Nonlinear axisymmetric elastic analysis of deep imperfect spherical shells

The particular problem that is addressed in this thesis is the nonlinear elastic analysis of incomplete thin deep spherical shells, where the displacements on the boundary surface are fully restrained and the shell is loaded by a uniform pressure load. The shell may contain initial axisymmetric geometric or stress imperfections, and the initial response of the shell, the fundamental path, is axisymmetric. Solution techniques are developed and presented for the nonlinear fundamental path, and the nonlinear eigenvalue problem that yields the location of the points of the axisymmetric or periodic secondary paths that bifurcate from the axisymmetric fundamental path and the initial mode shapes of the secondary paths at the point of bifurcation of the secondary paths from the nonlinear axisymmetric fundamental path. Using the nonlinear elastic deep shell theory developed in this thesis, the behaviour of perfect and imperfect incomplete spherical shells with fully restrained boundary surface displacements under uniform pressure loading is examined. This thesis also attempts to derive and present the equations and solution methods used in the nonlinear elastic analysis of thin spherical caps in as general a way as possible, in order that the solution methods developed in the thesis may be applied to shell structures composed of one or more incomplete thin elastic shells of arbitrary shape under arbitrary loading. By extending the derivation of the strain-displacement expressions for shells to include the terms that are quartic in displacements, the limitations present in linear thin shell theory may be lifted, and partial differential equations governing the nonlinear elastic behaviour of thin shells of arbitrary shape may be developed. The methods used to develop the total potential energy functional for pressure loaded spherical shells may be extended and used to express the total potential energy of shell structures composed of one or more incomplete shells of arbitrary shape under arbitrary loading

Supernatants derived from chemotherapy-treated cancer cell lines can modify angiogenesis

BACKGROUND: There is evidence that tumours produce substances such as cytokines and microvesicular bodies bearing bioactive molecules, which support the carcinogenic process. Furthermore, chemotherapy has also been shown to modify these exudates and in doing so, neutralise their tumourigenic influence. METHODS: In the current study, we have investigated the effect of chemotherapy agents on modifying the cytokine profile and microvesicular cargo of supernatants derived from cancer cell lines. In addition, we have explored the effect of these tumour-derived supernatants on angiogenesis, and how chemotherapy can alter the supernatants rendering them less pro-angiogenic. RESULTS: Herein, we show that supernatants contain a rich cocktail of cytokines, a number of which are potent modulators of angiogenesis. They also contain microvesicular bodies containing RNA transcripts that code for proteins involved in transcription, immune modulation and angiogenesis. These supernatants altered intracellular signalling molecules in endothelial cells and significantly enhanced their tubulogenic character; however, this was severely compromised when supernatants from tumours treated with chemotherapy was used instead. CONCLUSION: This study suggests tumour exudates and bioactive material from tumours can influence cellular functions, and that treatment with some chemotherapy can serve to negate these pro-tumourigenic processes

Pathological or physiological erosion—is there a relationship to age?

This conventional literature review discusses whether pathological tooth wear is age dependant. It briefly reviews the components of tooth wear and the prevalence of tooth wear in children, adolescents and adults. The emphasis on terminology relating to tooth wear varies. In some countries, the role of erosion is considered the most important, whereas others consider the process to be a combination of erosion, attrition and abrasion often with one being more dominant. The importance of tooth wear or erosion indices in the assessment and the evidence for progression within subject and within lesions is described. The data from the few studies reporting pathological levels of wear reported in children and adults are discussed, in particular its relationship with age. There is little evidence to support the concept that pathological levels of erosion or wear are age dependant. There is, however, some evidence to suggest that normal levels of erosion or wear are age dependant

Modelling rotational failure in confined geometries using DLO

Discontinuity layout optimisation (DLO) is a generally applicable numerical limit analysis procedure that can be used to identify critical plastic collapse mechanisms in engineering problems. Considering the modelling of in-plane failure, the authors have previously presented a formulation capable of identifying rotational failure mechanisms in non-dilating media. However, the formulation presented did not explicitly address cases involving confined geometries, where curved slip lines could potentially intersect boundaries. In this paper, methods are outlined which permit efficient modelling of such cases. Details of the kinematic and equilibrium formulations are provided, which are then verified through application to various geotechnical and structural mechanics problems. It is shown that results of high accuracy can be obtained, both in terms of the predicted collapse load and the corresponding failure mechanism

Demonstration of multi-channel 80 Gbit/s integrated transmitter and receiver for wavelength-division multiplexing passive optical network and fronthauling applications

The performance evaluation of a multi-channel transmitter that employs an arrayed reflective electroabsorption modulator-based photonic integrated circuit and a low-power driver array in conjunction with a multi-channel receiver incorporating a pin photodiode array and integrated arrayed waveguide grating is reported. Due to their small footprint, low power consumption and potential low cost, these devices are attractive solutions for future mobile fronthaul and next generation optical access networks. A BER performance of <10(-9) at 10.3 Gbit/s per channel is achieved over 25 km of standard single mode fibre. The transmitter/receiver combination can achieve an aggregate bit rate of 82.4 Gbit/s when eight channels are active

Novel translational model of resolving inflammation triggered by UV-killed E. coli

Whilst numerous studies investigating the aetiology of inflammatory diseases have been performed in rodents, the applicability of these data to human pathophysiology is frequently debated. Regardless of the strengths and weaknesses of rodent models in biomedical research, there is a need to develop models of experimental inflammation in humans. Here, we describe a self-resolving acute inflammatory response triggered by the intradermal injection of UV-killed Escherichia coli into the forearm of healthy volunteers. Cells and exudates were harvested from onset to resolution by applying negative pressure over the inflamed site. Onset was characterized by high blood flow, neutrophilia and peak levels of pro-inflammatory cytokines, whilst resolution showed a decline in blood blow, reduction in neutrophils, increase in monocytes/macrophages and waning of classic pro-inflammatory cytokine levels. An anti-inflammatory effect, defined as suppression of onset phase events, was demonstrated by administering naproxen, a conventional non-steroidal anti-inflammatory drug. In summary, this model of resolving acute inflammation is minimally invasive, highly tractable and allows simultaneous investigation of the vascular response, cellular trafficking and chemical mediator profile of onset and resolution phases of acute inflammation in humans. It can serve as a translational platform to provide mechanistic insights and to test the clinical efficacy of novel anti-inflammatory and pro-resolving drugs, and also as a tool in patients to explore inherent defects in resolution pathways