Change of dielectric property with water-treed region

By dividing a water-treed XLPE sheet sample into a non-degraded layer and a water-treed one, relative permittivity ε_r2' and dielectric loss factor ε_r2^" of the water-treed layer have been estimated using an equivalent circuit. The way of changes in ε_r2' and ε_r2^" with the water tree length r estimated by the pulsed electroacoustic method has been discussed based on a Maxwell-Wagner-Sillars (MWS) model. It has been concluded that the MWS model gives a reasonable fit to the experimental data providing that the water conductivity in voids lies between 1×10^-3 S/m and 8×10^-3 S/m, and the minor and major axis ratio of the ellipsoids, to which water-filled voids are compared, lies in the range of 1:20 to 1:50     

Low temperature growth of sol-gel SrBi2Ta2O9 thin films by low-pressure annealing

A new low-temperature processing method to prepare SrBi₂Ta₂O₉ thin films is proposed. These thin films were prepared on Pt/Ta/SiO₂/Si substrates by a sol-gel method, and their structural and electrical properties were investigated. Films were annealed before and after the top Pt electrode deposition. The first annealing was performed in a 760-Torr oxygen atmosphere at 600 °C for 30 min, and the second annealing was performed in a 5-Torr oxygen atmosphere at 600 °C for 30 min. The films were well crystallized and fine-grained after the second annealing. The electrical characteristics of the 200-nm-thick film obtained by this new process were as follows: remanent polarization, P_r = 8.5 μC/cm²; coercive field, E_c = 36 kV/cm; and leakage current density, I_L = 1 × 10⁻⁷ A/cm² (at 150 kV/cm). This process is very attractive for highly integrated ferroelectric nonvolatile memory applications. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(2): 27–33, 1997     

Microemulsion Radical Polymerization of Alkyl Acrylates

The oil/water microemulsion polymerizations of alkyl (methyl (MA), ethyl (EA), butyl (BA), hexyl (HA) and 2-ethylhexyl (EHA)) acrylates initiated by a water-soluble (ammonium peroxodisulphate (APS)) initiator were investigated. The rate of polymerization versus conversion curve shows two inconstant intervals. The maximum rate of polymerization of MA, EA, BA and EHA is found to be proportional to the 0·53, 0·17, 0·46 and 0·59 powers of the APS concentration and to the first power of the monomer (MA, BA and EHA) concentration. Homogeneous (solution) radical polymerization is operative in the MA, BA and EHA systems. The strong rate dependence on the EA monomer concentration is assumed to be caused by both the polymerization within the micelle core and the gel effect. The particle size was observed to increase with conversion in the EA and BA runs and to decrease in the EHA and HA runs. The number of particles increased with conversion during the whole polymerization. The polymer particles grow by recruiting monomer and emulsifier from the free monomer-swollen micelles and dead particles. © 1997 SCI.     

A High-Methionine Diet for One-Week Induces a High Accumulation of Methionine in the Cerebrospinal Fluid and Confers Bipolar Disorder-like Behavior in Mice

Methionine (Met) is considered the most toxic amino acid in mammals. Here, we investigated biochemical and behavioral impacts of ad libitum one-week feeding of high-Met diets on mice. Adult male mice were fed the standard rodent diet that contained 0.44% Met (1×) or a diet containing 16 graded Met doses (1.2×–13×). High-Met diets for one-week induced a dose-dependent decrease in body weight and an increase in serum Met levels with a 2.55 mM peak (versus basal 53 µM) on the 12×Met diet. Total homocysteine (Hcy) levels were also upregulated while concentrations of other amino acids were almost maintained in serum. Similarly, levels of Met and Hcy (but not the other amino acids) were highly elevated in the cerebrospinal fluids of mice on the 10×Met diet; the Met levels were much higher than Hcy and the others. In a series of behavioral tests, mice on the 10×Met diet displayed increased anxiety and decreased traveled distances in an open-field test, increased activity to escape from water soaking and tail hanging, and normal learning/memory activity in a Y-maze test, which were reflections of negative/positive symptoms and normal cognitive function, respectively. These results indicate that high-Met ad libitum feeding even for a week can induce bipolar disorder-like disease models in mice.     

Surface Engineering of Top7 to Facilitate Structure Determination

Top7 is a de novo designed protein whose amino acid sequence has no evolutional trace. Such a property makes Top7 a suitable scaffold for studying the pure nature of protein and protein engineering applications. To use Top7 as an engineering scaffold, we initially attempted structure determination and found that crystals of our construct, which lacked the terminal hexahistidine tag, showed weak diffraction in X-ray structure determination. Thus, we decided to introduce surface residue mutations to facilitate crystal structure determination. The resulting surface mutants, Top7sm1 and Top7sm2, crystallized easily and diffracted to the resolution around 1.7 Å. Despite the improved data, we could not finalize the structures due to high R values. Although we could not identify the origin of the high R values of the surface mutants, we found that all the structures shared common packing architecture with consecutive intermolecular β-sheet formation aligned in one direction. Thus, we mutated the intermolecular interface to disrupt the intermolecular β-sheet formation, expecting to form a new crystal packing. The resulting mutant, Top7sm2-I68R, formed new crystal packing interactions as intended and diffracted to the resolution of 1.4 Å. The surface mutations contributed to crystal packing and high resolution. We finalized the structure model with the R/R_free values of 0.20/0.24. Top7sm2-I68R can be a useful model protein due to its convenient structure determination.     

Fe-W非晶态合金镀膜技术及其最佳制备条件的研究

采用电镀的方法制得了光亮的Fe-W非晶态合金镀膜,研究了各种制备条件对镀膜表面状态、微观结构、磁性特征的影响。     

Improvement in Reactivity and Grindability of Belite-Rich Cement by Remelting Reaction

A new modification of belite-rich cement, a "remelted belite cement," exhibits higher hydration activity and better grindability than conventional belite-rich cement. The belite constituent in the new cement completely undergoes a remelting reaction and thus is distinctly different from the belite in conventional cement, which is rapidly quenched to depress the reaction. The remelted belite has a weaker resistance to fracture than does the quenched material and thus has better grindability. When the two cements, with nearly the same particle-size distributions, are compared, the specific surface area of the remelted belite cement is higher, resulting in higher hydration activity.     

CO hydrogenation over a rhodium vanadate catalyst: Reduction and regeneration of RhVO4 on SiO2

The hydrogenation of CO over an Rh vanadate (RhVO₄) catalyst supported on SiO₂ (RhVO₄/SiO₂) has been investigated after H₂ reduction at 500°C, and the results are compared with those of vanadia-promoted (V₂O₅–Rh/SiO₂) and unpromoted Rh/SiO₂ catalysts. The mean size of Rh particles, which were dispersed by the decomposition of RhVO₄ after the H₂ reduction, was smaller (41 Å) than those (91–101 Å) of V₂O₅–Rh/SiO₂ and Rh/SiO₂ catalysts. The RhVO₄/SiO₂ catalyst showed higher activity and selectivity to C₂ oxygenates than the unpromoted Rh/SiO₂ catalyst after the H₂ pretreatment. The CO conversion of the RhVO₄/SiO₂ catalyst was much higher than that of V₂O₅–Rh/SiO₂ catalyst, and the yield of C₂ oxygenates increased. We also found that the RhVO₄/SiO₂ catalyst can be regenerated by calcination or O₂ treatment at high temperature after the reaction.     

Effect of Crystal Grain Size and Thermal Stress on Martensitic Transformation of Phosphorus-Bearing Dicalcium Silicates

A series of P₂O₅-bearing Ca₂SiO₄ solid solutions, (Ca_{2- x /2}open square _{x /2})(Si_{1- x} P _x )O₄ with x = 0.02 and 0.06 lessthan equal to 0.11, was prepared. The alpha´_L <–> ß martensitic transformation temperatures were determined by high-temperature XRD for powder specimens with x = 0.02. With decreasing particle size, both M _s and M _f decreased, while both A _s and A _f were almost unchanged. Each transformation temperature was lower than that of pure Ca₂SiO₄. The phase composition at 25°C for the crystals with 0.075 lessthan equal to x lessthan equal to 0.10 was dependent not only on the x -value but also on the particle size and the intensity of the thermal stress upon quenching. The effect of the latter two was most clearly recognized in the phase composition of the crystals with x = 0.09. The phase composition was changed between the two extremes; one was composed of 8% alpha´_L-phase and 92%ß-phase and the other was 96% alpha´_L-phase and 4%ß-phase. For the crystals with 0.06 lessthan equal to x lessthan equal to 0.065 (ß-phase) and 0.105 lessthan equal to x lessthan equal to 0.11 (alpha´_L-phase), only the x -value governed the phase composition.     

Fine structure and physical properties of polyethylene/poly(ethylene terephthalate) bicomponent fibers in high‐speed spinning. I. Polyethylene sheath/poly(ethylene terephthalate) core fibers

The high‐speed melt spinning of sheath/core type bicomponent fibers was performed and the change of fiber structure with increasing take‐up velocity was investigated. Two kinds of polyethylene, high density and linear low density (HDPE, LLDPE) with melt flow rates (MFR) of 11 and 50, [HDPE(11), LLDPE(50)], and poly(ethylene terephthalate) (PET) were selected and two sets of sheath/core combinations [HDPE(11)/PET and LLDPE(50)/PET bicomponent fibers] were studied. The fiber structure formation and physical property effects on the take‐up velocities were investigated with birefringence, wide‐angle X‐ray diffraction, thermal analysis, tensile tests, and so forth. In the fiber structure formation of PE/PET, the PET component was developed but the PE components were suppressed in high‐speed spinning. The different kinds of PE had little affect on the fine structure formation of bicomponent fibers. The difference in the mechanical properties of the bicomponent fiber with the MFR was very small. The instability of the interface was shown above a take‐up velocity of 4 km/min, where the orientation‐induced crystallization of PET started. LLDPE(50)/PET has a larger difference in intrinsic viscosity and a higher stability of the interface compared to the HDPE(11)/PET bicomponent fibers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2254–2266, 2000