De retibus socialibus et legibus momenti

Online Social Networks (OSNs) are a cutting edge topic. Almost everybody --users, marketers, brands, companies, and researchers-- is approaching OSNs to better understand them and take advantage of their benefits. Maybe one of the key concepts underlying OSNs is that of influence which is highly related, although not entirely identical, to those of popularity and centrality. Influence is, according to Merriam-Webster, "the capacity of causing an effect in indirect or intangible ways". Hence, in the context of OSNs, it has been proposed to analyze the clicks received by promoted URLs in order to check for any positive correlation between the number of visits and different "influence" scores. Such an evaluation methodology is used in this paper to compare a number of those techniques with a new method firstly described here. That new method is a simple and rather elegant solution which tackles with influence in OSNs by applying a physical metaphor.Comment: Changes made for third revision: Brief description of the dataset employed added to Introduction. Minor changes to the description of preparation of the bit.ly datasets. Minor changes to the captions of Tables 1 and 3. Brief addition in the Conclusions section (future line of work added). Added references 16 and 18. Some typos and grammar polishe

Copula selection models for non-Gaussian responses that are missing not at random

Missing not at random (MNAR) data poses key challenges for statistical inference because the model of interest is typically not identifiable without imposing further (e.g., distributional) assumptions. Sample selection models have been routinely used for handling MNAR by jointly modelling the outcome and selection variables assuming that these follow a bivariate normal distribution. Recent studies have advocated parametric selection model approaches, for example estimated by multiple imputation and maximum likelihood, that are more robust to departures from the normality assumption. However, the proposed methods have been mostly restricted to a specific joint distribution (e.g., bivariate t-distribution). This paper discusses a flexible copula-based selection approach (which accommodates a wide range of non-Gaussian outcome distributions and offers great flexibility in the choice of functional form specifications for both the outcome and selection equations) and proposes a flexible imputation procedure that generates plausible imputed values from the copula selection model. A simulation study characterises the relative performance of the copula model compared with the most commonly used selection models for estimating average treatment effects with MNAR data. We illustrate the methods in the REFLUX study, which evaluates the causal effect of laparoscopic surgery compared to usual medical management on long-term quality of life in patients with reflux disease. We provide software code for implementing the proposed copula framework using the R package GJRM

Períodos de actividad y dieta de Dasyprocta punctata (Gray, 1842) (Rodentia; Dasyproctidae) en agroecosistemas con café, San Ramón, Costa Rica

La guatusa Dasyprocta punctata (Gray, 1842) es una especie clasificada como de población estable y presente en distintos hábitats, no obstante, sus hábitos (dieta, periodos de actividad y comportamiento) han sido poco descritos. La presente investigación se basa en determinar los hábitos D. punctata en agroecosistemas con café en Rincón de Mora, San Ramón, Alajuela, Costa Rica. Para ello, se colocaron cuatro cámaras trampa en sitios estratégicos (fuentes de alimentación, madrigueras, cuerpos de agua y transición con el bosque secundario). La revisión de los videos arrojó nuevos hábitos en cuanto a dieta que no se habían registrado para esta especie, incluyendo el consumo de Polyporus sp. Asimismo, se observó que el mayor periodo de actividad anual en el cafetal se da en la etapa fenológica con fruto, mientras que el periodo de actividad diario se amplió el espectro en horas de la noche. De igual forma, se registraron comportamientos ya identificados, donde uno de los más importantes es la dispersión de semillas.The guatusa Dasyprocta punctata (Gray, 1842) is a species classified as having a stable population and present in different habitats, however, its habits (diet, periods of activity and behavior) have been little described. This research is based on determining D. punctata habits in coffee agroecosystems in Rincón de Mora, San Ramón, Alajuela, Costa Rica. For this, four camera traps were placed in strategic places (food sources, burrows, creeks, and transition with the secondary forest). The review of the videos revealed new dietary habits that had not been recorded for this species, including the consumption of Polyporus sp. Likewise, it was observed that the greatest period of annual activity in the coffee plantation occurs in the phenological stage with fruit, while the period of daily activity broadened the spectrum in hours of the night. Similarly, already identified behaviors were recorded, where one of the most important is seed dispersal

INDIGO : better geomagnetic observatories where we need them

The INDIGO project aims to improve the global coverage of digital observatories by deploying digital magnetometer systems in: i) Observatories where existing analog recording equipment is in need of upgrading. ii) Newly established digital observatories. iii) Existing digital observatories for the purpose of quality control and redundancy. In implementing the project and selecting suitable sites, special attention is paid to parts of the Earth devoid of magnetic observatories, increasing the reliability and long-term operation of existing observatories and cost-effective use of local resources. The Poster reviews the current status of the project. We examine the different steps and initiatives taken since the initiation of INDIGO in 2004 and assess their effectiveness in achieving progress towards our aims of improving global coverage and enhanced data quality

Results of D-IMPACT

Summary Aims:  Diagnosis IMprovement in PrimAry Care Trial (D-IMPACT) was a prospective, multicentre epidemiological study in three European countries to identify the optimal subset of simple tests applied in primary care to diagnose benign prostatic hyperplasia (BPH) in men who spontaneously present with lower urinary tract symptoms (LUTS). Methods:  Consecutive male patients aged ≥ 50 years who spontaneously attended their regular general practitioner (GP) office with LUTS were eligible for inclusion if they had not previously undergone BPH diagnostic tests or received treatment for BPH. Patients were assessed on three occasions, twice by their regular GP (visits 1 and 2) and once by a urologist (visit 3). The diagnostic accuracy of each variable was determined using the urologists' final BPH diagnosis (at visit 3) as gold-standard. Independent variables analysed were as follows: age; BPH diagnosis performed by GP in visit 1 (yes/no); probability of BPH diagnosis assessed by GP in visit 1; urinalysis (normal/abnormal); prostate-specific antigen (PSA); International Prostate Symptom Score (IPSS); diagnosis of BPH performed by GP in visit 2 (yes/no); and probability of BPH diagnosis assessed by GP in visit 2. Statistically significant variables (p 1.5 ng/ml and prostate volume ≥ 30 cm3). Among the independent variables analysed, only age, IPSS and PSA showed a statistically significant relationship with BPH diagnosis. In a logistic regression model including age, IPSS, PSA and probability of BPH (based on physical examination and symptoms), positive predictive value (PPV) was 77.1%. Exclusion of BPH probability resulted in a PPV of 75.7%. Conclusions:  A diagnostic algorithm including only objective variables (age, IPSS and PSA), easily implemented in any GP office, allows GPs to accurately diagnose BPH in approximately three-quarters of patients spontaneously reporting LUTS

Insights on Hydrothermal‐Magmatic Interactions and Eruptive Processes at Poás Volcano (Costa Rica) From High‐Frequency Gas Monitoring and Drone Measurements

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Safety assessment of chronic oral exposure to iron oxide nanoparticles

Iron oxide nanoparticles with engineered physical and biochemical properties are finding a rapidly increasing number of biomedical applications. However, a wide variety of safety concerns, especially those related to oral exposure, still need to be addressed for iron oxide nanoparticles in order to reach clinical practice. Here, we report on the effects of chronic oral exposure to low doses of γ-Fe2O3 nanoparticles in growing chickens. Animal observation, weight, and diet intake reveal no adverse signs, symptoms, or mortality. No nanoparticle accumulation was observed in liver, spleen, and duodenum, with feces as the main excretion route. Liver iron level and duodenal villi morphology reflect the bioavailability of the iron released from the partial transformation of γ-Fe2O3 nanoparticles in the acid gastric environment. Duodenal gene expression studies related to the absorption of iron from γ-Fe2O3 nanoparticles indicate the enhancement of a ferric over ferrous pathway supporting the role of mucins. Our findings reveal that oral administration of iron oxide nanoparticles is a safe route for drug delivery at low nanoparticle doses.Peer Reviewe