A review on the fluidity of al based alloys

Fluidity of molten metals is of significant importance in producing sound castings, particularly thin-walled castings.To meet the industrial demands of complex shaped castings, the knowledge of the parameters affecting fluidity is required in order to have a better control of the production processes.Since fluidity is one of the measures by which the castability of metals can be quantified, a definition and a description of castability are presented in this study.A definition of fluidity follows. Fluidity depends on many factors and this study reports the influence of the main factors: alloy composition, heat of fusion, superheat, grain refinement, modifying agents, mould material and temperature, melt cleanliness, coating and viscosity

Simulation of fluidity in AL-SI alloys

In this study, MAGMA soft® commercial software package was used to simulate the fluidity of A356 alloy. Established an optimum mesh generation, the influence of important metallurgical parameters, such as heat transfer coefficient, casting temperature and coherency temperature, on fluidity were simulated. The simulation results were compared with fluidity laboratory tests carried out with spiral-shaped sand moulds and the results from the simulations were found to be consistent with the experiments. Therefore, this study sets a basis for more extensive use of simulations as a means for predicting and optimizing the fluidity of aluminium alloys. In addition, the results from the spiral-shaped mould tests were compared with vacuum fluidity tests carried out using an A356 alloy and the two techniques showed consistent results

State-of-the-art characterization tools for Al foundry alloys

In this manuscript we review some characterization toolsfor Al foundry alloys. Castability is the ability of an alloyto be cast without formation of defects such as cracks,pores or misruns. Being able to measure, hence to control,these defects is fundamental and plays a critical role forthe development of numerical models for castability.Also melt quality influences these defects formation.Alloy dependent phenomena that determine castabilityare, among others, fluidity and porosity. This manuscriptfocuses on the main characterization tools for measuringfluidity, porosity and melt quality

On the quality of A354 ingots and its impact on cast product

A study in an automotive casting plant was targeted to address the problem of high rejection rate of a cylinder head casting made from an A354 alloy. Ingots of an A354 alloy from three different suppliers, A, B and C, were analyzed by the reduced pressure test (RPT) and the pressure filtration (PREFIL) test, individually as well as in combination. Hydrogen measurements during casting trials was carried out with an ALSPEK H? analyzer. The results have shown a good agreement with the scrap rate data of the final cast product, and the problem of higher scrap rate was significantly reduced when the ingots of an A354 alloy with the highest oxide content from supplier C were replaced. In order to study the influence of transfer and de-gassing on the melt quality, reduced pressure tests were also conducted along the production line. The effect of melt holding time on the quality of the cast product is also presented. The results from these trials shows that the bifilm index data from the RPT has a potential to be used in an industrial environment for routine melt quality control as the cause of high scrap was successfully identified with this technique

Microparticle-mediated transfer of the viral receptors CAR and CD46, and the CFTR channel in a CHO cell model confers new functions to target cells

Cell microparticles (MPs) released in the extracellular milieu can embark plasma membrane and intracellular components which are specific of their cellular origin, and transfer them to target cells. The MP-mediated, cell-to-cell transfer of three human membrane glycoproteins of different degrees of complexity was investigated in the present study, using a CHO cell model system. We first tested the delivery of CAR and CD46, two monospanins which act as adenovirus receptors, to target CHO cells. CHO cells lack CAR and CD46, high affinity receptors for human adenovirus serotype 5 (HAdV5), and serotype 35 (HAdV35), respectively. We found that MPs derived from CHO cells (MP-donor cells) constitutively expressing CAR (MP-CAR) or CD46 (MP-CD46) were able to transfer CAR and CD46 to target CHO cells, and conferred selective permissiveness to HAdV5 and HAdV35. In addition, target CHO cells incubated with MP-CD46 acquired the CD46-associated function in complement regulation. We also explored the MP-mediated delivery of a dodecaspanin membrane glycoprotein, the CFTR to target CHO cells. CFTR functions as a chloride channel in human cells and is implicated in the genetic disease cystic fibrosis. Target CHO cells incubated with MPs produced by CHO cells constitutively expressing GFP-tagged CFTR (MP-GFP-CFTR) were found to gain a new cellular function, the chloride channel activity associated to CFTR. Time-course analysis of the appearance of GFP-CFTR in target cells suggested that MPs could achieve the delivery of CFTR to target cells via two mechanisms: the transfer of mature, membrane-inserted CFTR glycoprotein, and the transfer of CFTR-encoding mRNA. These results confirmed that cell-derived MPs represent a new class of promising therapeutic vehicles for the delivery of bioactive macromolecules, proteins or mRNAs, the latter exerting the desired therapeutic effect in target cells via de novo synthesis of their encoded proteins

Exploring the Effect of Structure-Based Scaffold Hopping on the Inhibition of Coxsackievirus A24v Transduction by Pentavalent N-Acetylneuraminic Acid Conjugates

Coxsackievirus A24 variant (CVA24v) is the primary causative agent of the highly contagious eye infection designated acute hemorrhagic conjunctivitis (AHC). It is solely responsible for two pandemics and several recurring outbreaks of the disease over the last decades, thus affecting millions of individuals throughout the world. To date, no antiviral agents or vaccines are available for combating this disease, and treatment is mainly supportive. CVA24v utilizes Neu5Ac-containing glycans as attachment receptors facilitating entry into host cells. We have previously reported that pentavalent Neu5Ac conjugates based on a glucose-scaffold inhibit CVA24v infection of human corneal epithelial cells. In this study, we report on the design and synthesis of scaffold-replaced pentavalent Neu5Ac conjugates and their effect on CVA24v cell transduction and the use of cryogenic electron microscopy (cryo-EM) to study the binding of these multivalent conjugates to CVA24v. The results presented here provide insights into the development of Neu5Ac-based inhibitors of CVA24v and, most significantly, the first application of cryo-EM to study the binding of a multivalent ligand to a lectin

Effects of oil and global environmental drivers on two keystone marine invertebrates

Ocean warming (OW) and acidification (OA) are key features of global change and are predicted to have negative consequences for marine species and ecosystems. At a smaller scale increasing oil and gas activities at northern high latitudes could lead to greater risk of petroleum pollution, potentially exacerbating the effects of such global stressors. However, knowledge of combined effects is limited. This study employed a scenario-based, collapsed design to investigate the impact of one local acute stressor (North Sea crude oil) and two chronic global drivers (pH for OA and temperature for OW), alone or in combination on aspects of the biology of larval stages of two key invertebrates: the northern shrimp (Pandalus borealis) and the green sea urchin (Strongylocentrotus droebachiensis). Both local and global drivers had negative effects on survival, development and growth of the larval stages. These effects were species- and stage-dependent. No statistical interactions were observed between local and global drivers and the combined effects of the two drivers were approximately equal to the sum of their separate effects. This study highlights the importance of adjusting regulation associated with oil spill prevention to maximize the resilience of marine organisms to predicted future global conditions

Human AdV-20-42-42, a promising novel adenoviral vector for gene therapy and vaccine product development

Preexisting immune responses toward adenoviral vectors limit the use of a vector based on particular serotypes and its clinical applicability for gene therapy and/or vaccination. Therefore, there is a significant interest in vectorizing novel adenoviral types that have low seroprevalence in the human population. Here, we describe the discovery and vectorization of a chimeric human adenovirus, which we call HAdV-20-42-42. Full-genome sequencing revealed that this virus is closely related to human serotype 42, except for the penton base, which is derived from serotype 20. The HAdV-20-42-42 vector could be propagated stably to high titers on existing E1-complementing packaging cell lines. Receptor-binding studies revealed that the vector utilized both CAR and CD46 as receptors for cell entry. Furthermore, the HAdV-20-42-42 vector was potent in transducing human and murine cardiovascular cells and tissues, irrespective of the presence of blood coagulation factor X. In vivo characterizations demonstrate that when delivered intravenously (i.v.) in mice, HAdV-20-42-42 mainly targeted the lungs, liver, and spleen and triggered robust inflammatory immune responses. Finally, we demonstrate that potent T-cell responses against vector-delivered antigens could be induced upon intramuscular vaccination in mice. In summary, from the data obtained we conclude that HAdV-20-42-42 provides a valuable addition to the portfolio of adenoviral vectors available to develop efficacious products in the fields of gene therapy and vaccination

Synchrotron radiography studies of shear-induced dilation in semi-solid Al alloys and steels

An improved understanding of the response of solidifying microstructures to load is required to further minimize casting defects and optimize casting processes. This article overviews synchrotron radiography studies that directly measure the micromechanics of semisolid alloy deformation in a thin sample direct-shear cell. It is shown that shear-induced dilation (also known as Reynolds’ dilatancy) occurs in semisolid alloys with morphologies ranging from equiaxed-dendritic to globular, at solid fractions from the dendrite coherency point to ~90% solid, and it occurs in both Al alloys and carbon steels. Discrete-element method simulations that treat solidifying microstructures as granular materials are then used to explore the origins of dilatancy in semisolid alloys