Transition temperature to crystal phase of Al86Mn14 quasicrystal ultrafine particles determined by direct observation and characterization of surface oxide layer

Al–Mn quasicrystal ultrafine particles can be produced by the advanced gas evaporation method (AGEM), which is a method of preparing ultrafine alloy particles by coalescence growth among the particles near the evaporation sources. We investigated the phase transition temperature from a quasicrystal to a stable crystal, by examining successive electron diffraction patterns of an ultrafine particle in an in situ experiment using a transmission electron microscope. In spite of the report that the Al₈₆Mn₁₄ quasicrystal transforms into the crystal phase at around 400–670 °C on thin film specimens, the quasicrystal ultrafine particle transformed at 800 °C, i.e., the quasicrystal ultrafine particle is more stable. Since the cross-sectional view of the surface oxide layer of the quasicrystal ultrafine particles can be easily observed, the surface oxides of η-Al₂O₃ and MnO were characterized as a result of the oxidation of residual atoms on the surface of the produced alloy particles including the quasicrystals. The conditions required for Al–Mn quasicrystal ultrafine particle formation by the AGEM can be estimated under the cooling rate of 10⁵ K/s.     

Investigation of Fiber Design for Discrete Raman Amplifiers

A eff,R and gR of the optical fibers for discrete Raman amplifiers are theoretically and experimentally investigated.It is demonstrated that Gaussian approximation is adaptable for Aeff,R of these fibers, and gR does not depend on only core materials.     

A mild procedure for the oxidative cleavage of substituted indoles catalyzed by plant cell cultures

We have developed a novel procedure for the oxidative cleavage of indole carbon double bonds in the presence of H₂O₂ using plant cell cultures as a catalytic system. The oxidative procedure has some advantages, such as mild reactions, good yields, easy work-up and safety.     

Structural change of radiation defects in graphite crystals induced by STM probing

It was found that STM (scanning tunneling microscopy) images of defects in highly oriented pyrolytic graphite introduced by bombardment of 400 eV Ar⁺ ions in ultra-high vacuum exhibit substantial changes in the course of STM probing. Detailed examination of abrupt changes in the tunneling current measured at defect sites during voltage scans shows that the primary cause of the defect-image change was found to be neither the injected current nor the injected power but the absolute value of the voltage applied between the probe tip and the sample. We propose that an electric polarization induced force attracting the sample surface toward the probe tip widens the layer spacing of the graphite surface, leading to an acceleration of the lateral diffusion of interstitial atoms introduced by the ion irradiation, which results in a change in the defect structures and the accompanying electronic structures sensible in the STMimaging. Received: 14 June 2001 / Accepted: 7 September 2001 / Published online: 20 December 2001     

Polymerization of bisdithiafulvenes with conjugated spacers using oxidative dimerization

Novel vinylogous tetrathiafulvalene (TTF) containing polymers ( 13 and 14 ) were prepared by the oxidative dimerization polymerization of bisdithiafulvenes. The obtained polymers were soluble in common organic solvents such as CHCl₃. The structures of the polymers were confirmed by ¹H NMR and cyclic voltammetry analysis. The number‐average molecular weights of 13 and 14 were estimated from gel permeation chromatography to be 3600 and 3800, respectively. Through the introduction of phenylene or phenylene–vinylene spacers, distortion between dialkoxybenzene and vinylogous TTF units was effectively prevented according to ultraviolet–visible analysis. The polymers exhibited a strong electron‐donating property investigated by cyclic voltammetry analysis. Chemical doping by CF₃SO₃H gave doped polymers having a cationic radical and a dication of a vinylogous TTF unit. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2027–2033, 2006     

Development of a surface-reaction system in a nanoliter droplet made by an ink-jet microchip.

A surface-reaction system in a nanoliter water pool using an ink-jet microchip was developed. The reaction system in the nanodroplets formed on a poly(dimethylsiloxane) (PDMS) coated glass slide increased the diffusion-controlled reaction without using a nano-pump, specialized connector or highly sensitive detector. When nanoliter droplets were placed on the PDMS surface with a distance of 100 microm between them by the ink-jet microchip, the repeatabilities of the fluorescence intensity were 2.9% RSD (n = 7). The used ink-jet microchip had 4 different injection ports, and the distance between the ports was 0.995 mm. It was necessary to correct the distance in order to mix or dilute samples in a small droplet. The correction was successfully performed by moving the X-Y stage using inhouse-made software. A linear relationship was obtained between the Resorufin concentrations and the fluorescence intensity. We applied this system to an enzyme-linked immunosorbent assay (ELISA) for immunoglobulin A (IgA), and observed a difference in the fluorescence intensity derived from the amount of IgA (blank, 6.25 ng/mL, 12.5 ng/mL). These results show the usefulness of the open-type micro-analytical systems proposed by us.     

Synthesis and properties of photocurable biodegradable multiblock copolymers based on poly(ε‐caprolactone) and poly(L‐lactide) segments

Photocurable biodegradable multiblock copolymers were synthesized from poly(ε‐caprolactone) (PCL) diol and poly(L ‐lactide) (PLLA) diol with 4,4′‐(adipoyldioxy)dicinnamic acid (CAC) dichloride as a chain extender derived from adipoyl chloride and 4‐hydroxycinnamic acid, and they were characterized with Fourier transform infrared and ¹H NMR spectroscopy, gel permeation chromatography, wide‐angle X‐ray diffraction, differential scanning calorimetry, and tensile tests. The copolymers were irradiated with a 400‐W high‐pressure mercury lamp from 30 min to 3 h to form a network structure in the absence of photoinitiators. The gel concentration increased with time, and a concentration of approximately 90% was obtained in 90–180 min for all the films. The photocuring hardly affected the crystallinity and melting temperature of the PCL segments but reduced the crystallinity of the PLLA segments. The mechanical properties, such as the tensile strength, modulus, and elongation, were significantly affected by the copolymer compositions and gel concentrations. Shape‐memory properties were determined with cyclic thermomechanical experiments. The CAC/PCL and CAC/PCL/PLLA (75/25) films photocured for 30–120 min showed good shape‐memory properties with strain fixity rates and recovery rates of approximately 100%. The formation of the network structure and the crystallization and melting of the PCL segments played very important roles for the typical shape‐memory properties. Finally, the degradation characteristics of these copolymers were investigated in a phosphate buffer solution at 37 °C with proteinase‐k and Pseudomonas cepacia lipase. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2426–2439, 2005     

Crystallographic report: Dichloro[bis(1‐methylimidazole‐2)disulfide]zinc(II)

The Zn center in [ZnCl₂(L‐S‐S‐L)], where L‐S‐S‐L = bis(1‐methylimidazole‐2)disulfide, adopts a tetrahedral configuration defined by two Cl atoms and two N atoms from L‐S‐S‐L, which was obtained by in situ oxidation of 1‐methylimidazole‐2‐thione. Copyright © 2005 John Wiley & Sons, Ltd.     

Anomalous enhancement of DD reaction in Pd and Au/Pd/PdO heterostructure targets under low-energy deuteron bombardment

Yields of protons emitted in the D+D reaction in Pd, Au/Pd/PdO, Ti, and Au foils are measured by a d E-E counter telescope for bombarding energies between 2.5 and 10 keV. The experimental yields are compared with those predicted from a parametrization of the cross section and stopping power at higher energies. It is found that for Ti and Au target the enhancement of the D(d,p)T reaction is similar to that observed with a deuterium gas target (several tens of eV). The dependence of the yields on the bombarding energy corresponds well to the screening potential parameters U _s=250±15 eV for Pd and 601 ±23 eV for Au/Pd/PdO. Possible models of the enhancement obtained are discussed. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 11, 785–790 (10 December 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Effects of cation- or oxide ion-defect on conductivities of apatite-type La–Ge–O system ceramics

A series of apatite-type La–Ge–O ceramics were prepared and their cation-defect at the 4f+6h sites and oxide ion-defect at 2a site were investigated. In La_xGe₆O_12+1.5x ceramics of x=6–12, the higher conductivities were obtained in the region of apatite composition, La_x(GeO₄)₆O_1.5x−12 (x=8–9.33), and the highest conductivity was achieved for La₉(GeO₄)₆O_1.5 (x=9), where the number of cation (La³⁺) occupying the 4f+6h sites is 9 and the number of oxide ion occupying the 2a site is 1.5. The ceramics with cation- and oxide ion-defects were La_9−0.66xSr_x(GeO₄)₆O_1.5 (x=0–1), La_9−1.33xZr_x(GeO₄)₆O_1.5 (x=0–1), La_9−xSr_x(GeO₄)₆O_1.5−0.5x (x=0–3), La_9−xZr_x(GeO₄)₆O_1.5+0.5x (x=0–1), La_x(GeO₄)_3x−21(AsO₄)_27−3xO_1.5 (x=0–3), La_x(GeO₄)_33−3x(AlO₄)_3x−27O_1.5 (x=0–3), La₉(GeO₄)_6−x (AlO₄)_xO_1.5−0.5x (x=0–3), La₉(GeO₄)_6−x(AsO₄)_xO_1.5+0.5x (x=0–1), La_9.33−xSr_x(GeO₄)₆O_2−0.5x (x=0–1.2) and La_x(GeO₄)_4.5(AlO₄)_1.5O_1.5x−12.75 (x=8.8–9.83), which were prepared by the partial substitution of La³⁺and GeO₄⁴⁻of the basic apatite La₉(GeO₄)₆O_1.5 with Sr²⁺ or Zr⁴⁺ and AlO₄⁵⁻ or AsO₄³⁻. Such substitutions lowered the conductivity of La₉(GeO₄)₆O_1.5. These results were discussed by the electrostatic interaction between Sr²⁺, Zr⁴⁺, AlO₄⁵⁻ or AsO₄³⁻ and oxide ion as a conductive species.