University of Oviedo

About: University of Oviedo is a education organization based out in Oviedo, Spain. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 13423 authors who have published 31649 publications receiving 844799 citations. The organization is also known as: Universidá d'Uviéu & Universidad de Oviedo.

A continental scale evaluation of the role of limpet grazing on rocky shores

Abstract: It is critical for our knowledge of biodiversity and ecosystem processes to understand how individual species contribute to ecosystem processes and how these contributions vary in space and time. We used a manipulative field experiment in five locations over 17° of latitude [from southern Portugal to the Isle of Man (British Isles)] to determine the relative response of rocky intertidal algal assemblages released from control by the grazing of limpets. Response ratios showed that when limpets were removed there was a trend of effects from north to south. In the north, grazing had a strong effect on algal assemblages, but removing grazers reduced spatial variability in assemblages. In the south, the effect of limpet grazing was far weaker and removal of grazers had a much reduced impact on spatial variability. Here we show a clear trophic control of an ecosystem in that grazing by limpets not only determines macroalgal abundance overall but also modifies ecosystem stability via variability in cover of algae.

Antioxidant properties of the melatonin metabolite N1-acetyl-5-methoxykynuramine (AMK): scavenging of free radicals and prevention of protein destruction

Abstract: In numerous experimental systems, the neurohormone melatonin has been shown to protect against oxidative stress, an effect which appears to be the result of a combination of different actions. In this study, we have investigated the possible contribution to radical scavenging by substituted kynuramines formed from melatonin via pyrrole ring cleavage. N1-Acetyl-5-methoxykynuramine (AMK), a metabolite deriving from melatonin by mechanisms involving free radicals, exhibits potent antioxidant properties exceeding those of its direct precursor N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) and its analog N1-acetylkynuramine (AK). Scavenging of hydroxyl radicals was demonstrated by competition with ABTS in a Fenton reaction system at pH 5 and by competition with DMSO in a hemin-catalyzed H2O2 system at pH 8. Under catalysis by hemin, oxidation of AMK was accompanied by the emission of chemiluminescence. AMK was a potent reductant of ABTS cation radicals, but, in the absence of catalysts, a poor scavenger of superoxide anions. In accordance with the latter observation, AMK was fairly stable in a pH 8 H2O2 system devoid of hemin. Contrary to AFMK, AMK was easily oxidized in a reaction mixture generating carbonate radicals. In an oxidative protein destruction assay based on peroxyl radical formation, AMK proved to be highly protective. No prooxidant properties of AMK were detected in a sensitive biological test system based on light emission by the bioluminescent dinoflagellate Lingulodinium polyedrum. AMK may contribute to the antioxidant properties of the indolic precursor melatonin.

Antecedents of the difference in perceived risk between store brands and national brands

Abstract: Purpose – The present study sets out to analyze the effects that a set of variables related to purchasing behaviour has on the difference in perceived risk between store brands and national brands.Design/methodology/approach – The methodology proposed to achieve the objective consists of analyzing the existing relationship between different aspects relating to purchasing behaviour of the consumer and the difference in perceived risk between the two types of brands through a causal and integrated model. Such a model covers both the direct effects and the indirect effects caused by these variables jointly. In order to do so data were obtained from two groups of people, which has allowed for cross‐validation of the methodology used, which, in turn, permitted a greater generalization of the results.Findings – The variables which have proven to be most relevant when explaining this difference are the perceived quality of the store as opposed to that of the national brands, familiarity with the store brands and...

Discrete-Time Current Regulator Design for AC Machine Drives

Abstract: This paper analyzes the behavior of discrete-time current regulators for ac machines operating at high ratios of fundamental-to-sampling frequencies, a situation common for high-speed automotive drives and large-traction drives. At high ratios of fundamental-to-sampling frequencies, highly oscillatory, or unstable, response can occur if the current regulator design does not properly incorporate the effects of the discrete nature of the controller, including delays between the sampling of signals and the application of the voltage commands through pulse-width modulation (PWM). This paper investigates these issues for different design methods and current regulator topologies. As part of this investigation, a simple discrete-time domain ac machine model is developed that includes the delays associated with PWM. This model is then used to design a discrete-time domain version of the complex vector PI current regulator that demonstrates improved response compared with the other regulators studied. Simulation and experimental results are provided to compare the performance, stability, and robustness of the current regulators analyzed.