3,090 research outputs found

    Application of molecular nucleic acid-based techniques for the study of microbial communities in monuments and artworks

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    Microorganisms play critical roles in every kind of habitat on Earth, including those constructed by humans. Thus, our cultural heritage is affected by microbial colonization. While classical microbiological methods based on culturing procedures have provided important, but limited information on the microbial diversity of natural samples, novel molecular techniques have been extremely valuable in unraveling the diversity of microbiota involved in the biodeterioration of our monuments and artworks. The knowledge gained from these approaches has allowed the design of strategies for conserving and protecting monuments for the benefit of future generations. This review describes the state-of-the-art of the application of molecular methods to the analysis of cultural assets, and provides nearfuture perspectives on the subject. [Int Microbiol 2005; 8(3):189-194

    The Fusarium oxysporum f. sp. ciceris/Cicer arietinum pathosystem: a case study of the evolution of plantpathogenic fungi into races and pathotypes

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    The use of resistant cultivars is one of the most practical and costefficient strategies for managing plant diseases. However, the efficiency of resistant cultivars in disease management is limited by pathogenic variability in pathogen populations. Knowledge of the evolutionary history and potential of the pathogen population may help to optimize the management of disease-resistance genes, irrespective of the breeding strategy used for their development. In this review, we examine the diversity in virulence phenotypes of Fusarium oxysporum f. sp. ciceris, the causal agent of Fusarium wilt of chickpeas, analyze the genetic variability existing within and among those phenotypes, and infer a phylogenetic relationship among the eight known pathogenic races of this fungus. The inferred intraspecific phylogeny shows that each of those races forms a monophyletic lineage. Moreover, virulence of races to resistant chickpea cultivars has been acquired in a simple stepwise pattern, with few parallel gains or losses. Although chickpea cultivars resistant to Fusarium wilt are available, they have not yet been extensively deployed, so that the stepwise acquisition of virulence is still clearly evident. [Int Microbiol 2004; 7(2):95–104

    Coordinating heterogeneous IoT devices by means of the centralized vision of the SDN controller

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    The IoT (Internet of Things) has become a reality during recent years. The desire of having everything connected to the Internet results in clearly identified benefits that will impact on socio economic development. However, the exponential growth in the number of IoT devices and their heterogeneity open new challenges that must be carefully studied. Coordination among devices to adapt them to their users' context usually requires high volumes of data to be exchanged with the cloud. In order to reduce unnecessary communications and network overhead, this paper proposes a novel network architecture based on the Software-Defined Networking paradigm that allows IoT devices coordinate and adapt them within the scope of a particular context.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

    Adaptive Responses of \u3cem\u3eBrachiaria\u3c/em\u3e Grasses to Hypoxia Stress

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    It is likely that oxygen shortage in waterlogged soils is the most limiting factor for plant growth, restricting root aerobic respiration and ATP production (Vartapetian and Jackson 1997). When oxygen becomes limiting for oxidative phosphorylation, plant cells depend on alternative metabolic pathways to produce ATP (Rocha et al. 2010). The induction of fermentative metabolism is considered of adaptive value to maintain ATP production under oxygen-limited conditions. Ethanol is the main end product of fermentation metabolism in plants. Alcohol dehydrogenase (ADH) is a key enzyme in ethanolic fermentation. Roots can sustain aerobic respiration under oxygen deficiency if aerenchyma is present. Aerenchyma commonly refers to tissue containing air-filled spaces that provide oxygen un-der oxygen-limited conditions (Colmer and Voesenek 2009). The main objective of the present study was to determine morpho-physiological adaptive responses of seven Brachiaria genotypes to hypoxia stress

    Aprendizaje cooperativo en educación superior: diferencias en la percepción de la contribución al grupo

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    Aquest document analitza l'aprenentatge cooperatiu en un grup de treball en el qual s'utilitza metodologia de l'aprenentatge basat en problemes. A més, s'avalua si la percepció que cada component del grup té de la seva aportació a l'aprenentatge cooperatiu és major o menor que la percebuda pels seus companys. S'analitzen diferents aspectes de la feina feta dins el grup, com ara l'esforç efectiu realitzat, la participació, l'organització del grup, la cohesió, la comunicació i la percepció global de la implicació en la feina i l'aprenentatge cooperatiu. S'observa que els estudiants perceben que la seva aportació és major que la percebuda pels seus companys, encara que trobem lleugeres diferències segons els aspectes analitzats.This document analyses cooperative learning in a working group using a problem-based learning methodology. We also evaluate if the perception that each member of the group has of his/her contribution to cooperative learning is greater or lesser than that observed by his/her team-mates. Different elements of the work carried out in the group are analysed, such as the effective effort made, their participation, the organisation of the group, cohesion, communication, and the overall perception of their involvement in the cooperative learning and work. It is observed that the students perceive their contribution as greater than that perceived by their team-mates, although we find slight differences depending on the elements analysed. Este documento analiza el aprendizaje cooperativo en un grupo de trabajo en el que se utiliza metodología del aprendizaje basado en problemas. Además, se evalúa si la percepción que cada componente del grupo tiene de su aportación al aprendizaje cooperativo es mayor o menor que la percibida por sus compañeros. Se analizan diferentes aspectos del trabajo desarrollado dentro del grupo, como son el esfuerzo efectivo realizado, su participación, la organización del grupo, la cohesión, la comunicación y la percepción global de su implicación en el trabajo y el aprendizaje cooperativo. Se observa que los estudiantes perciben que su aportación es mayor que la percibida por sus compañeros, aunque encontramos ligeras diferencias en función de los aspectos analizados

    Ultradiscrete kinks with supersonic speed in a layered crystal with realistic potentials

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    We develop a dynamical model of the propagating nonlinear localized excitations, supersonic kinks, in the cation layer in a silicate mica crystal. We start from purely electrostatic Coulomb interaction and add the Ziegler-Biersack-Littmark short-range repulsive potential and the periodic potential produced by other atoms of the lattice. This approach allows the construction of supersonic kinks which can propagate in the lattice within a large range of energies and velocities. The interparticle distances in the lattice kinks with high energy are physically reasonable values. The introduction of the periodic lattice potential results in the important feature that the kinks propagate with a single velocity and a single energy which are independent on the excitation conditions. The found kinks are ultra-discrete and can be described with the "magic wave number" q2π/3aq\simeq 2\pi/3a, which was previously revealed in the nonlinear sinusoidal waves and supersonic kinks in the Fermi-Pasta-Ulam lattice. The extreme discreteness of the supersonic kinks, with basically two particles moving at the same time, allows the interpretation of their double-kink structure. The energy of the supersonic kinks is between the possible source of 40^{40}K recoil in beta decay and the energy necessary for the ejection of an atom at the border as has been found experimentally.Comment: 14 pages, 15 figure

    Cooperative learning in higher education: differences in perceptions of contribution to the group

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    This document analyses cooperative learning in a working group using a problem-based learning methodology. We also evaluate if the perception that each member of the group has of his/her contribution to cooperative learning is greater or lesser than that observed by his/her team-mates. Different elements of the work carried out in the group are analysed, such as the effective effort made, their participation, the organisation of the group, cohesion, communication, and the overall perception of their involvement in the cooperative learning and work. It is observed that the students perceive their contribution as greater than that perceived by their team-mates, although we find slight differences depending on the elements analysed

    Ant colony optimized planning for unmanned surface marine vehicles

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    This paper presents some results achieved from a preliminary study on the use of the Ant Colony Algorithm to plan feasible optimal or suboptimal trajectories for an autonomous ship manoeuvring. The scenario, for this preliminary work, comprises only open sea manoeuvres. The goal involves obtaining the least time consuming ship trajectory between to points, departing from the start point with arbitrary initial speed and attitude values and arriving to the end point with predefined speed and attitude values. The specific dynamic of the ship imposes typical restrictions to its manoeuvrability. In the present case, the non-holonomicity, the rate speed/turn radius, and the imposed forward-only propulsion of the ship make up the main restrictions to the ship movement. For long distances, the problem could be tackled as a classical navigation problem, in which, for the most part of the ship trajectory, techniques such inertial navigation should be enough. The problem arises at short distances when it becomes a manoeuvring problem. In this case to obtain a optimal, --in some cases just a feasible--, trajectory could be a difficult problem.Peer Reviewe

    Low-frequency noise in downscaled silicon transistors: Trends, theory and practice

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    By the continuing downscaling of sub-micron transistors in the range of few to one deca-nanometers, we focus on the increasing relative level of the low-frequency noise in these devices. Large amount of published data and models are reviewed and summarized, in order to capture the state-of-the-art, and to observe that the 1/area scaling of low-frequency noise holds even for carbon nanotube devices, but the noise becomes too large in order to have fully deterministic devices with area less than 10nm×10nm. The low-frequency noise models are discussed from the point of view that the noise can be both intrinsic and coupled to the charge transport in the devices, which provided a coherent picture, and more interestingly, showed that the models converge each to other, despite the many issues that one can find for the physical origin of each model. Several derivations are made to explain crossovers in noise spectra, variable random telegraph amplitudes, duality between energy and distance of charge traps, behaviors and trends for figures of merit by device downscaling, practical constraints for micropower amplifiers and dependence of phase noise on the harmonics in the oscillation signal, uncertainty and techniques of averaging by noise characterization. We have also shown how the unavoidable statistical variations by fabrication is embedded in the devices as a spatial “frozen noise”, which also follows 1/area scaling law and limits the production yield, from one side, and from other side, the “frozen noise” contributes generically to temporal 1/f noise by randomly probing the embedded variations during device operation, owing to the purely statistical accumulation of variance that follows from cause-consequence principle, and irrespectively of the actual physical process. The accumulation of variance is known as statistics of “innovation variance”, which explains the nearly log-normal distributions in the values for low-frequency noise parameters gathered from different devices, bias and other conditions, thus, the origin of geometric averaging in low-frequency noise characterizations. At present, the many models generally coincide each with other, and what makes the difference, are the values, which, however, scatter prominently in nanodevices. Perhaps, one should make some changes in the approach to the low-frequency noise in electronic devices, to emphasize the “statistics behind the numbers”, because the general physical assumptions in each model always fail at some point by the device downscaling, but irrespectively of that, the statistics works, since the low-frequency noise scales consistently with the 1/area law

    Influence of individual biological traits on GPS fix-loss errors in wild bird tracking

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    In recent decades, global positioning system (GPS) location data and satellite telemetry systems for data transmission have become fundamental in the study of basic ecological traits in wildlife biology. Evaluating GPS location errors is essential in assessing detailed information about the behaviour of an animal species such as migration, habitat selection, species distribution or foraging strategy. While many studies of the influence of environmental and technical factors on the fix errors of solar-powered GPS transmitters have been published, few studies have focussed on the performance of GPS systems in relation to a species’ biological traits. Here, we evaluate the possible effects of the biological traits of a large raptor on the frequency of lost fixes—the fix-loss rate (FLR). We analysed 95,686 records obtained from 20 Bearded Vultures Gypaetus barbatus tracked with 17 solar-powered satellite transmitters in the Pyrenees (Spain, France and Andorra), between 2006 and 2019 to evaluate the influence of biological, technical, and environmental factors on the fix-loss rate of transmitters. We show that combined effects of technical factors and the biological traits of birds explained 23% of the deviance observed. As expected, the transmitter usage time significantly increased errors in the fix-loss rate, although the flight activity of birds revealed an unexpected trade-off: the greater the proportion of fixes recorded from perched birds, the lower the FLR. This finding seems related with the fact that territorial and breeding birds spend significantly more time flying than non-territorial individuals. The fix success rate is apparently due to the interactions between a complex of factors. Non-territorial adults and subadults, males, and breeding individuals showed a significantly lower FLR than juveniles-immatures females, territorial birds or non-breeding individuals. Animal telemetry tracking studies should include error analyses before reaching any ecological conclusions or hypotheses about spatial distribution.This work was funded by the Spanish Ministry of Economy, Industry and Competitiveness (project CGL2015-66966-C2-2-R), the Ministry of Science, Innovation and Universities (RTI2018-099609-B-C22). RGJ was supported by pre-doctoral Grant (FPI/BES-2016-077510) granted by the Spanish Ministry of Economy and Competitiveness
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