General Recursion via Coinductive Types

A fertile field of research in theoretical computer science investigates the representation of general recursive functions in intensional type theories. Among the most successful approaches are: the use of wellfounded relations, implementation of operational semantics, formalization of domain theory, and inductive definition of domain predicates. Here, a different solution is proposed: exploiting coinductive types to model infinite computations. To every type A we associate a type of partial elements Partial(A), coinductively generated by two constructors: the first, return(a) just returns an element a:A; the second, step(x), adds a computation step to a recursive element x:Partial(A). We show how this simple device is sufficient to formalize all recursive functions between two given types. It allows the definition of fixed points of finitary, that is, continuous, operators. We will compare this approach to different ones from the literature. Finally, we mention that the formalization, with appropriate structural maps, defines a strong monad.Comment: 28 page

Cost-Effectiveness of Total Hip and Knee Replacements for the Australian Population with Osteoarthritis: Discrete-Event Simulation Model

Background: Osteoarthritis constitutes a major musculoskeletal burden for the aged Australians. Hip and knee replacement surgeries are effective interventions once all conservative therapies to manage the symptoms have been exhausted. This study aims to evaluate the cost-effectiveness of hip and knee replacements in Australia. To our best knowledge, the study is the first attempt to account for the dual nature of hip and knee osteoarthritis in modelling the severities of right and left joints separately

Cost-Effectiveness of Pharmacotherapy to Reduce Obesity

Aims: Obesity causes a high disease burden in Australia and across the world. We aimed to analyse the cost-effectiveness of weight reduction with pharmacotherapy in Australia, and to assess its potential to reduce the disease burden due to excess body weight

Degenerative Disease in an Aging Population Models and Conjectures

This PhD thesis is rootcd in a mnltidisciplinary project, ca lied Technology Assessment lvlethods (TAM). The (ambitious) aim of the TAM project was to develop a comprehcllsive method of evalnating medical tcchnology in the perspective of multiple risk factors, multiple diseascs and multiple causes of death (Bonneux & Bai'endregt, 1991). Thc project was an attempt to bettel' llllderstand the dynamics of populatioll health status, in particnlar in relation to medical intervclltions, but it was "lso lllotivated by thc rapidly rising health care costs of the past decades, whieh fueled the feal' that ever expanding casts might become economically unsllstainahle in the future (van der Maas & Habbema, 1986). The TAM project would provide a better lUlderstanding of the consequcllces for beth casts and popt!lation hcalth status of a \\Vide array of preventivc aud therapeutic health care interventions, and through that offer the tools for policy makers to huy the better investments in health with a sustaillahle health carc budget. Two factors arc commanly held responsible for the increase in health care costs: aging and health care technology

Adult obesity and the burden of disability throughout life

OBJECTIVE: To analyze the prevalence of disability throughout life and life expectancy free of disability, associated with obesity at ages 30 to 49 years. RESEARCH METHODS AND PROCEDURES: We used 46 and 20 years of mortality follow-up, respectively, for 3521 Original and 3013 Offspring Framingham Heart Study participants 30 to 49 years and classified as normal weight, overweight, or obese at baseline. Disability measures were available between 36 and 46 years of follow-up for 1352 Original participants and at 20 years of follow-up for 2268 Offspring participants. We measured the odds of disability in the Original cohort after 46 years follow-up, and we estimated life expectancy with and without disability from age 50. Two disability measures were used, one representing limitations with mobility only and the second representing limitations with activities of daily living (ADL). RESULTS: Obesity at ages 30 to 49 years was associated with a 2.01-fold increase in the odds of ADL limitations 46 years later. Nonsmoking adults who were obese between 30 and 49 years lived 5.70 (95% confidence interval, 4.11 to 7.35) (men) and 5.02 (95% confidence interval, 3.36 to 6.61) (women) fewer years free of ADL limitations from age 50 than their normal-weight counterparts. There was no significant difference in the total number of years lived with disability throughout life between those obese or normal weight, due to both higher disability prevalence and higher mortality in the obese population. DISCUSSION: Obesity in adulthood is associated with an increased risk of disability throughout life and a reduction in the length of time spent free of disability, but no substantial change in the length of time spent with disability