The feasibility of vibration analysis as a technique to detect osseointegration of transfemoral implants

One of the main causes of above knee or transfemoral amputation (TFA) in the developed world is trauma to the limb. The number of people undergoing TFA due to limb trauma, particularly due to war injuries, has been increasing. Typically the trauma amputee population, including war-related amputees, are otherwise healthy, active and desire to return to employment and their usual lifestyle. Consequently there is a growing need to restore long-term mobility and limb function to this population. Traditionally transfemoral amputees are provided with an artificial or prosthetic leg that consists of a fabricated socket, knee joint mechanism and a prosthetic foot. Amputees have reported several problems related to the socket of their prosthetic limb. These include pain in the residual limb, poor socket fit, discomfort and poor mobility. Removing the socket from the prosthetic limb could eliminate or reduce these problems. A solution to this is the direct attachment of the prosthesis to the residual bone (femur) inside the residual limb. This technique has been used on a small population of transfemoral amputees since 1990. A threaded titanium implant is screwed in to the shaft of the femur and a second component connects between the implant and the prosthesis. A period of time is required to allow the implant to become fully attached to the bone, called osseointegration (OI), and be able to withstand applied load; then the prosthesis can be attached. The advantages of transfemoral osseointegration (TFOI) over conventional prosthetic sockets include better hip mobility, sitting comfort and prosthetic retention and fewer skin problems on the residual limb. However, due to the length of time required for OI to progress and to complete the rehabilitation exercises, it can take up to twelve months after implant insertion for an amputee to be able to load bear and to walk unaided. The long rehabilitation time is a significant disadvantage of TFOI and may be impeding the wider adoption of the technique. There is a need for a non-invasive method of assessing the degree of osseointegration between the bone and the implant. If such a method was capable of determining the progression of TFOI and assessing when the implant was able to withstand physiological load it could reduce the overall rehabilitation time. Vibration analysis has been suggested as a potential technique: it is a non destructive method of assessing the dynamic properties of a structure. Changes in the physical properties of a structure can be identified from changes in its dynamic properties. Consequently vibration analysis, both experimental and computational, has been used to assess bone fracture healing, prosthetic hip loosening and dental implant OI with varying degrees of success. More recently experimental vibration analysis has been used in TFOI. However further work is needed to assess the potential of the technique and fully characterise the femur-implant system. The overall aim of this study was to develop physical and computational models of the TFOI femur-implant system and use these models to investigate the feasibility of vibration analysis to detect the process of OI. Femur-implant physical models were developed and manufactured using synthetic materials to represent four key stages of OI development (identified from a physiological model), simulated using different interface conditions between the implant and femur. Experimental vibration analysis (modal analysis) was then conducted using the physical models. The femur-implant models, representing stage one to stage four of OI development, were excited and the modal parameters obtained over the range 0-5kHz. The results indicated the technique had limited capability in distinguishing between different interface conditions. The fundamental bending mode did not alter with interfacial changes. However higher modes were able to track chronological changes in interface condition by the change in natural frequency, although no one modal parameter could uniquely distinguish between each interface condition. The importance of the model boundary condition (how the model is constrained) was the key finding; variations in the boundary condition altered the modal parameters obtained. Therefore the boundary conditions need to be held constant between tests in order for the detected modal parameter changes to be attributed to interface condition changes. A three dimensional Finite Element (FE) model of the femur-implant model was then developed and used to explore the sensitivity of the modal parameters to more subtle interfacial and boundary condition changes. The FE model was created using the synthetic femur geometry and an approximation of the implant geometry. The natural frequencies of the FE model were found to match the experimental frequencies within 20% and the FE and experimental mode shapes were similar. Therefore the FE model was shown to successfully capture the dynamic response of the physical system. As was found with the experimental modal analysis, the fundamental bending mode of the FE model did not alter due to changes in interface elastic modulus. Axial and torsional modes were identified by the FE model that were not detected experimentally; the torsional mode exhibited the largest frequency change due to interfacial changes (103% between the lower and upper limits of the interface modulus range). Therefore the FE model provided additional information on the dynamic response of the system and was complementary to the experimental model. The small changes in natural frequency over a large range of interface region elastic moduli indicated the method may only be able to distinguish between early and late OI progression. The boundary conditions applied to the FE model influenced the modal parameters to a far greater extent than the interface condition variations. Therefore the FE model, as well as the experimental modal analysis, indicated that the boundary conditions need to be held constant between tests in order for the detected changes in modal parameters to be attributed to interface condition changes alone. The results of this study suggest that in a clinical setting it is unlikely that the in vivo boundary conditions of the amputated femur could be adequately controlled or replicated over time and consequently it is unlikely that any longitudinal change in frequency detected by the modal analysis technique could be attributed exclusively to changes at the femur-implant interface. Therefore further development of the modal analysis technique would require significant consideration of the clinical boundary conditions and investigation of modes other than the bending modes.

Real estate 2.0 : towards a value ecology?

This paper anatomises emerging developments in online community engagement in a major global industry: real estate. Economists argue that we are entering a ‘social network economy’ in which ‘complex social networks’ govern consumer choice and product value. In the light of this, organisations are shifting from thinking and behaving in the conventional ‘value chain’ model--in which exchanges between firms and customers are one-way only, from the firm to the consumer--to the ‘value ecology’ model, in which consumers and their networks become co-creators of the value of the product. This paper studies the way in which the global real estate industry is responding to this environment. This paper identifies three key areas in which online real estate ‘value ecology’ work is occurring: real estate social networks, games, and locative media / augmented reality applications. Uptake of real estate applications is, of course, user-driven: the paper not only highlights emerging innovations; it also identifies which of these innovations are actually being taken up by users, and the content contributed as a result. The paper thus provides a case study of one major industry’s shift into a web 2.0 communication model, focusing on emerging trends and issues.

Brisbane urban growth model : an integrated infrastructure management framework for Brisbane, Australia

In recent years, local government infrastructure management practices have evolved from conventional land use planning to more wide ranging and integrated urban growth and infrastructure management approaches. The roles and responsibilities of local government are no longer simply to manage daily operational functions of a city and provide basic infrastructure. Local governments are now required to undertake economic planning, manage urban growth; be involved in major infrastructure planning; and even engage in achieving sustainable development objectives. The Brisbane Urban Growth model has proven initially successful to ensure timely and coordinated delivery of urban infrastructure. This model may be the first step for many local governments to move toward an integrated, sustainable and effective infrastructure management.

Public-private partnerships in the promotion of sport and well-being : a governance model

This research focuses on exploring the links between sport, Indigenous self determination and deeper engagement within mainstream Australia especially with regard to the issue of promoting healthy lifestyles and the role of governance, through sport governance. Against all social, economic and health criteria Indigenous Australians are disadvantaged – despite government attention and financial input. It is well understood that education is a basis to better health, employment and lifestyle (Furneaux and Brown, 2008). However, many of the issues confronting Indigenous people have not responded to conventional government approaches based on program development and policy initiatives from single organisations (Ryan et al 2006). As a consequence, new approaches that both tap into the specific interests of Indigenous people and better engage them in the process of governance are required. The case material of the research focuses on the Australian Football League (AFL) Kickstart program.

Effects of dry density and grain size distribution on soil-water characteristic curves of sandy soils

The unsaturated soil mechanics is receiving increasing attention from researchers and as well as from practicing engineers. However, the requirement of sophisticated devices to measure unsaturated soil properties and time consumption have made the geotechnical engineers keep away from implication of the unsaturated soil mechanics for solving practical geotechnical problems. The application of the conventional laboratory devices with some modifications to measure unsaturated soil properties can promote the application of unsaturated soil mechanics into engineering practice. Therefore, in the present study, a conventional direct shear device was modified to measure unsaturated shear strength parameters at low suction. Specially, for the analysis of rain-induced slope failures, it is important to measure unsaturated shear strength parameters at low suction where slopes become unstable. The modified device was used to measure unsaturated shear strength of two silty soils at low suction values (0 ~ 50 kPa) that were achieved by following drying path and wetting path of soil-water characteristic curves (SWCCs) of soils. The results revealed that the internal friction angle of soil was not significantly affected by the suction and as well as the drying-wetting SWCCs of soils. The apparent cohesion of soil increased with a decreasing rate as the suction increased. Further, the apparent cohesion obtained from soil in wetting was greater than that obtained from soil in drying. Shear stress-shear displacement curves obtained from soil specimens subjected to the same net normal stress and different suction values showed a higher initial stiffness and a greater peak stress as the suction increased. In addition, it was observed that soil became more dilative with the increase of suction. A soil in wetting exhibited slightly higher peak shear stress and more contractive volume change behaviour than that of in drying at the same net normal stress and the suction.

Structural analysis of polymeric scaffolds by Micro-CT

The use of porous structures as tissue engineering scaffolds imposes demands on structural parameters such as porosity, pore size and interconnectivity. For the structural analysis of porous scaffolds, micro-computed tomography (μCT) is an ideal tool. μCT is a 3D X-ray imaging method that has several advantages over scanning electron microscopy (SEM) and other conventional characterisation techniques: • visualisation in 3D • quantitative results • non-destructiveness • minimal sample preparation

Designed tissue engineering scaffolds prepared by stereolithography

For the fabrication of tissue engineering scaffolds, the intended tissue formation process imposes requirements on the architecture. The chosen porosity often is a tradeoff between volume and surface area accessible to cells, and mechanical properties of the construct. Interconnectivity of the pores is essential for cell migration through the scaffold and for mass transport. Conventional techniques such as salt leaching often result in heterogeneous structures and do not allow for a precise control of the architecture. Stereolithography is a rapid prototyping method that can be utilised to make 3D constructs with high spatial control by radical photopolymerisation. In this study, a regular structure based on cyclic repetition of cell units were designed through CAD modelling.. One of these structures was built on a stereolithography apparatus (SLA). Furthermore, a polylactide-based resin was developed that can be applied in stereolithography. Polylactide has proven before to be a well-performing polymer in bone tissue engineering. The final objective in this study is to build newly designed PDLLA scaffolds with a precise SLA fabrication technique to study the effect of scaffold architecture on mechanical and biological properties.

“Now I know their secrets” : Kineikonic texts in the literacy classroom

Kineikonic texts – sites of the moving image – are increasingly prevalent with the rise of digital television, Web 2.0 tools, broadband Internet, and sophisticated mobile technologies. Digital practices are changing the shape of the literacy curriculum, calling for new metalanguages to describe digital and multimodal texts. This paper combines multiliteracies and functional approaches to map conventional and new textual features of a popular kineikonic text – the claymation movie. Enlivened with data from an ethnically diverse, Year 6 classroom, the author outlines filmic conventions to enable teachers and students to analyse and design movies

Landcorp Farming Limited : cultivating livestock, ideas and innovation

In 1987 Landcorp was corporatised as a state-owned enterprise under New Zealand's public sector reforms and began operating as a collection of farms located throughout the country. Twenty years later, Landcorp had established a record of careful land management, productivity growth and solid financial returns, transforming from a fledgling company into one of the country's largest farmers. Landcorp was a major agribusiness with assets of more than $1.4 billion, built on a culture of continuous improvement and an innovative approach to business. The challenge going forward was to continue growth without increasing land ownership : cultivating ideas to grow in less conventional ways. This case study examines the operations, development and innovative approach to business undertaken by Landcorp Farming Limited, concentrating on the challenges faced by the company to maintain profits and growth, and its strategic direction for the future.

The Australian response to climate change : business as usual or legal innovation?

Through international agreement to the United Nations Framework Convention on Climate Change and the Kyoto Protocol the global community has acknowledged that climate change is a global problem and sought to achieve reductions in global emissions, within a sufficient timeframe, to avoid dangerous anthropogenic interference with the climate system. The sheer magnitude of emissions reductions required within such an urgent timeframe presents a challenge to conventional regulatory approaches both internationally and within Australia. The phenomenon of climate change is temporally and geographically challenging and it is scientifically complex and uncertain. The purpose of this paper is to analyse the current Australian legal response to climate change and to examine the legal measures which have been proposed to promote carbon trading, energy efficiency, renewable energy, and carbon sequestration initiatives across Australia. As this paper illustrates, the current Australian approach is clearly ineffective and the law as it stands overwhelmingly inadequate to address Australia’s emissions and meet the enormity of the challenges posed by climate change. Consequently, the government should look towards a more effective legal framework to achieve rapid and urgent transformations in the selection of energy sources, energy use and sequestration initiatives across the Australian community.

Striving to realise the European idea : judging the news media’s accounts of how the Berlin Wall gave impetus to a new order across Europe

The 1990 European Community was taken by surprise, by the urgency of demands from the newly-elected Eastern European governments to become member countries. Those governments were honouring the mass social movement of the streets, the year before, demanding free elections and a liberal economic system associated with “Europe”. The mass movement had actually been accompanied by much activity within institutional politics, in Western Europe, the former “satellite” states, the Soviet Union and the United States, to set up new structures – with German reunification and an expanded EC as the centre-piece. This paper draws on the writer’s doctoral dissertation on mass media in the collapse of the Eastern bloc, focused on the Berlin Wall – documenting both public protests and institutional negotiations. For example the writer as a correspondent in Europe from that time, recounts interventions of the German Chancellor, Helmut Kohl, at a European summit in Paris nine days after the “Wall”, and separate negotiations with the French President, Francois Mitterrand -- on the reunification, and EU monetary union after 1992. Through such processes, the “European idea” would receive fresh impetus, though the EU which eventuated, came with many altered expectations. It is argued here that as a result of the shock of 1989, a “social” Europe can be seen emerging, as a shared experience of daily life -- especially among people born during the last two decades of European consolidation. The paper draws on the author’s major research, in four parts: (1) Field observation from the strategic vantage point of a news correspondent. This includes a treatment of evidence at the time, of the wishes and intentions of the mass public (including the unexpected drive to join the European Community), and those of governments, (e.g. thoughts of a “Tienanmen Square solution” in East Berlin, versus the non-intervention policies of the Soviet leader, Mikhail Gorbachev). (2) A review of coverage of the crisis of 1989 by major news media outlets, treated as a history of the process. (3) As a comparison, and a test of accuracy and analysis; a review of conventional histories of the crisis appearing a decade later.(4) A further review, and test, provided by journalists responsible for the coverage of the time, as reflection on practice – obtained from semi-structured interviews.

The effect of flocculants, shear, vacuum and depithing on the formation of thin bagasse pulp pads

The effect of bentonite micro-particles and cationic polyacrylamide (CPAM) on the filtration properties of bagasse pulp was investigated under shearing conditions. CPAM improves retention but the bentonite addition level must be optimised for further improvements in retention. A Dynamic Drainage Jar (‘Britt Jar’) was modified to allow bagasse pulp slurry to be subjected to vacuum allowing a thin pulp pad to be formed. Bagasse pulp which had had the majority of the fine fibre removed prior to pulping drained more quickly than a conventional bagasse pulp when vacuum was not applied, however this situation was reversed when vacuum was used. The flocculants continue to improve fibre retention under vacuum and shear conditions but with reduced effectiveness.

Advanced mathematical modelling and experimental investigation of new torque arms for shaft-mounted drives

Shaft-mounted gearboxes are widely used in industry. The torque arm that holds the reactive torque on the housing of the gearbox, if properly positioned creates the reactive force that lifts the gearbox and unloads the bearings of the output shaft. The shortcoming of these torque arms is that if the gearbox is reversed the direction of the reactive force on the torque arm changes to opposite and added to the weight of the gearbox overloads the bearings shortening their operating life. In this paper, a new patented design of torque arms that develop a controlled lifting force and counteract the weight of the gearbox regardless of the direction of the output shaft rotation is described. Several mathematical models of the conventional and new torque arms were developed and verified experimentally on a specially built test rig that enables modelling of the radial compliance of the gearbox bearings and elastic elements of the torque arms. Comparison showed a good agreement between theoretical and experimental results.

Operation and control of hybrid microgrid with angle droop controller

This paper compares the performance of two droop control schemes in a hybrid microgrid. With presence of both converter interfaced and inertial sources, the droop controller share power in a decentralized fashion. Both the droop controllers facilitate reactive power sharing based on voltage droop. However in frequency droop control, the real power sharing depends on the frequency, while in angle droop control, it depends on output voltage angle. For converter interfaced sources this reference voltage is tracked while for inertial DG, reference power for the prime mover is calculated from the reference angle with the proposed angle control scheme. This coordinated control scheme shows significant improvement in system performance. The comparison with the conventional frequency droop shows that the angle control scheme shares power with much lower frequency deviation. This is a significant improvement particularly in a frequent load changing scenario.

Designing participation : Reconsidering agile ridesharing with evolutionary distributed design thinking

This paper explores design thinking from the perspective of designing new forms of interaction to engage people in community change initiatives. A case study of an agile ridesharing system is presented. We describe the fundamental premise of the design approach taken—deploying simple interactive prototypes for use by communities in order to test the design hypothesis, evolve the design in use and grow the community of participants. Real-time use data and feedback from participants influences our understanding of the design approach and feeds into the gradual evolution of the prototype while it continues to be used. We then reflect upon this form of evolutionary distributed design thinking. In contrast to the conventional IT wisdom of building systems to automate ride matching and fare calculation using structured forms, our initial phase of design revealed a preference for informal messaging, negotiation and caution in the sharing of specific location information.