13,024 results for The University of Auckland Library, Journal article

  • The Time Course Of Calcium Current Between Epi And Endo Cardiomyocytes Contributes To The Transmural Heterogeneity Of Action Potential

    Kim, N; Cannell, Mark; Hunter, Peter (2009)

    Journal article
    The University of Auckland Library

    View record details
  • Toward a VPH/Physiome ToolKit

    Garny, A; Cooper, J; Hunter, Peter (2010-03)

    Journal article
    The University of Auckland Library

    The Physiome Project was officially launched in 1997 and has since brought together teams from around the world to work on the development of a computational framework for the modeling of the human body. At the European level, this effort is focused around patient-specific solutions and is known as the Virtual Physiological Human (VPH) Initiative. Such modeling is both multiscale (in space and time) and multiphysics. This, therefore, requires careful interaction and collaboration between the teams involved in the VPH/Physiome effort, if we are to produce computer models that are not only quantitative, but also integrative and predictive. In that context, several technologies and solutions are already available, developed both by groups involved in the VPH/Physiome effort, and by others. They address areas such as data handling/fusion, markup languages, model repositories, ontologies, tools (for simulation, imaging, data fitting, etc.), as well as grid, middleware, and workflow. Here, we provide an overview of resources that should be considered for inclusion in the VPH/Physiome ToolKit (i.e., the set of tools that addresses the needs and requirements of the Physiome Project and VPH Initiative) and discuss some of the challenges that we are still facing.

    View record details
  • Does oxygen concentration affect shedding of trophoblastic debris or production of inflammatory mediators from first trimester human placenta?

    Chen, Q; Liversidge, XL; Liu, B; Stone, Peter; Chamley, LW (2011)

    Journal article
    The University of Auckland Library

    Preeclampsia is a major cause of pregnancy morbidity and mortality. It is hypothesised that necrotic syncytial knots and/or inflammatory factors released from the placenta into the maternal circulation are responsible for inducing the widespread endothelial cell activation that is seen in preeclampsia. Poor placental perfusion has been associated with preeclampsia, this had led to the hypothesis that placental hypoxia has an important role in the pathogenesis of preeclampsia. In this study, using a placental explant model, we investigated whether different oxygen environments induced abnormal shedding of trophoblastic debris or secretion of cytokines from the placenta. There was no significant difference in the numbers of trophoblasts shed from explants cultured in 1% or 8% oxygen containing environments. There was also no difference in the levels of activated caspases in trophoblasts shed from explants cultured in these two oxygen environments nor was there a significant difference in the endothelial cell responses to trophoblasts shed from explants cultured in 1% or 8% oxygen. Similarly, there was no significant change in the secretion of nine cytokines into the conditioned medium from explants cultured in 1% or 8% oxygen. This study supports the growing evidence that levels of oxygen in the placental environment during the first trimester of pregnancy may not in itself be the essential component contributing to the pathogenesis of preeclampsia.

    View record details
  • Myocardial material parameter estimation: a comparison of invariant based orthotropic constitutive equations

    Schmid, Holger; Wang, Yikan; Ashton, Jesse; Ehret, AE; Krittian, Sebastian; Nash, Martyn; Hunter, Peter (2009)

    Journal article
    The University of Auckland Library

    This study investigated a number of invariant based orthotropic and transversely isotropic constitutive equations for their suitability to fit three-dimensional simple shear mechanics data of passive myocardial tissue. A number of orthotropic laws based on Green strain components and one microstructurally based law have previously been investigated to fit experimental measurements of stress-strain behaviour. Here we extend this investigation to include several recently proposed functional forms, i.e. invariant based orthotropic and transversely isotropic constitutive relations. These laws were compared on the basis of (i) ‘goodness of fit’: how well they fit a set of six shear deformation tests, (ii) ‘variability’: how well determined the material parameters are over the range of experiments. These criteria were utilised to discuss the advantages and disadvantages of the constitutive laws. It was found that a specific form of the polyconvex type as well as the exponential Fung-type law from the previous study were most suitable for modelling the orthotropic behaviour of myocardium under simple shear.

    View record details
  • Coupling multi-physics models to cardiac mechanics

    Nordsletten, David; Niederer, SA; Nash, Martyn; Hunter, Peter; Smith, Nicolas (2011)

    Journal article
    The University of Auckland Library

    We outline and review the mathematical framework for representing mechanical deformation and contraction of the cardiac ventricles, and how this behaviour integrates with other processes crucial for understanding and modelling heart function. Building on general conservation principles of space, mass and momentum, we introduce an arbitrary EulerianeLagrangian framework governing the behaviour of both fluid and solid components. Exploiting the natural alignment of cardiac mechanical properties with the tissue microstructure, finite deformation measures and myocardial constitutive relations are referred to embedded structural axes. Coupling approaches for solving this large deformation mechanics framework with three dimensional fluid flow, coronary hemodynamics and electrical activation are described. We also discuss the potential of cardiac mechanics modelling for clinical applications.

    View record details
  • Mental Schemas of Robots as More Human-Like Are Associated with Higher Blood Pressure and Negative Emotions in a Human-Robot Interaction

    Broadbent, Elizabeth; Lee, Y; Stafford, R; Kuo, I-Han; MacDonald, Bruce (2011)

    Journal article
    The University of Auckland Library

    Robots are often portrayed in the media as humanlike, yet research suggests that people prefer to interact with robots that are not human-like. This study aimed to investigate whether people’s mental schemas about robots’ humanness were associated with their reactions to a robot. It was hypothesised that people who thought of robots as more human-like would be more anxious when subsequently interacting with a robot. Fifty-seven participants aged over 40 years were asked to draw their idea of a healthcare robot using standardised instructions before seeing the real robot. They reported their emotions at baseline and a medical student measured their blood pressure. The drawings were categorised as human-like or box-like by the researchers and drawing size was measured. Participants were then introduced to a robot that measured their blood pressure, and they reported their emotions during the interaction. Participants who had drawn a human-like robot had significantly greater increases in blood pressure readings and negative emotions from baseline in reaction to the robot compared to those who had drawn a box-like robot. Larger drawings of healthcare robots predicted higher ratings of negative emotions during the robot interaction. This study suggests that people who have mental schemas that robots are human-like experience heightened wariness in interactions with robots. Larger drawings of robots may indicate greater anxiety towards them. Assessing mental schemas of robot human-likeness is an important consideration for the acceptance of social robots. Standardised drawing instructions and scoring are a useful method to assess cognitions and emotions towards robots.

    View record details
  • An Augmented Reality Debugging System for Mobile Robot Software Engineers

    Collett, THJ; MacDonald, Bruce (2009-09)

    Journal article
    The University of Auckland Library

    Robotics presents a unique set of challenges, which change the way that we must approach the debugging of robotic software. Augmented reality (AR) provides many opportunities for enhancing debugging, allowing the developer to see the real world as the robot does, superimposed in situ on the real world view of the human, intuitively displaying the limitations and discontinuities in the robot’s real world view. This paper contributes a systematic analysis of the challenges faced by robotic software engineers, and identifies recurring concepts for AR based visualisation of robotic data. This in turn leads to a conceptual design for an AR enhanced intelligent debugging space. Both an open source reference implementation of the conceptual design and an initial evaluation of the implementation’s efficacy are described. The AR system provides an opportunity to understand the types of errors that are encountered during debugging. The AR system analysis and design provide a reusable conceptual framework for future designers of robotic debugging systems, and guidelines for designing visualisations. In concert with common, standard robotics interfaces provided by Player/Stage, the AR system design supplies a set of common visualisations, so that many data visualisations can be provided to developers with little additional effort.

    View record details
  • Attitudes and Reactions to a Healthcare Robot

    Broadbent, Elizabeth; Kuo, I-Han; Lee, YI; Rabindran, J; Kerse, Ngaire; Stafford, R; MacDonald, Bruce (2010-06)

    Journal article
    The University of Auckland Library

    Objective: The use of robots in healthcare is a new concept. The public's perception and acceptance is not well understood. The objective was to investigate the perceptions and emotions toward the utilization of healthcare robots among individuals over 40 years of age, investigate factors contributing to acceptance, and evaluate differences in blood pressure checks taken by a robot and a medical student. Materials and Methods: Fifty-seven (n = 57) adults aged over 40 years and recruited from local general practitioner or gerontology group lists participated in two cross-sectional studies. The first was an open-ended questionnaire assessing perceptions of robots. In the second study, participants had their blood pressure taken by a medical student and by a robot. Patient comfort with each encounter, perceived accuracy of each measurement, and the quality of the patient interaction were studied in each case. Readings were compared by independent t-tests and regression analyses were conducted to predict quality ratings. Results: Participants' perceptions about robots were influenced by their prior exposure to robots in literature or entertainment media. Participants saw many benefits and applications for healthcare robots, including simple medical procedures and physical assistance, but had some concerns about reliability, safety, and the loss of personal care. Blood pressure readings did not differ between the medical student and robot, but participants felt more comfortable with the medical student and saw the robot as less accurate. Although age and sex were not significant predictors, individuals who held more positive initial attitudes and emotions toward robots rated the robot interaction more favorably. Conclusions: Many people see robots as having benefits and applications in healthcare but some have concerns. Individual attitudes and emotions regarding robots in general are likely to influence future acceptance of their introduction into healthcare processes.

    View record details
  • On internal knowledge representation for programming mobile robots by demonstration

    Abbas, T; MacDonald, Bruce (2010)

    Journal article
    The University of Auckland Library

    Intuitive learning of new behaviours is one of the important aspects of social robotics. Among various robot learning approaches, recently Programming by Demonstration (PbD) has gained significant recognition with a lot of potential. Internal representation of the knowledge is a key design choice in the learning process. Using machine learning techniques such as ANNs, HMMs and NARMAX models, simple skills can be encoded from raw sensory data. However, the abstract symbolic representations have demonstrated greater potential for learning complicated tasks but with less details and require a piece of prior knowledge as well. For a particular application, appropriate choice of the symbols is a key design issue. This paper discusses the choice of the symbols to build a PbD process for typical indoor navigation. The learning results are presented for a few tasks to demonstrate the potential of the proposed approach.

    View record details
  • The Effects of Synthesized Voice Accents on User Perceptions of Robots

    Tamagawa, R; Watson, Catherine; Kuo, IH; MacDonald, BA; Broadbent, Elizabeth (2011-08)

    Journal article
    The University of Auckland Library

    Human voice accents have been shown to affect people’s perceptions of the speaker, but little research has looked at how synthesized voice accents affect perceptions of robots. This research investigated people’s perceptions of three synthesized voice accents. Three male robot voices were generated: British (UK), American (US), and New Zealand (NZ). In study one, twenty adults listened through headphones to a recorded script repeated in the three different accents, rated the nationality, roboticness, and overall impression of each voice, and chose their preferred accent. Study two used these voices on a healthcare robot to investigate the influence of accent on user perceptions of the robot. Ninety-one individuals were randomized to one of three conditions. In each condition they interacted with a healthcare robot that assisted with blood pressure measurement but the conditions differed in the accent the robot spoke with. In study one, each accent was correctly identi- fied. There was no difference in impression ratings of each voice, but the US accent was rated as more robotic than the NZ accent, and the UK accent was preferred to the US accent. Study two showed that people randomized to the NZ accent had more positive feelings towards the robot and rated the robot’s overall performance as higher compared to the robot with the US voice. These results suggest that the employment of a less robotic voice with a local accent may positively affect user perceptions of robots.

    View record details
  • The management of managers: A review and conceptual framework

    Boxall, Peter; Gilbert, J (2007-06)

    Journal article
    The University of Auckland Library

    The management of managers is an important contemporary concern, but the literature on the issue is not well integrated. This paper reviews key sources on the topic across organizational economics, human resource development and strategic human resource management. It presents a novel interdisciplinary framework for analysing how firms manage senior managers and for guiding future research, arguing that firms adopt different styles to attract–defend, develop–renew and motivate–harvest their senior managerial resource, depending on their contexts and choices that are made in the firm over time. The notion that some styles draw on early identification of élites while others treat management identification as more of an emergent problem is central to the typology. Within each of the styles identified, effectiveness in the management of managers hinges on recognizing and handling certain strategic tensions and problems.

    View record details
  • The relationship between high-performance work practices and employee attitudes: An investigation of additive and interaction effects

    Macky, K; Boxall, Peter (2007)

    Journal article
    The University of Auckland Library

    In order to improve our understanding of mediating variables inside the ‘black box’ of the firm’s labour management, this paper examines the relationship between high-performance work system (HPWS) practices and employee attitudes. Using a randomly selected, national population sample, clear evidence was found for a positive relationship between HPWS practices and the attitudinal variables of job satisfaction, trust in management, and organizational commitment, implying that HPWS can provide winwin outcomes for employees and employers. However, the study also tests – from an employee perspective – the ‘complementarities thesis’ and finds negative interaction effects among HPWS practices. This strengthens the argument that there are likely to be limits to the positive outcomes of HPWSs for employees. Evidence of sequencing in the employee attitudinal responses to HPWSs was also found, with job satisfaction as the key mediating variable.

    View record details
  • Towards more accessible conceptions of statistical inference

    Wild, Christopher; Pfannkuch, Maxine; Regan, Matthew; Horton, NJ (2011)

    Journal article
    The University of Auckland Library

    Summary.  There is a compelling case, based on research in statistics education, for first courses in statistical inference to be underpinned by a staged development path. Preferably over a number of years, students should begin working with precursor forms of statistical inference, much earlier than they now do. A side benefit is giving younger students more straightforward and more satisfying ways of answering interesting real world questions. We discuss the issues that are involved in formulating precursor versions of inference and then present some specific and highly visual proposals. These build on novel ways of experiencing sampling variation and have intuitive connections to the standard formal methods of making inferences in first university courses in statistics. Our proposal uses visual comparisons to enable the inferential step to be made without taking the eyes off relevant graphs of the data. This allows the time and conceptual distances between questions, data and conclusions to be minimized, so that the most critical linkages can be made. Our approach was devised for use in high schools but is also relevant to adult education and some introductory tertiary courses.

    View record details
  • The concept of distribution

    Wild, Christopher (2006)

    Journal article
    The University of Auckland Library

    This paper is a personal exploration of where the ideas of “distribution” that we are trying to develop in students come from and are leading to, how they fit together, and where they are important and why. We need to have such considerations in the back of our minds when designing learning experiences. The notion of “distribution” as a lens through which statisticians look at the variation in data is developed. I explore the sources of variation in data, empirical versus theoretical distributions, the nature of statistical models, sampling distributions, the conditional nature of distributions used for modelling, and the underpinnings of inference.

    View record details
  • Assessment and student transformation: linking character and intellect

    Barrow, Mark (2006)

    Journal article
    The University of Auckland Library

    This article is concerned with the complex role played by student assessment in the formation of the human subjects that are the product of higher education. Using a framework informed by the work of Foucault, it explores the productive effects of assessment regimes. Drawing on narrative data collected during in‐depth, semi‐structured interviews with students, it contrasts assessment regimes in two degree programmes to consider the way in which assessment may draw students into varied power relations. It is argued that in playing out these relations assessment incites students (to varying extents) to develop, consider and disclose to the lecturer links between their intellect and character. In doing so, students expose their developing character to the interpretation and guidance of the lecturer, providing the potential for the lecturer to lead students to construct and conduct themselves in a manner appropriate for a complex contemporary state. Additionally, and significantly, such approaches may have the potential to overcome the normative effects inherent in all assessment. The extent to which assessment might assist students to develop the transformed nature that is required to purposefully and deliberately undermine the rules of the discipline is discussed.

    View record details
  • We’re a Weird Mob

    Sumpter, Paul (2010)

    Journal article
    The University of Auckland Library

    "A Time magazine cover story in 1992 appeared to imply that the merger of Australia and New Zealand was imminent". Political union between the two countries has been mentioned from time to time both before 1992 and since that date. ...

    View record details
  • A continuous-binding cross-linker model for passive airway smooth muscle.

    Donovan, Graham; Bullimore, SR; Elvin, AJ; Tawhai, Merryn; Bates, JH; Lauzon, AM; Sneyd, A (2010-11-17)

    Journal article
    The University of Auckland Library

    Although the active properties of airway smooth muscle (ASM) have garnered much modeling attention, the passive mechanical properties are not as well studied. In particular, there are important dynamic effects observed in passive ASM, particularly strain-induced fluidization, which have been observed both experimentally and in models; however, to date these models have left an incomplete picture of the biophysical, mechanistic basis for these behaviors. The well-known Huxley cross-bridge model has for many years successfully described many of the active behaviors of smooth muscle using sliding filament theory; here, we propose to extend this theory to passive biological soft tissue, particularly ASM, using as a basis the attachment and detachment of cross-linker proteins at a continuum of cross-linker binding sites. The resulting mathematical model exhibits strain-induced fluidization, as well as several types of force recovery, at the same time suggesting a new mechanistic basis for the behavior. The model is validated by comparison to new data from experimental preparations of rat tracheal airway smooth muscle. Furthermore, experiments in noncontractile tissue show qualitatively similar behavior, suggesting support for the protein-filament theory as a biomechanical basis for the behavior.

    View record details
  • A mathematical model of calcium-induced fluid secretion in airway epithelium

    Warren, Nicholas; Tawhai, Merryn; Crampin, Edmund (2009)

    Journal article
    The University of Auckland Library

    Regulation of periciliary liquid (PCL) depth is of central importance to mucociliary clearance by the airway epithelium. Without adequate hydration mucociliary transport would cease, leading to build up of mucus in the airways, and impairing the clearance of any trapped inhaled particulates. Airway epithelial cells are known to release ATP under a number of stress conditions. Cell surface receptors bind ATP and trigger an intracellular calcium response which regulates the gating of specific ion channels on the apical and basolateral cell membranes. This shifts the electrochemical balance, resulting in the accumulation of Na+ and Cl- in the periciliary liquid, and providing an osmotic driving force for water flux. In this study, we present a mathematical model of a single airway epithelial cell which describes the fluid secretion elicited after a rise in intracellular calcium. The model provides a basis to quantitatively analyse the influence of intracellular calcium signalling on fluid movement. The model demonstrates behaviour consistent with a number of experimental data on manipulating periciliary liquid volume and tonicity, and provides a quantitative basis for analysing the role of the different membrane ion channels in determining water flux following different physiological stimuli.

    View record details
  • Computational models of structure-function relationships in the pulmonary circulation and their validation

    Tawhai, Merryn; Burrowes, Kelly; Hoffman, Eric (2006)

    Journal article
    The University of Auckland Library

    The pulmonary airway, arterial, venous and capillary networks are vast complex branching and converging systems that are mechanically coupled to the surrounding lung tissue. Early studies that examined vascular or airway geometry relied on measurements from casts, but medical imaging now enables measurement of the lung in vivo, at controlled lung volumes. The highquality data that imaging provides have prompted development of increasingly sophisticated models of the geometry of the airway and pulmonary vascular trees. The accurate spatial relationships between airway, vessel and tissue in these imaging-derived models are necessary for computational analysis that aims to elucidate regional airway–vessel–tissue interactions. Predictions of blood flow through multiscale imaging-derived models of the pulmonary arteries and capillary bed reveal geometry-dependent patterns of perfusion in response to gravity and lung orientation that cannot be predicted with simplified, summary representations of the pulmonary transport trees. Validation of such predictions against measures from functional imaging holds significant potential for explaining and differentiating normal and disease-related heterogeneity in regional blood flow calculated using perfusion imaging.

    View record details
  • The contribution of serial and parallel micro-perfusion to spatial variability in pulmonary inter- and intra-acinar blood flow

    Clark, AR; Burrowes, KS; Tawhai, Merryn (2010)

    Journal article
    The University of Auckland Library

    This study presents a theoretical model of combined series and parallel perfusion in the human pulmonary acinus that maintains computational simplicity while capturing some important features of acinar structure. The model provides a transition between existing models of perfusion in the large pulmonary blood vessels and the pulmonary microcirculation. Arterioles and venules are represented as distinct elastic vessels that follow the branching structure of the acinar airways. These vessels are assumed to be joined at each generation by capillary sheets that cover the alveoli present at that generation, forming a “ladderlike” structure. Compared with a model structure in which capillary beds connect only the most distal blood vessels in the acinus, the model with combined serial and parallel perfusion provides greater capacity for increased blood flow in the lung via capillary recruitment when the blood pressure is elevated. Stratification of acinar perfusion emerges in the model, with red blood cell transit time significantly larger in the distal portion of the acinus compared with the proximal portion. This proximal-to-distal pattern of perfusion may act in concert with diffusional screening to optimize the potential for gas exchange.

    View record details