Preparation of Apatite Thin Films through rf-Sputtering from Calcium Phosphate Glasses

Apatite thin films of calcium phosphate were successfully prepared by rf-magnetron sputtering, followed by postannealing, from calcium phosphate glass targets with Ca/P atomic ratios of 0.6 to 0.75, much lower than the stoichio-metric value of 1.67 for hydroxyapatite. Using targets with low Ca/P ratios of 0.65 to 0.25, tricalcium and pyrocalcium phosphate thin films were obtained. The formation of these calcium phosphates phases was attributed to the phosphorus oxide losses during sputtering. H₂O vapor was effective in the formation of the apatite phase at high temperatures; apatite was the exclusive phase in the ambient H₂O, even when the target with the low Ca/P ratio of 0.4 was used. Based on phase stability at high temperatures, it was assumed that various kinds of apatites, such as stoichiometric and nonstoichiometric hydroxy- and Ca-deficient hydroxy-apatites were formed, depending on the composition of the glass targets.     

Mechanical-contact-induced transformation from the amorphous to the partially crystalline state in metallic glass

Sliding friction and wear experiments and electron microscopy and diffraction studies were conducted to examine the metallurgical microstructure of a metallic glass surface strained in sliding contact. Friction and wear experiments were conducted with aluminium oxide spheres 3.2 and 6.4 mm in diameter sliding, in reciprocating motion, on a metallic foil with a composition of Fe₆₇Co₁₈B₁₄Si₁ at a sliding velocity of 1.5 mm s^-1 (frictional heating is negligible) with a load of 2.5 N at room temperature and in a laboratory air atmosphere.The results of the investigation indicate that the amorphous alloy (metallic glass) can be crystallized during mechanical contact. Crystallites with a size range of 10–150 nm are produced on the wear surface of the amorphous alloy. A diffused honeycomb-shaped structure formed by dark gray bands is also produced during sliding. Considerable plastic flow occurs on an amorphous alloy surface with sliding and the flow film of the alloy transfers to the aluminium oxide pin surface. Multiple slip bands due to shear deformation are observed on the side of the wear track. Two distinct types of wear debris were observed as a result of sliding: an alloy wear debris and/or powdery and whiskery oxide debris. The wear rate of Fe₆₇Co₁₈B₁₄Si₁ was 5 × 10^-9 mm³ N^-1.     

On-chip integration of sequential ion-sensing system based on intermittent reagent pumping and formation of two-layer flow

A sequential ion-sensing system using a single microchip was successfully realized. The system developed here involves intermittent pumping of plural organic phases into a microchannel, followed by contact with a single aqueous phase to form a stable organic-aqueous two-layer flow inside the microchannel. Because the plural organic phases created by intermittent flow contain the same lipophilic pH indicator dye but different ion-selective neutral ionophores, different ions can be sequentially and selectively extracted into the different organic phases, where they can be determined by thermal lens microscopy (TLM). We used KD-A3 as the lipophilic pH indicator dye and valinomycin and DD16C5 as neutral ionophores to demonstrate sequential ion sensing of potassium and sodium ions by measuring the deprotonated dye caused by the ion extraction. The integrated microfluidic system proposed here allows multi-ion sensing, which is not easily demonstrated by conventional ion sensor technology using a solvent polymeric membrane. The minimum volume of single organic phase needed to obtain an equilibrium response without dilution by cross dispersion of two organic phases was ca. 500 nL in our system, indicating that the required amounts of expensive reagents in one measurement could be reduced to 1.7 ng and 2.8 ng for the dye and ionophore molecules, respectively.     

Characterization of bacteriocin N15 produced by Enterococcus faecium N15 and cloning of the related genes

Enterococcus faecium N15 was isolated from nuka (Japanese rice-bran paste), which is utilized as starter in the fermenting of vegetables, and was found to produce a bacteriocin that exhibited a broad spectrum of activity, including activity against Listeria monocytogenes and Bacillus circulans JCM2504. The bacteriocin was sensitive to proteases (alpha-chymotrypsin, proteinase K, trypsin, and pepsin) and alpha-amylase, but it was resistant to lipase. The bacteriocin was resistant to heat treatment at 100 degrees C for 2 h, but its activity was completely lost after autoclaving at 121 degrees C for 15 min. It was active over a wide pH range from 2.0 to 10.0. The bacteriocin showed bactericidal activity against Lactobacillus sake JCM1157 at a concentration of 40 AU/ml. Its molecular weight was estimated by SDS-PAGE to be about 3-5 kDa. PCR primers were designed based on the conserved amino acid sequences of class IIa bacteriocins. A 3-kb DNA fragment was amplified and three open reading frames (ORFs) were found. The first encodes a probable immunity protein of 103 amino acid residues and shows complete homology with the putative immunity protein of E. faecium DPC1146. The second and third ORFs respectively encode a probable transposase gene and an inducing factor. The upstream region of the immunity gene, in which the bacteriocin structural gene is located, was amplified. A homology search revealed that the bacteriocin produced by E. faecium N15 exhibits complete identity to enterocin A, a bacteriocin produced by E. faecium DPC1146. PCR using the primers designed in this study is a rapid and sufficient method of screening for bacteriocin-producing strains.     

Effect of surface pretreatment by acid pickling on the density of stannate conversion coatings formed on AZ91 D magnesium alloy

Hydrofluoric and hydrochloric acid solutions and a mixture of them were tested as pickling solutions for AZ91 D Mg alloy before application of stannate coatings. Optical microscopy and energy dispersive X-ray spectroscopy (EDX) of the alloy surface after the pickling process showed that the Mg-rich α phase dissolved preferentially rather than the Al-rich β phase in hydrochloric acid solution. On the other hand, in hydrofluoric acid solution, Mg dissolved in a form of pitting corrosion. Pickling pretreatment with a mixture of these acids at an optimal concentration and an optimal pickling time resulted in relatively uniform dissolution of the alloy surface. The potentiodynamic polarization technique was used to investigate the anodic behavior of the uncoated and coated magnesium alloy in borate buffer solution. The morphology of the coatings was observed using a scanning electron microscope (SEM) before and after corrosion tests. The experimental results showed that coating film density and corrosion resistance of stannate-coated samples prepared with pickling pretreatment were improved compared with those of the coated sample without pickling pretreatment.     

Japan's use of underground space in urban development and redevelopment

Nationwide, Japan has investigated the current state of underground space use for district in which urban redevelopment has been completed, as well as land utilization under buildings in ward sections of Tokyo. These investigations have shown that promotion of effective use of underground space is essential to integrating the surface and subsurface in order to create a community that provides good amenities and enhances safety in urban areas. To fully achieve this goal, it will be important to develop projects in close cooperation with planners, users and administrators.     

A carbon nanotube–enhanced SiC coating for the oxidation protection of C/C composite materials

A carbon nanotube–enhanced SiC (CNT–SiC) coating was deposited on C/C composites to improve the oxidation resistance of C/C. The CNT–SiC coating was prepared by direct growth of CNTs on C/C surface at 700 °C followed by deposition of SiC using chemical vapor deposition at 1150 °C for 1 h. SiC was deposited on the CNTs as well as the interface between CNTs and C/C, making CNTs strongly rooted on C/C surface. The final CNT–SiC coating consisted of two layers: the CNT–SiC layer and SiC layer. In comparison to the SiC coating, the CNT–SiC coating showed fewer cracks and a better oxidation resistance because the CNTs reduce the stress in the coating caused by the mismatch of the coefficient of thermal expansion between C/C and SiC.     

A novel approach to a fine particle coating using porous spherical silica as core particles

The applicability of porous spherical silica (PSS) was evaluated as core particles for pharmaceutical products by comparing it with commercial core particles such as mannitol (NP-108), sucrose and microcrystalline cellulose spheres. We investigated the physical properties of core particles, such as particle size distribution, flow properties, crushing strength, plastic limit, drying rate, hygroscopic property and aggregation degree. It was found that PSS was a core particle of small particle size, low friability, high water adsorption capacity, rapid drying rate and lower occurrence of particle aggregation, although wettability is a factor to be carefully considered. The aggregation and taste-masking ability using PSS and NP-108 as core particles were evaluated at a fluidized-bed coating process. The functional coating under the excess spray rate shows different aggregation trends and dissolution profiles between PSS and NP-108; thereby, exhibiting the formation of uniform coating under the excess spray rate in the case of PSS. This expands the range of the acceptable spray feed rates to coat fine particles, and indicates the possibility of decreasing the coating time. The results obtained in this study suggested that the core particle, which has a property like that of PSS, was useful in overcoming such disadvantages as large particle size, which feels gritty in oral cavity; particle aggregation; and the long coating time of the particle coating process. These results will enable the practical fine particle coating method by increasing the range of optimum coating conditions and decreasing the coating time in fluidized bed technology.