Relating Group Size and Posting Activity of an Online Community of Financial Investors: Regularities and Seasonal Patterns

Group size can potentially affect collective activity and individual propensity to contribute to collective goods. Mancur Olson, in his Logic of Collective Action, argued that individual contribution to a collective good tends to be lower in groups of large size. Today, online communication platforms represent an interesting ground to study such collaborative dynamics under possibly different conditions (e.g., lower costs related to gather and share information). This paper examines the relationship between group size and activity in an online financial forum, where users invest time in sharing news, analysis and comments with other investors. We looked at about 24 million messages shared in more than ten years in the finanzaonline.com online forum. We found that the relationship between the number of active users and the number of posts shared by those users is of the power type (with exponent α\u3e1) and is subject to periodic fluctuations, mostly driven by hour-of-the-day and day-of-the-week effects. The daily patterns of the exponent showed a divergence between working week and weekend days. In general, the exponent was lower before noon, where investors are typically interested in market news, higher in the late afternoon, where markets are closing and investors need better understanding of the situation. Further research is needed, especially at the micro level, to dissect the mechanisms behind these regularities

Novos registros de Aleyrodidae (Hemiptera) no estado de Roraima, Brasil.

Registra pela primeira vez a ocorrência de seis espécies de Aleyrodidae e respectivas plantas hospedeiras no Estado de Roraima. Dentre os registros constam Aleurocanthus woglumi Ashby, praga quarentenária presente no Brasil (A2) e alguns inimigos naturais

Focalization performance study of a novel bulk acoustic wave device

This work illustrates focalization performances of a silicon‐based bulk acoustic wave device applied for the separation of specimens owing to micrometric dimensions. Samples are separated in the microfluidic channel by the presence of an acoustic field, which focalizes particles or cells according to their mechanical properties compared to the surrounded medium ones. Design and fabrication processes are reported, followed by focalization performance tests conducted either with synthetic particles or cells. High focalization performances occurred at different microparticle concentrations. In addition, preliminary tests carried out with HL‐60 cells highlighted an optimal separation performance at a high flow rate and when cells are mixed with micro and nanoparticles without affecting device focalization capabilities. These encouraging results showed how this bulk acoustic wave device could be exploited to develop a diagnostic tool for early diagnosis or some specific target therapies by separating different kinds of cells or biomarkers possessing different mechanical properties such as shapes, sizes and densities

Primary tumor sidedness and benefit from FOLFOXIRI plus bevacizumab as initial therapy for metastatic colorectal cancer. Retrospective analysis of the TRIBE trial by GONO

Right-sided metastatic colorectal cancer (mCRC) patients have poor prognosis and achieve limited benefit from first-line doublets plus a targeted agent. In this unplanned analysis of the TRIBE study, we investigated the prognostic and predictive impact of primary tumor sidedness in mCRC patients and the differential impact of the intensification of the chemotherapy in subgroups defined according to both primary tumor sidedness and RAS and BRAF mutational status

Mosca branca: uma ameaça à produção do coqueiro no Brasil.

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First report on the whitefly, Aleurodicus pseudugesii on the coconut palm, Cocos nucifera in Brazil.

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Minería de datos educacional para determinar perfiles de alumnos recursantes en carreras de ingenierías

Las instituciones universitarias tienen el desafío de asegurar y mantener el nivel de calidad académica con el fin de proveer profesionales altamente capacitados que respondan a las demandas del mercado laboral actual, especialmente en el área de las TICs. Uno de los aspectos en donde las universidades deben poner mayor énfasis es en el rendimiento académico, ya que generalmente un bajo rendimiento académico está asociado con una alta tasa de deserción de alumnos. Para evaluar el rendimiento académico de un alumno es necesario conocer si existen patrones o perfiles comunes a grupos de alumnos, esto es de significativa importancia para definir acciones que permitan mejorar el desempeño de los alumnos. En este trabajo se propone el uso de minería de datos educacional para la construcción de modelos que permitan identificar perfiles de alumnos que recursan materias básicas en el primer año de las carreras de ingenierías. Los resultados de este proyecto serán un aporte para el área de gestión académica, ya que podrán contar con un instrumento objetivo que les permitirá definir acciones a futuro en pos de lograr la mejora en el rendimiento académico de los alumnos en materias básicas del primer año.Eje: Tecnología informática aplicada en educación.Red de Universidades con Carreras en Informátic