Influence of Nb dopant on the structural and optical properties of nanocrystalline TiO2 thin films

In this study, preparation of Nb-doped (0-20 mol% Nb) TiO₂ dip-coated thin films on glazed porcelain substrates via sol-gel process has been investigated. The effects of Nb on the structural, optical, and photo-catalytic properties of applied thin films have been studied by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Surface topography and surface chemical state of thin films was examined by atomic force microscope and X-ray photoelectron spectroscopy. XRD and Raman study showed that the Nb doping inhibited the grain growth. The photo-catalytic activity of the film was tested on degradation of methylene blue. Best photo-catalytic activity of Nb-doped TiO₂ thin films were measured in the TiO₂-1 mol% Nb sample. The average optical transmittance of about 47% in the visible range and the band gap of films became wider with increasing Nb doping concentration. The Nb⁵⁺ dopant presented substitutional Ti⁴⁺ into TiO₂ lattice.     

Study on waste heat recovery from exhaust smoke in cogeneration system using woody biomass fuels

In recent years, fossil fuels such as petroleum, coal, and natural gas have become limited resources. In addition, bad effects caused by excessive carbon dioxide (CO₂) emissions have now begun destroying our global environment seriously. Since current living and economical standards depend strongly on the fossil fuels, it is necessary to realize a new society that utilizes biomass as one of major sources of energy. In this background, we manufactured a practical Stirling engine using woody biomass fuels for the first time in Japan in 2005. Further we proposed a unique cogeneration system with the Stirling engine that uses woody biomass fuels such as sawdust, firewood, and wood pellets. In this cogeneration system, 43% of the input energy is wasted as heat loss from the exhaust smoke into the atmosphere. Therefore we tried to recover the waste heat by using a thermoelectric conversion module in this study. In this report, the results of basic performance test and demonstration experiment as a cogeneration system combined the waste heat recovery with a power generating system are reported. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20390     

Determination of benzo[a]pyrene-7,10-quinone in airborne particulates by using a chemiluminescence reaction of hydrogen peroxide and hydrosulfite

An ultraweak chemiluminescence (CL) was observed when sodium hydrosulfite (NaHSO(3)) reacts with hydrogen peroxide (H(2)O(2)) and was enhanced 70 times by adding 10 pmol benzo[a]pyrene-7,10-quinone (7,10-BaPQ). The CL reaction is fast, and it reached maximum intensity in 0.1 s, and then decayed to baseline in 3 s. Mechanism of NaHSO(3)-7,10-BaPQ-H(2)O(2) system were investigated by CL spectrum, radical scavengers and electron spin resonance (ESR). Hydroxyl radical ((?)OH), super oxide anion radical ((?)O(2)(-)), and sulfite radical ((?)SO(3)(-)) were generated in the NaHSO(3)-7, 10-BaPQ-H(2)O(2) system. Reduction of 7,10-BaPQ by (?)O(2)(-) radical gave excited semiquinone, which showed strong CL emission when decayed to its ground state. Maximum CL emission wavelength was located at 440 nm, which may belong to the excited semiquinone. This CL system was developed as post column detection of high performance liquid chromatography for the determination of 7,10-BaPQ. Linearity ranged from 50 fmol to 20 pmol (R(2) = 0.9995) with limit of detection of 30 fmol (S/N = 3). The proposed method was used to determine 7,10-BaPQ in airborne particulates. Average atmospheric concentrations of 7,10-BaPQ in Kanazawa in December 2010 and Wajima in October 2007 were 2.0 and 1.6 pg/m(3), respectively.     

Intracavity absorption spectroscopy with a tunable multimode traveling-wave ring Ti:sapphire laser

A tunable multimode unidirectional traveling-wave Ti:sapphire laser was developed to measure in situ the atmospheric absorption spectra using intracavity absorption spectroscopy. The effective absorption path length was 2100 km. O2 and H2O vapor lines in atmosphere with absorption coefficients of 10(-6)-10(-8) cm(-1) were measured with uncertainties <5%, and the absorption coefficients were in agreement with those estimated from the HITRAN database. By tuning the wavelength, a weak absorption line with an absorption coefficient of 10(-9) cm(-1) was measured with a sensitivity of 2×10(-10) cm(-1). The sensitivity was limited by the residual parasitic variation that appeared in the spectrum.     

PON with Automatic Protection switching for high reliable communication

PON (Passive Optical Network) permits the economical deployment of FTTH (Fiber to the Home) networks by sharing a single optical subscriber line among multiple subscribers. Especially since 2002, the deployment of PON systems has grown rapidly. This paper introduces the current status of FTTH in Japan then proposes a redundant optical access system with APS (Automatic Protection Switching) over PON which enables PONs for FTTBus (Fiber to the Business).     

High‐Density Carrier Accumulation in ZnO Field‐Effect Transistors Gated by Electric Double Layers of Ionic Liquids

Very recently, electric‐field‐induced superconductivity in an insulator was realized by tuning charge carrier to a high density level (1 × 10¹⁴ cm^?2). To increase the maximum attainable carrier density for electrostatic tuning of electronic states in semiconductor field‐effect transistors is a hot issue but a big challenge. Here, ultrahigh density carrier accumulation is reported, in particular at low temperature, in a ZnO field‐effect transistor gated by electric double layers of ionic liquid (IL). This transistor, called an electric double layer transistor (EDLT), is found to exhibit very high transconductance and an ultrahigh carrier density in a fast, reversible, and reproducible manner. The room temperature capacitance of EDLTs is found to be as large as 34 µF cm^?2, deduced from Hall‐effect measurements, and is mainly responsible for the carrier density modulation in a very wide range. Importantly, the IL dielectric, with a supercooling property, is found to have charge‐accumulation capability even at low temperatures, reaching an ultrahigh carrier density of 8×10¹⁴ cm^?2 at 220 K and maintaining a density of 5.5×10¹⁴ cm^?2 at 1.8 K. This high carrier density of EDLTs is of great importance not only in practical device applications but also in fundamental research; for example, in the search for novel electronic phenomena, such as superconductivity, in oxide systems.     

Succession of bacterial and fungal communities during a traditional pot fermentation of rice vinegar assessed by PCR-mediated denaturing gradient gel electrophoresis

Denaturing gradient gel electrophoresis (DGGE) based on small subunit rRNA gene was applied to a traditional rice vinegar fermentation process in which the conversion of rice starch into acetic acid proceeded in a pot. The fungal DGGE profile indicated that the transition from Aspergillus oryzae to Saccharomyces sp. took place at the initial stage at which alcohol production was observed. The early stage was characterized by the coexistence of Saccharomyces sp. and lactic acid bacteria. Almost all of the bacterial DGGE bands related to lactic acid bacteria were replaced by bands derived from Lactobacillus acetotolerance and Acetobacter pasteurianus at the stage at which acetic acid started to accumulate. The microbial succession, tested in three different pots, was found to be essentially identical. Among the bacteria isolated at the early stage, some species differed from those detected by DGGE. This is the first report to reveal the microbial community succession that occurs during a unique vinegar fermentation process, as determined by a culture-independent method.     

Rapid separation and counting of viable microbial cells in food by nonculture method with bioplorer, a focusing-free microscopic apparatus with a novel cell separation unit

A nonculture method utilizing a novel apparatus, the bioplorer, was developed. The bioplorer is composed of an efficient cell separation unit, a focusing-free microscopic device, and an image analysis program. A meat or vegetable suspension is poured into the cell separation funnel, and insoluble matter in the sample suspension is trapped by prefilters. Microbial cells passing through the two prefilters are then trapped by the membrane filter (pore size, 0.4 microm). Trapped cells are double-stained with 4',6'-diamidino-2-phenylindole and propidium iodide, and the membrane filter is removed and set on the focusing-free microscope. A fluorescent image is then recorded. Total numbers of viable and dead cells on the membrane filter can thus be determined automatically. One assay can be performed within 10 min, which is much faster than the culture method. The results obtained with both the nonculture method and the culture method for meat and vegetable samples were highly correlated (r = 0.953 to 0.998). This method is feasible for the practical purpose of food safety control.     

A miniaturized methanol reformer with Si-based microreactor for a small PEMFC

A miniaturized methanol reformer with Cu/ZnO/Al₂O₃ catalyst-based microreactor suitable for the supply of hydrogen for a small proton exchange membrane fuel cell is designed and fabricated using microfabrication techniques. The microreactor () is constructed from glass and silicon substrates to form a serpentine catalyst-coated microchannel of 333 mm in length and cross-section of , designed based on mass and heat balance analyses using a one-dimensional model. The use of the high-performance Cu/ZnO/Al₂O₃ catalyst allows for higher hydrogen production rates than possible using a commercial Cu/ZnO catalyst. The microreactor is demonstrated to be capable maintaining a hydrogen production rate suitable for powering 1 W-class devices such as cellular phones.