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Stretching Polymer and Lipid Membranes
Get PDFPolymer and lipid membranes can be used as model membranes to mimic real cells or in bio-compatible devices. Both materials self-assemble into vesicles and are similar in their ability to fuse to hydrophilic substrates and form patches with distinct heart or circular shapes. They differ in their composition and size, with polymers showing reduced fluidity and hydration repulsion forces behaviour at patch edges.
Stretching experiments are widely used to study mechanosensory signalling and physical process in cells and model membranes. A custom device to study lipid and polymer membrane stretching in uniaxial and biaxial directions was designed. This device was used in conjunction with fluorescence and atomic force microscopy to study membranes under strain.
Lipids under biaxial stretch open roundish pores and the membrane slides at the edges to accommodate stretch. Conversely, polymers under mechanical stretch open pores which are strongly affected by the friction coefficient between the membrane and substrate, and the tension diffusion in the membrane. This causes them to form roundish to dendritic structures under different temperatures and stretching rates. The immobile fraction which is left behind during stretching reorganises into micelles creating scars after the strain has been released.
Under uniaxial strain, continuous lipid bilayers open oval pores in contrast to circular pores in simulation prediction and pore theory. The membranes show stretching rate dependence with the distance between pores smaller at faster rates, in agreement with tension dissipation in the membrane
Whose Responsibility is it Anyway? Accountability and Standpoints for Disaster Risk Reduction in Nepal
Get PDFGeneralisation, universal knowledge claims, and recommendations within disaster studies are problematic because they lead to miscommunication and the misapplication of actionable knowledge. The consequences and impacts thereof are not often considered by experts; forgone as irrelevant to the academic division of labour. There is a disconnect between expert assertions for disaster risk reduction (DRR) and their practical suitability for laypersons. Experts currently assert independently of the context within which protective action measures (PAMs) are to be used, measures unconnected to the people for whom they are developed. This has knock-on effects for DRR: much expert-generated science and policy remains unused, unimplemented, and sometimes misapplied.
I use philosophical accounts of assertion and epistemic blame to highlight the epistemic relationship between experts and laypersons. This relationship includes responsibilities and agreements between epistemic agents. Since multilevel DRR knowledge still transfers top-down from experts to laypersons, if experts impair the epistemic relationship, they can be held epistemically blameworthy. To address the pervasiveness of top-down systems, I analyse the epistemic framings and narratives currently shaping DRR, and more specifically PAMs and campaigns. I deconstruct universal perspectives that dominate the epistemic processes of generating, disseminating, and implementing DRR knowledge and specifically for co-seismic landslide PAMs for Nepal.
I argue for more inclusive, contextual, and epistemically responsible DRR. Co-production of knowledge should begin from the standpoints of marginalised persons who may have an epistemic advantage due to their socio-politically marginalised positions. Often these epistemic contributions are left out of DRR efforts because marginalised persons are rarely afforded equal, if any, epistemic agency, which results in epistemic gaps and a large pool of relevant knowledge remaining unincorporated and unused in DRR research and policy
Ultraviolet line-driven disc winds as a feedback mechanism in bright active galactic nuclei
Get PDFAstronomical observations have shown that galaxies and the supermassive black holes (BH) located at their centres have evolved together over cosmic time. BH grow by accreting matter from their surroundings and the gravitational potential energy released by the infalling matter can power the enormous luminosities we see in active galaxies and quasars, and is in principle sufficient to significantly disrupt the structure of the host galaxy. However, the particular physical processes through which such active galactic nuclei feedback affects the host galaxy are still poorly understood. One possibility is that the accretion process powers winds that travel through the galactic bulge, displacing the gas reservoir and thus quenching star formation in the galaxy. There are various mechanisms that could drive such winds. In this thesis, we focus on the study of UV line-driven winds originating from the surface of accretion discs, which are driven by radiation pressure on spectral lines and are also present in hot stars. We develop a numerical simulation method for the study of such systems, building up on existing models and incorporating modern computational techniques to study the conditions under which these winds can be launched and accelerated. The resulting model, called Qwind, features relativistic corrections to the radiation flux, as well as an algorithm to perform ray tracing on axisymmetric geometries. We also develop a model to compute the initial conditions to launch the wind from the surface of the accretion disc, based on theoretical frameworks employed in the study of O-star winds. Using this new model, we are able to investigate the dependence of the wind properties on the BH mass, mass accretion rate, and the innermost launching radius of the wind, thus deriving the amount of momentum and energy carried by the wind for different AGN systems
Early Neanderthal social and behavioural complexity during the Purfleet Interglacial: handaxes in the latest Lower Palaeolithic.
Get PDFOnly a handful of ‘flagship’ sites from the Purfleet Interglacial (Marine Isotope Stage 9, c. 350-290,000 years ago) have been properly examined, but the archaeological succession at the proposed type-site at Purfleet suggests a period of complexity and transition, with three techno-cultural groups represented in Britain. The first was a simple toolkit lacking handaxes (the Clactonian), and
the last a more sophisticated technology presaging the coming Middle Palaeolithic (simple prepared core or proto-Levallois technology). Sandwiched between were Acheulean groups, whose handaxes comprise the great majority of the extant archaeological record of the period – these are the focus of this study. It has previously been suggested that some features of the Acheulean in the Purfleet Interglacial were chronologically restricted, particularly the co-occurrence of ficrons and cleavers. These distinctive forms may have exceeded pure functionality and were perhaps imbued with a deeper social and cultural meaning. This study supports both the previously suggested preference for narrow, pointed morphologies, and the chronologically restricted pairing of ficrons and cleavers. By drawing on a wide spatial and temporal range of sites these patterns could be identified beyond the handful of ‘flagship’ sites
previously studied. Hypertrophic ‘giants’ have now also been identified as a chronologically restricted form. Greater metrical variability was found than had been anticipated, leading to the creation of two new sub-groups (IA and IB) which are tentatively suggested to represent spatial and
perhaps temporal patterning. The picture in the far west of Britain remains unclear, but the possibility of different Acheulean groups operating in the Solent area, and a late survival of the Acheulean, are both suggested. Handaxes with backing and macroscopic asymmetry may represent prehensile or ergonomic considerations not commonly found on handaxes from earlier interglacial periods. It is argued that these forms anticipate similar developments in the Late Middle Palaeolithic in an example of convergent evolution
Trusts of the Family Home, the 'Familialisation' of Property Law and the Potential for Judicial Development
Get PDFThis thesis seeks to critically evaluate the current law governing trusts of the family home and its application to ownership disputes between former cohabitants. This exploration will be examined through the theoretical lens of ‘familialisation’, a term coined by Dewar to describe the modification of property law principles to respond to the familial dimension of ownership disputes.1 To support this thesis in analysing the contemporary issues visible in the modern trusts framework, the thesis will assess the historical development of familialisation. It will draw upon recent academic scholarship to evaluate contemporary criticism of the process of ‘familialisation’ of property law and the modern common intention constructive trust. A central debate intertwined within this area is the relationship between rules and discretion, which has been utilised to characterise and rationalise the tension between property law and family- centric concerns. This thesis will therefore explore how the judiciary could continue to shape this familialisation process so as to protect economically vulnerable cohabiting parties. It will be argued that in order to ascertain the ideal balance between legal certainty, ensured through rules, and flexibility, offered by discretion, further structuring of judicial discretion should be undertaken. This would involve a re-evaluation of the principles considered when determining the acquisition and quantification of a beneficial interest of a party in the family home, providing guidelines for the judiciary whilst retaining a degree of latitude to accommodate the diverse needs of modern families owning and sharing property. Ultimately, this thesis will conclude that further judicial clarification is necessary to address the current deficiencies of trusts of the family home and simultaneously adapt the framework to better respond to the nature of home-sharing
Learning by exporting and innovation performance: evidence from Thai SMEs
Get PDFThis study aims to analyze the crucial mediating role of tacit knowledge acquisition from foreign markets between the effect of sub-dimensions of export activities and the innovation performance of small and medium-sized enterprises (SMEs) in Thailand. The primary purpose is to demonstrate that a Learning-by-Exporting (LBE) concept cannot always enhance SMEs' innovation performance directly, and their relationship is not always linear. Contributing to the LBE literature, the study uses the Knowledge-Based View (KBV) to emphasize a driving mechanism that explains why the LBE concept may not always lead to a firm's innovation performance directly, together with discussing current issues related to the mixed results of LBE effects on innovation performance. Involving 220 Thai Manufacturing SMEs and using structural equation model, the results indicate that tacit knowledge acquisition mediates the relationship between export intensity and process innovation, not product innovation. Besides, the study suggests that the sub-dimensions of export activities are significant factors to reconcile the inconclusive effects between export and innovation performance. Each dimension is also found to provide different significant results on the firm's tacit knowledge acquisition; for instance, while export intensity positively impacts tacit knowledge acquisition, the number of markets negatively affects it. Furthermore, whereas the results of multigroup path analysis for young and mature firms do not support the model-level, a significantly positive impact of the numbers of customers on mature firms’ tacit knowledge acquisition is observed at the path-level, and the direct effect of the number of markets on young firms’ product innovation is noted. The findings of this study shed new light on the LBE literature in the SMEs context by proposing a scrutiny of the ages of firms in further LBE research
Grace, Disruption and Stability: The Christian Life in the Theologies of Rowan Williams and Oliver O’Donovan
Get PDFThis thesis explores the character of the Christian life in the writings of the contemporary
Anglican theologians Rowan Williams and Oliver O’Donovan. I display a set of theological
contrasts that arise from their respective accounts of creation and Christology, which are
amplified in their understandings of the affective shape of the Christian life. I argue that the
most constructive response to these differences is not to be found at the level of theological
synthesis. Indeed, I argue for a certain kind of theological irresolution in response to these
themes. When taken together, these thinkers’ works display a set of dissonant, yet equally
necessary aspects of the Christian vision which are fruitful for wise Christian living.
The dominant motif of Williams’ writings is the disruptive character of God’s transforming
work in human lives, as each person grows into conformity with the crucified and risen
Christ. In his vision, the Christian life involves a journey of being drawn by the Spirit into the
endless abundance of God. It is a life marked by continual repentance and renewal, and
learning to see Christ in new ways at the centre of all things. O’Donovan’s account of the
Christian gospel focusses on the centrality of creation as a stable order, assured and restored
through Christ’s resurrection. The Christian life entails seeking and joyously finding oneself
within this good order of God’s making and redeeming. The gospel offers an assured place to
survey one’s life, and a stable foundation from which to live well. I argue that these thinker’s
works, when taken together, can nourish an account of Christian wisdom and discernment
which brings to the foreground, in different ways and at different times, the disruptive and
stabilising aspects of the Christian gospel, for the sake of faithful and flourishing Christian
livin
Understanding Interfacial and Spin-Orbit Torque Effects in Thin Film Magnetic Multilayers.
Get PDFThe understanding of both the fundamentals of spin-orbit torques and the potential avenues for spin-orbit exploitation is crucial for the development of future spintronic devices. Accurate quantification of the relevant parameters, such as the spin-orbit effective field strengths, is vital for both performance comparisons and the understanding of the physical origins. In this work, a common effective field measurement technique is probed for its potential inaccuracies, a new method for achieving field-free magnetic reversal is demonstrated and both the structural and magnetic property variations in structurally inverted thin films are investigated. The design, construction and commissioning of a multi-functional MOKE instrument has been presented. The multi-functional nature of the instrument allowed for sample environments which included the simultaneous application of external fields and sample charge currents for spin-orbit torque effect measurements. Raster scanned 2D MOKE data were collected for multiple samples based upon a 20 µm-wide perpendicularly magnetised Pt/Co/Pt rectangular bar. Each rectangular bar had a differing lateral displacement with respect to the 60 µm wide electrical contacts, with positions varying from the centre of the electrical contacts to being parallel with the edge. It was shown that the series of samples exhibit deterministic bi-directional field-free magnetic reversal. After discussing the previously known methodologies for field-free magnetic reversal, a new methodology was required in order to explain the symmetry of the results, where the charge current Oersted field is the cause of both the initial domain nucleation and the overall bi-directional magnetic reversal pattern. The accuracy of a common methodology for quantifying the spin-orbit effective fields was studied by probing the effect of magnetic reversal. It was shown that if magnetic reversal occurs when otherwise unwanted, the resultant effective field values can be exaggerated by over an order of magnitude compared to their typical values. This inaccuracy can be undetectable, particularly in thin films with non unity magnetic remanence. Structural and magnetic property variations in Pt/CoFeTaB/Ir, together with its structural inverse, were probed with a variety of techniques including polarised neutron reflectometry. Both structural and magnetic variations were observed, with the most dominant change being a Curie temperature variation of over 100 K, where Ir/CoFeTaB/Pt is paramagnetic at room temperature whereas Pt/CoFeTaB/Ir is ferromagnetic
AGRICULTURAL DECISION-MAKING AND MANAGERIAL RESPONSE AT DURHAM CATHEDRAL PRIORY DURING THE LONG FOURTEENTH CENTURY, c.1300-1453
Get PDFABSTRACT: The role of agency and the framework which we use to discuss agriculture in the Later Middle Ages and in the medieval economy deserves fresh consideration. Previous scholars have often portrayed medieval economic actors as unmoved by or uninterested in the changing world around them. However, the true role of decision-making is obscured in much of this literature on medieval agriculture due to the common framework of proto-capitalistic and profit-maximising within which the field is often analysed. In such circumstances, the role of individuals is much too easily obscured. My thesis addresses these issues while paying particular attention the roles of manorial managers and monastic obedientiaries and the effect the actions of these individuals had on manorial farming. In this thesis, I examine the extant manorial accounts from the estate of the Durham Cathedral Priory bursar, of which there are over four hundred. I use the data gathered from these accounts to examine measures of arable productivity. I additionally use data from tithe receipts and rental books, which provide evidence for the extra-demesne economic activities of those who managed the bursar’s manors. The evidence from these sources is then examined in light of the agricultural treatises of the period, including Walter of Henley’s Husbandry, Les Reules de Seynt Roberd by Robert Grosseteste, Bishop of Lincoln, and the anonymous Senechausie. I argue throughout this thesis for a re- evaluation of the motives and capabilities of those involved in medieval agriculture. These activities of these very capable individuals too easily become lost when careful analysis is not undertaken to deliberately restore their agency
mNeonGreen-collagen1α2: a tool for real time, high resolution, visualisation of collagen I trafficking
Get PDFCollagen I is a fibrillar protein of the extracellular matrix, where it provides strength and support to a number of connective tissues. Collagen I is produced by the cells of connective tissues as a short procollagen peptide, which self-assembles into fibrils upon secretion. Despite its important role in the skin, there are still gaps in our understanding of the intracellular trafficking and extracellular fibril assembly of collagen I. The highly dynamic nature of collagen I trafficking makes light microscopy the best tool to further investigate this process.
In this thesis, an mNeonGreen-collagen1α2 fusion protein will permit live imaging of collagen I in real time and with a higher resolution than previously achieved within the field. Following design of the construct, the expression of mNeonGreen-collagen1α2 was characterised within three immortalised cell lines of interest and extensively controlled for. mNeonGreen-collagen1α2 successfully permitted imaging all stages of collagen I trafficking: from synthesis, through the cell secretory pathway, and fibril assembly in the extracellular matrix. mNeonGreen-collagen1α2 was also used to investigate biological and cosmetic questions within the field. Overall showing that mNeonGreen-collagen1α2 is a robust, replicable and biologically relevant tool to study collagen I trafficking in real time with high resolution
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