The <SPP> Green function and SU(3) breaking in Kl3 decays

Using the 1=/N-C expansion scheme and truncating the hadronic spectrum to the lowest-lying resonances, we match a meromorphic approximation to the Green function onto QCD by imposing the correct large-momentum falloff, both off- shell and on the relevant hadron mass shells. In this way we determine a number of chiral low-energy constants of O(p(6)), in particular the ones governing SU(3) breaking in the K-l3 vector form factor at zero momentum transfer. The main result of our matching procedure is that the known loop contributions largely dominate the corrections of O(p(6)) to f(+)(0). We discuss the implications of our final value f(+)(K0 pi-) (0) = 0.984 +/- 0.012 for the extraction of V-us from K-l3 decays

Formation and evolution of cosmic D-strings

We study the formation of D and F-cosmic strings in D-brane annihilation after brane inflation. We show that D-string formation by quantum de Sitter fluctuations is severely suppressed, due to suppression of RR field fluctuations in compact dimensions. We discuss the resonant mechanism of production of D and F-strings, which are formed as magnetic and electric flux tubes of the two orthogonal gauge fields living on the world-volume of the unstable brane. We outline the subsequent cosmological evolution of the D-F string network. We also compare the nature of these strings with the ordinary cosmic strings and point out some differences and similarities.Comment: Added discussion and reference

Speciation of OH reactivity above the canopy of an isoprene-dominated forest

Measurements of OH reactivity, the inverse lifetime of the OH radical, can provide a top&ndash;down estimate of the total amount of reactive carbon in an air mass. Using a comprehensive measurement suite, we examine the measured and modeled OH reactivity above an isoprene-dominated forest in the southeast United States during the 2013 Southern Oxidant and Aerosol Study (SOAS) field campaign. Measured and modeled species account for the vast majority of average daytime reactivity (80&ndash;95 %) and a smaller portion of nighttime and early morning reactivity (68&ndash;80 %). The largest contribution to total reactivity consistently comes from primary biogenic emissions, with isoprene contributing &sim;&thinsp; 60 % in the afternoon, and &sim;&thinsp; 30&ndash;40 % at night and monoterpenes contributing &sim;&thinsp; 15&ndash;25 % at night. By comparing total reactivity to the reactivity stemming from isoprene alone, we find that &sim;&thinsp; 20 % of the discrepancy is temporally related to isoprene reactivity, and an additional constant &sim;&thinsp; 1 s-1 offset accounts for the remaining portion. The model typically overestimates measured OVOC concentrations, indicating that unmeasured oxidation products are unlikely to influence measured OH reactivity. Instead, we suggest that unmeasured primary emissions may influence the OH reactivity at this site.</p

The effects of aging of scientists on their publication and citation patterns

The average age at which U.S. researchers get their first grant from NIH has increased from 34.3 in 1970, to 41.7 in 2004. These data raise the crucial question of the effects of aging on the scientific creativity and productivity of researchers. Those who worry about the aging of scientists usually believe that the younger they are the more creative and productive they will be. Using a large population of 13,680 university professors in Quebec, we show that, while scientific productivity rises sharply between 28 and 40, it increases at a slower pace between 41 and 50 and stabilizes afterward until retirement for the most active researchers. The average scientific impact per paper decreases linearly until 50-55 years old, but the average number of papers in highly cited journals and among highly cited papers rises continuously until retirement. Our results clearly show for the first time the natural history of the scientific productivity of scientists over their entire career and bring to light the fact that researchers over 55 still contribute significantly to the scientific community by producing high impact papers.Comment: 12 pages, 4 figure

Molecular and supramolecular chemistry of mono- and di-selenium analogues of metal dithiocarbamates

This bibliographic review summarises the coordination chemistry of mono- and diselenium analogues of metal dithiocarbamate ligands, [RRꞌNCS2]-, as revealed by X-ray crystallography and spectroscopy (77Se NMR and infrared). The Se-ligands are usually chelating but, bridging modes, up to 4, are known. Reflecting the larger size, greater polarisability and presence of a polar-cap (-hole), selenium atoms are more likely to be involved in secondary-bonding (chalcogen-bonding) than sulphur when a competition exists. Isostructural relationships are established across the series in about one-third of the structures

Prospects for e+e- physics at Frascati between the phi and the psi

We present a detailed study, done in the framework of the INFN 2006 Roadmap, of the prospects for e+e- physics at the Frascati National Laboratories. The physics case for an e+e- collider running at high luminosity at the phi resonance energy and also reaching a maximum center of mass energy of 2.5 GeV is discussed, together with the specific aspects of a very high luminosity tau-charm factory. Subjects connected to Kaon decay physics are not discussed here, being part of another INFN Roadmap working group. The significance of the project and the impact on INFN are also discussed. All the documentation related to the activities of the working group can be found in http://www.roma1.infn.it/people/bini/roadmap.html.Comment: INFN Roadmap Report: 86 pages, 25 figures, 9 table