A corresponding states approach to Small-Angle-Scattering for polydisperse ionic colloidal fluids

Approximate scattering functions for polydisperse ionic colloidal fluids are obtained by a corresponding states approach. This assumes that all pair correlation functions $g_{\alpha \beta}(r)$ of a polydisperse fluid are conformal to those of an appropriate monodisperse binary fluid (reference system) and can be generated from them by scaling transformations. The correspondence law extends to ionic fluids a {\it scaling approximation} (SA) successfully proposed for nonionic colloids in a recent paper. For the primitive model of charged hard spheres in a continuum solvent, the partial structure factors of the monodisperse binary reference system are evaluated by solving the Orstein-Zernike (OZ) integral equations coupled with an approximate closure. The SA is first tested within the mean spherical approximation (MSA) closure, which allows analytical solutions. The results are found in good overall agreement with exact MSA predictions up to relevant polidispersity. The SA is shown to be an improvement over the ``decoupling approximation'' extended to the ionic case. The simplicity of the SA scheme allows its application also when the OZ equations can be solved only numerically. An example is then given by using the hypernetted chain (HNC) closure. Shortcomings of the SA approach, its possible use in the analysis of experimental scattering data and other related points are also briefly addressed.Comment: 29 pages, 7 postscript figures (included), Latex 3.0, uses aps.sty, to appear in Phys. Rev. E (1999

Polydisperse star polymer solutions

We analyze the effect of polydispersity in the arm number on the effective interactions, structural correlations and the phase behavior of star polymers in a good solvent. The effective interaction potential between two star polymers with different arm numbers is derived using scaling theory. The resulting expression is tested against monomer-resolved molecular dynamics simulations. We find that the theoretical pair potential is in agreement with the simulation data in a much wider polydispersity range than other proposed potentials. We then use this pair potential as an input in a many-body theory to investigate polydispersity effects on the structural correlations and the phase diagram of dense star polymer solutions. In particular we find that a polydispersity of 10%, which is typical in experimental samples, does not significantly alter previous findings for the phase diagram of monodisperse solutions.Comment: 14 pages, 7 figure

Fano resonances in plasmonic core-shell particles and the Purcell effect

Despite a long history, light scattering by particles with size comparable with the light wavelength still unveils surprising optical phenomena, and many of them are related to the Fano effect. Originally described in the context of atomic physics, the Fano resonance in light scattering arises from the interference between a narrow subradiant mode and a spectrally broad radiation line. Here, we present an overview of Fano resonances in coated spherical scatterers within the framework of the Lorenz-Mie theory. We briefly introduce the concept of conventional and unconventional Fano resonances in light scattering. These resonances are associated with the interference between electromagnetic modes excited in the particle with different or the same multipole moment, respectively. In addition, we investigate the modification of the spontaneous-emission rate of an optical emitter at the presence of a plasmonic nanoshell. This modification of decay rate due to electromagnetic environment is referred to as the Purcell effect. We analytically show that the Purcell factor related to a dipole emitter oriented orthogonal or tangential to the spherical surface can exhibit Fano or Lorentzian line shapes in the near field, respectively.Comment: 28 pages, 10 figures; invited book chapter to appear in "Fano Resonances in Optics and Microwaves: Physics and Application", Springer Series in Optical Sciences (2018), edited by E. O. Kamenetskii, A. Sadreev, and A. Miroshnichenk

Low energy analysis techniques for CUORE

CUORE is a tonne-scale cryogenic detector operating at the Laboratori Nazionali del Gran Sasso (LNGS) that uses tellurium dioxide bolometers to search for neutrinoless double-beta decay of 130Te. CUORE is also suitable to search for low energy rare events such as solar axions or WIMP scattering, thanks to its ultra-low background and large target mass. However, to conduct such sensitive searches requires improving the energy threshold to 10 keV. In this paper, we describe the analysis techniques developed for the low energy analysis of CUORE-like detectors, using the data acquired from November 2013 to March 2015 by CUORE-0, a single-tower prototype designed to validate the assembly procedure and new cleaning techniques of CUORE. We explain the energy threshold optimization, continuous monitoring of the trigger efficiency, data and event selection, and energy calibration at low energies in detail. We also present the low energy background spectrum of CUORE-0 below 60keV. Finally, we report the sensitivity of CUORE to WIMP annual modulation using the CUORE-0 energy threshold and background, as well as an estimate of the uncertainty on the nuclear quenching factor from nuclear recoils inCUORE-0

Temperature and composition dependence of the Soret coefficient in Lennard-Jones mixtures presenting consolute critical phenomena

Nonequilibrium molecular dynamics calculations have been carried out on Lennard-Jones binary mixtures with the aim to investigate the dependence of the Soret coefficient on the temperature and on the composition for systems presenting phase transitions. By an appropriate choice of the cross interaction parameter, ε12 (0<ε12<min{ε11,ε22}), these systems show a mixing/demixing (consolute) phase transition. The other parameters are those of a binary mixture of Argon and Krypton. This system has been considered over a wide range of temperatures (up to ≃ 1000 K), of compositions (0.1 ≤ x1 ≤ 0.9), and of cross interaction parameter (0<ε12<min{ε11,ε22}). The study allows the formulation of a very simple expression for the Soret coefficient, ST, as a function of temperature and composition. Indeed the computed values of ST in the one phase region outside the critical region are closely fitted by the function [T−Tc(x1)]−1 where Tc(x1) is the demixing temperature of the mixture under study. This result indicates for this type of systems a dependence of ST, as a function of the temperature, on a unique characteristic property of the fluid mixture, the demixing temperature Tc, which, in turn, is a function of the binary mixture composition x1

Thermo-physical Properties of a Steel-making by-product to be used as Thermal Energy Storage Material in a Packed-bed System

AbstractIn this paper the valorisation of an industrial and cheap by-product from the steel manufacturing, Electric Arc Furnace slag, is studied as new thermal energy storage material in a packed-bed system. For this application, the driving thermo-physical and the thermal and chemical stability of two different slags have been studied. The obtained results have revealed that this material presents similar properties to other materials typically studied as filler/thermal energy storage material in a packed-bed arrangement. The thermal stability and compatibility analysis have indicated that the slag is stable, at least up to 1000°C when working in direct contact with air as heat transfer fluid. In addition, in this work, a heat storage system based on air-packed bed configuration is proposed. In this frame, different operation methods have been computationally analysed in order to maximize the storage capacity and efficiency of the packed-bed design. Overall, this work has demonstrated the high potential of this waste material to obtain an efficient and cost-effective thermal energy storage solution

Parabolic trough demonstrator for high temperature solar energy in sardinia using gas as heat transfer fluid

ESTATE Lab (Laboratorio per l’Energia Solare Termica ad Alta Temperatura) project is aimed towards building up a laboratory for the development of high temperature concentrated solar technologies in Sardinia, Italy. The main purpose of the R&D activities is the construction of a demonstration plant for the production and storage of energy at 550°C by means of sun-heated gaseous fluids. The plant will be built in the industrial area of Macchiareddu, nearby Cagliari and mainly consists of two 100 m. lines of parabolic trough collectors and one thermocline pebble-bed energy storage for each line. The Estate Lab project demonstrator will be developed in order to prove the good findings of the research activities and to validate the expected results. The optimisation of the system will be also investigated for a proper scale up of the plant to a commercial size for bulk electricity production. This paper presents the key technical data of the experimental facility and the significant and innovative aspects of the project