Ordered complex structures formed by paramagnetic particles via self-assembly under an ac/dc combined magnetic field

We apply ac and dc magnetic fields simultaneously in orthogonal directions to each other to a solution, in which paramagnetic microparticles are dispersed, and show that complex secondary structures composed of oscillating chain clusters, that is, long linear clusters interconnected by T-, L-, and criss-cross-junctions, are self-assembled. Disklike clusters are formed at some junctions and the number of disklike clusters increases as the frequency of the ac magnetic field increases. We finally show that the angle between long linear clusters can be altered by changing the ratio of the intensities of the ac and dc magnetic fields.     

Vertical immobilization of viable bacilliform bacteria into polypyrrole films

We have successfully developed a novel technique for inserting viable bacilliform bacteria into polypyrrole films. All of the five different bacterial cells (Pseudomonas aeruginosa, Acinetobacter calcoaceticus, Serratia marcescens, Bacillus subtilis and Escherichia coli) studied in this work were inserted normal to the film surface, and the viability of P. aeruginosa was unaffected by this immobilization procedure. It was also found that the polypyrrole layer was important to keep the cells alive.     

A GW+Bethe-Salpeter calculation on photoabsorption spectra of (CdSe)3 and (CdSe)6 clusters

Photoabsorption spectra are calculated for the magic number clusters, (CdSe)(3) and (CdSe)(6), using an all-electron mixed basis GW scheme with the excitonic effect incorporated by solving the Bethe-Salpeter equation (BSE). The GW+BSE calculation provided clear size dependence of the optical gap as expected, while magnitude of the gap is overestimated compared to available experimental one. The gap is found very similarly overestimated when using the local density approximation (LDA) within the density functional theory because accidental error cancellation occurs between the significantly underestimated LDA gap and the excitonic effect neglected therein. The excitonic states are described by superposition of many one-particle states that would not be properly described within a one-particle theory, as clearly visualized in the plot of the exciton wavefunctions.     

Electrode polarization effects on interfacial kinetics of ionic liquid at graphite surface: An extended lagrangian-based constant potential molecular dynamics simulation study

Computational models including electrode polarization can be essential to study electrode/electrolyte interfacial phenomena more realistically. We present here a constant-potential classical molecular dynamics simulation method based on the extended Lagrangian formulation where the fluctuating electrode atomic charges are treated as independent dynamical variables. The method is applied to a graphite/ionic liquid system for the validation and the interfacial kinetics study. While the correct adiabatic dynamics is achieved with a sufficiently small fictitious mass of charge, static properties have been shown to be almost insensitive to the fictitious mass. As for the kinetics study, electrical double layer (EDL) relaxation and ion desorption from the electrode surface are considered. We found that the polarization slows EDL relaxation greatly whereas it has little impact on the ion desorption kinetics. The findings suggest that the polarization is essential to estimate the kinetics in nonequilibrium processes, not in equilibrium. © 2019 Wiley Periodicals, Inc.     

Characterization of alkyl monolayer covalently bonded to Si(111) and soft-landing of vanadium-benzene sandwich clusters onto the alkyl monolayer substrate

A hexadecyl monolayer covalently attached to Si(111) surfaces (C₁₆–Si(111)) was prepared at 200 ^○C from 1-hexadecene. Formation of the monolayer was characterized by water contact angle measurement, attenuated total reflection infrared (ATR-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Gas phase synthesized vanadium (V)-benzene (Bz) 1:2 (VBz₂) sandwich clusters were size-selectively deposited onto the C₁₆–Si(111) substrate thus prepared and an oxidized Si substrate. Investigation of the resultant clusters was implemented by thermal desorption spectroscopy (TDS). About 30 K increase in threshold desorption temperature of the landed clusters was observed on going from the oxidized Si to the C₁₆–Si(111) substrate, a result indicating that the clusters are more strongly bound to the C₁₆–Si(111) than to the oxidized Si. This result was explained by the penetration of the landed clusters into the hexadecyl monolayer.     

Measurement of thermal lensing in a power amplifier of a terawatt Ti:sapphire laser

We have measured detailed thermal lensing in a power amplifier of a terawatt Ti:sapphire laser operating at 50 Hz. The thermal lensing in the amplifier was evaluated by measuring the optical path difference (OPD) using a Shack–Hartmann-type wavefront sensor. It was found that the radial dependence of the OPD was almost quadratic in the pumping region, despite inhomogeneous pumping. Therefore, a simple spherical lens or convex mirror effectively compensates for the thermal lens in our amplifier. We found that the thermal lens profile was temporally stable, and did not degrade the pointing stability of the amplified laser pulses. We also found that the time constant of the thermal distortion in our power amplifier was approximately 0.5 s. Received: 3 September 2001 / Revised version: 23 January 2002 / Published online: 14 March 2002     

Ion pairing between dissolved poly(o-phenylenediamine) and halogenide ions

An electrically conductive polymer, poly(o-phenylenediamine) (PoPD), is soluble in dimethylsulfoxide (DMSO) without any pretreatment. Cyclic voltammograms of dissolved PoPD were measured in DMSO solutions containing halogenide ions and two reversible redox peak currents were evident. The redox potential shifted with the concentration of the dissolved halogenide ion. The relationship between the potential shift and the concentration determined the relative association constant of PoPD for four halogenide ions: 104 mol⁻¹ dm⁻³ for F⁻; 32 mol⁻¹ dm⁻³ for Cl⁻; 29 mol⁻¹ dm⁻³ for Br⁻ and 9 mol⁻¹ dm⁻³ for I⁻.     

Time-dependent inactivation of human placental aromatase by bromoacetoxy 4-androsten-3-ones in the presence of reduced nicotinamide adenine dinucleotide phosphate (NADPH)

6-Bromoacetoxyandrostenediones (1 and 2) and 17 beta-bromoacetoxy-4-androsten-3-one having a 6 beta-bromo (3), 6-keto (4), or 6 beta-methoxyl (5) substituent were evaluated as mechanism-based inactivators of human placental aromatase. All of these compounds except the 6 alpha-bromoacetate 1 showed a time-dependent, pseudo-first-order inactivation of aromatase in the presence of reduced nicotinamide adenine dinucleotide phosphate (NADPH) with apparent Ki's of 40, 50, 30, and 34 microM and kinact's of 0.048, 0.364, 0.267, and 0.040 min-1, respectively, for compounds 2, 3, 4, and 5. The enzyme inactivation with compounds 3 and 4 was blocked by the addition of the substrate androstenedione to the incubates, and NADPH and oxygen were required for their effective time-dependent inactivation.     

Silyl-enolization-asymmetric Claisen rearrangement of 2-allyloxyindolin-3-one: enantioselective total synthesis of 3a-hydroxypyrrolo[2,3-b]indoline alkaloid alline

Asymmetric Claisen rearrangement triggered by silyl-enolization of 2-(1′-nonel-3′-yloxy)indolin-3-ones was performed in order to prepare 3-(2′-nonenyl)-3-hydroxyindolin-2-ones. Total synthesis of 3-hydroxypyrrolo[2,3-b]indoline alkaloid, (+)-alline was achieved by transformation of the allylic moiety of 3-(2′-nonenyl)-3-hydroxyindolin-2-one to amine followed by reductive cyclization.