A compliant, banded outflow cannula for decreased afterload sensitivity of rotary right ventricular assist devices

Biventricular support with dual rotary ventricular assist devices (VADs) has been implemented clinically with restriction of the right VAD (RVAD) outflow cannula to artificially increase afterload and, therefore, operate within recommended design speed ranges. However, the low preload and high afterload sensitivity of these devices increase the susceptibility of suction events. Active control systems are prone to sensor drift or inaccurate inferred (sensor-less) data, therefore an alternative solution may be of benefit. This study presents the in vitro evaluation of a compliant outflow cannula designed to passively decrease the afterload sensitivity of rotary RVADs and minimize left-sided suction events. A one-way fluid-structure interaction model was initially used to produce a design with suitable flow dynamics and radial deformation. The resultant geometry was cast with different initial cross-sectional restrictions and concentrations of a softening diluent before evaluation in a mock circulation loop. Pulmonary vascular resistance (PVR) was increased from 50 dyne s/cm5 until left-sided suction events occurred with each compliant cannula and a rigid, 4.5 mm diameter outflow cannula for comparison. Early suction events (PVR ∼ 300 dyne s/cm5) were observed with the rigid outflow cannula. Addition of the compliant section with an initial 3 mm diameter restriction and 10% diluent expanded the outflow restriction as PVR increased, thus increasing RVAD flow rate and preventing left-sided suction events at PVR levels beyond 1000 dyne s/cm5. Therefore, the compliant, restricted outflow cannula provided a passive control system to assist in the prevention of suction events with rotary biventricular support while maintaining pump speeds within normal ranges of operation.

GPX - Gardens Point XML Information Retrieval at INEX 2004

Traditional information retrieval (IR) systems respond to user queries with ranked lists of relevant documents. The separation of content and structure in XML documents allows individual XML elements to be selected in isolation. Thus, users expect XML-IR systems to return highly relevant results that are more precise than entire documents. In this paper we describe the implementation of a search engine for XML document collections. The system is keyword based and is built upon an XML inverted file system. We describe the approach that was adopted to meet the requirements of Content Only (CO) and Vague Content and Structure (VCAS) queries in INEX 2004.

Landmark

An inverted figurative monument to Victorian governor Charles Joseph Latrobe. By creating the impression that a nineteenth century statue has been made to stand precariously on its head, the work seeks to address the tension between the authority of the monument (as a civic marker and a form of portraiture) and its ‘invisibility’ in public space while simultaneously addressing (and subverting) the ‘authorless’ nature of the figurative monument. The work was awarded a judge’s commendation in the 2005 Helen Lempriere National Sculpture Award and had strong responses from the viewing public and widespread media coverage. Ironically, this parodic monument had the effect of raising the profile of Charles La Trobe in the media in ways that a conventional monument would not. Landmark now endures as part of the permanent sculpture collection of Latrobe University, Melbourne.

Medeleven

Medeleven was a practice-based research work that challenged conventional notions of how audiences ‘experience’ contemporary dance. It resulted in a 40 minute ‘experiential’ performance that inverted the traditional ‘passive’ presentation paradigm by situating the audience centrally within the creative process. The ‘traditional presentation paradigm’ was inverted in numerous ways including: asking the audience onstage with the performers, placing swings onstage for the audience to play on during the performance and guiding the audience through backstage corridors before entering onstage – all of which added elements of physicality, agency and liminality to the performance not usually available to audience members of contemporary dance. Five dancers moved throughout the space allowing the audience to choose where and how they engaged with this work and the swings were utilised both as a performance space and for audience seating. In addition to these spatial variations, the quadraphonic soundscore created distinct ‘environments’ throughout the stage space that varied individual experience possibilities. By positing performance as an experiential phenomenon, the pivotal objective of this work was to create a live-art experience that extended its performativity to include audience members as active meaning-makers, challenging both their role within this paradigm and their expectations of contemporary dance. The work produced strong responses from the audience with surveys indicating the presentation format, as well as the construction of the work, changed audience experience and ability to connect with the dance work. The research suggested that, in addition to existing research on dance audiences, barriers to engagement with contemporary dance may include how the art is constructed and where the audience is positioned within that creative framework. The research builds upon artistic practices being undertaken throughout the world that challenge the notion of existing ‘passive’ performance paradigms via creative ‘engagement’ with audience.

Initial CFD investigation of an MR fluid in a bicycle ergometer

A bicycle ergometer is a scientific device used by exercise physiologists which attempts to mimic on-road cycling characteristics such as foot technique, EMG activity, VO2, VCO2 and rider cardiology in a laboratory environment. Presently there are no known useful scientific ergometers that mimic these characteristics and are able to provide a satisfactory controlled resistance that is independent of speed. Previous research has suggested the use of a Magneto-Rheological (MR) Fluid as part of the ergometer design, as when used in a rotary brake application it is able to be controlled electronically to increase resistance instantly and independent of speed. In the target application, MR fluids are subject to immense tribological wear and temperature during viscous shearing, and will eventually show some degree of deterioration which is usually manifested as an increase in off-state viscosity. It is not known exactly how the fluid fails, however the amount of deterioration is related to the shear rate, temperature and duration and directly related to the power dissipation. Currently, there is very little literature that investigates the flow and thermal characteristics of MR fluid tribology using CFD. In this paper, we present initial work that aims to improve understanding of MR fluid wear via CFD modelling using Fluent, and results from the model are compared with those obtained from a experimental test rig of an MR fluid-based bicycle ergometer.

From mass communication to mass conversation : why 1984 wasn't like 1984

Marketers and commercial media alike are confronted by shifts in the social relations of media production and consumption in the global services economy, including the challenge of capturing, managing and commercialising media-user productivity. This trajectory of change in media cultures and economies is described here as ‘mass conversation’. Two media texts and a new media object provide a starting point for charting the ascendance and social impact of mass conversation. Apple’s 1984 television commercial, which launched the Macintosh computer, inverted George Orwell’s dystopian vision of the social consequences of panoptic communications systems. It invoked a revolutionary rhetoric to anticipate the social consequences of a new type of interactivity since theorised as ‘intercreativity’. This television commercial is contrasted with another used in Nike’s 2006 launch of its Nike+ (Apple iPod) system. The Nike+ online brand community is also used to consider how a multiplatform brand channel is seeking to manage the changing norms and practices of consumption and end-user agency. This analysis shows that intercreativity modifies the operations of ‘Big Brother’ but serves the more mundane than revolutionary purpose of generating commercial value from the affective labour of end-users.

Passive control of a bi-ventricular assist device : an experimental and numerical investigation

For the last two decades heart disease has been the highest single cause of death for the human population. With an alarming number of patients requiring heart transplant, and donations not able to satisfy the demand, treatment looks to mechanical alternatives. Rotary Ventricular Assist Devices, VADs, are miniature pumps which can be implanted alongside the heart to assist its pumping function. These constant flow devices are smaller, more efficient and promise a longer operational life than more traditional pulsatile VADs. The development of rotary VADs has focused on single pumps assisting the left ventricle only to supply blood for the body. In many patients however, failure of both ventricles demands that an additional pulsatile device be used to support the failing right ventricle. This condition renders them hospital bound while they wait for an unlikely heart donation. Reported attempts to use two rotary pumps to support both ventricles concurrently have warned of inherent haemodynamic instability. Poor balancing of the pumps’ flow rates quickly leads to vascular congestion increasing the risk of oedema and ventricular ‘suckdown’ occluding the inlet to the pump. This thesis introduces a novel Bi-Ventricular Assist Device (BiVAD) configuration where the pump outputs are passively balanced by vascular pressure. The BiVAD consists of two rotary pumps straddling the mechanical passive controller. Fluctuations in vascular pressure induce small deflections within both pumps adjusting their outputs allowing them to maintain arterial pressure. To optimise the passive controller’s interaction with the circulation, the controller’s dynamic response is optimised with a spring, mass, damper arrangement. This two part study presents a comprehensive assessment of the prototype’s ‘viability’ as a support device. Its ‘viability’ was considered based on its sensitivity to pathogenic haemodynamics and the ability of the passive response to maintain healthy circulation. The first part of the study is an experimental investigation where a prototype device was designed and built, and then tested in a pulsatile mock circulation loop. The BiVAD was subjected to a range of haemodynamic imbalances as well as a dynamic analysis to assess the functionality of the mechanical damper. The second part introduces the development of a numerical program to simulate human circulation supported by the passively controlled BiVAD. Both investigations showed that the prototype was able to mimic the native baroreceptor response. Simulating hypertension, poor flow balancing and subsequent ventricular failure during BiVAD support allowed the passive controller’s response to be assessed. Triggered by the resulting pressure imbalance, the controller responded by passively adjusting the VAD outputs in order to maintain healthy arterial pressures. This baroreceptor-like response demonstrated the inherent stability of the auto regulating BiVAD prototype. Simulating pulmonary hypertension in the more observable numerical model, however, revealed a serious issue with the passive response. The subsequent decrease in venous return into the left heart went unnoticed by the passive controller. Meanwhile the coupled nature of the passive response not only decreased RVAD output to reduce pulmonary arterial pressure, but it also increased LVAD output. Consequently, the LVAD increased fluid evacuation from the left ventricle, LV, and so actually accelerated the onset of LV collapse. It was concluded that despite the inherently stable baroreceptor-like response of the passive controller, its lack of sensitivity to venous return made it unviable in its present configuration. The study revealed a number of other important findings. Perhaps the most significant was that the reduced pulse experienced during constant flow support unbalanced the ratio of effective resistances of both vascular circuits. Even during steady rotary support therefore, the resulting ventricle volume imbalance increased the likelihood of suckdown. Additionally, mechanical damping of the passive controller’s response successfully filtered out pressure fluctuations from residual ventricular function. Finally, the importance of recognising inertial contributions to blood flow in the atria and ventricles in a numerical simulation were highlighted. This thesis documents the first attempt to create a fully auto regulated rotary cardiac assist device. Initial results encourage development of an inlet configuration sensitive to low flow such as collapsible inlet cannulae. Combining this with the existing baroreceptor-like response of the passive controller will render a highly stable passively controlled BiVAD configuration. The prototype controller’s passive interaction with the vasculature is a significant step towards a highly stable new generation of artificial heart.

A Theoretical and Analytical Synthesis of Autopoiesis and Sociolinguistics for the Study of Organisational Communication

The purpose of this paper is threefold. First, we propose a systemic view of communication based in autopoiesis, the theory of living systems formulated by Maturana & Varela (1980, 1987). Second, we show the links between the underpinning assumptions of autopoiesis and the sociolinguistic approaches of Halliday (1978), Fairclough (1989, 1992, 1995) and Lemke (1995, 1994). Third, we propose a theoretical and analytical synthesis of autopoiesis and sociolinguistics for the study of organisational communication. In proposing a systemic theory for organisational communication, we argue that traditional approaches to communication, information, and the role of language in human organisations have, to date, been placed in teleological constraints because of an inverted focus on organisational purpose-the generally perceived role of an organisation within society-that obscure, rather than clarify, the role of language within human organisations. We argue that human social systems are, according to the criteria defined by Maturana and Varela, third-order, non-organismic living systems constituted in language. We further propose that sociolinguistics provides an appropriate analytical tool which is both compatible and penetrating in synthesis with the systemic framework provided by an autopoietic understanding of social organisation.

Time alone

Time Alone is the introductory image to the exhibition Lightsite, which toured Western Australian galleries from February 2006 to November 2007. It is a five-minute-long exposure photographic image captured inside an abandoned building which the author converted into a camera obscura. It depicts an inverted image of the outside environment and the text 'time' - which is constructed by torch-light within the building interior and during the photographic exposure. The image evokes isolation and the temporality of inhabitation within the remote farmlands of the Great Southern Region of Western Australia: the region of focus for all of the twelve works in Lightsite. Indeed the owner of this now-abandoned house passed away and was not found for a week - bringing poignancy to the central theme of this creative work.

Five minutes at Nowanup

Five Minutes featured in the author's exhibition Lightsite, which toured Western Australian galleries from February 2006 to November 2007. It is a five-minute-long exposure photographic image captured inside a purpose-built, room-sized pinhole camera which is demountable and does not have a floor. Five Minutes depicts an inverted image of the outside environment where two botanists stand. The light from this exterior passes though the pinhole camera's aperture and illuminates the internal scene which includes the ground of the site which lies inside the room along with another two botanists standing inside. The image evokes the connectively the botanists have with this landscape, a site which they are presently revegetating with endemic and indigenous plant species. By illuminating the botanists only with light projected from the landscape itself (through the agency of the pinhole camera's aperture) the inhabitant and their landscape are depicted as inseparable subjects.

Self landcape - Hotspot

Self Landscape is an introductory image of the author's exhibition Lightsite, which toured Western Australian galleries from February 2006 to November 2007. It is a five-minute-long exposure photographic image captured inside a purpose-built, room-sized pinhole camera which is demountable and does not have a floor. Self Landscape depicts an inverted image of the outside environment - a revegetated farmland in the Great Southern Region of Western Australia. The light from the exterior landscape passes though the pinhole camera's aperture and illuminates the internal scene which includes that part of the landscape upon which the floorless room is erected, along with the author who is standing inside. The text "Hotspot" appears where the author has scribed that word with a torch during the long exposure. The image evokes the temporality of light. Here, light itself is portrayed as the primary medium through which we both perceive and describe landscape. It is through the agency of light that we construct our connectivity to landscape.

Jack's Bay

Jack's Bay expands understandings of the role of photographic media in the representation of landscapes. It does so by combining architectural construction with B&W photographic processing techniques. A purpose-built room-sized camera obscura is first constructed over a portion of the landscape to be recorded. Photosensitive paper is applied to the interior wall surfaces and is exposed to the inverted light entering a small aperture. These photographs are subsequently developed within the camera itself and consequently 'suffer' embellishments and aberrations from the makeshift darkroom conditions. In this way the specificity of both the landscape and the event of its recording are registered in the final image. Many images were destroyed in the process. The idea of the work is to help the viewer reflect on the role media plays in our understanding of landscape and to thus question the means by which they themselves record and interpret landscape representations.

Corackerup Breakaway

Corackerup Breakaway expands understandings of the role of photographic media in the representation of landscapes. It does so by combining architectural construction with B&W photographic processing techniques. A purpose-built room-sized camera obscura is first constructed over a portion of the landscape to be recorded. Photosensitive paper is applied to the interior wall surfaces and is exposed to the inverted light entering a small aperture. These photographs are subsequently developed within the camera itself and consequently 'suffer' embellishments and aberrations from the makeshift darkroom conditions. In this way the specificity of both the landscape and the event of its recording are registered in the final image. Many images were destroyed in the process. The idea of the work is to help the viewer reflect on the role media plays in our understanding of landscape and to thus question the means by which they themselves record and interpret landscape representations.

Working sheep

Working Sheep expands understandings of the role of photographic media in the representation of landscapes. It does so by combining architectural construction with B&W photographic processing techniques. A purpose-built room-sized camera obscura is first constructed over a portion of the landscape to be recorded. Photosensitive paper is applied to the interior wall surfaces and is exposed to the inverted light entering a small aperture. These photographs are subsequently developed within the camera itself and consequently 'suffer' embellishments and aberrations from the makeshift darkroom conditions. In this way the specificity of both the landscape and the event of its recording are registered in the final image. Many images were destroyed in the process. The idea of the work is to help the viewer reflect on the role media plays in our understanding of landscape and to thus question the means by which they themselves record and interpret landscape representations.

Towards dynamically-favourable quad-rotor aerial robots

This paper outlines progress towards realising practical quad-rotor robot helicopters and, in particular, the Australian National University’s ‘X-4 Flyer’ platform. Two challenges facing the X-4 are generating sufficient thrust and managing unstable dynamic behaviour. We address these issues with a rotor design technique for maximising thrust and the application of a novel rotor mast configuration. An aero-elastic blade design is described and its performance results are presented. A sprung teetering rotor hub that allows adjustment of the blade flapping characteristics and a quad-rotor dynamic model with blade flapping are introduced. The use of inverted rotors is shown to produce favorable stability properties for the Mark II X-4 Flyer.