Correlates of Within-Person (Across-Occasion) Variability in Reaction Time.

A total of 420 adults between 18 and 91 years of age carried palm pilot (Palm M100; PalmOne, Milpitas, CA) devices and performed several reaction time trials when prompted at random times during the day. On the average, within-person variability in median reaction time from one occasion to the next was nearly the same magnitude as the between-persons variability in across-occasion mean reaction time. Analyses controlling the variation in one variable when examining relations involving the other variable suggested that an individual's mean reaction time is a more powerful predictor of relations with age and with the level of various cognitive abilities than his or her across-occasion SD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is There Anything Special About the Aging of Source Memory?

A battery of cognitive tests designed to measure the constructs of episodic memory, perceptual speed, fluid ability, executive functioning, and vocabulary was administered to 330 adults between the ages of 18 and 89. Each participant also performed 4 different tasks designed to assess source memory. Structural equation modeling was used to evaluate the validity of a source-memory construct and to explore the relation of the source-memory construct to age and to the other cognitive variables. The variance common to the source-memory variables was strongly related to other cognitive abilities, suggesting that source memory may not have discriminant validity, and there were only small unique age-related effects on the source-memory construct after the influence of other abilities was considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chronic toxicological evaluation of dietary NovaSil Clay in Sprague-Dawley rats

NovaSil (NS) clay, a common anti-caking agent in animal feeds, has been shown to sorb aflatoxins in the GI tract and diminish their bioavailability and adverse effects in short-term animal studies. Based on this evidence, it is hypothesized that clay-based enterosorption of aflatoxins may be a useful strategy for the prevention of aflatoxicosis in human populations. However, the potential toxicity of long-term dietary exposure to NS has not been determined. In this research, 5-6-week-old male and female Sprague-Dawley rats were fed rations containing 0, 0.25, 0.5, 1.0, or 2.0% (w/w) levels of NS for 28 weeks. Analysis of the NS showed negligible levels of dioxin and furan contaminants. Total feed consumption, cumulative feed consumption, body weight, total body weight gain, feed conversion efficiency, cumulative feed conversion efficiency, and relative organ weights were unaffected in either sex at the doses tested. No NS-dependent differences in relative organ weights or gross or histopathological changes were observed. Analysis of hematological parameters, clinical chemistry, and selected vitamin and mineral levels revealed isolated significant differences between some treatments and control groups (mean corpuscular hemoglobin, serum Ca, serum vitamin A, and serum Fe). However, the differences observed in each case were not dose-dependent. These results suggest that dietary inclusion of NS at levels as high as 2.0% (w/w) does not result in overt toxicity. These findings (as well as others) support the use of NS clay for dietary intervention studies in human populations at high risk for aflatoxicosis.     

A Method for Measuring the Thermal Diffusivity of Intermediate Thickness Surface Absorbing Samples and Obtaining the Ratio of Anisotropy by the Converging Wave Flash Method

The converging thermal wave, flash technique for measuring thermal diffusivity is suitable for use on samples that are sufficiently thick or thin in comparison to the annular heat source, to be described by a three-dimensional or two-dimensional approximation of the heat conduction equation, and sufficiently absorbing to ensure generation of a heat source at the surface. However, samples of intermediate thickness, which lie between these regimes, cannot be analyzed. In this article, heat diffusion in the samples of varying thicknesses is modeled, and a semi-analytic expression is used to describe the dimensionality of any thickness, allowing the converging wave method to be extended to intermediate thickness samples. Applying the analysis to anisotropic samples, a method is proposed to find the anisotropy ratio of the in-plane to perpendicular-to-plane diffusivity using the converging wave method.     

THREE-DIMENSIONAL INTEGRATION IN MICROELECTRONICS: MOTIVATION, PROCESSING, AND THERMOMECHANICAL MODELING

Three-dimensional integration (3D-I) of multiple layers of active devices into a single chip is opening up opportunities for disruptive microelectronic, optoelectronic, and microelectromechanical systems. Integrated circuit (IC) designers are driving 3D-I for new products, which in turn is providing opportunities in process technology and modeling. This article reviews the status of 3D-I and describes some research opportunities for both process engineers and modeling and simulation engineers. The opportunities discussed center around “stacking” and interconnecting multiple active and/or passive layers or strata of traditional planar designs into “hyperfunctional” 3-D systems. The focus is on electrical 3D-ICs, using BCB as the adhesive to bond wafers, and copper-based, through-silicon-vias or through-strata-vias (TSVs) for interconnection. However, much of the material applies to other approaches to 3D-I and other 3-D systems. Both recently established methods and advanced research efforts are discussed for process technology and thermomechanical modeling and simulation of Cu-based TSVs and BCB-based bonding.     

Comparison of Metals Leaching from CCA- and ACQ-Treated Wood in Simulated Construction and Demolition Debris Landfills

Pressure-treated wood is often disposed of in landfills in the United States, very frequently in construction and demolition (C&D) debris landfills. C&D debris landfills in many states are not equipped with liner systems to protect groundwater. With the voluntary withdrawal of chromated copper arsenate (CCA) treated wood for most residential applications in January 2004, copper-based wood preservatives, including alkaline copper quaternary (ACQ), are more widely used. To evaluate the impact of metal losses from ACQ-treated wood disposed in C&D debris landfills and compare to those of CCA-treated wood under similar conditions, leachates from three simulated C&D debris landfills (lysimeters) were collected and analyzed for over a period of one year. The wood component in one lysimeter (the control lysimeter) contained pallet wood; the second lysimeter contained CCA-treated wood, and the third contained ACQ-treated wood. Each lysimeter was buried in an active landfill for temperature control. Several batch leaching tests [including the standardized toxicity characteristic leaching procedure (TCLP) and the synthetic precipitation leaching procedure (SPLP)] were also conducted for comparison purposes. Although the two lysimeters containing treated wood had elevated copper concentrations within the waste matrix, the concentration in the leachate samples from these lysimeters was below detection for Cu (<4?μg/L) throughout the duration of the experiment, likely a result of precipitation as copper sulfide mineral in the reducing conditions of the simulated C&D landfills. As expected, the lysimeter containing CCA-treated wood showed elevated concentrations of arsenic and chromium, with maximum concentrations of 1.16 mg/L and 0.2 mg/L respectively. Greater amounts of boron (B) leached from ACQ-treated wood than CCA-treated wood or pallet wood debris. The results suggest that copper leaching will not be a major concern upon the disposal of ACQ-treated wood in C&D debris landfills. Arsenic leaching from CCA-treated wood remains a concern for unlined C&D debris landfills.     

Modeling dissolution and spreading of Bi–Sn alloy drops on a Bi substrate

A dissolutive wetting model is employed to study the dynamics of axisymmetric Bi–Sn alloy drops spreading on Bi. The liquid drop surface is assumed to be a spherical cap, while the isothermal model for solute transport with simplified hydrodynamics computes the evolution of the solid–liquid interface. Simulations are performed on a millimeter scale to model experiments. The evolution of the drop radius, the flow and solute concentration profiles near the triple junction, the contact line mobility relationship, the apparent contact angles and the shape of the dissolution boundary during spreading are investigated as functions of initial Sn concentration, model parameters and initial conditions. Good agreement is obtained when compared with the experiments for the cases where diffusion is the dominant transport mode. The shape of the solid–liquid interface is predicted better when the initial experimentally determined dissolution boundary is implemented as the starting point of the subsequent simulation.     

Re-evaluating split-fovea processing in word recognition: Effects of retinal eccentricity on hemispheric dominance.

Several studies have claimed that hemispheric asymmetries affect word recognition right up to the point of fixation because each fovea is split precisely at its vertical midline and information presented either side of this midline projects unilaterally to different, contralateral hemispheres. To investigate this claim, four-letter words were presented to the left or right of fixation, either close to fixation entirely in foveal vision (0.15, 0.25, and 0.35 degrees from fixation) or further from fixation entirely in extrafoveal vision (2.00, 2.10, and 2.20 degrees from fixation). Fixation location and stimulus presentation were controlled using an eye-tracker linked to a fixation-contingent display and performance was assessed using a forced-choice task to suppress confounding effects of guesswork. A left hemisphere advantage was observed for words presented in extrafoveal locations but no hemisphere advantage (left or right) was observed for words presented in any foveal location. These findings support the well-established view that words encountered outside foveal vision project to different, contralateral hemispheres but indicate that this division for word recognition occurs only outside the fovea and provide no support for the claim that a functional split in hemispheric processing exists at the point of fixation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A study on the conversion of trona to sodium bicarbonate

The deactivation model was used to explain kinetics underlying the conversion reaction of trona to NaHCO₃ (sodium bicarbonate). The model showed good agreement with the experimental data obtained from the conversion reaction of trona to NaHCO₃. It gave the value of 0.94 as an average correlation coefficient with the experimental data. However, at lower temperature, the model was in poor agreement with the data. This would be related to the structural variation of trona particles at the lower temperature. A trona particle is initially nonporous and then it begins to crack. This structural variation creates more surface area for the reaction with CO₂ and water vapor. However, at the lower temperature, the fissures on the surface of the particles are not fully developed during the beginning of the reaction. As a consequence, the level of the conversion of trona at the lower temperature is low during the beginning of the reaction and the time to approach the complete conversion is shorter as temperature increases. However, since the deactivation model does not include the term articulating the degree of the structural variation during the reaction, it does not fit well to the experimental data at the lower temperature. The deactivation rate constant, k_d is strongly temperature dependent and the change of the slope suggests the reaction mechanism changes as the reaction temperature increases.     

Capitalizing on one's advantages: Role of core self-evaluations.

The authors examined (a) whether core self-evaluations in adolescence and young adulthood predict income at midlife and (b) whether people with positive core self-evaluations are more likely to capitalize on advantages resulting from family socioeconomic status and academic achievement, resulting in even higher levels of income at midcareer. The sample consisted of participants from the National Longitudinal Survey of Youth, a national probability sample that first surveyed participants in 1979. The authors found that core self-evaluations and family socioeconomic status and academic achievement predict income and that, furthermore, high core self-evaluations enhance the benefits derived from these factors. Overall, it appears that individuals with positive core self-evaluations are particularly adept at translating early advantages into later economic success. (PsycINFO Database Record (c) 2010 APA, all rights reserved)