Alkylation of aminohydroxy anion,dissociated species of hydroxylamine

Aminohydroxy anion ($\text{3}$), dissociated species of hydroxylamine, was demonstrated to be nucleophilic on oxygen atom from INDO calculation, and to give directly O-alkylhydroxylamines.     

Non-Debye excess heat capacity and boson peak of binary lithium borate glasses

The non-Debye excess heat capacities of binary lithium borate glasses with different Li₂O compositions of x = 8, 14 and 22 (mol%) are investigated to understand origin of the boson peak. The low-temperature heat capacities are measured between 2 and 50 K by a relaxation calorimeter. The experimental non-Debye heat capacities with x = 14 is successfully reproduced using the excess vibrational density of states measured by inelastic neutron scattering. This finding indicates that the non-Debye heat capacities of lithium borate glasses originate from the excess vibrational density of states measureable by inelastic neutron scattering. Moreover, it is demonstrated that all of the excess heat capacity spectra lie on a single master curve by the scaling using boson peak temperature and intensity.     

Measurements of mode field diameter and effective area of photonic crystal fibers by far-field scanning technique

We have demonstrated that the correction factor k _n = A _eff/(πw ²), where ω = MFD/2 (MFD: mode field diameter), is above 1.20 for photonic crystal fibers (PCFs) with structural parameters in the range of d/Λ ≅ 0.40 to 0.90 (d/Λ ratio of hole diameter d and pitch Λ). By using the far-field scanning (FFS) technique and the finite difference method, the results of experimental measurements and numerical simulations differed by only 0.9 to 3.0% for two types of PCFs. The finding that k _n ≠ 1.0 for PCFs indicates that their electrical field distribution is non-Gaussian and cannot be determined by assuming a conventional step-index distribution for PCFs. It was also found that the ITU-T Petermann II definition is the most suitable for MFD measurements of PCFs with non-Gaussian distribution.     

Low-temperature heat capacity of room-temperature ionic liquid, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Heat capacities of liquid, stable crystal, and liquid-quenched glass of a room-temperature ionic liquid (RTIL), 1-hexyl-3-methylimidazolium bis(trifluromethylsulfonyl)imide were measured between 5 and 310 K by adiabatic calorimetry. Heat capacity of the liquid at 298.15 K was determined for an IUPAC project as (631.6 +/- 0.5) J K(-1) mol(-1). Fusion was observed at T(fus) = 272.10 K for the stable crystalline phase, with enthalpy and entropy of fusion of 28.34 kJ mol(-1) and 104.2 J K(-1) mol(-1), respectively. The purity of the sample was estimated as 99.83 mol % by the fractional melting method. The liquid could be supercooled easily and the glass transition was observed around T(g) approximately 183 K, which was in agreement with the empirical relation, T(g) approximately ((2)/(3)) T(fus). The heat capacity of the liquid-quenched glass was larger than that of the crystal as a whole. In the lowest temperature region, however, the difference between the two showed a maximum around 6 K and a minimum around 15 K, at which the heat capacity of the glass was a little smaller than that of crystal.     

Regiocontrolled intramolecular cyclizations of carboxylic acids to carbon-carbon triple bonds promoted by acid or base catalyst

We systematically investigated, for the first time, the relationship between regioselectivity and acid/base effects in the cyclization reactions between carboxylic acids and carbon-carbon triple bonds. We found novel acid- and base-promoted cyclizations to selectively give isocoumarin or pyran-2(2H)-one and phthalide or furan-2(5H)-one skeletons, respectively, and established a catalytic version of regioselective heterocyclic ring synthesis. Density functional theory calculations and application to a short route to thunberginol A were also described. [reaction: see text].     

Characterization of [ZnO]m[ZnMgO]n multiple quantum wells grown by molecular beam epitaxy

Thermal stability of single-crystalline [ZnO]_m[Zn_0.7Mg_0.3O]_n multiple quantum wells (MQWs) grown on a-plane sapphire substrates by plasma-assisted molecular beam epitaxy is reported. X-ray diffraction analysis revealed that these MQWs were grown as designed with a fixed Zn_0.7Mg_0.3O barrier width of and a series of ZnO well widths of . Cathodoluminescence spectra from these MQWs consisted of two major peaks; one was the emission from the bound excitons in Zn_0.7Mg_0.3O barrier layers, and the other was that from the confined excitons in ZnO well layers. These structural and optical properties were found to be dramatically changed by the ex situ annealing treatments over 700 °C. These changes were presumably due to the onset of phase separation of the Zn_0.7Mg_0.3O barrier layers with pronounced Mg diffusion toward the ZnO wells.     

Halfway-plane and continuum calculations of blocking dips for displaced atoms

Abstract

Redistribution of phosphorus dopant in 1N2175 phototransistors damaged by a pulsed neodynium laser has been investigated using the electron microprobe technique. Four different effects observed in the concentration profdes were explained by the action of diffusion and segregation, in the presence of temperature and compositional gradients. One specific effect was analyzed using a simplified model consisting of diffusion in the melt followed by the segregation upon refreezing. It was estimated that certain areas of the phototransistor surface remained above the melting point for times of the order of 10^?4 sec. Correlation was made between the results of these microprobe measurements and previously observed laser-damage effects in the electrical characteristics. It is suggested that impurity migration may be an important mechanism for damage to junction devices by pulsed lasers in an intermediate energy range.     

An Unusual Skeletal Rearrangement in the Biosynthesis of the Sesquiterpene Trichobrasilenol from Trichoderma

The skeletons of some classes of terpenoids are unusual in that they contain a larger number of Me groups (or their biosynthetic equivalents such as olefinic methylene groups, hydroxymethyl groups, aldehydes, or carboxylic acids and their derivatives) than provided by their oligoprenyl diphosphate precursor. This is sometimes the result of an oxidative ring‐opening reaction at a terpene‐cyclase‐derived molecule containing the regular number of Me group equivalents, as observed for picrotoxan sesquiterpenes. In this study a sesquiterpene cyclase from Trichoderma spp. is described that can convert farnesyl diphosphate (FPP) directly via a remarkable skeletal rearrangement into trichobrasilenol, a new brasilane sesquiterpene with one additional Me group equivalent compared to FPP. A mechanistic hypothesis for the formation of the brasilane skeleton is supported by extensive isotopic labelling studies.     

3,3-Dimethoxypropylsulfonyl Group: A new versatile protecting and activating group for amine synthesis

3,3-Dimethoxypropylsulfonyl (Dimps) chloride was prepared and used as a new versatile sulfonating agent for ammonia, primary and secondary amines to afford corresponding Dimps-amides in excellent yields. The resulting N-nonsubstituted and N-monosubstituted Dimps-amides, activated amines, were alkylated satisfactorily under new Mitsunobu conditions. The Dimps group was removed by treatment in aqueous solution under acidic followed by basic conditions. Furthermore, epilachnene, the defensive droplets from the Mexican bean beetle, Epilachna varivestis, was synthesized utilizing this Dimps methodology in short steps.