Synthesis and biological activities of the tris-oxazole macrolactone analogs of mycalolides

Mycalolides are tris-oxazole macrolides isolated from the marine sponge Mycale sp., which shows cytotoxic, antifungal, and actin-depolymerizing activities. To develop an efficient synthetic route of mycalolides and to evaluate its functional mechanism of biological activities, tris-oxazole macrolactone analogs of mycalolides were synthesized through the use of ring-closing metathesis (RCM). The presence/absence of protecting groups at C3, solvent polarity, and reaction temperature significantly affected the stereoselectivity of RCM (E/Z=2.5/1.0–1.0/2.5). The 19E- and 19Z-stereoisomers both exhibited moderate cytotoxicity against tumor cells, but neither showed significant actin-depolymerizing properties or antimycotic activity against pathogenic fungi. Thus, both the side-chain (actin-binding) moiety and the macrolactone moiety were suggested to be essential for the potent biological activities of the parent molecules.     

Optical properties of fluorine-substituted zinc bismuth phosphate glasses

The effects of the substitution of fluoride ions for oxide ions on the thermal and optical properties of ternary ZnO-Bi₂O₃-P₂O₅ glass with low-P₂O₅ content (20-25 mol%) were investigated. Fluoride ions were introduced into the glass up to about 12 mol% as ZnF₂. Raman spectra indicated that fluoride ions were substituted for oxide ions connected with bismuth ions. Deformation and glass transition temperatures decreased monotonically with fluorine concentration. The absorption edge shifted toward higher energies with increasing fluorine concentration by about 0.3 eV for 12 mol% ZnF₂ substitution. The blue shift of the absorption edge is attributable to two effects. One was a blue shift of an absorption band which was observed as a peak at 4.7 eV in the reflection spectra and was attributed to the spin forbidden 6s-6p interband transition in Bi³⁺ ions. The blue shift originates from a change in electron-donating ability through anions as expected from electronegativity or optical basicity. Another is a disappearance of a shoulder at around 4.3 eV in the reflection spectra. The latter was the major reason for the large blue shift of the absorption edge energy, because the band relating to the 4.3 eV shoulder is close to the absorption edge.     

Phase Transition and Phase Transformation in Block Copolymer Nanoparticles

Block copolymer nanopaticles were prepared from the mixture solutions containing good/poor solvents by a simple evaporation process. The block copolymers formed disorder, unidirectionally stacked lamellar, and onion‐like structures in nanoparticles depending on preparation temperatures. Thermal annealing induced the disorder‐order phase transition and order‐order phase transformation in the block copolymer nanoparticles, even though the annealing temperature is lower than the of one polymer segment. The unusual thermal behaviors suggest that the glass transition temperature of the block copolymer is decreased by the effect of nanoparticle, whose surface areas are larger than their volumes.

     

Measurement method of particle concentration and acoustic properties in suspension using a focused ultrasonic impulse radiated from a plano-concave transducer

As a method to measure the concentration and property of a particle suspension, we proposed an ultrasonic measurement method using a plano-concave ultrasonic transducer. To carry out the experiment, we used a focused ultrasonic impulse with a broad frequency bandwidth radiated from the transducer, instead of utilizing continuous waves as in the conventional method. By analyzing the frequency components of the echo returned from the reflector put at the focal region of the transducer in suspension, we measured the concentration, etc., from variations of attenuation in the frequency spectrum. As specimens, we used some substances containing fine particles for which the acoustic properties or sizes are heterogeneous to each other. Specifically, the milk fat included in milk was examined in detail to characterize the best-tasting milk. In conclusion, we determined that the particle concentration and acoustic properties were easily and instantaneously measurable using the frequency spectrum obtained from pulse echoes passed through the specimen liquid, and the plano-concave transducer was advantageous in these measurements.     

Supramolecular Light‐Harvesting Antennas of Metal‐Coordinated Bis(8‐Hydroxyquinoline)‐Substituted Porphyrin Networks

Artificial antenna complexes of metal‐coordinated bis(8‐hydroxyquinoline)‐substituted porphyrin networks that mimic antenna chromophores in plants were organized on titanium dioxide electrodes in photoelectrochemical cells. The generated photocurrents can be optimized according to the two ways of porphyrin self‐assembly due to the “antenna effect”: changing the number of assembled porphyrin monolayers and the number of generations of the metal‐coordinated porphyrin networks.     

Silica coating of Co–Pt alloy nanoparticles prepared in the presence of poly(vinylpyrrolidone)

This article describes a method for silica coating of Co–Pt alloy nanoparticles prepared in the presence of poly(vinylpyrrolidone) (PVP) as a stabilizer. The Co–Pt nanoparticles were prepared in an aqueous solution at 25–80 °C from CoCl₂ (3.0 × 10⁻⁴ M), H₂PtCl₆ (3.0 × 10⁻⁴ M), PVP (0–10 g/L), and NaBH₄ (4.8 × 10⁻³–2.4 × 10⁻² M). The silica coating was performed for the Co–Pt nanoparticle colloid containing the PVP ([Co] = [Pt] = 3.0 × 10⁻⁵ M) at 25 °C in (1/4) (v/v) water/ethanol solution with tetraethoxyorthosilicate (TEOS) (7.2 × 10⁻⁵–7.2 × 10⁻³ M) and ammonia (0.1–1.0 M). Silica particles, which had an average size of 43 nm and contained multiple cores of Co–Pt nanoparticles with a size of ca. 8 nm, were produced at 1.4 × 10⁻³ M TEOS and 0.5 M ammonia after the preparation of Co–Pt nanoparticles at 80 °C, 5 g/L PVP, and 2.4 × 10⁻² M NaBH₄. Their core particles were fcc Co–Pt alloy crystallites. Their saturation magnetization was 2.0-emu/g sample, and their coercive field was 12 Oe.     

A finite element/volume method model of the depth‐averaged horizontally 2D shallow water equations

Analysis of surface water flows is of central importance in understanding and predicting a wide range of water engineering issues. Dynamics of surface water is reasonably well described using the shallow water equations (SWEs) with the hydrostatic pressure assumption. The SWEs are nonlinear hyperbolic partial differential equations that are in general required to be solved numerically. Application of a simple and efficient numerical model is desirable for solving the SWEs in practical problems. This study develops a new numerical model of the depth‐averaged horizontally 2D SWEs referred to as 2D finite element/volume method (2D FEVM) model. The continuity equation is solved with the conforming, standard Galerkin FEM scheme and momentum equations with an upwind, cell‐centered finite volume method scheme, utilizing the water surface elevation and the line discharges as unknowns aligned in a staggered manner. The 2D FEVM model relies on neither Riemann solvers nor high‐resolution algorithms in order to serve as a simple numerical model. Water at a rest state is exactly preserved in the model. A fully explicit temporal integration is achieved in the model using an efficient approximate matrix inversion method. A series of test problems, containing three benchmark problems and three experiments of transcritical flows, are carried out to assess accuracy and versatility of the model. Copyright © 2014 John Wiley & Sons, Ltd.     

A criterion for non-integrability of Hamiltonian systems with nonhomogeneous potentials

A necessary condition for integrability is presented for two degrees of freedom Hamiltonian systems with nonhomogeneous potentials. This is based on a theorem of Ziglin and gives also an efficient criterion for non-integrability. As an application, it is used to single out integrable cases among the Hénon-Heiles Hamiltonians.

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Résumé On démontre une condition nécessaire pour l'intégrabilité de systèmes hamiltoniens à deux degrés de liberté qui possèdent des potentiels inhomogènes. La démonstration repose sur un théorème de Ziglin et l'on obtient aussi un critère de non-integrabilité. Comme application, on s'en sert pour trouver des cas intégrables dans les hamiltoniens de Hénon-Heiles.

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Dedicated to Prof. Yoshikazu Hirasawa on his 60th birthday

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This research was partially supported by Grant-in-Aid for Scientific Research (No. 60740069), Ministry of Education. Japan.

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Staying at Forschungsinstitut für Mathematik, ETH-Zentrum, Zürich until the end of August, 1987.