Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O estudo da instabilidade do desenvolvimento (ID) em organismos pode ser útil para identificar os primeiros sinais de estresse ambiental. Alterações na ID também influenciam a aptidão dos organismos. A variação entre a simetria dos lados esquerdo e direito, manifestada como assimetria flutuante (AF), é um indicador da ID. Ao quantificarmos a literatura científica referente aos estudos de assimetria em répteis identificamos as seguintes tendências: perturbações ambientais aumentam a AF nas populações, fêmeas tendem a escolher machos com características sexuais simétricas, a instabilidade térmica durante o desenvolvimento do ovo pode produzir indivíduos com maior assimetria, a ocorrência de lesões é mais frequente em indivíduos assimétricos para um determinado lado e há uma correlação negativa entre a assimetria e o desempenho locomotor. Considerando os nossos critério de busca, não encontramos estudos sobre assimetria em répteis na América do Sul. Neste estudo, utilizamos diferentes caracteres merísticos e métricos bilaterais para identificar a AF em diferentes populações de cinco espécies de lagartos do gênero Cnemidophorus (C. abaetensis, C. lacertoides, C. littoralis, C. nativo, C. ocellifer) em 15 áreas de restinga ao longo da costa leste do Brasil. A AF foi maior em populações de Cnemidophorus com maior densidade, menor em populações de restingas com maior degradação ambiental e a sua relação com a concentração de mercúrio variou dependendo da espécie. Provavelmente os agentes estressores ambientais avaliados atuam com intensidades diferentes. O nível de degradação ambiental e a concentração de mercúrio causariam a deterioração precoce dos indivíduos com maiores valores de AF. Isso resulta em uma relação inversa entre esses estresses e a AF das populações. Indivíduos com vestígios de autotomia caudal tiveram maiores valores de AF, o que pode ser um indicativo de que indivíduos com menor aptidão efetuam mais autotomia caudal do que aqueles com maior aptidão. Lagartos com evidências de autotomia também tiveram maior tamanho corpóreo, provavelmente devido a estes estarem expostos a mais tempo aos riscos de predação. Não encontramos diferenciação entre as espécies na frequência de autotomia caudal sendo esta talvez melhor explicada por fatores ambientais como a intensidade de predação. Os índices de AF para caracteres múltiplos se mostraram mais eficientes do que a AF de caracteres individuais nas comparações entre indivíduos vivendo em populações com diferentes níveis de estresse e entre indivíduos com e sem autotomia caudal / The study of developmental instability (DI) in organisms may be a useful tool to identify early signals of environmental stress. Variations in DI also influence the organisms fitness. The variation between the symmetry of the left and right sides, manifested as fluctuating asymmetry (FA), is widely used as a measure of DI. We screened the available scientific literature on asymmetry in reptiles and identified the following trends: environmental disturbances increase FA in populations, females tend to select males with symmetrical sexual traits, thermal instability during egg development can produce individuals with a higher asymmetry, occurrence of injuries is more frequent in asymmetrical individuals for a particular side, and there is a negative correlation between asymmetry and locomotor performance. There was no study on reptiles asymmetry at South America, considering our screening criteria. In this study, we used meristic and metrics bilateral traits to identify FA in populations of five species of Cnemidophorus lizards (C. abaetensis, C. lacertoides, C. littoralis, C. nativo, C. ocellifer) spread at 15 restinga areas along Brazilian east coast. The FA of individuals was higher at higher Cnemidophorus populations density, it was lower at restingas with higher environmental disturbance, and its relation to mercury concentration varied depending on the species. Probably the evaluated environmental stressors act with different intensities. The level of environmental disturbance and mercury concentration should cause earlier deterioration of individuals with higher FA. This results in an inverse relationship between these stressors and FA in populations. Individuals with autotomized tail had higher FA, which may indicate that individuals with lower fitness perform more tail autotomy than those with higher fitness. Lizards with tail autotomy also had higher body size, probably because older lizards have had more encounters with predator. We found no differentiation among species on tail autotomy frequency. Perhaps tail autotomy is better explained by environmental factors such as intensity of predation. The multiple traits FA indexes were more efficient than single traits index to compare individuals in different levels of environmental stress and to compare individuals with and without tail autotomy

Made available in DSpace on 2014-06-11T19:22:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-22Bitstream added on 2014-06-13T18:09:00Z : No. of bitstreams: 1 perez_dg_me_rcla.pdf: 821493 bytes, checksum: 938fad7997660774f8c919574b04e6e2 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Embora os invertebrados sejam conhecidos pela grande facilidade de acúmulo de poluentes presentes em seu ambiente, e muitos serem utilizados como espécies sentinelas em estudos de biomonitoramento, pouco ainda é conhecido sobre o impacto de toxicantes sobre o sistema imune desses animais. Nesse sentido, os hemócitos desempenham um papel fundamental: estas células circulam livremente através da hemolinfa dos invertebrados e atuam no reconhecimento de materiais estranhos ao organismo, mediando e efetuando reações de defesa celular. Diferentes tipos morfológicos podem ser reconhecidos, mas ainda há controvérsia entre os pesquisadores sobre a exata classificação dos hemócitos, devido à diversidade de técnicas para preservação e observação dessas células. A classificação mais aceita atualmente agrupa os hemócitos em sete tipos principais: pró-hemócitos, plasmatócitos, granulócitos, esferulócitos, adipohemócitos, oenocitóides e coagulócitos. Por meio da utilização de técnicas histológica, histoquímica e ultra-estrutural, o presente trabalho objetivou caracterizar morfofisiologicamente os hemócitos circulantes na hemolinfa do diplópodo Rhinocricus padbergi, bem como aqueles encontrados por entre as células da camada de corpo gorduroso no intestino médio de animais expostos a substratos contendo diferentes amostras de lodo de esgoto, resíduo gerado nas Estações de Tratamento de Esgoto (ETEs). Este resíduo tem sido cogitado como um bom condicionador de solo em áreas degradadas e como um potencial fertilizante agrícola, apesar do risco de estar contaminado com patógenos e/ou metais pesados. A partir das análises realizadas, foram identificados três tipos morfológicos distintos de hemócitos circulantes na hemolinfa dessa espécie: pró-hemócitos, plasmatócitos e granulócitos (subtipos I e II). Também foram observadas células com características... / Although invertebrates are known for ease accumulation of pollutants present in their environment and several are used as sentinel species in biomonitoring studies, little is known about the impact of toxicants on the immune system of these animals. In this sense, hemocytes play an important role: these cells circulate freely through the hemolymph of invertebrates and act in the recognition of foreign materials to the organism, mediating and performing cellular defence reactions. Different morphological types are recognized, but there is still controversy among the researchers about the exact classification of the hemocytes due to the diversity of techniques for preservation and observation of these cells. Currently, the most accepted classification groups the hemocytes into seven main types: pro-hemocytes, plasmatocytes, granulocytes, spherulocytes, adipohemocytes, oenocytoids and coagulocytes. By histological, histochemical and ultra-structural techniques, the present study aimed to characterize morpho-physiologically the hemocytes circulating in the hemolymph of the diplopod Rhinocricus padbergi, as well as those found among the cells of the fat body layer of the midgut of animals exposed to substrates containing samples of sewage sludge, residue generated in the Sewage Treatment Plants (STPs). This residue has been considered as a good soil conditioner on degraded areas and as a potential agricultural fertilizer, despite the risk of being contaminated with pathogens and/or heavy metals. From the analyses carried out, it was identified three distinct morphological types of hemocytes circulating in the hemolymph of this species: pro-hemocytes, plasmatocytes and granulocytes (subtypes I and II). It was also observed cells with intermediate characteristics between pro-hemocytes and plasmatocytes, suggesting a probable cellular differentiation in the hemolymph... (Complete abstract click electronic access below)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O estudo da instabilidade do desenvolvimento (ID) em organismos pode ser útil para identificar os primeiros sinais de estresse ambiental. Alterações na ID também influenciam a aptidão dos organismos. A variação entre a simetria dos lados esquerdo e direito, manifestada como assimetria flutuante (AF), é um indicador da ID. Ao quantificarmos a literatura científica referente aos estudos de assimetria em répteis identificamos as seguintes tendências: perturbações ambientais aumentam a AF nas populações, fêmeas tendem a escolher machos com características sexuais simétricas, a instabilidade térmica durante o desenvolvimento do ovo pode produzir indivíduos com maior assimetria, a ocorrência de lesões é mais frequente em indivíduos assimétricos para um determinado lado e há uma correlação negativa entre a assimetria e o desempenho locomotor. Considerando os nossos critério de busca, não encontramos estudos sobre assimetria em répteis na América do Sul. Neste estudo, utilizamos diferentes caracteres merísticos e métricos bilaterais para identificar a AF em diferentes populações de cinco espécies de lagartos do gênero Cnemidophorus (C. abaetensis, C. lacertoides, C. littoralis, C. nativo, C. ocellifer) em 15 áreas de restinga ao longo da costa leste do Brasil. A AF foi maior em populações de Cnemidophorus com maior densidade, menor em populações de restingas com maior degradação ambiental e a sua relação com a concentração de mercúrio variou dependendo da espécie. Provavelmente os agentes estressores ambientais avaliados atuam com intensidades diferentes. O nível de degradação ambiental e a concentração de mercúrio causariam a deterioração precoce dos indivíduos com maiores valores de AF. Isso resulta em uma relação inversa entre esses estresses e a AF das populações. Indivíduos com vestígios de autotomia caudal tiveram maiores valores de AF, o que pode ser um indicativo de que indivíduos com menor aptidão efetuam mais autotomia caudal do que aqueles com maior aptidão. Lagartos com evidências de autotomia também tiveram maior tamanho corpóreo, provavelmente devido a estes estarem expostos a mais tempo aos riscos de predação. Não encontramos diferenciação entre as espécies na frequência de autotomia caudal sendo esta talvez melhor explicada por fatores ambientais como a intensidade de predação. Os índices de AF para caracteres múltiplos se mostraram mais eficientes do que a AF de caracteres individuais nas comparações entre indivíduos vivendo em populações com diferentes níveis de estresse e entre indivíduos com e sem autotomia caudal / The study of developmental instability (DI) in organisms may be a useful tool to identify early signals of environmental stress. Variations in DI also influence the organisms fitness. The variation between the symmetry of the left and right sides, manifested as fluctuating asymmetry (FA), is widely used as a measure of DI. We screened the available scientific literature on asymmetry in reptiles and identified the following trends: environmental disturbances increase FA in populations, females tend to select males with symmetrical sexual traits, thermal instability during egg development can produce individuals with a higher asymmetry, occurrence of injuries is more frequent in asymmetrical individuals for a particular side, and there is a negative correlation between asymmetry and locomotor performance. There was no study on reptiles asymmetry at South America, considering our screening criteria. In this study, we used meristic and metrics bilateral traits to identify FA in populations of five species of Cnemidophorus lizards (C. abaetensis, C. lacertoides, C. littoralis, C. nativo, C. ocellifer) spread at 15 restinga areas along Brazilian east coast. The FA of individuals was higher at higher Cnemidophorus populations density, it was lower at restingas with higher environmental disturbance, and its relation to mercury concentration varied depending on the species. Probably the evaluated environmental stressors act with different intensities. The level of environmental disturbance and mercury concentration should cause earlier deterioration of individuals with higher FA. This results in an inverse relationship between these stressors and FA in populations. Individuals with autotomized tail had higher FA, which may indicate that individuals with lower fitness perform more tail autotomy than those with higher fitness. Lizards with tail autotomy also had higher body size, probably because older lizards have had more encounters with predator. We found no differentiation among species on tail autotomy frequency. Perhaps tail autotomy is better explained by environmental factors such as intensity of predation. The multiple traits FA indexes were more efficient than single traits index to compare individuals in different levels of environmental stress and to compare individuals with and without tail autotomy

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-12T13:09:04Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertacao_MitalleMatos_PPGG.pdf: 3448234 bytes, checksum: fe598459348fe967a8f1c2e5067f7d99 (MD5) / Made available in DSpace on 2016-07-12T13:09:04Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertacao_MitalleMatos_PPGG.pdf: 3448234 bytes, checksum: fe598459348fe967a8f1c2e5067f7d99 (MD5) Previous issue date: 2015-03-02 / CNPq / Danos causados por doenças virais estão entre os principais fatores limítrofes da produtividade do feijão-caupi. Em condições de estresse os fatores de transcrição (TFs) participam ativamente das etapas iniciais do processo de detecção e sinalização, regulando a expressão de vários grupos gênicos. Neste sentido, objetivou-se caracterizar TFs da família MYB e avaliar sua expressão diferencial frente à infecção viral, bem como determinar genes de referência (RGs) para normalização dos dados em RT-qPCR sob diferentes condições de estresse e controles. Por meio de análises in silico no banco NordEST, identificamos no transcriptoma do feijão-caupi um total de 86 candidatos a TF MYB, classificados em três subfamílias. A análise dos componentes estruturais do domínio R2R3-MYB permitiu observar a conservação dos aminoácidos característicos desta classe protéica em feijão-caupi. Por sua vez, o padrão de distribuição em pseudocromossomos de Phaseolus vulgaris indicou que genes MYB sofreram duplicações em tandem e intercromossomais, contribuindo para sua expansão no feijão-caupi. A análise filogenética formou 18 subclados, apoiados pela estrutura dos motivos funcionais da região C-terminal das proteínas. Das tags SuperSAGE diferencialmente expressas sob infecção viral, três foram reguladas positivamente, indicando a participação de candidatos MYB na resposta ao estresse viral. Dos sete RGs avaliados em três conjuntos experimentais, β-tubulina, Skip16 e Act2/7 + Skip16 foram as melhores combinações para seca, salinidade e vírus, respectivamente, podendo ser recomendados como normalizadores para estudos de expressão diferencial em feijão-caupi. Neste estudo identificamos a maior família de TFs em plantas observando sua participação ativa na resposta de defesa contra estresses em feijão-caupi. / Damages caused by viral diseases are among the main factors affecting the cowpea productivity. Under stress conditions, transcription factors (TFs) actively participate in the initial stages of the detection and signaling process by regulating the expression of various gene groups. In this sense, the objective of the present work was to characterize members of the MYB TF-family and evaluate their differential expression under viral infection, also determining reference genes (RGs) for data normalization in RT-qPCR under different stress and control conditions. Using in silico approaches to analyze the NordEST databank, a total of 86 MYB TF-candidates could be identified, being classified into three subfamilies. An analysis of the structural components of the R2R3-MYB domain allowed the identification of conserved amino acid residues of this protein class in cowpea. In turn, the MYB distribution pattern in the pseudochromosomes of Phaseolus vulgaris indicated that MYB members suffered in tandem and interchromosomal duplications, contributing to their expansion in cowpea. Phylogenetic analysis formed 18 subclades, supported by structural features of motifs in the C-terminal region of the protein. Of differentially expressed SuperSAGE tags under viral infection, three were upregulated, indicating the involvement of MYB candidates in response to viral stress. Considering the seven tested RGs under three experimental conditions, β-tubulin, Skip16 and Act2/7 + Skip16 were the best combinations for drought, salinity and viruses, respectively, recommended as normalizer genes in studies of differential expression in cowpea. In the present work we identified members of the largest family of TFs in plants observing their active participation in defense against stress response in cowpea.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2014-10-30T14:05:00Z No. of bitstreams: 2 Dissertação - Renan Nunes Costa - 2014.pdf: 650263 bytes, checksum: 0a242695b84bbbe8d03ab17bd0c2d681 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2014-10-30T14:30:09Z (GMT) No. of bitstreams: 2 Dissertação - Renan Nunes Costa - 2014.pdf: 650263 bytes, checksum: 0a242695b84bbbe8d03ab17bd0c2d681 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-10-30T14:30:09Z (GMT). No. of bitstreams: 2 Dissertação - Renan Nunes Costa - 2014.pdf: 650263 bytes, checksum: 0a242695b84bbbe8d03ab17bd0c2d681 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2014-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / There is a consensus among researchers in the world that the declining number of amphibian species and the increasing frequency of abnormalities in individual attributes of anurans are associated with habitat reduction and environmental contamination. With advance of agriculture crops, also increased the use of agrochemicals defensives, and the fragility of Brazilian laws for aquatic environmental protection burst the level of environmental stress significantly. Organisms can show biological responses related to these environmental modifications, that can be used to assess the environmental impact of agricultural practices. This biological response can be particularly useful, especially when we are able to correlate the biological response in morphological and/or physiological attributes with environmental impacts. The fluctuating asymmetry (FA) is a tool based on observation of deviations in the homeostasis of bilateral traits throughout the organism development and can be used for biomonitoring protocols. The FA can clarify which type of stressor is acting on a population. In this context, the present study assesses how the FA in anurans larvae can elucidate the impact of stressful factors. In the first chapter, our objective was to test experimentally if exposure to glyphosate dosages (Roundup® Original herbicide) affect the survival and increase the development deviations in the Physalaemus cuvieri larvae. In acute exposure, the survival rate was decreased at higher levels of contamination and the LC50 observed was considered to moderately toxic. In the chronic exposure, resulting from contamination, individuals showed higher levels of FA in relation to control larvae. In the second chapter, based on field sampling, our objective was to assess if reduction of physical habitat integrity, expressed by land use and reduction of marginal vegetation near to water bodies, reflected in higher levels in fluctuating asymmetry in P. cuvieri and Scinax fuscomarginatus larvae. In this case, with increased level of impact on the surrounding matrix, the larvae of both species showed increased of FA levels. In S. fuscomarginatus, the FA levels were also higher in environments with lower percentage of edge vegetation. In summary, it’s observed that increasing environmental stress, either through contamination by glyphosate or increased anthropogenic modification of the margins of water bodies, reflects in the higher development deviations on the frog’s larvae. The affected structures can be associated with sensory capabilities of the species, in which the increased frequency of these deviations can reduce individual fitness and influence the population homeostasis over time, directly contributing to species declines. / Há um consenso entre os pesquisadores do mundo de que a redução do número de espécies de anfíbios e o aumento da frequência de anormalidades nos atributos individuais estão associados à redução e à contaminação de hábitats. Com o avanço dos cultivos agrícolas, o aumento da aplicação de produtos químicos e a fragilidade das leis de proteção de ambientes aquáticos, os níveis de estresse ambiental aumentam significativamente. Dessa forma, as respostas biológicas podem favorecer as avaliações de impacto ambiental, principalmente em espécies que apresentam plasticidade em seus atributos comportamentais, morfológicos e/ou fisiológicos, como as larvas de anuros. A assimetria flutuante (AF) é uma ferramenta que se baseia na observação de desvios na homeostase do desenvolvimento de caracteres bilaterais e pode favorecer o biomonitoramento, esclarecendo qual tipo de fator estressante está agindo sobre uma população. Neste contexto, o presente estudo avalia como a assimetria flutuante em larvas de anuros pode elucidar o impacto de fatores estressantes. No primeiro capítulo, o objetivo foi testar, experimentalmente, se a exposição a doses de glifosato (herbicida Roundup® Original) afetam a sobrevivência e aumentam os desvios no desenvolvimento de larvas da espécie Physalaemus cuvieri. Na exposição aguda, a taxa de sobrevivência foi reduzida em níveis maiores de contaminação e o LC50 observado foi considerado moderadamente tóxico. Na exposição crônica, decorrente da contaminação, os indivíduos apresentaram maiores níveis de AF em relação às larvas do controle. No segundo capítulo, baseado em coletas de campo, o objetivo foi avaliar se a redução da integridade física dos hábitats, expressa pelo uso do solo nas proximidades e pela redução da vegetação marginal nos corpos d’água, refletem em maiores níveis de assimetria flutuante nas larvas de P. cuvieri e Scinax fuscomarginatus. Neste caso, com o aumento do nível de impacto na matriz circundante, as larvas de ambas as espécies apresentaram um aumento dos níveis de AF. Em S. fuscomarginatus, os níveis de AF também foram maiores em ambientes com menor porcentagem de vegetação nas bordas. Em suma, observa-se que o aumento do estresse ambiental, seja pela contaminação por glifosato ou pelo aumento da influência antrópica nas margens dos corpos d’água, reflete em maiores desvios no desenvolvimento das larvas de anuros. As estruturas afetadas podem estar associadas à capacidade sensorial das espécies, no qual o aumento da frequência destes desvios pode reduzir a aptidão individual e influenciar a homeostase da população ao longo do tempo, contribuindo diretamente com o declínio de espécies.

Introduction and Aim Stress and how individuals cope with environmental stressors is an essential issue in urban settings, where expanding and densely developed artificial environments have negative effects on the psychosocial health of the urban population. The aim of this thesis was therefore to explore and identify environmental stressors and coping strategies among young adults.   Method Collection of data was made through five focus group discussions with four to five university students, between 20 to 30 years of age in Tokyo, Japan. The data was then further analyzed with thematic analysis.   Findings Three themes with sub-themes were identified from the thematic analysis, highlighting exposure of external pressures and stressors that threatens young adult’s capability in coping with these stressors on a daily basis. The study identified the urban environment, including transportation and crowds as main sources of stress. Furthermore, young adults in Tokyo expressed interpersonal relationships as a significant factor when coping with environmental stressors.   Conclusion The present study identifies several different and similar perceived stressful threats and coping strategies among young adults in Tokyo. Where potential stressful threats were created by person-environment transactions that determines how one can adapt and cope with these stressors. Further research on the subject of environmental stressors will be needed to further outline the relationship and influence of environmental stressors on individuals wellbeing and health.

The influence of two lubricating and cleaning agents and diesel fuel on environmental stress cracking of polyamide reinforced by glass fibers and polycarbonate was studied in this master thesis. Testing of environmental stress cracking was performed by the method of critical bending deformation. Bergen elliptical strain jig was used for testing. The test liquids caused varying levels of environmental stress cracking of amorphous polycarbonate, but they did not cause environmental stress cracking of glass fiber reinforced polyamide. The test method used allows testing the resistance of both materials against environmental stress cracking of any liquid. The results can be used to design products that are expected to be exposed to corrosive liquids. Quantification of the influence of stress free corrosion on the static and impact properties of polycarbonate and glass fiber reinforced polyamide was performed by accelerated test. Specimens were exposed to test liquid and an elevated temperature of 70 °C. The mechanical properties of the tested materials were significantly affected by elevated temperature exposure. The yield strength of the polycarbonate has increased and the toughness has decreased due to physical aging. The tensile strength of glass fiber reinforced polyamide has increased due to a decrease of the moisture content of the material.

The Environmental Stress Hypothesis (ESH) illustrates the underlying mechanisms of internalizing problems in children with Developmental Coordination Disorder (DCD), indicating that the relationship between DCD and internalizing problems could be influenced by numerous physical and psychosocial consequences. However, the potential pathways described in this conceptual framework have not been comprehensively examined. Furthermore, given that child development is a dynamic process, these pathways have not been investigated from a developmental perspective. In order to address these gaps in knowledge, this dissertation sought to advance our understanding of the ESH by examining the underlying mediating pathways connecting DCD and internalizing problems in three age groups: early childhood, late childhood/early adolescence, and young adulthood. Study 1 showed that preschool children at risk for DCD (rDCD) experience more internalizing problems than typically developing children. However, physical activity and BMI do not mediate the relationship between rDCD and internalizing problems. Overall, our findings confirm that rDCD and internalizing problems co-occur in early childhood. Nevertheless, as there is no mediation of physical activity or BMI, the underlying mechanisms may be more related to other psychosocial outcomes (e.g., self-concept or perceived social support), suggested in the ESH. Study 2 examined school-aged children and included global self-worth, one of the psychological outcomes identified in the ESH, to address one of the limitations in Study 1. Findings support the ESH by showing a sequential mediating pathway from probable DCD (pDCD), through physical activity/BMI and global self-worth, to self-reported internalizing problems. Sex was found to moderate the underlying mechanisms of internalizing problems, altering the pathways from pDCD to internalizing problems. Study 3 was conducted to test the full ESH in emerging adults. Results support the mediating effects of psychosocial well-being, including stress, global relationships, perceived social support, and self-concept, on the relationship between poor motor coordination and self-reported psychological distress in young adults. However, in this age group, physical inactivity and higher BMI, did not mediate the relationship between motor coordination and internalizing problems. In conclusion, this dissertation highlights the co-occurrence of motor difficulties and internalizing problems across three developmental stages. The underlying mechanisms of internalizing problems may differ by age and sex. It is also worth noting that compared to physical health, psychosocial well-being may play a more important role as a mediator in the relationship between motor coordination and internalizing problems. / Thesis / Doctor of Philosophy (PhD) / Developmental Coordination Disorder (DCD) or poor motor coordination has been linked to the higher levels of internalizing problems, such as anxiety and/or depression. However, the underlying mechanisms remain unclear. Although the Environmental Stress Hypothesis (ESH) provides a theoretical framework illustrating that physical and psychosocial consequences of DCD may play important roles, this model has not been comprehensively examined. Therefore, this dissertation tested different components of the ESH in three age groups (i.e., preschool age, school age, and young adulthood) in an attempt to provide a better understanding of why motor difficulties cause more internalizing problems from a developmental perspective. Findings confirm that children with DCD and adults with poor motor coordination are at greater risk for internalizing problems, and that perceptions of self may play a more important role explaining the relationship. However, the potential pathways from motor difficulties to internalizing problems may differ by sex and age. In summary, it is recommended that, in order to prevent or improve mental health problems, interventions should target improvements in self-concept, such as self-esteem, through participation in physical activity or weight control, while taking into account sex and age.

Environmental stress cracking (ESC) is a significant problem that has plagued the plastics industry since its discovery nearly 70 years ago. The accelerated brittle failure brought about when a stressed polymer comes in contact with an aggressive environment can happen suddenly with destructive results. Many classes of polymers are susceptible to this type of slow crack growth; however special emphasis has typically been placed on polyolefins due to their wide range of working environments, market dominance and their seemingly chemical resistance. Much research has been focused on formulating environmentally resistant materials, while the evaluation techniques for gauging environmental stress cracking resistance (ESCR) seem to have been left behind. This research focuses on developing a reliable testing technique for evaluating the ESCR of polyethylene resins. Passive acoustic monitoring was adapted to an industrially accepted ESCR test in an attempt to hear polymer damage before it was visually apparent. It was discovered that the low energy released during the early stages of damage and excessive background noise masked passive signals, making this method of evaluation impractical. Alternatively, active ultrasonic monitoring through velocity and attenuation measurements was investigated to see if probing techniques could be used to detect structural damage. Active ultrasonic monitoring of static and tensile stressed samples were able to differentiate plasticization after ageing, however no indication of ESCR properties could be inferred. A novel forced based monitoring system was developed in response to the acoustic testing techniques. Force monitoring was able to provide useful information regarding the failure cycle of ESC and the acquired profiles could describe a failure onset time. Several ageing environments were also tested with force monitoring and a traditional ESCR test to reveal the stress cracking ability of biodiesel, an important finding. / Thesis / Master of Applied Science (MASc) / Accelerated failure of stressed plastics can occur upon exposure to fluids through a phenomenon known as environmental stress cracking (ESC). The following research outlines the development of a novel testing technique to gauge a material’s environmental stress cracking resistance (ESCR). Adaption of passive acoustics to an existing stress cracking test was unable to provide any indication of ESCR, however the use of active ultrasonics was able to show sample plasticization. A novel forced based measuring technique was found to uniquely map the failure progression of a sample undergoing ESC, providing valuable information for understanding the phenomenon. Additional testing was also completed on various environmental fluids to reveal biodiesel’s ability to provoke ESC, an important observation.

The first paper, “Dye Penetrant Induced Microcracking in High-Performance Thermoplastic Polyimide Composites”, studied the possibility of spurious microcracking in three high-performance thermoplastic polyimide composite materials due to zinc iodine dye penetrant. The material systems were IM7/LaRC™-IAX, IM7/LaRC™-IAX2, and IM7/LaRC™-8515. Specimens from each material system were subjected to one of three immersion tests. The first immersion test involved soaking composite specimens previously prepared with different polishing techniques in dye penetrant. In the second test, specimens were immersed in the individual components of the dye penetrant. The final test involved exposure of specimens to one of six solvents followed by exposure to dye penetrant. Results showed that the composite materials have sufficiently high thermal residual stresses to drive microcracking in the presence of dye penetrant without external mechanical loading. There was no evidence that the different polishing techniques had an effect on dye penetrant-induced stress cracking. The dye penetrant components did not produce microcracks in the composites. Some combination of the components must be present to induce microcracking. Observations also revealed that polishing had an effect on the microcracking process of the composites that were initially exposed to solvents then dye penetrant. The second paper, “The Effect of Environmental Stress Cracking on High-Performance Polymeric Composites”, studied solvent stress cracking and solvent-induced strength degradation on four polyimide matrix materials developed at NASA-Langley Research Center. These materials are LaRC™-IAX, LaRC™-IAX2, LaRC™-8515, and LaRC™-PETI-5. Cross-ply specimens were used to characterize solvent stress cracking in composites. Matrix cracking due to solvent exposure was observed in all of the materials. The solvent exposure time of the materials ranged from 1 minute to 96 hours. The results show that residual thermal stresses due to processing in the cross-ply composite specimens are sufficient to drive solvent stress cracking in the matrix. Solvent application lowers the microcracking toughness, G_mc ,values such that the available strain energy, G_m, within the transverse ply groups is sufficient to initiate microcracking. In the absence of a solvent, the same G_m value would not induce microcracking. Transverse flexure tests were performed on unidirectional specimens to determine the effects of the solvents on the material strengths. The presence of certain solvents severely degraded the materials. The manner in which the solvents were applied to the materials determined the degree of material degradation. The results revealed a synergistic effect between stress and solvent. The tests showed that diglyme, MEK, and acetone produced the most severe damage to the materials. The most solvent resistant material was LaRC™-PETI-5. This is followed by LaRC™-8515, LaRC™-IAX2, and LaRC™-IAX respectively. LaRC™- PETI-5 is a thermoset whereas the remaining materials are thermoplastics. / Master of Science