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The mechanism of pumping action caused by axially vibrating one of the seal faces with continuous parallel film thickness is clarified experimentally. The results obtained in the experiment confirm the theory developed in a previous investigation [11]. The fundamental design principles of mechanical seals are also described from the viewpoint of this pumping phenomenon.

Xanthine oxidase (XO) and xanthine dehydrogenase (XDH) were inactivated by incubation with nitric oxide under anaerobic conditions in the presence of xanthine or allopurinol. The inactivation was not pronounced in the absence of an electron donor, indicating that only the reduced enzyme form was inactivated by nitric oxide. The second-order rate constant of the reaction between reduced XO and nitric oxide was determined to be 14.8 +/- 1.4 M-1 s-1 at 25 degrees C. The inactivated enzymes lacked xanthine-dichlorophenolindophenol activity, and the oxypurinol-bound form of XO was partly protected from the inactivation. The absorption spectrum of the inactivated enzyme was not markedly different from that of the normal enzyme. The flavin and iron-sulfur centers of inactivated XO were reduced by dithionite and reoxidized readily with oxygen, and inactivated XDH retained electron transfer activities from NADH to electron acceptors, consistent with the conclusion that the flavin and iron-sulfur centers of the inactivated enzyme both remained intact. Inactivated XO reduced with 6-methylpurine showed no "very rapid" spectra, indicating that the molybdopterin moiety was damaged. Furthermore, inactivated XO reduced by dithionite showed the same slow Mo(V) spectrum as that derived from the desulfo-type enzyme. On the other hand, inactivated XO reduced by dithionite exhibited the same signals for iron-sulfur centers as the normal enzyme. Inactivated XO recovered its activity in the presence of a sulfide-generating system. It is concluded that nitric oxide reacts with an essential sulfur of the reduced molybdenum center of XO and XDH to produce desulfo-type inactive enzymes.

This is an analytical study of the mechanism of pumping action produced in two axially symmetrical disks. The disks have a continuous parallel film thickness between them, and one of them has a recess at the center and is subjected to a normal sinusoidal oscillation. It is found out that whether the pumping action is inward or outward depends upon a shift of phase between a variation of flow resistance due to a periodic fluctuation of the film thickness between seal faces and a variation of pressure in the recess.

The relationship between hydrogen states present in the vicinity of the fracture surface and hydrogen embrittlement susceptibility was investigated for ferrite-martensitic dual-phase steels. Hydrogen embrittlement susceptibility was evaluated in tensile tests based on the ratio of the fracture strength of hydrogen charged and not-charged specimens. Tensile tests at strain rates of 8.33x10[?]6 s[?]1 and 1.67x10[?]6 s[?]1 were conducted on specimens containing different amounts of hydrogen. The hydrogen states present near the fracture surface were analyzed by thermal desorption analysis just after the specimens fractured. The results indicated that hydrogen embrittlement susceptibility markedly increased as the amount of hydrogen increased. Additionally, only the specimen that fractured at the highest amount of hydrogen showed not only a lower temperature peak but also a higher temperature peak. Hydrogen embrittlement susceptibility also increased at slower strain rates, and also showed the higher temperature peak. The relationship between hydrogen states present in the vicinity of the fracture surface and mechanical properties indicated that the defects corresponding to higher temperature peaks probably increased hydrogen embrittlement susceptibility. Since microvoids at the crack tips were observed by SEM only in specimens that fractured at lower strain rates, the defects corresponding to higher temperature peaks were probably voids.