<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Dust particle growth in protoplanetary disks"^^ . "This thesis deals with the initial stages of planet formation in protoplanetary disks. Particular interest lies on the growth process from sub-micrometer-sized dust grains towards planetesimals of km-size. To form such large objects in protoplanetary disks, the primary coagulation mechanism has to circumvent at least two severe obstacles, namely the rapid loss of solid material due to radial inward drift and particle fragmentation due to destructive collisions with high velocities. These two hurdles together are called the \"Meter size barrier\" for particle growth, whose investigation is the main subject of this thesis. We find that the initial dust-to-gas ratio is essential for the particles to overcome the radial drift barrier, i.e. the first part of the meter size barrier. If this ratio is increased by a factor of two compared with the canonical value for the interstellar medium, planetesimals can form within short time scales in the disk. Our simulation results also suggest that the fragmentation barrier, the second part of the meter size barrier, is only overcome if implausible high critical threshold velocities for particle fragmentation are assumed. For this reason, we investigate disk environments which could favour planetesimal formation. We focus on non-turbulent regions, so-called dead zones, around the disk midplane in the presence of the ice evaporation front. We find that in this specific disk environment, particle fragmentation is no longer an obstacle and boulders of km-size can form within only a few thousand years. One major conclusion of this thesis is, therefore, that solid material can overcome the meter size barrier of particle growth and that planetesimal formation due to hit-and-stick mechanisms is in fact possible."^^ . "2008" . . . . . . . . "Frithjof"^^ . "Brauer"^^ . "Frithjof Brauer"^^ . . . . . . "Dust particle growth in protoplanetary disks (PDF)"^^ . . . "dissertation_frithjof_brauer.pdf"^^ . . . "Dust particle growth in protoplanetary disks (Other)"^^ . . . . . . "indexcodes.txt"^^ . . . "Dust particle growth in protoplanetary disks (Other)"^^ . . . . . . "lightbox.jpg"^^ . . . "Dust particle growth in protoplanetary disks (Other)"^^ . . . . . . "preview.jpg"^^ . . . "Dust particle growth in protoplanetary disks (Other)"^^ . . . . . . "medium.jpg"^^ . . . "Dust particle growth in protoplanetary disks (Other)"^^ . . . . . . "small.jpg"^^ . . "HTML Summary of #9213 \n\nDust particle growth in protoplanetary disks\n\n" . "text/html" . . . "520 Astronomie"@de . "520 Astronomy and allied sciences"@en . .