Weak disorder: anomalous transport and diffusion are normal yet again

Particles driven through a periodic potential by an external constant force are known to exhibit a pronounced peak of the diffusion around a critical force that defines the transition between locked and running states. It has recently been shown both experimentally and numerically that this peak is greatly enhanced if some amount of spatial disorder is superimposed on the periodic potential. Here we show that beyond a simple enhancement lies a much more interesting phenomenology. For some parameter regimes the system exhibits a rich variety of behaviors from normal diffusion to superdiffusion, subdiffusion and even subtransport.Comment: Substantial improvements in presentatio

An analytical approach to sorting in periodic potentials

There has been a recent revolution in the ability to manipulate micrometer-sized objects on surfaces patterned by traps or obstacles of controllable configurations and shapes. One application of this technology is to separate particles driven across such a surface by an external force according to some particle characteristic such as size or index of refraction. The surface features cause the trajectories of particles driven across the surface to deviate from the direction of the force by an amount that depends on the particular characteristic, thus leading to sorting. While models of this behavior have provided a good understanding of these observations, the solutions have so far been primarily numerical. In this paper we provide analytic predictions for the dependence of the angle between the direction of motion and the external force on a number of model parameters for periodic as well as random surfaces. We test these predictions against exact numerical simulations

Phase Separation Driven by External Fluctuations

The influence of external fluctuations in phase separation processes is analysed. These fluctuations arise from random variations of an external control parameter. A linear stability analysis of the homogeneous state shows that phase separation dynamics can be induced by external noise. The spatial structure of the noise is found to have a relevant role in this phenomenon. Numerical simulations confirm these results. A comparison with order-disorder noise induced phase transitions is also made.Comment: 4 pages, 4 Postscript figures included in text. LaTeX (with Revtex macros

Lifshitz-Slyozov Scaling For Late-Stage Coarsening With An Order-Parameter-Dependent Mobility

The coarsening dynamics of the Cahn-Hilliard equation with order-parameter dependent mobility, $\lambda(\phi) \propto (1-\phi^2)^\alpha$, is addressed at zero temperature in the Lifshitz-Slyozov limit where the minority phase occupies a vanishingly small volume fraction. Despite the absence of bulk diffusion for $\alpha>0$, the mean domain size is found to grow as $\propto t^{1/(3+\alpha)}$, due to subdiffusive transport of the order parameter through the majority phase. The domain-size distribution is determined explicitly for the physically relevant case $\alpha = 1$.Comment: 4 pages, Revtex, no figure

The development and interlinkage of a drought vocabulary in the EuroGEOSS interoperable catalogue infrastructure

Metadata catalogues are used for facilitating the discovery of data and web services in, e.g., growing collections of Earth observation resources. Two conditions need to be met in order to successfully retrieve resources in catalogues: the metadata describing resources have to be complete and accurate and the keywords used in searches semantically related to the keywords contained in the metadata descriptions. One method to increase the rate of successfully retrieved metadata in catalogues is the use of controlled vocabularies. Such vocabularies can be used for annotating metadata with appropriate keywords and then also presented to users of the catalogue for specifying search terms. In the process of preparing metadata for drought-related data and services within the EuroGEOSS project, the need of a drought-specific vocabulary arose. This paper presents this drought vocabulary, the methodology followed for its development, its integration in the EuroGEOSS drought infrastructure and discusses its usefulness for the drought thematic area. The usefulness of the vocabulary is hereby measured by an increased use of search terms coming from an appropriate vocabulary and by an increase in the successful retrieval of resources. In particular, metadata must be annotated with appropriate keywords from a controlled vocabulary, thesaurus or ontology suitable for that particular field

A software processing chain for evaluating thesaurus quality

Thesauri are knowledge models commonly used for information classification and retrieval whose structure is defined by standards that describe the main features the concepts and relations must have. However, following these standards requires a deep knowledge of the field the thesaurus is going to cover and experience in their creation. To help in this task, this paper describes a software processing chain that provides different validation components that evaluates the quality of the main thesaurus features

A method for checking the quality of geographic metadata based on ISO 19157

With recent advances in remote sensing, location-based services and other related technologies, the production of geospatial information has exponentially increased in the last decades. Furthermore, to facilitate discovery and efficient access to such information, spatial data infrastructures were promoted and standardized, with a consideration that metadata are essential to describing data and services. Standardization bodies such as the International Organization for Standardization have defined well-known metadata models such as ISO 19115. However, current metadata assets exhibit heterogeneous quality levels because they are created by different producers with different perspectives. To address quality-related concerns, several initiatives attempted to define a common framework and test the suitability of metadata through automatic controls. Nevertheless, these controls are focused on interoperability by testing the format of metadata and a set of controlled elements. In this paper, we propose a methodology of testing the quality of metadata by considering aspects other than interoperability. The proposal adapts ISO 19157 to the metadata case and has been applied to a corpus of the Spanish Spatial Data Infrastructure. The results demonstrate that our quality check helps determine different types of errors for all metadata elements and can be almost completely automated to enhance the significance of metadata