Development and application of an enzyme immunoassay based on a monoclonal antibody against gonyautoxin components of paralytic shellfish poisoning toxins

With a gonyautoxin 2/3 (GTX2/3)-specific monoclonal antibody (designated GT-13A) and a saxitoxin-horseradish peroxidase conjugate (STX-HRP), a direct competitive enzyme immunoassay (GTX-EIA) was established and its sensitivity to various toxin components was investigated. The concentrations resulting in 50% inhibition of the binding of STX-HRP to the solid-phase GT-13A antibody for GTX2/3, decarbamoyl-GTX2/3 (dc-GTX2/3), N-sulfocarbamoyl-GTX2/3 (C1/2), GTX1/4, STX, and neosaxitoxin (neoSTX) in GTX-EIA were found to be 0.28, 0.41, 0.52, 3.46, 4.06, and 89.37 ng/ml, respectively. When the minimum detection limit was assumed to be at a toxin concentration causing 30% inhibition of the binding of STX-HRP to the solid-phase GT-13A antibody, the detection limits for GTX2/3, dc-GTX2/3, C1/2, GTX1/4, STX, and neoSTX were found to be 0.15, 0.18, 0.19, 1.09, 1.50, and 22.93 ng/ml, respectively. These results indicate that all of the GTX components examined and STX are detectable at concentrations lower than the regulatory limit of 80 microg/100 g of shellfish tissue, even when a minimum dilution factor of 100 is applied to tissue extracts with the extraction procedure of the Association of Official Analytical Chemists. Therefore, GTX-EIA is thought to be a useful qualitative screening method for GTX components and STX in the mass monitoring of toxin-contaminated shellfish.     

Si-rich surface layer of photochemically deposited silicon nitride

The etching reaction of a photochemically deposited silicon nitride film with F₂ has been observed in situ using polarization-modulation infrared spectroscopy and quadruple mass spectrometry. The infrared spectrum of the silicon nitride film before etching exhibited two bands at 1030 and 975 cm^–1, arising from Si-N vibration. Exposure of the film at 423 K to F₂ led to an intensity decrease of the lower-frequency band, while the higher-frequency band increased. Simultaneous mass analysis revealed that the etching products evolved into the gas phase were SiF₄ and H₂. However, a further admission of F₂ resulted in a slight decrease in intensity of the 975 cm^–1 band as well as a slight evolution of SiF₄. These results strongly suggest the presence of a metastable Si-rich layer on the surface of the silicon nitride film prior to reaction with F₂. Infrared measurements have also been made in the Si-H stretching region, the results of which are described and discussed.     

Thermal Conductivity Measurement of Thermally-Oxidized SiO<Subscript>2</Subscript> Films on a Silicon Wafer Using a Thermo-Reflectance Technique

This paper describes the development of an advanced method to measure the normal-to-plane thermal conductivity of very-thin insulating films. In this method the metal film layer, which is deposited on thin insulating films, is Joule heated periodically and the ac-temperature response at the center of the metal film surface is measured by a thermo-reflectance technique. The one-dimensional thermal conduction equation of the three-layered system was solved analytically, and a quite simple and accurate approximate equation was derived. In this method, calibration factors of the thermo-reflectance coefficient were determined using the known thermal effusivity of the substrate. The present method was examined for thermally-oxidized SiO₂ films (1000--20 nm thick) on a silicon wafer. The present results of the thermal conductivity agree with those of VAMAS TWA23 within ±10%.Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22--27, 2003, Boulder, Colorado, U.S.A.     

Identification of a Hydra homologue of the beta-catenin/plakoglobin/armadillo gene family

The effect of a single neonatal convulsion on subsequent behaviour was investigated in the male rat. Convulsions were induced by heat or pentylenetetrazol on days 1, 10 or 21. As adults, locomotor activity, spatial ability and convulsion susceptibility were measured. Significant differences were seen in some measures and some groups but a single neonatal convulsion did not induce a consistent and significant pattern of behavioural change, despite the persistent change in hippocampal physiology shown in a previous study.     

Liquid/liquid optical waveguides using sheath flow as a new tool for liquid/liquid interfacial measurements

A liquid/liquid optical waveguide was constructed using a sheath flow. Since the refractive index of an organic solvent is generally higher than that of water (nD = 1.33), light introduced into the inner organic flow should proceed with total multi-reflection within the inner flow, so that the inner part of the sheath flow acts as the core of an optical waveguide. This sheath flow liquid/liquid optical waveguide was stable and showed no substantial background scattering. Moreover, it is applicable to both miscible and immiscible liquid/ liquid interfaces. Thus, it may become a new tool for studying liquid/liquid interfaces as well as for sensitive optical measurements.     

Tensile properties of fine-grained 7475 aluminium alloy at various temperatures and strain rates

For a superplastic 7475 alloy, tensile properties are tested under various conditions in order to investigate the effects of the tensile conditions on the mechanical properties as well as on the microstructure after working. The results obtained here suggest a possibility of high-speed forming of this alloy. Under conditions of 400°C and 8.3×10⁻²s⁻¹ strain rate, a comparatively large elongation of about 200% can be attained. This may be due to the fact that the fine subgrains arise during the deformation. Also, mechanical properties at room temperature of the specimen prestrained under this condition are found to be fairly satisfactory.     

Metallographic observations of stainless steel sheets produced by twin-roll type strip caster

Microstructures and textures of austenitic stainless steel sheets produced by a twin-roll type strip caster are investigated at various stages of casting, cold-rolling and annealing processes. Strip casting is a rapid solidification process and, therefore, the cast strip sheets have fine columnar dendrites and very sharp (100) textures. After cold-rolling and annealing the strip sheets have equiaxial and somewhat finer grains than those produced by the conventional process, and the texture is composed mainly of the (110)[1?2] orientation.     

Predictable modelling for cooling process of a hot steel plate by a laminar water bar

A numerical model is proposed to predict the cooling process of a hot steel plate by a laminar water bar. This model gives a close agreement with the experimental cooling history for arbitrary water flow rate and water temperature.     

Fundamental property of electric field in rapeseed ester oil based on Kerr electro-optic measurement

In the future, environmentally friendly insulating oil such as rapeseed ester oil is expected to be utilized as a substitute for mineral oil for power transformers. In addition, electrical insulation design for transformers becomes more important regarding size reduction and enhancement of electric field stress. The fundamental property of the electric field distribution in the rapeseed ester oil and in the oil/solid dielectrics composite insulation system should be clarified. In this paper, we have directly measured the electric field in the rapeseed ester oil with parallel-plane electrode and the rapeseed ester oil/pressboard (PB) composite insulation systems under DC voltage application using the Kerr electro-optic technique. From the results, we compared measurements of electric field and charge behavior for the rapeseed ester oil and the mineral oil and confirmed the applicability of the rapeseed ester oil for use in transformers.     

Effects of exogenous polyamines on growth,toxicity, and toxin profile of dinoflagellate Alexandrium minutum

The effect of exogenous polyamines (cadaverine, putrescine, norspermidine, spermidine, and spermine) on the growth, toxicity, and toxin profile of the dinoflagellate Alexandrium minutum T1 was examined. It was found that cadaverine at concentrations of 0.1-2.0 mumol/L enhanced the growth of A. minutum T1. Putrescine and norspermidine at a low level (0.1 mumol/L) also promoted the algal growth. Spermidine depressed the algal growth. However, the cell toxicity levels of A. minutum T1 cultured with or without cadaverine, putrescine, norspermidine, and spermidine were almost the same. The toxic components of A. minutum T1 were GTXs 1-4 only, and GTXs 1 and 4 were predominant (74.6 +/- 7.1%) in all cultures. On the other hand, spermine did not effect the growth of A. minutum T1, though it decreased the cell toxicity and the ratio of GTX 2 + GTX 3 (15.0 +/- 6.6%).