The effect of the dielectric properties of electrorheological fluids on electrorheology was investigated in DC electric fields by using both hydrous and anhydrous electrorheological fluids. The relaxation frequency, which is defined by a local maximum of the dielectric loss factor of an electrorheological fluid, was in the range from 100- whenever the electrorheological fluid had a large electrorheological effect. This effect increased with increasing difference between the dielectric constants below and above the relaxation frequency both for hydrous and anhydrous electrorheological fluids, when the relaxation frequency was in the range 100-. For the electrorheological fluid containing microcrystalline cellulose, the change of the rheology curve, namely the shear rate versus shear stress ( versus ) curve, with increasing adsorbed water content could be interpreted in terms of the relation between the shear rate and the polarization rate. The mechanism of electrorheology could also explain the effect of the current density on the ER effect.
Multi-walled carbon nanotubes (MWCNTs), dispersed in suspensions consisting mainly of individual tubes, were used for intratracheal instillation and inhalation studies. Rats intratracheally received a dose of 0.2 mg, or 1 mg of MWCNTs and were sacrificed from 3 days to 6 months. MWCNTs induced a pulmonary inflammation, as evidenced by a transient neutrophil response in the low-dose groups, and presence of small granulomatous lesion and persistent neutrophil infiltration in the high-dose groups. In the inhalation study, rats were exposed to 0.37 mg/m(3) aerosols of well-dispersed MWCNTs (>70% of MWCNTs were individual fibers) for 4 weeks, and were sacrificed at 3 days, 1 month, and 3 months after the end of exposure. The inhalation exposures delivered less amounts of MWCNTs into the lungs, and therefore less pulmonary inflammation responses was observed, as compared to intratracheal instillation. The results of our study show that well-dispersed MWCNT can produce pulmonary lesions, including inflammation.
Since nanoparticles easily agglomerate to form larger particles, it is important to maintain the size of their agglomerates at the nano-level to evaluate the harmful effect of the nanoparticles. We prevented agglomeration of nickel oxide nanoparticles by ultrasound diffusion and filtration, established an acute exposure model using animals, and examined inflammation and chemokine expression. The mass median diameter of nickel oxide nanoparticle agglomerates suspended in distilled water for intratracheal instillation was 26 nm (8.41 nm weighted average surface primary diameter). Male Wistar rats received intratracheal instillation of nickel oxide nanoparticles at 0.1 mg (0.33 mg/kg) or 0.2 mg (0.66 mg/kg), and were dissected 3 days, 1 week, 1 month, 3 months, and 6 months after the instillation. The control group received intratracheal instillation of distilled water. Three chemokines (cytokine-induced neutrophil chemoattractant-1 (CINC-1), CINC-2alphabeta, and CINC-3) in the lung tissue and bronchoalveolar lavage fluid (BALF) were determined by quantitative measurement of protein by ELISA. Both CINC-1 and CINC-2alphabeta concentration was elevated from day 3 to 3 months in lung tissue and from day 3 to 6 months in BALF. On the other hand, CINC-3 was elevated on day 3 in both lung tissue and BALF, and then decreased. The total cell and neutrophil counts in BALF were increased from day 3 to 3 months. In lung tissue, infiltration of mainly neutrophils and alveolar macrophages was observed from day 3 to 6 months in alveoli. These results suggest that CINC was involved in lung injury by nickel oxide nanoparticles.
Metal nanoparticles play an important role in chemical vapor deposition (CVD) synthesis of carbon nanotubes because nanoparticles not only catalyze the nanotube growth but also determine the structural characteristics of the nanotubes. We report on the synthesis of single-wall carbon nanotubes (SWNTs) on the basis of the gas-phase reaction of colloidal solutions of metal nanoparticles containing Co and Mo. The colloidal solution of the nanoparticles is prepared by a reverse micelle method and injected into a furnace, where the solvent serves as the carbon source while the nanoparticles act as the catalyst. We have found that addition of a small amount of thiophene leads to formation of the SWNTs. The formation mechanism of the SWNTs is discussed by comparing the present CVD and laser-ablation methods.
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