Probing shells against buckling: a non-destructive technique for laboratory testing

This paper addresses testing of compressed structures, such as shells, that exhibit catastrophic buckling and notorious imperfection sensitivity. The central concept is the probing of a loaded structural specimen by a controlled lateral displacement to gain quantitative insight into its buckling behaviour and to measure the energy barrier against buckling. This can provide design information about a structure's stiffness and robustness against buckling in terms of energy and force landscapes. Developments in this area are relatively new but have proceeded rapidly with encouraging progress. Recent experimental tests on uniformly compressed spherical shells, and axially loaded cylinders, show excellent agreement with theoretical solutions. The probing technique could be a valuable experimental procedure for testing prototype structures, but before it can be used a range of potential problems must be examined and solved. The probing response is highly nonlinear and a variety of complications can occur. Here, we make a careful assessment of unexpected limit points and bifurcations, that could accompany probing, causing complications and possibly even collapse of a test specimen. First, a limit point in the probe displacement (associated with a cusp instability and fold) can result in dynamic buckling as probing progresses, as demonstrated in the buckling of a spherical shell under volume control. Second, various types of bifurcations which can occur on the probing path which result in the probing response becoming unstable are also discussed. To overcome these problems, we outline the extra controls over the entire structure that may be needed to stabilize the response.Comment: as accepted in International Journal of Bifurcation and Chaos (18 pages

Trends in life satisfaction in European and North-American adolescents from 2002 to 2010 in over 30 countries

Publisher Copyright: © 2015 The Author. Published by Oxford University Press on behalf of the European Public Health Association. All rights reserved.Background: Life satisfaction (LS) is an indicator which is widely used for assessing the perception of a child's feeling about his life. Methods: LS is assessed in Health Behaviour in School-aged Children via the Cantril ladder with 10 steps indicating the worst and best possible life. This range of values (0-10) was dichotomized into 'low' (0-5) vs. 'high' (6-10). Countries, age groups and genders were compared based on the odds ratio (OR) of declaring a higher LS in 2010 with respect to 2002. Results: Analyzing the difference between 2002 and 2010, six countries from Western Europe show decreasing LS: Austria, Canada, Switzerland, Denmark, Finland and Greenland. In contrast, a group of Eastern European Countries, that is, Estonia, Croatia, Lithuania, Latvia, Russia and Ukraine, show a significant increase in LS. Data on gender and age differences confirm the lower rating of LS in girls and a decreasing rating with age. Conclusion: The LS scale appears to be a tool capable of discriminating the level of wellbeing of adolescent population among countries.publishersversionPeer reviewe

Trends in self-rated health in European and North-American adolescents from 2002 to 2010 in 32 countries

Publisher Copyright: © 2015 The Author. Published by Oxford University Press on behalf of the European Public Health Association. All rights reserved.Background: Self-rated health (SRH) in adolescence is known to be associated with health outcomes in later life. We carried out a trend analysis on data coming from three waves of data collected in 32 countries (mostly European) from 2002 to 2010 coming from the Health Behaviour in School-Aged Children surveys. Methods: SRH in adolescents was assessed using a Likert scale (excellent, good, fair and poor). Responses were dichotomized into 'excellent' vs. 'rest'. Country, age and gender groups were compared based on the odds ratio of declaring excellent SRH in 2010 with respect to 2002 and 2006. Results: The trend for European adolescents indicates an improvement over the last decade, although, in the majority of countries, a higher proportion of adolescents rate their health as excellent during the period 2002-06 with respect to the second half of the decade (2006-10).Girls were found to constantly rate their health as poorer, compared to their male peers, in all countries. Age has also a very stable trend towards a decreasing rating of health with increasing age. Conclusion: Decreased rating of health in the period 2006-10 may be a signal of the socio-economic difficulties of Europe in the last part of this decade.publishersversionPeer reviewe

Trends in multiple recurrent health complaints in 15-year-olds in 35 countries in Europe, North America and Israel from 1994 to 2010

Publisher Copyright: © 2015 The Author. Published by Oxford University Press on behalf of the European Public Health Association. All rights reserved.Background: Health complaints are a good indicator of an individual's psychosocial health and well-being. Studies have shown that children and adolescents report health complaints which can cause significant individual burden. Methods: Using data from the international Health Behaviour in School-aged Children study, this article describes trends in multiple recurrent health complaints (MHC) in 35 countries among N = 237 136 fifteen-year-olds from 1994 to 2010. MHC was defined as the presence of two or more health complaints at least once a week. Logistic regression analysis was performed to evaluate trends across the five survey cycles for each country. Results: Lowest prevalence throughout the period 1994-2010 was 16.9% in 1998 in Austria and highest in 2006 in Israel (54.7%). Overall, six different trend patterns could be identified: No linear or quadratic trend (9 countries), linear decrease (7 countries), linear increase (5 countries), U-shape (4 countries), inverted U-shape (6 countries) and unstable (4 countries). Conclusion: Trend analyses are valuable in providing hints about developments in populations as well as for benchmarking and evaluation purposes. The high variation in health complaints between the countries requires further investigation, but may also reflect the subjective nature of health complaints.publishersversionPeer reviewe

Trends in health complaints from 2002 to 2010 in 34 countries and their association with health behaviours and social context factors at individual and macro-level

Publisher Copyright: © 2015 The Author. Published by Oxford University Press on behalf of the European Public Health Association. All rights reserved.Background: This article describes trends and stability over time in health complaints in adolescents from 2002 to 2010 and investigates associations between health complaints, behavioural and social contextual factors at individual level and economic factors at macro-level. Methods: Comprising N = 510 876 11-, 13- and 15-year-old children and adolescents in Europe, North America and Israel, data came from three survey cycles of the international Health Behaviour in School-aged Children (HBSC) study. Age- and gender-adjusted trends in health complaints were examined in each country by means of linear regression. By using the country as the random effects variable, we tested to what extent individual and contextual variables were associated with health complaints. Results: Significant associations are stronger for individual level determinants (e.g. being bullied, smoking) than for determinants at macro-level (e.g. GDP, Gini), as can be seen by the small effect sizes (less than 5% for different trends). Health complaints are fairly stable over time in most countries, and no clear international trend in health complaints can be observed between 2002 and 2010. The most prominent stable determinants were being female, being bullied, school pressure and smoking. Conclusion: Factors associated with health complaints are more related to the proximal environment than to distal macro-level factors. This points towards intensifying targeted interventions, (e.g. for bullying) and also targeting specific risk groups. The comparably small effect size at country-level indicates that country-level factors have an impact on health and should not be ignored.publishersversionPeer reviewe

Cross-national time trends in adolescent mental well-being from 2002 to 2018 and the explanatory role of schoolwork pressure

Purpose: Previous research has shown inconsistent time trends in adolescent mental well-being, but potential underlying mechanisms for such trends are yet to be examined. This study investigates cross-national time trends in adolescent mental well-being (psychosomatic health complaints and life satisfaction) in mainly European countries and the extent to which time trends in schoolwork pressure explain these trends. Methods: Data from 915,054 adolescents from 36 countries (50.8% girls; meanage = 13.54; standard deviationage = 1.63) across five Health Behaviour in School-aged Children surveys (2002, 2006, 2010, 2014, and 2018) were included in the analyses. Hierarchical multilevel models estimated cross-national trends in adolescent mental well-being and schoolwork pressure. We also tested whether schoolwork pressure could explain these trends in mental well-being. Results: A small linear increase over time in psychosomatic complaints and schoolwork pressure was found. No change in life satisfaction emerged. Furthermore, there was large cross-country variation in the prevalence of, and trends over time in, adolescent mental well-being and schoolwork pressure. Overall, declines in well-being and increases in schoolwork pressure were apparent in the higher income countries. Across countries, the small increase in schoolwork pressure over time partly explained the increase in psychosomatic health complaints. Conclusions: Our findings do not provide evidence for substantial declines in mental well-being among adolescents. Yet, the small increase in mental well-being and increases in schoolwork pressure appear to be quite consistent across high-income countries. This calls for the attention of public health professionals and policy-makers. Country differences in trends in both adolescent mental well-being outcomes and schoolwork pressure were considerable, which requires caution regarding the cross-national generalization of national trends

Research inventory of child health: A report on roadmaps for the future of child health research in Europe

RICHE was the response to a call under HEALTH-2009-3.3-5, with the title of 'European child health research platform'. The call text asked us to “address the diversity and fragmentation in child health research in Europe in an inclusive multidisciplinary way, identifying existing research programmes in Member States, recent advances and identification of gaps to explore road maps for the future of child health research in Europe”. Project structure A consortium, with a final total of 23 partners, and two associate (i.e. unfunded) partners, responded to this call. We designed a project with a linear structure, where the main focus of activity moved from work on the Inventory, and Indicators and Measurement, in Year 1, to work on Gaps in Year 2, finishing with the preparation of the Roadmap in year 3. The final 6 months (Year 4) were largely dissemination. The Platform, which is instantiated in our website, supported all of the other parts,, and was a focus for communication and dissemination throughout the project. Each workpackage focused on a specific area of work, but each fed into its successors, and all leaders and partners worked closely together. Each group produced a number of technical reports and other outputs. The final output was a Roadmap for future investment in European child health research. This has been widely disseminated, and has fed at Commission level and National level into the Horizon 2020 call preparation process. RICHE Roadmap The RICHE Roadmap is based upon a sound, scientific evidence base, which we had gathered as part of our earlier work. The project prepared an inventory of child health research and of measurements and indicators of child health in Europe (WP1 and WP2) . This was collated using a web platform – which can be found at www.childhealthresearch.eu. In addition to this exercise, a formal study of the gaps in child health research was undertaken by carrying out surveys and interviews of researchers and research users across Europe (WP3). This allowed our initial views on the research gaps to be refined and corrected by an iterative process, involving, both project partners, and the wider scientific community, so seeking grounding and validation for this key phase. These results formed the basis for the RICHE Roadmap. The Roadmap is based on a life-course perspective. It covers the important phases of a child’s development, including maternal health, and pregnancy, through to adolescence and the protective and risk factors, and health services encountered throughout childhood and adolescence as he or she moves towards adulthood. RICHE looked upstream to identify where more work needed to be done to prevent avoidable physical and mental ill-health, disability and death in the population of European children aged 0-18 years. This shows how the many influences and outcomes of children’s health are interrelated; a pattern reflected in the Roadmap. The work necessarily involved a series of value judgements, especially on setting priorities, because there are no objective and unconditionally valid answers to the question “Is there enough research on this topic?”, nor to the question “Is this a topic of significance?”. Nevertheless, the RICHE Roadmap uses an inclusive and transparent process to explain the recommendations it made, and the subjects it chose, making our values, and the reasons for judgements as explicit as possible. The report is organised into broad subject areas, that reflect the key ‘gaps’ in knowledge about children and young people, or about particular aspects of their lifestyle and health. These key areas, and selected findings within each area, are briefly summarised here. Life Course and Lifestyle This section focuses on children as they age, and recognises the importance of continuing to research how factors before conception, during gestation and in the very early years of life can affect present and future health. The challenges that children face as they grow up are also highlighted – these can be created because of policy decisions that fail to take account of children and young people’s lives or because of the pervasive influences of individual circumstances that act ask protective or risk factors for children’s actions. The concept of resilience in childhood is also highlighted, and how research needs to focus on this important and powerful means of improving children’s lives. A key issue, throughout the life course, is mental health and well-being. Fostering well-being in children from birth, and throughout childhood will provide numerous individual and societal benefits. It deserves a greater research focus. Socio-economic and Cultural Factors The socio-economic and cultural environment in which a child is born and grows up has a potent effect on a child’s health and well-being. Inequity and inequalities in health, between and within nations depending on socio-economic circumstances, are known to affect health outcomes. Those in the poorest areas have worse health, and shorter lives than those in the wealthiest areas. Other groups are at risk of marginalisation from health services and from opportunities that can maximise their health. These include migrant children where the question is how best to support their integration into their new societies and communities, while retaining their individual identity; children in the state care system have poor health and social outcomes, so improving these, by focused research is important for the future health of these children; children from minority population groups, in particular those who travel across nations, such as the Roma, need to have focused attention, to ensure that their health outcomes begin to match those of the general European child population. Social and Community Networks The main influences on children and young people are their immediate family and community networks. This extends from the influence of the family as a warm and nurturing environment in which to grow up – and conversely a place of the most profound danger and threat if such a family environment is toxic; to the wider influence of school, and finally the broader community. Becoming engaged and involved in community life is beneficial for the entire population, not just for the children and young people directly involved. It is an aspect of children and young people’s experience that is important for well-being and social inclusion. Environment The term 'environment' covers several different concepts, and the RICHE Roadmap describes the physical, virtual and also the perceived environment – all of which interlink in children’s lives, and have a profound effect on their health and development. These include the physical environment, the virtual (digital) environment, physical safety, including injury prevention, and protection form crime, anti-social behaviour and violence (both as perpetrators and victims). Complex Health Issues The majority of children in Europe are healthy, and ill-health is not a characteristic of this population as it is in, for example, an ageing population. However, there are certain health issues that affect children, and as such can blight an entire lifetime. Our Roadmap does not cover clinical issues, but takes a population perspective. There are certain disorders that have a population-wide effect and are prevalent enough in the child population to warrant particular attention from a public health viewpoint. Four specific areas of concern were identified – overweight and obesity, mental health, sexual and reproductive health, and neuro-developmental disorders. Health Services The main research needs of the health services focuses on the prevention of poor health. Comparing health services across Europe and evaluating the means of conveying health promotion messages are important directions for health research to investigate. Indicators need developing which reflect the effect of preventive actions, particularly among younger children. Vulnerable populations, such as those in deprived communities, need to have health prevention services particularly targeted. There is little systematic evaluation of such interventions, which compromises the development of new interventions and their implementation. Those who do not access services and those who need particular attention can be identified. Public Health Infrastructure Health surveillance is essential so that health needs can be identified and addressed effectively for the benefit of the child population. Yet, many existing sources of data are neither analysed, nor made available in a child-centric way. Children need to be made more visible in the data so that they can have more effective health promotion and health care on a population level. Specific examples include work on autism and morbidity due to injury. Europe also needs to establish proper measures and indicators of children’s health and children’s lives. We cannot act properly without first identifying and measuring the problem. Electronic health records are an emerging technology that has great potential, both for research, and for improved access to care. They need to be developed and investigated further to encourage their use across the European Union. Improving Research Capacity It is necessary to ensure that there are enough resources, both to do research, and to make use of the research findings. To sustain research activity, specialist training for junior child health researchers is needed, as are sufficient resources to maintain a critical mass of researchers and provide attractive career paths for them. Children and young people as subjects of research need to continue to be safeguarded by a consistently ethical framework, and information collected about children needs to be accurate, comprehensive and used intelligently so that interventions and services can be correctly directed. Using the roadmap The roadmap is a complex document, addressed to a number of different stakeholders. One key group are those who make decision bout research finding priorities. We have disseminated the roadmap widely at EU level, to reach into the process of priority setting for Horizon 2020. This has been done thought National Contact Points in each partner country, through relevant NGO's, and by sending copes to and meeting with relevant parts of the European Commission. Readers using the roadmap will most likely use it in two ways, first to make a general case for investment in Child Health Research, and secondly to target that investment, by considering the questions we have identified, and reviewing our justifications for these choices. We do not expect our work to determine future investments in child health, but we are confident that using our work would lead to better decisions overall. Conclusions Our core value is to put children first in our work. We take the rights of the child seriously, and we are conscious that many children do not have the opportunity to exercise the right to health and healthcare that European children they ought to have. The topics in this Roadmap are pragmatic in that they are researchable (within the grasp of presently available research methods and resources) and that are likely to have a significant effect on the lives of European children. This will go a considerable distance in improving the health and well-being of European children who may not have benefited from Europe’s good fortune up until this point. At the very least, the RICHE Roadmap aims to begin a serious conversation across Europe about the need for research to focus on children and how this will ultimately benefit all members of the European population. There is a need for children to become substantially more visible in European society. At present many children’s lives are invisible to health surveillance and to research. Sometimes they are submerged with their families, as in the case of Roma or for children of illegal and undocumented immigrant families. Even in well-documented societies, children’s circumstances are invisible as data are collected from the perspective of economically active adults, or households. Therefore, an overarching recommendation in this road map is the establishment of a European Child Health Observatory with a simple remit to make European Children, and their lives, health and attainment of rights more visible. We also recommend continuing and extending the discussion to the edge of existing child health boundaries, to address topics such as the effects on children’s health of urban design and architecture, fiscal policy (which can affect many health issues), welfare, or health effects of immigration policy. The RICHE Roadmap hopes to point the way in which children can be fully recognised and respected as forming a valuable population and whose health and well-being contributes to the health of our present and future European society

Factors associated with self-rated health status in university students: a cross-sectional study in three European countries

Mikolajczyk RT, Brzoska P, Maier C, et al. Factors associated with self-rated health status in university students: a cross-sectional study in three European countries. BMC Public Health. 2008;8(1): 215.Background: Self-rated health status (SRHS) is a reliable and valid measure for assessing the subjective and objective health of individuals. Previous studies have either focused predominantly on the elderly or investigated only a narrow range of factors potentially associated with SRHS. In examining student populations, these past studies were limited to single countries. The objectives of this study were to assess which candidate variables were independently associated with SRHS in university students, to compare these variables by country and by gender, and to investigate which of the variables was most important as a rating frame for SRHS. Methods: The data is from the Cross-National Student Health Survey, conducted in 2005 in universities in Germany, Bulgaria, and Poland (n = 2103; mean age = 20.7 years). SRHS was assessed with a single question using a five-point scale ranging from "excellent" to "poor". The study also measured a wide range of variables including: physical and psychological health, studying, social contacts/social support, and socio-demographic status. Results: Psychosomatic complaints (considered an aspect of physical health and, adjusted for psychological health) were the most important indicators in forming a rating frame for students' SRHS. There were few differences in the effects of variables associated with SRHS by gender (well-being: a measure of psychological health) and the variables associated with SRHS by country (well-being and self-efficacy). The remaining variables showed homogenous effects for both genders and for all three countries. Conclusion: The results suggest that SRHS can be reasonably used to compare students' health across countries. SRHS is affected by different physical, psychological and psychosomatic aspects of health; however, its strongest association is with psychosomatic complaints