Vacuum-annealing induced band bending in phosphorus-doped (111) diamond

High-temperature annealing effects on hydrogen (H)-terminated phosphorus (P)-doped diamond (111) surfaces were investigated by X-ray photoelectron spectroscopy (XPS) and reflection high energy electron diffraction (RHEED) experiments. Thermally activated, surface band bending was observed, which is clearly attributed to surface structural changes and adsorbates dynamics. The XPS results are compared between boron (B)- and P-doped diamond surfaces and an energy band model has been introduced to the P-doped diamond surface. The annealing process induces downward band bending (to a maximum of 1.3 eV) in B-doped diamond whereas it reduces the internal barrier height (by about 1 eV) in P-doped diamond and finally, the surface bands are pinned in the middle of the band gap. The depletion layer widths are calculated for both diamond surfaces. The band bending imposed by the annealing process can be effective in tuning the surface barrier height.     

Fast pH‐thermo‐responsive copolymer hydrogels with micro‐porous structures

Micro‐porous copolymer hydrogels were prepared by γ‐ray irradiation of mixed solutions of N‐isopropylacrylamide (NIPAAm) and acrylic acid (AAc) above the lower critical solution temperature (LCST). From Cryo‐SEM observations, the gels were found to consist of three‐dimensional fibrous micro‐gels and micro‐pores. The copolymer gels swelled at temperatures below the LCST and shrunk at temperatures above it, and they showed rapid volume transitions on a time scale on the order of a minute when experiencing temperature changes between 10 and 40°C. The transition times for thermal shrinking were almost the same regardless of AAc composition, but the transition times for thermal swelling were increased with increasing AAc contents. The copolymer gels also showed rapid volume transitions with time constants on the order of an hour on experiencing pH changes between 2 and 12. The transition times for pH volume change at 10°C were within one hour, except for the gels containing only small amounts of AAc. On the other hand, the transition times for pH‐dependent volume change at 40°C were increased with increasing AAc content. The lower responsiveness of the transition results from an increase in hydrophobicity arising from the formation of inter‐ and intra‐molecular hydrogen bonds between the non‐ionized carboxylic acid groups and the amide groups. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 75–84, 2003     

A numerical model for current transients during micro-indentation of passive iron surface

During in situ micro-indentation of passive iron in pH 8.4 borate solution, a couple of anodic current peaks emerged; the first peak during loading and the second peak during unloading. The current transients, associated with rupture and repair of the passive film, were influenced by the indentation conditions. For instance, the current peak height, the current peak area and the time required for complete repassivation are strongly dependent on indentation rate. A numerical model was proposed to correlate the current transient during loading with mechanical deformation of the passive surface. The comparison between the current transient measured experimentally and that estimated from the load transient suggested that the ruptured area of passive film was about 10% of the surface area deformed by the contact with the indenter.     

The synthesis and thermotropic liquid crystalline behavior of the novel poly(aryl ether ketone)s containing chloro-side group

The novel poly(aryl ether ketone)s containing chloro-side group were synthesized by nucleophilic substitution reactions of 4,4′-biphenol and chlorohydroquinone with either 4,4′-difluorobenzophenone (BP/CH/DF) or 1,4-bis(p-fluorobenzoyl)benzene (BP/CH/BF) and their thermotropic liquid crystalline properties were characterized by a variety of experimental techniques. The thermotropic liquid crystalline behavior was observed in the copolymers containing 50 and 70% biphenol. Melting transition (Tm) and isotropization transition (Ti) both appeared in the DSC thermograms. A banded texture was formed after shearing the sample in the liquid crystalline state. The novel poly(aryl ether ketone)s had relatively higher glass transition temperature (Tg) in the range of 168 ∼ 200 °C and lower melting temperature (Tm) in the range of 290 ∼ 340 °C. The thermal stability (Td) was in the range of 430 ∼ 490 °C. Received: 7 February 1997/Revised: 31 March 1997/Accepted: 2 April 1997     

Thin film characteristics of fluorine-substituted monolayers prepared by chemical adsorption from solution

Monolayers containing a fluorine-substituted carbon chain were prepared by the chemical adsorption (CA) technique. Characteristics of the monolayers were evaluated by spectroscopy, copper decoration technique, current-voltage characteristics (current density and resistivity), measurement of the contact angle, and friction tests. By the copper decoration technique, the CA monolayer was more pinhole free and uniform than a Langmuir-Blodgett film. The characteristics (such as the leakage current density, resistivity, critical surface tension and coefficient of kinetic friction) of the fluorine-substituted monolayers depended markedly on the number of substituted fluorine atoms.     

Discussion on optimisation below dose limit for public using background-cancer-risk-based approach

To improve a radiological protection system, the lower bound of optimisation was discussed using a newly proposed background-cancer-risk-based approach. This approach provides a new finding that the standard deviation of the background cancer risk in Japan is 7.4 × 10(-5) y(-1). If this risk level corresponding to 1σ can be regarded as a non-concern level, it would be possible that the lower bound of optimisation of radiological protection could be set at 1 mSv y(-1), since the assumed risk of 1 mSv y(-1) is equivalent to ~5 × 10(-5) y(-1) obtained using the overall fatal risk coefficient of 5 % Sv(-1), which is lower than the non-concern level.     

Modeling of eddy characteristic time in LES for calculating turbulent diffusion flame

We have constructed an eddy characteristic time derived from large-scale motion to calculate the combustion reaction rate using a new eddy dissipation concept (EDC) model, and estimated combustion characteristics in the combustor. The calculated temperature and CH₄ mole fraction distribution are in fairly good agreement with the experimental data. However, the calculated CO mole fraction distribution does not agree well with the measured result of CO mole fraction because of using a simple CO reaction mechanism. This study shows that the combustion simulation using LES with EDC model is effective for calculating the characteristics of turbulent diffusion flame.     

Performance analysis of slotted ALOHA and network coding for single-relay multi-user wireless networks

Deployment of wireless relay nodes can enhance system capacity, extend wireless service coverage, and reduce energy consumption in wireless networks. Network coding enables us to mix two or more packets into a single coded packet at relay nodes and improve performances in wireless relay networks. In this paper, we succeed in developing analytical models of the throughput and delay on slotted ALOHA (S-ALOHA) and S-ALOHA with network coding (S-ALOHA/NC) for single-relay multi-user wireless networks with bidirectional data flows. The analytical models involve effects of queue saturation and unsaturation at the relay node. The throughput and delay for each user node can be extracted from the total throughput and delay by using the analytical models. One can formulate various optimization problems on traffic control in order to maximize the throughput, minimize the delay, or achieve fairness of the throughput or the delay. In particular, we clarify that the total throughput is enhanced in the S-ALOHA/NC protocol on condition that the transmission probability at the relay node is set at the value on the boundary between queue saturation and unsaturation. Our analysis provides achievable regions in throughput on two directional data flows at the relay node for both the S-ALOHA and S-ALOHA/NC protocols. As a result, we show that the achievable region in throughput can be enhanced by using network coding and traffic control.     

Determination of pindone in animal products, fishery products, and honey by LC-MS/MS

A sensitive and selective analytical method for the determination of the rodenticide pindone in animal products, fishery products, and honey by LC-MS/MS was developed. Pindone was extracted with acidified acetone, and the crude extract was purified by liquid-liquid partitioning, followed by silica gel and ODS column chromatography. LC separation was performed on an ODS column with methanol/water containing ammonium acetate as the mobile phase, and detection was carried out using tandem mass spectrometry (MS/MS) with electrospray ionization (ESI) in the negative mode. The average recoveries from fortified bovine muscle, bovine liver, bovine fat, chicken muscle, salmon, eel, freshwater clam, egg, milk, and honey spiked at 0.001 mg/kg were in the range of 76-92%, and the relative standard deviations were 4-8%. The limit of quantitation (S/N≥10) of the developed method was 0.001 mg/kg for all the tested foods.     

Identification of Diacylglycerol Acyltransferase Inhibitors from <Emphasis Type="Italic">Rosa centifolia</Emphasis> Petals

Diacylglycerol acyltransferase (DGAT) catalyzes the final step of triacylglycerol (TAG) synthesis, and is considered as a potential target to control hypertriglyceridemia or other metabolic disorders. In this study, we found that the extract of rose petals suppressed TAG synthesis in cultured cells, and that the extract showed DGAT inhibitory action in a dose-dependent manner. Fractionation of the rose extract revealed that the DGAT inhibitory substances in the extract were ellagitannins; among them rugosin B, and D, and eusupinin A inhibited DGAT activity by 96, 82, and 84% respectively, at 10 μM. These substances did not inhibit the activities of other hepatic microsomal enzymes, glucose-6-phosphatase and HMG-CoA reductase, or pancreatic lipase, suggesting that ellagitannins inhibit DGAT preferentially. In an oral fat load test using mice, postprandial plasma TAG increase was suppressed by rose extract; TAG levels 2 h after the fat load were significantly lower in mice administered a fat emulsion containing rose extract than in control mice (446.3 ± 33.1 vs 345.3 ± 25.0 mg/dL, control vs rose extract group; P < 0.05). These results suggest that rose ellagitannins or rose extract could be beneficial in controlling lipid metabolism and used to improve metabolic disorders.