DellUniversity Firenze

Sesto Fiorentino, Italy

DellUniversity Firenze

Sesto Fiorentino, Italy
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Lapini A.,Lens Inc | Lapini A.,DellUniversity Firenze | Lapini A.,CNR Institute of Neuroscience | Pagliai M.,DellUniversity Firenze | And 9 more authors.
Journal of Physical Chemistry Letters | Year: 2016

Clarifying the structure/dynamics relation of water hydrogen-bond network has been the aim of extensive research over many decades. By joining anvil cell high-pressure technology, femtosecond 2D infrared spectroscopy, and molecular dynamics simulations, we studied, for the first time, the spectral diffusion of the stretching frequency of an HOD impurity in liquid water as a function of pressure. Our experimental and simulation results concordantly demonstrate that the rate of spectral diffusion is almost insensitive to the applied pressure. This behavior is in contrast with the previously reported pressure-induced speed up of the orientational dynamics, which can be rationalized in terms of large angular jumps involving sudden switching between two hydrogen-bonded configurations. The different trend of the spectral diffusion can be, instead, inferred considering that the first solvation shell preserves the tetrahedral structure with pressure and the OD stretching frequency is only slight perturbed. © 2016 American Chemical Society.

Martelli F.,DellUniversity Firenze | Bianco S.D.,DellUniversity Firenze | Bianco S.D.,CNR Institute of Applied Physics Nello Carrara | Zaccanti G.,DellUniversity Firenze
Physics in Medicine and Biology | Year: 2012

We propose the use of a retrieval procedure for time-resolved near-infrared tissue spectroscopy based on the optimal estimation method. The aim of this retrieval method is to obtain an improved estimate of the target parameters compared with standard nonlinear least-squares routines, since the inverse problem dedicated to retrieve the optical properties of tissue is ill posed. A priori information on target and forward model parameters is used, so that a larger number of target parameters can be retrieved, and/or a better accuracy and precision can be achieved on the retrieved target parameters. The procedure has been tested on time-resolved simulated experiments generated, using solutions of the diffusion equation and with solutions of the radiative transfer equation reconstructed with Monte Carlo simulations. The results obtained show that, by using a priori information on target parameters, we have a smaller difference between retrieved values and true values, and lower retrieved error bars. Similarly, a more correct estimate of the errors of the forward model parameters improves the retrieval of the target parameters. © 2012 Institute of Physics and Engineering in Medicine.

Di Ninni P.,DellUniversity Firenze | Martelli F.,DellUniversity Firenze | Zaccanti G.,DellUniversity Firenze
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2011

A reference standard for tissue-simulating phantoms, i.e., a phantom with well known and stable optical properties, reproducible, and easy to be found, would be very useful for many applications based on measurements of diffused light. Although many tissue-equivalent phantoms have been proposed, to our knowledge none of them has been characterized sufficiently well to be suggested as a reference standard. Based on the results of measurements of optical properties we carried out at visible and NIR wavelengths, the use of Intralipid 20% diluted in water as diffusive medium, and of India ink as absorber, is here suggested as a first step towards a diffusive reference standard for tissue-simulating phantoms. As for Intralipid 20%, measurements carried out on samples from nine different batches with expiry dates spreading over ten years showed surprisingly small batch-to-batch variations. For the reduced scattering coefficient the maximum deviation from the value averaged over the nine batches was of about 2%, and the results for the absorption coefficient were very close to those for pure water. As for India ink measurements on samples from different batches and from five different brands showed large inter-brand and inter-batch variations for both the absorption and the extinction coefficient. On the contrary, small variations have been observed for the ratio between the absorption and the extinction coefficient. Intralipid 20% and Indian ink can be therefore easily mixed to obtain liquid phantoms with well known optical properties. This phantom can be a first step towards a reference standard for optical tissue phantoms.

Pietraperzia G.,DellUniversity Firenze | Pietraperzia G.,University of Florence | Pasquini M.,DellUniversity Firenze | Pasquini M.,University of Florence | And 15 more authors.
Journal of Physical Chemistry A | Year: 2011

The present paper reports on an integrated spectroscopic study of the anisole-phenol complex in a molecular beam environment. Combining REMPI and HR-LIF spectroscopy experimental data with density functional computations (TD-M05-2X/M05-2X//N07D) and first principle spectra simulations, it was possible to locate the band origin of the S 1 ← S 0 electronic transition and determine the equilibrium structure of the complex, both in the S 0 and S 1 electronic states. Experimental and computational evidence indicates that the observed band origin is due to an electronic transition localized on the phenol frame, while it was not possible to localize experimentally another band origin due to the electronic transition localized on the anisole molecule. The observed structure of the complex is stabilized by a hydrogen bond between the phenol, acting as a proton donor, and the anisole molecule, acting as an acceptor through the lone pairs of the oxygen atom. A secondary interaction involving the hydrogen atoms of the anisole methyl group and the π electron system of the phenol molecule stabilizes the complex in a nonplanar configuration. Additional insights about the landscapes of the potential energy surfaces governing the ground and first excited electronic states of the anisole-phenol complex, with the issuing implications on the system photodynamic, can be extracted from the combined experimental and computational studies. © 2011 American Chemical Society.

Migliori A.,DellUniversity Firenze | Migliori A.,National Institute of Nuclear Physics, Italy | Migliori A.,CNR Institute of Neuroscience | Bonanni P.,DellUniversity Firenze | And 8 more authors.
Nuovo Cimento della Societa Italiana di Fisica B | Year: 2010

An innovative portable X-Ray Fluorescence (XRF) spectrometer designed and realised at the Laboratorio di tecniche nucleari per i Beni Culturali (LABEC) has been successfully applied to investigate material composition of a gilded bronze relief by Lorenzo Ghiberti coming from the "Gate of Paradise" of the Florence Baptistery. The analysis was intended to study both the original materials and the deposition and alteration layer. Technical features and performances of the instrumentation will be briefly explained in the text, with special emphasis to the innovative aspects which permit to exploit the potentiality of the technique at a higher level with respect to devices commercially available. The results of the measurements on the relief are then presented, including the quantitative characterisation of some areas. Useful information to art historians and conservators was obtained concerning the production techniques and the corrosion processes. © Società Italiana di Fisica.

Straulino S.,DellUniversity Firenze | Cartacci A.,DellUniversity Firenze | Gambi C.M.C.,DellUniversity Firenze
Nuovo Cimento della Societa Italiana di Fisica B | Year: 2010

We describe some of the educational experiments carried out in the framework of the "OpenLab" at the Florence University. In particular we focus our attention on three measurements, which can be carried out in a laboratory of the secondary school and concern the electromagnetism: the determination of the Earth's magnetic field in two methods, the construction of a simple electrometer and some measurements showing the operation of a moving-iron ammeter. The described measurements are quantitative and well reproducible, and have been tested with students and teachers. © Società Italiana di Fisica.

Di Ninni P.,DellUniversity Firenze | Berube-Lauziere Y.,Université de Sherbrooke | Mercatelli L.,National Research Council Italy | Sani E.,National Research Council Italy | Martelli F.,DellUniversity Firenze
Applied Optics | Year: 2012

Intralipid 20% was recently suggested as a diffusive reference standard for tissue simulating phantoms. In this work, we extend previously obtained results to other fat emulsions, specifically Intralipid 10%, Intralipid 30%, Lipovenoes 10%, Lipovenoes 10% PhosphoLipid Reduced, Lipovenoes 20%, Lipofundin S 10%, and Lipofundin S 20%. Of particular importance for practical applications, our measurements carried out at a wavelength of 751 nm show the following features. First, these products show high stability and small batch-to-batch variations in their diffusive optical properties, similar to Intralipid 20%. Second, the absorption coefficient of Intralipid, Lipovenoes, and Lipofundin S are very similar and their measured values are within the experimental errors; moreover the reduced scattering coefficient of Intralipid 20%, Lipovenoes 20%, and Lipofundin S 20% are similar and their measured values are within 5%. Third, the reduced scattering coefficient of Intralipid 10% and Intralipid 30% can be scaled from that of Intralipid 20% with an error of 9% and 2%, respectively. A similar scaling property is valid for Lipovenoes and Lipofundin S. We have verified that this scaling property depends on the composition of the fat emulsions: If the ingredients exactly scale with the concentration then the reduced scattering coefficient almost exactly scale as well. © 2012 Optical Society of America.

Sassaroli A.,Tufts University | Martelli F.,DellUniversity Firenze
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2012

In the field of photon migration in turbid media, different Monte Carlo methods are usually employed to solve the radiative transfer equation. We consider four different Monte Carlo methods, widely used in the field of tissue optics, that are based on four different ways to build photons' trajectories. We provide both theoretical arguments and numerical results showing the statistical equivalence of the four methods. In the numerical results we compare the temporal point spread functions calculated by the four methods for a wide range of the optical properties in the slab and semi-infinite medium geometry. The convergence of the methods is also briefly discussed. © 2012 Optical Society of America.

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