Science

Publication Search Results

Now showing 1 - 2 of 2
  • (2021) Djuandhi, Lisa
    Thesis
    With a theoretical capacity of 1672 mA h g-1, more than five times higher than any commercially available lithium-ion (Li-ion) cell systems, the lithium-sulfur (Li-S) cell is an attractive candidate for next generation energy storage. Despite this high theoretical capacity, Li-S cells generally suffer from poor capacity retention and working lifetimes that prevent them from mass commercialisation. This is mainly due to current limitations in managing the inherent Li-S redox reactions which involve diffusion and migration of electrochemically active polysulfides. One approach to prevent polysulfide migration is by rational design of the sulfur electrode framework. The aim of this research is to investigate the electrochemical implications of using different frameworks for entrapment of redox active species, mainly designed for the Li-S cell system. The two types of frameworks investigated are: (1) mixed-morphology carbon feeds derived from waste sources wherein the intention is for the carbon to purely act as a structural framework to trap lithium polysulfides, and (2) sulfur-rich copolymers wherein redox active sulfur is covalently bound within the framework. More specifically, the goals involve determining: (1) whether carbon acts purely as a structural framework to trap redox active species during electrochemistry, and (2) whether sulfur-rich copolymers act purely as a sulfur feed. Achieving these goals requires a thorough understanding of what properties in each framework are ideal for the Li-S cell. The main conclusion drawn from this work is that neither of the materials studied behaved as pure structural or covalent frameworks partaking in various side processes. Using specialised techniques such as X-ray powder diffraction, solid-state NMR, and X-ray absorption near-edge structure spectroscopy, the beneficial and parasitic side processes involved in each framework are able to be determined. Overall, a significantly enhanced understanding of the Li S cell chemistry when using these materials is presented in this work.

  • (2023) Ireland, Jake
    Thesis
    Pluripotent stem cell-derived cardiomyocytes (hPSC–CM) have great importance for predicting safety parameters for pharmaceutical compounds and models of healthy versus disease states of the human heart. In recent years, there has been an insistence that all new pharmaceutical products are tested on in vitro models for potential proarrhythmic effects and the increased demand for improved biomimetic hPSC-CM in pharmaceutical safety assays such as the Comprehensive in vitro Proarrhythmic Assay (CiPA). In addition, hPSC-CM are being utilised in cell therapies to treat and reverse the effects of ischaemic heart disease, offering potential cures for cardiovascular diseases instead of treatments for delaying progressive heart failure. In the first part of this thesis, I will examine how purified extracellular matrix proteins (ECMPs) can influence pluripotent stem cell (PSC) behaviour and how we may use this to precondition cardiac progenitor lineage specifications. I use array-based techniques to investigate how protein combinations affect proliferation, pluripotency, germ layer, and cardiac progenitors. This method allows us to visualise how individual proteins can affect cells' behaviour in a larger array whilst highlighting how specific combinations can precondition pluripotent cells towards a cardiomyocyte lineage. This combinatorial approach led to the identification of several unique matrices that promote differentiation, which will aid efforts at producing therapeutically useful cell types with greater efficiency. In the second part of this thesis, I demonstrate a novel bioreactor that attenuates a magnetic field to dynamically modulate the stiffness of magnetoactive hydrogel to look at how biomimetic dynamic stiffening of a substrate can influence cardiomyocyte lineage specification. We investigate how biomimetic in vivo mechanics may influence cell fate by following the expression profiles of cells in different dynamic environments. Non-invasive electromagnetic signals affect substrate stiffness when combined with magnetic particles and magnetic fibres and how this can help direct cell orientation and accompanying lineage specification Finally, I investigate how variability in cell phenotypes and expression patterns are influenced by biomimetic cues and how these variabilities could be utilised in future safety assessment protocols and cell therapy treatments for cardiovascular disease.