Biomedical subjects

J M Allin

Publications and source records attributed to J M Allin.

3 recordsLinked to original sources

PubMed2003

Design and construction of a low frequency wide band non-resonant transducer.

Commercially available low frequency transducers often have a bandwidth of much less than 100%. This paper reviews the current technology for low frequency transducer construction and presents a non-resonant design giving an improved low frequency performance. Small, undamped piezo-electric cubic elements of 2 mm side length are used which operate below their first resonance frequency. In construction, the elements are air-backed and the front faces are bonded to a thin membrane across the end of an enclosure of 15 mm diameter. Using a low frequency excitation signal which has little energy at the first resonance frequency of the elements, an operating frequency range of 200-500 kHz can be achieved. A single element behaves virtually as a point source, but by arranging an array of elements over the membrane, a more collimated beam profile is obtained.

Journal Article↗

PubMed1992

Repression-sensitization differences in recovery from learned helplessness.

The performance of repressors and sensitizers on a solvable anagram task was assessed after either a short delay (0 to 30 min) or a long delay (2 to 6 hr) following a standard learned helplessness induction. Results indicated that all subjects exposed to the learned helplessness induction exhibited performance deficits, compared with control subjects exposed to no induction. Furthermore, subjects who were tested after the short delay did not perform as well as subjects tested after a long delay. No difference in overall anagram performance was found between repressors and sensitizers. Consistent with theoretical predictions, however, the anagram performance of repressor subjects was significantly better in the long-delay than in the short-delay condition; this significant recovery effect between short- and long-delay conditions was not obtained for sensitizer subjects. Possible theoretical mechanisms for these effects and implications for future research are noted.

Adaptation, Psychological↗

PubMed1986

Persistence of learned helplessness in humans.

The duration of the effects of a common learned helplessness induction procedure, exposure to insoluble concept-formation problems, was assessed by varying the interval between the induction procedure and subsequent exposure to soluble anagrams. Participants tested immediately or 30 min after the induction procedure exhibited reliable helplessness deficits on all dependent measures. These effects, relative to the performance of a nonhelpless control group, were absent in subjects who experienced delays of 2 or 6 hr before anagram testing. The implications of these results for the development of more enduring helplessness effects and for the conducting of research into analogue intervention are discussed.

Achievement↗