Transition metal imido complexes: synthesis and applications to polymerisation catalysis

This thesis describes studies into Group 5 and Group 6 transition metal imido complexes, with particular emphasis on the development of complexes which can be applied to catalytic processes. Chapter 1 highlights the electronic and structural aspects of the imido and alkylidene ligands. The isolobal analogy between Group 4 bent metallocene. Group 5 half-sandwich imido and Group 6 bis(imido) metal fragments is outlined. In addition, Ziegler-Natta type a-olefin polymerisation and Ring Opening Metathesis Polymerisation (ROMP) are briefly reviewed. Chapter 2 describes initial screening of half-sandwich vanadium imido and chromium bis((^t)butylimido) dichloride complexes as catalyst precursors. Synthesis of the chromium bis(imido) dialkyl complex Cr(N(^t)Bu)(_2)(CH(_2)Ph)(_2) (1) is described, its conversion to a cationic alkyl species is probed and the polymerisation activity associated with the resultant compound is addressed. Finally this chapter details the synthesis and characterisation of a range of bis(adamantylimido) chromium complexes. Chapter 3 presents a synthetic entry point into the bis(arylimido) chemistry of chromium. The complex Cr(NAr)(_2)(NH(^t)Bu)Cl (12) is described (Ar = 2,6-(^i)Pr(_2)C(_6)H(_3)) and its conversion to the dichloride complex Cr(NAr)(_2)Cl(_2) (14) is examined. 14 forms the stable monoadduct with pyridine, the X-ray crystallographic study of which reveals a distorted square based pyramidal geometry about the chromium atom. The inclusion of the arylimido ligand at the metal centre allows stabilisation of the chromium bis- phosphine complexes Cr(NAr)(_2)(PMe(_3))(_2) (18) and Cr(NAr)(_2)(PMe(_2)Ph)(_2) (19). The reactivity of 18 towards unsaturated hydrocarbon substrates is briefly investigated. Chapter 4 focuses on the organometallic chemistry of the [Cr(NAr)(_2)] moiety. A range of dialkyl derivatives are isolated and the molecular structures of a selection are solved. The generation of the nascent species [Cr(NAr)(_2)(=CHCMe(_3))] is investigated and the conversion of Cr(NAr)(_2)(CH(_2)CMe(_3))(_2) (24) to Cr(NAr)(-2)(CHDCMe(_3))(C(_6)D(_5)) (25) is the subject of a kinetic study. In chapter 5, the ROMP of a series of amino acid derived norbomene monomers is studied. The resultant polymers are fully characterised and a brief molecular modelling study is carried out on representative polymers chain lengths. Chapter 6 contains experimental details to chapters 2-5

Style in the Music of Arthur Sullivan: An Investigation

This thesis examines Sullivan’s output of music in all genres and assesses the place of musical style within them. Of interest is the case of the comic operas where the composer uses parody and allusion to create a persuasive counterpart to the libretto. The thesis attempts to place Sullivan in the context of his time, the conditions under which he worked and to give due weight to the fact that economic necessity often required him to meet the demands of the market. The influence of his early training is examined as well as the impact of the early Romantic German school of composers such as Mendelssohn, Schubert and Schumann. In the second half of the thesis, selected features of Sullivan’s style are analysed in detail as is the influence of prominent European composers such as Berlioz and Liszt. The final section is a close examination of Sullivan’s most successful choral work, The Golden Legend. One of the principal aims is to address the dearth of scholarship on the technical aspects of this composer’s music. Where a great deal of information is available about his biography, not least from the diary he kept from 1876 until his death, the sharply defined contrasts in Sullivan’s use of musical style seem to have deterred commentators from enquiring too closely into his compositional techniques and this has led to certain false assumptions and misunderstandings. A close examination of these techniques may encourage a greater recognition of Sullivan’s considerable achievements and foster a more open-minded attitude to his music and that of other nineteenth-century British composers

Wireless Accelerometer for Neonatal MRI Motion Artifact Correction

A wireless accelerometer has been used in conjunction with a dedicated 3T neonatal MRI system installed on a Neonatal Intensive Care Unit to measure in-plane rotation which is a common problem with neonatal MRI. Rotational data has been acquired in real-time from phantoms simultaneously with MR images which shows that the wireless accelerometer can be used in close proximity to the MR system. No artifacts were observed on the MR images from the accelerometer or from the MR system on the accelerometer output. Initial attempts to correct the raw data using the measured rotational angles have been performed, but further work will be required to make a robust correction algorithm

Modelling sediment supply and transport in the River Lugg: strategies for controlling sediment loads

The River Lugg has particular problems with high sediment loads that have resulted in detrimental impacts on ecology and fisheries. A new dynamic, process-based model of hydrology and sediments (INCA- SED) has been developed and applied to the River Lugg system using an extensive data set from 1995–2008. The model simulates sediment sources and sinks throughout the catchment and gives a good representation of the sediment response at 22 reaches along the River Lugg. A key question considered in using the model is the management of sediment sources so that concentrations and bed loads can be reduced in the river system. Altogether, five sediment management scenarios were selected for testing on the River Lugg, including land use change, contour tillage, hedging and buffer strips. Running the model with parameters altered to simulate these five scenarios produced some interesting results. All scenarios achieved some reduction in sediment levels, with the 40% land use change achieving the best result with a 19% reduction. The other scenarios also achieved significant reductions of between 7% and 9%. Buffer strips produce the best result at close to 9%. The results suggest that if hedge introduction, contour tillage and buffer strips were all applied, sediment reductions would total 24%, considerably improving the current sediment situation. We present a novel cost-effectiveness analysis of our results where we use percentage of land removed from production as our cost function. Given the minimal loss of land associated with contour tillage, hedges and buffer strips, we suggest that these management practices are the most cost-effective combination to reduce sediment loads

Game-based training to promote arithmetic fluency

The research team designed and evaluated a mobile game to promote rapid retrieval of arithmetic facts among a group of children aged 7–8 years (n = 97). The design of the game was based on principles drawn from research literature in mathematical cognition, game-based learning, and game design. The game trains basic number knowledge within a motivating context. It tested an implication of theory of automatization of arithmetic facts that training of recognition of multiples of single-digit numbers should lead to greater fluency in solving multiplication and division problems. A quasi-experimental design was employed to test whether the game improves retrieval of arithmetic facts. Children played the game in their classrooms for 20 min a day for 2 weeks. Comparisons between pre- and post-tests showed that the game playing group outperformed controls with a medium to large effect size (>0.6). These results suggest an improvement in arithmetic fluency equivalent to around 7 months' progress and provide rare empirical evidence supporting transfer of game-based training to a pencil-and-paper test. The findings are consistent with a connectionist theory of arithmetic skill, by showing that improved recognition of multiples contributes to multiplication and division skill. The theoretical and practical implications of these findings are discussed

Researching adaptivity for individual differences in numeracy games

There is increasing evidence that mathematics video games can play a large role in mathematics education, in support of children's learning. However, despite the interdisciplinary nature of the subject, research in this area has traditionally been fragmented between disciplines. The RAIDING project was conceived to bring together researchers in neuroscience, maths cognition, and game-based learning to develop a maths game that can act as a research platform for furthering knowledge in this field. The game will employ free-to-play design elements, alongside an adaptive learner model to investigate how children learn maths, through a range of empirical studies

Impacts of Droughts and Acidic Deposition on Long-Term Surface Water Dissolved Organic Carbon Concentrations in Upland Catchments in Wales

Concerns have been raised about rising trends in surface water dissolved organic carbon (DOC) concentrations in UK upland catchments over the past decades. Several mechanisms have been proposed to explain these trends, including changes in climate and declines in sulfate deposition across Europe. Drier summers and wetter winters are projected in the UK, and there is an increasing interest in whether the rising trends of DOC would be continued or stabilized. In this paper, the INCA (INtegrated CAtchment) water quality model was applied to the upland catchment of the River Severn at Plynlimon in Wales and used to simulate the effects of both climate and sulfate deposition on surface water DOC concentrations. We introduced new parameter sets of INCA to explain enzymatic latch effect in peatlands during droughts. The model was able to simulate recent past (1995-2013) rising trends in DOC in Plynlimon. Climatic projections were employed to estimate the future trends on DOC in the uplands and to consider potential impacts on catchment management. The model was run with climatic scenarios generated using the weather@home2 climate modeling platform and with sulfate deposition scenarios from the European Monitoring and Evaluation Programme (EMEP) for 1975-2100. The modeling results show that the rising DOC trends are likely to continue in the near future (2020-2049) and the level of DOC concentrations is projected to stabilize in the far future (2070-2099). However, in the far future, the seasonal patterns of DOC concentrations will change, with a post-drought DOC surge in autumn months

Outcomes of Cement in Cement revision, in Revision Total Hip Arthroplasty

BACKGROUND: The cement-in-cement femoral revision technique involves removing a femoral component from a well-fixed femoral cement mantle and cementing a new stem into the original mantle. This technique, when carried out for the correct indications, is fast, relatively inexpensive and carries a reduced short-term risk for the patient compared with conventional way of removing well-fixed cement. AIM: To analyze the effectiveness of cement in cement revision of the femoral stem while performing a revision Total Hip Arthroplasty (THA). METHODS: We analyzed a consecutive series of 79 patients who underwent a cement in cement revision THA between June-2015 to June-2018. All the patients were retrospectively analysed for operative time, complications, clinical and radiological outcomes. RESULTS: Average age was 76 years (49-86). The mean follow-up was 16.2 months (12-45). The average operative time was 184.6 (90-290) minutes. Most common indication was cup loosening in 28 patients (42.4%), dislocation in 14 patients (21.2%) and stem loosening in 12 patients (18.2%) Nine patients (11%) had one or more complications. Pre-operatively, 10 patients (13%) had lucency at the cement bone interface. Recent review has shown that 8 of these patients’ radiographs have remained unchanged, and in 2 of them there is a slight progression of lucency. Common post op clinical complaintswere persistent pain and abductor weakness. Five (6.3%) patients required a re-revision. Most of the patients had a good or satisfactory outcome.No stems showed radiological loosening. CONCLUSION: The cement-in-cement technique for revision of the femoral component gave promising results and had the advantages of speed, less blood or bone stock loss, less risk of femoral perforation or fracture, decreased financial costs and reduced post op morbidity