Effect of Impurity and Pretreatment Conditions on the Catalytic Activity of Au Powder for CO Oxidation

Recent X-ray photoelectron spectrometer(XPS) analysis of Au powder synthesized by evaporating high purity gold metal (> 99. 99%) in an inert gas detected impurity metals such as Ag and In at levels which far exceed those expected from the impurity levels of raw gold metal. Several samples of Au powder containing different amount of impurity metals were prepared to examine whether the activity of the Au powder for CO oxidation depends upon the impurity or not. The activity of the powder showed a strong correlation with the surface concentration of Ag.     

Enhancement of catalytic activity of alumina by copper addition for selective reduction of nitrogen monoxide by ethene in oxidizing atmosphere

The catalytic activity of alumina for the title reaction has been found to be greatly improved by the loading of copper. The addition of copper resulted in lowering the active temperature region, the higher maximum activity, and the enhancement of the reaction rate. The maximum effect was observed at 0.3 wt% of the loading amount of copper. A similar enhancement was also confirmed on SiO₂-Al₂O₃.     

Crystallization of carbon fibre reinforced polypropylene

Polypropylene (PP) was compounded with carbon fibre of various contents (0, 5, 10, 15, 20 vol%) using a single and a twin screw extruder. The influence of both the carbon fibre content and the compounding method on the thermal behaviour and characteristics of crystallization was studied using differential scanning calorimetry (DSC), polarizing optical microscopy and scanning electron microscopy (SEM). Melting and crystallization temperatures increased with the amount of carbon fibre. Isothermal crystallization was observed using DSC and it was found that crystallization was accelerated by the presence of carbon fibres. Using polarizing optical microscopy, it was found that the nucleation of polypropylene started at the crossing point of two or more fibres.     

Spectroscopic studies of autofluorescence substances existing in human tissue: influences of lactic acid and porphyrins

The influence of lactic acid or porphyrins on the optical properties of tissue fluorophores is investigated by autofluorescence (AF) spectroscopy measurement with a GaN-based ultraviolet laser diode along with Fourier-transform IR (FTIR) spectroscopy measurement. As the lactic-acid concentration becomes dense, the AF peak intensity from elastin and desmosine solutions become wholly weak. A similar reduction in the AF intensity is observed for nicotinamide adenine dinucleotide (NADH) solutions. FTIR analysis indicates that the lactic acid causes the conformational change in elastin and the oxidation of NADH, which can be related to changes in the AF properties. The peak intensity of the tissue fluorophores also becomes weak when porphyrins are added, although the conformational change in each tissue fluorophore is not confirmed from FTIR analysis. Judging from the change in the scattering-light intensity of the excitation source, the observed change mainly originates from the absorption of the excitation source by porphyrins.     

Novel fast atom beam (FAB) processes for fabricating functional nanostructures on three-dimensional microstructures

 We have developed four manufacturing processes that use a fast atom beam (FAB) for fabricating functional nanostructures on three-dimensional (3-D) microstructures. Such fabrication involves two steps: (1) producing the 3-D microstructure; and (2) producing the nanometer-size functional structures at a local point on this microstructure. The FAB methods that we developed for the first step are the separated (non-contact) mask FAB (SM-FAB) and moving mask FAB (MM-FAB), and those for the second step are the nanometer-motion moving mask FAB (NMM-FAB) and electron-beam deposition-pattern FAB (ED-FAB). We previously demonstrated the capability of the SM-FAB, by producing a multi-faced microstructure, a micro gojyunoto (named after an old Japanese temple tower). In this study, we describe and demonstrate the capability of the MM-FAB, by producing multiple, multi-curved and sloped structure, a diffraction grating structure; the NMM-FAB, by producing ultra-fine stairs, 30 nm wide and 30 nm high; and the ED-FAB, by producing a GaAs line structure, 55.3 nm wide and 13.6 nm high. These results show that these FAB methods are effective in producing 3-D microstructures and nano-structures. Combinations of these methods will make it possible to produce functional nanostructures on 3-D microstructures. Received: 3 November 1996 / Accepted: 13 November 1996     

Studies on the state of permeant in the membrane and its effect on pervaporation phenomena

Pervaporation experiments of pure water and 2-propanol through poly-dimethylsiloxane membranes were carried out in order to study the effect of the interaction between permeant and membrane material on pervaporation phenomena. From the effect of downstream pressure on the pervaporation rate, the saturation vapor pressure of water in the membrane was determined to be 2.799 × 10³ Pa (21.0 mmHg), which is the same as the literature value, whereas that of 2-propanol in the membrane was estimated to be 5.865 × 10³ Pa (44.0 mm Hg), which is 8.53 × 10² Pa (6.4 mmHg) higher than that of pure 2-propanol. In the differential scanning calorimetry analyses of permeants in the membrane, it was evident that the state of 2-propanol in the polydimethylsiloxane membrane was different from that of bulk 2-propanol. On the other hand, the state of water in the membrane was assigned to that of bulk water. Throughout the present study, it was observed that the interaction between permeant and membrane material plays an important role in determining pervaporation phenomena.     

Laminated polarizers exhibiting high performance over a wide rangeof wavelength

A laminated polarizer exhibiting high performance over a wide range of wavelengths has been fabricated for the first time. The polarizer consists of alternate layers of laminated silica film and metal-included semiconductor ultra-thin film as the transparent and absorptive layers, respectively. Extinction ratios of greater than 50 dB with insertion losses of less than 0.4 dB have been obtained over the wavelength range of 0.8-1.55 μm. At the wavelength 0.98 μm where previously no viable laminated polarizer had been available, the extinction ratio is as high as greater than 60 dB and the insertion loss less than 0.3 dB