Associative deficit in recognition memory in a lifespan sample of healthy adults.

Advanced age is associated with decrements in episodic memory, which are more pronounced in memory for associations than for individual items. The associative deficit hypothesis (ADH) states that age differences in recognition memory reflect difficulty in binding components of a memory episode and retrieving bound units. To date, ADH has received support only in studies of extreme age groups, and the influence of sex, education, and health on age-related associative deficit is unknown. We address those issues using a verbal paired-associate yes–no recognition paradigm on a lifespan sample of 278 healthy, well-educated adults. In accord with the ADH, greater age was associated with lower hit and greater false alarm rates and more liberal response bias on associative recognition tests. Women outperformed men on recognition of items and associations, but among normotensive participants, women outperformed men only on memory for associations and not on item recognition. Thus, although supporting ADH in a large lifespan sample of healthy adults, the findings indicate that the effect may be partially driven by an age-related increase in liberal bias in recognition of associations. Sex differences and health factors may modify the associative deficit regardless of age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

GP-Gammon: Genetically Programming Backgammon Players

We apply genetic programming to the evolution of strategies for playing the game of backgammon. We explore two different strategies of learning: using a fixed external opponent as teacher, and letting the individuals play against each other. We conclude that the second approach is better and leads to excellent results: Pitted in a 1000-game tournament against a standard benchmark player—Pubeval—our best evolved program wins 62.4% of the games, the highest result to date. Moreover, several other evolved programs attain win percentages not far behind the champion, evidencing the repeatability of our approach.     

Spectral methods on triangles and other domains

This article shows how to obtain multidimensional spectral methods as a warped product of one-dimensional spectral methods, thus generalizing direct (tensor) products. This generalization includes the fast Fourier transform. Applications are given for spectral approximation on a disk and on a triangle. The use of the disk spectral method for simulating the Navier-Stokes equations in a periodic pipe is detailed. The use of the triangle method in a spectral element scheme is discussed. The degree of approximation of the triangle method is computed in a new way, which favorably compares with the classical approximation estimates.     

Oil-shale gasification by concentrated sunlight: An open-loop solar chemical heat pipe

Gasification of oil shales followed by catalytic reforming can yield synthesis gas, which is easily transportable and may also be used for producing liquid fuels. We report here on experiments performed at the Weizmann Institute's Solar Central Receiver involving the use of concentrated solar energy as the heat source for the gasification. A number of dual-axis tracking heliostat mirrors provided primary concentration, and compound parabolic concentrators (CPCs) were used for secondary concentration. In addition to being the first experimental study on this particular type of chemical storage of concentrated sunlight, new aspects of this work include demonstrations of the following:

1. (i)significantly higher synthesis gas yields than previously reported;

2. (ii) marked improvements in conversion efficiency in transparent reactors, as opposed to opaque reactors, both as fluidized beds, primarily due to better heat transfer;

3. (iii) a substantial increase in deliverable energy compared to the conventional retorting of oil shales, and considerable reduction in the resulting spent shale.

     

Two types of test-anxious students: Support for an information processing model.

The purpose of this research was to further investigate the information processing model suggested by Benjamin, McKeachie, Lin, and Holinger (1981) in explaining the poor academic performance of highly test-anxious students. Whereas previous studies pointing to deficits in the organization stage of processing mainly relied on self-reports, the first study of this research used a technique that enabled us to measure objectively the organization of course material by students in a nonevaluative situation. Results indicated that highly test-anxious students showed a disadvantage in organization of course material, in comparison with other students. In the second study, we investigated whether types of highly test-anxious students can be differentiated by their information processing skills. The first type includes those with good study habits who do not have problems in encoding and organizing the information but, rather, have a major problem in retrieval for a test. The second type includes those with poor study habits who have problems in all stages of processing. Such a distinction was supported by results comparing performance of these types of highly test-anxious students in an evaluative and a nonevaluative situation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Test of the cultural bias hypothesis: Some Israeli findings.

The major aim of this study was to examine the cross-cultural validity of the test bias contention, with particular concern for possible sociocultural group differences in the construct and predictive validity of college entrance scholastic aptitude tests in Israel. The analyses were based on the test scores of 1,538 Israeli college student candidates of varying ethnic group membership, applying for admission to a major Israeli campus. The psychometric properties of the test battery were compared by ethnic group via a variety of internal (factor structure, reliability, etc.) and external (predictive validity, homogeneity of regression, etc.) test bias criteria. On the whole, the data provided little evidence for differential construct or predictive validity of aptitude test scores as a function of ethnic group membership, thus lending a greater deal of generality to previous research on test bias, generally negating the cultural bias hypothesis. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dynamics of catalytic reactions and reactors

Heterogeneous catalytic reactions and catalytic reactors are known to exhibit complex dynamic behavior and significant progress has been made, in the past two decades, in understanding this complexity using the tools of nonlinear dynamics and advanced experimental methods. This article presents an overview of complex dynamic behavior in heterogeneous catalysis and points out their intriguing nature along with practical implications. The issues discussed are the source of oscillatory behavior, classification of complex motions, transitions to chaotic solutions and spatiotemporal patterns in reactors of various geometries.     

Signal transduction in human hematopoietic cells by vascular endothelial growth factor related protein, a novel ligand for the FLT4 receptor

We have recently identified a novel ligand of the vascular endothelial growth factor (VEGF) family termed VEGF-related protein (VRP), which specifically binds to the FLT4 receptor. To characterize the signaling events after VRP engagement of its cognate receptor in hematopoietic cells, a population of human erythroleukemia (HEL) cells, termed HEL-JW, expressing high levels of FLT4 receptor was isolated. Stimulation of HEL-JW cells with VRP alone and in combination with the c-kit ligand/stem cell factor increased cell growth. VRP induced tyrosine phosphorylation of various proteins, including the FLT4 receptor. Further characterization of these tyrosine phosphorylated molecules revealed that Shc, Grb2, and SOS form a complex with the activated FLT4 receptor. HEL-JW cells also expressed RAFTK, a recently identified member of the focal adhesion kinase family. RAFTK was phosphorylated and activated upon VRP treatment, and there was an enhanced association of this kinase with the adaptor protein Grb2. Furthermore, the c-Jun NH2-terminal kinase (JNK), involved in growth activation and shown to mediate RAFTK signaling in other cell types, was activated by VRP stimulation. We also observed that VRP treatment of HEL-JW cells resulted in the phosphorylation of the cytoskeletal protein paxillin. This treatment resulted in an increased association of paxillin with RAFTK, which was mediated by the C-terminal region of RAFTK. These studies indicate that VRP stimulation induced the formation of a signaling complex at its activated receptor as well as activation of RAFTK. VRP-mediated activation of RAFTK may facilitate signal transduction to the cytoskeleton and downstream to the JNK pathway in FLT4-expressing blood cells.     

Effective water diffusivity in deep-fat fried restructured potato product

Water diffusivity was determined for a restructured potato product undergoing deep-fat frying. Pre-fried product gel-strength, expressed by its deformability modulus, varied from 37 to 127 kPa and markedly affected the effective diffusion coefficients, ranging from 3.31 to 1.58 × 10⁻⁹ m² s⁻¹, respectively. Pre- and post-fried effective water diffusivity decreased with higher deformability modulus. Frying time reduced the effective water diffusivity only when the initial deformability modulus was higher than 52 and 79 kPa for 1 and 5 min, respectively. Oil uptake criterion was found to increase with the effective water diffusivity for frying durations of 1 and 5 min.     

Spallation as an effect of laser-induced shock waves

Spallation resulting from laser-driven shock waves in metallic foils was investigated and the various stages of material failure were identified. The very high strain rate (10⁷sec^–1 ) characteristic of these experiments sets our results apart from those obtained by high explosives or hypervelocity impact. Numerical hydrodynamic simulations of the phenomenon were developed and are shown to be in qualitative agreement with the experimental results.