Common suppression pattern of eta and pi0 mesons at high transverse momentum in Au + Au collisions at square root S(NN) = 200 GeV

Inclusive transverse momentum spectra of eta mesons have been measured within p(T) = 2-10 GeV/c at midrapidity by the PHENIX experiment in Au + Au collisions at square root S(NN) = 200 GeV. In central Au+Au the eta yields are significantly suppressed compared to peripheral Au + Au, d + Au, and p + p yields scaled by the corresponding number of nucleon-nucleon collisions. The magnitude, centrality, and p(T) dependence of the suppression is common, within errors, for eta and pi0. The ratio of eta to pi0 spectra at high p(T) amounts to 0.40 < R(eta/pi)0 < 0.48 for the three systems, in agreement with the world average measured in hadronic and nuclear reactions and, at large scaled momentum, in e+e- collisions.     

Long range substrate mediated mass transport on metal surfaces induced by adatom clusters

Mass transport at surfaces can proceed either (i) by hopping diffusion of atoms on top of the surface from one site to another or (ii) by propagation of small displacements from one atom to the next within the topmost atomic layer. In the latter case, a long range substrate mediated mass transport has been postulated but never observed explicitly. Experimental and theoretical evidence is shown here for the occurrence of such a mechanism on the reconstructed Au(111) surface, where the movement is shown to be well described by a soliton.     

Measurement of single electrons and implications for charm production in Au+Au collisions at square root[s(NN)] = 130 GeV

Transverse momentum spectra of electrons from Au+Au collisions at square root[s(NN)] = 130 GeV have been measured at midrapidity by the PHENIX experiment at the Relativistic Heavy Ion Collider. The spectra show an excess above the background from photon conversions and light hadron decays. The electron signal is consistent with that expected from semileptonic decays of charm. The yield of the electron signal dN(e)/dy for p(T) > 0.8 GeV/c is 0.025+/-0.004(stat)+/-0.010(syst) in central collisions, and the corresponding charm cross section is 380+/-60(stat)+/-200(syst) microb per binary nucleon-nucleon collision.     

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Calix[4]phyrin based redox architectures: towards new molecular tools for electrochemical sensing

New redox active molecular macrocyclic architectures characterized by a direct connection between dipyrrin, tripyrrin and ferrocenyl fragments have been synthesized and characterized. Contrarily to fully conjugated porphyrins, in which four pyrrole moieties contribute to the overall aromatic pi-electronic system and behave as a unique electroactive species, calixphyrins can be regarded as an assembly of independent redox active pyrrole and conjugated oligopyrrole fragments linked through sp(3) hybridized meso carbon atoms. The disruption of the conjugation pathway not only multiplies the number of redox centres throughout the molecule but also leads to a large variety of molecular architectures with specific physico-chemical properties. These novel ferrocene containing hybrid macrocycles exhibit especially attractive electronic and structural features suited for use as molecular sensing tools. An efficient voltammetric sensing of exogenic electron rich anionic species could especially be performed using a metallo-calix[4]phyrin-(1.1.1.1) through the displacement of the labile axial binding site, the perturbation of the Fc(0/+) redox couple being directly related to complexed species features.     

Observation of a BCS spectral function in a conventional superconductor by photoelectron spectroscopy

We present high-resolution photoelectron spectra on the A15-type conventional superconductor V 3Si, where-for the first time-both singularities of the BCS density of states can be resolved by photoemission spectroscopy (PES). With a transition temperature of about T(c) approximately 17 K the gap Delta(gap) of this compound has a magnitude of approximately 5 meV. A measurement by PES on this small energy scale requires a very high energy resolution (DeltaE less, similar5 meV) and sample temperatures significantly below T(c).     

Self-assembly of a ferrocene-substituted porphyrin capable of electrochemically sensing neutral molecules via a "tail on-tail off" process

The supramolecular assembly of a ferrocene-porphyrin conjugate allowed ferrocene-based electrochemical sensing of the metalloporphyrin axial coordination via a "tail on-tail off" binding process.