Strategy Synthesis for Autonomous Agents Using PRISM

We present probabilistic models for autonomous agent search and retrieve missions derived from Simulink models for an Unmanned Aerial Vehicle (UAV) and show how probabilistic model checking and the probabilistic model checker PRISM can be used for optimal controller generation. We introduce a sequence of scenarios relevant to UAVs and other autonomous agents such as underwater and ground vehicles. For each scenario we demonstrate how it can be modelled using the PRISM language, give model checking statistics and present the synthesised optimal controllers. We conclude with a discussion of the limitations when using probabilistic model checking and PRISM in this context and what steps can be taken to overcome them. In addition, we consider how the controllers can be returned to the UAV and adapted for use on larger search areas

Metabolic Profiling of the Diabetic Heart: Towards a Richer Picture

The increasing global prevalence of diabetes has been accompanied by a rise in diabetes-related conditions. This includes diabetic cardiomyopathy, a progressive form of heart disease that occurs with both insulin-dependent (type-1) and insulin-independent (type-2) diabetes and arises in the absence of hypertension or coronary artery disease. Over time, diabetic cardiomyopathy can develop into overt heart failure. Like other forms of cardiomyopathy, diabetic cardiomyopathy is accompanied by alterations in metabolism which could lead to further progression of the pathology, with metabolic derangement postulated to precede functional changes in the diabetic heart. Moreover in the case of type-2 diabetes, underlying insulin resistance is likely to prevent the canonical substrate switch of the failing heart away from fatty acid oxidation towards increased use of glycolysis. Analytical chemistry techniques, collectively known as metabolomics, are useful tools for investigating the condition. In this article, we provide a comprehensive review of those studies that have employed metabolomic techniques, namely chromatography, mass spectrometry and nuclear magnetic resonance spectroscopy, to profile metabolic remodelling in the diabetic heart of human patients and animal models. These studies collectively demonstrate that glycolysis and glucose oxidation are suppressed in the diabetic myocardium and highlight a complex picture regarding lipid metabolism. The diabetic heart typically shows an increased reliance on fatty acid oxidation, yet triacylglycerols and other lipids accumulate in the diabetic myocardium indicating probable lipotoxicity. The application of lipidomic techniques to the diabetic heart has identified specific lipid species that become enriched and which may in turn act as plasma-borne biomarkers for the condition. Metabolomics is proving to be a powerful approach, allowing a much richer analysis of the metabolic alterations that occur in the diabetic heart. Careful physiological interpretation of metabolomic results will now be key in order to establish which aspects of the metabolic derangement are causal to the progression of diabetic cardiomyopathy and might form the basis for novel therapeutic intervention.RCUK and BH

Chaotic zone boundary for low free eccentricity particles near an eccentric planet

We consider particles with low free or proper eccentricity that are orbiting near planets on eccentric orbits. Via collisionless particle integration we numerically find the location of the boundary of the chaotic zone in the planet's corotation region. We find that the distance in semi-major axis between the planet and boundary depends on the planet mass to the 2/7 power and is independent of the planet eccentricity, at least for planet eccentricities below 0.3. Our integrations reveal a similarity between the dynamics of particles at zero eccentricity near a planet in a circular orbit and with zero free eccentricity particles near an eccentric planet. The 2/7 law has been previously explained by estimating the semi-major at which the first order mean motion resonances are large enough to overlap. Orbital dynamics near an eccentric planet could differ due to first order corotation resonances that have strength proportional to the planet's eccentricity. However, we find the corotation resonance width at low free eccentricity is small. Also the first order resonance width at zero free eccentricity is the same as that for a zero eccentricity particle near a planet in a circular orbit. This accounts for insensitivity of the chaotic zone width to planet eccentricity. Particles at zero free eccentricity near an eccentric planet have similar dynamics to those at zero eccentricity near a planet in a circular orbit.Comment: accepted for publication in MNRA

Identification of proteins that bind extracellular microRNAs secreted by the parasitic nematode Trichinella spiralis

Small non-coding RNAs such as microRNAs (miRNAs) are conserved across eukaryotes and play key roles in regulating gene expression. In many organisms, miRNAs are also secreted from cells, often encased within vesicles such as exosomes, and sometimes extravesicular. The mechanisms of miRNA secretion, how they are stabilised outside of cells and their functional importance are poorly understood. Recently, we characterised the parasitic nematode Trichinella spiralis as a model to study miRNA secretion. T. spiralis muscle-stage larvae (MSL) secrete abundant miRNAs which are largely extravesicular. Here, we investigated how T. spiralis miRNAs might remain stable outside of cells. Using proteomics, we identified two RNA binding proteins secreted by T. spiralis larvae and characterised their RNA binding properties. One, a homologue of the known RNA binding protein KSRP, binds miRNA in a selective and sequence-specific fashion. Another protein, which is likely a novel RNA binding protein, binds to miRNA without exhibiting sequence specificity. Our results suggest a possible mechanism for miRNA secretion by T. spiralis and may have relevance for understanding the biology of extracellular miRNA more widely

Autonomous agent behaviour modelled in PRISM -- a case study

This work was supported by the Engineering and Physical Sciences Research Council [grant number EP/N508792/1].Formal verification of agents representing robot behaviour is a growing area due to the demand that autonomous systems have to be proven safe. In this paper we present an abstract definition of autonomy which can be used to model autonomous scenarios and propose the use of small-scale simulation models representing abstract actions to infer quantitative data. To demonstrate the applicability of the approach we build and verify a model of an unmanned aerial vehicle (UAV) in an exemplary autonomous scenario, utilising this approach.Publisher PD

An Extended Double Row Layout Problem

The double row layout problem (DRLP) seeks to determine optimal machine locations on either side of an aisle, where the objective has been defined as the minimization of material ow cost among ma- chines while meeting machine clearance constraints. In this paper, we extend existing DRLP formulations in two respects. First, we consider the minimization of layout area besides the usual material ow cost objective. Second, we present a mixed integer linear programming formulation that permits non-zero aisle widths. This new formulation also includes new constraints that eliminate layout \mirroring, thus reducing the solution space significantly and thus solution times. Although small-scale problems may be solved optimally by commercial integer programming solvers, solution times are highly sensitive to the number of machines in a layout. A tabu search heuristic is shown to work well for moderately-sized problems. Numerical examples demonstrating the impact of both ow and area objectives, as well as aisle widths, are included

Essays in Applied Microeconomics

This dissertation consists of three essays in applied microeconomics. The first chapter looks at whether the Social Security claiming behavior of husbands respond to the presence of Social Security spouse and survivor benefits paid to wives based on his earnings record. I separately estimate the claiming response to incentives for each of the three types of Social Security benefits: retired worker, spousal, and survivor. This approach departs from the previous literature, which estimates behavioral responses to household incentives. I begin by documenting that failure to maximize household Social Security wealth results in a financial burden borne primarily by the wife. I next estimate husbands' behavioral response to Social Security benefit incentives, with my focus exclusively upon incentives due to the actuarial adjustment from delayed claiming. Variation in incentives comes from rule changes to the Social Security benefit calculation, in addition to the age difference between spouses and the relative strength of the wife's labor force history. I find while husbands are responsive to their own benefit incentives, they are barely responsive to household, spousal, and survivor benefit incentives. A variety of robustness checks looking at segments of the population predicted to be more responsive to incentives provide very similar results to main specification. The second chapter examines the incidence of health insurance coverage for displaced workers during the periods preceding and subsequent to job displacement. Most individuals lose health insurance coverage upon job separation. There is concern that individuals are unable to recover insurance coverage following separation. I find within 18 months following job loss the level of health insurance coverage returns to pre-displacement level. Furthermore, I find that obtaining insurance coverage upon reemployment does not impact wages. The third chapter first examines how much of the fall in poverty among elderly women can be attributed to changes in the distributions of age, marital status, and education of elderly women using the Current Population Survey. Increased educational attainment has put tremendous downward pressure on the poverty rate driven primarily by the shift of high school dropouts to those with a high school diploma. I also find poverty would be slightly lower in the absence of changes to the age distribution and no direct impact on poverty levels due to the changes in distribution of marital status. I also investigate the role of both labor force participation and marital status over the life-cycle on old age outcomes using survey data matched to administrative earnings records from the Census Bureau. I find even after controlling for Social Security and marital status over prime-age years, lifetime earnings and labor force experience still has a significant impact on poverty incidence of elderly women. Projecting poverty for cohorts who have not reached old age, I find increased wages and LFP over the life-cycle places large downward pressure on predicted poverty. Marital status over the life-cycle exerts its own negative impact on poverty