The Topological Nonconnectivity Threshold and magnetic phase transitions in classical anisotropic long-range interacting spin systems

We review, with emphasis on the dynamical point of view, the classical characteristics of the Topological Nonconnectivity Threshold (TNT), recently introduced in F. Borgonovi, G.L. Celardo, M. Maianti and E. Pedersoli, J. Stat. Phys. 116, 1435 (2004). This shows interesting connections among Topology, Dynamics, and Thermo-Statistics of ferro/paramagnetic phase transition in classical spin systems, due to the combined effect of anisotropy and long-range interactions.     

Broken Ergodicity in Classically Chaotic Spin Systems

A one dimensional classically chaotic spin chain with asymmetric coupling and two different inter-spin interactions, nearest neighbors and all-to-all, has been considered. Depending on the interaction range, dynamical properties such as ergodicity and chaoticity are very different. Indeed, even in the presence of chaoticity, the model displays a lack of ergodicity only in presence of all to all interaction and below an energy threshold, that persists in the thermodynamical limit. The energy threshold can be found analytically and results can be generalized for a generic XY model with asymmetric coupling.     

The topological non-connectivity threshold in quantum long-range interacting spin systems

Quantum characteristics of the Topological Non-connectivity Threshold (TNT), introduced in [F. Borgonovi, G.L. Celardo, M. Maianti, E. Pedersoli, J. Stat. Phys. 116, 516 (2004)], have been analyzed in the hard quantum regime. New interesting perspectives in term of the possibility to study the intriguing quantum-classical transition through Macroscopic Quantum Tunneling have been addressed.     

Distribution of resonance widths and dynamics of continuum coupling

We analyze the statistics of resonance widths in a many-body Fermi system with open decay channels. Depending on the strength of continuum coupling, such a system reveals growing deviations from the standard chi-square (Porter-Thomas) width distribution. The deviations emerge from the process of increasing interaction of intrinsic states through common decay channels; in the limit of perfect coupling this process leads to the superradiance phase transition. The width distribution depends also on the intrinsic dynamics (chaotic versus regular). The results presented here are important for understanding the recent experimental data concerning the width distribution for neutron resonances in nuclei.     

Aggregation and fractal formation of Au and TiO<Subscript>2</Subscript> nanostructures obtained by fs-pulsed laser deposition: experiment and simulation

In the synthesis of nanostructures by pulsed laser deposition (PLD), a crucial role is played by the environmental deposition pressure and the substrate temperature. Due to the high temperature of nanoparticles (NPs) at landing, other factors may determine the structure of the resulting aggregates. Here, Au and TiO₂ nanostructures are obtained by non-thermal fs-PLD in ambient conditions. On Si(100), only TiO₂ NPs form fractals with areas up to ~ 1 × 10⁶ nm², while on quartz Au NPs also form fractals with areas up to ~ 5 × 10³ nm², a much smaller size with respect to the TiO₂ case. The aggregation is described by a simple diffusive model, taking into account isotropic diffusion of the NPs, allowing quantitative simulations of the NPs and fractal area. The results highlight the key role of substrate thermal conductivity in determining the formation of fractals.

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Dynamics of two quantum entangled particles interacting with a potential barrier in an EPR experiment

The effect of a position measurement on one component of a two-particle wave packet in a regularized space-momentum entangled state is analyzed. The wave packet interacts in the physical space with a potential barrier. When a position or momentum measurement is performed on one particle, a consequent strong modification of the dynamics of the other particle occurs.     

Simultaneous determination of isbufylline and its major metabolites in rabbit blood and urine by reversed-phase high-performance liquid chromatography.

A sensitive high-performance liquid chromatographic assay for isbufylline and its major metabolites in rabbit blood and urine is described. After extraction, samples were eluted by a linear reversed-phase gradient. Specimens obtained after intravenous administration of isbufylline to rabbits were analysed to identify and subsequently quantify the potential metabolites. Using the ultraviolet absorption trace on the recorder as a reference, elution fractions were collected and analysed by mass spectrometry with the direct inlet system and gas chromatography-mass spectrometry after derivatization. Seven metabolites were identified and another five quantified. The method is specific, accurate, reproducible and recommended for pharmacokinetic studies.