Heterogeneous palladium–cobalt bimetal catalyst for the oxidative carbonylation of bisphenol A to polycarbonate

Polycarbonates (PCs) were prepared by the oxidative carbonylation of bisphenol A and carbon monoxide with a hydrotalcite‐supported Pd–Co complex, a Pd–Co–poly(4‐vinylpyridine) complex [Pd–Co–(p‐4vpy)], a Pd–Co–polystyrene‐supported triphenylphosphine complex (Pd–Co–PS‐TPP), or a Pd–Co–polyvinylpyrrolidone complex (Pd–Co–pvp) as a heterogeneous Pd–Co bimetal catalyst to separate the PC solution and the Pd–Co bimetal catalyst after the reaction. Propylene carbonate was used as a halogen‐free solvent. Pd–Co–(p‐4vpy) and Pd–Co–PS‐TPP showed recycling potential, whereas Pd–Co–pvp, though not having recycling potential, yielded a high turnover number with a maximum of 1462. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Two-Directional Nodal Model for Co-Condensation Growth of Multicomponent Nanoparticles in Thermal Plasma Processing

A more precise but easy-to-use model is developed and proposed to clarify nanoparticle growth with two-component co-condensation in thermal plasma processing. Computations performed for the molybdenum-silicon and titanium-silicon systems demonstrate that the model quantitatively estimates both the particle size distribution and the composition distribution of the silicide nanoparticles produced through co-condensation as well as nucleation and coagulation. The model also successfully obtains information that cannot be acquired by any other models. As a consequence, the detailed growth mechanisms of the silicide nanoparticles are eventually revealed. The present model is thus an “adaptable” and useful tool for analyzing nanoparticle growth processes, including co-condensation, with sufficient accuracy.     

A study of generator system selection for large wind turbine generator system

This paper focuses on selection of wind turbine generation systems that include generators, converters, and gears. We study three systems: a permanent magnet generator (PMG) system, a doubly‐fed generator (DFG) system, and a synchronous generator (SYG) system in terms of the system efficiencies and running costs. The system efficiencies and running costs are calculated by considering the relationship between wind power and wind conditions. According to these results, the one‐step gear PMG system is the best choice for a large wind turbine system. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(1): 51–57, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20506     

Micromixer-based time-resolved NMR: applications to ubiquitin protein conformation

Time-resolved NMR spectroscopy is used to studychanges in protein conformation based on the elapsed time after a change in the solvent composition of a protein solution. The use of a micromixer and a continuous-flow method is described where the contents of two capillary flows are mixed rapidly, and then the NMR spectra of the combined flow are recorded at precise time points. The distance after mixing the two fluids and flow rates define the solvent-protein interaction time; this method allows the measurement of NMR spectra at precise mixing time points independent of spectral acquisition time. Integration of a micromixer and a microcoil NMR probe enables low-microliter volumes to be used without losing significant sensitivity in the NMR measurement. Ubiquitin, the model compound, changes its conformation from native to A-state at low pH and in 40% or higher methanol/water solvents. Proton NMR resonances of the His-68 and the Tyr-59 of ubiquitin are used to probe the conformational changes. Mixing ubiquitin and methanol solutions under low pH at microliter per minute flow rates yields both native and A-states. As the flow rate decreases, yielding longer reaction times, the population of the A-state increases. The micromixer-NMR system can probe reaction kinetics on a time scale of seconds.     

Thermal properties and characteristics of thin layers of nickel dithiolene complexes

Thermal properties of near infra–red–absorbing nickel dithiolene complexes have been examined by thermal gravimetric and differential scanning calorimetry analysis. The nickel complexes with relatively low melting points gave a DRAW disc with better recording characteristics, when they were used as inhibitors of the photofading of thin layers of cyanine dyes. Thin layers of the nickel complexes on polymethylmethacrylate or glass were formed by spin coating and by the radio–frequency reactive ion plating technique. Their reflectance, absorption spectra and optical recording characteristics have been recorded.     

Adaptive type-II hybrid broadcast ARQ system

In this letter, a type-II hybrid broadcast automatic-repeat-request (ARQ) scheme with adaptive forward error correction (AFEC) using BCH codes is proposed and analyzed. The basic idea in the proposed scheme is to increase the error correcting capability of BCH codes according to each channel state using incremental redundancy. The numerical results for the analysis and the simulation show that the proposed scheme maintains high throughput even if channels become noisy and the number of receivers is large     

Induced radioactive nuclides of 10-MeV radiotherapy accelerators detected by using a portable HP-Ge survey meter

The radioactivation of linear accelerator components for radiation therapy is interest for radiation protection in general, and particularly, when decommissioning these structures. The energy spectra of gamma rays emitted from the heads of two accelerator models, EXL-15SP and Clinac iX, after 10-MeV X-ray irradiation, were measured using a high-purity germanium semiconductor survey meter. After spectrum analyses, activities of (24)Na, (28)Al, (54)Mn, (56)Mn, (57)Ni, (58)Co, (60)Co, (64)Cu, (65)Zn, (122)Sb, (124)Sb, (181)W, (187)W, (196)Au, and (198)Au were detected. One centimetre deep dose-equivalent rate of the heads of the linear accelerator was measured using the survey meter. The dose rate decreased to ～10 % of its initial rate after 1 week. Long-term activations were few, the radioactivity level was low, and a cooling time of several days was effective for reducing dose rate to an acceptable level for decommissioning.     

Investigation of optimum design for nanoparticle dispersion in centrifugal bead mill using DEM-CFD simulation

A bead mill is commonly used to produce nanomaterials. The design of the bead mill rotor is an important factor in efficient nanomaterial production to avoid re-agglomeration. We investigated the effect of bead-mill rotor shape on the dispersion state using experimental tests and the discrete-element method (DEM) coupled with computational fluid dynamics (CFD) simulations. Experimental results using TiO₂ in the bead mill showed that the high rotor rotation speed caused TiO₂ particles re-agglomeration, and a sharp particle-size distribution was obtained by dispersion with a mill with a wide gap between the rotor and the chamber. To evaluate the dispersion performance, bead collisions were analyzed using the DEM-CFD simulation. The simulation results indicated that an increase in bead-collision energy lead to damage of the TiO₂ primary particles and re-agglomeration at a high rotation speed. A uniform dispersion was achieved when the frequency of high-energy collision between the particle and wall decreased and a small standard deviation of the collision energy frequency was obtained by the mill with a wide gap. These simulation results correlate with the experimental results. Therefore, this study shows that the DEM-CFD simulation could contribute to an appropriate rotor design for uniform dispersion.     

Optical Resolution of Chirally Functionalized [60]Fullerene Through Formation of Diastereomeric Methoxyphenylacetic Acid Esters

Abstract

Optical resolution of chirally functionalized [60]fullerene has been achieved through formation of diastereomeric α-methoxyphenylacetic acid (MPA) esters. The diastereomeric ester products were easily separated either by open column silica gel chromatography or by high pressure liquid chromatography (HPLC) with BuckyPrep® column.     

Molecular orientation of nonlinear optical polymer nanosheets on silica nanoparticle monolayer studied by optical waveguide spectroscopy

The paper describes molecular orientation of nonlinear optical (NLO) polymer monolayer transferred onto a sphere-shaped silica nanoparticle monolayer using optical waveguide spectroscopy. Structurally well-defined hybrid polymer nanoassemblies were constructed through bottom-up approaches: Langmuir–Blodgett technique and immersion method. Silica nanoparticles (SiO₂ NPs, 40–50 nm diameter) were immobilized on a quartz waveguide using cationic polymer Langmuir–Blodgett films (nanosheets) as a template. The SiO₂ NPs took a uniformly distributed monolayer formation without any aggregates, which minimizes light scattering. This allows us to gain reproducible absorption spectra of dye molecules embedded in polymer nanosheet monolayer on the nanoscale rough surface using optical waveguide spectroscopy. The NLO polymer nanosheets containing disperse red 1 (DR) were transferred onto the SiO₂ NP monolayer. The polarized absorption spectra were obtained; the s-light absorption was larger than the p-light absorption, indicating that polymer nanosheets are wrapped around SiO₂ NPs so that DR moieties undergo molecular disorientation not to form H-aggregates. This method provides us with useful information on structure–property relationship between nanoshaped inorganic nanoparticle and organic functional molecules in hybrid nanoassemblies.