Influence of geography on language competition

Competition between languages or cultural traits diffusing in the same geographical area is studied combining the language competition model of Abrams and Strogatz and a human dispersal model on an inhomogeneous substrate. Also, the effect of population growth is discussed. It is shown through numerical experiments that the final configuration of the surviving language can be strongly affected by geographical and historical factors. These factors are not related to the dynamics of culture transmission, but rather to initial population distributions as well as geographical boundaries and inhomogeneities, which modulate the diffusion process.Comment: typos in contact information have been corrected - text/figures not change

Solution procedures for block selection and sequencing in flat-bedded potash underground mines

Phosphates, and especially potash, play an essential role in the increase in crop yields. Potash is mined in Germany in underground mines using a conventional drill-and-blast technique. The most commercially valuable mineral contained in potash is the potassium chloride that is separated from the potash in aboveground processing plants. The processing plants perform economically best if the amount of potassium contained in the output is equal to a specific value, the so-called optimal operating point. Therefore, quality-oriented extraction plays a decisive role in reducing processing costs. In this paper, we mathematically formulate a block selection and sequencing problem with a quality-oriented objective function that aims at an even extraction of potash regarding the potassium content. We, thereby, have to observe some precedence relations, maximum and minimum limits of the output, and a quality tolerance range within a given planning horizon. We model the problem as a mixed-integer nonlinear program which is then linearized. We show that our problem is NP-hard in the strong sense with the result that a MILP-solver cannot find feasible solutions for the most challenging problem instances at hand. Accordingly, we develop a problem-specific constructive heuristic that finds feasible solutions for each of our test instances. A comprehensive experimental performance analysis shows that a sophisticated combination of the proposed heuristic with the mathematical program improves the feasible solutions achieved by the heuristic, on average, by 92.5%

Tailoring Membrane Surface Charges: A Novel Study on Electrostatic Interactions during Membrane Fouling

In this work we aim to show that the overall surface potential is a key factor to understand and predict anti-fouling characteristics of a polymer membrane. Therefore, polyvinylidene fluoride membranes were modified by electron beam-induced grafting reactions forming neutral, acidic, alkaline or zwitterionic structures on the membrane surface. The differently charged membranes were investigated regarding their surface properties using diverse analytical methods: zeta potential, static and dynamic water contact angle, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Porosimetry measurements proved that there is no pore blocking due to the modifications. Monodisperse suspensions of differently charged polystyrene beads were synthesized by a radical emulsion polymerization reaction and were used as a model fouling reagent, preventing comparability problems known from current literature. To simulate membrane fouling, different bead suspensions were filtered through the membranes. The fouling characteristics were investigated regarding permeation flux decline and concentration of model fouling reagent in filtrate as well as by SEM. By considering electrostatic interactions equal to hydrophobic interactions we developed a novel fouling test system, which enables the prediction of a membrane’s fouling tendency. Electrostatic forces are dominating, especially when charged fouling reagents are present, and can help to explain fouling characteristics that cannot be explained considering the surface wettability

Screening for Mutations Related to Atovaquone/ Proguanil Resistance in Treatment Failures and Other Imported Isolates of Plasmodium falciparum in Europe

Background. Two single-point mutations of the Plasmodium falciparum cytochrome b gene (Tyr268Asn and Tyr268Ser) were recently reported in cases of atovaquone/proguanil (Malarone) treatment failure. However, little is known about the prevalence of codon-268 mutations and their quantitative association with treatment failure. Methods. We set out to assess the prevalence of codon-268 mutations in P. falciparum isolates imported into Europe and to quantify their association with atovaquone/proguanil treatment failure. Isolates of P. falciparum collected by the European Network on Imported Infectious Disease Surveillance between April 2000 and August 2003 were analyzed for codon-268 mutations, by use of polymerase chain reaction-restriction fragment-length polymorphism. Results. We successfully screened 504 samples for the presence of either Tyr268Ser or Tyr268Asn. One case of Ser268 and no cases of Asn268 were detected. Therefore, we can be 95% confident that the prevalence of Ser268 in the European patient pool does not exceed 0.96% and that Asn268 is less frequent than 0.77%. In 58 patients treated with atovaquone/proguanil, Tyr268Ser was present in 1 of 5 patients with treatment failure but in 0 of 53 successfully treated patients. Conclusions. Tyr268Ser seems to be a sufficient, but not a necessary, cause for atovaquone/proguanil treatment failure. The prevalence of both codon-268 mutations is currently unlikely to be >1% in the European patient poo

Automatic loop centring with a high-precision goniometer head at the SLS macromolecular crystallography beamlines

An automated loop-centring program and a high-precision goniometer head used at the Swiss Light Source are described

Simulative and experimental investigation of the surface integrity obtained by Non-Circular-Rotary-Turning (NCRT)

Components with non-circular contours are increasingly used in technical applications, for example in shaft-hub connections or for medical implants with bionic-induced contours. A novel process approach for the production of these contours is the Non-Circular-Rotary-Turning (NCRT). The technology is based on the principle of kinematic coupling of workpiece and tool rotation, which allows to transfer the non-circular shape of the tool to the component within certain limits. All linear axes except the feed axis are not in motion during this process. In contrast to conventional turning, the non-circular contour and the complex kinematics of NCRT lead to surfaces that are strongly depending on the measuring position on the component. In this work, the surfaces obtainable by NCRT are generally investigated. Using an example cross section, a kinematic dexel-based simulation is utilized to predict the kinematic surface topography depending on the process parameters. The surfaces are also investigated in experiments and compared with the simulation. The results show a characteristic surface topography, as well as a strong dependence on the ratio of tool to workpiece diameter. Better surfaces are generally achieved in downturning