Mesophases in Nearly 2D Room-Temperature Ionic Liquids

Computer simulations of (i) a [C12mim][Tf2N] film of nanometric thickness squeezed at kbar pressure by a piecewise parabolic confining potential reveal a mesoscopic in-plane density and composition modulation reminiscent of mesophases seen in 3D samples of the same room-temperature ionic liquid (RTIL). Near 2D confinement, enforced by a high normal load, relatively long aliphatic chains are strictly required for the mesophase formation, as confirmed by computations for two related systems made of (ii) the same [C12mim][Tf2N] adsorbed at a neutral solid surface and (iii) a shorter-chain RTIL ([C4mim][Tf2N]) trapped in the potential well of part i. No in-plane modulation is seen for ii and iii. In case ii, the optimal arrangement of charge and neutral tails is achieved by layering parallel to the surface, while, in case iii, weaker dispersion and packing interactions are unable to bring aliphatic tails together into mesoscopic islands, against overwhelming entropy and Coulomb forces. The onset of in-plane mesophases could greatly affect the properties of long-chain RTILs used as lubricants.Comment: 24 pages 10 figure

Jahn-Teller Spectral Fingerprint in Molecular Photoemission: C60

The h_u hole spectral intensity for C60 -> C60+ molecular photoemission is calculated at finite temperature by a parameter-free Lanczos diagonalization of the electron-vibration Hamiltonian, including the full 8 H_g, 6 G_g, and 2 A_g mode couplings. The computed spectrum at 800 K is in striking agreement with gas-phase data. The energy separation of the first main shoulder from the main photoemission peak, 230 meV in C60, is shown to measure directly and rather generally the strength of the final-state Jahn-Teller coupling.Comment: 5 pages, 3 figure

Low-energy excitations of a linearly Jahn-Teller coupled orbital quintet

The low-energy spectra of the single-mode h x (G+H) linear Jahn-Teller model is studied by means of exact diagonalization. Both eigenenergies and photoemission spectral intensities are computed. These spectra are useful to understand the vibronic dynamics of icosahedral clusters with partly filled orbital quintet molecular shells, for example C60 positive ions.Comment: 14 pages revte

Circular Economy: A Performance Evaluation Perspective

Circular Economy has emerged in the last years as an industrial pattern that rethinks the entire design and production cycle of products and goods, to obtain the minimal environmental impact and maximize the energy efficiency. This pattern creates product transformation cycles, that allow to re-use parts and renew energy, defining Circular Economy Ecosystems. Such cycles, are very interesting systems from a performance evaluation point of view: in this paper we give a Colored Petri Net perspective to circular economy. In particular, we focus on an example taken from the literature that considers car manufacturing, and we show how we can deal with the problem using standard performance evaluation techniques. Results from performance analysis of the case study, allow to focus on new interesting metrics and performance indicators, that might not be fully studied with conventional techniques applied by expert of the economical domain

Exactly quantized dynamics of classical incommensurate sliders

We report peculiar velocity quantization phenomena in the classical motion of an idealized 1D solid lubricant, consisting of a harmonic chain interposed between two periodic sliders. The ratio v_cm/v_ext of the chain center-of-mass velocity to the externally imposed relative velocity of the sliders stays pinned to exact "plateau" values for wide ranges of parameters, such as sliders corrugation amplitudes, external velocity, chain stiffness and dissipation, and is strictly determined by the commensurability ratios alone. The phenomenon is explained by one slider rigidly dragging the kinks that the chain forms with the other slider. Possible consequences of these results for some real systems are discussed.Comment: 5 pags 4 fig

The role of the Berry Phase in Dynamical Jahn-Teller Systems

The presence/absence of a Berry phase depends on the topology of the manifold of dynamical Jahn-Teller potential minima. We describe in detail the relation between these topological properties and the way the lowest two adiabatic potential surfaces get locally degenerate. We illustrate our arguments through spherical generalizations of the linear T x h and H x h cases, relevant for the physics of fullerene ions. Our analysis allows us to classify all the spherical Jahn-Teller systems with respect to the Berry phase. Its absence can, but does not necessarily, lead to a nondegenerate ground state.Comment: revtex 7 pages, 2 eps figures include

Antioxidant activities of hydroxylated naphthalenes: the role of aryloxyl radicals

Herein is delineated a first systematic framework for the definition of structure-antioxidant property relationships in the dihydroxynaphthalene (DHN) series. The results obtained by a combined experimental and theoretical approach revealed that 1,8-DHN is the best performing antioxidant platform, with its unique hydrogen-bonded peri-hydroxylation pattern contributing to a fast H atom transfer process. Moreover, the comparative analysis of the antioxidant properties of DHNs carried out by performing DPPH and FRAP assays and laser flash photolysis experiments, revealed the higher antioxidant power associated with an α-substitution pattern (i. e. in 1,8- and 1,6-DHN) with respect to DHNs exhibiting a β-substitution pattern (i. e. in 2,6- and 2,7-DHN). DFT calculations and isolation and characterization of the main oligomer intermediates formed during the oxidative polymerization of DHNs supported this evidence by providing unprecedented insight into the generation and fate of the intermediate naphthoxyl radicals, which emerged as the main factor governing the antioxidant activity of DHNs

Surprises in the Orbital Magnetic Moment and g-Factor of the Dynamic Jahn-Teller Ion C_{60}^-

We calculate the magnetic susceptibility and g-factor of the isolated C_{60}^- ion at zero temperature, with a proper treatment of the dynamical Jahn-Teller effect, and of the associated orbital angular momentum, Ham-reduced gyromagnetic ratio, and molecular spin-orbit coupling. A number of surprises emerge. First, the predicted molecular spin-orbit splitting is two orders of magnitude smaller than in the bare carbon atom, due to the large radius of curvature of the molecule. Second, this reduced spin-orbit splitting is comparable to Zeeman energies, for instance, in X-band EPR at 3.39KGauss, and a field dependence of the g-factor is predicted. Third, the orbital gyromagnetic factor is strongly reduced by vibron coupling, and so therefore are the effective weak-field g-factors of all low-lying states. In particular, the ground-state doublet of C_{60}^- is predicted to show a negative g-factor of \sim -0.1.Comment: 19 pages RevTex, 2 postscript figures include