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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Membrane transport studies : novel methods, model systems and thermodynamics

Burgess, Sarah Elisabeth January 2005 (has links)
The work in this thesis shows that it is possible to design a diffusion cell which will allow access to the flux and lag time of a permeant without the need for invasive sampling and that this novel cell is both sensitive and reproducible. It was also shown that the cell could be used in conjunction with both simple model membranes and more complex biological membranes, namely the epidermis. From the data achieved from the cell it was possible to derive a series of equations which allowed access to thermodynamic parameters such as ?H, ?G and ?S. An extension of this calculational approach revealed that manipulation of the van’t Hoff isochore, under the condition where enthalpy is constant over the temperature range, it should be possible to calculate the partition coefficient. Ultimately these parameters can be used in the description of structure activity relationships. The systems described in this thesis are of a complex biological nature consequently the returned data reflect this complexity. In order to utilise the data to their full potential some method for dealing with this complexity was sought. One approach widely discussed in the literature is that of chemometric analysis or soft modelling. Initial studies into the use of chemometric analysis proved positive for the data presented in this thesis, and suggested that formulation contributions from components with close absorbance maxima could be separated.
2

Tracking sperm whales using passive acoustics and particle filters

Hadley, Mark Lyndon January 2011 (has links)
Passive acoustics provides a powerful tool for marine mammal research and mitigation of the risk posed by high energy anthropogenic acoustic activities through monitoring animal positions. Animal vocalisations can be detected and utilised in poor visibility conditions and while animals are dived. Marine mammal research is often conducted on restricted financial budgets by non-government organisations and academic institutions from boats or ships towing hydrophone arrays often comprising only two elements. The arrival time-delay of the acoustic wavefront from the vocalising animals across the array aperture is computed, often using freely available software, and typically regarded as the bearing of the animal to the array. This methodology is limited as it provides no ranging information and, until a boat manoeuvre is performed, whether the animal is to the left or right of the array remains ambiguous. Methods of determining range that have been suggested either negate the fact the animal is moving, rely on robust detection of acoustic reflections, rely on accurate equipment calibration and knowledge of the animal’s orientation or require modification of hydrophone equipment. There is a clear need to develop an improved method of estimating animal position as relative bearing, range and elevation to a hydrophone array or boat based on time-delay measurements. To avoid the costs of upgrading hydrophone arrays, and potentially the size of the vessels required to tow them, a software solution is desirable. This thesis proposes that the source location be modelled as a probability density function and that the source location is estimated as the mean. This is developed into a practical method using particle filters to track sperm whales. Sperm whales are the ideal subject species for this kind of development because the high sound pressure levels of their impulsive vocalisations (up to 236 dB re 1 μPa) makes them relatively simple to detect. Simulation tracking results demonstrate particle filters are capable of tracking a manoeuvring target using time-delay measurements. Tracking results for real data are presented and compared to the pseudotrack reconstructed from a tag equipped with accelerometers, magnetometers, a depth sensor and an acoustic recorder placed on the subject animal. For the majority of datasets the animal is tracked to a position relatively close to the surface sighting position. Sperm whales are typically encountered in groups, therefore a viable tracking solution needs to be capable of tracking multiple animals. A multiple hypothesis tracking method is proposed and tested for associating received vocalisations with animals, whereby vocalisations are correctly associated for periods exceeding 15 minutes

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