Three-dimensionally Perforated Calcium Phosphate Ceramics

1Introduction Calciumphosphateceramicswithopenporousstruc tureandsufficientmechanicalstrengthareusefulfor combingmedicines,growthfactorsandcellswiththece ramicsbecausetheopenporescanbeusedasthespace forpreservingthesesubstancesandcells.However,most ofconv…     

Tankyrase Regulates Neurite Outgrowth through Poly(ADP-ribosyl)ation-Dependent Activation of β-Catenin Signaling

Poly(ADP-ribosyl)ation is a post-translational modification of proteins by transferring poly(ADP-ribose) (PAR) to acceptor proteins by the action of poly(ADP-ribose) polymerase (PARP). Two tankyrase (TNKS) isoforms, TNK1 and TNK2 (TNKS1/2), are ubiquitously expressed in mammalian cells and participate in diverse cellular functions, including wnt/β-catenin signaling, telomere maintenance, glucose metabolism and mitosis regulation. For wnt/β-catenin signaling, TNKS1/2 catalyze poly(ADP-ribosyl)ation of Axin, a key component of the β-catenin degradation complex, which allows Axin’s ubiquitination and subsequent degradation, thereby activating β-catenin signaling. In the present study, we focused on the functions of TNKS1/2 in neuronal development. In primary hippocampal neurons, TNKS1/2 were detected in the soma and neurites, where they co-localized with PAR signals. Treatment with XAV939, a selective TNKS1/2 inhibitor, suppressed neurite outgrowth and synapse formation. In addition, XAV939 also suppressed norepinephrine uptake in PC12 cells, a rat pheochromocytoma cell line. These effects likely resulted from the inhibition of β-catenin signaling through the stabilization of Axin, which suggests TNKS1/2 enhance Axin degradation by modifying its poly(ADP-ribosyl)ation, thereby stabilizing wnt/β-catenin signaling and, in turn, promoting neurite outgrowth and synapse formation.     

Effect of Monovalent Cation Additives on the γ-Al2O3-to-α-Al2O3 Phase Transition

The effect of monovalent cation addition on the γ-Al₂O₃-to-α-Al₂O₃ phase transition was investigated by differential thermal analysis, powder X-ray diffractometry, and specific-surface-area measurements. The cations Li⁺, Na⁺, Ag⁺, K⁺, Rb⁺, and Cs⁺ were added by an impregnation method, using the appropriate nitrate solution. β-Al₂O₃ was the crystalline aluminate phase that formed by reaction between these additives and Al₂O₃ in the vicinity of the γ-to-α-Al₂O₃ transition temperature, with the exception of Li⁺. The transition temperature increased as the ionic radii of the additive increased. The change in specific surface area of these samples after heat treatment showed a trend similar to that of the phase-transition temperature. Thus, Cs⁺ was concluded to be the most effective of the present monovalent additives for enhancing the thermal stability of γ-Al₂O₃. Because the order of the phase-transition temperature coincided with that of the formation temperature of β-Al₂O₃ in these samples, suppression of ionic diffusion in γ-Al₂O₃ by the amorphous phase containing the added cations must have played an important role in retarding the transition to α-Al₂O₃. Larger cations suppressed the diffusion reaction more effectively.     

Vibrations of probe used for the defect detection of helical heating tubes in a fast breeder reactor: Part 2. Vibration analysis and numerical simulations

A detection of a defect of a helical heating tube installed in the fast breeder reactor “Monju” in Japan is done by a feeding of an eddy current testing (ECT) probe with magnetic sensor into the tube. An undesirable vibration of the ECT probe always happens under a certain condition and makes the inspection difficult. Several characteristics of the vibration have been made clear by some experiments using a mock-up, but the essential factor of the vibration is still unclear. In this paper, a numerical simulation of the vibration is implemented on the assumption that the vibration is caused by Coulomb friction. An analytical model, which is obtained as a lumped mass model, is a large-scale non-linear vibration system and many computational costs are ordinarily required to carry out the simulations. The Transfer Influence Coefficient Method is applied so that the simulation is efficiently carried out. The results of simulation qualitatively agree well with the experimental results. It confirms the validity of the assumption that the vibration is caused by Coulomb friction.     

Spectroscopic Assessments of Domain Texture in Barium Titanate: II. Cathodoluminescence Analysis

An analytical procedure has been developed according to basic principles of electro-stimulated luminescence spectroscopy aimed at quickly visualizing with high spatial resolution the domain texture developed in tetragonal BaTiO₃ (BT) materials. In the first part of the paper, the relative intensity of the cathodoluminescence (CL) emission has been systematically collected from different crystallographic planes of BT single-crystal and modeled as a function of anisotropic crystal properties. In this context, an analytical expression has been put forward for quantitatively describing the response function of the CL probe, which links the intensity emission to refractive indexes and absorption coefficients pertaining to different planes of the perovskitic crystal. In the second part of the paper, the CL method is applied to visualize with nanometer-scale resolution the domain texture developed in a polycrystalline BT sample. This study demonstrates that CL spectroscopy is a valuable and efficient tool for the assessment of domain orientation in ferroelectric materials. The CL method possesses both wide-range screening capacity and the scanning flexibility of conventional scanning electron microscopy, coupled with a spatial resolution that is comparable with that obtainable by scanning probe microscopy techniques.     

In vitro assessment of the cytotoxicity of anti-allergic eye drops using 5 cultured corneal and conjunctival cell lines

The aim of this study was to evaluate the cytotoxicity of anti-allergic eye drops for human corneal endothelial cells (HCEC) and commercially available ocular surface cells. A primary HCEC culture was derived from human eye bank specimens. SIRC (rabbit corneal epithelium), BCE C/D-1b (bovine corneal epithelial cells), RC-1 (rabbit corneal epithelium), and Chang (human conjunctival cells) were obtained commercially. The WST-1 assay was used to measure HCEC viability, and the viability of other cells was measured using the MTT assay. Cells were treated with 7 commercially available anti-allergic eye drops for 48 h and cell viability was measured and calculated as a percentage of control. The degree of toxicity for each eye-drop solution was based on the cell viability score (CVS). HCECs treated with a 1000-fold dilution of the eye-drop solution had a viability score of 67% for Rizaben and ≥80% for the other solutions with Zepelin being the least toxic. Cell viability in response to eye-drop solutions preserved with benzalkonium chloride (BAK) was dependent on the concentration of the drug solution and exposure time. Treatment of ocular surface cells with a 20-fold dilution of the eye-drop solution resulted in the following order of cell viability as determined by their CVS: Zepelin > Ketas = Zaditen ≥ Tramelas PF = Patanol ≥ Rizaben ≥ Livostin. This order was similar to that observed for HCECs, and cell viability was found to be concentration-dependent. Based on the penetration of the drug into eye tissues, HCECs are only likely to be pharmaceutically damaging in rare cases. Epithelial cell viability depends primarily on the concentration of BAK rather than on the action of the active component in the eye-drop solution. CVS values were useful for comparison of toxicity.     

Characterization and Adsorption Behavior of ZSM-5 Zeolite Film on Cordierite Honeycombs Prepared by a Novel in situ Crystallization Method

Thin films of ZSM-5 zeolite prepared on three types of cordierite ceramic honeycomb substrates by a novel in situ crystallization method were characterized by XRD, FTIR, XRF, SEM-EDX, NH₃-TPD and propane gas adsorption to examine the effect of the substrate on various properties of the ZSM-5 films. The substrates were both as-prepared and acid treated cordierite honeycombs. The XRD, FTIR and XRF results showed that silica-rich surface layers were formed on the surface of the honeycombs by the acid treatments. The SiO₂/Al₂O₃ ratios of the ZSM-5 zeolite formed on these layers increased with increasing time of acid treatment. Both Al₂O₃ and SiO₂ from the substrates were found to contribute to the formation reaction of the zeolite films corresponding to the composition of the interfacial layer. The porous properties of the honeycomb substrates also varied in relation to the amount of zeolite film, which increased linearly with acid treatment time. The presence of the silica-rich interfacial layer between the substrate and zeolite film increased the amount of ZSM-5 and the physical adsorption but decreased the solid acidity and amount of chemisorption.     

Low temperature synthesis of AlN by addition of various Li-salts

The effect of various Li-salts on the low temperature synthesis of AlN by direct nitridation of Al metal was investigated using four Al powders with average particle sizes of 3, 20, 100 and 150 μm. These were mixed with various Li-salts (LiNO₃, LiOH·H₂O and Li₂CO₃) in different concentrations and fired at various temperatures under flowing N₂. The as-received Al powders without Li addition showed AlN formation at about 600 °C in the 3 and 20 μm samples but no AlN formation up to 850 °C in the 100 and 150 μm samples. The crystallinity of the AlN products, where formed, was however low. By contrast, all the Al powders with added Li-salts showed AlN formation up to 800 °C, with LiOH·H₂O being especially effective. Thus, the AlN formation temperature can be significantly lowered in the coarser powders by the addition of Li-salts but the effect is less in the finer powders which undergo low temperature nitridation below the melting point of Al metal even without Li. The crystallinity of the AlN products was higher in the samples containing Li-salts than without Li-salts.     

Proposal of 98.5% high‐efficiency chopper circuit QRAS for the electric vehicle and the verification

A high‐efficiency and high‐power chopper based on a novel soft switching scheme QRAS (Quasi‐resonant Regenerating Active Snubber) has been proposed in this paper. Operating efficiency of the proposed QRAS has been investigated by simulation and experiments. For the purposes of this study we fabricated a one‐tenth prototype model and tested it under the rated load, light load, current discontinuous mode, and under operation out of the resonant stable operational region. The overall evaluation of these test results is provided and the possibility of implementation of an 80‐kW practical model is demonstrated by these successful test results. In addition, as an approach to the next study, the feasibility of 8‐kW SiC‐QRAS is examined and a preliminary evaluation of the efficiency enhancement due to the use of silicon carbide (SiC) power devices is given based on successful experimental results. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 158(4): 68– 80, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20439     

Energy absorption of a thin-walled cylinder with ribs subjected to axial impact

We performed experimental and theoretical analyses that show a thin-walled cylinder with stiff ribs can be used as a structural element to improve or adjust energy absorption characteristics. We conducted impact crushing tests using several different cylinders with ribs. The experimental results showed that the axisymmetric and non-axisymmetric crushing modes were dependent on not only the cross-section size but also on the distances between the ribs. A critical distance between the ribs was found to exist for generating axisymmetric and non-asxisymmetric crushing modes and it was more than double the wavelength of axisymmetric wrinkles regardless of cylinder size. The mean crushing forces of the axisymmetric modes were found to be roughly 1.3 times larger than those of the non-axisymmetric modes. The theoretical results based on plastic hinge behavior showed good agreement with the experimental results. The effects of material and cylinder size on the crushing behavior of a cylinder with ribs were expressed using approximate mathematical equations. The critical distance between ribs for generating axisymmetric or non-axisymmetric crushing mode was also expressed approximately. Stiff ribs appropriately spaced in a cylinder were found to be effective in absorbing a large amount of energy with a short crushing deformation.