Leaching and cytotoxicity of formaldehyde and methyl methacrylate from acrylic resin denture base materials

Acrylic resin dentures have the potential to elicit irritation, inflammation, and an allergic response of the oral mucosa. Studies of substances leachable from acrylic resins, their cytotoxicity to cultured cells, and means of reducing their leaching were systematically conducted. Under in vivo and in vitro conditions, formaldehyde and methyl methacrylate were significantly leached into human saliva and saliva-substitute buffer, especially from autopolymerized resins. Both leachable substances showed cytotoxic potentials in the range of their leaching concentrations. Formaldehyde was cytotoxic at lower concentrations than methyl methacrylate. Preleaching in water reduced subsequent leaching of both formaldehyde and methyl methacrylate, and the amount of reduction depended on an increase in the preleaching temperatures. Immersion of acrylic resin dentures in hot water (50 degrees C) before insertion is recommended, especially for autopolymerized resins used either for rebasing or as denture base materials, to minimize the risk of adverse reactions in patients who wear acrylic resin dentures.     

Ribotyping and a study of transmission of Staphylococcus aureus collected from food preparation facilities

Food poisoning from Staphylococcus aureus is sometimes caused by improper handling of food items in food preparation facilities. Prevention of contamination by employees is particularly important in facilities where a significant amount of food preparation is performed by hand. Some experiments have been performed to describe bacterial cross-contamination in the food preparation process, but there have been few studies of cross-contamination in actual food preparation facilities. Aiming to shed light on the transmission of S. aureus in food preparation facilities, this study collected samples of 66 strains of this bacterium from the fingers of food preparation staff, foodstuffs, prepared foods, cooking utensils, and cooking equipment and typed them with the ribotyping method. S. aureus from the same ribogroup was detected on the hands of a study participant, a faucet, knife, frying pan, and a salad, indicating that bacteria found on the hands of the study participant was transmitted to cooking utensils and prepared foods. Transmission (from a faucet to a frying pan handle) of bacteria by another person, a third party, was also detected.     

Molecular cloning of porcine growth differentiation factor 9 (GDF-9) cDNA and its role in early folliculogenesis: direct ovarian injection of GDF-9 gene fragments promotes early folliculogenesis

Growth differentiation factor-9 (GDF-9) is a growth factor secreted by oocytes in growing ovarian follicles. To investigate the ovarian function of GDF-9 in pigs, we first cloned porcine GDF-9 complementary DNA (cDNA), and then injected its gene fragments into the ovary in gilts. Porcine GDF-9 has open reading frame (ORF) homologies of 81.4%, 84.6%, 84.2%, 72.7% and 72.6% with its human, bovine, ovine, rat and mouse counterparts respectively. Regarding the deduced amino-acid sequence of the mature protein, the corresponding homologies reach 92.1%, 97.8%, 97.0%, 89.6% and 88.1% respectively. To investigate the role of GDF-9 in early folliculogenesis, the ovaries of 2-month-old prepubertal gilts were injected with GDF-9 gene fragments. The injection of porcine GDF-9 gene fragments resulted in an increase in the number of primary, secondary and tertiary follicles, concomitant with a decrease in the number of primordial follicles. These results indicated that exogenous GDF-9 can promote early folliculogenesis in the porcine ovary, and that a technique for direct ovarian injection of GFD-9 gene fragments may contribute to a novel therapy for prevention and treatment of infertility associated with ovarian dysfunction.     

Evaluation of TEM samples of an Mg-Al alloy prepared using FIB milling at the operating voltages of 10 kV and 40 kV

Transmission electron microscopy (TEM) samples of an Mg-Al alloy has been prepared using a Ga-focused ion beam (FIB) milling at two different operating voltages of 10 kV and 40 kV to investigate the influence of the FIB energy on the sample quality. The fine structures of the samples have been studied using a high resolution TEM, and the concentration of the implanted Ga was analysed using an energy dispersive X-ray (EDX) analysis. The result of the TEM observation revealed that point defects were introduced to the sample finally milled at 40 kV but not at 10 kV. However, crystal lattice images and electron diffraction patterns were clearly observed on both the samples. The typical influence of the FIB energy was indicated in the elemental analysis. The relative Ga concentration in the thin sample finally milled at 10 kV was 1.0-2.0 at% that is less than half of 4.0-6.0 at% of the Ga concentration in the sample finally milled at 40 kV. A comparison between the experimental results of the Ga concentration measurement with simulation was also discussed.     

Optical topography: practical problems and new applications

We will briefly review the present status of optical topography and then discuss the method of improving practicality, i.e., the signal-to-noise (S/N) ratio and the spatial resolution in observations of higher-order brain functions. The optimum wavelength pair improved the S/N ratio sixfold for deoxyhemoglobin, and new configurations of light irradiation and detection positions doubled the spatial resolution. We also report on developing application fields of optical topography. This modality will bridge the gap between natural sciences, neuroscience, and pedagogy, and show actual real-time brain activity.     

Efficient frequency doubling of 1-W continuous-wave Ti:sapphire laser with a robust high-finesse external cavity

We demonstrated an intrinsic conversion efficiency of 56% from the input fundamental power to the generated second-harmonic power. The second-harmonic power of 581 mW was obtained from the external cavity with a LiB3O5 crystal through the frequency doubling of a 1.17-W Ti:sapphire laser at 746 nm, when the finesse of the robust external cavity was 260.     

Chemiluminescence detection for a microchip capillary electrophoresis system fabricated in poly(dimethylsiloxane)

Chemiluminescence (CL) detection integrated with a microchip capillary electrophoresis (MCE) system that was fabricated in poly(dimethylsiloxane) was demonstrated for chemical and biochemical analyses. Two model CL systems were involved here: metal ion-catalyzed luminol-peroxide reaction and dansyl species conjugated peroxalate-peroxide reaction. Different strategies based on three chip patterns (cross, cross combining with Y, and cross combining with V) to perform on-line CL detection for MCE were evaluated and compared in terms of sensitivity, reproducibility, and peak symmetry. The chip pattern of cross combining with Y proved to be promising for the luminol-peroxide CL system, while the chip pattern of cross combining with V was preferred for the peroxalate-peroxide system where CL reagent could not be effectively transported by electroosmotic flow. A detection limit down to submicromolar concentrations (midattomole) was achieved with good reproducibility and symmetric peak shape. Successful separation of three metal cations such as Cr(III), Co(II), and Cu(II) and chiral recognition of dansyl phenylalanine enantiomers within 1 min revealed distinct advantages of combining MCE with CL detection for rapid and sensitive analyses.     

Magnetization Curve of Two-Dimensional Anti-ferromagnetic Solid 3He on Graphite

Two-dimensional anti-ferromagnetic solid ³He on graphite, so called 4/7 phase, is a highly frustrated magnetic system and its ground state is considered to be a gapless spin liquid. Then how is the behavior in high magnetic fields? We tried to observe the magnetization curve at around 1 mK in high magnetic fields up to 10 T, using a Faraday-type magnetometer. To eliminate a large background signal from graphite as a substrate and copper as a thermal link, a double gradient coil system is employed to produce opposite field gradients in two regions equidistant from the field center. Preliminary results of the 4/7 phase on graphite show no saturated magnetization even at 1 mK and 10 T, suggesting the existence of magnetization plateau.     

A novel spacer‐free panel structure and glass for FEDs

Abstract— A new design for an FED envelope, composed of box‐shaped front glass, sheet‐like rear glass, and metal members, has been devised. This design structure is effective in reducing tensile stress induced by vacuum at the sealing points. Also, a new glass composition, a new physical tempering method, and a lead‐free hermetic sealing material have been developed. As a result, a novel lightweight spacer‐free panel structure for FEDs has been developed by integrating these new technologies. It will assist in maximizing the essential advantages of FED such as high image quality, high reliability, and low cost.