Sinterability of β-Calcium Orthophosphate Powder Prepared by Spray-Pyrolysis

Mixed solutions of Ca(NO₃)₂ and (NH₄)₂HPO₄ with Ca/P = 1.50 were spray-pyrolyzed at 600°C to produce β-calcium orthophosphate (β-Ca₃(PO₄)₂) powder; the spray-pyrolyzed powder was ground and then calcined at 600°C for 1 h. The best crystalline β-Ca₃(PO₄)₂ powder was obtained from the solution with 1.80 mol.L^–1 Ca(NO₃)₂, 1.20 mol.L^–1 (NH₄)₂HPO₄. The resulting powder was composed of primary particles with sizes of <0.5 μm. Dense β-Ca₃(PO₄)₂ ceramics with a relative density of 96.1% could be fabricated by firing this compressed powder at 1070°C for 5 h.     

Surface wettability improvement of silicone elastomers synthesized with water‐soluble polyacrylic acid molds

The aim of this work was to evaluate the use of water‐soluble hydrophilic plastic molds for preparing siloxane based random copolymers and for enhancing the surface wettability of resultant polymers, with a view for contact lens manufacture. The random copolymer consisted of silicone monomers and a small amount of N‐vinyl‐2‐pyrrolidone (NVP) along with vinyl acetate and diethyleneglycoldiallylether as a crosslinker. The surface of this copolymer, which faced against a polyacrylic acid (PAA) mold, showed a higher degree of wettability compared to that obtained against a hydrophobic polypropylene (PP) mold. After heating at 80°C for 4 h, the surface of this copolymer became hydrophobic. When it was immersed in water, however, the high degree of surface wettability regained within 30 s, whereas no significant change in wettability was observed for the PP‐facing surface. The results obtained from X‐ray photoelectron spectroscopy indicated that the polar fraction, which is attributed to NVP fractions of the copolymer, concentrated at the vicinity of the PAA facing surface and, in consequence, improved the surface wettability. This surface also showed a dynamic rearrangement of the wettability in response to changes of the surrounding environment. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3786–3789, 2003     

Synthesis of novel photo-cross-linkable polymers with redissolution property

p-Styrenesulfonate derivatives having cycloaliphatic epoxide in a molecule, were synthesized. Oligomerization of the monomers and co-polymerization of the novel monomers with tert-butyl methacrylate were carried out. When the polymer films containing a photoacid generator (PAG) were irradiated, they became insoluble in solvents. The insoluble films became soluble in water on baking at 120-200 °C. The insolubilization and redissolution profiles were strongly affected by the structure of the monomer, irradiation and baking conditions, and a type of PAG used. The reaction mechanism was studied by TGA analysis and FT-IR spectroscopy.     

Digital image processing for nonperiodic objects and an on-line image processing system for high resolution electron microscopy

A digital image processing method for noise removal and image enhancement in nonperiodic structural images is described. The method for noise removal uses a reversible transform between an image and image autocorrelation function. The Laplacian filter is then employed for image enhancement. Furthermore, an on-line image processing system for highresolution TEM is presented.     

Adhesion control of fungal spores on solid surfaces using hydrophilic nanoparticles

Mold growth can trigger a variety of serious problems such as allergies and asthma. Designing surfaces that are unfavorable for the adhesion of fungal spores is considered an effective method to prevent fungal growth. In this study, the effect of hydrophilic surface treatment on the adhesion of fungal spores onto substrates was investigated using Aspergillus oryzae as a model fungus. The fungal spores that strongly adhered on the hydrophilic substrates under atmospheric conditions were easily removed by lightly washing by hand in water. These experimental results agreed well with thermodynamic predictions based on contact angle measurements. In addition, the removal ratio of the fungal spores on substrates coated with silica nanoparticles was higher than that on plasma-treated glass. It is believed that the contact area between a spore and substrate depended on the substrate roughness. Atomic force microscopy revealed that there was almost no adhesive force between the spores and glass substrate coated with silica nanoparticles. These results suggest that hydrophilic treatment using hydrophilic silica nanoparticles is more effective than hydrophilic plasma treatment to prevent fungal spore adhesion on glass substrates.     

Preparation and characterization of gelatin sponge millispheres from air-in-water-in-oil-type emulsions

A novel method for the preparation of gelatin sponge millispheres (GSMs) for biomaterials such as embolic agents and cell scaffolds was developed using an air-in-water-in-oil-type emulsion. The droplets, consisting of a foamy gelatin suspension in caprylic triglyceride, were gelled and rinsed with isopropanol. Sonication and depressurization were used during the rinsing process to create interconnected pores. GSMs cross-links created over 4 h at 155°C without any agent were insoluble and had short and long diameters of 1.1 ± 0.2 mm and 1.3 ± 0.2 mm, respectively. The residual isopropanol and caprylic triglyceride were <0.05% (w/w) and <1% (w/w) respectively. The level of bacterial endotoxins in the extracts was below 0.025 EU/ml, and no bacterial or fungal growth was found during sterility testing. The GSMs produced using this method were considered to meet the basic requirements of embolic agents.     

Phenomenological studies of optical properties of Cu nanowires

We report on the experimental observation of surface plasmon resonance in Cu nanowires fabricated by shadow deposition method. When the incident light is polarized perpendicular to the wire axes, plasmon maxima appeared at about 2.3 eV in the absorption spectra. Plasmon resonance appeared at lower photon energy when the incident light is polarized parallel to the wire axes. Resonance peaks move to lower energy when the nanowire widths are increased. We have found that finite-difference time-domain (FDTD) simulation gives better results than Maxwell-Garnett model in explaining the relation between the light polarization and the energies of the observed absorption maxima.     

Cloning and characterization of a novel phytase from wastewater treatment yeast Hansenula fabianii J640 and expression in Pichia pastoris

Phosphohydrolysis of organic phosphorus compounds by acid phosphatases (EC 3.1.3.1 and EC 3.1.3.2) is an important method for efficient removal of phosphorus from high concentration organic wastewater. Another important method is supplementation of animal feed with phytase (EC 3.1.3.8 and EC 3.1.3.26), which improves the availability of phytate-phosphates (phosphate that are hydrolyzed by phytases), making it possible to add less phosphate to animal feed and resulting in the excretion of less phosphorus by the animals. In the present study, we purified a novel phytase from the wastewater treatment yeast Hansenula fabianii J640 (Hfphytase), cloned the 1456 bp open reading frame (ORF) encoding Hfphytase, and characterized Hfphytase. The molecular weight of Hfphytase after deglycosylation by PNGaseF was 49 kDa. The optimal pH and temperature for enzyme activity were 4.5 and 50 °C, respectively. Hfphytase exhibits 40% identity with Debaryomyces castellii phytase, 37% identity with Aspergillus niger PhyB, and 34% identity with Saccharomyces cerevisiae Pho5p. Recombinant Hfphytase was transformed and expressed in Pichia pastoris. The yield was 23 g/l by jar fermenter cultivation. The marked phosphohydrolysis activity exhibited by Hfphytase on six substrates (pNP-P, sodium phytate, glucose-1 phosphate, glucose-6 phosphate, α-glycerophosphate and β-glycerophosphate) indicated that it is a non-specific acid phosphatase.     

Splitting of guest atom sites and lattice thermal conductivity of type-I and type-III clathrate compounds in the Ba–Ga–Ge system

The crystal structures of type-I and type-III clathrate compounds in the Ba–Ga–Ge system have been investigated by synchrotron X-ray powder diffraction at room temperature with single- and split-site models to describe thermal vibration of the Ba atoms that are believed to ‘rattle’ in the encapsulating cages. The split-site model is verified to be more plausible when judged from the changes of the extent of thermal vibration of the Ba atoms and the shape changes of the encapsulating cages with the Ga content for both types of compound. When described with the split-site model, the value of lattice thermal conductivity at room temperature decreases with increasing split distance of the Ba atom site for both types of compound, indicating that the split distance can be used as a parameter to describe the extent of thermal vibration (rattling motion) of the Ba guest atoms in the encapsulating cages.     

PAD1 and FDC1 are essential for the decarboxylation of phenylacrylic acids in Saccharomyces cerevisiae

The volatile phenols, to which Saccharomyces cerevisiae converts from phenylacrylic acids including ferulic acid, p-coumaric acid, and cinnamic acid, generate off-flavors in alcoholic beverages such as beer and wine. Using gene disruptants, transformants and cell-free extracts of these strains, we have verified that the adjacent PAD1 (phenylacrylic acid decarboxylase, YDR538W) and FDC1 (ferulic acid decarboxylase, YDR539W) genes are essential for the decarboxylation of phenylacrylic acids in S. cerevisiae. Pad1p and Fdc1p are homologous with UbiX and UbiD, respectively, in the ubiquinone synthetic pathway of Escherichia coli. However, ubiquinone was detected quantitatively in all of the yeast single-deletion mutants, Δpad1, Δfdc1, and double-deletion mutant, Δpad1Δfdc1.