Chirally autocatalytic reaction performed in highly supersaturated conditions

Spontaneous chiral asymmetry generation, which is the preferential production of one enantiomer in a non‐chiral environment by chiral autocatalysis, could be observed in a preparation of a octahedral cobalt complex, cis‐[CoBr(NH₃)(en)₂]Br₂. A concentration fluctuation in a far‐from‐equilibrium chemical system will grow if the rate of local autocatalytic production of a compound in a small volume overcomes its loss due to diffusion. In a chirally autocatalytic system, this phenomenon could produce a large variation in the enantiomeric excess. In a reaction that produces the cobalt complex, the reaction rate was found to increase in the highly supersaturated solution of the product. In supersaturated solutions, before crystals of the solute have nucleated, embryos, which are the clusters of the solute, are formed. Ternary water‐solubility isotherm of each enantiomer of the cobalt complex suggests that each embryo consists of one exclusive enantiomer. Each chiral cluster, which could be regarded as polymeric material, thus formed in a highly supersaturated solution, may act as catalyst for the production of the same enantiomer. Life is a far‐from‐equilibrium self‐organized polymeric system in which chiral symmetry is broken. This reaction system is thus a model for the generation and amplification of chiral asymmetry in polymeric materials; it provides some insight in to the mechanisms that might have produced the observed biomolecular homochirality.     

Preparation and porous control of amorphous carbons by co-defluorination of perfluorooctane and octafluorotoluene in vapor phases at 423 K

Two types of perfluorocarbon compounds, aliphatic perfluorooctane and aromatic octafluorotoluene, were co-defluorinated using sodium metal, and amorphous carbons were deposited from the vapor phase at very low temperature, 423 K. The products showed morphologies composed of fibrous, platelet, and spherical forms, which were dependent on the mixing ratio of the two. The BET surface areas also correlated well with the ratio of the starting mixtures, indicating that the surface area could be adjusted by changing the mixing ratio of these two compounds. However, when the carbonaceous product was further annealed in situ at 573 or 673 K, the porosities also modified. First the porosity decreased at 573 K, then increased greatly at 673 K, where radical interaction to shrink the pores and crystal growth of template fluoride occurred at 573 K and 673 K, respectively.     

Synthesis and biological evaluation of γ-fluoro-β,γ-unsaturated acids

Several γ-fluoro-β,γ-unsaturated acids, fluorine-containing analogues of N-acyl glycines, were synthesized via Julia-Lythgoe olefination. The antimicrobial activities of these compounds and synthetic intermediates were evaluated. Analogues with an octyl group showed in vitro antifungal activity agaist Penicillium chrysogenum IFO4626.     

Noether-Lefschetz locus for Beilinson-Hodge cycles I

We discuss the Noether-Lefschetz locus for Beilinson's Hodge cycles. Here ``Beilinson's Hodge cycles' mean the cohomology class of Bloch's higher Chow cycles on smooth varieties. The main result is to give an estimate of the dimension of the maximal component of the Noether-Lefschetz locus for the universal family of open complete intersections.     

Deformation and motion by gravity and magnetic field of a droplet of water-based magnetic fluid on a hydrophobic surface

Motion and deformation of a water-based magnetic fluid on a hydrophobic surface were investigated under gravity and a magnetic field. Surface energy and the resultant contact angle of the magnetic fluid depend on the surfactant concentration. The fluid viscosity is governed mainly by magnetite concentration. The front edge of the droplet moved under a weak external field. The rear edge required a higher external field for movement. The forces of gravity and the magnetic field for moving of the front edge are almost equal. However, those of the rear edge are different. The motion of magnetic fluids by an external field depends on concentrations of surfactants and magnetic particles, the external field, and experimental assembly.     

Effects of citric acid additive on photoluminescence properties of YAG:Ce nanoparticles synthesized by glycothermal reaction

We synthesize Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce³⁺) nanoparticles in the presence of citric acid by glycothermal method. Fourier transform infrared absorption spectroscopy measurement indicates that the intensity of the peak corresponding to carboxyl groups coordinating to the nanoparticles increases with increasing amount of citric acid. At the same time, the primary particle diameter decreases from 10.2 to 4.0 nm. In addition, the internal quantum efficiency of the photoluminescence (PL) due to the 4f-5d transition of Ce³⁺ increases from 22.0% to 40.1% with increasing amount of citric acid. Two kinds of PL decay lifetimes, 16-26 and 72-112 ns, are detected for YAG:Ce³⁺ nanoparticles, whereas the micron sized YAG:Ce³⁺ bulk shows the lifetime of 57 ns. We discuss these phenomena from the aspects of the coordination of citric acid and the incorporation of Ce³⁺ ions into the nanoparticles.     

Two-dimensional measurements of flow velocity in a microscopic region using two rotating gratings

A two-dimensional vector velocimeter is proposed on the basis of the time-varying spatial filtering method using a rotating disc with two transmission gratings. The filtering characteristics of the spatial filter used in the velocimeter are studied theoretically. This velocimeter was applied to measure the velocity vector of flowing water in a small glass pipe. The experimental results show the usefulness of the present velocimeter for measurements of the flow velocity in a microscopic region.