Asymmetric Michael addition of boronic acids to a γ-hydroxy-α,β-unsaturated aldehyde catalyzed by resin-supported peptide

A resin-supported peptide catalyst effective for the asymmetric Michael addition of boronic acids to (E)-4-hydroxybut-2-enal was developed. From a spectral study, it was revealed that the optimum peptide consisted of both a β-turn and helix. Such a combination of secondary structures was essential for achieving a high catalytic ability.     

Synthesis and helical properties of aromatic multilayered oligoureas

Several aromatic multilayered oligoureas with different chain lengths and different numbers of chiral N-substituents were synthesized, and their helical conformation and induced handedness were examined by means of CD spectroscopy. Introduction of one chiral N-substituent is enough to induce handedness, and all the oligoureas examined exist predominantly as helical structures with all-S axial chirality. The hexaureas 6 and 7 had similar CD intensity to the tetraureas 4 and 5, and had larger CD intensity than diurea 8. The results indicate that the effect of a chiral N-substituent at the central benzene ring in inducing well-ordered handedness at the terminal positions of hexaureas 6 and 7 is relatively weak, even though these compounds mainly take the form of aromatic multilayered foldamers.     

Comparison between sonodynamic effect and photodynamic effect with photosensitizers on free radical formation and cell killing

Although enhancement of ultrasound-induced cell killing by photodynamic reagents has been shown, the sonochemical mechanism in detail is still not clear. Here, comparison between sonodynamic effect and photodynamic effect with photosensitizers at a concentration of 10 μM on free radical formation and cell killing was made. When electron paramagnetic-resonance spectroscopy (EPR) was used to detect 2,2,6,6-tetramethyl-4-piperidone-N-oxyl (TAN) after photo-irradiation or sonication with 2,2,6,6-tetramethyl-4-piperidone (TMPD), the order of TAN formation in the photo-irradiated samples was as follows: rhodamine 6G (R6) > sulforhodamine B (SR) > hematoporphyrin (Hp) > rhodamine 123 (R123) > rose bengal (RB) > erythrosine B (Er) = 0; although there was time-dependent TAN formation when the samples were sonicated, no significant difference among these agents were observed. All these agents suppressed ultrasound-induced OH radical formation detected by EPR-spin trapping. Sensitizer-derived free radicals were markedly observed in SR, RB and Er, while trace level of radicals derived from R6 and R123 were observed. Enhancement of ultrasound-induced decrease of survival in human lymphoma U937 cells was observed at 1.5 W/cm² (less than inertial cavitation threshold) for R6, R123, SR and Er, and at 2.3 W/cm² for R6, R123, Er, RB and SR. On the other hand, photo-induced decrease of survival was observed for R6, Hp and RB at the same concentration (10 μM). These comparative results suggest that (1) ¹O₂ is not involved in the enhancement of ultrasound-induced loss of cell survival, (2) OH radicals and sensitizer-derived free radicals do not take part in the enhancement, and (3) the mechanism is mainly due to certain mechanical stress such as augmentation of physical disruption of cellular membrane by sensitizers in the close vicinity of cells and/or cavitation bubbles.     

Pressure effect on bulk weak ferromagnets: (BDH-TTP)[M(isoq)2(NCS)4] (M = Cr(III), Fe(III); isoq = Isoquinoline)

The pressure dependence of the magnetic properties of weak ferromagnets (BDH-TTP)[M(isoq)2(NCS)4] [BDH-TTP = 2,5-bis(1',3'-dithiolan-2'-ylidene)-1,3,4,6-tetrathiapentalene; M = Cr, Fe; isoq = isoquinoline] is discussed. These salts form two-dimensional magnetic sheets, where ferrimagnetic chains of donor cation radical (S = 1/2) and anion [S = 3/2 (Cr), 5/2 (Fe)] are antiferromagnetically connected by weak donor-donor and anion-anion interchain S...S contacts. Under ambient pressure, both the Cr and Fe salts undergo a weak ferromagnetic transition at Tc = 7.6 K, below which a spontaneous magnetization emerges along the direction perpendicular to the sheets. The application of the pressure elevates the transition temperatures up to 16.6 and 11.6 K at 9 kbar for M = Cr and Fe, respectively. As the pressure increases, the remanent magnetization M(r) decreases, whose pressure dependence for the Cr salt is larger than that for the Fe salt. This difference indicates that the spin-canting angle of the Cr salt is reduced because of the increase of antiferromagnetic interaction by applied pressure, in contrast to the Fe salt, where single-ion anisotropy contributes less. The quantitative analysis of the magnetization curves of the Cr salt using the mean-field approximation reveals that the intermolecular exchange interaction increases as the pressure increases, among which the interchain anion-anion interaction has the highest pressure sensitivity. This result is consistent with the temperature dependence of the crystal structure showing that the thermal contraction in the distances of interchain anion-anion S...S contacts is the most remarkable in intrachain S...S contacts. The large pressure dependence of the transition temperature of these salts is therefore explained as a result of the fact that the interchain interactions, the anion-anion interaction in particular, are strengthened by applied pressure.     

Pressure effect on the electrical conductivity and superconductivity of beta-(BDA-TTP)2I3

The pressure-induced electrical conductivity properties of beta-(BDA-TTP)2I3 have been investigated; the salt exhibits a dramatic change in the conductivity behaviour above ca. 10 kbar and undergoes a superconducting transition with an onset near 10 K.     

A granularity-based framework of deduction, induction, and abduction

In this paper, we propose a granularity-based framework of deduction, induction, and abduction using variable precision rough set models proposed by Ziarko and measure-based semantics for modal logic proposed by Murai et al. The proposed framework is based on α-level fuzzy measure models on the basis of background knowledge, as described in the paper. In the proposed framework, deduction, induction, and abduction are characterized as reasoning processes based on typical situations about the facts and rules used in these processes. Using variable precision rough set models, we consider β-lower approximation of truth sets of nonmodal sentences as typical situations of the given facts and rules, instead of the truth sets of the sentences as correct representations of the facts and rules. Moreover, we represent deduction, induction, and abduction as relationships between typical situations.     

High-Precision Calculation of the Energy Levels and Auger Decay Rates of the Metastable States of the Antiprotonic Helium Atoms

We precisely calculated the energy levels and the Auger decay rates of the antiprotonic helium atoms with the coupled rearrangement channel method and the complex-coordinate-rotation method. Calculated transition frequencies were in excellent agreement with observed values. This agreement gives best limit of the antiproton mass with 5×10⁻⁸ uncertainty. This revised version was published online in August 2006 with corrections to the Cover Date.