Correcting magnetic probe perturbations on current density measurements of current carrying plasmas.

A method to infer the current density distribution in the current sheath of a plasma focus discharge from a magnetic probe is formulated and then applied to experimental data obtained in a 1.1 kJ device. Distortions on the magnetic probe signal caused by current redistribution and by a time-dependent total discharge current are considered simultaneously, leading to an integral equation for the current density. Two distinct, easy to implement, numerical procedures are given to solve such equation. Experimental results show the coexistence of at least two maxima in the current density structure of a nitrogen sheath.

Effects of relaxation training on fear and arousal during in vivo exposure to a caged snake among DSM-III-R simple (snake) phobics.

Eight pairs of DSM-III-R snake phobic subjects (Ss) were exposed to a caged snake while seated in front of a package-conveyor apparatus during eight 4-minute trials. Heart rates and skin-conductance levels were recorded before and during each of the eight trials. Self-reports of fear were obtained after each trial. One S in each pair controlled the conveyor on alternating trials. One subject (S) in each pair had received a representative regimen of relaxation training beforehand. Heart-rate decreased more in Ss controlling the conveyor than in their yoked partners. Ss who had received relaxation training showed lower heart-rate change, lower skin-conductance change, and lower self-reports of fear after the exposure trials. Relaxed Ss also moved the snake closer to themselves than did unrelaxed subjects on some trials.

Control and attention during exposure influence arousal and fear among insect phobics.

Heart beats, skin conductance, and subjective fear levels were recorded among eight pairs of DSM-III-R spider-phobic subjects (Experiment 1) and among eight pairs of DSM-III-R cockroach-phobic subjects (Experiment 2) who were exposed simultaneously to an approaching specimen during eight 4-minute trials. Control over the approach of the specimen alternated between subjects over trials. On different trials, both subjects were instructed either to attend closely to the features of the specimen or to attend closely to their bodily fear reactions. Among spider-phobic subjects (Experiment 1), Self-Control over the specimen produced higher skin conductance during exposure than did Partner-Control over the specimen; instructions to attend closely to the features of the specimen produced higher skin-conductance than did instructions to attend closely to one's bodily fear reactions. Among cockroach-phobic subjects (Experiment 2), Self-Control over the specimen produced higher skin conductance and higher self-reported fear than did Partner-Control over the specimen during the early exposures. Instructions to attend closely to the specimen produced higher skin conductance and higher self-reported fear throughout the experiment and higher heart rates early during the experiment than did instructions to attend to one's bodily reactions. Empirical generalizations based on these data are intended as contributions toward a fund of experimental information that, in due course, will be used to conceptualize the means by which exposure to feared stimuli leads to fear reduction.

Saliency metric for subadditive dissimilarity judgments of rectangles.

Previous findings that dissimilarity judgments for rectangles are strongly subadditive, that qualitative individual differences are always present, and that four-parameter psychophysical maps can reproduce the average ratings (Schönemann & Lazarte, 1987) are replicated. However, the present study in addition suggests that the metric for bounded response transformation, previously used to restore additivity of responses, has a modest effect on the fits of the psychophysical maps. The differential weighing of the coordinates already incorporates segmental subadditivity predictions into the maps. In fact, the psychophysical maps define a subadditive saliency metric that depends on assigning larger weights to larger coordinates. This constraint on the weights of these maps, together with the response times, allows us to identify a strategy shift when subjects respond to two classes of stimulus pairs: For rectangle-rectangle pairs, subjects center on the shape and size of the rectangles; for square-rectangle pairs, the focus is on height and width.