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Biomedical subjects

F Sacchetti

Publications and source records attributed to F Sacchetti.

At least 19 recordsLinked to original sources

Clinical implications of hepatitis C virus infection in MALT-type lymphoma of the ocular adnexa.

BACKGROUND: A pathogenic link between hepatitis C virus (HCV) and MALT-type lymphomas has been suggested. However, studies assessing the role of HCV infection separately in different forms of MALT lymphomas are not available. PATIENTS AND METHODS: The prevalence and clinical implications of HCV seropositivity were analyzed in 55 patients with ocular adnexa lymphoma (OAL) of MALT-type. RESULTS: HCV seropositivity was detected in seven (13%) patients. At presentation, HCV infection was significantly associated with concomitant extra-orbital disease, lymph node dissemination and involvement of additional extranodal organs. HCV seropositivity was associated also with a higher relapse rate and worse progression-free survival. In fact, 16 patients experienced relapse after first-line treatment: five (71%) were HCV-seropositive and 11 (23%) were HCV-seronegative, with a median TTP of 31 and 50+ months (P = 0.01), and a 5-year progression-free survival of 43 +/- 18% and 77 +/- 7% (P = 0.005), respectively. HCV-seropositive patients experienced frequent relapses despite further lines of therapy; relapses were systemic in all cases but one; multiple subcutaneous nodules were common at relapse. CONCLUSIONS: HCV seropositivity is present in 13% of OAL of MALT-type. Concomitant HCV infection is associated with more disseminated disease and aggressive behavior in OAL, with a consequent potential negative impact in patients managed with radiotherapy alone.

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Direct experimental evidence of free-fermion antibunching.

Fermion antibunching was observed on a beam of free noninteracting neutrons. A monochromatic beam of thermal neutrons was first split by a graphite single crystal, then fed to two detectors, displaying a reduced coincidence rate. The result is a fermionic complement to the Hanbury Brown and Twiss effect for photons.

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Quasielastic neutron scattering investigation of the pressure dependence of molecular motions in liquid water.

We report on a high-resolution, high-statistics, quasielastic neutron scattering (QENS) experiment on liquid water, aimed at accurately measuring the pressure dependence of the single-particle dynamic response function at low wave vector transfers, namely, from 0.26 to 1.32 A(-1). High-pressure QENS data were collected along the T = 268 K isothermal path over the rather extended pressure range of 80 up to 350 MPa, a thermodynamic region so far unexplored by this microscopic technique. The analysis of the measured line shapes enabled us to draw a consistent picture of the wave vector and pressure dependences of the diffusion mechanisms in liquid water, against which the most recent models for water dynamics can be checked. In close similarity with the case of supercooled water, the relaxing-cage model was found to provide a quantitatively more accurate description of the molecular motions and their pressure evolution in liquid water.

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Brillouin neutron scattering in heavy water: evidence for two-mode collective dynamics.

A high resolution (1.5 meV) inelastic neutron scattering experiment was carried out, aiming at an accurate investigation of the high frequency and low momentum dynamic response in heavy water. The experimental data confirm the existence of a dispersionless mode, besides the ordinary longitudinal collective dynamics. A simplified model, based on the interaction of two vibrational branches, is proposed to interpret the observed features of the dynamic spectra. The validity extent of this scheme is proved by applying it to room temperature neutron and x-ray data, to temperature and pressure dependent x-ray data, and to room temperature neutron data of vibrational density of states. The overall successfull results provided by this model, in conjunction with the combined analysis of the x-ray and neutron data on collective dynamics, enable a deeper insight into the complex mechanisms of the water dynamics and provide a simple phenomenological explanation for the transition from ordinary to fast sound.

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Complex particles produced from graphite powder by acoustic cavitation in water.

Spaghetti-like structures made of fibers whose diameter are of about 1-2 microns, straight structures from about 10-20 microns and optically semitransparent particles, with linear dimension up to about 0.3 mm, were obtained from fine graphite powder in water subjected for 20 h to acoustic cavitation at a frequency of 19.5 kHz. A picture of spaghetti-like structures obtained by scanning electron microscopy is reported. From X-ray diffraction pattern, it was found that the semitransparent precipitates have an amorphous nature.

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Neutron investigation of the ion dynamics in liquid mercury: evidence for collective excitations.

The ion dynamics of liquid mercury was investigated by inelastic neutron scattering. By exploiting an optimized high-resolution ( approximately 1 meV) experimental configuration, the dynamic response function was accurately measured. Collective excitations extending up to 0.6 A(-1) were observed with an associated velocity of 2100+/-80 m/s. This value is notably greater than the sound velocity, but it is provided by a simple Bohm-Staver calculation. The latter finding emphasizes those electron-related features in the ion dynamics, which are common to systems as different as polyvalent and alkali metals.

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Neutron investigation of collective excitations in liquid K-Cs alloys: the role of the electron density.

The investigation of the ion dynamics in the liquid alloy K52Cs48, which has the same electron density as Rb, was carried out by neutron inelastic scattering. Well defined collective excitations were observed up to the maximum value of momentum transfer of the experiment. A scaling of the dispersion relation data was found to hold between K-Cs alloys, Rb and Cs. The suggested scaling points out the key role of the conduction electron density in the collective dynamics of alkali metals.

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High-resolution neutron scattering measurement of the dynamic structure factor of heavy water

The low momentum collective dynamics of heavy water has been investigated by means of neutron three-axis spectroscopy. Working at the resolution limit of this instrument, an energy resolution of 2.6 meV was achieved for a constant analyzer energy of 120 meV. This good resolution allowed us to establish definitely that the collective dynamics of water is dominated by the presence and interaction of opticlike and acousticlike branches, coupling at wave-vector transfers of 0.3 to 0.35 A(-1). The transition from slow to fast sound has been attributed to the interaction between opticlike modes and a solidlike fast acoustic mode.

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Sonochemical production of a non-crystalline phase of palladium.

A non-crystalline phase of palladium was produced by cavitation technique starting from a solution of palladium acetylacetonate and toluene. The microscopic structure of the sample, a very fine powder, was investigated by X-ray diffraction and it showed the characteristic features of a disordered system. Further details about the phase of the sample were gained by studying the crystallization process induced by thermal treatments.

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