Exact calculations for false discovery proportion with application to least favorable configurations

In a context of multiple hypothesis testing, we provide several new exact calculations related to the false discovery proportion (FDP) of step-up and step-down procedures. For step-up procedures, we show that the number of erroneous rejections conditionally on the rejection number is simply a binomial variable, which leads to explicit computations of the c.d.f., the {$s$-th} moment and the mean of the FDP, the latter corresponding to the false discovery rate (FDR). For step-down procedures, we derive what is to our knowledge the first explicit formula for the FDR valid for any alternative c.d.f. of the $p$-values. We also derive explicit computations of the power for both step-up and step-down procedures. These formulas are "explicit" in the sense that they only involve the parameters of the model and the c.d.f. of the order statistics of i.i.d. uniform variables. The $p$-values are assumed either independent or coming from an equicorrelated multivariate normal model and an additional mixture model for the true/false hypotheses is used. This new approach is used to investigate new results which are of interest in their own right, related to least/most favorable configurations for the FDR and the variance of the FDP

Stratégies de prévention de la maladie de Gumboro dans les élevages semi-industriels de la région de Dakar, Sénégal

La maladie de Gumboro est une maladie virale très contagieuse qui affecte le jeune poulet. Elle est répandue de manière universelle et les pertes directes et indirectes induites la placent en tête de liste des maladies contagieuses d'importance économique. Sa lutte, basée sur des mesures prophylactiques à la fois hygiéniques et vaccinales, s'avère complexe. Cette maladie, après une flambée épizootique en 1998 au Sénégal, se maintient à des taux de prévalence élevés et sa maîtrise constitue une priorité pour le développement de l'aviculture sénégalaise. L'auteur présente l'aviculture au Sénégal et la maladie de Gumboro avant d'exposer une étude des stratégies de prévention de cette maladie dans les élevages semi-industriels de poulets de chair de la région de Dakar. Les pratiques hygiéniques et vaccinales ont été analysées grâce à un questionnaire dans 29 élevages ; parallèlement, un suivi sérologique a été réalisé afin de suivre la cinétique des anticorps et évaluer la protection des bandes au cours de la durée d'élevage (10 individus prélevés à 1 jour, à la primovaccination, au rappel et à 35 jours d'âge). Il apparaît que les mesures de décontamination ne sont pas maîtrisées et que les bandes sont particulièrement exposées au virus sauvage, du fait du non respect de la conduite en bande unique, de la présence de volailles traditionnelles et de barrières hygiéniques spatiales très insuffisantes. D'autres part, la protection vaccinale des bandes n'est jamais continue ; l'échec quasi systèmatique des primovaccinations semble lié à l'inhibition du virus vaccinal par les anticorps maternels. D'autres facteurs d'échec de la vaccination sont mis en cause, comme la qualité variable de l'eau ou la maîtrise technique d'administration, ce qui conduit l'auteur à proposer des investigations supplémentaires afin de hiérarchiser leur importance relative

Le droit des contrats : outil de sécurité alimentaire dans le commerce et les investissements internationaux ?

Chapitre de l’ouvrage collectif Penser une démocratie alimentaire Volume II – Proposition Lascaux entre ressources naturelles et besoins fondamentaux, F. Collart Dutilleul et T. Bréger (dir), Inida, San José, 2014, pp. 357-364International audienceLa sécurité alimentaire des pays du Nord n’est pas celle des pays du Sud. Aux objectifs de diversité, de qualité des produits, d’information et de santé des consommateurs des premiers, répondent des préoccupations vitales d’autosuffisance alimentaire des seconds, traversant la propriété des terres, leurs cultures, l’approvisionnement en produits agroalimentaires et en intrants. Dès lors, les échanges commerciaux et les investissements internationaux dont les objets sont ces biens particuliers que sont la terre agricole et l’aliment, répondent à des objectifs inéluctablement différents, dont on sait qu’ils ne permettent pas pour l’essentiel, d’assurer l’effectivité du droit à l’alimentation, droit subjectif pourtant fondamental. Par ailleurs, au-delà de cette préoccupation essentielle, il peut s’avérer intéressant de s’interroger sur les outils contractuels qui régissent ces rapports économiques. S’il est bien un domaine dans lequel le sacro-saint principe de sécurité juridique n’est pas ébranlé, c’est celui des échanges agroalimentaires internationaux. Cependant, c’est paradoxalement à cet endroit qu’il est utile d’engager quelques réflexions

On least favorable configurations for step-up-down tests

This paper investigates an open issue related to false discovery rate (FDR) control of step-up-down (SUD) multiple testing procedures. It has been established in earlier literature that for this type of procedure, under some broad conditions, and in an asymptotical sense, the FDR is maximum when the signal strength under the alternative is maximum. In other words, so-called "Dirac uniform configurations" are asymptotically {\em least favorable} in this setting. It is known that this property also holds in a non-asymptotical sense (for any finite number of hypotheses), for the two extreme versions of SUD procedures, namely step-up and step-down (with extra conditions for the step-down case). It is therefore very natural to conjecture that this non-asymptotical {\em least favorable configuration} property could more generally be true for all "intermediate" forms of SUD procedures. We prove that this is, somewhat surprisingly, not the case. The argument is based on the exact calculations proposed earlier by Roquain and Villers (2011), that we extend here by generalizing Steck's recursion to the case of two populations. Secondly, we quantify the magnitude of this phenomenon by providing a nonasymptotic upper-bound and explicit vanishing rates as a function of the total number of hypotheses

Two-photon Imaging of Microglial Processes' Attraction Toward ATP or Serotonin in Acute Brain Slices

International audienceMicroglial cells are resident innate immune cells of the brain that constantly scan their environment with their long processes and, upon disruption of homeostasis, undergo rapid morphological changes. For example, a laser lesion induces in a few minutes an oriented growth of microglial processes, also called "directional motility", toward the site of injury. A similar effect can be obtained by delivering locally ATP or serotonin (5-hydroxytryptamine [5-HT]). In this article, we describe a protocol to induce a directional growth of microglial processes toward a local application of ATP or 5-HT in acute brain slices of young and adult mice and to image this attraction over time by multiphoton microscopy. A simple method of quantification with free and open-source image analysis software is proposed. A challenge that still characterizes acute brain slices is the limited time, decreasing with age, during which the cells remain in a physiological state. This protocol, thus, highlights some technical improvements (medium, air-liquid interface chamber, imaging chamber with a double perfusion) aimed at optimizing the viability of microglial cells over several hours, especially in slices from adult mice

Fanny Copeland and the geographical imagination

Raised in Scotland, married and divorced in the English south, an adopted Slovene, Fanny Copeland (1872 – 1970) occupied the intersection of a number of complex spatial and temporal conjunctures. A Slavophile, she played a part in the formation of what subsequently became the Kingdom of Yugoslavia that emerged from the First World War. Living in Ljubljana, she facilitated the first ‘foreign visit’ (in 1932) of the newly formed Le Play Society (a precursor of the Institute of British Geographers) and guided its studies of Solčava (a then ‘remote’ Alpine valley system) which, led by Dudley Stamp and commended by Halford Mackinder, were subsequently hailed as a model for regional studies elsewhere. Arrested by the Gestapo and interned in Italy during the Second World War, she eventually returned to a socialist Yugoslavia, a celebrated figure. An accomplished musician, linguist, and mountaineer, she became an authority on (and populist for) the Julian Alps and was instrumental in the establishment of the Triglav National Park. Copeland’s role as participant observer (and protagonist) enriches our understanding of the particularities of her time and place and illuminates some inter-war relationships within G/geography, inside and outside the academy, suggesting their relative autonomy in the production of geographical knowledge

Accelerated global glacier mass loss in the early twenty-first century

Glaciers distinct from the Greenland and Antarctic ice sheets are shrinking rapidly, altering regional hydrology1, raising global sea level2 and elevating natural hazards3. Yet, owing to the scarcity of constrained mass loss observations, glacier evolution during the satellite era is known only partially, as a geographic and temporal patchwork4,5. Here we reveal the accelerated, albeit contrasting, patterns of glacier mass loss during the early twenty-first century. Using largely untapped satellite archives, we chart surface elevation changes at a high spatiotemporal resolution over all of Earth’s glaciers. We extensively validate our estimates against independent, high-precision measurements and present a globally complete and consistent estimate of glacier mass change. We show that during 2000–2019, glaciers lost a mass of 267 ± 16 gigatonnes per year, equivalent to 21 ± 3 per cent of the observed sea-level rise6. We identify a mass loss acceleration of 48 ± 16 gigatonnes per year per decade, explaining 6 to 19 per cent of the observed acceleration of sea-level rise. Particularly, thinning rates of glaciers outside ice sheet peripheries doubled over the past two decades. Glaciers currently lose more mass, and at similar or larger acceleration rates, than the Greenland or Antarctic ice sheets taken separately7,8,9. By uncovering the patterns of mass change in many regions, we find contrasting glacier fluctuations that agree with the decadal variability in precipitation and temperature. These include a North Atlantic anomaly of decelerated mass loss, a strongly accelerated loss from northwestern American glaciers, and the apparent end of the Karakoram anomaly of mass gain10. We anticipate our highly resolved estimates to advance the understanding of drivers that govern the distribution of glacier change, and to extend our capabilities of predicting these changes at all scales. Predictions robustly benchmarked against observations are critically needed to design adaptive policies for the local- and regional-scale management of water resources and cryospheric risks, as well as for the global-scale mitigation of sea-level rise.ISSN:0028-0836ISSN:1476-468

Glacial and geomorphic effects of a supraglacial lake drainage and outburst event, Everest region, Nepal Himalaya

A set of supraglacial ponds filled rapidly between April and July 2017 on Changri Shar Glacier in the Everest region of Nepal, coalescing into a similar to 180 000 m(2) lake before sudden and complete drainage through Changri Shar and Khumbu glaciers (15-17 July). We use PlanetScope and Pleiades satellite orthoimagery to document the system's evolution over its very short filling period and to assess the glacial and proglacial effects of the outburst flood. We also use high-resolution stereo digital elevation models (DEMs) to complete a detailed analysis of the event's glacial and geomorphic effects. Finally, we use discharge records at a stream gauge 4 km downstream to refine our interpretation of the chronology and magnitude of the outburst. We infer largely subsurface drainage through both of the glaciers located on its flow path, and efficient drainage through the lower portion of Khumbu Glacier. The drainage and subsequent outburst of 1.36 +/- 0.19 x 10(6) m(3) of impounded water had a clear geomorphic impact on glacial and proglacial topography, including deep incision and landsliding along the Changri Nup proglacial stream, the collapse of shallow englacial conduits near the Khumbu terminus and extensive, enhanced bank erosion at least as far as 11 km downstream below Khumbu Glacier. These sudden changes destroyed major trails in three locations, demonstrating the potential hazard that short-lived, relatively small glacial lakes pose