Finite element formulation to study thermal stresses in nanoencapsulated phase change materials for energy storage

Nanoencapsulated phase change materials (nePCMs) – which are composed of a core with a phase change material and of a shell that envelopes the core – are currently under research for heat storage applications. Mechanically, one problem encountered in the synthesis of nePCMs is the failure of the shell due to thermal stresses during heating/cooling cycles. Thus, a compromise between shell and core volumes must be found to guarantee both mechanical reliability and heat storage capacity. At present, this compromise is commonly achieved by trial and error experiments or by using simple analytical solutions. On this ground, the current work presents a thermodynamically consistent and three-dimensional finite element (FE) formulation considering both solid and liquid phases to study thermal stresses in nePCMs. Despite the fact that there are several phase change FE formulations in the literature, the main novelty of the present work is its monolithic coupling – no staggered approaches are required – between thermal and mechanical fields. Then, the FE formulation is implemented in a computational code and it is validated against one-dimensional analytical solutions. Finally, the FE model is used to perform a thermal stress analysis for different nePCM geometries and materials to predict their mechanical failure by using Rankine’s criterion

Anti epidermal growth factor receptor therapy in small bowel adenocarcinoma

Rationale:Small bowel adenocarcinoma (SBA) is an uncommon gastrointestinal cancer, thus limited data about treatment for advanced disease are available. The lack of specific guidelines has justified the use of therapeutic protocols usually applied in advanced colorectal cancer. Few and preliminary data have suggested possible clinical benefit from the use of target therapy such as bevacizumab and cetuximab.Patient concerns:We present the case of a young woman who was admitted to the emergency department for acute abdominal pain, nausea, and vomiting related to a jejunal stenosis.Diagnoses:An enteroscopy with jejunal biopsy showed poorly differentiated cancerous cells suggestive for primary intestinal cancer. There were no signs of metastatic disease at radiological evaluation. A jejunal resection was subsequently carried out and the diagnosis of mucinous adenocarcinoma of the jejunum was confirmed.Interventions:The computed tomography scan performed 1 month after surgery showed metastatic disease. Therefore, the patient received combined protocols of chemotherapy and either bevacizumab or the anti-epidermal growth factor receptor (EGFR) panitumumab.Outcomes:A partial response (PR) was achieved with Folfox plus panitumumab and a maintenance therapy with panitumumab is being conducted with a mild toxicity and a progression free survival of 19 months since the beginning of panitumumab.Lessons:This is, to the best of our knowledge, the first report in the literature of a patient with SBA who has benefitted from panitumumab with an overall survival of 83 months

Influence of collagen fibril alignment in collagen scaffolds mineralization

Bone extracellular matrix (ECM) gives bone its unique mechanical properties, thus being important in bone tissue engineering to mimic its native composition and microstructure. The main component in bone ECM is Type-I collagen, which works as a scaffold for bone cell attachment and mineral deposition. There are two locations where mineralization takes place: the intrafibrillar and interfibrillar spaces of collagen fibrils. Several theories try to explain mineral formation in bone tissue. However, none of them was proven right, and so, the mechanism for mineralization facilitated by the collagen lattice is still unknown. This way, it is essential to study such a mechanism and develop bone tissue engineering approaches to mimic bone ECM. In this work, we hypothesized that collagen fibrils alignment would promote scaffolds mineralization. To prove it, we 3D printed fibrillar collagen hydrogels scaffolds using the suspension 3D printing technique, in which a gelatin slurry was used as a suspension bath. First, an optimization of the printing process was performed. Then scaffolds were printed, choosing the finest (123 ± 25 µm) and largest fiber diameter (215 ± 66 µm) obtained. Fiber diameter size was proven to affect the collagen fiber alignment inside the scaffolds and, consequently, affect mineral precipitation. The smallest fiber diameter scaffold showed signs of mineralization after one day inside a mineralization solution. In contrast, the largest fiber scaffold only presented mineralization signs after three days of submersion. Moreover, suspended electrowriting was introduced in this dissertation, obtaining a 40 µm jet diameter inside a castor oil bath, proving to be a promising additive manufacturing technology to achieve higher resolution constructs when 3D printing hydrogels.A matrix extra celular (ECM) do osso confere-lhe as suas únicas propriedades mecânicas e, portanto, torna-se importante mimetizar a composição e microestrutura nativa da ECM em engenharia de tecidos ósseos. O colagénio tipo-I é o principal componente da ECM e funciona como suporte para adesão celular e deposição de minerais, podendo a mineralização ocorrer nos espaços Intra e interfibrilares do colagénio. Existem algumas teorias que tentam explicar os mecanismos de formação de minerais no tecido ósseo. Contudo, nenhuma foi comprovada, fazendo com que, o mecanismo pelo qual a mineralização facilitada por colagénio ocorre, seja ainda desconhecido. Desta forma, estudar este mecanismo e desenvolver técnicas, em engenharia de tecidos, para que seja possível mimetizar a ECM do osso, torna-se essencial. Neste projeto, teorizámos que o alinhamento das fibrilas de colagénio em scaffolds iriam promover a sua mineralização. Deste modo, hidrogéis de colagénio fibrilar foram impressos recorrendo à técnica de impressão em suspensão, na qual foi utilizado um banho de suspensão à base de gelatina. Inicialmente, a otimização do processo de impressão foi efetuada. De seguida, as fibras mais estreitas (123 ± 25 µm) e largas (215 ± 66 µm) foram escolhidas para realizar a impressão das estruturas desejadas. Foi provado que o diâmetro das fibras influencia o alinhamento das fibrilas de colagénio nas estruturas e, consequentemente, a sua mineralização. As fibras de menor dimensão apresentaram sinais de mineralização após um dia de submersão na solução de mineralização, enquanto que, as fibras mais largas exibiram sinais de deposição de minerais apenas após três dias. Adicionalmente, a técnica de suspended electrowriting foi introduzida nesta dissertação, obtendo-se um diâmetro de jato de 40 µm dentro de um banho de óleo de ricínio, provando que esta é uma técnica promissora de fabrico aditivo, que nos permite atingir melhores resoluções na impressão 3D de hidrogéis

Soil carbon sequestration rates under Mediterranean woody crops using recommended management practices : A meta-analysis

This work was supported by the projects: CARBOLIVAR (P11-RNM-7186) funded by Consejería de Innovación, Ciencia y Empresa of Junta de Andalucía and GEISpain project (CGL2014‐52838‐C2‐1‐R) funded by Ministerio de Economía y Competitividad, both including European Union ERDF funds. This work was also supported by the FPU 2012 grant program of the Ministerio de Educación, Cultura y Deporte of Spain. Dr. Roberto Garcia-Ruiz and Eduardo Aguilera gratefully acknowledge support by the Sustainable Farm Systems project (SSHRC 895-2011-1020) funded by the Canadian Social Sciences and Humanities Research Council.Peer reviewedPostprin