Stochastic Desertification

The process of desertification is usually modeled as a first order transition, where a change of an external parameter (e.g. precipitation) leads to a catastrophic bifurcation followed by an ecological regime shift. However, vegetation elements like shrubs and trees undergo a stochastic birth-death process with an absorbing state; such a process supports a second order continuous transition with no hysteresis. We present a numerical study of a minimal model that supports bistability and catastrophic shift on spatial domain with demographic noise and an absorbing state. When the external parameter varies adiabatically the transition is continuous and the front velocity renormalizes to zero at the extinction transition. Below the transition one may identify three modes of desertification: accumulation of local catastrophes, desert invasion and global collapse. A catastrophic regime shift occurs as a dynamical hysteresis, when the pace of environmental variations is too fast. We present some empirical evidence, suggesting that the mid-holocene desertification of the Sahara was, indeed, continuous

Carcass and meat quality of different pig genotypes in an organic extensive outdoor fatting system

Carcass, meat, and fat quality were evaluated of 37 castrates of 4 different genotypes [Pi*Du*GLR (10), Pi*AS (7), Du (10), Du*GLR (10)] kept on grass clover and fed with coarse meal made up of farm grown cereal and grain legumes without optimising the amount of amino acids and their relation to the energy content. Due to the energy surplus in the diet and in relation to the diminishing muscularity of the genotypes (corresponding to the above-mentioned sequence) lean meat contents were on a low level whereas intramuscular fat contents increased distinctly. Sensory meat quality was only at a medium level and did not differ noticeably between the genotypes. It is concluded that adipose carcasses associated with increased intramuscular fat contents do not lead automatically to higher sensory meat qualities. Therefore the system boundaries of organic pig fattening cannot be used without further efforts supplying market niches for pork of high eating quality

Ensemble Kalman filter for neural network based one-shot inversion

We study the use of novel techniques arising in machine learning for inverse problems. Our approach replaces the complex forward model by a neural network, which is trained simultaneously in a one-shot sense when estimating the unknown parameters from data, i.e. the neural network is trained only for the unknown parameter. By establishing a link to the Bayesian approach to inverse problems, an algorithmic framework is developed which ensures the feasibility of the parameter estimate w.r. to the forward model. We propose an efficient, derivative-free optimization method based on variants of the ensemble Kalman inversion. Numerical experiments show that the ensemble Kalman filter for neural network based one-shot inversion is a promising direction combining optimization and machine learning techniques for inverse problems

A simple interpretation of quantum mirages

In an interesting new experiment the electronic structure of a magnetic atom adsorbed on the surface of Cu(111), observed by STM, was projected into a remote location on the same surface. The purpose of the present paper is to interpret this experiment with a model Hamiltonian, using ellipses of the size of the experimental ones, containing about 2300 atoms. The charge distribution for the different wavefunctions is analyzed, in particular, for those with energy close to the Fermi energy of copper Ef. Some of them show two symmetric maxima located on the principal axis of the ellipse but not necessarily at the foci. If a Co atom is adsorbed at the site where the wavefunction with energy $E_F$ has a maximum and the interaction is small, the main effect of the adsorbed atom will be to split this particular wavefunction in two. The total charge density will remain the same but the local density of states will present a dip at Ef at any site where the charge density is large enough. We relate the presence of this dip to the observation of quantum mirages. Our interpretation suggests that other sites, apart from the foci of the ellipses, can be used for projecting atomic images and also indicates the conditions for other non magnetic adsorbates to produce mirages.Comment: 3 pages, 3 Fig

Impact of different types of local concentrates on productivity, health, behaviour and welfare of pigs and poultry in different production phases, D3.4

The overall discussion of the projects resulted in the following conclusions concerning: Pigs From a biological point of view, 100% organic feeding (with focus on protein/essential amino acid supply) seems to be feasible. It seems to be questionable whether the quantities and qualities of the required feeding stuffs are available at present and in the near future if only regional till EC-wide origin is aimed. (These views are also based on the previous of wp 1 and wp 2 discussions.) 100% organic feeding will stress economy. Poultry Regarding the issue of supplying organic concentrates main findings were: Protein from organically produced Spirulina algae can fully replace protein from traditional organic sources in broiler diets. Refining of ingredients of plant origin enriching the relative content of Methionine seems to be a useful way to supply relevant protein sources for poultry, eg for sunflower seed expeller. Insects meal (Hermetia illucens) up to 12 % in the diet can replace soybean cake without any difference in egg production, feed conversion, health and taste of eggs. Crushed mussel shells (particle size 10-20 mm) supplied in the litter on every day basis to layers affected neither birds’ feather cover, nor other welfare parameters or production performance. Crushed mussel shells cannot fully replace dietary calcium as calcium source without impairing bone health and egg shell strength

Nanoscale Impurity Structures on the Surface of dx2−y2d_{x^2-y^2}-wave Superconductors

We study the effects of nanoscale impurity structures on the local electronic structure of $d_{x^2-y^2}$-wave superconductors. We show that the interplay between the momentum dependence of the superconducting gap, the geometry of the nanostructure and its orientation gives rise to a series of interesting quantum effects. Among these are the emergence of a zero bias conductance peak in the superconductor's density of states and the suppression of impurity states for certain nanostructures. The latter effect can be used to screen impurity resonances in the superconducting state.Comment: 4 pages, 5 figure