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.     

Synthesis of fluoride-releasing carbonate apatites for bone substitutes

Fluoride (F⁻)-substituted B-type carbonate hydroxyapatite (CHAP) powders were prepared for application as bone substitute materials having the ability to enhance bone formation and to suppress bone resorption due to the therapeutic effect of F⁻. F⁻ was adsorbed on CHAP in a sodium fluoride solution followed by heating at 700°C in carbon dioxide flow to substitute F⁻ for the hydroxyl ion in the CHAP structure. The F⁻ contents in the F-substituted CHAP powders were 16–22 times greater than that in normal adult human bones. The carbonate ion contents in the F-substituted CHAP powders corresponded to or were higher than that in normal adult human bones. F-substituted CHAP powder with CO₃²⁻ and F⁻ contents of 11.03 and 0.66 wt%, respectively, slowly released F⁻ in a physiological salt solution to a sufficiently high F⁻ level. The F⁻ concentration slowly increased and reached 67.20 ± 4.81 μg l⁻¹, which was 1.5–9.3 times higher than that in the body fluid of normal adult humans, near the therapeutic window of F⁻, and far lower than the estimated toxic level. Therefore, the F-substituted CHAP can promote bone formation. The present F-substituted CHAP has the advantage of slow F⁻ release over sodium fluoride and sodium monofluorophosphate which are highly soluble salts and cannot be sintered into a ceramic body.     

Electron microscopic analysis of a fusion protein of postsynaptic density-95 and metallothionein in cultured hippocampal neurons

The subcellular localization of biomolecules at high resolution has traditionally been investigated by combining transmission electron microscopy (TEM) and chemical staining with heavy metals or immuno-based labeling with gold-conjugated antibodies. Here, we employ genetically encoded tags to examine the localization of proteins in transfected cultured cells by TEM. We purified a fusion protein of postsynaptic density-95 (PSD-95) coupled to three tandem repeats of metallothionein (MT) (PDS-95-3MT) from COS7 cells grown in the presence of Cd2+. PSD-95-3MT was detected as black particles by TEM. To visualize the subcellular localization of PSD-95-3MT, expression constructs encoding this fusion protein were transfected into primary hippocampal neurons cultured in medium containing Cd2+. The subcellular accumulation of PSD-95-3MT and Cd2+ provided excellent contrast in TEM micrographs. To address if genetically encoded tags affect the function of the target proteins, we found that the conjugation of 3MT to PSD-95 did not alter its association with known binding partners. These results demonstrate that 3MT coordinating Cd2+ is a valuable genetically encoded tag to study the localization of proteins by TEM.     

Estimation of infiltration and surface run-off characteristics of radionuclides from gamma dose rate change after rain

A method to estimate the infiltration and surface run-off characteristics of radionuclides on three types of ground surface from gamma dose rate change due to rain has been developed. We proposed the estimation methods based on the differences in the dose rate increases between monitoring stations caused by different attenuation of gamma ray due to infiltration and by the different run-off characteristics. The gamma dose rate data used for the estimation were measured at near-by monitoring stations in which the ground type around the detector differed from each other. Rain events were selected by the criteria in which ²¹⁴Pb and ²¹⁴Bi deposition amounts are considered to be uniform with in the area in which objective monitoring stations are deployed. We also calculated the surface concentration considering both infiltration and surface run-off processes. As a result, it was shown that the calculated surface concentration was about 40% larger than that considering neither processes of the infiltration and surface run-off.     

Novel decaffeination of green tea using a special picking method and shortening of the rolling process

We have recently succeeded in manufacturing low-caffeine tea (LCT) by employing a special picking method in the 3rd leaf period and shortening the leaf-rolling process. In the present study, the effect of this special method on the content of other physiologically active substances, such as catechins, theanine, and vitamin C, as well as the mechanism of reduction of caffeine content in the LCT were investigated using capillary electrophoresis. By comparing the various components of tea leaves at different picking periods with or without shortening of the rolling process, it was found that the delayed leaf picking period and shortening of the rolling process used in the manufacture of LCT selectively reduced the caffeine content while retaining catechins, theanine, and vitamin C at a sufficient level. Therefore, our study demonstrated that this modified method may be useful in the manufacture of decaffeinated green tea.     

3D microstructure and crack pathways of toughened CaO–Al2O3–SiO2 glass by precipitation of hexagonal CaAl2Si2O8 crystal

We investigated CaO–Al₂O₃–SiO₂ glass partially crystallized with molybdenum particles as nucleating agents. Microstructure of the material was characterized as a house-of-cards structure composed of plate-like crystals. Microcracks propagated along the crystal plane parallel to the double layer of SiO₄/AlO₄ tetrahedrons separated by layers of calcium atoms. To investigate the fracture behavior of the hexagonal CaAl₂Si₂O₈ crystals, molecular dynamics simulations were performed, which demonstrated that a crack can be easily triggered by shear deformation along the calcium layer. Additionally, once a crack was generated in the calcium layer, it propagated rapidly, whereas the crack perpendicular to the calcium layer hardly propagated. This simulated behavior is consistent with the experimentally observed cleavage behavior of the hexagonal CaAl₂Si₂O₈ crystal. The experimental and simulation results effectively explained the non-elastic fracture behavior of the material.     

Effect of coprecipitation temperature on the properties and activity of fibroblast growth factor-2 apatite composite layer

Fibroblast growth factor-2 (FGF-2) apatite composite layers were formed on anodically oxidized titanium (Ti) rods at temperatures lower than the previously used 37 °C to reduce the risk of the inactivation of FGF-2 in calcium phosphate solution. A two-step procedure was used to coprecipitate FGF-2 apatite composite layers on Ti rods. Continuous and homogeneous carbonate-containing low-crystalline apatite layers incorporating FGF-2 were formed on the surface of the Ti. The amounts of apatite and FGF-2 coprecipitated on the Ti rod surface decreased with decreasing coprecipitation temperature. When the coprecipitation temperatures were 15 and 20 °C, the amounts of FGF-2 precipitated on the Ti rods were 0.19 ± 0.03 and 0.20 ± 0.03 μg/cm², respectively. A cell proliferation assay for evaluating the mitogenic activity of FGF-2 immobilized in the layer showed that when FGF-2 was coprecipitated at 15 and 20 °C, the number of NIH3T3 cells cultured with FGF-2 extract was significantly larger than that at 4, 10, 25 and 30 °C. To obtain the largest amount of active FGF-2 on a Ti surface, a temperature of 15 or 20 °C should be used for coprecipitating FGF-2.     

Construction of an autonomously replicating plasmid in n-alkane-assimilating yeast, Candida tropicalis

A transformation system using the autonomously replicating plasmid in the n-alkane-assimilating and asporogenic diploid yeast, Candida tropicalis, was developed. For the cloning of a DNA fragment containing a potential autonomously replicating sequence (ARS) from the genomic DNA of C. tropicalis, the ura3 mutant obtained using ethylmethane sulfonate as the host and the URA3 gene amplified by PCR using the C. tropicalis genomic DNA as a selectable marker were prepared. Comparison of ARSs among yeasts revealed that the consensus sequence found in S. cerevisiae was also present in C. tropicalis. The autonomously replicating plasmid containing the putative ARS as the shuttle vector, capable of replicating in both E. coli and C. tropicalis, was first constructed. The transformation system using this plasmid, in addition to the integrative transformation system, will be applicable to genetic studies of C. tropicalis.     

Extraction of Exotic Fullerenes and Purification of Single-Walled Nanotubes

In this report, we presented a novel and simple extraction method, namely Hydrothermally Initiated Dynamic Extraction (HIDE) method, which allows the extraction of exotic fullerenes remaining in the fullerene soot. In the HIDE method, the soot was treated in boiling water that neither dissolved fullerenes nor produced minimal by-products but untangles the fullerenes from the soot, prior to the extraction by organic solvent. As a result, the HIDE method allowed the extraction of exotic fullerenes, such as dimeric fullerene oxides, higher fullerenes having a low symmetry and oxidized higher fullerenes. Accordingly, the single walled nanotubes (SWNTs) with a purity of 99% by wt was achieved for the first time with the application of the HIDE method.