Dynamics and Scaling of 2D Polymers in a Dilute Solution

The breakdown of dynamical scaling for a dilute polymer solution in 2D has been suggested by Shannon and Choy [Phys. Rev. Lett. {\bf 79}, 1455 (1997)]. However, we show here both numerically and analytically that dynamical scaling holds when the finite-size dependence of the relevant dynamical quantities is properly taken into account. We carry out large-scale simulations in 2D for a polymer chain in a good solvent with full hydrodynamic interactions to verify dynamical scaling. This is achieved by novel mesoscopic simulation techniques

Surface three-body recombination in spin-polarized atomic hydrogen

We determine the rate of b+b+b surface dipole recombination for hydrogen atoms adsorbed on a 4He film. The calculation is based on the Kagan mechanism adapted to a 2(1/2-dimensional initial state. We find a rate constant Lseff=2.7(7)×10-25 cm4 s-1 at B=7.6 T and T=0.4 K, which is roughly a factor of 6 smaller than the experimental results. The magnetic-field dependence also disagrees with experiment. A scaling approach, although leading to the correct order of magnitude, is discussed and shown to be unsatisfactory. The reliability of some of our approximations is estimated. We conclude that the dipole-exchange mechanism is probably responsible for the discrepancies with experimen

Surface three-body recombination in spin-polarized atomic hydrogen

We determine the rate of b+b+b surface dipole recombination for hydrogen atoms adsorbed on a 4He film. The calculation is based on the Kagan mechanism adapted to a 2(1/2-dimensional initial state. We find a rate constant Lseff=2.7(7)×10-25 cm4 s-1 at B=7.6 T and T=0.4 K, which is roughly a factor of 6 smaller than the experimental results. The magnetic-field dependence also disagrees with experiment. A scaling approach, although leading to the correct order of magnitude, is discussed and shown to be unsatisfactory. The reliability of some of our approximations is estimated. We conclude that the dipole-exchange mechanism is probably responsible for the discrepancies with experiment

Evaluation de systèmes de culture de légumes frais à bas intrants phytosanitaires en Bretagne : l’expérimentation système DEPHY Ecophyto BREIZLEG

Les systèmes de culture légumiers actuels reposent sur l’utilisation d’intrants dont principalement les produits phytosanitaires. L’objectif du projet DEPHY EXPE Ecophyto BREIZLEG est d’évaluer des systèmes de culture de légumes frais à bas intrants phytosanitaires, en agriculture conventionnelle et biologique. Il s’agit d’une expérimentation système d’une durée de 6 ans, incluant les principales cultures légumières implantées dans le Nord de la Bretagne, à savoir : chou-fleur, artichaut et échalote. Les systèmes de culture testés ont pour objectif d’être plus durables ; pour ce faire, des leviers déjà éprouvés dans de précédents essais analytiques et relevant de l’efficience et de la substitution ont été combinés. Le bilan réalisé consiste en une évaluation ex post, à partir d’indicateurs de performances. Les résultats indiquent qu’il est possible de réduire l’IFT sans perte de rendements sur le système conventionnel bas intrant (-54 %/référence). Une diminution des rendements de 18 % est notée dans les systèmes biologiques. La combinaison des leviers a permis de conserver les performances économiques sur le système conventionnel bas intrant et de les améliorer sur les systèmes biologiques, tout en améliorant les performances environnementales. Les temps de travaux n’ont pas été pour autant augmentés. Cependant, dans les systèmes conventionnels, l’indicateur IFTsa (substance active) met en évidence l’utilisation de substances actives présentant des risques de transfert vers les eaux. La finalité de BREIZLEG est de diffuser les résultats au plus grand nombre et de transférer des outils simples d’utilisation pour les producteurs (Règles de décision).Assessment of the performance of fresh vegetable cropping systems with low Plant Protection Products inputd in Brittany: the DEPHY Ecophyto Breizleg experimentation. Current vegetable cropping systems are highly intensive and require the use of inputs, including plant protection products (PPP). These inputs are used to ensure quality products for the market and consumers. Today however, they are often responsible for environmental issues, raising questions around the sustainability of these cropping systems. The aim of DEPHY EXPE Ecophyto Breizleg was to evaluate vegetables cropping systems with low inputs, in conventional and organic agriculture. This was a six-year experiment, including the main vegetable crops grown in the North of Brittany: cauliflower, artichoke and shallot. To improve the sustainability of the tested cropping systems, proven levers already tested in previous analytical experiments, have been combined. The assessment carried out consist of an ex post evaluation, using performance indicators. The results indicate that the Treatment Frequency Index (TFI) can be reduced without any loss of yield in the conventional low input system (-54%/control). An 18% decrease in yield is noted in the organic systems. The combination of levers has maintained economic performance in the conventional low input system, and even improved it in the organic systems, while improving environmental performance. Working time was not significantly increased. However, in conventional systems, the indicator “TFI active substances (AS)” highlights the use of AS presenting a risk of transfer to the surface waters. The aim of the study is to communicate the results to multiple growers and to transfer easy-to-use tools (e.g. decision rules)

Evaluation de systèmes de culture de légumes frais à bas intrants phytosanitaires en Bretagne : l’expérimentation système DEPHY Ecophyto BREIZLEG

Ce numéro est constitué d’articles de synthèse des projets DEPHY EXPE publiés à l’occasion du colloque national DEPHY, qui s’est déroulé les 13 et 14 novembre 2018 à la Cité des Sciences et de l'Industrie (Paris). Nous vous invitons à découvrir le bilan et les enseignements des 21 projets conduits sur la période 2012-2017.Assessment of the performance of fresh vegetable cropping systems with low Plant Protection Productsinputd in Brittany: the DEPHY Ecophyto Breizleg experimentation.Current vegetable cropping systems are highly intensive and require the use of inputs, including plantprotection products (PPP). These inputs are used to ensure quality products for the market and consumers. Today however, they are often responsible for environmental issues, raising questionsaround the sustainability of these cropping systems. The aim of DEPHY EXPE Ecophyto Breizleg wasto evaluate vegetables cropping systems with low inputs, in conventional and organic agriculture. Thiswas a six-year experiment, including the main vegetable crops grown in the North of Brittany:cauliflower, artichoke and shallot. To improve the sustainability of the tested cropping systems, provenlevers already tested in previous analytical experiments, have been combined. The assessment carriedout consist of an ex post evaluation, using performance indicators. The results indicate that theTreatment Frequency Index (TFI) can be reduced without any loss of yield in the conventional low inputsystem (-54%/control). An 18% decrease in yield is noted in the organic systems. The combination oflevers has maintained economic performance in the conventional low input system, and even improvedit in the organic systems, while improving environmental performance. Working time was notsignificantly increased. However, in conventional systems, the indicator “TFI active substances (AS)”highlights the use of AS presenting a risk of transfer to the surface waters. The aim of the study is tocommunicate the results to multiple growers and to transfer easy-to-use tools (e.g. decision rules).Les systèmes de culture légumiers actuels reposent sur l’utilisation d’intrants dont principalement lesproduits phytosanitaires. L’objectif du projet DEPHY EXPE Ecophyto BREIZLEG est d’évaluer dessystèmes de culture de légumes frais à bas intrants phytosanitaires, en agriculture conventionnelle etbiologique. Il s’agit d’une expérimentation système d’une durée de 6 ans, incluant les principalescultures légumières implantées dans le Nord de la Bretagne, à savoir : chou-fleur, artichaut et échalote.Les systèmes de culture testés ont pour objectif d’être plus durables ; pour ce faire, des leviers déjàéprouvés dans de précédents essais analytiques et relevant de l’efficience et de la substitution ont étécombinés. Le bilan réalisé consiste en une évaluation ex post, à partir d’indicateurs de performances.Les résultats indiquent qu’il est possible de réduire l’IFT sans perte de rendements sur le systèmeconventionnel bas intrant (-54 %/référence). Une diminution des rendements de 18 % est notée dansles systèmes biologiques. La combinaison des leviers a permis de conserver les performanceséconomiques sur le système conventionnel bas intrant et de les améliorer sur les systèmes biologiques,tout en améliorant les performances environnementales. Les temps de travaux n’ont pas été pourautant augmentés. Cependant, dans les systèmes conventionnels, l’indicateur IFTsa (substance active)met en évidence l’utilisation de substances actives présentant des risques de transfert vers les eaux. Lafinalité de BREIZLEG est de diffuser les résultats au plus grand nombre et de transférer des outilssimples d’utilisation pour les producteurs (Règles de décision)

The C9ORF72 expansion mutation is a common cause of ALS+/-FTD in Europe and has a single founder

A massive hexanucleotide repeat expansion mutation (HREM) in C9ORF72 has recently been linked to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Here we describe the frequency, origin and stability of this mutation in ALS+/-FTD from five European cohorts (total n = 1347). Single-nucleotide polymorphisms defining the risk haplotype in linked kindreds were genotyped in cases (n = 434) and controls (n = 856). Haplotypes were analysed using PLINK and aged using DMLE+. In a London clinic cohort, the HREM was the most common mutation in familial ALS+/-FTD: C9ORF72 29/112 (26%), SOD1 27/112 (24%), TARDBP 1/112 (1%) and FUS 4/112 (4%) and detected in 13/216 (6%) of unselected sporadic ALS cases but was rare in controls (3/856, 0.3%). HREM prevalence was high for familial ALS+/-FTD throughout Europe: Belgium 19/22 (86%), Sweden 30/41 (73%), the Netherlands 10/27 (37%) and Italy 4/20 (20%). The HREM did not affect the age at onset or survival of ALS patients. Haplotype analysis identified a common founder in all 137 HREM carriers that arose around 6300 years ago. The haplotype from which the HREM arose is intrinsically unstable with an increased number of repeats (average 8, compared with 2 for controls, P<10(-8)). We conclude that the HREM has a single founder and is the most common mutation in familial and sporadic ALS in Europe