Attenuation and enhancement of instrumental responding by signals for reinforcement on a variable interval schedule.

In three experiments we used pigeons responding on a variable interval schedule to examine the effects of signaling reinforcement on instrumental performance. Using a four-component multiple schedule, we found in Experiment 1 that when reinforcement was delayed by 0.5 s for two of the components, response rates were attenuated by signaling reinforcement relative to performance in the unsignaled delay condition. A delay of 3 s in the remaining two components resulted in an enhancement of responding when the delay was signaled. An enhancement of responding occurred when we used a scheduled 0.5-s delay when the procedure ensured that responding was prevented during the delay interval by extinguishing the keylight (Experiment 2) or by resetting the delay timer when responses were emitted during the delay (Experiment 3). These results are discussed with reference to the theories of signaling reinforcement during instrumental responding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fabrication of air-channel structures for microfluidic,microelectromechanical, and microelectronic applications

A method is presented for fabricating micro-air-channel structures encapsulated by a dielectric material using a sacrificial polymer based on polynorbornene (PNB) chemistry. A spin-coated film of PNB was patterned to define the exact geometry of the air-channels using conventional lithographic and etching techniques. The sacrificial polymer was encapsulated with a permanent dielectric material. The composite was then raised to elevated temperatures to produce gaseous products which permeate through the encapsulating material (SiO₂ , SiN_x or other polymer) leaving behind minimal solid residue. Air-channels integrated with metal interconnections can be formed via a Damascene, or in-lay process. After patterning the sacrificial polymer, copper was electroplated, followed by encapsulation with the dielectric. Various issues pertaining to the processing steps have been investigated and are discussed, such as type of encapsulants, feasible air-channel sizes, and processing conditions. Such air-channel structures are believed to have potential applications in microelectronics, displays, printers, multilevel wiring boards, microscale chemical reactors on a chip, and microelectromechanical devices     

Schedules of reinforcement as determinants of human causality judgments and response rates.

Experiments examined the effect of relationships between a response and an outcome on human judgments of causal effectiveness. In Experiment 1, the time between outcomes obtained on a variable ratio (VR) schedule became the intervals for a yoked variable interval (VI) schedule. Response rates were higher on the VR than on the VI schedule. In Experiment 2, the number of responses required per outcome on a VR schedule were matched to that on a master VI 20-s schedule. Both ratings of causal effectiveness and response rates were higher in the VR schedule. In Experiment 3, tandem VI fixed-ratio (FR) schedules produced higher rates and judgments than equivalent conjunctive VI FR schedule. In Experiment 4, a VI schedule with a reinforcement requirement for a short interresponse time (IRT) produced higher rates and judgments than a simple VI schedule. These results corroborate the view that schedules are a determinant of both response rates and causal judgments. Few current theories of causal judgment predict this pattern of results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rotation and Concentration Effects in High-Shear Ultrafiltration

A parametric waste-specific study was conducted to assess the effects of membrane rotational speed and feed oil concentration on the pressure independent “limiting” flux in a high-shear rotary ultrafiltration (HSRUF) system. The limiting flux data were adequately described by the thin-film model. The transition from pressure dependent to pressure independent behavior occurred at lower oil concentrations as membrane rotational speed was decreased and pressure was increased due to an increase in the thickness of the solute boundary layer at the membrane surface. A gel layer oil concentration, OCgel, of 39% was reported, and OCgel was determined to be constant with respect to average transmembrane pressure and membrane rotational speed. The solute mass transfer coefficient increased with membrane rotation and was greater than reported for conventional ultrafiltration systems. The greater mass transfer characteristics determined for the HSRUF system were attributed to the efficient delivery of “cleaning energy” to the membrane surface due to the effective decoupling of feed pressurization from recirculation∕hydraulic turbulence.     

Characteristics of garden dormice that contribute to their capacity as reservoirs for lyme disease spirochetes

To describe the contribution of garden dormice to the epizootiology of Lyme disease, we compared their reservoir capacity for these pathogens to that of other sympatric hosts. Garden dormice are trapped most abundantly during early spring and again during midsummer, when their offspring forage. They are closely associated with moist forests. Garden dormice serve as hosts to nymphal ticks far more frequently than do other small mammals. Spirochetal infection is most prevalent in dormice, and many more larval ticks acquire infection in the course of feeding on these than on other rodents in the study site. Mature dormice appear to contribute more infections to the vector population than juveniles do. Replete larval ticks generally detach while their dormouse hosts remain within their nests. The population of garden dormice contributes five- to sevenfold more infections to the vector population than the mouse population does. Their competence, nymphal feeding density, and preference for a tick-permissive habitat combine to favor garden dormice over other putative reservoir hosts of Lyme disease spirochetes.     

A fast CFAR detection space-time adaptive processing algorithm

All of the conventional CFAR detection algorithms that use space-time processing involve a time-consuming matrix-inversion operation. Based on today's technology, this computational complexity sometimes makes the full-rank solution difficult to realize. In this correspondence, a CFAR detection algorithm, which does not need a matrix inversion, is developed by an adaptation and extension of Hotelling's principal-component method studied recently by Kirsteins and Tufts (1994). Finally, the performance of the new CFAR test statistic is analyzed, and the effect of the rank reduction on performance is evaluated for an example scenario