Image encryption system based on a nonlinear joint transform correlator for the simultaneous authentication of two users

We propose a new encryption system based on a nonlinear joint transform correlator (JTC) using the information of two biometrics (one digital fingerprint for each user) as security keys of the encryption system. In order to perform the decryption and authentication in a proper way, it is necessary to have the two digital fingerprints from the respective users whose simultaneous authentication is pursued. The proposed security system is developed in the Fourier domain. The nonlinearity of the JTC along with the five security keys given by the three random phase masks and the two digital fingerprints of the two users allow an increase of the system security against brute force and plaintext attacks. The feasibility and validity of this proposal is demonstrated using digital fingerprints as biometrics in numerical experiments.Peer ReviewedPostprint (published version

Effects of using an encrypted image corrupted by noise and occlusion in a security system based on joint transform correlator and Gyrator transform

Postprint (published version

Image quality and security through nonlinear joint transform encryption

Postprint (published version

Determination of Soluble Sugars in Arabidopsis thaliana Leaves by Anion Exchange Chromatography

Determination of soluble sugars is basic for the study of carbon metabolism in plants. Soluble sugar quantitation can be achieved by enzymatic methods implying different coupled reactions. Here we describe a simple method that allows rapid determination of the most abundant soluble sugars (glucose, fructose and sucrose) in Arabidopsis leaves by anion exchange chromatography. We have applied this method to study the levels of soluble sugars during the photoperiodic transition to flowering (Ortiz-Marchena et al., 2014).España, MINECO projects CSD2007-00057, BIO2008-02292, and BIO2011-28847-C02-00España, Junta de Andalucía P06-CVI-01450 and P08-AGR-0358

Machine learning techniques to select Be star candidates. An application in the OGLE-IV Gaia south ecliptic pole field

Statistical pattern recognition methods have provided competitive solutions for variable star classification at a relatively low computational cost. In order to perform supervised classification, a set of features is proposed and used to train an automatic classification system. Quantities related to the magnitude density of the light curves and their Fourier coefficients have been chosen as features in previous studies. However, some of these features are not robust to the presence of outliers and the calculation of Fourier coefficients is computationally expensive for large data sets. We propose and evaluate the performance of a new robust set of features using supervised classifiers in order to look for new Be star candidates in the OGLE-IV Gaia south ecliptic pole field. We calculated the proposed set of features on six types of variable stars and on a set of Be star candidates reported in the literature. We evaluated the performance of these features using classification trees and random forests along with K-nearest neighbours, support vector machines, and gradient boosted trees methods. We tuned the classifiers with a 10-fold cross-validation and grid search. We validated the performance of the best classifier on a set of OGLE-IV light curves and applied this to find new Be star candidates. The random forest classifier outperformed the others. By using the random forest classifier and colour criteria we found 50 Be star candidates in the direction of the Gaia south ecliptic pole field, four of which have infrared colours consistent with Herbig Ae/Be stars. Supervised methods are very useful in order to obtain preliminary samples of variable stars extracted from large databases. As usual, the stars classified as Be stars candidates must be checked for the colours and spectroscopic characteristics expected for them

Purification of Starch Granules from Arabidopsis Leaves and Determination of Granule-Bound Starch Synthase Activity

Starch constitutes the most important carbon reserve in plants and is composed of branched amylopectin and linear amylose. The latter is synthesized exclusively by the Granule-Bound Starch Synthase (GBSS, EC 2.4.1.21). Here we report a readily reproducible, specific and highly sensitive protocol, which includes the isolation of intact starch granules from Arabidopsis thaliana leaves and the subsequent determination of GBSS activity. We have applied this method to study GBSS activity in diurnal cycles in vegetative growth and during the photoperiodic transition to flowering in Arabidopsis (Tenorio et al., 2003; Ortiz-Marchena et al., 2014).España,MINECO CSD2007-00057, BIO2008-02292, and BIO2011-28847-C02-00España, Junta de Andalucía P06-CVI-01450 and P08-AGR-0358

Geometric detection of hierarchical backbones in real networks

Hierarchies permeate the structure of real networks, whose nodes can be ranked according to different features. However, networks are far from tree-like structures and the detection of hierarchical ordering remains a challenge, hindered by the small-world property and the presence of a large number of cycles, in particular clustering. Here, we use geometric representations of undirected networks to achieve an enriched interpretation of hierarchy that integrates features defining popularity of nodes and similarity between them, such that the more similar a node is to a less popular neighbor the higher the hierarchical load of the relationship. The geometric approach allows us to measure the local contribution of nodes and links to the hierarchy within a unified framework. Additionally, we propose a link filtering method, the similarity filter, able to extract hierarchical backbones containing the links that represent statistically significant deviations with respect to the maximum entropy null model for geometric heterogeneous networks. We applied our geometric approach to the detection of similarity backbones of real networks in different domains and found that the backbones preserve local topological features at all scales. Interestingly, we also found that similarity backbones favor cooperation in evolutionary dynamics modelling social dilemmas.Comment: 13 pages, 5 figures. Supplementary material available as appendi

Los ajustes deprimen el empleo. Análisis de coyuntura del mercado de trabajo en el segundo trimestre de 2012

La economía española ha entrado en recesión en el segundo trimestre de 2012, por segunda vez desde que estalló la crisis económica. La intensa caída de la actividad económica provoca una nueva oleada de destrucción de empleo. Como consecuencia, se ha alcanzado la tasa de paro más alta en un trimestre en la serie histórica de la EPA que ofrece el INE. En el artículo presente se analizan la evolución de las principales variables laborales en el mercado de trabajo español y de Andalucía. Se presta especial atención a la formación de la mano de obra y a la evolución de los diferentes grupos de trabajadores cualificados de acuerdo con la evolución del ciclo económico en el periodo 2008-2012.In the second quarter of 2012, Spanish economy has come into a new recession period for the second time since the beginning of the economic crisis. The big decrease of economic activity is the cause of a new wave of employment destruction. As a result, the highest rate of unemployment in modern Spanish economic history has been reached, according to the data provided by the National Institute of Statistics. In this paper, we analyse the evolution of the main labour indicators in the Spanish and Andalusian Labour Markets. We pay special attention to the impact of economic crisis on different groups of workers according to their educational levels in the period 2008-2012

Instalados en la recesión económica. Análisis de coyuntura del mercado de trabajo en el segundo semestre de 2012

A lo largo de 2012, España experimenta una profundización en la recesión económica que está sufriendo. Durante los cuatro trimestres de este año, no se han visto cifras positivas de crecimiento, sino una caída constante. La misma tendencia se observa en el resto de economías europeas, que en la última parte del año están adentrándose, o van camino de caer, de nuevo en la recesión. Como consecuencia de esta evolución, el deterioro del mercado de trabajo español sigue aumentando. Cae la ocupación y aumenta el desempleo hasta casi seis millones de personas, alcanzándose la tasa de paro más elevada de los registros de la EPA (26,02%). En el presente trabajo se presenta una panorámica sobre la evolución de la economía y el mercado de trabajo en España en el segundo semestre de 2012. El artículo también recoge un epígrafe dedicado al análisis de la evolución de las variables económicas y laborales más relevantes en Andalucía