Formation of Atomic Carbon Chains from Graphene Nanoribbons

The formation of one-dimensional carbon chains from graphene nanoribbons is investigated using it ab initio molecular dynamics. We show under what conditions it is possible to obtain a linear atomic chain via pulling of the graphene nanoribbons. The presence of dimers composed of two-coordinated carbon atoms at the edge of the ribbons is necessary for the formation of the linear chains, otherwise there is simply the full rupture of the structure. The presence of Stone-Wales defects close to these dimers may lead to the formation of longer chains. The local atomic configuration of the suspended atoms indicates the formation of single and triple bonds, which is a characteristic of polyynes.Comment: 4 pages, 5 figure

Ejection force of tubular injection moldings. Part II : a prediction model

The integrated knowledge of the injection molding process and the material changes induced by processing is essential to guarantee the quality of technical parts. In the case of parts with deep cavities, quite often the ejection phase of the molding cycle is critical. Thus, in the mold design stage, the aspects associated with the ejection system will require special consideration. In particular, the prediction of the ejection force will contribute to optimizing the mold design and to guarantee the integrity of the moldings. In this work, a simulation algorithm based on a thermomechanical model is described and their predictions are compared with experimental data obtained from a fully-instrumented mold (pressure, temperature, and force). Three common thermoplastics polymers were used for the tubular moldings: a semicrystalline polypropylene and two amorphous thermoplastics: polystyrene and polycarbonate. The thermomechanical model is based on the assumption of the polymer behavior changing from purely viscous to purely elastic below a transition point. This point corresponds to solidification determined by temperature in the case of amorphous materials and by critical crystallinity for semicrystalline polymers. The model results for the ejection force closely agree with the experimental data for the three materials used

Model to predict shrinkage and ejection forces of injection moulded tubular parts of short glass fiber reinforced thermoplastics

This work presents a model to predict shrinkage and ejection forces for glass fiber reinforced thermoplastics of tubular geometry. This mathematical model was based in Jansen’s Model to predict shrinkage and residual stresses in fiber reinforced injection molded products and Pontes’s Model to predict ejection forces for tubular parts of pure PP. The model used the modified classical laminate theory applied to injection moulding and it uses the fiber orientation state, temperature and pressure field as input and which predicts the shrinkage and ejection forces. The fiber orientation state was determined experimentally and the temperature and pressure fields were obtained by MOLDFLOW simulations. The model to predict ejection forces considers also the fiber orientation state, friction coefficient between steel and polymer, elastic modulus of polymer, both in the ejection temperature and diametrical shrinkage. The model is validated by experimental results

Assessment of the shrinkage and ejection forces of reinforced polypropylene based on nanoclays and short glass fibre

In this study the influence of nanoclay and glass fibre in the shrinkage and ejection forces in polypropylene matrix in tubular parts moulded by injection moulding were analysed. An instrumented mould was used to measure the part surface temperature and ejection forces in tubular parts. The materials used were a polypropylene homopolymer Domolen 1100L nanoclay for polyolefin nanocomposites P-802 Nanomax in percentages of 2%, 6% and 10% and a polypropylene homopolymer with content of 10% of glass fibre Domolen P1-013-V10-N and 30% of glass fibre Domolen P1-102-V30-N with 2% of nanoclay. The shrinkage and ejection forces were analysed. The results show that the incorporation of nanoclays decreases the shrinkage and ejection forces whereas glass fibre decreases the shrinkage and increase ejection forces due to the increase of the elastic modulus. The nanoclays decrease the ejection force when compared with glass fibre and pure PP. The effects of nanoclays are less pronounced than those of glass fibre. The effect of the mould temperatures on the ejection forces in the mouldings produced with the mentioned materials were also analysed. The ejection force decreases with the increase of the temperature of the mould

Unraveling the molecular basis of host cell receptor usage in SARS-CoV-2 and other human pathogenic β-CoVs

The recent emergence of the novel SARS-CoV-2 in China and its rapid spread in the human population has led to a public health crisis worldwide. Like in SARS-CoV, horseshoe bats currently represent the most likely candidate animal source for SARS-CoV-2. Yet, the specific mechanisms of cross-species transmission and adaptation to the human host remain unknown. Here we show that the unsupervised analysis of conservation patterns across the beta-CoV spike protein family, using sequence information alone, can provide valuable insights on the molecular basis of the specificity of beta-CoVs to different host cell receptors. More precisely, our results indicate that host cell receptor usage is encoded in the amino acid sequences of different CoV spike proteins in the form of a set of specificity determining positions (SDPs). Furthermore, by integrating structural data, in silico mutagenesis and coevolution analysis we could elucidate the role of SDPs in mediating ACE2 binding across the Sarbecovirus lineage, either by engaging the receptor through direct intermolecular interactions or by affecting the local environment of the receptor binding motif. Finally, by the analysis of coevolving mutations across a paired MSA we were able to identify key intermolecular contacts occurring at the spike-ACE2 interface. These results show that effective mining of the evolutionary records held in the sequence of the spike protein family can help tracing the molecular mechanisms behind the evolution and host-receptor adaptation of circulating and future novel b-CoVs. (C) 2021 The Author(s). Published by Elsevier B.V. on behalf of Research Network of Computational and Structural Biotechnology

Intervalo e número de aplicações do acibenzolar-s-metil no manejo da mancha bacteriana em tomate para processamneto industrial.

Esse trabalho objetivou avaliar o efeito do intervalo entre aplicações (4, 7, 10 e 14 dias) e do número de aplicações (4,6, 8 e 10) do ASM na eficiência de controle da doença em campo e na produtividade final, bem como na relação beneficio/custo dos tratamentos.Suplemento. Edição dos resumos do 44º Congresso Brasileiro de Fitopatologia, 2011, Bento Gonçalves. Resumo 318

Ocorrência de Xanthomonas perforans e X. gardneri em plantas infestantes em lavouras de tomate.

Este estudo objetivou relatar a ocorrencia natural de Xanthomonas spp. que causam a mancha bacteriana do tomateiro em plantas infestantes encontradas em lavouras comerciais de tomate para mesa e para industria.Resumo 1024. Edição dos resumos do 44º Congresso Brasileiro de Fitopatologia, 2011, Bento Gonçalves