Highly Complex Magnetic Microstructures in Hierarchically Phase Separated AlCo(Cr)FeNi High-entropy Alloys

The hierarchical microstructures of high-entropy alloys (HEAs) can result in highly complex magnetic textures and properties. Here, we use high spatial resolution correlative magnetic, structural and chemical imaging to investigate magnetic textures in phase separated AlCoxCr1 – xFeNi (x = 0.5 and 1) HEAs. The AlCoFeNi HEA, which contains nm-sized A2 precipitates in a B2 matrix, supports large magnetic domains with small-angle magnetization variations. In contrast, the AlCo(Cr)FeNi HEA, which undergoes hierarchical phase separation, contains an unexpected distribution of magnetic vortices within individual A2 precipitates in a weakly ferromagnetic B2 host, in addition to weakly ferromagnetic or nonmagnetic B2 precipitates in large magnetic domains of the A2 phase, as well as Fe-Co-rich inter-phase A2 regions that have strong magnetization. The coercivity is attributed to a complicated magnetization reversal process, which includes the successive reversal of the magnetic vortices. These results provide important insight for the rational design of HEAs with unique and tailored magnetic properties.

Interrelated Effects of Dilantin and Electroconvulsive Shock upon One-Trial Reversal Learning in White Rats

The purpose of this study was to isolate the effect of convulsions from electroconvulsive shock and to study the differential effects upon learning by white rats of 20 successive reversal problems. Convulsion is effectively controlled and prevented by the pharmacological pretreatment with Dilantin. Analysis indicates that convulsions and not the cranial electro-shock of 35 Ma at 0.2-sec. durations are responsible for the learning decrement that ensues. Also, Dilantin, if not followed by electroconvulsive shock may produce some slight detrimental effect on subsequent learning as well.

Relative Effects of Scopolamine and Electroconvulsive Shock upon Habit Reversal in White Rats

30 adult male white rats were equally divided into control, scopolamine, and electroconvulsive shock groups to learn 20 successive reversal problems in an E-maze for water after 23 ½ hr. of deprivation. The noncorrection method was used. After 1 mo. of preliminary training, each scopolamine animal received an intraperitoneal injection of 1 mgm of scopolamine hydro-bromide per kgm of body weight while each in the shock group was given an ECS of 35 mA for .2 sec. at the end of every 10 daily trials. When a rat obtained 9 correct of 10 trials, the goal was switched to the opposite side of the maze. Controls were much superior to both experimental groups. While scopolamine animals experienced more detrimental effects initially, they caught up with the shock group and finally became superior. This shift is interpreted in terms of building tolerance to scopolamine and increasing anxiety to shock as effects of differential treatments accumulated.

Successive Visual Reversal Learning in Rats as a Function of Amount of Training per Reversal and Reduced Spatial Cues

An experiment is reported which examined the effects of varying amounts of training per reversal over successive brightness discrimination reversals in rats, in a situation which reduced visual cues to spatial position. The results were similar to those of studies showing that amount of training affects successive reversal improvement on spatial problems but no differences were observed as a result of varying the cues for spatial position. The latter finding failed to confirm the result of a recent experiment in which a learning criterion was employed rather than a fixed-trials procedure.

The Effect of Reduced Spatial Cues on the Learning of Successive Visual Reversals

The performance of rats over 12 brightness discrimination reversals was studied under two experimental conditions. Under one condition all visual cues external to the apparatus were eliminated so that only the relative positions of the discriminanda could serve as a visual cue to spatial position. Under the other condition all visual cues to position were eliminated. Under the former condition performance deteriorated with successive reversals but under the latter condition performance improved. Implications of these results for theories of successive reversal improvement were discussed and two possible explanations were suggested.