Sofia University

About: Sofia University is a education organization based out in Sofia, Bulgaria. It is known for research contribution in the topics: Large Hadron Collider & Laser. The organization has 8533 authors who have published 15730 publications receiving 306320 citations. The organization is also known as: University of Sofia & BFUS.

Dynamics of mercury species in surface sediments of a macrotidal estuarine–coastal system (Adour River, Bay of Biscay)

Abstract: Estuarine and coastal surface sediments from the Adour estuary and adjacent coastal area (South Bay of Biscay) have been investigated to establish mercury species variability in a macrotidal system submitted to contrasted seasonal river discharges and downstream urbanisation. Surface sediments were sampled during three campaigns in the major sediment deposits of the Adour estuary and at selected discharge points. Concentrations of Hg2+ and MeHg+ in Adour estuarine sediments average 1600 and 1.3 pmol g−1, and range from <2 to 7300 pmol g−1 and from <0.5 to 8.0 pmol g−1, respectively. The concentrations of inorganic ionic mercury (Hg2+) and monomethylmercury (MeHg+) in the surface sediments display large seasonal variation, being one order of magnitude higher in June 2001 for Hg2+ and in October 2000 for MeHg+. The results show that Hg2+ can be accumulated in the estuarine sediments after seasonal river inputs and both remobilised and methylated during dry period. Mercury species concentrations in coastal sediments collected in June 2001 assessed the impact of estuarine inputs on the nearby coastal area. Except direct anthropogenic discharge points, the variability and transfer of Hg2+ and MeHg+ in surface sediments of the whole estuarine–coastal macrotidal system can be depicted by simple geochemical parameters of the bulk sediments, such as grain size distribution, organic carbon and total sulphur.

Search for a light pseudoscalar Higgs boson in the dimuon decay channel in pp collisions at √s=7TeV

Abstract: The dimuon invariant mass spectrum is searched in the range between 5.5 and 14 GeV for a light pseudoscalar Higgs boson a, predicted in a number of new physics models, including the next-to-minimal supersymmetric standard model. The data sample used in the search corresponds to an integrated luminosity of 1.3 fb(-1) collected in pp collisions at √s = 7 TeV with the CMS detector at the LHC. No excess is observed above the background predictions and upper limits are set on the cross section times branching fraction σ × B(pp→a→μ(+)μ(-)) in the range of 1.5-7.5 pb. These results improve on existing bounds on the abb coupling for m(a) m(Υ(3S)). Constraints on the supersymmetric parameter space are presented in the context of the next-to-minimal model.

Modeling of microwave discharges in the presence of plasma resonances.

Abstract: This study presents a kinetic model of microwave generated discharges sustained, under the conditions of a diffusion controlled regime, by the propagation of azimuthally symmetric surface waves. The effect of the plasma resonances, which can appear over the radial density profile in the vicinity of the walls and lead to sharp peaks in the radial component of the high-frequency wave electric field in the plasma, is introduced. This effect modifies the surface wave damping and results in a collisional as well as collisionless (quasilinear) transfer of energy from the radial field component to the plasma. In the Boltzmann equation the latter appears as a third channel of energy transfer, which is added to the Joule heating by the axial and radial wave field components. The spatially inhomogeneous Boltzmann equation for the electron-energy distribution function, which accoutns for the radial ambipolar field, is solved in the nonlocal approximation. A complete set of relations is formed by simultaneous consideration of the fluid equations for the ion motion and the field equations for the surface wave electric field. The problem is solved numerically. It yields self-consistent radial electron density profiles and radial electric field distributions. The obtained solutions evidence indeed the occurrence of plasma resonances. The study is extended also to obtaining results for the axial variation of the (radially averaged) electron density. It turns out that the widely used concept of approximate constancy of wave power absorbed by one electron in a diffusion controlled regime keeps its validity also in the presence of plasma resonances and of the corresponding collisional, as well as collisionless, power transfer to the plasma in the resonance regions.

Measurement of the ZZ production cross section and search for anomalous couplings in 2ℓ2ℓ′ final states in pp collisions at \( \sqrt{s}=7 \) TeV

Abstract: A measurement is presented of the ZZ production cross section in the ZZ → 2l2l′ decay mode with l = e, μ and l′ = e, μ, τ in proton-proton collisions at s√=7 TeV with the CMS experiment at the LHC. Results are based on data corresponding to an integrated luminosity of 5.0 fb^(−1). The measured cross section σ(pp→ZZ)=6.24^(+0.86)_(−0.80)(stat.)^(+0.41)_(−0.32)(syst.)±0.14(lumi.)pb is consistent with the standard model predictions. The following limits on ZZZ and ZZγ anomalous trilinear gauge couplings are set at 95% confidence level: −0.011