Ehrlich-Schwoebel barrier controlled slope selection in epitaxial growth

We examine the step dynamics in a 1+1 dimensional model of epitaxial growth based on the BCF-theory. The model takes analytically into account the diffusion of adatoms, an incorporation mechanism and an Ehrlich-Schwoebel barrier at step edges. We find that the formation of mounds with a stable slope is closely related to the presence of an incorporation mechanism. We confirm this finding using a Solid-On-Solid model in 2+1 dimensions. In the case of an infinite step edge barrier we are able to calculate the saturation profile analytically. Without incorporation but with inclusion of desorption and detachment we find a critical flux for instable growth but no slope selection. In particular, we show that the temperature dependence of the selected slope is solely determined by the Ehrlich-Schwoebel barrier which opens a new possibility in order to measure this fundamental barrier in experiments.Comment: 17 pages, 4 figure

Sortenbedingte Unterschiede der N-Effizienz und Beziehung zum Wurzelwachstums von Weizen (Triticum aestivum L.) unter den Bedingungen des Ökologischen Landbaus

N Uptake at EC 32, 62 and 92 was determined in 6 wheat varieties in field trials under conditions of conventional and organic farming over 3 years. Root growth potential was assessed in a separate trial under controlled conditions. Rank of varieties regarding N-uptake was dependent on yield level of the test environments and was mainly due to differences in uptake during grain filling. In one variety high N uptake potential coincided with high root growth in later growth stages

A New Stochastic Strategy for the Minority Game

We present a variant of the Minority Game in which players who where successful in the previous timestep stay with their decision, while the losers change their decision with a probability $p$. Analytical results for different regimes of $p$ and the number of players $N$ are given and connections to existing models are discussed. It is shown that for $p \propto 1/N$ the average loss $\sigma^2$ is of the order of 1 and does not increase with $N$ as for other known strategies.Comment: 4 pages, 3 figure

Online Learning with Ensembles

Supervised online learning with an ensemble of students randomized by the choice of initial conditions is analyzed. For the case of the perceptron learning rule, asymptotically the same improvement in the generalization error of the ensemble compared to the performance of a single student is found as in Gibbs learning. For more optimized learning rules, however, using an ensemble yields no improvement. This is explained by showing that for any learning rule $f$ a transform $\tilde{f}$ exists, such that a single student using $\tilde{f}$ has the same generalization behaviour as an ensemble of $f$-students.Comment: 8 pages, 1 figure. Submitted to J.Phys.

Einfluss des Ertragspotentials des Standorts und des Anbausystems auf den Züchtungserfolg bei Weizen in Deutschland

Baking quality is a major problem of wheat production in organic farming in Germany. The main reason is low protein content, but also different gluten characteristics. The aim of our investigations was to verify, whether selection of varieties with special adaptation to organic farming (or OF systems with particular low input) is advantageous. 66 Genotypes of winter wheat (registered German varieties, breeding lines, older varieties and varieties bred for organic farming) were compared in 5 environments over two years. Yield, protein content and quality parameters were assessed. Aptitude to LI- or HI- conditions was determined using intravarietal linear regression. While selection for special adaptation proved to be superior for yield and protein yield, this could not be confirmed for gluten characteristics