6,632 research outputs found
Microwave - Plasma based Thermal Treatment of Asphaltene - derived Carbon Fibres
Asphaltene-based carbon fibres have emerged as a significant and sustainable alternative to conventional Polyacrylonitrile (PAN)-based carbon fibres, owing to their abundant availability, aromatic nature, and high carbon content. This thesis investigates the utilization of asphaltenes, extracted from bitumen in Alberta oilsands, as a valuable precursor for the manufacturing of carbon fibres. The precursor employed in commercial carbon fibre manufacturing accounts for approximately 51% of the total production cost. The utilization of asphaltene as a precursor offers the potential for cost reduction in carbon fibre production. With this reduced cost, carbon fibres, renowned for their exceptional mechanical properties such as high stiffness, remarkable tensile strength, chemical resistance, and capacity to withstand higher temperatures, can find applications across wide range of industries. Moreover, this cost reduction also contributes to the economic viability of converting industrial waste into valuable products. Conventional post-treatment processes in carbon fibre manufacturing, such as furnace stabilization and carbonization, play a crucial role in the production process, demanding considerable time and energy resources. Post-treatment alone, comprising 38% of the overall cost of carbon fibre production, significantly impacts the economic aspects of the manufacturing process. In this thesis, asphaltenes derived from Alberta oilsands are pretreated with solvents such as pentane and toluene to remove coke residues. Later, these asphaltenes are transformed into fibres through the process of melt spinning using a twin-screw extruder. An innovative approach involving microwave plasma thermal treatment, replacing conventional post-treatment methods, specifically carbonization, is then applied to convert these fibres into carbon fibres. The study of microwave plasma behaviour and its corresponding temperatures is successfully conducted through the use of Multiphysics Finite Element Analysis (FEA). An experimental optimization study involving the thermal treatment of stabilized fibres under varying power levels and treatment durations using microwave plasma has been conducted. The study successfully implemented microwave plasma techniques to achieve carbonization of asphaltene fibres, resulting in an increase in carbon content and the development of a well-ordered crystalline structure. The Element analysis revealed the dynamic changes in elemental composition, showcasing the effectiveness of microwave plasma in achieving carbonization. X-ray diffraction patterns and Raman spectroscopy provided valuable insights into the structural evolution, highlighting the unique impact of microwave plasma treatment on the development of a layered graphite-like structure and higher graphitic content. However, it is essential to acknowledge limitations, such as the observed surface damage and reduced tensile strength in microwave-plasma treated fibres, emphasizing the need for further optimization of parameters to maximize the benefits of this innovative approach. Overall, this research contributes valuable insights to the field of carbon fibre manufacturing, paving the way for more sustainable and economically feasible production processes with the utilization of asphaltene-based precursors and microwave plasma techniques
A model system to investigate microbiome effects on age-related health in C. elegans
With the advancement of modern medicine, our aging population is rising sharply. In recent years there has been more focus in increasing healthspan, as well as lifespan, to improve the quality of life of older adults. The microbiome has been shown to play a huge role in human biological functions in both health and disease. This study focuses on two major healthcare concerns (a) Alzheimerâs disease and (b) Sarcopenia, using the model organism Caenorhabditis elegans. The research aims to investigate a microbiome approach towards treatment or prevention of these diseases. When using a C. elegans AD model, an experimental microbiome (EM) diet was shown to be protective against Aβ toxicity. From this EM, one bacterial species â Stenotrophomonas sp.Myb57 â became a focus due to its significant protective effects. It was found that this protection was genus-specific, with some species releasing a compound in its cell-free media which elicits this effect. Further study will hopefully allow us to isolate the gene or compound that is causing the protection, as a potential for an Alzheimerâs disease treatment. C. elegans was additionally used as a model for aging muscles. When testing the effects of an experimental microbiome on muscles, results showed that it made no difference to the body wall muscle cell morphology in early adulthood or the muscle contractability throughout aging. When muscle function was assessed, however, it seems that worms fed the EM had lower muscle strength in early adulthood, but were much more able to maintain this strength as they aged compared to the control. Overall, there is very promising evidence that the microbiome may be great source of research for therapeutic techniques against Alzheimerâs disease, Sarcopenia and many more
Nernst-Planck-Gaussian modelling of electrodiffusional recovery from ephaptic excitation between mammalian cardiomyocytes
Introduction: In addition to gap junction conduction, recent reports implicate possible ephaptic coupling contributions to action potential (AP) propagation between successive adjacent cardiomyocytes. Here, AP generation in an active cell, withdraws Na+ from, creating a negative potential within, ephaptic spaces between the participating membranes, activating the initially quiescent neighbouring cardiomyocyte. However, sustainable ephaptic transmission requires subsequent complete recovery of the ephaptic charge difference. We explore physical contributions of passive electrodiffusive ion exchange with the remaining extracellular space to this recovery for the first time.Materials and Methods: Computational, finite element, analysis examined limiting, temporal and spatial, ephaptic [Na+], [Clâ], and the consequent Gaussian charge differences and membrane potential recovery patterns following a ÎVâź130 mV AP upstroke at physiological (37°C) temperatures. This incorporated Nernst-Planck formalisms into equations for the time-dependent spatial concentration gradient profiles.Results: Mammalian atrial, ventricular and purkinje cardiomyocyte ephaptic junctions were modelled by closely apposed circularly symmetric membranes, specific capacitance 1 ΟF cm-2, experimentally reported radii a = 8,000, 12,000 and 40,000 nm respectively and ephaptic axial distance w = 20 nm. This enclosed an ephaptic space containing principal ions initially at normal extracellular [Na+] = 153.1 mM and [Clâ] = 145.8 mM, respective diffusion coefficients DNa = 1.3 Ă 109 and DCl = 2 Ă 109 nm2s-1. Stable, concordant computational solutions were confirmed exploring â¤1,600 nm mesh sizes and Îtâ¤0.08 ms stepsize intervals. The corresponding membrane voltage profile changes across the initially quiescent membrane were obtainable from computed, graphically represented a and w-dependent ionic concentration differences adapting Gaussâs flux theorem. Further simulations explored biological variations in ephaptic dimensions, membrane anatomy, and diffusion restrictions within the ephaptic space. Atrial, ventricular and Purkinje cardiomyocytes gave 40, 180 and 2000 ms 99.9% recovery times, with 720 or 360 ms high limits from doubling ventricular radius or halving diffusion coefficient. Varying a, and DNa and DCl markedly affected recovery time-courses with logarithmic and double-logarithmic relationships, Varying w exerted minimal effects.Conclusion: We thereby characterise the properties of, and through comparing atrial, ventricular and purkinje recovery times with interspecies in vivo background cardiac cycle duration data, (blue whale âź2000, humanâź90, Etruscan shrew, âź40 ms) can determine physical limits to, electrodiffusive contributions to ephaptic recovery
Digital Innovations for a Circular Plastic Economy in Africa
Plastic pollution is one of the biggest challenges of the twenty-first century that requires innovative and varied solutions. Focusing on sub-Saharan Africa, this book brings together interdisciplinary, multi-sectoral and multi-stakeholder perspectives exploring challenges and opportunities for utilising digital innovations to manage and accelerate the transition to a circular plastic economy (CPE).
This book is organised into three sections bringing together discussion of environmental conditions, operational dimensions and country case studies of digital transformation towards the circular plastic economy. It explores the environment for digitisation in the circular economy, bringing together perspectives from practitioners in academia, innovation, policy, civil society and government agencies. The book also highlights specific country case studies in relation to the development and implementation of different innovative ideas to drive the circular plastic economy across the three sub-Saharan African regions. Finally, the book interrogates the policy dimensions and practitioner perspectives towards a digitally enabled circular plastic economy.
Written for a wide range of readers across academia, policy and practice, including researchers, students, small and medium enterprises (SMEs), digital entrepreneurs, non-governmental organisations (NGOs) and multilateral agencies, policymakers and public officials, this book offers unique insights into complex, multilayered issues relating to the production and management of plastic waste and highlights how digital innovations can drive the transition to the circular plastic economy in Africa.
The Open Access version of this book, available at https://www.taylorfrancis.com, has been made available under a Creative Commons Attribution-Non Commercial-No Derivatives (CC-BY-NC-ND) 4.0 license
Innovative unidirectional recycled carbon fiber tape structure for high performance thermoplastic composites: technological developments, technology-structure-property relationship and modeling of composite tensile properties
The rapidly growing demand for carbon fiber reinforced plastics in high-tech industries, such as aerospace, defense, automotive, wind turbine engineering, building and sports, resulted in a high amount of waste in the form of dry waste (e.g., production off-cuts), wet waste (e.g., out-of-date prepreg) and end-of-life components waste (e.g., aircraft components). Furthermore, the production of carbon fibers is cost and energy-intensive. Therefore, technological developments for the gentle processing of recycled carbon fiber and its integration into high-performance composites with promising tensile properties have gained considerable attention. Consequently, injection molding, nonwovens and hybrid yarn technologies were developed in recent years to integrate recycled carbon fiber into the high-performance thermoplastic composite. It is unfortunate that these technologies develop composites with a lack of unidirectional fiber orientation; therefore, the potential of recycled carbon fiber in high-performance composites is not thoroughly exhausted.
This thesis primarily addresses the development of an innovative structure with a unidirectional fiber orientation termed âunidirectional recycled carbon fiber tape structureâ for high-performance thermoplastics composites. The technological concept of the unidirectional structure comprises fiber opening, carding, drawing and a novel tape-forming process. In this concept, fiber opening, carding, and drawing processes were utilized to develop homogeneous, uniform, and highly oriented hybrid slivers. In the next step, these hybrid slivers were converted into a unidirectional recycled carbon fiber tape structure through a novel tape-forming process. To implement this concept, technological developments (investigations, modifications, optimization and further developments), were carried out in fiber opening, carding and drawing processes to develop a hybrid sliver with improved uniformity, homogeneity and unidirectional orientation. In the second phase, conception, design, technological developments, construction and prototype development were implemented to develop a novel tape-forming process. The result confirms that tape development technology comprising fiber opening, carding, drawing and prototype tape forming processes is an innovative, eco-friendly and sustainable technology compared to existing technologies.
Furthermore, the consolidation process transformed the unidirectional tape structure into high-performance thermoplastic composites. Subsequently, technology-structure-property relationships were established to develop composites with tailor-made properties. The analysis reveals that selecting optimum technological, consolidation and structural parameters develop tape and composite structures with unidirectional fiber orientation. As a result, experimental results of a high-performance composite developed from a unidirectional recycled carbon fiber tape structure show a very high tensile strength of 1350 Âą 28 MPa and an E-module of 84.7 Âą 2.3 GPa. This analysis confirms that unidirectional fibers configuration in composites brings a revolution toward developing cost-efficient, high-performance composites for load-bearing structural applications. Finally, theoretical and finite element modeling of tensile properties of high-performance composites reveals that modified models show good agreement with composite tensile properties
Dissecting Extracellular Matrix Internalisation Mechanisms using Functional Genomics
Breast and ovarian malignancies account for one third of female cancers. The role of the stroma in supporting invasive growth in breast cancer has become clear. Breast cancer cells interact and respond to the cues from the surrounding extracellular matrix (ECM). Integrins are main cell adhesion receptors and key players in invasive migration by linking the ECM to the actin cytoskeleton. In addition, integrins mediate distinctive biochemical and biomechanical signals to support cancer invasion. The role of matrix proteases in promoting ECM degradation and cancer dissemination has been extensively studied; however, cancer cells possess additional means to support those processes, such as integrin-mediated ECM endocytosis and consequent degradation in the lysosomes. Internalisation of the extracellular matrix is upregulated in invasive breast cancer. Nonetheless, the mechanisms by which cancer cells regulate this process are poorly understood. We developed a high throughput pH sensitive system to detect ECM uptake. Here, we show that MDA-MB-231 breast cancer cells converge in macropinocytosis to internalise diverse ECM components and we confirm that this process is modulated by PAK1. To unravel which ECM components breast cancer cells internalise in a complex environment (namely, cell derived matrices), we performed mass spectrometry. Proteomic analysis identified Annexin A6, Collagen VI, Tenascin C and fibronectin, among other matrisome proteins, to be internalised by invasive breast cancer cells. Following ECM endocytosis, ECM is targeted for lysosomal degradation. To unravel the molecular mechanisms behind this process, we performed a trafficking screen and identified the AP3 complex, VAMP7, Arf1 and ARFGEF2. Our results suggest that the AP3 complex may regulate ECM-integrin delivery to lysosomes.
To gain more insight on the signalling pathways governing macropinocytosis in breast cancer cells, we performed a kinase and phosphatase screen that unravelled MAP3K1 and PPP2R1A, a subunit of protein phosphatase 2A (PP2A) as relevant regulators of ECM endocytosis. Furthermore, our data suggests that p38 mitogen-activated protein kinase (MAPK) activation upon binding to the ECM is required for ECM macropinocytosis. Outstandingly, inhibiting p38 MAPK led to profound changes in the ability of breast cancer cells to migrate in cell derived matrices. Previous work from the Rainero lab focused on characterising the receptors involved in ECM internalisation; ι2β1 integrin was identified as the main regulator of ECM uptake in MDA-MB-231 cells. In particular, ι2β1 integrin has been shown to activate p38 MAPK pathway. Taken together, we hypothesise that binding of ECM to ι2β1 integrin results in the activation of PAK1 and MAP3K1, which in turn leads to ECM endocytosis. p38 MAPK activity may induce changes in actin polymerisation via PPP2R1A and/or focal adhesion turnover, which consequently promotes ECM macropinocytosis and invasive migration
Growth, Transport and Functionalization of Noble Metal Nanoparticles Inside and Outside a Gas Aggregation Cluster Source: Uncovered by in-situ Diagnostics
The Haberland type gas aggregation cluster source (HGAS), which was invented in 1992 by Haberland et al., provides the opportunity to synthesize different types of NPs and tailor their properties by adjusting the operating parameters of the HGAS. Although nowadays the HGAS is used by many groups for the synthesis of NPs, the processes inside the HGAS are not fully understood until today. Therefore, the aim of this dissertation is to increase the understanding of the ongoing processes inside the HGAS, because this opens the way for new fields of applications. In order to gain a better understanding of the HGAS, inâsitu diagnostics with a good spatial and temporal resolution are essential. Five different in-situ methods were used, which together contribute to a better understanding of growth, transport and functionalization of NPs inside a HGAS. By combining different in-situ methods it was possible to investigate dynamic processes in a HGAS and thereby gain new insights into growth, transport and trapping of NPs. Furthermore, the reliability of the multicomponent target approach could be enhanced, which makes it an excellent tool for the fabrication of alloy NPs with tailored composition. Finally, a new approach for the production of core-shell NPs in the gas phase was developed, which is expected to open up new applications for core-shell NPs because of its outstanding flexibility in terms of material combinations and reliability
Analytical validation of innovative magneto-inertial outcomes: a controlled environment study.
peer reviewe
Hybridization of Surface Plasmon Polaritons and Molecular Excitations
Starke Kopplung von MolekĂźlen mit einem räumlich begrenzten Lichtfeld fĂźhrt zur Bildung neuer polaritonischer Eigenzustände des Systems, die sowohl molekulare als auch photonische Eigenschaften erhalten und somit ein groĂes Potenzial fĂźr Anwendungen in der Chemie und Optoelektronik besitzen.
In dieser Arbeit wird die Kopplung zwischen Oberflächenplasmonen Polaritonen (SPPs), die als das räumlich begrenzte Lichtfeld agieren, und molekularen Anregungen wie Schwingungen und polaronischen Resonanzen untersucht.
Das starke Kopplungsregime zwischen einer Molekßlschwingung und einem SPP wird zum ersten Mal im mittleren Infrarot unter Verwendung der Carbonylschwingung von Poly(vinylmethylketon) Polymer und Silber als Ausbreitungsmedium von SPPs demonstriert. Die neu gebildeten Hybridmoden werden durch Experimente und numerische Modellierung untersucht, wobei Messungen der abgeschwächten Totalreflexion und der thermischen Emission sowie Berechnungen mittels der Transfermatrix und der linearen Dispersionstheorie verwendet werden. Ein Anticrossing in der Dispersion der Polariton-Zweige mit einer Energieaufspaltung bis zu 15 meV, was die Hauptsignatur des starken Kopplungsregimes ist, wird beobachtet.
Die starke Kopplung mit Zinkgalliumoxid, einem hochdotierten Halbleiter als Alternative zu Edelmetallen, wird auch untersucht. Experimentelle und simulierte Reflektometrie-Spektren sowie Dispersionsrelationen werden diskutiert, um RĂźckschlĂźsse auf die Eigenschaften des Systems zu ziehen. AuĂerdem wird ein Ansatz zur Verbesserung der Leitfähigkeit organischer Halbleiterpolymere durch starke Kopplung ihrer polaronischen Zustände an SPPs vorgestellt und Leitfähigkeitsmessungen durchgefĂźhrt. Ziel ist es, die Delokalisierung der Hybridzustände auszunutzen, um die Leitfähigkeit zu verändern.
Die präsentierten Ergebnisse bieten neue Einblicke in den Nutzen der Eigenschaften der Licht-Materie-Hybridisierung, um ihr volles Potenzial fßr verschiedene Bereiche und Anwendungen zu erforschen.Strong coupling of molecules with a confined light field results in the formation of new polaritonic eigenstates of the system called polaritons that inherit both molecular and photonic characteristics and thus holds strong potential for applications in chemistry and optoelectronics.
In this work, coupling between propagating surface plasmon polaritons (SPPs), as confined light field, and molecular excitations, such as vibrational resonances and polaronic features, is investigated.
The strong coupling regime between a molecular vibration and a propagating SPP is demonstrated for the first time in the mid-infrared spectral range using the carbonyl stretch vibration of Poly(vinyl methyl ketone) polymer and silver as metallic medium for SPPs propagation. The newly formed hybrid modes are investigated through experiments and numerical modelling, employing attenuated-total-reflection and thermal emission measurements as well as transfer-matrix and linear dispersion theory calculations. An anticrossing behavior in the dispersion of the polariton branches with an energy splitting up to 15meV, which is a key signature of the strong coupling regime, is observed.
Strong coupling involving zinc gallium oxide, which is a highly doped semiconductor, as an alternative to noble metals is also investigated. Experimental and simulated reflectometry spectra as well as the dispersion relations are discussed so as to draw conclusions about the properties of the system. Furthermore, an approach to enhance the conductivity of organic semiconductor polymers by strongly coupling their polaronic states to SPPs is presented and four-point probe measurements are conducted. The goal is to exploit the delocalization of the hybrid states to alter the conductivity of the organic semiconductor.
The results presented in this thesis provide new insights into the profit from the properties of light-matter hybridization in order to explore its full potential for several areas and applications
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