Numerical simulation of the filling and curing stages in reaction injection moulding, using CFX

Mestrado em Engenharia MecânicaOs métodos habitualmente utilizados para a simulação de injecção em moldes envolvem um número considerável de simplificações, originando reduções significativas do esforço computacional mas, nalguns casos também limitações. Neste trabalho são efectuadas simulações de Reaction Injection Moulding (RIM) com o mínimo de simplificações, através da utilização do software de CFD multi-objectivos CFX, concebido para a simulação numérica de escoamentos e transferência de calor e massa. Verifica-se que o modelo homogéneo para escoamentos multifásicos do CFX, geralmente considerado o apropriado para a modelação de escoamentos de superfície livre em que as fases estão completamente estratificadas, é incapaz de modelar correctamente o processo de enchimento. Este problema é ultrapassado através da implementação do modelo não homogéneo juntamente com a condição de fronteira de escorregamento livre para o ar. A reacção de cura é implementada no código como uma equação de transporte para uma variável escalar adicional, com um termo fonte. São testados vários esquemas transitórios e advectivos, com vista ao reconhecimentos de quais os que produzem os resultados mais precisos. Finalmente, as equações de conservação de massa, quantidade de movimento, cura e energia são implementadas conjuntamente para simular os processos simultâneos de enchimento e cura presentes no processo RIM. Os resultados numéricos obtidos reproduzem com boa fidelidade outros resultados numéricos e experimentais disponíveis, sendo necessários no entanto tempos de computação consideravelmente longos para efectuar as simulações. ABSTRACT: Commonly used methods for injection moulding simulation involve considerable number of simplifications, leading to a significant reduction of the computational effort but, in some cases also to limitations. In this work, Reaction Injection Moulding (RIM) simulations are performed with minimum of simplifications, by using the general purpose CFD software package CFX, designed for numerical simulation of fluid flow and heat and mass transfer. The CFX’s homogeneous multiphase flow model, which is generally considered to be the appropriate choice for modelling free surface flows where the phases are completely stratified and the interface is well defined, is shown to be unable to model the filling process correctly. This problem is overcome through the implementation of the inhomogeneous model in combination with the free-slip boundary condition for the air phase. The cure reaction is implemented in the code as a transport equation for an additional scalar variable, with a source term. Various transient and advection schemes are tested to determine which ones produce the most accurate results. Finally, the mass conservation, momentum, cure and energy equations are implemented all together to simulate the simultaneous filling and curing processes present in the RIM process. The obtained numerical results show a good global accuracy when compared with other available numerical and experimental results, though considerably long computation times are required to perform the simulations

Insights into sucrose pathway of chicory stems by integrative transcriptomic and metabolic analyses

The worldwide-cultivated chicory (Cichorium intybus L.) produces food and beneficial compounds, and young pre-flowering inflorescence stems are newly marketed vegetables. These sink-organs undergo growth by metabolizing sugars of leaf origin; the carbohydrate content and sweetness are crucial aspects for consumers' nutrition and acceptance. NMR profiling of 31 hydrosoluble phytochemicals showed that stem contents varied as influenced by genotype, environment and interaction, and that higher sucrose levels were associated with the sweeter of two landraces. Integrative analyses of metabolic and transcriptomic profile variations allowed the dissection of sucrose pathway. Overall, 427 and 23 unigenes respectively fell into the categories of sucrose metabolism and sugar carriers. Among 10 differentially expressed genes, the 11474/sucrose synthase, 53458/fructokinase, 9306 and 17035/hexokinases, and 20171/SWEET-type genes significantly associated to sugar content variation, and deduced proteins were characterised in silico. Correlation analyses encompassing sugar level variation, expressions of the former genes and of computationally assigned transcription factors (10938/NAC, 14712/bHLH, 40133/TALE and 17846/MIKC) revealed a gene network. The latter was minimally affected by the environment and accomplished with markers, representing a resource for biological studies and breeding

Superior Myocardial Protection Using "Polarizing" Adenosine, Lidocaine, and Mg2+ Cardioplegia in Humans

[abstract not available

Transcriptome driven characterization of curly- and smooth-leafed endives reveals molecular differences in the sesquiterpenoid pathway

Diving into the genetics of endives Genetic analyses show molecular differences that could explain why curly endives taste bitterer than smooth ones. Donato Giannino of the Institute of Agricultural Biology and Biotechnology and colleagues in Italy analyzed the genetic differences between curly and smooth endives, a leafy vegetable used in salads. They found more than 3000 single sequence variations in genes distinguishing the two types from each other. Twenty six genes were involved in the biosynthesis of sesquiterpenoids, metabolites important for plant survival that also contribute to the bitter taste of endives and have antimalarial, sedative and analgesic effects when isolated for humans. Their levels were higher in curly than in smooth endives, potentially contributing to their more bitter taste. The information expands the genetic data available on endives for breeding programs

Venoarterial extracorporeal membrane oxygenation after coronary artery bypass grafting : Results of a multicenter study

Background: The evidence of the benefits of using venoarterial extracorporeal membrane oxygenation (VA-ECMO) after coronary artery bypass grafting (CABG) is scarce. Methods: We analyzed the outcomes of patients who received VA-ECMO therapy due to cardiac or respiratory failure after isolated CABG in 12 centers between 2005 and 2016. Patients treated preoperatively with ECMO were excluded from this study. Results: VA-ECMO was employed in 148 patients after CABG for median of 5.0 days (mean, 6.4, SD 5.6 days). Inhospital mortality was 64.2%. Pooled in-hospital mortality was 65.9% without significant heterogeneity between the centers (I-2 8.6%). The proportion of VA-ECMO in each center did not affect in-hospital mortality (p = 0.861). No patients underwent heart transplantation and six patients received a left ventricular assist device. Logistic regression showed that creatinine clearance (p = 0.004, OR 0.98, 95% CI 0.97-0.99), pulmonary disease (p = 0.018, OR 4.42, 95% CI 1.29-15.15) and pre-VA-ECMO blood lactate (p = 0.015, OR 1.10, 95% CI 1.02-1.18) were independent baseline predictors of in-hospital mortality. One-, 2-, and 3-year survival was 31.0%, 27.9%, and 26.1%, respectively. Conclusions: One third of patients with need for VA-ECMO after CABG survive to discharge. In view of the burden of resources associated with VA-ECMO treatment and the limited number of patients surviving to discharge, further studies are needed to identify patients who may benefit the most from this treatment. (C) 2017 Elsevier B.V. All rights reserved.Peer reviewe

Venoarterial extracorporeal membrane oxygenation after coronary artery bypass grafting: Results of a multicenter study.

BACKGROUND: The evidence of the benefits of using venoarterial extracorporeal membrane oxygenation (VA-ECMO) after coronary artery bypass grafting (CABG) is scarce. METHODS: We analyzed the outcomes of patients who received VA-ECMO therapy due to cardiac or respiratory failure after isolated CABG in 12 centers between 2005 and 2016. Patients treated preoperatively with ECMO were excluded from this study. RESULTS: VA-ECMO was employed in 148 patients after CABG for median of 5.0days (mean, 6.4, SD 5.6days). In-hospital mortality was 64.2%. Pooled in-hospital mortality was 65.9% without significant heterogeneity between the centers (I2 8.6%). The proportion of VA-ECMO in each center did not affect in-hospital mortality (p=0.861). No patients underwent heart transplantation and six patients received a left ventricular assist device. Logistic regression showed that creatinine clearance (p=0.004, OR 0.98, 95% CI 0.97-0.99), pulmonary disease (p=0.018, OR 4.42, 95% CI 1.29-15.15) and pre-VA-ECMO blood lactate (p=0.015, OR 1.10, 95% CI 1.02-1.18) were independent baseline predictors of in-hospital mortality. One-, 2-, and 3-year survival was 31.0%, 27.9%, and 26.1%, respectively. CONCLUSIONS: One third of patients with need for VA-ECMO after CABG survive to discharge. In view of the burden of resources associated with VA-ECMO treatment and the limited number of patients surviving to discharge, further studies are needed to identify patients who may benefit the most from this treatment