Accurate nonrelativistic ground-state energies of 3d transition metal atoms

We present accurate nonrelativistic ground-state energies of the transition metal atoms of the 3d series calculated with Fixed-Node Diffusion Monte Carlo (FN-DMC). Selected multi-determinantal expansions obtained with the CIPSI method (Configuration Interaction using a Perturbative Selection made Iteratively) and including the most prominent determinants of the full CI expansion are used as trial wavefunctions. Using a maximum of a few tens of thousands determinants, fixed-node errors on total DMC energies are found to be greatly reduced for some atoms with respect to those obtained with Hartree-Fock nodes. The FN-DMC/(CIPSI nodes) ground-state energies presented here are, to the best of our knowledge, the most accurate values reported so far. Thanks to the variational property of FN-DMC total energies, the results also provide lower bounds for the absolute value of all-electron correlation energies, $|E_c|$.Comment: 5 pages, 3 table

New electrocatalysts for hydrogen-oxygen fuel cells

Platinum-silver, palladium-gold, and platinum-gold alloys serve as oxygen reduction catalysts in high-current-density cells. Catalysts were tested on polytetrafluoroethylene-bonded cathodes and a hydrogen anode at an operating cell temperature of 80 degrees C

Development of cathodic electrocatalysts for use in low temperature H2/O2 fuel cells with an alkaline electrolyte Second quarterly report, Oct. 1 - Dec. 31, 1965

Cathodic electrocatalysts for use in low temperature hydrogen-oxygen fuel cells with an alkaline electrolyte-corrosion resistance and activity testing of materials and element

Several new catalysts for reduction of oxygen in fuel cells

Test results prove nickel carbide or nitride, nickel-cobalt carbide, titanium carbide or nitride, and intermetallic compounds of the transition or noble metals to be efficient electrocatalysts for oxygen reduction in alkaline electrolytes in low temperature fuel cells

Resonant hyper-Raman scattering in spherical quantum dots

A theoretical model of resonant hyper-Raman scattering by an ensemble of spherical semiconductor quantum dots has been developed. The electronic intermediate states are described as Wannier-Mott excitons in the framework of the envelope function approximation. The optical polar vibrational modes of the nanocrystallites (vibrons) and their interaction with the electronic system are analized with the help of a continuum model satisfying both the mechanical and electrostatic matching conditions at the interface. An explicit expression for the hyper-Raman scattering efficiency is derived, which is valid for incident two-photon energy close to the exciton resonances. The dipole selection rules for optical transitions and Fr\"ohlich-like exciton-lattice interaction are derived: It is shown that only exciton states with total angular momentum $L=0,1$ and vibrational modes with angular momentum $l_p=1$ contribute to the hyper-Raman scattering process. The associated exciton energies, wavefunctions, and vibron frequencies have been obtained for spherical CdSe zincblende-type nanocrystals, and the corresponding hyper-Raman scattering spectrum and resonance profile are calculated. Their dependence on the dot radius and the influence of the size distribution on them are also discussed.Comment: 12 pages REVTeX (two columns), 2 tables, 8 figure

Electron-phonon interaction in quantum-dot/quantum-well semiconductor heterostructures

Polar optical phonons are studied in the framework of the dielectric continuum approach for a prototypical quantum-dot/quantum-well (QD/QW) heterostructure, including the derivation of the electron-phonon interaction Hamiltonian and a discussion of the effects of this interaction on the electronic energy levels. The particular example of the CdS/HgS QD/QW is addressed and the system is modelled according to the spherical geometry, considering a core sphere of material "1" surrounded by a spherically concentric layer of material "2", while the whole structure is embedded in a host matrix assumed as an infinite dielectric medium. The strength of the electron-LO phonon coupling is discussed in details and the polaronic corrections to both ground state and excited state electron energy levels are calculated. Interesting results concerning the dependence of polaronic corrections with the QD/QW structure size are analyzed.Comment: 8 pages, 5 figure

Interface optical phonons in spheroidal dots: Raman selection rules

The contribution of interface phonons to the first order Raman scattering in nanocrystals with non spherical geometry is analyzed. Interface optical phonons in the spheroidal geometry are discussed and the corresponding Frohlich-like electron-phonon interaction is reported in the framework of the dielectric continuum approach. It is shown that the interface phonon modes are strongly dependent on the nanocrystal geometry, particularly on the ellipsoid's semi-axis ratio. The new Raman selection rules have revealed that solely interface phonon modes with even angular momentum are allowed to contribute to the first order phonon-assisted scattering of light. On this basis we are able to give an explanation for the observed low frequency shoulders present in the Raman cross-section of several II-VI semiconductor nanostructures.Comment: 8 pages, 2 figure

HBIM FROM A FIRST CENTURY ICONOGRAPHY

Abstract. Protecting and enhancing inherited assets is a duty of every age; ours requires disclosure through the services of the interconnected network, the only one, to date, capable of reaching a wide audience and with it attracting adequate economic resources for the implementation of programs. In keeping with the international definition of "Cultural Heritage", the paper describes the methodology that guided the construction in 3D of the monumental building sculpted in the iconographies between 52 and 62 AD on the marble slab now preserved at the archaeological museum of Perugia. An informative workflow on what has been collected is proposed to then discuss the potential of its uses. The focus lies in particular on the possibility of the model to act as an interoperable collector to compare the reconstructive hypotheses.The final objective looks at the opportunity to create multimedia, multimodal and cross modal collaboration spaces to remedy aspects that, by affecting a wider audience of users, encourage socio-economic policies