PubMed · 4344175
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R M David, W M Portnoy. 1972. Insulated electrocardiogram electrodes.. https://doi.org/10.1007/bf02477385
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A force transducer with variable sensitivity and speed is described. Its moving element is a cantilever beam that projects vertically into a muscle bath. A brace constrains bending of the beam to a short, proximal "hinge." Rotation of the beam about the hinge is amplified 30-fold by an optical lever consisting of a laser diode beam reflected from a mirror on the cantilever to a photodiode pair. This design places the electrical components at a distance from the damp environment of the muscle bath. Large changes in sensitivity and speed can be obtained by substituting different cantilevers. Smaller changes can be made by varying the length of the hinge. A transducer with a 6-mm cantilever optimized for the study of single, skinned skeletal muscle fibers is described in detail. This device had a resonant frequency of 22 kHz and sensitivity such that the total root-mean-square noise in the circuit was more than 500-fold smaller than the expected maximum force. Variations of this device with orders of magnitude different sensitivities are also described.
An array of autonomous hydrophones moored in the eastern tropical Pacific was monitored for one year to examine the occurrence of whale calls in this region. Six hydrophones which recorded from 0-40 Hz were placed at 8 degrees N, 0 degree, and 8 degrees S along longitudes 95 degrees W and 110 degrees W. Seven types of sounds believed to be produced by large whales were detected. These sound types were categorized as either moan-type (4) or pulse-type (3) calls. Three of the moan-type calls, and probably the fourth, may be attributed to blue whales. The source(s) of the remaining calls is unknown. All of the call types studied showed seasonal and geographical variation. There appeared to be segregation between northern and southern hemispheres, such that call types were recorded primarily on the northern hydrophones in the northern winter and others recorded primarily on the southern hemisphere hydrophones in the southern winter. More calls and more call types were recorded on the eastern hydrophones than on the western hydrophones.
The transmission beam pattern of an echolocating harbor porpoise (Phocoena phocoena) was measured in both the vertical and horizontal planes. An array of seven Brüel and Kjaer 8103 hydrophones connected to an amplifier-line driver module was used to measure the beam patterns. The porpoise was trained to station in a hoop and echolocate a cylindrical target located at a range between 7 and 9 m while the array was located 2 m in front of the hoop. The 3-dB beamwidth in both the vertical and horizontal planes was the same at approximately 16 degrees and the beam was pointed toward the forward direction. The individual hydrophones in both the vertical and horizontal arrays measured signal waveforms that were similar throughout the 40-degree span of the array. The porpoise emitted signals with intervals that were 20 to 35 ms longer than the round trip travel time between the animal and the target. The average source level, peak frequency, and bandwidth were 157 dB, 128 kHz, and 16 kHz, respectively.