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.

Actions executed toward obtaining a reward are frequently associated with the probability of harm occurring during action execution. Learning this probability allows for appropriate computation of future harm to guide action selection. Impaired learning of this probability may be critical for the pathogenesis of anxiety or reckless and impulsive behavior. Here we designed a task for punishment probability learning during reward-guided actions to begin to understand the neuronal basis of this form of learning, and the biological or environmental variables that influence action selection after learning. Male and female Long-Evans rats were trained in a seek-take behavioral paradigm where the seek action was associated with varying probability of punishment. The take action remained safe and was followed by reward delivery. Learning was evident as subjects selectively adapted seek action behavior as a function of punishment probability. Recording of neural activity in the mPFC during learning revealed changes in phasic mPFC neuronal activity during risky-seek actions but not during the safe take actions or reward delivery, revealing that this region is involved in learning of probabilistic punishment. After learning, the variables that influenced behavior included reinforcer and punisher value, pretreatment with the anxiolytic diazepam, and biological sex. In particular, females were more sensitive to probabilistic punishment than males. These data demonstrate that flexible encoding of risky actions by mPFC is involved in probabilistic punishment learning and provide a novel behavioral approach for studying the pathogenesis of anxiety and impulsivity with inclusion of sex as a biological variable.

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Recent clinical and preclinical research suggests that cannabidiol (CBD) and Δ9-tetrahydrocannabinol (Δ9-THC) have interactive effects on measures of cognition; however, the nature of these interactions is not yet fully characterized. To address this, the effects of Δ9-THC and CBD were investigated independently and in combination with proposed therapeutic dose ratios of 1:1 and 1:3 Δ9-THC:CBD in adult rhesus monkeys (n=6) performing a stop signal task (SST). Additionally, the development of tolerance to the effects of THC on SST performance was evaluated by determining the effects of acutely administered Δ9-THC (0.1-3.2 mg/kg), during a 24-day chronic Δ9-THC treatment period with Δ9-THC alone or with CBD. Results indicate that Δ9-THC (0.032 - 0.32 mg/kg) dose-dependently decreased ‘go’ success but did not alter ‘go’ reaction time or stop signal reaction time (SSRT); CBD (0.1-1.0 mg/kg) was without effect on all measures and, when co-administered in a 1:1 dose-ratio, did not exacerbate or attenuate the effects of Δ9-THC. When co-administered in a 1:3 dose-ratio, CBD (1.0 mg/kg) attenuated the disruptive effects of 0.32 mg/kg Δ9-THC but did not alter the effects of other Δ9-THC doses. Increases in ED50 values for the effects of Δ9-THC on SST performance were apparent during chronic Δ9-THC treatment, with little evidence for modification of changes in sensitivity by CBD. These results indicate that CBD, when combined with THC in clinically available dose-ratios does not exacerbate and, under restricted conditions, may even attenuate Δ9-THC’s behavioral effects.

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Cyclic fatigue growth rates in R‐curve ceramics have been observed to depend very strongly on the maximum applied stress intensity, Kmax, and only weakly on the stress intensity range, Δ This behavior is rationalized through measurement of crack wake shielding characteristics as a function of these fatigue parameters in a gas‐pressure‐sintered silicon nitride. In particular, evidence for a mechanical equilibrium between shielding accumulation by crack growth and shielding degradation by frictional wear of sliding interfaces is found for steady‐state cyclic fatigue. This equilibrium gives rise to a rate law for cyclic fatigue. The data suggest that the accumulation process is the origin of the strong Kmax dependence, and that the degradation process is the origin of the weak Δ dependence. These features are shown to be related to the “cyclic”R‐curve and to the cyclic crack opening displacement, respectively.