Tensile properties of precracked tempered martensitic steel specimens tested at ultralow strain rates in high-pressure hydrogen atmosphere

Tensile tests were performed on precracked Cr–Mo martensitic steel (C: 0.38, Si: 0.22, Mn: 0.84, P: 0.024, S: 0.021, Ni: 0.08, Cr: 1.11, Mo: 0.15, Cu: 0.12, Fe: bal. (wt%)) specimens at various strain rates (ranging from 6.5 × 10^?8 s^?1 to 1.0 × 10^?4 s^?1) in high-pressure (95 MPa) hydrogen and helium atmospheres. Irrespective of the strain rate, the tensile strength in the helium atmosphere was 1400 MPa. In the hydrogen atmosphere, the tensile strength decreased to less than 600 MPa at a strain rate of 2.0 × 10^?5 s^?1. However, the tensile strength increased to 900 MPa when the strain rate was decreased to 6.5 × 10^?8 s^?1. This recovery of the tensile strength was because of the decrease in the local stress in the vicinity of the precrack because of hydrogen.     

Psychological and autonomic effects of art making in college-aged students

Background and objectives: Anxiety disorders comprise the most common category of mental illness among US young adults. Art making might be one method to help reduce anxiety, but the few studies investigating this have used only subjective measures of anxiety. Design: This study employed both subjective (self-reported state anxiety from the State-Trait Anxiety Inventory) and objective (heart rate variability) measures to assess whether 30-minute periods of art making reduced anxiety in 47 first-year college students prior to their final examinations. Methods: Students participated in free-form painting, mandala coloring, clay modeling, and control sessions. Results: Repeated-measures ANOVA with post hoc analysis revealed significantly greater pre- to post-session reductions in anxiety for all three types of art-making sessions than for the control session, as measured objectively. Measured subjectively, only free-form painting yielded a significant decrease in anxiety compared to the control session. Conclusions: Given the health benefits of anxiety reduction, further study is warranted to determine the duration of art making's anxiety-reducing effect.     

Prevalence and behavioural risk factors of light or moderate and heavy cigarette smoking in 32 countries

The aim of this study was to predict the prevalence of light or moderate and heavy smoking from lifestyle behavioural risk factors among South African adults compared to others from 31 countries around the world. Secondary data from 53 391 adults who completed the International Social Survey Program (ISSP), 2011–2013, Health and Health Care Module were accessed for this study (South Africans, N = 3 004). Findings from multinomial logistic regression with adjustment for personal factors (e.g. physical and psychological well-being variables) were used to explain a significant proportion of both light or moderate smoking and heavy smoking among South African adults as well as adults from the other countries. Specifically, lifestyle factors of being underweight and overweight or obese were negatively associated with light or moderate smoking, but body mass index (BMI) weight status was not associated with heavy smoking. Smoking interventions should target modifiable lifestyle factors to prevent risk for light or moderate smoking and heavy smoking.     

Prenatal origins of temperament: Fetal cardiac development & infant surgency,negative affectivity,and regulation/orienting

Temperament, i.e. individual differences in reactivity and self-regulation, emerges early in infancy; might temperament originate during fetal development? Mixed findings and methodological issues in the literature examining this consideration limit our understanding of the continuity between these fetal indices and infant temperament. The primary aims of the current study were to improve on published studies by (a) using standardized and well-accepted fetal cardiac (actocardiograph) and infant temperament measures (the Infant Behavior Questionnaire—Revised; IBQ-R) (b) expanding fetal assessments to include coupling (the cross correlation of heart rate with movement), and (c) examining a diverse sample to determine if findings of associations between fetal neurobehavior and infant temperament generalize beyond cohorts that are demographically well-resourced and predominantly white. Building on theory and empirical findings, we hypothesized that (1) FHR would be positively associated with Surgency and Negative Affectivity, (2) FHRV would be positively associated with Surgency, and Regulation/Orienting and inversely associated with Negative Affectivity, and (3) fetal coupling would be positively associated with Regulation/Orienting and Surgency and inversely associated with Negative Affectivity. We collected 20 min of fetal data (m gestational age = 34.42 weeks) and mothers completed the IBQ-R (n = 90 women; 60 % non-Caucasian race; 63 % Latina ethnicity). We found that FHR was positively associated with Negative Affectivity but not associated with Surgency (or Regulation/Orienting). FHRV was inversely associated with Surgency but not associated with Negative Affectivity or Regulation/Orienting. Coupling was positively associated with Regulation/Orienting and Surgency but not associated with Negative Affectivity. Our findings, from a more diverse sample and with established measures, provide further evidence that individual differences in reactivity and regulation can be identified in the in-utero period and show theory-based continuity to specific infant temperament constructs.     

Stressing the feedback: attention and cardiac vagal tone during a cognitive stress task

Objectives: The present study examined relationships among gaze behaviour and cardiac vagal tone using a novel stress-inducing task.

Methods: Participants’ (N?=?40) eye movements and heart rate variability (HRV) were measured during an unsolvable computer-based task randomly presenting feedback of “Right” and “Wrong” answers distinctly onscreen after each trial. Subgroups were created on the basis of more frequent eye movements to the right (“Correct”-Attenders; n?=?23) or wrong (“Incorrect”-Attenders; n?=?17) areas onscreen.

Results: Correct-Attenders maintained HRV from baseline to the stress task. In contrast, Incorrect-Attenders spent significantly more time viewing “Wrong” feedback, exhibited a reduction in HRV during the stress condition (p?Conclusions: Results demonstrate that pervasive attention to negative feedback (“Wrong”) elicits perseverative stress and negative self-evaluations among university students. This study highlights the potential for studying attentional biases and emotional distress through combined measures of gaze behaviour and cardiac vagal tone.     

Response strength in extreme multiple schedules

Four pigeons were trained in a series of two-component multiple schedules. Reinforcers were scheduled with random-interval schedules. The ratio of arranged reinforcer rates in the two components was varied over 4 log units, a much wider range than previously studied. When performance appeared stable, prefeeding tests were conducted to assess resistance to change. Contrary to the generalized matching law, logarithms of response ratios in the two components were not a linear function of log reinforcer ratios, implying a failure of parameter invariance. Over a 2 log unit range, the function appeared linear and indicated undermatching, but in conditions with more extreme reinforcer ratios, approximate matching was observed. A model suggested by McLean (1991), originally for local contrast, predicts these changes in sensitivity to reinforcer ratios somewhat better than models by Herrnstein (1970) and by Williams and Wixted (1986). Prefeeding tests of resistance to change were conducted at each reinforcer ratio, and relative resistance to change was also a nonlinear function of log reinforcer ratios, again contrary to conclusions from previous work. Instead, the function suggests that resistance to change in a component may be determined partly by the rate of reinforcement and partly by the ratio of reinforcers to responses.     

Seeing is believing: Priors,trust, and base rate neglect

Kahneman and Tversky (1973) described an effect they called ‘insensitivity to prior probability of outcomes’, later dubbed base rate neglect, which describes people’s tendency to underweight prior information in favor of new data. As probability theory requires that prior probabilities be taken into account, via Bayes’ theorem, the fact that most people fail to do so has been taken as evidence of human irrationality and, by others, of a mismatch between our cognitive processes and the questions being asked (Cosmides & Tooby, 1996). In contrast to both views, we suggest that simplistic Bayesian updating using base rates is not necessarily rational. To that end, we present experiments in which base rate neglect is often the right strategy, and show that people’s base rate usage varies systematically as a function of the extent to which the data that make up a base rate are perceived as trustworthy.     

Temporal pattern of pre-shooting psycho-physiological states in elite athletes: A probabilistic approach

Objective

The IZOF-based probabilistic approach provides a methodology to study within-individual patterns of a performer's states. So far, the time course of physiological data before performance have not been investigated within the probabilistic methodology framework. The purpose of this study was to examine the value of the probabilistic approach in the assessment of the time course of physiological indicators of arousal/activation and vigilance during the period preceding the shot, in comparison with the performance-based method.

Design

Longitudinal assessment of psycho-physiological data and performance outcomes was conducted on eight elite pistol shooters in a controlled setting.

Methods

Each participant performed 60 air-pistol shots in 2 sessions. Skin conductance level and cardiac activity were recorded. Affective states intensity was evaluated on a modified 11-point Borg scale. Affect, HR and SC level were evaluated with a Performance-based approach and a Probabilistic method, and results compared at an individual level.

Results

Findings showed the higher effectiveness of the probabilistic method to analyse physiological parameters (skin conductance and heart rate) and to describe the physiological mechanisms associated with shooters’ performance.

Conclusions

The probabilistic method better discerned the contribution of arousal/activation and vigilance to optimal and non-optimal performance in elite shooters, thereby providing a sharper representation of the temporal pattern of performers' states before shooting. From an applied perspective, we believe that the probabilistic approach can help athletes become aware of the subtle variations occurring in their psychophysical states during the preparatory period preceding the shot and not only at the moment of shot release.     

Context affects the interpretation of low but not high numerical probabilities: A hypothesis testing account of subjective probability

Low numerical probabilities tend to be directionally ambiguous, meaning they can be interpreted either positively, suggesting the occurrence of the target event, or negatively, suggesting its non-occurrence. High numerical probabilities, however, are typically interpreted positively. We argue that the greater directional ambiguity of low numerical probabilities may make them more susceptible than high probabilities to contextual influences. Results from five experiments supported this premise, with perceived base rate affecting the interpretation of an event’s numerical posterior probability more when it was low than high. The effect is consistent with a confirmatory hypothesis testing process, with the relevant perceived base rate suggesting the directional hypothesis which people then test in a confirmatory manner.