An Electric Trap: Electron-Rich Carbonyl Axis Ends Slow Threading/Dethreading Exchange Dynamics of Pillar[5]arene Ring along Axis

Viologen axes with negative carbonyl ends such as carboxylic acid and carbonylethyl groups were synthesized. The threading/dethreading exchange dynamics of the pillar[5]arene ring and these axes were studied by variable-temperature ¹H NMR and two-dimensional exchange spectroscopy NMR spectroscopies. The exchange rate increased on introduction of electron-rich carbonyl ends into the axis: the exchange rate constants of the pillar[5]arene ring along the carboxylic acid-ended and carbonylethyl-ended viologen axes were ca. 2000 and 360 times smaller, respectively, than that along the alkyl-ended viologen axis.     

Optically transparent aromatic poly(ester imide)s with low coefficients of thermal expansion. 2: Effect of the introduction of alkyl‐substituted p‐biphenylene units

A series of ester‐linked tetracarboxylic dianhydrides (TA‐X) were synthesized from trimellitic anhydride chloride and 4,4′‐biphenol analogs containing different numbers and positions of methyl substituents. Aromatic poly(ester imide)s (PEsIs) were polymerized from TA‐Xs and 2,2′‐bis(trifluoromethyl)benzidine to investigate the film properties systematically. A significant substituent effect on the target properties (T_g, optical transparency, the linear coefficient of thermal expansion (CTE) and ductility) was observed. A PEsI containing 2,2′,3,3′,5,5′‐hexamethyl‐substituted p‐biphenylene units was chemically imidized in a homogeneous state. It was highly soluble at room temperature, even in less hygroscopic non‐amide solvents such as cyclopentanone (CPN), and provided a stable CPN solution with a high solid content. The CPN‐cast PEsI film was almost colorless as suggested from the rather low yellowness index (3.2), high light transmittance at 400 nm (71.5%) and very low haze (1.15%). This PEsI film also had a high T_g (294 °C, determined by thermomechanical analysis) in addition to a low CTE (21.7 ppm K^?1), moderate film ductility and very low water uptake. A structural modification of the PEsI by copolymerization with a tetracarboxylic dianhydride with a rigid/linear structure was effective in further reducing the CTE while maintaining the other excellent target properties. Thus, some of the PEsIs developed in this work are promising candidates as novel plastic substrates for use in image display devices. © 2017 Society of Chemical Industry     

An approach to exascale visualization: Interactive viewing of in-situ visualization

In the coming era of exascale supercomputing, in-situ visualization will be a crucial approach for reducing the output data size. A problem of in-situ visualization is that it loses interactivity if a steering method is not adopted. In this paper, we propose a new method for the interactive analysis of in-situ visualization images produced by a batch simulation job. A key idea is to apply numerous (thousands to millions) in-situ visualizations simultaneously. The viewer then analyzes the image database interactively during postprocessing. If each movie can be compressed to 100 MB, one million movies will only require 100 TB, which is smaller than the size of the raw numerical data in exascale supercomputing. We performed a feasibility study using the proposed method. Multiple movie files were produced by a simulation and they were analyzed using a specially designed movie player. The user could change the viewing angle, the visualization method, and the parameters interactively by retrieving an appropriate sequence of images from the movie dataset.     

Improvement of In-Flight Alumina Spheroidization Process Using a Small Power Argon DC-RF Hybrid Plasma Flow System by Helium Mixture

For the further improvement of in-flight alumina spheroidization process with a low-power direct-current radiofrequency (DC-RF) hybrid plasma flow system, the effect of a small amount of helium gas mixture in argon main gas and also the effect of increasing DC nozzle diameter on powder spheroidization ratio have been experimentally clarified with correlating helium gas mixture percentage, plasma enthalpy, powder in-flight velocity, and temperature. The alumina spheroidization ratio increases by helium gas mixture as a result of enhancement of plasma enthalpy. The highest spheroidization ratio is obtained by 4% mixture of helium in central gas with enlarging nozzle diameter from 3 to 4 mm, even under the constant low input electric power given to a DC-RF hybrid plasma flow system.     

Mechanics of shape evolution of particle aggregates in viscous sintering

Sintering of glass/amorphous particles takes place by viscous flow driven by surface tension. While the viscous sintering of two particles is described by the growth of contact area, the shape evolution of aggregates of particles is very complicated and requires analytical methods for the characterization. Here, we analyzed the viscous sintering of linear chains of particles by finite element simulation. Consider a plane which cuts the chain perpendicular to its axis. We show that the growth rate of cross-sectional area is driven by the difference between the integral of pressure on the cross-section and the surface tension acting along its circumference, i.e., the sintering force. The cross-sectional area increases when the sintering force is positive, and decreases when it is negative. This relationship is generalized to particles aggregate of any shape, so that its shape evolution is characterized by the distribution function of growth rate of cross-sectional area.     

The effect of milk polar lipids separated from butter serum on the lipid levels in the liver and the plasma of obese-model mouse (KK-A)

The effect of lipid concentrated-butter serum (LC-BS) on the plasma and hepatic cholesterol and triacylglycerol levels of obese-model mouse (KK-A^y) was evaluated. The same analysis was done on the main lipid fractions from LC-BS, namely, ceramide rich fraction (Ceramide-fr), phosphatidylethanolamine (PE) rich fraction (PE-fr), and sphingomyelin (SPM) rich fraction (SPM-fr). Plasma cholesterol of mice fed LC-BS and Ceramide-fr was significantly (P < 0.05) lower than that of the control. Hepatic total cholesterol and triacylglycerol levels was also reduced significantly by Ceramide-fr feeding (P < 0.05). Although there was no significant difference in the fatty acid composition of all dietary lipids, significant decrease (P < 0.05) in content of 18:1n-9 was found in the liver lipids of the mice fed Ceramide-fr containing diet. The level of 16:1n-7 and 18:1n-7 was also reduced by Ceramide-fr feeding. This result suggests the down-regulation of stearoyl-CoA desaturase-1 (SCD1) by milk ceramides, which would be related to the decrease in triacylglycerol and cholesterol levels in the liver and in the plasma.     

Transcritical phenomena of autoignited fuel droplet at high pressures under microgravity

An experimental study has been performed under microgravity to obtain the detailed information needed for the deep understanding of the combustion phenomena of single fuel droplets which autoignite in supercritical gaseous environment. The microgravity environments both in a capsule of a drop shaft and during the parabolic flight of an aircraft were utilized for the experiments. An octadecanol droplet suspended at the tip of a fine quartz fiber in the cold section of the high-pressure combustion chamber was transferred quickly to be subjected to a hot gaseous medium in an electric furnace, this followed by autoignition and combustion of the fuel droplet in supercritical gaseous environment. High-pressure gaseous mixture of oxygen and nitrogen was used as the ambient gas. Temporal variation of temperature of the fuel droplet in supercritical gaseous environment was examined using an embedded fine thermocouple. Sequential backlighted images of the autoignited fuel droplet or the lump of fuel were acquired in supercritical gaseous environment with reduced oxygen concentration. The observed pressure dependence of the ignition delay and that of the burning time of the droplet with the embedded thermocouple were consistent with the previous results. Simultaneous imaging with thermometry showed that the appearance of the fuel changed remarkably at measured fuel temperatures around the critical temperature of the pure fuel. The interface temperature of the fuel rose well beyond the critical temperature of the pure fuel in supercritical gaseous environment. The fuel was gasified long before the end of combustion in supercritical gaseous environment. The proportion of the gasification time to the burning time decreased monotonically with increasing the ambient pressure.     

Energy levels and degeneracy ratios for chromium in silicon

The energy levels and the degeneracy ratios for chromium in silicon have been determined by the Hall coefficients which were measured by the van der Pauw method. Using the curve fitting method for carrier concentration based on the charge balance equation with the root mean square deviation, the analysis shows that chromium in silicon gives rise to two donor levels. The energy levels of the upper and lower donors are located at E_c-0.226(±0.010)eV and E_v+0.128(±0.005)eV, and their degeneracy ratios are 1/3 and 1/4, respectivel     

Liquid volume measurement for cryogen under microgravity condition

A Helmholtz resonance technique was employed as an effective technique for measuring volumes of cryogenic propellants in orbit. A closed-type resonator was developed and experiments that measured the volume of liquid nitrogen in micro-gravity conditions during parabolic flights were conducted. A loudspeaker installed in the resonator was driven by a swept sound from 249.5 to 649.5 Hz, and the response of the electrical impedance was analyzed by the maximum entropy method to determine the resonant frequency every 743 ms. The resonant frequencies obtained under the micro-gravity conditions agree with the data obtained under normal gravity conditions.     

Activation Energy for Solid Nucleation in Overpressurized Superfluid He-4

Activation energy for solid nucleation in overpressurized superfluid He-4 is calculated. On the basis of a model free energy of solidification of superfluid He-4, I found that both the critical shape of nucleus and the activation energy deviate from the standard model (the ‘thin wall’ model) as pressure increases. These deviations are similar, even quantitatively, to what Harrowell and Oxtoby (J. Chem. Phys. 80:1639, 1984) calculated for solid nucleation in a supercooled classical liquid. The activation energy can be a few times greater than what the thin wall model predicts.