On the Complexity of Local Search for Weighted Standard Set Problems

In this paper, we study the complexity of computing locally optimal solutions for weighted versions of standard set problems such as SetCover, SetPacking, and many more. For our investigation, we use the framework of PLS, as defined in Johnson et al., [JPY88]. We show that for most of these problems, computing a locally optimal solution is already PLS-complete for a simple neighborhood of size one. For the local search versions of weighted SetPacking and SetCover, we derive tight bounds for a simple neighborhood of size two. To the best of our knowledge, these are one of the very few PLS results about local search for weighted standard set problems

Multiple okulare Kolobome (MOC) mit persistierender Pupillarmembran beim Schneeleopard (Panthera unica)

In a litter of three snow leopards, bilateral colobomata of the upper temporal eyelids, bilateral persistent pupillary membranes and a unilateral coloboma of the optic nerve entrance are described as "Multiple Ocular Colobomata" (MOC). The causal pathogenesis of each of the colobomata is discussed comparatively. The colobomata of the eyelids, essential feature of the MOC syndrome in snow leopards, are most probably not of hereditary, but rather of intrauterine infectious viral origin

Continental-scale patterns of pathogen prevalence: a case study on the corncrake

Pathogen infections can represent a substantial threat to wild populations, especially those already limited in size. To determine how much variation in the pathogens observed among fragmented populations is caused by ecological factors, one needs to examine systems where host genetic diversity is consistent among the populations, thus controlling for any potentially confounding genetic effects. Here, we report geographic variation in haemosporidian infection among European populations of corncrake. This species now occurs in fragmented populations, but there is little genetic structure and equally high levels of genetic diversity among these populations. We observed a longitudinal gradient of prevalence from western to Eastern Europe negatively correlated with national agricultural yield, but positively correlated with corncrake census population sizes when only the most widespread lineage is considered. This likely reveals a possible impact of local agriculture intensity, which reduced host population densities in Western Europe and, potentially, insect vector abundance, thus reducing the transmission of pathogens. We conclude that in the corncrake system, where metapopulation dynamics resulted in variations in local census population sizes, but not in the genetic impoverishment of these populations, anthropogenic activity has led to a reduction in host populations and pathogen prevalence

Stochastic dynamics and pattern formation of geometrically confined skyrmions

Ensembles of magnetic skyrmions in confined geometries are shown to exhibit thermally driven motion on two different time scales. The intrinsic fluctuating dynamics (t ∼ 1 ps) are governed by short-range symmetric and antisymmetric exchange interactions, whereas the long-time limit (t ≳ 10 ns) is determined by the coaction of skyrmion–skyrmion-repulsion and the system’s geometry. Micromagnetic simulations for realistic island shapes and sizes are performed and analyzed, indicating the special importance of skyrmion dynamics at finite temperatures. We demonstrate how the competition between skyrmion mobility and observation time directly affects the addressability of skyrmionic bits, which is a key challenge on the path of developing skyrmion-based room-temperature applications. The presented quasiparticle Monte Carlo approach offers a computationally efficient description of the diffusive motion of skyrmion ensembles in confined geometries, like racetrack memory setups

New approach for a comprehensive method for urban vehicle concepts with electric powertrain and their necessary vehicle structures

By the strict discussions regarding energy saving and the goal to reduce CO2 emissions to 95g CO2/km, which is specified for the year 2020, [1] there is a keen demand for lighter and lightweight designed automotive structures to support the energy saving targets. In view of a holistic approach and also to prospectively meet the requirements of the automotive sector, beside the previously mentioned challenges, economic and production-orientated aspects, as well as joining technologies, within the scope of multi-material design, have to be considered to realize a great leap forward medium to large-scale productions. To achieve these goals, a comprehensive method for urban vehicle concepts with electric powertrain and their necessary vehicle structures is presented. The dimensions and packaging of the presented vehicle is based on demands of a future urban vehicle with space for four occupants including baggage, steerable front system wheels and a rear axle including an electric powertrain. At the beginning of the method the relevant user requirements, e.g. space for persons and baggage, range for the urban vehicle are defined. In addition, input variables are discharged through the state of the art of electric vehicles. It is also an important point in this step to look on further requirements such as crash requirements or requirements for electrical components in the vehicle design. With the defined requirements the package of the urban car has to be defined. Two paths are determined to a geometrically and a simulative way. The simulative consideration is limited to the vehicle longitudinal dynamics, thus a rough dimensioning of the drive components is derived. The outputs of the simulation are the performance measures which are then converted into components for the overall model for dimensioning for example electric motor or battery. The geometric design phase begins with the positioning of the occupants in the passenger compartment and ergonomic layout. Based on this conception of the complete vehicle, various FEM optimizations (topology, topography, size) are carried out for the body in white in order to construct structures towards individual (functional) components/modules. This top-down approach raises the opportunity to extract constructive innovations, which must be integrated within this early concept phase, also to reduce costs when aiming to development of a series product. With this holistic approach a load-specific optimized structural design is virtually generated and evaluated, and also an outlook on dynamic loads (crash behavior) is given. The focus here is on the potential in innovations by the definition of novel package alignments in combination with the useful application of multi-material-design method, resulting in a light modular vehicle structure

Dissipation in Dynamics of a Moving Contact Line

The dynamics of the deformations of a moving contact line is studied assuming two different dissipation mechanisms. It is shown that the characteristic relaxation time for a deformation of wavelength $2\pi/|k|$ of a contact line moving with velocity $v$ is given as $\tau^{-1}(k)=c(v) |k|$. The velocity dependence of $c(v)$ is shown to drastically depend on the dissipation mechanism: we find $c(v)=c(v=0)-2 v$ for the case when the dynamics is governed by microscopic jumps of single molecules at the tip (Blake mechanism), and $c(v)\simeq c(v=0)-4 v$ when viscous hydrodynamic losses inside the moving liquid wedge dominate (de Gennes mechanism). We thus suggest that the debated dominant dissipation mechanism can be experimentally determined using relaxation measurements similar to the Ondarcuhu-Veyssie experiment [T. Ondarcuhu and M. Veyssie, Nature {\bf 352}, 418 (1991)].Comment: REVTEX 8 pages, 9 PS figure