Stereoselective Syntheses of all the Possible Stereoisomers of Coronafacic Acid

An efficient and stereoselective syntheses of all the possible stereoisomers of coronafacic acid (CFA) has been developed. The stereochemistries of C3a and C7a were controlled in a diastereoselective Diels-Alder type cycloaddition using a chiral auxiliary. CFA and 6-epi-CFA were synthesized by hydrogenation of a common intermediate. During the synthesis of 6-epi-CFA, we established that its cis-fused configuration is important for the introduction of C4-C5 double bond by dehydration. This report is the first practical synthesis of both 6-epi-CFA, and its enantiomer.     

Suppression of particle generation in a plasma process using a sine-wave modulated rf plasma

Sine-wave modulated rf plasma has been used to control particle generation and growth in a plasma-enhanced chemical vapor deposition of silicon dioxide thin films using TEOS/O₂. The density and the size of particles generated in the plasma are greatly reduced when the plasma is modulated with sine-wave modulation at low modulation frequency (<1000 Hz). In addition, particle contamination on the films is significantly reduced also for nanoparticles, and the film growth rates at the range of modulation frequencies where particle generation are greatly reduced do not decrease appreciably. Compared to its counterpart pulse-wave modulation plasma, the sine-wave modulation plasma has demonstrated a better performance in terms of reduction of particle generation and film contamination, and of film growth rate. Thus, the sine-wave modulation plasma has shown as a promising method to be applied in the production of thin film with a high deposition rate and a low particle contamination.     

Superionic Conduction in Co‐Vacant P2‐NaxCoO2 Created by Hydrogen Reductive Elimination

The layered P2‐Na_xMO₂ (M: transition metal) system has been widely recognized as electronic or mixed conductor. Here, we demonstrate that Co vacancies in P2‐Na_xCoO₂ created by hydrogen reductive elimination lead to an ionic conductivity of 0.045 S cm^?1 at 25 °C. Using in situ synchrotron X‐ray powder diffraction and Raman spectroscopy, the composition of the superionic conduction phase is evaluated to be Na_0.61(H₃O)_0.18Co_0.93O₂. Electromotive force measurements as well as molecular dynamics simulations indicate that the ion conducting species is proton rather than hydroxide ion. The fact that the Co‐stoichiometric compound Na_x(H₃O)_yCoO₂ does not exhibit any significant ionic conductivity proves that Co vacancies are essential for the occurrence of superionic conductivity.     

Deformation band evolution in [110] Al single crystals strained in tension

Several types of deformation bands form during uniaxial extension of Al single crystals for which the tensile axis is initially parallel to [110]. The objectives of the present work are to analyse crystal orientation evolution in the deformation bands and adjoining regions, and to integrate the experimental observations with a crystal mechanics model. The most prominent deformation bands contain secondary slip traces and exhibit crystal rotations consistent with unpredicted slip on a secondary slip system. These special bands of secondary slip (SBSS) become more closely aligned with the tensile axis as extension increases. The evolution of SBSS inclination with extension indicates that SBSS form initially as kink bands and that SBSS boundaries are immobile. SBSS grow during straining by expansion of the volume of material in which secondary slip operates. Deformed matrix (DM) bands are zones between SBSS; primary slip predominates in DM bands. Small intra-DM bands result from spatial variation of the shear amplitudes for the two primary slip systems. The evolution of intra-DM band inclination with extension indicates that intra-DM bands form initially as kink bands and that the band boundaries are mobile, at least to some extent.     

Evaluation and comparison of three novel microbubbles: Enhancement of ultrasound-induced cell death and free radicals production

Three novel lipid-shell-type microbubbles (MBs), AS-0100, BG6356A and BG6356B, have been evaluated for their impact on ultrasound (US)-induced cell death and free radicals production. Previously studied and well-characterized US exposure conditions were employed in which human myelomonocytic lymphoma U937 cells were exposed to 1 MHz pulsed US beam (0.3 W/cm², 10% duty factor) for 1 min with or without MBs. Three different concentrations of each MB were used. Apoptosis and cell lysis were assessed by examining phosphatidylserine externalization and by counting viable cells, respectively, 6 h post-exposure. Free radicals production and scavenging activities were evaluated using electron paramagnetic resonance (EPR)-spin trapping. The results showed that only AS-0100 and BG6356A were able to enhance the US-induced apoptosis, mainly by increasing the secondary necrosis. Apoptosis and cell lysis seemed to depend more on mechanical forces exerted by oscillating MBs while free radicals played a trivial role. BG series MBs exhibited pronounced scavenging activities. Generally, despite the need for further optimization, AS-0100 and BG6356A appear to be promising as adjuncts in cases where US-induced cell death is required.     

Rapid fermentation of beer using an immobilized yeast multistage bioreactor

The characteristics of yeast sulfite metabolism in a multistage bioreactor system for beer fermentation were investigated. No sulfite was produced in the continuous stirred-tank reactor (CSTR). However, large amounts were produced in the packed-bed reactor (PBR). Production of sulfite in the PBR seems to be inevitable when it is operated continuously. In order to control the sulfite level in the young beer, the yeast needs to be reactivated into the growth phase. One possible strategy to achieve this is to aerate and periodically remove yeast clogged in the reactor once every 6–7 months before the sulfite level exceeds a given concentration (e.g., 20 mg/L). It was confirmed that sulfite production is closely related to the growth condition of the yeast and is therefore important to consider in the control strategy for sulfite when using the immobilized yeast reactor for beer production.     

Nitrogen-containing organozinc and organoaluminum as catalyst for stereospecific polymerization of propylene oxide

Catalytic activities of the reaction products of diethylzinc or triethylaluminum with primary amines in the polymerization of propylene oxide were studied. Generally, organozinc compounds give higher ratio of the crystalline to the amorphous polymer than the organoaluminums. In the reactions of organometallic compounds with primary amines, Et₂AlNPhAlEt₂, Et₂AlN-t-BuAlEt₂, EtZnNH-t-Bu, and EtZn-t-BuZnEt were isolated in crystalline state. EtZnN-t-BuZnEt proved to be an excellent catalyst for the stereospecific polymerization of propylene oxide and forms coordination complexes with some electron donors such as dioxane, pyridine, epichlorohydrin and propylene oxide. The propylene oxide complex is unstable in solution and decomposes at temperatures above room temperature to give poly(propylene oxide), while the pyridine complex has no catalytic activity. Therefore, it is concluded that the polymerization of propylene oxide with this catalyst proceeds through the coordination of propylene oxide to the zinc atom of the catalyst.     

Hydrofluoroarylation of alkynes with fluoroarenes

A combination of Ni(cod)(2) and PCyp(3) is found to be an effective catalyst for chemoselective activation of the C-H bond of fluoroarenes over C-F bonds followed by insertion of alkynes to allow direct alkenylation of the electron-deficient arenes. The characteristics of the reactions are: a C-H bond ortho to a fluorine substituent is selectively activated; the reactivity of fluorobenzenes is roughly proportional to the number of fluorine atoms. The reaction conditions tolerate a broad range of both alkynes and fluoroarenes containing both electron-withdrawing and -donating groups, thus allowing efficient synthesis of a variety of substituted ethenes containing a fluoroaryl motif in high regio- and stereoselective manners. Mechanistic studies including both labeling experiments and stoichiometric reactions reveal that oxidative addition of C-H bonds in fluoroarenes to nickel(0) is kinetically highly facile whereas that of C-F bonds is thermodynamically favoured.