Melt viscosity of acrylic copolymers

The melt flow behavior of methyl methacrylate (MMA) copolymerized with methyl acrylate (MA) was measured and analyzed in terms of the molecular structure of the copolymers. Measurement was done by using a capillary rheometer in the shear rate range from 6 × 10⁰ to 3 × 10³ s^?1 and in temperatures from 160°C to 280°C. The Newtonian flow pattern appeared in lower shear rate and higher temperature regions. However, with increasing shear rate at lower temperature, viscosity decreased to a constant slope on a logarithmic scale. The melt fracture arose at the critical shearing stress point S_c of 6 × 10⁶ dyn/cm². A die swell also appeared in the shear rate range larger than 1 × 10⁶ dyn/cm², and its maximum value was two times larger than that of the capillary diameter. The decrease in viscosity with increasing shear rate is explained in terms of the apparent energy of activation in flow E. E also decreases with increasing shear rate. The exponential relation of E to η is maintained in the higher shear rate. The lowering of viscosity in lower shear rate, however, is attributed to not only the change in E but also the change in the volume of flow unit. The melt viscosity increases in inverse proportion to the MA content in the copolymers which form more flexible chains. Syndiotactic form of MMA has increased viscosity, caused by the rigidifying of segmented chains, rather than the strengthening of intermolecular interaction.     

First-principles study on cerium ion behavior in irradiated cerium dioxide

In order to clarify, from the electronic structure, the origin of the appearance of the tri-valent Ce state in irradiated cerium dioxide with swift heavy ions, we performed comprehensive first-principles calculations on various defective structures in cerium dioxide. The calculated results show that an oxygen mono-vacancy or an oxygen Frenkel pair can induce two tri-valent Ce states neighboring the oxygen vacancy. The calculation of the oxygen Frenkel pair further reveals that an interstitial oxygen atom that moves from the lattice position and an oxygen atom on the lattice can form a dimer that behaves as an oxygen molecule of negative di-valence. This bonding state can also produce excess electrons and the tri-valent Ce state in cerium dioxide.     

Control strategies for multiple parallel current-source convertersof SMES system

Multiple structured current-source converters are applied for a superconducting magnetic energy storage (SMES) system. Suitable control method and control block diagram are proposed by taking much use of the advantage of this multiple structure. A multi-modular pulse width modulation (PWM) control strategy of current-source converters for the purpose of higher efficiency and less harmonic distortion is developed with an idea for practical application. A design of a multi-reduced instruction set computer (RISC) controller is presented to put the proposed control blocks into practice. The results of the digital simulation by Electromagnetic Transients Program (EMTP) and the experimental results of the test module are provided to validate the proposed control method of SMES power conditioning     

High power output InGaAsP/InP buried heterostructure lasers

A novel InGaAsP/InP buried heterostructure (BH) laser was fabricated on a p-InP substrate. This laser can provide a peak pulse output of 0.8 W per facet with a stable lateral transverse mode oscillation and enables the fault location measurement of a single mode fibre cable over 20 km.     

Immunomodulation of Melanoma by Chemo-Thermo-Immunotherapy Using Conjugates of Melanogenesis Substrate NPrCAP and Magnetite Nanoparticles: A Review

A major advance in drug discovery and targeted therapy directed at cancer cells may be achieved by the exploitation and immunomodulation of their unique biological properties. This review summarizes our efforts to develop novel chemo-thermo-immunotherapy (CTI therapy) by conjugating a melanogenesis substrate, N-propionyl cysteaminylphenol (NPrCAP: amine analog of tyrosine), with magnetite nanoparticles (MNP). In our approach, NPrCAP provides a unique drug delivery system (DDS) because of its selective incorporation into melanoma cells. It also functions as a melanoma-targeted therapeutic drug because of its production of highly reactive free radicals (melanoma-targeted chemotherapy). Moreover, the utilization of MNP is a platform to develop thermo-immunotherapy because of heat shock protein (HSP) expression upon heat generation in MNP by exposure to an alternating magnetic field (AMF). This comprehensive review covers experimental in vivo and in vitro mouse melanoma models and preliminary clinical trials with a limited number of advanced melanoma patients. We also discuss the future directions of CTI therapy.     

Mechanism of suspension polymerization of uniform monomer droplets prepared by glass membrane (Shirasu Porous Glass) emulsification technique

The mechanism of the unique suspension polymerization of uniform monomer droplets, without coalescence and breakup during the polymerization, was investigated using styrene (S) as a monomer mixed with water‐insoluble hexadecane (HD). The glass membrane (Shirasu Porous Glass, SPG) emulsification technique was employed for the preparation of uniform droplets. Depending on the pore sizes of the SPG membranes (1.0, 1.4, and 2.9 μm), polymer particles of an average diameter ranging from 5.6 to 20.9 μm were obtained with the coefficient of variation (CV) being close to 10%. The role of HD was to prevent the degradation of the droplets by the molecular diffusion process. Sodium nitrite was added in the aqueous phase to kill the radicals desorbed from the droplets (polymer particles), thereby suppressing the secondary nucleation of smaller particles. Each droplet behaved as an isolated locus of polymerization. With the presence of HD, the initial polymerization rate was proportional to 0.24th power of the benzoil peroxide (BPO) concentration. This peculiar behavior as compared with the ordinary suspension polymerization was explained by introducing the assumption that each droplet was composed of isolated compartments (cells) in which active polymeric radicals were dissolved in an S‐rich phase and surrounded by a rather incompatible S/HD (continuous) phase. The average number of radicals in the droplet increased initially due to the separate existence of polymeric radicals in compartments. As the polymerization progressed, the HD‐rich phase gradually separated, eventually forming macrodomains, which were visible by an optical microscope. The phase separation allowed polystyrene chains to dissolve in a more favorable S phase, and the homogeneous bulk polymerization kinetics took over, resulting in a gradual decrease of the average number of radicals in the droplet until the increase of viscosity induced the gel effect. When no HD was present in the droplets, the polymerization proceeded in accordance with the bulk mechanism except for the initial retardation by the entry of inhibiting radicals generated from sodium nitrite in the aqueous phase. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1025–1043, 2000     

Collagen of edible jellyfish exumbrella

The edible jellyfish exumbrella collagen was prepared by limited pepsin digestion. The yield of collagen was very high; 46.4% on the basis of lyophilised dry weight. This collagen was comprised of α1α2α3‐heterotrimers, moreover it was relatively stable at 26.0 °C for 60 min. Thus, the edible jellyfish exumbrella will have potential as an important collagen source for use in various industries and it is expected that the development thus so far unutilised resource will advance in the future. © 1999 Society of Chemical Industry     

Morphologies and properties of cured epoxy/brominated‐phenoxy blends

Morphologies of cured epoxy/brominated‐phenoxy blends were observed by scanning transmission electron microscopy (STEM) and energy dispersive X‐ray fluorescence spectroscopy (EDX). When brominated‐phenoxy content was 30 wt %, cocontinuous phase structures between cured epoxy and brominated‐phenoxy were found. Since every loss tangent (tan δ) curve as a function of temperature on dynamic mechanical analysis (DMA) showed 2 peaks at 128°C and 155°C respectively, cured epoxy phases and brominated‐phenoxy phases were incompatible together and T_gs of cured epoxy phases were not decreased. Tensile strength and tensile elongation of the cured blends were increased together. T‐peel adhesion strength and the lap‐shear adhesion strength were also increased together. These phenomena could be due to the cocontinuous structures consisted by the rigid cured epoxy phases of thermosets and ductile the brominated‐phenoxy phases of thermoplastics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1702–1713, 2007     

Nanostructural evolution in surveillance test specimens of a commercial nuclear reactor pressure vessel studied by three-dimensional atom probe and positron annihilation

The nanostructural evolution of irradiation-induced Cu-rich nanoprecipitates (CRNPs) and vacancy clusters in surveillance test specimens of in-service commercial nuclear reactor pressure vessel steel welds of Doel-1 and Doel-2 are revealed by combining the three-dimensional local electrode atom probe and positron annihilation techniques. In both medium (0.13 wt.%) and high (0.30 wt.%) Cu welds, the CRNPs are found to form readily at the very beginning of the reactor lifetime. Thereafter, during the subsequent 30 years of operation, the residual Cu concentration in the matrix shows a slight decrease while the CRNPs coarsen. On the other hand, small vacancy clusters of V₃–V₄ start appearing after the initial Cu precipitation and accumulate steadily with increasing neutron dose. The observed nanostructural evolution is shown to provide unique and fundamental information about the mechanisms of the irradiation-induced embrittlement of these specific materials.