On the assimilation of altimetric data in 1D Saint-Venant river flow models

Given altimetry measurements, the identification capability of time varying inflow discharge Qin(t) and the Strickler coefficient K (defined as a power-law in h the water depth) of the 1D river Saint-Venant model is investigated. Various altimetry satellite missions provide water level elevation measurements of wide rivers, in particular the 21 future Surface Water and Ocean Topography (SWOT) mission. An original and synthetic reading of all the available information (data, wave propagation and the Manning-Strickler’s law residual) are represented on the so-called identifiability map. The latter provides in the space-time plane a comprehensive overview of the inverse problem features. Inferences based on Variational Data Assimilation (VDA) are investigated at the limit of the data-model inversion capability : relatively short river portions, relatively infrequent observations, that is inverse problems presenting a low identifiability index . The inflow discharge Qin(t) is infered simultaneously with the varying coefficient K(h). The bed level is either given or infered from a lower complexity model. The experiments and analysis are conducted for different scenarios (SWOT-like or multi-sensors-like). The scenarios differ by the observation frequency and by the identifiability index. Sensitivity analyses with respect to the observation errors and to the first guess values demonstrate the robustness of the VDA inferences. Finally this study aiming at fusing relatively sparse altimetric data and the 1D Saint-Venant river flow model highlights the spatiotemporal resolution lower limit, also the great potential in terms of discharge inference including for a single river reach

Non-linear photochemical pathways in laser induced atmospheric aerosol formation

We measured the chemical composition and the size distribution of aerosols generated by femtosecond-Terawatt laser pulses in the atmosphere using an aerosol mass spectrometer (AMS). We show that nitric acid condenses in the form of ammonium nitrate, and that oxidized volatile organics also contribute to particle growth. These two components account for two thirds and one third, respectively, of the dry laser-condensed mass. They appear in two different modes centred at 380 nm and 150 nm. The number concentration of particles between 25 and 300 nm increases by a factor of 15. Pre-existing water droplets strongly increase the oxidative properties of the laser-activated atmosphere, substantially enhancing the condensation of organics under laser illumination.Comment: 19 pages, 5 figure

La commande publique par enchère électronique inversée

La récente réforme du Code des marchés publics prévoit l’usage de procédures d’enchères électroniques inversées. Sur la base des résultats récents de la littérature économique, cet article présente les avantages et inconvénients d’une telle réforme, en terme de prix de passation, d’efficacité allocative et de sensibilité à la collusion. En analysant à la fois le contexte d’une attribution d’un seul lot ou de plusieurs, selon le critère du prix ou de l’offre économiquement la plus avantageuse, cet article met en lumière l’importance d’une définition préalable rigoureuse des règles de l’enchère électronique inversée.The last reform of the French procurement regulation has introduced the possibility of awarding the contracts by means of electronic reverse auctions. According to recent literature, this article presents the benefits and drawbacks of electronic reverse auctions, in terms of expected costs and efficiency as well as the vulnerability to collusion. We consider different environments, single or multi-unit auctions and multi-attribute auctions. This article shows that the optimal design of electronic reverse auctions is very sensitive to details. This emphasizes the necessity to carefully design these auctions

Energy relaxation and heating in the afterglow of high electric field ns-discharges in ambient air using spontaneous Raman scattering

The spatio-temporal rovibrational excitation and relaxation mechanisms of N2(X) in the post-discarge of a 10 ns high-voltage diffuse discharge are studied by Spontaneous Raman Scattering. It is shown that the vibrational excitation of nitrogen molecules remains high despite the strong electric fields applied during the discharge itself and the relaxation processes are similar to lower voltage ns discharges. The main differences with the lower field discharges are rather visible at the beginning of the discharge with a specific spatial volume distribution and a significant vibrational non-equilibrium between v=0,1 and v>1. The spatial distribution of the rovibrational excitation of the diffuse discharge is very wide radially, consistent with the sustainability of fields greater than 100 Td over nearly 8 mm during propagation. The initial rovibrational excitation is inhomogeneous along the axis. The gas temperature reaches up to about 1200 K close to the pin (85 kV, ambient air) while it remains below 500 K in the rest of the volume. It is possible to control the heating of the discharge without greatly modifying the energy transfer mechanisms by adjusting the duration of the voltage pulse. In terms of reactivity, high atomic oxygen densities seem to be very localized in the vicinity of the pin (10^24 m-3 at 1.5 mm from the pin, corresponding to about 20 % dissociation). This inhomogeneity reflects the distribution of energy in the volume of the discharge. The main effects of humidity are also studied. It amplifies the fast heating and accelerates the decay of atomic oxygen in the post-discharge. No significant acceleration of the V-T relaxation of nitrogen due to the addition of water vapour was observed for the studied conditions. A shock wave was identified which is triggered at around 500 ns

New insights on lake sediment DNA from the catchment: importance of taphonomic and analytical issues on the record quality

Over the last decade, an increasing number of studies have used lake sediment DNA to trace past landscape changes, agricultural activities or human presence. However, the processes responsible for lake sediment formation might affect DNA records via taphonomic and analytical processes. It is crucial to understand these processes to ensure reliable interpretations for “palaeo” studies. Here, we combined plant and mammal DNA metabarcoding analyses with sedimentological and geochemical analyses from three lake-catchment systems that are characterised by different erosion dynamics. The new insights derived from this approach elucidate and assess issues relating to DNA sources and transfer processes. The sources of eroded materials strongly affect the “catchment-DNA” concentration in the sediments. For instance, erosion of upper organic and organo-mineral soil horizons provides a higher amount of plant DNA in lake sediments than deep horizons, bare soils or glacial flours. Moreover, high erosion rates, along with a well-developed hydrographic network, are proposed as factors positively affecting the representation of the catchment flora. The development of open and agricultural landscapes, which favour the erosion, could thus bias the reconstructed landscape trajectory but help the record of these human activities. Regarding domestic animals, pastoral practices and animal behaviour might affect their DNA record because they control the type of source of DNA (“point” vs. “diffuse”)

Assessing changes in global fire regimes

PAGES, Past Global Changes, is funded by the Swiss Academy of Sciences and the Chinese Academy of Sciences and supported in kind by the University of Bern, Switzerland. Financial support was provided by the U.S. National Science Foundation award numbers 1916565, EAR-2011439, and EAR-2012123. Additional support was provided by the Utah Department of Natural Resources Watershed Restoration Initiative. SSS was supported by Brigham Young University Graduate Studies. MS was supported by National Science Centre, Poland (grant no. 2018/31/B/ST10/02498 and 2021/41/B/ST10/00060). JCA was supported by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 101026211. PF contributed within the framework of the FCT-funded project no. UIDB/04033/2020. SGAF acknowledges support from Trond Mohn Stiftelse (TMS) and University of Bergen for the startup grant ‘TMS2022STG03’. JMP participation in this research was supported by the Forest Research Centre, a research unit funded by Fundação para a Ciência e a Tecnologia I.P. (FCT), Portugal (UIDB/00239/2020). A.-LD acknowledge PAGES, PICS CNRS 06484 project, CNRS-INSU, Région Nouvelle-Aquitaine, University of Bordeaux DRI and INQUA for workshop support.Background The global human footprint has fundamentally altered wildfire regimes, creating serious consequences for human health, biodiversity, and climate. However, it remains difficult to project how long-term interactions among land use, management, and climate change will affect fire behavior, representing a key knowledge gap for sustainable management. We used expert assessment to combine opinions about past and future fire regimes from 99 wildfire researchers. We asked for quantitative and qualitative assessments of the frequency, type, and implications of fire regime change from the beginning of the Holocene through the year 2300. Results Respondents indicated some direct human influence on wildfire since at least ~ 12,000 years BP, though natural climate variability remained the dominant driver of fire regime change until around 5,000 years BP, for most study regions. Responses suggested a ten-fold increase in the frequency of fire regime change during the last 250 years compared with the rest of the Holocene, corresponding first with the intensification and extensification of land use and later with anthropogenic climate change. Looking to the future, fire regimes were predicted to intensify, with increases in frequency, severity, and size in all biomes except grassland ecosystems. Fire regimes showed different climate sensitivities across biomes, but the likelihood of fire regime change increased with higher warming scenarios for all biomes. Biodiversity, carbon storage, and other ecosystem services were predicted to decrease for most biomes under higher emission scenarios. We present recommendations for adaptation and mitigation under emerging fire regimes, while recognizing that management options are constrained under higher emission scenarios. Conclusion The influence of humans on wildfire regimes has increased over the last two centuries. The perspective gained from past fires should be considered in land and fire management strategies, but novel fire behavior is likely given the unprecedented human disruption of plant communities, climate, and other factors. Future fire regimes are likely to degrade key ecosystem services, unless climate change is aggressively mitigated. Expert assessment complements empirical data and modeling, providing a broader perspective of fire science to inform decision making and future research priorities.Peer reviewe

La commande publique par enchère électronique inversée

La récente réforme du Code des marchés publics prévoit l'usage de procédures d'enchères électroniques inversées. Sur la base des résultats récents de la littérature économique, cet article présente les avantages et inconvénients d'une telle réforme, en terme de prix de passation, d'efficacité allocative et de sensibilité à la collusion. En analysant à la fois le contexte d'une attribution d'un seul lot ou de plusieurs, selon le critère du prix ou de l'offre économiquement la plus avantageuse, cet article met en lumière l'importance d'une définition préalable rigoureuse des règles de l'enchère électronique inversée. [Auteurs] The last reform of the French procurement regulation has introduced the possibility of awarding the contracts by means of electronic reverse auctions. According to recent literature, this article presents the benefits and drawbacks of electronic reverse auctions, in terms of expected costs and efficiency as well as the vulnerability to collusion. We consider different environments, single or multi-unit auctions and multi-attribute auctions. This article shows that the optimal design of electronic reverse auctions is very sensitive to details. This emphasizes the necessity to carefully design these auctions. [Authors]]]> fre oai:serval.unil.ch:BIB_51F95D535A1F 2022-05-07T01:17:52Z openaire documents urnserval <oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> https://serval.unil.ch/notice/serval:BIB_51F95D535A1F Islam et économie de la dépense. Une approche anthropologique Kilani, M. info:eu-repo/semantics/article article 1988 Revue européenne des sciences sociales, vol. 82, pp. 109-119 fre https://serval.unil.ch/resource/serval:BIB_51F95D535A1F.P001/REF.pdf http://nbn-resolving.org/urn/resolver.pl?urn=urn:nbn:ch:serval-BIB_51F95D535A1F9 info:eu-repo/semantics/altIdentifier/urn/urn:nbn:ch:serval-BIB_51F95D535A1F9 info:eu-repo/semantics/publishedVersion info:eu-repo/semantics/openAccess Copying allowed only for non-profit organizations https://serval.unil.ch/disclaimer application/pdf oai:serval.unil.ch:BIB_51F9BB2E39F2 2022-05-07T01:17:52Z <oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> https://serval.unil.ch/notice/serval:BIB_51F9BB2E39F2 Le 'Pour-cent culturel Migros' en Suisse, ou quand une entreprise privée joue les pouvoirs publics Moeschler, Olivier info:eu-repo/semantics/article article 2010-04 Pouvoirs locaux. Les Cahiers de la décentralisation, vol. I, no. 84, pp. 92-94 fre oai:serval.unil.ch:BIB_51FA11095D07 2022-05-07T01:17:52Z <oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> https://serval.unil.ch/notice/serval:BIB_51FA11095D07 Tail asymptotics of generalized deflated risks with insurance applications info:doi:10.1016/j.insmatheco.2016.09.012 info:eu-repo/semantics/altIdentifier/doi/10.1016/j.insmatheco.2016.09.012 http://www.sciencedirect.com/science/article/pii/S0167668715303449 Ling, C. Peng, Z. info:eu-repo/semantics/article article 2016 Insurance: Mathematics and Economics, vol. 71, pp. 220-231 info:eu-repo/semantics/altIdentifier/pissn/0167-6687 <![CDATA[Let X and S is an element of (0, 1) be two independent risk variables. This paper investigates approximations of generalized deflated risks E{(XII)-I-kappa{SX &gt; x}} with a flexible constant kappa &gt;= 0 under extreme value theory framework. Our findings are illustrated by three applications concerning higher-order tail approximations of deflated risks as well as approximations of the Haezendonck Goovaerts and expectile risk measures. Numerical analyses show that higher-order approximations obtained in this paper significantly improve lower-order approximations