Agent-oriented Modeling for Collaborative Learning Environments: A Peer-to-Peer Helpdesk Case Study

In this paper, we present the analysis and modelling of Help&Learn, an agent-based peer-to-peer helpdesk system to support extra-class interactions among students and teachers. Help&Learn expands the student’s possibility of solving problems, getting involved in a cooperative learning experience that transcends the limits of classrooms. To model Help&Learn, we have used Agent-Object-Relationship Modeling Language (AORML), an UML extension for agent-oriented information systems modeling. The aim of this research is two-fold. On one hand, we aim at modeling the variety of roles and the complexity of their interactions and activities within the Help&Learn system. On the other hand, we aim at showing the expressive power and the modeling strengths of AORML

Exchange interaction effects in the thermodynamic properties of quantum dots

We study electron-electron interaction effects in the thermodynamic properties of quantum-dot systems. We obtain the direct and exchange contributions to the specific heat C_v in the self-consistent Hartree-Fock approximation at finite temperatures. An exchange-induced phase transition is observed and the transition temperature is shown to be inversely proportional to the size of the system. The exchange contribution to C_v dominates over the direct and kinetic contributions in the intermediate regime of interaction strength (r_s ~ 1). Furthermore, the electron-electron interaction modifies both the amplitude and the period of magnetic field induced oscillations in C_v.Comment: 4 pages, 4 figures; To appear in Phys. Rev.

Atomic Charge Transfer-counter Polarization Effects Determine Infrared Ch Intensities Of Hydrocarbons: A Quantum Theory Of Atoms In Molecules Model.

Atomic charge transfer-counter polarization effects determine most of the infrared fundamental CH intensities of simple hydrocarbons, methane, ethylene, ethane, propyne, cyclopropane and allene. The quantum theory of atoms in molecules/charge-charge flux-dipole flux model predicted the values of 30 CH intensities ranging from 0 to 123 km mol(-1) with a root mean square (rms) error of only 4.2 km mol(-1) without including a specific equilibrium atomic charge term. Sums of the contributions from terms involving charge flux and/or dipole flux averaged 20.3 km mol(-1), about ten times larger than the average charge contribution of 2.0 km mol(-1). The only notable exceptions are the CH stretching and bending intensities of acetylene and two of the propyne vibrations for hydrogens bound to sp hybridized carbon atoms. Calculations were carried out at four quantum levels, MP2/6-311++G(3d,3p), MP2/cc-pVTZ, QCISD/6-311++G(3d,3p) and QCISD/cc-pVTZ. The results calculated at the QCISD level are the most accurate among the four with root mean square errors of 4.7 and 5.0 km mol(-1) for the 6-311++G(3d,3p) and cc-pVTZ basis sets. These values are close to the estimated aggregate experimental error of the hydrocarbon intensities, 4.0 km mol(-1). The atomic charge transfer-counter polarization effect is much larger than the charge effect for the results of all four quantum levels. Charge transfer-counter polarization effects are expected to also be important in vibrations of more polar molecules for which equilibrium charge contributions can be large.1623224-3

Operant measurement of auditory threshold in prelingually deaf users of cochlear implants: II

Two experiments evaluated an operant procedure for establishing stimulus control using auditory and electrical stimuli as a baseline for measuring the electrical current threshold of electrodes implanted in the cochlea. Twenty-one prelingually deaf children, users of cochlear implants, learned a Go/No Go auditory discrimination task (i.e., pressing a button in the presence of the stimulus but not in its absence). When the simple discrimination baseline became stable, the electrical current was manipulated in descending and ascending series according to an adapted staircase method. Thresholds were determined for three electrodes, one in each location in the cochlea (basal, medial, and apical). Stimulus control was maintained within a certain range of decreasing electrical current but was eventually disrupted. Increasing the current recovered stimulus control, thus allowing the determination of a range of electrical currents that could be defined as the threshold. The present study demonstrated the feasibility of the operant procedure combined with a psychophysical method for threshold assessment, thus contributing to the routine fitting and maintenance of cochlear implants within the limitations of a hospital setting.FAPESPConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNP

Multi-score Learning for Affect Recognition: the Case of Body Postures

An important challenge in building automatic affective state recognition systems is establishing the ground truth. When the groundtruth is not available, observers are often used to label training and testing sets. Unfortunately, inter-rater reliability between observers tends to vary from fair to moderate when dealing with naturalistic expressions. Nevertheless, the most common approach used is to label each expression with the most frequent label assigned by the observers to that expression. In this paper, we propose a general pattern recognition framework that takes into account the variability between observers for automatic affect recognition. This leads to what we term a multi-score learning problem in which a single expression is associated with multiple values representing the scores of each available emotion label. We also propose several performance measurements and pattern recognition methods for this framework, and report the experimental results obtained when testing and comparing these methods on two affective posture datasets

CHEMICAL CHARACTERIZATION AND ANTIMICROBIAL ACTIVITY OF HYDROETHANOLIC CRUDE EXTRACT OF EUGENIA FLORIDA DC (MYRTACEAE) LEAVES

Objective: The present study aimed to characterize and quantify the total phenolics, flavonoids and tannins in a hydroethanolic crude extract (70% (v/v) (EB)) of the leaves of E. florida DC, as well as to evaluate the antimicrobial activity of the extract against different species of micro-organisms.Methods: EB was characterized using a mass spectrometer equipped with a direct insertion device for in-stream injection (FIA). Quantitative analyses of major compounds were carried out by spectrophotometry. In addition, we evaluated the sensitivity profiles of different strains of yeast and bacteria against different concentrations of EB.Results: The classes found were in agreement with those described in the literature: flavonoids, tannins, phenolic acids and saponins. EB showed levels of phenolic compounds, flavonoids and tannins equal to 25.82 mg gallic acid equivalents per gram of extract (EAG/g), 8.42 mg quercetin equivalents per gram of extract (EQ/g) and 7.30 mg tannic acid equivalents per gram of extract (AT/g), respectively. In the analysis of antimicrobial activity, EB was more active against yeasts but was not effective against the bacteria used in the test.Conclusion: We can conclude that E. florida DC has antimicrobial potential, due to the presence of bioactive secondary metabolites.Keywords: Phenolics, Micro-organisms, Mass spectrometer, Yeasts, Bacteria, PotentialÂ

Short-range interactions in a two-electron system: energy levels and magnetic properties

The problem of two electrons in a square billiard interacting via a finite-range repulsive Yukawa potential and subjected to a constant magnetic field is considered. We compute the energy spectrum for both singlet and triplet states, and for all symmetry classes, as a function of the strength and range of the interaction and of the magnetic field. We show that the short-range nature of the potential suppresses the formation of ``Wigner molecule'' states for the ground state, even in the strong interaction limit. The magnetic susceptibility $\chi(B)$ shows low-temperature paramagnetic peaks due to exchange induced singlet-triplet oscillations. The position, number and intensity of these peaks depend on the range and strength of the interaction. The contribution of the interaction to the susceptibility displays paramagnetic and diamagnetic phases as a function of $T$.Comment: 12 pages,6 figures; to appear in Phys. Rev.

Is serum HMGB1 a biomarker in ANCA-associated vasculitis?

Background: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) are systemic inflammatory disorders that include granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), Churg-Strauss syndrome and renal limited vasculitis (RLV). Extracellular high-mobility group box 1 (HMGB1) acts as an alarmin and has been shown to be a biomarker of disease activity as well as an autoantigen in systemic lupus erythematosus (SLE) and, possibly, in AAV. This study aims to assess antibodies against HMGB1 and HMGB1 levels as biomarkers for AAV disease activity and predictors of relapsing disease.Methods: AAV patients with active disease and healthy controls (HC) were evaluated for anti-HMGB1 antibodies while serum HMGB1 levels were measured longitudinally in AAV patients at presentation, during remission, prior to and at relapses.Results: HMGB1 levels were similar between AAV patients at presentation (n = 52) and HC (n = 35) (2.64 +/- 1.80 ng/ml vs. 2.39 +/- 1.09 ng/ml; P = 0.422) and no difference regarding HMGB1 levels could be found among AAV disease subsets (GPA: 2.66 +/- 1.83 ng/ml vs. MPA: 3.11 +/- 1.91 ng/ml vs. RLV: 1.92 +/- 1.48 ng/ml; P = 0.369). AAV patients with renal involvement had lower HMGB1 levels than patients without renal involvement at presentation (2.35 +/- 1.48 ng/ml vs. 3.52 +/- 2.41 ng/ml; P = 0.042). A negative correlation was observed between HMGB1 levels and 24-hour proteinuria (rho = -0.361, P = 0.028). Forty-nine AAV patients were evaluated for HMGB1 levels during follow-up and no differences were observed between relapsing and nonrelapsing patients (P = 0.350). No significant increase in HMGB1 levels was observed prior to a relapse compared with the remission period and changes in HMGB1 levels were not associated with an increased risk for relapse in AAV. Positivity for anti-HMGB1 antibodies was low in patients with active AAV (three out of 24 patients).Conclusions: Serum HMGB1 levels at presentation are not increased and are lower in patients with renal involvement. Relapses are not preceded or accompanied by significant rises in HMGB1 levels and changes in HMGB1 levels are not related to ensuing relapses. Anti-HMGB1 antibodies are present in only a few patients in AAV. in contrast to SLE, HMGB1 is not a useful biomarker in AAV.Univ Groningen, Univ Med Ctr Groningen, Dept Rheumatol & Clin Immunol, NL-9713 GZ Groningen, NetherlandsUniversidade Federal de São Paulo, Escola Paulista Med Unifesp EPM, Div Rheumatol, BR-04023900 São Paulo, BrazilUniv Groningen, Univ Med Ctr Groningen, Dept Lab Med, NL-9713 GZ Groningen, NetherlandsUniv Groningen, Univ Med Ctr Groningen, Div Nephrol, Dept Internal Med, NL-9713 GZ Groningen, NetherlandsMartini Hosp, Dept Rheumatol & Internal Med, NL-9728 NT Groningen, NetherlandsUniversidade Federal de São Paulo, Escola Paulista Med Unifesp EPM, Div Rheumatol, BR-04023900 São Paulo, BrazilWeb of Scienc