The Five Factor Model of personality and evaluation of drug consumption risk

The problem of evaluating an individual's risk of drug consumption and misuse is highly important. An online survey methodology was employed to collect data including Big Five personality traits (NEO-FFI-R), impulsivity (BIS-11), sensation seeking (ImpSS), and demographic information. The data set contained information on the consumption of 18 central nervous system psychoactive drugs. Correlation analysis demonstrated the existence of groups of drugs with strongly correlated consumption patterns. Three correlation pleiades were identified, named by the central drug in the pleiade: ecstasy, heroin, and benzodiazepines pleiades. An exhaustive search was performed to select the most effective subset of input features and data mining methods to classify users and non-users for each drug and pleiad. A number of classification methods were employed (decision tree, random forest, $k$-nearest neighbors, linear discriminant analysis, Gaussian mixture, probability density function estimation, logistic regression and na{\"i}ve Bayes) and the most effective classifier was selected for each drug. The quality of classification was surprisingly high with sensitivity and specificity (evaluated by leave-one-out cross-validation) being greater than 70\% for almost all classification tasks. The best results with sensitivity and specificity being greater than 75\% were achieved for cannabis, crack, ecstasy, legal highs, LSD, and volatile substance abuse (VSA).Comment: Significantly extended report with 67 pages, 27 tables, 21 figure

Jet physics in electron--proton scattering

Hadronic jets in electron–proton collisions at HERA have been used for some considerable time as a tool for tests of the theory of strong interactions, quantum chromodynamics. Using jet final states, basic concepts like the factorisation ansatz for cross-section calculations, the perturbative approach to the cross section and the universality of the proton parton distribution functions can be examined. More concretely, jet measurements provide ready access to the strong coupling of QCD, α s , and to the parton distributions. In this report, an overview of jet results from the HERA experiments H1 and ZEUS and their interpretation is given together with a description of the theoretical foundations of jet physics in electron–proton collisions and of the experimental environment at HERA. Special emphasis is put on extractions of α s values and on the influence of jet data on fits of the proton parton distribution functions. Where useful, the HERA results are also discussed in the light of results from other colliders like LEP, the Tevatron or the LHC. The central message from these studies is that QCD does not only describe most of the measurements very well, but that QCD at HERA has achieved the status of a precision theory. On the other hand it is shown that further understanding of problematic issues relies critically on theoretical progress in the form of improved models or of increased precision in analytical calculations