Viscosity measurement of gelcasting slurry during in-situ gelation by a micro X-ray CT scan system

This paper reports the use of a micro X-ray CT scan system to measure the viscosity increase during in-situ gelation of a gelcasting slurry. Three small steel balls were dropped in the slurry at a desired time interval after the addition of the gelling agent, while being monitored by the CT scan system. It was determined that the plot of the logarithm of the calculated viscosities based on the settling velocity of the falling ball versus the gelation time can be classified into three regions with increasing slopes. The first region is designated as the idle time during which the gelcasting slurry can be further processed and cast into a mold. The second region is the onset of gelation during which the polymer networks start to form with a gradual increase in the viscosity, whereas the third region is attributed to the increased concentration of the polymerized networks as typified by the significant increase in the slurry viscosity. Moreover, the falling ball method was found to be more sensitive to detecting the onset of gel formation in the gelcasting slurry than stress-controlled rheometric analyses.     

Relation Between Shear Relaxation and Molecular Structure of Lubricating Oils

The viscoelastic property of various lubricating oils was measured with the oscillating crystal technique. The relation between the shear relaxation behavior and the molecular structure of the lubricating oils is discussed. Eyring's theory for viscous flow is used to explain the relaxation behavior from a molecular point of view. Some insight into a procedure for estimating the relaxation time from the molecular structure is presented.     

Interaction between peroxisome proliferator-activated receptor γ and its agonists: docking study of oximes having 5-benzyl-2,4-thiazolidinedione

The molecular modelling of oximes having 5-benzyl-2,4-thiazolidinedione moieties, agonists of the peroxisome proliferator-activated receptor γ (PPARγ), was performed with respect to their structures complexed with the ligand binding domain of PPARγ. For each ligand molecule, the 5-benzyl-2,4-thiazolidinedione head group was used as an anchor and the conformation of the rest of the molecule was searched for the most energetically favorable interaction with the receptor by systematic conformation search and manual modelling. Although both tail-up and tail-down configurations, which have been observed in the crystal structure of eicosapentaenoic acid when complexed with PPARδ, appeared among the lowest energy structures for most of the compounds, potent agonists were found to adopt a configuration similar to that of rosiglitazone when bound to PPARγ, according to the crystal structure. The structure–activity relationships were analyzed based on the receptor–ligand interaction. The alkyl group and the aromatic ring of the tail group of the ligands had hydrophobic interactions with the receptor, and these interactions were found to be essential for the strong activity.     

Characterization and gas permeation properties of UV‐cured fluorine‐containing telechelic polyimide membranes with a crosslinker

The characterization and gas permeation properties of ultraviolet (UV)‐cured fluorine‐containing telechelic polyimide membranes and end‐capped with a crosslinker with acryloyl groups were investigated. Membrane formation property was improved by the addition of crosslinker by using UV irradiation. The densities of UV‐cured membranes were almost similar to each other, and high gel fraction was shown on the UV‐cured membranes. This result suggests that the crosslinker promotes crosslink reaction at the polymer chain ends and does not induce appreciable membrane densification. Furthermore, the gas permeability of the UV‐cured membranes was higher than that of the membrane without the crosslinker. The higher gas permeability is due to the new crosslink structure formed at the polymer chain ends, which was promoted by the crosslinker after UV irradiation, but did not induce appreciable membrane densification. The use of a BEI crosslinker in the telechelic polyimide membranes promoted the crosslink reaction and increased the H₂ selectivity because H₂ permeability was not sensibly affected by the crosslink reaction. POLYM. ENG. SCI., 54:1089–1099, 2014. © 2013 Society of Plastics Engineers     

Classification of Barley Shochu Samples Produced Using Submerged Culture and Solid‐state Culture of Koji Mold by Solid‐phase Microextraction and Gas Chromatography‐Mass Spectrometry

An easy and fast method of analyzing volatile components contained in shochu, by headspace solid‐phase microextraction and gas chromatography‐mass spectrometry, was established to determine the difference in the content of the various components of barley shochu produced using a submerged culture of koji mold (submerged‐culture shochu) and a solid‐state culture of koji mold (solid‐culture shochu). The contents of the volatile components between the two types of shochu were compared. The results of the comparison revealed that the content of ethyl lactate, ethyl benzoate, 3‐methyl‐1‐pentanol, diethyl succinate, citronellol, and 2‐phenethyl acetate differed between the submerged‐culture and the solid‐culture shochu samples. In addition, the classification of barley shochu samples, including those on the market, into submerged‐culture shochu and solid‐culture shochu, was carried out by multivariate analysis using the quantitative values of the above‐mentioned six compounds, and distinct discrimination was found possible.     

An atomic study of hydrogen effect on the early stage oxidation of transition metal surfaces

Density functional theory (DFT) and tight-binding quantum chemical molecular dynamics (QCMD) have been applied to analyze the role of interstitial hydrogen in the process of oxygen adsorption to Ni (111) and Cr-doped Ni (111) surfaces and diffusion within these metal surfaces. The DFT calculations demonstrate that the fcc hollow and octahedral sites are the most favorable for hydrogen adsorption on the surface and subsurface, respectively. A clean metal surface has a slight inward relaxation in the topmost layer, whereas the metal atoms show outward relaxation (2%) due to interstitial hydrogen. The adsorption energies of oxygen and OH have decreased to 0.26 and 0.13 eV, respectively, and the metal atomic bond further extended in the range of 1–2% in order to hydrogen remained interstitial site. Hydrogen changes to a negatively charged in the interstitial site by receiving electron. The QCMD results reveal that the oxygen penetration depth increases when hydrogen occupy into interstitial octahedral site. The deeply diffused or interstitial hydrogen receives electrons from the metal. Additionally, interstitial hydrogen initiates the charge transfer and extends the metal atomic bond. The localized process weakens the metal–metal bonds and it makes the surface chemically active for further interaction. This process can help oxygen or other species to diffuse into the structure. As a result, the subsurface hydrogen accelerates the early stage of oxidation initiation.     

The control of crack arrays in thin films

Thin-film fracture can be used as a nano-fabrication technique, but generally, it is a stochastic process that results in nonuniform patterns. Crack spacings depend on the interaction between intrinsic flaw populations and the fracture mechanics of crack channeling. Geometrical features can be used to trigger cracks at specific locations to generate controlled crack patterns. However, while this basic idea is intuitive, it is not so obvious how to realize the concept in practice, nor what the limitations are. The control of crack arrays depends on the nature of the intrinsic flaw population. If there is a relatively large density of long flaws, as commonly assumed in fracture mechanics analyses, reliable crack patterns can be obtained fairly robustly using relatively blunt geometrical features to initiate cracks, provided the applied strain is carefully matched to the properties of the system and the desired crack spacing. This process is analyzed both for cracks confined to the thickness of a film and for cracks growing into a substrate. The latter analysis is complicated by the fact that increases in strain can either drive cracks deeper into the substrate or generate new cracks at shallower depths. If the intrinsic flaws are all very short, the geometrical features need to be very sharp to achieve the desired patterns. While careful control of the applied strain is not required, the strain needs to be relatively large compared to that which would be required to propagate a large flaw across the film. This results in an approach that is not robust against the introduction of accidental damage or a few large flaws.     

Lipid bilayer formation by contacting monolayers in a microfluidic device for membrane protein analysis

Artificial planar lipid bilayers are a powerful tool for the functional study of membrane proteins, yet they have not been widely used due to their low stability and reproducibility. This paper describes an accessible method to form a planar lipid bilayer, simply by contacting two monolayers assembled at the interface between water and organic solvent in a microfluidic chip. The membrane of an organic solvent containing phospholipids at the interface was confirmed to be a bilayer by the capacitance measurement and by measuring the ion channel signal from reconstituted antibiotic peptides. We present two different designs for bilayer formation. One equips two circular wells connected, in which the water/solvent/water interface was formed by simply injecting a water droplet into each well. Another equips the cross-shaped microfluidic channel. In the latter design, formation of the interface at the sectional area was controlled by external syringe pumps. Both methods are extremely simple and reproducible, especially in microdevices, and will lead to automation and multiple bilayer formation for the high-throughput screening of membrane transport in physiological and pharmaceutical studies.     

Wideband design of nonreciprocal phase shift magneto-optical isolators using phase adjustment in Mach-Zehnder interferometers

A wideband design is proposed for nonreciprocal phase shift magneto-optical isolators based on Mach-Zehnder interferometers. The wavelength dependence of nonreciprocal phase difference between the backward waves propagating in two interferometer arms is compensated for by that of reciprocal phase difference. This is realized by introducing an appropriate phase bias in one of interferometer arms. Two design examples are presented with a backward loss of >30 dB in the wavelength range of 1.40-1.63 microm for a magnetic garnet waveguide isolator and of 1.485-1.630 microm for a Si-wire waveguide isolator.     

Combined effects of work hardening and precipitation strengthening on the cyclic stability of TiNiPdCu-based high-temperature shape memory alloys

The combined effects of work hardening and precipitation strengthening were employed to improve the cyclic stability of TiNiPdCu-based high-temperature shape memory alloys. Annealing after cold deformation resulted in the formation of nano-scale TiPdCu and Ti₂Pd precipitates, stable at high temperatures in Ti₅₀Ni_25?xPd₂₅Cu_x alloys. The nano-scale precipitates were also observed to retard recovery/recrystallization processes at higher temperatures. It was found that the combined effects of work hardening and precipitation strengthening remarkably enhanced the high-temperature stability of the Ti₅₀Ni₂₀Pd₂₅Cu₅ alloy and increased its maximum working temperature range while keeping the transformation temperatures and recovery strains at sufficiently high levels. Precipitation strengthening helped to greatly improve the high-temperature cyclic stability of the alloy. Creep tests at 673 K under 500 MPa confirmed that the better high-temperature cyclic stability of the precipitate-containing alloy was mainly due to its higher creep resistance.