Tight Performance Guarantees of Imitator Policies with Continuous Actions

Behavioral Cloning (BC) aims at learning a policy that mimics the behavior demonstrated by an expert. The current theoretical understanding of BC is limited to the case of finite actions. In this paper, we study BC with the goal of providing theoretical guarantees on the performance of the imitator policy in the case of continuous actions. We start by deriving a novel bound on the performance gap based on Wasserstein distance, applicable for continuous-action experts, holding under the assumption that the value function is Lipschitz continuous. Since this latter condition is hardy fulfilled in practice, even for Lipschitz Markov Decision Processes and policies, we propose a relaxed setting, proving that value function is always H\"older continuous. This result is of independent interest and allows obtaining in BC a general bound for the performance of the imitator policy. Finally, we analyze noise injection, a common practice in which the expert’s action is executed in the environment after the application of a noise kernel. We show that this practice allows deriving stronger performance guarantees, at the price of a bias due to the noise addition

Glycaemic variability-based classification of impaired glucose tolerance vs. type 2 diabetes using continuous glucose monitoring data

Many glycaemic variability (GV) indices extracted from continuous glucose monitoring systems data have been proposed for the characterisation of various aspects of glucose concentration profile dynamics in both healthy and non-healthy individuals. However, the inter-index correlations have made it difficult to reach a consensus regarding the best applications or a subset of indices for clinical scenarios, such as distinguishing subjects according to diabetes progression stage. Recently, a logistic regression-based method was used to address the basic problem of differentiating between healthy subjects and those affected by impaired glucose tolerance (IGT) or type 2 diabetes (T2D) in a pool of 25 GV-based indices. Whereas healthy subjects were classified accurately, the distinction between patients with IGT and T2D remained critical. In the present work, by using a dataset of CGM time-series collected in 62 subjects, we developed a polynomial-kernel support vector machine-based approach and demonstrated the ability to distinguish between subjects affected by IGT and T2D based on a pool of 37 GV indices complemented by four basic parameters—age, sex, BMI, and waist circumference—with an accuracy of 87.1%.Peer reviewe

Autoregressive Bandits

Autoregressive processes naturally arise in a large variety of real-world scenarios, including e.g., stock markets, sell forecasting, weather prediction, advertising, and pricing. When addressing a sequential decision-making problem in such a context, the temporal dependence between consecutive observations should be properly accounted for converge to the optimal decision policy. In this work, we propose a novel online learning setting, named Autoregressive Bandits (ARBs), in which the observed reward follows an autoregressive process of order $k$, whose parameters depend on the action the agent chooses, within a finite set of $n$ actions. Then, we devise an optimistic regret minimization algorithm AutoRegressive Upper Confidence Bounds (AR-UCB) that suffers regret of order $\widetilde{\mathcal{O}} \left( \frac{(k+1)^{3/2}\sqrt{nT}}{(1-\Gamma)^2} \right)$, being $T$ the optimization horizon and $\Gamma < 1$ an index of the stability of the system. Finally, we present a numerical validation in several synthetic and one real-world setting, in comparison with general and specific purpose bandit baselines showing the advantages of the proposed approach

Compensation for Energy Infrastructures: Can a Capability Approach be More Equitable?

In this article, we deal with the evaluation of the losses suffered by persons living in urban areas as a result of energy services. In the first part, we analyse how by adopting different informational foci we obtain contrasting interpersonal evaluations regarding the same loss. In the second part, we distinguish between a diachronic and a hypothetical/moralised threshold for harm in order to assess whether individuals are benefiting from or being harmed by a given energy service. Our argument is that the most accurate evaluation of an individual damage caused by an energy service can be obtained by using capabilities as informational focus, instead of realised wellbeing or means to wellbeing, and by interpreting the loss in relation to a hypothetical/moralised threshold that corresponds to a list of central capabilities. In the last part, we address monetary and non-monetary compensations for a loss that is evaluated in terms of capabilities. Accordingly, we expound how compensation policies can either restore the capabilities lost due to energy services or monetarily compensate the individual for the fact that a given capability (or set of capabilities) has been irremediably lost

Resistance to bribery when aggregating soft constraints

Abstract We consider a multi-agent scenario, where the preferences of several agents are modelled via soft constraint problems and need to be aggregated to compute a single &quot;socially optimal&quot; solution. We study the resistance of various ways to compute such a solution to influence the result, such as those based on the notion of bribery. In doing this, we link the cost of bribing an agent to the effort needed by the agent to make a certain solution optimal, by only changing preferences associated to parts of the solution. This leads to the definition of four notions of distance from optimality of a solution in a soft constraint problem. The notions differ on the amount of information considered when evaluating the effort

Influence of nanoliposomes incorporation on properties of film forming dispersions and films based on corn starch and sodium caseinate

The incorporation of potentially antimicrobial volatile compounds (orange essential oil and limonene) into soy and rapeseed nanoliposomes was carried out by encapsulating them trough sonication of their aqueous dispersions. Nanoliposomes were added to starch-sodium caseinate (50:50) film forming dispersions, which were dried to obtain films without losses of the volatile compounds. Structural, mechanical and optical properties of the films were analysed, as well as their antimicrobial activity against Listeria monocytogenes. The addition of liposomes in the polymeric matrix supposed a decrease of the mechanical resistance and extensibility of the films. The natural colour of lecithin conferred a loss of lightness, a chroma gain and a redder hue to the films, which were also less transparent than the control one, regardless the lecithin and volatile considered. The possible antimicrobial activity of the films containing orange essential oil or limonene was not observed, which could be due to their low antilisterial activity or to the inhibition effect of the encapsulation which difficult their release from the matrix.Jiménez Marco, A.; Sánchez González, L.; Desobry, S.; Chiralt Boix, MA.; Arab Tehrany, E. (2014). Influence of nanoliposomes incorporation on properties of film forming dispersions and films based on corn starch and sodium caseinate. Food Hydrocolloids. 35:159-169. doi:10.1016/j.foodhyd.2013.05.006S1591693

The Transcriptional Response in Human Umbilical Vein Endothelial Cells Exposed to Insulin: A Dynamic Gene Expression Approach

BACKGROUND: In diabetes chronic hyperinsulinemia contributes to the instability of the atherosclerotic plaque and stimulates cellular proliferation through the activation of the MAP kinases, which in turn regulate cellular proliferation. However, it is not known whether insulin itself could increase the transcription of specific genes for cellular proliferation in the endothelium. Hence, the characterization of transcriptional modifications in endothelium is an important step for a better understanding of the mechanism of insulin action and the relationship between endothelial cell dysfunction and insulin resistance. METHODOLOGY AND PRINCIPAL FINDINGS: The transcriptional response of endothelial cells in the 440 minutes following insulin stimulation was monitored using microarrays and compared to a control condition. About 1700 genes were selected as differentially expressed based on their treated minus control profile, thus allowing the detection of even small but systematic changes in gene expression. Genes were clustered in 7 groups according to their time expression profile and classified into 15 functional categories that can support the biological effects of insulin, based on Gene Ontology enrichment analysis. In terms of endothelial function, the most prominent processes affected were NADH dehydrogenase activity, N-terminal myristoylation domain binding, nitric-oxide synthase regulator activity and growth factor binding. Pathway-based enrichment analysis revealed "Electron Transport Chain" significantly enriched. Results were validated on genes belonging to "Electron Transport Chain" pathway, using quantitative RT-PCR. CONCLUSIONS: As far as we know, this is the first systematic study in the literature monitoring transcriptional response to insulin in endothelial cells, in a time series microarray experiment. Since chronic hyperinsulinemia contributes to the instability of the atherosclerotic plaque and stimulates cellular proliferation, some of the genes identified in the present work are potential novel candidates in diabetes complications related to endothelial dysfunction

A Utilisation Focussed and Viable Systems Approach for Evaluating Technology Supported Learning

The paper uses a higher education case study to illustrate a participative theory of change approach to evaluating technology supported learning. The approach is informed by the Viable Systems Model (VSM) and utilisation-focussed evaluation and, falls within the tradition of facilitated modelling approaches to operational research. We argue that this approach worked well in engaging primary evaluation users in a process of collaborative action research to improving an educational development initiative and that the approach helped generate information relevant to answering its primary users’ questions, to inform their specific decisions and actions relevant to their quality enhancement responsibilities. Through a case study, concerning the evaluation of an educational development initiative in a large UK university, we illustrate how the VSM and utilisation-focussed evaluation could be used to: (a) conceptualise the connection between strategies and their components at different levels of organisation; (b) to clarify the role and interests of stakeholders in these strategies; and (c) to scope evaluation to be relevant to informing the decisions and actions of these stakeholders. The paper contributes to illustrate how VSM principles can underpin a theory of change approach to engaging primary stakeholders in planning an intervention and its evaluation in the context of educational development work, in order to improve evaluation to be more relevant to their needs. The paper should be of interest to researchers exploring the use of systems theory in evaluation, in particular in the context of educational development work in higher education