Die Taubeniederung : Maßnahmen der Stadt Dessau zur Grundwasserregulierung, Renaturierung und zum Gewässerausbau

Die Taubeniederung und der Flusslauf der Taube befinden sich in einem alten Muldetal. Dos hier rezensierte Heft der "Naturwissenschaftlichen Beiträge des Museums Dessou" informiert vorrangig über den Teil der Niederung, der am Siedlungsrand der Stadt Dessou liegt, gekennzeichnet durch Neubau- und Gewerbegebiete. Für die angrenzende Landschaft wurde ohne akuten Handlungsdruck eine Planung vorgenommen, die als Reaktion auf die Stadtentwicklung notwendige Veränderungen im Übergangsbereich vorstellt. Wegen der vorausschauenden Behandlung des Themas verdient die Planung besondere Beachtung

Molecular traffic control in single-file networks with fast catalysts

As a model for molecular traffic control (MTC) we investigate the diffusion of hard core particles in crossed single-file systems. We consider a square lattice of single-files being connected to external reservoirs. The (vertical) alpha-channels, carrying only A-particles, are connected to reservoirs with constant density ra. B-particles move along the (horizontal) beta-channels, which are connected to reservoirs of density rB. We allow the irreversible transition A to B at intersections. We are interested in the stationary density profile in the alpha- and beta- channels, which is the distribution of the occupation probabilities over the lattice. We calculate the stationary currents of the system and show that for sufficiently long channels the currents (as a function of the reservoir densities) show in the limit of large transition rates non analytic behavior. The results obtained by direct solution of the master equation are verified by kinetic Monte Carlo simulations.Comment: 11 page

Effect of tool coatings on surface grain refinement in orthogonal cutting of AISI 4140 steel

Recrystallization mechanisms leading to the generation of ultrafine grains (UFG) by surface severe plastic deformation (S2PD) at low temperatures (< 0.5Tm (melting temperature)) have been investigated over the last years. Material removal processes like broaching impose large plastic strains along the shear plane during chip formation, leading in many cases to changes in the workpiece subsurface microstructure. In this work the influence of the cutting material on surface grain recrystallization were studied on broaching of AISI 4140q&t steel. Orthogonal cutting tests were carried out in dry conditions on a broaching machine using tools with different coatings. Uncoated cemented carbide inserts were geometrically prepared using fixed abrasive grinding processes and then coated by physical vapor deposition (PVD) with Al2O3 and CrVN thin films. Workpiece subsurface layers were analyzed after machining by Focused Ion Beam (FIB-SEM) and X-ray diffraction (XRD). The presented results show the influence of the cutting material on the final microstructure of the machined workpieces through the determination of the final grain sizes and dislocation densities

Context and prediction matter for the interpretation of social interactions across species

Predictions about others’ future actions are crucial during social interactions, in order to react optimally. Another way to assess such interactions is to define the social context of the situations explicitly and categorize them according to their affective content. Here we investigate how humans assess aggressive, playful and neutral interactions between members of three species: human children, dogs and macaques. We presented human participants with short video clips of real-life interactions of dyads of the three species and asked them either to categorize the context of the situation or to predict the outcome of the observed interaction. Participants performed above chance level in assessing social situations in humans, in dogs and in monkeys. How accurately participants predicted and categorized the situations depended both on the species and on the context. Contrary to our hypothesis, participants were not better at assessing aggressive situations than playful or neutral situations. Importantly, participants performed particularly poorly when assessing aggressive behaviour for dogs. Also, participants were not better at assessing social interactions of humans compared to those of other species. We discuss what mechanism humans use to assess social situations and to what extent this skill can also be found in other social species.Introduction Methods - Subjects - Stimuli - Procedure - Design and coding - Statistical analyses Results - Context decisions - Outcome decisions - Comparison between context and outcome decisions Discussio

Products, coproducts and singular value decomposition

Products and coproducts may be recognized as morphisms in a monoidal tensor category of vector spaces. To gain invariant data of these morphisms, we can use singular value decomposition which attaches singular values, ie generalized eigenvalues, to these maps. We show, for the case of Grassmann and Clifford products, that twist maps significantly alter these data reducing degeneracies. Since non group like coproducts give rise to non classical behavior of the algebra of functions, ie make them noncommutative, we hope to be able to learn more about such geometries. Remarkably the coproduct for positive singular values of eigenvectors in $A$ yields directly corresponding eigenvectors in A\otimes A.Comment: 17 pages, three eps-figure

Design of thin-film photonic metamaterial L\"uneburg lens using analytical approach

We design an all-dielectric L\"uneburg lens as an adiabatic space-variant lattice explicitly accounting for finite film thickness. We describe an all-analytical approach to compensate for the finite height of subwavelength dielectric structures in the pass-band regime. This method calculates the effective refractive index of the infinite-height lattice from effective medium theory, then embeds a medium of the same effective index into a slab waveguide of finite height and uses the waveguide dispersion diagram to calculate a new effective index. The results are compared with the conventional numerical treatment - a direct band diagram calculation, using a modified three-dimensional lattice with the superstrate and substrate included in the cell geometry. We show that the analytical results are in good agreement with the numerical ones, and the performance of the thin-film L\"uneburg lens is quite different than the estimates obtained assuming infinite height.Comment: 11 pages, 8 figures, uses opex3.st

Nonlinear coherent heat machines and closed-system thermodynamics

All existing heat machines are dissipative open systems. Hence, they cannot operate fully coherently. We propose to replace this conventional thermodynamic paradigm by a completely different one, whereby heat machines are nonlinear coherent closed systems comprised of few field modes. Their thermal-state input is transformed by nonlinear interactions into non-thermal output with controlled quantum fluctuations and the capacity to deliver work in a chosen mode. This new paradigm allows the bridging of quantum coherent and thermodynamic descriptions.Comment: 10 pages, 4 figures. Updated version, modified title and extended number of author

Statistical properties of genealogical trees

We analyse the statistical properties of genealogical trees in a neutral model of a closed population with sexual reproduction and non-overlapping generations. By reconstructing the genealogy of an individual from the population evolution, we measure the distribution of ancestors appearing more than once in a given tree. After a transient time, the probability of repetition follows, up to a rescaling, a stationary distribution which we calculate both numerically and analytically. This distribution exhibits a universal shape with a non-trivial power law which can be understood by an exact, though simple, renormalization calculation. Some real data on human genealogy illustrate the problem, which is relevant to the study of the real degree of diversity in closed interbreeding communities.Comment: Accepted for publication in Phys. Rev. Let

A quark model analysis of the charge symmetry breaking in nuclear force

In order to investigate the charge symmetry breaking (CSB) in the short range part of the nuclear force, we calculate the difference of the masses of the neutron and the proton, $\Delta {\rm M}$, the difference of the scattering lengths of the p-p and n-n scatterings, $\Delta a$, and the difference of the analyzing power of the proton and the neutron in the n-p scattering, $\Delta A(\theta)$, by a quark model. In the present model the sources of CSB are the mass difference of the up and down quarks and the electromagnetic interaction. We investigate how much each of them contributes to $\Delta {\rm M}$, $\Delta a$ and $\Delta A(\theta)$. It is found that the contribution of CSB of the short range part in the nuclear force is large enough to explain the observed $\Delta A(\theta)$, while $\Delta a$ is rather underestimated.Comment: 26 pages,6 figure

Why do dogs (Canis familiaris) select the empty container in an observational learning task?

Many argue that dogs show unique susceptibility to human communicative signals that make them suitable for being engaged in complex co-operation with humans. It has also been revealed that socially provided information is particularly effective in influencing the behaviour of dogs even when the human’s action demonstration conveys inefficient or mistaken solution of task. It is unclear, however, how the communicative nature of the demonstration context and the presence of the human demonstrator affect the dogs’ object-choice behaviour in observational learning situations. In order to unfold the effects of these factors, 76 adult pet dogs could observe a communicative or a non-communicative demonstration in which the human retrieved a tennis ball from under an opaque container while manipulating another distant and obviously empty (transparent) one. Subjects were then allowed to choose either in the presence of the demonstrator or after she left the room. Results showed a significant main effect of the demonstration context (presence or absence of the human’s communicative signals), and we also found some evidence for the response-modifying effect of the presence of the human demonstrator during the dogs’ choice. That is, dogs predominantly chose the baited container, but if the demonstration context was communicative and the human was present during the dogs’ choice, subjects’ tendency to select the baited container has been reduced. In agreement with the studies showing sensitivity to human’s communicative signals in dogs, these findings point to a special form of social influence in observational learning situations when it comes to learning about causally opaque and less efficient (compared to what comes natural to the dog) action demonstrations