The effect of the counter anion on the transport of thiourea in a PVC-based polymer inclusion membrane using Capriquat as carrier

This paper describes the effect of four counter anions (CH₃COO⁻, Cl⁻, NO₃⁻, ClO₄⁻) of the trioctylmethylammonium (TOMA) cation on the rate of solvent extraction of thiourea and its transport across poly(vinyl chloride) (PVC)-based polymer inclusion membranes (PIMs). The membranes also contained 2-nitrophenyl octyl ether (NPOE) as the plasticizer while chloroform was used as diluent in the solvent extraction studies. It is demonstrated that the counter anion affects substantially the rate of membrane transport and the degree of extraction follows the order: CH₃COO⁻ > Cl⁻ > NO₃⁻ ? ClO₄⁻. The transport rate is negligible for the perchlorate anion. This order is consistent with thiourea interacting with the counter anion through hydrogen bonding to form a heteroconjugate anion.     

Aggregation modeling of calcium carbonate particles by Monte Carlo simulation

The mechanism on aggregation of spindle granular particles of calcite was investigated for the carbonation of calcium hydroxide in aqueous suspension for the purpose of controlling morphology of CaCO₃. The experimental carbonation process was carried out in a semi-batch bubble column reactor under different conditions. Although, fine rhombic nano-particles diameter ranged from 100 to 200 nm were obtained at 291 K, a higher temperature of 300 K provided spindle granular particles with a length of 1.0–1.5 μm and a width of 0.3–0.5 μm. The average crystallite size was 28 nm for the fine rhombic nano-particles and 43 nm for the spindle granules. Zeta potential measurement for the spindle granules indicated that the suspension tended to be aggregated during the carbonation process. The effect of the degree of particle aggregation on the shape of the obtained calcite particles was studied by Monte Carlo simulations. Our simulation results elucidated the dependence of aggregation on unit particles, i.e., primary particles, on the experiment carbonation condition where the spindle granules were formed out of the unit particles under the same condition as the experiments. In addition, the formation mechanism of the granules was investigated by applying classical nucleation theory to the present simulations.     

Applicability of locally reacting boundary conditions to porous material layer backed by rigid wall: Wave-based numerical study in non-diffuse sound field with unevenly distributed sound absorbing surfaces

To clarify the applicability of locally reacting boundary conditions in wave-based numerical analyses of sound fields in rooms, we numerically analyzed a non-diffuse sound field in a room with unevenly distributed sound absorbing surfaces and investigated the differences between the extended and local reactions. Each absorbing surface was a porous material layer backed by a rigid wall. Simulations were performed by the fast multipole boundary element method, a highly efficient boundary element method using the fast multipole method. At low frequencies, the extended and local reactions yielded similar reverberation decay curves because of the influence of the room. However, when the random incidence absorption coefficients were small at low frequencies or frequencies were high, the difference was greater than expected from the corresponding Eyring decay lines. We conclude at high frequencies, the locally reacting boundary conditions lead to a longer reverberation time than that expected from the absorption coefficient differences between the extended and local reactions. These differences were similar in sound-pressure-level and sound-intensity-level distributions, and in the oblique incidence absorption coefficient of the absorbing surfaces, but were increased at low frequencies.     

Excitation of high-spin particle-hole states in A = 28 nuclei by 27Al(α, t) and (α, 3He) reactions

The ²⁷Al(α, t) and (α, ³He) reactions have been measured at E_α = 64.5 MeV. The experimental angular distributions were analyzed by the exact finite-range DWBA calculations assuming a nucleon stripping mechanism. The distributions of spectroscopic strengths for the single-particle transitions with transferred angular momenta l = 0, 1, 2, 3 and 4 have been obtained. The strengths for the transitions to the stretched 6^? states in ²⁸Si and ²⁸Al are compared to those obtained from inelastic scattering on ²⁸Si. The present results show no distinctive differences in the structures for 6^?T = 0 and 1 states in ²⁸Si such as are observed in proton and pion inelastic scattering on ²⁸Si.     

A liquid film or droplet of miscible binary fuel burning on a heated surface at elevated pressures

An experimental study has been made of the combustion and evaporation of miscible binary fuels on a heated surface at elevated pressures. Photographic observation was made for elucidating how the binary fuel droplets or films behaved on the heated surface and for obtaining the characteristic lifetime as a function of the surface temperature, the ambient pressure and the initial concentration of highly volatile component of the fuels. The binary fuels tested were mixtures of n-hexane and n-decane. The results showed that the lifetime curve both for the combustion and for the evaporation of n-hexane/n-decane on the heated surface had two peaks at lower pressures, the first peak in the film-type evaporation region and the second peak in the spheroid-type evaporation region. The preferential evaporation of the highly volatile component was responsible for the appearance of the first peak in the film-type evaporation region. The second peak corresponded to Leidenfrost point. The increase in the ambient pressure caused a shift of the lifetime curve toward higher surface temperature and a decrease in the lifetime at two peaks. The lifetime curve decreased monotonically with increasing the surface temperature and the spheroid-type evaporation was not observed at higher pressures. The increase in the initial concentration of highly volatile component caused a shift of the first peak toward higher surface temperature, a decrease in its lifetime and a slight shift of the second peak toward lower surface temperature. The combustion caused a remarkable decrease in the lifetimes around the first peak and in the spheroid-type evaporation region and a slight increase in the surface temperature at the first peak, while the surface temperature at the second peak remained almost unchanged.     

Stereocontrolled synthesis of the macrolactone core of neopeltolide

A stereoselective synthesis of the macrolactone core of neopeltolide is described. The tetrahydropyran moiety was constructed via the intramolecular allylation of an α-acetoxy ether. A late-stage macrolactonization provided a known synthetic intermediate of neopeltolide.     

Sulfonium Salt Reagents for the Introduction of Deuterated Alkyl Groups in Drug Discovery

The pharmacokinetics of pharmaceutical drugs can be improved by replacing C−H bonds with the more stable C−D bonds at the α-position to heteroatoms, which is a typical metabolic site for cytochrome P450 enzymes. However, the application of deuterated synthons is limited. Herein, we established a novel concept for preparing deuterated reagents for the successful synthesis of complex drug skeletons with deuterium atoms at the α-position to heteroatoms. (d_n-Alkyl)diphenylsulfonium salts prepared from the corresponding nondeuterated forms using inexpensive and abundant D₂O as the deuterium source with a base, were used as electrophilic alkylating reagents. Additionally, these deuterated sulfonium salts were efficiently transformed into d_n-alkyl halides and a d_n-alkyl azide as coupling reagents and a d_n-alkyl amine as a nucleophile. Furthermore, liver microsomal metabolism studies revealed deuterium kinetic isotope effects (KIE) in 7-(d₂-ethoxy)flavone. The present concept for the synthesis of deuterated reagents and the first demonstration of a KIE in a d₂-ethoxy group will contribute to drug discovery research based on deuterium chemistry.     

Systematics of low-lying octupole states in the doubly-even nuclei from Ge to Sr

Low-lying octupole states of doubly-even ^78–86Kr isotopes have been studied with inelastic scattering of 51.9 MeV protons. It is shown that in the doubly-even nuclei from Ge to Sr with N = 42–50, the lowest octupole vibrational energies of nuclei with equal neutron excess are almost the same. The transition strengths of these states increase with Z.     

Constituents of the leaves of Woodfordia fruticosa Kurz. I. Isolation, structure, and proton and carbon-13 nuclear magnetic resonance signal assignments of woodfruticosin (woodfordin C), an inhibitor of deoxyribonucleic acid topoisomerase II

Woodfruticosin (woodfordin C), a new cyclic dimeric hydrolyzable tannin having an inhibitory activity toward deoxyribonucleic acid (DNA) topoisomerase II, has been isolated from the leaves of Woodfordia fruticosa Kurz (Lythraceae) along with three known flavonol glycosides and three known flavonol glycoside gallates. The structure of wood fruticosin (woodfordin C) was determined by the use of two-dimensional nuclear magnetic resonance (2-D NMR) spectroscopy including heteronuclear multiple quantum coherence (HMQC) and heteronuclear multiple bond connectivity (HMBC) techniques. Detailed analyses of the proton and carbon-13 NMR (1H- and 13C-NMR) spectra of six known flavonoids were performed.     

Etching Efficiency for Si and SiO2 by CF+x,F+, and C+ Ion Beams Extracted from CF4 Plasmas

Fluorocarbon (CF⁺ _x), fluorine (F⁺), and carbon (C⁺) ion beams with highcurrent density (50i<800 A/cm²) were irradiated to Si and SiO₂surfaces to investigate the influence of the ion species on the etchingefficiency. The ion beams were extracted from magnetized helicon-wave CF₄plasmas operated in pulsed modes. The CF⁺ ₃ beam had the largest etchingefficiency for Si at the same beam energy. When the same data weresummarized as a function of the momentum of the incident ion beam, thedifference in the etching efficiency became small, although the CF⁺ ₃ beamstill had a slightly larger etching efficiency. On the other hand, theetching efficiency for SiO₂ by the CF⁺ ₃ beam was larger than that by theother ion beams in the low-momentum region. In addition, in the low-momentumregion, the etching efficiency for SiO₂ by CF⁺ ₃ was larger than that forSi. These results suggest the high chemical reactivity of CF⁺ ₃ with SiO₂,leading to the high etching selectivity of SiO₂ over underlying Si in thefabrication of semiconductor devices.