A superconducting proximity effect existing in a two-dimensional electron gas in the native inversion layer on a p-iype InAs substrate has been confirmed. A supercurrent in the inversion layer was observed for the first time, in addition to an ac Josephson effect, with superconducting electrodes separated by 0.2-0.5 /xm. The coherence lengths obtained coincide well with each other, both experimentally and theoretically. A junction with a metal gate electrode showed the controllability of the supercurrent by the gate voltage.

Effects of annealing ambient of an oxygen and nitrogen mixed gas on the electrical properties were studied for Au-based ohmic contacts (NiAu, CoAu, CuAu, PdAu, and PtAu) to p-type GaN. Addition of oxygen to the nitrogen gas reduced the specific contact resistances (ρ c ) and resitivities of the p-GaN epilayers (ρ s ) of the contacts after annealing at temperatures of 500~600°C. The microstructural analysis at the p-GaN/metal interfaces did not detect the heterostructural intermediate semiconductor layer at the GaN/metal interfaces. The reason for reduction of both the ρ c and ρ s values by the oxygen gas addition was believed to be due to formation of the p-GaN epilayer with high hole concentrations, caused by removal of hydrogen atoms which bonded with Mg atoms.

Reactions of sunscreen agents, octyl dimethyl-p-aminobenzoate (ODPABA) and octyl-p-methoxycinnamate (OMC), with hypochlorite in aqueous solution were investigated under the conditions that simulate swimming pool disinfection sites. Chlorination byproducts were determined by GC-MS. At a concentration of 9 µM, ODPABA reacted rapidly with free chlorine in the buffered solution at pH 7.0, OMC reacted with hypochlorite reasonably slowly under the same condition. ODPABA and OMC produced chlorine-substituted compounds as intermediates, which were decomposed to cleavaged products of ester-bond during the aqueous chlorination process. The chlorination intermediates of OMC exhibited weak mutagenic on Salmonella typhimurium TA100 strain without the S9 mix. The extent of the reactions depended on the chlorine dose, solution pH, and compound structures.

No abstract

The amino acid derivative reactivity assay (ADRA) is an in chemico alternative to animal testing for skin sensitization that solves certain problems found in the use of the direct peptide reactivity assay (DPRA). During a recent validation study conducted at multiple laboratories as part of the process to include ADRA in an existing OECD test guideline, one of the nucleophilic reagents used in ADRA-N-(2-(1-naphthyl)acetyl)-l-cysteine (NAC)-was found to be susceptible to oxidation in much the same manner that the cysteine peptide used in DPRA was. Owing to this, we undertook a study to clarify the cause of the promotion of NAC oxidation. In general, cysteine and other chemicals that have thiol groups are known to oxidize in the presence of even minute quantities of metal ions. When metal ions were added to the ADRA reaction solution, Cu promoted NAC oxidation significantly. When 0.25 μm of EDTA was added in the presence of Cu , NAC oxidation was suppressed. Based on this, we predicted that the addition of EDTA to the NAC stock solution would suppress NAC oxidation. Next, we tested 82 chemicals used in developing ADRA to determine whether EDTA affects ADRA's ability to predict sensitization. The results showed that the addition of EDTA has virtually no effect on the reactivity of NAC with a test chemical, yielding an accuracy of 87% for predictions of skin sensitization, which was roughly the same as ADRA.

The aim of this study was to determine the concentrations of six phthalic acid diesters (PAEs) [di(2-ethylhexyl) phthalate (DEHP), di-n-butyl phthalate (DBP), butyl benzyl phthalate (BBP), diisononyl phthalate (DINP), di-n-octyl phthalate (DNOP), and diisodecyl phthalate (DIDP)], two non-phthalic plasticizers [di(2-ethylhexyl) adipate (DEHA), 2,2,4-trimethyl-1,3-pentanediol diisobutylate (TMPDIB)], and mono 2-ethylhexyl phthalate(MEHP) in polyvinyl chloride (PVC) household products that children often places in their mouths and/or contact with their skin (41 products, 47 samples) in Japan. The detection frequencies of the studied compounds were as follows: DEHP (79 %), DINP-2 (13 %), DINP-1 (11 %), DBP (8.5 %), DEHA (8.5 %), DIDP (4.3 %), and DNOP (2.1 %). Concentrations of these compounds ranged from 0.021 % to 48 %. BBP and TMPDIB were not detected in the all samples. Most samples contained DEHP and DINP at high concentrations over 0.1 %. High concentrations of PAEs were detected in PVC household products that appear appealing to children and can possibly be licked and chewed by them. Di(2-ethylhexyl) terephtalete, diisononyl 1,2-cyclohexanedicarboxylic acid, acetyl tributyl citrate, and di(2-ethylhexyl) 4-cyclohexene-1,2-dicarboxylate used as substitute plasticizers were also detected in several samples. MEHP was present in 70 % of the samples, with concentrations ranging from trace amounts to 140 μg/g. The ratios of MEHP against DEHP were 6.2 × 10(-4) to 1.6 × 10(-1) %. MEHP in the household products investigated in this study was most probably an impurity in DEHP. The high concentrations of PAEs detected in products that children often place in their mouth reveal the importance of replacing plasticizers in common household products, and not just children's toys, with safer alternatives.

Although extensive efforts have continued to develop Ohmic contacts for p-type GaN, which have specific contact resistance (ρc) lower than that (ρc∼10−2 Ω cm2) of conventional Ni/Au contacts, to the best of our knowledge no breakthrough has been reported in open literature. We demonstrated that bilayered Ta/Ti contacts have a ρc value of around 3×10−5 Ω cm2 for p-type GaN with a hole concentration of 7×1017 cm−3. This contact has resistance low enough to manufacture blue laser diodes, but deterioration of the ρc value during room-temperature storage is the key issue.

We probe the ''normal'' state in electron-doped (n-type) Sm 2ÿx Ce x CuO 4ÿ through interlayer tunneling transport in magnetic fields up to 45 T. The behavior of intrinsic high-field c-axis negative magnetoresistance (MR), which is accessed in small 30 nm-high mesa structures, is characteristic of the pseudogap state. It follows a universal correlation between the excess low-energy dissipation due to the pseudogap and its closing field H pg and is in close correspondence with the hole-doped (p-type) Bi 2 Sr 2 CaCu 2 O 8y . The MR in the mesas and in the bulk crystals consistently gives a Zeeman relation between the pseudogap temperature T and its closing field, pointing to a preeminent role of spin-singlet correlations in forming the pseudogap in cuprates, regardless of their n or p type.