Fitting Prediction Rule Ensembles with R Package pre

Prediction rule ensembles (PREs) are sparse collections of rules, offering highly interpretable regression and classification models. This paper presents the R package pre, which derives PREs through the methodology of Friedman and Popescu (2008). The implementation and functionality of package pre is described and illustrated through application on a dataset on the prediction of depression. Furthermore, accuracy and sparsity of PREs is compared with that of single trees, random forest and lasso regression in four benchmark datasets. Results indicate that pre derives ensembles with predictive accuracy comparable to that of random forests, while using a smaller number of variables for prediction

Phase Separation and Self-Assembly in a Fluid of Mickey Mouse Particles

Recent developments in the synthesis of colloidal particles allow for control over shape and inter-particle interaction. One example, among others, is the so-called "Mickey Mouse" (MM) particle for which the self-assembly properties have been previously studied yielding a stable cluster phase together with elongated, tube-like structures. Here, we investigate under which conditions a fluid of Mickey Mouse particles can yield phase separation and how the self-assembly behaviour affects the gas-liquid coexistence. We vary the distance between the repulsive and the attractive lobes (bond length), and the interaction range, and follow the evolution of the gas-liquid (GL) coexistence curve. We find that upon increasing the bond length distance the binodal line shifts to lower temperatures, and that the interaction range controls the transition between phase separation and self-assembly of clusters. Upon further reduction of the interaction range and temperature, the clusters assume an increasingly ordered tube-like shape, ultimately matching the one previously reported in literature. These results are of interest when designing particle shape and particle-particle interaction for self-assembly processes

Changing spatial planning systems and the role of the regional government level; Comparing the Netherlands, Flanders and England

Several European countries are adapting their planning system to current requirements of public and private sector and society. Examples of such countries are England and the Netherlands. The paper start with an overview of theoretical concepts of planning systems in relation to spatial planning. We then focus on the proposed and recent changes in the English and Dutch planning systems. What are the main objectives for the changes and how are they elaborated in planning instruments, procedures and institutional framework? The paper concludes with relating the changes in the two presented planning systems to the theoretical concepts op planning systems.

Crystal nucleation of colloidal hard dumbbells

Using computer simulations we investigate the homogeneous crystal nucleation in suspensions of colloidal hard dumbbells. The free energy barriers are determined by Monte Carlo simulations using the umbrella sampling technique. We calculate the nucleation rates for the plastic crystal and the aperiodic crystal phase using the kinetic prefactor as determined from event driven molecular dynamics simulations. We find good agreement with the nucleation rates determined from spontaneous nucleation events observed in event driven molecular dynamics simulations within error bars of one order of magnitude. We study the effect of aspect ratio of the dumbbells on the nucleation of plastic and aperiodic crystal phases and we also determine the structure of the critical nuclei. Moreover, we find that the nucleation of the aligned CP1 crystal phase is strongly suppressed by a high free energy barrier at low supersaturations and slow dynamics at high supersaturations.Comment: Accepted by J. Chem. Phy

The Geographic Distribution of Patents and Value Added Across European

Until recently, the geographic element of concentrations of economic activity and knowledge spillovers was almost completely disregarded by economic theory. Although space is a central concept in theories in the field of geography, geographers have not attached great value to technology as a motivating factor for clustering of economic activity. A pooled market of skilled labour and the availability of nontraded inputs are considered much more important as factors that induce the clustering of firms (Krugman 1991). Several recent studies for the US (among others Jaffe, Trajtenberg and Henderson 1993, Audretsch and Feldman 1994, Feldman 1994) examined the extent to which innovative as well as economic activity clusters spatially. Until recently there were no data available for Europe on this issue. By means of a new data set, namely regional patent data for Europe, this paper will try to identify differences in geographic concentration in patents (as a proxy for innovation) and manufacturing value added over several industries. Several statistical techniques will be used to gather information on the spatial pattern of variation in patents and manufacturing value added across European regions.regional and urban economics ;

Regional differences in technology : theory and empirics

The aim of this paper is, on the one hand, to give a review of several streams in the litera-ture which differ with respect to the extent they assume knowledge to spread over regions. On the other hand, this paper shows the extent to which these theories are supported empirically. The regional neoclassical growth model focuses on the immediate diffusion of technological knowledge. Alternative theories like cumulative causation and imperfect diffusion theories focus on the issue that technology gaps between regions will persist over time. Cumulative causation assumes that there exists no diffusion of knowledge, while imperfect diffusion theories assume that diffusion will take place, though slowly. These theoretical insights lead to several testable hypotheses on the presence and the development over time of regional technology gaps. This paper attempts to use a new set of data on R&D in the European Union to explore this field. Evidence from regional R&D statistics will be used to highlight differences in technological activity between the regions within the leading European economies. Also the factors that are proposedly related to the relative technological activity of a region are analysed, in addition to the long term implications of technology gaps.research and development ;