No abstract

The dissolution rates of rare earth oxides and two types of rare earth containing functional materials into water, saline solution, and Gamble's fluid were measured in order to evaluate the biological effects of rare earth-containing functional materials. The tested materials were yttrium, lanthanum, cerium and neodymium oxides, and neodymium-boron-iron magnet alloy (NdBFe) and lanthanum-mish-metal-nickel-cobalt (LmNiCo) hydrogen-containing alloy. The dissolution rates of the rare earth oxides were very low, resulting in concentrations of rare earth elements in the test solutions of the order of ppb. In the most extreme case, Gamble's fluid dissolved 1,400 times more of the rare earth oxides than pure water. Fairly high concentration of neodymium were found in the dissolving fluids, which means that trace neodymium present as an impurity in each rare earth oxide dissolved preferentially. For yttrium oxide, the ratio of neodymium to yttrium that dissolved in the saline solution was greater than 78,000 to 1, taking into account the amount of each that was originally present in the yttrium oxide.

Various applications of multiwalled carbon nanotubes (MWCNT) have been developed.One of these applications is an efficient sheet heating element that is woven from MWCNT-coated yarn. in this research, we assessed the exposure to MWCNT and/or the probability of particle release from broken MWCNT-coated yarn during the weaving process. This was accomplished using particle concentrations, microscopic observation, and carbon analysis. in the weaving process, neither an increase in the number of particles nor a difference in particle-size distribution was observed. in the scanning electron micrographic observation, nanosize MWCNT particles were not detected, but there were micron-size particles containing MWCNT as fragments of the yarn. Carbon analysis showed the concentration of micron-size particles containing MWCNT did not exceed 0.0053 mg-C/m 3 around the loom. This value was much lower than the respirable dust mass concentration. Most of micron-size particles seemed to originate from polyester yarn without MWCNT coating. it is recommended that workers use conventional (even not specialized for nanoparticles) personal protective equipment such as respirators and gloves to prevent exposure to respirable-size MWCNT-containing particles. The probability of MWCNT fall-off from the MWCNT-coated yarn was not detected by transmission electron microscopic observation of MWCNT-coated yarn before or after the weaving process.

In this study, "Argonsol" is de ned as an assembly of liquid or solid particles suspended in argon, just as an aerosol is a suspension in air. Argonsol can be generated by a nebulizer and fed into a plasma torch for measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). We have developed a new gas-conversion method, by means of a DMA, from normal aerosol to size-classi ed Argonsol for a chemical analysis using ICP-MS. A test aerosol containing lead as a typical toxic heavy metal was introduced into this system. With this system the size-related elemental concentration of lead nitrate particles in the range of 30 to 140 nm was measured. The sensitivity of this system is better than fg (10 ¡ 15 g) of lead in the total mass of particles introduced into ICP-MS. In principle, it is possible for our system to analyze all the elements that ICP-MS and/or ICP-AES can analyze.

No abstract