Harms and benefits associated with psychoactive drugs: findings of an international survey of active drug users.

There have been several recent efforts in the UK and the Netherlands to describe the harms of psychoactive substances based on ratings of either experts or drug users. This study aimed to assess the perceived benefits as well as harms of widely used recreational drugs, both licit and illicit, in an international sample of drug users. The survey was hosted at https://www.internationaldrugsurvey.org/ and was available in three languages. Residents reported their experience of 15 commonly used drugs or drug classes; regular users then rated their harms and benefits. In all, 5791 individuals from over 40 countries completed the survey, although the majority were from English speaking countries. Rankings of drugs differed across 10 categories of perceived benefits. Skunk and herbal cannabis were ranked consistently beneficial, whilst alcohol and tobacco fell below many classified drugs. There was no correlation at all between users' harm ranking of drugs and their classification in schedules of the USA or ABC system in the UK. Prescription analgesics, alcohol and tobacco were ranked within the top 10 most harmful drugs. These findings suggest that neither the UK nor US classification systems act to inform users of the harms of psychoactive substances. It is hoped the results might inform health professionals and educators of what are considered to be both the harms and benefits of psychoactive substances to young people

A climatology of tropical wind shear produced by clustering wind profiles from the Met Office Unified Model (GA7.0)

Toward the goal of linking wind shear with the mesoscale organization of deep convection, a procedure for producing a climatology of tropical wind shear from the output of the Met Office Unified Model climate model is presented. Statistical information from wind profiles from tropical grid columns is used to produce a tractable number (10) of profiles that efficiently span the space of all wind profiles. Physical arguments are used to filter wind profiles that are likely to be associated with organized convection: only grid columns with substantial CAPE and those with shear in the upper quartile are considered. The profiles are rotated so that their wind vectors at 850 hPa are aligned, in order to be able to group like profiles together, and their magnitudes at each level are normalized. To emphasize the effect of lower levels, where the organization effects of shear are thought to be strongest, the profiles above 500 hPa are multiplied by 4. Principal Component Analysis is used to truncate the number of dimensions of the profiles to seven (which explains 90 % of the variance), and the truncated profiles are clustered using a K-means clustering algorithm. The median of each cluster defines a Representative Wind Profile (RWP). Each cluster contains information from thousands of wind profiles with different locations, times, and 850 hPa wind directions. To summarize the clusters statistically, we interpret the RWPs as pseudo-wind profiles, and display the geographic frequency, seasonal frequency, and histograms of wind direction at 850 hPa for each cluster. Geographic patterns are evident, and certain features of the spatio-temporal distributions are matched to observed distributions of convective organization. The form of the RWPs are also matched to specific wind profiles from case studies of organized convection. By performing the analysis on climate-model output, we lay the foundations for the development of the representation of shear-induced organization in a Convection Parametrization Scheme (CPS). This would use the same methodology to diagnose where the organization of convection occurs, and modify the CPS in an appropriate manner to represent it. The procedure could also be used as a diagnostic tool for evaluating and comparing climate models

The Use of Prolog for Improving the Rigour and Accessibility of Ecological Modelling

We introduce three concepts that offer considerable benefit to the process of ecological modelling: the descriptive representation of models; the explicit representation of knowledge about how to model; and the development of knowledge-based systems that can help ecologists construct models. Prolog, a computer language based on formal logic, has much to offer in realising these ideas. We introduce the concept of a ‘model blueprint’, a complete, formal specification of the structure of a model, and show how a blueprint can be represented as a Prolog program, basing our analysis on system dynamics models for simplicity. We consider ways in which the Prolog interpreter can be used selectively to retrieve information about the model, to check for errors in the formulation of the model, and to evaluate the model mathematically. However, there are drawbacks with this approach, so we discuss ways of overcoming these by implementing - also in Prolog - programs which buffer the user from the difficulties of working at the level of the Prolog interpreter. These include the generation of descriptions of model structure, and the development of a program to help in the construction of simulation models

The ECO Program Construction System: Ways of Increasing its Representational Power and their Effects on the User Interface

There is a growing interest in programs which help users with little experience of computing to construct simulation models. Much recent development work on such systems has utilized comparatively simple mathematical methods (such as system Dynamics) to facilitate the development of a friendly user interface. The problem with these simple modelling languages is that they assume that users have preconceived ideas of the simulation models which they want to build. In the ECO project, which involved the construction and testing of programs to help ecologists build simulation models, it became clear that users could not always adapt their ideas to fit into these mathematical frameworks. They required a more expressive input language in which to describe their modelling problems, rather than being forced directly to specify the programs which solved those problems. However, we found that as the input language became more sophisticated the complexity of the user interface became disproportionally larger. We attempt to clarify the reasons for this phenomenon by comparing the various systems which we built to try to solve this problem. This comparison is facilitated by the use of a sorted logic as a lingua franca for the various formalisms used in each system. Our analysis centres around a small number of key characteristics which we use to highlight the strengths and weaknesses of various dialogue techniques