800 research outputs found

    Optimal control-based methodology for active vibration control of pedestrian structures

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    This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Civil structures such as floor systems with open-plan layouts or lightweight footbridges can be susceptible to excessive levels of vibrations caused by human activities. Active vibration control (AVC) via inertial-mass actuators has been shown to be a viable technique to mitigate vibrations, allowing structures to satisfy vibration serviceability limits. It is generally considered that the determination of the optimal placement of sensors and actuators together with the output feedback gains leads to a tradeoff between the regulation performance and the control effort. However, the "optimal" settings may not have the desired effect when implemented because simplifications assumed in the control scheme components may not be valid and/or the actuator/sensor limitations are not considered. This work proposes a design methodology for multi-input multi-output vibration control of pedestrian structures to simultaneously obtain the sensor/actuator placement and the control law. This novel methodology consists of minimising a performance index that includes all the significant practical issues involved when inertial-mass actuators and accelerometers are used to implement a direct velocity feedback in practice. Experimental results obtained on an in-service indoor walkway confirm the viability of the proposed methodology.The authors acknowledge the financial support provided by the Fundación Caja Madrid through the grant “II Convocatoria de Becas de Movilidad para profesores de las universidades públicas de Madrid durante el curso académico 2012/2013” and also the UK Engineering and Physical Sciences Research Council (EPSRC) though grant EP/J004081/2 entitled “Advanced Technologies for Mitigation of Human-Induced Vibration”

    The role of cyanoprokaryota in the rhizospheres of gypsophytes and effects of drought and water pulses on microbial functionality

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    In a Mediterranean environment plants are subject to water stress and lack of nutrients, among others. The adaptations that they can present are very varied and depend on the type of soil and the climate itself. In gypsiferous soils the adaptations of gypsophytes are numerous and unclear. Cyanoprokaryota had a relevant role in the rhizospheres of gypsophytes in drought conditions. We detect the responses to the availability of water in the rhizospheres of three gypsophytes and in non-rhizospheric soil during a summer drought and during spring. Water retention and water loss were studied. We were obtained the highest values in drought conditions due to the association of Cyanoprokaryota with the rhizospheres. The results are also explained by two water pulses that occurred before the samplings. Several parameters, whose values changed markedly due to the microbiological activation just after the drought and water pulses, are proposed as indicators of this activation: microbial biomass carbon and basal respiration rate, together with urease and protease. However, it was the dehydrogenase activity in spring that best reflected the microbiology associated with the carbon cycle, together with β-glucosidase. The interrelationships between carbon and nitrogen were shown through the indices: water soluble nitrogen and water soluble carbon. We propose three functional adaptation mechanisms of these plants associated with the Cyanoprokaryota in their rhizospheres and related to the water availability as determined by drought and water pulse effects. Financing: This study was funded by the Spanish National Government (CICYTCGL2009-12582-C02-02) and by the Valencian Autonomous Government (AICO/2019/258

    Plant residue chemical quality modulates the soil microbial response related to decomposition and soil organic carbon and nitrogen stabilization in a rainfed Mediterranean agroecosystem

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    Soils play a major role in the global carbon cycle and are crucial to the management of climate change. Changes in plant cover derived from different agricultural practices induce variations in the quality of plant residue inputs and in the soil microbial community structure and activity, which may enhance the storage and protection of organic carbon (OC) and nitrogen (N) within aggregates. The aim of this study was to assess how differences in the chemical composition of plant residues in combination with tillage management practices affect the local microbial community activity and structure, and subsequent soil aggregation and OC and N dynamics in an organic, rainfed almond (Prunus dulcis Mill.) orchard. In the laboratory, three types of plant residue (shoots, roots, and the combination of both) coming from different species belonging to each agricultural practice (reduced tillage, reduced tillage plus green manure, reduced tillage plus organic manure, and no-tillage) were mixed with their respective soils and the CO2 released was measured over 243 days at 60% WHC and 28 °C. Water-stable aggregates (including microaggregates within macroaggregates), enzymatic activities related to carbon (dehydrogenase and ß-glucosidase) and N (urease) cycling, and the microbial biomass and community structure through phospholipid fatty acid analysis, were measured at the end of the incubation period. Our results indicate that the chemical composition of plant residues controls the microbial community response, mediating decomposition and the incorporation of OC and N in stable aggregates. Therefore, the incorporation of labile and N-rich plant residues into the soil by reduced tillage is recommended since mixing roots and shoots from green manure increased the formation of free micro-aggregates and improved OC and N stabilization in our semiarid agroecosystem. © 2021 Elsevier LtdThis research was supported with funds from the Fundaci?n S?neca of the Murcia Region (projects 08757/PI/08, EMISEMUR 19350/PI/14 and DECADE 20917/PI/18). Parts of this research were performed within the framework of the project IMPASEC AGL2011-25069 funded by the Spanish Ministerio de Econom?a y Competitividad. Mar?a Almagro was supported by the Juan de la Cierva Program (Grant IJCI-2015-23500) and Antonio Ruiz-Navarro by the Fundaci?n General from the Spanish Research Council (CSIC, ConFuturo Progamme). We thank members of the Soil and Water Conservation Group - Eloisa Garc?a, Inmaculada Montoya, and Mar?a Jos? Espinosa - for helping us with the field and laboratory work, and Gonzalo Barber? for his useful advice with statistical analyses. We also thanks Gonzalo Herv?s, from the Instituto de Ganader?a de Monta?a of the Spanish Research Council, for performing the fiber fraction analysis. We are also grateful to Claire Chenu and two anonymous reviewers for their constructive and insightful comments on earlier versions of the manuscript

    The nuclear and extended mid-infrared emission of Seyfert galaxies

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    We present subarcsecond resolution mid-infrared (MIR) images obtained with 8-10 m-class ground-based telescopes of a complete volume-limited (DL<40 Mpc) sample of 24 Seyfert galaxies selected from the Swift/BAT nine month catalog. We use those MIR images to study the nuclear and circumnuclear emission of the galaxies. Using different methods to classify the MIR morphologies on scales of ~400 pc, we find that the majority of the galaxies (75-83%) are extended or possibly extended and 17-25% are point-like. This extended emission is compact and it has low surface brightness compared with the nuclear emission, and it represents, on average, ~30% of the total MIR emission of the galaxies in the sample. We find that the galaxies whose circumnuclear MIR emission is dominated by star formation show more extended emission (650+-700 pc) than AGN-dominated systems (300+-100 pc). In general, the galaxies with point-like MIR morphologies are face-on or moderately inclined (b/a~0.4-1.0), and we do not find significant differences between the morphologies of Sy1 and Sy2. We used the nuclear and circumnuclear fluxes to investigate their correlation with different AGN and SF activity indicators. We find that the nuclear MIR emission (the inner ~70 pc) is strongly correlated with the X-ray emission (the harder the X-rays the better the correlation) and with the [O IV] lambda 25.89 micron emission line, indicating that it is AGN-dominated. We find the same results, although with more scatter, for the circumnuclear emission, which indicates that the AGN dominates the MIR emission in the inner ~400 pc of the galaxies, with some contribution from star formation.Comment: 27 pages, 12 figures, accepted by MNRA

    Long-term effectiveness of sustainable land management practices to control runoff, soil erosion, and nutrient loss and the role of rainfall intensity in Mediterranean rainfed agroecosystems

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    Mediterranean environments are especially susceptible to soil erosion and to inappropriate soil management, leading to accelerated soil loss. Sustainable Land Management (SLM) practices (such as reduced tillage, no-tillage, cover crops, etc.,) have the potential to reduce soil, organic carbon (OC), and nutrient losses by erosion. However, the effectivity of these practices is site-dependent and varies under different rainfall conditions. The objective of this paper was to evaluate the effects of SLM practices in two rainfed systems (a wheat field and an almond orchard) representative of a large area of the driest Mediterranean regions - on runoff, soil erosion, particle size distribution, and OC and nutrient (N and P) contents in sediments. The influence of the rainfall characteristics on the effectiveness of the SLM practices was also evaluated. The SLM implemented were: reduced tillage (RT) in the wheat field and almond orchard and reduced tillage combined with green manure (RTG) in the almond orchard; these were compared to conventional tillage, the usual practice in the area. Open erosion plots were set up to monitor the effects of SLM on soil carbon and nutrients and on soil erosion after each rainfall event over six years (2010 2016). The results show that the SLM practices evaluated resulted in increased organic carbon (OC) and nutrients (N and P) contents in the soil, and reduced runoff, erosion, and mobilization of organic carbon and nutrients in sediments. Reductions in runoff of 30% and 65% and decreases in erosion of 65 and 85% were found in the wheat field and almond orchards, respectively. In addition, the total OC, N, and P losses in the wheat field were reduced by 56%, 45%, and 64%, respectively, while in the almond field the OC, N, and P losses were reduced by 90% under RT and by 85% under RTG. The beneficial effect of the SLM practices on soil erosion was observed within 18 months of their implementation and continued throughout the six years of the study. Furthermore, the effectiveness of tillage reduction with respect to erosion control and carbon and nutrients mobilization was highest during the most intense rainfall events, which are responsible for the highest erosion rates in Mediterranean areas. Our results support the key role of SLM practices under semiarid conditions as useful tools for climate change mitigation and adaptation, given the expected increase in high-intensity rainfall events in semiarid areas. © 2019 The AuthorsThis study site has been funded by several national (CYCIT AGL201125069//CICYT AGL2010-20941//CGL2013-42009-R//CGL2014-55-405-R), Regional (Séneca Foundation: 08757/PI/08//19350/PI/14), and European Commission H2020 (F6 DG RTD 037046 and Grant 728003, DIVERFARMING projects). Joris de Vente acknowledges support from a Ramón y Cajal research grant (RYC-2012-10375) and María Almagro was supported by the Juan de la Cierva Program (IJCI-2015-23500)

    Corrigendum

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    Twenty microsatellites (SSRs) reveal two main origins ofvariability in grapevine cultivars from Northwestern SpainVitis 49 (2), 55-62 (2010

    Corrigendum

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    Twenty microsatellites (SSRs) reveal two main origins ofvariability in grapevine cultivars from Northwestern SpainVitis 49 (2), 55-62 (2010

    Twenty microsatellites (SSRs) reveal two main origins of variability in grapevine cultivars from Northwestern Spain

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    The grapevine germplasm bank in the “Estación de Viticultura y Enología de Galicia, Xunta de Galicia”, holds fifteen grapevine cultivars with a total of 98 accessions: ‘Brancellao’, ‘Albarello’, ‘Caíño Astureses’, ‘Caíño Bravo’, ‘Caíño Blanco’, ‘Caíño Gordo’, ‘Albarín Negro’, ‘Caíño Longo’, ‘Caíño Redondo’, ‘Castañal’, ‘Mencía’, ‘Merenzao’, ‘Mouratón’, ‘Sousón’, and ‘Verdello’. Cultivars ‘Syrah’ and ‘Pinot Noir’ were included as references. Two different lineages were detected, one originating in ‘Caíño Astureses’ and the other in ‘Merenzao’, synonymy of the French cultivar ‘Trousseau’. Cultivars from Northwestern Spain derived from both of these cultivars by hybridization and selected genotypes that had adapted to local climatic conditions and became fixed by cuttings, explaining the domestication process of these grapevine cultivars. Both lineages differed in allelic frequencies and were distributed differently in Northwestern Spain, the first lineage in the west and the second, related with the French cultivar ‘Trousseau’, in the east. ‘Caíño Astureses’ was the most frequent genotype related by hybridization, indicating the importance that this cultivar had in the origin of grapevines in Galicia. In addition a total of 13 different genotypes were identified. The identity of ‘Brancellao’ and ‘Albarello’ was confirmed by SSR-markers. Other two synonyms were ‘Caíño Astureses’ and ‘Caíño Bravo’, and ‘Caíño Gordo’ and ‘Albarín Negro’. ‘Caíño Redondo’ showed two different genotypes, one related to ‘Caíño Astureses’ and the other to ‘Merenzao’. Two cultivars included in the collection from EVEGA were not reported previously, ‘Verdello’ and ‘Caíño Longo’.
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