VictorJuiz/thesis huggingface dataset:
Picosecond X-ray diffraction from shock-compressed metals

In this thesis, Molecular Dynamics simulations of shocked single crystals of Copper and Iron are studied using simulated X-ray diffraction. Strains and volumetric compression in modeled Copper crystals shock-compressed on picosecond time-scales are found. By comparing the shifts in the second and fourth diffraction orders, the density of dislocations is calculated. In Iron, simulated X-ray diffraction is used to verify the modelling of the α-ε phase transition induced by shock-compression on picosecond time-scales. No plastic deformation of Iron is found in the studied pressure range of ~ 15-53 GPa.
The results are then compared with data from in situ X-ray diffraction experiments of laser-shocked single crystals. Near-hydrostatic compression of shock-compressed Copper on nanosecond time-scales is confirmed using a new wide-angle film diagnostic capturing diffraction from multiple crystal planes. Also, the first in situ X-ray diffraction evidence of the onset of the α-ε phase transition in laser-shocked single crystal Iron is shown. No plastic yield of the crystal lattice is found, which is in agreement with the simulation results.
Results from both the Molecular Dynamics simulations and experiments are used to suggest enhancements in computer modelling of shocked crystals, as well as future experimental studies. In particular, the need for a measurement of dislocation densities during the shock wave passage through a crystal is highlighted, and a method enabling such a measurement is proposed.

Advisor: Wark, J
Cosmological consequences of supersymmetric flat directions

In this work we analyze various implications of the presence of large field vacum expectation values (VEVs) along supersymmetric flat directions during the early universe. First, we discuss supersymmetric leptogenesis and the gravitino bound. Supersym- metric thermal leptogenesis with a hierarchical right-handed neutrino mass spectrum normally requires the mass of the lightest right-handed neutrino to be heavier than about 109 GeV. This is in conflict with the upper bound on the reheating temperature which is found by imposing that the gravitinos generated during the reheating stage after inflation do not jeopardize successful nucleosynthesis. We show that a solution to this tension is actually already incorporated in the framework, because of the presence of flat directions in the supersymmetric scalar potential. Massive right- handed neutrinos are efficiently produced non-thermally and the observed baryon asymmetry can be explained even for a reheating temperature respecting the gravitino bound if two conditions are satisfied: the initial value of the flat direction must be close to Planckian values and the phase-dependent terms in the flat direction potential are either vanishing or sufficiently small. We then show that flat directions also contribute to the total curvature perturbation. Such perturbation is generated at the first oscillation of the flat direction condensate when the latter relaxes to the minimum of its potential after the end of inflation. If the contribution to the total curvature perturbation from supersymmetric flat direction is the dominant one, then a significant level of non-Gaussianity in the cosmological perturbation is also naturally expected. Finally, we argue that supersymmetric flat direction VEVs can decay non perturbatively via preheating even in the case where they undergo elliptic motion in the complex plane instead of radial motion through the origin. It has been generally argued that in this case adiabaticity is never violated and preheating is inefficient. Considering a toy U(1) gauge theory, we explicitly calculate the scalar potential, in the unitary gauge, for excitations around several flat directions. We show that the mass matrix for the excitations has non-diagonal entries which vary with the phase of the flat direction vacuum expectation value. Furthermore, this mass matrix has zero eigenvalues whose eigenstates change with time. We show that these light degrees of freedom are produced copiously in the non-perturbative decay of the flat direction VEV.

Keywords: Early Universe
Supersymmetry
Advisor: March-Russell, J
Sarkar, S
The political history of the Sāmānid state

The Sāmānids (204/819-395/1005) were the last Iranian dynasty to rule Eastern Iran before the advent of the Turkish Muslim states which dominated the_central Islamic lands during the medieval period. The Sāmānid state was the largest and most prosperous of the "Abbasid successor states and one of the most vigorous culturally. Yet like all successor states, the Samanids were beset by a high level of political instability which led finally to the dismemberment of the state between two Turkish dynasties, the Qarākhānid steppe rulers and the Ghaznavids, former vassals of the Sāmānids. This thesis explores the causes of this instability and attempts to account for the fall of the state, using the works of V.V. Barthold and R.N. Frye as points of reference. Barthold's hypothesis, which concludes that the Samanids and their bureaucrats were overwhelmed by an alliance of military and scholarly interests before the arrival of the Qarākhānids, is rejected. Instead the fatal weakness in the state structure is sought in the institution of patronage which controlled appointments to provincial governorships. Chapter one presents a survey of the sources with particular reference to the chronicle literature and the geographers, Iṣtakhrī, Ibn Hawqal and Muqaddasī; the unpublished works of the chronicler Ibn Ẓafir al-Azdī (d. 613/1216) and Muhammad ibn ˋAbd al-Jalll al-Samarqandī's 12th century biographical dictionary of Transoxanian scholars are also analysed. Chapter two comprises an overview of the physical and human geography of the 10th century mashriq. The following six chapters form a narrative of the political history of the dynasty from the obscure pre-monarchical period to 395/1005. Chapters five and six are devoted to the reign of Nasr ibn Aḥmad, a watershed in the Sāmānid period during which the earliest works of Persian literature were composed and many senior courtiers converted to Ismāˋīlīsm. Chapter nine examines the Sāmānids 1 sources of revenue, the state apparatus, the nature of Sāmānid politics and the ways in which rulers sought to legitimize their authority and Chapter ten summarizes my conclusions regarding Barthold's interpretation of the fall of the dynasty. The appendices include prosopographical studies of members of the state elite, notes on the Ismāˋīlī rebellion of 295/907, the history of the Khwārazmshāhs and an edition of Ibn Ẓāfir al-Azdī's chapter on Sāmānid history.
Quantal analysis of synaptic plasticity in the rat hippocampus

Long-term potentiation (LTP) is a long-lasting increase in efficacy shown by some synapses in the brain and elsewhere that might be involved in certain types of learning and memory. It has been most intensively studied in the hippocampus, a brain area known to be important in memory. LTP induction is triggered by a rise in calcium concentration inside the postsynaptic cell. Whether LTP is expressed presynaptically or postsynaptically is less clear, with results from different laboratories appearing to contradict one another.
Quantal analysis is one approach to this question. Neurotransmitter is released from the presynaptic cell in discrete packets of roughly equal size, known as quanta. If the increased response recorded during LTP is composed of a greater number of quanta, it would suggest a presynaptic change. On the other hand, an increase in the postsynaptic effect produced by each quantum would suggest that there had been a change in the postsynaptic cell.
I made intracellular voltage recordings of small excitatory postsynaptic potentials (EPSPs) from pyramidal neurones in area CA1 of rat hippocampal slices. I induced LTP and determined the site of the change using three quantal analysis procedures: 1/CV² graphs, amplitude frequency histograms and 'constant N analysis'. The results indicate that EPSPs can show both presynaptic and postsynaptic changes. However, the proportions varied considerably between individual EPSPs and seemed to depend on the initial 'setting' of the synapse. This, in turn, can depend on the experimental conditions, which might explain at least some of the contradictions in earlier results.
I also carried out a similar study of a briefer form of enhancement known as shortterm potentiation (STP). I found that this too is caused by both presynaptic and postsynaptic changes and that their proportions seem to obey a similar rule to LTP. This suggests that LTP and STP are not separate phenomena, as some have suggested, but are closely related.
I attempted a similar study of mossy fibre inputs to pyramidal cells in area CA3 of hippocampal slices. However, it was difficult to obtain uncontaminated mossy fibre responses, so the results of this study are preliminary.

Advisor: Larkman, A
Mechanisms of carding

A model for a slender thread or fibre in a slow viscous incompressible fluid is derived. The material of the thread is assumed to have no bending stiffness and to be strictly inextensible. The model is then applied to a simplified industrial situation found in carding, where a thread hangs off a hook. In two limiting cases, perturbation methods give approximate asymptotic solutions, and numerical solutions are found for the general case.
Large-N correlator systems for low frequency radio astronomy

Low frequency radio astronomy has entered a second golden age driven by the development of a new class of large-N interferometric arrays. The low frequency array (LOFAR) and a number of redshifted HI Epoch of Reionization (EoR) arrays are currently undergoing commission and regularly observing. Future arrays of unprecedented sensitivity and resolutions at low frequencies, such as the square kilometer array (SKA) and the hydrogen epoch of reionization array (HERA), are in development. The combination of advancements in specialized field programmable gate array (FPGA) hardware for signal processing, computing and graphics processing unit (GPU) resources, and new imaging and calibration algorithms has opened up the oft underused radio band below 300 MHz. These interferometric arrays require efficient implementation of digital signal processing (DSP) hardware to compute the baseline correlations. FPGA technology provides an optimal platform to develop new correlators. The significant growth in data rates from these systems requires automated software to reduce the correlations in real time before storing the data products to disk. Low frequency, widefield observations introduce a number of unique calibration and imaging challenges. The efficient implementation of FX correlators using FPGA hardware is presented. Two correlators have been developed, one for the 32 element BEST-2 array at Medicina Observatory and the other for the 96 element LOFAR station at Chilbolton Observatory. In addition, calibration and imaging software has been developed for each system which makes use of the radio interferometry measurement equation (RIME) to derive calibrations. A process for generating sky maps from widefield LOFAR station observations is presented. Shapelets, a method of modelling extended structures such as resolved sources and beam patterns has been adapted for radio astronomy use to further improve system calibration. Scaling of computing technology allows for the development of larger correlator systems, which in turn allows for improvements in sensitivity and resolution. This requires new calibration techniques which account for a broad range of systematic effects. And, a deep integration between DSP hardware and software data reduction into a single backend.

Keywords: Digital Signal Processing
Metrewave
Correlators and Interferometers
Radio Astronomy
Advisor: Rawlings, S
Jones, M
‘The stories most of all’: a content analysis of bestselling children’s books in Britain (1964-2004)

I use content analysis to address the relationship between sex and race with interactions and activities in bestselling children’s books. Research into children’s books presents a mixed picture for changing portrayals, with different patterns in representations appearing for protagonists and central characters compared to characters in general. I argue that interactions are important for assessing representations and that there is a difference between being present and being involved. The actor is utilized to strike a balance between presence and importance by showing who is participating. Interactions are used to examine how actors interrelate. These show the nature of the interactions that occur between groups of actors and in specific spheres of activity (work, leisure, home, school, sport, play, beautification and emotion). This approach goes beyond most research into representations. My findings come from a content analysis using functional coding categories which are based upon a Quantitative Narrative Analysis text grammar. This means that connections between coding categories are explicitly specified by the grammar and that I can link actors, as grammatical subjects and objects, through actions. This is very different from findings based on subjectively selected themes; the coding categories used here are grounded within the linguistic characteristics of the text itself.

Advisor: Jackson, M
Franzosi, R
The development of Mahler's symphonic technique with special reference to the compositions of the period 1899 to 1905

By his historical position, Gustav Mahler has acquired an aura which threatens to obscure his music. Born into an era which questioned the norms of musical expression, his importance for composers both traditional and progressive has overshadowed his real achievement, the preservation of the symphony in the first decade of the century when many came to regard it as an outworn genre. The significance of this achievement was not fully realised until the 1960's when Adorno's writings created a synthesis from the composer's interest in the folk-like, his position with regards to the Austrian tradition, his literary attitudes, and such concepts as Erwin Stein's Sachlichkeit. His study attempted a comprehensive view; this thesis concentrates on the period of the Fifth and Sixth Symphonies, Mahler's first maturity.
Mahler's orchestral technique arises from a fusion of symphony and opera orchestras effected in Das klagende Lied. Procedures related to Bruckner and Schubert co-exist with direct echoes of Lohengrin and Der Ring des Nibelungen. While much of Das klagende Lied is characteristic in its sound sources, these are as yet traditional in their harmonic and thematic deployment; this is only marginally less true of First and Second Symphonies. The extensive use of brass declamation in the Third Symphony's first movement and the density of polyphony in the march sections are indicative of new developments though traditional harmonic patterns are still in control.
[Please see pdf. for full abstract.]
The children's progress

This thesis situates the life and work of Virginia Woolf in a socio-literary history of writing by, and attitudes towards, children. It explores late-Victorian middle-class children's lives, and the relationships between parents and children during the period. Although Darwinian ideals had begun to influence parents earlier in the century, it was not until the 1870s that they seem to have become prevalent in middle-class families. Through an examination of the expansion of evolutionary and developmental stage theories in the late Victorian years, the thesis puts forth the theory that middle-class adults of the period saw children as containing adult potential. It makes a study of how this view affected middle-class family life, child rearing, and children's culture during the period. It particularly investigates linguistic developmental theory and its effect on reading and writing education, and late-Victorian ideas of children's sexual development and the need for sexual education. The thesis examines how such theories led to changes in writing by children during the period, exploring nineteenth-century works by children, and focusing on the home manuscript magazine genre. It questions the late-Victorian belief that children wrote spontaneously and "naturally." It situates the juvenile writings of the Stephen children (of whom Woolf was one), using these texts as typical products of the late-nineteenth-century middle-class familial and cultural context that the thesis examines. This study allows me to propose a critical definition of late-nineteenth-century children's home magazine writing. The thesis goes on to argue that Woolf, while recognizing herself as a product of the late-Victorian middle classes and retaining some of the authorial qualities evident in her family's juvenile works, rebelled against the late- Victorian evolutionist-developmentalist view of childhood, and helped to create a new language in the process.

Advisor: Lee, H
Systematic overviews of the randomised evidence for the effects of traditional non-steroidal anti-inflammatory drugs and selective inhibitors of cyclo-oxygenase-2 on vascular and upper gastrointestinal outcomes

Background: Comparative assessments of the vascular and upper gastrointestinal risks of different regimens of non-steroidal anti-inflammatory drugs (NSAIDs) are required.
Methods: Meta-analyses were conducted, using individual participant data where possible, of placebo-controlled trials of a selective cyclo-oxygenase [COX]-2 inhibitor ('coxib') or traditional NSAID, or randomised trials of a coxib versus traditional NSAIDs. A prespecified subdivision of traditional NSAID regimens of those with antiplatelet activity (mainly naproxen) and those without (mainly diclofenac) was made. Primary outcomes were major vascular events (MVEs; nonfatal myocardial infarction, nonfatal stroke or vascular death) and upper gastrointestinal complications (UGICs; perforation, obstruction or bleed).
Findings: Searches identified 788 trials: 200 comparisons of a coxib vs placebo (88,604 participants, mean follow-up 0.60 years), 206 comparisons of a traditional NSAID vs placebo (43,482 participants, 0.46 years) and 149 comparisons of a coxib vs traditional NSAID (137,466 participants, mean follow-up 0.95 years).
Compared to placebo, allocation to a coxib increased the risk of MVEs (rate ratio 1.38, 95% CI 1.14-1.66), vascular mortality (1.58, 1.11-2.24) and UGICs (1.81, 1.17-2.81). Overall, in the population studied, coxibs were associated with three additional major vascular events (one fatal) and two (rarely fatal) upper gastrointestinal complications per 1000 person-years exposure. There was no evidence of heterogeneity by duration of follow-up, coxib type, dose (other than for celecoxib), or patient characteristics, for the primary outcomes.
The risk of MVEs for traditional NSAIDs without antiplatelet activity (mostly diclofenac 75mg bd or ibuprofen 800mg tds) were comparable to coxibs (1.40, 1.15-1.72); but the risk of UGICs (1.98, 1.39-2.84) was significantly greater. For traditional NSAIDs with antiplatelet activity (mostly naproxen 500mg bd) there were no significant excess of MVEs (0.84, 0.66-1.08), but UGICs were substantially increased (4.06, 2.85-5.78). Both coxibs and traditional NSAIDs increased risk of hospitalisation for heart failure by about two-fold.
Interpretation: The vascular and upper gastrointestinal risks of coxibs and high-dose tNSAID regimens can be predicted, allowing the choice of analgesia to be tailored for particular patients.

Keywords: Randomised Trials
Epidemiology
Coxibs
Clinical medicine
Meta-analyses
Vascular
Non-steroidal anti-inflammatory drugs
Gastrointestinal Ulcers
Advisor: Baigent, C
Carbon Nanotube Growth on Perovskite Substrates

This thesis reports on the chemical vapour deposition (CVD) growth of carbon nanostructures (mainly carbon nanotubes (CNTs)) on perovskite oxide surfaces with the aid of various catalysts. Two types of perovskite oxide, single crystal SrTiO3 (001) and polycrystalline BaSrTiO3, have been used as catalyst supports (in metal-catalyst-involved CVD routes) or as catalysts (via metal-catalyst-free CVD routes) for the growth of carbon nanostructures.
In metal-catalyst-involved cases, SrTiO3 (001) single crystal has been proven, for the first time, to serve as a substrate for the growth of CNTs. Fe and Ni catalysts can be tailored in a controllable manner on SrTiO3 (001) surfaces prior to the CNT synthesis, forming truncated pyramid shaped nanocrystals with uniform size distributions. The growth of vertically aligned CNT carpets was realised with the aid of Fe on SrTiO3 (001) surfaces, and it was further found that the CNTs grow via a base growth model. Furthermore, it is possible to grow helical carbon nanostructures on BaSrTiO3 substrates by introducing a Sn catalyst into the system. The synthesised helical carbon nanostructures follow a tip growth mode, where the structural and chemical aspects of catalyst particles gave rise to a wide range of carbon morphologies.
CNTs were also grown on single crystal SrTiO3 (001) and polycrystalline BaSrTiO3 substrates via metal-catalyst-free routes. The surface-roughness-tailored growth of CNTs was surprisingly achieved on a series of engineered SrTiO3 (001) surfaces, where a correlation between the surface roughness/morphology of the substrates and the relevant catalytic activity was revealed. The growth of CNTs arises because the catalyst fabrication methods lead to the formation of SrTiO3 asperities with nanoscale curvatures, over which the CNTs are generated throughout a lift-off process. Facet-selective growth of CNTs was observed on polycrystalline BaSrTiO3 surfaces, where BaSrTiO3 (110) facets lead to the growth of CNTs on them, whereas the (001) facets result in no growth at all. This observation was further analysed in the content of the adsorption and diffusion of carbon species on distinct BaSrTiO3 facets, before reaching the conclusion that the formation of CNTs occurs through a metal-free, stack-up process driven by the assembly of the carbon fragments.

Keywords: Strontium Titanate
Barium Strontium Titanate
catalyst
Carbon nanotubes
Carbon Nanocoil
chemical vapour deposition
Advisor: Castell, M
Grobert, N