Mobility and sociality in proximity-sensitive digital urban ecologies: ‘Timid encounters’ and ‘seam-sensitive walks’

This paper is a case study of the use of a proximity-sensitive game played on mobile gaming terminals, in Japan and in France, Dragon Quest 9, and of distinctive forms of mobility and urban encounters which emerge around it. We show how players, when assembled together, walk the ‘connected walk,’ that is they adopt a particular gait, slower than the usual walking pace, with repeated pauses which appears as a tentative and exploratory kind of mobility oriented towards the random occurrence of proximity-based screen-mediated events, and therefore both adjusted to and constitutive of the proximity-sensitive hybrid ecology as a serendipitous place, to be experienced as such. With respect to urban encounters, we have identified a characteristic tension, relevant to locative media in general, in which concerns with potential identification and recognition ‘in the game’ contrasts with the interaction order of urban traffic encounters, characterized by ‘civil inattention.’ This gives rise to the phenomenon of ‘timid encounters,’ in which players strive to experience game encounters with other players a few meters away, while trying to elude visual or verbal recognition.     

Estimation of Causal Odds of Concordance using the Aalen Additive Model

A simple summary of a treatment effect is attractive, which is part of the explanation of the success of the Cox model when analysing time‐to‐event data since the relative risk measure is such a convenient summary measure. In practice, however, the Cox model may fail to give a reasonable fit, very often because of time‐changing treatment effect. The Aalen additive hazards model may be a good alternative as time‐changing effects are easily modelled within this model, but results are then evidently more complicated to communicate. In such situations, the odds of concordance measure (OC) is a convenient way of communicating results, and recently Martinussen & Pipper (2012) showed how a variant of the OC measure may be estimated based on the Aalen additive hazards model. In this study, we propose an estimator that should be preferred in observational studies as it always estimates the causal effect on the chosen scale, only assuming that there are no un‐measured confounders. The resulting estimator is shown to be consistent and asymptotically normal, and an estimator of its limiting variance is provided. Two real applications are provided.     

On perfect simulation for some mixtures of distributions

This paper studies the implementation of the coupling from the past (CFTP) method of Propp and Wilson (1996) in the set-up of two and three component mixtures with known components and unknown weights. We show that monotonicity structures can be exhibited in both cases, but that CFTP can still be costly for three component mixtures. We conclude with a simulation experiment exhibiting an almost perfect sampling scheme where we only consider a subset of the exhaustive set of starting values.     

On robust forecasting in dynamic vector time series models

In this article, robust estimation and prediction in multivariate autoregressive models with exogenous variables (VARX) are considered. The conditional least squares (CLS) estimators are known to be non-robust when outliers occur. To obtain robust estimators, the method introduced in Duchesne [2005. Robust and powerful serial correlation tests with new robust estimates in ARX models. J. Time Ser. Anal. 26, 49–81] and Bou Hamad and Duchesne [2005. On robust diagnostics at individual lags using RA-ARX estimators. In: Duchesne, P., Rémillard, B. (Eds.), Statistical Modeling and Analysis for Complex Data Problems. Springer, New York] is generalized for VARX models. The asymptotic distribution of the new estimators is studied and from this is obtained in particular the asymptotic covariance matrix of the robust estimators. Classical conditional prediction intervals normally rely on estimators such as the usual non-robust CLS estimators. In the presence of outliers, such as additive outliers, these classical predictions can be severely biased. More generally, the occurrence of outliers may invalidate the usual conditional prediction intervals. Consequently, the new robust methodology is used to develop robust conditional prediction intervals which take into account parameter estimation uncertainty. In a simulation study, we investigate the finite sample properties of the robust prediction intervals under several scenarios for the occurrence of the outliers, and the new intervals are compared to non-robust intervals based on classical CLS estimators.     

Serial dependence and regression of Poisson INARMA models

Time series of counts occur in many fields of practice, with the Poisson distribution as a popular choice for the marginal process distribution. A great variety of serial dependence structures of stationary count processes can be modelled by the INARMA family. In this article, we propose a new approach to the INMA(q) family in general, including previously known results as special cases. In the particular case of Poisson marginals, we will derive new results concerning regression properties and the serial dependence structure of INAR(1) and INMA(q) models. Finally, we present explicit expressions for the distribution of jumps in such processes.     

Inaction over retractions of identified fraudulent publications: ongoing weakness in the system of scientific self-correction

Published articles may be retracted when their findings are no longer considered reliable due to honest error, publication misconduct, or research misconduct. This article focuses on the case of a single serial violator of research and publication ethics in anesthesiology and critical care, which is widely publicized. A chain of events led to detection of misconduct that had substantial impact on the evidence base for the safety of hydroxyethyl starch, an intravenous artificial colloid solution, which is reflected in current guidelines on fluid management and volume resuscitation. As citations to retracted works continue to be a cause for concern, this article reviews the retraction status of this author’s published articles to determine whether sufficient action has been taken to retract his body of work. Results show that retraction practices are not uniform and that guidelines for retraction are still not being fully implemented, resulting in retractions of insufficient quantity and quality. As retractions continue to emerge for the author’s publications, with ten more since 2011, and as they are generally increasing, these data on retractions not only provide findings of misconduct, but also allow us to make inferences about ongoing weaknesses in the system of scientific literature.