VictorJuiz/thesis huggingface dataset:
Constitutive modelling of composite materials under impact loading

In this thesis a constitutive model is developed for the numerical prediction of UD composite material behaviour under impact loading. Impact induced loading usually results in three dimensional stress states which significantly influences the failure behaviour. The heterogeneous nature of composite materials, in particular, results in a complex failure behaviour which manifests itself in various failure modes. Predicting the onset and evolution of these failure modes requires the use of physically based three dimensional theories for the prediction of the onset of damage and subsequent damage evolution. Furthermore, the use of polymeric matrices in continuous fibre reinforced composites results in a distinct directional strain rate dependent material behaviour which needs to be incorporated in constitutive models for the numerical simulation of impact events. The developed constitutive model relies on the prediction of the onset of damage evolution by the use of physically based three dimensional stress based failure criteria. A special feature of the proposed model is the identification of potential fracture planes. Numerically efficient algorithms for finding such planes are developed thus enabling the implementation into an explicit FE environment which was prohibitive so far. Damage evolution is simulated by degrading the tractions which are acting on the failure mode dependent fracture planes. The damage evolution and consequent energy dissipation is thereby driven by physically based dissipation potentials which consider only stresses which contribute to damage growth. The well known mesh dependent energy dissipation in Continuum Damage Mechanics is reduced by the introduction of an element size dependent parameter into the constitutive equations. An experimental program is conducted to investigate the compressive behaviour of composites. The focus of the study is on the rate dependent failure behaviour. The experiments are designed such that the failure mechanisms can be studied at varying strain rates with identical boundary conditions. This allows for direct conclusions about the strain rate dependent material behaviour. Novel optical measurement techniques are applied across all investigated strain rates thus ensuring an improved observation of the failure modes. The proposed constitutive model is finally verified by modelling of three point beam bending experiments which were performed quasi-statically and at impact velocities. The experimental technique for beam bending at impact loading was therefore improved thus yielding significantly more accurate experimental data.

Keywords: composites
impact
finite elements
Advisor: Petrinic, N
Structure and function of bacterial proteins secreted by the type three secretion and twin arginine translocation pathways

The Type Three Secretion Systems (T3SSs) of Gram-negative bacteria, including Shigella, Salmonella, and Enteropathogenic/Enterohaemorrhagic Escherichia coli (EPEC/EHEC), pass virulence factors directly into the host to mediate invasion. Prior to secretion down the narrow T3SS channel, effector proteins associate with chaperone proteins. The binding enables the T3SS to keep effectors soluble and partially unfolded for secretion. In the first part of this thesis, the association of one promiscuous chaperone, Spa15 of Shigella flexneri, with three of its cognate effectors has been studied. In addition to the role this plays in secretion, the binding of one particular substrate leads to Spa15 being involved in the regulation of the T3SS. The oligomerisation and impact of substrate binding upon Spa15 has been determined by crystallography and EPR. Once secreted, T3SS effectors subvert the host cytoskeleton for the benefit of the bacteria. Soluble homologues of Spa15 effectors from EHEC and Salmonella have been purified, and their interactions with host GTPases which lead to stress fibre phenotypes observed.
The Twin Arginine Translocation (Tat) pathway provides a contrasting view of bacterial secretion. Instead of preventing folding in the cytoplasm, it is a criterion of transport that the protein be folded. One of the reasons for internal folding is the necessity to insert cofactors which could not be incorporated externally. In the second part of this thesis, a protein which exemplifies this necessity is studied. This is PhoD, the model protein for Tat export from Bacillus subtilis. PhoD is an alkaline phosphodiesterase expressed to scavenge phosphate in times of phosphate deficiency. The structure of PhoD has been solved, and the protein is shown to be able to cleave a component of its own cell wall. It uses an unusual catalytic site more reminiscent of the eukaryotic purple acid phosphatases than of other currently known alkaline phosphatases. Furthermore this site appears to require metal binding before export from the bacterial cytoplasm.

Keywords: Protein Crystallography
Electron Paramagnetic Resonance
Bacterial secretion
Type Three Secretion
Twin Arginine Translocation
Advisor: Lea, S
Timmel, C
The ecology and conservation of the Adonis Blue (Polyommatus bellargus) and the Chalkhill Blue (Polyommatus coridon) butterflies in the UK

A combination of habitat loss, degradation and fragmentation are causing declines in butterfly species across Europe, with habitat specialists more vulnerable than generalists. The influence of climate change is serving to complicate matters, particularly at the edge of geographic ranges. Improving the quality of habitats is a key tool for the conservation of threatened species at both a local and landscape scale and this requires a thorough understanding of the ecology and habitat requirements of species. From this perspective this thesis examines and compares the ecology of two closely butterfly species, Polyommatus bellargus (the Adonis Blue) and Polyommatus coridon (the Chalkhill Blue) in southern England; calcareous grassland specialists, found in a highly fragmented ecosystem at the northern most edge of their geographic range.
Chapter 2 explores whether there has been an expansion in the larval niche of P. bellargus due to a warming climate in recent decades, and finds no indication of change once concurrent local habitat change has been accounted for. Chapter 3 examines the role that differences in microhabitat requirements play in differentiating the larval niche of P. bellargus and P. coridon, showing P. coridon has broader microhabitat requirements. Chapter 4 experimentally examines the specificity of mutualistic interactions between the larvae of each butterfly species with the ants Myrmica sabuleti and Lasius niger. Chapter 5 uses microsatellites to explore the genetic structure of both P. bellargus and P. coridon, showing (as predicted) that P. coridon has a less fragmented population structure than P. bellargus, but both species have high levels of inbreeding.

Keywords: Myrmecophily
Polyommatus coridon
Conservation
Habitat
Ecology
Population Genetics
Climate Change
Polyommatus bellargus
Advisor: Thomas, J
Hails, R
Vascular smooth muscle oxidative metabolism and function during vasospasm after subarachnoid haemorrhage

Aims: The purpose of the research presented in this thesis is to elucidate the mechanism of the stimulation of oxidative metabolism and contractile function that occurs in vascular smooth muscle during cerebral vasospasm (CV) after subarachnoid haemorrhage (SAH). The biochemical mechanisms leading to CV were investigated using an in vitro model of CV developed for this research. CSF (cerebrospinal fluid) from SAH patients at risk of vasospasm which stimulated oxygen consumption (CSF S ) was used to model vasospasm. The hypothesis is CSFS contains a substance which stimulates tension generation over that of CSFN ,(non-stimulatory cerebrospinal fluid) and also inhibits the myosin light chain phosphatase.
Methods: The porcine carotid artery was used as a model for the human basilar artery. The rate of oxygen consumption (JO2) was measured in response to CSFS and tension generation was also examined. Various agents were used to treat or pretreat the tissue such as magnesium and andalpha;1-adrenergic receptor agonists. Their effects on the CSFS-induced stimulation were measured to study the mechanism of vasospasm. A myosin light chain phosphatase (MLCP) assay was developed to study the mechanisms leading to CV.
Results and conclusion: Addition of CSFS to the porcine carotid artery is a reliable and reproducible in vitro model of CV. Using this model, it was found that Mg++ loading and andalpha;1-adrenergic receptor agonists attenuated the vasospasm, but a non-specific endothelin antagonist had no effect. Acute addition of 12mM Mg++ relaxed the tissue from a CSFS induced contraction significantly and rendered the contraction rinsible. Okadaic acid (InM), a phosphatase inhibitor, had very similar effects to CSFS because it stimulated JO2 and slowed relaxation after a stretch. There was also significant inhibition of phosphatase caused by the CSFS. Vasospasm appears to be caused by a combination of a contractile stimulus, and inhibition of MLCP activity.

Advisor: Dixon, R
Cadoux-Hudson, T
Control of typhoid fever: evaluating herd protection through public health use of typhoid VI polysaccharide vaccine

Typhoid fever remains an important public health problem globally. Cluster randomized effectiveness trials with typhoid Vi polysaccharide vaccine were conducted in Kolkata, India and Karachi, Pakistan, to provide evidence for vaccine introduction. While efficacy trials are limited to estimate vaccine's performance on the vaccine recipients, effectiveness trials consider the public health impact, notably the herd protection, or indirect effect, which can only be seen when vaccines are administered to groups rather than to individuals.
The observed total protection by the Vi polysaccharide vaccine in school-aged children was consistent in Kolkata and Karachi (61% and 56%, respectively), and was associated with minimal side-effects. The total protection in young children, however, was different (80% in Kolkata and no protection in Karachi). The Kolkata trial demonstrated significant herd protective effects, as demonstrated by indirect protection of non-vaccinees (45%), which was not shown in the Karachi trial. The difference in the effectiveness estimates between the trials may be due to the difference in study design and the population characteristics.
Immunogenicity studies were undertaken for randomly selected persons from both sites at pre-vaccination, 6 weeks, and 2 years post-vaccination. Serum Vi antibody titres (IgG) were measured through ELISA. At baseline, the GMTs were below the protective level for both sites. At six weeks after vaccination, though there is a significant increase in the GMTs in children from both site, the level of GMTs were significantly lower from those in Karachi (2,307.0 ELU vs. 1,189.1 ELU). GMT declined from 6 week to 2 year testing points for both sites but maintained the protective level.
These effectiveness trials gave a conclusive evidence of the protection conferred by the Vi polysaccharide vaccine in children older than 5 years of age. Targeted vaccination programme in high endemic areas, as stipulated in the WHO Position Paper, suggest the potential for effective control of typhoid fever in places like India and Pakistan with the school-based Vi vaccination.

Keywords: Vaccine
Epidemiology
Typhoid fever
Advisor: Farrar, J
Mnemonic functions in the macaque monkey: further insight into the role of the fornix

The fornical tract, a major input-output pathway of the hippocampus, of the primate brain makes crucial contributions to visual memory, as effects after surgical or aetiological lesions of this tract are widely documented in the monkey and human literature. Here, a series of experiments sought to further elucidate the functions of this structure with a battery of novel tasks in macaque monkeys, conducted either on a touchscreen or in an ambulatory chamber, so as to offer a more global view of the mnemonic role accomplished by it. After receiving bilateral transection of the fornix, monkeys are impeded in the 'fast learning' phase of a large number of new visuospatial conditional problems, with major impairments seen in eliminating non-perseverative errors. These fornix transected monkeys are however facilitated in the initial acquisition of a visuovisual conditional task, with facilitation seen in their improved ability in eliminating perseverative errors. It is also demonstrated in an ambulatory apparatus, in comparison to control monkeys, these monkeys are impaired in the new learning of visuospatial context of environments, albeit still displaying intact locomotor and exploratory behaviour patterns. Contrary to the relatively clear role in new learning, the involvement of the fornix in memory retention over the very long-term is unknown. It is shown here that once some visuospatial information is learnt; the fornix is no longer implicated in the retention of the material. The effects of fornix transection are also found to be detrimental on a spatial recognition task, with impairments observed in acquisition of the more demanding stages of the task. The overall results covered in this thesis support previous work suggesting that the fornix mediates the new learning of visual information, and I further propose that this fornical involvement lies primarily in the learning of spatio-temporal contexts, particularly during 'fast learning', as well as in task-sets acquisition. I also argue for dissociation in the contributions of the fornix and hippocampus to some memory processes in the macaque.

Keywords: behavioural neuroscience
learning
memory
Advisor: Buckley, M
British influence on the federation of the Australian colonies, 1880-1901

Despite the obvious importance of federation in the political and general history of Australia it has received surprisingly little attention from historians. The three major accounts of the federal movement by Deakin, Wise, and Quick and Garran, were all written during or immediately after the events narrated, by men who had participated in them; though each is a valuable primary document, all exhibit inevitable limitations of bias and concentration on those aspects of the subject best known to the author. The only full length academic study of the federal movement, H.L.Hall's, Victoria's Part in the Australian Federal Movement (London,1931), relies heavily on the earlier accounts, concentrates narrowly on one colony, and is generally disappointing. The excellent scholarly articles more recently published by Parker, Blainey, Bastin, Martin, McMinn, MacCallum et al have been concerned mainly with the reassessment of the role of a few key individuals, and discussion of the significance of economic factors in promoting federation. The general emphasis of the whole corpus of material available is on the domestic politics associated with the federal movement with particular reference to New South Wales and to the eighteen-nineties.
[Please see pdf. for full abstract.]
Slavery in Early Mesopotamia from Late Uruk until the Fall of Babylon in the Longue Durée

This dissertation looks at slavery in early Mesopotamia (ca. 3200-1595 BC) in the longue durée and establishes theoretical foundations for interpreting the data preserved in the extant sources. Rather than attempting to define slavery, the forms the social institution took from proto-history into the historical era of early Mesopotamia are contextualised, while identifying the broader social changes which might explain the non-linear evolution of the practice.
After considering the difficulty of defining the term ‘slave’ in relation to early Mesopotamia in general and numerous attempts to approach the problem, this work moves beyond definition, attempting to historicise slavery. To achieve this, slavery in early Mesopotamia is considered in the high points of the record in relation to key diagnostic features. The acquisition of slaves is studied alongside the release of slaves, demonstrating the numerous ways people in early Mesopotamia could be reduced to some form of bondage or slavery, while there remained relatively few means by which a person could experience upward movement out of slavery, opportunities which were reduced further for foreign and houseborn slaves.
The following discussion of the economics of slavery seeks to place the question in an historical context of modern scholarship before assessing the motivations, benefits, and risks of owning slaves in early Mesopotamia. After this chapter which looks at slavery from the perspectives of the elite, the subsequent chapter attempts to move beyond the elite bias of the documentation to understand history from the bottom, by studying flight and the related means of coercion. By considering the ways in which runaways were pursued and the risks members of the lower stratum community were willing to take for a change in status, the discussion presents a way forward to understanding slavery in early Mesopotamia. These diagnostic features of slavery reveal a traceable non-linear evolution of slavery in early Mesopotamia.

Keywords: social status
flight
slavery
Advisor: Dahl, J
Regulation of utilities in developing countries

The efficient operation and expansion of utilities in developing countries is crucial for growth and poverty reduction. However, recent reforms aimed at improving the performance of these sectors through privatization and the introduction of new regulatory regimes have had limited success. This thesis aims to consider the most pertinent problems for utility regulation in developing countries and how policy may need to be adapted appropriately.
The thesis begins by surveying the most recent empirical and theoretical work on the area. I argue that four key institutional limitations commonly found in developing countries must be considered when designing regulatory policy: Limited capacity, limited accountability, limited commitment and limited fiscal efficiency. The remainder of the thesis then focuses on two of these weaknesses – limited commitment and limited accountability – to develop further insights into how regulatory policy may be most suitably adapted.
In considering the effect of limited commitment, I pursue a theoretical approach. I first focus on the relationship between the government and the utility operator when the government cannot commit to a time-inconsistent policy of not expropriating investment. After building a model where reputation is used to sustain investment in equilibrium, I consider the model’s implications for policy. The thesis then builds a different model to consider the impact of governments’ inability to commit when trading electricity internationally. I focus on the resulting hold-up problem and the impact this has on investment levels within trading countries.
The effect of limited accountability is then investigated empirically through the analysis of data on electricity firms and regulators in Latin America. In particular, I consider how firms’ performance is affected by corruption, ownership and regulatory governance, looking in detail at interactions between these variables and attempting to break down regulatory governance into its various components.

Keywords: institutions
development
regulation
Advisor: Vickers, J
Contemporary ecologies of expert knowledge: classic and novel conundrums across professional boundaries in the NHS

Classic studies in the Sociology of the Professions have explored knowledge barriers across traditional forms of professionalism, quintessentially represented by medical doctors, lawyers, and university professors. Thus, the impact of distinctive professional identities and communal boundaries on processes of knowledge sharing have been well documented. More recently, however, many scholars have suggested that those classical analyses need to be revisited and reassessed (see for e.g. the recent call for papers of Teelken and colleagues at EGOS 2011, cf. also Evetts, 2006; Noordegraaf, 2007) in the light of three contemporary trends: a changing context of professional practice, the associated erosion of classic forms of professionalism, and the emergence of new forms.
While classical studies have laid the foundation of our understanding of the conditions that render knowledge sharing across more established forms of professionalism problematic, the processes and potential barriers across more novel and hybrid forms are less clear (cf. Noordegraaf, 2007). In order to address this gap, this thesis presents a comparative investigation of expert knowledgesharing across professional boundaries in four cross-occupational teams in the English National Health Service; two of them primarily composed of established professionals and two of hybrid professionals. By analysing these two types of cross-occupational teams, this thesis’ contribution is the identification of a different configuration of knowledge barriers affecting the sharing of knowledge within the two forms of professionalism.
These findings further highlight the existence of two very different ecologies of (inter) professional knowledge within established and hybrid forms of professionalism. First, distinctive knowledge bases underlie professional practice and interaction in established and hybrid forms of professionalism. For established forms knowledge is more substantive and disciplinary based, whereas for hybrid forms it is general and situated, and characterized by a syncretic use of different disciplines, theories, and information. Second, the types of indeterminacies that permeate the two types of ecologies also vary. While the more established forms of professionalism face higher levels of ambiguity (semantic indeterminacy), the more transient and hybrid forms of professionalism face higher levels of uncertainty (de re indeterminacy). Finally, the nature of professional boundaries is different between these two types. While in established forms of professionalism boundaries are relatively well defined, and hence recognizable; in hybrids forms they are vague and transient.

Keywords: knowledge
ambiguity
occupations
knowledge barriers
professionalism
NHS
Advisor: Dopson, S