Voltammetric determination of trace mercury in chloride media at glassy carbon electrodes modified with polycationic ionomers.

The perfluorinated polycationic polymer Tosflex @ is used for preparing polymer modified electrodes able to preconcentrate and detect the anionic complex HgCl$-, which is the prevailing inorganic Hg(II) species in sea water and other chloride media. The study of the ion-exchange voltammetric behaviour of the tetrachloromercurate(I1) complex at Tosflex-modified electrodes indicates the efficient incorporation of the analyte into the polymeric coating to which a remarkable positive shift in the reduction potential of HgCli- to Hg” is associated. The partition and selectivity coefficient values for the ion-exchange equilibrium involved are calculated from voltammetric data. When using an ion-exchange preconcentration step under open circuit conditions followed by a cyclic voltammetry detection step, a detection limit in the 10m8 M range is achieved, the exact figure depending on the scan rate employed. The application of a reducing potential during the preconcentration (i.e., using a mixed ion-exchange + Faradaic preconcentration regime) and the use of differential pulse voltammetry, lower the relevant detection limit by about three orders of magnitude. Results concerning optimization of the experimental parameters as well as lowering of the influence of possible interferents, such as copper and competing anions, are reported. Finally, an analytical procedure for exploiting the peculiar properties of Tosflex-modified electrodes for the determination of mercury in coastal waters samples is proposed and experimentally tested

Towards a better understanding of gold electroless deposition in track-etched templates

The template method for preparing nanomaterials entails synthesis of tubular or fibrillar nanostructures within the pores of a microporous membrane. If the holes are completely filled, solid nanowires result, while a partial filling with a continuous coating gives rise to nanotubes. This paper focused on the study of the parameters controlling electroless gold deposition in track-etched polycarbonate membranes. The structure and morphology of the obtained nanomaterials are examined and compared by a variety of electron microscopies and atomic force microscopy and examined in relation to electrochemical and spectrophotometric results. As far as nanotubes are concerned, problems with obtaining such a nanostructure are observed, in particular when membranes with pore diameters equal to or smaller than 30 nm are used. In the case of nanowires, defects related to fabrication problems are evidenced when they are used to prepare nanoelectrode ensembles (NEEs), because defects dramatically influence their voltammetric behavior. The role of deposition time and pH on gold nucleation and growth is studied in detail. We demonstrate that these parameters indeed determine the formation of nanowires versus nanotubes. In all cases the deposit is started by the formation of gold nuclei on the walls of the previously activated membrane. Then the nuclei grow, until they are bound together to produce the final nanomaterial. A significantly better control of the deposition is achieved by separating the nuclei formation step from the growth process. At pH 10 the nuclei growth is more regular but slower, whereas at pH 12 the process is faster but their size distribution is wider. At pH 10 the formation of nanotubes is better controlled, whereas at pH 12 continuous nanofibers are more quickly formed

Thermal shape fluctuation effects in the description of hot nuclei

The behavior of several nuclear properties with temperature is analyzed within the framework of the Finite Temperature Hartree-Fock-Bogoliubov (FTHFB) theory with the Gogny force and large configuration spaces. Thermal shape fluctuations in the quadrupole degree of freedom, around the mean field solution, are taken into account with the Landau prescription. As representative examples the nuclei $^{164}$Er, $^{152}$Dy and $^{192}$Hg are studied. Numerical results for the superfluid to normal and deformed to spherical shape transitions are presented. We found a substantial effect of the fluctuations on the average value of several observables. In particular, we get a decrease in the critical temperature ($T_c$) for the shape transition as compared with the plain FTHFB prediction as well as a washing out of the shape transition signatures. The new values of $T_c$ are closer to the ones found in Strutinsky calculations and with the Pairing Plus Quadrupole model Hamiltonian.Comment: 17 pages, 8 Figure

Bismuth modified gold nanoelectrode ensemble for stripping voltammetric determination of lead

The preparation of bismuth modified ensembles of gold nanoelectrodes (Bi-NEE) is described for the first time. Bi-NEEs are characterized and successfully applied for anodic stripping voltammetric measurement of trace Pb(II). Optimization of the experimental parameters provided low detection limits of 60 ng L−1 and 30 ng L−1 by using in-situ and ex-situ bismuth film deposition, respectively, after a 3 min accumulation step

Polycyclic aromatic hydrocarbons degradation by composting in a soot-contaminated alkaline soil

none7noThis study deals with the biodegradation of the polycyclic aromatic hydrocarbons (PAH)s present in a soil contaminated by soot waste, characterised by a total PAHs content in the 200 mg kg−1 range. A challenging characteristic of the waste soil treated was its high alkalinity, with a pH of about 12.8. The waste came from a soot-contaminated area located in the industrial zone of Porto Marghera, Venice (Italy). The biodegradation process employed was the composting of the waste with sewage sludge and yard waste. The process was carried out on a pilot scale using a closed tank with forced aeration for a period of 60 days, followed by 70 days with natural aeration. The time evolution of the process was monitored by following the time change in the concentration of the 16 US-EPA PAHs, as well as temperature, pH, electrical conductivity, C and N contents. Also phytotoxicity parameters, such as the growth and respiration indexes, were monitored. An induction time of about 30 days was observed, which corresponded to the time required before observing a significant self-drop in the waste pH and an increase in mass temperature. Afterward, a progressive drop in the PAHs concentration was observed, up to reaching after 130 days an overall degradation percentage in the order of 68%. The degradation was more effective on rather low molecular weight PAHs (2–4 rings).mixedMoretto, L.M.; Silvestri, S.; Ugo, P; Zorzi, G.; Abbondanzi, F.; Baiocchi, C.; Iacondini, A.Moretto, L.M.; Silvestri, S.; Ugo, P; Zorzi, G.; Abbondanzi, F.; Baiocchi, C.; Iacondini, A

Long-range Angular Correlations On The Near And Away Side In P-pb Collisions At √snn=5.02 Tev

7191/Mar294

Measurement of jet suppression in central Pb-Pb collisions at root s(NN)=2.76 TeV

The transverse momentum(p(T)) spectrum and nuclear modification factor (R-AA) of reconstructed jets in 0-10% and 10-30% central Pb-Pb collisions at root s(NN) = 2.76 TeV were measured. Jets were reconstructed using the anti-k(T) jet algorithm with a resolution parameter of R = 0.2 from charged and neutral particles, utilizing the ALICE tracking detectors and Electromagnetic Calorimeter (EMCal). The jet p(T) spectra are reported in the pseudorapidity interval of \eta(jet)\ 5 GeV/c to suppress jets constructed from the combinatorial background in Pb-Pb collisions. The leading charged particle requirement applied to jet spectra both in pp and Pb-Pb collisions had a negligible effect on the R-AA. The nuclear modification factor R-AA was found to be 0.28 +/- 0.04 in 0-10% and 0.35 +/- 0.04 in 10-30% collisions, independent of p(T), jet within the uncertainties of the measurement. The observed suppression is in fair agreement with expectations from two model calculations with different approaches to jet quenching. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V.Peer reviewe

Centrality dependence of inclusive J/\u3c8 production in p-Pb collisions at 1asNN = 5.02 TeV

We present a measurement of inclusive J/\u3c8 production in p-Pb collisions at 1asNN = 5.02TeV as a function of the centrality of the collision, as estimated from the energy deposited in the Zero Degree Calorimeters. The measurement is performed with the ALICE detector down to zero transverse momentum, pT, in the backward ( 124.46 < ycms < 122.96) and forward (2.03 < ycms < 3.53) rapidity intervals in the dimuon decay channel and in the mid-rapidity region ( 121.37 < ycms < 0.43) in the dielectron decay channel. The backward and forward rapidity intervals correspond to the Pb-going and p-going direction, respectively. The pT-differential J/\u3c8 production cross section at backward and forward rapidity is measured for several centrality classes, together with the corresponding average pT and pT2 values. The nuclear modification factor is presented as a function of centrality for the three rapidity intervals, and as a function of pT for several centrality classes at backward and forward rapidity. At mid- and forward rapidity, the J/\u3c8 yield is suppressed up to 40% compared to that in pp interactions scaled by the number of binary collisions. The degree of suppression increases towards central p-Pb collisions at forward rapidity, and with decreasing pT of the J/\u3c8. At backward rapidity, the nuclear modification factor is compatible with unity within the total uncertainties, with an increasing trend from peripheral to central p-Pb collisions