Investigaciones financiadas por la Unión Europea (OpenAire) - Europar Batasunak finantzatutako ikerketak (OpenAire)

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Open Access
Spatial distribution and risk factors of brucellosis in Iberian wild ungulates
(BioMed Central, 2010) Muñoz Álvaro, Pilar María; Boadella, Mariana; Arnal, Maricruz; Miguel, María Jesús de; Revilla, Miguel; Martínez, David; Vicente, Joaquín; Acevedo, Pelayo; Oleaga, Álvaro; Ruiz Fons, Francisco; Marín, Clara M.; Prieto, José M.; Fuente, José de la; Barral, Marta; Barberán, Montserrat; Fernández de Luco, Daniel; Blasco Canet, José María; Gortázar, Christian; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
Background: The role of wildlife as a brucellosis reservoir for humans and domestic livestock remains to be properly established. The aim of this work was to determine the aetiology, apparent prevalence, spatial distribution and risk factors for brucellosis transmission in several Iberian wild ungulates. Methods: A multi-species indirect immunosorbent assay (iELISA) using Brucella S-LPS antigen was developed. In several regions having brucellosis in livestock, individual serum samples were taken between 1999 and 2009 from 2, 579 wild bovids, 6, 448 wild cervids and4, 454 Eurasian wild boar (Sus scrofa), and tested to assess brucellosis apparent prevalence. Strains isolated from wild boar were characterized to identify the presence of markers shared with the strains isolated from domestic pigs. Results: Mean apparent prevalence below 0.5% was identified in chamois (Rupicapra pyrenaica), Iberian wild goat (Capra pyrenaica), and red deer (Cervus elaphus). Roe deer (Capreolus capreolus), fallow deer (Dama dama), mouflon (Ovis aries) and Barbary sheep (Ammotragus lervia) tested were seronegative. Only one red deer and one Iberian wild goat resulted positive in culture, isolating B. abortus biovar 1 and B. melitensis biovar 1, respectively. Apparent prevalence in wild boar ranged from 25% to 46% in the different regions studied, with the highest figures detected in South-Central Spain. The probability of wild boar being positive in the iELISA was also affected by age, age-by-sex interaction, sampling month, and the density of outdoor domestic pigs. A total of 104 bacterial isolates were obtained from wild boar, being all identified as B. suis biovar 2. DNA polymorphisms were similar to those found in domestic pigs. Conclusions: In conclusion, brucellosis in wild boar is widespread in the Iberian Peninsula, thus representing an important threat for domestic pigs. By contrast, wild ruminants were not identified as a significant brucellosis reservoir for livestock.
Open Access
ETOMIC advanced network monitoring system for future Internet experimentation
(Springer-Verlag Berlin Heidelberg, 2010) Csabai, István; Fekete, Attila; Hága, Péter; Hullár, Béla; Kurucz, Gábor; Laki, Sándor; Mátray, Péter; Stéger, József; Vattay, Gábor; Espina Antolín, Félix; García-Jiménez, Santiago; Izal Azcárate, Mikel; Magaña Lizarrondo, Eduardo; Morató Osés, Daniel; Aracil Rico, Javier; Gómez, Francisco; González, Iván; López Buedo, Sergio; Moreno, Víctor; Ramos, Javier; Automática y Computación; Automatika eta Konputazioa
ETOMIC is a network traffic measurement platform with high precision GPS-synchronized monitoring nodes. The infrastructure is publicly available to the network research community, supporting advanced experimental techniques by providing high precision hardware equipments and a Central Management System. Researchers can deploy their own active measurement codes to perform experiments on the public Internet. Recently, the functionalities of the original system were significantly extended and new generation measurement nodes were deployed. The system now also includes well structured data repositories to archive and share raw and evaluated data. These features make ETOMIC as one of the experimental facilities that support the design, development and validation of novel experimental techniques for the future Internet. In this paper we focus on the improved capabilities of the management system, the recent extensions of the node architecture and the accompanying database solutions.
Open Access
The lipopolysaccharide core of Brucella abortus acts as a shield against innate immunity recognition
(Public Library of Science, 2012) Conde Álvarez, Raquel; Bargen, Kristine von; Grilló Dolset, María Jesús; Jerala, Roman; Brandenburg, Klaus; Llobet, Enrique; Bengoechea Alonso, José Antonio; Moreno, Edgardo; Moriyón Uría, Ignacio; Gorvel, Jean-Pierre; Arce Gorvel, Vilma; Iriarte, Maite; Mancek Keber, Mateja; Barquero-Calvo, Elías; Palacios Chaves, Leyre; Chacón Díaz, Carlos; Chaves Olarte, Esteban; Martirosyan, Anna; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua; Gobierno de Navarra / Nafarroako Gobernua
Innate immunity recognizes bacterial molecules bearing pathogen-associated molecular patterns to launch inflammatory responses leading to the activation of adaptive immunity. However, the lipopolysaccharide (LPS) of the gram-negative bacterium Brucella lacks a marked pathogen-associated molecular pattern, and it has been postulated that this delays the development of immunity, creating a gap that is critical for the bacterium to reach the intracellular replicative niche. We found that a B. abortus mutant in the wadC gene displayed a disrupted LPS core while keeping both the LPS O-polysaccharide and lipid A. In mice, the wadC mutant induced proinflammatory responses and was attenuated. In addition, it was sensitive to killing by non-immune serum and bactericidal peptides and did not multiply in dendritic cells being targeted to lysosomal compartments. In contrast to wild type B. abortus, the wadC mutant induced dendritic cell maturation and secretion of pro-inflammatory cytokines. All these properties were reproduced by the wadC mutant purified LPS in a TLR4-dependent manner. Moreover, the core-mutated LPS displayed an increased binding to MD-2, the TLR4 co-receptor leading to subsequent increase in intracellular signaling. Here we show that Brucella escapes recognition in early stages of infection by expressing a shield against recognition by innate immunity in its LPS core and identify a novel virulence mechanism in intracellular pathogenic gram-negative bacteria. These results also encourage for an improvement in the generation of novel bacterial vaccines.
Open Access
Is N-feedback involved in the inhibition of nitrogen fixation in drought-stressed Medicago truncatula?
(Oxford University Press, 2013) Gil Quintana, Erena; Larrainzar Rodríguez, Estíbaliz; Arrese-Igor Sánchez, César; González García, Esther; Ciencias del Medio Natural; Natura Ingurunearen Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa: 735/2008
Drought stress is a major factor limiting nitrogen fixation (NF) in crop production. However, the regulatory mechanism involved and the origin of the inhibition, whether local or systemic, is still controversial and so far scarcely studied in temperate forage legumes. Medicago truncatula plants were symbiotically grown with a split-root system and exposed to gradual water deprivation. Physiological parameters, NF activity, and amino acid content were measured. The partial drought treatment inhibited NF in the nodules directly exposed to drought stress. Concomitantly, in the droughted below-ground organs, amino acids accumulated prior to any drop in evapotranspiration (ET). It is concluded that drought exerts a local inhibition of NF and drives an overall accumulation of amino acids in diverse plant organs which is independent of the decrease in ET. The general increase in the majority of single amino acids in the whole plant questions the commonly accepted concept of a single amino acid acting as an N-feedback signal.
Open Access
Local inhibition of nitrogen fixation and nodule metabolism in drought-stressed soybean
(Oxford University Press, 2013) Gil Quintana, Erena; Larrainzar Rodríguez, Estíbaliz; Seminario Huárriz, Amaia; Díaz Leal, Juan Luis; Alamillo, Josefa M.; Pineda, Manuel; Arrese-Igor Sánchez, César; Wienkoop, Stefanie; González García, Esther; Ciencias del Medio Natural; Natura Ingurunearen Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa: 735/2008; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa: 134/2012
Drought stress is a major factor limiting symbiotic nitrogen fixation (NF) in soybean crop production. However, the regulatory mechanisms involved in this inhibition are still controversial. Soybean plants were symbiotically grown in a split-root system (SRS), which allowed for half of the root system to be irrigated at field capacity while the other half remained water deprived. NF declined in the water-deprived root system while nitrogenase activity was maintained at control values in the well-watered half. Concomitantly, amino acids and ureides accumulated in the water-deprived belowground organs regardless of transpiration rates. Ureide accumulation was found to be related to the decline in their degradation activities rather than increased biosynthesis. Finally, proteomic analysis suggests that plant carbon metabolism, protein synthesis, amino acid metabolism, and cell growth are among the processes most altered in soybean nodules under drought stress. Results presented here support the hypothesis of a local regulation of NF taking place in soybean and downplay the role of ureides in the inhibition of NF
Open Access
Deletion of the GI-2 integrase and the wbkA flanking transposase improves the stability of Brucella melitensis Rev 1 vaccine
(BioMed Central, 2013) Mancilla, Marcos; Grilló Dolset, María Jesús; Miguel López, María Jesús de; López Goñi, Ignacio; San Román Aberasturi, Beatriz; Zabalza Baranguá, Ana; Moriyón Uría, Ignacio; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
Brucella melitensis Rev 1 is the best vaccine available for the prophylaxis of small ruminant brucellosis and, indirectly, for reducing human brucellosis. However, Rev 1 shows anomalously high rates of spontaneous dissociation from smooth (S) to rough (R) bacteria, the latter being inefficacious as vaccines. This S-R instability results from the loss of the O-polysaccharide. To overcome this problem, we investigated whether some recently described mechanisms promoting mutations in O-polysaccharide genes were involved in Rev 1 S-R dissociation. We found that a proportion of Rev 1 R mutants result from genome rearrangements affecting the wbo O-polysaccharide loci of genomic island GI-2 and the wbkA O-polysaccharide glycosyltransferase gene of the wbk region. Accordingly, we mutated the GI-2 int gene and the wbk IS transposase involved in those arrangements, and found that these Rev 1 mutants maintained the S phenotype and showed lower dissociation levels. Combining these two mutations resulted in a strain (Rev 2) displaying a 95% decrease in dissociation with respect to parental Rev 1 under conditions promoting dissociation. Rev 2 did not differ from Rev 1 in the characteristics used in Rev 1 typing (growth rate, colonial size, reactivity with O-polysaccharide antibodies, phage, dye and antibiotic susceptibility). Moreover, Rev 2 and Rev 1 showed similar attenuation and afforded similar protection in the mouse model of brucellosis vaccines. We conclude that mutations targeting genes and DNA sequences involved in spontaneous O-polysaccharide loss enhance the stability of a critical vaccine phenotype and complement the empirical stabilization precautions taken during S Brucella vaccine production.
Open Access
Consensus image method for unknown noise removal
(Elsevier, 2014) González Jaime, Luis; Kerre, Etienne E.; Nachtegael, Mike; Bustince Sola, Humberto; Automática y Computación; Automatika eta Konputazioa
Noise removal has been, and it is nowadays, an important task in computer vision. Usually, it is a previous task preceding other tasks, as segmentation or reconstruction. However, for most existing denoising algorithms the noise model has to be known in advance. In this paper, we introduce a new approach based on consensus to deal with unknown noise models. To do this, different filtered images are obtained, then combined using multifuzzy sets and averaging aggregation functions. The final decision is made by using a penalty function to deliver the compromised image. Results show that this approach is consistent and provides a good compromise between filters.
Open Access
Control strategies to smooth short-term power fluctuations in large photovoltaic plants using battery storage systems
(MDPI, 2014) Marcos Álvarez, Javier; Parra Laita, Íñigo de la; García Solano, Miguel; Marroyo Palomo, Luis; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The variations in irradiance produced by changes in cloud cover can cause rapid fluctuations in the power generated by large photovoltaic (PV) plants. As the PV power share in the grid increases, such fluctuations may adversely affect power quality and reliability. Thus, energy storage systems (ESS) are necessary in order to smooth power fluctuations below the maximum allowable. This article first proposes a new control strategy (step-control), to improve the results in relation to two state-of-the-art strategies, ramp-rate control and moving average. It also presents a method to quantify the storage capacity requirements according to the three different smoothing strategies and for different PV plant sizes. Finally, simulations shows that, although the moving-average (MA) strategy requires the smallest capacity, it presents more losses (2–3 times more) and produces a much higher number of cycles over the ESS (around 10 times more), making it unsuitable with storage technologies as lithium-ion. The step-control shown as a better option in scenery with exigent ramp restrictions (around 2%/min) and distributed generation against the ramp-rate control in all ESS key aspects: 20% less of capacity, up to 30% less of losses and a 40% less of ageing. All the simulations were based on real PV production data, taken every 5 s in the course of one year (2012) from a number of systems with power outputs ranging from 550 kW to 40 MW.
Open Access
Nodule carbohydrate catabolism is enhanced in the Medicago truncatula A17-Sinorhizobium medicae WSM419 symbiosis
(Frontiers Media, 2014) Larrainzar Rodríguez, Estíbaliz; Gil Quintana, Erena; Seminario Huárriz, Amaia; Arrese-Igor Sánchez, César; González García, Esther; Ciencias del Medio Natural; Natura Ingurunearen Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The symbiotic association between Medicago truncatula and Sinorhizobium meliloti is a well-established model system in the legume–Rhizobium community. Despite its wide use, the symbiotic efficiency of this model has been recently questioned and an alternative microsymbiont, S. medicae, has been proposed. However, little is known about the physiological mechanisms behind the higher symbiotic efficiency of S. medicae WSM419. In the present study, we inoculated M. truncatula Jemalong A17 with either S. medicae WSM419 or S. meliloti 2011 and compared plant growth, photosynthesis, N2-fixation rates, and plant nodule carbon and nitrogen metabolic activities in the two systems. M. truncatula plants in symbiosis with S. medicae showed increased biomass and photosynthesis rates per plant. Plants grown in symbiosis with S. medicae WSM419 also showed higher N2-fixation rates, which were correlated with a larger nodule biomass, while nodule number was similar in both systems. In terms of plant nodule metabolism, M. truncatula–S. medicae WSM419 nodules showed increased sucrose-catabolic activity, mostly associated with sucrose synthase, accompanied by a reduced starch content, whereas nitrogen-assimilation activities were comparable to those measured in nodules infected with S. meliloti 2011. Taken together, these results suggest that S. medicae WSM419 is able to enhance plant carbon catabolism in M. truncatula nodules, which allows for the maintaining of high symbiotic N2-fixation rates, better growth and improved general plant performance.
Open Access
Strength and endurance training prescription in healthy and frail elderly
(International Society on Aging and Disease (ISOAD), 2014) Lusa Cadore, Eduardo; Pinto, Ronei Silveira; Bottaro, Martim; Izquierdo Redín, Mikel; Ciencias de la Salud; Osasun Zientziak
Aging is associated with declines in the neuromuscular and cardiovascular systems, resulting in an impaired capacity to perform daily activities. Frailty is an age-associated biological syndrome characterized by decreases in the biological functional reserve and resistance to stressors due to changes in several physiological systems, which puts older individuals at special risk of disability. To counteract the neuromuscular and cardiovascular declines associated with aging, as well as to prevent and treat the frailty syndrome, the strength and endurance training seems to be an effective strategy to improve muscle hypertrophy, strength and power output, as well as endurance performance. The first purpose of this review was discuss the neuromuscular adaptations to strength training, as well as the cardiovascular adaptations to endurance training in healthy and frail elderly subjects. In addition, the second purpose of this study was investigate the concurrent training adaptations in the elderly. Based on the results found, the combination of strength and endurance training (i.e., concurrent training) performed at moderate volume and moderate to high intensity in elderly populations is the most effective way to improve both neuromuscular and cardiorespiratory functions. Moreover, exercise interventions that include muscle power training should be prescribed to frail elderly in order to improve the overall physical status of this population and prevent disability.
Open Access
Drought stress provokes the down-regulation of methionine and ethylene biosynthesis pathways in Medicago truncatula roots and nodules
(Wiley, 2014) Larrainzar Rodríguez, Estíbaliz; Molenaar, Johanna A.; Wienkoop, Stefanie; Gil Quintana, Erena; Alibert, Bénédicte; Limami, Anis M.; Arrese-Igor Sánchez, César; González García, Esther; Ciencias del Medio Natural; Natura Ingurunearen Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, 735/2008
Symbiotic nitrogen fixation is one of the first physiological processes inhibited in legume plants under water-deficit conditions. Despite the progress made in the last decades, the molecular mechanisms behind this regulation are not fully understood yet. Recent proteomic work carried out in the model legume Medicago truncatula provided the first indications of a possible involvement of nodule methionine (Met) biosynthesis and related pathways in response to waterdeficit conditions. To better understand this involvement, the drought-induced changes in expression and content of enzymes involved in the biosynthesis of Met, S-adenosyl-Lmethionine (SAM) and ethylene in M. truncatula root and nodules were analyzed using targeted approaches. Nitrogenfixing plants were subjected to a progressive water deficit and a subsequent recovery period. Besides the physiological characterization of the plants,the content of total sulphur,sulphate and main S-containing metabolites was measured. Results presented here show that S availability is not a limiting factor in the drought-induced decline of nitrogen fixation rates in M. truncatula plants and provide evidences for a downregulation of the Met and ethylene biosynthesis pathways in roots and nodules in response to water-deficit conditions.
Open Access
Implementation and control of a residential electrothermal microgrid based on renewable energies, a hybrid storage system and demand side management
(MDPI, 2014) Pascual Miqueleiz, Julio María; Sanchis Gúrpide, Pablo; Marroyo Palomo, Luis; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua
This paper proposes an energy management strategy for a residential electrothermal microgrid, based on renewable energy sources. While grid connected, it makes use of a hybrid electrothermal storage system, formed by a battery and a hot water tank along with an electrical water heater as a controllable load, which make possible the energy management within the microgrid. The microgrid emulates the operation of a single family home with domestic hot water (DHW) consumption, a heating, ventilation and air conditioning (HVAC) system as well as the typical electric loads. An energy management strategy has been designed which optimizes the power exchanged with the grid profile in terms of peaks and fluctuations, in applications with high penetration levels of renewables. The proposed energy management strategy has been evaluated and validated experimentally in a full scale residential microgrid built in our Renewable Energy Laboratory, by means of continuous operation under real conditions. The results show that the combination of electric and thermal storage systems with controllable loads is a promising technology that could maximize the penetration level of renewable energies in the electric system.
Open Access
Real-time simulation technique of a microgrid model for DER penetration
(EAI, 2014) Mentesidi, Konstantina; Rikos, Evangelos; Kleftakis, Vasilis; Kotsampopoulos, Panos; Aguado Alonso, Mónica; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Comprehensive analysis of Distributed Energy Resources (DER) integration requires tools that provide computational power and flexibility. In this context, throughout this paper PHIL simulations are performed to emulate the energy management system of a real microgrid including a diesel synchronous machine and inverter-based sources. Moreover, conventional frequency and voltage droops were incorporated into the respective inverters. The results were verified at the real microgrid installation in the Centre for Renewable Energy Sources (CRES) premises. This research work is divided into two steps: A) Real time in RSCAD/RTDS and Power Hardware-in-the-Loop (PHIL) simulations where the diesel generator´s active power droop control is evaluated, the battery inverter´s droop curves are simulated and the load sharing for parallel operation of the system´s generation units is examined. B) microgrid experiments during which various tests were executed concerning the diesel generator and the battery inverters in order to examine their dynamic operation within the LV islanded power system.
Open Access
Novel blaROB-1-bearing plasmid conferring resistance to β-lactams in Haemophilus parasuis isolates from healthy weaning pigs
(American Society for Microbiology, 2015) Moleres Apilluelo, Javier; Santos López, Alfonso; Lázaro, Isidro; Labairu, Javier; Prat, Cristina; Ardanuy, Carmen; González Zorn, Bruno; Aragon, Virginia; Garmendia García, Juncal; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
Haemophilus parasuis, the causative agent of Glässer’s disease, is one of the early colonizers of the nasal mucosa of piglets. It is prevalent in swine herds, and lesions associated with disease are fibrinous polyserositis and bronchopneumonia. Antibiotics are commonly used in disease control, and resistance to several antibiotics has been described in H. parasuis. Prediction of H. parasuis virulence is currently limited by our scarce understanding of its pathogenicity. Some genes have been associated with H. parasuis virulence, such as lsgB and group 1 vtaA, while biofilm growth has been associated with nonvirulent strains. In this study, 86 H. parasuis nasal isolates from farms that had not had a case of disease for more than 10 years were obtained by sampling piglets at weaning. Isolates were studied by enterobacterial repetitive intergenic consensus PCR and determination of the presence of lsgB and group 1 vtaA, biofilm formation, inflammatory cell response, and resistance to antibiotics. As part of the diversity encountered, a novel 2,661-bp plasmid, named pJMA-1, bearing the blaROB-1 β-lactamase was detected in eight colonizing strains. pJMA-1 was shown to share a backbone with other small plasmids described in the Pasteurellaceae, to be 100% stable, and to have a lower biological cost than the previously described plasmid pB1000. pJMA-1 was also found in nine H. parasuis nasal strains from a separate collection, but it was not detected in isolates from the lesions of animals with Glässer’s disease or in nontypeable Haemophilus influenzae isolates. Altogether, we show that commensal H. parasuis isolates represent a reservoir of β-lactam resistance genes which can be transferred to pathogens or other bacteria.
Open Access
Comparative study of nonparametric and parametric PV models to forecast AC power output of PV plants
(EU PVSEC, 2015) Almeida, Marcelo Pinho; Muñoz Escribano, Mikel; Parra Laita, Íñigo de la; Perpiñán, Óscar; Narvarte Fernández, Luis; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, a comparison between two approaches to predict the AC power output of PV systems is carried out in terms of forecast performance. Each approach uses one of the two main types of PV modeling, parametric and nonparametric, and both use as inputs several forecasts of meteorological variables from a Numerical Weather Prediction model. Furthermore, actual AC power measurements of a PV plant are used to train the nonparametric model, to adjust the parameters of the different PV components models used in the parametric approach and to assess the quality of the forecasts. The approaches presented similar behavior, although the nonparametric approach, based on Quantile Regression Forests, showed smaller biased errors due to the machine learning tool used.
Open Access
Holographic acoustic elements for manipulation of levitated objects
(Nature Publishing Group, 2015) Marzo Pérez, Asier; Seah, Sue Ann; Drinkwater, Bruce W.; Sahoo, Deepak Ranjan; Long, Benjamin; Subramanian, Sriram; Ingeniería Matemática e Informática; Matematika eta Informatika Ingeniaritza
Sound can levitate objects of different sizes and materials through air, water and tissue. This allows us to manipulate cells, liquids, compounds or living things without touching or contaminating them. However, acoustic levitation has required the targets to be enclosed with acoustic elements or had limited manoeuvrability. Here we optimize the phases used to drive an ultrasonic phased array and show that acoustic levitation can be employed to translate, rotate and manipulate particles using even a single-sided emitter. Furthermore, we introduce the holographic acoustic elements framework that permits the rapid generation of traps and provides a bridge between optical and acoustical trapping. Acoustic structures shaped as tweezers, twisters or bottles emerge as the optimum mechanisms for tractor beams or containerless transportation. Single-beam levitation could manipulate particles inside our body for applications in targeted drug delivery or acoustically controlled micro-machines that do not interfere with magnetic resonance imaging.
Open Access
Ecophysiological roles of abaxial anthocyanins in a perennial understorey herb from temperate deciduous forests
(Oxford University Press, 2015) Fernández Marín, Beatriz; Esteban Terradillos, Raquel; Míguez, Fátima; Artetxe, Unai; Castañeda Presa, Verónica; Pintó Marijuan, Marta; Becerril, José María; García Plazaola, José Ignacio; Natura Ingurunearen Zientziak; Ciencias del Medio Natural; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
Accumulation of abaxial anthocyanins is an intriguing leaf trait particularly common among deeply shaded understorey plants of tropical and temperate forests whose ecological significance is still not properly understood. To shed light on it, possible ecophysiological roles of abaxial anthocyanins were tested in the perennial understorey herb of temperate deciduous forests Saxifraga hirsuta, chosen as a model species due to the coexistence of green and anthocyanic leaves and the presence of an easily removable lower anthocyanic epidermis. Anthocyanins accumulated during autumn, which temporally matched the overstorey leaf fall. Patterns of development of abaxial anthocyanins and direct measurements of photochemical efficiency under monochromatic light were not consistent with a photoprotective hypothesis. Enhancement of light capture also seemed unlikely since the back-scattering of red light towards the lower mesophyll was negligible. Seed germination was similar under acyanic and anthocyanic leaves. A relevant consequence of abaxial anthocyanins was the dramatic reduction of light transmission through the leaf. The dark environment generated underneath the Saxifraga canopy was enhanced by the horizontal repositioning of leaves, which occurs in parallel with reddening. This might play a role in biotic interactions by inhibiting vital processes of competitors, which may be of especial importance in spring before the overstorey leaves sprout.
Open Access
Resilience assessment of lowland plantations using an ecosystem modeling approach
(MDPI, 2015) Wu, Chia-Hsin; Lo, Yueh-Hsin; Blanco Vaca, Juan Antonio; Chang, Shih-Chieh; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
As afforestation programs of former farmlands take hold in Taiwan to achieve a variety of ecological and socio-economic values, it is becoming necessary to define best forest management. Hence, we simulated mixed stands of Cinnamomum camphora and Fraxinus griffithii planted through a gradient of soil fertility and varying camphor/ash density ratios, but maintaining a fixed total stand density of 1500 trees ha −1 . Total stand productivity was slightly lower in mixed stands than the combination of both monocultures in rich and poor sites. Maximum negative yield surpluses for 50-year old stands were 7 Mg ha −1 and 6 Mg ha −1 for rich and poor sites with a 1:1 camphor laurel/ash ratios. Maximum stand woody biomass in rich sites was reached in camphor laurel monocultures (120 Mg ha −1 ) and in poor sites for Himalayan ash monocultures (58 Mg ha −1 ). However, for medium-quality sites, a small yield surplus (11 Mg ha −1 ) was estimated coinciding with a maximum stand woody biomass of 95 Mg ha −1 for a 1:1 camphor laurel/ash density ratio. From an ecological resilience point of view, rotation length was more important than stand composition. Long rotations (100 years) could improve soil conditions in poor sites. In rich sites, short rotations (50 years) should be avoided to reduce risks or fertility loss.
Open Access
Land use change effects on carbon and nitrogen stocks in the Pyrenees during the last 150 years: a modelling approach
(Elsevier, 2015) Lo, Yueh-Hsin; Blanco Vaca, Juan Antonio; Canals Tresserras, Rosa María; González de Andrés, Ester; San Emeterio Garciandía, Leticia; Imbert Rodríguez, Bosco; Castillo Martínez, Federico; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
In the southern Pyrenees, human population and therefore land uses have changed from forests to pastures, then crops, and back to pastures and secondary forests during the last two centuries. To understand what such rapid land use changes have meant for carbon (C) and nitrogen (N) stocks, we used data from two forest sites in the western Pyrenees, combined with regional data on pastures and crop production (potato, cereal), to calibrate the ecosystem-level model FORECAST. Then, we simulated 150-year of land use for each site, emulating historical changes. Our estimates show that the conversion from forests into pastures and crops created C and N deficits (378-427 Mg C ha-1, 4.0-4.6 Mg N ha-1) from which these sites are still recovering. The main ecological process behind the creation of these deficits was the loss of the ecological legacy of soil organic matter (SOM) created by the forest, particularly during conversion to farming. Pastures were able to reverse, stop or at least slow down the loss of such legacy. In conclusion, our work shows the deep impact of historical land use in ecosystem attributes, both in magnitude of removed C and N stocks and in duration of such impact. Also, the usefulness of ecological modelling in absence of historical data to estimate such changes is showcased, providing a framework for potential C and N stocks to be reached by climate change mitigation measures such as forest restoration.
Open Access
Coupled biomechanical response of the cornea assessed by non-contact tonometry. A simulation study
(Public Library of Science, 2015) Ariza Gracia, Miguel A.; Zurita Gabasa, Jesús; Piñero, David P.; Rodríguez Matas, José F.; Calvo, Begoña; Ingeniería Mecánica, Energética y de Materiales; Mekanika, Energetika eta Materialen Ingeniaritza
The mechanical response of the cornea subjected to a non-contact air-jet tonometry diagnostic test represents an interplay between its geometry, the corneal material behavior and the loading. The objective is to study this interplay to better understand and interpret the results obtained with a non-contact tonometry test. A patient-specific finite element model of a healthy eye, accounting for the load free configuration, was used. The corneal tissue was modeled as an anisotropic hyperelastic material with two preferential directions. Three different sets of parameters within the human experimental range obtained from inflation tests were considered. The influence of the IOP was studied by considering four pressure levels (10–28 mmHg) whereas the influence of corneal thickness was studied by inducing a uniform variation (300–600 microns). A Computer Fluid Dynamics (CFD) air-jet simulation determined pressure loading exerted on the anterior corneal surface. The maximum apex displacement showed a linear variation with IOP for all materials examined. On the contrary, the maximum apex displacement followed a cubic relation with corneal thickness. In addition, a significant sensitivity of the apical displacement to the corneal stiffness was also obtained. Explanation to this behavior was found in the fact that the cornea experiences bending when subjected to an air-puff loading, causing the anterior surface to work in compression whereas the posterior surface works in tension. Hence, collagen fibers located at the anterior surface do not contribute to load bearing. Non-contact tonometry devices give useful information that could be misleading since the corneal deformation is the result of the interaction between the mechanical properties, IOP, and geometry. Therefore, a noncontact tonometry test is not sufficient to evaluate their individual contribution and a complete in-vivo characterization would require more than one test to independently determine the membrane and bending corneal behavior.