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Biomedical subjects

P W Moore

Publications and source records attributed to P W Moore.

26 records · Page 2Linked to original sources
PubMed1984

Receiving beam patterns and directivity indices of the Atlantic bottlenose dolphin Tursiops truncatus.

The receiving beam patterns of an Atlantic bottlenose dolphin was measured in both the vertical and horizontal planes for frequencies of 30, 60, and 120 kHz. Measurements in the vertical plane were performed by training the dolphin to rotate on its side and station on a vertically oriented biteplate device. A signal source was positioned 3.5 m directly in front of the animal on an arc while the position of a broadband noise source was varied in azimuth along the arc, with the animal stationed at the origin of the arc. Using a go/no-go response procedure, the masked threshold of the dolphin was determined by varying the intensity of the noise source via a tracking method of stimulus presentation, for different azimuth's of the noise source. Measurements in the horizontal plane were obtained with the dolphin stationing on a horizontal biteplate. Two masking noise sources, projecting equal levels of uncorrelated noise, were located at +/- 20 degrees on either side of the arc midpoint. The levels of the noise source were held constant and the masked thresholds determined by varying the level of the signal source while positioned at different azimuths along the arc. Results indicated that maximum sensitivity in the vertical plane (the major axis of the beam) occurred between 5 degrees and 10 degrees above the midline of the animal's mouth and that the beam patterns were not symmetrical about the major axis. The sensitivity dropped off more quickly with increasing angle above the head than below. The beam patterns in the horizontal plane were directed forward and were fairly symmetrical about the midline of the animal's body.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

The critical interval in dolphin echolocation: what is it?

A backward masking function relating target detection to masker delay was generated for a bottlenosed dolphin in an active echolocation target detection task. The masker was triggered by each outgoing echolocation click and could be temporally adjusted from coincidence with the target echo to delays of 700 microseconds. The animal reported target condition using a go/no-go response procedure. A modified method of constants was used to present the four masking delay intervals. Results indicated that 700- and 500-microseconds delays had little effect on target detection. However, as the delay was reduced to 100 microseconds, detection dropped to chance performance. The calculated 70% detection threshold corresponded to a delay of 265 microseconds. The results are discussed in support of the view that time separation pitch (TSP) may be an analytic mechanism used by the dolphin to discern various within-echo target attributes rather than an analytic mechanism for determining target range.

Animals↗
PubMed1984

Technetium-99 in generator systems.

Technetium-99m solutions always contain Tc-99. The amount varies considerably, depending on production methods and conditions, generator performance, and the time between production or separation and use. There is increasing evidence that labeling and imaging with some radiopharmaceutical kits is adversely affected when the Tc-99 exceeds certain amounts. The sensitivity of particular kits to Tc-99 depends on the ligand, the amount of usable Sn2+, and the ratio of Tc to ligand. Although Tc-99 formed during production is removed in the final steps of generator manufacture, some may appear in early extractions in the solvent extraction process. If elution or extraction efficiencies are high, any Tc-99 is reduced within about two elutions to an insignificant level that is maintained in subsequent elutions. If efficiencies are below about 40%, however, the ratio of Tc-99 to Tc-99m increases with each elution.

Drug Contamination↗