Microprocessor-Based Control of an Ion Beam Deposition System

A microprocessor-based system with 32 A/D, 24 D/A, and 16 ac load controllers, has been designed and built to monitor and control an ion beam thin-film deposition system. The A/D and D/A channels have electrical isolation of 7.5 kV between channels and between input and output. The microprocessor system keeps the ion beam deposition parameters stable for extended periods of operation and it is proposed as a means to greatly simplify switching from one deposition species to another to grow thin multilayer or alloy films.     

The effect of penicillin on fatty acid synthesis and excretion inStreptococcus mutans BHT

Treatment of exponentially growing cultures ofStreptococcus mutans BHT with growth-inhibitory concentrations (0.2 μg/ml) of benzylpenicillin stimulates the incorporation of [2-¹⁴C] acetate into lipids excreted by the cells by as much as 69-fold, but does not change the amount of¹⁴C incorporated into intracellular lipids. At this concentration of penicillin cellular lysis does not occur. The radioactive label is incorporated exclusively into the fatty acid moieties of the glycerolipids. The increase in the radioactive content of the extracellular lipids reflects an actual net increase in the total fatty acid content as determined by a chemical assay. During a 4-hr incubation in the presence of penicillin, the extracellular fatty acid ester concentration (per mg cell dry weight) increases 1.5 fold, even though there is no growth or cellular lysis. No change is observed in the intracellular fatty acid ester content. An indication of the relative rate of fatty acid synthesis was most readily obtained by placingS. mutans BHT in a buffer containing¹⁴C-acetate. Under these nongrowing conditions free fatty acids are the only lipids labeled, a factor which simplifies the assay. The addition of glycerol to the buffer causes all of the nonesterified fatty acids to be incorporated into glycerolipid. The cells excrete much of the lipid whether glycerol is present or not. Addition of penicillin to the nongrowth supporting buffer system does not stimulate the incorporation of [¹⁴C]-acetate into fatty acids. However, if cells are exposed to penicillin in a growth-supporting medium and then are transferred to the nongrowing buffer system containing no penicillin, the previously exposed cells retain the ability to incorporate [¹⁴C]-acetate into fatty acid at a higher rate than untreated cells over a prolonged period of time. The stimulation of [¹⁴C]-acetate into fatty acids in this system parallels but is not dependent on the stimulation by penicillin of the incorporation of [¹⁴C]-glycerol into glycerolipid and lipoteichoic acid synthesis previously demonstrated by our laboratory. The material of this paper is part of a thesis to be submitted by J.L.B. in partial fulfillment of the requirements for the Ph.D. degree from the Department of Biochemistry, Temple University.     

Theoretical Analysis of the Fiber Pullout and Pushout Tests

The fiber pullout and pushout tests have been analyzed to predict the load-displacement behavior in terms of fiber/matrix interface parameters. The effects of residual axial strain in the fiber and fiber surface topography were included. The residual axial strain was found to be a significant parameter. It is shown that the interface failure can be progressive or catastrophic. In the case of a progressive failure of the interface, the load-displacement curve is nonlinear. The portion of the curve from above the first nonlinearity to near the peak load can be predicted in terms of parameters of the interface, viz., the friction coefficient, the radial stress at the interface, the fracture toughness of the interface, and the residual axial strain in the fiber. Values for these parameters can be obtained from a single loaddeflection curve. The peak load and load drop, which are usually reported, are found not to be directly relatable to any interface property, since the length of the last portion of the fiber to debond is influenced by end effects and hence not easily predicted. However, for data which describe the peak load as a function of initial embedded length, that factor can be eliminated and the data reduced to yield the relevant interface parameters. In pullout, the peak and friction loads saturate with large specimen thickness. Catastrophic failure is favored when the debond initiation load is high or when residual stress is low. Finally, a methodology to extract interface parameters from experimental data is suggested.     

Enhancing the construct validity of differential response latencies for personality test items.

Evaluated the effects of increasing scale reliability and of priming dimensional activation on the construct validity of personality test item differential response latencies. 93 undergraduates were computer-administered items from the 3 lengthened scales of the Personality Research Form. Findings show that differential response latencies can demonstrate remarkably strong evidence for their construct validity. In addition, the priming of personality traits may enhance the construct validity of their corresponding differential response latencies. Results support a model of test item responding where differential item response latencies reflect the interaction of an individual's schema with test item content. (French abstract) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Evidence for Remote Effects of Dreissenid Mussels on the Amphipod Diporeia: Analysis of Lake Ontario Benthic Surveys, 1972–2003

The status of invasive dreissenid mussels (Dreissena polymorpha and D. bugensis) and native amphipods (Diporeia spp.) in Lake Ontario was assessed in 2003 and compared with historical data. D. polymorpha (zebra mussels) were rarely observed in 2003, having been displaced by D. bugensis (quagga mussels). D. bugensis expanded its depth range from 38 m depth in 1995 to 174 m in 2003 and this dreissenid reached densities averaging 8,000/m² at all sites < 90 m. During the same time period, Diporeia populations almost completely disappeared from 0–90 m depth, continuing a declining trend from 1994–1997 reported in previous studies. The average density of Diporeia in the 30–90 m depth interval decreased from 1,380/m² to 63/m² between 1997 and 2003. Prior to 2003, areas deeper than 90 m represented a refuge for Diporeia, but even these deep populations decreased, with densities declining from 2,181/m2 in 1999 to 545/m2 in 2003. Two common hypotheses for the decline of Diporeia in the Great Lakes are food limitation and a toxin/pathogen associated with dreissenid pseudofeces. The Diporeia decline in deep waters preceded the expansion of D. bugensis to these depths, and suggests that shallow dreissenid populations remotely influence profundal habitats. This pattern of decline is consistent with mechanisms that act from some distance including nearshore dreissenid grazing and downslope transport of pseudofeces.