Modification of PTFE using low-pressure and atmospheric-pressure plasma methods

As an inherently chemically inert and physically stable polymer, PTFE has the potential to be used in medical applications as replacement ligaments or vascular stents. In the work presented in this thesis, atmospheric and low-pressure plasma processes were used to modify PTFE surfaces without altering the bulk properties of the substrate. The coupling of two low-pressure gas plasma treatments together into a two-step process was investigated as a method of producing a stable hydrophilic PTFE surface. A roughening oxygen plasma treatment was used to create a high water contact angle (WCA) Cassie-Baxter surface, before an ammonia plasma treatment transformed it into a hydrophilic Wenzel state. Although these surfaces initially exhibited a WCA of <10°, solvent washing caused significant hydrophobic recovery which was attributed to the washing off of low molecular weight oxidised species (LMWOS). Economically, an atmospheric-pressure plasma process is industrially favourable to low-pressure methods. The simple equipment required for a dielectric barrier discharge (DBD) process means that PTFE modification could be carried out in situ to prevent contamination or hydrophobic recovery being an issue in surgeries. The work presented here produced surfaces with a stable surface potential, the polarity of which was determined by the feed gas. Doping in water and/or ammonia molecules into inert feed gases was found to change the polarity of the surface potential. The use of the theory of electrowetting to decrease the WCA of DBD plasma-treated surfaces was successful, although only a small decrease in WCA was observed on the charged surfaces. However, the surface potential of the substrates was used to initialise the grafting and subsequent polymerization of a number of monomers, as well as deposition of a sulfobetaine zwitterionic layer. The lowest WCA was produced by the dipping of DBD-charged PTFE substrates into an aqueous sulfobetaine solution which produced a WCA of <10° recovering to 39° after solvent washing. The methods described in this thesis present a number of ways in which stable hydrophilic PTFE surfaces can be produced: an effective low-pressure treatment altered the wetting state of the surface using roughening effect, and DBD plasma-treated surfaces used the surface potential imparted by the plasma to initialise further grafting processes to achieve stable hydrophilicity

Aspects of the biology of Thyasira Gouldi (Philippi) and its copepod parasite Axinophilus Thyasirae (Bresciani and Ockelmann).

Taxonomic differences exist between Thyasira gould! and T. flexuosa both in conchological features and in the soft parts, perhaps the best of these differences are those concerning the sperm which are easily seen even in badly curated specimens. The occurrence of a population of T. gouldi within Loch Etive on the west coast of Scotland extends the known distribution of this arctic bivalve considerably further south. The development is nonpelagic and this, associated with the non-synchronized reproductive activity , means that independence is gained from plankton blooms and other external triggers allowing the characteristic dense but patchy populations to be built up. Salinity and sediment particle size both limit the distribution of T. souidi within L. Etive, the VI naturally occurring sediment is altered by the inhabi tants of the area into a sediment vlhich is better suited to the needs of T. gouldi. Asynchronized breeding, slow growth rate, longevi ty of life and 10\'1 adul t mortality all combine to give a characteristic bimodal population, the modes of which do not appear to shift with time. A method is described whereby an indication of both the mean state of the population and the state of the individual can be obtained for any period of the year. The biochemical composition varies with size and time of the year as well as with gonad state. Dry weight fluctuations are, however, not entirely explained by variations in the stage of gonad development as seasonal variations in the amount of somatic tissue do exist. Thyasira gouldi is one of the Lucinaceans infected by the much modified copepod parasite Axinophilus thyasirae. The life cycle and infective stage of this parasite are described as is the external morphology of the nauplius copopedite and adult. The reproductive system of both the male and the female are also described. The first infected parasite is always female and only rarely does more than one female reach maturity within anyone host even though up to five parasites may be present. The parasite has been shown to affect the biochemical composition of the host, reducing the amount of each of the components present, but tending to reduce the amount of nitrogenous material in preference to the amount of carbohydrate. VII The parasite affects the gonad of the host resulting in castration probably as an indirect effect of 'food robbing'. The interference to the host's food supply by the parasite is thought to be so great as to reduce the host to starvation levels of food

SARCASTIC v2.0 - High-performance SAR simulation for next-generation ATR systems

Synthetic aperture radar has been a mainstay of the remote sensing field for many years, with a wide range of applications across both civilian and military contexts. However, the lack of openly available datasets of comparable size and quality to those available for optical imagery has severely hampered work on open problems such as automatic target recognition, image understanding and inverse modelling. This paper presents a simulation and analysis framework based on the upgraded SARCASTIC v2.0 engine, along with a selection of case studies demonstrating its application to well-known and novel problems. In particular, we demonstrate that SARCASTIC v2.0 is capable of supporting complex phase-dependent processing such as interferometric height extraction whilst maintaining near-realtime performance on complex scenes

Statistical Modeling of SAR Images: A Survey

Statistical modeling is essential to SAR (Synthetic Aperture Radar) image interpretation. It aims to describe SAR images through statistical methods and reveal the characteristics of these images. Moreover, statistical modeling can provide a technical support for a comprehensive understanding of terrain scattering mechanism, which helps to develop algorithms for effective image interpretation and creditable image simulation. Numerous statistical models have been developed to describe SAR image data, and the purpose of this paper is to categorize and evaluate these models. We first summarize the development history and the current researching state of statistical modeling, then different SAR image models developed from the product model are mainly discussed in detail. Relevant issues are also discussed. Several promising directions for future research are concluded at last

Synthetic aperture radar motion compensation using autofocus with implications for super-resolution

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