Jet-fluid string formation and decay in high-energy heavy-ion collisions

We propose a new hadronization mechanism, jet-fluid string (JFS) formation and decay, to understand observables in intermediate to high-$p_{T}$ regions comprehensively. In the JFS model, hard partons produced in jet lose their energy in traversing the QGP fluid, which is described by fully three-dimensional hydrodynamic simulations. When a jet parton escapes from the QGP fluid, it picks up a partner parton from a fluid and forms a color singlet string, then it decays to hadrons. We find that high-$p_T$ $v_2$ values in JFS are about two times larger than in the independent fragmentation model.Comment: 6 pages, 2 figures; Proceeding for poster sessions at Quark Matter 2006, Shanghai, China, 14-20 November 2006; to appear in Int. J. of Mod. Phys.

The solvent effect on the electrocatalytic cleavage of carbon-halogen bonds on Ag and Au

In recent years it has been shown in detail how the electrocatalytic cleavage of carbonhalogen bonds is modulated by (a) the stepwise or concerted nature of the dissociative electrontransfer mechanism, which is influenced by the nature of the electrode surface, the type of halogen atom and the molecular structure of RX as a whole, and (b) the double-layer structure (as a function of the nature and bulkiness of the supporting electrolyte ions). In order to both complete and support the interpretative scheme thus developed, this work is focused on the solvent role. When one compares aprotic with protic organic solvents after appropriate intersolvental normalization, interesting peculiarities emerge, especially concerning protic media. Solvent proticity deeply affects both the reaction mechanism (on both non-catalytic and catalytic electrodes) and the extent of the catalytic effects. These items are discussed on the basis of a complete investigation carried out with a carefully controlled experimental protocol on two chloride and bromide couples, one aromatic and one aliphatic, representative of stepwise and concerted mechanisms, respectively, in four aprotic and four protic solvents, on both non-catalytic GC and catalytic Ag and Au electrodes. The results are discussed in the framework of a recently developed interpretative scheme of the carbon-halogen cleavage mechanism

Search for a Ridge Structure Origin with Shower Broadening and Jet Quenching

We investigate the role of jet and shower parton broadening by the strong colour field in the $\Delta\eta$-$\Delta\phi$ correlation of high $p_T$ particles. When anisotropic momentum broadening ($\Delta p_z > \Delta p_T$) is given to jet and shower partons in the initial stage, a ridge-like structure is found to appear in the two hadron correlation. The ratio of the peak to the pedestal yield is overestimated.Comment: Talk given at 20th Int. Conf. on Ultra-Relativistic Nucleus-Nucleus Collisions, Jaipur, India, Feb.4-10, 200

"Egg of Columbus": single-step complete removal of chloride impurities from ionic liquids by AgCl deposition on silver electrode

Chloride impurities in ionic liquids (ILs), which can be present even in huge amounts depending on the IL synthetic route, are particularly critical for electrochemical processes; thus, their abatement is often mandatory. However, while their analytical quantification has been the subject of many studies involving a variety of techniques, the so far available processes for their abatement are still unsatisfactory, having low efficiency, and/or involving multiple steps, and/or being far from mild and easily scalable. In this context, like an "egg of Columbus", a quite simple and safe process for chloride abatement in ILs is proposed, practically coinciding with the electrolytic preparation of a Ag|AgCl electrode. It proceeds in a single step, at room temperature, at very low potentials, with nearly ideal current efficiencies, and with negligible side effects on the electrolyzed IL. The chloride impurities are quantitatively captured and accumulated on the silver wire and eliminated by simply removing the resulting Ag|AgCl electrode from the solution, with no need of subsequent treatments

When ring makes the difference: coordination properties of Cu2+/Cu+ complexes with sulfur-pendant polyazamacrocycles for radiopharmaceutical applications

Three polyazamacrocyclic ligands, i.e. 1,5,9-tris[2-(methylsulfanyl)ethyl]-1,5,9-triazacyclododecane (TACD3S), 1,4,7,10-tetrakis[2-(methylsulfanyl)ethyl]-1,4,7,10-tetrazacyclotridecane (TRI4S) and 1,4,8,11-tetrakis[2-(methylsulfanyl)ethyl]-1,4,8,11-tetrazacyclotetradecane (TE4S), were considered as potential chelators for the medically relevant copper radioisotopes. The ligands have been synthesized through facile, single-step reactions, and their acidity constants have been measured in aqueous solution at 25 degrees C. The kinetic, thermodynamic, electrochemical and structural properties of their Cu2+ and Cu+ complexes were investigated in aqueous solution at 25 degrees C using spectroscopic (UV-Visible, EPR, NMR) and electrochemical techniques (pH-potentiometric titrations, cyclic voltammetry and electrolysis). TACD3S was demonstrated to be unable to stabilize Cu2+, whereas for TRI4S and TE4S the formation of stable monocupric (CuL2+) and monocuprous (CuL+) complexes was detected. TRI4S coordinates Cu(2+)via a [4N] and a [4N]S array of donor atoms while with TE4S only the latter geometry exists. The thermodynamic stability and the kinetic inertness of the copper complexes formed by TACD3S, TRI4S and TE4S were compared with those previously reported for 1,4,7,10-tetrakis-[2-(methylsulfanyl)ethyl]-1,4,7,10-tetrazacyclododecane (DO4S) to unravel the influence of the ring size and the nitrogen donor array on the copper chelation properties of these sulfur-rich macrocycles. The copresence of four nitrogen atoms is an essential feature to allow effective copper coordination when a 12-member ring is employed, as the Cu2+-DO4S complexes were far more stable than those of Cu2+-TACD3S. Furthermore, the larger ring size of TRI4S and TE4S, when compared to DO4S, progressively increases the rate of the Cu2+ complexation reactions but decreases the thermodynamic stability of the Cu2+ complexes. Despite this, the ability of TRI4S and TE4S to stably accommodate both copper oxidation states makes them very attractive for application in nuclear medicine as they could avoid the demetallation after the biologically triggered Cu2+/Cu+ reduction

Nonextensive statistical effects in the quark-gluon plasma formation at relativistic heavy-ion collisions energies

We investigate the relativistic equation of state of hadronic matter and quark-gluon plasma at finite temperature and baryon density in the framework of the non-extensive statistical mechanics, characterized by power-law quantum distributions. We impose the Gibbs conditions on the global conservation of baryon number, electric charge and strangeness number. For the hadronic phase, we study an extended relativistic mean-field theoretical model with the inclusion of strange particles (hyperons and mesons). For the quark sector, we employ an extended MIT-Bag model. In this context we focus on the relevance of non-extensive effects in the presence of strange matter.Comment: 12 pages, 5 figure

Re-Hardening of Hadron Transverse Mass Spectra in Relativistic Heavy-Ion Collisions

We analyze the spectra of pions and protons in heavy-ion collisions at relativistic energies from 2 A GeV to 65+65 A GeV by using a jet-implemented hadron-string cascade model. In this energy region, hadron transverse mass spectra first show softening until SPS energies, and re-hardening may emerge at RHIC energies. Since hadronic matter is expected to show only softening at higher energy densities, this re-hardening of spectra can be interpreted as a good signature of the quark-gluon plasma formation.Comment: 10 pages, 3 figures, 1 table, Poster presentation at QM2001, Revised to correct latex error in citation on April 6, 200

Smooth crack-free targets for nuclear applications produced by molecular plating

Vascon A, Santi S, Isse AA, et al. Smooth crack-free targets for nuclear applications produced by molecular plating. Nuclear Instruments and Methods in Physics Research A. 2013;714:163-175.The production process of smooth and crack-free targets by means of constant current electrolysis in organic media, commonly known as molecular plating, was optimized. Using a Nd salt, i.e., [Nd(NO3)(3)center dot 6H(2)O], as model electrolyte several constant current density electrolysis experiments were carried out to investigate the effects of different parameters, namely the plating solvent (isopropanol and isobutanol mixed together, pyridine, and N,N-dimethylformamide), the electrolyte concentration (0.11, 0.22, 0.44 mM), the applied current density (0.17, 0.3, 0.7, and 1.3 mA/cm(2)), and the surface roughness of the deposition substrates (12 and 24 nm). Different environments (air and Ar) were used to dry the samples and the effects on the produced layers were investigated. The obtained deposits were characterized using gamma-ray spectroscopy for determining Nd deposition yields, X-ray photoelectron spectroscopy for chemical analysis of the produced surfaces, radiographic imaging for surface homogeneity inspection, atomic force microscopy for surface roughness evaluation, and scanning electron microscopy for surface morphology investigation. The results allowed identifying the optimum parameters for the production of smooth and crack-free targets by means of molecular plating. The smoothest layers, which had an average RMS roughness of ca. 20 nm and showed no cracks, were obtained using 0.22 mM [Nd(NO3)(3)center dot 6H(2)O] plated from N,N-dimethylformamide at current densities in the range of 0.3-0.7 mA/cm(2) on the smoothest deposition substrate available. (c) 2013 Elsevier B.V. All rights reserved

Towards inherently chiral Ionic liquids: molecular design strategies and electrochemical properties

Chiral Ionic Liquids (CILs) constitute a class of chiral solvents of steadily increasing importance in the last years; they are employed inter alia as chiral solvents for asymmetric synthesis and stereoselective polymerization, as chiral phases in gas chromatography and as chiral shift reagents in NMR spectroscopy. Although their application to electrochemical processes is a field still requiring exploration, they should have a huge impact for instance in asymmetric electropolymerizations and in regioregular electrochemically activated polymerizations, as well as in preparative electrosynthetic processes of chiral compounds. The current general design of CILs follows rather intuitive strategies. The use of a chiral anion (e.g. from lactic acid, \uf061-aminoacids, 10-camphorsulfonic acid, 1,1\u2019- binaphthylphosphoric acid) is a simple but scarcely innovative strategy. More possibilities are afforded by the chiral cation approach; in this case a wide range of building blocks have been so far explored to confer chirality, from the classical 1- phenylethyl group to derivatives of tartaric acid, pinene, myrtanol, citronellol, menthol, carvone, etc. Our group has recently proposed electroactive thiophene-based polyconjugated films of unprecedented chirality manifestations and enantiorecognition ability[1] based on the concept of the whole electroactive backbone coinciding with the stereogenic element, consisting in a tailored torsion induced by an atropisomeric bithiophene scaffold. Now we are trying to apply the same "inherent chirality" approach to the development of inherently chiral ionic liquids, hopefully endowed with high enantioselectivity, like the formerly developed inherently chiral electrodes. An overview will be given of the first structures obtained and of their electrochemical properties. The new molecules are based on cations including different atropisomeric bis-benzimidazolium groups acting as the stereogenic element, responsible for both the molecular chirality and the IL properties of the material, modulated by the number, position and length of alkyl chain substituents

Electrocatalytic Reduction of Bromothiophenes on Gold and Silver Electrodes: an Example of Synergism in Electrocatalysis

The reductive cleavage of C\u2013Br bonds on silver electrodes can be regarded as an ideal model of dissociative electron transfer (DET) in electrocatalytic conditions, modulated by many factors, among which the molecular structure is of particular relevance. A detailed mechanistic study based on a large set of compounds with different molecular structures allowed us a full rationalization of the process for the case of aryl bromides in acetonitrile. [1] Now we are extending this research to heteroaromatic halides, in which the heteroatom not only makes the aromatic ring asymmetric from the perspective of the electron density but also can have its own specific interactions with the electrode surface, in addition to those of the halide ions. [2] As a first approach, we have selected the mono-, di-, tri- and tetra-bromothiophene series, plus a series of substituted bromothiophenes together with the corresponding bromobenzenes as benchmarks, investigating (by CV, supported by EIS in selected cases) the electrochemical reduction of the whole family: (i) on glassy carbon, GC, assumed as a non-catalytic reference electrode accounting for intrinsic reactivity; (ii) on the highly catalytic silver electrode; (iii) on gold electrode, showing in former halide cases lower catalytic effects than silver but having the highest affinity for the sulphur atom in the thiophene ring. While the results on GC and on Ag are fully consistent with the formerly studied aryl bromide case on the same two electrodes [1] the catalytic effects of Au appear to be neatly modulated by the relative position of the Br leaving group with respect to the sulphur atom. This feature is quite evident and reproducible in the whole series (including polysubstituted cases provided by our organic partner group), and points to the S atom acting as an asymmetrically anchoring group for the molecule on the Au surface. [1] S. Arnaboldi, A. Gennaro, A.A. Isse, P.R. Mussini (2015) Electrochimica Acta, 158, 427-436 [2] S. Arnaboldi, A. Bonetti, E. Giussani, P.R. Mussini, T. Benincori, S. Rizzo, A.A. Isse, A. Gennaro (2014) Electrochemistry Communications, 38, 100-10