Mechanism based failure of 3D-printed continuous carbon fiber reinforced thermoplastic composites

The present work describes a computational mechanism based failure analysis conducted for 3D-printed continuous carbon fiber reinforced thermoplastic composites (CFRTPCs), which could not be seen in the available literature. The material failure is investigated based on intraply failure evaluation and adopts different failure criteria for the material constituents. The micromechanical modeling employs the Asymptotic Homogenization technique and comprises the selection of a representative volume element statistically equivalent to the microstructure of the material, which is identified from cross-section micrographs. In contrast to recent work, it is demonstrated that an additional relation is required for the macroscopic deviatoric stresses acting over the matrix. This avoids an overestimation of the matrix failure when the reinforced lamina is subjected to longitudinal and shear loads. The resulting failure envelopes are presented and compared to those provided by analytical failure theories available in the literature. The results obtained by the micromechanical approach showed its ability to predict failure of 3D-printed CFRTPCs, in addition to bring different elements for the discussion that could not be captured with analytical models. In this context, it is believed that the characteristics inherent to the microstructure reproduced in the RVE,\ua0 articularly contributed to obtaining more realistic failure envelopes

Expanding Puck and Sch\ufcrmann Inter Fiber Fracture Criterion for Fiber Reinforced Thermoplastic 3D-Printed Composite Materials

The present work expands the application of Puck and Sch\ufcrmann Inter-Fiber Fracture criterion to fiber reinforced thermoplastic 3D-printed composite materials. The effect of the ratio between the transverse compressive strength and the in-plane shear strength is discussed and a new transition point between the fracture conditions under compressive loading is proposed. The recommended values of the inclination parameters, as well as their effects on the proposed method, are also discussed. Failure envelopes are presented for different 3D-printed materials and also for traditional composite materials. The failure envelopes obtained here are compared to those provided by the original Puck and Sch\ufcrmann criterion and to those provided by Gu and Chen. The differences between them are analyzed with the support of geometrical techniques and also statistical tools. It is demonstrated that the Expanded Puck and Sch\ufcrmann is capable of providing more suitable failure envelopes for fiber reinforced thermoplastic 3D-printed composite materials in addition to traditional semi-brittle, brittle and intrinsically brittle composite materials

Experimental investigation on the effect of carbon fiber reinforcements in the mechanical resistance of 3D printed specimens

In the last years, fiber-reinforced polymer composites have been under study for additive manufacturing. For this purpose, it is important to assess the behavior of these materials in terms of mechanical properties. The present experimental study evaluates the mechanical resistance of both PLA and carbon fiber reinforced PLA. The work used a full factorial Design of Experiments (108 tests) selecting as factors the infill density, infill pattern, material, number of perimeters and printing orientation. The main results highlight that the most influential factors on the tensile strength are both type of material and number of perimeters. In this study, the use of reinforcements did not improve the mechanical resistance attained by the corresponding virgin material. Particularly, for some selected specimens, the porosity measured in the fracture section is larger for the reinforced PLA specimens, so they showed a smaller cross-section

Identification of Representative Equivalent Volumes on the Microstructure of 3D-Printed Fiber-Reinforced Thermoplastics Based on Statistical Characterization

The present work describes a methodology to compute equivalent volumes representing the microstructure of 3D-printed continuous fiber-reinforced thermoplastics, based on a statistical characterization of the fiber distribution. In contrast to recent work, the methodology herein presented determines the statistically equivalent fiber distribution directly from cross-section micrographs, instead of generating random fiber arrangements. For this purpose, several regions, with different sizes and from different locations, are cropped from main cross-section micrographs and different spatial descriptor functions are adopted to characterize the microstructures in terms of agglomeration and periodicity of the fibers. Detailed information about the adopted spatial descriptors and the algorithm implemented to identify the fiber distribution, as well as to define the location of cropped regions, are given. From the obtained statistical characterization results, the minimum size of the equivalent volume required to be representative of the fiber distribution, which is found in the cross-section micrographs of 3D-printed composite materials, is presented. To support the findings, as well as to demonstrate the effectiveness of the proposed methodology, the homogenized properties are also computed using representative equivalent volumes obtained in the statistical characterization and the results are compared to those experimentally measured, which are available in the literature

A utilização de vídeo-aulas e videoconferências no aprendizado do estudante na educação a distância

A educação a distância vem crescendo impulsionada pela demanda de pessoas com formação superior, bem como pela possibilidade de utilização de tecnologias de informação, que se desenvolveram intensamente nos últimos anos. Assim, essas novas formas de interação possibilitaram uma maior aproximação entre o aluno a distância e o docente, como é o caso da vídeo-aula e da videoconferência, porém para que essa aproximação seja eficiente é necessário uma estrutura de apoio com diversos equipamentos e um desenho que se preocupe em despertar a atenção do aluno, fazendo com que o mesmo sinta-se atraído pela explanação do conteúdo e sinta-se a vontade para participar. Dessa maneira, o desenho destas duas ferramentas foram alterados quando da passagem do primeiro para o segundo módulo do curso, havendo assim uma mudança na percepção da qualidade das mesmas por parte dos alunos. Nesse sentido, o presente artigo tem como objetivo mensurar por base da percepção dos estudantes, a utilização de vídeo-aulas e videoconferências no aprendizado do mesmo na educação a distância. Quanto à metodologia, caracteriza-se como: descritiva, estudo de caso, predominantemente quantitativa, pesquisa-ação, bibliográfica e documental. As primeiras conclusões deste estudo permitiram observar que o desenho das videoconferências e vídeo-aula apesar de eficazes, necessitaram de mudanças ao longo do curso. Estas mudanças estabeleceram uma maior qualidade e aceitação por parte dos estudantes, verificado nos resultados obtidos por meio de questionários aplicados nas disciplinas estudadas

MODELO DE JOGO, ESTRATÉGIA DE JOGO, ESTILO DE JOGO E TÁTICA DE JOGO: CONCEPÇÕES ÚTEIS PARA COMPREENDER O CONTEXTO DO JOGO ESPORTIVO

Misconceptions of sport concepts hinder an articulation of paramount conceptions to understand and intervene in training-competition dyad. This article aimed to propose definitions of the terms “game model”, “game strategy”, “playing style”, and “game tactics”, and to propose an articulation between these terms to guide sport intervention and analysis. A theoretical-conceptual research of these terms was carried out, which resulted in the elaboration of a Conceptual Map, through the CmapTools program. The Propositional Clarity Table was used to analyze the elaborated propositions. It was defined that: the game model corresponds to a representation of sport game basic functioning, game strategy comprises the set of plans in competition, playing style is a qualification of game actions, and game tactics is synonymous of action within the game. We expect the articulation of these conceptions can help the comprehension of sport context.La falta de claridad de conceptos deportivos dificulta la articulación de concepciones importantes para compreender y intervenir en la díada entrenamiento-competéncia. El objetivo del artículo fué proponer una definición de los conceptos “modelo de juego”, “estrategia de juego”, “estilo de juego” y “táctiva de juego”, y proponer una articulación de los conceptos para orientar la intervención y analisis deportiva. Se realizó una investigación teórico-conceptual que resultó en uno Mapa Conceptual elaborado por el software CmapTools. Se utilizó la Tabla de Claridad Proposicional para analizar las proposiciones elaboradas. Se definió que: modelo de juego se refiere a la representación del funcionamento básico del juego; estrategia de juego se refiere al conjunto de planes de competición; estilo de juego es una calificación de las acciones en el juego, y táctica es sinónimo de acción en el juego. Se espera que la articulación de estas concepciones ayude en la compreensión del contexto deportivo.A ausência de precisão e clareza de conceitos do esporte dificulta a articulação de concepções importantes para compreender e intervir na díade treino-competição. O artigo teve como objetivo propor definições operacionais dos termos “modelo de jogo”, “estratégia de jogo”, “estilo de jogo” e “tática de jogo”, e propor articulações entre esses termos visando orientar a intervenção e análise no esporte. Foi realizada uma pesquisa teórico-conceitual dos termos-alvo que resultou na elaboração de um Mapa Conceitual, pelo programa CmapTools. Foi utilizada a Tabela de Clareza Proposicional para analisar o conteúdo das proposições elaboradas. Foi definido que: modelo de jogo refere-se à representação do funcionamento básico do jogo, estratégia de jogo refere-se ao conjunto de planos na competição, estilo de jogo é uma qualificação das ações no jogo e tática de jogo é sinônimo de ação no jogo. Espera-se que a articulação dessas concepções auxilie na compreensão do contexto esportivo

Erythrina velutina Willd. alkaloids: Piecing biosynthesis together from transcriptome analysis and metabolite profiling of seeds and leaves

Introduction: Natural products of pharmaceutical interest often do not reach the drug market due to the associated low yields and difficult extraction. Knowledge of biosynthetic pathways is a key element in the development of biotechnological strategies for plant specialized metabolite production. The scarce studies regarding non-model plants impair advances in this field. Erythrina spp. are mainly used as central nervous system depressants in folk medicine and are important sources of bioactive tetracyclic benzylisoquinoline alkaloids, which can act on several pathology-related biological targets. Objective: Herein the purpose is to employ combined transcriptome and metabolome analyses (seeds and leaves) of a non-model medicinal Fabaceae species grown in its unique arid natural habitat. The study tries to propose a putative biosynthetic pathway for the bioactive alkaloids by using an omic integrated approach. Methods: The Next Generation Sequencing-based transcriptome (de novo RNA sequencing) was carried out in a Illumina NextSeq 500 platform. Regarding the targeted metabolite profiling, Nuclear Magnetic Resonance and the High-Performance Liquid Chromatography coupled to a micrOTOF-QII, High Resolution Mass Spectrometer, were used. Results: This detailed macro and micromolecular approach applied to seeds and leaves of E. velutina revealed 42 alkaloids by metabolome tools. Based on the combined evidence, 24 gene candidates were put together in a putative pathway leading to the singular alkaloid diversity of this species. Conclusion: These results contribute by indicating potential biotechnological targets Erythrina alkaloids biosynthesis as well as to improve molecular databases with omic data from a non-model medicinal plant. Furthermore, they reveal an interesting chemical diversity in Erythrina velutina harvested in Caatinga. Last, but not least, this data may also contribute to tap Brazilian biodiversity in a rational and sustainable fashion, promoting adequate public policies for preservation and protection of sensitive areas within the Caatinga

Rarity of monodominance in hyperdiverse Amazonian forests.

Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such "monodominant" forests are known from all of the main tropical regions. For Amazonia, we sampled the occurrence of monodominance in a massive, basin-wide database of forest-inventory plots from the Amazon Tree Diversity Network (ATDN). Utilizing a simple defining metric of at least half of the trees ≥ 10 cm diameter belonging to one species, we found only a few occurrences of monodominance in Amazonia, and the phenomenon was not significantly linked to previously hypothesized life history traits such wood density, seed mass, ectomycorrhizal associations, or Rhizobium nodulation. In our analysis, coppicing (the formation of sprouts at the base of the tree or on roots) was the only trait significantly linked to monodominance. While at specific locales coppicing or ectomycorrhizal associations may confer a considerable advantage to a tree species and lead to its monodominance, very few species have these traits. Mining of the ATDN dataset suggests that monodominance is quite rare in Amazonia, and may be linked primarily to edaphic factors

Convalescent plasma for COVID-19 in hospitalised patients : an open-label, randomised clinical trial

Background: The effects of convalescent plasma (CP) therapy in hospitalised patients with coronavirus disease 2019 (COVID-19) remain uncertain. This study investigates the effect of CP on clinical improvement in these patients. Methods: This is an investigator-initiated, randomised, parallel arm, open-label, superiority clinical trial. Patients were randomly (1:1) assigned to two infusions of CP plus standard of care (SOC) or SOC alone. The primary outcome was the proportion of patients with clinical improvement 28 days after enrolment. Results: A total of 160 (80 in each arm) patients (66.3% critically ill, 33.7% severely ill) completed the trial. The median (interquartile range (IQR)) age was 60.5 (48–68) years; 58.1% were male and the median (IQR) time from symptom onset to randomisation was 10 (8–12) days. Neutralising antibody titres >1:80 were present in 133 (83.1%) patients at baseline. The proportion of patients with clinical improvement on day 28 was 61.3% in the CP+SOC group and 65.0% in the SOC group (difference −3.7%, 95% CI −18.8–11.3%). The results were similar in the severe and critically ill subgroups. There was no significant difference between CP+SOC and SOC groups in pre-specified secondary outcomes, including 28-day mortality, days alive and free of respiratory support and duration of invasive ventilatory support. Inflammatory and other laboratory marker values on days 3, 7 and 14 were similar between groups. Conclusions: CP+SOC did not result in a higher proportion of clinical improvement on day 28 in hospitalised patients with COVID-19 compared to SOC alone

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio