Congener-specific analysis of Pcbs in food samples by using GC/MS

A GC/MS method for congener-specific analysis of polychlorinated biphenyls (PCBs) in food samples was evaluated. There was good agreement between total concentration of PCBs in fish samples (n = 16) measured by using the GC/MS method and the conventional GC-ECD method. The total diet study samples (fishery food, meat, egg, milk, and their products) collected from Osaka in 1982-2001 were analyzed by using the GC/MS method to estimate the temporal trend of daily intake of PCBs from food. The estimated daily intake of total PCBs (sum of tri- to heptaCBs) was in the range of 0.7-4.4 microg/person/day, far below the Japanese provisional acceptable daily intake (250 microg/50 kg-person/day). The dominant congener was 2,2',4,4',5,5'-hexachlorobiphenyl (#153), which accounted for 9-15% of total PCB. The ratio of lower chlorinated congeners decreased from the 1980's to post-2000. The results indicate that the PCB congener profile in foods has gradually changed.     

An analytical method for three-dimensional non-linear responses of prestressed concrete nuclear reactor vessels

This paper describes the results of an investigation to develop an analytical method for assessing the non-linear behaviour and strength of three-dimensional concrete structures such as prestressed concrete nuclear reactor vessels (PCRVs) under monotonically increasing internal pressure. This three-dimensional finite element method uses a proposed material model for the non-linear response of concrete under a multiaxial stress state. Three numerical examples were analysed to investigate the feasibility of the analysis. The first was the calculation of the two-dimensional response of Kupfer's plain concrete. The second involved the analysis of a small-scale axisymmetric PCRV test model with a solid end slab. The third was the analysis of a three-dimensional PCRV test model with penetrations in the end slab. Good agreeement between experimental and analytical results was obtained.     

Evaluation of the Wear Energy Consumption of Nitrogenated Diamond-Like Carbon Against Alumina

The wear energy consumption of nitrogenated diamond-like carbon (NDLC) in the tribo-test against alumina was evaluated. The energy input induced by the power source of the tribometer is applied to the contact area of two sliding bodies. The energy is dissipated into the two bodies with various transforming energies, such as (1) wear energy, (2) friction heat, (3) strain energy, (4) plastic deformation energy, and (5) chemical reaction energy used to form the tribo-layer. Determining the breakdown of the energy consumption into each mode is notably important for the investigation of the tribological mechanism. The surface fracture energy of NDLCs was evaluated by the micro-indentation method. The newly created surface area was estimated using the wear particles size distribution measured by image processing. The consumed wear energy was obtained by the surface fracture energy multiplied by the new created surface area corresponding to the generation of the wear particles in the tribo-test. The index numbers of the wear consumption energy/energy input ratio of the NDLCs were almost the same as those of their wear coefficients.     

Structure and magnetic properties of mono- and bi-layer graphene films on ultraprecision figured 4H-SiC(0001) surfaces

Monolayer and bilayer graphene films with a few hundred nm domain size were grown on ultraprecision figured 4H-SiC(0001) on-axis and 8 degrees -off surfaces by annealing in ultra-high vacuum. Using X-ray photoelectron spectroscopy (XPS), atomic force microscopy, reflection high-energy electron diffraction, low-energy electron diffraction (LEED), Raman spectroscopy, and scanning tunneling microscopy, we investigated the structure, number of graphene layers, and chemical bonding of the graphene surfaces. Moreover, the magnetic property of the monolayer graphene was studied using in-situ surface magneto-optic Kerr effect at 40 K. LEED spots intensity distribution and XPS spectra for monolayer and bilayer graphene films could become an obvious and accurate fingerprint for the determination of graphene film thickness on SiC surface.     

Simultaneous plasma treatment for carburizing and carbonitriding using hollow cathode discharge

Ion carburizing and nitriding are effective processes for saving energy and providing polutionless surface treatment but have the disadvantage of using much electric energy. A cylindric subsidiary cathode was set up around a rod-shaped workpiece with a gap, and hollow cathode discharge for ion carburizing was studied. Thus, simultaneous plasma treatments for ion carburizing and ion car-bonitriding in one workpiece were researched using Cr-Mo steel to save electric treatment power. First, the effects of the gap between the test piece and subsidiary cathode and the pressure of electric discharge gas, including methane gas, on fundamental plasma treatment conditions were experimen-tally researched. It was found that the temperature for ion carburizing in a H₂-N₂-Ar-CH₄ gas mixture was 1123 to 1193 K with a gap of 3 to 5 mm under a gas pressure of 133 to 532 Pa. Next, the test piece was ion carburized with hollow cathode discharge and carbonitrided with normal glow dis-charge simultaneously. The ion-carburized layer was formed in the area covered by the subsidiary cathode. The surface hardness was 800 Hv, the effective case depth was 0.6 mm, and the surface carbon content was 0.75 wt pct. An ion carbonitriding layer was formed in the area without the subsidiary cathode. The surface hardness was 700 Hv and the case depth was 0.1 mm. It is useful to form the different layers of ion carburizing and ion carbonitriding in one treatment process and to give different mechanical and tribological properties on one workpiece simultaneously.     

Recurrence of thyrotoxicosis after attack of allergic rhinitis in patients with Graves' disease

Graves' disease is frequently aggravated during antithyroid drug therapy; however, little is known of its aggravating factors. We studied 83 patients with Graves' disease who were euthyroid for at least 6 months under antithyroid maintenance therapy, and we examined the relationship between thyrotoxicosis relapse, attack of allergic rhinitis, and peripheral eosinophil increase. Forty-one patients showed thyrotoxicosis relapse; of these, 22 (54%) showed peripheral eosinophil increase, and 14 (34%) had attacks of allergic rhinitis. In the remaining 42 patients without thyrotoxicosis relapse, only 4 (10%, P < 0.001) showed an increase in peripheral eosinophils, and only 3 (7%, P < 0.01) had allergic rhinitis. Recurrence of thyrotoxicosis was observed with the increase in serum levels of TSH-receptor antibodies and increase in eosinophils 2 months after the attack of allergic rhinitis. Three patients with seasonal allergic rhinitis showed thyrotoxicosis relapse at the same time of year within 2 consecutive years. Our findings indicate that allergic rhinitis can be an aggravating factor of Graves' disease and suggest that the preceding increase in peripheral eosinophils can be a predictive indicator of recurrence of thyrotoxicosis during antithyroid drug therapy.