A graded BDI agent model to represent and reason about preferences

In this research note, we introduce a graded BDI agent development framework, g-BDI for short, that allows to build agents as multi-context systems that reason about three fundamental and graded mental attitudes (i.e. beliefs, desires and intentions). We propose a sound and complete logical framework for them and some logical extensions to accommodate slightly different views on desires.     

Evaluation of Performance Improvement Capabilities of PAPR-reducing Methods

One of the major drawbacks of multicarrier modulation is the large envelope fluctuations which either require an inefficient use of high power amplifiers or decrease the system performance. Peak-to-average power ratio (PAPR) is a very well known measure of the envelope fluctuations and has become the cost function used to evaluate and design multicarrier systems. Several PAPR-reducing techniques have been proposed with the aim to alleviate back-off specifications or increase the system performance. Besides the fact that these techniques have varying PAPR-reduction capabilities, power, bandwidth and complexity requirements, it is interesting to notice that the performance of a system employing these techniques has not been fully analyzed. In this paper we, first, develop a theoretical framework for both PAPR and the distortion introduced by a nonlinearity, and then simulate an OFDM system employing several well known PAPR-reducing techniques from the literature. By means of the theoretical analysis and the simulation results we will show the relation between PAPR and the performance of OFDM systems when a clipping device is present and we will evaluate the real performance improvement capabilities of the PAPR-reducing methods. The agreement between the theoretical and the simulation results demonstrate the validity of the analysis.

Multi-user Detection of Nonlinearly Distorted MC-CDMA Symbols by Microstatistic Filtering

Multi-carrier code division multiple access is a powerful modulation technique that is being considered in many emerging broadband communication systems. In a downlink scenario orthogonal spreading sequences are used since they reduce multiple access interference compared to non-orthogonal. However, the nonlinear amplification of the transmitted signal destroys the orthogonality and, thus, reduces the system performance. In order to avoid performance degradation without requiring large back-offs in the transmitter amplifier, it becomes necessary to use multi-user detection techniques at the receiver side. Conventional multi-user detectors (MUD) are designed for linear environments and, as a result, might not exhibit enough performance improvement. In this paper a new MUD based on microstatistic filtering is proposed. The presented MUD uses piece-wise linear filtering in conjunction with threshold decomposition of the input signal, which introduces a nonlinear effect, to improve performance when a nonlinearity is present. Maximum performance improvement compared to conventional MUD is achieved for low spreading factors and user loads no greater than 50%.

Temporal Constraints: A Survey

Temporal Constraint Satisfaction is an information technology useful for representing and answering queries about temporal occurrences and temporal relations between them. Information is represented as a Constraint Satisfaction Problem (CSP) where variables denote event times and constraints represent the possible temporal relations between them. The main tasks are two: (i) deciding consistency, and (ii) answering queries about scenarios that satisfy all constraints. This paper overviews results on several classes of Temporal CSPs: qualitative interval, qualitative point, metric point, and some of their combinations. Research has progressed along three lines: (i) identifying tractable subclasses, (ii) developing exact search algorithms, and (iii) developing polynomial-time approximation algorithms. Most available techniques are based on two principles: (i) enforcing local consistency (e.g. path-consistency) and (ii) enhancing naive backtracking search.     

A guaranteed minimum throughput service for TCP flows using measurement‐based admission control

We propose a new scheme for a network service that guarantees a minimum throughput to flows accepted by admission control (AC). The whole scheme only uses a small set of packet classes in a core‐stateless network. At the ingress of the network each flow packet is marked into one of the sets of classes, and within the network, each class is assigned a different discarding priority. The AC method is based on edge‐to‐edge per‐flow throughput measurements using the first packets of the flow, and it requires flows to send with a minimum rate. We evaluate the scheme through simulations in a simple bottleneck topology with different traffic loads consisting of TCP flows that carry files of varying sizes. We use a modified TCP source with a new algorithm that forces the source to send with a minimum rate. We compare our scheme with the best‐effort service and we study the influence of the measurement duration on the scheme's performance. The results prove that the scheme guarantees the requested throughput to accepted flows and achieves a high utilization of network resources. Copyright © 2006 John Wiley & Sons, Ltd.     

Reusable impedimetric aptasensor

A novel impedimetric aptasensor using a mixed self-assembled monolayer composed of thiol-modified thrombin binding aptamer and 2-mercaptoethanol on a gold electrode is reported. The changes of interfacial features of the electrode were probed in the presence of the reversible redox couple, Fe(CN)6(3-/4-), using impedance measurements. The electrode surface was partially blocked due to the self-assembly of aptamer or the formation of the aptamer-thrombin complex, resulting in an increase of the interfacial electron-transfer resistance detected by electrochemical impedance spectroscopy or cyclic voltammetry. The aptasensor was regenerated by breaking the complex formed between the aptamer and thrombin using 2.0 M NaCl solution, and the immobilized aptamer subsequently was used for repeated detection of thrombin. The aptamer-functionalized electrode showed a linear response of the charge-transfer resistance to the increase of thrombin concentration in the range of 5.0-35.0 nM and the thrombin was easily detectable to a concentration of 2.0 nM.     

Chemically Diverse Multifunctional Peptide Platforms with Antimicrobial and Cell Adhesive Properties

Bacterial infections and incomplete biomaterial integration are major problems that can lead to the failure of medical implants. However, simultaneously addressing these two issues remains a challenge. Here, we present a chemical peptide library based on a multifunctional platform containing the antimicrobial peptide LF1-11 and the cell-adhesive motif RGD. The scaffolds were customized with catechol groups to ensure straightforward functionalization of the implant surface, and linkers of different length to assess the effect of peptide accessibility on the biological response. The peptidic platforms significantly improved the adhesion of mesenchymal stem cells and showed antimicrobial effects against Staphylococcus aureus. Of note is that peptides bearing spacers that were too long displayed the lowest efficiency. Subsequently, we designed a platform replacing linear RGD by cyclic RGD; this further enhanced eukaryotic cell adhesion while retaining excellent antimicrobial properties, thus being a suitable candidate for tissue engineering applications.