Large Growth Deformations of Thin Tissue using Solid-Shells

Simulating large scale expansion of thin structures, such as in growing leaves, is challenging. Sold-shells have a number of potential advantages over conventional thin-shell methods, but have thus far only been investigated for small plastic deformation cases. In response, we present a new general-purpose FEM growth framework for simulating large plastic deformations using a new solid-shell growth approach while supporting morphogen diffusion and collision handling. Large plastic deformations are handled by augmenting solid-shell elements with \textit{plastic embedding} and strain-aware adaptive remeshing. Plastic embedding is an approach to model large plastic deformations by modifying the rest configuration in response to displacement strain. We exploit the solid-shell's ability of describing both stretching and bending in terms of displacement strain to implement both plastic stretching and bending using the same plasticity model. The large deformations are adaptively remeshed using a strain-aware criteria to anticipate buckling and eliminate low-quality elements. We perform qualitative investigations on the capabilities of the new solid-shell growth approach in reproducing buckling, rippling, rolling, and collision deformations, relevant towards animating growing leaves, flowers, and other thin structures. The qualitative experiments demonstrates that solid-shells are a viable alternative to thin-shells for simulating large and intricate growth deformations

Circular Tutelage: a Sustainable Approach Toward Remediation and Enhancement of Endangered Areas

Nowadays, one of the most important topics in the public dialogue concerns the concept of sustainability and its application in everyday life, given the urgence to reduce or counteract the negative effects partly caused by human activities. Fighting poverty, eradicating hunger and malnutrition, increasing the quality of life, protecting and restoring biodiversity, ensuring access to energy sources are just some of the goals for sustainable development included in the United Nations Organization's 2030 Agenda. Every country is called to make its contribution to jointly face these great challenges, rising from the awareness that the planet's resources are limited, unequally distributed and their exploitation often involves the alteration of delicate environmental balances. In the present work, a very productive transitional area prone to suffer from pollution and dangerous algal blooms, has been studied in order to propose methodologies and solutions which, if adopted, can contribute not only to mitigate environmental damages but also to provide new tools that can contribute to the development of local populations in a circular economy perspective. In particular, research has been carried out aimed at the development of solutions for the environmental restoration of ecosystems threatened by human pressure, proposing highly circular and sustainable processes based on the use of biomass from wastes or by-products. The proposed production processes are aimed at exploiting and valorizing these wastes, avoiding the compromission of the hygiene and quality of the ecosystem. In addition to the environmental sustainability also the economic and social one are considered in the proposed solutions. The area is characterized by a semi-enclosed lagoon structure, depths of up to two meters, over 25 km2. This area alone is responsible for the production of 55% of all clams produced in Italy, with over fifty million euros in turnover; essentially a collective heritage for the cities and economies that depend precisely on mussel farming and supporting activities. In order to mitigate the effects related to the excessive presence of algal biomass in the area, a cost / benefit analysis was carried out to determine the possibility of exploit this biomass as a secondary raw material for the production of market goods such as biofuels, drugs, supplements, and much more. The possibilities for economic exploitations of the biomass would in fact make the collection of this component from the environment advantageous and would avoid negative phenomena in the aquatic environment. The feasibility of the proposed solutions was also accompanied by a foresight analysis in which possible social dynamics were considered which have led, in the past, to the failure of a project whose mission was to safeguard and improve the conditions of the lagoon. In order to carry out the feasibility study, in addition to the composition of the constituent elements of algae determination, their possible contamination by various classes of pollutants, whose presence could constitute an obstacle to their exploitation, was also studied. The thesis also considers another voluminous waste biomass present in the lagoon, namely byproduct seashells which constitute a process waste from the bivalves that are produced in the lagoon and which, unfortunately, are often illegally discharged into the canals or deployed in landfill and classified as special waste. Landfilling not only has an economic impact on small fishing businesses but also reduces the sustainability of aquaculture activities, which according to many, will be a key sector for development in the coming years. Hence, the shell of the clam essentially consists of calcium carbonate and can be used as a constituent of soil conditioners and fertilizers for agricultural purposes or as an adsorbent material in biofilters and in environmental bioremediation methodologies.Oggigiorno, una delle tematiche di maggior rilievo nel dialogo comune riguarda il concetto di sostenibilità e della sua applicazione nel quotidiano per rispondere all’esigenza di ridurre o contrastare vari effetti negativi in parte causati dalle attività umane. Contrastare la povertà, eradicare la fame e la malnutrizione, tutelare e ripristinare la biodiversità, sicurezza energetica, sono solo alcuni degli obiettivi per lo sviluppo sostenibile presenti nell’Agenda 2030 dell’Organizzazione delle Nazioni Unite. Ogni Paese è chiamato a fornire il suo contributo per affrontare in comune queste grandi sfide, nate dalla consapevolezza che le risorse del pianeta sono limitate, distribuite iniquamente e il loro sfruttamento spesso comporta l’alterazione di delicati equilibri ambientali. Nel presente lavoro di tesi si è studiato un ecosistema di transizione molto produttivo, ma fragile, per proporre metodologie e soluzioni che se adottate possano contribuire non solo a mitigare i danni ambientali, ma anche a fornire nuovi strumenti che possano contribuire allo sviluppo delle popolazioni locali in un’ottica di economia circolare. In particolare, si sono effettuate ricerche orientate allo sviluppo di soluzioni per il ripristino ambientale di ecosistemi minacciati dalla pressione antropica, proponendo processi altamente circolari e sostenibili basati sull’utilizzo di biomasse provenienti da scarti o sottoprodotti. I processi produttivi proposti sono orientati a sfruttare e valorizzare questi scarti evitando che compromettano l’igiene e la qualità degli ecosistemi in cui essi sono presenti o in cui vengono riversati. In questo ambito si sono approfonditi argomenti propri della sfera sociale ed economica, per garantire oltre alla sostenibilità ambientale anche quella economica e sociale delle soluzioni proposte. La zona è caratterizzata da una struttura lagunare semichiusa, fondali profondi massimo due metri e complessivamente è uno specchio d’acqua di 25 km2. Quest’area sola è responsabile per la produzione del 55% di tutte le vongole prodotte in Italia, con oltre cinquanta milioni di euro di volume d’affari; sostanzialmente un patrimonio collettivo per le città e le economie che dipendono appunto dalle attività di mitilicoltura e dalle attività consortili e coadiuvanti. Allo scopo di mitigare gli effetti legati alla presenza eccessiva di biomassa algale nella zona, si è svolta una analisi costi / benefici per determinare la possibilità di sfruttare al meglio tale biomassa come materia prima seconda per la produzione di oggetti e beni di consumo, come biocombustibili, farmaci, integratori e tanto altro. La possibilità di sfruttare economicamente la biomassa renderebbe infatti vantaggiosa la raccolta di questa componente dall’ambiente. La realizzabilità delle soluzioni proposte è stata inoltre corredata da un’analisi in previsione in cui si sono considerate possibili dinamiche sociali che hanno portato, in passato, al fallimento di un progetto che aveva la missione di salvaguardare e migliorare le condizioni della laguna. inoltre, è stata studiata la composizione degli elementi costitutivi di alghe e anche la loro possibile contaminazione da parte di varie classi di inquinanti la cui presenza potrebbe costituire un ostacolo per il loro sfruttamento. Nella tesi viene inoltre considerata anche un’altra voluminosa biomassa di scarto presente nella laguna, “il capulerio” che costituisce uno scarto di lavorazione dei bivalvi prodotti. Lo smaltimento in discarica non solo incide economicamente sulle piccole imprese di pescatori, ma riduce la sostenibilità delle attività di acquacultura. In un’ottica di sostenibilità e circolarità, il guscio delle conchiglie è costituito da carbonato di calcio e può trovare impiego come costituente di ammendanti e fertilizzanti per scopi agricoli o come materiale adsorbente in biofiltri e in altre metodologie di bioremediazione ambientale

Multiphysics simulation of drug-coated balloon deployment and drug delivery

The treatment of ischaemic arterial disease has improved substantially in recent decades largely due to the inclusion of local delivery of anti-restenotic drugs in percutaneous intervention. To perform drug delivery without an implant, a drug-coated balloon (DCB) is inflated endovascularly for a one-time drug transfer from its coating to the target artery upon contact, serving as an alternative or complementary therapy to drug-eluting stents. While this therapy may avoid the potential complications of implants, namely in-stent restenosis and thrombosis, its greatest challenge is providing sufficient drug delivery and subsequent retention in the tissue without sustained release from a permanent drug reservoir. The mechanisms of drug delivery from DCBs are not completely understood, and the literature lacks models that describe the mechanics and drug release parts of the problem simultaneously. Aiming to improve this understanding, this work proposes modelling efforts towards an in silico simulation framework of simultaneous DCB deployment and drug delivery that studies procedural parameters such as inflation pressure, inflation duration, and drug loading and their effect on drug delivery performance. First, the foundation for the modelling assumptions is set with a drug delivery problem considering an idealised 2D-axisymmetric multilayered arterial wall and a prescribed set of boundary conditions to represent the DCB’s role. Then, a more realistic geometrical representation of a DCB is proposed based on the specifications of a DCB that has undergone clinical trials, along with the modelling of the inflation procedure and drug release from the coating. Ultimately, the two previous models are combined, culminating in a novel multiphysics simulation of DCB deployment that includes time-dependent structural mechanics, contact interaction, transmural filtration, and drug transport and retention simultaneously. All models are implemented in COMSOL Multiphysics® based on the finite element method. Results are assessed throughout the simulation of DCB deployment and 28-day follow-up, evaluating safety and efficacy indicators common to preclinical testing (drug content and receptor saturation) from the spatiotemporal drug distribution. Although further studies and experimental data are still required to improve the model validation and achieve clinical utility, this work demonstrates the potential of in silico modelling as a powerful tool to complement traditional methods of medical device testing. The valuable mechanistic insights obtained can enhance the design process of DCBs and improve drug-delivery therapies, substantially reduce development costs, and expedite the technology

Diamond and sp² carbon for green energy applications

Carbon is a ubiquitous element on earth, with 6 protons, electrons, and neutrons. It is tetravalent, with a range of hybridised bonding configurations, it can form materials with superlative and varied properties. These materials range from soft and conductive sp2 bonded allotropes like graphite and carbon nanotubes, to the insulating and hardest natural material on earth, sp3 bonded diamond. The first half of this thesis presents an investigation of the properties of a promising novel carbon nanomaterial, CNS, and its application to ultracapacitor electrodes for the first time. High surface area conductive carbon nanomaterials are capable of high power and long service life energy storage in ultracapacitors, a critical green technology. The development of this technology to increase energy density to compete with chemical batteries could accelerate a transition to sustainable energy infrastructure. CNS/polymer composite electrodes were assembled using a conductive diamond collector substrate, then characterised using electrochemical techniques to measure capacitative performance. The second half of this thesis concerns the development of amperometric dissolved oxygen sensors for extreme environments. Diamonds controllable electronic properties, corrosion resistance, wide electrochemical window, and resistance to fouling make it an ideal potential material for this application. Conductive boron doped diamond electrodes were functionalised with platinum nanoparticles. Aphotolithographyprocesswasusedtoproduceanarrayofmicrodiscelectrodesusingan SU-8 photoresist mask, for the first time in this application and material system. A custom electrochemical cell was designed and built to provide a new electrochemical capability to the lab at approximately 1/10th the cost of a commercial solution; the project will be made open source. The microdisc array was tested as an oxygen sensor using the cell; calibration standards were produced by controlling the flow of oxygen and nitrogen gasses through the cell. A control measurement was provided for by a calibrated oxygen gauge incorporated into the test cell

A Tracking Review on Non Arc Melting Processes for Improved Surface Properties in Metallic Materials

Most metallic materials lack the adequate surface characteristics to satisfactorily perform intended service functions. In such instance, the surface properties are modified by altering the chemistry, structure and/topology of the top surface of the surface via modification techniques. There exists wide options of techniques for modifying the surface properties and these are well documented in the literature. However, these techniques have different scientific underpinnings controlling them such that it is difficult to use a single mechanism to characterize the techniques. Arising from this, it is imperative that a holistic understanding of the various processes is provided. Therefore, in this paper, research status on the wide range of non-melting technique for surface modification is presented. The presentation discusses the investigation conducted on the various non-surface melting techniques and provides a comparison across the techniques. Recent developments in these techniques are equally presented. Existing challenges and emerging trends in the field are also highlighted.  . Keywords: coating composition, coating techniques, metallic materials, substrate, surface properties DOI: 10.7176/CMR/13-2-01 Publication date:May 31st 202

Optimal Grading for Strength and Functionality of Parts Made of Interpenetrating Polymer Networks: Load Capacity Enhancement

Uniform parts with stress concentrations or singularities are prone to failure under relatively small loads, which motivates researchers to seek methods to enhance the strength of these parts. This dissertation studies the optimization of material grading to design parts made of functionally graded interpenetrating polymer networks (FG-IPNs) to improve their load capacity. An acrylate/epoxy IPN with variations of elastic Young’s modulus, Poisson’s ratio, and ultimate stress at failure is used for optimization of a plate with stress concentration. The grading is optimized by attaching the finite element method (FEM) solver to a general purpose bound-constrained optimizer. Two examples, a plate with a hole and a bent bracket, show more than 100% improvement in the part’s load capacity when compared to the uniform IPNs. Parts with stress singularities are studied using a PMMA/PU IPN system. For this system, we have the elastic modulus and the critical stress intensity factor KIC as a function of the concentration of the components. A material mesh is utilized to control the grading near the crack tip and uniform material is assumed outside the tip area. The displacement correlation technique (DCT) is used to calculate stress intensity factors and the maximum hoop stress criterion is selected as the fracture criterion. Parts with edge cracks, interior cracks and interacting cracks under tension are considered. For the PMMA/PU IPN system, improvements in load capacity in the order of one hundred percent were commonly obtained through grading the region around the crack tip, compared to both optimal uniform plates, and plates with simple toughening of the region around the crack. In addition, in FEM modelling of FGM part with graded elements, the polynomial interpolations used in such elements can be prone to oscillations that can result in regions of negative elastic modulus, even with only positive nodal values of elastic moduli. The result of these negative modulus regions, even if the region is small, can be unexpected singularities in the solution. To avoid this potential problem, conditions for robust higher order materially graded elements were developed. Advisor: Mehrdad Negahba

Protein sequences bound to mineral surfaces persist into deep time.

Proteins persist longer in the fossil record than DNA, but the longevity, survival mechanisms and substrates remain contested. Here, we demonstrate the role of mineral binding in preserving the protein sequence in ostrich (Struthionidae) eggshell, including from the palaeontological sites of Laetoli (3.8 Ma) and Olduvai Gorge (1.3 Ma) in Tanzania. By tracking protein diagenesis back in time we find consistent patterns of preservation, demonstrating authenticity of the surviving sequences. Molecular dynamics simulations of struthiocalcin-1 and -2, the dominant proteins within the eggshell, reveal that distinct domains bind to the mineral surface. It is the domain with the strongest calculated binding energy to the calcite surface that is selectively preserved. Thermal age calculations demonstrate that the Laetoli and Olduvai peptides are 50 times older than any previously authenticated sequence (equivalent to ~16 Ma at a constant 10°C)

Protein sequences bound to mineral surfaces persist into deep time

Proteins persist longer in the fossil record than DNA, but the longevity, survival mechanisms and substrates remain contested. Here, we demonstrate the role of mineral binding in preserving the protein sequence in ostrich (Struthionidae) eggshell, including from the palaeontological sites of Laetoli (3.8 Ma) and Olduvai Gorge (1.3 Ma) in Tanzania. By tracking protein diagenesis back in time we find consistent patterns of preservation, demonstrating authenticity of the surviving sequences. Molecular dynamics simulations of struthiocalcin-1 and -2, the dominant proteins within the eggshell, reveal that distinct domains bind to the mineral surface. It is the domain with the strongest calculated binding energy to the calcite surface that is selectively preserved. Thermal age calculations demonstrate that the Laetoli and Olduvai peptides are 50 times older than any previously authenticated sequence (equivalent to ~16 Ma at a constant 10°C)