTF) type temperature dependence, indicating that proton transfer is cooperated by local polymer chain motion. All CL-HBP-SAs were thermally stable up to 260 °C, and they had suitable thermal stability as electrolyte membranes for the high-temperature fuel cells under dry condition. Fuel cell measurement using a single membrane electrode assembly cell with a cross-linked electrolyte membrane was successfully performed under non-humidified condition. It was demonstrated that applying the concept of dry polymer system to proton conduction is one possible approach toward high-temperature fuel cells.