In surface science there is great effort to move from studying simple, flat model surfaces in vacuum to investigating more complex model catalysts in gas environments (in situ). This thesis gives... Show moreIn surface science there is great effort to move from studying simple, flat model surfaces in vacuum to investigating more complex model catalysts in gas environments (in situ). This thesis gives three examples of such studies using microscopy and spectroscopy.Exposure of ZnO(10-10) to moderate pressures of water in an in situ scanning tunneling microscope reveals that the surface roughens. The flat ZnO(10-10) is thus only conditionally suited as a model catalyst for reactions involving water.In the same microscope, surface gold oxide formation is observed on TiO2/Au(111) during CO oxidation at 1 bar pressure. Comparisons to the Au(111) surface suggest that the titania does not supply atomic oxygen to the Au(111) substrate as part of the reaction mechanism of the CO oxidation.Co(0001) is investigated as a model catalyst for Fischer-Tropsch synthesis, the reaction of CO and H2 to form hydrocarbons. In this thesis the oxidation behavior of the cobalt and the adsorption of carbon species during the reaction are investigated using near-ambient pressure X-ray photoelectron spectroscopy.Generally, this thesis exemplifies the significant influence that small concentrations of contaminants in gases and materials can have on the structure and behavior of surfaces in in situ studies. Show less
The importance and character of exchange in the Carolingian period has long been a subject of academic debate. There is much discussion on the relative importance of local, regional and... Show moreThe importance and character of exchange in the Carolingian period has long been a subject of academic debate. There is much discussion on the relative importance of local, regional and international exchange, the role of various groups of actors, and the nature of exchange. What is largely lacking is a consideration of non-elite rural dwellers as constitutive elements in the economy. The present study focusses on the role of rural communities in the development of exchange systems during the Carolingian period. To what extent did the consumptive preferences of rural communities influence the flow of goods at a regional and interregional level? This is examined by cataloguing the finds from Carolingian sites in the Netherlands and comparing their distributions between regions. It can be demonstrated that rural dwellers indeed played a part in developments in the production and distribution of goods. At the same time the conducted analyses do not allow the establishment of a single model of how rural dwellers participated in exchange networks of the period. In fact, this study contends that there is little meaning in determining the relative importance of different groups in society for the establishment and maintenance of exchange networks at any one time. Show less
