The Effect of Aluminium Surface Treatments on the Bonding Properties of Silica-Modified Epoxy Adhesive Joints: A Statistical Approach

A full factorial design is carried out to investigate the effects of different surface treatments, the inclusion of silica microparticles and the use of wash primer on the apparent shear strength and adherent strength of single-lap aluminium joints. Scanning electron microscopy, surface energy and roughness measurements are performed to characterise the aluminium surface. The results show that the use of wash primer decreases the apparent shear strength of the joints significantly. The cohesive failure of the primer is the main cause of the reduction in strength. On the other hand, the inclusion of 10 wt.% of silica microparticles in the adhesive layers increases the shear strength by 26%. Surfaces treated with NaOH for one minute, without using a wash primer, result in the most resistant joint. In contrast to the apparent shear strength, adherent strength is most effective when only degreasing is considered

Effect of titania addition on the properties of freeze-cast alumina samples

This work investigated the behavior of TiO2-containing α-Al2O3 samples prepared by the freeze-casting technique. Camphene and liquid nitrogen were used as the solvent and cooling fluid, respectively. Camphene resulted in the formation of dendritic pores, in the direction of the freeze-casting cold front during sample preparation. The formation of β-Al2TiO5 phase occurred at 1300°C, and became more evident as the sintering temperatures reached 1500°C. The TiO2 loading did not affect the sample porosity at a given temperature, but it was detrimental in the case of mechanical properties under certain conditions. For instance, the flexural strength slightly improved with increasing the TiO2 loading and sintering temperature from 1100 to 1300°C. This effect was attributed to the occurrence of a more effective sintering of alumina. However, as the heat treatment temperature was raised from 1300 to 1500°C, the flexural strength did not increase as a function of the TiO2 loading, even though the densification occurred with loss of porosity. The loss of mechanical strength was found to be associated with the formation of microcracks which stemmed from the formation of β-Al2TiO5 phase for TiO2 loadings in excess of 4wt% at these high sintering temperatures

The influence of Fe2O3 doping on the pore structure and mechanical strength of TiO2-containing alumina obtained by freeze-casting

This work investigated TiO/FeO doped alumina prepared by the freeze-casting technique and using camphene as the solvent. Dendritic pores were formed in the TiO doped alumina, a structure conferred by the frozen camphene. Contrary to this trend, further FeO doping of TiO-containing alumina resulted in the formation of non-dendritic structures. This behavior was attributed to the higher density of α-FeO (5.24 g cm) when compared to α-AlO (3.95 g cm) and anatase TiO (3.89 g cm), which reduced critical solidification front velocity, thus forming material with different pore shape. FeO doping also improved the densification of TiO-alumina and inhibited the formation of cracks, reflected by superior mechanical strength with best results ∼150% higher for 10% FeO loaded samples as compared to TiO-alumina samples

Modeling Rett syndrome with human patient-specific forebrain organoids

Copyright © 2020 Gomes, Fernandes, Vaz, Silva, Bekman, Xapelli, Duarte, Ghazvini, Gribnau, Muotri, Trujillo, Sebastião, Cabral and Diogo. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.Engineering brain organoids from human induced pluripotent stem cells (hiPSCs) is a powerful tool for modeling brain development and neurological disorders. Rett syndrome (RTT), a rare neurodevelopmental disorder, can greatly benefit from this technology, since it affects multiple neuronal subtypes in forebrain sub-regions. We have established dorsal and ventral forebrain organoids from control and RTT patient-specific hiPSCs recapitulating 3D organization and functional network complexity. Our data revealed a premature development of the deep-cortical layer, associated to the formation of TBR1 and CTIP2 neurons, and a lower expression of neural progenitor/proliferative cells in female RTT dorsal organoids. Moreover, calcium imaging and electrophysiology analysis demonstrated functional defects of RTT neurons. Additionally, assembly of RTT dorsal and ventral organoids revealed impairments of interneuron's migration. Overall, our models provide a better understanding of RTT during early stages of neural development, demonstrating a great potential for personalized diagnosis and drug screening.We also acknowledge financial support from Fundação para a Ciência e a Tecnologia (FCT), Portugal, through iBB, Institute for Bioengineering and Biosciences (UIDB/04565/2020) and from Programa Operacional Regional de Lisboa 2020 (Project No. 007317). AG was supported by FCT (PD/BD/128373/2017).info:eu-repo/semantics/publishedVersio

Alternativas à agricultura de corte e queima em processos de transição agroecológica: um desafio para a agricultura amazónica

A paisagem agrícola amazônica abriga uma diversidade de situações onde, com frequência, ocorre a prática do corte-e-queima para preparo de área para plantio. A constatação dos impactos adversos dessa prática evidencia a necessidade de promover a sua substituição via sistemas alternativos que viabilizem a produção agrícola, reduzindo ou evitando o uso do fogo. Embora muitas alternativas disponíveis tenham características de passos de processos de transição agroecológica e a ampliação da sua adoção possa ser beneficiada pela implantação de estratégias de transição social agroecológica, este tipo de prática não vem sendo abordado em estudos sobre processos de transição agroecológica. Este artigo se propõe a analisar exemplos de práticas alternativas à derruba-e-queima na Amazônia brasileira, à luz de processos de transição agroecológica e social agroecológica, como subsídio ao avanço no seu desenvolvimento e adoção, e à formulação e implantação de políticas públicas.The Amazonian agricultural landscape is home to a diversity of situations where often occurs the practice of slash-and-burn for land preparation for planting. The observation of the adverse impacts of this practice highlights the need to promote its replacement via alternative systems that enable agricultural production, reducing or avoiding the use of fire. Although many of the available alternatives have characteristics of ecological transition process steps and the expansion of its adoption can be benefited by the implementation of social-ecological transition strategies, this type of practice has not been addressed in studies on agroecological transition processes. This article sets out to analyse examples of alternatives to practices of slash-and-burn in the Brazilian Amazon, in the light of processes of agroeclogical and social-agroecological transitions, as subsidy to the advancement in their development and adoption and to the formulation and implementation of public policies.Eje A1 Sistemas de producción de base agroecológica (Trabajos científicos)Facultad de Ciencias Agrarias y Forestale

Alternativas à agricultura de corte e queima em processos de transição agroecológica: um desafio para a agricultura amazónica

A paisagem agrícola amazônica abriga uma diversidade de situações onde, com frequência, ocorre a prática do corte-e-queima para preparo de área para plantio. A constatação dos impactos adversos dessa prática evidencia a necessidade de promover a sua substituição via sistemas alternativos que viabilizem a produção agrícola, reduzindo ou evitando o uso do fogo. Embora muitas alternativas disponíveis tenham características de passos de processos de transição agroecológica e a ampliação da sua adoção possa ser beneficiada pela implantação de estratégias de transição social agroecológica, este tipo de prática não vem sendo abordado em estudos sobre processos de transição agroecológica. Este artigo se propõe a analisar exemplos de práticas alternativas à derruba-e-queima na Amazônia brasileira, à luz de processos de transição agroecológica e social agroecológica, como subsídio ao avanço no seu desenvolvimento e adoção, e à formulação e implantação de políticas públicas.The Amazonian agricultural landscape is home to a diversity of situations where often occurs the practice of slash-and-burn for land preparation for planting. The observation of the adverse impacts of this practice highlights the need to promote its replacement via alternative systems that enable agricultural production, reducing or avoiding the use of fire. Although many of the available alternatives have characteristics of ecological transition process steps and the expansion of its adoption can be benefited by the implementation of social-ecological transition strategies, this type of practice has not been addressed in studies on agroecological transition processes. This article sets out to analyse examples of alternatives to practices of slash-and-burn in the Brazilian Amazon, in the light of processes of agroeclogical and social-agroecological transitions, as subsidy to the advancement in their development and adoption and to the formulation and implementation of public policies.Eje A1 Sistemas de producción de base agroecológica (Trabajos científicos)Facultad de Ciencias Agrarias y Forestale

Generation of Induced Pluripotent Stem Cells from the Prairie Vole

The vast majority of animals mate more or less promiscuously. A few mammals, including humans, utilize more restrained mating strategies that entail a longer term affiliation with a single mating partner. Such pair bonding mating strategies have been resistant to genetic analysis because of a lack of suitable model organisms. Prairie voles are small mouse-like rodents that form enduring pair bonds in the wild as well as in the laboratory, and consequently they have been used widely to study social bonding behavior. The lack of targeted genetic approaches in this species however has restricted the study of the molecular and neural circuit basis of pair bonds. As a first step in rendering the prairie vole amenable to reverse genetics, we have generated induced pluripotent stem cell (IPSC) lines from prairie vole fibroblasts using retroviral transduction of reprogramming factors. These IPSC lines display the cellular and molecular hallmarks of IPSC cells from other organisms, including mice and humans. Moreover, the prairie vole IPSC lines have pluripotent differentiation potential since they can give rise to all three germ layers in tissue culture and in vivo. These IPSC lines can now be used to develop conditions that facilitate homologous recombination and eventually the generation of prairie voles bearing targeted genetic modifications to study the molecular and neural basis of pair bond formation

Transcriptional Signature and Memory Retention of Human-Induced Pluripotent Stem Cells

Genetic reprogramming of somatic cells to a pluripotent state (induced pluripotent stem cells or iPSCs) by over-expression of specific genes has been accomplished using mouse and human cells. However, it is still unclear how similar human iPSCs are to human Embryonic Stem Cells (hESCs). Here, we describe the transcriptional profile of human iPSCs generated without viral vectors or genomic insertions, revealing that these cells are in general similar to hESCs but with significant differences. For the generation of human iPSCs without viral vectors or genomic insertions, pluripotent factors Oct4 and Nanog were cloned in episomal vectors and transfected into human fetal neural progenitor cells. The transient expression of these two factors, or from Oct4 alone, resulted in efficient generation of human iPSCs. The reprogramming strategy described here revealed a potential transcriptional signature for human iPSCs yet retaining the gene expression of donor cells in human reprogrammed cells free of viral and transgene interference. Moreover, the episomal reprogramming strategy represents a safe way to generate human iPSCs for clinical purposes and basic research

Differential Functional Constraints on the Evolution of Postsynaptic Density Proteins in Neocortical Laminae

The postsynaptic density (PSD) is a protein dense complex on the postsynaptic membrane of excitatory synapses that is implicated in normal nervous system functions such as synaptic plasticity, and also contains an enrichment of proteins involved in neuropsychiatric disorders. It has recently been reported that the genes encoding PSD proteins evolved more slowly than other genes in the human brain, but the underlying evolutionary advantage for this is not clear. Here, we show that cortical gene expression levels could explain most of this effect, indicating that expression level is a primary contributor to the evolution of these genes in the brain. Furthermore, we identify a positive correlation between the expression of PSD genes and cortical layers, with PSD genes being more highly expressed in deep layers, likely as a result of layer-enriched transcription factors. As the cortical layers of the mammalian brain have distinct functions and anatomical projections, our results indicate that the emergence of the unique six-layered mammalian cortex may have provided differential functional constraints on the evolution of PSD genes. More superficial cortical layers contain PSD genes with less constraint and these layers are primarily involved in intracortical projections, connections that may be particularly important for evolved cognitive functions. Therefore, the differential expression and evolutionary constraint of PSD genes in neocortical laminae may be critical not only for neocortical architecture but the cognitive functions that are dependent on this structure