Bone tissue engineering : reconstruction of critical sized segmental bone defects in the ovine tibia

Well-established therapies for bone defects are restricted to bone grafts which face significant disadvantages (limited availability, donor site morbidity, insufficient integration). Therefore, the objective was to develop an alternative approach investigating the regenerative potential of medical grade polycaprolactone-tricalcium phosphate (mPCL-TCP) and silk-hydroxyapatite (silk-HA) scaffolds. Critical sized ovine tibial defects were created and stabilized. Defects were left untreated, reconstructed with autologous bone grafts (ABG) and mPCL-TCP or silk-HA scaffolds. Animals were observed for 12 weeks. X-ray analysis, torsion testing and quantitative computed tomography (CT) analyses were performed. Radiological analysis confirmed the critical nature of the defects. Full defect bridging occurred in the autograft and partial bridging in the mPCL-TCP group. Only little bone formation was observed with silk-HA scaffolds. Biomechanical testing revealed a higher torsional moment/stiffness (p < 0.05) and CT analysis a significantly higher amount of bone formation for the ABG group when compared to the silk-HA group. No significant difference was determined between the ABG and mPCL-TCP groups. The results of this study suggest that mPCL-TCP scaffolds combined can serve as an alternative to autologous bone grafting in long bone defect regeneration. The combination of mPCL-TCP with osteogenic cells or growth factors represents an attractive means to further enhance bone formation.

Numerical and experimental studies of cold-formed steel floor systems under standard fire conditions

Light gauge cold-formed steel frame (LSF) structures are increasingly used in industrial, commercial and residential buildings because of their non-combustibility, dimensional stability, and ease of installation. A floor-ceiling system is an example of its applications. LSF floor-ceiling systems must be designed to serve as fire compartment boundaries and provide adequate fire resistance. Fire rated floor-ceiling assemblies formed with new materials and construction methodologies have been increasingly used in buildings. However, limited research has been undertaken in the past and hence a thorough understanding of their fire resistance behaviour is not available. Recently a new composite panel in which an external insulation layer is used between two plasterboards has been developed at QUT to provide a higher fire rating to LSF floors under standard fire conditions. But its increased fire rating could not be determined using the currently available design methods. Research on LSF floor systems under fire conditions is relatively recent and the behaviour of floor joists and other components in the systems is not fully understood. The present design methods thus require the use of expensive fire protection materials to protect them from excessive heat increase during a fire. This leads to uneconomical and conservative designs. Fire rating of these floor systems is provided simply by adding more plasterboard sheets to the steel joists and such an approach is totally inefficient. Hence a detailed fire research study was undertaken into the structural and thermal performance of LSF floor systems including those protected by the new composite panel system using full scale fire tests and extensive numerical studies. Experimental study included both the conventional and the new steel floor-ceiling systems under structural and fire loads using a gas furnace designed to deliver heat in accordance with the standard time- temperature curve in AS 1530.4 (SA, 2005). Fire tests included the behavioural and deflection characteristics of LSF floor joists until failure as well as related time-temperature measurements across the section and along the length of all the specimens. Full scale fire tests have shown that the structural and thermal performance of externally insulated LSF floor system was superior than traditional LSF floors with or without cavity insulation. Therefore this research recommends the use of the new composite panel system for cold-formed LSF floor-ceiling systems. The numerical analyses of LSF floor joists were undertaken using the finite element program ABAQUS based on the measured time-temperature profiles obtained from fire tests under both steady state and transient state conditions. Mechanical properties at elevated temperatures were considered based on the equations proposed by Dolamune Kankanamge and Mahendran (2011). Finite element models were calibrated using the full scale test results and used to further provide a detailed understanding of the structural fire behaviour of the LSF floor-ceiling systems. The models also confirmed the superior performance of the new composite panel system. The validated model was then used in a detailed parametric study. Fire tests and the numerical studies showed that plasterboards provided sufficient lateral restraint to LSF floor joists until their failure. Hence only the section moment capacity of LSF floor joists subjected to local buckling effects was considered in this research. To predict the section moment capacity at elevated temperatures, the effective section modulus of joists at ambient temperature is generally considered adequate. However, this research has shown that it leads to considerable over- estimation of the local buckling capacity of joist subject to non-uniform temperature distributions under fire conditions. Therefore new simplified fire design rules were proposed for LSF floor joist to determine the section moment capacity at elevated temperature based on AS/NZS 4600 (SA, 2005), NAS (AISI, 2007) and Eurocode 3 Part 1.3 (ECS, 2006). The accuracy of the proposed fire design rules was verified with finite element analysis results. A spread sheet based design tool was also developed based on these design rules to predict the failure load ratio versus time, moment capacity versus time and temperature for various LSF floor configurations. Idealised time-temperature profiles of LSF floor joists were developed based on fire test measurements. They were used in the detailed parametric study to fully understand the structural and fire behaviour of LSF floor panels. Simple design rules were also proposed to predict both critical average joist temperatures and failure times (fire rating) of LSF floor systems with various floor configurations and structural parameters under any given load ratio. Findings from this research have led to a comprehensive understanding of the structural and fire behaviour of LSF floor systems including those protected by the new composite panel, and simple design methods. These design rules were proposed within the guidelines of the Australian/New Zealand, American and European cold- formed steel structures standard codes of practice. These may also lead to further improvements to fire resistance through suitable modifications to the current composite panel system.

Selective essays in competitive environments

This thesis is a collection of essays that utilises descriptive and empirical tools to examine competitive environments such as in academia, superrich and sport. The essays capture different aspects of the winner-take-all phenomenon by looking at citation and publication inequality in a top tier economics journal namely the American Economic Review. How globalisation and corruption influence the accumulation of extraordinary wealth and finally, how in a fairly equal competition, that is in the National Rugby League in Australia, wearing red shirts could lead to a comparative advantage and hence, tip the balance between winning and losing. The results within academia indicate that a highly unequal distribution exist, in which only a few top authors or institutions produce the majority of output. Furthermore, the results obtained in the superrich environment indicate that corruption and globalisation enhances the accumulation of extraordinary wealth. Finally, the results in the sport environment are mixed. While we find support for a positive effect of wearing red jerseys in our descriptive analysis, we find a negative effect when we control at the team level. However, when we investigate the relative difference in the degree of redness between home and away team, we find a quite strong positive effect of wearing red shirts even after controlling at the team level.

Moments of action provide insight into critical times for advection–diffusion–reaction processes

In 2010 Berezhkovskii and coworkers introduced the concept of local accumulation time (LAT) as a finite measure of the time required for the transient solution of a reaction diffusion equation to effectively reach steady state(Biophys J. 99, L59 (2010); Phys Rev E. 83, 051906 (2011)). Berezhkovskii’s approach is a particular application of the concept of mean action time (MAT) that was introduced previously by McNabb (IMA J Appl Math. 47, 193 (1991)). Here, we generalize these previous results by presenting a framework to calculate the MAT, as well as the higher moments, which we call the moments of action. The second moment is the variance of action time; the third moment is related to the skew of action time, and so on. We consider a general transition from some initial condition to an associated steady state for a one–dimensional linear advection–diffusion–reaction partial differential equation(PDE). Our results indicate that it is possible to solve for the moments of action exactly without requiring the transient solution of the PDE. We present specific examples that highlight potential weaknesses of previous studies that have considered the MAT alone without considering higher moments. Finally, we also provide a meaningful interpretation of the moments of action by presenting simulation results from a discrete random walk model together with some analysis of the particle lifetime distribution. This work shows that the moments of action are identical to the moments of the particle lifetime distribution for certain transitions.

Attunement to haptic information helps skilled performers select implements for striking a ball in cricket

This study examined the perceptual attunement of relatively skilled individuals to physical properties of striking implements in the sport of cricket. We also sought to assess whether utilising bats of different physical properties influenced performance of a specific striking action: the front foot straight drive. Eleven, skilled male cricketers (mean age = 16.6 ± 0.3 years) from an elite school cricket development programme consented to participate in the study. Whist blindfolded, participants wielded six bats exhibiting different mass and moment of inertia (MOI) characteristics and were asked to identify their three most preferred bats for hitting a ball to a maximum distance by performing a front foot straight drive (a common shot in cricket). Next, participants actually attempted to hit balls projected from a ball machine using each of the six bat configurations to enable kinematic analysis of front foot straight drive performance with each implement. Results revealed that, on first choice, the two bats with the smallest mass and MOI values (1 and 2) were most preferred by almost two-thirds (63.7%) of the participants. Kinematic analysis of movement patterns revealed that bat velocity, step length and bat-ball contact position measures significantly differed between bats. Data revealed how skilled youth cricketers were attuned to the different bat characteristics and harnessed movement system degeneracy to perform this complex interceptive action.

The gender wage gap : a comparison of Australia and Canada

Using data from the 1989 Canadian Labour Market Activity Survey and, for Australia, the 1989-90 Income Distribution Survey, the authors investigate the reasons for the significantly lower gender wage gap in Australia than in Canada. Key similarities and differences between these two countries, the authors argue, make them a good basis for a "natural experiment" to investigate the effects of different labor market institutions. In particular, Australia has a stronger union movement and a greater degree of centralization in wage determination than Canada, and most of its workers are covered by legally binding minimum working conditions. The authors conclude that several differences between the countries in labor market structure-notably, a lower rate of return to education, a lower rate of return to labor market experience, and a lower level of wage inequality in Australia than in Canada- are largely responsible for the smaller gender wage gap in Australia.

Return distribution predictability and its implications for portfolio selection

The inquiries to return predictability are traditionally limited to conditional mean, while literature on portfolio selection is replete with moment-based analysis with up to the fourth moment being considered. This paper develops a distribution-based framework for both return prediction and portfolio selection. More specifically, a time-varying return distribution is modeled through quantile regressions and copulas, using quantile regressions to extract information in marginal distributions and copulas to capture dependence structure. A preference function which captures higher moments is proposed for portfolio selection. An empirical application highlights the additional information provided by the distributional approach which cannot be captured by the traditional moment-based methods.

Beat phenomena in metal nanowires, and their implications for resonance-based elastic property measurements

The elastic properties of 1D nanostructures such as nanowires are often measured experimentally through actuation of the nanowire at its resonance frequency, and then relating the resonance frequency to the elastic stiffness using elementary beam theory. In the present work, we utilize large scale molecular dynamics simulations to report a novel beat phenomenon in [110]oriented Ag nanowires. The beat phenomenon is found to arise from the asymmetry of the lattice spacing in the orthogonal elementary directions of the [110] nanowire, i.e. the [-110] and [001] directions, which results in two different principal moments of inertia. Because of this, actuations imposed along any other direction are found to decompose into two orthogonal vibrational components based on the actuation angle relative to these two elementary directions, with this phenomenon being generalizable to <110> FCC nanowires of different materials (Cu, Au, Ni, Pd and Pt). The beat phenomenon is explained using a discrete moment of inertia model based on the hard sphere assumption, the model is utilized to show that surface effects enhance the beat phenomenon, while the effect is reduced with increasing nanowires cross-sectional size or aspect ratio. Most importantly, due to the existence of the beat phenomena, we demonstrate that in resonance experiments only a single frequency component is expected to be observed, particularly when the damping ratio is relatively large or very small. Furthermore, for a large range of actuation angles, the lower frequency is more likely to be detected than the higher one, which implies that experimental predictions of Young’s modulus obtained from resonance may in fact be under predictions. The present study therefore has significant implications for experimental interpretations of Young’s modulus as obtained via resonance testing.

Talk and web searching in an early years classroom

Recent Australian early childhood policy and curriculum guidelines promoting the use of technologies invite investigations of young children’s practices in classrooms. This study examined the practices of one preparatory year classroom, to show teacher and child interactions as they engaged in Web searching. The study investigated the in situ practices of the teacher and children to show how they accomplished the Web search. The data corpus consists of eight hours of videorecorded interactions over three days where children and teachers engaged in Web searching. One episode was selected that showed a teacher and two children undertaking a Web search. The episode is shown to consist of four phases: deciding on a new search subject, inputting the search query, considering the result options, and exploring the selected result. The sociological perspectives of ethnomethodology and conversation analysis were employed as the conceptual and methodological frameworks of the study, to analyse the video-recorded teacher and child interactions as they co-constructed a Web search. Ethnomethodology is concerned with how people make ‘sense’ in everyday interactions, and conversation analysis focuses on the sequential features of interaction to show how the interaction unfolds moment by moment. This extended single case analysis showed how the Web search was accomplished over multiple turns, and how the children and teacher collaboratively engaged in talk. There are four main findings. The first was that Web searching featured sustained teacher-child interaction, requiring a particular sort of classroom organisation to enable the teacher to work in this sustained way. The second finding was that the teacher’s actions recognised the children’s interactional competence in situ, orchestrating an interactional climate where everyone was heard. The third finding was that the teacher drew upon a range of interactional resources designed to progress the activity at hand, that of accomplishing the Web search. The teacher drew upon the interactional resources of interrogatives, discourse markers, and multi-unit turns during the Web search, and these assisted the teacher and children to co-construct their discussion, decide upon and co-ordinate their future actions, and accomplish the Web search in a timely way. The fourth finding explicates how particular social and pedagogic orders are accomplished through talk, where children collaborated with each other and with the teacher to complete the Web search. The study makes three key recommendations for the field of early childhood education. The study’s first recommendation is that fine-grained transcription and analysis of interaction aids in understanding interactional practices of Web searching. This study offers material for use in professional development, such as using transcribed and videorecorded interactions to highlight how teachers strategically engage with children, that is, how talk works in classroom settings. Another strategy is to focus on the social interactions of members engaging in Web searches, which is likely to be of interest to teachers as they work to engage with children in an increasingly online environment. The second recommendation involves classroom organisation; how teachers consider and plan for extended periods of time for Web searching, and how teachers accommodate children’s prior knowledge of Web searching in their classrooms. The third recommendation is in relation to future empirical research, with suggested possible topics focusing on the social interactions of children as they engage with peers as they Web search, as well as investigations of techno-literacy skills as children use the Internet in the early years.

Behavioural beliefs concerning gender and high-risk sexual behaviours in the context of HIV/AIDS in PNG : views from within teacher education

Education is often viewed as a key approach to address sexual-health issues; the current concern is the burgeoning HIV/AIDS epidemic. This ethnographic study investigates the gender practices associated with high-risk sexual behaviour in Papua New Guinea as viewed by educators there. A number of practices, including gender inequality and associated sexual behaviours have been highlighted by male and female participants as escalating PNG’s HIV/AIDS epidemic. The study finds that although participants were well-informed concerning HIV/AIDS, they had varying beliefs concerning the prevailing gender/sexual issues involved in escalating highrisk behaviour and how to address the problem. The study further examines the behavioural beliefs and intentions of the educators themselves. Subsequently, within the data a number of underpinning factors, pertaining to gender, education and life experience, were found to be related to the behaviour beliefs and intentions of participants towards embracing change with regard to behaviours associated with gender equality in PNG. These factors appeared to encourage participants to adopt healthier gender and sexual behavioural intentions and, arguably, could provide the basis for ways to help address the gender inequality and high-risk behaviours associated with HIV/AIDS in PNG.

Inequities, alternatives and future directions : inside perspectives of Indigenous sentencing in Queensland

In Australia, sentencing researchers have generally focussed on whether there is statistical equality/inequality in outcomes by reference to Indigenous status. However, contextualising the sentencing process requires us to move away from a reliance on statistical analyses alone, as this approach cannot tell us whether sentencing is an equitable process for Indigenous people. Consultation with those working at the sentencing ‘coal face’ provides valuable insight into the nexus between Indigenous status and sentencing. This article reports the main themes from surveys of the judiciary and prosecutors, and focus groups of Community Justice Groups undertaken in Queensland. The aim is to understand better the sentencing process for Indigenous Queenslanders. Results suggest that while there have been some positive developments in sentencing (e.g. the Murri Court, Community Justice Groups) Indigenous offenders still face a number of inequities.

Architecture post mortem : the diastolic architecture of decline, dystopia, and death

Architecture Post Mortem surveys architecture’s encounter with death, decline, and ruination following late capitalism. As the world moves closer to an economic abyss that many perceive to be the death of capital, contraction and crisis are no longer mere phases of normal market fluctuations, but rather the irruption of the unconscious of ideology itself. Post mortem is that historical moment wherein architecture’s symbolic contract with capital is put on stage, naked to all. Architecture is not irrelevant to fiscal and political contagion as is commonly believed; it is the victim and penetrating analytical agent of the current crisis. As the very apparatus for modernity’s guilt and unfulfilled drives-modernity’s debt-architecture is that ideological element that functions as a master signifier of its own destruction, ordering all other signifiers and modes of signification beneath it. It is under these conditions that architecture theory has retreated to an “Alamo” of history, a final desert outpost where history has been asked to transcend itself. For architecture’s hoped-for utopia always involves an apocalypse. This timely collection of essays reformulates architecture’s relation to modernity via the operational death-drive: architecture is but a passage between life and death. This collection includes essays by Kazi K. Ashraf, David Bertolini, Simone Brott, Peggy Deamer, Didem Ekici, Paul Emmons, Donald Kunze, Todd McGowan, Gevork Hartoonian, Nadir Lahiji, Erika Naginski, and Dennis Maher. Contents: Introduction: ‘the way things are’, Donald Kunze; Driven into the public: the psychic constitution of space, Todd McGowan; Dead or alive in Joburg, Simone Brott; Building in-between the two deaths: a post mortem manifesto, Nadir Lahiji; Kant, Sade, ethics and architecture, David Bertolini; Post mortem: building deconstruction, Kazi K. Ashraf; The slow-fast architecture of love in the ruins, Donald Kunze; Progress: re-building the ruins of architecture, Gevork Hartoonian; Adrian Stokes: surface suicide, Peggy Deamer; A window to the soul: depth in the early modern section drawing, Paul Emmons; Preliminary thoughts on Piranesi and Vico, Erika Naginski; architectural asceticism and austerity, Didem Ekici; 900 miles to Paradise, and other afterlives of architecture, Dennis Maher; Index.

Framing sexual harassment through media representations

This article examines mainstream news media texts reporting sexual harassment in four industrialized countries. The study first identifies the aspects of sexual harassment cases considered newsworthy by asking how the media texts characterize such cases. Second, the study illuminates the discourses evident in these texts, which are theorized as a mode by which understandings of workplace gender (in)equality shape, and are shaped by, individuals, organizations and the community. The analysis reveals that the media most frequently reports “classic” sexual harassment and emphasizes scandalous allegations and overtly sexualized conduct. The hegemony of a discourse of sexual harassment as an individualized problem of inappropriate employee behavior is also evident. By contrast, discourses presenting sexual harassment as a systemic issue, or as symptomatic of broader gender inequality, are less frequent. We argue that these media representations limit opportunities to frame sexual harassment as dynamic, complex, and part of the practice of gendering in and beyond organizational boundaries.

Near-Wall Turbulent Pressure Diffusion Modeling and Influence in Three-Dimensional Secondary Flows

The purpose of this paper is to develop a second-moment closure with a near-wall turbulent pressure diffusion model for three-dimensional complex flows, and to evaluate the influence of the turbulent diffusion term on the prediction of detached and secondary flows. A complete turbulent diffusion model including a near-wall turbulent pressure diffusion closure for the slow part was developed based on the tensorial form of Lumley and included in a re-calibrated wall-normal-free Reynolds-stress model developed by Gerolymos and Vallet. The proposed model was validated against several one-, two, and three-dimensional complex flows.