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Item Metadata only Extending mixtures of factor models using the restricted multivariate skew-normal distribution(Elsevier, 2016) Lin, T.-I.; McLachlan, G.J.; Lee, S.X.The mixture of factor analyzers (MFA) model provides a powerful tool for analyzing high-dimensional data as it can reduce the number of free parameters through its factor-analytic representation of the component covariance matrices. This paper extends the MFA model to incorporate a restricted version of the multivariate skew-normal distribution for the latent component factors, called mixtures of skew-normal factor analyzers (MSNFA). The proposed MSNFA model allows us to relax the need of the normality assumption for the latent factors in order to accommodate skewness in the observed data. The MSNFA model thus provides an approach to model-based density estimation and clustering of high-dimensional data exhibiting asymmetric characteristics. A computationally feasible Expectation Conditional Maximization (ECM) algorithm is developed for computing the maximum likelihood estimates of model parameters. The potential of the proposed methodology is exemplified using both real and simulated data.Item Metadata only Transnational comparison of sustainability assessment programs for viticulture and a case-study on programs' engagement processes(MDPI, 2014) Santiago-Brown, I.; Metcalfe, A.; Jerram, C.; Collins, C.This article documents and compares the most prominent sustainability assessment programs for individual organisations in viticulture worldwide. Certification and engagement processes for membership uptake; benefits; motives; inhibiting factors; and desirable reporting system features of viticultural sustainability programs, are all considered. Case-study results are derived from nine sustainability programs; 14 focus groups with 83 CEOs, Chief Viticulturists or Winemakers from wine grape production organizations from five countries (Australia, Chile, New Zealand, South Africa and the United States); 12 semi-structured interviews with managers either currently or formerly in charge of the sustainability programs; researcher observations; and analysis of documents. Programs were categorized by their distinct program assessment methods: process-based, best practice-based, indicator-based and criterion-based. We found that programs have been created to increase growers’ sustainability, mainly through the direct and indirect education they receive and promote, and the economic benefit to their business caused by overall improvement of their operations. The main finding from this study is that the success of each of these programs is largely due to the people driving the programs (program managers, innovative growers and/or early adopters) and the way these people communicate and engage with their stakeholders and peers.Item Metadata only Existence, uniqueness and comparisons for BSDEs in general spaces(Inst Mathematical Statistics, 2012) Cohen, S.; Elliott, R.We present a theory of backward stochastic differential equations in continuous time with an arbitrary filtered probability space. No assumptions are made regarding the left continuity of the filtration, of the predictable quadratic variations of martingales or of the measure integrating the driver. We present conditions for existence and uniqueness of square-integrable solutions, using Lipschitz continuity of the driver. These conditions unite the requirements for existence in continuous and discrete time and allow discrete processes to be embedded with continuous ones.We also present conditions for a comparison theorem and hence construct time consistent nonlinear expectations in these general spaces.Item Metadata only A Bayesian approach for optimal reinsurance and investment in a diffusion model(Kluwer Academic Publ, 2012) Zhang, X.; Elliott, R.; Siu, T.A Bayesian adaptive control approach to the combined optimal investment/reinsurance problem of an insurance company is studied. The insurance company invests in a money market and a capital market index with an unknown appreciation rate, or “drift”. Using a Bayesian approach, the unknown drift is described by an unobservable random variable with a known (prior) probability distribution. We assume that the risk process of the company is governed by a diffusion approximation to the compound Poisson risk process. The company also purchases reinsurance. The combined optimal investment/reinsurance problem is formulated as a stochastic optimal control problem with partial observations. We employ filtering theory to transform the problem into one with complete observations. The control problem is then solved by the dynamic programming Hamilton–Jacobi–Bellman (HJB) approach. Semi-analytical solutions are obtained for the exponential utility case.Item Metadata only Bayesian Value-at-Risk and expected shortfall forecasting via the asymmetric Laplace distribution(Elsevier Science BV, 2012) Chen, Qian; Gerlach, Richard; Lu, Zudi; School of Mathematical Sciences : StatisticsItem Metadata only Factors affecting survival after endovascular aneurysm repair: results from a population based audit(W B Saunders Co Ltd, 2007) Boult, M.; Maddern, G.; Barnes, M.; Fitridge, R.Objectives: To determine the effect of pre-operative factors on mid-term survival of patients enrolled in an Australian audit of endovascular aneurysm repair (EVAR). Design: Prospective longitudinal national register (audit) of patients undergoing EVAR. Methods: 961 individuals who had elective or semi-urgent EVAR of abdominal aortic aneurysms were enrolled in the audit between November 1999 and May 2001. Data was contributed by 81 surgeons from 64 hospitals. Kaplan-Meier survival analysis was used to determine survival rates and factors significantly influencing survival. Parametric survival analysis with log-exponential distribution was used to estimate expected 3 and 5 year survival for different ages, ASA, creatinine and aneurysm sizes. Results: Overall survival was 93% at 1 year, 80% at 3 years and 67% at five years. Survival rates were found to be statistically associated with ASA, age, aneurysm size and creatinine levels. ASA has the largest effect. Five year survival rates for aneurysms ≥65 mm and <55 mm were 54% and 76% respectively. Pre-operative creatinine levels ≥ 160 μmol/L lowered the survival rate from 71% to 40%. Conclusions: Survival for EVAR patients is strongly correlated with a number of pre-operative factors. This survival analysis provides a useful decision-making tool for surgeons particularly for individuals with smaller aneurysms.Item Metadata only Response to discussion of `AIDS: modelling and predicting' by N.E. Day.(Cambridge University Press., 1996) Solomon, P.Item Metadata only AIDS: Modelling and Predicting.(Cambridge University Press., 1996) Solomon, P.Item Metadata only The influence of urban land-use on non-motorised transport casualties(Pergamon-Elsevier Science Ltd, 2006) Wedagama, D.; Bird, R.; Metcalfe, A.The relationship between non-motorised road traffic casualties and land-use was investigated in two zones of approximately 8 km2 in Newcastle upon Tyne, England. Road traffic accidents are, more usually, analysed in relation to traffic flow, on the assumption that the latter can be derived from land-use data. Here, a direct relationship between primary functional land-use and non-motorised casualties is estimated. We review past work in this area. A shortcoming of casualty data is that it does not record the origin and destination of the journeys being undertaken when the accident occurred. A method was established to identify zones within which most accidents could reasonably be expected to be related to the land-uses within that zone. Generalised linear models were developed using non-motorised casualties as the response variable, with primary functional land-use, population density and junction density as explanatory variables. Separate models were constructed for each combination of cyclists and pedestrians, adults and children, working and non-working hours in city centre and suburban analysis zones. In general, the study found that pedestrian casualties in the city centre zone are particularly associated with an increase in retail and community land-use during working hours. In the city centre zone, out of working hours, an increase in retail land-use (almost certainly clubs and bars) is also associated with an increase in pedestrian casualties. An increase in cyclist casualties during working hours (in the non-pedestrianised area) is associated with an increase in retail land-use.Item Open Access Does dog or cat ownership lead to increased gastroenteritis in young children in South Australia?(Cambridge Univ Press, 2006) Heyworth, J.; Cutt, H.; Glonek, G.The aim of this study was to investigate the relationship between dog and cat ownership and gastroenteritis in young children. A diary study of 965 children aged 4–6 years living in rural or semi-rural South Australia was undertaken. Data were collected on pet ownership, drinking water and other risk factors for gastroenteritis. Overall 89% of households had pets and dog ownership was more common than cat ownership. The multivariable models for gastroenteritis and pet ownership indicated that living in a household with a dog or cat was associated with a reduced risk of gastroenteritis (adj. OR 0·71, 95% CI 0·55–0·92; OR 0·70, % CI 0·51–0·97 respectively). This paper adds to the evidence that pets are not a major source of gastroenteritis in the home and lends support to the health benefits of pet ownership. However, this must be weighed against the potential negative consequences, such as dog bites, particularly for this age group.Item Metadata only Incidence, impact on the family and cost of gastroenteritis among 4 to 6-year-old children in South Australia(Blackwell Publishing Asia, 2006) Heyworth, J.; Jardine, A.; Glonek, G.; Maynard, E.Background: Gastroenteritis is an important cause of morbidity in both adults and children worldwide. Although the burden of morbidity and mortality is highest in developing countries, gastroenteritis is still a significant cause of morbidity in Australia, particularly in young children. The aims of the present study were to determine the incidence of gastroenteritis among 4–6-year-old children in South Australia, to describe the impact on daily activities of the child and caregiver and estimate the cost of gastroenteritis in this population. Methods: A diary study of drinking water consumption and gastrointestinal and respiratory symptoms was undertaken among 965 rural children in South Australia over a 6-week period during February–May 1999. Data on the response to gastrointestinal episodes were collected by telephone surveys midway and at the end of the 6-week period. Costing was based on the methods of Hellard et al . Results: The incidence of community gastroenteritis among 4–6-year-old children was 5.53 episodes per child-year (95% confidence interval: 4.87–5.80). The costs associated with childhood gastroenteritis were estimated to be between $AU16 858 360 and $AU22 477 814 per annum. Conclusions: The incidence of community gastroenteritis among the 4–6-year-olds in the South Australian population is high and it costs the community a significant amount of money in terms of direct medical costs and time lost by parents and carers looking after their ill children.Item Open Access Assessment of outcome over a 10-year period of patients admitted to a multidisciplinary adult intensive care unit with haematological and solid tumours(Australian Soc Anaesthetists, 2005) Moran, J.; Solomon, P.; Williams, P.The risk factors for time to mortality, censored at 30 days, of patients admitted to an adult teaching hospital ICU with haematological and solid malignancies were assessed in a retrospective cohort study. Patients, demographics and daily ICU patient data, from admission to day 8, were identified from a prospective computerised database and casenote review in consecutive admissions to ICU with haematological and solid tumours over a 10 year period (1989-99). The cohort, 108 ICU admissions in 89 patients was of mean age (+/-SD) 55+/-14 years; 43% were female. Patient diagnoses were leukaemia (35%), lymphoma (38%) and solid tumours (27%). Median time from hospital to ICU admission was five days (range 0-67). On ICU admission, 50% had septic shock and first day APACHE II score was 28+/-9. Forty six per cent of patients were ventilated. ICU and 30 day mortality were 39% and 54% respectively. Multivariate Cox model predictors (P<0.05), using only ICU admission day data were: Charlson comorbidity index (CCI), time to ICU admission (days) and mechanical ventilation. For daily data (admission through day 8), predictors were: cohort effect (2nd vs 1st five year period); CCI; time to ICU admission (days); APACHE II score and mechanical ventilation. Outcomes were considered appropriate for severity of illness and demonstrated improvement over time. Ventilation was an independent outcome determinant. Controlling for other factors, mortality has improved over time (1st vs 2nd five year period). Analysis restricted to admission data alone may be insensitive to particular covariate effects.Item Metadata only Goodness-of-fit tests via characterizations(International Journal of Pure and Applied Mathematics, 2005) Morris, K.; Szynal, D.Item Metadata only Characterizations of continuous distributions and associated goodness of fit tests(Kluwer Academic/plenum Publishers, 2005) Morris, K.; Szynal, D.Item Metadata only Tests resulting from characterizations using record values(Kluwer Academic/plenum Publishers, 2005) Morris, K.; Szynal, D.Item Metadata only Effect of social networks on 10 year survival in very old Australians: the Australian longitudinal study of aging(British Med Journal Publ Group, 2005) Giles, L.; Glonek, G.; Luszcz, M.; Andrews, G.Study objectives: To examine if social networks with children, relatives, friends, and confidants predict survival in older Australians over 10 years after controlling for a range of demographic, health, and lifestyle variables. Design: Prospective longitudinal cohort study (the Australian longitudinal study of aging) Setting: Adelaide, South Australia. Participants: 1477 persons aged 70 years or more living in the community and residential care facilities. Main results: After controlling for a range of demographic, health, and lifestyle variables, greater networks with friends were protective against mortality in the 10 year follow up period. The hazard ratio for participants in the highest tertile of friends networks compared with participants in the lowest group was 0.78 (95%CI 0.65 to 0.92). A smaller effect of greater networks with confidants (hazard ratio = 0.84; 95%CI = 0.71 to 0.98) was seen. The effects of social networks with children and relatives were not significant with respect to survival over the following decade. Conclusions: Survival time may be enhanced by strong social networks. Among older Australians, these may be important in lengthening survival.Item Metadata only Expression profiling reveals functionally important genes and coordinately regulated signaling pathway genes during in vitro angiogenesis(American Physiological Society, 2005) Hahn, C.; Su, Z.; Drogemuller, C.; Tsykin, A.; Waterman, S.; Brautigan, P.; Yu, S.; Kremmidiotis, G.; Gardner, A.; Solomon, P.; Goodall, G.; Vadas, M.; Gamble, J.Angiogenesis is a complex multicellular process requiring the orchestration of many events including migration, alignment, proliferation, lumen formation, remodeling, and maturation. Such complexity indicates that not only individual genes but also entire signaling pathways will be crucial in angiogenesis. To define an angiogenic blueprint of regulated genes, we utilized our well-characterized three-dimensional collagen gel model of in vitro angiogenesis, in which the majority of cells synchronously progress through defined morphological stages culminating in the formation of capillary tubes. We developed a comprehensive three-tiered approach using microarray analysis, which allowed us to identify genes known to be involved in angiogenesis and genes hitherto unlinked to angiogenesis as well as novel genes and has proven especially useful for genes where the magnitude of change is small. Of interest is the ability to recognize complete signaling pathways that are regulated and genes clustering into ontological groups implicating the functional importance of particular processes. We have shown that consecutive members of the mitogen-activated protein kinase and leukemia inhibitory factor signaling pathways are altered at the mRNA level during in vitro angiogenesis. Thus, at least for the mitogen-activated protein kinase pathway, mRNA changes as well as the phosphorylation changes of these gene products may be important in the control of blood vessel morphogenesis. Furthermore, in this study, we demonstrated the power of virtual Northern blot analysis, as an alternative to quantitative RT-PCR, for measuring the magnitudes of differential gene expression.Item Metadata only The structured ancestral selection graph and the many-demes limit(Genetics, 2005) Slade, Paul Frederick; Wakeley, John; School of Mathematical SciencesItem Metadata only Meta-analysis of controlled trials of ventilator therapy in acute lung injury and acute respiratory distress syndrome: an alternative perspective(Springer, 2005) Moran, J.; Bersten, A.; Solomon, P.Objective: The role of protective ventilation in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) is controversial. Evidence was sought from published randomised trials for a consistent treatment effect of protective ventilation and any covariate modification. Design: Meta-analysis of protective ventilation trials in ALI/ ARDS and meta-regression of covariates on treatment effect (log odds ratio), with respect to 28-day mortality. Heterogeneity impact on the meta-analysis was assessed by the H statistic (substantial impact, >1.5) and graphical analysis. Five trials with a total of 1,202 patients were considered. Measurements and results: Average 28-day mortality was 0.40 in the treatment group (protective ventilation, n=605) vs. 0.46 in the control group (control ventilation, n=597). The treatment effect (odds ratio) was: fixed-effects, 0.71 (95% CI 0.56–0.91, p=0.006; heterogeneity, p=0.06) and random effects: 0.80 (95% CI 0.49–1.31, p=0.37). Heterogeneity impact (H statistic=1.50) was adjudged as modest. The treatment effect was significant and (a) favoured protective ventilation for a tidal volume less than 7.7 ml/kg predicted (treatment group) and a mean plateau pressure of 30 cmH2O or higher (control group) but was not influenced by plateau pressure 21– 30 cmH2O (treatment group) and (b) depended upon plateau pressure difference greater than 5–7 cmH2O between protective ventilation and standard ventilation. Conclusions: Overall treatment effect estimate favoured protective ventilation but did not achieve statistical significance. Protective ventilation depended upon threshold levels of tidal volume, plateau pressure, and plateau pressure difference.Item Metadata only S and S-PLUS: An Eclectic Tour of the Environment(1998) Venables, William N.
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