Separation of bacterial spores from flowing water in macro-scale cavities by ultrasonic standing waves

The separation of micron-sized bacterial spores (Bacillus cereus) from a steady flow of water through the use of ultrasonic standing waves is demonstrated. An ultrasonic resonator with cross-section of 0.0254 m x 0.0254 m has been designed with a flow inlet and outlet for a water stream that ensures laminar flow conditions into and out of the resonator section of the flow tube. A 0.01905-m diameter PZT-4, nominal 2-MHz transducer is used to generate ultrasonic standing waves in the resonator. The acoustic resonator is 0.0356 m from transducer face to the opposite reflector wall with the acoustic field in a direction orthogonal to the water flow direction. At fixed frequency excitation, spores are concentrated at the stable locations of the acoustic radiation force and trapped in the resonator region. The effect of the transducer voltage and frequency on the efficiency of spore capture in the resonator has been investigated. Successful separation of B. cereus spores from water with typical volume flow rates of 40-250 ml/min has been achieved with 15% efficiency in a single pass at 40 ml/min.Comment: 11 pages, 6 figure

Using behavior-analytic implicit tests to assess sexual interests among normal and sex-offender populations

The development of implicit tests for measuring biases and behavioral predispositions is a recent development within psychology. While such tests are usually researched within a social-cognitive paradigm, behavioral researchers have also begun to view these tests as potential tests of conditioning histories, including in the sexual domain. The objective of this paper is to illustrate the utility of a behavioral approach to implicit testing and means by which implicit tests can be built to the standards of behavioral psychologists. Research findings illustrating the short history of implicit testing within the experimental analysis of behavior are reviewed. Relevant parallel and overlapping research findings from the field of social cognition and on the Implicit Association Test are also outlined. New preliminary data obtained with both normal and sex offender populations are described in order to illustrate how behavior-analytically conceived implicit tests may have potential as investigative tools for assessing histories of sexual arousal conditioning and derived stimulus associations. It is concluded that popular implicit tests are likely sensitive to conditioned and derived stimulus associations in the history of the test-taker rather than 'unconscious cognitions', per se

The propagation of N waves through turbulence : an experimental study

a model experiment to study the effect of atmospheric turbulence on sonic booms is reported. The model sonic booms are N waves produced by electric sparks, and the model turbulence is created by a plane jet. The important parameters are the waveform, peak pressure, and rise time because they determine the annoyance caused by sonic booms. Our experiment was designed so that the scale factor (approximately 10-4) relating the model turbulence to atmospheric turbulence was the same as that relating the model N waves to sonic booms. Results are reported for plane waves and are as follows. 1. The model experiment successfully simulates sonic boom propagation through the atmosphere. 2. Passage through turbulence almost always causes rise time to increase. 3. Average rise time is always increased by turbulence. 4. Average peak pressure is always decreased by turbulence

Experimental Investigations of Three-Dimensional Shock-Vortex Loop Interaction: Shock Reflection and Diffraction Phenomena

Estimation of the sonic boom and its effect are necessary to develop supersonic transport vehicles. The typical sonic boom is produced by the shock waves generated from a supersonic transport vehicle cruising at more than the speed of sound. The shock waves pass through the real atmosphere and reach ground level. The sonic boom pressure signatures are affected by atmospheric conditions such as turbulence, humidity, and temperature [1]. These atmospheric conditions cannot be controlled; however, they must be considered. Atmospheric effects have to be well understood because it is extremely important to accurately estimate the sonic boom magnitude at ground level