Power, discourse and city trajectories

Examines social theory and contemporary human geography in the context of urban development. Covers theoretical debates in political ecology, the cultural turn in the economy, social relations and scale, space and place, and colonialism and post-colonialism

Holographic mensuration of suspended particles in aquatic systems

The distribution and dynamics of aggregates in the aquatic environment play an important role in the modelling of biogeochemical processes. Previous work on aggregates in the ocean (e.g. sedimentary 'marine snow' particles), which vary in size from tens of microns to several millimetres, has used electronic counting or conventional photography coupled with image analysis. Here we describe a non-destructive in situ approach by use of holographic mensuration, hologrammetry, that affords greater scope and higher accuracy for the enumeration, sizing, and spatial distribution determination of aggregate particles. By means of two complimentary techniques, in-line and offaxis transmission holography, we present the initial experiments conducted in our laboratory and discuss the preliminaiy results from real image analysis

Off-axis transmission holographic system for recording aquatic particles

We describe a holographic system for recording particles suspended in water. The hologram plate is located in air, separated from the test tank by an air/glass/water boundary. The holographic emulsion is therefore unaffected by adverse aquatic conditions within the tank (i.e. surface contamination, non-uniform swelling). The design geometry is intended to minimise the aberrations that arise from recording subjects located in water and replaying their hologram image in air. Third order aberrations, most crucially spherical aberration and astigmatism, are suppressed to give an experimental resolution of 7 lp/mm using USAF 1951 target in water 600mm from the boundary. Particles (plankton species) in the sub-millimeter to several millimeters size range are observed at planar sections within the recording volume by visual inspection of the hologram replayed in real image mode

In situ off-axis holography of marine plankton

We present an off-axis transmission holographic technique for recording marine plankton in situ within a test tank of 36,000 ml with a pulsed laser in a 40 ns interval. The holographic plate is located in air and is therefore unaffected by aquatic conditions that may cause emulsion degradation (e.g. non-uniform swelling and surface contamination). The reference beam traverses a path in air only, and thus remains unaffected by dense concentrations of plankton. Third order aberrations, notably spherical aberration and astigmatism, are suppressed to yield an experimental resolution of 7 lp/mm (70 micrometres) with a USAF 1951 target located 600 mm in water from the observation window. Plankton particle counts examined by real image reconstruction show a strong correlation with duplicate samples examined under a microscope

Were rivers flowing across the Sahara during the last interglacial? Implications for human migration through Africa.

Human migration north through Africa is contentious. This paper uses a novel palaeohydrological and hydraulic modelling approach to test the hypothesis that under wetter climates c.100,000 years ago major river systems ran north across the Sahara to the Mediterranean, creating viable migration routes. We confirm that three of these now buried palaeo river systems could have been active at the key time of human migration across the Sahara. Unexpectedly, it is the most western of these three rivers, the Irharhar river, that represents the most likely route for human migration. The Irharhar river flows directly south to north, uniquely linking the mountain areas experiencing monsoon climates at these times to temperate Mediterranean environments where food and resources would have been abundant. The findings have major implications for our understanding of how humans migrated north through Africa, for the first time providing a quantitative perspective on the probabilities that these routes were viable for human habitation at these times

The future of the city centre: Urbanisation, transformation and resilience – a tale of two Newcastle cities

Recent debates over the content and theoretical orientation of urban studies act as a strong reminder that the nature and existence of the city as a form of spatial urban agglomeration is changing. They have acted positively as a heuristic to inspire critical analysis of urbanisation and helped to illuminate the considerable empirical variation over time and space in urban agglomeration forms. However, in shifting the focus onto the planetary reach of urbanisation, such debates risk deflecting attention away from the city core at a time when it too is being subjected to transformation. The city centre has been taken for granted as critical attention has been given to the impact of development and enterprise in extending the city outwards. The recent proliferation of public and policy interest in the future of the city centre as the archetypal expression of urban agglomeration has not been matched by similar growth in academic and theoretical accounts of its transformation. Drawing on the examples of two city centres, and placing them in the context of the recent debates of urban agglomeration theory, this article seeks to initiate deeper analysis and dialogue about the future of the urban core, including how it is being articulated and by whom. It argues for a greater analytic understanding of the ways in which the city centre as a physical and emotional entity has been so resilient, and advocates for stronger engagement with initiatives seeking to reactivate the city centre as a crucial epicentre of urban agglomeration

Studentification and commodification of student lifestyle in Braamfontein, Johannesburg

Abstract: The process of studentification has emerged as a new form of neighbourhood change in the global North over the past 16 years and often situated within broader debates on gentrification. The growth of private student housing across cities globally has been linked to the increased neoliberalisation and massification of higher education and the lack of universities to keep up with the supply of student housing. Limited scholarship, however, exists on studentification in the global South. Notwithstanding that, in South Africa there has been growing recognition of the impact of studentification on urban environments. Despite some recognition in smaller cities, studentification has been neglected in large urban contexts. Using interviews with key informants and focus groups with students, this paper explores the impact of studentification in the urban neighbourhood of Braamfontein in Johannesburg. Over the past decade and a half there has been evidence of the concentration of student geographies and the commodification of student lifestyle in Braamfontein, Johannesburg

Suburban creativity: The geography of creative industries in Johannesburg

Creativity is an increasing scholarly focus for urban and economic geographers. The aim in this paper is to contribute to what is so far mainly a Northern literature around the locational characteristics of creative industries. The results are analysed from a comprehensive audit undertaken of creative industries in Johannesburg, South Africa's leading economic hub. In common with certain other investigations of creative industries the largest component of enterprises in Johannesburg is creative services involving the production of goods or services for functional purposes. An aggregate picture emerges of the geography of creative industries in Johannesburg as strongly focused in suburban areas rather than the inner-city and its fringe areas. Nevertheless, certain differences are observed across the eight categories of creative industries. The evidence concerning the spatial distribution of creative industries in Johannesburg provides a further case for re-positioning the suburbs in post-Fordist debates around creative city economies and for re-examining neo-liberal cultural policies that preference inner-city areas