Stability of ferromagnetism in the Hubbard model on the kagome lattice

The Hubbard model on the kagome lattice has highly degenerate ground states (the flat lowest band) in the corresponding single-electron problem and exhibits the so-called flat-band ferromagnetism in the many-electron ground states as was found by Mielke [J. Phys. A 24, L73 (1991)]]. Here we study the model obtained by adding extra hopping terms to the above model. The lowest single-electron band becomes dispersive, and there is no band gap between the lowest band and the other band. We prove that, at half filling of the lowest band, the ground states of this perturbed model remain saturated ferromagnetic if the lowest band is nearly flat.     

360-W average power operation with a single-stage diode-pumped Nd:YAG amplifier at a 1-kHz repetition rate

We report a high-average-power laser-diode-pumped Nd:YAG master oscillator power amplifier system that has a minimum number of elements in the single multipass zigzag-slab amplifier stage and is used to pump a high-peak-power and high-average-power Ti:sapphire laser system. This phase-conjugated system produces an average power of 362 W at 1 kHz in a 30-ns pulse with an optical-to-optical conversion efficiency of 14%. With an external KTP doubler this system generates 132 W of green average output power at 1 kHz with a conversion efficiency of 60% when pumped at a power level of 222 W. To the best of our knowledge these results represent the highest average output power at both infrared and green wavelengths achieved in a single amplifier stage.     

Cationic palladium-catalyzed hydrosilylative cross-coupling of alkynes with alkenes

A cationic palladium complex-catalyzed cross-coupling of alkynes with alkenes is presented, which occurs selectively under the hydrosilylation conditions using trichlorosilane. The unique reaction might be well understood in terms of an initial hydropalladation of a given 1-alkyne to form regioselectively a 1-alkenylpalladium species, which, in turn, undergoes easily and specifically an alkene insertion. The resulting homoallylic organopalladium species terminates one catalytic cycle by substituting the palladium center with a trichlorosilyl group to give product(s).     

A stochastic study of the non-stationary non-negative random process based on two models of time series: multiplication and addition

As is well-known, there are two contrasting and fundamental models for simulating actual random processes with time series: a multiplication model and an addition model. In this letter, two explicit expressions of the probability density function for a non-stationary non-negative random process (a statistical Laguerre expansion type and a statistical Hermite expansion type) are derived from the above two fundamental viewpoints of modeling a time series, in relation to the statistical method described in a previous paper by the authors, in which the analysis was based on the use of a Hankel transform type characteristic function. The unified theory introduced in this previous paper can be obtained by a very simplified calculation as compared with that of the previous study, by the natural introduction of a random time series multiplication model.     

Collision-induced dissociation actualized the H+-promoted reaction as observed in vitro; harman formation from beta-carboline-type monoterpenoid glucoindole alkaloids

The fragmentation from beta-carboline-type monoterpenoid glucoindole alkaloids to harman, which is a hypothetical pathway to generate simple beta-carbolines, was actualized in the collision-induced dissociation in MS.     

Formation of an unusual dimeric compound by lead tetraacetate oxidation of a corynanthe-type indole alkaloid,mitragynine

Lead tetraacetate oxidation of a Corynanthe-type indole alkaloid, mitragynine, produced mainly 7-acetoxyindolenine derivative (2) together with a dimeric compound (4) as a minor product. The novel structure having a bridge between the C-11' and C-7 positions in the respective indolenine parts and its formation mechanism were studied.     

Aqueous dip-coating route to dense and porous silica thin films using silica nanocolloids with an aid of polyvinylpyrrolidone

An aqueous dip-coating route without using volatile alcohols for preparing dense and porous silica thin films is presented. The films were prepared by dip-coating on Si(100) and silica glass substrates using aqueous suspension of 8–11 nm colloidal silica where no alcohols were added. The addition of polyvinylpyrrolidone (PVP) in the suspension greatly improved the wettability, allowing homogeneous films to be formed on the substrates while the substrates showed poor wettability without PVP. When the as-deposited films were fired at 500–1,000 °C, optically transparent porous films with smooth surface were obtained. The porous films had homogeneous distribution and packing of silica nanoparticles, refractive indices of 1.24–1.33, and pencil hardness lower than 6B. The porous films underwent significant densification by viscous sintering when fired at temperatures over 1,000 °C. The viscous sintering was accompanied by the progress of condensation reaction and by the structural relaxation of siloxane network, which was revealed in the infrared absorption spectra. The resulting dense films had optical transparency, smooth surface, pencil hardness over 9H and refractive indices close to that of silica glass.     

Production of $$^{178}$$ 178 Hfm2 and a simple chemical separation method for Hf recovery

Journal of Radioanalytical and Nuclear Chemistry - The nuclear isomer $$^{178}$$ Hfm2 enables various investigations owing to its unique properties. To study exotic nuclear reactions induced by...