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Purification procedures for both multi-(MWNTs) and single-wall carbon nanotubes (SWNTs) are introduced in this paper. Intermediate stages in the purification procedure are monitored by scanning electron microscopy, which clearly shows the increase of the nanotube content with increasing purification. The magnetic properties are investigated by using electron spin resonance (ESR). Two kinds of samples are used in the ESR measurements for MWNTs and for SWNTs. One is dispersed in hexane to make loosely contacting tubules and the other is a dried-deposited tubule to realize a close contacting tubule state. By use of these samples, it is found that the ESR lineshape is closely related to the contact between nanotubes. The curved nature of the tube wall plays an important role in the explanation of the ESR properties.

The bifurcations to periodic and chaotic states in an all-optical bistable system proposed by Ikeda et at. have been observed. A single-mode optical fiber was used as a nonlinear medium in a ring cavity. The incident beam was the second harmonic of a pulse train from an actively mode-locked and Q-switched yttrium-aluminum-garnet laser whose cavity length was equal to one-half that of the ring cavity. The bifurcation to period-two state was clearly observed at a certain level of the incident power, and further increase in power resulted in a chaotic state.

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Serum antioxidant activity (AOA) was examined in 35 healthy subjects and 111 patients with chronic renal failure (CRF), consisting of 13 patients in the predialysis stage, 11 requiring the start of regular dialysis therapy (RDT) and 87 undergoing RDT. Serum AOA was determined by assaying serum activity to inhibit malondialdehyde (MDA) generation. AOA levels were significantly lower in CRF patients, and the lowest levels were noticed in patients with uremic symptoms requiring the start of RDT. These levels were restored to a subnormal level during RDT. Defective serum AOA appears to be an endogenous metabolic consequence in uremia. Sera with low AOA tended to show high MDA levels, indicating that patients with low serum AOA were susceptible to cellular injury by lipid peroxidation. It is proposed that defective serum AOA may contribute to a certain uremic toxicity through peroxidative cell damage.