Topological characteristics of oil and gas reservoirs and their applications

We demonstrate applications of topological characteristics of oil and gas reservoirs considered as three-dimensional bodies to geological modeling.Comment: 12 page

Stability analysis of polarized domains

Polarized ferrofluids, lipid monolayers and magnetic bubbles form domains with deformable boundaries. Stability analysis of these domains depends on a family of nontrivial integrals. We present a closed form evaluation of these integrals as a combination of Legendre functions. This result allows exact and explicit formulae for stability thresholds and growth rates of individual modes. We also evaluate asymptotic behavior in several interesting limits.Comment: 12 pages, 3 figures, Late

Enhancement of laser-driven ion acceleration in non-periodic nanostructured targets

Using particle-in-cell simulations, we demonstrate an improvement of the target normal sheath acceleration (TNSA) of protons in non-periodically nanostructured targets with micron-scale thickness. Compared to standard flat foils, an increase in the proton cutoff energy by up to a factor of two is observed in foils coated with nanocones or perforated with nanoholes. The latter nano-perforated foils yield the highest enhancement, which we show to be robust over a broad range of foil thicknesses and hole diameters. The improvement of TNSA performance results from more efficient hot-electron generation, caused by a more complex laser-electron interaction geometry and increased effective interaction area and duration. We show that TNSA is optimized for a nanohole distribution of relatively low areal density and that is not required to be periodic, thus relaxing the manufacturing constraints.Comment: 11 pages, 8 figure

Damping by slow relaxing rare earth impurities in Ni80Fe20

Doping NiFe by heavy rare earth atoms alters the magnetic relaxation properties of this material drastically. We show that this effect can be well explained by the slow relaxing impurity mechanism. This process is a consequence of the anisotropy of the on site exchange interaction between the 4f magnetic moments and the conduction band. As expected from this model the magnitude of the damping effect scales with the anisotropy of the exchange interaction and increases by an order of magnitude at low temperatures. In addition our measurements allow us to determine the relaxation time of the 4f electrons as a function of temperature

Dewetting of thin films on heterogeneous substrates: Pinning vs. coarsening

We study a model for a thin liquid film dewetting from a periodic heterogeneous substrate (template). The amplitude and periodicity of a striped template heterogeneity necessary to obtain a stable periodic stripe pattern, i.e. pinning, are computed. This requires a stabilization of the longitudinal and transversal modes driving the typical coarsening dynamics during dewetting of a thin film on a homogeneous substrate. If the heterogeneity has a larger spatial period than the critical dewetting mode, weak heterogeneities are sufficient for pinning. A large region of coexistence between coarsening dynamics and pinning is found.Comment: 4 pages, 4 figure

The relation of steady evaporating drops fed by an influx and freely evaporating drops

We discuss a thin film evolution equation for a wetting evaporating liquid on a smooth solid substrate. The model is valid for slowly evaporating small sessile droplets when thermal effects are insignificant, while wettability and capillarity play a major role. The model is first employed to study steady evaporating drops that are fed locally through the substrate. An asymptotic analysis focuses on the precursor film and the transition region towards the bulk drop and a numerical continuation of steady drops determines their fully non-linear profiles. Following this, we study the time evolution of freely evaporating drops without influx for several initial drop shapes. As a result we find that drops initially spread if their initial contact angle is larger than the apparent contact angle of large steady evaporating drops with influx. Otherwise they recede right from the beginning

Stratified spatiotemporal chaos in anisotropic reaction-diffusion systems

Numerical simulations of two dimensional pattern formation in an anisotropic bistable reaction-diffusion medium reveal a new dynamical state, stratified spatiotemporal chaos, characterized by strong correlations along one of the principal axes. Equations that describe the dependence of front motion on the angle illustrate the mechanism leading to stratified chaos

The participatory market chain approach: stimulating pro-poor market-chain innovation

Innovation in the food and agriculture sector is frequently short-circuited by a lack of trust and communication between actors in the market chain. To overcome these problems and stimulate innovation, the Participatory Market Chain Approach (PMCA) brings together small farmers, market agents, and service providers for an intense process of facilitated interaction. The PMCA uses a flexible three-stage participatory process to improve communication, build trust, and facilitate collaboration among participants so that they can jointly identify, analyze, and exploit new market opportunities. The PMCA focuses on innovation in products, technologies, and ways of working together. By carefully selecting market chains and partners, and building in social responsibility, the PMCA can lead to favourable outcomes and impacts for poor farmers, typically the weakest link in the chain. The PMCA requires facilitation and technical support from professionals with good social skills, research experience, and marketing knowledge, based in a neutral research and development organization. To ensure that impacts are sustained, the PMCA is best used as part of a broader programme of market chain development

The night-sky at the Calar Alto Observatory

We present a characterization of the main properties of the night-sky at the Calar Alto observatory for the time period between 2004 and 2007. We use optical spectrophotometric data, photometric calibrated images taken in moonless observing periods, together with the observing conditions regularly monitored at the observatory, such as atmospheric extinction and seeing. We derive, for the first time, the typical moonless night-sky optical spectrum for the observatory. The spectrum shows a strong contamination by different pollution lines, in particular from Mercury lines, which contribution to the sky-brightness in the different bands is of the order of ~0.09 mag, ~0.16 mag and ~0.10 mag in B, V and R respectively. The zenith-corrected values of the moonless night-sky surface brightness are 22.39, 22.86, 22.01, 21.36 and 19.25 mag arcsec^-2 in U, B, V, R and I, which indicates that Calar Alto is a particularly dark site for optical observations up to the I-band. The fraction of astronomical useful nights at the observatory is ~70%, with a ~30% of photometric nights. The typical extinction at the observatory is k_V~0.15 mag in the Winter season, with little dispersion. In summer the extinction has a wider range of values, although it does not reach the extreme peaks observed at other sites. The median seeing for the last two years (2005-6) was ~0.90", being smaller in the Summer (~0.87") than in the Winter (~0.96"). We conclude in general that after 26 years of operations Calar Alto is still a good astronomical site, being a natural candidate for future large aperture optical telescopes.Comment: 16 pages, 5 figures, accepted for publishing in the Publications of Astronomical Society of the Pacific (PASP