Paper-structured catalyst with porous fiber-network microstructure for autothermal hydrogen production

Copper–zinc oxide catalyst powders were supported on a microstructured matrix composed of ceramic fiber-network by a papermaking technique. As-prepared catalyst materials, called paper-structured catalyst, were applied to the autothermal reforming (ATR) of methanol to produce hydrogen for fuel cell applications. The paper-structured catalyst demonstrated higher methanol conversion and lower undesirable carbon monoxide concentration, as compared with commercial catalysts. Besides, excellent catalyst durability was exhibited by the suppression of Cu sintering during the ATR reaction. The paper-structured catalyst showed remarkable superiority in methanol conversion even in the case of using sintered catalysts. Such features were possibly induced by the unique fiber-network microstructure (average pore size: ca. 20 μm and porosity: ca. 50%) of the paper composites, which may allow the effective transfer of heat and reactants to the catalyst surfaces. The porous paper-structured catalyst is expected as a promising catalytic material for improving the practical performances in the catalytic gas-reforming process.     

Linearity performance comparison of cascode current source and single-device current source IDPs; analyses,simulations and measurements

The input differential pair (IDP) is usually a major source of nonlinear distortion in any op-amp. This is especially true if the input signal has a large common-mode component, as is the case when an op-amp functions as a unity-gain buffer or as part of a single-ended sample-hold (S/H) circuit. In this paper, we analyse the distortion of the commonly used cascode current source IDP structure and explain the sources of its nonlinear behaviour. Next, a special design technique is proposed which enhances the linearity of IDPs. The circuit uses a single device current source that has the same channel length while its width is double those of IDP devices. Theoretical analysis, as well as simulation and experimental results, is given to confirm the improved linearity of a unity gain buffer. Simulations predict improvements up to 20 dB. 15 dB total harmonic distortion (THD) reduction was also achieved for a 15 MHz input signal based on measurement of a test chip. The method is valuable as power supply voltages shrink, and the design offers extra voltage headroom at input.     

Preparation of flat and dense conjugated polymer films from dilute solutions by means of electrophoretic deposition

Some experimental results on the electrophoretic deposition of conjugated polymer are reported. The scanning electron micrographs clearly indicate that the the morphology of filmsof a fluorene-based polymer PDOF-MEHPV by the electrophoretic deposition strongly depends on the toluene/acetonitrile ratio of the parent suspensions. It is also shown that the suspension prepared from a 0.1 g/l toluene solution of the polymer, can give flat and dense polymer films with a thickness in the order of 100 nm by using the electrophoretic deposition. The electrical current originating from the movement of colloial particles has been measured for the suspensions containing polymer more than 0.2 g/l. However, the current due to impurities in the solvent makes it difficult to detect the electrical current corresponding to the particle movement in the suspensions containing smaller amount of the polymer. Polymer light-emitting devices having PDOF-MEHPV films with various thickness prepared by electrophoretic deposition have also been demonstrated.     

Construction of an autonomously replicating plasmid in n-alkane-assimilating yeast, Candida tropicalis

A transformation system using the autonomously replicating plasmid in the n-alkane-assimilating and asporogenic diploid yeast, Candida tropicalis, was developed. For the cloning of a DNA fragment containing a potential autonomously replicating sequence (ARS) from the genomic DNA of C. tropicalis, the ura3 mutant obtained using ethylmethane sulfonate as the host and the URA3 gene amplified by PCR using the C. tropicalis genomic DNA as a selectable marker were prepared. Comparison of ARSs among yeasts revealed that the consensus sequence found in S. cerevisiae was also present in C. tropicalis. The autonomously replicating plasmid containing the putative ARS as the shuttle vector, capable of replicating in both E. coli and C. tropicalis, was first constructed. The transformation system using this plasmid, in addition to the integrative transformation system, will be applicable to genetic studies of C. tropicalis.     

New fabrication technique of conductive polymer/insulating polymer composite films and evaluation of biocompatibility in neuron cultures

Poly(vinyl alcohol), PVA, produces a flexible composite polymer film with electrical, optical and electrochemical properties very similar to those of polypyrrole (PPy). The rate of electrochemical polymerization depends on the diffusion rate of the electrolyte across the PVA film to the indium tin oxide (ITO) electrode. In particular, a solvent with a hydrophilic nature easily penetrates into the PVA film. By applying this new process, we demonstrate a unique method of forming an electrically conductive pattern in PVA film. It will be possible to develop electrodes for electrical stimulation of the nervous system using the conducting polymer, PPy. Then, by applying a similar technique, we fabricated poly(3,4-ethylenedioxythiophene), PEDOT/PVA, composite films and investigated their basic electrochemical properties. Moreover, in this study, in order to develop a novel cell-culture system which makes it possible to communicate with cultured cells, fibroblasts were cultured on PPy- and PEDOT-coated ITO conductive glass plates for 7 days. The result reveals that the PPy and PEDOT films support the secretory functions of the cells cultured on its surface. The PPy- and PEDOT-coated electrodes may be useful to culture the cells on.     

Effects of pressure and shear stress on material removal rate in ultra-fine polishing of optical glass with magnetic compound fluid slurry

Optical glasses used in a range of industrially important optoelectronic devices must be polished to nano-level roughness for proper device operation. Polishing process with magnetic compound fluid slurry (MCF polishing) under a rotary magnetic field is an influential candidate for the method to precisely polish optical glass. MCF slurry has been successfully utilized to polish a variety of materials, ranging from soft optical polymers to hard optical glasses. MCF was developed by mixing a magnetic fluid and a magnetorheological fluid with the same base solvent, and hence includes not only μm-sized iron particles but also nm-sized magnetite particles. To elucidate the behaviour of material removal in MCF polishing, this study measured the normal and shear forces generated in the polishing zone during polishing. From these measurements, the distributions of pressure P and shear stress τ were obtained. The distribution of material removal rate (MRR) was investigated through spot polishing of borosilicate glass. The effects of three process parameters, namely magnet revolution speed, MCF carrier rotational speed and working gap, on pressure P, shear stress τ and the MRR were also investigated. The results revealed that P is higher near the centre of the interacting area (i.e. the polishing spot centre) and the point of maximum shear stress τ appears at about 5 mm from the polishing spot centre. All of P, τ and MRR are sensitive to MCF carrier rotational speed and working gap but insensitive to magnet revolution speed. Shear stress is more sensitive to these process parameters than the pressure. Cross-sectional profiles of the polishing spots exhibit a characteristic symmetric W-shape; material removals are minimal at the spot centre and maximal at approximately 8.2–10.2 mm from the spot centre depending on the process parameters. MRR is proportional to the MCF carrier rotational speed and is negatively correlated with working gap. An MRR model involving both the pressure and shear stress in MCF polishing is proposed. In the model, MRR is more dominated by shear stress than by pressure.     

Normal macrophage functions, but impaired induction of gamma delta T cells, at the site of bacterial infection in CD45 exon 6-deficient mice

We investigated the protective functions of macrophages and gamma delta T cells in adult CD45 exon 6-deficient (CD45 -/-) mice against an intraperitoneal (i.p.) infection with Listeria monocytogenes. gamma delta T cells are preferentially localized in the spleen, liver, and intraperitoneal cavity of the adult CD45-/- mice. Increased numbers of gamma delta T cells were observed after i.p. infection with L. monocytogenes in the peritoneal cavity of C57BL/6 (CD45 +/+) mice but not in CD45 -/- mice. The gamma delta T cells showed predominant usage of V delta 5 and V delta 6 rearranged to J delta 1 in the infected CD45 -/- mice which are the same as those used by resident gamma delta T cells of noninfected CD45 +/+ and CD45 -/- mice. Furthermore, we analyzed the protective abilities of the CD45 -/-, CD45 +/+, and gamma delta T cell-depleted mice at the early stage of the listerial infection. The numbers of bacteria in the spleens and livers of the CD45 -/- mice 5 days after the listerial infection were almost ten times larger than those in the CD45 -/- and gamma delta T cell-depleted CD45 +/+ mice. Macrophages showed normal antigen presentation, nitric oxide production and bactericidal activity for L. monocytogenes despite their lacking CD45 surface expression, suggesting that CD45-negative macrophages have a minimal influence on the increased bacterial multiplication in the CD45-/- mice. These results suggest that the gamma delta T cells are induced by the bacterial infection in a CD45-dependent manner, and that unresponsiveness of the gamma delta T cells results in only weak protection against L. monocytogenes in CD45 -/- mice.     

Color-tuning of polymer light-emitting devices through maskless dye diffusion technique

The maskless dye diffusion technique is a method to dope dye molecules into polymer films by thermal activation. Since the patterned indium tin oxide (ITO) electrodes for the future devices are used as heat source so that the dye doping area mimics the shape of the ITO pattern heated, this method can remove the precise positioning between the ITO electrode and dye doping area which is usually required in other techniques. This paper reports some results on the polymer light-emitting devices made through the maskless dye diffusion technique. When poly(9,9-dioctylfluorene) (PDOF) was used as host material, diffusion of Coumarin 6 and a phosphorescent dye BtpIr yields green and red emission, respectively. In the case of BtpIr-diffused device, the quantum efficiency of the device was found to be about 2.5 times of the device with non-treated PDOF film. It is also found that the poly(N-vinylcarbazole) can be a host material for both green and red phosphorescent dyes.     

Rheological properties of ionically and covalently crosslinked polypropylene‐type thermoplastic elastomers

Maleic anhydride was grafted onto a polypropylene‐type thermoplastic elastomer PER by reactive processing with a screw extruder, and a maleated PER (MPER) was prepared. Aiming at ionic crosslinking, magnesium 12‐hydroxy stearate (MgStOH), zinc oxide (ZnO), and zinc sulfide (ZnS), and aiming at covalent crosslinking, melamine as an amino compound, and Epocizer and GRYCI‐ALE as epoxy compounds, were added to the MPER, melt‐mixed by use of the screw extruder, and crosslinked compounds were obtained. The rheological properties such as capillary flow properties and dynamic viscoelasticities of the compounds were measured and their melt processabilities were evaluated. The degree of crosslinking was in the order of epoxy compounds > MgStOH > melamine > ZnO, ZnS > MPER (blank). In the case of the compound with MgStOH of a moderately high degree of crosslinking, the non‐Newtonian behavior is remarkable and the die swell ratio is low and suitable for extrusion. However, in the case of compounds with epoxy compounds of an excessive degree of crosslinking, fine extrudate cannot be obtained due to the lack of fusion and the control of degree of crosslinking is necessary. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 762–773, 2002