MRI-based measurement of carotid mechanical properties in asymptomatic patients

Arterial mechanical property may be a potential variable for risk stratification. Large artery and central arterial compliance have been shown not only to correlate well with overall cardiovascular outcome in large epidemiological studies [1, 2] but also to correlate with coronary atherosclerotic burden as measured by conventional angiography [3]. Until recently, real-time B-mode ultrasound combined with simultaneous blood pressure measurements have been used to assess large artery compliance [4]. These techniques have an excellent temporal resolution but are unable to provide adequate spatial resolution to determine changes in vessel area as opposed to diameter and make the assumption that the vessel is perfectly round. Attempts to use MR imaging to measure large artery compliance have been published previously [5]. However, they have not utilised simultaneous blood pressure measurements during sequence acquisition. We report a technique using regular and simultaneous blood pressure measurement during 2 dimensional phase contrast magnetic resonance imaging 2DPC-MRI to determine local carotid compliance.

Experimental measurement of the mechanical properties of carotid atherothrombotic plaque fibrous cap

Eleven carotid atherothrombotic plaque samples were harvested from patients. Three samples that were highly calcified were discarded, while eight yielded results. The elastic properties of the material were estimated by fitting the measured indentation response to finite element simulations. The methodology was refined and its accuracy quantified using a synthetic rubber. The neo-Hookean form of the material model gave a good fit to the measured response of the tissue. The inferred shear modulus μ was found to be in the range 7-100 kPa, with a median value of 11 kPa. A review of published materials data showed a wide range of material properties for human atherothrombotic tissue. The effects of anisotropy and time dependency in these published results were highlighted. The present measurements were comparable to the static radial compression tests of Lee et al, 1991 [Structure-dependent dynamic behaviour of fibrous caps from human atherosclerotic plaques. Circulation 83, 1764-1770].

Measurement of stenotic carotid arterial compliance with MRI

Arterial compliance has been shown to correlate well with overall cardiovascular outcome and it may also be a potential risk factor for the development of atheromatous disease. This study assesses the utility of 2-D phase contrast Magnetic Resonance (MR) imaging with intra-sequence blood pressure measurement to determine carotid compliance and distensibility. 20 patients underwent 2-D phase contrast MR imaging and also ultrasound-based wall tracking measurements. Values for carotid compliance and distensibility were derived from the two different modalities and compared. Linear regression analysis was utilised to determine the extent of correlation between MR and ultrasound derived parameters. In those variables that could be directly compared, an agreement analysis was undertaken. MR measures of compliance showed a good correlation with measures based on ultrasound wall-tracking (r=0.61, 95% CI 0.34 to 0.81 p=0.0003). Vessels that had undergone carotid endarterectomy previously were significantly less compliant than either diseased or normal contralateral vessels (p=0.04). Agreement studies showed a relatively poor intra-class correlation coefficient (ICC) between diameter-based measures of compliance through either MR or ultrasound (ICC=0.14). MRI based assessment of local carotid compliance appears to be both robust and technically feasible in most subjects. Measures of compliance correlate well with ultrasound-based values and correlate best when cross-sectional area change is used rather than derived diameter changes. If validated by further larger studies, 2-D phase contrast imaging with intra-sequence blood pressure monitoring and off-line radial artery tonometry may provide a useful tool in further assessment of patients with carotid atheroma.

In vivo positive contrast IRON sequence and quantitative T2* measurement confirms inflammatory burden in a patient with asymptomatic carotid atheroma after USPIO-enhanced MR Imaging

The authors report an in vivo human examination of carotid atheroma by using the inversion-recovery ON resonance (IRON) sequence, which is able to produce positive contrast after the infusion of an ultrasmall super paramagnetic iron oxide (USPIO) contrast medium. This technique provides a method of potentially identifying inflammatory burden within carotid atheroma. This may be particularly useful in patients who currently do not meet criteria for intervention (ie, moderate symptomatic stenosis or <70% asymptomatic stenosis) to further risk-stratify this important patient cohort. A 63-year-old man was imaged at 1.5 T before and 36 hours after USPIO infusion by using the IRON sequence. Regions of interest showing profound signal loss at T2*-weighted imaging corresponded well with regions of positive contrast at IRON imaging after the administration of USPIO. These regions also showed a profound decrease in T2* measurements after USPIO infusion, whereas surrounding tissue did not. It has been shown that such strong signal loss on T2*-weighted images after USPIO infusion is indicative of USPIO uptake.

The Connor-Davidson Resilience Scale (CD-RISC): Dimensionality and age-related measurement invariance with Australian cricketers

Objective This study explored the dimensionality and measurement invariance of the 25-item Connor-Davidson Resilience Scale (CD-RISC; Connor & Davidson, 2003) across samples of adult (n = 321; aged 20–36) and adolescent (n = 199; aged 12–18) Australian cricketers. Design Cross-sectional, self-report survey Methods An online, multi-section questionnaire. Results Confirmatory factor and item level analyses supported the psychometric superiority of a revised 10-item, unidimensional model of resilience over the original 25-item, five-factor measurement model. Positive and moderate correlations with hardiness as well as negative and moderate correlations with burnout components were evidenced thereby providing support for the convergent validity of the unidimensional model. Measurement invariance analyses of the unidimensional model across the two age-group samples supported configural (i.e., same factor structure across groups), metric (i.e., same pattern of factor loadings across the groups), and partial scalar invariance (i.e., mostly the same intercepts across the groups). Conclusion Evidence for a psychometrically sound measure of resilient qualities of the individual provides an important foundation upon which researchers can identify the antecedents to and outcomes of resilience in sport contexts.

Can the direct measurement of the load applied on the residuum of individuals with transfemoral amputation fitted with bone-anchored prosthesis help to improve the rehabilitation program?

To strive to improve the rehabilitation program of individuals with transfemoral amputation fitted with bone-anchored prosthesis based on data from direct measurements of the load applied on the residuum we first of all need to understand the load applied on the fixation. Therefore the load applied on the residuum was first directly measured during standardized activities of daily living such as straight line level walking, ascending and descending stairs and a ramp and walking around a circle. From measuring the load in standardized activities of daily living the load was also measured during different phases of the rehabilitation program such as during walking with walking aids and during load bearing exercises.[1-15] The rehabilitation program for individuals with a transfemoral amputation fitted with an OPRA implant relies on a combination of dynamic and static load bearing exercises.[16-20] This presentation will focus on the study of a set of experimental static load bearing exercises. [1] A group of eleven individuals with unilateral transfemoral amputation fitted with an OPRA implant participated in this study. The load on the implant during the static load bearing exercises was measured using a portable system including a commercial transducer embedded in a short pylon, a laptop and a customized software package. This apparatus was previously shown effective in a proof-of-concept study published by Prof. Frossard. [1-9] The analysis of the static load bearing exercises included an analysis of the reliability as well as the loading compliance. The analysis of the loading reliability showed a high reliability between the loading sessions indicating a correct repetition of the LBE by the participants. [1, 5] The analysis of the loading compliance showed a significant lack of axial compliance leading to a systematic underloading of the long axis of the implant during the proposed experimental static LBE.

Direct measurement of inner prosthesis loading during activities of daily living: Proposal for classification of functional outcome

Background The purpose of this presentation is to outline the relevance of the categorization of the load regime data to assess the functional output and usage of the prosthesis of lower limb amputees. The objectives are • To highlight the need for categorisation of activities of daily living • To present a categorization of load regime applied on residuum, • To present some descriptors of the four types of activity that could be detected, • To provide an example the results for a case. Methods The load applied on the osseointegrated fixation of one transfemoral amputee was recorded using a portable kinetic system for 5 hours. The load applied on the residuum was divided in four types of activities corresponding to inactivity, stationary loading, localized locomotion and directional locomotion as detailed in previously publications. Results The periods of directional locomotion, localized locomotion, and stationary loading occurred 44%, 34%, and 22% of recording time and each accounted for 51%, 38%, and 12% of the duration of the periods of activity, respectively. The absolute maximum force during directional locomotion, localized locomotion, and stationary loading was 19%, 15%, and 8% of the body weight on the anteroposterior axis, 20%, 19%, and 12% on the mediolateral axis, and 121%, 106%, and 99% on the long axis. A total of 2,783 gait cycles were recorded. Discussion Approximately 10% more gait cycles and 50% more of the total impulse than conventional analyses were identified. The proposed categorization and apparatus have the potential to complement conventional instruments, particularly for difficult cases.

PMU measurement based dynamic load modeling using SVC devices in online environment

Online dynamic load modeling has become possible with the availability of Static Voltage Compensator (SVC) and Phasor Measurement Unit (PMU) devices. The power of the load response to the small random bounded voltage fluctuations caused from SVC can be measured by PMU for modelling purposes. The aim of this paper is to illustrate the capability of identifying an aggregated load model from high voltage substation level in the online environment. The induction motor is used as the main test subject since it contributes the majority of the dynamic loads. A test system representing simple electromechanical generator model serving dynamic loads through the transmission network is used to verify the proposed method. Also, dynamic load with multiple induction motors are modeled to achieve a better realistic load representation.

Analyzing hysteresis behavior of capacitance-voltage characteristics of IZO/C₆₀/pentacene/Au diodes with a hole-transport electron-blocking polyterpenol layer by electric-field-induced optical second-harmonic generation measurement

By using electric-field-induced optical second-harmonic generation (EFISHG) measurement, we analyzed hysteresis behavior of capacitance-voltage (C-V) characteristics of IZO/polyterpenol (PT)/C₆₀/pentacene/Au diodes, where PT layer is actively working as a hole-transport electron-blocking layer. The EFISHG measurement verified the presence of interface accumulated charges in the diodes, and showed that a space charge electric field from accumulated excess electrons (holes) that remain at the PT/C₆₀ (C₆₀/pentacene) interface is responsible for the hysteresis loop observed in the C-V characteristics.

Information sharing in distance collaboration: A software engineering perspective

Information sharing in distance collaboration: A software engineering perspective, QueenslandFactors in software engineering workgroups such as geographical dispersion and background discipline can be conceptually characterized as "distances", and they are obstructive to team collaboration and information sharing. This thesis focuses on information sharing across multidimensional distances and develops an information sharing distance model, with six core dimensions: geography, time zone, organization, multi-discipline, heterogeneous roles, and varying project tenure. The research suggests that the effectiveness of workgroups may be improved through mindful conducts of information sharing, especially proactive consideration of, and explicit adjustment for, the distances of the recipient when sharing information.

Dark-energy constraints and correlations with systematics from CFHTLS weak lensing, SNLS supernovae Ia and WMAP5

Aims We combine measurements of weak gravitational lensing from the CFHTLS-Wide survey, supernovae Ia from CFHT SNLS and CMB anisotropies from WMAP5 to obtain joint constraints on cosmological parameters, in particular, the dark-energy equation-of-state parameter w. We assess the influence of systematics in the data on the results and look for possible correlations with cosmological parameters. Methods We implemented an MCMC algorithm to sample the parameter space of a flat CDM model with a dark-energy component of constant w. Systematics in the data are parametrised and included in the analysis. We determine the influence of photometric calibration of SNIa data on cosmological results by calculating the response of the distance modulus to photometric zero-point variations. The weak lensing data set is tested for anomalous field-to-field variations and a systematic shape measurement bias for high-redshift galaxies. Results Ignoring photometric uncertainties for SNLS biases cosmological parameters by at most 20% of the statistical errors, using supernovae alone; the parameter uncertainties are underestimated by 10%. The weak-lensing field-to-field variance between 1 deg2-MegaCam pointings is 5-15% higher than predicted from N-body simulations. We find no bias in the lensing signal at high redshift, within the framework of a simple model, and marginalising over cosmological parameters. Assuming a systematic underestimation of the lensing signal, the normalisation increases by up to 8%. Combining all three probes we obtain -0.10 < 1 + w < 0.06 at 68% confidence ( -0.18 < 1 + w < 0.12 at 95%), including systematic errors. Our results are therefore consistent with the cosmological constant . Systematics in the data increase the error bars by up to 35%; the best-fit values change by less than 0.15.

Finite element modelling of lamb wave propagation in prestress concrete and effect of the prestress force on the wave’s characteristic

In order to assess the structural reliability of bridges, an accurate and cost effective Non-Destructive Evaluation (NDE) technology is required to ensure their safe and reliable operation. Over 60% of the Australian National Highway System is prestressed concrete (PSC) bridges according to the Bureau of Transport and Communication Economics (1997). Most of the in-service bridges are more than 30 years old and may experience a heavier traffic load than their original intended level. Use of Ultrasonic waves is continuously increasing for (NDE) and Structural Health Monitoring (SHM) in civil, aerospace, electrical, mechanical applications. Ultrasonic Lamb waves are becoming more popular for NDE because it can propagate long distance and reach hidden regions with less energy loses. The purpose of this study is to numerically quantify prestress force (PSF) of (PSC) beam using the fundamental theory of acoustic-elasticity. A three-dimension finite element modelling approach is set up to perform parametric studies in order to better understand how the lamb wave propagation in PSC beam is affected by changing in the PSF level. Results from acoustic-elastic measurement on prestressed beam are presented, showing the feasibility of the lamb wave for PSF evaluation in PSC bridges.

Designing experiences with wearables : A case study exploring the blurring boundaries of art, design, technology, culture and distance

This paper details a workshop aimed at exploring opportunities for experience design through wearable art and design concepts. Specifically it explores the structure of the workshop with respect to facilitating learning through technology in the development of experiential wearable art and design. A case study titled Cloud Workshop: Wearables and Wellbeing; Enriching connections between citizens in the Asia-Pacific region was initiated through a cooperative partnership between Hong Kong Baptist University (HKBU), Queensland University of Technology (QUT) and Griffith University (GU). Digital technologies facilitated collaboration through an inter-disciplinary, inter-national and inter- cultural approach (Facer & Sandford, 2010) between Australia and Hong Kong. Students cooperated throughout a two-week period to develop innovative wearable concepts blending art, design and technology. An unpacking of the approach, pedagogical underpinning and final outcomes revealed distinct educational benefits as well as certain learning and technological challenges of the program. Qualitative feedback uncovered additional successes with respect to student engagement and enthusiasm, while uncovering shortcomings in the delivery and management of information and difficulties with cultural interactions. Potential future versions of the program aim to take advantage of the positives and overcome the limitations of the current pedagogical approach. It is hoped the case study will become a catalyst for future workshops that blur the boundaries of art, design and technology to uncover further benefits and potentials for new outcomes in experience design.

Creating physical education in remote Australian schools: Overcoming the tyranny of distance through communities of practice

This paper reports on a qualitative case study undertaken in a remote part of Queensland, Australia. While there is some modest agreement about the capacity of contemporary information technologies to overcome the problems of schooling in areas of extreme remoteness, generally, children educated in such contexts are considered to be disadvantaged. The experiential areas of the curriculum, which often require specific teaching expertise, present the greatest challenge to teachers, and of these, physical education is perhaps the most problematic. This research reports on a case study of three remote Queensland multi-age primary (elementary) schools that come together to form a community of practice to overcome the problems of teaching physical education in such difficult circumstances. Physical education is constructed in these contexts by blurring the school and community boundaries, by contextualizing the subject content to make it relevant, and by adjusting the school day to accommodate potential physical education experiences. Each community gathers its collective experience to ensure the widest possible experiences are made available for the children. In doing so, the children develop a range of competencies that enable seamless transition to boarding high schools.

The entitled tourist: The influence of psychological entitlement and cultural distance on tourist judgments in a hotel context

This research examines how a tourist’s degree of psychological entitlement (sense of deservingness) influences their responses to hotels that differ in cultural distance. Using a visit to China by Western tourists as a context, an experiment shows that entitled tourists respond more negatively to high cultural distance hotel environments compared with low cultural distance environments. Results are mediated by tourist irritation. Research contributions include demonstrating how entitlement moderates cultural distance effects, revealing tourist irritation as a mechanism that explains these effects, and showing how psychological entitlement influences how tourists react to hotel environments when visiting a foreign destination.