General solution of certain matrix equations arising in filter design applications

In this work we present the explicit expression of all rectangular Toeplitz matrices B,C which verify the equation BBH +CCH = aI for some a > 0. This matrix equation arises in some signal processing problems. For instance, it appears when designing the even and odd components of paraunitary filters, which are widely used for signal compression and denoising purposes. We also point out the relationship between the above matrix equation and the polynomial B´ezout equation |B(z)|2 +|C(z)|2 = a > 0 for |z| = 1. By exploiting this fact, our results also yield a constructive method for the parameterization of all solutions B(z),C(z). The main advantage of our approach is that B are C are built without need of spectral factorization. Besides these theoretical advances, in order to illustrate the effectiveness of our approach, some examples of paraunitary filters design are finally given

TeV Gamma-ray Astronomy: A Summary

The field of TeV gamma-ray astronomy has produced many exciting results over the last decade. Both the source catalogue, and the range of astrophysical questions which can be addressed, continue to expand. This article presents a topical review of the field, with a focus on the observational results of the imaging atmospheric Cherenkov telescope arrays. The results encompass pulsars and their nebulae, supernova remnants, gamma-ray binary systems, star forming regions and starburst and active galaxies.Comment: 19 pages. Astroparticle Physics, in press. See published article for higher resolution figures. Cite as: J. Holder, TeV gamma-ray astronomy: A summary, Astropart. Phys. (2012), http://dx.doi.org/10.1016/j.astropartphys.2012.02.01

Emotional context enhances auditory novelty processing: behavioural and electrophysiological evidence

Abstract Viewing emotionally negative pictures has been proposed to attenuate brain responses towards sudden auditory events, as more attentional resources are allocated to the affective visual stimuli. However, peripheral reflexes have been shown intensified. These observations have raised the question of whether an emotional context actually facilitates or attenuates processing in the auditory novelty system. Using scalp event-related potentials we measured brain responses induced by novel sounds when participants responded to visual stimuli displaying either threatening or neutral sceneries. We then tested the modulatory effect of the emotional task conditions on auditory responses. Novel sounds yielded a stronger behavioural disruption on subjects' visual task performance when responding to negative pictures compared with when responding to the neutral ones. Accordingly, very early novelty-P3 responses to novel sounds were enhanced in negative context. These results provide strong evidence that the emotional context enhances the activation of neural networks in the auditory novelty system, gating acoustic novelty processing under potentially threatening conditions

Implications of chloride-enhanced cadmium uptake in saline agriculture: modeling cadmium uptake by maize and tobacco

Chloride salinity has been strongly related to enhanced cadmium (Cd) uptake by plants due to increased solubility in the soil solution, even in agricultural soil with very low levels of cadmium. This finding is relevant because the cadmium content of food crops is an important concern for human health. Therefore, the aim of this study was to predict and discuss the chlorine-enhanced uptake of cadmium by two common crops: maize and tobacco under “non-saline” (1 mM) and “very strongly saline” (200 mM) scenarios using a modified ‘biotic ligand model’ and datasets from a set of soil and hydroponic experiments. Results indicated that predicted cadmium uptake rates (expressed as cadmium in plant μmol m-2 root) by maize and tobacco plants were consistently higher (54 and 15%, respectively) assuming conditions of ‘very strong salinity’ soil compared to the simulated ‘non-saline’ soil. In the light of the results of the present research, valuable information is given on modeled cadmium phytoavailability as an indication of the potential risk due to increased cadmium uptake by crops under saline conditions, especially as the enhancement of cadmium uptake in the presence of Cl- salinity may be a general trend that occurs in many edible crops. The biotic ligand model parameterization applied in the present study attempted to simulate conditions commonly found in natural cadmium and salt-affected soils. However, caution is needed to extrapolate results obtained from these models to real soil conditions

Authoring and Verification of Clinical Guidelines: a Model Driven Approach

ObjectivesThe goal of this research is to provide a framework to enable authoring and verification of clinical guidelines. The framework is part of a larger research project aimed at improving the representation, quality and application of clinical guidelines in daily clinical practice. MethodsThe verification process of a guideline is based on (1) model checking techniques to verify guidelines against semantic errors and inconsistencies in their definition, (2) combined with Model Driven Development (MDD) techniques, which enable us to automatically process manually created guideline specifications and temporal-logic statements to be checked and verified regarding these specifications, making the verification process faster and cost-effective. Particularly, we use UML statecharts to represent the dynamics of guidelines and, based on this manually defined guideline specifications, we use a MDD-based tool chain to automatically process them to generate the input model of a model checker. The model checker takes the resulted model together with the specific guideline requirements, and verifies whether the guideline fulfils such properties. ResultsThe overall framework has been implemented as an Eclipse plug-in named GBDSSGenerator which, particularly, starting from the UML statechart representing a guideline, allows the verification of the guideline against specific requirements. Additionally, we have established a pattern-based approach for defining commonly occurring types of requirements in guidelines. We have successfully validated our overall approach by verifying properties in different clinical guidelines resulting in the detection of some inconsistencies in their definition. ConclusionsThe proposed framework allows (1) the authoring and (2) the verification of clinical guidelines against specific requirements defined based on a set of property specification patterns, enabling non-experts to easily write formal specifications and thus easing the verification process. © 2010 Elsevier Inc