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A Lithostratigraphic and Microfossil Investigation into Late Holocene Coseismic Land Level Change and Tsunami Inundation on Nagai Island, Shumagin Islands, Alaska.
Get PDFCycles of earthquakes and tsunamis are complex, occurring over timescales greater than the instrumental data, therefore, palaeoseismic reconstructions best constrain seismic and tsunami hazards. This research investigates late Holocene great earthquakes (Mw >8.0) and high tsunami inundation (>present-day intertidal zone) on Nagai Island in the Shumagin section of the Alaska-Aleutian subduction zone (AASZ) through palaeoseismic reconstruction of sediment
cores from four sites across Nagai Island. DV.19.03 and 19.DV.17 are selected for detailed lithostratigraphic, diatom, grain size, and chronological analysis. Nagai Island does not exhibit identifiable land level change or sand beds conclusively demonstrating high tsunamis over the last ~2900 years, supporting the geological evidence from nearby Simeonof Island where no land level change >0.3 m or tsunami inundation exceeding the present-day intertidal zone are
identified. Thus, it appears that the Shumagin section of the AASZ has accommodated plate convergence throughout the late Holocene through long term persistent creep, neither
generating a great earthquake nor coseismically weakening from the propagation of a great earthquake from adjacent Semidi or Unimak sections. Further, absence of geological evidence for high tsunami inundation on Nagai Island alongside Simeonof Island suggests that the Shumagin section of AASZ has neither generated a high tsunami nor exhibited deposition of high tsunamis sourced from teletsunamis generated elsewhere along the AASZ or other subduction zones throughout the late Holocene. The geological evidence from Nagai Island combined with Simeonof Island implies low hazard for great earthquakes and high tsunamis generating or propagating into the Shumagin section. This suggests a low hazard for Shumagin sourced tsunamis to far field communities in the Pacific. However, great earthquakes and high tsunamis cannot be ruled out because the geological evidence may not extend to the Shumagin section recurrence intervals of great earthquakes, potential future changes in the locking of the plate interface, and possible missing geological evidence
The high energy properties of the Galactic X-ray binary population, as seen with the Fermi Large Area Telescope
Get PDFThe Fermi Large Area Telescope (Fermi-LAT) is a space instrument which has been in orbit since June 2008, and is sensitive to photons from 30 MeV to approximately 1 TeV. I use the Fermi-LAT data, alongside X-ray and optical data to perform an investigation of the high energy γ-ray properties of the X-ray binaries, stellar systems where either a neutron star or a black hole is in a close orbit with a main sequence star. The complex case of the low mass X-ray binary, V404 Cygni, is looked at; it is determined that there is no evidence for γ-ray emission from this system. The majority of the remaining Galactic X-ray binary population is then surveyed, and evidence for γ-ray emission is found from 5 systems: the high mass X-ray binaries SAX J1324.4-6200, GRO J1008-57, 1A 0535+262 and RX J2030.5+4751 and the low mass X-ray binary GS 1826-238. There are a number of additional systems where spatially coincident γ-ray excesses are identified, however evidence to associate these with their respective X-ray binaries is weak. I examine these systems alongside the X-ray binaries with known γ-ray emission and determine that γ-ray emission in high mass X-ray binaries is highly dependent on orbital phase, and X-ray accretion state so that many undetected systems may be weakly emitting transients. In the case of the low mass systems, I determine that these are nearby sources, and that almost all are known transitional millisecond pulsars. Future observatories such as CTA, SWGO and AMEGO are likely to discover more γ-ray emitting X-ray binaries, and these facilities are discussed
Promethean Forms of Grief in the Works of Byron, P.B. Shelley and Leopardi
No full textDrawing on Nietzsche’s views of Prometheus and archival material on Romantic Europe from Nietzsche’s Nachlass, my thesis investigates the notion of Prometheanism as an aesthetic phenomenon and a Zeitgeist that illuminates Byron, Shelley and Leopardi’s meditations on art and subjectivity. My study shows how Byron, Shelley and Leopardi’s visionary navigations of truth and knowledge stumble on a series of moral riddles about art and its hovering between real and ideal that problematise the premises of their poetic quests for truth and knowledge. My introductory chapter suggests that Nietzsche’s views of Prometheus are informed by his reading of Byron, Shelley and Leopardi, as exhibited in Nietzsche’s letters (and an unpublished essay on Byron) in which Nietzsche celebrates these Romantic poets. Chapter 1 examines the imaginative reconfigurations of Aeschylus’s Prometheus Bound in Byron’s Canto I and II of Childe Harold’s Pilgrimage and ‘Prometheus’ to elaborate on a form of scepticism and self-modelling discourse central to Byronic poetics. Chapter 2 explores Byronic subjectivity as performative in Canto III and IV of Childe Harold, Manfred and Cain to trace out what is conceived of as Byron’s Promethean tragic identity. Chapters 3 and 4 turn to Shelley’s own Promethean dilemma. In Chapter 3, this difficulty centres on Shelley’s treatment of the tensions between the self and states of being and becoming as registered in the visionary accounts of Alastor and Julian and Maddalo, and his eventual attempt to transcend the subject beyond the realm of being and be one with a process of becoming in Prometheus Unbound. Chapter 4, however, examines the darker aspects of Shelleyan visionary quests and Shelley’s awareness of a tragic realization, latent in early poems, but foregrounded in Epipsychdion, Adonais and The Triumph of Life. Considering a sense of grief modelled on the Promethean topos in an Italian context, Chapter 5 delineates Leopardi’s philological methodology to view modernity in the light of classical culture and to disclose the moral stakes of Promethean techné in Alla Primavera and La scommessa di Prometeo. In a reading of Operette Morali and Canti, chapter 6 illustrates the premises of Leopardi’s nihilism that utilises lyricism to endure the nullity of existence. Finally, a coda briefly sketches the Promethean bequest of Byron, Shelley and Leopardi in later literary traditions
Balthasar and Theological Style
Get PDFAmong the multiple volumes of his great Herrlichkeit, Hans Urs von Balthasar pointed to the volumes on theological style as particular favorites, and in a retrospective essay, he mused that the meaning of theological style should be taken up as an alternative to typical discourse about theology. On the basis of Balthasar’s exhortation, this thesis examines the meaning and import of the concept of theological style. I argue that, considered in light of Balthasar’s stated preoccupation with masterpieces, his use of the term theological style is a shorthand way for considering what Balthasar takes to be the characteristics of truly great theology in distinctly aesthetic terms. For Balthasar, a great theological style results from the confluence of three factors, the glory of divine revelation as understood by the teaching of the Church, both of which are brought to expression by the particular charism of the theologian.
But even more interesting than the what of a particular theological style is how Balthasar goes about discerning each theological style. In the second part of the thesis, I argue that each of his essays on the twelve exemplars of theological style seek to “sketch” the given theologian, much in the same way that an artist might sit before a masterpiece and sketch it. Balthasar’s sketching reveals what he takes to be the essential qualities of each theological style and his broader thematic preoccupations within his theological aesthetics. In closely considering these sketches, we see a set of interlocking and mutually complicating themes emerge, themes which I argue bear directly on Balthasar's vision of theological aesthetics. I consider the themes of eros, kairos, and kenosis, both as a way to examine the individual theological styles within these volumes, and as a way to evaluate Balthasar himself. In the final section, I take up Balthasar’s strange, lyrical work of spirituality, Heart of the World, and offer a reading of that work in terms of Balthasar’s own theological style and the three themes
Hunting for the cosmic neutrino background
Get PDFWe present the first comprehensive discussion of constraints on the cosmic neutrino background (CB) overdensity, including theoretical, experimental and cosmological limits for a wide range of neutrino masses and temperatures. Additionally, we calculate the sensitivities of future direct and indirect relic neutrino detection experiments and compare the results with the existing constraints, extending several previous analyses by taking into account that the CB reference frame may not be aligned with that of the Earth. The Pauli exclusion principle strongly disfavours overdensities at small neutrino masses, but allows for overdensities at the KATRIN mass bound . On the other hand, cosmology strongly favours in all scenarios. We find that direct detection proposals are capable of observing the CB without a significant overdensity for neutrino masses , but require an overdensity outside of this range. We also demonstrate that relic neutrino detection proposals are sensitive to the helicity composition of the CB, whilst some may be able to distinguish between Dirac and Majorana neutrinos
The Effect of Tunnelling in Quantum Field Theory
Get PDFThe phenomenon of quantum tunnelling is a familiar one, allowing
a particle to ‘escape’ from a potential well where it does not have enough energy classically to penetrate the potential barrier. Quantum tunnelling is well studied and familiar to most physicists from processes such as alpha decay. In this thesis we will examine the phenomenon of tunnelling in Quantum Field Theory which will yield a rich phenomenology. In the strong and electroweak sectors it gives rise to the instanton, a field configuration which tunnels between degenerate minima of the field strength. In the strong sector we will compute the cross section for these processes at hadron colliders before examining potential search strategies. In the electroweak sector we will show that such processes are always exponentially suppressed and hence unobservable at any present or future colliders. Finally we will look at the phenomenon of tunnelling in the early universe in the context of first-order phase transitions; here tunnelling can lead to the production of gravitational waves which could be observable at future gravitational wave detectors, and models giving rise to such signals can also be used to solve other shortcomings of the Standard Model such as the hierarchy problem and the absence of dark matter
The Synthesis of Peptide-Based Tools for Drug Discovery and Chemical-Biology Applications
Get PDFPeptidyl mono-fluoromethyl ketones (mFMK) are a class of compounds that have shown potential as protease inhibitors for the treatment of a range of diseases. They have also found application as chemical-biology probes that can be used in the interrogation of cellular processes. Despite the aforementioned applications, the number of synthetically viable routes reported for accessing these compounds is currently rather limited.
To address this issue, the work herein reports the efforts that have been made towards developing a novel synthetic pathway for preparing mFMKs. Initial attempts (Chapter 2) involved the formation of a tri-carbonyl system derived from a Boc-protected amino acid and Meldrum’s acid, with the intention of subsequently fluorinating, converting to the corresponding β-ketoester and coupling to a peptide of choice in solution. The idea was that the resulting substrate could then be saponified and decarboxylated, allowing access to the fluoromethyl ketone (FMK). However, the inherent reactivity of the moisture-sensitive fluorinated tri-carbonyl systems made them difficult to handle and isolate.
Attention was therefore turned towards the direct electrophilic fluorination of β-ketoesters, derived from either an N-Fmoc (Chapter 3) or N-Boc-protected (Chapter 4) amino acid of choice and formed as the tert-butyl ester. Selective mono-fluorination of the resulting 1,3-dicarbonyl was then achieved using CpTiCl3 in conjunction with Selectfluor, through utilisation of adapted literature protocols. The resulting N-Fmoc-protected substrate was carefully transformed to the β-ketoacid (Chapter 3) before attempted resin loading was performed, with the intention of allowing on-resin peptide growth followed by concomitant resin cleavage, global deprotection and decarboxylation to the FMK. However, unsuccessful resin loading attempts, coupled with evidence for premature FMK formation having occurred during these endeavours, suggested the presence of the fluorine atom had significantly reduced the nucleophilicity of the carboxylate, thus favouring decarboxylation over resin loading.
Given the challenges encountered with resin loading, the application of N-Boc-protected mono-fluorinated β-ketoesters in solution-phase peptide chemistry was explored (Chapter 4). Selective removal of the N-Boc group in the presence of the tert-butyl ester, through the modification of conditions reported in the literature, enabled coupling to a peptide of choice. Subsequent deprotection and decarboxylation led to the desired FMK. Whilst some epimerisation did appear to occur during peptide coupling, this route represents a straightforward approach for accessing these desirable and highly expensive molecular warheads in only 5 steps.
A slightly adapted approach, in which the N-Boc protected β-ketoester was first decarboxylated to the corresponding FMK prior to peptide coupling in solution, was also trialled (Chapter 4). However, this appeared to lead to challenges in purification of the resultant mFMKs, along with an accompanying low yield. Nonetheless, this methodology was successfully adapted and utilised for the synthesis of a peptidyl mono-chloromethyl ketone (mCMK) in only four steps (Chapter 5), although epimerisation was apparent. Furthermore, it is believed that extension of this methodology could allow access to other peptide-based C-terminal modified species, such as peptidyl bromomethyl ketones and di-fluoromethyl ketones.
In summary, the methodology developed for accessing both peptidyl mono-fluoromethyl ketones and peptidyl mono-chloromethyl ketones offers ready access to chemical-probes that can be used to interrogate cellular functions in a range of disease relevant systems
Development of an Immune Competent In Vitro Skin Equivalent to Investigate the Impact of Air Pollution on Skin Health
No full textThe impact of air pollution on skin health remains an understudied topic but there is mounting evidence to suggest it can cause damage to the structure and function of the tissue. Critical to understanding this impact is the generation of in vitro skin equivalent models that can accurately recapitulate the complex anatomy of the in vivo tissue. In this thesis, we have bioengineered a novel immune competent full thickness skin equivalent that contains functional Langerhans cells These skin equivalents have been utilised to investigate the effect of pollution on the inflammatory responses of the skin.
We have successfully developed a system to apply particulate matter, one of the main components of air pollution, to the surface of skin equivalent models that does not in itself damage the tissue. We have demonstrated though in depth ultrastructural analysis that particulate matter adheres to the surface of the stratum corneum, but significantly showed that the particles do not penetrate deeper into the tissue.
Many previous studies have utilised two dimensional monolayer cultures or simple epidermal models to investigate the deleterious effects of air pollution on skin. In this project we have developed an immune-competent full thickness skin equivalent model that contains an Alvetex® Scaffold based dermis that contains human fibroblast that secrete endogenous extracellular matrix proteins and a stratified epidermis containing MUTZ-3 cell line derived Langerhans cells. We subsequently demonstrated that these Langerhans cell containing skin models show a greater increase in pro-inflammatory cytokine production in response to known allergens and irritants. Thus, we have shown that these cell line derived Langerhans cells behave like their in vivo counterparts.
Skin equivalent models exposed to particulate matter showed an increase in pro-inflammatory mediator production which suggest that even without the particulate physically penetrating the epidermal barrier these pollutants can still initiate deleterious responses. Additionally, full thickness models containing Langerhans cells showed a greater inflammatory response to particulate matter than the non-immune-competent skin equivalents. Overall, this demonstrates the involvement of the skin’s immune system in responding to air pollution exposure
Reasonable Latitude: Learning and Adaptability in British Army Despatch Riders During the Second World War
Get PDFCommunications are essential for success in war. Armies capable of reliable, sustained communications have a distinct advantage over armies who experience communications failures. This thesis uses communications as its main case study to examine the degree to which the British Army was capable of learning, innovation, and adaptability during the Second World War. Utilising the development and experience of the Royal Corps of Signals, it demonstrates that a pattern of informal and formal learning processes emerged during the war, shedding light onto how the wider British Army not only learned but made use of the knowledge it generated.
This study utilises oral histories and archival documents to find evidence of both informal and formal learning, focusing specifically on the role of despatch rider where possible. It finds that a complex process developed as the war developed, integrating battlefield adaptations, innovative strategy, and lessons-learned committees to evaluate and institute best practice. It determines that communications policy, strategy, and practice changes originated at all levels as the British Army sought to respond to a rapidly changing war.
This thesis contributes to a wide range of fields within history: the Second World War, learning during war, communications, policy and strategy formation, oral history studies, lived experiences, and even that of the motorcycle during war. It relies on the stories of individuals alongside broader developments in both British and Allied operational decisions. Though it looks deeply at individuals and their understandings of the war, this thesis considers broader issues of executing changes during war, integrating new knowledge, and determining the best path forward. My research demonstrates that looking at both individual and collective responses are crucial in answering these questions
Investigating the role of the cell wall in cold acclimation and freezing tolerance in Arabidopsis thaliana
Get PDFMany plants are susceptible to freezing stress, including crops necessary for the production of staple foods. Climate change is predicted to increase the occurrence of early autumn and late spring frosts, striking at times when plants are especially vulnerable. Most perennial plants can undergo cold acclimation, wherein freezing tolerance is increased through exposure to low, non-freezing temperatures. Encapsulating every plant cell is a thin, dynamic layer of complex polysaccharides and proteins – the cell wall. It offers structural rigidity, extensibility, a means of water transport, and protection from pathogens. The cell wall undergoes significant structural, compositional and physical remodelling during cold acclimation; it is therefore increasingly thought to have a role in freezing tolerance, perhaps by acting as a physical barrier to ice propagation and providing mechanical reinforcement against freezing-induced dehydration, though this remains unconfirmed.
In the present study, the potential role of the cell wall in both cold acclimation and basal freezing tolerance was explored further. An increase in freezing tolerance in
cold-acclimated Arabidopsis was shown to be correlated with both reduced cell-wall porosity and enhanced cell-wall mechanical integrity. These properties are thought to limit the nucleation and spread of ice through plant tissues and protect against cellular dehydration and collapse during freezing, respectively. Comprehensive microarray polymer profiling revealed a number of compositional changes that
occur in the Arabidopsis cell wall during cold acclimation. Most notably, there was an accumulation of extensins, a family of important structural proteins, and a shift
towards the demethylesterified form of pectin, a reorganisation which can have considerable impacts on the physical properties of the cell wall by facilitating the
formation of cross-links between pectic backbones. Mutants deficient in either extensin or demethylesterified pectin were shown to have impaired freezing tolerance, cell-wall porosity and mechanical properties.
In wild-type cell walls, the pectic polysaccharide rhamnogalacturonan-II (RG-II)
exists predominantly as a dimer centred on a borate-ester cross-link. The freezingsensitive sfr8 mutant, which lacks RG-II dimerisation, was also found to have compromised wall porosity and mechanics. These defects were partially reversed when RG-II dimerisation was restored by boron supplementation, as was its freezing sensitivity, suggesting that RG-II cross-linking is critical to full freezing
tolerance. A number of other mutants with defective cell walls, including those with structurally- or compositionally-impaired cellulose, hemicellulose, or pectins, were screened for freezing sensitivity and aberrant physical properties. The data largely
support the idea that plant freezing tolerance is dependent on the porosity and mechanical properties of the cell wall, themselves dependent on the structure, composition, and organisation of its constituent polymers
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