Damage modelling of fibre reinforced polymer matrix composite open hole tension specimens using the Ladevèze damage model in Pam-CRASH

non-peer-reviewedThe goal of this project was to accurately predict the ultimate failure strengths of fibre reinforced polymer matrix composite open hole tension specimens using the Ladevèze continuum mechanics damage model, currently available within the ESI Group Pam-CRASH software, using input parameters experimentally derived at the University of Limerick. This report presents the work carried out at the University of Limerick, both experimental and numerical, as part of the project. Results of an experimental test series carried out to derive Ladevèze damage model parameters for a carbon fibre reinforced polymer matrix composite are presented and discussed. In addition, the results of a numerical study carried out to calibrate the Ladevèze damage model, used to predict the ultimate strength of fibre reinforced open hole tension specimens are presented and discussed. Section 2 presents the procedures used and results of an experimental test series to derive Ladevèze damage model parameters. Section 3 presents the numerical work carried out at the University of Limerick as part of this project

Seeing distinct groups where there are none : spurious patterns from between-group PCA

Using sampling experiments, we found that, when there are fewer groups than variables, between-groups PCA (bgPCA) may suggest surprisingly distinct differences among groups for data in which none exist. While apparently not noticed before, the reasons for this problem are easy to understand. A bgPCA captures the g-1 dimensions of variation among the g group means, but only a fraction of the∑ni-g  dimensions of within-group variation ( are the sample sizes), when the number of variables, p, is greater than g-1. This introduces a distortion in the appearance of the bgPCA plots because the within-group variation will be underrepresented, unless the variables are sufficiently correlated so that the total variation can be accounted for with just g-1 dimensions. The effect is most obvious when sample sizes are small relative to the number of variables, because smaller samples spread out less, but the distortion is present even for large samples. Strong covariance among variables largely reduces the magnitude of the problem, because it effectively reduces the dimensionality of the data and thus enables a larger proportion of the within-group variation to be accounted for within the g-1-dimensional space of a bgPCA. The distortion will still be relevant though its strength will vary from case to case depending on the structure of the data (p, g, covariances etc.). These are important problems for a method mainly designed for the analysis of variation among groups when there are very large numbers of variables and relatively small samples. In such cases, users are likely to conclude that the groups they are comparing are much more distinct than they really are.  Having many variables but just small sample sizes is a common problem in fields ranging from morphometrics (as in our examples) to molecular analyses

Morphometric maps of bilateral asymmetry in the human humerus: An implementation in the R package morphomap

In biological anthropology, parameters relating to cross-sectional geometry are calculated in paired long bones to evaluate the degree of lateralization of anatomy and, by inference, function. Here, we describe a novel approach, newly added to the morphomap R package, to assess the lateralization of the distribution of cortical bone along the entire diaphysis. The sample comprises paired long bones belonging to 51 individuals (10 females and 41 males) from The New Mexico Decedent Image Database with known biological profile, occupational and loading histories. Both males and females show a pattern of right lateralization. In addition, males are more lateralized than females, whereas there is not a significant association between lateralization with occupation and loading history. Body weight, height and long-bone length are the major factors driving the emergence of asymmetry in the humerus, while interestingly, the degree of lateralization decreases in the oldest individuals

Assay of matrix metalloproteinases types 1, 2, 3 and 9 in breast cancer.

Matrix metalloproteinases (MMPs) are zinc dependent endopeptidases implicated in cancer invasion and metastasis. Gelatin zymography was performed on 84 human breast carcinomas and seven normal breast tissues. The precursor form of MMP-2 (72 kDa) was found in 11 (12%) samples, while its two activated forms, i.e. 62 kDa and 59 kDa, were found in three (6%) and 34 (40%) samples respectively. In contrast to MMP-2, most of the samples (52%) contained MMP-9 in its precursor form. Using ELISA, MMP-1 levels were found in 12% of the samples while MMP-3 levels were found in only 2% of the samples. Levels of MMP-2, -3 and -9 correlated inversely with numbers of nodal metastases. Neither MMP-2 nor -9 levels were significantly related to patient outcome. However, patients with high levels of a 50-kDa gelatinase band after zymography had a significantly better survival than patients with low levels. This species was never observed in normal breast tissue

Divergent evolutionary processes associated with colonization of offshore islands

Peer reviewedPublisher PD

Differential growth and development of the upper and lower human thorax

The difficulties in quantifying the 3D form and spatial relationships of the skeletal components of the ribcage present a barrier to studies of the growth of the thoracic skeleton. Thus, most studies to date have relied on traditional measurements such as distances and indices from single or few ribs. It is currently known that adult-like thoracic shape is achieved early, by the end of the second postnatal year, with the circular cross-section of the newborn thorax transforming into the ovoid shape of adults; and that the ribs become inclined such that their anterior borders come to lie inferior to their posterior. Here we present a study that revisits growth changes using geometric morphometrics applied to extensive landmark data taken from the ribcage. We digitized 402 (semi) landmarks on 3D reconstructions to assess growth changes in 27 computed tomography-scanned modern humans representing newborns to adults of both sexes. Our analyses show a curved ontogenetic trajectory, resulting from different ontogenetic growth allometries of upper and lower thoracic units. Adult thoracic morphology is achieved later than predicted, by diverse modifications in different anatomical regions during different ontogenetic stages. Besides a marked increase in antero-posterior dimensions, there is an increase in medio-lateral dimensions of the upper thorax, relative to the lower thorax. This transforms the pyramidal infant thorax into the barrel-shaped one of adults. Rib descent is produced by complex changes in 3D curvature. Developmental differences between upper and lower thoracic regions relate to differential timings and rates of maturation of the respiratory and digestive systems, the spine and the locomotor system. Our findings are relevant to understanding how changes in the relative rates of growth of these systems and structures impacted on the development and evolution of modern human body shapeCGL2012-37279 (Spanish Ministry for Economy and Competition) Fyssen-foundation (http://www.fondationfyssen.fr

Parental mediation in pandemic: predictors and relationship with children's digital skills and time spent online in Ireland

During the COVID-19 pandemic, an increasing reliance on digital technology to carry out social, entertainment, work and school activities increased, which may have affected the ways in which parents mediated their children's digital technology use. Given the prominent role that digital technology will have in the future, it is important to investigate parent and child characteristics which impacted parental mediation of children's digital technology use. Therefore, the present study aimed at analysing the frequency of parental mediation strategies (i.e. active and restrictive) during lockdown, their determinants, and how the two strategies affected children's digital skills and time spent online. Data were collected from 461 parent and 461 child participants. Results showed that almost half of parents (46%) practiced parental mediation with the same frequency, while the 42.6% applied it more often. Active mediation was predicted by parental worries about online risks, while restrictive mediation was predicted by time spent online by children, parental worries about online risks, parental negative attitudes towards digital technology and parents' digital skills. Children developed more digital skills when their parents applied higher levels of both active and restrictive mediation, and they spent the lowest amount of time online when their parents employed higher levels of restrictive and lower levels of active mediation. Practical implications for families and children's wellbeing are discussed

Children’s internet use, self-reported life satisfaction, and parental mediation in Europe: an analysis of the EU kids online dataset

The present research examines how children’s time spent online is associated with their perceived life satisfaction accounting for their age, gender, socio-economic status (SES), emotional problems, country, and family environmental factors. This article is based on the data of the large scale cross-sectional EU Kids Online survey from 16 European countries with nationally representative samples of children aged 9–17 (N = 11,200, Mage = 13.3, SD = 2.36; 50.6% boys, 49.4% girls). The results indicated that the time children spent online appeared to have no considerable negative effect on their self-reported life satisfaction (SRLS). Comparatively, the positive effects of children’s SES and family environment accounted for 43% of the overall 50% of the variance in children’s SRLS scores. Considering that children’s SES alone accounted for 42% of the variance, children’s emotional problems, country of residence, and enabling parental mediation accounted for the remaining 3, 4, and 1% of the variance, respectively. In line with previous studies that urge caution when discussing the negative influence of time spent online on children’s mental health and overall wellbeing, the current findings suggest that social-ecological characteristics and how children use the Internet, need to be examined furthe

“It's not just sexy pics”: an investigation into sexting behaviour and behavioural problems in adolescents

Sexting has been identified as an emerging online phenomenon among adolescents. However, research investigating its behavioural correlates and the sexting behaviours (i.e., sending and/or receiving) is still scarce. The present study investigated the association between different sexting behaviours and various behavioural problems among Irish adolescents. A sample of 848 students aged 15–18 participated in the study (Mage = 16.4 years). A self-report measure assessing the sharing of sexual images among teenagers was created and administered for the purpose of this study. The Strengths and Difficulties Questionnaire was adopted to detect emotional and behavioural problems. Findings showed that senders of sexts are more likely to be girls, whereas receivers are more likely to be boys. Two-way sexting (i.e., sending and receiving sexts) was more prominent among boys, LGBTQ adolescents, and positively associated with peer problems. Findings are discussed in terms of their theoretical and practical relevance

Challenges of achieving good environmental status in the Northeast Atlantic

The sustainable exploitation of marine ecosystem services is dependent on achieving and maintaining an adequate ecosystem state to prevent undue deterioration. Within the European Union, the Marine Strategy Framework Directive (MSFD) requires member states to achieve Good Environmental Status (GEnS), specified in terms of 11 descriptors. We analyzed the complexity of social-ecological factors to identify common critical issues that are likely to influence the achievement of GEnS in the Northeast Atlantic (NEA) more broadly, using three case studies. A conceptual model developed using a soft systems approach highlights the complexity of social and ecological phenomena that influence, and are likely to continue to influence, the state of ecosystems in the NEA. The development of the conceptual model raised four issues that complicate the implementation of the MSFD, the majority of which arose in the Pressures and State sections of the model: variability in the system, cumulative effects, ecosystem resilience, and conflicting policy targets. The achievement of GEnS targets for the marine environment requires the recognition and negotiation of trade-offs across a broad policy landscape involving a wide variety of stakeholders in the public and private sectors. Furthermore, potential cumulative effects may introduce uncertainty, particularly in selecting appropriate management measures. There also are endogenous pressures that society cannot control. This uncertainty is even more obvious when variability within the system, e.g., climate change, is accounted for. Also, questions related to the resilience of the affected ecosystem to specific pressures must be raised, despite a lack of current knowledge. Achieving good management and reaching GEnS require multidisciplinary assessments. The soft systems approach provides one mechanism for bringing multidisciplinary information together to look at the problems in a different light