Showing papers by "University of Extremadura published in 2010"

Development of the EQ-5D-Y: a child-friendly version of the EQ-5D

Abstract: Purpose To develop a self-report version of the EQ-5D for younger respondents, named the EQ-5D-Y (Youth); to test its comprehensibility for children and adolescents and to compare results obtained using the standard adult EQ-5D and the EQ-5D-Y.

Semisupervised Hyperspectral Image Segmentation Using Multinomial Logistic Regression With Active Learning

Abstract: This paper presents a new semisupervised segmentation algorithm, suited to high-dimensional data, of which remotely sensed hyperspectral image data sets are an example. The algorithm implements two main steps: 1) semisupervised learning of the posterior class distributions followed by 2) segmentation, which infers an image of class labels from a posterior distribution built on the learned class distributions and on a Markov random field. The posterior class distributions are modeled using multinomial logistic regression, where the regressors are learned using both labeled and, through a graph-based technique, unlabeled samples. Such unlabeled samples are actively selected based on the entropy of the corresponding class label. The prior on the image of labels is a multilevel logistic model, which enforces segmentation results in which neighboring labels belong to the same class. The maximum a posteriori segmentation is computed by the α-expansion min-cut-based integer optimization algorithm. Our experimental results, conducted using synthetic and real hyperspectral image data sets collected by the Airborne Visible/Infrared Imaging Spectrometer system of the National Aeronautics and Space Administration Jet Propulsion Laboratory over the regions of Indian Pines, IN, and Salinas Valley, CA, reveal that the proposed approach can provide classification accuracies that are similar or higher than those achieved by other supervised methods for the considered scenes. Our results also indicate that the use of a spatial prior can greatly improve the final results with respect to a case in which only the learned class densities are considered, confirming the importance of jointly considering spatial and spectral information in hyperspectral image segmentation.

Feasibility, reliability, and validity of the EQ-5D-Y: Results from a multinational study

Abstract: Purpose To examine the feasibility, reliability, and validity of the newly developed EQ-5D-Y.

Delineation of management zones using mobile measurements of soil apparent electrical conductivity and multivariate geostatistical techniques

Abstract: Site-specific management promotes the identification and management of areas within the field, which represent subfield regions with homogeneous characteristics (management zones). However, determination of subfield areas is difficult because of the complex combination of factors which could affect crop yield. One possibility to capture yield variability is the use of soil physical properties to define the management zones as they are related to plant available water. With the aim of characterizing the spatial variability of the main soil physical variables and using this information to determine potential management zones, soil samples were taken from 70 locations in a 33-ha field in Badajoz, southwestern Spain. Firstly, accurate spatial distribution maps of the soil attributes were generated by using regression kriging as the most suitable algorithm in which exhaustive secondary information on soil apparent electrical conductivity (ECa) was incorporated. ECa measurements were carried out with a Veris 3100 operating in both shallow (0–30 cm), ECs, and deep (0–90 cm), ECd, mode. Clay, coarse sand and fine sand were the soil physical properties which exhibited higher correlation with ECa (positively correlated with the finer texture component, clay, and negatively correlated with the coarser ones, coarse and fine sands), particularly with ECs. Thus, this was the secondary variable used to obtain the kriged maps. Later, principal component analysis and fuzzy cluster classification were performed to delineate management zones, resulting in two subfields to be managed separately. This number of subfields was determined using the fuzzy performance index and normalized classification entropy as the way to optimize the classification algorithm.

Mitochondrial DNA Mutations Induce Mitochondrial Dysfunction, Apoptosis and Sarcopenia in Skeletal Muscle of Mitochondrial DNA Mutator Mice

Abstract: Background: Aging results in a progressive loss of skeletal muscle, a condition known as sarcopenia. Mitochondrial DNA (mtDNA) mutations accumulate with aging in skeletal muscle and correlate with muscle loss, although no causal relationship has been established. Methodology/Principal Findings: We investigated the relationship between mtDNA mutations and sarcopenia at the gene expression and biochemical levels using a mouse model that expresses a proofreading-deficient version (D257A) of the mitochondrial DNA Polymerase c, resulting in increased spontaneous mtDNA mutation rates. Gene expression profiling of D257A mice followed by Parametric Analysis of Gene Set Enrichment (PAGE) indicates that the D257A mutation is associated with a profound downregulation of gene sets associated with mitochondrial function. At the biochemical level, sarcopenia in D257A mice is associated with a marked reduction (35–50%) in the content of electron transport chain (ETC) complexes I, III and IV, all of which are partly encoded by mtDNA. D257A mice display impaired mitochondrial bioenergetics associated with compromised state-3 respiration, lower ATP content and a resulting decrease in mitochondrial membrane potential (Dym). Surprisingly, mitochondrial dysfunction was not accompanied by an increase in mitochondrial reactive oxygen species (ROS) production or oxidative damage. Conclusions/Significance: These findings demonstrate that mutations in mtDNA can be causal in sarcopenia by affecting the assembly of functional ETC complexes, the lack of which provokes a decrease in oxidative phosphorylation, without an increase in oxidative stress, and ultimately, skeletal muscle apoptosis and sarcopenia.

Preparation and characterization of magnetic TiO2 nanoparticles and their utilization for the degradation of emerging pollutants in water

Abstract: Magnetic TiO 2 /Fe 3 O 4 and TiO 2 /SiO 2 /Fe 3 O 4 nanoparticles (NPs) were prepared by an ultrasonic-assisted sol–gel method using a commercial nanosized magnetic iron oxide as a support. Magnetic NPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption (BET surface area) and SQUID magnetometer. Structure analyses indicated that TiO 2 /Fe 3 O 4 NPs presented a core–shell structure with a TiO 2 (anatase) coating wrapped around the magnetic iron oxide surface. TiO 2 /SiO 2 /Fe 3 O 4 NPs showed a ternary structure with a core of Fe 3 O 4 , a SiO 2 mesosphere and a TiO 2 (anatase) crust. Both types of NPs exhibited magnetic properties with saturation magnetization about 40 emu/g and low remanent magnetization and coercivity. Stability of TiO 2 /SiO 2 /Fe 3 O 4 NPs in an aqueous solution under UV illumination was better than that of TiO 2 /Fe 3 O 4 NPs as the presence of the insulation SiO 2 layer prevented photodissolution of iron. Both catalysts showed the ability to catalyze the photodegradation of acetaminophen and other four pharmaceutical and personal care products (PPCPs) (antipyrine, caffeine, metoprolol and bisphenol A) from an aqueous solution. In terms of catalytic activity the synthesized magnetic NPs were almost comparable to the commercial Degussa P25 TiO 2 photocatalyst. In addition, the easily recoverable magnetic photocatalysts showed good reusability, especially in the case of TiO 2 /SiO 2 /Fe 3 O 4 NPs.

Using Self-Determination Theory to Explain Sport Persistence and Dropout in Adolescent Athletes

Abstract: Motivational characteristics are influential in shaping adolescents' desire to persist in sport or to discontinue their sport participation. Self-determination theory (Deci & Ryan, 2000) was utilized as the theoretical framework for this study. This theory examines whether sustained participatory involvement, defined as continued participation in the sport through the next year, was influenced by individuals' self-determined motivation and by the fulfillment of the three basic psychological needs of autonomy, competence, and relatedness. Four hundred ninety two soccer players between the ages of 13 and 17 years comprised the sample. Results indicated sport dropout was explained by higher levels of amotivation, external regulation, and introjected regulation and by lower satisfaction of relatedness and autonomy needs. The findings of this study contribute to the knowledge base on sport dropout as they supported many of self-determination theory.

Application of blocking diagnosis methods to General Circulation Models. Part I: a novel detection scheme

Abstract: This paper aims to provide a new blocking definition with applicability to observations and model simulations. An updated review of previous blocking detection indices is provided and some of their implications and caveats discussed. A novel blocking index is proposed by reconciling two traditional approaches based on anomaly and absolute flows. Blocks are considered from a complementary perspective as a signature in the anomalous height field capable of reversing the meridional jet-based height gradient in the total flow. The method succeeds in identifying 2-D persistent anomalies associated to a weather regime in the total flow with blockage of the westerlies. The new index accounts for the duration, intensity, extension, propagation, and spatial structure of a blocking event. In spite of its increased complexity, the detection efficiency of the method is improved without hampering the computational time. Furthermore, some misleading identification problems and artificial assumptions resulting from previous single blocking indices are avoided with the new approach. The characteristics of blocking for 40 years of reanalysis (1950–1989) over the Northern Hemisphere are described from the perspective of the new definition and compared to those resulting from two standard blocking indices and different critical thresholds. As compared to single approaches, the novel index shows a better agreement with reported proxies of blocking activity, namely climatological regions of simultaneous wave amplification and maximum band-pass filtered height standard deviation. An additional asset of the method is its adaptability to different data sets. As critical thresholds are specific of the data set employed, the method is useful for observations and model simulations of different resolutions, temporal lengths and time variant basic states, optimizing its value as a tool for model validation. Special attention has been paid on the devise of an objective scheme easily applicable to General Circulation Models where observational thresholds may be unsuitable due to the presence of model bias. Part II of this study deals with a specific implementation of this novel method to simulations of the ECHO-G global climate model.

Profile or group discriminative techniques? Generating reliable species distribution models using pseudo‐absences and target‐group absences from natural history collections

Abstract: Aim The presence-only data stored in natural history collections is the most important source of information available regarding the distribution of organisms These data and profile techniques can be used to generate species distribution models (SDMs), but pseudo-absences must be generated to use group discriminative techniques In this study, we evaluated whether the SDMs generated with pseudo-absences are reliable and also if there are differences in the results obtained with profile and group discriminative techniques Location Ecuador, South America Methods The SDMs were generated with a training data set for each of the five species of Anthurium and six different methods: two profile techniques (BIOCLIM and Gower’s distance index), three group discriminative techniques [logistic multiple regression (LMR), multivariate adaptative regression splines (MARS) and Maxent] and a mixed modelling approach genetic algorithm for rule-set production (GARP), which employs a combination of profile and group discriminative techniques and generates its own pseudo-absences For LMR, MARS and Maxent, three types of absences were generated: (1) random pseudo-absences in equal number to presences and excluding a buffer area around presences (except for Maxent, which assumes that this background sample includes presences), (2) a large number (10,000) of random pseudo-absences, also excluding a buffer area around each presence and (3) ‘target-group absences’ (TGA), consisting of sites where other species of the group have been collected by the specialist, but not the species being modelled To compare the predictive performance of the SDMs, the area under the curve statistic was calculated using an independent testing data set for each species Results MARS, Maxent and LMR produce better results than the profile techniques The models created with TGA are generally more accurate than those generated with pseudo-absences Main conclusions The advantages and disadvantages of different options for using pseudo-absences and TGA with profile and group discriminative modelling techniques are explained and recommendations are made for the future

Comparison of different geostatistical approaches to map climate variables: application to precipitation

Abstract: The benefits of an integrated geographical information system (GIS) and a geostatistics approach to accurately model the spatial distribution pattern of precipitation are known. However, the determination of the most appropriate geostatistical algorithm for each case is usually neglected, i.e. it is important to select the best interpolation technique for each study area to obtain accurate results. In this work, the ordinary kriging (OK), simple kriging (SK) and universal kriging (universal kriging) methods are compared with three multivariate algorithms which take into account the altitude: collocated ordinary cokriging (OCK), simple kriging with varying local means (SKV) and regression-kriging (RK). The different techniques are applied to monthly and annual precipitation data measured at 136 meteorological stations in a region of southwestern Spain (Extremadura). After carrying out cross-validation, the smallest prediction errors are obtained for the three multivariate algorithms but, particularly, SKV and RK outperform collocated OCK, which needs a more demanding variogram analysis. These algorithms are easily implemented in a GIS, requiring the residual estimates and map algebra capability to generate the final maps. Results evidence the necessity of accounting for spatially dependent precipitation data and the collocated altitude, to accurately define monthly and annual precipitation maps. Copyright © 2009 Royal Meteorological Society

Multivariate plug-in bandwidth selection with unconstrained pilot bandwidth matrices

Abstract: Multivariate kernel density estimation is an important technique in exploratory data analysis. Its utility relies on its ease of interpretation, especially by graphical means. The crucial factor which determines the performance of kernel density estimation is the bandwidth matrix selection. Research in finding optimal bandwidth matrices began with restricted parameterizations of the bandwidth matrix which mimic univariate selectors. Progressively these restrictions were relaxed to develop more flexible selectors. In this paper, we propose the first plug-in bandwidth selector with the unconstrained parameterizations of both the final and pilot selectors. Up till now, the development of unconstrained pilot selectors was hindered by the traditional vectorization of higher-order derivatives which lead to increasingly intractable matrix algebraic expressions. We resolve this by introducing an alternative vectorization which gives elegant and tractable expressions. This allows us to quantify the asymptotic and finite sample properties of unconstrained pilot selectors. For target densities with intricate structure (such as multimodality), our unconstrained selectors show the most improvement over the existing plug-in selectors.

Rich Internet Applications

Abstract: Modern Web solutions resemble desktop applications, enabling sophisticated user interactions, client-side processing, asynchronous communications, and multimedia. A pure HTTP/HTML architecture fails to support these required capabilities in several respects. The "network as platform computing" idea, strengthened by Web 2.0's emergence, has accentuated HTML/HTTP's limits. This is the reason why many developers are switching to novel technologies, known under the collective name of rich Internet applications (RIAs). RIAs combine the Web's lightweight distribution architecture with desktop applications' interface interactivity and computation power, and the resulting combination improves all the elements of a Web application (data, business logic, communication, and presentation). This special issue briefly introduces the main characteristics and benefits of RIAs and highlights the research challenges in their development. The issue features two articles that address some of these open problems. One focuses on language and architecture issues, whereas the other deals with the methodological principles at the base of a model-driven approach to RIA development. Despite these efforts, the research community must continue investigating to propose novel methods and tools to make their development more systematic and efficient.

Degradation of ozone-refractory organic phosphates in wastewater by ozone and ozone/hydrogen peroxide (peroxone): the role of ozone consumption by dissolved organic matter.

Abstract: Ozonation is very effective in eliminating micropollutants that react fast with ozone (k > 103 M−1 s−1), but there are also ozone-refractory (k < 10 M−1 s−1) micropollutants such as X-ray contrast media, organic phosphates, and others Yet, they are degraded upon ozonation to some extent, and this is due to •OH radicals generated in the reaction of ozone with organic matter in wastewater (DOM, determined as DOC) The elimination of tri-n-butyl phosphate (TnBP) and tris-2-chloroisopropyl phosphate (TCPP), added to wastewater in trace amounts, was studied as a function of the ozone dose and found to follow first-order kinetics TnBP and TCPP concentrations are halved at ozone to DOC ratios of ∼025 and ∼10, respectively The •OH rate constant of TCPP was estimated at (7 ± 2) × 108 M−1 s−1 by pulse radiolysis Addition of 1 mg H2O2/L for increasing the •OH yield had very little effect This is due to the low rate of reaction of H2O2 with ozone at wastewater conditions (pH 8) that competes unfavorably with t

Stress relaxation and creep on living cells with the atomic force microscope: a means to calculate elastic moduli and viscosities of cell components

Abstract: In this work we present a unified method to study the mechanical properties of cells using the atomic force microscope Stress relaxation and creep compliance measurements permitted us to determine, the relaxation times, the Young moduli and the viscosity of breast cancer cells (MCF-7) The results show that the mechanical behaviour of MCF-7 cells responds to a two-layered model of similar elasticity but differing viscosity Treatment of MCF-7 cells with an actin-depolymerising agent results in an overall decrease in both cell elasticity and viscosity, however to a different extent for each layer The layer that undergoes the smaller decrease (36-38%) is assigned to the cell membrane/cortex while the layer that experiences the larger decrease (70-80%) is attributed to the cell cytoplasm The combination of the method presented in this work, together with the approach based on stress relaxation microscopy (Moreno-Flores et al 2010 J Biomech 43 349-54), constitutes a unique AFM-based experimental framework to study cell mechanics This methodology can also be extended to study the mechanical properties of biomaterials in general

Phosphorylation of STIM1 at ERK1/2 target sites modulates store-operated calcium entry.

Abstract: Store-operated calcium entry (SOCE) is an important Ca2+ entry pathway that regulates many cell functions. Upon store depletion, STIM1, a transmembrane protein located in the endoplasmic reticulum (ER), aggregates and relocates close to the plasma membrane (PM) where it activates store-operated calcium channels (SOCs). Although STIM1 was early defined as a phosphoprotein, the contribution of the phosphorylation has been elusive. In the present work, STIM1 was found to be a target of extracellular-signal-regulated kinases 1 and 2 (ERK1/2) in vitro, and we have defined the ERK1/2-phosphorylated sites on the STIM1 sequence. Using HEK293 cells stably transfected for the expression of tagged STIM1, we found that alanine substitution mutants of ERK1/2 target sites reduced SOCE significantly, suggesting that phosphorylation of these residues are required to fully accomplish SOCE. Indeed, the ERK1/2 inhibitors PD184352 and PD0325901 decreased SOCE in transfected cells. Conversely, 12-O-tetradecanoylphorbol-13-acetate, which activates ERK1/2, enhanced SOCE in cells expressing wild-type tagged STIM1, but did not potentiate Ca2+ influx in cells expressing serine to alanine mutations in ERK1/2 target sites of STIM1. Alanine substitution mutations decreased Ca2+ influx without disturbing the aggregation of STIM1 upon store depletion and without affecting the relocalization in ER-PM punctae. However, our results suggest that STIM1 phosphorylation at ERK1/2 target sites can modulate SOCE by altering STIM1 binding to SOCs, because a significant decrease in FRET efficiency was observed between alanine substitution mutants of STIM1-GFP and ORAI1-CFP.