Cathodic pulse breakdown of anodic films on aluminium in alkaline silicate electrolyte – Understanding the role of cathodic half-cycle in AC plasma electrolytic oxidation

Sequential anodic and cathodic pulse voltages were applied on anodised Al micro-electrodes in alkaline silicate electrolyte to explore the role of cathodic pulse in AC or bipolar plasma electrolytic oxidation (PEO) process. SEM observation was carried out to observe the sites of anodic and cathodic breakdown and their morphologies. The prior anodic breakdown accelerated the cathodic breakdown at ?50 V, and the acceleration was associated with the preferential cathodic breakdown at the anodic breakdown sites. However, the succeeding anodic breakdown during applying anodic pulse of 420 V for 2 ms was highly suppressed at the cathodic breakdown sites. This would randomise the anodic breakdown sites. Such role may contribute to the formation of rather uniform coatings on aluminium in this electrolyte without large discharge channels when larger cathodic current is applied with respect to the anodic current in AC PEO.     

Rapid separation of shikimic acid from Chinese star anise (Illicium verum Hook. f.) with hot water extraction

Shikimic acid can be rapidly separated (ca. 5 min) from Chinese star anise with hot water extraction at temperatures of 120 °C or higher to obtain recoveries of 100%. Extraction recoveries of shikimic acid close to 97% can be obtained with water at 70 °C using slightly longer extraction times (ca. 10 min) than those at 120 °C. A semi-batch flow apparatus was used to study the effect of temperature, average particle size, water flow rate, and extraction time on the experimental recoveries. For 0.5 g Chinese star anise raw material that contained ca. 8% shikimic acid, 100% recoveries of shikimic acid could be obtained with 60 g water at 150 °C at 15 MPa in 4 min for star anise material having a particle size range from 355 to 600 μm. A one-site kinetic model was found to provide good correlation of the data and the kinetic parameters of the model could be written in terms of linearized contributions in temperature, average particle diameter and flow rate.     

Metal Complexes of π-Conjugated Polymers

π-Conjugated chelating polymers such as poly(2,2′-bipyridine-5,5′-diyl), poly(1,10-phenanthroline-3,8-diyl), and salophen polymers have been prepared by organometallic polycondensations. The obtained polymers form metal complexes with various metal species such as [Ru(bpy)₂]²⁺ and CuCl₂. Metal complexes of π-conjugated ligands are also polymerized by dehalogenative organometallic polycondensations. Some of the metal complexes of π-conjugated polymers exhibit electrical conducting nature and show catalytic activity for redox reactions.     

Development of In Vitro and In Vivo Evaluation Systems for Vitamin D Derivatives and Their Application to Drug Discovery

We have developed an in vitro system to easily examine the affinity for vitamin D receptor (VDR) and CYP24A1-mediated metabolism as two methods of assessing vitamin D derivatives. Vitamin D derivatives with high VDR affinity and resistance to CYP24A1-mediated metabolism could be good therapeutic agents. This system can effectively select vitamin D derivatives with these useful properties. We have also developed an in vivo system including a Cyp27b1-gene-deficient rat (a type I rickets model), a Vdr-gene-deficient rat (a type II rickets model), and a rat with a mutant Vdr (R270L) (another type II rickets model) using a genome editing method. For Cyp27b1-gene-deficient and Vdr mutant (R270L) rats, amelioration of rickets symptoms can be used as an index of the efficacy of vitamin D derivatives. Vdr-gene-deficient rats can be used to assess the activities of vitamin D derivatives specialized for actions not mediated by VDR. One of our original vitamin D derivatives, which displays high affinity VDR binding and resistance to CYP24A1-dependent metabolism, has shown good therapeutic effects in Vdr (R270L) rats, although further analysis is needed.     

Molecular Bases of Human Malformation Syndromes Involving the SHH Pathway: GLIA/R Balance and Cardinal Phenotypes

Human hereditary malformation syndromes are caused by mutations in the genes of the signal transduction molecules involved in fetal development. Among them, the Sonic hedgehog (SHH) signaling pathway is the most important, and many syndromes result from its disruption. In this review, we summarize the molecular mechanisms and role in embryonic morphogenesis of the SHH pathway, then classify the phenotype of each malformation syndrome associated with mutations of major molecules in the pathway. The output of the SHH pathway is shown as GLI activity, which is generated by SHH in a concentration-dependent manner, i.e., the sum of activating form of GLI (GLIA) and repressive form of GLI (GLIR). Which gene is mutated and whether the mutation is loss-of-function or gain-of-function determine in which concentration range of SHH the imbalance occurs. In human malformation syndromes, too much or too little GLI activity produces symmetric phenotypes affecting brain size, craniofacial (midface) dysmorphism, and orientation of polydactyly with respect to the axis of the limb. The symptoms of each syndrome can be explained by the GLIA/R balance model.     

Cross-section corrosion-potential profiles of aluminum-alloy brazing sheets observed by the flowing electrolyte scanning-droplet-cell technique

The scanning-droplet-cell (SDC), recently used for studying electrochemistry of electrodes in micro-areas, was modified to a flowing electrolyte-type one (f-SDC), in which fresh electrolyte was continuously supplied on the surface to be examined. The f-SDC with a coaxial double capillary structure could avoid the contamination of electrolyte by species dissolved from the measuring electrode surface. In the present study, the f-SDC technique was applied successfully to obtain profiles of the corrosion potential for the cross-sections of aluminum-alloy brazing sheets, used for the heat exchanger of the automobile. The brazing sheets consist of an Al-Zn alloy sacrificial anode layer, an Al-Mn-Cu core layer and an Al-Si brazing filler. The profiles of the corrosion potential, important to evaluate the corrosion protection performance of the sacrificial anode, revealed that the potential gradient arising from the sacrificial anode to the core layer is mainly controlled by zinc, which diffuses from the former layer to the latter during the cladding treatment and the post-heat treatment.     

Phase separation and dewetting in polystyrene/poly(vinyl methyl ether) blend thin films in a wide thickness range

Phase separation and dewetting processes of blend thin films of polystyrene (PS) and poly(vinyl methyl ether) (PVME) in two phase region have been studied in a wide film thickness range from 65 μm to 42 nm (∼2.5R_g, R_g being radius of gyration of a polymer) using optical microscope (OM), atomic force microscope (AFM) and small-angle light scattering (LS). It was found that both phase separation and dewetting processes depend on the film thickness and were classified into four thickness regions. In the first region above ∼15 μm the spinodal decomposition (SD) type phase separation occurs in a similar manner to bulk and no dewetting is observed. This region can be regarded as bulk. In the second region between ∼15 and ∼1 μm, the SD type phase separation proceeds in the early stage while the characteristic wavelength of the SD decreases with the film thickness. In the late stage dewetting is induced by the phase separation. In the third region between ∼1 μm and ∼200 nm the dewetting is observed even in the early stage. The dewetting morphology is very irregular and no definite characteristic wavelength is observed. It is expected that the irregular morphology is induced by mixing up the characteristic wavelengths of the phase separation and the dewetting. In the fourth region below ∼200 nm the dewetting occurs after a long incubation time with a characteristic wavelength, which decreases with the film thickness. It is considered that the layered structure is formed in the thin film during the incubation period and triggers the dewetting through the capillary fluctuation mechanism or the composition fluctuation one.     

Anodic dissolution of titanium in NaCl-containing ethylene glycol

Anodic dissolution behavior of titanium in NaCl-containing ethylene glycol has been examined to obtain electropolished titanium surface. During anodic polarization in 1 mol dm^?3 NaCl ethylene glycol solution at 293 K, the titanium electrode covered with oxide dissolves with gas evolution at potentials higher than 10 V (Ag/AgCl) while it is in passive state at potentials lower than 5 V. However, after removal of the oxide layer by pre-polarization at gas-evolving potentials, no gas evolution is observed, and the titanium electrode shows a limiting dissolution current as tetravalent species at potentials higher than 5 V, producing a smooth surface. The polarization of the rotating disk titanium electrode reveals that the kinetics of the mass transfer reaction for electropolishing of titanium is controlled by titanium species dissolved into the solution, not by chloride ions or water containing in the solution. Repetition of dynamic polarization gives a well-electropolished surface.     

Preparation of nanocomposites by melt compounding polylactic acid/polyamide 12/organoclay at different screw rotating speeds using a twin screw extruder

This study analyzes the effect of different screw rotating speeds on the clay dispersion and mechanical properties of nanocomposites prepared by melt compounding polylactic acid (PLA) with an organoclay in a co‐rotating twin screw extruder. Polyamide 12 (PA12) was used as an additive. Two different screw rotating speeds, 65 rpm and 150 rpm, were used in this study. According to the tensile strength data, the Young's modulus of the PLA/clay nanocomposites showed improvement at a screw rotating speed of 150 rpm. The Young's modulus improved with the addition of the organoclay to PLA matrix, but decreased when PA12 was added to the PLA matrix. The tensile strengths and elongations become small by adding organoclay to PLA matrix. The tensile strengths of the PLA/organoclay nanocomposites increased for the higher screw rotating speed (150 rpm). The d‐spacing of PLA/PA12/Clay nanocomposites was independent of the addition of PA12. The size of the clay aggregates in the PLA/PA12/Clay nanocomposites is smaller than that of PLA/Clay. Furthermore, the thermal stability of the PLA/Clay nanocomposite increases with addition of PA12, while on the whole, it had little influence on the tensile properties. POLYM. COMPOS., 29:1–8, 2008. © 2007 Society of Plastics Engineers     

Application concepts and evaluation of small-scale catalytic combustors for natural gas

Basic application concepts of catalytic combustion are roughly classified into three types, and the development of catalysts, combustion performance and applicability are stated. On the diffusive catalytic combustion method, completeness of methane combustion and its reaction mechanism have been demonstrated by detailed combustion analysis of the burner and reaction kinetics. On the adiabatic lean premixed catalytic combustion method, applicability of a high-temperature catalyst system based on Mn-substituted hexaaluminate monolithic honeycomb to a 1.5 MW gas turbine combustor has been investigated through pressurized combustion tests and prototype engine-rig tests. As a result, a good outlook of the basic technical problems to overcome including the catalyst durability and the combustor control method was obtained, but another problem was that of the combustor capacity. In view of the progress of the non-catalytic lean premixed combustion method, it was concluded that a hybrid catalytic combustion method limiting catalytic combustion to the low-temperature range in this concept might become efficient in the future, but that it would depend on the development of efficient catalysts initiating their activity at about 350°C and having durability at 1000°C.