Melbourne Institute of Applied Economic and Social Research - Research Publications
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ItemRe-engaging with survey non-respondents: Evidence from three household panels(Wiley, 2014)Previous research into the correlates and determinants of non‐response in longitudinal surveys has focused exclusively on why it is that respondents at one survey wave choose not to participate at future waves. This is very understandable if non‐response is always an absorbing state, but in many longitudinal surveys, and certainly most household panels, this is not so. Indeed, in these surveys it is normal practice to attempt to make contact with many non‐respondents at the next wave. This study differs from previous research by examining re‐engagement with previous wave non‐respondents. Drawing on data from three national household panels it is found that the re‐engagement decision is indeed distinctly different from the decision about continued participation. Further, these differences have clear implications for the way that panel surveys should be administered given the desire to enhance overall response rates.
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ItemAssessing Individual Income Growth(WILEY, 2016-10)We develop methods for describing distributions of income growth across individuals and for comparing changes in growth distributions over time. The methods include graphical devices (‘income growth profiles’) and dominance conditions, and also summary indices, together with associated methods of estimation and inference. Taking an explicitly longitudinal perspective, our approach illuminates clearly who are the gainers and the losers, and also provides distributionally‐sensitive assessments—ones that allow the income growth for different individuals to be weighted differently. Our empirical application shows that the pattern of income growth in Britain over the period 1992–6 was less pro‐poor than that for 1998–2002, and not significantly different from the pattern for 2001–5.
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ItemEuropean and Australasian Econometrics and Health Economics Workshop papers Introduction(WILEY-BLACKWELL, 2016-09)
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ItemResearch Funding Mechanisms and Biomedical Research Outputs(WILEY, 2016-06)We use scientist‐level panel data in order to estimate the effect which the number, type and source of research grants has on subsequent commercial contracts, publications and patent outputs. In so doing, we control for time‐invariant factors including individual researcher preferences, the nature of the work and the business model of the researcher's laboratory. We find that, whereas Fellowships and Project or program grants had a positive effect on whether the scientist subsequently signed a commercial contract, Equipment and Development grants had the largest impact per grant. Finally, we find that International grants were negatively associated with the number of commercial contracts signed. The data were drawn from 488 biomedical researchers at the Walter and Eliza Hall Institute over the period 2009–2012.
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ItemExplaining Improved Use of High-Risk Medications in Medicare Between 2007 and 2011(WILEY-BLACKWELL, 2016-03)
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ItemRegulating electronic cigarettes(Wiley, 2016-03-01)
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ItemOptimisation of a Stirred Bioreactor through the Use of a Novel Holographic Correlation Velocimetry Flow Measurement Technique(PUBLIC LIBRARY SCIENCE, 2013-06-11)We describe a method for measuring three dimensional (3D) velocity fields of a fluid at high speed, by combining a correlation-based approach with in-line holography. While this method utilizes tracer particles contained within the flow, our method does not require the holographic reconstruction of 3D images. The direct flow reconstruction approach developed here allows for measurements at seeding densities in excess of the allowable levels for techniques based on image or particle reconstruction, thus making it suited for biological flow measurement, such as the flow in bioreactor. We outline the theory behind our method, which we term Holographic Correlation Velocimetry (HCV), and subsequently apply it to both synthetic and laboratory data. Moreover, because the system is based on in-line holography, it is very efficient with regard to the use of light, as it does not rely on side scattering. This efficiency could be utilized to create a very high quality system at a modest cost. Alternatively, this efficiency makes the system appropriate for high-speed flows and low exposure times, which is essential for imaging dynamic systems.
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ItemIn Vivo Wall Shear Measurements within the Developing Zebrafish Heart(PUBLIC LIBRARY SCIENCE, 2013-10-04)Physical forces can influence the embryonic development of many tissues. Within the cardiovascular system shear forces resulting from blood flow are known to be one of the regulatory signals that shape the developing heart. A key challenge in investigating the role of shear forces in cardiac development is the ability to obtain shear force measurements in vivo. Utilising the zebrafish model system we have developed a methodology that allows the shear force within the developing embryonic heart to be determined. Accurate wall shear measurement requires two essential pieces of information; high-resolution velocity measurements near the heart wall and the location and orientation of the heart wall itself. We have applied high-speed brightfield imaging to capture time-lapse series of blood flow within the beating heart between 3 and 6 days post-fertilization. Cardiac-phase filtering is applied to these time-lapse images to remove the heart wall and other slow moving structures leaving only the red blood cell movement. Using particle image velocimetry to calculate the velocity of red blood cells in different regions within the heart, and using the signal-to-noise ratio of the cardiac-phase filtered images to determine the boundary of blood flow, and therefore the position of the heart wall, we have been able to generate the necessary information to measure wall shear in vivo. We describe the methodology required to measure shear in vivo and the application of this technique to the developing zebrafish heart. We identify a reduction in shear at the ventricular-bulbar valve between 3 and 6 days post-fertilization and demonstrate that the shear environment of the ventricle during systole is constantly developing towards a more uniform level.
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ItemQuantification of heterogeneity in lung disease with image-based pulmonary function testing(NATURE PORTFOLIO, 2016-07-27)Computed tomography (CT) and spirometry are the mainstays of clinical pulmonary assessment. Spirometry is effort dependent and only provides a single global measure that is insensitive for regional disease, and as such, poor for capturing the early onset of lung disease, especially patchy disease such as cystic fibrosis lung disease. CT sensitively measures change in structure associated with advanced lung disease. However, obstructions in the peripheral airways and early onset of lung stiffening are often difficult to detect. Furthermore, CT imaging poses a radiation risk, particularly for young children, and dose reduction tends to result in reduced resolution. Here, we apply a series of lung tissue motion analyses, to achieve regional pulmonary function assessment in β-ENaC-overexpressing mice, a well-established model of lung disease. The expiratory time constants of regional airflows in the segmented airway tree were quantified as a measure of regional lung function. Our results showed marked heterogeneous lung function in β-ENaC-Tg mice compared to wild-type littermate controls; identified locations of airway obstruction, and quantified regions of bimodal airway resistance demonstrating lung compensation. These results demonstrate the applicability of regional lung function derived from lung motion as an effective alternative respiratory diagnostic tool.
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ItemTechnical Note: Contrast free angiography of the pulmonary vasculature in live mice using a laboratory x-ray source(WILEY, 2016-11)PURPOSE: In vivo imaging of the pulmonary vasculature in small animals is difficult yet highly desirable in order to allow study of the effects of a host of dynamic biological processes such as hypoxic pulmonary vasoconstriction. Here the authors present an approach for the quantification of changes in the vasculature. METHODS: A contrast free angiography technique is validated in silico through the use of computer-generated images and in vivo through microcomputed tomography (μCT) of live mice conducted using a laboratory-based x-ray source. Subsequent image processing on μCT data allowed for the quantification of the caliber of pulmonary vasculature without the need for external contrast agents. These measures were validated by comparing with quantitative contrast microangiography in the same mice. RESULTS: Quantification of arterial diameters from the method proposed in this study is validated against laboratory-based x-ray contrast microangiography. The authors find that there is a high degree of correlation (R = 0.91) between measures from microangiography and their contrast free method. CONCLUSIONS: A technique for quantification of murine pulmonary vasculature without the need for contrast is presented. As such, this technique could be applied for longitudinal studies of animals to study changes to vasculature without the risk of premature death in sensitive mouse models of disease. This approach may also be of value in the clinical setting.