Urban consumption of place : Maboneng as a case study

Read abstract in the documentMini Dissertation (MA Fine Arts)--University of Pretoria, 2018.Visual ArtsMA Fine ArtsUnrestricte

Orbiting Rainbows: Optical Manipulation of Aerosols and the Beginnings of Future Space Construction

Our objective is to investigate the conditions to manipulate and maintain the shape of an orbiting cloud of dust-like matter so that it can function as an ultra-lightweight surface with useful and adaptable electromagnetic characteristics, for instance, in the optical, RF, or microwave bands. Inspired by the light scattering and focusing properties of distributed optical assemblies in Nature, such as rainbows and aerosols, and by recent laboratory successes in optical trapping and manipulation, we propose a unique combination of space optics and autonomous robotic system technology, to enable a new vision of space system architecture with applications to ultra-lightweight space optics and, ultimately, in-situ space system fabrication. Typically, the cost of an optical system is driven by the size and mass of the primary aperture. The ideal system is a cloud of spatially disordered dust-like objects that can be optically manipulated: it is highly reconfigurable, fault-tolerant, and allows very large aperture sizes at low cost. See Figure 1 for a scenario of application of this concept. The solution that we propose is to construct an optical system in space in which the nonlinear optical properties of a cloud of micron-sized particles are shaped into a specific surface by light pressure, allowing it to form a very large and lightweight aperture of an optical system, hence reducing overall mass and cost. Other potential advantages offered by the cloud properties as optical system involve possible combination of properties (combined transmit/receive), variable focal length, combined refractive and reflective lens designs, and hyper-spectral imaging. A cloud of highly reflective particles of micron-size acting coherently in a specific electromagnetic band, just like an aerosol in suspension in the atmosphere, would reflect the Sun's light much like a rainbow. The only difference with an atmospheric or industrial aerosol is the absence of the supporting fluid medium. This new concept is based on recent understandings in the physics of optical manipulation of small particles in the laboratory and the engineering of distributed ensembles of spacecraft clouds to shape an orbiting cloud of micron-sized objects. In the same way that optical tweezers have revolutionized micro- and nano-manipulation of objects, our breakthrough concept will enable new large scale NASA mission applications and develop new technology in the areas of Astrophysical Imaging Systems and Remote Sensing because the cloud can operate as an adaptive optical imaging sensor. While achieving the feasibility of constructing one single aperture out of the cloud is the main topic of this work, it is clear that multiple orbiting aerosol lenses could also combine their power to synthesize a much larger aperture in space to enable challenging goals such as exoplanet detection. Furthermore, this effort could establish feasibility of key issues related to material properties, remote manipulation, and autonomy characteristics of cloud in orbit. There are several types of endeavors (science missions) that could be enabled by this type of approach, i.e. it can enable new astrophysical imaging systems, exoplanet search, large apertures allow for unprecedented high resolution to discern continents and important features of other planets, hyperspectral imaging, adaptive systems, spectroscopy imaging through limb, and stable optical systems from Lagrange-points. Future micro-miniaturization might hold promise of a further extension of our dust aperture concept to other more exciting smart dust concepts with other associated capabilities

Syphilis, skin, and subjectivity : historical clinical photographs in the Saint Surgical Pathology Collection

Thesis MA(VA)--Stellenbosch University, 2017.ENGLISH ABSTRACT: This study concerns an archive of disused historical clinical photographs within the Saint Surgical Pathology Collection (SSC) that originally served as teaching aids for the benefit of student doctors at the University of Cape Town's (UCT) medical school. Focusing on images of patients diagnosed with syphilis produced between 1920 and 1961, this study represents the first critical visual enquiry of these images and, as such, has directly contributed to their current life within a (publically accessible) learning collection at UCT's Pathology Learning Centre (PLC). Set against a backdrop of psycho-social notions of health and disease, this study engages the visual coding of syphilis in relation to Cape Town's medical history, and the developing conventions of photography within this scientific field. Through close readings of selected images, a critical focus on extra-clinical details, inconsistencies, and emotive qualities within the photographic frame allows a consideration of how these photographs take part in a continuous meaning-making process that troubles any easy, fixed, or disinterested reading. By focusing on concepts of sublimation and projection, I unpack the photographic depiction of ruptured skin in the SSC as an attempt to render the syphilitic patient-body a passive object of medical knowledge. To achieve this the work of Hal Foster, Erin O'Connor, and Jill Bennett form the theoretical foundation to address the affective potential of imaging disease necessarily limited in efforts to secure the diagnostic function of this clinical material. However, while these photographs emerge in this discussion as decisively structured and composed, I likewise address how the 'Syphilis' images offer a way of seeing beyond their institutional use. While acknowledging the disciplinary motivations of the Foucauldian medical gaze, my argument ultimately privileges the subjects of these images while critically considering how the conspicuous nature of this disease may have seen it pose a particular threat to a notion of stable subjecthood. This was especially the case in the context of 20th century South Africa where those most vulnerable to the disease were in many respects second-class citizens. Ultimately, this investigation seeks to (re)address the SSC in an attempt to unpack how these photographs may speak beyond their historical medical purpose. By examining how photographic representations of patients provide a means of seeing beyond their institutional intent, I suggest ways in which these images offer up points of fracture that offset and even resist a medical gaze and instead provide an opportunity for the human subject to be retrieved from the objectifying tendencies of medicine.AFRIKAANSE OPSOMMING: Hierdie studie vervat 'n argief van historiese kliniese foto's wat deel vorm van die Saint Surgical Pathology Collection (SSC) en oorspronklik gedien het as onderrighulpmiddels ten bate van die student-dokters aan die Universiteit van Kaapstad (UK) se mediese skool. Hierdie studie van foto’s van pasiënte wat met sifilis gediagnoseer is en wat tussen 1920 en 1961 geneem is, is die eerste kritiese visuele ondersoek van hierdie beelde en sodanig dra dit direk by tot hul huidige bestaan binne 'n (openbaar toeganklike) opvoedkundige versameling by die UK se Pathology Learning Centre (PLC). Teen ‘n agtergrond van psigososiale begrippe van gesondheid en siekte, betrek die studie visuele kodering van sifilis in verhouding tot die mediese geskiedenis van Kaapstad en die ontwikkeling van konvensies van fotografie in hierdie wetenskaplike veld. Deur noue evaluering van geselekteerde beelde, 'n kritiese fokus op buite-kliniese besonderhede, teenstrydighede, en emosionele kwaliteite binne die fotografiese raam, kan oorweeg word hoe hierdie foto’s deel uitmaak van 'n proses van deurlopende-betekenis wat enige maklike, vaste, of belangelose interpretasie kwel. Deur te fokus op konsepte van sublimasie en projeksie, ontleed ek die fotografiese uitbeelding van geskeurde vel in die SSC in 'n poging om die liggaam van die sifilispasiënt as 'n passiewe voorwerp van mediese kennis daar te stel. Om dit te bereik, vorm die werk van Hal Foster, Erin O'Connor en Jill Bennett die teoretiese grondslag om die affektiewe potensiaal van die uitbeelding van siekte, wat noodwendig beperk word deur pogings om die diagnostiese funksie van hierdie kliniese materiaal te verseker, aan te spreek. Alhoewel hierdie foto’s in hierdie bespreking as beslissend gestruktureer en saamgestel na vore kom, spreek ek ook aan hoe die 'Sifilis'-beelde 'n manier bied om hulle buite hul institusionele gebruik te betrag. Met inagneming van die dissiplinêre motivering agter Foucault se medical gaze, bevoordeel my argument oplaas die menslike onderwerpe van hierdie fotografiese beelde, terwyl dit die opvallende aard van hierdie siekte se besonderse bedreiging tot die denkbeeld van 'n stabiele subjektiwiteit krities oorweeg. Dit was veral die geval in die konteks van 20ste eeu Suid-Afrika waar die kwesbaarste vir dié siekte in vele opsigte as tweedeklas burgers beskou was. Ten laaste word die SSC in hierdie ondersoek aangespreek in ‘n poging om die foto’s buite hul historiese mediese doeleindes te laat getuig. Deur verdere ondersoek in te stel namate fotografiese uitbeeldings van pasiënte ‘n manier kan voorsien om buite hul institusionele doel gesien te word, stel ek wyse voor waarop hierdie beelde fraktuurpunte bied wat die medical gaze kontrasteer en selfs teenstaan. In hierdie studie bied die beelde eerder ‘n geleenthheid om die menslike onderwerp vanuit die objektiverende neigings van geneeskunde te verwyder en hierdeur hul menslikheid te herstel.National Research Foundation (NRF

Dispersion Relations in Scattering and Antenna Problems

This dissertation deals with physical bounds on scattering and absorption of acoustic and electromagnetic waves. A general dispersion relation or sum rule for the extinction cross section of such waves is derived from the holomorphic properties of the scattering amplitude in the forward direction. The derivation is based on the forward scattering theorem via certain Herglotz functions and their asymptotic expansions in the low-frequency and high-frequency regimes. The result states that, for a given interacting target, there is only a limited amount of scattering and absorption available in the entire frequency range. The forward dispersion relation is shown to be valuable for a broad range of frequency domain problems involving acoustic and electromagnetic interaction with matter on a macroscopic scale. In the modeling of a metamaterial, i.e., an engineered composite material that gains its properties by its structure rather than its composition, it is demonstrated that for a narrow frequency band, such a material may possess extraordinary characteristics, but that tradeoffs are necessary to increase its usefulness over a larger bandwidth. The dispersion relation for electromagnetic waves is also applied to a large class of causal and reciprocal antennas to establish a priori estimates on the input impedance, partial realized gain, and bandwidth of electrically small and wideband antennas. The results are compared to the classical antenna bounds based on eigenfunction expansions, and it is demonstrated that the estimates presented in this dissertation offer sharper inequalities, and, more importantly, a new understanding of antenna dynamics in terms of low-frequency considerations. The dissertation consists of 11 scientific papers of which several have been published in peer-reviewed international journals. Both experimental results and numerical illustrations are included. The General Introduction addresses closely related subjects in theoretical physics and classical dispersion theory, e.g., the origin of the Kramers-Kronig relations, the mathematical foundations of Herglotz functions, the extinction paradox for scattering of waves and particles, and non-forward dispersion relations with application to the prediction of bistatic radar cross sections

Contemporary Portraiture in Australia: 1990s to 2010s

Contemporary portraiture in Australia is undergoing a revolutionary change in response to the growth of new media, digital imaging and the proliferation of selfies in the networked-digital age. While the effects of new technologies on portraiture are undeniable, this thesis argues contemporary portraiture from the 1990s to 2010s is a synthesis of both traditional modes of representation and new art forms that is expanding our understanding of what is a portrait. Some contemporary portraits have vestiges of Western historic portraiture conventions—mimesis, physiognomy and authenticity—while in others the links have become fragile and contestable. This thesis analyses how contemporary portraiture extends beyond established portraiture traditions to create alternate forms of representation in new and unexpected ways. The study shows contemporary portraiture is becoming increasingly ambiguous and fragmented in form, style, and subject matter. Particular attention is paid to how the desire for social connectedness, that is, being linked up to social media and linked in to internet sites, and the need to take selfies on hand-held devices is redefining portraiture. Furthermore, it examines how the contemporary portrait contributes to changing perceptions of Australian society, national and cultural identity, and ideas of selfhood. It also analyses how new media is disrupting conventional ways of curating and presenting portraits in the gallery setting offering unparalleled opportunities for visitor engagement by presenting portraits on and off the walls. An important distinction made in this thesis, is the significance of portraits of country that gives rise to an alternative concept of subjectivity as a visual and spiritual marker of Indigenous cultural identity. When considered in this way, Indigenous portraits of country go beyond the Western concept of individual difference that allows for a more expansive meaning of portraiture. The outcome of this research study is a body of knowledge and scholarly discourse on recent developments in contemporary portraiture and visual culture brought about by a significant gap in knowledge of the subject

Partially Coherent Lab Based X-ray Micro Computed Tomography

X-ray micro computed tomography (CT) is a useful tool for imaging 3-D internal structures. It has many applications in geophysics, biology and materials science. Currently, micro-CT’s capability are limited due to validity of assumptions used in modelling the machines’ physical properties, such as penumbral blurring due to non-point source, and X-ray refraction. Therefore many CT research in algorithms and models are being carried out to overcome these limitations. This thesis presents methods to improve image resolution and noise, and to enable material property estimation of the micro-CT machine developed and in use at the ANU CTLab. This thesis is divided into five chapters as outlined below. The broad background topics of X-ray modelling and CT reconstruction are explored in Chapter 1, as required by later chapters. It describes each X-ray CT component, including the machines used at the ANU CTLab. The mathematical and statistical tools, and electromagnetic physical models are provided and used to characterise the scalar X-ray wave. This scalar wave equation is used to derive the projection operator through matter and free space, and basic reconstruction and phase retrieval algorithms. It quantifies the four types of X-ray interaction with matter for X-ray energy between 1 and 1000 keV, and presents common assumptions used for the modelling of lab based X-ray micro-CT. Chapter 2 is on X-ray source deblurring. The penumbral source blurring for X-ray micro-CT systems are limiting its resolution. This chapter starts with a geometrical framework to model the penumbral source blurring. I have simulated the effect of source blurring, assuming the geometry of the high-cone angle CT system, used at the ANU CTLab. Also, I have developed the Multislice Richardson-Lucy method that overcomes the computational complexity of the conjugate gradient method, while produces less artefacts compared to the standard Richardson-Lucy method. Its performance is demonstrated for both simulated and real experimental data. X-ray refraction, phase contrast and phase retrieval (PR) are investigated in Chapter 3. For weakly attenuating samples, intensity variation due to phase contrast is a significant fraction of the total signal. If phase contrast is incorrectly modelled, the reconstruction would not correctly account the phase contrast, therefore it would contribute to undesirable artefacts in the reconstruction volume. Here I present a novel Linear Iterative multi-energy PR algorithm. It enables material property estimation for the near field submicron X-ray CT system and reduces the noise and artefacts. This PR algorithm expands the validity range in comparison to the single material and data constrained modelling methods. I have also extended this novel PR algorithm to assume a polychromatic incident spectrum for a non-weakly absorbing object. Chapter 4 outlines the space filling X-ray source trajectory and reconstruction, on which I contributed in a minor capacity. This space filling trajectory reconstruction have improved the detector utilisation and reduced nonuniform resolution over the state-of-the-art 3-D Katsevich’s helical reconstruction, this patented work was done in collaboration with FEI Company. Chapter 5 concludes my PhD research work and provides future directions revealed by the present research

Doctor of Philosophy

dissertationTraversing the vectors and tensions of everyday places is to experience a profoundly powerful rhetorical force. Through the particularities of place, identity is forged, communities are created, and ideological wars are waged through images, aesthetics, and materiality. The (Em)placed Vernacular: Rhetorics of Transgression and Control in New York City explores these intersections and the larger rhetorical possibilities of taking a vernacular approach to the study place through an exploration of New York City as an ideological text and site of rhetorical acts of place-making. This project develops the notion of the (em)placed vernacular as a critical framework that acknowledges the important ways that place is perpetually created, maintained, and re-coded by the actions and reactions of users. The (em)placed vernacular is defined as the visual, aesthetic, and material codes embedded in the particularities of place. These codes not only provide the symbolic resources for living in the contemporary moment, they are one of the fundamental ways that ideology is materialized and acts of transgression and control emerge in the city. I explore three particular engagements within the (em)placed vernacular of New York City. As a larger dwelling place that has historically existed as a microcosm for the larger United States, I study the use of Zuccotti Park by Occupy Wall Street, the everyday surfaces used by British street artist Banksy, and the memory place of the 9/11 Memorial. Because of the intersectional dimensions of the (em)placed vernacular, I engage the virtual contexts and (cyber)places where the images roam, the constitutive force of materiality in producing ideal and transgressive subjectivities, and the larger political and rhetorical implications of transforming contemporary (non)places into places where new subjectivities can emerge through acts of place-making. I argue that acts of place-making provide particular ways of seeing the world, through which the possibilities of transformation are seen and engaged. The (em)placed vernacular provides a useful critical framework for studying acts of transgression and control that work always within the contingent foundations of postmodern politics