Composition Games for Distributed Systems: the EU Grant games

We analyze ways by which people decompose into groups in distributed systems. We are interested in systems in which an agent can increase its utility by connecting to other agents, but must also pay a cost that increases with the size of the sys- tem. The right balance is achieved by the right size group of agents. We formulate and analyze three intuitive and realistic games and show how simple changes in the protocol can dras- tically improve the price of anarchy of these games. In partic- ular, we identify two important properties for a low price of anarchy: agreement in joining the system, and the possibil- ity of appealing a rejection from a system. We show that the latter property is especially important if there are some pre- existing constraints regarding who may collaborate (or com- municate) with whom.

Discovery of an RNA virus 3'->5' exoribonuclease that is critically involved in coronavirus RNA synthesis

Replication of the giant RNA genome of severe acute respiratory syndrome (SARS) coronavirus (CoV) and synthesis of as many as eight subgenomic (sg) mRNAs are mediated by a viral replicase-transcriptase of outstanding complexity that includes an essential endoribonuclease activity. Here, we show that the CoV replicative machinery, unlike that of other RNA viruses, also uses an exoribonuclease (ExoN) activity, which is associated with nonstructural protein (nsp) 14. Bacterially expressed forms of SARS-CoV nsp14 were shown to act on both ssRNAs and dsRNAs in a 3'5' direction. The activity depended on residues that are conserved in the DEDD exonuclease superfamily. The protein did not hydrolyze DNA or ribose-2'-O-methylated RNA substrates and required divalent metal ions for activity. A range of 5'-labeled ssRNA substrates were processed to final products of 8–12 nucleotides. When part of dsRNA or in the presence of nonlabeled dsRNA, the 5'-labeled RNA substrates were processed to significantly smaller products, indicating that binding to dsRNA in cis or trans modulates the exonucleolytic activity of nsp14. Characterization of human CoV 229E ExoN active-site mutants revealed severe defects in viral RNA synthesis, and no viable virus could be recovered. Besides strongly reduced genome replication, specific defects in sg RNA synthesis, such as aberrant sizes of specific sg RNAs and changes in the molar ratios between individual sg RNA species, were observed. Taken together, the study identifies an RNA virus ExoN activity that is involved in the synthesis of multiple RNAs from the exceptionally large genomic RNA templates of CoVs.

Transfer ionization process p+He -> H-0+He2++e(-) with the ejected electron detected in the plane perpendicular to the incident beam direction

A joint experimental and theoretical study of the transfer ionization process p+He→ H-0+He2++e(-) is presented for 630-keV proton impact energy, where the electron is detected in a plane perpendicular to the proton beam direction. With this choice of kinematics we find the triple-differential cross section to be particularly sensitive to angular correlation in the helium target. There is a good agreement between the experimental data and theoretical calculations.

Electrooxidation of the iodides [C(4)mim]I, LiI, NaI, KI, RbI, and CsI in the room temperature ionic liquid [C(4)mim][NTf2]

The electrochemical oxidation of 1-butyl-3-methylimidazolium iodide, [C(4)mim]I, has been investigated by cyclic voltammetry at a platinum microelectrode at varying concentrations in the RTIL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(4)mim][NTf2]. Two oxidation peaks were observed. The first peak is assigned to the oxidation of iodide to triiodide, in an overall two-electron process: 3I(-)- 2e(-) -> I-3(-). At higher potentials, the electrogenerated triiodide oxidizes to iodine, in an overall one-electron process: I-3(-) - e(-) -> 3/2I(2). An average diffusion coefficient, D, for I- of 1.55 x 10(-11) m(2) s(-1) was obtained. A digital simulation program was used to simulate the voltammetric response, and kinetic parameters were successfully extracted. The parameters deduced from the simulation include D for I-, I-3(-), and I-2 and K-eq,K-2, the equilibrium constant for the reaction of iodide and iodine to form triiodide. Values for these parameters are of the same order as those previously published for the oxidation of Br- in the same RTIL [Allen et al. J. Electroanal. Chem. 2005, 575, 311]. Next, the cyclic voltammetry of five different inorganic iodide salts was studied by dissolving small amounts of the solid in [C(4)mim][NTf2]. Similar oxidation peaks were observed, revealing diffusion coefficients of ca. 0.55, 1.14, 1.23, 1.44, and 1.33 x 10(-11) m(2) s(-1) and solubilities of 714, 246, 54, 83, and 36 mM for LiI, NaI, KI, RbI, and CsI, respectively. The slightly smaller diffusion coefficients for the XI salts (compared to [C(4)mim]I) may indicate that I- is ion-paired with Li+, Na+, K+, Rb+, and Cs+ in the RTIL medium.

SO and CS observations of molecular clouds - II. Analysis and modelling of the abundance ratios - probing O-2/CO with SO/CS?

We here analyse the observational SO and CS data presented in Nilsson ct al. (2000). The SO/CS integrated intensity ratio maps are presented for 19 molecular clouds, together with tables of relevant ratios at strategic positions, where we have also observed (SO)-S-34 and/or (CS)-S-34. The SO/CS abundance ratio as calculated from an LTE analysis is highly varying within and between the sources. Our isotopomer observations and Monte Carlo simulations verify that this is not an artifact due to optical depth problems. The variation of the maximum SO/CS abundance ratio between the clouds is 0.2-7. The largest variations within a cloud are found for the most nearby objects, possibly indicating resolution effects. We have also performed time dependent chemical simulations. We compare the simulations with our observed SO/CS abundance ratios and suggest a varying oxygen to carbon initial abundance, differing temporal evolution, density differences and X-ray sources associated with young stellar objects as possible explanations to the variations. In particular, the observed variation of the maximum SO/CS abundance ratio between the clouds can be explained by using initial O/C+ abundance ratios in the range 1.3-2.5. We finally derive a relationship between the SO/CS and O-2/CO abundance ratios, which may be used as a guide to find the most promising interstellar O-2 search targets.