PubMed · 7071370
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J C Chu, P H Bloch. 1982. A simulator-mounted three-dimensional contouring device.. https://doi.org/10.1148/radiology.143.2.7071370
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An ultrasonic interferometry method was designed to study sedimentation of particles in liquid. The method, based on A mode echography, measures the amplitude of ultrasonic waves reflected (echo E1) by a fixed interface I1 called "solid plate-sediment" interface formed when particles are sedimenting on a solid plate. The amplitude of the echo depends both on mechanical properties of the three media (solid plate, sediment and suspension) on the thickness of the sediment and on the presence of a second mobile interface I2 called "sediment-suspension" interface. In the first phase of sedimentation when the second interface is very close to the first, two reflected waves interfere. Then, in the second phase of sedimentation when the sediment is thick enough, the amplitude of the echo E1 depends only on the sediment and solid plate properties. The first phase will give information on the sedimentation rate of particles (SR). We have compared SR of particles determined by this method with SR measured in a cylindrical tube of the same geometry as the ultrasonic measurement cell and with theoretical values of the sedimentation rate given by theoretical models.
Moiré interference effects have been noted in gamma camera images for some time. Recent work has shown that the effects are still prevalent with the current generation of cameras, though apparently dependent upon collimator design. All previous work has been related to bar phantom images only. This paper also demonstrates a variety of moiré effects using the Anger "pie" phantom. Some of the principles underlying moiré interference as they apply to gamma cameras are given and possible uses of the effects are discussed, as well as the limitations they impose upon the use of certain test objects in routine quality assurance testing.
A laser controller that uses a fixed frequency clock and a digital rate-multiplying circuit to synchronize the triggering of a pulsed laser to the spinning of an analytical ultracentrifuge rotor has been designed. The circuit is simple, inexpensive, and virtually free of any adjustments. It tracks rotors undergoing full acceleration or deceleration. At constant rotor speed it provides triggering that is accurate and reproducible to better than 0.5 microseconds. The settings of this controller are independent of rotor speed over the full range of the ultracentrifuge.