Radiation and Relaxation of Oscillons

We study oscillons, extremely long-lived localized oscillations of a scalar field, with three different potentials: quartic, sine-Gordon model and in a new class of convex potentials. We use an absorbing boundary at the end of the lattice to remove emitted radiation. The energy and the frequency of an oscillon evolve in time and are well fitted by a constant component and a decaying, radiative part obeying a power law as a function time. The power spectra of the emitted radiation show several distinct frequency peaks where oscillons release energy. In two dimensions, and with suitable initial conditions, oscillons do not decay within the range of the simulations, which in quartic theory reach 10^8 time units. While it is known that oscillons in three-dimensional quartic theory and sine-Gordon model decay relatively quickly, we observe a surprising persistence of the oscillons in the convex potential with no sign of demise up to 10^7 time units. This leads us to speculate that an oscillon in such a potential could actually live infinitely long both in two and three dimensions.Comment: 16 pages, 28 eps figure

Numerical Investigations of Oscillons in 2 Dimensions

Oscillons, extremely long-living localized oscillations of a scalar field, are studied in theories with quartic and sine-Gordon potentials in two spatial dimensions. We present qualitative results concentrating largely on a study in frequency space via Fourier analysis of oscillations. Oscillations take place at a fundamental frequency just below the threshold for the production of radiation, with exponentially suppressed harmonics. The time evolution of the oscillation frequency points indirectly to a life time of at least 10 million oscillations. We study also elliptical perturbations of the oscillon, which are shown to decay. We finish by presenting results for boosted and collided oscillons, which point to a surprising persistence and soliton-like behaviour.Comment: Matches the published version (12 pages, 34 figures

Heavy Quark Parameters and Vcb from Spectral Moments in Semileptonic B Decays

We extract the heavy quark masses and non-perturbative parameters from the Delphi preliminary measurements of the first three moments of the charged lepton energy and hadronic mass distributions in semileptonic B decays, using a multi-parameter fit. We adopt two formalisms, one of which does not rely on a 1/mc expansion and makes use of running quark masses. The data are consistent and the level of accuracy of the experimental inputs largely determines the present sensitivity. The results allow to improve on the uncertainty in the extraction of Vcb.Comment: 13 pages, 2 figure

Oscillons and Domain Walls

Oscillons, extremely long-lived localized oscillations of a scalar field, are shown to be produced by evolving domain wall networks in quartic theory in two spatial dimensions. We study the oscillons in frequency space using the classical spectral function at zero momentum, and obtain approximate information of their velocity distribution. In order to gain some insight onto the dilute oscillon 'gas' produced by the domain walls, we prepare a denser gas by filling the simulation volume with oscillons boosted in random directions. We finish the study by revisiting collisions between oscillons and between an oscillon and a domain wall, showing that in the latter case they can pass straight through with minimal distortion.Comment: 11 pages, 28 eps figure

Metabolic plasticity of mixotrophic algae is key for their persistence in browning environments

Light availability is the main regulator of primary production, shaping photosynthetic communities and their production of ecologically important biomolecules. In freshwater ecosystems, increasing dissolved organic carbon (DOC) concentrations, commonly known as browning, leads to lower light availability and the proliferation of mixotrophic phytoplankton. Here, a mixotrophic algal species (Cryptomonas sp.) was grown under five increasing DOC concentrations to uncover the plastic responses behind the success of mixotrophs in browning environments and their effect in the availability of nutritionally important biomolecules. In addition to the browning treatments, phototrophic, heterotrophic and mixotrophic growth conditions were used as controls. Despite reduced light availability, browning did not impair algal growth compared to phototrophic conditions. Comparative transcriptomics showed that genes related to photosynthesis were down-regulated, whereas phagotrophy gene categories (phagosome, lysosome and endocytosis) were up-regulated along the browning gradient. Stable isotope analysis of phospholipid fractions validated these results, highlighting that the studied mixotroph increases its reliance on heterotrophic processes with browning. Metabolic pathway reconstruction using transcriptomic data suggests that organic carbon is acquired through phagotrophy and used to provide energy in conjunction with photosynthesis. Although metabolic responses to browning were observed, essential fatty acid content was similar between treatments while sterol content was slightly higher upon browning. Together, our results provide a mechanistic model of how a mixotrophic alga responds to browning and how such responses affect the availability of nutritionally essential biomolecules for higher trophic levels.Peer reviewe

SPh functionalized bridging-vinyliminium diiron and diruthenium complexes

The SPh functionalized vinyliminium complexes [Fe2{μ-η1:η3-Cγ(R′)Cβ(SPh)CαN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] [R = Xyl, R′ = Me, 2a; R = Me, R′ = Me, 2b; R = 4-C6H4OMe, R′ = Me, 2c; R = Xyl, R′ = CH2OH, 2d; R = Me, R′ = CH2OH, 2e; Xyl = 2,6-Me2C6H3] are generated in high yields by treatment of the corresponding vinyliminium complexes [Fe2{μ-η1:η3-Cγ(R′)Cβ(H)CαN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (1a–e) with NaH in the presence of PhSSPh. Likewise, the diruthenium complex [Ru2{μ-η1:η3-Cγ(Me)Cβ(SPh)CαN(Me)(Xyl)}(μ-CO)(CO)(Cp)2][SO3CF3] (2f) was obtained from the corresponding vinyliminium complex [Ru2{μ-η1:η3-Cγ(Me)Cβ(H)CαN(Me)(Xyl)}(μ-CO)(CO)(Cp)2] (1f). The synthesis of 2c is accompanied by the formation, in comparable amounts, of the aminocarbyne complex [Fe2{μ-CN(Me)(4-C6H4OMe)}(SPh)(μ-CO)(CO)(Cp)2] (3). The molecular structures of 2d, 2e and 3 have been determined by X-ray diffraction studies