Web-monitoring activities are essential for mapping the diffusion of NPS and the use of technological tools can be successfully incorporated in specific prevention programmes. Furthermore, the involvement of multi-disciplinary international partnerships was and continues to be fundamental for responding to such a prominent challenge.

On the basis of the material available both in the scientific literature and on the web, this paper aims to provide a pharmacological, chemical and behavioural overview of the novel compound methoxetamine. This is a dissociative drug related to ketamine, with a much longer duration of action and intensity of effects. A critical discussion of the availability of information on the web of methoxetamine as a new recreational trend is here provided. Those methodological limitations, which are intrinsically associated with the analysis of online, non-peer reviewed, material, are here discussed as well. It is concluded that the online availability of information on novel psychoactive drugs, such as methoxethanine, may constitute a pressing public health challenge. Better international collaboration levels and novel forms of intervention are necessary to tackle this fast-growing phenomenon.

Background The combustion of tobacco is the main cause of tobacco-related morbidity and mortality. E-cigarettes are potentially disruptive innovations with considerable potential for population health. A key question is whether e-cigarettes are replacing tobacco cigarettes, which requires mapping their prevalence. Collecting information on nicotine use is difficult for many countries due to cost. The objective of this study was to derive a global estimate of e-cigarette use (vaping). Methods Since 2018 we have collected information on the prevalence of e-cigarette use. To estimate the prevalence of vaping in countries lacking information, we used the method of assumed similarity between countries in the same region and economic condition. Based on surveys, we calculated the average prevalence of vaping for each WHO region, World Bank income classification group, and the legal status of e-cigarettes in each country. For each of these groups the average prevalence of vaping was calculated. These values were used as substitutes for the prevalence figures in the countries with absent data. The number of vapers was calculated by taking as the denominator the adult population. Results Survey data on e-cigarette users were available for 49 countries covering 2.8 b of the adult population in 2018 and unavailable for 2.9 b. Information on vaping was lacking for half of the world's population. We estimated a total of 58.1 m vapers worldwide in 2018. By reference to market growth the data were adjusted to arrive at estimates for 2020. Results were fitted to revenue data at the 2018. For the year 2020, the projection is for 68 m vapers globally. Conclusions Many global epidemiological studies use the method of assumed similarity between countries with shared characteristics in order to estimate missing data. The methodological limitations are likely to overestimate the global number of vapers. Our estimate of 68 m vapers indicates considerable uptake given that: e-cigarettes have been available on most markets for only a decade; there is either no support, or there is opposition to vaping in many countries; and countries which regulate e-cigarettes have controls over advertising and promotion. However, given the global scale of tobacco smoking (at 1.1 billion people), progress in adoption of alternative products is slow. Those using e-cigarettes are still a small fraction of those who smoke.

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Based on the material available in both the scientific literature and on the web, the present paper provides an updated pharmacological, chemical, toxicological and behavioural overview of Bromo-Dragonfly (1-(8-bromobenzo[1,2-b;4,5-b']difuran-4-yl)-2-aminopropane; 'B-fly'). B-Fly is a powerful, long lasting, LSD-like, hallucinogenic drug, which has been associated with a number of acute intoxications and fatalities in a number of countries. A critical discussion of the potential of misuse of B-fly but also of the methodological limitations, which are intrinsically associated with the analysis of online, non-peer reviewed, material, is presented. It is concluded that the availability of online information on novel psychoactive drugs, such as B-fly, may constitute a public health challenge. Better international collaboration levels may be needed to tackle this novel and fast growing phenomenon.

An empirical analysis of algorithms c o n s t r u c t i n g a m i n i m u m s p a n n i n g t r e e Bernard M.E. Moret and Henry D. Shapiro 1 Department of Computer ScienceUniversity of New Mexico Albuquerque, NM 87131 A b s t r a c tWe compare algorithms for the construction of a minimum spanning tree through largescale experimentation on randomly generated graphs of different structures and different densities. In order to extrapolate with confidence, we use graphs with up to 130,000 nodes (sparse) or 750,000 edges (dense). Algorithms included in our experiments are Prim's algorithm (implemented with a variety of priority queues), Kruskal's algorithm (using presorting or demand sorting), Cheriton and Tarjan's algorithm, and Fredman and Tarjan's algorithm. We also ran a large variety of tests to investigate low-level implementation decisions for the data structures, as well as to enable us to eliminate the effect of compilers and architectures.Within the range of sizes used, Prim's algorithm, using pairing heaps or sometimes binary heaps, is clearly preferable. While versions of Prim's algorithm using efficient implementations of Fibonacci heaps or rank-relaxed heaps often approach and (on the densest graphs) sometimes exceed the speed of the simpler implementations, the code for binary or pairing heaps is much simpler, so that these two heaps appear to be the implementation of choice.Some conclusions regarding implementation of priority queues also emerge from our study: in the context of a greedy algorithm, pairing heaps appear faster than other implementations, closely followed by binary, rank-relaxed and Fibonacci heaps, the latter two implemented with sacks, while splay trees finish a decided last.

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