The Effect of Pok\'emon Go on The Pulse of the City: A Natural Experiment

Pok\'emon Go, a location-based game that uses augmented reality techniques, received unprecedented media coverage due to claims that it allowed for greater access to public spaces, increasing the number of people out on the streets, and generally improving health, social, and security indices. However, the true impact of Pok\'emon Go on people's mobility patterns in a city is still largely unknown. In this paper, we perform a natural experiment using data from mobile phone networks to evaluate the effect of Pok\'emon Go on the pulse of a big city: Santiago, capital of Chile. We found significant effects of the game on the floating population of Santiago compared to movement prior to the game's release in August 2016: in the following week, up to 13.8\% more people spent time outside at certain times of the day, even if they do not seem to go out of their usual way. These effects were found by performing regressions using count models over the states of the cellphone network during each day under study. The models used controlled for land use, daily patterns, and points of interest in the city. Our results indicate that, on business days, there are more people on the street at commuting times, meaning that people did not change their daily routines but slightly adapted them to play the game. Conversely, on Saturday and Sunday night, people indeed went out to play, but favored places close to where they live. Even if the statistical effects of the game do not reflect the massive change in mobility behavior portrayed by the media, at least in terms of expanse, they do show how "the street" may become a new place of leisure. This change should have an impact on long-term infrastructure investment by city officials, and on the drafting of public policies aimed at stimulating pedestrian traffic.Comment: 23 pages, 7 figures. Published at EPJ Data Scienc

Parallel Construction of Wavelet Trees on Multicore Architectures

The wavelet tree has become a very useful data structure to efficiently represent and query large volumes of data in many different domains, from bioinformatics to geographic information systems. One problem with wavelet trees is their construction time. In this paper, we introduce two algorithms that reduce the time complexity of a wavelet tree's construction by taking advantage of nowadays ubiquitous multicore machines. Our first algorithm constructs all the levels of the wavelet in parallel in $O(n)$ time and $O(n\lg\sigma + \sigma\lg n)$ bits of working space, where $n$ is the size of the input sequence and $\sigma$ is the size of the alphabet. Our second algorithm constructs the wavelet tree in a domain-decomposition fashion, using our first algorithm in each segment, reaching $O(\lg n)$ time and $O(n\lg\sigma + p\sigma\lg n/\lg\sigma)$ bits of extra space, where $p$ is the number of available cores. Both algorithms are practical and report good speedup for large real datasets.Comment: This research has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sk{\l}odowska-Curie Actions H2020-MSCA-RISE-2015 BIRDS GA No. 69094

Communication of suicide intent by schizophrenic subjects: data from the Queensland Suicide Register

<p>Abstract</p> <p>Background</p> <p>Suicide in mentally ill subjects, like schizophrenics, remains unbearably frequent in Australia and elsewhere. Since these patients are known to constitute a high-risk group, suicide in them should be amongst the most preventable ones. The objective of this study is to investigate the frequency of suicide communication in subjects with reported history of schizophrenia who completed suicide.</p> <p>Method</p> <p>The Queensland Suicide Register (QSR) was utilised to identify suicide cases. Frequency of suicide communication was examined in subjects with schizophrenia, and compared with persons with other psychiatric conditions and with subjects with no reported diagnosis. Socio-demographic variables, history of suicidal behaviour, pharmacological treatment and mental health service utilisation were also compared among the three groups.</p> <p>Results and discussion</p> <p>Subjects with a reported diagnosis of schizophrenia comprised 7.2% (n = 135) of the 1,863 suicides included in this study. Subjects with schizophrenia and those with other psychiatric disorders communicated their suicide intent more frequently than those with no psychiatric diagnosis, and persons with schizophrenia communicated their intent more than those with other psychiatric diagnoses. Seventy one per cent of schizophrenia subjects had contact with a mental health professional within the three months prior to suicide.</p> <p>Conclusion</p> <p>The fact that subjects with schizophrenia had the highest prevalence of suicide intent communication could offer concrete opportunities for suicide prevention.</p