Influence of test temperature on the size effect in molybdenum small-scale compression pillars

Previous research has shown that body-centred cubic (bcc) metals exhibit a smaller size dependence of strength than what is commonly observed in face-centred cubic (fcc) metals. This work investigates compression testing of focused ion beam-manufactured molybdenum pillars ranging in size from 300?nm to 5?μm, both above and below its critical temperature at 300 and 500?K. At 500?K the size effect is found to be consistent with what is observed in fcc metals, owing to the increased mobility of screw dislocations.     

Site preference and alloying effect of Re atoms in the edge dislocation cores in Ni3Al

Using Cambridge sequential total energy package method based on the density functional theory, we investigated the site preference and alloying effect of Re atoms in the [1 0 0] (0 1 0) edge dislocation cores in Ni₃Al. Due to the introduction of a Re atom, the energetic and electronic structure of dislocation core systems have been changed a lot. The binding energy results suggest Re atom prefers Al site, especially the centre site in the centre-Al system, which can be explained by the results of Mulliken orbital population and density of states. When Re atom occupies the centre site in the centre-Al system, the DC system has the highest stability and stronger bonds formed between the Re atom and its nearest neighbouring atom due to hybridization of the Re-5d and Ni-3d orbitals.     

Experimental observation of the dislocation walls in heterostructures with two interfaces: Ge/Ge0.5Si0.5 10 nm/Si(001) as an example

High-resolution electron microscopy (HREM) at the atomic scale has been applied to study the edge dislocation redistribution between interfaces in Ge/Ge_0.5Si_0.5/Si(0?0?1) heterostructures. Our results provide a direct explanation that plastic relaxation of the GeSi buffer layer proceeds owing to motion of Lomer-type dislocation complexes consisting of a pair of complementary 60° dislocations with the ends of the {1?1?1} extra planes being located at a distance of ~2–12 interplanar spacings from each other. It is demonstrated that edge dislocations belonging to the upper and lower interfaces become arranged one under the other and dislocation walls are formed. The distributions of tension and compression in the [0?0?1] direction between two edge dislocations, obtained by processing the HREM image, testify to superposition of strain fields.     

Molecular dynamics study on compressive yield strength in Ni3Al micro-pillars

Recent nanoindentation experiments on bulk samples as well as compression tests on micro-pillars indicate that the micron-sized material volumes exhibit a first yield point that strongly depends on the sample size. In this work, molecular dynamics (MD) simulations are carried out to investigate the onset of yielding in Ni₃Al nano-sized pillars. The MD results show that dislocation generation is from the free surfaces of the micro-pillars, when thermal vibration induces too large a local interatomic displacement. The statistical distributions of the near-surface thermal atomic displacements gathered from the MD simulations are used in conjunction with a survival probability model to predict the yield conditions of real-sized micro-pillars in real time scales. The predicted results agree fairly well with experimental results in the literature.     

The atomic structure of the dislocation cores in a small-angle grain boundary in BaTiO3 thin films

The atomic structure of the cores of the dislocations forming a [110] tilt boundary of 10^o misorientation in a BaTiO₃ film is characterized by means of focal-series reconstruction. Along the small-angle grain boundary, facets with different inclinations are accompanied by different types of dislocation. The dislocation with a Burgers vector of a [001] appears as a perfect edge type. Those with a Burgers vector of a [111] are dissociated into three partials with a Burgers vector of (a/3)[111], leading to two segments of stacking faults. Structural models of these dislocation cores are suggested on the basis of the phase of the reconstructed wavefunction and tested by simulation of the wavefunction.     

The need to reform our assessment of evidence from clinical trials: A commentary

The ideology of evidence-base medicine (EBM) has dramatically altered the way we think, conceptualize, philosophize and practice medicine. One of its major pillars is the appraisal and classification of evidence. Although important and beneficial, this process currently lacks detail and is in need of reform. In particular, it largely focuses on three key dimensions (design, [type I] alpha error and beta [type II] error) to grade the quality of evidence and often omits other crucial aspects of evidence such as biological plausibility, reproducibility, generalizability, temporality, consistency and coherence. It also over-values the randomized trial and meta-analytical techniques, discounts the biasing effect of single centre execution and gives insufficient weight to large and detailed observational studies. Unless these aspects are progressively included into systems for grading, evaluating and classifying evidence and duly empirically assessed (according to the EBM paradigm), the EBM process and movement will remain open to criticism of being more evidence-biased than evidence-based.     

Dislocation evolution in twins of cyclically deformed copper

The evolution of dislocation structure in twins of different thicknesses has been investigated in polycrystalline copper fatigued at room temperature under constant plastic axial strain amplitude control. The dislocation structure and its evolution strongly depend on twin thickness. Three critical thicknesses must be distinguished, i.e. (i) characteristic size of fatigue dislocation structures, about 1?µm; (ii) critical height of stable dislocation wall structure, about 200?nm; (iii) critical spacing of dislocation dipole, about 20?nm. It is considered that the size effect is mainly caused by twin boundaries (TBs) which play different roles on slip behaviors in twins.     

Determination of the Burgers vector of dislocations in icosahedral quasicrystals by a high-resolution lattice-fringe technique

A technique for the determination of the full six-dimensional Burgers vector characterizing a dislocation in an icosahedral quasicrystal is presented. It is based on the lattice-fringe analysis of two high-resolution transmission electron microscopy images taken at two different sample orientations. As an example we present the analysis of a dislocation in a bent icosahedral Al-Pd-Mn quasicrystal. We obtained a Burgers vector B = A₀[-2,0,3,-2,3,0] where A₀ = 0.645nm is the six-dimensional hyperlattice constant. This result is consistent with previous results obtained by diffraction contrast analysis and convergent-beam electron diffraction techniques.     

Trait perfectionism, self-determination, and self-presentation processes in relation to exercise behavior

Objectives

Motivational and self-presentational processes pervade all aspects of our lives including exercise behaviors. Furthermore, trait perfectionism has been shown to heighten self-presentational tendencies and energize achievement striving ( [Flett and Hewitt, 2002] and [Hewitt et?al., 2003]). How maladaptive and adaptive perfectionism traits relate to these cognitive and behavioral processes specific to the exercise context remains to be determined. This study employed structural equation modeling to examine the associations between maladaptive and adaptive perfectionism, self-determination of exercise behavior, self-presentation in exercise, and exercise behavior.

Method

Two hundred and fifty-four undergraduate students completed items assessing frequency, intensity, and duration of aerobic exercise behavior, along with measures of Multidimensional Perfectionism (Cox, Enns, & Clara, 2002), Self-Presentation in Exercise ( [Conroy et?al., 2000] and [Gammage et?al., 2004]), and self-determination of exercise behavior utilizing the Behavioral Regulation in Exercise Questionnaire (BREQ-2; Markland & Tobin, 2004).

Results

Results supported a structural model in which the associations between perfectionism dimensions and aerobic exercise behavior were mediated by opposing relationships with relative autonomy (RAI; Markland & Tobin, 2004) and self-presentation processes. Distinctively, maladaptive perfectionism demonstrated an inverse direct effect on the RAI and positive direct effects on self-presentation processes. In contrast, adaptive perfectionism exerted a positive direct effect on the RAI and inverse direct effects on self-presentation processes.

Conclusions

These findings highlight the importance of both maladaptive and adaptive dimensions of perfectionism in the study of exercise outcomes and within the broader social context linking perfectionism and motivation.     

high-resolution electron microscopy at a (113) symmetric Thermally activated step motion observed by tilt grain-boundary in aluminium

Grain-boundary migration is demonstrated to proceed by lateral propagation of a small step in a (113), [110] symmetric Al tilt grain-boundary. In-situ high-resolution (transmission) electron microscopy (HREM) at 523K allowed the study of atomic-scale detail at video rates during the migration process. The grain-boundary translational states on both sides of the step are identical, which leads to a step dislocation. This defect can move laterally by a combination of climb and glide. Dynamic HREM images indicate considerable atomic agitation within the dislocation core. A detailed temporal analysis of the step movements shows small random displacements of the dislocation core.     

Dislocation multiplication in bcc molybdenum: A dislocation dynamics simulation

Plastic deformation of Mo single crystals is examined by direct simulation of dislocation dynamics under stress. Initial dislocation populations are made to mimic real dislocation microstructures observed in transmission electron microscopy cross-sections of pure annealed Mo single crystals. No a priori sources for dislocation multiplication are introduced, and yet multiplication takes place through a sequence involving aggregation of grown-in superjogs, bowing of screw dislocation segments and fast lateral motion of edge segments, producing a large number of elongated loops and a characteristic cross-grid pattern of screw dislocations.     

School programs targeting stress management in children and adolescents: A meta-analysis

Introduction

This meta-analysis evaluates the effect of school programs targeting stress management or coping skills in school children.

Methods

Articles were selected through a systematic literature search. Only randomized controlled trials or quasi-experimental studies were included. The standardized mean differences (SMDs) between baseline and final measures were computed for experimental and control groups. Experimental groups were groups that either received an intervention of (a) relaxation training, (b) social problem solving, (c) social adjustment and emotional self-control, or (d) a combination of these interventions. If no baseline measurement was available, SMDs were calculated between final measures of the groups. The overall pooled effect size was calculated and the pooled effect sizes of improvement on stress, coping, (social) behavior, and self-efficacy by random effects meta-analysis. The dependence of the results on study characteristics (i.e. methodological quality and type of intervention) was evaluated using meta-regression analysis.

Results

Nineteen publications met the inclusion criteria of controlled trials for class programs, teaching coping skills or stress management. Overall effect size for the programs was − 1.51 [95% confidence interval (CI) − 2.29, − 0.73], indicating a positive effect. However, heterogeneity was significant (p < .001). Sensitivity analyses showed that study quality and type of intervention were sources of heterogeneity influencing the overall result (p values < .001). The heterogeneity in quality may be associated with methodological diversity and differences in outcome assessments, rather than variety in treatment effect. Effect was calculated per intervention type, and positive effects were found for stress symptoms with a pooled effect size of − 0.865 (95% CI: − 1.229, − 0.502) and for coping with a pooled effect size of − 3.493 (95% CI: − 6.711, − 0.275).

Conclusion

It is tentatively concluded that school programs targeting stress management or coping skills are effective in reducing stress symptoms and enhancing coping skills. Future research should use clear quality criteria and strive for less diversity in methodology and outcome assessment.     

Contextual effects in vowel perception II: Evidence for two processing mechanisms

Recent experiments have indicated that contrast effects can be obtained with vowels by anchoring a test series with one of the endpoint vowels. These contextual effects cannot be attributed to feature detector fatigue or to the induction of an overt response bias. In the present studies, anchored ABX discrimination functions and signal detection analyses of identification data (before and after anchoring) for an [i]-[I] vowel series were used to demonstrate that [i] and [I] anchoring produce contrast effects by affecting different perceptual mechanisms. The effects of [i] anchoring were to increase within-[i] category sensitivity, while [I] anchoring shifted criterion placements. When vowels were placed in CVC syllables to reduce available auditory memory, there was a significant decrease in the size of the [I]-anchor contrast effects. The magnitude of the [i]-anchor effect was unaffected by the reduction in vowel information available in auditory memory. These results suggest that [i] and [I] anchors affect mechanisms at different levels of processing. The [i] anchoring results may reflect normalization processes in speech perception that operate at an early level of perceptual processing, while the [I] anchoring results represent changes in response criterion mediated by auditory memory for vowel information.     

The central tendency of a social group can affect ratings of its intragroup variability in the absence of social identity concerns

People report less variability within in-groups than within out-groups when they make their ratings on traits on which the in-group has a higher central tendency than the out-group. [Simon, 1992a] and [Simon, 1992b] proposed that this effect is motivated by the need to protect a positive social identity. The present research tested the necessity of the social identity motive by using participants who were not members of any of the target groups that they judged. In Study 1 (N = 60), psychology undergraduate students reported significantly less intragroup variability on positive traits among a group of fashion designers that won a fashion competition than among a group that lost. Study 2 (N = 75) found a reverse effect on negative traits and confirmed the mediating role of perceived central tendency. These results demonstrate that the social identity motive is not necessary to explain the effect of central tendency on ratings of intragroup variability, and that the effect is more general than previously reported.     

家庭支持型主管行为对员工的影响与作用机制：基于元分析的证据

为厘清家庭支持型主管行为对员工的独特影响,并比较不同的作用机制,本研究对包含204个独立样本、340个效应值及91145名员工的164篇文献进行了元分析,结果发现：(1)与一般主管支持行为相比,家庭支持型主管行为对员工的任务绩效、创新行为和生活满意度有更强的积极影响。(2)工作对家庭冲突(资源视角)、领导-成员交换(交换视角)和情感承诺(情感视角)均能解释家庭支持型主管行为对员工的作用机制,并互为补充。具体而言,三者均能中介家庭支持型主管行为对任务绩效的影响;领导-成员交换和情感承诺在家庭支持型主管行为与创新行为间起中介作用;工作对家庭冲突和领导-成员交换则在家庭支持型主管行为影响生活满意度中发挥中介效应。研究结果为家庭支持型主管行为的影响效果提供了可靠结论,也有助于深入理解其作用机制。     

The Sound of Grasp Affordances: Influence of Grasp‐Related Size of Categorized Objects on Vocalization

Previous research shows that simultaneously executed grasp and vocalization responses are faster when the precision grip is performed with the vowel [i] and the power grip is performed with the vowel [ɑ]. Research also shows that observing an object that is graspable with a precision or power grip can activate the grip congruent with the object. Given the connection between vowel articulation and grasping, this study explores whether grasp‐related size of observed objects can influence not only grasp responses but also vowel pronunciation. The participants had to categorize small and large objects into natural and manufactured categories by pronouncing the vowel [i] or [ɑ]. As predicted, [i] was produced faster when the object's grasp‐related size was congruent with the precision grip while [ɑ] was produced faster when the size was congruent with the power grip (Experiment 1). The effect was not, however, observed when the participants were presented with large objects that are not typically grasped by the power grip (Experiment 2). This study demonstrates that vowel production is systematically influenced by grasp‐related size of a viewed object, supporting the account that sensory‐motor processes related to grasp planning and representing grasp‐related properties of viewed objects interact with articulation processes. The paper discusses these findings in the context of size–sound symbolism, suggesting that mechanisms that transform size‐grasp affordances into corresponding grasp‐ and articulation‐related motor programs might provide a neural basis for size‐sound phenomena that links small objects with closed‐front vowels and large objects with open‐back vowels.     

Do Self-Incentives and Self-Rewards Change Behavior? A Systematic Review and Meta-Analysis

Encouraging people to self-incentivize (i.e., to reward themselves in the future if they are successful in changing their behavior) or self-reward (i.e., prompt people to reward themselves once they have successfully changed their behavior) are techniques that are frequently embedded within complex behavior change interventions. However, it is not clear whether self-incentives or self-rewards per se are effective at bringing about behavior change. Nine databases were searched alongside manual searching of systematic reviews and online research registers. One thousand four hundred papers were retrieved, spanning a range of behaviors, though the majority of included papers were in the domain of “health psychology”. Ten studies matched the inclusion criteria for self-incentive but no studies were retrieved for self-reward. The present systematic review and meta-analysis is therefore the first to evaluate the unique effect of self-incentives on behavior change. Effect sizes were retrieved from 7 of the 10 studies. Analysis of the 7 studies produced a very small pooled effect size for self-incentives (k = 7, N = 1,161), which was statistically significant, d₊ = 0.17, CI [0.06, 0.29]. The weak effect size and dearth of studies raises the question of why self-incentivizing is such a widely employed component of behavior change interventions. The present research opens up a new field of inquiry to establish: (a) whether or not self-incentivizing and self-rewarding are effective behavior change techniques, (b) whether self-incentives and self-rewards need to be deployed alongside other behavior change techniques, and, (c) when and for whom self-incentives and self-rewards could support effective behavior change.     

Textured Foot Orthotics on Dynamic Stability and Turning Performance in Parkinson’s Disease

Abstract

The purpose of this study was to facilitate sensory feedback, with textured foot orthotics, to evaluate dynamic stability and turning behavior in Parkinson’s disease individuals. Seven participants with a diagnosis of idiopathic Parkinson’s disease, aged 55–80?years old, participated in this study. Participants completed three testing sessions; baseline, 4?weeks post-baseline, and 5?weeks post-baseline. Three experimental conditions were tested: footwear only (F), footwear?+?non-textured orthotic (FO), and footwear?+?textured orthotic (FOT). Kinematic, kinetic, and video data were collected during the steps preceding a turn task. Variables of interest included dynamic stability (maximum mediolateral (ML), minimum ML, and ML range of the center of mass (COM)-base of support (BOS) relationship) and turning performance (gait velocity and step count). There was a statistically significant increase in maximum ML COM-BOS distance (week 4 [0.1298 m?±?0.054] compared to week 0 [0.1069 m?±?0.050] p = .0076), and a significant decrease in step count (week 0-F [5.52 steps ± 1.08] to week 0-FO [5.23 steps ± 0.87] p = .0296) and (week 4-FO [5.24 steps ± 1.31] to week 4–FOT [4.67 steps ± 0.76] p = .0004). Textured foot orthotics modified dynamic stability and turning performance in Parkinson’s disease individuals completing a 180° degree turn. These preliminary results support this potential treatment option for rehabilitation professionals treating Parkinson’s disease.     

Dislocations in Bi-Pb-Sr-Ca-Cu-O superconductors

Abstract

Dislocations and dislocation networks in superconducting Bi-Pb-Sr-Ca-Cu-O have been observed by means of TEM, confirming that this compound is a layer structure with low stacking fault energy. On the basal plane, dislocations and dislocation networks dissociate into partial dislocations and partial dislocation networks. However, the dissociation of [010] dislocations is hardly observed, which is related to the structural characteristics of the compound.     

Microstructure evolution and hardness variation of pack-rolled nanocrystalline nickel

The microstructure evolution and hardness of nanocrystalline nickel during pack rolling at room temperature have been investigated. It was found that the roll-bonding side (R) and non-roll-bonding side (NR) behaved quite differently. The hardness of side R is higher than that of side NR. No obvious work softening was observed in either side R or side NR until the strain reached ~ 0.611. Quantitative X-ray diffraction analysis indicated that the grain size in side NR increases faster than that in side R, a result confirmed by transmission electron microscopy. Texture analysis showed that (2 0 0) preferred orientation first strengthens but then weakens in both sides NR and R, while a strong (2 2 0) preferred orientation emerges, particularly in side R. Further texture analysis suggests that dislocation slip is responsible for the texture discrepancy between side NR and side R. The dislocation activity, grain rotation and grain growth are discussed based on the experimental results.