«La relation de limitation et d’exception dans le français d’aujourd’hui : excepté, sauf et hormis comme pivots d’une relation algébrique »

L’analyse des emplois prépositionnels et des emplois conjonctifs d’ “excepté”, de “sauf” et d’ “hormis” permet d’envisager les trois prépositions/conjonctions comme le pivot d’un binôme, comme la plaque tournante d’une structure bipolaire. Placées au milieu du binôme, ces prépositions sont forcées par leur sémantisme originaire dûment métaphorisé de jouer le rôle de marqueurs d’inconséquence systématique entre l’élément se trouvant à leur gauche et celui qui se trouve à leur droite. L’opposition qui surgit entre les deux éléments n’est donc pas une incompatibilité naturelle, intrinsèque, mais extrinsèque, induite. Dans la plupart des cas (emplois limitatifs), cette opposition prend la forme d’un rapport entre une « classe » et le « membre (soustrait) de la classe », ou bien entre un « tout » et une « partie » ; dans d’autres (emplois exceptifs), cette opposition se manifeste au contraire comme une attaque de front portée par un « tout » à un autre « tout ». De plus, l’inconséquence induite mise en place par la préposition/conjonction paraît, en principe, tout à fait insurmontable. Dans l’assertion « les écureuils vivent partout, sauf en Australie » (que l’on peut expliciter par « Les écureuils vivent partout, sauf [qu’ils ne vivent pas] en Australie »), la préposition semble en effet capable d’impliquer le prédicat principal avec signe inverti, et de bâtir sur une telle implication une sorte de sous énoncé qui, à la rigueur, est totalement inconséquent avec celui qui le précède (si « les écureuils ne vivent pas en Australie », le fait qu’ils « vivent partout » est faux). Néanmoins, l’analyse montre qu’alors que certaines de ces oppositions peuvent enfin être dépassées, d’autres ne le peuvent pas. C’est, respectivement, le cas des relations limitatives et des relations exceptives. La relation limitative, impliquant le rapport « tout » - « partie », permet de résoudre le conflit dans les termes d’une somme algébrique entre deux sous énoncés pourvus de différent poids informatif et de signe contraire. Les valeurs numériques des termes de la somme étant déséquilibrées, le résultat est toujours autre que zéro. La relation exceptive, au contraire, qui n’implique pas le rapport « tout » - « partie », n’est pas capable de résoudre le conflit entre deux sous énoncés pourvus du même poids informatif et en même temps de signe contraire : les valeurs numériques des termes de la somme étant symétriques et égales, le résultat sera toujours équivalent à zéro

Group 2i Isochrysidales produce characteristic alkenones reflecting sea ice distribution

AbstractAlkenones are biomarkers produced solely by algae in the order Isochrysidales that have been used to reconstruct sea surface temperature (SST) since the 1980s. However, alkenone-based SST reconstructions in the northern high latitude oceans show significant bias towards warmer temperatures in core-tops, diverge from other SST proxies in down core records, and are often accompanied by anomalously high relative abundance of the C37 tetra-unsaturated methyl alkenone (%C37:4). Elevated %C37:4 is widely interpreted as an indicator of low sea surface salinity from polar water masses, but its biological source has thus far remained elusive. Here we identify a lineage of Isochrysidales that is responsible for elevated C37:4 methyl alkenone in the northern high latitude oceans through next-generation sequencing and lab-culture experiments. This Isochrysidales lineage co-occurs widely with sea ice in marine environments and is distinct from other known marine alkenone-producers, namely Emiliania huxleyi and Gephyrocapsa oceanica. More importantly, the %C37:4 in seawater filtered particulate organic matter and surface sediments is significantly correlated with annual mean sea ice concentrations. In sediment cores from the Svalbard region, the %C37:4 concentration aligns with the Greenland temperature record and other qualitative regional sea ice records spanning the past 14 kyrs, reflecting sea ice concentrations quantitatively. Our findings imply that %C37:4 is a powerful proxy for reconstructing sea ice conditions in the high latitude oceans on thousand- and, potentially, on million-year timescales.</jats:p

Progress in the astrid sodium gas heat exchanger development

International audienceWithin the framework of the French 600MWe Advanced Sodium Technological Reactor for Industrial Demonstration project (ASTRID), a Gas Power Conversion System (PCS) based on a Brayton cycle is studied. This innovative option has never been implemented in any Sodium Fast Reactor and is mainly justified by safety and acceptance considerations in inherently eliminating the sodium-water and sodium-water-air reaction risk existing in Steam Generators with a Rankine cycle.The present work describes the progress in the design of the ASTRID innovative compact Sodium Gas Heat Exchanger (SGHE) and highlights the industrial challenges this technology raises.This paper presents the details of the design of the SGHE which allows a high thermal compactness. The main studies supporting the development are described whether on the external pressure vessel or on the compact internal heat exchanger modules.At last, the qualification process is presented through a number of qualification phases at different scales

Status of studies on ASTRID Gas Power Conversion System option

International audienceWithin the framework of the French 600 MWe Advanced Sodium Technological Reactor for Industrial Demonstration ASTRID project, two options of Power Conversion System (PCS) were studied during the conceptual design phase (2010-2015)- the use of a classical Rankine water-steam cycle, similar to the solution implemented in France in Phenix and Superphenix , but with the goal of greatly reducing the probability of occurrence and limiting the potential consequences of a sodium-water reaction; chosen as the reference during the ASTRID conceptual design phase due its high level of maturity,- an approach which has never been implemented in any Sodium Fast Reactor using a Brayton gas cycle. Its application is mainly justified by safety and acceptance considerations in inherently eliminating the sodium-water reaction risk existing with a Rankine cycle. A choice between the two options is foreseen in December 2015.This paper synthetizes the important efforts focused during the ASTRID Conceptual Design phase on the Gas Power Conversion System option, especially Nitrogen system, in order to increase its maturity level. It describes the main characteristics defined, throughout Option Selection Processes, as the reference for the further ASTRID Basic Design phase particularly on the Balance of Plant (BOP), the turbomachinery, the Sodium Gas Heat Exchangers (SGHE) as well as expected performances, operability and safety analysis

Main operation procedures for ASTRID gas power conversion system

International audienceUntil the end of the first part of the basic design phase (2017), the ASTRID project has made the choice of studying a power conversion system (PCS) based on a Brayton cycle with nitrogen as coolant. The justification is related to a safety and public acceptance considerations in order to inherently eliminate the sodium-water and sodium-water-air reactions risks. The objective of the studies engaged is to enhance the level of maturity of the gas PCS. The choice of two PCS of 300 MWe each has been made in order to limit the gas inventory, the size and length of gas pipes as well as maintaining a high level of availability. This paper presents specific operating procedures as start-up and normal shutdown of the plant, scram, rapid shutdowns, gas inventory control system, house load and grid frequency control. The current procedures of the plant and the expected regulation are presented. A focus will be made on the nitrogen inventory control which takes part of the electric power regulation provided to the grid. Finally some perspectives of remaining operation studies to be performed until the end of 2017 will be presented. Indeed the level of maturity of the gas PCS must be at a similar level than the classic water-steam Rankine cycle in order to make the best choice for the future of the sodium fast reactors in terms of better cost-effectiveness and reliability through optimization of the Brayton cycle technology and operations

Status of the astrid gas power conversion system option

International audienceWithin the framework of the French 600 MWe Advanced Sodium Technological Reactor for Industrial Demonstration project, two options of Power Conversion System (PCS) were studied during the conceptual design phase (2010-2015)- the use of a classical Rankine water-steam cycle, similar to the solution implemented in France in Phenix and Superphenix , but with the goal of greatly reducing the probability of occurrence and limiting the potential consequences of a sodium-water reaction; chosen as the reference for the ASTRID Plant Model during the conceptual design phase due its high level of maturity,- the use of a Brayton gas cycle which has never been implemented in a Sodium Fast Reactor. Its application is mainly justified by safety and public acceptance considerations in inherently eliminating the sodium-water and sodium-water-air reaction risk existing with a Rankine cycle.The ASTRID conceptual design phase period allowed to greatly increase the maturity level of a standalone Gas Power Conversion System option. It has been thus decided to lay during the 2016-2017 phase the ASTRID Gas PCS integration studies at the same level as that achieved by ASTRID Water based PCS at the end of 2015. The 2016-2017 period, in which the Gas PCS has been integrated in the overall layout of the reactor, has allowed to better specify the technical and economic implications of the selection of gas PCS taking into account all the aspects of the integration of such an option. A well-documented comparison between the two systems is therefore facilitated.This paper resumes progress in the integration of the Gas Power Conversion System in the ASTRID Reactor Plant Model. It describes the main characteristics defined particularly on the Balance of Plant (BOP), the turbomachinery, the Sodium Gas Heat Exchangers (SGHE) as well as expected performances, operability and safety analysis

Progress in the ASTRID Gas Power Conversion System development

International audienceWithin the framework of the French 600 MWe Advanced Sodium Technological Reactor for Industrial Demonstration project (ASTRID), two options of Power Conversion System (PCS) were studied during the conceptual design phase (2010-2015)- the use of a classical Rankine water-steam cycle, similar to the solution implemented in France in Phenix and Superphenix, but with the goal of greatly reducing the probability of occurrence and limiting the potential consequences of a sodium-water reaction; chosen as the reference for the ASTRID Plant Model during the conceptual design phase due its high level of maturity,- an alternative approach using a Brayton gas cycle which has never been implemented in any Sodium Fast Reactor. Its application is mainly justified by safety and acceptance considerations in inherently eliminating the sodium-water and sodium-water-air reaction risk existing with a Rankine cycle.The ASTRID conceptual design phase period allowed to greatly increase the maturity level of a standalone Gas Power Conversion System option. Thus, it has been decided to lay during the 2016-2017 phase the ASTRID Gas PCS integration studies at the same level as that achieved by the ASTRID water-steam based PCS at the end of 2015. The 2016-2017 period, in which the Gas PCS is integrated in the overall layout of the reactor, will allow to better specify the technical and economic implications of the selection of the Gas PCS taking into account all the aspects of the integration of such an option. A well-documented comparison between the two systems will be therefore facilitated.This paper resumes progress in the integration of the Gas Power Conversion System in the Astrid Reactor Plant Model. It describes the characteristics of main systems particularly the turbomachinery, the Heat Exchangers (Sodium/Gas, Gas/Gas and Gas/Water) and the Gas Inventory Management System