Flux creep in Bi2Sr2Ca1Cu2O(8+x) single crystals

Dissipative effects were investigated in Bi2Sr2Ca1Cu2O(8+x) single crystals by critical current and magnetic relaxation measurements. Activation energies for the flux motion were determined from the temperature dependence of the critical current and from the time decay of the zero field cooled and the remanent magnetization. The effective activation energy was found to increase with temperature, in agreement with the existence of a distribution of activation energies (E sub o 20 meV at 4.2 K for H + 10 kOe applied parallel to the c-axis.)

Geometrical aspects of integrable systems

We review some basic theorems on integrability of Hamiltonian systems, namely the Liouville-Arnold theorem on complete integrability, the Nekhoroshev theorem on partial integrability and the Mishchenko-Fomenko theorem on noncommutative integrability, and for each of them we give a version suitable for the noncompact case. We give a possible global version of the previous local results, under certain topological hypotheses on the base space. It turns out that locally affine structures arise naturally in this setting.Comment: It will appear on International Journal of Geometric Methods in Modern Physics vol.5 n.3 (May 2008) issu

Hybrid Optical Switching for Data Center Networks

Current data centers networks rely on electronic switching and point-to-point interconnects.When considering future data center requirements, these solutions will raise issues in terms of flexibility, scalability, performance, and energy consumption. For this reason several optical switched interconnects, which make use of optical switches and wavelength division multiplexing (WDM), have been recently proposed. However, the solutions proposed so far suffer from low flexibility and are not able to provide service differentiation. In this paper we introduce a novel data center network based on hybrid optical switching (HOS). HOS combines optical circuit, burst, and packet switching on the same network. In this way different data center applications can be mapped to the optical transportmechanism that best suits their traffic characteristics. Furthermore, the proposed HOS network achieves high transmission efficiency and reduced energy consumption by using two parallel optical switches. We consider the architectures of both a traditional data center network and the proposed HOS network and present a combined analytical and simulation approach for their performance and energy consumption evaluation. We demonstrate that the proposed HOS data center network achieves high performance and flexibility while considerably reducing the energy consumption of current solutions

Flux creep in Bi2Sr2CaCu2O8(sub +x) single crystals

The results of a magnetic study on a Bi2Sr2CaCu2O(8+x) single crystal are reported. Low field susceptibility (dc and ac), magnetization cycles and time dependent measurements were performed. With increasing the temperature the irreversible regime of the magnetization cycles is rapidly restricted to low fields, showing that the critical current J(sub c) becomes strongly field dependent well below T(sub c). At 2.4 K the critical current in zero field, determined from the remanent magnetization by using the Bean formula for the critical state, is J(sub c) = 2 10(exp 5) A/sq cm. The temperature dependence of J(sub c) is satisfactorily described by the phenomenological law J(sub c) = J(sub c) (0) (1 - T/T(sub c) (sup n), with n = 8. The time decay of the zero field cooled magnetization and of the remanent magnetization was studied at different temperatures for different magnetic fields. The time decay was found to be logarithmic in both cases, at least at low temperatures. At T = 4.2 K for a field of 10 kOe applied parallel to the c axis, the average pinning energy, determined by using the flux creep model, is U(sub o) = 0.010 eV

Assessment of Identity Disturbance: Factor Structure and Validation of the Personality Structure Questionnaire in an Italian Sample

here are few brief measures of identity disturbance for use in clinical practice that have been subject to any cross - culturally validation . This study investigated the construct validity of the Personality Structure Questionnaire (PSQ) in Italian clinical (N=237) and community ( N=296) samples . Confirmatory factor analysis was conducted to investigate the internal structure of the PSQ. A three – factor structure (i.e., differing self - states, mood variability and behavioral loss of control) including a second - order factor provided the best fit to the data . This structure was demonstrated to be invariant across sex and clinical diagnosis , with clinical diagnosis significantly predicting increased PSQ scores . A g lobal PSQ score of between 26 - 28 was found to be an appropriate cut-off for assisting in diagnostic processes. Implications for the assessment and treatment of psychological disorders with a marked identity disturbance component are discussed

Exchange bias effect in the phase separated Nd_{1-x}Sr_{x}CoO_3 at the spontaneous ferromagnetic/ferrimagnetic interface

We report the new results of exchange bias effect in Nd_{1-x}Sr_{x}CoO_3 for x = 0.20 and 0.40, where the exchange bias phenomenon is involved with the ferrimagnetic (FI) state in a spontaneously phase separated system. The zero-field cooled magnetization exhibits the FI (T_{FI}) and ferromagnetic (T_C) transitions at ~ 23 and \sim 70 K, respectively for x = 0.20. The negative horizontal and positive vertical shifts of the magnetic hysteresis loops are observed when the system is cooled through T_{FI} in presence of a positive static magnetic field. Training effect is observed for x = 0.20, which could be interpreted by a spin configurational relaxation model. The unidirectional shifts of the hysteresis loops as a function of temperature exhibit the absence of exchange bias above T_{FI} for x = 0.20. The analysis of the cooling field dependence of exchange bias field and magnetization indicates that the ferromagnetic (FM) clusters consist of single magnetic domain with average size around \sim 20 and ~ 40 \AA ~ for x = 0.20 and 0.40, respectively. The sizes of the FM clusters are close to the percolation threshold for x = 0.20, which grow and coalesce to form the bigger size for x = 0.40 resulting in a weak exchange bias effect.Comment: 9 pages, 9 figure

Scelte di sviluppo, innovazione organizzativa e rendicontazione sociale: il bilancio di mandato dell'Università degli Studi di Roma Tor Vergata

The aim of this paper is to show the latest developments about social accountability in the university sector. In the first section the authors examine different approaches developed at European and International levels: social reports in Italy, “knowledge” reports (Wissensbilanz) in continental Europe and “Key Facts” statements in US. In the second section the focus is on the recent University of Rome “Tor Vergata” accountability report, which underlines and comments many performance indicators

INNOVATIVE TOOLS FOR MANAGING HISTORICAL BUILDINGS: THE USE OF GEOGRAPHIC INFORMATION SYSTEM AND ONTOLOGIES FOR HISTORICAL CENTERS

A recent study and the digitalization of historical centres have developed a completely new strategy for the conservation management of urban buildings through the ‘Risk Map’ of MiBAC. Issues, aims and structure of the Territory Information System (TIS) have been wholly outlined in a dedicated book that describes the structure of the system, also following a historical framing of the debate and the previous experiences. The elaboration of a dedicated ontology adds the opportunity to make the same data available to other kind of software, beginning from HBIM Systems. This aim is pursued developing a special extension of CIDOC-CRM, an already consolidated ontology initially dedicated to the conservation issue of museums. The work has firstly considered the field of architectural conservation and recently further developed addressing historical centres. In this way, a synthetic description of the buildings, including the main features together with vulnerability and transformation index, will allow, through the 3D representation of the town, a stable monitoring of the urban tissue, constantly up to date with the new data deriving from the interventions gradually realized

Global action-angle coordinates for completely integrable systems with noncompact invariant submanifolds

The obstruction to the existence of global action-angle coordinates of Abelian and noncommutative (non-Abelian) completely integrable systems with compact invariant submanifolds has been studied. We extend this analysis to the case of noncompact invariant submanifolds.Comment: 13 pages, to be published in J. Math. Phys. (2007