Trust networks for recommender systems

Recommender systems use information about their user’s profiles and relationships to suggest items that might be of interest to them. Recommenders that incorporate a social trust network among their users have the potential to make more personalized recommendations compared to traditional systems, provided they succeed in utilizing the additional (dis)trust information to their advantage. Such trust-enhanced recommenders consist of two main components: recommendation technologies and trust metrics (techniques which aim to estimate the trust between two unknown users.) We introduce a new bilattice-based model that considers trust and distrust as two different but dependent components, and study the accompanying trust metrics. Two of their key building blocks are trust propagation and aggregation. If user a wants to form an opinion about an unknown user x, a can contact one of his acquaintances, who can contact another one, etc., until a user is reached who is connected with x (propagation). Since a will often contact several persons, one also needs a mechanism to combine the trust scores that result from several propagation paths (aggregation). We introduce new fuzzy logic propagation operators and focus on the potential of OWA strategies and the effect of knowledge defects. Our experiments demonstrate that propagators that actively incorporate distrust are more accurate than standard approaches, and that new aggregators result in better predictions than purely bilattice-based operators. In the second part of the dissertation, we focus on the application of trust networks in recommender systems. After the introduction of a new detection measure for controversial items, we show that trust-based approaches are more effective than baselines. We also propose a new algorithm that achieves an immediate high coverage while the accuracy remains adequate. Furthermore, we also provide the first experimental study on the potential of distrust in a memory-based collaborative filtering recommendation process. Finally, we also study the user cold start problem; we propose to identify key figures in the network, and to suggest them as possible connection points for newcomers. Our experiments show that it is much more beneficial for a new user to connect to an identified key figure instead of making random connections

Trust- and Distrust-Based Recommendations for Controversial Reviews

Recommender systems that incorporate a social trust network among their users have the potential to make more personalized recommendations compared to traditional collaborative filtering systems, provided they succeed in utilizing the additional trust and distrust information to their advantage. We compare the performance of several well-known trust-enhanced techniques for recommending controversial reviews from Epinions.com, and provide the first experimental study of using distrust in the recommendation process

Malignant disease in childhood : the price of cure : late physical and socioeconomic effects of treatment

The aim of cancer therapy in childhood is to achieve a lasting cure without physical and psychosocial harm and, preferably, at a low financial cost. Although cure is possible in many types of childhood cancer, this is often accompanied by complications as a consequence of intensive therapy. These late effects primarily affect fertility, the cardio-respiratory and endocrinological systems. Psychosocial adverse effects may have serious implications on the marriage and employment prospects of those patients surviving into adulthood. Furthermore, the risk of treatment-induced, secondary malignancies may increase as survival improves. With current intensive chemotherapy and radiotherapy, the attainment of cure rates in (EXC)ess of 60-70% is, inevitably, associated with significant morbidity. Indeed, recent developments in cancer therapy have focused on ways of reducing this morbidity, whilst still maintaining the overall improvement in survival.peer-reviewe

Magnetocaloric Effect Caused by Paramagnetic Austenite–Ferromagnetic Martensite Phase Transformation

In the present work, the magnetization of Ni50Mn17.5Ga25Cu7.5 alloy undergoing the first-order phase transition from paramagnetic austenite to ferromagnetic martensite was measured to evaluate the magnetic-field-induced entropy change (MFIEC) and refrigerant capacity (RC) of the alloy. A standard method (SM) of evaluation of MFIEC is based on thermodynamic Maxwell relation. In view of the criticism of SM expressed by some scientists, the alternative method (AM), which is based on thermodynamic relationships for free energy, was proposed recently for the determination of MFIEC. We developed this method and computed MFIEC in two ways—by AM and SM. The values of MFIEC obtained for Ni50Mn17.5Ga25Cu7.5 alloy by these methods appeared to be large but very different from each other. Moreover, AM reveals the possibility of both normal and inverse magnetocaloric effects in the adjoining temperature ranges, while SM results only in the normal magnetocaloric effect.This research was funded by AEI/FEDER, UE (projects MAT2014-56116-C04-01-R and MAT2012- 37923-C02-01), NASU (project 0117U000433), MESU (project 0117U004340) and SFFR (President’s of Ukraine grant F75/156-2018)

A Comparison of Student Behavior and Performance between an Instructor-Regulated versus Student-Regulated Online Undergraduate Finance Course

In a study conducted at a large, public university, the authors collected data to measure the relationship between student behavior and performance in an online undergraduate finance class based on two different course formats: instructor-regulated versus student-regulated. The quantitative study indicated significant differences in student behavior when given the self-regulated option, which correlated with deterioration in overall student performance. The study found that when students were given the flexibility to fully control course pacing, there was a statistically significant difference in their pattern of taking quizzes, especially missing quizzes entirely. Also, these students collectively exhibited statistically significant lower overall exam scores. This suggests that some students either do not choose to or experience difficulty with managing their time in a self-paced learning structure

Le travail des enseignants en éducation à la santé : Analyse des dynamiques collectives de travail des écoles impliquée dans le dispositif " Apprendre à Mieux Vivre Ensemble à l'Ecole "

Rapport d'étudeQuestions of health can never be far removed from the concerns of those involved in education of the human being that's why school is considered as one of the main settings for health education. In France health education is not a subject, it is part of citizenship education. Due to its specific status, very different from that of regular subjects, health education led teachers to new practices more open to the school environment. This qualitative research was based on the analysis of 698 documents collected during a 3 years period in 22 primary schools involved in the device " Apprendre à mieux vivre ensemble à l'école ". Results show that school staff had 4 different modes of collective work: opportunist, innovator, operator and opponent.L'enseignement des disciplines qui reste la structure cellulaire du travail à l'école ne recouvre pas l'ensemble des activités scolaires. De nouvelles formes d'organisation du travail scolaire, telles que les éducations à... en général et l'éducation à la santé en particulier, tiennent une place de plus en plus significative. Ceci n'est pas sans générer de tensions. Du fait de leurs spécificités, notamment leur lien aux problématiques sociales, les éducations à... appellent à une ouverture de l'école et à une réorganisation des activités scolaires. Cette recherche qualitative de type ethnographique, fondée sur l'analyse de 698 écrits professionnels récoltés sur une période de 3 ans, montre que les équipes d'école impliquées dans le dispositif " Apprendre à mieux vivre ensemble à l'école " adoptent des fonctionnements collectifs qui peuvent être catégorisés selon quatre grands modes: opportuniste, novateur, opérateur et opposant. L'analyse des mécanismes d'échange laisse apercevoir comment les écoles organisent leur sensibilité à leur environnement

Gravimetric determination of the continental oceanic boundary of the Argentine continental margin (from 36°S to 50°S)

This paper presents the gravimetric analysis together with seismic data as an integral application in order to identify the continental?oceanic crust boundary (COB) of the Argentine continental margin from 36◦S to 50◦S in a continuous way. The gravimetric and seismic data are made up of large grids of data obtained from satellite altimetry and marine research. The methodology consists of three distinct methods: (i) the application of enhancement techniques to gravimetric anomalies, (ii) the calculation of crustal thinning from 3-D gravity inversion modelling of the crust?mantle discontinuity and (iii) 2-D gravimetric modelling supported by multichannel reflection and refraction seismic profiles. In the first method, the analytic signal, Theta map, and tilt angle and its horizontal derivative were applied. In the second method, crustal thickness was obtained as the difference in the depths of the crystalline basement and the crust?mantle discontinuity; the latter was obtained via gravimetric inversion. Finally, 2-D modelling was performed from free-air anomalies in two representative sections by considering as restriction surfaces those coming from the interpretation of seismic data. The results of the joint application of enhancement techniques and 2-D and 3-D modelling have enabled continuous interpretation of the COB. In this study, the COB was determined continuously from the integration of 2-D profiles of the enhancement techniques, taking account of crustal thickness and performing 2-D gravimetric modelling. The modelling technique was complemented by regional studies integrated with multichannel seismic reflection and seismic refraction lines, resulting in consistent enhancement techniques.Fil: Arecco, Maria Alejandra. Universidad de Buenos Aires. Facultad de Ingeniería; ArgentinaFil: Ruiz, Francisco. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; ArgentinaFil: Pizarro, Guillermo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; ArgentinaFil: Gimenez, Mario Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; ArgentinaFil: Martínez, Myriam Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; ArgentinaFil: Ramos, Victor Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentin