Spreading recruitment over time to cope with environmental variability

10 paginas, 3 figuras, 2 tablas.-- El PDF es la versión de autor.Seedling establishment is one of the most vulnerable life cycle stages, and a key component for the population dynamics in short-lived plants. In unpredictable environments, timing of emergence is critical for the success of plant performance, and different adaptive bet-hedging strategies have evolved to reduce the risk of failure in recruitment. In this study we describe the spatio-temporal pattern of seedling emergence (overall rate and timing) and survival in four contrasting Mediterranean habitats for Plantago coronopus, a small herb with dimorphic seeds. We then explore the importance of spreading germination within years, as well as the role of the two types of seeds from a broader temporal perspective. Populations strongly differed for all recruitment components analyzed in a given year, but this spatial differentiation diluted when a longer period was considered. Apical (smaller) seeds germinated later and in a significantly lower proportion than basal (larger) seeds. Both late emergents and seedlings from apical seeds had lower survival probability in a rainy year. However, our results suggest that in a population having the lowest production of apical seeds, late emergents coming from apical seeds may constitute a large fraction of yearly recruitment and that their performance was non-significantly different from that of early emergents over the 4-year study period. This study provides evidence of the importance of two related traits (spreading seedling emergence through time by producing dimorphic seeds) as bet-hedging strategies to cope with environmental unpredictability. This is at least partly accomplished by increasing the potential of recruitment in favourable years, instead of buffering such important process in extremely bad years.This study was funded by the Spanish Ministry of Science, under projects BOS2002-01162 and CGL2006-08507 to MBG.Peer reviewe

Design and route optimisation for an airship with onboard solar energy harvesting

Based on commercial passenger-carrying airships like LZ129 or R100, a hypothetical electric rigid framed airship including a solar cell covered surface and a lithium-ion battery is designed. The size of the battery and the coverage with solar cells are selected such that long-haul flights are possible. To simulate flight times, weather data from 2019 and time-dependent solar irradiation are used. Travel route and battery use are optimised in order to reduce flight times. For a mid-range and long-haul use case for passenger or freight transport, travel times have been calculated. Building on these results, analysis of CO2 emissions, land-use, and operating costs are carried out to reveal that depending on the use case, CO2 emissions of solar-powered airships could be as low as 1% to 5% of the emissions of a conventional aircraft at an estimated energy consumption in USD per km of 0.5% to 2.5%

Advances in the techno-economic assessment to identify the ideal plant configuration of a new biomass-to-liquid process

In 2020, the European methanol demand stood at 9.71 Million Tonnes. While it is expected that the demand continues to grow, the feedstock is currently fossil-based. Therefore, a change in the feedstock towards renewable resources such as renewable electricity and biogenic residues is needed. To evaluate their potential contribution to a sustainable energy transition, however, it is necessary to identify a process design reliant on the site-specific boundary conditions related to the local biomass potential and the availability of renewably generated electricity. While biomass-based pathways benefit from more established technologies, the addition of sustainably produced hydrogen offers the chance to boost the extent of carbon utilization dramatically. Different plant scales and setups should be deployed based on feedstock availability and transport distances. Methanol synthesis is a viable method for producing fuel since it has a high selectivity for methanol regarding direct CO2 conversion. Furthermore, methanol is a very appealing intermediate chemical due to its various applications as a fuel and feedstock for the chemical industry. To identify a site-specific setup of a sustainable methanol production plant (i.e., Grade AA), different process options are implemented, such as a pure biomass-to-liquid process with two different steam utilization strategies, a power&biomass-to-liquid process, and a power-to-liquid process. The processes are evaluated based on detailed flowsheet simulations in Aspen Plus®, and to extend the process analysis, a techno-economic evaluation methodology incorporated in the in-house software tool TEPET (Techno-Economic Process Evaluation Tool) is applied. Hence, an advantageous process design is defined and depicted for the European region. Furthermore, a correlation between economic boundary conditions, such as the electricity and heat market, and the process design will be presented. Finally, the potential contribution of the investigated power&biomass-to-liquid process to a renewable methanol economy is discussed

Magnetic control of flame stability : Application to oxygen-enriched and carbon dioxide-diluted sooting flames

International audienc

Combustion instability mitigation by magnetic fields

International audienceThe present interdisciplinary study combines electromagnetics and combustion to unveil an original and basic experiment displaying a spontaneous flame instability that is mitigated as the non-premixed sooting flame experiences a magnetic perturbation. This magnetic instability mitigation is reproduced by direct numerical simulations to be further elucidated by a flow stability analysis. A key role in the stabilization process is attributed to the momentum and thermo-chemistry coupling that the magnetic force, acting mainly on paramagnetic oxygen, contributes to sustain. The spatial local stability analysis based on the numerical simulations shows that the magnetic field tends to reduce the growth rates of small flame perturbations

Scalability strategies for automated reaction mechanism generation

Detailed modeling of complex chemical processes, like pollutant formation during combustion events, remains challenging and often intractable due to tedious and error-prone manual mechanism generation strategies. Automated mechanism generation methods seek to solve these problems but are held back by prohibitive computational costs associated with generating larger reaction mechanisms. Consequently, automated mechanism generation software such as the Reaction Mechanism Generator (RMG) must find novel ways to explore reaction spaces and thus understand the complex systems that have resisted other analysis techniques. In this contribution, we propose three scalability strategies — code optimization, algorithm heuristics, and parallel computing — that are shown to considerably improve RMG's performance as measured by mechanism generation time for three representative simulations (oxidation, pyrolysis, and combustion). The improvements create new opportunities for the detailed modeling of diverse real-world processes.Keywords: Chemical kinetics; Mechanism generation; Scalability; Parallel computin