Initiator‐fragment incorporation radical copolymerization of divinylbenzene and N‐isopropylacrylamide with dimethyl 2,2′‐azobisisobutyrate: Formation of soluble hyperbranched polymer nanoparticle

The copolymerization of divinylbenzene (DVB) and N‐isopropylacrylamide (NIPAm) with dimethyl 2,2′‐azobisisobutyrate of a concentration as high as 0.50 mol/L proceeded homogeneously without any gelation at 80 °C in N,N‐dimethylformamide, where the concentrations of DVB and NIPAm were 0.15 and 0.50 mol/L. The copolymer yield increased with time and leveled off over 50 min. Although DVB was consumed more rapidly than NIPAm, both comonomers were completely consumed in 50 min. The homogeneous polymerization system at 80 °C involved electron spin resonance‐observable propagating polymer radicals, the total concentration of which increased with time. The resulting copolymer was soluble in tetrahydrofuran, chloroform, acetone, ethyl acetate, acetonitrile, N,N‐dimethylformamide, dimethyl sulfoxide, and methanol, but insoluble in benzene, n‐hexane, and water. The copolymer showed an upper critical solution temperature (50 °C on cooling) in a methanol–water [11:3 (v/v)] mixture. Dimethyl 2,2′‐azobisisobutyrate fragments as high as 37–45 mol % were incorporated as terminal groups in the copolymers through initiation and primary radical termination. The contents of DVB and NIPAm were 10–30 mol % and 30–50 mol %, respectively. The intrinsic viscosity of the copolymer was very low (0.09 dL/g) at 30 °C in tetrahydrofuran despite high weight‐average molecular weight (1.2 × l0⁶ by multi‐angle laser light scattering). These results indicate that the copolymer was of hyperbranched structure. By transmission electron microscopy observation, the individual copolymer molecules were visualized as nanoparticle of 6–20 nm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1609–1617, 2004     

Spin-oriented projectile fragments: The first application tog-factor measurements

Ejectile nuclei in the fragmentation of intermediate-energy heavy-ion projectiles were found to be largely spin polarized. The observed polarization as a function of the outgoing momentum was nicely explained by a simple kinematical argument based on the participant-spectator model of projectile fragmentation. The measurements extended to cover several different targets, incident energies, exit channels, and emission angles revealed that substantial polarization shows up widely in projectile fragmentation reactions. Furthermore, this polarization exhibits an interesting behavior which may be interpreted as a manifestation of a gradual change in the deflection angle from positive to negative values as the energy increases and/or the target-Z decreases. The present polarization results also suggests various applications of spin polarized radioactive beams. As the first example of such an application, we present a recent result on theg-factor measurements on neutron-rich nuclei.     

Selective XANES spectroscopy from RIXS contour maps

Kβ resonant inelastic X-ray scattering (RIXS) spectra of Mn and Ga compounds are studied to examine different types of selective XANES. RIXS spectra of MnO in Mn Kβ_1,3 region and of GaCl₂ in Ga Kβ₂ region are plotted as contour maps over wide energy ranges in both excitation and emission. Through analyses of RIXS contour maps by the use of the Kramers-Heisenberg equation, spin-selective XANES spectra are deduced for MnO. In the case of a mixed valence compound GaCl₂ selective XANES of Ga³⁺ ion can be obtained by making use of a large difference in transition probabilities.     

Oxygen ion conductivity of yttria-niobia mixed oxide with fluoride related structure

The oxygen ion conductivity of Y₂O₃---Nb₂O₅ with a fluorite-like structure was studied. Substitutional solid solutions of Nb₂ O₅ in Y₂O₃ lattice formed the defect fluorite phase and remarkably enhanced the oxygen ion conductivity. Doping with tetravalent cations, especially Ti⁴⁺ or Ce⁴⁺, in yttria-niobia oxide is effective in enhancing the oxygen ion conductivity. Although the n-type semiconducting property appeared below P_O2 = 10⁻¹⁸ atm at 1243 K, the yttria-niobia mixed oxide doped with Ce⁴⁺, Ti⁴⁺, and Zr⁴⁺ stably exhibited oxygen-ion conduction in the wide range of oxygen partial pressures studied.     

X-ray study of field induced deformation of sliding CDW in K0.30MoO3

A deformation of the CDW is investigated under the electric field whose magnitude is intensionally made inhomogeneous in the one-dimensional conductor K_0.30MoO₃. It is verified that the CDW's deformation, which occurs in the transverse (2a¹-c¹)-direction, is caused by the field gradient in the sample. In the sample where the CDW deformation is found without the intensional inhomogeneity of the electroc field, the deformation is not uniform from point to point. Possible relations are discussed between the structural change and the electrical polarization observed in pulse measurements of the conductivity.     

Effects of 3,3'-dihydroxy-alpha,beta-diethylstilbene and 3,3',4,5'-tetrahydroxystilbene on microtubule assembly in vitro, aneuploidy induction, and cellular microtubule and actin networks.

We examined the inhibitory activities of 3,3'-dihydroxy-alpha,beta-diethylstilbene (DDS) and 3,3',4,5'-tetrahydroxystilbene (THS) on microtubule assembly in vitro and their effects on chromosome number and cellular microtubule networks in Chinese hamster V79 cells. DDS showed half the inhibitory activity of diethylstilbestrol (DES) on microtubule assembly in vitro, while THS had none of the inhibitory activity. DDS induced tetraploid at 30 microM, whereas THS was found to be inactive. Furthermore, DDS disturbed cellular microtubule networks at 100 microM. We also examined the effects of DES, DDS and THS on cellular actin networks in mouse BALB 3T3 cells. DES induced a change of actin stress fiber distribution and THS had similar activity, while DDS showed no activity.     

Single-electron transport through an individual InAs SAQD embedded in a graded-dope semiconductor nano-pillar

By using the semiconductor nano-pillar with a graded-dope configuration, we implemented the measurement for a single-electron transport through an individual InAs self-assembled quantum dot (SAQD). An atomic-force microscope observation showed that the SAQD had a disk-like shape with a diameter of 30 nm. We succeeded in observing a significant diamagnetic shift of the Coulomb oscillation peak under the magnetic field applied perpendicular to the disk plane. The measurement gave us a lateral confinement energy of 14 meV and an electron effective mass of 0.039, which provided us with quantitative evidence that the constituent material of the observed quantum dot originates from the InAs SAQD.     

Synthesis and silica coating of calcia-doped ceria/mica nanocomposite by seeded polymerization technique

Calcia-doped ceria is of potential interest as an ultraviolet (UV) radiation blocking material in personal care products because of the excellent UV light absorption property and low catalytic ability for the oxidation of organic materials superior to undoped ceria. In order to reduce the oxidation catalytic activity further, calcia-doped ceria was coated with amorphous silica by means of seeded polymerization technique. Generally, nanoparticles of inorganic materials do not provide a good coverage for human skin because of the agglomeration of the particles. The platy particles are required to enhance the covering ability of inorganic materials. This can be accomplished by synthesis of calcia-doped ceria/mica nanocomposite with subsequent silica coating to control catalytic activity of calcia-doped ceria. Calcia-doped ceria/mica nanocomposite was prepared by soft solution chemical method followed by silica coating via seeded polymerization technique. Silica coated calcia-doped ceria/mica nanocomposite was characterized by X-ray diffraction, SEM, TEM, XPS and FT-IR.     

Anomalous magnetism in three-dimensional orthogonal dimer lattice system: (Ba1−xSrx)2Ru3O9 (x≈0.35)

The magnetic and transport properties of a new cubic KSbO₃-type ruthenate, (Ba_1−xSr_x)₂Ru₃O₉ (x≈0.35), have been investigated. The crystal structure has a singular geometry in which ruthenium atoms form an ideal three-dimensional orthogonal dimer lattice. The magnetic susceptibility is Pauli-paramagnetic but exhibits an anomalous temperature dependence reminiscent of a gap-like behavior. The resistivity exhibits a metallic behavior, except for a rise at low temperature.