Viscoelastic flow asymmetries in a helical static mixer and their impact on mixing performance

Helical static mixers are often used during the processing of formulated products with complex rheological properties, such as viscoelasticity. Previous experimental studies have highlighted that increasing the viscoelasticity of the flow hinders the mixing performance in the laminar flow regime. In this study, we use computational fluid dynamics to investigate the flow of a FENE-CR model fluid in a helical static mixer. The numerical results show clearly that the reduced mixing performance is caused by flow distribution asymmetries which develop at the mixer element intersections. The results allow us to quantify the degree of asymmetry for the range of conditions studied, which is correlated with the quantified mixing performance for each simulation. The mixing is quantified using a Lagrangian particle tracking technique, and a new mixing index is defined based on the mean nearest distance between the two sets of tracked particles. The results show that the asymmetry parameter does not follow a pitchfork bifurcation, as it typically does for elastic instabilities in symmetrical geometries such as the cross-slot. For low values of the extensibility parameter, L2, the flow remained (Eulerian) steady for all Reynolds Re and Weissenberg Wi numbers studied. At fixed Re and Wi, increasing L2 causes the flow to become transient and greatly increases the magnitude of the asymmetry. The results presented in this study help us to understand the effects that viscoelasticity can cause in mixing processes

Metal alloys, matrix inclusions and manufacturing techniques of Moinhos de Golas collection (North Portugal): a study by micro-EDXRF, SEM–EDS, optical microscopy and X-ray radiography

"Article:820"A collection of 35 metallic artefacts comprising various typologies, some of which can be attributed to the Bronze Age and others to later periods, were studied to provide detailed information on elemental composition, manufacturing techniques and preservation state. Elemental analysis by micro-EDXRF and SEM–EDS was performed to investigate the use of different alloys and to study the presence of microstructural heterogeneities, as inclusions. X-ray radiography, optical microscopy and SEM–EDS were used to investigate manufacturing techniques and degradation features. Results showed that most of the artefacts were produced in a binary bronze alloy (Cu–Sn) with 10–15 wt% Sn and a low concentration of impurities. Other artefacts were produced in copper or in brass, the latest with varying contents of Zn, Sn and Pb. A variety of inclusions in the metal matrices were also found, some related to specific types of alloys, as (Cu–Ni)S2 in coppers, or ZnS in brasses. Microstructural observations revealed that the majority of the artefacts were subjected to cycles of thermomechanical processing after casting, being evident that among some artefacts different parts were subjected to distinct treatments. The radiographic images revealed structural heterogeneities related to local corrosion processes and fissures that seem to have developed in wear-tension zones, as in the handle of some daggers. Radiographic images were also useful to detect the use of different materials in one particular brass artefact, revealing the presence of a possible Cu–Sn solder.This work was funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT— Fundação para a Ciência e a Tecnologia under the project UID/CTM/ 50025/2013 to CENIMAT/I3N. C2 TN/IST authors gratefully acknowledge the FCT support through the UID/Multi/04349/2013 project. EF acknowledges FCT for the grant SFRH/BPD/97360/2013. JF acknowledge FCT for the grant SFRH/BD/65143/2009. Part of this project has been done in the framework of the FCT project ENARDAS (PTDC/HISARQ/112983/2009).info:eu-repo/semantics/publishedVersio

Absence of Ataxin-3 Leads to Enhanced Stress Response in C. elegans

Ataxin-3, the protein involved in Machado-Joseph disease, is able to bind ubiquitylated substrates and act as a deubiquitylating enzyme in vitro, and it has been involved in the modulation of protein degradation by the ubiquitin-proteasome pathway. C. elegans and mouse ataxin-3 knockout models are viable and without any obvious phenotype in a basal condition however their phenotype in stress situations has never been described

A comparison between the FENE-P and sPTT constitutive models in large-amplitude oscillatory shear

The finitely extensible nonlinear elastic with Peterlin closure (FENE-P) and simplified Phan-Thien–Tanner (sPTT) viscoelastic models are used widely for modelling of complex fluids. Although they are derived from distinct micro-structural theories, these models can become mathematically identical in steady and homogeneous flows with a particular choice of the values of the model parameters. However, even with this choice of parameter values, the model responses are known to differ from each other in transient flows. In this work, we investigate the responses of the FENE-P and sPTT constitutive models in large-amplitude oscillatory shear (LAOS). In steady shear, the shear stress scales with the non-dimensional group $Wi/(aL)$ ( $Wi\,\sqrt {\epsilon }$ ) for the FENE-P (sPTT) model, where $Wi$ is the Weissenberg number, $L^2$ is the limit of extensibility in the FENE-P model ( $a$ being $L^2/(L^2-3)$ ), and $\epsilon$ is the extensibility parameter in the sPTT model. Our numerical and analytical results show that in LAOS, the FENE-P model shows this universality only for large values of $L^2$ , whereas the sPTT model shows it for all values of $\epsilon$ . In the strongly nonlinear region, there is a drastic difference between the responses of the two models, with the FENE-P model exhibiting strong shear stress overshoots that manifest as self-intersecting secondary loops in the viscous Lissajous curves. We quantify the nonlinearity exhibited by each constitutive model using the sequence of physical processes framework. Despite the high degree of nonlinearity exhibited by the FENE-P model, we also show using fully nonlinear one-dimensional simulations that it does not shear band in LAOS within the range of conditions studied.</jats:p

Gênese do serviço de enfermagem do Hospital Federal de Bonsucesso: contribuição da escola Ana Néri Génesis del servicio de enfermería en el Hospital Federal de Bonsucesso: contribución de la Escuela Ana Neri Genesis of nursing service in Hospital Federal Bonsucesso: contribution of Ana Neri School

O objeto deste estudo é a implantação do Serviço de Enfermagem no Hospital do Instituto de Aposentadoria e Pensões dos Empregados em Transportes e Cargas, atual Hospital Federal de Bonsucesso, no período 1946-1948. Seu objetivo é discutir a participação da Escola Ana Néri nesse processo. Fontes primárias: documentos escritos e depoimentos orais. Fontes secundárias: bibliografias acerca da temática. A abordagem teórico-metodológica apoiou-se em conceitos dos sociólogos Pierre Bourdieu e Maria Cecília Minayo. Evidenciou-se que a contribuição da Escola Ana Néri além de ter sido decisiva para o sucesso da implantação do Serviço de Enfermagem no Hospital do Instituto de Aposentadoria e Pensões dos Empregados em Transportes e Cargas também contribuiu para reforçar sua posição no espaço hospitalar da capital federal no governo Dutra.<br>El objeto de este estudio es la implementación del Servicio de Enfermería en el Hospital del Instituto de Aposentadoria e Pensões dos Empregados em Transportes e Cargas, actual Hospital Federal de Bonsucesso, en el periodo 1946-1948. Su objetivo es discutir la participación de la Escuela Ana Neri en ese proceso. Fuentes primarias: documentos escritos y testimonios orales. Las fuentes secundarias: bibliografías sobre el tema. Los enfoques teóricos y metodológicos se basaron en los conceptos de los sociólogos Pierre Bourdieu y María Cecilia Minayo. Era evidente que la contribución de la Escuela Ana Neri, además de decisiva para la exitosa implementación del Servicio de Enfermería en el Hospital del Instituto de Aposentadoria e Pensões dos Empregados em Transportes e Cargas también contribuyó para fortalecer su posición en el espacio hospitalario de la Capital Federal en el Gobierno Dutra.<br>The object of this study is the implementation of the Nursing Service at the Hospital of the Institute of Retirement and Pension Employee Transport and Cargo current Federal Bonsucesso Hospital in the period 1946-1948. Your goal is to discuss the participation of Ana Neri School in the process. Primary sources: written documents and oral testimony. Secondary sources: bibliographies on the subject. The theoretical-methodological approach was based on the concepts of the sociologist Pierre Bourdieu and Maria Cecilia Minayo. It was evident that the contribution of Ana Neri School as well as having been crucial to the successful implementation of the Nursing Service at the Hospital of the Institute of Retirement and Pension Employee Transport and Cargo also helped to strengthen its position in the hospital in the federal capital Dutra