A cure modelling study of an unsaturated polyester resin system for the simulation of curing of fibre-reinforced composites during the vacuum infusion process

This study presents the cure kinetics and cure modelling of an ambient curing unsaturated polyester (UP) resin system for its cure simulation in the vacuum infusion (VI) process. The curing of the UP resin system was investigated using differential scanning calorimetry (DSC). The dynamic DSC test measurements were conducted to find out the ultimate heat of reaction and enable experimental conversion determination for the isothermal curing. The empirical autocatalytic cure kinetics model incorporating the Arrhenius law represented the cure behaviour. The results of the cure kinetics study, the cure model, the material properties and the boundary conditions were the inputs in PAM-RTM software for the simulation of the degree of cure and the exothermic temperature during the infusion and the room temperature curing stages. The simulation results were compared with experimentally measured data. A vacuum infusion (VI) experiment involving a non-crimp glass fibre preform was performed in order to monitor the curing using thermocouples and validate the temperature simulation result. It was shown that the degree of cure and the exothermic temperature of a room temperature curing thermoset resin system during the VI process could be predicted through the steps of this study

Prospective associations of different contexts of physical activity with psychological distress and well-being among middle-aged adults: an analysis of the 1970 British Cohort Study

Background: Our aim was to investigate whether different types and social contexts of physical activity (PA) participation are prospectively associated with psychological distress and well-being among middle-aged adults. / Methods: Data from the 1970 British Cohort Study was used (N=5,144-2,733 women). At age 42y, participants reported their type of leisure-time PA, which was classified as individual PA or group PA (exposure). At age 46y, participants reported co-primary outcomes: psychological distress (Malaise Inventory) and well-being (Warwick-Edinburgh scale). Highest academic achievement, employment status, country of interview, baseline values of psychological distress and well-being, smoking, alcohol use, TV-viewing and total physical activity at 42y were used as covariates. Main analyses included linear regression stratifying by sex. / Results: Jogging, cross-country, road-running (both sexes) as well as team sports (men) were associated with higher well-being. Health, fitness, gym or conditioning activities and jogging, cross-country (women), road-running (women) and team sports (men) were associated with lower psychological distress. Participation in both individual and group PA were associated with lower psychological distress and higher well-being for both sexes in crude models. However, adjusted models revealed that only group PA was associated with lower psychological distress (B: -0.106; 95%CI:-0.188 to -0.025) and higher well-being (0.835; 0.050 to 1.619) among men but not women. In the sensitivity analysis, group PA was associated with higher well-being (0.855; 0.094 to 1.616) when compared with individual PA among men. Group PA was not associated with psychological distress among both sexes and well-being among women when compared with individual PA. / Conclusion: Group PA was prospectively associated with lower psychological distress and higher well-being among men but not females. Future PA interventions could focus on group activities for males. Further research to understand the relationship between individual/group PA and mental health is required in females

Does physical activity moderate the association between device-measured sedentary time patterns and depressive symptoms in adults?

OBJECTIVES: To investigate the association between sedentary time (ST) patterns and depressive symptoms, and whether moderate-to-vigorous physical activity (MVPA) can moderate this association. METHODS: This cross-sectional study included a representative sample of 243 adults (mean age 41.8616.7 years, 56.4% women) from a city in Southeast Brazil. Depressive symptoms were estimated through the Hospital Anxiety and Depression Scale (HADS). ST patterns (i.e., number of breaks, mean length of sedentary bouts, and number of long sedentary bouts), total ST, and MVPA were assessed using accelerometers. RESULTS: Poisson regression models revealed associations of total ST (b = 0.063; 95%CI 0.011 to 0.116) and number of long bouts (0.108; 0.047 to 0.171) with depressive symptoms among men. MVPA moderated the associations of breaks and longer bouts of ST with depressive symptoms, with an increase of one break/hour, the increase of one long bout, and a decrease of 1 minute in mean bout length being associated with a reduction of 0.211 and increases of 0.081 and 0.166, respectively, in the number of depressive symptoms among men with physical inactivity (breaks =-0.211;-0.360 to-0.063; mean bout length = 0.081; 0.003 to 0.158; number of long bouts = 0.166; 0.090 to 0.242). CONCLUSIONS: Interventions that encourage breaking up ST should be helpful to reduce depressive symptoms among people with physical inactivity. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov (NCT03986879)

Micromechanical finite element analyses of fire retardant woven fabric composites at elevated temperatures using unit cells at multiple length scales

This paper presents a micromechanical Finite Element (FE) model developed to predict the effective mechanical properties of glass fibre-reinforced (woven fabric) polymer composites with/without fire retardant particulate additives at elevated temperatures. The elevated mechanical properties of glass fibre-reinforced epoxy composites with/without fire retardants were predicted using three unit cells of varying length scales in micromechanical FE analysis. Theoretically predictions of flexural behaviour of these fibre-reinforced polymer composites at elevated temperatures were satisfactorily validated against experimentally measured data. The numerical model developed herein was then used for the prediction of other mechanical properties of fibre-reinforced polymer composites that would have been difficult to collect at elevated temperatures. Micromechanical FE models such as the one contained in this paper are useful to architectural engineers as they can be used to guide the design and qualification of new engineering composites that satisfy stringent Building codes in fire prone engineering applications

What are the effects of preventative interventions on major depressive disorder (MDD) in young adults? A systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: Depression is a prevalent disorder with a peak rate of onset in young adulthood from 18 to 25 years. To date, no review has systematically assessed the effectiveness of programs that aim to reduce depressive symptoms or diagnosis of depression in young adults. METHOD: A systematic search was performed in Cochrane, PubMed, PsycINFO and EMBASE. We performed a random-effects meta-analysis of the randomized controlled studies that compared an intervention for young adults (aged 18-25) without a diagnosis or history of depression and a control condition. Comparisons between intervention and control group outcomes were carried out at the post-intervention time point. We also compared intervention and control group outcomes at later follow-up time points where data were available. RESULTS: Twenty-six randomized controlled trials among 2865 young adults were included in the analysis. The pooled effect size of the interventions versus control at post-intervention was g?=?0.37 (95% CI: 0.28-0.47, NNT?=?9) and heterogeneity was moderate I2?=?36 (95% CI: 11-64). There were no significant effects in terms of the type of delivery, focus of study, type of control, or type of support within the interventions. LIMITATIONS: The authors were unable to assess the effects of interventions on the onset of depression as none of the included studies measured incidence. The risk of bias was high in most studies (81%). Only one study included a follow-up of more than a year. Demographic factors were inconsistently reported in the included articles. CONCLUSION: While it was not possible to investigate the effects of interventions on depression incidence, some evidence was found for the effectiveness of preventative interventions in reducing depressive symptoms in young adults. Future research should address limitations of the current evidence base to allow stronger conclusions to be drawn

Impact on adolescent mental health of replacing screen-use with exercise: A prospective cohort study

BACKGROUND: Screen-based device use could increase the risk of adolescent depression. Distinct modalities of screen-use may have differential effects on mental health. We used compositional data analysis to examine how theoretically replacing different screen-uses with exercise might influence future adolescent emotional distress. METHODS: In 4,599 adolescents (55% female) from a nationally-representative, prospective cohort, we used time-use diary data at age 14 to estimate daily screen use (television, social media, video game, general computer use) and exercise (team sport and individual exercise). The outcome was emotional distress at age 17, assessed using the emotional symptoms subscale of the Strengths and Difficulties Questionnaire. RESULTS: Theoretically replacing 60 minutes of total screen time with exercise at age 14 was associated with a 0.05 (95%CI -0.08, -0.02) score reduction on the emotional symptoms' subscale at 17 in fully-adjusted models. Replacing 60 minutes of television or social media use with team sports was associated with a reduction of 0.17 (95%CI, -0.31, -0.04) and 0.15 (95%CI, -0.29, -0.01) in emotional symptom scores, respectively. We found no change in emotional symptom scores when replacing video game or general computer use with team sport, or when replacing any screen time with individual exercise. LIMITATIONS: No direct measure of depressive symptoms at follow-up. CONCLUSIONS: Replacing any screen time with exercise could reduce emotional distress, but the largest effect sizes were associated with replacing time in television watching and social media with team sports. Recommendations to limit screen-use in adolescents may require a nuanced approach for protecting mental health

The role of loneliness in the association between chronic physical illness and depressive symptoms among older adults: A prospective cohort study

BACKGROUND: Chronic physical illness increases the risk of subsequent depressive symptoms, but we know little about the mechanisms underlying this association that interventions can target. We investigated whether loneliness might explain associations between chronic illness and subsequent depressive symptoms. METHODS: We used English Longitudinal Study of Ageing data, a prospective cohort of adults over 50. Our exposure was chronic illnesses (wave two) including arthritis, cancer, diabetes, cardiovascular disease, stroke, and chronic obstructive pulmonary disease. Loneliness scores were a mediator on the short University of California, Los Angeles Loneliness Scale at wave three. Depressive symptom scores (outcome) were measured using the Centre for Epidemiologic Studies Depression Scale (wave four). We examined associations of chronic physical illness with loneliness and depressive symptoms in univariable and multivariable regression models. RESULTS: Fully-adjusted models included 2436 participants with the depression outcome and 2052 participants with the loneliness outcome. Chronic physical illness was associated with 21 % (incident rate ratio = 1.21, 95%CI = 1.03–1.42) higher depression scores at follow-up. We found no evidence of an association between chronic physical illness and loneliness and therefore did not proceed to analyses of mediation. LIMITATIONS: More prevalent chronic illnesses could have driven our results, such as cardiovascular disease. CONCLUSIONS: Chronic physical illnesses increase the risk of depressive symptoms in older adults. However, we did not find any that chronic physical illnesses were associated with an increased risk of subsequent loneliness. Therefore, interventions targeting loneliness to reduce depression in older adults with chronic physical illness may be insufficient

Physical activity across age and study: a guide to data in six CLOSER studies

Explore the measures used to assess diverse aspects of physical activity within and across six CLOSER partner studie