A case is presented of postirradiation atypical fibroxanthoma of the skin, metastatic to cervical lymph node, in a young female. Although such skin tumors characteristically have a malignant microscopic appearance, and although they occasionally recur following surgical excision, they have previously been noted for their consistently benign clinical behavior. This is thought to be the second recorded instance of metastasis from a n atypical fibroxanthoma of skin.
The effects of environment on cyclic and static fatigue behavior were investigated with hot-pressed silicon nitride materials. Tests were conducted at ambient temperature on standard compact tension specimens, and a dc electric potential technique was used to monitor crack lengths in situ. The results indicate that the environmental sensitivity of our materials under both cyclic and static loading mirrors that of durable glasses in static fatigue. The materials were most sensitive to water in the environment, while changes in pH had no significant effect in the range tested. In addition, NH, was much less reactive with our materials than with vitreous SO,. In some cases, the intergranular glass appears to be the site of environmental interaction. Evidence was also found that cyclic fatigue is not simply a manifestation of static fatigue. Cyclic fatigue was seen to occur in the absence of measurable static fatigue, and the data indicate that the mechanism of cyclic fatigue involves damage to the crack wake shielding zone.
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