A Review of the Erosion of Thermal Barrier Coatings.

The application of thermal barrier coatings (TBCs) to components with internal cooling in the hot gas stream of gas turbine engines has facilitated a steep increase in the turbine entry temperature and the associated increase in performance and efficiency of gas turbine engines. However, TBCs are susceptible to various life limiting issues associated with their operating environment including erosion, corrosion, oxidation, sintering and foreign object damage (FOD). This is a review paper that examines various degradation and erosion mechanisms of TBCs, especially those produced by electron beam physical vapour deposition (EB-PVD). The results from a number of laboratory tests under various impact conditions are discussed before the different erosion and FOD mechanisms are reviewed. The transitions between the various erosion mechanisms are discussed in terms of the D/d ratio (contact area diameter/column diameter), a relatively new concept that relates the impact size to the erosion mechanism. The effects of ageing, dopant additions and calciumâ  magnesiumâ  aluminaâ  silicates on the life of TBCs are examined. It is shown that while ageing increases the erosion rate of EB-PVD TBCs, ageing of plasma sprayed TBCs in fact lowers the erosion rate. Finally modelling of EB-PVD TBCs is briefly intr

Perceptions of coach-athlete relationship are more important to coaches than athletes in predicting dyadic coping and stress appraisals: An actor-partner independence mediation model

Most attempts to manage stress involve at least one other person, yet coping studies in sport tend to report an athlete’s individual coping strategies. There is a limited understanding of coping involving other people, particularly within sport, despite athletes potentially spending a lot of time with other people, such as their coach. Guided by the systemic-transactional model of stress and coping among couples (Bodenmann, 1995), from relationship psychology, we assessed dyadic coping, perceptions of relationship quality, and primary stress appraisals of challenge and threat among 158 coach–athlete dyads (n D 277 participants). The athletes competed at amateur (n D 123), semiprofessional (n D 31), or professional levels (n D 4). Coaches and athletes from the same dyad completed a measure of dyadic coping, coach–athlete relationship, and stress appraisals. We tested an Actor–Partner Interdependence Mediation Model to account for the non-independence of dyadic data. These actor–partner analyses revealed differences between athletes and coaches. Although the actor effects were relatively large compared to partner effects, perceptions of relationship quality demonstrated little impact on athletes. The mediating role of relationship quality was broadly as important as dyadic coping for coaches. These findings provide an insight in to how coach–athlete dyads interact to manage stress and indicate that relationship quality is of particular importance for coaches, but less important for athletes. In order to improve perceptions of relationship quality among coaches and athletes, interventions could be developed to foster positive dyadic coping among both coaches and athletes, which may also impact upon stress appraisals of challenge and threat

Precompetitive achievement goals, stress appraisals, emotions, and coping among athletes

Grounded in Lazarus’ (1991, 1999, 2000) Cognitive-Motivational-Relational theory of emotions, we tested a model of achievement goals, stress appraisals, emotions, and coping. We predicted that pre-competitive achievement goals would be associated with appraisals; appraisals with emotions; and emotions with coping in our model. The mediating effects of emotions among the overall sample of 827 athletes and two stratified random sub-samples were also explored. The results of this study support our proposed model in the overall sample and the stratified sub-samples. Further, emotion mediated the relationship between appraisal and coping. Mediation analyses revealed that there were indirect effects of pleasant and unpleasant emotions, which indicates the importance of examining multiple emotions to reveal a more accurate representation of the overall stress process. Our findings indicate that both appraisals and emotions are just as important in shaping coping

The development of a new sport-specific classification of coping and a meta-analysis of the relationship between different coping strategies and moderators on sporting outcomes

There is an ever growing coping and sports performance literature, with researchers using many different methods to assess performance and different classifications of coping. As such, it makes it difficult to compare studies and therefore identify how coping is related to performance. Furthermore, there are no quantitative syntheses of the results from these studies. A quantitative synthesis would facilitate a more comprehensive understanding of how coping is associated with athletic performance. In order to accurately compare studies, our first aim was to develop a new coping classification that would make this possible. Firstly, we reviewed the strengths and limitations of the different coping classifications and then identified the commonalities and differences between such classifications. We opted for a three-factor classification of coping, because the evidence suggests that a three-factor classification provides a superior model fit to two-factor approaches. Our new classification of coping was based on an existing model from the developmental literature, which received an excellent model fit. We made some adaptations, however, as our classification was intended for an athletic population. As such, we classified coping as mastery (i.e., controlling the situation and eliminating the stressor), internal regulation (i.e., managing internal stress responses), or goal withdrawal (i.e., ceasing efforts towards goal attainment). Undertaking a meta-analysis, our second aim was to identify which coping strategies correlated with sports performance and whether this relationship varied according to moderator variables. Articles were sourced from online electronic databases and manual journal searches. PRISMA guidelines were used to search, select, and synthesize relevant studies. Random effects meta-analyses were performed to identify associations between coping classification and sport performance. Q, I2, and R2 values assessed heterogeneity. Eighteen published investigations, including 3900 participants and incorporating fifty-nine correlations, indicated an overall positive effect for mastery coping, a negligible negative effect for internal regulation coping, and a negative effect for goal withdrawal strategies. The findings of this meta-analysis could be used by sports practitioners to help them deliver effective coping interventions. In order to maximize performance, practitioners could encourage the use of mastery coping, but advise their athletes not to use goal withdrawal strategies

The applicability of self-regulation theories in sport : goal adjustment capacities, stress appraisals, coping and well-being among athletes

Objectives: We examined a model, informed by self-regulation theories, which included goal adjustment capacities, appraisals of challenge and threat, coping, and well-being. Design: Prospective. Methods: Two hundred and twelve athletes from the United Kingdom (n = 147) or Australia (n = 65), who played team (n = 135) or individual sports (n = 77), and competed at international (n = 7), national (n = 11), county (n = 67), club (n = 84), or beginner (n = 43) levels participated in this study. Participants completed measures of goal adjustment capacities and stress appraisals two days before competing. Athletes also completed questions on coping and well-being within three hours of their competition ending. Results: The way an athlete responds to an unattainable goal is associated with his or her well-being in the period leading up to and including the competition. Goal reengagement positively predicted well-being, whereas goal disengagement negatively predicted well-being. Further, goal reengagement was positively associated with challenge appraisals, which in turn was linked to task-oriented coping, and task-oriented coping positively associated with well-being. Conclusion: When highly-valued goals become unattainable, consultants could encourage athletes to seek out alternative approaches to achieve the same goal or help them develop a completely new goal

Pleasant emotions widen thought-action repertoires, develop long-term resources, and improve reaction time performance: A multi-study examination of the Broaden-and-Build theory among athletes

The authors investigated relationships between emotions, coping, and resilience across two studies. In Study 1a, 319 athletes completed dispositional questionnaires relating to the aforementioned constructs. In Study 1b, 126 athletes from Study 1a repeated the same questionnaires 6months later. In Study 2, 21 athletes were randomly allocated to an emotional (e.g., pleasant or unpleasant emotions) or control group and undertook a laboratory-based reaction-time task across three time points. Questionnaires and salivary cortisol samples were collected before and after each performance with imagery-based emotional manipulations engendered during the second testing session. Partial longitudinal evidence of the broaden-and-build effects of pleasant emotions was found. Pleasant emotions may undo lingering cognitive resource losses incurred from previous unpleasant emotional experiences. In Study 2, pleasant and unpleasant emotions had an immediate and sustained psychophysiological and performance impact. Taken together, this research supports the application of broaden-and-build theory in framing emotional interventions for athletes

Stress appraisals influence athletic performance and psychophysiological response during 16.1 km cycling time trials

Objectives: We examined how stress appraisals were associated with emotions, coping behaviours, as well as subjective and objective measures of performance.Design: Prospective field- and laboratory-based studies.Methods: In Study 1, 192 athletes completed process-oriented psychometrics pertaining to the aforementioned constructs throughout a sporting competition. Study 2 utilised an experimental design to assess the causal influence of stress appraisals on performance, cortisol, and psychological variables. Thirty gender-matched athletes were randomly assigned to either a stress appraisal (e.g., challenge, threat, benefit, or harm/loss) or the control group. Participants completed three 16.1km cycling time trials (TT) on a cycle ergometer, with their appropriate stress appraisal engendered via falsified performance feedback throughout the final TT. Salivary cortisol samples and psychometrics (e.g., appraisals, emotions, and coping) were collected before and after each TT.Results: The results of Study 1 revealed a sequential link between challenge stress appraisals and perceived goal attainment via pleasant emotions and task-oriented coping behaviours. Threat stress appraisals inversely related to goal attainment via unpleasant emotions and both distraction- and disengagement-oriented coping. In Study 2, no significant psychophysiological or performance differences were found across genders. The temporal orientation of stress appraisals influenced objective cycling TT performance. Benefit and harm/loss stress appraisals significantly facilitated or inhibited performance, respectively. Cortisol spikes were observed in the stress appraisal group’s threat, challenge, and benefit, with a decline detected within the harm/loss group. Whilst the process of winning is physiologically stressful, the fear of defeat may be more stressful than losing itself. Conclusion: Stress appraisals influence subjective and objective performance, as well as neuroendocrine and psychological responses to stress. Stress Appraisals Influence Athletic Performance and Psych

Bioinspired metal–polymer thin films with varying hydrophobic properties

Nanocomposites involve the inclusion of one material into the layers of another material at a nanoscale level. Inspired by nature, nanocomposites material systems offer functionalities over their bulk forms which in some cases have evolved over millions of years. Here, thin film coatings have been fabricated by PVD sputtering, comprising a soft PTFE phase which is combined with a hard metallic NiTi phase. A series of coatings with PTFE ranging from 10 to 75 vol% have been prepared, and their surface energies and microstructures investigated. The surface energy of the nanocomposite films changes with the PTFE content, falling in the range between PTFE and NiTi with water contact angles between 80° and 102° for a thin film with 25 and 75 vol% of PTFE, respectively. Here, both TEM and EDX reveal PTFE forming along NiTi column boundaries. Coatings with PTFE content greater than 50 vol% failed due to a build-up of intrinsic stress. The degree of hybridization between NiTi and PTFE was found to be dependent on the PTFE layer thickness. SEM analysis of this coating reveals PTFE at the surface embedded within the NiTi matrix

Intracellular Recording, Sensory Field Mapping, and Culturing Identified Neurons in the Leech, \u3cem\u3eHirudo medicinalis\u3c/em\u3e

The freshwater leech, Hirudo medicinalis, is a versatile model organism that has been used to address scientific questions in the fields of neurophysiology, neuroethology, and developmental biology. The goal of this report is to consolidate experimental techniques from the leech system into a single article that will be of use to physiologists with expertise in other nervous system preparations, or to biology students with little or no electrophysiology experience. We demonstrate how to dissect the leech for recording intracellularly from identified neural circuits in the ganglion. Next we show how individual cells of known function can be removed from the ganglion to be cultured in a Petri dish, and how to record from those neurons in culture. Then we demonstrate how to prepare a patch of innervated skin to be used for mapping sensory or motor fields. These leech preparations are still widely used to address basic electrical properties of neural networks, behavior, synaptogenesis, and development. They are also an appropriate training module for neuroscience or physiology teaching laboratories