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Synergy in Nano-Fe<sub>3</sub>O<sub>4</sub> and MOF-808 composites enriches their applications in sludge anaerobic fermentation
No full textWaste activated sludge is an important resource rich in carbon and phosphorus. While volatile fatty acids (VFAs) and phosphate can be produced or released into the aqueous phase during anaerobic fermentation, increasing the yield of VFAs and simultaneously recovering phosphate in a fast and economical manner has proven to be challenging. This study demonstrates a possible approach to address this challenge using a magnetic composite material named [email protected]. The introduction of [email protected] into anaerobic fermenters increased the VFAs concentration by 1.68 times due to its highly defective structure, unsaturated Zr active sites, proton-electron conductivity, and inhibition of methanogenesis by acting as an electron competitor. Moreover, the defective structure as well as the synergistic effect between the two components endow [email protected] excellent phosphate adsorption capacity and efficiency. The main forces between MOF-808 and phosphate are ligand exchange and weak interactions according to the molecular dynamic simulation results. Although the magnetic recovery rate of [email protected] in the absence of biosolids is perfect, how to improve its performance with biosolids should be further explored in the future
Importance of Material, Product and System Analysis in Design for Plastic Circularity
No full textPlastic, although recognised as a revolutionary material integral to various aspects of our lives, has emerged as a stark emblem of human environmental impact. Despite active calls and emerging policies supporting a transition to the circular economy to help mitigate climate change and resource depletion, the current state of plastic circularity remains far from satisfactory. In the past two decades, European plastic flows have continued, and will continue, to grow exponentially, with most waste directed towards incineration or landfilling. In the idealised concept of circular economy (CE), plastic waste is envisioned as a valuable resource that can substitute virgin primary materials if effectively recirculated back into production systems, potentially eliminating the demand for new raw primary materials. In this perspective, recycling has been promoted as a solution for transforming waste into a valuable secondary resource. However, the circular material use rate (CMUR) of all materials, which measures the share of materials replacing virgin primary material in production processes, is 12% in the European Union (EU). Nevertheless, this rate highlights the gap between the amount of recyclable plastic fed back in plastic production and the demand for primary resources. Considering the ever-increasing demand for plastic, this low rate indicates that a large amount of primary raw material for plastic production is still needed. As such, implementing the concept of the CE in plastics requires identifying and addressing the barriers to plastic circularity in order to shift from disposable plastic waste to valuable circular materials.This PhD thesis aimed to evaluate and identify barriers and levers encountered in moving towards CE for plastics. The goal of conducting comprehensive analyses is to gain insights into whether or not we are advancing closer to achieving the overarching plastic circularity, i.e., reducing waste, keeping materials in circulation, and reducing reliance on fossil resources. The study seeks to provide a nuanced understanding of the current state of plastic circularity and pave the way for informed strategies to overcome barriers and accelerate progress towards achieving circularity goals in the plastic sector.This research is structured into three analysis levels: system, product, and material. These analysis levels are identified as key layers within which plastic circularity practices must be investigated (Chapter 1). This includes the following four analyses:1. Analysis of the organisation of the plastic value chain to implement initia-tives that promote plastic circularity, complying with the CE principles.2. Analysis of the circularity of plastic products by examining their potential for recycling and their ability to substitute virgin materials once recycled.3. Analysis of how material selection for plastic products influences plastic circularity, with a focus on identifying contaminants that may impede recycling efforts.4. Analysis of circularity indicators to estimate the implementation of plastic circularity in EU27 from 2020 to 2050, comparing two scenarios that promote plastic circularity to a business-as-usual (BAU) approach.The findings of this thesis comprehensively capture the various contexts, challenges, and intricacies linked to implementing plastic circularity at the system, product, and material levels. First, at the system level, the effectiveness of the plastic value chain in fostering circularity is analysed through a systematic qualitative framework (Chapter 4.1). The analysis of 54 initiatives underscored the necessity for coordinated waste management, enhanced stakeholder awareness, improved understanding of the end-market, and the need for policies to support the transition. This thesis then goes on to explore the role of design in plastic circularity at both the product and material scales to understand where and why failures occur when considering recycling as waste treatment. A recyclable product is defined as a product undergoing collection, sorting, reprocessing, and replacement of virgin resources in production (Chapter 4.2). Considering these steps independently or partially is found insufficient to assess plastic circularity. Thus, estimating the potential substitution values must account for quality and physical losses during the waste treatment processes from initial collection to finally being returned to market. Insights from this discussion highlight the need to bridge polymer science–which quantifies property changes in mixed plastic waste for use in new products–with environmental engineering to build models and assessment tools that prevent overestimating plastic circularity. Lastly, at the material level, the impact of inks printed on flexible plastic packaging during mechanical recycling is investigated (Chapter 4.3). The analysis revealed that the selection of inks does not hinder blown-film sample production. However, the pigment aggregation occurring upon degradation of the nitrocellulose binder, and the emission of volatile organic compounds from the polyurethane binder contribute to lowering the quality of the recycled material. The analysis identifies the two solvent-based inks as contaminating the recycled material by restricting the use of re-cycled materials in low requirements products, such as bin bags.In addition to investigating plastic circularity at the system, product and material levels, this PhD research examines forecasted plastic circularity improvements of the European plastic flows between 2020 and 2050 (Chapter 4.4). The material flow analysis (MFA) provides a comprehensive perspective on large-scale plastic flows and allows for a discussion of societal implications (Chapter 5). Implementing an enhanced circular scenario that promotes CE principles to the system boundary of the MFA is projected to increase the CMUR from 14% in the BAU scenario to 42% in the most optimistic scenario by 2050. The MFA forecasts show that recycling rates will increase when improved waste management scenarios are implemented. However, the increasing plastic consumption might out-balance the implementation of plastic circularity.This PhD research highlights the imperative to analyse plastic circularity through multiple lenses, first independently at the material, product and system levels and then by forecasting the EU plastic circularity in 2050. The results demonstrated that the future of plastic circularity relies on the ability of the plastic value chain to implement concerted efforts to implement a systemic change. Plastic should be designed and manufactured for durability and circularity, ensuring compatibility with effective waste management systems. In this way, plastics can serve continuously without compromising the integrity and utility of recycled materials. This thesis serves as a call for discussion to act, first to build upon drastic upstream measures (pre-consumption, e.g., reducing production and designing plastic for circularity) and then continue implementing downstream measures (post-consumption, e.g., effective collection and recycling)
Fracture mechanisms of Al-steel resistance spot welds: The role of intermetallic compound phases
No full textThis study explores the mechanical and metallographic characteristics of Al-Steel dissimilar resistance spot welds (RSW), with a particular focus on the intermetallic compound (IMC) phases and their impact on fracture mechanisms. Detailed metallographic analyses and novel miniature lap shear tests with in-situ Digital Image Correlation techniques were conducted to observe the crack propagation behavior. The findings revealed that the IMC phases significantly influence the crack path and fracture mechanisms, leading to variations in fracture energy. Specifically, three distinct IMC phases were identified at the weld interface, each exhibiting unique structural and mechanical properties, with corresponding fracture energies of approximately 0.03 kJ/m2, 1.1 kJ/m2, and 7.5 kJ/m2. These variations highlight the critical role of the IMC phase in determining the fracture behavior of the weld. The study further supported the development and validation of a finite element (FE) model, incorporating a Cohesive Zone Model to simulate debonding behavior and the Hosford-Mean fracture criterion to predict ductile fracture in the Al fusion zone, thereby successfully linking local material characteristics to mechanical properties
Effect of grain orientation angles and compressive parameters on the deformation characteristics and corrosion property of 6061 Al alloy
No full textThe influence of grain orientation angle and processing parameters on the compressive flow stress and corrosion behaviour of 6061 Al alloy was investigated in this study by altering the grain orientation angles in relation to the compressive direction. At relatively low processing temperatures (≤ 300 °C), an increase in the grain orientation angle from 0° to 90°reduced flow stress at low strain ranges (< 0.1) due to facilitated slip of Al grains. As strain and processing temperature increased, changes in orientation angles had a negligible effect on the flow stress, attributed to the enhanced contribution of intermetallic particles (IMPs) and the occurrence of recrystallisation. Microstructural analysis revealed that higher processing temperatures resulted in a diverse range of IMPs, including Mg2Si (β phase) and Al15(Fe,Mn)3Si2 phases. When the Al alloy was compressed at a high strain rate (25 s−1) and processed at 500 °C, submicron-scale β”, β’, and β phases coexisted. Corrosion tests indicated that a wider distribution of Al15(Fe,Mn)3Si2 phases reduced the corrosion resistance of the Al alloy. This led to the formation of connected corrosion sites in specimens compressed at 500 °C, where a larger corrosion area and enhanced charge transfer ability were confirmed by equivalent circuit fitting. However, no significant variation in corrosion resistance was observed for Al alloys with various grain orientation angles, due to similar grain structure and precipitation behaviour at similar processing temperatures
Multi-domain simulation for the holistic assessment of the indoor environment:A systematic review
No full textThe multi-domain comfort theory investigates human-environmental perception and comfort by accounting for people's simultaneous exposure to various stimuli from different physical domains. Multi-domain studies describe human reactions to environmental conditions, including indoor occupants' behaviour and comfort. Building simulation is essential to analyse Indoor Environmental Quality (IEQ) and energy consumption in buildings. Introducing multi-domain comfort theories in building simulation practices could improve reliability. A systematic literature review investigated the approaches adopted in multi-domain building simulation during the last decade. The simulation studies discussed herein combine two or more domains related to IEQ in buildings, indicating the state of the art, limitations, and potential trends. This review showed that multi-domain simulation comprising all the IEQ domains is still missing due to its complexity and the lack of standards for multi-domain comfort. Simulation studies mostly involved two domains - thermal and air quality or thermal and visual. The most common engines and software combinations were presented, and related interoperability issues were discussed. The most common inputs and outputs for each domain were described to identify common ground where to start building up an efficient multi-domain simulation framework. The role of the quality report was also addressed, pointing out that the current validation procedures are incipient. Advancing multi-domain simulation knowledge concurrently with understanding multi-domain comfort growth would benefit researchers and practitioners. Therefore, multi-domain simulations can become a powerful tool to guide occupant-centric building design and operation
Simultaneous ammonia and nitrate removal by novel integrated partial denitrification-anaerobic ammonium oxidation-bioelectrochemical system
No full textThe current study explored the performance of an integrated partial denitrification-anaerobic ammonium oxidation (anammox)-bioelectrochemical system on simultaneous removal of ammonia nitrogen and nitrate nitrogen. Different operational conditions were selected to optimize critical parameters of the process for improving nitrogen removal. The results indicated that more than 90 % of total inorganic nitrogen removal efficiency was achieved under the optimal conditions: ammonia nitrogen/nitrate nitrogen ratio of 1:2, external resistance of 200 Ω and inoculation volume ratio of anammox bacteria/denitrifying at 2:1. Improved nitrogen removal under the optimal conditions were confirmed by microbial community changes (Candidatus Brocadia and Thiobacillus) and enhanced of nitrogen metabolism-related genes (hao, hzsA/C and hdh). Increases of Limnobacter indicated an enhanced electron transfer efficiency. Overall, high-efficiency and stable nitrogen removal efficiency without nitrite nitrogen accumulation could be achieved by the integrated system under the optimal conditions, providing novel insights for simultaneous treatment of domestic wastewater and groundwater
Mechanistic study of a silicon-based intumescent coating system
No full textThe performance and working mechanism of a silicon-based intumescent coating system, comprising primarily silicone binder, fumed silica, and sodium silicate particles, were investigated. Water release from sodium silicate particles coupled with softening of the matrix, induced efficient coating expansion. The residual dehydrated silicates underwent ceramification at high temperatures, resulting in the formation of a compact and thermally stable heat barrier composed of SiO2. Optimization of the coating involved adjusting the amount of sodium silicate particles and introducing kaolin. The best-performed formulation, evaluated in a laboratory-scaled electrical furnace under UL 1709 fire scenario, exhibited a critical time of 56 min, which surpassed that of a commercial epoxy-based intumescent coating by 8 min.</p
Extraction of bioactive compounds froms Lion's Mane mushroom by-product using supercritical CO<sub>2</sub> extraction
No full textSupercritical fluid extraction using CO2 (SCFE-CO2) was used to examine extraction efficiency of bioactive compounds from irregular-shaped Lion's Mane (LM) mushroom by-products. Optimal SCFE-CO2 conditions (46.38 °C, 100 bar, and 0.99 mL/min of EtOH flow rate) for maximum yield (a mass fraction of 11.64%), ergosterol (3.74 mg/g dried LM), total phenolic content, TPC (815.93 µg GAE/g dried LM), and antioxidant activity (42.97 µg TE/g dried LM) were determined using following parameters: temperature (40 °C to 60 °C), pressure (100 bar to 300 bar), and EtOH flow rate (0 mL/min to 1 mL/min). EtOH flow rate was a key factor in raising extraction yield and quality. SCFE-CO2 was equally effective compared to conventional extraction (Maceration) for LM, as there were no significant differences (p ≥ 0.05) in yield, ergosterol content, TPC, or antioxidant activity. This green extraction technology could be an excellent alternative method for recovering bioactive compounds from medicinal mushrooms
In-situ and adhesive repair of continuous fiber composites using 3D printing
No full textThe development of automated repair processes for continuous carbon fiber reinforced thermoplastic (CFRTP) composites is still in its early stages. However, the emergence of 3D printing technology presents a significant opportunity for the automated repair process to evolve alongside CFRTP composites. This study aims to evaluate the 3D printing repair of continuous fiber composites (CFCs) and characterize the mechanical performance of the repaired specimens. Two methods are proposed for repairing CFRTP utilizing additive manufacturing (AM): repair by a separately 3D-printed and subsequently adhesively bonded patch and repair with 3D printing in-situ at a recess damage. To compare the performance of the proposed methods, 16 test specimens were 3D printed, consisting of 4 intact and 12 damaged samples. Among the damaged samples, 4 were used as damaged specimens, 4 were repaired with adhesively bonded patches, and the remainder were repaired by in-situ printing. Mechanical tests were conducted on all four types of specimens, and the results indicate that the 3D-printed in-situ repair of carbon-reinforced polycarbonate has both the highest strength and elastic modulus. The results show that the repair using adhesive patches and repair in-situ improves the elastic modulus of the damaged specimens by 30% and 44%, respectively. Similarly, the tensile strength of the specimens repaired by adhesive patches and in-situ printing is 20% and 28%, respectively, higher than that of the damaged samples. An analytical model was developed to predict the elastic modulus of damaged and intact specimens, and the analytically predicted stiffnesses showed good agreement with the experimental measurements. Overall, this study demonstrates the potential of 3D printing technology for repairing CFRTP composites and highlights the advantages of in-situ printing over adhesive patch repair
Studies on the development and nature of T-bet expressing B cells in humans and mice
No full textB cells are critical for normal immune functions and protection against pathogens by producing antibodies, secreting cytokines, and presenting antigens. However, disruption in the mechanisms controlling these processes can lead to inappropriate B cell responses and have been associated with pathological conditions such as autoimmunity. B cell depletion therapies have accordingly been introduced for treatment of several autoimmune conditions, including systemic lupus erythematosus (SLE) and rheumatoid arthritis. A subset of B cells expressing the transcription factor T-bet, which is known to be the master regulator of Th1 responses, has become a focus during the recent years due to their increased numbers in several autoimmune and inflammatory disorders in both humans and mice. They have been shown to contribute to disease pathologies by, for instance, the secretion of autoreactive antibodies. On the other hand, several studies have reported a critical function of T-bet expressing B cells in protective immune responses against intracellular pathogens and the generation of complement-fixing IgG antibodies appear to be closely associated with this B cell subset. T-bet expressing B cells have therefore gained considerable interest in both protective and pathological responses. However, the phenotype, heterogeneity and developmental pathways of these cells are still not fully elucidated.In Manuscript I of the current thesis, the phenotype and heterogeneity of T-bet expressing B cells, along with the pathways leading to their generation, were investigated. Using T-bet reporter mice, we show that T-bet expression in B cells at steady state conditions in particular is associated with activated B cell subsets, including germinal center (GC) B cells. Furthermore, T-bet+ B cells have previously been shown to accumulate with age and we show that this accumulation over time is lost in a mice model lacking T follicular helper (Tfh) cells and GCs. By using in vitro cell culture systems, we demonstrate that IFNγ is the most critical factor, rather than TLR7 ligation, to induce generation of T-bet+ B cells. Our results show that the TLR7 agonist R848 instead stimulates strong expansion of B cells and that this proliferative B cell response to R848 is antagonized by IFNγ. We further confirm these findings in vivo, where IFNγ neutralization results in expansion of GC B cells and a reduction in T-bet expression in B cells in mice immunized with R848 and OVA. Further to this, we show that IFNγ stimulation in vitro leads to increased Fas expression, indicating that Fas-dependent apoptosis could represent a mechanism by which IFNγ antagonizes the R848-induced B cell expansion. Lastly, we demonstrate that IFNγ-induced Fas expression and reduction of R848-induced B cell expansion is not dependent on B-cell intrinsic T-bet expression.In Manuscript II, T-bet expression in memory B cells expressing different IgG and IgA subclasses was investigated. We for the first time demonstrate that T-bet expression is not restricted to IgG expressing B cells but also expressed by many of the IgA1+ memory B cells in peripheral blood of healthy human subjects. In marked contrast, memory B cells expressing the IgA2 subclass did not express T-bet, demonstrating a hitherto unrecognized dichotomy between the two human IgA subclasses. While our results confirm previous observation that IFNγ induces T-bet expression in naïve human B cells activated in vitro, we also show that IFNγ inhibits the ability of retinoic acid (RA) and TGFβ, molecular cues underlying IgA switching in the small intestine, to promote IgA expression in these cultures. Reversely, RA and TGF-β suppress T-bet expression induced by IFNγ. As a consequence of this mutually antagonistic relationship between IFNγ on the one hand and RA and TGF-β on the other, IgA+ T-bet+ B cells were not generated under these culture conditions. This suggests that the IgA1+ T-bet+ B cells detected in peripheral blood are generated at sites distinct from the intestinal mucosa.Together, the studies presented in this PhD thesis provide insight into the phenotype and generation of T-bet+ B cells and reveal a hitherto unrecognized role of IFNγ in suppressing B cell expansion driven by B cell intrinsic TLR7 signaling. As T-bet+ B cells, TLR7, and IFNγ all have been implicated in pathogenesis of autoimmune diseases such as lupus, our study has important implications for the autoimmunity field