48 research outputs found
Interacting Brownian Motion with Resetting
We study two Brownian particles in dimension , diffusing under an
interacting resetting mechanism to a fixed position. The particles are subject
to a constant drift, which biases the Brownian particles toward each other. We
derive the steady-state distributions and study the late time relaxation
behavior to the stationary state.Comment: 13 pages, 4 figure
Mean perimeter of the convex hull of a random walk in a semi-infinite medium
We study various properties of the convex hull of a planar Brownian motion,
defined as the minimum convex polygon enclosing the trajectory, in the presence
of an infinite reflecting wall. Recently, in a Rapid Communication [Phys. Rev.
E \textbf{91}, 050104(R) (2015)], we announced that the mean perimeter of the
convex hull at time , rescaled by , is a non-monotonous function
of the initial distance to the wall. In the present article, we first give all
the details of the derivation of this mean rescaled perimeter, in particular
its value when starting from the wall and near the wall. We then determine the
physical mechanism underlying this surprising non-monotonicity of the mean
rescaled perimeter by analyzing the impact of the wall on two complementary
parts of the convex hull. Finally, we provide a further quantification of the
convex hull by determining the mean length of the portion of the reflecting
wall visited by the Brownian motion as a function of the initial distance to
the wall
Développement d'un outil pour la sélection assistée par marqueurs chez le ray-grass anglais
Forage varieties are synthetic varieties obtained by the intercross of a small number of elite genotypes selected in recurrent selection programs. This breeding method has been successful to improve forage species but its efficiency could be increased by the use of molecular markers. The goal of this study was to develop a tool for an easy genotyping of thousands of individuals with an hundred markers evenly spread across the genome in perennial ryegrass. The strategy was to design primer pairs in conserved regions on both sides of an intron for amplification and sequencing in genotypes of interest (polycross parents). Sequences were used to develop SNP markers. We developed 363 primer pairs evenly distributed across the genome with good amplification in perennial ryegrass. Moreover, these primer pairs showed an excellent transferability to other forage grass species (between 73 and 97% in fescues and 77% in cocksfoot). Polymorphism study on seven perennial ryegrass genotypes revealed one SNP every 42 bases on average. Only 38% of the SNPs were heterozygous in more than one genotype. This required to develop specific SNP markers in order to study segregating progenies within each of the seven genotypes.Les variĂ©tĂ©s fourragĂšres sont des variĂ©tĂ©s synthĂ©tiques obtenues par intercroisement en panmixie dâun certain nombre de constituants sĂ©lectionnĂ©s selon des schĂ©mas de sĂ©lection rĂ©currente. Cette stratĂ©gie dâamĂ©lioration a permis un progrĂšs gĂ©nĂ©tique indĂ©niable, mais son efficacitĂ© pourrait ĂȘtre accrue grĂące Ă lâutilisation de marqueurs molĂ©culaires. Lâobjectif de cette Ă©tude Ă©tait de dĂ©velopper un outil permettant de gĂ©notyper facilement plusieurs milliers dâindividus avec une centaine de marqueurs rĂ©partis sur lâensemble du gĂ©nome chez le ray-grass anglais. La stratĂ©gie a Ă©tĂ© de dĂ©velopper des couples dâamorces dans des rĂ©gions conservĂ©es encadrant un intron pour amplification et sĂ©quençage dans les gĂ©notypes dâintĂ©rĂȘt (parents de polycross). Les sĂ©quences ont ensuite Ă©tĂ© utilisĂ©es pour dĂ©velopper des marqueurs SNP. Au total, nous avons dĂ©veloppĂ© 363 couples dâamorces bien rĂ©partis sur le gĂ©nome et prĂ©sentant une amplification correcte chez le ray-grass anglais. De plus, ces amorces ont montrĂ© une excellente transfĂ©rabilitĂ© Ă dâautres espĂšces de graminĂ©es fourragĂšres (de 73 Ă 97 % pour les fĂ©tuques et 77 % pour le dactyle). LâĂ©tude du polymorphisme sur sept gĂ©notypes de ray-grass anglais a rĂ©vĂ©lĂ© en moyenne un SNP toutes les 42 bases. Seulement 38 % des SNP Ă©taient hĂ©tĂ©rozygotes chez plus dâun gĂ©notype, ceci a conduit Ă dĂ©velopper des marqueurs SNP spĂ©cifiques Ă chacun des sept gĂ©notypes pour lâĂ©tude de la sĂ©grĂ©gation de leurs descendances respectives