Localization is an essential service for many wireless sensor network applications. While several localization schemes rely on anchor nodes and range measurements to achieve fine-grained positioning, we propose a range-free, anchorfree solution that works using connectivity information only. The approach, suitable for deployments with strict cost constraints, is based on the neural network paradigm of SelfOrganizing Maps (SOM). We present a lightweight SOMbased algorithm to compute virtual coordinates that are effective for location-aided routing. This algorithm can also exploit the location information, if available, of few anchor nodes to compute absolute positions. Results of extensive simulations show improvements over the popular MultiDimensional Scaling (MDS) scheme, especially for networks with low connectivity, which are intrinsically harder to localize, and in presence of irregular radio pattern or anisotropic deployment. We analytically demonstrate that the proposed scheme has low computation and communication overheads; hence, making it suitable for resource-constrained networks.

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Background: There is growing evidence linking cocaine consumption with a broad spectrum of neurocognitive deficits. Despite of evidence suggesting that the route of administration should be taken into account to assess the short and long term effects of cocaine consumption, to our knowledge no study to date has characterized clinically relevant neuropsychological variables along with physiological variables separately in populations of individuals with histories of smoked cocaine dependence (SCD) and insufflated cocaine hydrochloride dependence (ICD). Methods: The present study examined a sample of (a) 25 participants who fulfilled criteria for SCD, (b) 22 participants who fulfilled criteria for ICD, and (c) 25 healthy controls matched by age, gender, education, and socioeconomic status. An exhaustive neuropsychological battery was used to assess different cognitive domains (attention, executive functions, fluid intelligence, memory, language and social cognition). We complemented this neuropsychological assessment with the acquisition and analysis of structural (MRI) and functional (fMRI) neuroimaging data. Results: Different routes of administration led to equally different profiles of neurocognitive impairment, with the SCD group being specifically associated with deficits in attention and executive functions. Consistent with risk models, executive function-attention deficit is better explained for age and age onset of consumption initiation. SCD also presented reduced grey matter density relative to ICD in the bilateral caudate, a key area for executive functions and attention. Connectivity between left caudate and inferior frontal regions mediates performance-structure association. Conclusions: Cocaine routes of administration are associated to a differential profile that may not be due direct effects of stimulant action but also driven by cognitive and biological differences in key executive functioning and attention areas. This point the critical importance of the routes of administration. This information could inform clinical management and should be taken into account in clinical research.

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