Decomposable representations and Lagrangian submanifolds of moduli spaces associated to surface groups

In this paper, we construct a Lagrangian submanifold of the moduli space associated to the fundamental group of a punctured Riemann surface (the space of representations of this fundamental group into a compact connected Lie group). This Lagrangian submanifold is obtained as the fixed-point set of an anti-symplectic involution defined on the moduli space. The notion of decomposable representation provides a geometric interpretation of this Lagrangian submanifold

Microfluidic platform for electrophysiological studies on Xenopus laevis oocytes under varying gravity levels

Voltage clamp measurements reveal important insights into the activity of membrane ion channels. While conventional voltage clamp systems are available for laboratory studies, these instruments are generally unsuitable for more rugged operating environments. In this study, we present a non-invasive microfluidic voltage clamp system developed for the use under varying gravity levels. The core component is a multilayer microfluidic device that provides an immobilisation site for Xenopus laevis oocytes on an intermediate layer, and fluid and electrical connections from either side of the cell. The configuration that we term the asymmetrical transoocyte voltage clamp (ATOVC) also permits electrical access to the cytosol of the oocyte without physical introduction of electrodes by permeabilisation of a large region of the oocyte membrane so that a defined membrane patch can be voltage clamped. The constant low level air pressure applied to the oocyte ensures stable immobilisation, which is essential for keeping the leak resistance constant even under varying gravitational forces. The ease of oocyte mounting and immobilisation combined with the robustness and complete enclosure of the fluidics system allow the use of the ATOVC under extreme environmental conditions, without the need for intervention by a human operator. Results for oocytes over-expressing the epithelial sodium channel (ENaC) obtained under laboratory conditions as well as under conditions of micro- and hypergravity demonstrate the high reproducibility and stability of the ATOVC system under distinct mechanical scenarios

Relevance of near-surface soil moisture vs. terrestrial water storage for global vegetation functioning

Soil water availability is an essential prerequisite for vegetation functioning. Vegetation takes up water from varying soil depths depending on the characteristics of its rooting system and soil moisture availability across depth. The depth of vegetation water uptake is largely unknown across large spatial scales as a consequence of sparse ground measurements. At the same time, emerging satellite-derived observations of vegetation functioning, surface soil moisture, and terrestrial water storage present an opportunity to assess the depth of vegetation water uptake globally. In this study, we characterize vegetation functioning through the near-infrared reflectance of vegetation (NIRv) and compare its relation to (i) near-surface soil moisture from the ESA's Climate Change Initiative (CCI) and (ii) total water storage from the Gravity Recovery and Climate Experiment (GRACE) mission at a monthly timescale during the growing season. The relationships are quantified through partial correlations to mitigate the influence of confounding factors such as energy- and other water-related variables. We find that vegetation functioning is generally more strongly related to near-surface soil moisture, particularly in semi-arid regions and areas with low tree cover. In contrast, in regions with high tree cover and in arid regions, the correlation with terrestrial water storage is comparable to or even higher than that of near-surface soil moisture, indicating that trees can and do make use of their deeper rooting systems to access deeper soil moisture, similar to vegetation in arid regions. At the same time, we note that this comparison is hampered by different noise levels in these satellite data streams. In line with this, an attribution analysis that examines the relative importance of soil water storage for vegetation reveals that they are controlled by (i) water availability influenced by the climate and (ii) vegetation type reflecting adaptation of the ecosystems to local water resources. Next to variations in space, the vegetation water uptake depth also varies in time. During dry periods, the relative importance of terrestrial water storage increases, highlighting the relevance of deeper water resources during rain-scarce periods. Overall, the synergistic exploitation of state-of-the-art satellite data products to disentangle the relevance of near-surface vs. terrestrial water storage for vegetation functioning can inform the representation of vegetation–water interactions in land surface models to support more accurate climate change projections.</p

Reviewing the use of resilience concepts in forest sciences

Purpose of the review Resilience is a key concept to deal with an uncertain future in forestry. In recent years, it has received increasing attention from both research and practice. However, a common understanding of what resilience means in a forestry context, and how to operationalise it is lacking. Here, we conducted a systematic review of the recent forest science literature on resilience in the forestry context, synthesising how resilience is defined and assessed. Recent findings Based on a detailed review of 255 studies, we analysed how the concepts of engineering resilience, ecological resilience, and social-ecological resilience are used in forest sciences. A clear majority of the studies applied the concept of engineering resilience, quantifying resilience as the recovery time after a disturbance. The two most used indicators for engineering resilience were basal area increment and vegetation cover, whereas ecological resilience studies frequently focus on vegetation cover and tree density. In contrast, important social-ecological resilience indicators used in the literature are socio-economic diversity and stock of natural resources. In the context of global change, we expected an increase in studies adopting the more holistic social-ecological resilience concept, but this was not the observed trend. Summary Our analysis points to the nestedness of these three resilience concepts, suggesting that they are complementary rather than contradictory. It also means that the variety of resilience approaches does not need to be an obstacle for operationalisation of the concept. We provide guidance for choosing the most suitable resilience concept and indicators based on the management, disturbance and application context

Impacts de la récurrence des incendies sur la végétation, son inflammabilité et sa combustibilité. application à la Provence cristalline (massif des Maures, Var, France)

A better understanding of the dynamic equilibrium between the vegetation and the fire recurrence is useful for Mediterranean ecosystems sustainability. The impacts of fire recurrence on vegetation, its flammability and fire behaviour, have been studied on a 50 years fire history on acidic soils in South-Eastern France (massif des Maures, Var department, France). A vegetation mosaics of woodlands and shrublands called maquis was described according to fire mosaics. Five classes of fire recurrence were defined, from zero to four fires with different time intervals. Time elapsed since last fire then the number of fires are the most important factors in observed modifications. Species and functional analyses confirm the resilience of most species which have been selected by a long fire history. However, some plant traits are negatively affected by fire recurrence, such as competitive strategy and zoochory. A resilience threshold can be estimated around three to four fires in 50 years. In high maquis, a very structuring species (Erica arborea L.) dominates the stand and decreases light and space for the other species. Its cover and long life duration entail a decrease in the functional diversity, leading to a slackening in dynamics. Flammability experiments on non-disturbed litters show significant differences between the facies. The most flammable are the high maquis and medium maquis with a high biomass, characterized by very high values of combustibility and vertical propagation ability. Fire behaviour simulations indicate contrasts between low and open formations and high and dense formations. High maquis, medium maquis and cork-oak woodlands on maquis lead to high fire intensity and rate of spread. Fire recurrence mainly impacts on vegetation structure and subsequently fire behaviour. These data are useful to predict the relationships between fire and vegetation in a climatic and disturbance change context.Une meilleure compréhension de l'équilibre dynamique entre la végétation et la récurrence des incendies est essentielle pour la gestion durable des écosystèmes méditerranéens. Les impacts de la récurrence des incendies sur la végétation, l'inflammabilité et la combustibilité, ont été étudiés sur un intervalle d'une cinquantaine d'années sur substrat siliceux en région méditerranéenne française (massif des Maures, Var). Une mosaïque de formations végétales a été décrite en réponse à une mosaïque de feux. Cinq modalités de récurrence ont été définies, de zéro à quatre feux selon des intervalles de temps différents entre ces feux. Le temps écoulé depuis le dernier feu puis le nombre de feux sont les facteurs les plus importants dans les modifications observées. Les analyses floristiques réalisées sous un angle spécifique et fonctionnel confirment la résilience de la plupart des espèces sélectionnées par une longue histoire du feu. Toutefois, certains traits de vie sont négativement affectés par la récurrence des feux, telles que la stratégie compétitive et la zoochorie. En outre, un seuil de résilience peut être fixé autour de trois à quatre feux en 50 ans. Dans les maquis hauts, une espèce fortement structurante (Erica arborea L.) domine le peuplement en limitant luminosité et espace pour les autres espèces. Son recouvrement dense et sa longue durée de vie entraînent une diminution de la diversité fonctionnelle, et un ralentissement dans la dynamique. Les expérimentations d'inflammabilité réalisées sur des litières non perturbées ont montré que les faciès les plus inflammables sont les maquis hauts et moyens arborés à forte biomasse présentant une combustibilité et une capacité de propagation verticale très élevées. Les simulations de comportement de feu ont indiqué des contrastes entre les formations basses et ouvertes et les formations hautes et fermées, avec de fortes intensités et vitesses de propagation du feu pour les maquis hauts, moyens arborés et les suberaies sur maquis. Ainsi, la récurrence des incendies affecte principalement la structure de la végétation et donc le risque d'incendie futur. Ces données sont importantes pour mieux appréhender les interrelations entre feu et végétation dans un contexte de changement climatique et des régimes de perturbations

Isotopic power materials development. Quarterly progress report for period ending March 31, 1976

The second in a series of quarterly reports for Technology and Space Applications materials programs conducted by the Metals and Ceramics Division of Oak Ridge National Laboratory for the Nuclear Research and Applications Division of ERDA is presented. These quarterly reports replace the monthly and annual reports previously issued on this work. The areas of research covered include high-temperature alloys for space isotopic heat sources, physical and mechanical metallurgy of heat source containment materials, isotope Brayton system materials support, and space nuclear flight systems hardware. (TFD

Isotopic power materials development. Quarterly progress report for period ending June 30, 1976

Research progress is reported on: (1) high-temperature alloys for space isotopic heat sources; (2) physical and mechanical metallurgy of heat-source containment materials; (3) isotope brayton system materials support; and (4) space nuclear flight systems hardware. (TFD

Isotopic power materials development. Quarterly progress report for period ending December 31, 1976

Research progress is reported on: (1) high-temperature alloys for space isotopic heat sources; (2) physical and mechanical metallurgy of heat source containment materials; (3) /sup 144/Cm fuel development; (4) terrestrial radioisotope applications; (5) selenide isotope generator system support; (6) isotope Brayton system materials support; and (7) space nuclear flight systems hardware. (TFD