Communication and Cooperation in Public Network Situations

This paper focuses on sharing the costs and revenues of maintaining a public network communication structure. Revenues are assumed to be bilateral and communication links are publicly available but costly. It is assumed that agents are located at the vertices of an undirected graph in which the edges represent all possible communication links. We take the approach from cooperative game theory and focus on the corresponding network game in coalitional form which relates any coalition of agents to its highest possible net benefit, i.e., the net benefit corresponding to an optimal operative network. Although finding an optimal network in general is a difficult problem, it is shown that corresponding network games are (totally) balanced. In the proof of this result a specific relaxation, duality and techniques of linear production games with committee control play a role. Sufficient conditions for convexity of network games are derived. Possible extensions of the model and its results are discussed. The research of Jeroen Suijs has been made possible by a fellowship of the Royal Netherlands Academy of Arts and Sciences.     

An Existential Divisibility Lemma for Global Fields

We generalize the Existential Divisibility Lemma by Th. Pheidas [7] to all global fields K of characteristic not 2, and for all sets of primes that are inert in a quadratic extension L of K. We also remove the conditions in real and ramifying primes, which were present in Pheidas’ version. As a Corollary, we recover the known fact that the set of integral elements at a prime in a global field is existentially definable.     

Light-induced multi-wavelength lasing in dye-doped chiral nematic liquid crystals due to strong pumping illumination

The influence of the pump laser beam on the lasing spectral characteristics in dye-doped cholesteric liquid crystal is investigated. Under the influence of the pump laser pulses with different repetition rates and energies, non-linear reorientation and light-induced flow reorientation of chiral nematic liquid crystals (CLC) molecules was observed. Independent of the reorientation mechanism, multi-wavelength lasing was achieved due to stepwise uncoiling of the CLC structure. Under the influence of a pump laser beam with low repetition rate, Cano–Grandjean disclination defect lines were induced which remain even after removal of the laser beam.     

Mapping the Relationship between Glycosyl Acceptor Reactivity and Glycosylation Stereoselectivity

The reactivity of both coupling partners—the glycosyl donor and acceptor—is decisive for the outcome of a glycosylation reaction, in terms of both yield and stereoselectivity. Where the reactivity of glycosyl donors is well understood and can be controlled through manipulation of the functional/protecting‐group pattern, the reactivity of glycosyl acceptor alcohols is poorly understood. We here present an operationally simple system to gauge glycosyl acceptor reactivity, which employs two conformationally locked donors with stereoselectivity that critically depends on the reactivity of the nucleophile. A wide array of acceptors was screened and their structure–reactivity/stereoselectivity relationships established. By systematically varying the protecting groups, the reactivity of glycosyl acceptors can be adjusted to attain stereoselective cis‐glucosylations.     

Two Bacterial Diterpene Synthases from Allokutzneria albata Produce Bonnadiene,Phomopsene, and Allokutznerene

Two diterpene synthases from Allokutzneria albata were studied for their products, resulting in the identification of the new compound bonnadiene from the first enzyme. Although phylogenetically unrelated to fungal phomopsene synthase, the second enzyme produced a mixture of phomopsene and a biosynthetically linked new compound, allokutznerene, as well as spiroviolene. Both enzymes were subjected to in‐depth mechanistic studies involving isotopic labelling experiments, metal‐cofactor variation, and site‐directed mutagenesis. Oxidation products of phomopsene and allokutznerene are also discussed.     

Chemometrics in analytical chemistry—part II: modeling,validation, and applications

Analytical and Bioanalytical Chemistry - The contribution of chemometrics to important stages throughout the entire analytical process such as experimental design, sampling, and explorative data...     

Chiral oligomers by iterative tandem catalysis

Iterative tandem catalysis is presented as a flexible tool for obtaining chiral macromolecules from racemic or prochiral monomers. Here, we combine lipase-catalyzed ring-opening of omega-substituted lactones with ruthenium-catalyzed racemization. In a two-pot system, enantioenriched oligomers of 6-methyl-epsilon-caprolactone were synthesized, which could not have been obtained by enzymatic ring-opening alone. A one-pot experiment proved highly promising in developing a novel route toward enantiopure polyesters.     

Biosynthesis of iso-fatty acids in myxobacteria

The fatty acid (FA) profiles of the myxobacteria Stigmatella aurantiaca and Myxococcus xanthus were investigated by acidic methanolysis of total cell extracts and GC or GC-MS analysis. The main components were 13-methyltetradecanoic acid (iso-15:0) and (Z)-hexadec-11-enoic acid (16:1, omega-5 cis). The biosynthesis of iso-FAs was investigated in several feeding experiments. Feeding of isovaleric acid (IVA) to a mutant impaired in the degradation of leucine to isovaleryl-CoA (IV-CoA)(bkd mutant) of M. xanthus only increased the amount of iso-odd FAs, whereas feeding of isobutyric acid (IBA) gave increased amounts only of iso-even FAs. In contrast, a bkd mutant of S. aurantiaca gave increased amounts of iso-odd and iso-even fatty acids in both experiments. We assumed that in S. aurantiacaalpha-oxidation takes place. [D(7)]-15-Methylhexadecanoic acid was synthesised and fed to S. aurantiaca as well as [D(10)]leucine and [D(8)]valine to elucidate this pathway in more detail. The iso-fatty acid was degraded by alpha- and beta-oxidation steps. [D(10)]Leucine was strongly incorporated into iso-odd and iso-even fatty acids, whereas the incorporation rates for [D(8)]valine into both types of fatty acids were low. Thus alpha-oxidation plays an important role in the biosynthesis of iso-fatty acids in S. aurantiaca. The incorporation rates observed after feeding of [D(10)]leucine and [D(8)]valine are the highest for iso-17:0 compared to the other acids. This indicates the central role of iso-17:0 in the biosynthesis of iso-FAs. The shorter homologues seem to be formed mainly by alpha-oxidation and beta-oxidation of this acid. After feeding of traces of unsaturated counterparts of this labelled FA occurred in the extracts indicating that desaturases are active in the biosynthesis of unsaturated fatty acids in S. aurantiaca.     

Alternating oligo(p-phenylene vinylene)--perylene bisimide copolymers: synthesis,photophysics, and photovoltaic properties of a new class of donor--acceptor materials

A Suzuki polycondensation reaction has been used to synthesize two copolymers consisting of alternating oligo(p-phenylene vinylene) (OPV) donor and perylene bisimide (PERY) acceptor chromophores. The copolymers differ by the length of the saturated spacer that connects the OPV and PERY units. Photoinduced singlet energy transfer and photoinduced charge separation in these polychromophores have been studied in solution and in the solid state via photoluminescence and femtosecond pump-probe spectroscopy. In both polymers a photoinduced electron transfer occurs within a few picoseconds after excitation of the OPV or the PERY chromophore. The electron transfer from OPV excited state competes with a singlet energy transfer state to the PERY chromophore. The differences in rate constants for the electron- and energy-transfer processes are discussed on the basis of correlated quantum-chemical calculations and in terms of conformational preferences and folding of the two polymers. In solution, the lifetime of the charge-separated state is longer than in the films where geminate recombination is much faster. However, in the films some charges are able to escape from geminate recombination and diffuse away and can be collected at the electrodes when the polymers are incorporated in a photovoltaic device.     

Characterization of some synthetic Ru and Ir complexes by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was applied to the analysis of Ru(OCOCF(3))(2)(CO)(PPh(3))(2), Ru(OCOC(3)F(7))(2)(CO)(PPh(3))(2), Ir(tBuppy)(3) and Ir(ppy)(2)(acac) complexes. A troublesome problem in the MALDI-TOFMS characterization of these metal complexes is the possible replacement of complex ligands by matrix. In this contribution, 10 matrices, ranging from acidic to basic, were investigated: alpha-cyano-4-hydroxycinnamic acid (CHCA), 2,5-dihydroxybenzoic acid (DHB), sinapinic acid (SA), dithranol, 2,4,6-trihydroxyactophenone (THAP), 6-azo-2-thiothymine (ATT), norharman, 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB), 4-nitroaniline (NA) and 2-amino-5-nitrophyridine (ANP). With most of the matrices, including the neutral and basic ones, matrix substitution of ligand could clearly be detected. Based on the experimental results, possible mechanisms of matrix substitution were discussed. It was demonstrated that the ligand exchange process might also occur through the gas-phase reactions initiated by laser shots. Among the matrices tested, DCTB was found to be the best one for the complexes that are prone to ligand exchange by matrix.