45,935 research outputs found

    The unquenched quark model

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    In this contribution, we briefly discuss the results for charmonium and bottomonium spectra with self-energy corrections in the unquenched quark model, due to the coupling to the meson-meson continuum. The UQM formalism can be extended to include also the effects of hybrid mesons, i.e. hybrid loops. Finally, we discuss the results of a calculation of hybrid mesons spectrum in Coulomb Gauge QCD.Comment: Talk given at the conference "Dark Matter, Hadron Physics and Fusion Physics", Messina (Italy), September 24-26, 201

    Waiting-times and returns in high-frequency financial data: an empirical study

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    In financial markets, not only prices and returns can be considered as random variables, but also the waiting time between two transactions varies randomly. In the following, we analyse the statistical properties of General Electric stock prices, traded at NYSE, in October 1999. These properties are critically revised in the framework of theoretical predictions based on a continuous-time random walk model.Comment: 8 pages, 4 figure, presented at the International Workshop "Horizons in Complex Systems", Messina, Italy, December 200

    Students with dyslexia between school and university: Post-diploma choices and the reasons that determine them. An Italian study

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    Italian Dyslexia Association (Messina section); Orientation and Placement Centre -University of Messina (Italy)Although the number of students with dyslexia enrolled in Italian universities is constantly growing, their presence remains relatively limited. The aim of this study was therefore to investigate the choices made by students with dyslexia in relation to university studies, and the underlying reasons for their choices. This study also compares these choices for students with and without dyslexia. In all, 440 high school students and their families agreed to take part in this project. Socio-demographic data was collected for the 47 students with dyslexia and 47 class-matched students without dyslexia, along with information on their current schools and their future educational plans. A specially developed questionnaire was used for the students, in combination with structured interviews with their families. The results show significant differences between these groups regarding both choices for university studies and the underlying motivations for these choices. Furthermore, certain psychological and emotional factors are implicated here in the decisions of the students with dyslexia regarding both university studies and their underlying reasons. Future research is needed to further investigate these factors in the educational choices of students with dyslexia.Italian Dyslexia Association (Messina section)Orientation and Placement Centre - University of Messina (Italy

    Messina 1908-2008: understanding crust dynamics and subduction in Southern Italy

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    To mark the centennial anniversary of the 1908 earthquake that shook Messina, Italy, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) has begun the "Messina 1908- 2008" research project. The aim is to clarify the extension deformation processes that occur in the Messina Strait and to understand relationships between subduction and crustal deformation there by merging existing data and studies, and by collecting new and more detailed seismological, geodetic, historical, and satellite observations. More than 20 permanent seismic stations and about 15 temporary stations are located in the study region. A dense permanent geodetic network also operates in the region, several campaign surveys are newly available, and new geodetic campaign measurements were performed in March 2008. In addition, during July 2008, five ocean bottom seismometers (OBS) were deployed to better monitor the area largely covered by the sea. Records of historical earthquakes that struck the Strait of Messina will be analyzed, and synthetic aperture radar images will help define surface deformation of the region. The Messina 1908-2008 project's assemblage of a database and integration of innovative technologies could transform our understanding of the crust and mantle structure of the active tectonics and seismic hazards of the Strait of Messina

    Numerical study of the glass-glass transition in short-ranged attractive colloids

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    We report extensive numerical simulations in the {\it glass} region for a simple model of short-ranged attractive colloids, the square well model. We investigate the behavior of the density autocorrelation function and of the static structure factor in the region of temperatures and packing fractions where a glass-glass transition is expected according to theoretical predictions. We strengthen our observations by studying both waiting time and history dependence of the numerical results. We provide evidence supporting the possibility that activated bond-breaking processes destabilize the attractive glass, preventing the full observation of a sharp glass-glass kinetic transition.Comment: 15 pages, 9 figures; Proceedings of "Structural Arrest Transitions in Colloidal Systems with Short-Range Attractions", Messina, Italy, December 2003 (submitted to J. Phys.: Condens. Matt.

    Excited lepton baryogenesis

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    The excited leptons that share the quantum numbers with the Standard Model leptons but have larger masses are widespread in many promising new physics theories. A subclass of excited leptons that at low energies interact with the SM fermions dominantly through the effective coupling to lepton and fermion-antifermion pair can be referred as leptomesons. I introduce possible generation of the baryon asymmetry of the universe using these new particles. The discussed baryogenesis mechanisms do not contradict to the small neutrino masses and the proton stability, and can be interesting for the collider experiments.Comment: 5 pages, 3 figures. v2: References and comments added. Proceedings to the conference "Advances in Dark Matter and Particle Physics", Messina, Italy, October 24-27, 201

    Critical Decay at Higher-Order Glass-Transition Singularities

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    Within the mode-coupling theory for the evolution of structural relaxation in glass-forming systems, it is shown that the correlation functions for density fluctuations for states at A_3- and A_4-glass-transition singularities can be presented as an asymptotic series in increasing inverse powers of the logarithm of the time t: ϕ(t)−f∝∑igi(x)\phi(t)-f\propto \sum_i g_i(x), where gn(x)=pn(ln⁥x)/xng_n(x)=p_n(\ln x)/x^n with p_n denoting some polynomial and x=ln (t/t_0). The results are demonstrated for schematic models describing the system by solely one or two correlators and also for a colloid model with a square-well-interaction potential.Comment: 26 pages, 7 figures, Proceedings of "Structural Arrest Transitions in Colloidal Systems with Short-Range Attractions", Messina, Italy, December 2003 (submitted

    The Mediterranean Red Alga Asparagopsis: A Source of Compounds against Leishmania

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    Crude extracts and column fractions from the red algae Asparagopsis taxiformis and A. armata from the Strait of Messina (Italy) were screened for the production of antimicrobial compounds. Extracts from both species revealed remarkable antiprotozoal activity against Leishmania, revealing such algae as a great source of natural antiprotozoal products
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