Ultrasonic cavitation in microspace

Ultrasound was irradiated to a micro-1D and -2D space having a characteristic length of 200 microm, and the presence of cavitation was confirmed from video images, and the generation of OH radicals, which was quantitatively evaluated with fluorometry.     

Optimum bubble temperature for the sonochemical production of oxidants

Numerical simulations of bubble oscillations in liquid water irradiated by an ultrasonic wave are performed for various acoustic amplitudes and various ambient pressures. In the numerical simulations, effect of non-equilibrium evaporation and condensation of water vapor at the bubble wall and that of chemical reactions of gases and vapor inside a bubble are taken into account. The oxidants such as OH radicals, O radicals, H(2)O(2) molecules, and O(3) molecules are created from water vapor inside a heated bubble when a bubble collapses strongly. They are dispersed into the liquid and solutes are oxidized by the oxidants, which is called sonochemical reactions. The computer simulations have revealed that there exists the optimum bubble temperature, which is about 5500 K, for the production of the oxidants inside an air bubble because at higher bubble temperature the oxidants are strongly consumed inside a bubble by oxidizing nitrogen. Correspondingly, there exists an optimum acoustic amplitude for the production of the oxidants, which is about 2.2 atm when the ultrasonic frequency is 140 kHz and the ambient pressure is 1 atm. For an oxygen bubble, on the other hand, the amount of the oxidants created inside a bubble becomes nearly independent of the bubble temperature at the collapse above about 6000 K because nitrogen is absent.     

High-throughput, high-damage-threshold broadband beam splitter for high-order harmonics in the extreme-ultraviolet region

We demonstrate a high-throughput and high-damage-threshold beam splitter for high-order harmonics in the soft-x-ray region that uses Si and (or) SiC plates set at Brewster's angle with respect to the pump wavelength. The beam splitters are guaranteed to have a damage threshold of at least 0.8 TW/cm2 (average power density, 0.25 W/cm2) and an attenuation rate of 10(-4)-10(-5) for a 30-fs pump pulse. The measured reflection efficiency at the 27th harmonic (29.6 nm) was 0.56 for Si and 0.45 for SiC. These beam splitters are useful not only for high harmonics but also for longitudinally pumped x-ray lasers.     

Synthesis of unnatural 1-methyl-2-quinolone derivatives

Unnatural 1-methyl-2-quinolone derivatives were synthesized by regioselective C-C bond formation. When 1-methyl-3,6,8-trinitro-2-quinolone (TNQ) was treated with enamines, nucleophilic addition readily occurred at the 4-position, and succeeding hydrolysis of enamine moiety followed by elimination of nitrous acid furnished 4-acylmethyl-1-methyl-6,8-dinitro-2-quinolones. The same products could be prepared by the reaction of TNQ with ketones in the presence of triethylamine. The present reaction enabled the introduction of various kinds of acylmethyl groups substituted with alkyl, aryl or hetaryl groups.     

Behavior of Ultrafine Particles generated from organic vapors by corona ionizers

This paper reports an experimental study on the stability, coagulation and diffusion of molecular clusters and ultrafine particles generated from organic vapors by corona ionizers. Upon leaving the ionizer, particles are made to flow within several types of vessels: depending on the specific geometry of the flow system, clusters either coagulate into large particles or are deposited on the walls. Particles larger than 4nm and molecular clusters penetrate through a wire-screen type diffusion battery, but particles in the size range between 2 and 4nm are collected. Among the organic compounds tested (aromatics, alcohols, ketones and others), only aromatic compounds appear to yield unstable clusters which grow into detectable particles (>2nm) through Brownian coagulation. The other compounds either do not undergo the gas-to-particle conversion process or are too small to be detected. Furthermore, the presence of moisture seems to be of fundamental importance in the particle generation phenomenon. The addition of alcohols to the vapor mixture inhibits particle formation.     

Synthesis of star polystyrene by radical polymerization with 1,2,4,5-tetrakis(p-tert-butylphenyl selenomethyl)benzene as a novel photoiniferter

1,2,4,5-Tetrakis(p-tert-butylphenylselenomethyl)benzene was synthesized and used as a tetrafunctional photoiniferter for the polymerization of styrene. Both the yield and the number average molecular weight () of polymers increased with reaction time and linearly increased with yield of polymer. The polymerization of styrene using this novel photoiniferter permitted formation of star-shaped polystyrene containing arylseleno groups at the chain ends, and the average degree of functionality was 3.2. Photopolymerization of styrene with end-functional star polystyrene as polymeric photoiniferter afforded polystyrene having high molecular weight.     

Ruthenium complexes carrying a disialo complex-type oligosaccharide: enzymatic synthesis and its application to a luminescent probe to detect influenza viruses

Tris-bipyridine ruthenium-complexes carrying a disialo complex-type oligosaccharide were prepared via a one-pot transglycosylation using endo-glycosidase (Endo M); they bind to type-A influenza viruses with excellent affinity (IC50 = 8.4 microM), and their luminescence intensity is strongly depressed by virus-binding.     

Moment analysis of retention equilibrium, mass transfer kinetics, and thermodynamic properties in reversed-phase liquid chromatography using phenyl bonded silica gel

Information about retention equilibrium, mass transfer kinetics, and related thermodynamic properties of chromatography using phenyldimethylsilyl (Ph)-silica gel was derived by moment analysis of pulse response peak profiles. The results for the Ph-silica gel were compared with those for octadecyldimethylsilyl (C18)-silica gel. Some parameters characterizing the chromatographic behavior of the two stationary phases were correlated with the hydrophobic surface area of sample molecules. Surface diffusion had a predominant role for intraparticle diffusion. An enthalpy-entropy compensation was established for both the retention equilibrium and surface diffusion. A linear correlation was observed between the logarithm of surface diffusion coefficient (Ds) and that of retention equilibrium constant (Ka), suggesting the establishment of a linear free energy relationship. The ratio of Ds to molecular diffusivity (Dm) decreased with increasing Ka and was correlated by a single curved line. The value of Ds was of the same order of magnitude with Dm when Ka became negligible. These results suggest the presence of a sort of correlation between surface diffusion and molecular diffusion and the restriction of the molecular mobility by surface diffusion due to the retention strength.