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No description available.

The pattern of inactivation in the DXS8237E-UBE1-PCTK1 region is of particular interest, since the mechanisms of X chromosome inactivation and the escape from inactivation are, as yet, not fully understood. The inactivation status of the DXS8237E and PCTKl gene differ: the first undergoes normal inactivation and the second escapes this process. The status of the UBEl gene has been controversial, although it is widely excepted that it does escape X chromosome inactivation. Physical mapping of the region employing YACs and subsequently P ACs has been undertaken, but was restricted in scope by the high frequency of rearrangements occurring. DNA sequences between DXS8237E, UBE1, PCTKl and the distal gene, UHX1, have been investigated with regard to LINEI elements, which are thought to playa role in X-inactivation. The results obtained strongly suggest a link between LINE1 elements and X chromosome inactivation. Sequence analysis results also contributed to the understanding of difficulties with restriction mapping of the region. Further, this work includes the first reported establishment of the UBEl exonintron boundaries. Additionally, genomic sequence analysis showed that only 46kb separate DXS8237E from UHX1, which confirms that this region is extremely gene rich.

Hardware texture mapping is essential for real-time rendering. Unfortunately the memory bandwidth and latency often bounds performance in current graphics architectures. Bandwidth consumption can be reduced by compressing the texture map or by using a cache. However, the way a texture map occupies memory and how it is accessed affects the pattern of memory accesses, which in turn affects cache performance. Thus texture compression schemes and cache architectures must be designed in conjunction with each other. We define a sparse texture to be a texture where a substantial percentage of the texture is constant. Sparse textures are of interest as they occur often, and they are used as parts of more general texture compression schemes. We present a hardware compatible implementation of sparse textures based on B-tree indexing and explore cache designs for it. We demonstrate that it is possible to have the bandwidth consumption and miss rate due to the texture data alone scale with the area of the region of interest. We also show that the additional bandwidth consumption and hideable latency due to the B-tree indices are low. Furthermore, the caches necessary for these textures can be quite small.

Several contemporary art historians have been interested in exploring how their discipline could respond to the increasing globalisation of knowledge and information by encompassing global perspectives into the methodologies that underpin their approaches to art historiography. This dissertation aims to explore how, in developing their new approaches to world art history, they have drawn on a range of natural and social sciences, thus enabling their work to be placed in a wider social, political and indeed global context. While their individual approaches are many and varied it is important to identify commonalities between them so as to highlight unifying approaches across such diversity. The dissertation begins with literature review of the key concepts I want to explore. The work of the 19th century historian, Aby Warburg is highlighted to draw attention to his early pioneering attempts to provide an intercultural perspective to art history. Recent attempts to develop new approaches to world art history are then analysed. These include works by David Carrier, Ben-Ami Scharfstein, David Summers, Esther Pasztory and John Onians. The thesis concludes with a discussion on the recent exhibition at the British Museum entitled A History of the World in 100 Objects. The dissertation will show that despite the diverse methodologies used by all of these writers and the challenges of the different media employed, all utilise concepts of borders and objects in an explicitly geopolitical context.

Data Exchange is the problem of transforming data in one format (the source schema) into data in another format (the target schema). Its core component is a schema mapping, which is a high level specification of how such transformation should be done. Relational data exchange has been extensively studied, but exchanging XML data have been paid much less attention. The goal of this thesis is to develop a theory of XML data exchange with expressive schema mappings, extending a previous work using restricted mappings. Our mapping language is based on tree patterns that can use horizontal navigation and data comparison in addition to downward navigation. First we look at static analysis problems concerning a single mapping. More specif- ically, we consider consistency problems with different flavours. One such problem, for instance, asks if any tree has a solution under the given mapping. Then we turn to analyse the complexity of mapping themselves, i.e., recognising pairs of trees such that the one is mapped to the other. For both problems, we provide classifications based on sets of features used in the mappings. Second we investigate the composition of XML schema mappings. Generally it is hard, or rather simply impossible, to achieve closure under composition in XML settings unlike in relational settings. Nevertheless we identify a class of XML schema mappings that is closed under composition. Lastly we consider the problem of query answering. It is important to exchange data so that we can feasibly answer queries while it often leads to intractability. We identify the dividing line between tractable and intractable cases: answering queries with extended features is always intractable while tractability of answering simple queries can be retained in extended mappings.