Modeling Adoption and Usage of Competing Products

The emergence and wide-spread use of online social networks has led to a dramatic increase on the availability of social activity data. Importantly, this data can be exploited to investigate, at a microscopic level, some of the problems that have captured the attention of economists, marketers and sociologists for decades, such as, e.g., product adoption, usage and competition. In this paper, we propose a continuous-time probabilistic model, based on temporal point processes, for the adoption and frequency of use of competing products, where the frequency of use of one product can be modulated by those of others. This model allows us to efficiently simulate the adoption and recurrent usages of competing products, and generate traces in which we can easily recognize the effect of social influence, recency and competition. We then develop an inference method to efficiently fit the model parameters by solving a convex program. The problem decouples into a collection of smaller subproblems, thus scaling easily to networks with hundred of thousands of nodes. We validate our model over synthetic and real diffusion data gathered from Twitter, and show that the proposed model does not only provides a good fit to the data and more accurate predictions than alternatives but also provides interpretable model parameters, which allow us to gain insights into some of the factors driving product adoption and frequency of use

An index of political support for decentralization: the Spanish case.

This paper presents a method to make measurable what was not: the discourses of politicians regarding decentralization. For this purpose, we develop a “matrix of arguments” and a set of indexes, and apply them to provide a snapshot of the politicians’ views on the “General Law of Budgetary Stability”, a landmark for the process of decentralization in Spain.political party, matrix of decentralization, arguments, index of decentralization.

Variation in dengue virus plaque reduction neutralization testing: systematic review and pooled analysis.

BackgroundThe plaque reduction neutralization test (PRNT) remains the gold standard for the detection of serologic immune responses to dengue virus (DENV). While the basic concept of the PRNT remains constant, this test has evolved in multiple laboratories, introducing variation in materials and methods. Despite the importance of laboratory-to-laboratory comparability in DENV vaccine development, the effects of differing PRNT techniques on assay results, particularly the use of different dengue strains within a serotype, have not been fully characterized.MethodsWe conducted a systematic review and pooled analysis of published literature reporting individual-level PRNT titers to identify factors associated with heterogeneity in PRNT results and compared variation between strains within DENV serotypes and between articles using hierarchical models.ResultsThe literature search and selection criteria identified 8 vaccine trials and 25 natural exposure studies reporting 4,411 titers from 605 individuals using 4 different neutralization percentages, 3 cell lines, 12 virus concentrations and 51 strains. Of 1,057 titers from primary DENV exposure, titers to the exposure serotype were consistently higher than titers to non-exposure serotypes. In contrast, titers from secondary DENV exposures (n = 628) demonstrated high titers to exposure and non-exposure serotypes. Additionally, PRNT titers from different strains within a serotype varied substantially. A pooled analysis of 1,689 titers demonstrated strain choice accounted for 8.04% (90% credible interval [CrI]: 3.05%, 15.7%) of between-titer variation after adjusting for secondary exposure, time since DENV exposure, vaccination and neutralization percentage. Differences between articles (a proxy for inter-laboratory differences) accounted for 50.7% (90% CrI: 30.8%, 71.6%) of between-titer variance.ConclusionsAs promising vaccine candidates arise, the lack of standardized assays among diagnostic and research laboratories make unbiased inferences about vaccine-induced protection difficult. Clearly defined, widely accessible reference reagents, proficiency testing or algorithms to adjust for protocol differences would be a useful first step in improving dengue PRNT comparability and quality assurance

Shaping Social Activity by Incentivizing Users

Events in an online social network can be categorized roughly into endogenous events, where users just respond to the actions of their neighbors within the network, or exogenous events, where users take actions due to drives external to the network. How much external drive should be provided to each user, such that the network activity can be steered towards a target state? In this paper, we model social events using multivariate Hawkes processes, which can capture both endogenous and exogenous event intensities, and derive a time dependent linear relation between the intensity of exogenous events and the overall network activity. Exploiting this connection, we develop a convex optimization framework for determining the required level of external drive in order for the network to reach a desired activity level. We experimented with event data gathered from Twitter, and show that our method can steer the activity of the network more accurately than alternatives

Estimation of blood velocity vectors using transverse ultrasound beam focusing and cross-correlation

Modern ultrasound scanners estimate the blood velocity by tracking the movement of the blood scatterers along the ultrasound beam. This is done by emitting pulsed ultrasound fields and finding the shift in position from pulse to pulse by correlating the received signals. Only the velocity component along the beam direction is found, and this is a serious limitation in the current scanners, since most blood vessels are parallel to the skin surface. A method to find the velocity across the vessel has been suggested by Bonnefous (1988). Here a number of parallel receive beams are measured and used in a correlation estimator to find the velocity across the beam. This approach is extended in this paper by making beamforming along the direction of the flow. A fairly broad beam is emitted and the received signal is then focused along a selected direction. This direction can be along the ultrasound beam or across it or in any direction to the beam. The focused lines, thus, follow the flow and a cross-correlation of lines from different pulses can find the movement of the blood particles between pulse emissions and, thus, the blood velocity. The new approach is investigated using the Field II simulation program. Simulations are shown for a parabolic velocity profile for flow-to-beam angles of 30, 45, 60, and 90 degrees using a 64 elements linear array with a center frequency of 3 MHz, a pitch of 0.3 mm, and an element height of 5 mm. The peak velocity in the parabolic flow was 0.5 m/s, and the pulse repetition frequency was 3.5 kHz. Using four pulse-echo lines, the parabolic flow profile was found with a standard deviation of 0.028 m/s at 60 degrees and 0.092 m/s at 90 degrees (transverse to the ultrasound beam), corresponding to accuracies of 5.6% and 18.4%. Using ten lines gave standard deviations of 0.021 m/s and 0.089 m/s, respectively, corresponding to accuracies of 4.2% and 17.8

Learning and Forecasting Opinion Dynamics in Social Networks

Social media and social networking sites have become a global pinboard for exposition and discussion of news, topics, and ideas, where social media users often update their opinions about a particular topic by learning from the opinions shared by their friends. In this context, can we learn a data-driven model of opinion dynamics that is able to accurately forecast opinions from users? In this paper, we introduce SLANT, a probabilistic modeling framework of opinion dynamics, which represents users opinions over time by means of marked jump diffusion stochastic differential equations, and allows for efficient model simulation and parameter estimation from historical fine grained event data. We then leverage our framework to derive a set of efficient predictive formulas for opinion forecasting and identify conditions under which opinions converge to a steady state. Experiments on data gathered from Twitter show that our model provides a good fit to the data and our formulas achieve more accurate forecasting than alternatives

Support policies for the renovations and restructuration of mature tourist destinations: a retrospective evaluation from case studies

La necesidad de reformulación del modelo de desarrollo turístico asociado a la fórmula sol y playa en el litoral mediterráneo español ha estado presente en la política turística a lo largo de los últimos veinte años, lo que ha conducido a la puesta en marcha de diferentes estrategias y programas de actuación dirigidos a la mejora y renovación de los destinos turísticos maduros del litoral a desarrollar por parte del sector público y privado. Bajo este planteamiento, el análisis de las últimas y más emblemáticas iniciativas y proyectos emprendidos resulta de interés para la mejor ilustración de la compleja realidad en la que se desenvuelven los procesos de reestructuración y renovación de los destinos turísticos costeros. Por esta razón, el presente trabajo analiza y elabora una síntesis integradora de los cuatro proyectos piloto de reconversión de destinos maduros impulsados por la Administración turística con el propósito de reflexionar sobre su naturaleza, y nivel de ejecución de las propuestas contempladas, de forma que pueda realizarse una evaluación de la efectividad y alcance de esta política. Las experiencias piloto analizadas han demostrado tener efectos positivos en la renovación aunque lejos ha quedado el cumplimiento de los objetivos de mayor envergadura, poniéndose así de manifiesto el gap existente entre lo proyectado desde el ámbito de la política y lo efectivamente conseguido en su ejecución. Este trabajo trata de evaluar desde una visión crítica, objetiva y de conjunto el desempeño de dichos proyectos.The need for a reformulation of the touristic development model associated to the “sun and beach” formula in the Spanish Mediterranean coast have been present in the touristic policy over the last twenty years, which conducted to has led to the implementation of various strategies, programs and actions aimed at the improvement and renewal of the mature tourist destinations on the coast by the public and private sector. Along these lines, the analysis of the latest and most emblematic initiatives and projects undertaken is of interest for the best illustration of the complex reality in which processes of restructuring and renovation of coastal tourist destinations operate. For this reason, this paper discusses an analysis and inclusive synthesis for the four pilot restructuring projects promoted by the Tourism Administration in order to reflect on its nature, the execution level of its initial proposals and, at the same time, facilitate an easier understanding and assessment of the support policy for the mature destinations conversion. Analyzed pilot experiences have demonstrated positive effects in the renewal yet far from the fulfillment of large magnitude objectives, revealing the existing gap between what is projected from political arena and what is actually achieved in its implementation. This work tries to evaluate in a pioneer manner from a critical, objective and overall perspective, the performance of these projects.El presente trabajo se enmarca en el proyecto de investigación “Metodología, criterios y aplicaciones para la configuración de clusters en áreas turísticas consolidadas: innovación, complementariedad y competitividad territorial” (CSO2011-26396), financiado por el Plan Nacional de I+D+i del Ministerio de Economía y Competitividad

Au-Cu/SBA(Ti) based catalysts for photocatalytic applications

Comunicación a congresoIn this work, it has been synthesized several Au and Au-Cu alloy photocatalysts supported on two different mesoporous supports: a non-commercial SBA-15 and a post-synthesis TiO2 modified SBA-15 (TiSBA-15), with which a high dispersion of TiO2 species have been achieved maintaining the SBA-15 structure. In addition, it has also been obtained highly dispersed Au nanoparticles confined in SBA-15 pore channels, as can be observed in Figure 1. The photocatalysts have been preliminary tested in the preferential CO oxidation in a H2-rich stream (CO-PROX) at room temperature and atmospheric pressure under simulated solar light irradiation. In spite of the very low gold and copper loading (1.5 wt% and 0.5wt% respectively), the catalysts resulted active and selective in the low temperature photo-CO-PROX.Universidad de Málaga, Campus de Excelencia Internacional Andalucía Tec

Does diversity in top management teams contribute to organizational performance? The response of IBEX 35 companies

This study contributes to the spread of theoretical and empirical knowledge regarding the Upper Echelons Theory, considering the training and demographic diversity in the Top Management Team (TMT) as a singular characteristic of each company, in our case those belonging to the IBEX35 index. Taking into account the skills of the members, a greater financial performance is expected. Once we obtained the statistical results, we concluded that the inclusion of women in the TMT increased Net Sales and EBITDA. Features such as age, training and nationality are also examined in this work.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech