308 research outputs found
Pescanova frente a la SoberanÃa Alimentaria
Contiene las notas "Rodaballos y Pescanova", de Manoel Santos (Revista Altermundo) y "España, sobrepesca y las grandes empresas", de Ocean Sentry.La pesca es una de las actividades humanas más antiguas y que más tiempo ha tardado en evolucionar. Sólo desde hace medio siglo se han empezado a introducir innovaciones tecnológicas con respecto a la actividad conocida desde hace milenios. Sin embargo, este último medio siglo está suponiendo una etapa convulsa que mantiene a la pesca enredada en grandes debates que enfrentan el sector. La pesca industrial, liderada por grupos como PESCANOVA, es un buen ejemplo de cómo los patrones de modernización en un entorno de mercados desregulados (en ocasiones de mercado ilegal) no se corresponden con las necesidades reales del planeta
Influence of the honeybee and trait similarity on the effect of a non-native plant on pollination and network rewiring
Introduced entomophilous non-native plants usually become well integrated into the diet of generalist pollinators. This integration can affect the entire recipient plant–pollinator network. Effects vary from facilitative to competitive, and understanding the factors that govern such variability is one of the fundamental goals in invasion ecology. Species traits determine the linking patterns between plant and pollinator species. Therefore, trait similarity among plants or among pollinators might modulate how they affect each other.
We conducted a flower removal experiment to investigate the effects of the non-native entomophilous legume Hedysarum coronarium on the pollination patterns of a Mediterranean shrubland plant–pollinator network. Specifically, we explored whether effects were influenced by similarity with the resident plant species in flower morphology (papilionate vs. non-papilionate), and whether effects on the pollinator community were influenced by similarity in functional group with its main visitor species (bees vs. non-bees). In addition, we explored whether Hedysarum had an effect on the identity of interactions. For this purpose, we calculated the interaction rewiring, that is the number of plant–pollinator interactions that were gained or lost after invasion.
Hedysarum was well integrated into the diet of 15 generalist pollinators having the honeybee as its main visitor species. Such integration did not affect visitation rates, normalized degree (i.e. proportion of pollinators they are visited by) nor niche overlap (i.e. proportion of plant species they share pollinators with) of plants, irrespective of their flower morphology. Only the proportion of honeybee visits to resident plants decreased with invasion. On the other hand, Hedysarum reduced visitation rates and niche overlap of pollinators, mainly those of bee species. Finally, we observed that changes in the foraging behaviour of the honeybee were positively associated with the interaction rewiring involving the rest (92 taxa) of pollinators.
In conclusion, pollinators show a plastic use of floral resources, responding to the presence of non-native plants. When the non-native attracts highly competitive pollinators such as the honeybee, plasticity is especially significant in pollinators that are functionally close to that competitive pollinator. The result is an interaction rewiring, probably due to pollinators avoiding competition with the honeybee. Though this plasticity might not quantitatively affect the pollination of plants, consequences on their reproduction and the functioning of the network can derive from the interaction rewiring.Peer reviewe
Direct and Indirect Influence of Non-Native Neighbours on Pollination and Fruit Production of a Native Plant
Entomophilous non-native plants can directly affect the pollination and reproductive success
of native plant species and also indirectly, by altering the composition and abundance
of floral resources in the invaded community. Separating direct from indirect effects is critical
for understanding the mechanisms underlying the impacts of non-native species on
recipient communities.
Objectives
Our aims are: (a) to explore both the direct effect of the non-native Hedysarum coronarium
and its indirect effect, mediated by the alteration of floral diversity, on the pollinator visitation
rate and fructification of the native Leopoldia comosa and (b) to distinguish whether the
effects of the non-native species were due to its floral display or to its vegetative
interactions.
Methods
We conducted field observations within a flower removal experimental setup (i.e. non-native
species present, absent and with its inflorescences removed) at the neighbourhood scale.
Results
Our study illustrates the complexity of mechanisms involved in the impacts of non-native
species on native species. Overall, Hedysarum increased pollinator visitation rates to Leopoldia
target plants as a result of direct and indirect effects acting in the same direction. Due
to its floral display, Hedysarum exerted a direct magnet effect attracting visits to native target
plants, especially those made by the honeybee. Indirectly, Hedysarum also increased
the visitation rate of native target plants. Due to the competition for resources mediated by
its vegetative parts, it decreased floral diversity in the neighbourhoods, which was negatively
related to the visitation rate to native target plants. Hedysarum overall also increasedthe fructification of Leopoldia target plants, even though such an increase was the result of
other indirect effects compensating for the observed negative indirect effect mediated by
the decrease of floral diversityPeer reviewedEstación Biológica de Doñana/Unidad de Excelencia Severo Ochoa. Ministerio de EconomÃa y Competitividad (España). (SEV-2012-0262
Mass flowering crops in a patchy agricultural landscape can reduce bee abundance in adjacent shrublands
Pollinator spill-over among habitats can arise in order to fulfill the pollination function and whenever differences in floral offering change over time or space. Flowering crops offer pulsed and abundant floral resources (i.e., mass flowering crops) that might promote pollinator spill-over between cultivated and adjacent natural areas. We explored pollinator patterns in the mass flowering legume crop Hedysarum coronarium and its influence on the bee pollinator communities of adjacent shrublands in a heterogeneous and patchy agricultural landscape. We studied the temporal (i.e., during vs. after mass flowering in adjacent shrublands) and spatial (i.e., inside crops, adjacent and distant shrublands during mass flowering) functional pollinator spill-over. The honeybee was highly attracted to Hedysarum crops, yet its abundance and that of other bee species visiting native plants in adjacent shrublands did not differ during and after Hedysarum mass flowering. However, at the landscape scale, the honeybee and the other bee species were less abundant in shrublands adjacent to Hedysarum crops compared to distant ones; their visitation rates showing a similar trend.
These results show that some mass flowering crops can influence pollinator patterns in the surrounding landscape by competing for generalist pollinators with native plants. The characteristics of the crop species and the landscape can modulate and determine the role of mass flowering crops as competitors or supporters of wild pollinators for adjacent natural areas.Peer reviewe
Environmental sustainability analysis of the clam (Ruditapes decussatus, Linaeus 1758) fishery in Zaboussa production area (southeastern Tunisia) using the MSC fisheries standard
The Tunisian grooved carpet clam Ruditapes decussatus (Linaeus 1758) fishery is of interest to the authorities due to its social importance and its economic contribution given the export nature of its product. Efforts have been made to ensure proper management and development of this fishery. A sustainable exploitation of the natural resource is of crucial relevance to guarantee the socio-economic role of the fishery. Therefore, sustainability should be integrated within those management measures and development actions. To analyse the sustainability level of the fishery concerning the main obstacles and actions needed to achieve it, the most recognized tool worldwide is the MSC certification program throughout its fisheries standard. The present study assesses the Zaboussa production area clam fishery using the 31 performance indicators of the 3 principles of the MSC standard for sustainable fisheries. The results of the assessment show that this fishery could be potentially considered sustainable and, therefore, certifiable though implementing an action plan to satisfy four conditions to improve research, surveillance and monitoring measures.La pêcherie tunisienne de la palourde croisée d’Europe Tunisienne Ruditapes decussatus (Linaeus 1758) présente un intérêt certain en raison de son poids social et économique et sa contribution dans la dynamique des exportations des produits de la pêche. Des efforts ont été déployés pour assurer la gestion et la promotion de cette filière. Une exploitation durable de la ressource naturelle est donc d’une importance cruciale pour garantir le rôle socio-économique de la pêche. Ainsi, la durabilité devrait impérativement être intégrée au niveau des mesures de gestion et des actions de développement. Pour analyser le niveau de durabilité d’une pêcherie en mettant en exergue les principales contraintes et les actions nécessaires pour y remédier, l’outil le plus reconnu au monde est le programme de certification MSC dont les standards sont souvent utilisés pour plusieurs pêcheries. La présente étude a évalué la pêche à pied de la palourde dans la zone de production de Zaboussa en utilisant 31 indicateurs de performance des 3 principes de la norme MSC. Les résultats de l’évaluation montrent que cette pêcherie pourrait être considérée potentiellement bien gérée et, par conséquent, éligible à cette certification à condition d’établir un plan d’action pour remplir quatre conditions ayant pour principaux thèmes la recherche et investigations de l’espèce cible et le contrôle et surveillance de l’activité de pêche
Expanded VLA Detection of 36.2 GHz Class I Methanol Masers in Sagittarius A
We report on the interferometric detection of 36.2 GHz Class I methanol
emission with the new 27-40 GHz Ka band receivers available on the Expanded
Very Large Array (EVLA). The brightness temperatures of the interferometric 36
GHz detections unambiguously indicate for the first time that the emission is
maser emission. The 36 GHz methanol masers are not co-spatial with 1720 MHz OH
masers, indicating that the two species trace different shocks. The 36 GHz and
44 GHz methanol masers, which both are collisionally pumped, do not necessarily
co-exist and may trace different methanol gas. The methanol masers seem
correlated with NH_3(3,3) density peaks. We favor an explanation in which the
36 GHz Class I methanol masers outline regions of cloud-cloud collisions,
perhaps just before the onset of the formation of individual massive stars.
The transition of the Very Large Array (VLA) to the EVLA is well under way,
and these detections demonstrate the bright future of this completely renewed
instrument.Comment: accepted to ApJ Letter
Object-based semi-automatic approach for forest structure characterization using lidar data in heterogeneous Pinus sylvestris stands.
In this paper, we present a two-stage approach for characterizing the structure of Pinus sylvestris L. stands in forests of central Spain. The first stage was to delimit forest stands using eCognition and a digital canopy height model (DCHM) derived from lidar data. The polygons were then clustered (k-means algorithm) into forest structure types based on the DCHMdata within forest stands. Hypsographs of each polygon and field data validated the separability of structure types. In the study area, 112 polygons of Pinus sylvestris were segmented and classified into five forest structure types, ranging from high dense forest canopy (850 trees ha_1 and Lorey´ s height of 17.4 m) to scarce tree coverage (60 tree ha_1 and Lorey´ s height of 9.7 m). Our results indicate that the best variables for the definition and characterization of forest structure in these forests are the median and standard deviation (S.D.), both derived from lidar data. In these forest types, lidar median height and standard deviation (S.D.) varied from 15.8 m (S.D. of 5.6 m) to 2.6 m (S.D. of 4.5 m). The present approach could have an operational application in the inventory procedure and forest management plans
Gas infall towards Sgr A* from the clumpy circumnuclear disk
We present the first large-scale mosaic performed with the Submillimeter
Array (SMA) in the Galactic center. We have produced a 25-pointing mosaic,
covering a ~2' x 2' area around Sgr A*. We have detected emission from two
high-density molecular tracers, HCN(4-3) and CS(7-6), the latter never before
reported in this region. The data have an angular resolution of 4.6" x 3.1",
and the spectral window coverage is from -180 km/s to 1490 km/s for HCN(4-3)
and from -1605 km/s to 129 km/s for CS(7-6). Both molecular tracers present a
very clumpy distribution along the circumnuclear disk (CND), and are detected
with a high signal-to-noise ratio in the southern part of the CND, while they
are weaker towards the northern part. Assuming that the clumps are as close to
the Galactic center as their projected distances, they are still dense enough
to be gravitationally stable against the tidal shear produced by the
supermassive black hole. Therefore, the CND is a non-transient structure. This
geometrical distribution of both tracers suggests that the southern part of the
CND is denser than the northern part. Also, by comparing the HCN(4-3) results
with HCN(1-0) results we can see that the northern and the southern parts of
the CND have different excitation levels, with the southern part warmer than
the northern. Finally, we compare our results with those obtained with the
detection of NH3, which traces the warmer and less dense material detected in
the inner cavity of the CND. We suggest that we are detecting the origin point
where a portion of the CND becomes destabilized and approaches the dynamical
center of the Milky Way, possibly being impacted by the southern streamer and
heated on its way inwards.Comment: 35 pages, 25 figures, 2 tables, accepted for publication in ApJ,
emulate-apj styl
Calculations of Some Doping Nanostructurations and Patterns Improving the Functionality of High-Temperature Superconductors for Bolometer Device Applications
We calculate the effects of doping nanostructuration and the patterning of thin films of
high-temperature superconductors (HTS) with the aim of optimizing their functionality as sensing
materials for resistive transition-edge bolometer devices (TES). We focus, in particular, on spatial
variations of the carrier doping into the CuO2 layers due to oxygen off-stoichiometry, (that induce,
in turn, critical temperature variations) and explore following two major cases of such structurations:
First, the random nanoscale disorder intrinsically associated to doping levels that do not maximize
the superconducting critical temperature; our studies suggest that this first simple structuration
already improves some of the bolometric operational parameters with respect to the conventional,
nonstructured HTS materials used until now. Secondly, we consider the imposition of regular
arrangements of zones with different nominal doping levels (patterning); we find that such regular
patterns may improve the bolometer performance even further. We find one design that improves,
with respect to nonstructured HTS materials, both the saturation power and the operating temperature
width by more than one order of magnitude. It also almost doubles the response of the sensor
to radiationThis work was supported by projects FIS2016-79109-P (AEI/FEDER, UE) and
AYA2016-78773-C2-2-P(AEI/FEDER,UE), by the Xunta de Galicia under grants ED431D 2017/06 and ED431C
2018/11, the ConsellerÃa de Educación Program for Development of a Strategic Grouping in Materials AeMAT
under Grant No. ED431 2018/08, Xunta de Galicia, and by the CA16218 nanocohybri COST Action. JCV thanks
the Spanish Ministry of Education for grant FPU14/00838S
Effect of adhesive application on the shear bond strength using different cementing agents in molar and premolar attachments
[Abstract] Objectives: The purpose of the study was to evaluate the effect of adhesive application on the shear bond strength (SBS) of orthodontic brackets and tubes to acid-etched human enamel when using different cementing agents. Study Design: One hundred and sixty metal attachments (80 tubes and 80 brackets) were bonded to human third molars and premolars that were randomly divided into identical groups of four: Transbond XT (XT); Wave MV Flow (WF); APC Plus System (APC); and Fuji Ortho LC (LC). For each experimental group, half of the specimens were bonded in combination with Transbond XT adhesive. After 72 h, a SBS test was performed using a universal testing machine. Statistical analysis was performed using ANOVA with Bonferroni post hoc comparisons, χ2 tests, and linear regression modeling. Adhesive remnant index scores were determined for the teeth after failure. Representative tooth surfaces from each subgroup were assessed under SEM. Results: Considering that each cement was observed, each of them showed similar SBS when the adhesive system was applied as when the adhesive was not applied. By comparing all cements together, it was noted that if an adhesive is not applied, all cements have similar values. If an adhesive is applied, cement XT, WF, and APC showed significantly higher SBS values than LC did. The tubes showed higher SBS than the brackets did in cements XT and WF with or without an adhesive, as well as APC Plus with an adhesive. Conclusions: The use of an adhesive system in bonding brackets and tubes does not influence the SBS obtained, independently of the cement
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