OBSERVER: An Approach for Query Processing in Global Information Systems Based on Interoperation Across Pre-Existing Ontologies

There has been an explosion in the types, availability and volume of data accessible in an information system, thanks to the World Wide Web (the Web) and related inter-networking technologies. In this environment, there is a critical need to replace or complement earlier database integration approaches and current browsing and keyword-based techniques with concept-based approaches. Ontologies are increasingly becoming accepted as an important part of any concept or semantics based solution, and there is increasing realization that any viable solution will need to support multiple ontologies that may be independently developed and managed. In particular, we consider the use of concepts from pre-existing real world domain ontologies for describing the content of the underlying data repositories. The most challenging issue in this approach is that of vocabulary sharing, which involves dealing with the use of different terms or concepts to describe similar information. In this paper, we describe the architecture, design and implementation of the OBSERVER system. Brokering across the domain ontologies is enabled by representing and utilizing interontology relationships such as (but not limited to) synonyms, hyponyms and hypernyms across terms in different ontologies. User queries are rewritten by using these relationships to obtain translations across ontologies. Well established metrics like precision and recall based on the extensions underlying the concepts are used to estimate the loss of information, if any.     

Stress osteotomy of the distal radius- and ulna metaphysis (Illarramendi procedure): an alternative treatment method in lunate necrosis

Using conventional in vitro extracellular field potential recordings we have investigated both short- and long-term synaptic plasticity in the hippocampal CA1 area of mice infected with ME7 scrapie. In agreement with earlier studies, no changes were seen in the properties of the Sch?ffer collateralevoked field excitatory postsynaptic potential during the early stages of the disease (up to 160 days, post inoculation, d.p.i) after which time the recorded potentials were seen to attenuate. Also, up to this time no changes were seen in either paired-pulse facilitation or post-tetanic potentiation, which are short-term phenomena associated with brief elevations in presynaptic calcium levels. However, there was a significant shift from the ability of slices to maintain long-term potentiation (LTP) from 100 d.p.i. onwards. In all of these experiments short-term potentiation (STP) was preserved, suggesting that from the time that abnormal PrP becomes detectable, or perhaps even earlier, the mechanisms responsible for stabilizing the maintenance phase of LTP are impaired. This result is discussed in terms of the relationship between STP and LTP and how this might be compromised by the conversion of cellular prion protein (PrPC) to the scrapie, protease resistant form of PrP (PrPSc).     

Towards a satisfactory conversion of messages among agent-based information systems

Over the last years, there has been a change of perspective concerning the management of information systems, since they are no longer isolated and need to communicate with others. However, from a semantic point of view, real communication is difficult to achieve due to the heterogeneity of the systems. We present a proposal which, considering information systems are represented by software agents, provides a framework that favors a semantic communication among them, overcoming the heterogeneity of their agent communication languages. The main components of the framework are a suite of ontologies – conceptualizing communication acts – that will be used for generating the communication conversion, and an Event Calculus interpretation of the communications, which will be used for formalizing the notion of a satisfactory conversion. Moreover, we present a motivating example in order to complete the explanation of the whole picture.     

Architecture, cost-model and customization of real-time monitoring systems based on mobile biological sensor data-streams

Innovation in the fields of wireless data communications, mobile devices and biosensor technology enables the development of new types of monitoring systems that provide people with assistance anywhere and at any time. In this paper we present an architecture useful to build those kind of systems that monitor data streams generated by biological sensors attached to mobile users. We pay special attention to three aspects related to the system efficiency: selection of the optimal granularity, that is, the selection of the size of the input data stream package that has to be acquired in order to start a new processing cycle; the possible use of compression techniques to store and send the acquired input data stream and; finally, the performance of a local analysis versus a remote one. Moreover, we introduce two particular real systems to illustrate the suitability and applicability of our proposal: an anywhere and at any time monitoring system of heart arrhythmias and an apnea monitoring system.     

Random laser performance of NdxY1−xAl3(BO3)4 laser crystal powders

We report random laser action in ground powders of Nd_xY_1?xAl₃(BO₃)₄ (x = 0.5–1) laser crystals under nanosecond pulse excitation at 802 nm. The dependence of the random laser threshold energy on the neodymium concentration and focusing conditions is investigated. The slope efficiency of the output random laser emission is determined as a function of Nd³⁺ concentration.     

Location-dependent queries in mobile contexts: distributed processing using mobile agents

With the current advances of mobile computing technology, we are witnessing an explosion in the development of applications that provide mobile users with a wide range of services. In this paper, we present a system that supports distributed processing of continuous location-dependent queries in mobile environments. The system that we propose presents the following main advantages: 1) it is a general solution for the processing of location-dependent queries in scenarios where not only the users issuing queries, but also other interesting objects can move; 2) it performs an efficient processing of these queries in a continuous way; 3) it is especially well adapted to environments where location data are distributed in a network and processing tasks can be performed in parallel, allowing a high scalability; and 4) it optimizes wireless communications. We use mobile agents to carry the processing tasks wherever they are needed. Thus, agents are in charge of tracking the location of interesting moving objects and refreshing the answer to a query efficiently. We evaluate the usefulness of the presented proposal showing that the system achieves a good precision and scales up well.     

New Control Techniques Based on State Space Observers for Improving the Precision and Dynamic Behaviour of Machine Tools

This paper describes control techniques based on state space observers that have been developed to improve the precision and dynamic behaviour of machine tools.To improve precision, an accelerometer located close to the tool centre point (TCP) is used, so that its position is estimated by an state space observer and used as position feedback instead of the position read by the linear scale. This way, the structural deformation from the slide to the tool is compensated.Dynamic behaviour is improved estimating the acceleration of the TCP by the aforementioned observer and feeding this noiseless signal into the control system, rather than the noisy signal of the accelerometer itself.These techniques provide a simple way to achieve considerable improvements without using complex and expensive TCP position measurement devices. Tests on actual machines have shown that errors produced by deflections between the slide and the TCP can be reduced by 70%.     

Interoperation among agent-based information systems through a communication acts ontology

Information technology is evolving from focusing on local systems to encompassing a more global interaction among multiple systems in enterprises and communities. On the one hand, new advances in the area of network communications have facilitated in some way the intercommunication among heterogeneous information systems located at different places. However, what is still missing is the possibility of a real and efficient interoperation among those systems in an open environment as the one favoured by Internet. On the other hand, agent technology provides platforms where cooperative work of information systems is concernable because of the software agents working on behalf of these information systems. But, nowadays that cooperation is in general restricted and requires a laborious a priori preparation. In this paper we present the features of a formal ontology that can play a relevant role in the development of a new kind of information systems interoperation frameworks. The ontology includes classes and properties for describing communication acts among agents. We claim that the communication acts ontology provides interoperability support due to the recognition of communication acts from one Agent Communication Language (acl) as instances of communication acts in another acl. Sometimes the comprehension will not be complete, but partial comprehension of the communication may be useful and preferable to the “not understood” answer given nowadays. Terms of the ontology are described as classes or properties using the Web Ontology Language owl.