University of Extremadura

About: University of Extremadura is a education organization based out in Badajoz, Spain. It is known for research contribution in the topics: Population & Hyperspectral imaging. The organization has 7856 authors who have published 18299 publications receiving 396126 citations. The organization is also known as: Universidad de Extremadura.

Semisupervised Self-Learning for Hyperspectral Image Classification

Abstract: Remotely sensed hyperspectral imaging allows for the detailed analysis of the surface of the Earth using advanced imaging instruments which can produce high-dimensional images with hundreds of spectral bands. Supervised hyperspectral image classification is a difficult task due to the unbalance between the high dimensionality of the data and the limited availability of labeled training samples in real analysis scenarios. While the collection of labeled samples is generally difficult, expensive, and time-consuming, unlabeled samples can be generated in a much easier way. This observation has fostered the idea of adopting semisupervised learning techniques in hyperspectral image classification. The main assumption of such techniques is that the new (unlabeled) training samples can be obtained from a (limited) set of available labeled samples without significant effort/cost. In this paper, we develop a new approach for semisupervised learning which adapts available active learning methods (in which a trained expert actively selects unlabeled samples) to a self-learning framework in which the machine learning algorithm itself selects the most useful and informative unlabeled samples for classification purposes. In this way, the labels of the selected pixels are estimated by the classifier itself, with the advantage that no extra cost is required for labeling the selected pixels using this machine-machine framework when compared with traditional machine-human active learning. The proposed approach is illustrated with two different classifiers: multinomial logistic regression and a probabilistic pixelwise support vector machine. Our experimental results with real hyperspectral images collected by the National Aeronautics and Space Administration Jet Propulsion Laboratory's Airborne Visible-Infrared Imaging Spectrometer and the Reflective Optics Spectrographic Imaging System indicate that the use of self-learning represents an effective and promising strategy in the context of hyperspectral image classification.

Critical behavior of the three-dimensional Ising spin glass

Abstract: We have simulated, using parallel tempering, the three-dimensional Ising spin glass model with binary couplings in a helicoidal geometry. The largest lattice (L520) has been studied using a dedicated computer (the SUE machine). We have obtained, measuring the correlation length in the critical region, strong evidence for a second-order finite-temperature phase transition, ruling out other possible scenarios like a KosterlitzThouless phase transition. Precise values for the ν and ƞ critical exponents are also presented.

Associations of Yeasts with Spotted-Wing Drosophila (Drosophila suzukii; Diptera: Drosophilidae) in Cherries and Raspberries

Abstract: A rich history of investigation documents various Drosophila-yeast mutualisms, suggesting that Drosophila suzukii similarly has an association with a specific yeast species or community. To discover candidate yeast species, yeasts were isolated from larval frass, adult midguts, and fruit hosts of D. suzukii. Terminal restriction fragment length polymorphism (TRFLP) technology and decimal dilution plating were used to identify and determine the relative abundance of yeast species present in fruit juice samples that were either infested with D. suzukii or not infested. Yeasts were less abundant in uninfested than infested samples. A total of 126 independent yeast isolates were cultivated from frass, midguts, and fruit hosts of D. suzukii, representing 28 species of yeasts, with Hanseniaspora uvarum predominating. This suggests an association between D. suzukii and H. uvarum that could be utilized for pest management of the highly pestiferous D. suzukii.

Detection of "apoptosis-like" changes during the cryopreservation process in equine sperm.

Abstract: The kinematics of the appearance of apoptotic markers was studied by flow cytometry and immunoblot assays in equine spermatozoa subjected to freezing and thawing. Caspase activity, low mitochondrial membrane potential, and increases in sperm membrane permeability were observed in all of the phases of the cryopreservation procedure. Freezing and thawing caused an increase in membrane permeability and changes in the pattern of caspase activity; decreases in mitochondrial membrane potential were observed after centrifugation and cooling to 4 degrees C and after freezing and thawing. It is proposed that sperm mitochondria may be directly involved in the subtle damage that is present in most spermatozoa surviving freezing and thawing.

Pharmacokinetics of losartan and its metabolite E-3174 in relation to the CYP2C9 genotype.

Abstract: Background And Aim Losartan is metabolized by polymorphic CYP2C9 to E-3174. Our aim was to evaluate the pharmacokinetics of losartan and E-3174 in relation to the CYP2C9 genotype. Methods A 50-mg oral dose of losartan was given to 22 Swedish volunteers with different CYP2C9 genotypes. Losartan and E-3174 were analyzed by HPLC in plasma and urine samples collected up to 24 hours after drug intake. Furthermore, losartan and E-3174 were analyzed in 8-hour urine samples collected from 17 Spanish subjects after a single oral dose of 25 mg losartan. Results The maximum plasma concentration of E-3174 was significantly (P < .05) lower in the CYP2C9*1/*3 (n = 5) and CYP2C9*2/*3 (n = 4) groups compared with the CYP2C9*1/*1 (n = 6) and CYP2C9*1/*2 (n = 3) groups and extremely low in 1 subject with the CYP2C9*3/*3 genotype. The ratio of the total losartan area under the plasma concentration–time curve (AUC) to the total E-3174 AUC (AUClosartan/AUCE-3174) was higher in the subject with the CYP2C9*3/*3 genotype (30-fold) and also in the CYP2C9*1/*3 and *2/*3 groups (approximately 2- and 3-fold, respectively) compared with the CYP2C9*1/*1 group. The plasma ratios correlated significantly with the 0- to 8-hour urinary losartan/E-3174 ratios. Among the total of 39 subjects, the urinary ratio was significantly higher in subjects with the CYP2C9*1/*3 (n = 10) and *2/*3 (n = 4) genotypes than in those with the CYP2C9*1/*1 genotype (n = 11; P < .01) and approximately 40-fold higher in subjects with the CYP2C9*3/*3 genotype (n = 3). Conclusion The CYP2C9*3 allele was shown to be associated with decreased formation of E-3174 from losartan. The significant differences between genotypes in plasma and urine losartan/E-3174 ratios and the good correlation between the plasma and urine ratios suggest that the losartan/E-3174 ratio in 0- to 8-hour urine specimens may serve as a phenotyping assay for CYP2C9 activity. Further studies in larger populations will be required to establish this. Clinical Pharmacology & Therapeutics (2002) 71, 89–98; doi: 10.1067/mcp.2002.121216