Incorporating spatial correlations into multispecies mean-field models

In biology, we frequently observe different species existing within the same environment. For example, there are many cell types in a tumour, or different animal species may occupy a given habitat. In modelling interactions between such species, we often make use of the mean field approximation, whereby spatial correlations between the locations of individuals are neglected. Whilst this approximation holds in certain situations, this is not always the case, and care must be taken to ensure the mean field approximation is only used in appropriate settings. In circumstances where the mean field approximation is unsuitable we need to include information on the spatial distributions of individuals, which is not a simple task. In this paper we provide a method that overcomes many of the failures of the mean field approximation for an on-lattice volume-excluding birth-death-movement process with multiple species. We explicitly take into account spatial information on the distribution of individuals by including partial differential equation descriptions of lattice site occupancy correlations. We demonstrate how to derive these equations for the multi-species case, and show results specific to a two-species problem. We compare averaged discrete results to both the mean field approximation and our improved method which incorporates spatial correlations. We note that the mean field approximation fails dramatically in some cases, predicting very different behaviour from that seen upon averaging multiple realisations of the discrete system. In contrast, our improved method provides excellent agreement with the averaged discrete behaviour in all cases, thus providing a more reliable modelling framework. Furthermore, our method is tractable as the resulting partial differential equations can be solved efficiently using standard numerical techniques.

Sessional Academic Success : A distributed framework for academic support and development

With approximately half of Australian university teaching now performed by sessional academics, there has been growing recognition of the contribution they make to student learning. At the same time, sector-wide research and institutional audits continue to raise concerns about academic development, quality assurance, recognition and belonging. In response, universities have increasingly begun to offer academic development programs for sessional academics. However, such programs may be centrally delivered, generic in nature, and contained within the moment of delivery, while the Faculty contexts and cultures that sessional academics work within are diverse, and the need for support unfolds in ad-hoc and often unpredictable ways. In this paper we present the Sessional Academic Success (SAS) program–a new framework that complements and extends the central academic development program for sessional academic staff at Queensland University of Technology. This program recognises that experienced sessional academics have much to contribute to the advancement of learning and teaching, and harnesses their expertise to provide school-based academic development opportunities, peer-to-peer support, and locally contextualized community building. We describe the program’s implementation and explain how Sessional Academic Success Advisors (SASAs) are employed, trained and supported to provide advice and mentorship and, through a co-design methodology, to develop local development opportunities and communities of teaching practice within their schools. Besides anticipated benefits to new sessional academics in terms of timely and contextual support and improved sense of belonging, we explain how SAS provides a pathway for building leadership capacity and academic advancement for experienced sessional academics. We take a collaborative, dialogic and reflective practice approach to this paper, interlacing insights from the Associate Director, Academic: Sessional Development who designed the program, and two Sessional Academic Success Advisors who have piloted it within their schools.

A simplified approach for calculating the moments of action for linear reaction-diffusion equations

The mean action time is the mean of a probability density function that can be interpreted as a critical time, which is a finite estimate of the time taken for the transient solution of a reaction-diffusion equation to effectively reach steady state. For high-variance distributions, the mean action time under-approximates the critical time since it neglects to account for the spread about the mean. We can improve our estimate of the critical time by calculating the higher moments of the probability density function, called the moments of action, which provide additional information regarding the spread about the mean. Existing methods for calculating the nth moment of action require the solution of n nonhomogeneous boundary value problems which can be difficult and tedious to solve exactly. Here we present a simplified approach using Laplace transforms which allows us to calculate the nth moment of action without solving this family of boundary value problems and also without solving for the transient solution of the underlying reaction-diffusion problem. We demonstrate the generality of our method by calculating exact expressions for the moments of action for three problems from the biophysics literature. While the first problem we consider can be solved using existing methods, the second problem, which is readily solved using our approach, is intractable using previous techniques. The third problem illustrates how the Laplace transform approach can be used to study coupled linear reaction-diffusion equations.

Virtual worlds in Australian and New Zealand higher education : remembering the past, understanding the present and imagining the future

3D virtual reality, including the current generation of multi-user virtual worlds, has had a long history of use in education and training, and it experienced a surge of renewed interest with the advent of Second Life in 2003. What followed shortly after were several years marked by considerable hype around the use of virtual worlds for teaching, learning and research in higher education. For the moment, uptake of the technology seems to have plateaued, with academics either maintaining the status quo and continuing to use virtual worlds as they have previously done or choosing to opt out altogether. This paper presents a brief review of the use of virtual worlds in the Australian and New Zealand higher education sector in the past and reports on its use in the sector at the present time, based on input from members of the Australian and New Zealand Virtual Worlds Working Group. It then adopts a forward-looking perspective amid the current climate of uncertainty, musing on future directions and offering suggestions for potential new applications in light of recent technological developments and innovations in the area.

The recovery concept and crisis intervention : time for a revolution in the realm of acute psychiatric care

“Mental illness is a tough illness to survive, it is incurable but manageable. Living with the illness when at its full potency can disrupt your life at any moment.” Intensive care for patients experiencing acute psychiatric distress is an essential yet complex part of mental health services as a whole system. Psychiatric intensive care units remain a source of controversy; despite promising developments to health services incorporating recovery goals and processes outlined by people with a mental illness themselves. In past decades changes in the provision of mental health services have focused on the restoration of a meaningful and empowered life with choice and hope as a defining attribute of recovery. Yet, what does recovery mean and how are recovery principles accomplished in psychiatric intensive care arrangements for someone experiencing acute psychiatric distress?

Experimental studies of hollow flange channel beams subject to combined bending and shear actions

This paper presents the details of an experimental study of a cold-formed steel hollow flange channel beam known as LiteSteel Beam (LSB) subject to combined bending and shear actions. The LSB sections are produced by a patented manufacturing process involving simultaneous cold-forming and electric resistance welding. Due to the geometry of the LSB, as well as its unique residual stress characteristics and initial geometric imperfections resultant of manufacturing processes, much of the existing research for common cold-formed steel sections is not directly applicable to LSB. Experimental and numerical studies have been carried out to evaluate the behaviour and design of LSBs subject to pure bending actions and predominant shear actions. To date, however, no investigation has been conducted into the strength of LSB sections under combined bending and shear actions. Combined bending and shear is especially prevalent at the supports of continuous span and cantilever beams, where the interaction of high shear force and bending moment can reduce the capacity of a section to well below that for the same section subject only to pure shear or moment. Hence experimental studies were conducted to assess the combined bending and shear behaviour and strengths of LSBs. Eighteen tests were conducted and the results were compared with current AS/NZS 4600 and AS 4100 design rules. AS/NZS 4600 design rules were shown to grossly underestimate the combined bending and shear capacities of LSBs and hence two lower bound design equations were proposed based on experimental results. Use of these equations will significantly improve the confidence and cost-effectiveness of designing LSBs for combined bending and shear actions.

Popular Appeal : Books and Films in Contemporary Youth Culture

Now is an opportune moment to consider the shifts in youth and popular culture that are signalled by texts that are being read and viewed by young people. In a world seemingly compromised by climate change, political and religious upheavals and economic irresponsibility, and at a time of fundamental social change, young people are devouring fictional texts that focus on the edges of identity, the points of transition and rupture, and the assumption of new and hybrid identities. This book draws on a range of international texts to address these issues, and to examine the ways in which key popular genres in the contemporary market for young people are being re-defined and re-positioned in the light of urgent questions about the environment, identity, one's place in the world, and the fragile nature of the world itself. The key questions are: what are the shifts and changes in youth culture that are identified by the market and by what young people read and view? How do these texts negotiate the addressing of significant questions relating to the world today? Why are these texts so popular with young people? What are the most popular genres in contemporary best-sellers and films? Do these texts have a global appeal, and, if so, why? These over-arching themes and ideas are presented as a collection of inter-related essays exploring a rich variety of forms and styles from graphic novels to urban realism, from fantasy to dystopian writing, from epic narratives to television musicals. The subjects and themes discussed here reveal the quite remarkable diversity of issues that arise in youth fiction and the variety of fictional forms in which they are explored. Once seen as not as important as adult fiction, this book clearly demonstrates that youth fiction (and the popular appeal of this fiction) is complex, durable and far-reaching in its scope.

Structure, magnetism and colour in simple bis­(phosphine)nickel(II) dihalide complexes : an experimental and theoretical investigation

The complex [1,2-bis­(di-tert-butyl­phosphan­yl)ethane-[kappa]2P,P']di­iodido­nickel(II), [NiI2(C18H40P2] or (dtbpe-[kappa]2P)NiI2, [dtbpe is 1,2-bis­(di-tert-butyl­phosphan­yl)ethane], is bright blue-green in the solid state and in solution, but, contrary to the structure predicted for a blue or green nickel(II) bis­(phos­phine) complex, it is found to be close to square planar in the solid state. The solution structure is deduced to be similar, because the optical spectra measured in solution and in the solid state contain similar absorptions. In solution at room temperature, no 31P{1H} NMR resonance is observed, but the very small solid-state magnetic moment at temperatures down to 4 K indicates that the weak paramagnetism of this nickel(II) complex can be ascribed to temperature independent paramagnetism, and that the complex has no unpaired electrons. The red [1,2-bis­(di-tert-butyl­phosphan­yl)ethane-[kappa]2P,P']di­chlorido­nickel(II), [NiCl2(C18H40P2] or (dtbpe-[kappa]2P)NiCl2, is very close to square planar and very weakly paramagnetic in the solid state and in solution, while the maroon [1,2-bis­(di-tert-butyl­phosphan­yl)ethane-[kappa]2P,P']di­bromido­nickel(II), [NiBr2(C18H40P2] or (dtbpe-[kappa]2P)NiBr2, is isostructural with the diiodide in the solid state, and displays paramagnetism inter­mediate between that of the dichloride and the diiodide in the solid state and in solution. Density functional calculations demonstrate that distortion from an ideal square plane for these complexes occurs on a flat potential energy surface. The calculations reproduce the observed structures and colours, and explain the trends observed for these and similar complexes. Although theoretical investigation identified magnetic-dipole-allowed excitations that are characteristic for temperature-independent paramagnetism (TIP), theory predicts the mol­ecules to be diamagnetic.

The vanishing endpoint of settler colonialism

In this paper, we interrogate the way that narratives about the unfolding of settler colonialism through time are encoded in recent Australian Indigenous policy frameworks. We argue that the postcolonial image of a single transformative moment of radical political break is embedded in Australian policy frameworks, but is deployed in ways that fuse this idea with the moment of colonial completion and in so doing assist the colonial project. By merging the moment of decolonisation and the moment of colonial completion, temporal narratives mobilise conservative and progressive settler voices towards colonial goals. We identify three recent policy approaches: reconciliation, neoliberal contractualism and intervention, and interrogate the narratives of the present and future that they reflect and deploy. We argue these unacknowledged stories of the colonial future must be contested, so that debates about how settler and Indigenous people might live together differently across time are not foreclosed.

Primary stability of two uncemented acetabular components of different geometry : hemispherical or peripherally enhanced?

Objective This study compared the primary stability of two commercially available acetabular components from the same manufacturer, which differ only in geometry; a hemispherical and a peripherally enhanced design (peripheral self-locking (PSL)). The objective was to determine whether altered geometry resulted in better primary stability. Methods Acetabular components were seated with 0.8 mm to 2 mm interference fits in reamed polyethylene bone substrate of two different densities (0.22 g/cm3 and 0.45 g/cm3). The primary stability of each component design was investigated by measuring the peak failure load during uniaxial pull-out and tangential lever-out tests. Results There was no statistically significant difference in seating force (p = 0.104) or primary stability (pull-out p = 0.171, lever-out p = 0.087) of the two components in the low-density substrate. Similarly, in the high-density substrate, there was no statistically significant difference in the peak pull-out force (p = 0.154) or lever-out moment (p = 0.574) between the designs. However, the PSL component required a significantly higher seating force thanthe hemispherical cup in the high-density bone analogue (p = 0.006). Conclusions Higher seating forces associated with the PSL design may result in inadequate seating and increased risk of component malpositioning or acetabular fracture in the intra-operative setting in high-density bone stock. Our results, if translated clinically, suggest that a purely hemispherical geometry may have an advantage over a peripherally enhanced geometry in high density bone stock.

Agreement between temporal and spatial gait parameters from an instrumented walkway and treadmill system at matched walking speed

Background Commercially available instrumented treadmill systems that provide continuous measures of temporospatial gait parameters have recently become available for clinical gait analysis. This study evaluated the level of agreement between temporospatial gait parameters derived from a new instrumented treadmill, which incorporated a capacitance-based pressure array, with those measured by a conventional instrumented walkway (criterion standard). Methods Temporospatial gait parameters were estimated from 39 healthy adults while walking over an instrumented walkway (GAITRite®) and instrumented treadmill system (Zebris) at matched speed. Differences in temporospatial parameters derived from the two systems were evaluated using repeated measures ANOVA models. Pearson-product-moment correlations were used to investigate relationships between variables measured by each system. Agreement was assessed by calculating the bias and 95% limits of agreement. Results All temporospatial parameters measured via the instrumented walkway were significantly different from those obtained from the instrumented treadmill (P < .01). Temporospatial parameters derived from the two systems were highly correlated (r, 0.79–0.95). The 95% limits of agreement for temporal parameters were typically less than ±2% of gait cycle duration. However, 95% limits of agreement for spatial measures were as much as ±5 cm. Conclusions Differences in temporospatial parameters between systems were small but statistically significant and of similar magnitude to changes reported between shod and unshod gait in healthy young adults. Temporospatial parameters derived from an instrumented treadmill, therefore, are not representative of those obtained from an instrumented walkway and should not be interpreted with reference to literature on overground walking.

Learner-focused evaluation cycles : facilitating learning using feedforward, concurrent and feedback evaluation

There is a growing trend to offer students learning opportunities that are flexible, innovative and engaging. As educators embrace student-centred agile teaching and learning methodologies, which require continuous reflection and adaptation, the need to evaluate students’ learning in a timely manner has become more pressing. Conventional evaluation surveys currently dominate the evaluation landscape internationally, despite recognition that they are insufficient to effectively evaluate curriculum and teaching quality. Surveys often: (1) fail to address the issues for which educators need feedback, (2) constrain student voice, (3) have low response rates and (4) occur too late to benefit current students. Consequently, this paper explores principles of effective feedback to propose a framework for learner-focused evaluation. We apply a three-stage control model, involving feedforward, concurrent and feedback evaluation, to investigate the intersection of assessment and evaluation in agile learning environments. We conclude that learner-focused evaluation cycles can be used to guide action so that evaluation is not undertaken simply for the benefit of future offerings, but rather to benefit current students by allowing ‘real-time’ learning activities to be adapted in the moment. As a result, students become co-producers of learning and evaluation becomes a meaningful, responsive dialogue between students and their instructors.

The Sessional Academic Success (SAS) project

The Sessional Academic Success (SAS) project is a sustainable, distributed model for supporting sessional staff at QUT. Developed by the Learning and Teaching Unit. SAS complements our Sessional Academic Program (SAP): a sequence of formal academic development workshops explained in complementary nomination. SAS recognises that while these programs are very well received and a crucial aspect of preparing and advancing sessional teachers, they are necessarily encapsulated in the moment of their delivery and are generic, as they address all faculties (with their varied cultures, processes and pedagogies). The SAS project extends this formal, centrally offered activity into local, ‘just in time’, ongoing support within schools. It takes a distributed leadership approach. Experienced sessional academics are recruited and employed as Sessional Academic Success Advisors (SASAs). They provide sessional staff in their schools with contextually specific, needs based, peer-to-peer development opportunities; one-on-one advice on classroom management and strategies for success; and help to trouble-shoot challenges. The SASAs are trained by the Learning and Teaching Unit co-ordinator, and ongoing support is provided centrally and by school-based co-ordinators. This team approach situates the SASAs at the centre of an organisation map (see diagram of support relationships below). The SAS project aims to support sessional staff in their professional development by: • Offering contextual, needs-based support at school level by harnessing local expertise; • Providing further development opportunities that are local and focal; SAS aims to retain Sessional Staff by: • Responding to self-nominated requests for support and ‘just in time’, safe and reliable advice in times of need; • Building sessional staff confidence through help with dealing with challenges from a trusted peer; • Building a supportive academic community for sessional staff, which helps them feel a part of faculty life, and a community of teaching practice. SAS aims to support sessional staff in the development of academic teaching careers by: • Recognising the capacity of experienced sessional staff to support their peers in ways that are unique, valuable and valued and providing the agency to do so; • Providing career advancement and leadership opportunities for sessional staff. SAS takes unique approaches within each school using strategies such as: • Welcomes and schools orientation by SASAs; • Regular check ins; face-to-face advice and online support; • Compiling local resources to complement university wide resources. • Sessional-to-sessional ‘just in time’ training (eg. assessment and marking when marking commences); • Peer feedback and mentoring (the opportunities to sit in more experiences sessionals’ classes; • Sessional staff awards (nominated by students); • Communities of practice to discuss topics and issues with a view to (and support for) publishing on learning and teaching. In these ways, SASAs complement support offered by unit coordinators, administrators, and the Learning and Teaching Unit. Pairing senior and ‘understudy’ advisors ensures a line of succession, sustainability and continuity. A pilot program commenced in 2012 involving three schools (Psychology and Social Work; Electrical Engineering and Computer Science; Media, Entertainment and Creative Arts). It will be expanded across schools in 2013.

The relationship between kurtosis- and envelope-based indexes for the diagnostic of rolling element bearings

The coupling of kurtosis based-indexes and envelope analysis represents one of the most successful and widespread procedures for the diagnostics of incipient faults on rolling element bearings. Kurtosis-based indexes are often used to select the proper demodulation band for the application of envelope-based techniques. Kurtosis itself, in slightly different formulations, is applied for the prognostic and condition monitoring of rolling element bearings, as a standalone tool for a fast indication of the development of faults. This paper shows for the first time the strong analytical connection which holds for these two families of indexes. In particular, analytical identities are shown for the squared envelope spectrum (SES) and the kurtosis of the corresponding band-pass filtered analytic signal. In particular, it is demonstrated how the sum of the peaks in the SES corresponds to the raw 4th order moment. The analytical results show as well a link with an another signal processing technique: the cepstrum pre-whitening, recently used in bearing diagnostics. The analytical results are the basis for the discussion on an optimal indicator for the choice of the demodulation band, the ratio of cyclic content (RCC), which endows the kurtosis with selectivity in the cyclic frequency domain and whose performance is compared with more traditional kurtosis-based indicators such as the protrugram. A benchmark, performed on numerical simulations and experimental data coming from two different test-rigs, proves the superior effectiveness of such an indicator. Finally a short introduction to the potential offered by the newly proposed index in the field of prognostics is given in an additional experimental example. In particular the RCC is tested on experimental data collected on an endurance bearing test-rig, showing its ability to follow the development of the damage with a single numerical index.

Transnational Whiteness Matters

"The collection contributes to transnational whiteness debates through theoretically informed readings of historical and contemporary texts by established and emerging scholars in the field of critical whiteness studies. From a wide range of disciplinary perspectives, the book traces continuity and change in the cultural production of white virtue within texts, from the proud colonial moment through to neoliberalism and the global war on terror in the twenty-first century. Read together, these chapters convey a complex understanding of how transnational whiteness travels and manifests itself within different political and cultural contexts. Some chapters address political, legal and constitutional aspects of whiteness while others explore media representations and popular cultural texts and practices. The book also contains valuable historical studies documenting how whiteness is insinuated within the texts produced, circulated and reproduced in specific cultural and national locations."--Google eBook