Nano peel-off fabrication pattern with polymer overcoat layer on glassy carbon electrodes for Pt electrodeposition

This article describes a new technique for fabricating an electrocatalyst model in which the particle size and interparticle distance are controlled independently. We designed a uniform insulating polymer layer as a mask on an electroconductive glassy carbon substrate and then peeled off a part of the layer in nano-sized dots by scratching the overcoat layer using an atomic force microscope (AFM) cantilever. Pt particles electrodeposited only on the peeled off area of the glassy carbon. To peel-off a small area on the glassy carbon, a 29 ± 2 nm thick insulating polymer overcoat layer and a cantilever operating area of 10 nm × 10 nm were used, and the smallest peel-off area obtained was 30 nm × 30 nm. Thereafter, we performed the peel-off procedure on the polymer overcoat layer of the glassy carbon substrate having a cantilever operating area of 80 nm × 80 nm. Pt deposition of 100–150 nm in diameter was successfully achieved by adjusting the interparticle distance.     

Differentiation between isomeric oxidative metabolites of a piperidine-containing drug by liquid chromatography-tandem mass spectrometry with stable-isotope tracer technique

This report describes the application of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to differentiation of hydroxylations and N-oxidations and of two different aliphatic hydroxylations in the investigation of the metabolism of pibutidine hydrochloride, a novel H2 antagonist, the structure of which includes a piperidine ring. Pibutidine metabolites in urine samples from adult male volunteers after oral administration of pibutidine hydrochloride were separated by reversed-phase LC and ionized using an electrospray ionization (ESI) interface. A hydroxylated form of pibutidine was distinguished from the N-oxide by comparison of their product ion spectra, although their mass-to-charge ratios of protonated molecules were identical. Further, two hydroxylated compounds were present in rat microsomal incubation mixtures with pibutidine. The distinction between their positions of hydroxylation (beta- and gamma-carbon hydroxylation) on the piperidine ring was studied using [piperidine-2H10] pibutidine as incubation substrate. The production of the beta-hydroxylated form was accompanied by the elimination of three 2H, resulting from a mechanism including the formation of iminium/enamine. The participation of the iminium ion intermediate in the beta-hydroxylation was confirmed by the observation that a cyanide adduct of pibutidine was formed instead of the beta-hydroxylated form when another incubation was performed in the presence of cyanide.     

On the sound sources of screech tones radiated from choked circular jets

The generation mechanism of the screech tone in the helical oscillation mode is mainly investigated using a series of instantaneous schlieren photographs. From the photographs, five evanescent sound sources are observed as prominent points along the jet axis. The sound source for the dominant helical oscillation mode is found to be the second prominent point which moves along a circular orbit in a plane perpendicular to the jet axis and just downstream of the rear edge of the third shock cell. It is shown that the speed of a moving sound source is supersonic and that the Mach cone generated by the moving sound source forms the helical-shaped wave front of the screech tone for the helical oscillation mode of the jet. This idea of the moving sound source is well supported by a measured directionality of the screech tone. Sound sources of the other oscillation modes appearing in the other pressure ratio ranges are also described.     

Improvement of parallelization performance of GAMESS: global sum and (semi-)direct integral calculation in multireference perturbation calculation

Performance benchmark tests of the multireference perturbation theory (MRPT2) calculation in the GAMESS suite of programs have been performed on a 128-node PC cluster system. The benchmark results point to two kinds of problems with GAMESS: network delay and slow access to disk files. To overcome these bottlenecks, we employ (semi-)direct atomic orbital integral calculations and a new algorithm for the "global sum" operation. These modifications produce remarkable performance improvements, especially in the 128-node PC cluster system, which was almost twice as fast in our version as in the original version. The modification of "global sum" also improved the performance of other types of molecular orbital calculations in GAMESS, such as density functional theory.     

Compact Branched Optical Waveguides Using High-Index-Contrast Stacked Structure

We have developed a novel branched optical waveguide using a stacked directional coupler, which consists of two Si₃N₄ core layers (each 0.3 μm thick) stacked with a thin (0.2 μm) SiO₂ film in between. Using this stacked high-index-contrast system, the size of the multiple branched waveguides can be dramatically reduced compared with the conventional Y-shaped branches. A four-branch optical waveguide is designed and fabricated, and good performance of distribution power of 25 ± 4% to each branch has been achieved.     

The (d, 6Li) reaction on 12C, 16O, 24Mg, 40Ca and 58Ni at 54.25 MeV

The (d, ⁶Li) reaction was studied at E_d = 54.25 MeV on the target nuclei ¹²C, ¹⁶O, ²⁴Mg, ⁴⁰Ca and ⁵⁸Ni. The data were analyzed with finite-range DWBA calculations. The absolute values of the α-cluster spectroscopic factors and the target mass dependence of the relative S_α were in agreement with those in the (p, pα) reaction at E_p = 100 and 157 MeV. The theoretical calculations of the relative S_α were in better agreement with the experimental data at higher energy than at the lower energies.     

Synthesis of chiral vinylic sulfoxides by Pd-catalyzed asymmetric sulfinylzincation

Novel asymmetric sulfinylzincation of alkynoates has been accomplished via a Pd-catalyzed sulfinylzincation using 1-alkynyl sulfoxides bearing chiral auxiliaries as a sulfinylating reagent. The reaction proceeded in a highly syn-selective fashion, giving the (E)-β-sulfinyl α,β-unsaturated ester exclusively. Among the chiral sulfinylating reagents tested, an isoborneol-type compound (Rs)-4 showed the best results in terms of both yield and diastereoselectivity. As a result of optimization of the reaction, the selectivity was improved up to 92:8 dr, and stereochemistry of the newly formed sulfur stereogenic center was revealed as (Ss)-configuration.     

Synthesis of 4-O-[3-(aryl)prop-2-ynyl]-Neu5Ac2en and its 4-epi-analogs modified at C-4 by Sonogashira coupling reaction

To explore new inhibitors of the sialidase of human parainfluenza virus type 1 (hPIV-1), a series of novel Neu5Ac2en derivatives were synthesized. Thus, 8,9-O-isopropylidene-4-O-2-propynyl-Neu5Ac2en methyl ester 8 was subjected to a Sonogashira coupling reaction with a variety of heteroaryl halides to produce a series of 4-O-(3-heteroaryl-2-propynyl) compound 9. Treatment of 9 with 80% acetic acid followed by alkaline hydrolysis afforded deprotected Neu5Ac2en compounds. The 4-epi-analogs of this type of Neu5Ac2en were synthesized in a similar manner. Compound 5d showed the most potent inhibitory activity (IC₅₀ 1.2 μM) against hPIV-1 sialidase.