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Search Results: 1 - 10 of 14519 matches for " Valentina Di Liberto "
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Work performed by a Classical-"reversible"-Carnot cycle: Raising's distribution for the small "driving weights"
Francesco di Liberto
Physics , 2000,
Abstract: The expansions or the compressions of the ideal gas in the quasi-static Carnot cycle, can be performed (on adiabatic or isothermal way) by slowly increasing or decreasing the external pressure by means of small weights acting on the piston of the vessel containing the gas. We call them shortly the ``driving weights'' (dw). Let N be their number, a large one. To determine the work performed by the ideal gas in the cycle the ``driving weights'' must be handled carefully. If we let them move on-off the piston only horizontally, their vertical motions will be due only to the gas. Here we show that, at the end, while some of them will have moved down (will have negative raising) the remaining ones (the majority) will have moved up (will have positive raising) so that the total work performed by the ideal gas equals the total variation of the gravitational potential energy of the ``driving weghts''. The cycle is performed in 2N time-steps. For each step t_i, with i in 1,..,2N, we give H(t_i), and DH(t_{i-1},t_i), respectively the height and the raising of the piston. Moreover the overall raising of the individual dw's (i.e. h_k, with k in 1...N), and their distribution are given in simple, general cases. The efficiency and the dissipated work are also evaluated. This paper is aimed at imparting a deeper understanding of the ideal Carnot Engine and may also be useful as a segment in a didactic path on elementary calculus and statistics.
Mean Field Critical Behaviour for a Fully Frustrated Blume-Emmery-Griffiths Model
F. di Liberto,F. Peruggi
Physics , 2000, DOI: 10.1016/S0378-4371(00)00576-8
Abstract: We present a mean field analysis of a fully frustrated Ising spin model on an Ising lattice gas. This is equivalent to a degenerate Blume-Emery-Griffiths model with frustration, which we analyze for different values of the quadrupolar interaction. This model might be useful in the study of structural glasses and related systems with disorder.
Activation of mGlu3 Receptors Stimulates the Production of GDNF in Striatal Neurons
Giuseppe Battaglia, Gemma Molinaro, Barbara Riozzi, Marianna Storto, Carla L. Busceti, Paola Spinsanti, Domenico Bucci, Valentina Di Liberto, Giuseppina Mudò, Corrado Corti, Mauro Corsi, Ferdinando Nicoletti, Natale Belluardo, Valeria Bruno
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006591
Abstract: Metabotropic glutamate (mGlu) receptors have been considered potential targets for the therapy of experimental parkinsonism. One hypothetical advantage associated with the use of mGlu receptor ligands is the lack of the adverse effects typically induced by ionotropic glutamate receptor antagonists, such as sedation, ataxia, and severe learning impairment. Low doses of the mGlu2/3 metabotropic glutamate receptor agonist, LY379268 (0.25–3 mg/kg, i.p.) increased glial cell line-derived neurotrophic factor (GDNF) mRNA and protein levels in the mouse brain, as assessed by in situ hybridization, real-time PCR, immunoblotting, and immunohistochemistry. This increase was prominent in the striatum, but was also observed in the cerebral cortex. GDNF mRNA levels peaked at 3 h and declined afterwards, whereas GDNF protein levels progressively increased from 24 to 72 h following LY379268 injection. The action of LY379268 was abrogated by the mGlu2/3 receptor antagonist, LY341495 (1 mg/kg, i.p.), and was lost in mGlu3 receptor knockout mice, but not in mGlu2 receptor knockout mice. In pure cultures of striatal neurons, the increase in GDNF induced by LY379268 required the activation of the mitogen-activated protein kinase and phosphatidylinositol-3-kinase pathways, as shown by the use of specific inhibitors of the two pathways. Both in vivo and in vitro studies led to the conclusion that neurons were the only source of GDNF in response to mGlu3 receptor activation. Remarkably, acute or repeated injections of LY379268 at doses that enhanced striatal GDNF levels (0.25 or 3 mg/kg, i.p.) were highly protective against nigro-striatal damage induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyri?dinein mice, as assessed by stereological counting of tyrosine hydroxylase-positive neurons in the pars compacta of the substantia nigra. We speculate that selective mGlu3 receptor agonists or enhancers are potential candidates as neuroprotective agents in Parkinson's disease, and their use might circumvent the limitations associated with the administration of exogenous GDNF.
Fluctuation-dissipation theorem and harmonic oscillators
Vincenzo Branchina,Marco Di Liberto,Ivano Lodato
Physics , 2009,
Abstract: The question of the "physical meaning" and "origin" of the Bose-Einstein (BE) factor in the fluctuation-dissipation theorem (FDT) is often raised and this term is sometimes interpreted as originating from a real harmonic oscillator composition of the physical system. Such an interpretation, however, is not really founded. Inspired by the famous work of Caldeira and Leggett, we have been able to show that, whenever linear response theory is applicable, which is the main hypothesis under which the FDT is established, any generic bosonic and/or fermionic system at temperature $T$ can be mapped onto a fictitious system of harmonic oscillators so that the suscettivity and the mean square of the fluctuating observable of the real system coincide with the corresponding quantities of the fictitious one. We claim that it is in this sense, and only in this sense, that the BE factor can be interpreted in terms of harmonic oscillators, no other physical meaning can be superimposed to it. At the best of our knowledge, this is the first time that such a mapping is explicitly worked out.
Dark energy and Josephson junctions
Vincenzo Branchina,Marco Di Liberto,Ivano Lodato
Physics , 2009, DOI: 10.1088/1475-7516/2009/08/011
Abstract: It has been recently claimed that dark energy can be (and has been) observed in laboratory experiments by measuring the power spectrum $S_I(\omega)$ of the noise current in a resistively shunted Josephson junction and that in new dedicated experiments, which will soon test a higher frequency range, $S_I(\omega)$ should show a deviation from the linear rising observed in the lower frequency region because higher frequencies should not contribute to dark energy. Based on previous work on theoretical aspects of the fluctuation-dissipation theorem, we carefully investigate these issues and show that these claims are based on a misunderstanding of the physical origin of the spectral function $S_I(\omega)$. According to our analysis, dark energy has never been (and will never be) observed in Josephson junctions experiments. We also predict that no deviation from the linear rising behavior of $S_I(\omega)$ will be observed in forthcoming experiments. Our findings provide new (we believe definite) arguments which strongly support previous criticisms.
Mapping Fermion and Boson systems onto the Fock space of harmonic oscillators
Vincenzo Branchina,Marco Di Liberto,Ivano Lodato
Physics , 2010, DOI: 10.1103/PhysRevE.81.011120
Abstract: The fluctuation-dissipation theorem (FDT) is very general and applies to a broad variety of different physical phenomena in condensed matter physics. With the help of the FDT and following the famous work of Caldeira and Leggett, we show that, whenever linear response theory applies, any generic bosonic or fermionic system at finite temperature $T$ can be mapped onto a fictitious system of free harmonic oscillators. To the best of our knowledge, this is the first time that such a mapping is explicitly worked out. This finding provides further theoretical support to the phenomenological harmonic oscillator models commonly used in condensed matter. Moreover, our result helps in clarifying an interpretation issue related to the presence and physical origin of the Bose-Einstein factor in the FDT.
Assessing the Open Trenches in Screening Railway Ground-Borne Vibrations by Means of Artificial Neural Network
Gaetano Di Mino,Marinella Giunta,Ciro Maurizio Di Liberto
Advances in Acoustics and Vibration , 2009, DOI: 10.1155/2009/942787
Abstract: Reducing ground borne vibrations in urban areas is a very challenging task in railway transportation. Many mitigation measures can be considered and applied; among these open trenches are very effective. This paper deals with the study of the effect, in terms of reduction of vertical and horizontal displacements and velocities, of the open trenches. 2D FEM simulations have been performed and several open trench configurations have been analysed varying the main geometric features such as width and depth, distance from the rail, thickness of the soil layer over the rigid bedrock, type of the ground, ratio between the depth of the trench, and the thickness of the soil layer. For quantifying the influence of the above specified parameters in reducing ground-borne vibrations an analysis using artificial neural networks (ANNs) has been carried out. Results show that among the geometric parameters the role of the depth of the trench is very significant; however the influence of the depth must be also evaluated in relation to the thickness of the soil layer.
The RAMNI airborne lidar for cloud and aerosol research
F. Cairo, G. Di Donfrancesco, L. Di Liberto,M. Viterbini
Atmospheric Measurement Techniques (AMT) & Discussions (AMTD) , 2012,
Abstract: We describe an airborne lidar for the characterization of atmospheric aerosol. The system has been set up in response to the need to monitor extended regions where the air traffic may be posed at risk by the presence of potentially harmful volcanic ash, and to study the characteristics of volcanic emissions both near the source region and when transported over large distances. The lidar provides backscatter and linear depolarization profiles at 532 nm, from which aerosol and cloud properties can be derived. The paper presents the characteristics and capabilities of the lidar system and gives examples of its airborne deployment. Observations from three flights, aimed at assessing the system capabilities in unperturbed atmospheric conditions, and at characterizing the emissions near a volcanic ash source (Mt. Etna) and transported far away from the source, are presented and discussed.
The RAMNI airborne lidar for cloud and aerosol research
F. Cairo,G. Di Donfrancesco,L. Di Liberto,M. Viterbini
Atmospheric Measurement Techniques Discussions , 2012, DOI: 10.5194/amtd-5-1253-2012
Abstract: We describe an airborne lidar for the characterization of atmospheric aerosol. The system has been set up in response to the need to monitor extended regions where the air traffic may be posed at risk by the presence of potentially harmful volcanic ash, and to study the characteristics of volcanic emissions both near the source region and when transported over large distances. The lidar provides backscatter and linear depolarization profiles at 532 nm, from which aerosol and cloud properties can be derived. The paper presents the characteristics and capabilities of the lidar system and gives examples of its airborne deployment. Observations from three flights, aimed at assessing the system capabilities in unperturbed atmospheric conditions, and at characterizing the emissions near a volcanic ash source region, the Mt. Etna, and transported far away from the source, are presented and discussed.
Spatial Distribution of Plant-Associated Invertebrates and Environmental Bioassessment in a Natural Riverine Lake (Lake Fibreno, Central Italy)  [PDF]
Luciana Mastrantuono, Valentina Di Vito, Marcello Bazzanti
Journal of Water Resource and Protection (JWARP) , 2014, DOI: 10.4236/jwarp.2014.610087
Abstract:

Lake Fibreno is a Mediterranean riverine lake located in Central Italy and fed by large flows of groundwater and characterized by the presence of a wide reed stand area and of the only floating island of the South Europe. It is enclosed in a Natural Reserve recognized as Special Area of Conservation (SAC-IT6050015) for the presence of habitats and species (92/43/EEC) of relevant scientific interest. In this paper, we compare the plant-associated meio-macrobenthic invertebrates among sites with different environmental characteristics. Both vegetation and invertebrates of Lake Fibreno were well diversified and abundant and were composed of a mixing of species typical of lentic and lotic waters. Our results show that a gradient of orthophosphate and nitrite contents and current velocity appeared to be the driver factors affecting the flora and fauna spatial distribution at the sampling sites. To obtain a bioassessment of the ecological quality of the vegetation zone, we compared the riverine Lake Fibreno with typical lentic lakes previously studied in Central Italy. We selected metrics, such as macrophyte belt extent and taxa richness, invertebrate species richness and Shannon diversity, ETOM (Ephemeropta + Trichoptera + Odonata + Mollusca), ETOC (Ephemeropta + Trichoptera + Odonata + Coleoptera) and LCrM (Large Crustacea + Mollusca). The comparison indicated a good ecological status of the vegetation zone of Lake Fibreno mainly due to the continuous washout effects (dilution and fast water removal) which reduce the nutrient content available for phytoplankton and maintain the

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