Hal - Université Grenoble Alpes
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    Power in Firms as Political Entities: Dependency, Strategy and Resistance

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    International audienceConcomitant with the exacerbation of globalization, the firm has become a major institutional actor of economic change. However, it must be noted that the economics of the firm has been developed since the 1970s as a disciplinary subfield of economic science without paying any real attention to the concepts and practices of power. The firm is undoubtedly not only an economic but also a social and political entity. One cannot free the firm from the relations of power without missing a very substantial part of the constitutive elements of the firm, notably the struggling games and strategies of actors (firm members) who evolve in open institutional systems. Therefore, it is useful to turn to certain influent sociological and philosophical perspectives to understand power dynamics in the firm from an economic point of view. More precisely, to highlight the individual actors’ games that constitute the evolution of firms’ dynamics as complex and strategic systems, it is essential to pay particular attention to three aspects: (1) dependency; (2) strategy; and (3) resistance

    Voltammetric techniques for low-cost on-site routine analysis of thymol in the medicinal plant Ocimum gratissimum

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    International audienceThe composition of essential oils varies according to culture conditions and climate, which induces a need for simple and inexpensive characterization methods close to the place of extraction. This appears particularly important for developing countries. Herein, we develop an analytical strategy to determine the thymol content in Ocimum Gratissimum, a medicinal plant from Benin. The protocol is based on electrochemical techniques (cyclic and square wave voltammetry) implemented with a low cost potentiostat. Thymol is a phenol derivative and was directly oxidized at the electrode surface. We had to resort to submillimolar concentrations (25–300 ÎŒM) in order to minimize production of phenol oligomers that passivate the electrode. We worked first on two essential oils and realized that in one of them the thymol concentration was below our detection method. These results were confirmed by gas chromatography – mass spectrometry. Furthermore, we optimized the detection protocol to analyze an infusion made directly from the leaves of the plant. Finally, we studied whether the cost of the electrochemical cell may also be minimized by using pencil lead as working and counter electrodes

    Une importante production de bois flottants dans les cours d'eau lors d'une crue extrĂȘme (tempĂȘte Alex, octobre 2020, vallĂ©e de la Roya, France) : Estimation de la fourniture, du transport et du dĂ©pĂŽt Ă  l'aide d'un SIG

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    article intĂ©gralement accessible pendant 50 jours avec le lien suivanthttps://authors.elsevier.com/a/1i92b,3sl3xFPkInternational audienceDuring major floods, rivers erode their banks and thus recruit large wood pieces from the riparian zones. There is still a lack of knowledge about the transport of large wood, the volumes involved and the flux distribution, i.e. the large wood connectivity at catchment scale. During storm Alex (October 2020), the French Roya catchment (394 km2) experienced a paroxysmal morphogenic flood involving massive bank erosion. The riparian vegetation was largely recruited, with large wood contributing to logjams and bridge destruction. This paper presents a methodology for volumetric assessment of the large wood fluxes involved. Simple approaches are used to (i) quantify the inputs from stand density data from the national forest inventory and from source areas based on diachronic analysis of active channels highlighting the erosion of 87 ha of wooded areas; and (ii) quantify the volumes deposited via an exhaustive manual digitisation of 16,846 pieces of large wood deposited on 59 km of channels on the Roya and its tributaries. This catchment-scale, large wood connectivity analysis shows that the flood recruited and transported downstream a volume of around 14,000 m3 of large wood (uncertainty range: 7000–29,500 m3). Drone observations of the Roya River mouth in Italy and satellite images showing a raft of driftwood, several km long, drifting off the Roya River mouth in the aftermath of the flood corroborate our findings.Lors des grandes crues, les riviĂšres Ă©rodent leurs berges et recrutent ainsi de gros morceaux de bois dans les zones riveraines. Le transport de gros bois, les volumes concernĂ©s et la rĂ©partition des flux, c'est-Ă -dire la connectivitĂ© du gros bois Ă  l'Ă©chelle du bassin versant, sont encore mal connus. Lors de la tempĂȘte Alex (octobre 2020), le bassin versant français de la Roya (394 km2) a connu une crue morphogĂšne paroxystique impliquant une Ă©rosion massive des berges. La vĂ©gĂ©tation riveraine a Ă©tĂ© largement recrutĂ©e, les gros bois contribuant aux embĂącles et Ă  la destruction des ponts. Cet article prĂ©sente une mĂ©thodologie pour l'Ă©valuation volumĂ©trique des flux de gros bois impliquĂ©s. Des approches simples sont utilisĂ©es pour (i) quantifier les apports Ă  partir des donnĂ©es de densitĂ© de peuplement de l'inventaire forestier national et des zones sources basĂ©es sur l'analyse diachronique des chenaux actifs mettant en Ă©vidence l'Ă©rosion de 87 ha de zones boisĂ©es ; et (ii) quantifier les volumes dĂ©posĂ©s via une numĂ©risation manuelle exhaustive de 16 846 morceaux de gros bois dĂ©posĂ©s sur 59 km de chenaux de la Roya et de ses affluents. Cette analyse de la connectivitĂ© du gros bois Ă  l'Ă©chelle du bassin versant montre que l'inondation a recrutĂ© et transportĂ© en aval un volume d'environ 14 000 m3 de gros bois (plage d'incertitude : 7 000-29 500 m3). Des observations par drone de l'embouchure de la Roya en Italie et des images satellites montrant un radeau de bois flottĂ© de plusieurs kilomĂštres de long dĂ©rivant de l'embouchure de la Roya au lendemain de l'inondation corroborent nos rĂ©sultats

    L'expression spécifique à la couche cellulaire du facteur de transcription homéotique MADS-box PhDEF contribue à la morphogenÚse modulaire des pétales chez le pétunia

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    International audienceFloral homeotic MADS-box transcription factors ensure the correct morphogenesis of floral organs, which are organized in different cell layers deriving from distinct meristematic layers. How cells from these distinct layers acquire their respective identities and coordinate their growth to ensure normal floral organ morphogenesis is unresolved. Here, we studied petunia (Petunia x hybrida) petals that form a limb and tube through congenital fusion. We identified petunia mutants (periclinal chimeras) expressing the B-class MADS-box gene DEFICIENS in the petal epidermis or in the petal mesophyll, called wico and star, respectively. Strikingly, wico flowers form a strongly reduced tube while their limbs are almost normal, while star flowers form a normal tube but greatly reduced and unpigmented limbs, showing that petunia petal morphogenesis is highly modular. These mutants highlight the layer-specific roles of PhDEF during petal development. We explored the link between PhDEF and petal pigmentation, a well-characterized limb epidermal trait. The anthocyanin biosynthesis pathway was strongly down-regulated in star petals, including its major regulator ANTHOCYANIN2 (AN2). We established that PhDEF directly binds to the AN2 terminator in vitro and in vivo, suggesting that PhDEF might regulate AN2 expression and therefore petal epidermis pigmentation. Altogether, we show that cell layerspecific homeotic activity in petunia petals differently impacts tube and limb development, revealing the relative importance of the different cell layers in the modular architecture of petunia petals

    Detailed catalyst layer structure of Proton Exchange Membrane Fuel Cell from contrast variation small-angle neutron scattering

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    International audienceDespite significant decrease in past decades, the cost of Proton Exchange Membrane Fuel Cell (PEMFC), largely due to the rare and expensive electro-catalyst made of platinum, restrains its massive deployment. Therefore, reducing the platinum content in the electrode is the keystone of intense research efforts to increase catalyst activity or utilisation. Catalyst layer structure, and especially the water and ionomer distributions, rule the active sites availability for electrochemical reactions, and thus catalyst utilisation, because of their influence on the transport of protons and oxygen. However, the rational design of more efficient electrodes faces the lack of accurate knowledge of its complex nanoporous structure. Specifically, ionomer and water distribution are very difficult to probe with conventional electron microscopy or X-Ray techniques. This work provides quantitative and new information on electrode structure, regarding ionomer and water distributions thanks to an extensive analysis of Small Angle Neutron Scattering (SANS) profiles at different relative humidity (RH) and contrast. A 2 to 3 nm thin ionomer film spreads around the Pt/C catalyst particles while a condensed water layer appears at the catalyst/ionomer interface depending on the type of carbon support

    The extraordinary March 2022 East Antarctica “heat” wave. Part II: impacts on the Antarctic ice sheet

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    International audienceBetween March 15-19, 2022, East Antarctica experienced an exceptional heatwave with widespread 30-40° C temperature anomalies across the ice sheet. In Part I, we assessed the meteorological drivers that generated an intense atmospheric river (AR) which caused these record-shattering temperature anomalies. Here in Part II, we continue our large, collaborative study by analyzing the widespread and diverse impacts driven by the AR landfall. These impacts included widespread rain and surface melt which was recorded along coastal areas, but this was outweighed by widespread, high snowfall accumulations resulting in a largely positive surface mass balance contribution to the East Antarctic region. An analysis of the surface energy budget indicated that widespread downward longwave radiation anomalies caused by large cloud-liquid water contents along with some scattered solar radiation produced intense surface warming. Isotope measurements of the moisture were highly elevated, likely imprinting a strong signal for past climate reconstructions. The AR event attenuated cosmic ray measurements at Concordia, something previously never observed. Finally, an extratropical cyclone west of the AR landfall likely triggered the final collapse of the critically unstable Conger Ice Shelf while further reducing an already record low sea-ice extent

    The extraordinary March 2022 East Antarctica “heat” wave. Part I: observations and meteorological drivers

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    International audienceBetween March 15-19, 2022, East Antarctica experienced an exceptional heatwave with widespread 30-40° C temperature anomalies across the ice sheet. This record-shattering event saw numerous monthly temperature records being broken including a new all-time temperature record of -9.4° C on March 18 at Concordia Station despite March typically being a transition month to the Antarctic coreless winter. The driver for these temperature extremes was an intense atmospheric river advecting subtropical/mid-latitude heat and moisture deep into the Antarctic interior. The scope of the temperature records spurred a large, diverse collaborative effort to study the heatwaves meteorological drivers, impacts, and historical climate context. Here we focus on describing those temperature records along with the intricate meteorological drivers that led to the most intense atmospheric river observed over East Antarctica. These efforts describe the Rossby wave activity forced from intense tropical convection over the Indian Ocean. This led to an atmospheric river and warm conveyor belt intensification near the coastline which reinforced atmospheric blocking deep into East Antarctica. The resulting moisture flux and upper-level warm air advection eroded the typical surface temperature inversions over the ice sheet. At the peak of the heatwave, an area of 3.3 million km2 in East Antarctica exceeded previous March monthly temperature records. Despite a temperature anomaly return time of about one hundred years, a closer recurrence of such an event is possible under future climate projections. In a subsequent manuscript, we describe the various impacts this extreme event had on the East Antarctic cryosphere

    Gravity-gauge Anomaly Constraints on the Energy-momentum Tensor

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    International audienceWe derive constraints on the four dimensional energy-momentum tensor from gravitational and gauge anomalies. Our work can be considered an extension of Duff's analysis [1] to include parity-odd terms and explicit symmetry breaking. The constraints imply the absence of the parity-odd RR~R\tilde R-term in a model-independent way. Remarkably, even in the case of explicit symmetry breaking the □R\Box R-anomaly is found to be finite and unambiguous after applying the symmetry constraints. We compute mixed gravity-gauge anomalies at leading order and deduce phenomenological consequences for vector bosons associated with global chiral symmetries

    Approximations to Study the Impact of the Service Discipline in Systems with Redundancy

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    International audienceAs job redundancy has been recognized as an effective means to improve performance of large-scale computer systems, queueing systems with redundancy have been studied by various authors. Existing results include methods to compute the queue length distribution and response time but only when the service discipline is First-Come-First-Served (FCFS). For other service disciplines, such as Processor Sharing (PS), or Last-Come-First-Served (LCFS), only the stability conditions are known. In this paper we develop the first methods to approximate the queue length distribution in a queueing system with redundancy under various service disciplines. We focus on a system with exponential job sizes, i.i.d. copies, and a large number of servers. We first derive a mean field approximation that is independent of the scheduling policy. In order to study the impact of service discipline, we then derive refinements of this approximation to specific scheduling policies. In the case of Processor Sharing, we provide a pair and a triplet approximation. The pair approximation can be regarded as a refinement of the classic mean field approximation and takes the service discipline into account, while the triplet approximation further refines the pair approximation. We also develop a pair approximation for three other service disciplines: First-Come-First-Served, Limited Processor Sharing and Last-Come-First-Served. We present numerical evidence that shows that all the approximations presented in the paper are highly accurate, but that none of them are asymptotically exact (as the number of servers goes to infinity). This makes these approximations suitable to study the impact of the service discipline on the queue length distribution. Our results show that FCFS yields the shortest queue length, and that the differences are more substantial at higher loads

    Entropy Constraints for Ground Energy Optimization

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    21 pages, comments welcomeWe study the use of von Neumann entropy constraints for obtaining lower bounds on the ground energy of quantum many-body systems. Known methods for obtaining certificates on the ground energy typically use consistency of local observables and are expressed as semidefinite programming relaxations. The local marginals defined by such a relaxation do not necessarily satisfy entropy inequalities that follow from the existence of a global state. Here, we propose to add such entropy constraints that lead to tighter convex relaxations for the ground energy problem. We give analytical and numerical results illustrating the advantages of such entropy constraints. We also show limitations of the entropy constraints we construct: they are implied by doubling the number of sites in the relaxation and as a result they can at best lead to a quadratic improvement in terms of the matrix sizes of the variables. We explain the relation to a method for approximating the free energy known as the Markov Entropy Decomposition method


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    Hal - Université Grenoble Alpes is based in France
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