Prenatal cocaine exposure and neurobehavioral development: How subjects lost to follow-up bias study results

Ninety-four prenatally cocaine-exposed and 50 non-cocaine-exposed infants were enrolled at birth and seen at 3,6, and 12 months. Applying a recently developed model (Cicchetti&Nelson, 1994) produced four independent groups: those infants assessed at birth only (n=61), those returning for at least one (n=29) or two (n=15) assessments after birth, and those returning for all three (n=35). Among those infants having all follow-up assessments, cocaine-exposed infants showed significantly lower psychomotor performance on the Bayley Scales of Infant Development (BSID) than did non-exposed infants. Results approached statistical significance for mental development. Except for birthweight (cocaine-exposed infants weighed significantly less), none of a wide range of maternal, perinatal, or neurobehavioral demographic variables biased study results or the generalization of findings to the total sample from those who returned for all visits.     

The impact of cognitive control on children’s goal monitoring in a time-based prospective memory task

The present study investigated whether developmental changes in cognitive control may underlie improvements of time-based prospective memory. Five-, 7-, 9-, and 11-year-olds (N = 166) completed a driving simulation task (ongoing task) in which they had to refuel their vehicle at specific points in time (PM task). The availability of cognitive control resources was experimentally manipulated by imposing a secondary task that required divided attention. Children completed the driving simulation task both in a full-attention condition and a divided-attention condition where they had to carry out a secondary task. Results revealed that older children performed better than younger children on the ongoing task and PM task. Children performed worse on the ongoing and PM tasks in the divided-attention condition compared to the full-attention condition. With respect to time monitoring in the final interval prior to the PM target, divided attention interacted with age such that older children’s time monitoring was more negatively affected by the secondary task compared to younger children. Results are discussed in terms of developmental shifts from reactive to proactive monitoring strategies.     

Analysis of intrinsic diffusivities in multicomponent alloys

In this letter we consider the intrinsic diffusivities in a multicomponent random alloy in terms of the ratios of atom-vacancy exchange frequencies. Using the exact sum rule due to Moleko and Allnatt, which relates phenomenological coefficients in the multicomponent random alloy, we deduce an exact relationship between the intrinsic diffusivities and the ratios of the exchange frequencies. We exemplify the finding with a consideration of binary and ternary random alloys. We show that the new relationship should be robust enough for employment in multicomponent alloys showing non-ideality.     

Distortion analysis of magnetic excitation – a novel method for non-destructive evaluation of depth of surface-hardening in ferritic steels

The influence of ferritic steel samples with different case-depths on the distortion behaviour of magnetic excitation voltage has been investigated. The systematic changes in the height and position of the peak and the trough on the ((dV_E/dt) vs. V_T) profile (distortion analysis of the magnetic excitation, DAME profile) reflect the difference in the magnetization process and hence the effect of distortion of V_E in samples with different case-depths. This study shows the potential of this simple DAME method for evaluation of ferromagnetic steel components.     

Long-term natural ageing of a dissociated dislocation in a Cu-13.43 at.% Al alloy

The nature of impurity-dislocation interactions is one of the key questions governing the strength and plasticity of solid-solution materials. To investigate the influence of impurities on the mechanical properties of intermetallic NiAl, the electronic structure and energy of NiAl with a <100>{010} edge dislocation and transition-metal impurities was calculated using the real-space tight-binding linear muffin-tin orbital method. The localized electronic states, appearing in the core of the dislocation, are found to lead to strong impurity-dislocation interactions via two mechanisms: firstly, chemical locking, due to strong hybridization between impurity electronic states and dislocation localized states; secondly, electrostatic locking, due to long-range charge oscillations caused by the electron localization in the dislocation core. The results obtained explain qualitatively why the solid-solution hardening effect in NiAl correlates with the electronic structure of impurities rather than with size misfit, as expected according to traditional views.     

Diffusion kinetics for divacancies in the bcc lattice

In this letter we employ high-precision Monte Carlo simulations to investigate tracer diffusion kinetics for diffusion via divacancies in the bcc lattice. We utilize the mechanisms originally identified by Mehrer in which the divacancy can move by nearest-neighbour jumps with stable first-nearest-neighbour, second-nearest-neighbour and fourth-nearest-neighbour configurations of the divacancy. The tracer correlation factor and the 'impurity-form' correlation factor were found to be some 4-6% lower than those found by the matrix method. The tracer diffusion data and isotope effect for sodium were revisited in terms of monovacancy and divacancy contributions. The main change is a revision upwards from 0.55 to 0.61 of the j K kinetic factor for divacancies.     

Real temperature of nanoparticles in electron microscope beams

Abstract

This Letter presents a solution of the problem of the real temperature of nanoparticles under conditions of electron microscope beam irradiation. It is shown that the average temperature of the nanoparticles (NPs) may increase to several hundred degrees depending on contact conditions with the substrate, the intensity of the beam and the size of the NPs. The temperature increases with NP size a according to the dependence: T α a² for sufficiently small particles.     

The kinetics of infralow-frequency viscoelastic internal friction induced by irreversible structural relaxation of a metallic glass

This letter presents the results of internal-friction measurements of Co 70 Fe 5 Si 15 B10 metallic glass at temperatures 400K h T h 700K and frequencies 0.01 Hz h f h 0.05Hz. It is shown that Maxwellian viscoelastic damping is predominant in this case. The nature of this damping is determined by irreversible structural relaxation. The kinetic relaxation law is derived.     

Determination of electrostatic characteristics at a 24°, [001] tilt grain boundary in a SrTiO3 bicrystal by electron holography

The electrostatic potential and associated space charge across a 24°, [001] tilt boundary of SrTiO₃ ceramic have been determined using electron holography. The results reveal a positive charged interface with a negative space charge on either side. The form of the double Schottky barrier and the local charge-density distribution at the interface are derived from the results.     

Structural and thermal investigations of a high-strength Cu-Zr-Ti-Co bulk metallic glass

Cu 55 Zr 30 Ti 10 Co 5 bulk metallic glass exhibits a high compressive fracture strength of 2.31 GPa and Young's modulus of 130 GPa, values that are higher than those of other Cu- and Zr-based metallic glasses. The addition of Co to the ternary Cu-Zr-Ti alloy stabilizes the supercooled liquid. On heating, the Cu 55 Zr 30 Ti 10 Co 5 metallic glass devitrified and formed an intermediate intermetallic compound prior to reaching equilibrium by diffusion-controlled growth at constant nucleation rate. In the fully annealed state the structure consists of the equilibrium Cu 10 Zr 7 phase with the slightly reduced lattice parameters a = 0.933 nm, b = 0.928 nm and c = 1.254 nm and a small fraction of an unidentified phase.