http://bura.brunel.ac.uk/handle/2438/3672 2013-05-24T06:10:36Z 2013-05-24T06:10:36Z Hall, Grahame http://bura.brunel.ac.uk/handle/2438/6587 2012-09-19T15:47:12Z 1981-01-01T00:00:00Z

Title: A study of nitrification in lakes of the English Lake District Authors: Hall, Grahame Abstract: Nitrification became the dominant nitrogen transformation in a number of lakes which accumulated ammonium, in hypolimnetic water, under aerobic conditions. The timing and duration of this activity varied between lakes but was characterized by decreasing ammonium, and increasing nitrate, concentrations. In Grasmere lake this phase was found to be due to the activity of planktonic chemolithotrophic nitrifying bacteria. The observed nitrate concentration increased during this phase and accounted for up to 15% of the total oxygen deficit of the hypolimnion. At similar in situ temperatures nitrification rates and nitrifying bacterial populations were greater in oxidised sediments than in the water column. Littoral sediments were more important than profundal sediments as sites of nitrification due to higher temperatures and the persistance of oxidising conditions to greater depths into these deposits. Within the littoral zone the physical characteristics of the sediment were important with organic rich deposits sustaining greater rates of nitrification than sandy sediments. Nitrate reduction was the primary determining factor of nitrate concentrations in sediment interstitial waters. Some observations on the culture of chemolithotrophic nitrifying bacteria from lakewater were discussed. Reviews of the methodology for nitrification research and nitrification in the lacustrine environment are presented. Description: This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University.

1981-01-01T00:00:00Z Round, Robert http://bura.brunel.ac.uk/handle/2438/6512 2012-09-21T15:57:01Z 1996-01-01T00:00:00Z

Title: Evaluation of reaction kinetics and material properties of cementitious ceramic materials using ultrasonic velocity and attenuation measurements Authors: Round, Robert Abstract: Ultrasonic velocity and attenuation measurements have been used to characterise a range of phosphate bonded, alumina filled, magnesia ceramics and other ceramic materials... Measurements were made over a range of frequency from 50kHz - 1 OM Hz, using a variety of commercial probes and equipment, and a variety of techniques. An ultrasonic double-probe method was used to monitor the setting process of the cementitious ceramics using commercial 2.25MHz and 2MHz transducers, for compressional and shear wave modes, respectively, in samples with alumina content in the range of 0 - 60 wt 0/0. The elastic properties of the material were determined from ultrasonic velocity measurements and were found to be dependent upon the filler volume fraction. The measured elastic moduli were found to Increase as porosity decreased, and this effect might possibly be used to estimate porosity. The composition dependence of the elastic moduli is compared with the Hashin and Shtrikman theoretical bounds for the elastic moduli of two-phase materials. All data lie between these bounds, suggesting that the alumina particles were well dispersed and well bonded to the matrix. However, the fact that the data are slightly above the lower bound suggested that the particles are not spherical, and this, together with other evidence obtained from an analysis of reaction rates, indicates the predominence of plate-like gram structures. Description: This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.

1996-01-01T00:00:00Z Rawson, Keith http://bura.brunel.ac.uk/handle/2438/6380 2012-10-10T11:28:55Z 1997-01-01T00:00:00Z

Title: Shear controlled orientation effects with injection mouldings produced by the SCORIM process Authors: Rawson, Keith Abstract: Injection moulding using the process of Shear Controlled Orientation Injection Moulding (SCORIM) to enhance the aesthetic characteristics of plastics was investigated. Unsightly surface weld lines were successfully removed from highly reflective aluminium flake pigmented plastics by the application of a single macroscopic SCORIM shear when used in series with Bright Surface Moulding (BSM). A gonio spectrophotometer (GSP) was used for the quantitative characterisation of the Al flake pigmented mouldings as a measure of surface reflectivity and preferred angle of reflection. The different directional properties of surface reflectivities to either side of a conventional weld line are unacceptable, but were successfully reoriented approximately uniformly with the use of SCORIM and BSM moulding (i. e. SBM) used in series. SBM therefore provided an acceptable quality of surface finish for mouldings originally containing a weld line, without deterioration of mechanical properties. Indeed, some improvements in mechanical properties were observed. Translucent two-colour mouldings were used to successfully demonstrate the flow paths taken by sheared material during the application of macroscopic shears. The use of intermittent shearing to encapsulate shear oriented material in the solidifying layers, manifested original and profound aesthetic effects. This resulted from mixing the two colours and was reproducible and widely variable. The morphology of isotactic polypropylene (iPP) processed in this way and examined by light and electron microscopy revealed how only one or two intermittent shears were required to orient a large volume of the moulding in the shear direction. Moreover, U-shaped flow paths demonstrated that the easiest shear route was close to the mouldings edges, an observation supported by x-ray analysis. The addition of Al flake pigment was found to act as a heterogeneous nucleant for ß-spherulites. This acted as a suitable marker for the clear identification of the displaced weld interface using polarised light microscopy, of filled and unfilled iPP. y-phase was identified with the use of only one or two intermittent shears which reflects an increase in molecular alignment and consequent improved mechanical properties. The intensity of the y-phase increased with the volume of material sheared. Strong evidence was also obtained of a linear relationship between the logarithm of the time lapse between two intermittent shears and the corresponding values of a-phase index, crystallinity index and percentage crystallinity. The values of each increasing proportionally with the length of time used. Microhardness characterisation revealed anisotropy within SCORIM samples consistent with preferred orientation and increased modulus in the shear direction. The skin layers were characterised as the softest region through the thickness of SCORIM mouldings. The results of this work were used to provide the basis of a computer simulation of the SCORIM process under development at the University of Wales Swansea. Description: This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.

1997-01-01T00:00:00Z Lea, Rachel http://bura.brunel.ac.uk/handle/2438/6376 2012-12-03T12:21:37Z 2001-01-01T00:00:00Z

Title: The performance of control and the control of performance: Towards a social anthropology of defecation Authors: Lea, Rachel Abstract: Defecation has remained overlooked within anthropology and sociology, despite recent focus on the body. The thesis suggests that this is related to its construction as something hidden in the last few hundred years of modern Western society. It is physically and mentally dismissed as personal and biological rather than social or cultural. The few references that exist enable one to argue that it always has significance as a repetitive daily activity needing careful social management and which is crucial to the definition of personhood. Its praxis reveals much about social values concerning differentiation by age, sex, gender and generation. Freud, Elias, Bakhtin and Douglas have influenced its image but do not adequately explain it. Phenomenological theories of embodiment and ideas of cultural performance are shown to be more useful in demonstrating that defecation is a lived cultural experience. The focus is on contemporary Britain, studied through participant observation and day-to-day participation, using material from conversations, anecdotes, observations, experiences, media reports, novels, and films encountered during the period of research. The main themes that emerge are privacy, hiddenness, embarrassment and concern but also that it is welcomed as physical release, and as offering valued periods of time-out and solitude. It is also a symbol of both all that is low and all that is deep. These contradictions are analysed through the two axes of control/loss of control and release/containment. It is argued against recent medical anthropological and sociological studies of incontinence that it cannot be assumed that the opposite of incontinence is continence and containment. The issue of control is paramount, rather than the issue of containment in itself. Description: This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.

2001-01-01T00:00:00Z