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Liquid Deposition Modeling of Biobased Epoxy Composites: Natural Fillers as Rheology Modifiers and Reinforcements
Get PDFIn this work, aimed at developing biomass-based composite pastes for liquid deposition modeling (LDM) 3D printing, we investigated the tuning of the rheological properties of a cardanol-based epoxy resin through the incorporation of various fillers: microcrystalline cellulose (MCC), microfibrillated cellulose (MFC), and nanoclay (MMT). The thermal cross-linking of the amine-cured composite pastes was monitored by ATR-FTIR and DSC analyses, confirming complete conversion of epoxy functionalities. The rheological behavior of the uncured composites was studied in view of LDM 3D printing. Viscosity data were fitted with the Herschel–Bulkley model to determine yield stress (τ0), consistency index (K), and flow behavior index (n). Shear-thinning behavior with solid-like to liquid-like transition at relatively low strain (0.5–5%) was induced by the addition of fillers, with adequate structural recovery. MFC proved to be the most effective rheological and mechanical property enhancer but could not be used alone due to curing-induced shrinkage at high loadings. Partial substitution of MCC with MFC, instead, drastically increased viscosity and reinforced shear thinning while retaining solid-like behavior at rest and yielded the highest tensile mechanical properties. In contrast, partial substitution of MCC with MMT slightly improved the tensile properties without significantly changing the rheology. Overall, increasing the filler content improved the mechanical properties of the composites to an extent that depended on the type and amount of filler. An optimized formulation containing 22 vol % of MCC and 1 vol % of MFC showed promising properties for LDM 3D printing, exhibiting proper extrusion (τ0 = 281.54 Pa, K = 855.43 Pa·sn, and n = 0.57), good shape fidelity, and, after curing, tensile modulus and strength equal to 5.34 and 1.31 MPa, respectively
Cellulose From Aloe Vera Plant Waste as Crosslinker for Vat 3D Printable Vitrimers: Toward a Circular Economy Approach in Additive Manufacturing
Get PDFThe reduction of the environmental impact of photocurable resins, commonly used in vat 3D printing, is an urgent request. In
order to truly enable vat additive manufacturing (AM) to adopt a circular economy approach, this can be done by both selecting
non-fossil carbon feedstocks and considering the end-of-life and reprocessability of the resulting thermosets. Pursuing this goal,
we present the study of a 3D printing-compatible vitrimeric resin capable of dynamically reorganizing the polymeric network and
exhibiting self-repair properties following heat treatment at 160◦C. For the development of the resin, microcrystalline cellulose
(MCC) is extracted from aloe vera peel, the main waste from the cultivation of this plant. MCC is then functionalized and used as
an added-value crosslinker for the monofunctional monomer 2-hydroxy-3-phenoxypropyl acrylate (HPPA), which is considered
green asit can be obtained from renewable resources. The materialstudied possesses excellent printing resolution,remodeling, and
self-healing ability, leading to a significant recovery of mechanical properties after breakage. This work highlights the possibility
of combining renewable raw materials, waste utilization, and vitrimeric chemistry to create sustainable, easily recyclable resin
Supramolecular cooperativity through the lens of enhanced sampling molecular dynamics
Get PDFSupramolecular polymers are dynamic aggregates whose properties arise from their constitutive bonds, based on reversible, non-covalent interactions. A central aspect in the design and function of these materials is the cooperativity of polymerization, by which the addition of monomers becomes increasingly favorable as the polymer grows. Cooperativity strongly influences both the structure and collective behavior of supramolecular materials, with significant implications for their properties. Understanding the origins and consequences of cooperativity is crucial for the rational design of new functional supramolecular polymer systems. Herein, we systematically explore the cooperativity of supramolecular polymer systems via Molecular Dynamics simulations, powered by On-the-fly Probability Enhanced Sampling, to accurately characterize the free energy landscape associated with polymerization. We validate our approach via ad hoc, minimalistic coarse-grained models of cooperative and non-cooperative self-assembling monomers. We then apply our analysis to ureidopyrimidinone (UPy) supramolecular polymers, widely used in biohydrogel design. Our work provides detailed insights into the UPy polymerization process and how cooperativity can emerge from the hierarchical character of its supramolecular structure. The results underscore the importance of an extensive molecular simulation approach to obtain a quantitative characterization of the self-assembly thermodynamics, which is crucial to guide the rational development of next-generation supramolecular materials
Assessment of the Runaway Electrons induced damage to the Tokamak First Wall
No full textThe study assessed the damage caused by Runaway Electrons (RE) on First Wall tiles, comparing the effects on Beryllium and Tungsten. This was done by using realistic RE energy distribution functions to simulate RE impacts through the FLUKA code. These energy distribution functions are based on the ASDEX Upgrade experiment # 39012. The parametric analysis carried out with FLUKA in the presence of magnetic fields indicated a clear relationship between the beam impact angle and the material deposited energy, demonstrating that higher impact angles lead to deeper electron penetration and greater deposited energies. A finite element model based on apparent heat capacity formulation in FreeFEM++ was developed to analyze the material thermal response to such thermal loads using volumetric energy density profiles from FLUKA simulations as input. Different RE current values were simulated to show its influence on the evolution of the material temperature and melting thickness
Modulation of corticospinal excitability and muscle synergies during visuomotor locomotor task in individuals with and without cerebral palsy: a TMS and EMG study
No full textIntroduction: Studies using transcranial magnetic stimulation and electromyography suggest that disrupted functional corticospinal connectivity significantly contributes to difficulty in initiating and controlling voluntary movements such as walking. In individuals with Cerebral Palsy (CP), the corticospinal tract (CST) may therefore be identified as a potential target for improving gait control. Increasing corticospinal excitability may enhance voluntary control of lower-limb muscles and improve selective activation patterns during gait. However, it remains uncertain whether this pathway can be further activated given the damage caused by the brain lesion. Moreover, muscle synergies, a cooperative activation of groups of muscles, play an essential role in efficient and adaptive locomotion. Disrupted CST projections may reduce the specificity and strength of descending commands, which can lead to the fusion or splitting of muscle synergies. This impaired descending modulation could explain the reduced number of synergies and lower variance often reported in people with CP. Understanding and improving the modulation of these synergies could lead to better rehabilitation strategies for individuals with CP. The objective of this study was to assess whether a visuomotor walking task promotes an increase in corticospinal excitability and a modulation of muscle synergies compared to a simple walking task in individuals with CP.Methods: Sixteen individuals with CP were initially recruited, muscle synergy analyses were conducted in 14 participants and TMS-based corticospinal excitability assessments in 11 participants, due to contraindications to TMS or technical issues. In addition, 14 control subjects took part in this study. Each participant performed a simple walking task and a visuomotor walking task (i.e., stepping onto virtual targets) at comfortable speed, in counterbalanced order. Transcranial magnetic stimulations were delivered during walking at approximately 40% of the gait cycle (late stance phase), corresponding to minimal tibialis anterior activity. Muscle synergies were extracted from full gait cycles recorded throughout each condition. Motor evoked potentials (MEPs) in the tibialis anterior muscle were induced using transcranial magnetic stimulation. Muscle synergies were extracted from surface electromyography signals acquired from six key lower-limb muscles during both tasks. Values were expressed as (median [Q1–Q3]).Results: In the visuomotor task, MEPs increased by 59.4% in the CP group (simple task MEP = 1.89 [1.00–3.09] a.u vs. visuomotor task MEP = 2.70 [1.59–4.80] a.u; p ≤ 0.01) and 113.8% in the control group (simple task MEP = 1.95 [0.99–2.72] a.u vs. visuomotor task MEP = 2.91 [1.97–3.66] a.u; p ≤ 0.01). An increase in the number of synergies was observed during visuomotor task in CP group (p = 0.018).Conclusion: These results suggest that performing a visuomotor walking task allows to enhance the corticospinal excitability in both individuals with CP and control subjects. Moreover, CP individuals showed that either the number or the structure of synergies are modulated by the visuomotor task, in comparison to control subjects. Longitudinal studies are recommended to assess the impact of the integration of complex tasks in gait rehabilitation interventions
Valorisation of biomass-derived wastewaters via aqueous phase reforming for energy recovery: a multi-level performance assessment
No full textL'abstract è presente nell'allegato / the abstract is in the attachmen
High-income countries dietary trajectories diverge from the global nutrition transition
No full textCountries with rising incomes typically undergo a nutrition transition, marked by increasing consumption of animal-sourced foods and declining intakes of cereals and other plant-based products. However, large-scale, data-driven assessments of how diets worldwide align with this transition remain scarce. Here, we analyse dietary regimes in 188 countries, from 1970 to 2021, covering 370 food products, and identify a nutrition transition occurring at the global scale. On average, every tenfold increase in a country’s per capita gross domestic product corresponds to a 13% rise in the dietary share of calories supplied by animal products and to a 15% decline in the share supplied by cereals. Nonetheless, in several high-income countries, such as Canada, Finland, Norway, New Zealand, Switzerland, and the UK, the dietary composition diverges from global trends, exhibiting declining caloric shares from animal-sourced foods alongside rising contributions from cereals and plant-based product
Bridge Failure Risk Prediction Using Geospatial Data Processing via Multi-Head Attention Deep Learning Model
No full textBridge failures are a significant threat to infrastructure safety and public security, which demand cost-effective and scalable monitoring systems. This work proposes a novel data-driven framework for early warning of bridge collapse risk, leveraging Interferometric Synthetic Aperture Radar (InSAR) displacement time series and Deep Learning. A mathematical formulation of a bridge-collapse risk index is introduced, allowing quantitative estimation of the probability of failure from displacement data. To overcome data scarcity, a synthetic bridge dataset is generated through a combination of geometrical transformations and stochastic perturbations applied to real InSAR observations. Then, a Multi-Head Attention-based Neural Network is trained to predict the risk increment over time windows, using both on-bridge and surrounding geospatial points as input. The model is validated on the historical collapse of the Tadcaster bridge and stress tested on the Cantiano bridge, which failed during the 2022 Marche flood in Italy. The results show that the proposed approach effectively captures the temporal evolution of structural instability, with a conservative (risk-overestimating) but consistent prediction trend. These findings demonstrate the potential of combining InSAR data and attention-based Deep Learning models for scalable, non-invasive bridge health monitoring
Circular Diversification and Design: The Contribution of the Design Discipline and Practice to Identify New Production Opportunities and Create a Closed Loop System
No full textThe current global climate crisis demands an immediate shift towards new business models that operate in circular and non-linear logic. However, despite discussions about this transition from the late 1960s, achieving a circular economy remains lengthy and challenging. Manufacturing companies must acquire and develop new skills and expertise to implement this change successfully. Additionally, they must continually analyze and evaluate their performance from multiple perspectives over an extended period to obtain optimal results. The main objective of this research is to delve into the approaches and tactics
utilized by four companies based in Italy, representing manufacturing realities, including circular models in their portfolio diversification strategy. The research theorized this model as "Circular Diversification" (CD), and the study seeks to analyze how these companies have implemented it in practice, placing particular
emphasis on the role of Design, actual or presumed, by going to find out which Design professions play a crucial role in CD. The research uses qualitative case-based reasoning methods to extrapolate meta-knowledge; Issue-Concept-Form (ICF) is the semantic model chosen to break down information from case studies. Next, three parameters are crossed through an Alluvial Diagram to show intersections: problem/motivation (former Issues), strategy (former Concept), and form/solution (former Form), which
Designers adopt are identified. Three relevant Design figures operating for a Circular Diversification are determined from the intersections: Systemic-Circular Designer, Product Designer, and Strategic Designer. Specific forms/solutions can be replicable and scalable recommendations in other manufacturing and territorial contexts, paving the way toward a Circular Diversification support service
Near-field measurement and four-wave mixing in single-polarization elliptical multimode VCSELs
No full textWe investigate the impact of transverse mode coupling caused by four-wave mixing (FWM) in elliptical multimode vertical cavity surface emitting lasers (VCSELs) with polarization control. Our study includes relative intensity noise (RIN) and near-field measurements, with a particular focus on the near-field pattern of sidebands of the lasing modes observed in the optical spectrum. Our model, which includes coherent mode coupling via FWM and spatial hole burning, shows a very good agreement between numerical and experimental results, providing a detailed explanation of the fine spectral features observed in the optical and RIN spectra. These results identify the primary causes of RIN degradation in multimode VCSELs and highlight the importance of considering FWM when approaching the design of VCSELs for high-speed and datacom applications