In CARSWe Trust: How Context-Aware Recommendations Affect Customers’ Trust And Other Business Performance Measures Of Recommender Systems

Most of the work on Context-Aware Recommender Systems (CARSes) has focused on demonstrating that the contextual information leads to more accurate recommendations and on developing efficient recommendation algorithms utilizing this additional contextual information. Little work has been done, however, on studying how much the contextual information affects purchasing behavior and trust of customers. In this paper, we study how including context in recommendations affects customers’ trust, sales and other crucial business-related performance measures. To do this, we performed a live controlled experiment with real customers of a commercial European online publisher. We delivered content-based recommendations and context-aware recommendations to two groups of customers and to a control group. We measured the recommendations’ accuracy and diversification, how much customers spent purchasing products during the experiment, quantity and price of their purchases and the customers’ level of trust. We aim at demonstrating that accuracy and diversification have only limited direct effect on customers’ purchasing behavior, but they affect trust which drives the customer purchasing behavior. We also want to prove that CARSes can increase both recommendations’ accuracy and diversification compared to other recommendation engines. This means that including contextual information in recommendations not only increases accuracy, as was demonstrated in previous studies, but it is crucial for improving trust which, in turn, can affect other business-related performance measures, such as company’s sales.Polytechnic of Bari, Italy; NYU Stern School of Busines

A contextual modeling approach for model-based recommender systems

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-642-40643-0_5Proceedings of 15th Conference of the Spanish Association for Artificial Intelligence, CAEPIA 2013, Madrid, Spain, September 17-20, 2013.In this paper we present a contextual modeling approach for model-based recommender systems that integrates and exploits both user preferences and contextual signals in a common vector space. Differently to previous work, we conduct a user study acquiring and analyzing a variety of realistic contextual signals associated to user preferences in several domains. Moreover, we report empirical results evaluating our approach in the movie and music domains, which show that enhancing model-based recommender systems with time, location and social companion information improves the accuracy of generated recommendations

Comparing Context-Aware Recommender Systems in Terms of Accuracy and Diversity: Which Contextual Modeling, Pre-filtering and Post-Filtering Methods Perform the Best

Although the area of Context-Aware Recommender Systems (CARS) has made a significant progress over the last several years, the problem of comparing various contextual pre-filtering, post-filtering and contextual modeling methods remained fairly unexplored. In this paper, we address this problem and compare several contextual pre-filtering, post-filtering and contextual modeling methods in terms of the accuracy and diversity of their recommendations to determine which methods outperform the others and under which circumstances. To this end, we consider three major factors affecting performance of CARS methods, such as the type of the recommendation task, context granularity and the type of the recommendation data. We show that none of the considered CARS methods uniformly dominates the others across all of these factors and other experimental settings; but that a certain group of contextual modeling methods constitutes a reliable “best bet” when choosing a sound CARS approach since they provide a good balance of accuracy and diversity of contextual recommendations.Politecnico di Bari, Italy; NYU Stern School of Busines

LA MATRICE EXTRACELLULARE COME FONTE DI INIBIZIONE DELLA PLASTICITA' SINAPTICA:EFFETTI DELLA SUA DEGRADAZIONE IN CORTECCIA VISIVA, IN VIVO.

La plasticità del sistema nervoso è definibile come la sua capacità di adattarsi in risposta all’esperienza; questa proprietà è legata a cambiamenti strutturali e funzionali a livello delle sinapsi già esistenti, e alla formazione di nuove sinapsi. E’ ormai dimostrato che la matrice extracellulare (MEC) gioca un ruolo centrale nella regolazione della plasticità, sia durante lo sviluppo che nell’adulto: essa è una struttura complessa, multimolecolare, che occupa lo spazio extracellulare di tutti i tessuti, e nel sistema nervoso è costituita principalmente da glicosamminoglicani (GAG), in particolare condroitin solfato (CSPGs) ed eparan solfato (HSPGs). Recentemente si è arrivati a parlare di una sinapsi tetrapartita: secondo questa nuova visione la comunicazione cellulare dipende dall’interazione di quattro elementi: presinaptico, postsinaptico, cellule della glia e molecole della matrice. Manipolando la matrice extracellulare con metodi genetici o farmacologici e accoppiando paradigmi esperienza-dipendenti, si assiste ad alterazioni della trasmissione sinaptica e della morfologia delle spine, le quali sono i più importanti correlati morfo-funzionali della plasticità. In particolare è stato possibile riaprire la plasticità in corteccia visiva adulta in seguito all’utilizzo dell’enzima batterico CondroitinasiABC, che degrada le catene di CSPGs. Partendo da queste premesse abbiamo voluto utilizzare lo stesso enzima per poter studiare gli effetti della digestione della matrice a livello delle spine dendritiche dei neuroni del V strato della corteccia visiva primaria. Il nostro studio si è concentrato sia sulle conseguenze morfologiche che su quelle funzionali. Nel primo caso, la tecnica della microscopia a due fotoni ci ha consentito di valutare, in vivo, le variazioni della motililtà e delle fluttuazioni della testa delle spine. Il modello utilizzato è un topo transgenico in cui alcune cellule dello strato V esprimono la GFP. L’imaging è stato effettuato sia in acuto che a distanza di tre giorni dalla somministrazione dell’enzima. Per ricercare possibili conseguenze funzionali abbiamo messo a punto un protocollo di LTP in corteccia visiva in vivo, non ancora presente in letteratura. Con questo studio abbiamo dunque voluto valutare il ruolo della MEC sui meccanismi di plasticità della corteccia visiva di topo adulto, svelando, seppur in maniera indiretta, possibili relazioni tra i cambiamenti morfologici delle spine e la trasmissione sinaptica a livello dei dendriti apicali dei neuroni piramidali del V strato. Le osservazioni effettuate possono rappresentare un punto di partenza per ulteriori studi che trovino una relazione di causa-effetto tra la composizione della MEC e le variazioni morfo-funzionali delle spine dendritiche

Context-aware movie recommendations: An empirical comparison of pre-filtering, post-filtering and contextual modeling approaches

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-642-39878-0_13Proceedings of 14th International Conference, EC-Web 2013, Prague, Czech Republic, August 27-28, 2013.Context-aware recommender systems have been proven to improve the performance of recommendations in a wide array of domains and applications. Despite individual improvements, little work has been done on comparing different approaches, in order to determine which of them outperform the others, and under what circumstances. In this paper we address this issue by conducting an empirical comparison of several pre-filtering, post-filtering and contextual modeling approaches on the movie recommendation domain. To acquire confident contextual information, we performed a user study where participants were asked to rate movies, stating the time and social companion with which they preferred to watch the rated movies. The results of our evaluation show that there is neither a clear superior contextualization approach nor an always best contextual signal, and that achieved improvements depend on the recommendation algorithm used together with each contextualization approach. Nonetheless, we conclude with a number of cues and advices about which particular combinations of contextualization approaches and recommendation algorithms could be better suited for the movie recommendation domain.This work was supported by the Spanish Government (TIN2011-28538-C02) and the Regional Government of Madrid (S2009TIC-1542

Context-aware user modeling strategies for journey plan recommendation

Popular journey planning systems, like Google Maps or Yahoo! Maps, usually ignore user’s preferences and context. This paper shows how we applied context-aware recommendation technologies in an existing journey planning mobile application to provide personalized and context-dependent recommendations to users. We describe two different strategies for context-aware user modeling in the journey planning domain. We present an extensive performance comparison of the proposed strategies by conducting a user-centric study in addition to a traditional offline evaluation methodPeer ReviewedPostprint (published version

The lost maps: two-photon investigations of the fine scale organization of auditory cortex

The spatial arrangement of neuronal responses in primary auditory cortex (A1) has so far been investigated by using microelectrode recording techniques or imaging of the intrinsic signal, which led to controversial results, at present still discussed. On the other hand, two-photon calcium imaging allows us to investigate the cortical functions at an unprecedented level of spatial detail, and has recently offered new insight into the fine-scale organization of frequency responses in A1. In this thesis, I used two-photon calcium imaging to compare, for the first time, the fine-scale cortical representation of sound frequency to that of two other sound features, crucial for survival and communication in all mammals: differences in intensity between the two ears (interaural level differences; ILDs), and frequency modulation (FM). I found that most neurons in layers II-III of the mouse A1 were tuned to ILDs favouring the contralateral ear, but midline and ipsilateral tuning were present too. Binaural preferences were heterogeneously distributed in space, both on the fine scale (within ∼ 200 μm) and on the global one (up to ∼ 1 mm). Moreover, A1 neurons were mostly tuned to slow FM sweeps within the range of those used in species-specific calls. Cells activated by similar rates tended to be spatially proximal, indicating a level of local organization similar to the one I found for frequency tuning, and higher than that of ILD responses. Finally, I set the groundwork for two-photon studies of the A1 of the ferret, by presenting the first evidence of the microscopic organization of the tonotopic map in this species. My results shed light on some long-held questions about the response properties of A1, and confirm two-photon imaging as a powerful tool for investigating the processing of sensory signals in the cortex of both small and large mammals

The Ring Imaging Cherenkov detector (RICH) of the AMS experiment

The Alpha Magnetic Spectrometer (AMS) experiment to be installed on the International Space Station (ISS) will be equipped with a proximity focusing Ring Imaging Cherenkov (RICH) detector for measuring the electric charge and velocity of the charged cosmic particles. A RICH prototype consisting of 96 photomultiplier units, including a piece of the conical reflector, was built and its performance evaluated with ion beam data. Preliminary results of the in-beam tests performed with ion fragments resulting from collisions of a 158 GeV/c/nuc primary beam of Indium ions (CERN SPS) on a Pb target are reported. The collected data included tests to the final front-end electronics and to different aerogel radiators. Cherenkov rings for a large range of charged nuclei and with reflected photons were observed. The data analysis confirms the design goals. Charge separation up to Fe and velocity resolution of the order of 0.1% for singly charged particles are obtained.Comment: 29th International Conference on Cosmic Rays (Pune, India

Hybrid photonic-bandgap accelerating cavities

In a recent investigation, we studied two-dimensional point-defected photonic bandgap cavities composed of dielectric rods arranged according to various representative periodic and aperiodic lattices, with special emphasis on possible applications to particle acceleration (along the longitudinal axis). In this paper, we present a new study aimed at highlighting the possible advantages of using hybrid structures based on the above dielectric configurations, but featuring metallic rods in the outermost regions, for the design of extremely-high quality factor, bandgap-based, accelerating resonators. In this framework, we consider diverse configurations, with different (periodic and aperiodic) lattice geometries, sizes, and dielectric/metal fractions. Moreover, we also explore possible improvements attainable via the use of superconducting plates to confine the electromagnetic field in the longitudinal direction. Results from our comparative studies, based on numerical full-wave simulations backed by experimental validations (at room and cryogenic temperatures) in the microwave region, identify the candidate parametric configurations capable of yielding the highest quality factor.Comment: 13 pages, 5 figures, 3 tables. One figure and one reference added; minor changes in the tex

Discovery of VHE Gamma Radiation from IC443 with the MAGIC Telescope

We report the detection of a new source of very high energy (VHE, E_gamma >= 100GeV) gamma-ray emission located close to the Galactic Plane, MAGIC J0616+225, which is spatially coincident with SNR IC443. The observations were carried out with the MAGIC telescope in the periods December 2005 - January 2006 and December 2006 - January 2007. Here we present results from this source, leading to a VHE gamma-ray signal with a statistical significance of 5.7 sigma in the 2006/7 data and a measured differential gamma-ray flux consistent with a power law, described as dN_gamma/(dA dt dE) = (1.0 +/- 0.2)*10^(-11)(E/0.4 TeV)^(-3.1 +/- 0.3) cm^(-2)s^(-1)TeV^(-1). We briefly discuss the observational technique used and the procedure implemented for the data analysis. The results are put in the perspective of the multiwavelength emission and the molecular environment found in the region of IC443.Comment: Accepted by ApJ Letter