ORCID Profile
0000-0002-8641-1374
Current Organisation
Flinders University
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Publisher: Springer International Publishing
Date: 2014
Publisher: Cambridge University Press (CUP)
Date: 02-07-2018
DOI: 10.1017/S1049023X18000493
Abstract: Mass gatherings are common in Australia. The interplay of variables, including crowd density and behavior, weather, and the consumption of alcohol and other drugs, can pose a unique set of challenges to attendees’ well-being. On-site health services are available at most mass gatherings and reduce the strain on community health facilities. In order to efficiently plan and manage these services, it is important to be able to predict the number and type of presenting problems at mass gatherings. There is a lack of reliable tools to predict patient presentations at mass gatherings. While a number of factors have been identified as having an influence on attendees’ health, the exact contribution of these variables to patient load is poorly understood. Furthermore, predicting patient load at mass gatherings is an inherently nonlinear problem, due to the nonlinear relationships previously observed between patient presentations and many event characteristics. Data were collected at 216 Australian mass gatherings and included event type, crowd demographics, and weather. Nonlinear models were constructed using regression trees. The full data set was used to construct each model and the model was then used to predict the response variable for each event. Nine-fold cross validation was used to estimate the error that may be expected when applying the model in practice. The mean training errors for total patient presentations were very high however, the distribution of errors per event was highly skewed, with small errors for the majority of events and a few large errors for a small number of events with a high number of presentations. The error was five or less for 40% of events and 15 or less for 85% of events. The median error was 6.9 presentations per event. This study built on previous research by undertaking nonlinear modeling, which provides a more realistic representation of the interactions between event variables. The developed models were less useful for predicting patient presentation numbers for very large events however, they were generally useful for more typical, smaller scale community events. Further research is required to confirm this conclusion and develop models suitable for very large international events. Arbon P, Bottema M, Zeitz K, Lund A, Turris S, Anikeeva O, Steenk M. Nonlinear modelling for predicting patient presentation rates for mass gatherings. Prehosp Disaster Med. 2018 (4):362–367
Publisher: Elsevier BV
Date: 12-2012
DOI: 10.1016/J.MBS.2012.06.006
Abstract: A model is presented for characterizing the process by which cancellous bone changes in volume and structure over time. The model comprises simulations of local changes resulting from in idual remodelling events, known as bone multicellular units (BMU), and an ordinary differential equation for connecting the number of remodelling events to real time. The model is validated on micro-CT scans of tibiae of normal rats, estrogen deprived rats and estrogen deprived rats treated with bisphosphonates. The model explains the asymptotic trends seen in changes of bone volume over time resulting from estrogen deprivation as well as trends seen subsequent to treatment. The model demonstrates that both bone volume and structure changes can be explained in terms of resetting remodelling parameters. The model also shows that either current understanding of the effects of bisphosphonates is not correct or that the simplest description of remodelling does not suffice to explain both the change in bone volume and structure of rats treated with bisphosphonates.
Publisher: Elsevier BV
Date: 07-2013
Publisher: IEEE
Date: 2009
Publisher: Informa UK Limited
Date: 11-01-2017
Publisher: ASME International
Date: 03-11-2016
DOI: 10.1115/1.4034831
Abstract: Assessing the sensitivity of a finite-element (FE) model to uncertainties in geometric parameters and material properties is a fundamental step in understanding the reliability of model predictions. However, the computational cost of in idual simulations and the large number of required models limits comprehensive quantification of model sensitivity. To quickly assess the sensitivity of an FE model, we built linear and Kriging surrogate models of an FE model of the intact hemipelvis. The percentage of the total sum of squares (%TSS) was used to determine the most influential input parameters and their possible interactions on the median, 95th percentile and maximum equivalent strains. We assessed the surrogate models by comparing their predictions to those of a full factorial design of FE simulations. The Kriging surrogate model accurately predicted all output metrics based on a training set of 30 analyses (R2 = 0.99). There was good agreement between the Kriging surrogate model and the full factorial design in determining the most influential input parameters and interactions. For the median, 95th percentile and maximum equivalent strain, the bone geometry (60%, 52%, and 76%, respectively) was the most influential input parameter. The interactions between bone geometry and cancellous bone modulus (13%) and bone geometry and cortical bone thickness (7%) were also influential terms on the output metrics. This study demonstrates a method with a low time and computational cost to quantify the sensitivity of an FE model. It can be applied to FE models in computational orthopaedic biomechanics in order to understand the reliability of predictions.
Publisher: Springer Berlin Heidelberg
Date: 2008
Publisher: IOP Publishing
Date: 25-09-2003
Publisher: Elsevier BV
Date: 03-2018
DOI: 10.1016/J.MEATSCI.2017.11.024
Abstract: Twenty Angus steers were fed a diet low in β-carotene and vitamin A for 10months. Ten steers were supplemented with vitamin A weekly, while the other ten steers did not receive any additional vitamin A. The results demonstrated that the restriction of vitamin A intake increased intramuscular fat (IMF) by 46%. This was a function of the total number of marbling flecks increasing by 22% and the average marbling fleck size increasing by 14%. Vitamin A restriction resulted in marbling flecks that were less branched (22%) and slightly more round (4%) with an increased minor axis length (7%). However, restricting vitamin A did not affect the size of the intramuscular or subcutaneous adipocyte cells or the subcutaneous fat depth. The results suggest that vitamin A affects the amount of marbling and other attributes of the marbling flecks due to hyperplasia rather than hypertrophy. This may explain why vitamin A restriction specifically affects IMF rather than subcutaneous fat deposition.
Publisher: Wiley
Date: 09-07-2007
DOI: 10.1359/JBMR.070706
Abstract: The aim of this study was to investigate the effects of overload in orthogonal directions on longitudinal and transverse mechanical integrity in human vertebral trabecular bone. Results suggest that the trabecular structure has properties that act to minimize the decrease of apparent toughness transverse to the primary loading direction. The maintenance of mechanical integrity and function of trabecular structure after overload remains largely unexplored. Whereas a number of studies have focused on addressing the question by testing the principal anatomical loading direction, the mechanical anisotropy has been overlooked. The aim of this study was to investigate the effects of overload in orthogonal directions on longitudinal and transverse mechanical integrity in human vertebral trabecular bone. T(12)/L(1) vertebral bodies from five cases and L(4)/L(5) vertebral bodies from seven cases were retrieved at autopsy. A cube of trabecular bone was cut from the centrum of each vertebral body and imaged by microCT. Cubes from each T(12)/L(1) and L(4)/L(5) pairs were assigned to either superoinferior (SI) or anteroposterior (AP) mechanical testing groups. All s les were mechanically tested to 10% apparent strain by uniaxial compression according to their SI or AP allocation. To elucidate the extent to which overload in orthogonal directions affects the mechanical integrity of the trabecular structure, s les were retested (after initial uniaxial compression) in their orthogonal direction. After mechanical testing in each direction, apparent ultimate failure stresses (UFS), apparent elastic moduli (E), and apparent toughness moduli (u) were computed. Significant differences in mechanical properties were found between SI and AP directions in both first and second overload tests. Mechanical anisotropy far exceeded differences resulting from overloading the structure in the orthogonal direction. No significant differences were found in mean UFS and mean u for the first or second overload tests. A significant decrease of 35% was identified in mean E for cubes overloaded in the SI direction and then overloaded in the AP direction. Observed differences in the mechanics of trabecular structure after overload suggests that the trabecular structure has properties that act to minimize loss of apparent toughness, perhaps through energy dissipating sacrificial structures transverse to the primary loading direction.
Publisher: Elsevier BV
Date: 11-2018
Publisher: Elsevier BV
Date: 03-2014
Publisher: Elsevier BV
Date: 11-2015
Publisher: Springer Berlin Heidelberg
Date: 2006
DOI: 10.1007/11783237_86
Publisher: Cambridge University Press (CUP)
Date: 26-06-2018
DOI: 10.1017/S1049023X1800050X
Abstract: Mass gatherings are complex events that present a unique set of challenges to attendees’ health and well-being. There are numerous factors that influence the number and type of injuries and illnesses that occur at these events, including weather, event and venue type, and crowd demographics and behavior. While the impact of some factors, such as weather conditions and the availability of alcohol, on patient presentations at mass gatherings have been described previously, the influence of many other variables, including crowd demographics, crowd behavior, and event type, is poorly understood. Furthermore, a large number of studies reporting on the influence of these variables on patient presentations are based on anecdotal evidence at a single mass-gathering event. Data were collected by trained fieldworkers at 15 mass gatherings in South Australia and included event characteristics, crowd demographics, and weather. De-identified patient records were obtained from on-site health care providers. Data analysis included the calculation of patient proportions in each variable category, as well as the total number of patient presentations per event and the patient presentation rate (PPR). The total number of expected attendees at the 15 mass gatherings was 303,500, of which 146 presented to on-site health care services. The majority of patient presentations occurred at events with a mean temperature between 20°C and 25°C. The PPR was more than double at events with a predominantly male crowd compared to events with a more equal sex distribution. Almost 90.0% of patient presentations occurred at events where alcohol was available. The results of the study suggest that several weather, crowd, and event variables influence the type and number of patient presentations observed at mass-gathering events. Given that the study s le size did not allow for these interactions to be quantified, further research is warranted to investigate the relationships between alcohol availability, crowd demographics, crowd mobility, venue design, and injuries and illnesses. Anikeeva O, Arbon P, Zeitz K, Bottema M, Lund A, Turris S, Steenk M. Patient presentation trends at 15 mass-gathering events in South Australia. Prehosp Disaster Med. 2018 (4):368–374.
Publisher: Wiley
Date: 2003
DOI: 10.1002/NME.649
Publisher: IEEE
Date: 11-2015
Publisher: Wiley
Date: 26-02-2008
Publisher: IEEE
Date: 12-2005
Publisher: IEEE
Date: 2005
Publisher: Elsevier BV
Date: 2006
Publisher: SPIE
Date: 06-03-2008
DOI: 10.1117/12.770322
Publisher: IEEE
Date: 2009
Publisher: Elsevier BV
Date: 09-2007
Publisher: Springer Science and Business Media LLC
Date: 06-2005
DOI: 10.1007/S10548-005-6029-X
Abstract: Neural activity within the human brain produces electrical potentials that are transmitted through the various tissues of the head to the scalp. A three-dimensional finite difference model has been applied to simulate this process and used as the basis for an inverse model, wherein known potentials on the scalp are used to locate sources of neural activity within the brain. The inverse model uses linear and nonlinear response functions, together with nonlinear regression to determine the source location. The model has been applied to three different simulations, and in each case was able to locate the source using a combination of linear and nonlinear response functions.
Publisher: IEEE
Date: 11-2016
Publisher: IEEE
Date: 11-2015
Publisher: IEEE
Date: 12-2007
Publisher: The Royal Society
Date: 10-2018
DOI: 10.1098/RSOS.180820
Abstract: Pseudohyphal growth of the dimorphic yeast Saccharomyces cerevisiae is analysed using two-dimensional top-down binary images. The colony morphology is characterized using clustered shape primitives (CSPs), which are learned automatically from the data and thus do not require a list of predefined features or a priori knowledge of the shape. The power of CSPs is demonstrated through the classification of pseudohyphal yeast colonies known to produce different morphologies. The classifier categorizes the yeast colonies considered with an accuracy of 0.969 and standard deviation 0.041, demonstrating that CSPs capture differences in morphology, while CSPs are found to provide greater discriminatory power than spatial indices previously used to quantify pseudohyphal growth. The analysis demonstrates that CSPs provide a promising avenue for analysing morphology in high-throughput assays.
Publisher: Springer Berlin Heidelberg
Date: 2012
Publisher: Elsevier BV
Date: 2014
Publisher: SPIE
Date: 23-02-2012
DOI: 10.1117/12.911862
No related grants have been discovered for Murk Bottema.