178 research outputs found
26. La storia di Anania e Saffira già in San Giovanni in Laterano (Pinacoteca Vaticana, depositi)
No full textscheda epigrafica in La pittura medievale a Roma 312-1431, Corpus e Atlante, IV vol., Riforma e Tradizione, a cura di S. Romano, Milano, Jaca Book, 200
Nonlocal equation for the superconducting gap parameter
No full textThe properties are considered in detail of a nonlocal (integral) equation for the superconducting gap parameter, which is obtained by a coarse-graining procedure applied to the Bogoliubov-de Gennes (BdG) equations over the whole coupling-versus-temperature phase diagram associated with the superfluid phase. It is found that the limiting size of the coarse-graining procedure, which is dictated by the range of the kernel of this integral equation, corresponds to the size of the Cooper pairs over the whole coupling-versus-temperature phase diagram up to the critical temperature, even when Cooper pairs turn into composite bosons on the BEC side of the BCS-BEC crossover. A practical method is further implemented to solve numerically this integral equation in an efficient way, which is based on a novel algorithm for calculating the Fourier transforms. Application of this method to the case of an isolated vortex, throughout the BCS-BEC crossover and for all temperatures in the superfluid phase, helps clarifying the nature of the length scales associated with a single vortex and the kinds of details that are in practice disposed off by the coarse-graining procedure on the BdG equations
VOC Air Pollution in Urban Areas – A Microscale Model experimentally validated
No full textPrevious theoretical and experimental studies (S. T. A.- Università di Pisa (DIMNP), 1998; Agostini E., M. Corezzi, I. Ciucci, M. Mazzini 2003; Agostini E., I. Ciucci, M. Mazzini, S. Strinati, 2003) even if partial, evidenced the problem of atmospheric pollution by Volatile Organic Compounds (VOC) in Livorno (Tuscany). This pollution is caused mainly by the presence of an important refinery, other industries and traffic. Other relevant VOC emission sources are linked to port activities and to numerous small companies using paints and solvents. Figure 1 shows the map of Livorno, situated on the Tyrrhenian sea. This is a simple site from the orography point of view, except for the southern zone where a promontory and a chain of hills impose a more complex pattern of air fluxes. The industrial zone is localized in the north of the map and the harbour activities along the coast (west area). It’s difficult to define a specific zone for the companies using solvents and paints, even though a grater concentration is present around the axis Viale Carducci – Piazza Repubblica – Via Grande.
The map outlines also the air pollution measurement stations managed by ARPAT (points) and the meteorological stations (crosses).
The simulation of the emission scenario, was done by using ISC3 (U. S. Environmental Protection Agency) code for treating diffuse sources and CALINE4 (California Department of Transportation) for those related to traffic on main roads.
The research work focuses the attention on the results of model validation by experimental data obtained along the roads of the studied area. The possibility to extend the application of this model to sites with similar orography and town-planning characteristics is also discussed in the aim of obtaining information about the level of atmospheric pollution on sites where there aren’t measurement stations
Approfondimenti sul modello di dispersione atmosferica di particelle sedimentabili implementato nel codice ISC3 dell'US-EPA
No full textDimensional crossover in the magnetic properties of highly anisotropic antiferromagnets
No full textMagnetic properties of highly anisotropic perovskites based on copper oxide planes have commonly been interpreted in terms of the spin-wave approximation to the Heisenberg model ..
Bound states in a superfluid vortex: A detailed study along the BCS-BEC crossover
No full textThe bound states that can occur in a superfluid vortex have recently called for attention owing to the capability
of detecting them experimentally. However, a detailed theoretical account for the presence of these vortex bound states is still lacking for all temperatures in the superfluid phase and couplings along the BCS-BEC crossover. Here, we fill this gap and present a systematic theoretical study based on the Bogoliubov–de Gennes equations for the bound states that occur over the two characteristic (inner and outer) spatial ranges in which the extension of a superfluid vortex can be partitioned. It is found that the total number of bound states decreases from the BCS (weak-coupling) side of the crossover toward the intermediate-coupling region where they are still present, whereas the bound states disappear upon entering the BEC (strong-coupling) side. A scaling relation is also obtained that connects the number of bound states in the inner spatial range of the vortex to the depth and width of the vortex itself. A criterion is finally provided in terms of the local density of states, to distinguish where a given fermionic superfluid is located in the coupling-temperature phase diagram of the BCS-BEC crossover
Dimensional crossover in the magnetic properties of highly anisotropic antiferromagnets. II. Paramagnetic phase
No full textWe calculate the magnetic properties of a spin-1/2 antiferromagnet ..
Optimizing the proximity effect along the BCS side of the BCS-BEC crossover
No full textThe proximity effect, which arises at the interface between two fermionic superfluids with different critical
temperatures, is examined with a nonlocal (integral) equation whose kernel contains information about the size
of Cooper pairs that leak across the interface. This integral approach avoids reference to the boundary conditions
at the interface that would be required with a differential approach. The temperature dependence of the pair
penetration depth on the normal side of the interface is determined over a wide temperature range also varying
the interparticle coupling along the BCS side of the BCS-BEC crossover independently on both sides of the
interface. In this way, the size of Cooper pairs evolves from being much larger than (BCS limit) the interparticle
distance to being comparable with (unitarity limit, halfway between the BCS and BEC limits) the interparticle
distance. Conditions are then found for which the proximity effect is optimized in terms of the extension
of the pair penetration depth
Josephson effect at finite temperature along the BCS-BEC crossover
No full textThe Josephson current-phase characteristics, that arise when a supercurrent flows across two fermionic superfluids separated by a potential barrier, can be controlled by varying either the interparticle coupling or the temperature. While the coupling dependence has been addressed in detail both theoretically and experimentally for an attractive Fermi gas undergoing the BCS-BEC crossover, a corresponding study of the temperature dependence of the Josephson characteristics is still lacking in this context. Here, we investigate the combined coupling and temperature dependence of the Josephson characteristics in a systematic way for a wide set of barriers, within ranges of height and width that can be experimentally explored. Our study smoothly connects the two limiting cases, of nonoverlapping composite bosons at low temperature described by the Gross-Piatevskii equation, and of strongly overlapping Cooper pairs near the critical temperature described by the Ginzburg-Landau equation. In this way, we are able to explore several interesting effects related to how the current-phase characteristics evolve along the BCS-BEC crossover as a function of temperature and of barrier shape. These effects include the coherence length outside the barrier and the pair penetration length inside the barrier (which is related to the proximity effect), as well as the temperature evolution of the Landau criterion in the limit of a vanishingly small barrier. A comparison is also presented between the available experimental data for the critical current and our theoretical results over a wide range of couplings along the BCS-BEC crossover
- …
