Measurement of neutrino oscillation with KamLAND: evidence of spectral distortion

We present results of a study of neutrino oscillation based on a 766 ton/year exposure of KamLAND to reactor antineutrinos. We observe 258 nu (e) candidate events with energies above 3.4 MeV compared to 365.2+/-23.7 events expected in the absence of neutrino oscillation. Accounting for 17.8+/-7.3 expected background events, the statistical significance for reactor nu (e) disappearance is 99.998%. The observed energy spectrum disagrees with the expected spectral shape in the absence of neutrino oscillation at 99.6% significance and prefers the distortion expected from nu (e) oscillation effects. A two-neutrino oscillation analysis of the KamLAND data gives Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2). A global analysis of data from KamLAND and solar-neutrino experiments yields Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2) and tan((2)theta=0.40(+0.10)(-0.07), the most precise determination to date.     

Effect of ultrasonic wave on the syntheses of Au and ZnO nanoparticles by laser ablation in water

We synthesized Au and ZnO nanoparticles by laser ablation in distilled water with the superposition of an ultrasonic wave. The effect of the ultrasonic wave was examined on the optical absorbance of colloidal solution and the crystallinity of synthesized nanoparticles. The absorbance of colloidal solution was enhanced by the ultrasonic wave, indicating more efficient production rate of nanoparticles. In addition, the ultrasonic wave enhanced the crystallinity of synthesized nanoparticles. These enhancements are attributed to the fact that the ultrasonic wave drives the repetitive formations and collapses of cavitation bubbles.     

Photoxidation of di-t-butyl thioketone

The photo-oxygenation of the title compound leads to the corresponding ketone and sulfine. A mechanism for the reaction is elucidated.     

Theory of angle-resolved X-ray photoemission compared with exafs

Angle-resolved photoemission from deep core orbitals on irradiation with soft X-rays is theoretically considered and compared with EXAFS results. Numerical calculations are carried out for ionization from the 1s orbital of O adsorbed on an Al (110) surface, and the results show that the variations of the differential photoionization cross-section in special directions are rapid in comparison with that given by EXAFS with respect to final kinetic-energy variation.     

Effects of metal salts on polymerization. Part II. Polymerization of vinylpyridine complexed with the group IIb metal salts

The following stoichiometric vinylpyridine complexes have been prepared: (4-VP)₂—Zn(SCN)₂, (2-VP)₂—Zn(SCN)₂, (MVP)₂—Zn(SCN)₂, (MVP)₂—ZnCl₂, (MVP)₂—ZnBr₂, (MVP)₂—ZnI₂, and (MVP)₂—HgCl₂, where 4-VP, 2-VP, and MVP denote 4-vinylpyridine, 2-vinylpyridine, and 2-methyl-5-vinylpyridine, respectively. Results of radical polymerization initiated by azobisisobutyronitrile indicate that the effect of complex formation between the monomers and the metal salts is to enhance the rate of polymerization with the exception of the 2-VP complex. The R_p for the solution polymerization in dimethylformamide increases in the following order: (1) (MVP)₂—Zn-(SCN)₂ > (MVP)₂-ZnCl₂ > (MVP)₂—ZnBr₂ > (MVP)₂—ZnI₂ > free MVP; (2) (4-VP)₂—Zn(SCN)₂ > (MVP)₂—Zn(SCN)₂ > free MVP > (2-VP)₂—Zn(SCN)₂; and (3) MVP + Zn(CH₃COO)₂ < MVP + Cd(CH₃COO)₂. When ethanol, acetone, or tetrahydrofuran is used as solvent, the change in R_p is more marked, partly due to insolubility of the PMVP complexed with the metal salts. The increase in R_p would be attributed to the change in k_p since the molecular weights of PMVP are nearly proportional to R_p when (MVP)₂—ZnX₂ where X is Cl^?, Br^?, I^?, or SCN^? is polymerized in DMF under fixed conditions. Copolymerizations of MVP—ZnX₂ complexes (where X is Cl^?, Br^?, I^?, or CH₃COO^?) with styrene indicate that the e values of complexed MVP are more positive than that of free vinylpyridine, and the amounts of the positive shift in e values increase with decreasing polarizability of the halide anions. These results are discussed in terms of the charge-transfer properties of anions, the nature of coordination bonds, and the structures of vinylpyridines. The complexed monomers are hardly polymerized by a cationic or an anionic mechanism. Radiation-induced solid-state polymerization gives polymers in low yields.     

Radiation-induced polymerization of 1,2-cyclohexene oxide in the plastic crystalline state

Radiation-induced solid state polymerization of 1,2-cyclohexene oxide has been investigated. By the differential thermal analysis and x-ray diffraction analysis, it was found that this compound has a phase transition point at ?81°C and behaves as a plastic crystal in the temperature range from ?81°C to ?36°C (melting point). The in-source polymerization proceeded not only in the plastic crystalline state but also in the ordinary crystalline state at temperatures below the phase transition point. The overall rate of polymerization and the rate of chain transfer to monomer in the plastic crystalline state were larger than those in the ordinary crystalline state by a factor of about forty, but the kinetic mechanisms were identical, i.e., the termination mechanisms were unimolecular in both solid states. In contrast, the kinetic mechanisms in the plastic crystalline state and in the liquid state were different. From these observations, the effects of molecular motion and molecular arrangement on the polymerizations of 1,2-cyclohexene oxide in the three phases were discussed.     

Polymerization of cyclic ethers in the presence of maleic anhydride. Part II. Investigation of the polymerization mechanism

In order to elucidate the reaction mechanism of both the radiation-induced and benzoyl peroxide-catalyzed polymerizations of cyclic ethers in the presence of maleic anhydride, the development of color during reaction and copolymerization of oxetane derivatives were investigated. Upon addition of a small amount of the γ-ray or ultraviolet-irradiated equimolar solution of a cyclic ether and maleic anhydride to isobutyl vinyl ether, a rapid polymerization took place, and the resulting polymer was confirmed to be a homopolymer of isobutyl vinyl ether. A heated solution of dioxane, maleic anhydride, and a small amount of benzoyl peroxide can initiate the polymerization of isobutyl vinyl ether in the same manner. The electrical conductivity of a 1:1 mixture of maleic anhydride and dioxane is increased by about a factor of ten after ultraviolet irradiation. These results indicate that some cationic species are actually formed in the system by irradiation or the decomposition of added benzoyl peroxide. The mechanism of formation of the cationic species responsible for the initiation may be explained as follows. A free radical of an ether is formed by abstraction of a hydrogen atom attached to the carbon adjacent to oxygen atom, followed by a one-electron transfer from the resulting radical to maleic anhydride, an electron acceptor, to yield the cationic species of the ether and the anion-radical of maleic anhydride, respectively. The resulting cationic species as well as the counteranion-radical are resonance-stabilized. Therefore, the present polymerization may be designated a radical-induced cationic polymerization.     

Surface and interface studies of GaN epitaxy on Si(111) via buffer layers

Gallium nitride films, epitaxially grown on Si(111) via a lattice-matched ZrB(2) buffer layer by plasma-assisted molecular beam epitaxy, have been studied in situ by noncontact atomic force microscopy and also in real time by reflection high-energy electron diffraction. The grown films were determined to be always N-polar. First-principles theoretical calculations modeling the interface structure between GaN(0001) and ZrB(2)(0001) clarify the origin of the N polarity.     

Structure-fluorescence relationship of push-pull 2-phenylbenzothiazole derivatives designed based on the firefly light-emitter

6-Dimethylamino-2-phenylbenzothiazole (1a) mimicking the firefly oxyluciferin structure and the derivatives with an electron-withdrawing substituent on the phenyl group were prepared, and their fluorescence properties were investigated in various solvents. 1a showed solvatochromic fluorescence with good fluorescence quantum yields (Φ_f >0.8). The introduction of an electron-withdrawing group led to a red-shift of the emission maximum. In particular, the derivatives with the 2,2-dicyanoethenyl and (1,3-dihydro-1,3-dioxo-2H-inden-2-ylidene)methyl groups showed near-infrared fluorescence in chloroform. In addition, the derivative with the phenylimine moiety showed efficient solid-state fluorescence, resulted from a molecular arrangement inhibiting intermolecular interactions for quenching the fluorescence state in crystals.