Occurrence of paralytic shellfish poison (PSP)-producing dinoflagellate Alexandrium tamarense in Hiroshima Bay, Hiroshima Prefecture, Japan, during 1993-2004 and its PSP profiles

To assess levels of shellfish intoxication by the paralytic shellfish poison (PSP)-producing dinoflagellate Alexandrium tamarense, potential health risks to human shellfish consumers and the possible need for regulatory intervention, yearly variations of maximum cell density of this species were examined from 1993 to 2004 in Kure Bay and Kaita Bay, which are located within Hiroshima Bay, Hiroshima Prefecture, Japan. The seawater temperature was determined concomitantly. In Kure Bay, maximum concentrations of 1,400 and 1,300 cells/mL at 0 and 5 m depths were observed on 21 and 24 April 1997. In Kaita Bay, remarkably high concentrations above 1,000 cells/mL of A. tamarense were observed in two out of three years investigated. These facts suggest that the environment in both bays is favorable for the propagation of A. tamarense. The temperature range at which the natural population of A. tamarense blooms was generally from 12 to 16 degrees C. Four strains (ATKR-94, -95, -97 and -01) from Kure Bay and one strain (ATKT-97) from Kaita Bay were established. The strain ATKR-94, cultured in modified SW-2 medium at 15 degrees C for 15 days, showed a specific toxicity of 33.8 x 10(-6) MU/cell. The toxins in all five strains exist almost exclusively as beta-epimers (C2 (PX2 or GTX8), GTX3, dcGTX3 and GTX4), which accounted for 54.9 to 73.0 mol% of the total. The corresponding a-epimers (C1 (PX1 or epi-GTX8), GTX2, dcGTX2 and GTX1) accounted for 6.0 to 28.9 mol%. The toxin profiles of ATKR-97 and ATKT-97 were characterized by unusually high proportions of low-potency sulfocarbamoyl toxin, which comprised 62.4 and 68.2 mol%, respectively, of total toxins. In the toxic bivalves, the low-toxicity sulfocarbamoyl components, major components of A. tamarense, were present in amounts of only a few percent, suggesting that in vivo conversion of PSP occurs after ingestion. A comparison of the toxin profiles of the causative dinoflagellate and contaminated bivalves showed that PSP components exist in the bivalves in the form of alpha-epimers, presumably owing to accumulation or storage of the toxins.     

Chlorine auto-doping by chloride vapor phase epitaxial growth of InP

Chlorine auto-doping phenomenon was found for the first time in InP epitaxial growth by using a PCl₃/InP/H₂ system. Chlorine atoms act as a donor in the epitaxial layer and the carrier concentration is dependent on the facet of InP substrate. The carrier concentration of the InP layer on ( 111)B facet was over 10³ times higher than that on (111)A substrate.     

Effect of cross-flow on the frequency of bubble formation from a single-hole nozzle

Bubble formation from a single-hole nozzle placed vertically upward in a rotating water bath was investigated using a high-speed video camera. Air was used as the working gas. The measured values of the frequency of bubble formation, f _B, were compared with those observed in a stationary bath, f _B0. The velocity of cross-flow, ν_θ, affected the bubble formation significantly when it exceeded a critical value, ν_θc . The ratio of f _B to f _B0 was unity for ν_θ≦ν_θc , but it changed in a complex manner for ν_θ>ν_θc . In the latter case, when the air flow rate Q _g was relatively low, f _B/f _B0 became larger than unity irrespective of Q _g, and an empirical correlation of f _B/f _B0 was proposed as a function of ν_θ and the inner diameter of the nozzle, d _ni. As the gas flow rate increased, f _B/f _B0 decreased monotonically and became smaller than unity, and an empirical correlation of f _B/f _B0 was derived as a function of Q _g, ν_θ, and d _ni. These empirical correlations could approximate the measured values of f _B/f _B0 within a scatter of −15 to +20 pct.     

Evaluation of Tensile Strength and Fracture Toughness of Yttria-Stabilized Zirconia Polycrystals with Fracture Surface Analysis

The tensile strength of yttria-stabilized tetragonal zirconia polycrystals (Y-TZPs) was measured and the fracture surfaces were analyzed with the scanning electron microscope and X-ray microanalyzer. The fracture origins of the pressureless-sintered samples were voids or inclusions such as A1₂O₃, A1₂O₃ with SiO₂, and cubic-ZrO₂, while the fracture origins of the hot isostatically pressed samples were inclusions; no voids were detected at fracture origins. The higher strengths of the hot isostatically pressed samples versus those of the pressureless-sintered samples were consistent with the change in fracture origins. The fracture toughness of the samples calculated from the tensile strength and analysis of the fracture origins was 3.4 to 3.7 MPa √m. These values are lower than those measured with the SEPB method. These discrepancies might be caused by the difference in the state of the fracture origin and its neighborhood, such as the size of the fracture origin and interaction between two surfaces in the precrack.     

Improvement of fatigue-crack growth resistance by grain-boundary reaction precipitates at high temperature

Effects of grain-boundary reaction precipitates on fatigue-crack growth rate were investigated using austenitic 21 wt% Cr-4 wt% Ni-9wt% Mn heat-resisting steel at 973 K in air. Grain boundaries were serrated by-the grain-boundary reaction precipitates. The crack growth rate was considerably decreased by these precipitates, especially at low crack growth rates. Fatigue cracks extended to the serrated grain boundaries or to the interface between the grain-boundary reaction nodule and the grain. Therefore, the cracks grew along zigzag paths, and brittle intergranular fracture was inhibited. The decrease in the fatigue-crack growth rate was explained by these changes in fracture mode.     

Intrahypothalamic, but not hippocampal, administration of muscimol suppresses hyperglycemia induced by hippocampal neostigmine in anesthetized rats

We investigated the effects of intrahypothalamic or hippocampal injection of GABA receptor agonists on hyperglycemia induced by hippocampal neostigmine. Prior to the injection of neostigmine (50 nmol) into the hippocampus (HPC), muscimol (0.01-1 nmol) or baclofen (1 nmol) was injected into the bilateral ventromedial hypothalamus (VMH). Muscimol suppressed the hyperglycemia in a dose-dependent manner, but baclofen affected it only minimally. In contrast, neither hippocampal muscimol (1 or 2.5 nmol) nor baclofen (1 nmol) suppressed the hippocampal neostigmine-dependent hyperglycemia. Intrahypothalamic muscimol (1 nmol) also decreased the changes in hepatic venous plasma glucagon and epinephrine significantly. These results indicate that intrahypothalamic muscimol suppresses hyperglycemia caused by cholinergic neurons originating from the HPC, indicating existence of the location specificity.     

A Binomial Error Model with a Truncated Latent Distribution and its Application

Behaviormetrika - A binomial error model which has a truncated beta distribution as its latent trait distribution is proposed for the analysis of test scores. This model can be used when the...     

The relative neighborhood graph for mixed feature variables

The rectangular influence graph (RIG) is presented as an extension of the relative neighborhood graph (RNG). The RNG is an efficient tool for analyzing the clustering of multidimensional feature vectors when all the features are quantitative. The RIG is a similar tool that can accommodate feature vectors some of whose components are qualitative. We show that the RIG is a superset of the Gabriel graph with respect to any Minkowski metric.As tools to analyze interclass structure, the interclass RIG (IRIG) and the mutual neighborhood graph (MNG) are presented. These graphs can be used to reduce the training set in the design of piecewise linear classifiers. The MNG leads also to a sufficient condition for the linear separability between classes.     

Magnesium and lanthanide ions promoted electrochemical coupling of aliphatic esters and tetrahydrofuran for the synthesis of acetals

Electroreduction of aliphatic esters in THF was found to be promoted by the catalytic amount of porphine-magnesium(II) complexes and afforded 2-alkoxytetrahydrofuran derivatives, the coupling products between alkoxide anions formed by the electroreduction of aliphatic esters and THF cation generated by the anodic oxidation of the solvent (THF). In this reaction, chlorophyll a extracted from Trifolium repens L was remarkably effective. In addition, lanthanide metal(III) ions such as samarium trichloride were also found to be effective for the electroreduction of aliphatic esters.