Giant capacitance of a plane capacitor with a two-dimensional electron gas in a magnetic field

If a clean two-dimensional electron gas (2DEG) with small concentration $n$ comprises one (or both) electrodes of a plane capacitor, the resulting capacitance $C$ can be larger than the "geometric capacitance" $C_g$ determined by the physical separation $d$ between electrodes. A recent paper [1] argued that when the effective Bohr radius $a_B$ of the 2DEG satisfies $a_B << d$, one can achieve $C >> C_g$ at low concentration $nd^2 << 1$. Here we show that even for devices with $a_B > d$, including graphene, for which $a_B$ is effectively infinite, one also arrives at $C >> C_g$ at low electron concentration if there is a strong perpendicular magnetic field.Comment: 6 pages, 5 figures; updated discussion about bilayer systems; added discussion of fractional quantum Hall state

FRAT-up, a Web-based fall-risk assessment tool for elderly people living in the community.

Background: About 30% of people over 65 are subject to at least one unintentional fall a year. Fall prevention protocols and interventions can decrease the number of falls. To be effective, a prevention strategy requires a prior step to evaluate the fall risk of the subjects. Despite extensive research, existing assessment tools for fall risk have been insufficient for predicting falls. Objective: The goal of this study is to present a novel web-based fall-risk assessment tool (FRAT-up) and to evaluate its accuracy in predicting falls, within a context of community-dwelling persons aged 65 and up. Methods: FRAT-up is based on the assumption that a subject\u2019s fall risk is given by the contribution of their exposure to each of the known fall-risk factors. Many scientific studies have investigated the relationship between falls and risk factors. The majority of these studies adopted statistical approaches, usually providing quantitative information such as odds ratios. FRAT-up exploits these numerical results to compute how each single factor contributes to the overall fall risk. FRAT-up is based on a formal ontology that enlists a number of known risk factors, together with quantitative findings in terms of odds ratios. From such information, an automatic algorithm generates a rule-based probabilistic logic program, that is, a set of rules for each risk factor. The rule-based program takes the health profile of the subject (in terms of exposure to the risk factors) and computes the fall risk. A Web-based interface allows users to input health profiles and to visualize the risk assessment for the given subject. FRAT-up has been evaluated on the InCHIANTI Study dataset, a representative population-based study of older persons living in the Chianti area (Tuscany, Italy). We compared reported falls with predicted ones and computed performance indicators. Results: The obtained area under curve of the receiver operating characteristic was 0.642 (95% CI 0.614-0.669), while the Brier score was 0.174. The Hosmer-Lemeshow test indicated statistical significance of miscalibration. Conclusions: FRAT-up is a web-based tool for evaluating the fall risk of people aged 65 or up living in the community. Validation results of fall risks computed by FRAT-up show that its performance is comparable to externally validated state-of-the-art tools. A prototype is freely available through a web-based interface. Trial Registration: ClinicalTrials.gov NCT01331512 (The InChianti Follow-Up Study); http://clinicaltrials.gov/show/NCT01331512 (Archived by WebCite at http://www.webcitation.org/6UDrrRuaR)

Artificial intelligence and cognitive psychology: How to solve mathematical problems

That a computer might autonomously solve mathematical puzzles described in natural language text and diagrams is still an open challenge in the field of Artificial Intelligence. Conversely, primary school children, aged 9/10 years, can solve them without any advanced computational skills, or a huge quantity of data. In this paper, we have tried to apply the AI approach to mathematical puzzles with models and terms from psychological cognitive studies, such as the Cattell-Horn-Carroll theory of cognitive abilities. We considered 147 ma thematical puzzles, used by Bocconi University for mathematical games among students in the 4th and 5th years of primary school, and we found that they can be viewed, in most cases, as Constraint-Based problems. In order to study the problem-solving process used by school children, some mathematical puzzles with a specific number of variables, domains and constraints, were created ad hoc for the study and were administered to 37 students in the 4th year of primary school. Results showed that problems with the same number of variables as domains were more easily solved than problems with a different number of variables and domains. These results were discussed from the viewpoints of Artificial Intelligence and of Cognitive Psychology in order to provide new insights into the definition of fully-fledged, intelligent agents able to solve mathematical puzzles

A hybrid approach to clinical guideline and to basic medical knowledge conformance

Abstract. Several computer-based approaches to Clinical Guidelines have been developed in the last two decades. However, only recently the community has started to cope with the fact that Clinical Guidelines are just a part of the medical knowledge that physicians have to take into account when treating patients. The procedural knowledge in the guidelines have to be complemented by additional declarative medical knowledge. In this paper, we analyse such an interaction, by studying the conformance problem, defined as evaluating the adherence of a set of performed clinical actions w.r.t. the behaviour recommended by the guideline and by the medical knowledge

HABITAT: An IoT solution for independent elderly

In this work, a flexible and extensive digital platform for Smart Homes is presented, exploiting the most advanced technologies of the Internet of Things, such as Radio Frequency Identification, wearable electronics, Wireless Sensor Networks, and Artificial Intelligence. Thus, the main novelty of the paper is the system-level description of the platform flexibility allowing the interoperability of different smart devices. This research was developed within the framework of the operative project HABITAT (Home Assistance Based on the Internet of Things for the Autonomy of Everybody), aiming at developing smart devices to support elderly people both in their own houses and in retirement homes, and embedding them in everyday life objects, thus reducing the expenses for healthcare due to the lower need for personal assistance, and providing a better life quality to the elderly users.In this work, a flexible and extensive digital platform for Smart Homes is presented, exploiting the most advanced technologies of the Internet of Things, such as Radio Frequency Identification, wearable electronics, Wireless Sensor Networks, and Artificial Intelligence. Thus, the main novelty of the paper is the system-level description of the platform flexibility allowing the interoperability of different smart devices. This research was developed within the framework of the operative project HABITAT (Home Assistance Based on the Internet of Things for the Autonomy of Everybody), aiming at developing smart devices to support elderly people both in their own houses and in retirement homes, and embedding them in everyday life objects, thus reducing the expenses for healthcare due to the lower need for personal assistance, and providing a better life quality to the elderly users

Exploiting Social Commitments in Programming Agent Interaction

Abstract. Modeling and regulating interactions among agents is a crit-ical step in the development of Multiagent Systems (MASs). Some re-cent works assume a normative view, and suggest to model interaction protocols in terms of obligations. In this paper we propose to model in-teraction protocols in terms of goals and commitments, and show how such a formalization promotes a deliberative process inside the agents. The proposal is implemented via JaCaMo+, an extension of JaCaMo, in which Jason agents can interact, while preserving their deliberative ca-pabilities, by exploiting commitment-based protocols, reified by special CArtAgO artifacts

The computational behaviour of the SCIFF abductive proof procedure and the SOCS-SI system

The high computational cost of abduction has limited the application of this powerful and expressive formalism to practical cases. SCIFF is an abductive proof procedure used for verifying the compliance of agent behaviour to interaction protocols in multi-agent systems; SCIFF has been integrated in SOCS-SI, a system able to observe the agent interaction, pass it to SCIFF for the reasoning process and to display in a GUI the results of the SCIFF computation. In order to assess the applicability of sciff and SOCS-SI to practical cases, we have evaluated qualitatively and experimentally (not yet formally) their computational behaviour, concerning limitations and scalability. In this paper we show the results of the analysis