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The dynamics of dissociative adsorption of hydrogen and oxygen on the Pt(533) (or 4(111) x (100)) surface has been studied under UHV conditions with a supersonic molecular beam. For hydrogen, the magnitude and characteristics of direct route to dissociation are very similar to that observed on the Pt(111) surface, and only at incident energies below 150meV does the behaviour deviate from the defect free surface. At incident energies up to 18meV trapping can occur into a physisorbed state that is fully accommodated. This state can act as a precursor to dissociation and displays typical precursor behaviour in surface temperature dependence and surface coverage dependence. At incident energies up to 150meV a third channel to adsorption exists. This channel is direct in nature, and may either be due to an unaccommodated precursor to dissociation or a direct channel where hydrogen molecules steer into the active step site. Oxygen adsorption of Pt(533) proceeds in the main part via the sequential precursor route to dissociation proposed for adsorption on the Pt(111) surface. The increased reactivity for oxygen on Pt(533), over that observed for Pt(111), is interpreted as being a direct result of the presence of a high density of steps on the Pt(533) surface. The steps provide low activation sites for the conversion of the physisorbed precursor to the chemisorbed precursor, and also promote the dissociation of the chemisorbed molecule. In addition to the two precursor channels described by the sequential precursor model, a highly activated direct channel to dissociation is present which is believed to proceed exclusively at step sites.

The extension from Quantitative Magnetic Resonance Imaging to synthetic imaging has the clear advantage of being able to continually image the patient after the exam. MR techniques such as DWI are commonly used but have some clear disadvantages resulting from the use of echoplanar imaging. It should then be asked whether one imaging technique is objectively better. If one technique is better, the incorporation in clinical settings could produce better diagnostic rates, and save valuable time. In order to quantitatively assess the quality of these techniques, the SNR and CNR values of similar tissues were compared. The pre-analysis discussion concentrating on the spatial resolution and artifacts, supports that synthetic images have an advantage over DWI due to higher resolution and absence of artifacts. The SNR and CNR values were calculated for each patient and image type for the comparison, initially assuming that the synthetic images would have a higher mean SNR and CNR. In most cases the differences between scan types was found to not be statistically significant. In conclusion, this analysis could not support the initial theory that the synthetic images had a higher SNR or CNR. The research shows that they are more likely to be comparable. An investigation of the diagnostic power of the synthetic in comparison to standard DWI would give clinical relevance to these results.