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Search Results: 1 - 10 of 5687 matches for " Simone Taioli "
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Finite-range effects in dilute Fermi gases at unitarity
Stefano Simonucci,Giovanni Garberoglio,Simone Taioli
Physics , 2011, DOI: 10.1103/PhysRevA.84.043639
Abstract: We develop a theoretical method going beyond the contact-interaction approximation frequently used in mean-field theories of many-fermion systems, based on the low-energy T-matrix of the pair potential to rigorously define the effective radius of the interaction. One of the main consequences of our approach is the possibility to investigate finite-density effects, which are outside the range of validity of approximations based on delta-like potentials. We apply our method to the calculation of density dependent properties of an ultracold gas of 6Li atoms at unitarity, whose two-body interaction potential is calculated using ab initio quantum chemistry methods. We find that density effects will be significant in ultracold gases with densities one order of magnitude higher than those attained in current experiments.
Mixed ab initio quantum mechanical and Monte Carlo calculations of secondary emission from SiO2 nanoclusters
Simone Taioli,Stefano Simonucci,Lucia Calliari,Massimiliano Filippi,Maurizio Dapor
Physics , 2009, DOI: 10.1103/PhysRevB.79.085432
Abstract: A mixed quantum mechanical and Monte Carlo method for calculating Auger spectra from nanoclusters is presented. The approach, based on a cluster method, consists of two steps. Ab initio quantum mechanical calculations are first performed to obtain accurate energy and probability distributions of the generated Auger electrons. In a second step, using the calculated line shape as electron source, the Monte Carlo method is used to simulate the effect of inelastic losses on the original Auger line shape. The resulting spectrum can be directly compared to 'as-acquired' experimental spectra, thus avoiding background subtraction or deconvolution procedures. As a case study, the O K-LL spectrum from solid SiO2 is considered. Spectra computed before or after the electron has traveled through the solid, i.e., unaffected or affected by extrinsic energy losses, are compared to the pertinent experimental spectra measured within our group. Both transition energies and relative intensities are well reproduced.
Theoretical Estimates of Stellar e-Captures. I. The half-life of 7Be in Evolved Stars
Stefano Simonucci,Simone Taioli,Maurizio Busso,Sara Palmerini
Physics , 2012, DOI: 10.1088/0004-637X/764/2/118
Abstract: The Li enrichment in the Universe still presents various puzzles to astrophysics. One open issue is that of obtaining estimates for the rate of e-captures on 7Be, for T and rho conditions different from solar. This is important to model the Galactic nucleosynthesis of Li. In this framework, we present a new theoretical method for calculating the e-capture rate in conditions typical of evolved stars. We show how our approach compares with state-of-the-art techniques for solar conditions, where various estimates are available. Our computations include: i) "traditional" calculations of the electronic density at the nucleus, to which the e-capture rate for 7Be is proportional, for different theoretical approaches including the Thomas--Fermi, Poisson--Boltzmann and Debye--Hueckel (DH) models of screening, ii) a new computation, based on a formalism that goes beyond the previous ones, adopting a mean-field "adiabatic" approximation to the scattering process. The results obtained with our approach as well as with the traditional ones and their differences are discussed in some detail, starting from solar conditions, where our method and the DH model converge to the same solution. We then analyze the applicability of the various models to a rather broad range of T and rho values, embracing those typical of red giant stars. We find that, over a wide region of the parameter space explored, the DH approximation does not stand, and the more general method we suggest is preferable. We then briefly reanalyze the 7Li abundances in RGB and AGB stars of the Galactic Disk using the new Be-decay rate. We also underline that the different values of the electron density at the nucleus we find should induce effects on electron screening (for p-captures on Li itself, as well as for other nuclei) so that our new approach might have wide astrophysical consequences.
Imaginary crystals made real
Simone Taioli,Ruggero Gabbrielli,Stefano Simonucci,Nicola Maria Pugno,Alfredo Iorio
Physics , 2015,
Abstract: We realize Lobachevsky geometry in a simulation lab, by producing a carbon-based mechanically stable molecular structure, arranged in the shape of a Beltrami pseudosphere. We find that this structure: i) corresponds to a non-Euclidean crystallographic group, namely a loxodromic subgroup of SL(2,Z); ii) has an unavoidable singular boundary, that we fully take into account. Our approach, substantiated by extensive numerical simulations of Beltrami pseudospheres of different size, might be applied to other surfaces of constant negative Gaussian curvature, and points to a general procedure to generate them. Our results also pave the way to test certain scenarios of the physics of curved spacetimes.
Fonte sísmica de pequeno diametro para ensaios entre furos de sondagens ("Crosshole")
Taioli, Fabio;
Revista Brasileira de Geofísica , 2001, DOI: 10.1590/S0102-261X2001000100007
Abstract: in civil engineering applications, the crosshole test is the most utilized method to determine the propagation velocities of in situ p and s waves of the different strata and, consequently, to calculate the dynamic elastic parameters of rock or soil samples. otherwise, its use has been limited just to very important studies since the associated cost is very high for smaller constructions such as residential and ordinary buildings. this is mainly due to the fact that the equipment normally used to perform these tests needs special boreholes, with diameter uncommon in the investigation phase. in order to decrease the crosshole overall cost, a simple and inexpensive seismic source was developed. this source can be used in the same boreholes made during the standard penetration test (spt). its maximum external diameter is 40 mm, fitting in a pvc casing of 50 mm external diameter (46 mm internal). at the same time, the casing can be easily installed in a 75 mm (3") maximum diameter, leaving place to fill the annular space with mortar. the seismic source clamps on the borehole wall by a pneumatic system and, by means of a sliding piston, generates mainly s type waves. it has proven to be easy to use besides being lightweight and of small size.
Silk reinforced with graphene or carbon nanotubes spun by spiders
Emiliano Lepore,Francesco Bonaccorso,Matteo Bruna,Federico Bosia,Simone Taioli,Giovanni Garberoglio,Andrea. C. Ferrari,Nicola Maria Pugno
Physics , 2015,
Abstract: Here, we report the production of silk incorporating graphene and carbon nanotubes directly by spider spinning, after spraying spiders with the corresponding aqueous dispersions. We observe a significant increment of the mechanical properties with respect to the pristine silk, in terms of fracture strength, Young's and toughness moduli. We measure a fracture strength up to 5.4 GPa, a Young's modulus up to 47.8 GPa and a toughness modulus up to 2.1 GPa, or 1567 J/g, which, to the best of our knowledge, is the highest reported to date, even when compared to the current toughest knotted fibres. This approach could be extended to other animals and plants and could lead to a new class of bionic materials for ultimate applications.
Towards room-temperature single-layer graphene synthesis by C60 Supersonic Molecular Beam Epitaxy
Roberta Tatti,Lucrezia Aversa,Roberto Verucchi,Emanuele Cavaliere,Giovanni Garberoglio,Nicola M. Pugno,Giorgio Speranza,Simone Taioli
Physics , 2015,
Abstract: High-kinetic energy impacts between inorganic surfaces and molecular beams seeded by organics represent a fundamental case study in materials science, most notably when they activate chemical-physical processes leading to nanocrystals growth. Here we demonstrate single-layer graphene synthesis on copper by C60 supersonic molecular beam (SuMBE) epitaxy at 645 {\deg}C, with the possibility of further reduction. Using a variety of electron spectroscopy and microscopy techniques, and first-principles simulations, we describe the chemical-physical mechanisms activated by SuMBE resulting in graphene growth. In particular, we find a crucial role of high-kinetic energy deposition in enhancing the organic/inorganic interface interaction, to control the cage openings and to improve the growing film quality. These results, while discussed in the specific case of graphene on copper, are potentially extendable to different metallic or semiconductor substrates and where lower processing temperature is desirable.
Contamination potential of the Ilhabela (SP) landfill
Anais da Academia Brasileira de Ciências , 2002,
On Line Media Market and New Advertising Agencies: Analysis of an Italian Case  [PDF]
Simone Guercini
Journal of Service Science and Management (JSSM) , 2009, DOI: 10.4236/jssm.2009.22015
Abstract: This article focuses on the profile of agencies which offer communication services through new media related to the information role of the major search engines systems (like Google, Yahoo and others). In particular, attention is paid to firms operating in that context which are taking an innovative profile when compared to communication agencies linked to traditional media. The article develops the following steps: in a first part the characteristics are taken into consideration through inno-vative communication systems search engines in relation to market trends and the latest configuration of actors linked to them; a second step considers the case of an Italian company acting as an agency in the so-called "online media market", highlighting the type of skills and relationships developed through this; finally in a third part some thoughts on the characteristics of the new communication agencies are proposed in comparison with those of the traditional ad-vertising agencies operating with the help of the more traditional mass media. At the conclusion of the article some implications of the analysis are developed and evaluations are made about the development of new business communication services object of our analysis.
Berezin Quantization of Gaussian Functions Depending by a Quantum and Compression Parameter  [PDF]
Simone Camosso
Journal of Quantum Information Science (JQIS) , 2019, DOI: 10.4236/jqis.2019.91002
Abstract: The aim of this work is to study the Berezin quantization of a Gaussian state. The result is another Gaussian state that depends on a quantum parameter α, which describes the relationship between the classical and quantum vision. The compression parameter λ>0 is associated to the harmonic oscillator semigroup.
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