Derivation of strain hardening in cyclic loading from that in tensile loading

The micromechanical model of extrusion formation in a single crystal under stress-controlled loading in high-cycle fatigue is reviewed. In the present letter, the microstress and strain fields of a single crystal under a high-amplitude fatigue are calculated by the boundary element method. Based on Schmidt's law, the resolved shear stress to activate or to cause the continuation of slip in a slip system is taken to depend on the amount of slip in that system. The cyclic strain hardening is calculated from the experimental tensile stress-strain curve. This calculated cyclic strain hardening is compared with the experimental cyclic hardening. Good agreement is shown.     

Intrinsic factor controlling the deformation and ductile-to-brittle transition of metallic glasses

The energetic driving force and resistance for shearing and cracking in metallic glasses (MGs) are quantitatively evaluated. A universal thermodynamic criterion is proposed for better understanding the intrinsic correlations between fracture toughness and Poisson’s ratio, the competitions between various deformation modes and the ductile-to-brittle transition in MGs and other materials. A new cooperation parameter δ is also introduced to depict quantitatively the relative propensity of shearing versus cracking. This work could provide insights into the long-standing issues of deformation mechanisms of glassy materials, and be helpful in searching for ductile and tough MGs.     

Solubility criterion for sequential disordering in metal-metal multilayers upon solid-state reaction

An n-body Ni-Ti potential is derived and applied in a molecular dynamics simulation to study the maximum supersaturated solubility of the terminal solid solutions and solid-state reaction in a Ni/Ti bilayer. It reveals that during interfacial reaction of the Ni/Ti bilayer the Ti lattice reaches its maximum solubility by dissolving Ni earlier than Ni does through dissolution of Ti, which results in a sequential disordering of first Ti and then Ni, although Ti has a higher melting point than Ni. In the Ni-Zr, Ni-Mo and Ni-Ta systems, however, the Ni lattice collapses more rapidly because it reaches a maximum solubility earlier than its partners, which have higher melting points than Ni. A solubility criterion is thus relevant for all the above cases; the lower the maximum solid solubility the less stable is the lattice of the metal upon solid-state reaction.     

Surface effect on the screw dislocation mobility over the Peierls barrier

The effect of the image force on the Peierls stress (τ _p ) of a screw dislocation below a free surface is studied via a self-consistent semidiscrete variational Peierls–Nabarro model. The consequence of reduction in elastic energy and increase in stacking fault energy by the presence of the free surface is found to additively increase the Peierls stress (τ _p ). This model gives a physical interpretation of the same tend observed in a recent molecular dynamic study, while previous continuum analysis predicted the opposite.     

Perceptual negativity predicts greater reactivity to negative events in daily life

Reinforcement sensitivity theory includes the idea that people differ in their sensitivity to negative events, but relevant process-based assessments have not been developed. The present studies assessed sensitivity to negative events in terms of the extent to which negative word stimuli were perceived to be larger than neutral word stimuli. There was a general tendency to overestimate the size of negative relative to neutral words, but individuals differed substantially in this form of what is termed perceptual negativity. Of more importance, two studies (total N = 151) found systematic relationships between individual differences in perceptual negativity and reactivity to negative events in daily diary protocols. Study 1 found that within-person variations in the occurrence of daily negative events undermined goal-related optimism to a greater extent at higher, relative to lower, levels of perceptual negativity. Study 2 conceptually replicated this interaction in the context of within-person associations between the occurrence of daily negative events and antisocial behavior. These findings are important in advancing reinforcement sensitivity theory, in operationalizing a particular component of it, and in extending it to reactivity processes in daily life.     

Adaptive midlife defense mechanisms and late-life health

A growing body of research suggests that personality characteristics relate to physical health; however, this relationship has primarily been tested in cross-sectional studies that have not followed the participants into old age. The present study utilizes data from a 70-year longitudinal study to prospectively examine the relationship between the adaptive defense mechanisms in midlife and objectively assessed physical health in late life. In addition to examining the direct effect, we test whether social support mediates this relationship. The sample consisted of 90 men who were followed for over seven decades beginning in late adolescence. Health ratings from medical records were made at three time points (ages 70, 75, and 80). Defense mechanisms were coded from narratives by trained independent raters (Vaillant, Bond, & Vaillant, 1986). Independent raters assessed social supports between ages 50 and 70. More adaptive defenses in midlife were associated with better physical health at all three time points in late life. These relationships were partially mediated by social support. Findings are consistent with the theory that defense maturity is important for building social relationships, which in turn contribute to better late-life physical health. Psychological interventions aimed at improving these domains may be beneficial for physical health.     

Analytical Problems and Suggestions in the Analysis of Behavioral Economic Demand Curves

Behavioral economic demand curves (Hursh, Raslear, Shurtleff, Bauman, & Simmons, 1988) are innovative approaches to characterize the relationships between consumption of a substance and its price. In this article, we investigate common analytical issues in the use of behavioral economic demand curves, which can cause inconsistent interpretations of demand curves, and then we provide methodological suggestions to address those analytical issues.

We first demonstrate that log transformation with different added values for handling zeros changes model parameter estimates dramatically. Second, demand curves are often analyzed using an overparameterized model that results in an inefficient use of the available data and a lack of assessment of the variability among individuals.

To address these issues, we apply a nonlinear mixed effects model based on multivariate error structures that has not been used previously to analyze behavioral economic demand curves in the literature. We also propose analytical formulas for the relevant standard errors of derived values such as P _max, O _max, and elasticity. The proposed model stabilizes the derived values regardless of using different added increments and provides substantially smaller standard errors. We illustrate the data analysis procedure using data from a relative reinforcement efficacy study of simulated marijuana purchasing.     

Discovery and a Preliminary Study of the Parallel Lines Illusion Change Effect

The parallel lines illusion change effect (discovered by the authors) was studied: When the plane of a parallel-lines illusion figure intersects obliquely with the line of vision and the figure is rotated, using an imaginary perpendicular line between the parallel lines as the axis, the smaller the intersecting angle, the more the illusory effect decreases, until it disappears. If the illusion figure is rotated and any one of the parallel lines is used as the axis, then the smaller the intersecting angle, the greater the illusory effect. The parallel lines illusion change effect may be applicable to the study of geometric-figure illusions.     

An Introduction to Normalization and Calibration Methods in Functional MRI

In functional magnetic resonance imaging (fMRI), the blood oxygenation level dependent (BOLD) signal is often interpreted as a measure of neural activity. However, because the BOLD signal reflects the complex interplay of neural, vascular, and metabolic processes, such an interpretation is not always valid. There is growing evidence that changes in the baseline neurovascular state can result in significant modulations of the BOLD signal that are independent of changes in neural activity. This paper introduces some of the normalization and calibration methods that have been proposed for making the BOLD signal a more accurate reflection of underlying brain activity for human fMRI studies.     

Mother–infant interaction improves with a developmental intervention for mother–preterm infant dyads

While premature infants have a high need for positive interactions, both infants and their mothers are challenged by the infant‘s biological immaturity. This randomized clinical trial of 198 premature infants born at 29–34 weeks gestation and their mothers examined the impact of the H-HOPE (Hospital to Home: Optimizing the Infant's Environment) intervention on mother–premature infant interaction patterns at 6-weeks corrected age (CA). Mothers had at least 2 social environmental risk factors such as minority status or less than high school education. Mother–infant dyads were randomly assigned to the H-HOPE intervention group or an attention control group. H-HOPE is an integrated intervention that included (1) twice-daily infant stimulation using the ATVV (auditory, tactile, visual, and vestibular-rocking stimulation) and (2) four maternal participatory guidance sessions plus two telephone calls by a nurse-community advocate team. Mother–infant interaction was assessed at 6-weeks CA using the Nursing Child Assessment Satellite Training–Feeding Scale (NCAST, 76 items) and the Dyadic Mutuality Code (DMC, 6-item contingency scale during a 5-min play session). NCAST and DMC scores for the Control and H-HOPE groups were compared using t-tests, chi-square tests and multivariable analysis. Compared with the Control group (n = 76), the H-HOPE group (n = 66) had higher overall NCAST scores and higher maternal Social-Emotional Growth Fostering Subscale scores. The H-HOPE group also had significantly higher scores for the overall infant subscale and the Infant Clarity of Cues Subscale (p < 0.05). H-HOPE dyads were also more likely to have high responsiveness during play as measured by the DMC (67.6% versus 58.1% of controls). After adjustment for significant maternal and infant characteristics, H-HOPE dyads had marginally higher scores during feeding on overall mother–infant interaction (β = 2.03, p = 0.06) and significantly higher scores on the infant subscale (β = 0.75, p = 0.05) when compared to controls. In the adjusted analysis, H-HOPE dyads had increased odds of high versus low mutual responsiveness during play (OR = 2.37, 95% CI = 0.97, 5.80). Intervening with both mother and infant is a promising approach to help premature infants achieve the social interaction patterns essential for optimal development.