El fenómeno de la economía colaborativa: nuevo campo de estudio por acotar

La evolución de las tecnologías de la información y la comunicación, junto con su uso generalizado, ha fomentado nuevas formas de interacción entre las personas que, a su vez, ha propiciado la irrupción de nuevas vías de intercambio de bienes y servicios que en muchos casos derivan en la constitución de nuevos mercados. A este fenómeno se le conoce como economía colaborativa y su delimitación es ambigua (Meelen y Frenken, 2013), encontrandónos con definiciones que se centran en la motivación altruista (Stokes, 2014) y definiciones centradas en la vertiente meramente lucrativa que están adoptando las grandes empresas de intermeciación a través de internet (Codagnone y Martens, 2016). En consecuencia, bajo el paraguas de la economía colaborativa encontramos un conjunto heterogéneo, emergente, de rápido cambio y evolución que da cobertura a modos de producción y consumo por el que las personas comparten activos, bienes o servicios normalmente infrautilizados, a cambio o no de un valor monetario. La principal particularidad de estas relaciones es que la interacción suele tener lugar mediante la intermediación de plataformas sociales digitales y, especialmente, de internet y de la web 2.0 (Hamai et al., 2014; Kaplan y Haenlein, 2010). En la actualidad este tipo de prácticas es ampliamente aceptado (Nadler, 2014) y respaldado por la sociedad, convirtiéndose la economía colaborativa en un fenómeno con un impacto económico y social importante (Bostman y Rodgers (2010) que, sin embargo, presenta grandes dificultades de estudio y cuantificación. Estas dificultades derivan de la heterogeneidad del fenómeno, de su dinamismo y permanente cambio, de su tamaño, así como del volumen y diversidad de agentes implicados. A ello hemos de añadir el hecho de tratarse de un campo de estudio novedoso que recientemente se ha comenzado a definir y describir desde el ámbito científico. Por esta razón, nuestro objetivo en el presente trabjao es tratar de definir el sector, abordar la dificultad de su cuantificación y plantear el problema que en la actualidad aún supone su acotación.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. El contenido de este trabajo forma parte del resultado científico del Proyectos de Investigación de I+D DER 2015-63701-C3-3-R "Instrumentos normativos sociales ante el nuevo contexto tecnológico 3.0" del Ministerio de Economía y Competitivida

Ultrathin high-index metasurfaces for shaping focused beams

The volume size of a converging wave, which plays a relevant role in image resolution, is governed by the wavelength of the radiation and the numerical aperture (NA) of the wavefront. We designed an ultrathin (λ/8 width) curved metasurface that is able to transform a focused field into a high-NA optical architecture, thus boosting the transverse and (mainly) on-axis resolution. The elements of the metasurface are metal-insulator subwavelength gratings exhibiting extreme anisotropy with ultrahigh index of refraction for TM polarization. Our results can be applied to nanolithography and optical microscopy.Spanish Ministry of Economy and Competitiveness (MEC) (TEC2013-50416-EXP)

Comparison of Methods for Analyzing Radiological Response of Colorectal Cancer Liver Metastasis After Neoadjuvant Chemotherapeutic Treatment

Background: We analyzed different methods used to assess the radiological responses of patients undergoing neoadjuvant chemotherapy and metastasectomy treatment for liver metastases associated with colorectal cancer (CRC) by comparing the response evaluation criteria in solid tumors (RECIST) 1.1, the modified RECIST, and the criteria of the European Association for the Study of the Liver (EASL) methods and the histological response obtained after metastasectomy. Objectives: We aimed to determine the optimal radiological method to assess the response of colorectal liver metastases to neoadjuvant chemotherapy. Materials and Methods: We conducted a retrospective study of CRC patients treated for liver metastases who had received neoadjuvant chemotherapy in our hospital between January 2000 and December 2017. We analyzed the agreement between the methods for analyzing the radiological response using the quadratic weighted kappa coefficient ( ). We studied the overall survival and analyzed factors related to survival using the Kaplan-Meier method.We performed multivariate analysis to study the prognostic factors of survival.We analyzed the relationship between the radiological and histological responses usingGoodmanand Kruskal?sgamma ( ). Results: A significant agreement was observed between the modified RECIST and EASL methods ( = 0.841, P< 0.001). Cox regression multivariate analysis indicated the RECIST 1.1 criteria as an independent prognostic factor (P = 0.03). The value showed a significant relationship between the three radiological response methods and histological response. Conclusion: In our study, we showed that using RECIST 1.1 criteria is the ideal radiological analysis method for studying CRC liver metastases treated with neoadjuvant chemotherapy when compared to other methods that are based on functional imaging markers

Stereovideo youtube channel: short educational videos for the on-line learning of the the stereographic projection technique in Structural Geology

Stereovideo channel https://www.youtube.com/user/geostereovideo) is a YouTube channel of short educational videos (<5 min) focused on learning the handling of the stereographic projection technique applied to Structural Geology (also to Engineering Geology). This type of videos aims to reinforce the traditional classroom lessons with the use of communication technologies resources. Such a einforcing facilitates the possibility to deepen more on conceptual aspects once the students dominate the representation tool helping them to develop their own critical thinking skills. After three years of being launched on-line (on 2014), we analyze the broadcast and acceptance of the channel by the academic community. For this purpose we have taken into account two different sources: (1) the analytics tool from YouTube (subscriptions, views, countries, comments from the users, type of device for viewing), and (2) our own survey among users (students and teachers) to get their opinion about the videos. By January, 2017 (date of sending of this abstract), the channel has a total of 650 subscriptions, with more than 85,000 views all around the world, mainly in Spanish speaking countries (as the videos are in Spanish). The main devices for viewing the videos are PCs, but is noteworthy the use of smart phones and tablets. The video users, both students and teachers, value this type of content positively

Stereovideo youtube channel: short educational videos for the on-line learning of the the stereographic projection technique in Structural Geology

Stereovideo channel https://www.youtube.com/user/geostereovideo) is a YouTube channel of short educational videos (<5 min) focused on learning the handling of the stereographic projection technique applied to Structural Geology (also to Engineering Geology). This type of videos aims to reinforce the traditional classroom lessons with the use of communication technologies resources. Such a einforcing facilitates the possibility to deepen more on conceptual aspects once the students dominate the representation tool helping them to develop their own critical thinking skills. After three years of being launched on-line (on 2014), we analyze the broadcast and acceptance of the channel by the academic community. For this purpose we have taken into account two different sources: (1) the analytics tool from YouTube (subscriptions, views, countries, comments from the users, type of device for viewing), and (2) our own survey among users (students and teachers) to get their opinion about the videos. By January, 2017 (date of sending of this abstract), the channel has a total of 650 subscriptions, with more than 85,000 views all around the world, mainly in Spanish speaking countries (as the videos are in Spanish). The main devices for viewing the videos are PCs, but is noteworthy the use of smart phones and tablets. The video users, both students and teachers, value this type of content positively

Applying lazy learning algorithms to tackle concept drift in spam filtering

A great amount of machine learning techniques have been applied to problems where data is collected over an extended period of time. However, the disadvantage with many real-world applications is that the distribution underlying the data is likely to change over time. In these situations, a problem that many global eager learners face is their inability to adapt to local concept drift. Concept drift in spam is particularly difficult as the spammers actively change the nature of their messages to elude spam filters. Algorithms that track concept drift must be able to identify a change in the target concept (spam or legitimate e-mails) without direct knowledge of the underlying shift in distribution. In this paper we show how a previously successful instance-based reasoning e-mail filtering model can be improved in order to better track concept drift in spam domain. Our proposal is based on the definition of two complementary techniques able to select both terms and e-mails representative of the current situation. The enhanced system is evaluated against other well-known successful lazy learning approaches in two scenarios, all within a cost-sensitive framework. The results obtained from the experiments carried out are very promising and back up the idea that instance-based reasoning systems can offer a number of advantages tackling concept drift in dynamic problems, as in the case of the anti-spam filtering domain

SpamHunting: An instance-based reasoning system for spam labelling and filtering

n this paper we show an instance-based reasoning e-mail filtering model that outperforms classical machine learning techniques and other successful lazy learners approaches in the domain of anti-spam filtering. The architecture of the learning-based anti-spam filter is based on a tuneable en-hanced instance retrieval network able to accurately generalize e-mail representations. The reuse of similar messages is carried out by a simple unanimous voting mechanism to determine whether the tar-get case is spam or not. Previous to the final response of the system, the revision stage is only performed when the assigned class is spam whereby the system employs general knowledge in the form of meta-rules

Relaxing Feature Selection in Spam Filtering by Using Case-Based Reasoning Systems

This paper presents a comparison between two alternative strategies for addressing feature selection on a well known case-based reasoning spam filtering system called SpamHunting. We present the usage of the k more predictive features and a percentage-based strategy for the exploitation of our amount of information measure. Finally, we confirm the idea that the percentage feature selection method is more adequate for spam filtering domain

Tracking Concept Drift at Feature Selection Stage in SpamHunting: An Anti-spam Instance-Based Reasoning System

In this paper we propose a novel feature selection method able to handle concept drift problems in spam filtering domain. The proposed technique is applied to a previous successful instance-based reasoning e-mail filtering system called SpamHunting. Our achieved information criterion is based on several ideas extracted from the well-known information measure introduced by Shannon. We show how results obtained by our previous system in combination with the improved feature selection method outperforms classical machine learning techniques and other well-known lazy learning approaches. In order to evaluate the performance of all the analysed models, we employ two different corpus and six well-known metrics in various scenarios

A Comparative Performance Study of Feature Selection Methods for the Anti-spam Filtering Domain

In this paper we analyse the strengths and weaknesses of the mainly used feature selection methods in text categorization when they are applied to the spam problem domain. Several experiments with different feature selection methods and content-based filtering techniques are carried out and discussed. Information Gain, χ 2-text, Mutual Information and Document Frequency feature selection methods have been analysed in conjunction with Naïve Bayes, boosting trees, Support Vector Machines and ECUE models in different scenarios. From the experiments carried out the underlying ideas behind feature selection methods are identified and applied for improving the feature selection process of SpamHunting, a novel anti-spam filtering software able to accurate classify suspicious e-mails