Nonlinear Relaxation in Population Dynamics

We analyze the nonlinear relaxation of a complex ecosystem composed of many interacting species. The ecological system is described by generalized Lotka-Volterra equations with a multiplicative noise. The transient dynamics is studied in the framework of the mean field theory and with random interaction between the species. We focus on the statistical properties of the asymptotic behaviour of the time integral of the i-th population and on the distribution of the population and of the local field.Comment: 11 pages, 4 figures, in press in Int. Journal of Fractals (2001

Ophthalmic manifestations of cat scratch disease

Cat scratch disease (CSD) is a worldwide distributed zoonosis caused by Bartonella henselae and other Bartonella spp. The reservoirs of Bartonella are domestic animals, especially cats, and the transmission to humans is thought to occur from a cat scratch or even through the cat flea Ctenocephalides felix. With more and more pet owners, the physicians should keep in mind signs and symptoms of CSD. A widespread infection may occur in 5-14% of cases, and ocular involvement, called ocular bartonellosis, is a quite common consequence of disseminated CSD. Although the most typical manifestations of ocular Bartonellosis are Parinaud's oculoglandular syndrome, neuroretinitis and retinochoroiditis, many other ophthalmic conditions have been reported. The diagnosis of CSD is often based on history of contact with a cat and high serum titers of immunoglobulin G antibodies against B. henselae. Polymerase chain reaction could be helpful for CSD diagnosis when serology is negative but clinical findings are suggestive for the disease. Multimodal imaging, including fundus autofluorescence, fluorescein and indocyanine green angiography, optical coherence tomography (OCT) and OCT angiography, can be used for diagnosis and monitoring of ocular Bartonellosis. Since CSD is more often a self-limited infection in immunocompetent individuals, no antibiotic treatment is usually needed. However, when a therapy is prescribed, doxycycline is the most used antibiotic. The aim of this article is to review the current literature relating to epidemiology, systemic and ocular manifestations, diagnosis, treatment and prognosis of bartonellosis, in order to give the ophthalmologists a useful tool for daily practice

Theoretical analysis of the implementation of a quantum phase gate with neutral atoms on atom chips

We present a detailed, realistic analysis of the implementation of a proposal for a quantum phase gate based on atomic vibrational states, specializing it to neutral rubidium atoms on atom chips. We show how to create a double--well potential with static currents on the atom chips, using for all relevant parameters values that are achieved with present technology. The potential barrier between the two wells can be modified by varying the currents in order to realize a quantum phase gate for qubit states encoded in the atomic external degree of freedom. The gate performance is analyzed through numerical simulations; the operation time is ~10 ms with a performance fidelity above 99.9%. For storage of the state between the operations the qubit state can be transferred efficiently via Raman transitions to two hyperfine states, where its decoherence is strongly inhibited. In addition we discuss the limits imposed by the proximity of the surface to the gate fidelity.Comment: 9 pages, 5 color figure

Nonlocal field correlations and dynamical Casimir-Polder forces between one excited- and two ground-state atoms

The problem of nonlocality in the dynamical three-body Casimir-Polder interaction between an initially excited and two ground-state atoms is considered. It is shown that the nonlocal spatial correlations of the field emitted by the excited atom during the initial part of its spontaneous decay may become manifest in the three-body interaction. The observability of this new phenomenon is discussed.Comment: 17 pages, 1 figure, sub. to Phys. Rev.

Casimir-Polder potentials as entanglement probe

We have considered the interaction of a pair of spatially separated two-level atoms with the electromagnetic field in its vacuum state and we have analyzed the amount of entanglement induced between the two atoms by the non local field fluctuations. This has allowed us to characterize the quantum nature of the non local correlations of the electromagnetic field vacuum state as well as to link the induced quantum entanglement with Casimir-Polder potentials.Comment: Published on Europhysics Letters 78 (2007) 3000

Time-dependent Casimir-Polder forces and partially dressed states

A time-dependent Casimir-Polder force is shown to arise during the time evolution of a partially dressed two-level atom. The partially dressed atom is obtained by a rapid change of an atomic parameter such as its transition frequency, due to the action of some external agent. The electromagnetic field fluctuations around the atom, averaged over the solid angle for simplicity, are calculated as a function of time, and it is shown that the interaction energy with a second atom yields a dynamical Casimir-Polder potential between the two atoms

Building materials and decay assessment of the Gerace Cathedral (Reggio Calabria, Southern Italy)

A multi-analytical approach was employed for the first time to study the stone materials, wall paintings and related degradation forms in the Cathedral of Gerace (Reggio Calabria, southern Italy). With an area of around 1898 square meters, the Gerace Cathedral is the largest in Calabria: its construction dates back to the Norman era (between 1085 and 1120), and currently displays distinct features of Greek and Latin architectural orders. Despite having undergone numerous restorations, the church perfectly preserves its original buildings materials. Following an extensive site inspection campaign, supported by the experts dealing with building restoration, several areas were selected for analyses. Both in situ investigations and laboratory tests were carried out on micro-fragments using Non-Destructive and Micro-Destructive Techniques (NDTs and MDTs). The first step involved an inspection through InfraRed Thermography (IRT) in order to map the internal walls of the Cathedral and identify zones with potential degradation phenomena. Subsequently, a more in-depth study was designed based on the thermographic results, and laboratory tests were carried out on micro-fragments and powders to characterize the different kinds of materials (i.e., stones, mortars, plasters and pigments) and decay agents (i.e., salts and efflorescences). Thirty-one samples were subjected to a complementary analytical approach which included Polarizing Optical Microscopy (POM), Ion Chromatography (IC), X-Ray Powder Diffraction (XRPD) and Scanning Electron Microscopy (SEM) coupled with microanalysis (EDS). The results allowed us to preliminarily characterize the different materials from which the Cathedral was built, determine its state of conservation and provide a better knowledge of the entire building, revealing details not visible to the naked eye which are important for future conservation interventions. As for the state of conservation, the integrated use of various techniques enabled the detection of rising damp generally correlated with the occurrence of water infiltration and migration phenomena which appear to affect a large part of the building, causing noticeable damage (i.e., loss of surface material, micro-cracks, white salt efflorescence, etc.). The characterization of the materials carried out on mortars, plasters, and pigments also confirmed the local origin of the raw materials. However, the provenance of the studied marbles and crystalline limestones, could not be established and, therefore, further in-depth studies are required

Comparison of unitary transforms

We analyze the problem of comparing unitary transformations. The task is to decide, with minimal resources and maximal reliability, whether two given unitary transformations are identical or different. It is possible to make such comparisons without obtaining any information about the individual transformations. Different comparison strategies are presented and compared with respect to their efficiency. With an interferometric setup, it is possible to compare two unitary transforms using only one test particle. Another strategy makes use of a two-particle singlet state. This strategy is more efficient than using a non-entangled two-particle test state, thus demonstrating the benefit of entanglement. Generalisations to higher dimensional transforms and to more than two transformations are made.Comment: 11 pages, 4 figures, revtex4, submitted to J. Phys.