Solving identity delegation problem in the e-government environment

At present, many countries allow citizens or entities to interact with the government outside the telematic environment through a legal representative who is granted powers of representation. However, if the interaction takes place through the Internet, only primitive mechanisms of representation are available, and these are mainly based on non-dynamic offline processes that do not enable quick and easy identity delegation. This paper proposes a system of dynamic delegation of identity between two generic entities that can solve the problem of delegated access to the telematic services provided by public authorities. The solution herein is based on the generation of a delegation token created from a proxy certificate that allows the delegating entity to delegate identity to another on the basis of a subset of its attributes as delegator, while also establishing in the delegation token itself restrictions on the services accessible to the delegated entity and the validity period of delegation. Further, the paper presents the mechanisms needed to either revoke a delegation token or to check whether a delegation token has been revoked. Implications for theory and practice and suggestions for future research are discussed.

Genetic characterization of chestnut (Castanea sativa Mill.) orchards and traditional nut varieties in El Bierzo, a glacial refuge and major cultivation site in Northwestern Spain

This paper presents a detailed genetic study of Castanea sativa in El Bierzo, a major nut production region with interesting features. It is located within a glacial refuge at one extreme of the distribution area (northwest Spain); it has a centenary tradition of chestnut management; and more importantly, it shows an unusual degree of genetic isolation. Seven nuclear microsatellite markers were selected to analyze the genetic variability and structure of 169 local trees grafted for nut production. We analyzed in the same manner 62 local nuts. The selected loci were highly discriminant for the genotypes studied, giving a combined probability of identity of 6.1 × 10−6. An unprecedented density of trees was sampled for this project over the entire region, and nuts were collected representing 18 cultivars marketed by local producers. Several instances of misclassification by local growers were detected. Fixation index estimates and analysis of molecular variance (AMOVA) data are supportive of an unexpectedly high level of genetic differentiation in El Bierzo, larger than that estimated in a previous study with broader geographical scope but based on limited local sampling (Pereira-Lorenzo et al., Tree Genet Genomes 6: 701–715, 2010a). Likewise, we have determined that clonality due to grafting had been previously overestimated. In line with these observations, no significant spatial structure was found using both a model-based Bayesian procedure and Mantel’s tests. Taken together, our results evidence the need for more fine-scale genetic studies if conservation strategies are to be efficiently improved.

Use of thermographic imaging to screen for drought-tolerant genotypes in Brachypodium distachyon

Thermal imaging has been used to evaluate the response to drought and warm temperatures in a collection of Brachypodium distachyon lines adapted to varied environmental conditions. Thermographic records were able to separate lines from contrasting rainfall regimes. Genotypes from dryer environments showed warmer leaves under water deficit, which suggested that decreased evapotranspiration was related to a more intense stomatal closure. When irrigated and under high temperature conditions, drought-adapted lines showed cooler leaves than lines from wetter zones. The consistent, inverse thermographic response of lines to water stress and heat validates the reliability of this method to assess drought tolerance in this model cereal. It additionally supports the hypothesis that stomatal-based mechanisms are involved in natural variation for drought tolerance in Brachypodium. The study further suggests that these mechanisms are not constitutive but likely related to a more efficient closing response to avoid dehydration in adapted genotypes. Higher leaf temperature under water deficit seems a dependable criterion of drought tolerance, not only in B. distachyon but also in the main cereal crops and related grasses where thermography can facilitate high-throughput preliminary screening of tolerant materials.