Preparation and characterization of polymers with oxadiazole on the side chain

Three styrene-type monomers having an oxadiazole group were prepared. The monomers were polymerized by a radical initiator into high molecular weight polymer. Polymers were soluble in many organic solvents such as chloroform, benzene and tetrahydrofuran. Polymer films were amorphous and transparent and showed no change after several months of preparation. The polymer had two reduction potentials around −2 V versus Ag/AgCl electrode. The polymer film dispersed with N,N,N′, N-tetraphenyldiaminobiphenyl (TPD) showed electroluminescence due to the exciplex with TPD. © 1997 John Wiley & Sons, Ltd.     

Preparation of alpha-elastin nanoparticles by gamma irradiation

Nanoparticles were prepared by utilizing the thermosensitive aggregation of alpha-elastin and gamma ray crosslinking. Three different heating process, “Slow heating”, “Fast heating”, and “Heat shock”, were applied for the aggregation of the alpha-elastin and examined to yield nanoparticles by gamma rays crosslinking. As a result, only “Slow heating” process yielded nanoparticles with diameters of about ca. 300 nm above cloud point (CP) and about ca. 100 nm below CP, and a narrow size distribution above 1.0 mg/ml concentration (exclude 1.0 mg/ml).     

Proton acceleration to 40 MeV using a high intensity, high contrast optical parametric chirped-pulse amplification/Ti:sapphire hybrid laser system

Using a high-contrast (10(10):1) and high-intensity (10(21) W/cm(2)) laser pulse with the duration of 40 fs from an optical parametric chirped-pulse amplification/Ti:sapphire laser, a 40 MeV proton bunch is obtained, which is a record for laser pulse with energy less than 10 J. The efficiency for generation of protons with kinetic energy above 15 MeV is 0.1%.     

Deacylative Carbon-Carbon Bond Cleavage of Ketone Equivalents: Applications to Radical Carbon-Carbon Bond Formation Reactions

This article describes the synthetic application of ketone-derived oxaziridines as alkyl radical precursors in copper-catalyzed Carbon-Carbon bond formation reactions. Experimental and computational studies indicate a free radical mechanism, where alkyl radicals are efficiently generated via cleavage of a Carbon-Carbon bond of oxaziridines. Acyclic and unstrained cyclic oxaziridines are applicable to the present radical process, allowing for the generation of various alkyl radicals with good functional group compatibility.     

Coherent convergent beam electron diffraction for analysis of lattice fitting in PbTe/MgO bi-crystals

Coherent convergent beam electron diffraction is for the first time applied to the analysis of lattice fitting between vacuum-deposited PbTe and MgO thin crystals in the plan-view mode. The possibility of determination of the rigid-body shift is discussed on the basis of simulated diffraction patterns from the bi-crystals as well as the preliminary experimental results obtained by a 200 kV transmission electron microscope with a field emission electron gun. In the analysis, the importance of the position of interference fringes at overlaps of PbTe 200 and MgO 200 diffraction disks and that of the corresponding mirror symmetry in the whole pattern are emphasized in order to determine the rigid-body shift and the probe-position.     

Controlling anisotropy of GaSb(As)/GaAs quantum dots by self-assembled molecular beam epitaxy

A systematic study was performed to control the geometrical anisotropy of GaSb(As)/GaAs quantum dot structures formed by the Stranski–Krastanov growth mode of molecular beam epitaxy. In particular, effects of both the Sb₄ beam flux and the As₄ background pressure on the geometrical anisotropy were clarified and elongated QDs with lateral aspect ratio greater than 3 were successfully formed. Under a low As₄ background pressure, As₄ is found to act as surfactant to influence the adatom diffusion and change the density of QDs. By contrast, under high As₄ background pressure, the intermixing of As and Sb takes place and reduces strains induced by the lattice mismatch.     

Minigap plasmons in a two-dimensional electron gas subjected to a one-dimensional periodic potential

We investigate the plasmon excitations in a two-dimensional electron gas subjected to a one-dimensional weak periodic potential. We derive and discuss the dispersion relations for both intrasubband and intersubband excitations within the framework of Bohm-Pines' random-phase approximation. For such an anisotropic system with spatially modulated charge density, we observe a splitting of the 2D plasmon dispersion. The splitting is caused by the superlattice effect of the charge-density modulation on the collective excitation spectrum. We also discuss how the tunneling and the potential amplitude affect the plasmon excitations.     

Equivalent electric circuit analyses of ionic thermocurrent in sodium-doped CaF2 crystals

The characteristics of high-temperature ionic thermocurrent (HT ITC) in CaF₂ doped with different sodium concentrations were studied by the Teflon-insulated electrode ITC method. It was shown that, with increasing sodium concentration, the HT ITC band moved toward a Na⁺-F_V dipole band with a peak at 162 K. The results of analyses of the HT ITC spectra using an equivalent electric circuit proved that the activation energy of space charge migration related to HT ITC was also strongly dependent on the doped sodium concentrations if varied from 0.94 to 0.46 eV with increasing sodium concentration in our ITC study. In addition, the broadening of the Na⁺-F_V dipole band was observed in 3 nominal mole% NaF-doped CaF₂, which was accompanied by a considerable decrease of the activation energy from 0.46 to 0.29 eV without showing marked temperature shifts of the peak ITC bands.