Simulation analysis of the consequences of shifting the balance of health care: a system dynamics approach

Objectives: The shift in the balance of health care, bringing services 'closer to home', is a well-established trend. This study sought to provide insight into the consequences of this trend, in particular the stimulation of demand, by exploring the underlying feedback structure. Methods: We constructed a simulation model using the system dynamics method, which is specifically designed for the analysis of feedback structure. The model was calibrated to two cases of the shift in cardiac catheterization services in the UK. Data sources included archival data, observations and interviews with senior health care professionals. Key model outputs were the basic trends displayed by waiting lists, average waiting times, cumulative patient referrals, cumulative patient activity and cumulative overall costs. Results: Demand was stimulated in both cases via several different mechanisms. We revealed the roles for clinical guidelines and capacity changes, and the typical responses to imbalances between supply and demand. Our analysis also demonstrated the potential benefits of changing the goals that drive activity by seeking a waiting list goal rather than a waiting time goal. Conclusions: Appreciating the wider consequences of shifting the balance of care is essential if services are to be improved overall. The underlying feedback mechanisms of both intended and unintended effects need to be understood. Using a systemic approach, more effective policies may be designed through coordinated programmes rather than isolated initiatives, which may have only a limited impact

Multi-Link Leisure Developments Ltd v North Lanarkshire Council: Commercial Interpretation or Relief From a Bad Bargain?

In the 2011 decision Multi-Link Leisure Developments Ltd v North Lanarkshire Council, the United Kingdom Supreme Court purported to apply a business common sense approach to the interpretation of an option clause in a lease.  In particular, several of the Lords identified that the one possible interpretation of the clause would lead to a "windfall" – a significant financial advantage – for the appellant. Their reasons hinged significantly on their view that this was a consequence inconsistent with commercial sense, which the parties were unlikely to have intended. This article analyses the relevance of a "windfall" in the context of the modern common sense approach to the construction of contracts. It concludes that the Court’s reliance upon a "windfall" of this kind goes beyond the bounds of commercial interpretation and introduces problematic notions of substantive fairness into a business common sense approach to the interpretation of contracts

Episodic Learning with Control Lyapunov Functions for Uncertain Robotic Systems

Many modern nonlinear control methods aim to endow systems with guaranteed properties, such as stability or safety, and have been successfully applied to the domain of robotics. However, model uncertainty remains a persistent challenge, weakening theoretical guarantees and causing implementation failures on physical systems. This paper develops a machine learning framework centered around Control Lyapunov Functions (CLFs) to adapt to parametric uncertainty and unmodeled dynamics in general robotic systems. Our proposed method proceeds by iteratively updating estimates of Lyapunov function derivatives and improving controllers, ultimately yielding a stabilizing quadratic program model-based controller. We validate our approach on a planar Segway simulation, demonstrating substantial performance improvements by iteratively refining on a base model-free controller

Large Deviations for Brownian Intersection Measures

We consider $p$ independent Brownian motions in $\R^d$. We assume that $p\geq 2$ and $p(d-2)<d$. Let $\ell_t$ denote the intersection measure of the $p$ paths by time $t$, i.e., the random measure on $\R^d$ that assigns to any measurable set $A\subset \R^d$ the amount of intersection local time of the motions spent in $A$ by time $t$. Earlier results of Chen \cite{Ch09} derived the logarithmic asymptotics of the upper tails of the total mass $\ell_t(\R^d)$ as $t\to\infty$. In this paper, we derive a large-deviation principle for the normalised intersection measure $t^{-p}\ell_t$ on the set of positive measures on some open bounded set $B\subset\R^d$ as $t\to\infty$ before exiting $B$. The rate function is explicit and gives some rigorous meaning, in this asymptotic regime, to the understanding that the intersection measure is the pointwise product of the densities of the normalised occupation times measures of the $p$ motions. Our proof makes the classical Donsker-Varadhan principle for the latter applicable to the intersection measure. A second version of our principle is proved for the motions observed until the individual exit times from $B$, conditional on a large total mass in some compact set $U\subset B$. This extends earlier studies on the intersection measure by K\"onig and M\"orters \cite{KM01,KM05}.Comment: To appear in "Communications on Pure and Applied Mathematics

The impact of endovascular treatment on cerebral aneurysm outcome at Groote Schuur Hospital

Objectives. Neuro-endovascular treatment was introduced at Groote Schuur Hospital in 2001. We sought to  assess whether this has resulted in a change in overall outcomes for patients treated for cerebral aneurysms.Design. Retrospective cohort study. The first cohort included cerebral aneurysm patients seen between 1994 and 1998 when only surgical treatment was available. The second cohort consisted of a group treated using both surgical and endovascular methods between 2002 and 2004.Subjects. Patients with ruptured and unruptured aneurysms were included in the study.Outcome measures. The Glasgow Outcome Score (GOS) was used to assess outcome. The primary  comparator between groups was major disability (GOS 3 and 2) and death (GOS 1)

Endovascular treatment of cerebral aneurysms - a cost analysis

Objectives. To determine if endovascular treatment of cerebral aneurysms is cost effective when  compared with conventional surgical treatment.Design. A retrospective study.Subjects. Seventeen patients treated between August 2002 and August 2003 had posterior communicating artery aneurysms. This group was selected for detailed analysis.Outcome measures. Total treatment costs, in South African rands (R), were calculated for each patient. Average treatment costs for each group were then compared.Results. Surgically clipped and endovascularly coiled groups were comparable for age, sex and clinical condition. The average cost for endovascular  treatment per patient was R37 041. Surgical treatment was more expensive at R44 104, a difference of 16%.Conclusions. Despite the high cost of endovascular devices, appropriate use of this technology ultimately  offers less expensive treatment than microsurgical clipping of aneurysms

Response of clay soil to three-dimensional tunnelling simulation in centrifuge models

Tunnelling-induced ground movements are complicated and investigations into them normally require some simplifications. This paper provides a brief literature review which highlights the advantages of adopting simplifications in physical modelling and addresses some of the deficiencies in the assessment of soil deformation due to a simulated tunnel excavation. A set of centrifuge tests modelling a tunnel heading located at different depths in clay was carried out at 125g. The tunnel was modelled by a semi-circular cavity partly supported by a stiff lining. The unlined tunnel heading was supported by a thin rubber bag supplied with compressed air pressure. Tunnel excavation was simulated by reducing air pressure. The induced ground movements at the subsurface and surface were measured by a 2D image analysis and a new, novel 3D imaging system. The results show that the experiment successfully reproduced key aspects of tunnelling-induced soil deformation in practice. In addition, a new equation to predict horizontal displacements in the longitudinal direction is proposed

The Effects of Menthol Concentrations on Germination Rates of Arabidopsis thaliana

Faculty Research Day 2018: Undergraduate Student Poster 3rd PlaceMenthol is a toxin found in plants. Arabidopsis thaliana was tested with several different concentrations of menthol to observe whether or not germination and fungal growth would be inhibited due to the menthol

Ground response to tunnelling incorporating a soil reinforcement system

The Forepole Umbrella System (FUS) uses steel pipes installed from within a tunnel to provide a canopy above the tunnel heading that both increases stability and reduces tunnelling-induced ground movements. Although the system is known to be beneficial and has been used in a number of projects, there is little information on how key parameters including length and forepole stiffness combine to produce effective support. To investigate this, centrifuge tests incorporating the three-dimensional geometry of a tunnel heading in clay and the model FUS have been undertaken. The tunnel heading was supported by a pressurised rubber bag lining with excavation being simulated by a reduction in air support pressure. Image analysis was used to obtain subsurface ground movements and a newly developed 3D imaging system was used to measure accurately the soil surface deformations. The performance of the FUS and the influences of key FUS parameters were quantified via the settlement reduction factor. The results showed that the FUS, arranged in various settings, reduced the maximum surface settlement by 35-75%. The effects of the FUS parameters to the reinforcing effectiveness is dependent on the ratio of cover depth to tunnel diameter. An optimum design arrangement of the FUS is suggested