David Hockney: The Yosemite Suite

Acidulées et singulières. Tels sont les premiers qualificatifs qui viennent à l’esprit lorsque l’on regarde les œuvres de la série Yosemite Suite de David Hockney. Le catalogue éponyme est édité à l’occasion de l’exposition à la Galerie Lelong (Paris, 20 mai-13 juillet 2017) et le lecteur avisé fera le lien avec la rétrospective consacrée à l’œuvre de l’artiste au Centre Pompidou (21 juin-23 octobre 2017). Avec un format vertical, l’artiste peint inlassablement des arbres jaunes et vert acide..

A l’Ouest, toute ! Travailleuses de Bretagne et d’ailleurs (sous la dir. de Fabienne Dumont, Sylvie Ungauer)

« A l’Ouest, toute ! » est le résultat d’un travail initié par Fabienne Dumont et Sylvie Ungauer, toutes deux enseignantes à l’Ecole supérieure d’art de Bretagne – la première à Quimper et la seconde à Brest. Il fallut trois ans et la participation d’artistes et d’étudiants dans le cadre de différents ateliers, projections publiques, conférences, workshops et séminaires, pour faire évoluer et aboutir la réflexion des participants. Des artistes comme Margaret Harrison, Marie Preston ou Mierle ..

Valérie Mréjen : images en quête d’histoires

Une enveloppe cartonnée. A l’intérieur, trente-six photos en noir et blanc. Photos de famille, instants volés, portraits figés, sourires, solennité, exotisme ou familiarité. Des photos souvenirs qui pourraient être les nôtres et qui suscitent tour à tour l’amusement ou la nostalgie. Au dos, chaque photo est divisée en deux parties, comme une carte postale. En haut de chaque partie, un titre devancé d’un numéro. Et sous chaque titre une phrase. On comprend alors qu’il s’agit de remettre les ph..

Automated fragment identification for electron ionisation mass spectrometry: application to atmospheric measurements of halocarbons

Non-target screening consists in searching a sample for all present substances, suspected or unknown, with very little prior knowledge about the sample. This approach has been introduced more than a decade ago in the field of water analysis, together with dedicated compound identification tools, but is still very scarce for indoor and atmospheric trace gas measurements, despite the clear need for a better understanding of the atmospheric trace gas composition.For a systematic detection of emerging trace gases in the atmosphere, a new and powerful analytical method is gas chromatography (GC) of preconcentrated samples, followed by electron ionisation, high resolution mass spectrometry (EI-HRMS). In this work, we present data analysis tools to enable automated fragment formula annotation for unknown compounds measured by GC-EI-HRMS. Based on co-eluting mass/charge fragments, we developed an innovative data analysis method to reliably reconstruct the chemical formulae of the fragments, using efficient combinatorics and graph theory. The method does not require the presence of the molecular ion, which is absent in ~40% of EI spectra. Our method has been trained and validated on \textgreater50 halocarbons and hydrocarbons, with 3 to 20 atoms and molar masses of 30 to 330 g mol-1, measured with a mass resolution of approx.~3500. For 90% of the compounds, more than 90% of the annotated fragment formulae are correct. Cases of wrong identification can be attributed to the scarcity of detected fragments per compound or the lack of isotopic constraint (no minor isotopocule detected).Our method enables to reconstruct most probable chemical formulae independently from spectral databases. Therefore, it demonstrates the suitability of EI-HRMS data for non-target analysis and paves the way for the identification of substances for which no EI mass spectrum is registered in databases. We illustrate the performances of our method for atmospheric trace gases and suggest that it may be well suited for many other types of samples. The L-GPL licenced Python code is released under the name ALPINAC for ALgorithmic Process for Identification of Non-targeted Atmospheric Compounds.Comment: Journal of Cheminformatics, Chemistry Central Ltd. and BioMed Central, 202

Reduction of radiation biases by incorporating the missing cloud variability by means of downscaling techniques: a study using the 3-D MoCaRT model

Handling complexity to the smallest detail in atmospheric radiative transfer models is unfeasible in practice. On the one hand, the properties of the interacting medium, i.e., the atmosphere and the surface, are only available at a limited spatial resolution. On the other hand, the computational cost of accurate radiation models accounting for three-dimensional heterogeneous media are prohibitive for some applications, especially for climate modelling and operational remote-sensing algorithms. Hence, it is still common practice to use simplified models for atmospheric radiation applications. <br><br> Three-dimensional radiation models can deal with complex scenarios providing an accurate solution to the radiative transfer. In contrast, one-dimensional models are computationally more efficient, but introduce biases to the radiation results. <br><br> With the help of stochastic models that consider the multi-fractal nature of clouds, it is possible to scale cloud properties given at a coarse spatial resolution down to a higher resolution. Performing the radiative transfer within the cloud fields at higher spatial resolution noticeably helps to improve the radiation results. <br><br> We present a new Monte Carlo model, MoCaRT, that computes the radiative transfer in three-dimensional inhomogeneous atmospheres. The MoCaRT model is validated by comparison with the consensus results of the Intercomparison of Three-Dimensional Radiation Codes (I3RC) project. <br><br> In the framework of this paper, we aim at characterising cloud heterogeneity effects on radiances and broadband fluxes, namely: the errors due to unresolved variability (the so-called plane parallel homogeneous, PPH, bias) and the errors due to the neglect of transversal photon displacements (independent pixel approximation, IPA, bias). First, we study the effect of the missing cloud variability on reflectivities. We will show that the generation of subscale variability by means of stochastic methods greatly reduce or nearly eliminate the reflectivity biases. Secondly, three-dimensional broadband fluxes in the presence of realistic inhomogeneous cloud fields sampled at high spatial resolutions are calculated and compared to their one-dimensional counterparts at coarser resolutions. We found that one-dimensional calculations at coarsely resolved cloudy atmospheres systematically overestimate broadband reflected and absorbed fluxes and underestimate transmitted ones

A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event stratigraphy

Due to their outstanding resolution and well-constrained chronologies, Greenland ice-core records provide a master record of past climatic changes throughout the Last Interglacial–Glacial cycle in the North Atlantic region. As part of the INTIMATE (INTegration of Ice-core, MArine and TErrestrial records) project, protocols have been proposed to ensure consistent and robust correlation between different records of past climate. A key element of these protocols has been the formal definition and ordinal numbering of the sequence of Greenland Stadials (GS) and Greenland Interstadials (GI) within the most recent glacial period. The GS and GI periods are the Greenland expressions of the characteristic Dansgaard–Oeschger events that represent cold and warm phases of the North Atlantic region, respectively. We present here a more detailed and extended GS/GI template for the whole of the Last Glacial period. It is based on a synchronization of the NGRIP, GRIP, and GISP2 ice-core records that allows the parallel analysis of all three records on a common time scale. The boundaries of the GS and GI periods are defined based on a combination of stable-oxygen isotope ratios of the ice (δ18O, reflecting mainly local temperature) and calcium ion concentrations (reflecting mainly atmospheric dust loading) measured in the ice. The data not only resolve the well-known sequence of Dansgaard–Oeschger events that were first defined and numbered in the ice-core records more than two decades ago, but also better resolve a number of short-lived climatic oscillations, some defined here for the first time. Using this revised scheme, we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the Last Glacial period that are represented in the Greenland ice records. The final product constitutes an extended and better resolved Greenland stratotype sequence, against which other proxy records can be compared and correlated. It also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations

A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event stratigraphy

Due to their outstanding resolution and well-constrained chronologies, Greenland ice-core records provide a master record of past climatic changes throughout the Last Interglacial–Glacial cycle in the North Atlantic region. As part of the INTIMATE (INTegration of Ice-core, MArine and TErrestrial records) project, protocols have been proposed to ensure consistent and robust correlation between different records of past climate. A key element of these protocols has been the formal definition and ordinal numbering of the sequence of Greenland Stadials (GS) and Greenland Interstadials (GI) within the most recent glacial period. The GS and GI periods are the Greenland expressions of the characteristic Dansgaard–Oeschger events that represent cold and warm phases of the North Atlantic region, respectively. We present here a more detailed and extended GS/GI template for the whole of the Last Glacial period. It is based on a synchronization of the NGRIP, GRIP, and GISP2 ice-core records that allows the parallel analysis of all three records on a common time scale. The boundaries of the GS and GI periods are defined based on a combination of stable-oxygen isotope ratios of the ice (δ18O, reflecting mainly local temperature) and calcium ion concentrations (reflecting mainly atmospheric dust loading) measured in the ice. The data not only resolve the well-known sequence of Dansgaard–Oeschger events that were first defined and numbered in the ice-core records more than two decades ago, but also better resolve a number of short-lived climatic oscillations, some defined here for the first time. Using this revised scheme, we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the Last Glacial period that are represented in the Greenland ice records. The final product constitutes an extended and better resolved Greenland stratotype sequence, against which other proxy records can be compared and correlated. It also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations

Atmospheric histories and emissions of chlorofluorocarbons CFC-13 (CClF3), ΣCFC-114 (C2Cl2F4), and CFC-115 (C2ClF5)

Based on observations of the chlorofluorocarbons CFC-13 (chlorotrifluoromethane), ΣCFC-114 (combined measurement of both isomers of dichlorotetrafluoroethane), and CFC-115 (chloropentafluoroethane) in atmospheric and firn samples, we reconstruct records of their tropospheric histories spanning nearly 8 decades. These compounds were measured in polar firn air samples, in ambient air archived in canisters, and in situ at the AGAGE (Advanced Global Atmospheric Gases Experiment) network and affiliated sites. Global emissions to the atmosphere are derived from these observations using an inversion based on a 12-box atmospheric transport model. For CFC-13, we provide the first comprehensive global analysis. This compound increased monotonically from its first appearance in the atmosphere in the late 1950s to a mean global abundance of 3.18 ppt (dry-air mole fraction in parts per trillion, pmol mol1) in 2016. Its growth rate has decreased since the mid-1980s but has remained at a surprisingly high mean level of 0.02 ppt yr⁻¹ since 2000, resulting in a continuing growth of CFC-13 in the atmosphere. ΣCFC-114 increased from its appearance in the 1950s to a maximum of 16.6 ppt in the early 2000s and has since slightly declined to 16.3 ppt in 2016. CFC-115 increased monotonically from its first appearance in the 1960s and reached a global mean mole fraction of 8.49 ppt in 2016. Growth rates of all three compounds over the past years are significantly larger than would be expected from zero emissions. Under the assumption of unchanging lifetimes and atmospheric transport patterns, we derive global emissions from our measurements, which have remained unexpectedly high in recent years: mean yearly emissions for the last decade (2007–2016) of CFC-13 are at 0.48 ± 0.15 kt yr⁻¹ (> 15 % of past peak emissions), of ΣCFC-114 at 1.90 ± 0.84 kt yr⁻¹ (∼ 10 % of peak emissions), and of CFC-115 at 0.80 ± 0.50 kt yr⁻¹(> 5 % of peak emissions). Mean yearly emissions of CFC-115 for 2015–2016 are 1.14 ± 0.50 kt yr⁻¹ and have doubled compared to the 2007–2010 minimum. We find CFC-13 emissions from aluminum smelters but if extrapolated to global emissions, they cannot account for the lingering global emissions determined from the atmospheric observations. We find impurities of CFC-115 in the refrigerant HFC-125 (CHF₂CF₃) but if extrapolated to global emissions, they can neither account for the lingering global CFC-115 emissions determined from the atmospheric observations nor for their recent increases. We also conduct regional inversions for the years 2012–2016 for the northeastern Asian area using observations from the Korean AGAGE site at Gosan and find significant emissions for ΣCFC-114 and CFC-115, suggesting that a large fraction of their global emissions currently occur in northeastern Asia and more specifically on the Chinese mainland

Pièces chantées écrites en breton vannetais au début du XXème siècle : processus de traditionalisation

The study of the process of traditionalization of songs, that is to say the various steps that make the creation of an author a piece of musical heritage common to a population, is based on a corpus of two hundred and seventy songs composed in the first half of the 20th century in Brittany. At this time, a strong impetus of creation crosses the country and many authorsstrive to renew the musical heritage, especially in the country of Vannes, geographical area of this study. The first part of this thesis studies this corpus by seeking to better understand the main authors of these songs, detailing the themes they cover and the historical context in which they evolve, as well as examining the literary and musical characteristics of their songs. Then comes the question of the mediation of the songs through various means, both oral and written, and in particular the press, so that it reaches the public for whom it is intended. The second part is to observe the fate of these songs a century later. This work is based on counting and listening to numerous collections and the reading of songbooks to determine which pieces survived their creation or on the contrary have disappeared or never even existed. It aims to try to understand what criteria can explain this phenomenon. To this census is added the analysis of ten cases of study with the detailedobservation of all collected collections of these examples, completed by interviews with several singers in order to perceive their feelings by listening to these ten songs. During this work, several constants were noted that allow to better understand the different transformations that a song undergoes to become traditional. The creation of a man then becomes collective.L’étude du processus de traditionalisation des chansons, c’est à dire les différentes étapes qui font de la création d’un auteur un élément de patrimoine musical commun à une population, se base sur un corpus de deux-cent-soixante-dix chants composés dans la première moitié du 20ème siècle en Bretagne. A cette époque, un fort élan de création traverse le pays et de nombreux auteurs s’attachent à renouveler le patrimoine musical, notamment dans le pays vannetais, secteur géographique de cette étude. La première partie de cette thèse étudie donc ce corpus en cherchant à mieux connaître les principaux auteurs de ces chants, en détaillant les thèmes qu’ils abordent et le contexte historique dans lesquels ilsévoluent ainsi qu’en examinant les caractéristiques littéraires et musicales de leurs oeuvres. Vient ensuite la question de la médiation de l’oeuvre par le biais de différents moyens tant oraux qu’écrits et notamment la presse afin qu’elle atteigne le public à laquelle elle est destinée. La seconde partie consiste à observer le devenir de ces chants un siècle plus tard. Ce travail se base sur le recensement et l’écoute de très nombreux collectages et la lecture de cahiers de chants pour déterminer quelles pièces ont survécu à leur création ou au contraire ont disparu ou n’ont même jamais existé. Il vise à essayer de comprendre quels critères permettent d’expliquer ce phénomène. À ce recensement s’ajoute l’analyse de dixcas d’étude avec l’observation détaillée de tous les collectages trouvés de ces exemples, complétée par des entretiens avec plusieurs chanteuses et chanteurs afin de percevoir leur ressenti à l’écoute de ces dix chants. Lors de ce travail, plusieurs constantes ont été relevées qui permettent de mieux appréhender les différentes transformations que subit un chant pour devenir traditionnel. La création d’un homme devient alors collective