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Title: Molecular and compound-specific stable isotope investigation of the fate of dung carbon in a temperate grassland soil
Author: Dungait, Jennifer Anne June
ISNI:       0000 0001 3435 2627
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2005
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Concrete is regarded as a skeleton of aggregate particles of various sizes, almost in direct contact with each other. The cement matrix acts as a filler and adhesive enabling the structure to be able to carry tensile stresses. A 2D circular rigid discrete element formulation based on the Discrete Element Method has been adopted. Random assemblies of particles based on a given sieve analysis can be generated enabling the simulation of the concrete structure at the meso-level. Contact models that are able to transmit moments through the contact plane have been implemented, namely, a developed contact model adopting more than one contact point at the contact plane. The steel reinforcement has been modelled with 1D beam finite elements or with 1D rigid discrete elements that interact with the discrete rigid particles through contact interfaces. Softening has been introduced into the microlevel constitutive equations. The traditional DEM has been enhanced with a boundary wall driven by force algorithm, an adaptive global damping algorithm and an arc-length control algorithm increasing the range of applicability and the performance of the model. The behavior of a double notched plain concrete specimen is investigated. Comparison of results in terms of crack patterns and load displacement relationships up to the peak load with both experimental and numerical results obtained using a lattice beam element formulation showed good agreement. The performance of the developed DEM model has also been evaluated for uniaxial tension, uniaxial compression and tensile splitting tests. The developed model showed good agreement in terms of peak strength, fracture localization and crack patterns. Finally the interaction between the stiffness of the reinforcement normal to the plane of cracking and the shear stiffness due to aggregate interlock is investigated. Good comparisons in terms of shear force and shear displacement relationships for a given crack width and reinforcement stiffness were obtained with known experimental dataFirstly, I would like to thank my supervisors, Richard Evershed and Roland Bol for supporting my metamorphosis from rusty biologist to fully-fledged Organic Geochemist. I would especially like to thank Richard for his close support, mentorship and advice on the biomolecular dimension that have been second to none, and for his kindness and understanding following a particular long haul flight after misplacing both my purse and work file en route! Special thanks to Roland for his unbounding enthusiasm and deep knowledge of the theoretical and practical side of carbon cycling in soil, even when sampling cow pats in horizontal rain on Dartmoor in December! I couldn't have wished for a more idyllic place for field work than IGER-NW. All of the staff were amazingly helpful and enthusiastic (particularly Mel who always knew where everything and everybody was when you needed them), so ready to share interest in soils and agricultural excreta that coffee breaks were a joy! Regrettably the Foot and Mouth epidemic prevented me from organising production of my own dung (no, really! ), so an enormous thank you is owed to Richard Dewhurst and Roger Evans at IGER-Aberystwyth for the supply of 25 large buckets of deep frozen cow dung. I would also like to acknowledge the valuable help and advice of Dan Dhanoa with statistical analysis. I was equally lucky to be part of a wonderful group known collectively as the OGU at Bristol. It would be impossible to acknowledge all of the individuals that have contributed to my training and support on a day-to-day basis. However, I would like to give special thanks to Dr Rob and Staffy for their technical expertise on most aspects of geochemistry. Thanks to Ian Bull for his training on lipid analysis, and respect for being able to recite the elution order of dung sterols backwards. I must also schtop here and thank Bart van Dongen for sharing his knowledge of off-line pyrolsyis and Nat for investigating its reproducibility, and Andy Rawlins and Zoe Crossman for their expertise and guidance on carbohydrates and PLFA analysis, respectively. Thanks also to John Webster and Mike Kitcherside at UOB Vet. School for access to forage fibre analysis. Last, but my no means least, thank you for the fantastic friendship of `the girls' Lorna, Anna, Claire E., Kate, Bickers, Zoe, Susie and Erin without whom I would be a little bit greyer! I would like to formally acknowledge funding for my PhD from BBSRC and IGER, and the UOB Alumni Foundation, British Mass Spectrometry Society and British Soil Science Society for travel awards. Most importantly, I wish to acknowledge the enormous support and love of my darling husband, Ben, who has put up with my ranting and raving for, well, longer than I care to mention; a lesser man would have run for hills a long time ago! I also wish to thank my fur baby Ted for making me laugh and chilling me out with long walkies when the going got too tough! Thanks to my parents for their support and ridiculous pride in my achievements, and for my brother, sister and non-work friends for tolerating my absentism -I promise to make up for it! And finally, some additional information on my favourite organic material: In the 16th and 17th centuries, everything had to be transported by ship, and it was also before commercial fertilizer's invention, so large shipments of manure were common. It was shipped dry, because in dryform it weighed a lot less than when wet, but once water (at sea) hit it, it not only became heavier, but the process of fermentation began again, of which a by-product is methane gas. As the stuff was stored below decks in bundles, you can see what could (and did) happen. Methane began to build up below decks and the first time someone came below at night with a lantern, BOOOOM! Several ships were destroyed in this manner before it was determined what caused the explosions. After that, the bundles of manure were always stamped with the term "Ship High In Transit" on them which meant for the sailors to stow it high enough off the lower decks so that any water that came into the hold would not touch this volatile cargo and start the production of methane. Thus evolved the term "S. H. I. T., " (Ship High In Transit) which has come down through the centuries and is in use to this very day.
Supervisor: Evershed, Richard Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available