875 resultados para Ethylene


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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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High molecular weight semi crystalline thermoplastic poly(ester urethanes), TPEUs, were prepared from a vegetable oil-based diisocyanate, aliphatic diol chain extenders and poly(ethylene adipate) macro diol using one-shot, pre-polymer and multi-stage polyaddition methods. The optimized polymerization reaction achieved ultra-high molecular weight TPEUs (>2 million as determined by GPC) in a short time, indicating a very high HPMDI diol reactivity. TPEUs with very well controlled hard segment (HS) and soft segment (SS) blocks were prepared and characterized with DSC, TGA, tensile analysis, and WAXD in order to reveal structure property relationships. A confinement effect that imparts elastomeric properties to otherwise thermoplastic TPEUs was revealed. The confinement extent was found to vary predictably with structure indicating that one can custom engineer tougher polyurethane elastomers by "tuning" soft segment crystallinity with suitable HS block structure. Generally, the HPMDI-based TPEUs exhibited thermal stability and mechanical properties comparable to entirely petroleum-based TPEUs. (C) 2014 Elsevier Ltd. All rights reserved.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Pós-graduação em Ciência e Tecnologia de Materiais - FC

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Background: The search for alternative and effective forms of training simulation is needed due to ethical and medico-legal aspects involved in training surgical skills on living patients, human cadavers and living animals. Aims : To evaluate if the bench model fidelity interferes in the acquisition of elliptical excision skills by novice medical students. Materials and Methods: Forty novice medical students were randomly assigned to 5 practice conditions with instructor-directed elliptical excision skills' training (n = 8): didactic materials (control); organic bench model (low-fidelity); ethylene-vinyl acetate bench model (low-fidelity); chicken legs' skin bench model (high-fidelity); or pig foot skin bench model (high-fidelity). Pre- and post-tests were applied. Global rating scale, effect size, and self-perceived confidence based on Likert scale were used to evaluate all elliptical excision performances. Results : The analysis showed that after training, the students practicing on bench models had better performance based on Global rating scale (all P < 0.0000) and felt more confident to perform elliptical excision skills (all P < 0.0000) when compared to the control. There was no significant difference (all P > 0.05) between the groups that trained on bench models. The magnitude of the effect (basic cutaneous surgery skills' training) was considered large (>0.80) in all measurements. Conclusion : The acquisition of elliptical excision skills after instructor-directed training on low-fidelity bench models was similar to the training on high-fidelity bench models; and there was a more substantial increase in elliptical excision performances of students that trained on all simulators compared to the learning on didactic materials.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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In the postharvest management, the fruits can be exposed to injuries that depreciated the quality and the shelf life. Thus, it was evaluated the modified atmosphere effects on guavas var. Paluma subjected to different mechanical damages. Once harvested, the fruits were selected, sanitized and submitted to the treatments T1 (control) - without injuries or packaging in bags of low density polyethylene (LDPE); T2 - without injuries + LDPE bags; T3 - damage by fall of 1 m + LDPE bags; T4 - damage by compression of 9 N + LDPE bags; T5 - damage by fall of 1 m + damage by compression of 9 N + LDPE bags and T6 - damage by fall of 1 m + damage by compression of 9 N without LDPE bags. The treatments were kept in cold storage at 10 ± 1 o C and 94 ± 2% de R.H. The analysis of CO2/ethylene production, enzymatic activity, total and soluble pectins, pulp firmness, titratable acidity (TA), soluble solids (SS), reducing sugars and ascorbic acid were performed every 10 days of refrigeration, and an additional day outside cold storage (22 ± 1o C and 75 ± 3% R.H.) for 30 days. Guavas packed in LDPE bags, not subject to mechanical damage, presented the best quality standards. The fruits suffered only one kind of damage, when packaged, presented satisfactory pattern compared to the fruits without package and not exposed to any mechanical damages. Applying the two kinds of damages, the LDPE packaging was not adequate to decrease the metabolic rate of these fruits, making them unfit for marketing.

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