Hokkaido University

About: Hokkaido University is a education organization based out in Sapporo, Hokkaidô, Japan. It is known for research contribution in the topics: Catalysis & Population. The organization has 53925 authors who have published 115403 publications receiving 2651647 citations. The organization is also known as: Hokudai & Hokkaidō daigaku.

Enhancement in Aerobic Alcohol Oxidation Catalysis of Au25 Clusters by Single Pd Atom Doping

Abstract: Au25 and Pd1Au24 clusters on multiwalled carbon nanotubes were developed via adsorption of Au25(SC12H25)18 and Pd1Au24(SC12H25)18, respectively, on the nanotubes, followed by calcination. Comparison of their catalysis for the aerobic oxidation of benzyl alcohol showed that single Pd atom doping significantly improved the catalytic performance of Au25 for the first time.

Empirical shear wave velocity equations in terms of characteristic soil indexes

Abstract: An investigation to systematize empirical equations for the shear wave velocity of soils was made in terms of four characteristic indexes. The adopted indexes are the N-value of the Standard Penetration Test, depth where the soil is situated, geological epoch and soil type. As some of these indexes are variates belonging to interval scales while others belong to nominal or ordinal scales, the technique known as a multivariate analysis cannot be employed. A new approach to the theory of quantification, after C. Hayashi, was introduced and developed for solving this difficulty. Fifteen sets of empirical equations to estimate low strain shear wave velocity theoretically may be obtained by combining the above four indexes. All of these sets were derived by use of about 300 data, and their accuracies were evaluated by means of correlation coefficients between the measured and estimated shear wave velocities. The best equation was found to be the one which included all the indexes, and its correlation coefficient was 0.86. The empirical equation relating the standard penetration N-value to the shear wave velocity provided a correlation of only 0.72, and is one of the lowest ranking among the 15 sets of equations.

Laser-matter interaction in the bulk of a transparent solid: confined microexplosion and void formation

Abstract: We present here the experimental and theoretical studies of a single femtosecond laser pulse interaction inside a bulk of transparent media (sapphire, glass, polymer). This interaction leads to the drastic transformations in a solid resulting in a void formation inside a dielectric. The laser pulse energy is absorbed within a volume of approximately $0.15\phantom{\rule{0.3em}{0ex}}\mathrm{\ensuremath{\mu}}{\mathrm{m}}^{3}$ creating a pressure and temperature comparable to that in the core of a strong multi-kilo-tons explosion. The material within this volume is rapidly atomized, ionized, and converted into a tiny super-hot dense cloud of expanding plasma that generates strong shock and rarefaction waves which result in the formation of a void, whose diameter is $\ensuremath{\sim}200\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ (for a $100\phantom{\rule{0.3em}{0ex}}\mathrm{nJ}$ pulse in sapphire). The way this structure forms can be understood from high-temperature plasma hydrodynamics. We demonstrate that unique states of matter characterized by temperatures $\ensuremath{\sim}{10}^{5}\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, heating rates up to the ${10}^{18}\phantom{\rule{0.3em}{0ex}}\mathrm{K}∕\mathrm{s}$, and pressures more than 100 times the strength of any material were created using a standard table-top laser in well-controlled laboratory conditions. We discuss the properties of the laser-affected solid and possible routes of laser-affected material transformation to the final state long after the pulse end. These studies will find application for the design of new materials and three-dimensional optical memory devices, and for formation of photonic band-gap crystals.