The evolution of stochastic strategies in the Prisoner's Dilemma

The evolution of reactive strategies for repeated 2×2-games occurring in biology is investigated by means of an adaptive dynamics.     

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Book reviews

     

Tailoring dispersion properties of photonic crystal waveguides by topology optimization

The paper describes a systematic method for the tailoring of dispersion properties of slab-based photonic crystal waveguides. The method is based on the topology optimization method which consists in repeated finite element frequency domain analyzes, analytical sensitivity analyzes and gradient based design updates. The goal of the optimization process is to come up with slow light, zero group velocity dispersion photonic waveguides or photonic waveguides with tailored dispersion properties for dispersion compensation purposes. Two examples concerning reproduction of a specific dispersion curve and design of a wide bandwidth, constant low group velocity waveguide demonstrate the efficiency of the method.     

Screening for benfluorex and its major urinary metabolites in routine doping controls

Benfluorex [1-(m-trifluoromethylphenyl)-2-(β-benzoyloxyethyl)aminopropane] has been widely used for the treatment of atherogenic metabolic disorders and impaired carbohydrate metabolism (particularly in obese type-II diabetic patients) as well as an anorectic drug. Due to its potentially performance-enhancing properties, benfluorex has been added to the list of prohibited compounds and methods of doping by the World Anti-Doping Agency (WADA) in 2010, necessitating the implementation of the drug as well as its major metabolites into routine doping control procedures. In the present study, human urinary metabolites of benfluorex were characterized by gas chromatography–electron ionization–mass spectrometry (GC-EI-MS) as well as liquid chromatography–electrospray ionization–high resolution/high accuracy tandem mass spectrometry (LC-ESI-MS/MS). Commonly employed sports drug testing approaches consisting of liquid–liquid extraction followed by GC-MS or urine dilution and immediate LC-MS/MS analysis were expanded and validated with regard to specificity, recovery (48–54%, GC-MS only), intra- and interday precision (<25%), limits of detection (5–8 ng/mL for LC-MS/MS and 80 ng/mL for GC-MS), and ion suppression (for LC-ESI-MS/MS only) to allow the detection of benfluorex metabolites 1-(m-trifluoromethylphenyl)-2-(2-hydroxyethyl)aminopropane (M1), 1-(m-trifluoromethylphenyl)-2-(2-carboxymethyl)aminopropane (M2), and 1-(m-trifluoromethylphenyl)-2-aminopropane (M3) as well as the glucuronic acid conjugate of M1.     

Discovery of kibdelomycin, a potent new class of bacterial type II topoisomerase inhibitor by chemical-genetic profiling in Staphylococcus aureus

Bacterial resistance to known therapeutics has led to an urgent need for new chemical classes of antibacterial agents. To address this we have applied?a Staphylococcus aureus fitness test strategy to natural products screening. Here we report the discovery of kibdelomycin, a novel class of antibiotics produced by a new member of the genus Kibdelosporangium. Kibdelomycin exhibits broad-spectrum, gram-positive antibacterial activity and is a potent inhibitor of DNA synthesis. We demonstrate through chemical genetic fitness test profiling and biochemical enzyme assays that kibdelomycin is a structurally new class of bacterial type II topoisomerase inhibitor preferentially inhibiting the ATPase activity of DNA gyrase and topoisomerase IV. Kibdelomycin is thus the first truly novel bacterial type II topoisomerase inhibitor with potent antibacterial activity discovered from natural product sources in more than six decades.     

Stopping of swift hydrogen diclusters: oscillator model

Enhanced stopping of swift hydrogen diclusters has been analysed theoretically. The target has been modeled as a gas of harmonic-oscillator atoms of variable density. This model predicts a proximity effect, i.e., enhanced stopping at high beam energy, and an oscillatory behavior at low energy. Both features get less pronounced with increasing target density due to increased screening of the ion-target interaction by polarization of the medium. Static screening by electrons accompanying the cluster likewise reduces the proximity effect. The Barkas-Andersen correction has been estimated in the Z₁³Z_1^3 limit. Our findings are in contrast with measurements on SiO₂ [S.M. Shubeita et al., Phys. Rev. B 77, 115327 (2008)] which showed a pronounced step in the energy dependence of the proximity effect.     

Stopping of slow ions

The 50th anniversary of the appearance of a series of seminal papers by O.B. Firsov is taken as an occasion to have a look at some central aspects of the stopping of slow ions in matter. A brief characterization of Firsov’s model of electronic energy loss is given in comparison with alternative views. The main part of the paper is devoted to central problems such as scaling behavior, Z ₁ and Z ₂ structure, deviations from velocity proportionality, threshold behavior, metal-insulator and gas-solid differences, and correlation between nuclear and electronic stopping.