Modified mean-random-field theory for spin glass—ferromagnetic systems

Spin glass—ferromagnetic systems such as AuFe alloys having both the ferromagnetic and RKKY interactions are studied on the basis of a mean-random-field approximation. We obtain the phase diagram of the systems in terms of the temperature and the magnetic impurity concentration. The results roughly explain the magnetism of AuFe type alloys.     

Fabrication of the smallest organic nanocolloids by a top‐down method based on laser ablation

Stable aqueous colloids of 10‐nm sized organic nanoparticles were tailored by laser ablation of microcrystalline quinacridone in water. The nanocolloids were flaky in shape and had the dimension of a width of 13 (±5) nm and a height of 1.4 (±0.5) nm. The formation mechanism is discussed in terms of laser‐induced fragmentation of organic solids and the potential application of aqueous organic nanocolloids free from any additives and chemicals is considered.     

Three-dimensional photochemical microfabrication of conductive polymers in transparent polymer sheet

By focused illumination at the wavelength of 800 nm using a femtosecond laser, the tris(2,2′-bipyridyl)ruthenium complex displayed a two-photon excitation as observed by the quadratic dependence of the emission intensity on the incident laser power. Since the oxidation of pyrrole is induced by the oxidative quenching of the excited state, polypyrrole can be formed by a continuous illumination. The polymerization area showed a high spatial selectivity which can be scanned in the XYZ axis by a piezo device. In the present study, three-dimensional (3D) polypyrrole microstructures were formed in the transparent polymer sheet.     

Rapid and Direct Conversion of Graphite Crystals into High‐Yielding,Good‐Quality Graphene by Supercritical Fluid Exfoliation

Graphene has attracted a great deal of attention in recent years due to its unusual electronic, mechanical, and thermal properties. Exploiting graphene properties in a variety of applications requires a chemical approach for the large‐scale production of high‐quality, processable graphene sheets (GS), which has remained an unanswered challenge. Herein, we report a rapid one‐pot supercritical fluid (SCF) exfoliation process for the production of high‐quality, large‐scale, and processable graphene for technological applications. Direct high‐yield conversion of graphite crystals to GS is possible under SCF conditions because of the high diffusivity and solvating power of SCFs, such as ethanol, N‐methyl‐pyrrolidone (NMP), and DMF. For the first time, we report a one‐pot direct conversion of graphite crystals to a high yield of graphene sheets in which about 90–95 % of the exfoliated sheets are <8 layers with approximately 6–10 % monolayers and the remaining 5–10 % are ≥10 layers.     

Purification and characterization of hamster hepatic microsomal N,O-acetyltransferase.

A microsomal N,O-acetyltransferase which activates carcinogenic arylacetohydroxamic acids was purified 75-fold from hamster liver sequentially by anion exchange column chromatography, chromatofocusing, gel filtration, and hydroxyapatite column chromatography. The purified enzyme, AT-2, was a glycoprotein with a molecular weight of 60000 and a pI value of 5.4. The N-terminal amino acid sequence of AT-2 was: 60000 and a pI value of 5.4. The N-terminal amino acid sequence of AT-2 was: Asp-Ser-Pro-Ser-Pro-Ile-Arg-Asn-Thr-His-Thr-Gly-Gln-Val-Arg-Gly-Leu-Val- His- Lys-. This sequence was highly homologous to that of the form 2 carboxylesterase of rabbit liver, but not to that of major hepatic microsomal carboxylesterases of hamster and other species. AT-2 catalyzed the hydrolysis of 4-nitrophenyl acetate and the N,O-acetyltransfer of N-hydroxy-2-acetylaminofluorene. Both enzyme activities were strongly inhibited by paraoxon, but not by iodoacetamide. These results demonstrate that this N,O-acetyltransferase is a member of carboxylesterase (EC 3.1.1.1).     

Spectroscopic and electrochemical studies on dinuclear mixed Ni(II)-chelates

Summary Solvatochromic dinuclear mixed Ni(II)-complexes with one 1,2-diacetyl-1,2-dibenzoyl-ethanate (dadb ^2–) and two tetramethylethylenediamine (tmen) ligands have been prepared and characterized. The tetraphenylborate is orange with molecules in bis-square-planar configuration and the nitrate is green with molecules in a bis-octahedral form. They have been investigated by UV, Vis, IR, and Far-IR spectroscopy as well as by electrochemical and magnetochemical methods. In strong donor solvents the nitrate ligands are replaced by solvent molecules. In weak donor solvents the anion-dependent equilibrium between the bis-planar, the bis-octahedral and an intermediate planar-octahedral form was investigated.Dedicated to Professor Dr. Edwin Hengge on occasion of his 60th birthday     

Reflection characteristics of a copper metal-organic chemical-vapor-deposited thin film for vertical micromirror applications

We introduce Cu metal-organic chemical-vapor deposition as a potential means of conformal metal coating of the sidewalls of micromachined vertical mirrors. The optimal process temperature was experimentally found to be 215 degrees C, which gives high step coverage of better than 90%, and the surface roughness was less than 27 nm. The roughness, measured with an atomic force microscope, will induce a scattering loss less than 0.12 dB, which is small enough for vertical micromirror application. The experimental reflectances of Cu thin film were measured with a distributed-feedback laser (1550 nm) and found to be greater than 0.9 for incidence angles of 22.5 degrees and 45 degrees , and these reflectances were in good agreement with theoretical values.     

New cyclic peptides from Citrus medica var. sarcodactylis SWINGLE

Two new cyclic peptides were isolated from the fruit peels of Citrus medica var. sarcodactylis SWINGLE. Their structures were elucidated as cyclo(-Gly-Asp-Leu-Thr-Val-Tyr-Phe-) and cyclo(-Gly-Leu-Pro-Trp-Leu-Ile-Ala-Ala-) by intensive two-dimensional (2D) NMR analysis and chemical evidence.