Semi-solid rapid compression testing of spray-formed hypereutectic Al-Si alloys

The rheology of Al-30Si-5Cu and Al-30Si-5Cu-2Mg spray-formed alloys has been characterized after holding at various times and temperatures, using semisolid rapid compression to obtain load-displacement curves. Microstructures were examined after partial remelting and compression in an attempt to understand the flow behavior. The initial resistance to flow generally increased with holding time at temperature. This increase was attributed to the increased strength of a three-dimensional (3-D) solid silicon network present in these alloys in the semisolid state, with the initial resistance to flow smaller in the magnesium-containing alloys. With increased temperature, the initial resistance decreased due to increased liquid content and grain spheroidization. The viscosity vs shear rate response was studied using the approach of Laxmanan and Flemings. The materials shear thinned rapidly during the test conditions, in which the shear rate rapidly increased from approximately 2.5 to 92 s⁻¹. The results were fitted to a power-law model, and the viscosities showed a drop of approximately two to four orders of magnitude when extrapolated to a shear rate of 1000 s⁻¹ (a typical value in actual component manufacture). The rapid compression test, which is close to conditions present in component manufacture, was shown to have more in common with a shear rate jump experiment, rather than steady-state viscometry.     

State psychological association creates a postdoctoral residency and internship training program.

State psychological associations can respond to supply and demand problems for postdoctoral residencies and internships by creating statewide training programs. A state psychological association training model is presented. The Arizona Psychological Association (AzPA) created a nonprofit subsidiary corporation- the Arizona Psychology Training Consortium-to increase the number of high-quality training opportunities in Arizona. The structure and operation of the program are described. The training model emphasizes cultural diversity, psychotherapy, and independent practice. Members of the practice community in Arizona serve as supervisors, trainers, and mentors. From 2001 through 2006, 19 postdoctoral residents and 51 interns completed the program. AzPA has benefited from increased student involvement. Many residents and interns later became association members. Arizona can serve as a model for other states that wish to help their professionals in training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An experimental study of the flow of dry powders over inclined surfaces

The behavior of dry particulate solids during unconfirmed flow over inclined surfaces has been investigated. The motion of individual particles is found to depend strongly on the nature of the surface over which they flow. For smooth surfaces, flow occurs primarily by sliding at the surface, and little or no shear is introduced into the stream. In the case of highly roughened surfaces consisting of, for example, a stationary layer of the same particles, there appears to be no slip at the surface, and flow occurs entirely by shear within the flowing stream. Surfaces of intermediate roughness lead to flow in which both slip at the surface and shear within the bed contribute significantly.Velocity profiles have been measured experimentally under a variety of conditions, and the effects of such variables as roughness and inclination of the surface, depth of the flowing stream and particle size have been evaluated quantitatively. Empirical relationships have been obtained which describe the flow behavior in all cases studied.     

Neutrophil apoptosis is associated with a reduction in CD16 (Fc gamma RIII) expression

Resolution of inflammation involves removal of recruited neutrophils from inflamed sites via a noninflammatory mechanism, possibly involving neutrophil apoptosis and engulfment/phagocytosis by macrophages. In this study, we describe the reduction in surface expression (> 90%) of the neutrophil molecule Fc gamma RIII (CD16) during in vitro culture at 37 degrees C, which was found to be temporally associated with the appearance of neutrophils with apoptotic morphology during in vitro culture and inhibitable by granulocyte-macrophage colony-stimulating factor (GM-CSF), which postpones apoptosis in the neutrophil. By using dual fluorescence analysis, CD16 "low" expressing neutrophils showed reduced staining with the DNA-binding dye propidium iodide, suggesting that CD16 low expressing neutrophils were apoptotic. Separation of CD16 "high" and CD16 "low" expressing neutrophils by fluorescence-activated cell sorting revealed that morphologically apoptotic cells exhibited the CD16 low phenotype. We did not observe similar marked changes in expression of other neutrophil surface molecules (including other phosphatidylinositol (PI)-linked molecules), indicating that generalized loss of surface molecules does not occur during apoptosis. We believe this to be the first reported cell type-specific membrane alteration in a surface glycoprotein associated with apoptosis, suggesting that the program of cell death in the neutrophil, in addition to morphologic and nuclear changes, includes alterations in expression of surface receptors.     

Prediction of the Failure Time of Glass Fiber Reinforced Plastic Reinforced Concrete Beams under Fire Conditions

A model is proposed to predict the time to failure of reinforced concrete beams in a fire. The model is developed specifically to predict the lifetime of beams reinforced with glass fiber reinforced plastic rebar, but is applicable to beams with any form of reinforcement. The model is based on the calculations for flexural capacity and shear capacity of beams embedded within ACI design codes where time and temperature dependent values for rebar modulus and strength and concrete strength replace the static design values. The base equations are modified to remove safety factors and where necessary the temperature induced reductions in strength for concrete and steel are derived using the equations presented by EUROCODE 2. In order to validate the model it was used to predict the failure times of steel rebar reinforced beams that had been documented in the literature. There was excellent agreement between the model and the reported lifetimes for these conventional beams. The model was applied to predict the lifetimes of two beams that had been manufactured and tested for destruction in a fire by the research group. The model predicted that the failure mode of the beams would be because of rebar rupture as opposed to the design condition of concrete crushing and this was confirmed by the experimental test results. The model provided reasonable agreement with experimental results with a lifetime of 108?min predicted based on flexural failure and 94 and 128?min observed in the experiments.     

Real-time tool control and job dispatching in flexible manufacturing systems

A method of loading a set of tools to the different machining centres of a shop is presented, where each part visits only one of the machining centres for its entire processing. Any tools which are required but unavailable for the processing of a part are borrowed from other machining centres. As a real-time control, the tool-returning policies for those borrowed tools and the job-dispatching rules at the machining centres are evaluated to maximize the throughput performance of the shop. Some experimental results are provided.     

Microbiological characterization of randomly selected Portuguese raw milk cheeses with reference to food safety

Seventy raw milk cheeses made in different regions of Portugal, both hard and soft varieties, made with cow's, ewe's, or goat's milk or combinations of these, were sampled within their quoted shelf lives for microbiological safety. On the basis of the presence or numbers of Escherichia coli, E. coli O157, Staphylococcus aureus, Salmonella, and Listeria monocytogenes, cheeses were categorized as satisfactory, acceptable, unsatisfactory, or unacceptable and potentially hazardous. Twenty-two of the 70 cheeses were classified as satisfactory or acceptable. Thirty-seven of the cheeses were considered unsatisfactory because of the presence of E. coli, S. aureus, or both, while 11 of the cheeses were graded as unacceptable and potentially hazardous because of the presence of excessive numbers of S. aureus, E. coli, or L. monocytogenes and the presence of Salmonella in three of these. All cheeses graded as unacceptable and potentially hazardous were soft or semisoft cheeses made with ewe's and goat's milk, with the exception of two hard cheeses made with cow's milk. E. coli O157 was not detected in any of the cheeses. According to the present results, it seems that the presence or counts of pathogenic or indicator organisms in raw milk cheeses cannot be related to the processing conditions, milk type, or region of production.     

Wet Reflectors in Millimeter-Wave Radiometry-Expenrment and Theory

Microwave radiometers are often required to operate under all weather conditions, including those under which an exposed surface of the antenna system becomes wetted by rain. Here we discuss the special case of a wetted flat reflector, with energy at 20.60 and 31.65 GHz linearly and orthogonally polarized at an incidence angle of 45°. The brightness temperatures produced by the wet reflector are computed from conventional theory, and are measured for various thicknesses of water layer. Both theory and experiment show that the brightness temperatures produced by the wet reflector have the same behavior throughout a range of water-layer thicknesses. The impact of these results on design of radiometers for research and operational application is discussed.