Design and mechanical characterization of voronoi structures manufactured by indirect additive manufacturing

Additive manufacturing (AM) is a production process for the fabrication of three-dimensional items characterized by complex geometries. Several technologies employ a localized melting of metal dust through the application of focused energy sources, such as lasers or electron beams, on a powder bed. Despite the high potential of AM, numerous burdens afflict this production technology; for example, the few materials available, thermal stress due to the focused thermal source, low surface finishing, anisotropic properties, and the high cost of raw materials and the manufacturing process. In this paper, the combination by AM of meltable resins with metal casting for an indirect additive manufacturing (I-AM) is proposed. The process is applied to the production of open cells metal foams, similar in shape to the products available in commerce. However, their cellular structure features were designed and optimized by graphical editor Grasshopper®. The metal foams produced by AM were cast with a lost wax process and compared with commercial metal foams by means of compression tests

Evaluation of the effects of the metal foams geometrical features on thermal and fluid-dynamical behavior in forced convection

Metal foams are a material, featuring interesting characteristics for the aeronautical and automotive fields because of their low specific weight, high thermal properties, and mechanical performances. In particular, this paper deals with thermal and fluid dynamic study of 24 open-cell aluminum EN43500 (AlSi10MnMg) metal foams produced by indirect additive manufacturing (I-AM), combining 3D printing and metal casting to obtain a controllable morphology. A study of foam behavior function of the morphological features (pores per inch (PPI), branch thickness (r), and edges morphology (smooth-regular)) was performed. The samples produced were heated by radiation and tested in an open wind circuit gallery to measure the fluid dynamic properties such as pressure drop (Delta p), inertial coefficient (f), and permeability (k), in an air forced convection flow. The thermal characterization was performed evaluating both the theoretical (k(th)) and effective (k(eff)) thermal conductivity of the foams. Also, the global heat transfer coefficient (HTCglobal) was evaluated with different airflow rates. Analysis of variance (ANoVA) was performed to figure out which geometrical parameters are significant during both thermal and fluid dynamic processes. The results obtained show how the controllable foam morphology can affect the involved parameters, leading to an ad hoc design for industrial applications that require high thermo-fluid-dynamical performances

Investigating curcumin/intestinal epithelium interaction in a millifluidic bioreactor

Multidrug resistance is still an obstacle for chemotherapeutic treatments. One of the proteins involved in this phenomenon is the P-glycoprotein, P-gp, which is known to be responsible for the efflux of therapeutic substances from the cell cytoplasm. To date, the identification of a drug that can efficiently inhibit P-gp activity remains a challenge, nevertheless some studies have identified natural compounds suitable for that purpose. Amongst them, curcumin has shown an inhibitory effect on the protein in in vitro studies using Caco-2 cells. To understand if flow can modulate the influence of curcumin on the protein’s activity, we studied the uptake of a P-gp substrate under static and dynamic conditions. Caco-2 cells were cultured in bioreactors and in Transwells and the basolateral transport of rhodamine-123 was assessed in the two systems as a function of the P-gp activity. Experiments were performed with and without pre-treatment of the cells with an extract of curcumin or an arylmethyloxy-phenyl derivative to evaluate the inhibitory effect of the natural substance with respect to a synthetic compound. The results indicated that the P-gp activity of the cells cultured in the bioreactors was intrinsically lower, and that the effect of both natural and synthetic inhibitors was up modulated by the presence of flow. Our study underlies the fact that the use of more sophisticated and physiologically relevant in vitro models can bring new insights on the therapeutic effects of natural substances such as curcumin

Neural network implementation for the prediction of load curves of a flat head indenter on hot aluminum alloy

The indentation test performed by means of a flat-ended indenter is a valuable non-destructive method for assessment of metals at a local scale. Particularly, from the indentation curves it is possible to achieve several mechanical properties. The aim of this paper is the implementation of an artificial neural network for the prediction of the indentation load as a function of the penetration depth for an aluminium substrate. In particular, the neural network is addressed to the mechanical characterization of the bulk in function of temperature and indentation rate. The results obtained showed a high accuracy in curves prediction

Cytotoxic and pro-inflammatory early effects of mineral fibres on human alveolar epithelial and immune cells

When interacting with macrophages and epithelial lung cells, inhaled harmful particles trigger the pro-inflammatory process which, in turn, promotes the recruitment of circulating monocytes at the site of injury and their subsequent differentiation towards a macrophage phenotype. In this study, we evaluated the early cytotoxic and pro-inflammatory effect of three well-known carcinogenic fibres (i.e., crocidolite, chrysotile and erionite) on human THP-1 naïve monocytes and A549 alveolar epithelial cells, mimicking the recruitment and engagement of circulating monocytes at the site of fibre deposition. In both cell lines, all fibres showed significant direct cytotoxicity, with crocidolite and chrysotile inducing a higher time-dependent increase of the oxidative stress respect to erionite. Moreover, the direct exposure to the three fibres prompted the activation of THP-1 naïve monocytes towards the M0 pro-inflammatory phenotype, upregulating the gene expression of differentiation markers and promoting the release of pro-inflammatory cytokines. Finally, we evaluated the differentiation and activation of THP-1 naïve cells in response to conditioned media from fibre-treated A549 alveolar epithelial cells and M0-THP-1 macrophages. Interestingly, the exposure to chrysotile-treated media promoted the highest upregulation of pro-inflammatory mediators, suggesting that the soluble factors secreted in response to this fibre cause a stronger recruitment and activation of naïve monocytes

Bridging the gap between toxicity and carcinogenicity of mineral fibres by connecting the fibre parameters to the key characteristics of carcinogens: A comprehensive model inspiring asbestos-induced cancer prevention strategies

Background: Today, many research groups in the world are struggling to fully understand the mechanisms leading to the carcinogenesis of hazardous mineral fibres, like asbestos, in view of devising effective cancer prevention strategies and therapies. Along this research line, our work attempts the completion of a model aimed at evaluating how, and to what extent, physical-crystal-chemical and morphological parameters of mineral fibres prompt adverse effects in vivo leading to carcinogenesis. Methods: In vitro toxicology tests that deliver information on the 10 key characteristics of carcinogens adopted by the International Association for Research on Cancer (IARC) have been systematically collected for a commercial chrysotile, standard UICC crocidolite and wollastonite. The analysis of the in vitro data allowed us to assess the major fibre parameters responsible for alterations in the key characteristics of carcinogens for each investigated fibre and the intensity of their effect. Results: Crystal habit and density of the fibres affect exposure but are not major parameters contributing to the KCs. For chrysotile, besides length, we found that fibre parameters that greatly contribute to the KCs are the surface area and the dissolution rate with the related velocity of release of metals (namely iron). For crocidolite, they are the fibre length, iron content and related parameters like the ferrous iron content, iron nuclearity, transition metals content and zeta potential. Conclusions: The results of our study can be a starting point for developing personalized cancer screening and prevention strategies as long as the nature of the fibre of the exposed patient is known. We can speculate on a future personalized prevention therapy targeting the fibres with surface-engineered nanocarriers with active complexes that are selective for the surface charge of the fibres. For chrysotile, a complex with deferasirox that can chelate Fe2+ and deferoxamine that preferentially chelates Fe3+ is proposed with the anchorage to the silica chrysotile surface driven by aspartic acid. For crocidolite, deferiprone chelating both Fe3+ and Fe2+ combined with lysine to attract the silica crocidolite surface is proposed

PRIN 2017 Fibres - A Multidisciplinary Mineralogical, Crystal-Chemical and Biological Project. What have we learned after four years of research?

This opening paper introduces the contributions of this special issue on mineral fibres and reports a gallery of the major results accomplished within the multidisciplinary project PRIN (PROGETTI DI RICERCA DI RILEVANTE INTERESSE NAZIONALE) 2017 “FIBRES: a multidisciplinary mineralogical, crystal-chemical and biological project to amend the paradigm of toxicity and cancerogenicity of mineral fibres” by the six different Research Units from the Universities of Ancona, Genova, Modena, Rome, Pisa-Parma, and Urbino. The main goal of the project was to increase the knowledge of the mechanisms by which mineral fibres, with special attention to asbestos and fibrous erionite, prompt adverse effects in vivo, linking the fibres’ crystal-chemical-physical parameters to their toxicity/carcinogenicity potential and recasting the existing mechanistic ‘fibre toxicity paradigms’. This special issue contains specific contributions from each Research Unit of the project. The implications of the findings of the project are beyond the advance of the knowledge in the world of mineralogy/crystallography and constitute a remarkable progress in the understanding of the biological activity of mineral fibres in vivo

Design and thermal comparison of random structures realized by indirect additive manufacturing

Additive manufacturing (AM) processes are used to fabricate three-dimensional complex geometries. There are several technologies that use laser or electron beam over metal powder beds. However, the direct AM processes have inconveniences such as specific set of materials, high thermal stress traced, high local energy absorbed, poor surface finish, anisotropic properties, high cost of material powder, and manufacturing with high-power beams. In this paper, an alternative process was developed. An indirect additive manufacturing (I-AM) combining a 3D print of castable resin and metal casting in order to obtain a cellular structure similar in shape to commercial metal foams but completely definable as design features was developed. Design of the cellular structure was made by the graphical algorithm editor Grasshopper®. Designed structures were realized by a lost-wax casting process and compared with commercial foam specimens by a system designed for this work. The designed metal foams showed a performance superior to that of commercial metal foam; in particular, the heat thermal coefficient of designed metal foams in the better case was 870W/m2·K, almost doubled in comparison with the commercial foam tested in this work

Improvement of thermal properties of micro head engine electroplated by graphene: experimental and thermal simulation

The present work deals with to improve knowledge of the mechanism of deposition of graphene on a complex geometry. The component of this study is an aluminum micro head engine that represents an interesting study case for its application in the field of heat dissipation. It has been coated with copper and graphene nanoplatelets by an electrodeposition process. The tests are conducted by realizing a system heat source similar to engine thermal behavior. The analysis has been developed on a micro head engine with a comparison between thermography results and finite element method (FEM) thermal analysis by commercial software Ansys. A three-dimensional heat conduction model in the coating structure was built, based on which FEM simulation was done. The influence of convection conditions has been evaluated by a comparison with FEM analysis without computational fluid dynamics simulations. The increase of thermal conductivity of coated specimen has been evaluated with the original one. Data analysis was performed by a comparison with 2-norm of fitting curves between the laboratory tests and simulations

Pulp and paper characterization by means of artificial neural networks for effluent solid waste minimization—A case study

Paper mills are among the most polluting industries, responsible for many organic and inorganic compounds emissions. The fibres electro-kinetic features strongly affect the ability to retain fillers since the fillers-fibres interactions are charge induced. The control and the prediction of these parameters would represent a precious aid for process management, allowing the fillers retention enhancement, a lower environmental impact and the paper sheet properties streamlining. The work presented deals with the implementation and training of four artificial neural networks (ANNs) for the prediction of the main electrochemical and physical features of cellulose pulp and paper. First, two ANNs predict the electrochemical parameters. Following, they were applied to predict the paper sheet properties and fillers retention. The neural models implemented showed outstanding prediction performance, with R-2 in the order of 0.999 and a low mean error. The results demonstrate how Artificial Neural Networks may be a valuable instrument for paper mill pollutant reduction. However, they suggest a more inclusive investigation for a better fibres behaviour representation. (C) 2021 Elsevier Ltd. All rights reserved