Electron transfer reactions of glucose oxidase at Au111 electrodes modified with phenothiazine derivatives

The catalytic reaction of glucose oxidase (GOx) mediated by 3-(10-phenothiazyl)propionic acid (PT-PA) and phenothiazine-labeled poly(ethylene oxide) (PT-PEO1000) that are covalently bonded to Au(111) electrodes has been investigated. The PT-PA and PT-PEO1000 are reacted with 2-aminoethanethiol (AET), followed by the formation of a self-assembled monolayer (SAM) onto the Au surface. The PT group immobilized on the SAM of AET acts as an effective mediator for the electron transfer (ET) between the electrode and the FAD center of freely diffusing GOx in solution. The ET rate constant estimated from the catalytic current using a newly derived equation is larger by 1 order of magnitude for the PT-PA-modified system (1.1 x 10(5) dm(3) mol(-1) s(-1)) than for the PT-PEO1000 system (1.4 x 10(4) dm(3) mol(-1) s(-1)). The order of the magnitude of the ET rate constant clearly contrasts with the GOx hybrid systems that we previously investigated (Anal. Chem. 2003, 75, 910-917), in which the presence of the PEO spacer enhances the ET reaction rate. The reduction in the apparent PT concentration at the electrode interface due to the high mobility of the PEO chain, leading to low efficiency in the formation of an enzyme-mediator complex, is a possible reason for the lower mediation ability of PT-PEO1000 than that of PT-PA for the ET between the FAD group and PT(+) immobilized on the electrode. Inhibition of the penetration of GOx molecules into the monolayer and of the accessibility of some part of PT groups to GOx molecules could also be reasons for the lower mediation ability of PT-PEO1000 thickly modified on the electrode.     

New Class of High-TC Diluted Ferromagnetic Semiconductors Based on CaO without Transition Metal Elements

We propose new-type ferromagnetic semiconductors based on CaO and K₂S without any transition metal elements. These materials show transparent and half-metallic ferromagnetism if the deep-impurity-band width (W) induced by doping of C, N, Si, or Ge impurities, and the electron-correlation energy (U) satisfy the Stoners condition of highly correlated electron system (U>W). Based on our first-principles calculations, we demonstrate that these materials satisfy the Stoners condition, and could be new candidates for transparent and half-metallic DMSs.     

Direct imaging of molecular chains in a poly(p-xylylene) single crystal

Individual chains comprising a β-form poly(p-xylylene) (PPX) single crystal were resolved with a high resolution electron microscope (JEM-500). In a polymer crystal the important limiting factor for resolution is radiation damage. The total end point dose of a PPX crystal is about 0.5 coulomb cm^?2 for 500 kV electron irradiation which is more than 20 times greater than that for a polyethylene crystal. The high resolution image obtained was processed by optical filtering to reduce noise due to the granularity of film. The processed image, which corresponds to the ab-plane projection of polymer chains, shows clearly the mutual arrangement of each molecule in the crystal. This high resolution image is sufficient to provide a starting point for determining the unknown crystal structure of the β-modification of PPX.     

Heat capacity of metallic uranium and thorium from 80 to 1000 k

The heat capacities of metallic uranium and thorium from 80 to 1000 K have been determined by laser-flash calorimetry. The results on uranium agree very well with those in the literature over the temperature range investigated. The results on thorium are several percent lower than the heat-capacity values hitherto reported, while the enthalpy data at high temperatures in the literature are in good agreement with the present results. Shomate's analysis showed that the present results are the most consistent through the temperature range from 80 to 1000 K. On this, a revised table of thermodynamic functions of thorium from 80 to 1000 K is presented. The excess heat capacity on thorium has been found to be not appreciable up to 1000 K, in contrast with the large excess heat capacity above 300 K for uranium.     

Effect of CNTs on morphology and electromagnetic properties of non-firing CNTs/silica composite ceramics

Carbon composite ceramics have much attention for industry because of their excellent properties such as strong toughness, high electrical conductivity as well as low percolation threshold. Therefore, carbon nanotubes (CNTs) were used to incorporate with silica ceramics in order to improve their electromagnetic properties. The amount of CNTs in CNTs/silica composite ceramics was varied in order to investigate its effect on morphologies and electromagnetic properties of those. The composites were successfully fabricated by non-firing process. The results revealed that the obtained CNTs/silica composite ceramic have an electrical resistivity of 66.6?Ω·cm with a bending strength of 13.8?MPa. At the same time, the electromagnetic wave absorption ability achieved 70% over a wild frequency. This indicates that the CNTs in CNTs/silica composite ceramics may be potentially applied for an electromagnetic wave reflective material.     

Effect of silane modification on CNTs/silica composites fabricated by a non-firing process to enhance interfacial property and dispersibility

Carbon nanotube/ceramic composites have been in the spotlight thanks to their excellent properties. Sintering is the vital part of ceramics fabrication in terms of reliability, however sintering the carbon nanotube (CNT) based ceramic composites is a challenging task. In this study, interfacial bonding of silane functionalized CNT with silica ceramic is investigated by a non-firing sintering process. CNTs are first treated by a mixed acid with the aid of a silane 3-aminopropyl triethoxysilane (APTES), which improves the chemical bonding and dispersibility of CNT in ceramic bodies. The extent of APTES chemical functionalization and mechanical property of CNT/silica ceramic composites are characterized using Raman spectrometer, FT-IR analysis, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and three-point bending strength measurement. Results show that composites are successfully prepared without sintering with stable CNT-silica interface, superior dispersibility, and good mechanical properties.     

The study of the effect of external additives on the synthesis of fumed TiO2 with a high content of rutile structure by the novel natural dropping thermal treatment

The effect of external additives on the synthesis of fumed TiO₂ with a high rutile structure content was studied. The focus of this investigation was on the external additive species, agglomerates of the fumed TiO₂ before and after the thermal treatment. The transformation ratio from the anatase to rutile structure of the thermally-treated fumed TiO₂ was investigated as a function of the fumed TiO₂ agglomerate before the thermal treatment. Small agglomerated powders resulted in a decrease of transformation temperature. Two novel results were obtained in this investigation. One was a new fumed TiO₂ with a 100% rutile structure having an excellent dispersibility being successfully synthesized by the thermal treatment of AEROXIDE® TiO₂ P 25 with a small portion of AEROSIL® R 972. The other was the remarkable acceleration of the transformation from the anatase to rutile structure and grain growth/sintering of the thermally-treated fumed TiO₂ observed at a relatively low thermal treatment temperature by the oxidation reaction of calcium stearate as an external additive.     

Studies on suspension and emulsion. XLVI. Emulsifier-free emulsion polymerization of styrene in acetone–water

Emulsifier-free emulsion polymerization of styrene in acetone–water medium was carried out using potassium persulfate as initiator. Below acetone content of 40 vol %, stable emulsion was prepared and polymerizations were remarkably fast compared with those in pure water. The particle size decreased from 0.5 to 0.17 μm with an increase in acetone content in the range 0–40 vol %, and the distributions were very sharp. The optimum polymerization for the preparation of the stable emulsion was: styrene, 20 vol %; acetone/water, 40/60 (v/v); KPS, 3.4 × 10^?3 mole/l; temp., 90°C.     

Morphology of composite polymer emulsion particles consisting of two kinds of polymers between which ionic bonding intermolecular interaction operates

The morphology of particles (I) produced by seeded emulsion copolymerization of styrene (S) and sodium p-styrene sulfonate (NaSS) with butyl acrylate (BA)-methacryloyloxyethyl-trimethylammonium chloride (QDM) copolymer particles as seed was examined in comparison with poly(butyl acrylate) (PBA)-polystyrene (PS) composite polymer emulsion particles (II). In an electron microscopic observation, it was observed that II particles had an anomalous shape and the electron densities at different points in the particle were heterogeneous, whereas I particles had an almost spherical shape and the electron densities were homogeneous. The maximum tensile strength and toughnes were much larger in II than I. The dynamic mechanical studies indicate that II film had a macroheterogeneous structure consisting of PS-rich and PBA-rich phases, whereas I film had a microheterogeneous structure. These ressults suggest that there is an effect of intermolecular interaction between polymers of different kinds on the formation of heterogeneous structure in particles consisting of two kinds of polymers.     

Detection of six single-nucleotide polymorphisms associated with rheumatoid arthritis by a loop-mediated isothermal amplification method and an electrochemical DNA chip

An electrochemical DNA chip using an electrochemically active intercalator and DNA probe immobilized on a gold electrode has been developed for genetic analysis. In this study, the six polymorphisms associated with rheumatoid arthritis (RA), N-acetyltransferase2 (NAT2) gene polymorphisms T341C, G590A, and G857A, methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms C677T and A1298C, and serum amyloid A1 (SAA1) gene promoter polymorphism C-13T were simultaneously detected by the electrochemical DNA chip and the loop-mediated isothermal amplification (LAMP) method, which is a novel technique for DNA amplification. Human genomic DNAs were extracted from blood, and the targets containing the six polymorphisms were amplified by the LAMP method. A sample containing the six LAMP products was reacted with the electrochemical DNA chip using a DNA detection system that controls hybridization reaction, washing, electrochemical detection, and data analysis automatically. A total of 31 samples were genotyped by this method, and the results were completely consistent with those determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis or the PCR direct sequence analysis. The time required for this method was only 2 h, and operations were very simple. Therefore, this method is expected to contribute to personalized medicine based on genotype.