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.

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

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

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

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

Particlization in hybrid models

In hybrid models, which combine hydrodynamical and transport approaches to describe different stages of heavy-ion collisions, conversion of fluid to individual particles, particlization, is a non-trivial technical problem. We describe in detail how to find the particlization hypersurface in a 3+1 dimensional model, and how to sample the particle distributions evaluated using the Cooper-Frye procedure to create an ensemble of particles as an initial state for the transport stage. We also discuss the role and magnitude of the negative contributions in the Cooper-Frye procedure.Comment: 18 pages, 28 figures, EPJA: Topical issue on "Relativistic Hydro- and Thermodynamics"; version accepted for publication, typos and error in Eq.(1) corrected, the purpose of sampling and change from UrQMD to fluid clarified, added discussion why attempts to cancel negative contributions of Cooper-Frye are not applicable her

Enantioselective voltammetry in chiral ionic liquid media

Enantioselective voltammetry in chiral ionic liquid media P. R. Mussini1*, S. Arnaboldi1, M. Longhi1, I.F. Buzzi1, S. Grecchi1, F. Sannicol\uf21, Simona Rizzo2, Voichita Michali1, E. Licandro1, S. Cauteruccio1, T. Bellini3, G. Zanchetta3, A. Gennaro,4 A.A. Isse4, C. Chiappe5, L. Guazzelli5 1 Universit\ue0 degli Studi di Milano, Dip. di Chimica, Via Golgi 19, 20133 Milano, Italy 2 Istituto di Scienze e Tecnologie Molecolari, CNR, via Golgi 19, 20133 Milano, Italy 3 Universit\ue0 degli Studi di Milano, Dip. di Biotecnologie Mediche e Medicina Traslazionale, Via Fratelli Cervi 93, 20090 Segrate (MI), Italy 4 Universit\ue0 degli Studi di Padova, Dip.di Scienze Chimiche, Via Marzolo 1, 35131 Padova, Italy 5 Universit\ue0 degli Studi di Pisa, Dip. di Farmacia, via Bonanno 33, 56126 Pisa, Italy. *[email protected] Chiral media enabling enantiorecognition of chiral probes on achiral electrodes (in terms of significantly different peak potentials for the two probe enantiomers) represent an attractive target in voltammetry. Concerning possible ad hoc strategies, (a) on one hand, transmission of the chiral information should be more and more efficient with increasing structural order at the chiral medium| charged electrode interphase, and it has been recently shown that ionic liquid|electrode interphases are extremely well organized for many layers [1]; (b) on the other hand, outstanding enantioselection performances have been recently observed on electrode surfaces consisting in "inherently chiral" oligomer films, in which chirality originates from the whole main molecular backbone (also determining the material electroactivity), on account of a tailored torsion with high racemization barrier [2-6]. Combining both approaches, we recently developed two "inherently chiral" ionic liquids, consisting of dialkylated bicollidinium salts, with an atropisomeric bipyridinium cation featuring at least one octyl chain and bistrifilimidate counteranions.[7] They show high enantioselectivity in terms of wide potential differences for the enantiomers of a chiral probe when tested even as low concentration additives in commercial achiral ionic liquids. Importantly, similar ability (increasing with additive concentration) was also shown by other selectors of the same family, having shorter alkyl chains and/or different counteranions, and thus solid at room temperature but easier to synthesize [7]. Using such chiral selectors as additives in an achiral ionic liquid rather than as bulk media is even more attractive, since only a small quantity of the enantiopure selector is needed and a low melting point is no more required, but only sufficient solubility in the achiral ionic liquid. For instance, this allowed us to successfully exploit as additives for chiral voltammetry in ionic liquids other inherently chiral selectors based on different stereogenic elements, i.e., a bibenzimidazole atropisomeric scaffold [8,9] and a helicene one. The study provides further evidence of the general validity of the "inherent chirality" strategy, since large potential differences are observed on achiral electrodes for the enantiomers of chiral probes even of very different structure and electroactivity (like in our parallel research on inherently chiral electrodes), and possibly even in experiments with more than one chiral probe. Work is also in progress to better elucidate the process, including evaluation of the twisting power of our selectors as well as comparison with a family of ionic liquids and additives having cations derived from the natural pool, in which chirality originates from one or more stereocentres. References [1] Langmuir 2016, 32, 9507-9512. [2] Angew. Chem. Int. Ed. 2014, 53, 2623 [3] Chem. Eur. J. 2014, 20, 15298. [4] Chem. Sci. 2015, 6,1706. [5] Chem. Eur. J. 2016 , 22,10839. [6] Anal. Bioanal. Chem. 2016, 408, 7243. [7] Angew. Chem. Int. Ed. 2017, 56, 2079. [8] Electrochim. Acta 2015, 179, 250-262. [9] Electrochem. Comm. 2018, accepted. Acknowledgment. The support of Fondazione Cariplo/Regione Lombardia "Avviso congiunto per l\u2019incremento dell\u2019attrattivit\ue0 del sistema di ricerca lombardo e della competitivit\ue0 dei ricercatori candidati su strumenti ERC - edizione 2016\u201d (Project 2016-0923) to our chiral electrochemistry and electroanalysis research is gratefully acknowledged