No abstract

Pesticides released into the environment may pose both ecological and human health risks. Governments set the regulations and guidelines for the allowable levels of active components of pesticides in various exposure sources, including drinking water. Several pesticide risk indicators have been developed using various methodologies, but such indicators are seldom used for the selection of pesticides to be included in national regulations and guidelines. The aim of the current study was to use risk indicators for the selection of pesticides to be included in regulations and guidelines. Twenty-four risk indicators were created, and a detection rate was defined to judge which indicators were the best for selection. The combination of two indicators (local sales of a pesticide for the purposes of either rice farming or other farming, divided by the guideline value and annual precipitation, and amended with the scores from the physical and chemical properties of the pesticide) gave the highest detection rates. In this case study, this procedure was used to evaluate 134 pesticides that are currently unregulated in the Japanese Drinking Water Quality Guidelines, from which 44 were selected as pesticides to be added to the primary group in the guidelines. The detection probability of the 44 pesticides was more than 72%. Among the 102 pesticides currently in the primary group, 17 were selected for withdrawal from the group.

No abstract

It has been proposed that a long-period stacking ordered (LPSO) structure is responsible for the excellent mechanical properties of lightweight alloys of MgZnRE (RE: rare earth elements) system. The phase separation of the metastable hexagonal close-packed (hcp) phase in the MgYZn alloy was simulated by means of the phase-field method to discuss the mechanism of formation of the LPSO structure. Near the Mg-corner of the MgYZn ternary system, metastable spinodal decomposition occurs before conventional spinodal decomposition, i.e., the supersaturated solid solution of Mg7 at% Y7 at% Zn alloy separates into two phases: Mg12 at% Y and Mg17 at% Zn. The resulting microstructure has a lamellar morphology, elongated along the [0001] direction of the hcp phase, with a wavelength of ³7 nm. The calculated orientation of the lamellar is completely different from that of the LPSO structure. Therefore, it is difficult to explain the formation of the LPSO structure directly in terms of a spinodal decomposition of the hcp phase in the MgYZn ternary system.

No abstract