A two-platform task reveals a deficit in the ability of rats to return to the start location in the water maze.

The ability of rats to return to the start location was examined with a 4-arm radial water maze. The task required rats to find 2 hidden platforms in sequence. Rats were released from 1 of 3 arms and there was a platform located in the fourth arm. Once a rat found this platform, a 2nd platform was raised in another location, which was either the start location, for 1 group, or another fixed location, for a control group. Across 3 experiments, all rats learned the location of the 1st fixed platform in 80 to 120 trials. However, rats had difficulty finding a 2nd platform if it was at the start location. Control groups revealed that rats could learn 2 platform locations and that the difficulty in learning to return to the start location did not seem to be attributable to its aversive nature. In separate groups, exposure to the start location was increased by starting the rats from an initially stable platform. Rats still did not readily learn to return to the start location. The authors suggest that start location, when varied, cannot readily be used to define the location of a hidden platform. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Numerical Modeling of Bolted Lap Joint Behavior

Nonlinear finite-element models are developed that predict the load-elongation behavior of conical-head bolted lap joints, and the load-elongation predictions are compared with experimental test data. The study is conducted for several panel thicknesses with three fastener sizes and three panel materials. The model load-elongation predictions are in excellent agreement with experimental test data. Model parameters, such as part discretization, material model selection, sliding interface friction coefficients, and convergence tolerances, are discussed. A means of inducing clamp in the joint is also developed. The results show that nonlinear finite-element analysis may reliably predict the behavior of conical-head bolted joints.     

Retarding effect of surface base compensation on degradation of noise characteristics of BiCMOS BJTs

Hot carrier degradation of 1/f noise characteristics of bipolar junction transistors is found to be substantially reduced by arsenic surface compensation of the base region, in agreement with former reports on the improvement in reliability of such devices, inferred from their static characteristics studies.     

Fracture mechanics models applied to delayed failure of LVL beams

Several theories for modelling fracture and slow growth of a crack in wood have been developed. The various models may be differentiated by the specifically regarded stress levels, failure mechanisms and averaging procedures. This paper deals with the application of viscoelastic fracture mechanics models to predict delayed failure of a timber element in bending. Simulations are compared to experimental results of bending tests carried out on LVL (Laminated Veneer Lumber) notched beams. This analysis emphasizes the influence of the geometry and of the size of the beam as well as of the damage area on the delayed failure.     

Evidence for the involvement of tyrosine-69 in the control of stereospecificity of porcine pancreatic phospholipase A2

We have studied the role of Tyr-69 of porcine pancreatic phospholipaseA₂ in catalysis and substrate binding, using site-directed mutagenesis.A mutant was constructed containing Phe at position 69. Kineticcharacterization revealed that the Phe-69 mutant has retainedenzymatic activity on monomeric and micellar substrates, andthat the mutation has only minor effects on k_cat and K_m. Thisshows that Tyr-69 plays no role in the true catalytic eventsduring substrate hydrolysis. In contrast, the mutation has aprofound influence on the stereospecificity of the enzyme. Whereasthe wild-type phospholipase A₂ is only able to catalyse thedegradation of sn-3 phospholipids, the Phe-69 mutant hydrolysesboth the sn-3 isomers and, at a low (1–2%) rate, the sn-1isomers. Despite the fact that the stereospecificity of themutant phospholipase has been altered, Phe-69 phospholipasestill requires Ca²⁺ ions as a cofactor and also retains itsspecificity for the sn-2 ester bond. Our data suggest that inporcine pancreatic phospholipase A₂ the hydroxyl group of Tyr-69serves to fix and orient the phosphate group of phospholipidmonomers by hydrogen bonding. Because no such interaction canoccur between the Phe-69 side-chain and the phosphate moietyof the substrate monomer, the mutant enzyme loses part of itsstereospecificity but not its positional specificity.     

Impact of silicon nitride CESL on NLDEMOS transistor reliability

Aging of the linear drain current during OFF stress on a N-type lateral drain extended MOS is shown to be induced by the amorphous silicon nitride Contact Etch Stop Layer (CESL). A design of experiment on its PECVD conditions enables to demonstrate that the higher its Si-rich composition or at least of its interface, the higher the degradation. Supported by TCAD simulations, we propose a charge displacement model in the CESL that leads to the depletion of the extended drain region during stress explaining the on-resistance increase monitored by the linear drain current.     

Metamemory judgments of the origin and content of course information: Comparing text and lecture materials.

The accuracy and relations between students' specific and general knowledge of content and origin were examined. Students answered multiple-choice questions derived from the text, lecture, or both sources, decided whether each question originated from one of these sources or from their own conclusions, decided whether they had lecture information in their notes, and rated their confidence in these judgments. The three types of questions were equally difficult to answer but were significantly different in the accuracy and confidence of origin judgments, and confidence in the answers' correctness. Students' origin judgments were equivalent when they correctly and incorrectly answered questions. Students who knew fewer correct answers tended to be more confused about the origin of their knowledge. The dissociation between origin and content knowledge is discussed within M. K. Johnson and C. L. Raye's (see record 1981-06694-001) reality-monitoring model, with emphasis on the inference and retrieval processes involved in judging the origin of one's knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multi-vibrational hydrogen release: Physical origin of Tbd,Qbd power-law voltage dependence of oxide breakdown in ultra-thin gate oxides

In this work we report an experimental observation of the current dependence on the defect generation probability driving to breakdown. We propose the MVHR model (multi-vibrational hydrogen release) based on the multi-vibrational excitation of the Si–H bond stretching mode. By this way we explain the power-law dependence of charge and time to breakdown and highlight its limit on PMOS inversion.     

Robustness of a Spline Element Method with Constraints

The spline element method with constraints is a discretization method where the unknowns are expanded as polynomials on each element and Lagrange multipliers are used to enforce the interelement conditions, the boundary conditions and the constraints in numerical solution of partial differential equations. Spaces of piecewise polynomials with global smoothness conditions are known as multivariate splines and have been extensively studied using the Bernstein-Bézier representation of polynomials. It is used here to write the constraints mentioned above as linear equations. In this paper, we illustrate the robustness of this approach on two singular perturbation problems, a fourth order problem and a Stokes-Darcy flow. It is shown that the method converges uniformly in the perturbation parameter.