Cell division is a universal cellular process responsible for the proliferation and differentiation of cells. After the chromosomes are faithfully segregated during mitosis, cells undergo cytokinesis, where one cell divides into two. Cytokinesis in many eukaryotes requires a structure known as the contractile ring, which contains actin, myosin and many other proteins assembled just beneath the plasma membrane. In this thesis, I present my studies on the function and organization of this ring. I used the powerful genetically tractable model organism the fission yeast Schizosaccharomyces pombe to study these processes in cytokinesis. First, I showed that one function of the cytokinetic ring is to regulate the assembly of the septum cell wall in a curvature dependent manner, suggesting a mechanosensitive mechanism. Second, I analyzed the substructure organization of the proteins within the ring, showing that ring proteins are arranged in clusters and in different layers. Finally, in a collaborative project, I studied the arrangement of chromosomes within the nucleus, and identified a protein required for linking centromeres to the spindle pole body at the nuclear envelope. In general, my thesis provides new insights into the spatial mechanisms of cytokinesis and chromosome organization.

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Jeremy S. Edwards, Dept. of Chemical Engineering. Includes bibliographical references.

Thesis (M.S.) in Spatial Information Science and Engineering--University of Maine, 2001. / Includes vita. Bibliography: leaves 74-79.

published_or_final_version / Urban Studies / Master / Master of Social Sciences

Thesis (PhD) -- University of South Australia, 1999

Thesis (Ph.D.)--University of Melbourne, Dept. , 20. / Typescript (photocopy). Includes bibliographical references (leaves 229-242).

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains ix, 139 p.; also includes graphics. Includes bibliographical references (p. 131-139). Available online via OhioLINK's ETD Center

published_or_final_version / Geography and Geology / Doctoral / Doctor of Philosophy

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2015. / This dissertation examines the imaginations and use of space by black residents in Suburban South Africa, with a particular focus on the small town of Mokopane, in the context of urban desegregation and integration. Given the segregated spatial legacy of apartheid, the post-apartheid state has and continues to seek ways to create a non-racial and integrated society. However, twenty years after the demise of the apartheid regime and the country remains segregated along racial and class lines. In understanding some of the reasons why integration remains a challenge, this research investigates black residents’ use of public spaces in the context of a supposedly desegregated space. It investigates the socio-spatial relations between residents of three adjoined suburbs, two of which are a product of apartheid and one a recent development of the state’s spatial policy to create integrated communities. The study is not focused solely on the social and spatial relations within the confines of the study area but most significantly beyond that in order to comprehend people’s relationship and meanings attached to space. Drawing from Lefebvre’s theory of the production of space, imagined and psychoanalytical geographies, the study reflects on how people’s identities, rooted in a history of colonialism and apartheid, affect the way they imagine and use space and, further, how the arrival of those considered as other reveals the symbolic meanings and boundaries that have been attached to space. The study further draws from post-colonial literature on space to challenge prevalent notions of the relationship between race and space, with a particular focus on the rural-township-urban mobilities and what those mean in the construction of blackness. Thematic content and discourse analysis are used to decode meaning embedded in language in terms of how people relate to others socially and spatially. The dissertation reveals that, even in contexts where spatial desegregation has been attained, the use and imagination of space and the relationship to others are rooted within historical configurations of racial and class identities. Further, black residents’ experience of historically white spaces remains rooted in their lived experiences and in their understanding of their belonging in urban spaces as inherently white. It is against this backdrop that this research argues that, in the quest to develop integrated post-apartheid communities, the state has given insufficient, if any, thought on the ways space, class and race are produced relationally.

In this thesis we investigate the performance of spatial reuse in wireless networks. More specifically, we investigate the performance of location-based spatial reuse built upon the identification of links in the network that form Collision-Free Sets (CFSs). We develop algorithms that efficiently find such CFSs. The main focus of this thesis is the application of our CFS-based algorithms to emerging WiMAX (Worldwide Interoperability for Microwave Access) networks. However, we will also apply our CFS-based algorithms to smaller scale networks, as well as to the issue of QoS routing. This thesis makes several contributions. We first show how CFSs can be found within polynomial time in small scale wireless networks. We then probe how CFSs can be used to enhance network efficiency when location is available. We also explore how CFS determination is affected by location error, determining what level of location error renders the use of CFSs ineffective. In this context, we discuss the density of access points required to ensure CFS-based spatial reuse remains effective. We then focus on the use of CFSs in emerging multihop WiMAX networks, showing in detail how enhanced spatial reuse is delivered. The spatial reuse gains are probed both in the presence of realistic channel conditions and realistic location errors. Within the context of the IEEE 802.16 standard we show how CFSs can enhance, by factors of two, the VoIP capacity of multihop WiMAX networks. We also discuss how our CFS algorithms can be applied to other ongoing efforts aimed at improving VoIP capacity in WiMAX networks. Finally, an application of our CFS algorithms in the context of QoS routing is studied. Specifically, we develop a two-hop QoS routing protocol that guarantees QoS specifications by securing higher bandwidth for the chosen routes.