Analysis of longitudinal bunching inan FEL driven two-beam accelerator

Recent experiments [1] have explored the use of a free-electron laser (FEL) as a buncher for a microwave two-beam accelerator, and the subsequent driving of a standing-wave rf output cavity. Here we present a deeper analysis of the longitudinal dynamics of the electron bunches as they are transported from the end of the FEL and through the output cavity. In particular, we examine the effect of the transport region and cavity aperture to filter the bunched portion of the beam. [1] T. Lefevre, et. al., Phys. Rev. Lett. 84 (2000), 1188.Comment: 3 pages, 8 figures. Submitted to XX Int'l LINAC Conferenc

Heat Release of Polyurethanes Containing Potential Flame Retardants based on Boron and Phosphorus Chemistries

Using a polyurethane of methylene diphenyl isocyanate and 1,3-propane diol, several new non-halogenated aromatic boron and phosphorus flame retardants were evaluated for heat release reduction potential using the pyrolysis combustion flow calorimeter (PCFC). The polyurethanes were prepared in the presence of the potential flame retardants via solvent mixing and copolymerization methods, and were then analyzed via spectroscopic methods to determine if the flame retardant was still present in the final product. PCFC testing on the resulting products showed that the flame retardant molecule can have different effects on heat release depending upon how it is mixed into the polyurethane. Some materials showed strong effects on heat release reduction when reacted into the polyurethane during copolymerization, while others were more effective at heat release reduction when simply solvent blending into the polyurethane. The results from this screening study show that flame retardant chemical structure and its environment in the polymer (covalently bonded vs. noncovalent interactions) greatly affects flammability behavior. From the combined data, aromatic boronates were found to be very effective at reducing heat release and inhibiting melt flow during thermal decomposition, as were some aromatic phosphonic acid terephthalic acid and terephthalate derivatives

Less rain, more water in ponds: a remote sensing study of the dynamics of surface waters from 1950 to present in pastoral Sahel (Gourma region, Mali)

Changes in the flooded area of ponds in the Gourma region from 1950 to present are studied by remote sensing, in the general context of the current multi-decennial Sahel drought. The seasonal and interannual variations of the areas covered by surface water are assessed using multi-date and multi-sensor satellite images (SPOT, FORMOSAT, LANDSAT-MSS, –TM, and -ETM, CORONA, and MODIS) and aerial photographs (IGN). Water body classification is adapted to each type of spectral resolution, with or without a middle-infrared band, and each spatial resolution, using linear unmixing for mixed pixels of MODIS data. The high-frequency MODIS data document the seasonal cycle of flooded areas, with an abrupt rise early in wet season and a progressive decrease in the dry season. They also provide a base to study the inter-annual variability of the flooded areas, with sharp contrasts between dry years such as 2004 (low and early maximal area) and wetter years such as 2001 and 2002 (respectively high and late maximal area).The highest flooded area reached annually greatly depends on the volume, intensity and timing of rain events. However, the overall reduction by 20% of annual rains during the last 40 years is concomitant with an apparently paradoxical large increase in the area of surface water, starting from the 1970's and accelerating in the mid 1980's. Spectacular for the two study cases of Agoufou and Ebang Mallam, for which time series covering the 1954 to present period exist, this increase is also diagnosed at the regional scale from LANDSAT data spanning 1972–2007. It reaches 108% between September 1975 and 2002 for 91 ponds identified in central Gourma. Ponds with turbid waters and no aquatic vegetation are mostly responsible for this increase, more pronounced in the centre and north of the study zone. Possible causes of the differential changes in flooded areas are discussed in relation with the specifics in topography, soil texture and vegetation cover over the watersheds that feed each of the ponds. Changes in rain pattern and in ponds sedimentation are ruled out, and the impact of changes in land use, limited in the area, is found secondary, as opposed to what has often been advocated for in southern Sahel. Instead, major responsibility is attributed to increased runoff triggered by the lasting impact of the 1970–1980's droughts on the vegetation and on the runoff system over the shallow soils prevailing over a third of the landscape

Region-wide glacier mass balances over the Pamir-Karakoram-Himalaya during 1999-2011 (vol 7, pg 1263, 2013)

ISI Document Delivery No.: 273OY Times Cited: 0 Cited Reference Count: 1 Cited References: Gardelle J, 2013, CRYOSPHERE, V7, P1263, DOI 10.5194/tc-7-1263-2013 Gardelle, J. Berthier, E. Arnaud, Y. Kaab, A. 0 COPERNICUS GESELLSCHAFT MBH GOTTINGEN CRYOSPHEREThe recent evolution of Pamir-Karakoram- Himalaya (PKH) glaciers, widely acknowledged as valuable high-altitude as well as mid-latitude climatic indicators, remains poorly known. To estimate the regionwide glacier mass balance for 9 study sites spread from the Pamir to the Hengduan Shan (eastern Himalaya), we compared the 2000 Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) to recent (2008- 2011) DEMs derived from SPOT5 stereo imagery. During the last decade, the region-wide glacier mass balances were contrasted with moderate mass losses in the eastern and central Himalaya (−0.22±0.12mw.e. yr−1 to −0.33±0.14mw.e. yr−1) and larger losses in the western Himalaya (−0.45±0.13mw.e. yr−1). Recently reported slight mass gain or balanced mass budget of glaciers in the central Karakoram is confirmed for a larger area (+0.10±0.16mw.e. yr−1) and also observed for glaciers in the western Pamir (+0.14±0.13mw.e. yr−1). Thus, the "Karakoram anomaly" should be renamed the "Pamir- Karakoram anomaly", at least for the last decade. The overall mass balance of PKH glaciers, −0.14±0.08mw.e. yr−1, is two to three times less negative than the global average for glaciers distinct from the Greenland and Antarctic ice sheets. Together with recent studies using ICESat and GRACE data, DEM differencing confirms a contrasted pattern of glacier mass change in the PKH during the first decade of the 21st century

Amir Biglari et Marc Bonhomme (dir.), La présupposition entre théorisation et mise en discours

Cet ouvrage collectif, qui compte vingt-deux contributions en plus d’une solide présentation générale, s’intéresse à la définition et aux manifestations de la « présupposition », concept qui, malgré de nombreuses utilisations du terme en linguistique et plusieurs ouvrages de synthèse, n’est pas encore stabilisé aujourd’hui. Selon l’approche, selon l’époque, le « centre de fixation » n’est pas le même : le présupposé est condition de vérité en logique, élément de contenu implicite, complémenta..

Michelle Lecolle, Les noms collectifs humains en français : enjeux sémantiques, lexicaux et discursifs

L’ouvrage s’intéresse aux enjeux de l’utilisation de noms collectifs humains en français contemporain. Les questions abordées, telles que la finalité du regroupement, les polysémies, les organisations en microsystèmes (ex. « majorité »/« opposition »), sont en effet fondamentales pour comprendre la vie en société : communauté, conflits, hiérarchie, sont au cœur des enjeux de regroupement, parfois sous-tendus par une idéologie forte, voire par une performativité. Si des études ponctuelles sur ..

The heuristics-and-biases inventory: An open-source tool to explore individual differences in rationality

Over the last two decades, there has been a growing interest in the study of individual differences in how people’s judgments and decisions deviate from normative standards. We conducted a systematic review of heuristics-and-biases tasks for which individual differences and their reliability were measured, which resulted in 41 biases measured over 108 studies, and suggested that reliable measures are still needed for some biases described in the literature. To encourage and facilitate future studies on heuristics and biases, we centralized the task materials in an online resource: The Heuristics-and-Biases Inventory (HBI; https://sites.google.com/view/hbiproject). We discuss how this inventory might help research progress on major issues such as the structure of rationality (single vs. multiple factors) and how biases relate to cognitive ability, personality, and real-world outcomes. We also consider how future research should improve and expand the HBI

NOBEL, LE JEU DE LA DECOUVERTE SCIENTIFIQUE

Popper a rompu avec une tradition épistémologique ancienne en introduisant une dissymétrie entre vérifiabilité et réfutation. Cette conception a d'importantes répercussions sur la manière d'envisager la croissance des connaissances scientifiques et l'activité du chercheur. La vérité, qui avait pu être considérée comme un but pour la recherche scientifique, est placée hors d'atteinte. Sans indicateur évident pour marquer le terme de ses recherches, le chercheur doit alors faire, en fonction de ses motivations, un compromis entre l'exploration des théories possibles et des manières de les tester, et l'exploitation de théories qui auront été suffisamment corroborées. Si les thèses épistémologiques de Popper sont pertinentes, ce compromis exploration/exploitation au niveau du chercheur a des conséquences notables sur le développement des connaissances scientifiques et notamment, sur la fiabilité des théories acceptées. Ce sont ces conséquences que nous nous proposons d'étudier par une approche analytique, expérimentale et computationnelle, dont nous présentons ici les grandes lignes et les premiers résultats. Au delà de préoccupations purement épistémologiques, cette étude cherche à proposer un schéma générique pour l'approche d'un vaste ensemble de phénomènes d'élaboration collective et distribuée de connaissances ou d'artefacts.découverte collective, développement de la connaissance, compromis exploration/exploitation, épistemologie popperienne, knowledge managment distribué

Linking glacier annual mass balance and glacier albedo retrieved from MODIS data

Albedo is one of the variables controlling the mass balance of temperate glaciers. Multispectral imagers, such as MODerate Imaging Spectroradiometer (MODIS) on board the TERRA and AQUA satellites, provide a means to monitor glacier surface albedo. In this study, different methods to retrieve broadband glacier surface albedo from MODIS data are compared. The effect of multiple reflections due to the rugged topography and of the anisotropic reflection of snow and ice are particularly investigated. The methods are tested on the Saint Sorlin Glacier (Grandes Rousses area, French Alps). The accuracy of the retrieved albedo is estimated using both field measurements, at two automatic weather stations located on the glacier, and albedo values derived from terrestrial photographs. For summers 2008 and 2009, the root mean square deviation (RMSD) between field measurements and the broadband albedo retrieved from MODIS data at 250 m spatial resolution was found to be 0.052 or about 10% relative error. The RMSD estimated for the MOD10 daily albedo product is about three times higher. One decade (2000–2009) of MODIS data were then processed to create a time series of albedo maps of Saint Sorlin Glacier during the ablation season. The annual mass balance of Saint Sorlin Glacier was compared with the minimum albedo value (average over the whole glacier surface) observed with MODIS during the ablation season. A strong linear correlation exists between the two variables. Furthermore, the date when the average albedo of the whole glacier reaches a minimum closely corresponds to the period when the snow line is located at its highest elevation, thus when the snow line is a good indicator of the glacier equilibrium line. This indicates that this strong correlation results from the fact that the minimal average albedo values of the glacier contains considerable information regarding the relative share of areal surfaces between the ablation zone (i.e. ice with generally low albedo values) and the accumulation zone (i.e. snow with a relatively high albedo). As a consequence, the monitoring of the glacier surface albedo using MODIS data can provide a useful means to evaluate the interannual variability of the glacier mass balance. Finally, the albedo in the ablation area of Saint Sorlin Glacier does not exhibit any decreasing trend over the study period, contrasting with the results obtained on Morteratsch Glacier in the Swiss Alps