Isothermal crystallization kinetics of poly(3‐hydroxybutyrate)/layered double hydroxide nanocomposites

Poly(3‐hydroxybutyrate) (PHB)/layered double hydroxides (LDHs) nanocomposites were prepared by mixing PHB and poly(ethylene glycol) phosphonates (PEOPAs)‐modified LDH (PMLDH) in chloroform solution. Both X‐ray diffraction data and TEM micrographs of PHB/PMLDH nanocomposites indicate that the PMLDHs are randomly dispersed and exfoliated into the PHB matrix. In this study, the effect of PMLDH on the isothermal crystallization behavior of PHB was investigated using a differential scanning calorimeter (DSC) and polarized optical microscopy. Isothermal crystallization results of PHB/PMLDH nanocomposites show that the addition of 2 wt % PMLDH into PHB induced more heterogeneous nucleation in the crystallization significantly increasing the crystallization rate and reducing their activation energy. By adding more PMLDH into the PHB probably causes more steric hindrance of the diffusion of PHB, reducing the transportation ability of polymer chains during crystallization, thus increasing the activation energy. The correlation among crystallization kinetics, melting behavior and crystalline structure of PHB/PMLDH nanocomposites can also be discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3337–3347, 2006     

Enhanced ferromagnetic properties of diluted Fe doped ZnO with hydrogen treatment

The single-phase diluted magnetic Fe-ion (5%) doped ZnO powders were prepared by solid-state reaction method. The powders were annealed in Ar or Ar/H₂(5%) atmosphere at 1200 °C. The crystal structure, electric and magnetic properties for the Zn_0.95Fe_0.05O powders have been studied with X-ray diffraction (XRD) vibrating sample magnetometer, resistance and Hall measurement. All the peaks for the XRD pattern of samples belong to the hexagonal (P6₃mc) lattice of ZnO, and no indication of a secondary phase. The lattice parameters for the Zn_0.95Fe_0.05O with an annealing in Ar/H₂(5%) atmosphere were a₀=3.256 Å and c₀=5.206 Å at room temperature. The hysteresis curve for the Zn_0.95Fe_0.05O at room temperature was enhanced ferromagnetic behaviour with an annealing in Ar/H₂(5%) atmosphere. We give an explanation for enhanced ferromagnetic behaviour with H₂ treatment by electric properties.     

Ruthenium-catalyzed regioselective synthesis of 2-substituted indoles via ring-opening of epoxides by anilines

Anilines react with epoxides in dioxane at 180°C in the presence of a catalytic amount of a ruthenium catalyst along with tin(II) chloride to afford 2-substituted indoles in moderate to good yields.     

Synthesis and electrical characteristics of polyaniline nanoparticles and their polymeric composite

Monodisperse polyaniline nanoparticles (PAPSSA) were synthesized from an oxidative dispersion polymerization using poly(sodium 4-styrenesulfonate) (PSSA) as both a polymeric stabilizer and a dopant agent due to its acidity. The nanoparticles were being stabilized with two different molecular weight of PSSA. Size effect of PAPSSA particles were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering (DLS). The d.c. electrical conductivity of composite films on the glass substrate was measured by a four-probe method. It was found that the electrical properties of the composite films are affected by the content of nano-sized polyaniline and different molecular weights of stabilizer in the poly(vinyl alcohol) (PVA) matrix.     

Investigation of the chemical state of ultrathin Hf-Al-O films during high temperature annealing

Al₂O₃ incorporated HfO₂ films grown by atomic layer deposition (ALD) were investigated by high-resolution X-ray photoelectron spectroscopy (HRXPS). The core level energy state of a 15 Å thick film showed a shift to higher binding energy, as the result of a silicate formation and Al₂O₃ incorporation. The incorporation of Al₂O₃ into the HfO₂ film had no effect on silicate formation at the interface between the film and Si, while the ionic bonding characteristics and hybridization effects were enhanced compared to a pure HfO₂ film. The dissociation of the film in an ultrahigh vacuum (UHV) is effectively suppressed compared to a pure HfO₂ film, indicating an enhanced thermal stability of Hf-Al-O. Any dissociated Al₂O₃ on the film surface was completely removed into the vacuum by vacuum annealing treatment over 850 °C, while HfO₂ contributed to Hf silicide formation on the film surface.     

Validation of a method for predicting the precision, limit of detection and range of quantitation in competitive ELISA.

The mathematical model for predicting the precision, limit of detection (LOD) and range of quantitation (ROQ) in a competitive enzyme-linked immunosorbent assay (ELISA) proposed by Hayashi et al. (Anal. Chem., 2004, 76, 1295) was validated. The model describes the relative standard deviation (RSD) of concentration estimates by the RSDs of pipetting volumes of analyte, enzyme-conjugated antigen, antibody and substrate solutions, and the standard deviation (SD) of inherent absorbances between the wells in an ELISA plate. For 6 kinds of direct competitive ELISA kits, the LOD and ROQ predicted by the model agreed well with those obtained by experiments with real samples. It was also confirmed that the model is applicable to the prediction of uncertainty that depends on the pipetting error of the viscous antiserum solution. The model was demonstrated to be useful for estimating the LOD and ROQ of competitive ELISA.     

Design of a widely tunable laser with a chirped ladder filter

We theoretically investigated a digitally tunable laser with a chirped ladder filter and a ring resonator to obtain a wide wavelength tuning range covering the whole C- or L- band. The clear relation between the tuning range and laser structure, especially the ladder filter, is described analytically. The introduction of a chirped structure into a ladder filter is effective in achieving both wide tunability and a stable lasing mode. A numerical simulation based on multimode rate equations shows that a tuning range of over 40 nm and a mode suppression ratio over 40 dB can be achieved by introducing a chirped ladder filter.     

A Reverse of bessel’s inequality in 2-inner product spaces and some grüss type related results with applications

A reverse of Bessel’s inequality in 2-inner product spaces and companions of Grüss inequality with applications for determinantal integral inequalities are given.     

Dielectrophoretically aligned GaN nanowire rectifiers

We demonstrate GaN nanowire (NW) current rectifiers which were formed by assembling n-GaN nanowires on a patterned p-Si substrate by means of alternating current (ac) dielectrophoresis. The dielectrophoresis was accomplished at a frequency of 10 kHz with three different ac bias voltages (5, 10, and 15 V_p–p), indicating that the number of aligned GaN nanowires increased with increasing ac bias voltage. The n-GaN NW/p-Si diodes showed well-defined current rectifying behavior with a forward voltage drop of 1.2–1.5 V at a current density of 200 A/cm². We observed that the GaN NW diode functioned well as a half-wave rectifier. PACS 71.20.Nr; 73.40.Cg; 73.40.Ei; 73.40.Kp