Disappointing model for ultrahigh-energy cosmic rays

Data of Pierre Auger Observatory show a proton-dominated chemical composition of ultrahigh-energy cosmic rays spectrum at (1 - 3) EeV and a steadily heavier composition with energy increasing. In order to explain this feature we assume that (1 - 3) EeV protons are extragalactic and derive their maximum acceleration energy, E_p^{max} \simeq 4 EeV, compatible with both the spectrum and the composition. We also assume the rigidity-dependent acceleration mechanism of heavier nuclei, E_A^{max} = Z x E_p^{max}. The proposed model has rather disappointing consequences: i) no pion photo-production on CMB photons in extragalactic space and hence ii) no high-energy cosmogenic neutrino fluxes; iii) no GZK-cutoff in the spectrum; iv) no correlation with nearby sources due to nuclei deflection in the galactic magnetic fields up to highest energies.Comment: 4 pages, 7 figures, the talk presented by A. Gazizov at NPA5 Conference, April 3-8, 2011, Eilat, Israe

R&D efforts towards a neutrino factory

The R&D efforts towards a neutrino factory are outlined with special emphasis on the muon cooling issue and the data collected for target optimization.Comment: contribution to NOW08, Conca Specchiulla, Otranto, 200

Formin-dependent TGF-β signaling for epithelial to mesenchymal transition.

The role of distinct actin filament architectures in epithelial plasticity remains incompletely understood. We therefore determined roles for formins and the Arp2/3 complex, which are actin nucleators generating unbranched and branched actin filaments, respectively, in the process of epithelial to mesenchymal transition (EMT). In clonal lung, mammary, and renal epithelial cells, the formin activity inhibitor SMIFH2 but not the Arp2/3 complex activity inhibitor CK666 blocked EMT induced by TGF-β. SMIFH2 prevented the proximal signal of increased Smad2 phosphorylation and hence also blocked downstream EMT markers, including actin filament remodeling, decreased expression of the adherens junction protein E-cadherin, and increased expression of the matrix protein fibronectin and the transcription factor Snail. The short hairpin RNA silencing of formins DIAPH1 and DIAPH3 but not other formins phenocopied SMIFH2 effects and inhibited Smad2 phosphorylation and changes in Snail and cadherin expression. Formin activity was not necessary for the cell surface expression or dimerization of TGF-β receptors, or for nuclear translocation of TAZ, a transcription cofactor in Hippo signaling also regulated by TGF-β. Our findings reveal a previously unrecognized role for formin-dependent actin architectures in proximal TGF-β signaling that is necessary for Smad2 phosphorylation but not for cross-talk to TAZ

Experimental and Analytical Investigation into the Effect of Ballasted Track on the Dynamic Response of Railway Bridges under Moving Loads

Ballasted tracks are among the most widespread railway track typologies. The ballast possesses multiple functions. Among them, it significantly affects the dynamic interaction between a rail bridge and a moving load in terms of damping and load distribution. These effects entail accurate modeling of the track-ballast-bridge interaction. The paper presents a finite-difference formulation of the governing equations of the track and the bridge, modeled as Euler-Bernoulli (EB) beams, and coupled by a distributed layer of springs representing the ballast. The two equations are solved under a moving load excitation using a Runge-Kutta family algorithm and the finite-difference method for the temporal and spatial discretization, respectively. The authors validated the mathematical model against the displacement response of a rail bridge with a ballasted substructure. In a first step, the modal parameters of the bridge, obtained from ambient vibration measurements, are used to estimate the bending stiffness of an equivalent EB beam representative of the tested bridge. In a second step, the authors estimated the coupling effect of the ballast by assessing the model sensitivity to the modeling parameters and optimizing the agreement with the experimental data. Comparing the bridge's experimental displacement responses highlights the ballast's significant effect on the load distribution and damping. The considerable difference between the damping estimated from output-only identification and that determined from the displacement response under moving load proves the dominant role of the ballast in adsorbing the vibrations transmitted to the bridge under the train passage and the different damping sources under high-amplitude excitation. The authors discuss the tradeoff between model accuracy and computational effort for a reliable estimation of ballasted tracks response under moving loads

Search for photons at the Pierre Auger Observatory

The Pierre Auger Observatory has a unique potential to search for ultra-high energy photons (above ~1 EeV). First experimental limits on photons were obtained during construction of the southern part of the Observatory. Remarkably, already these limits have proven useful to falsify proposals about the origin of cosmic rays, and to perform fundamental physics by constraining Lorentz violation. A final discovery of photons at the upper end of the electromagnetic spectrum is likely to impact various branches of physics and astronomy.Comment: 5 pages, 5 figures. Presented at CRIS 2008, Malfa, Ital

Finite Density Fat QCD

Lattice formulation of Finite Baryon Density QCD is problematic from computer simulation point of view; it is well known that for light quark masses the reconstructed partition function fails to be positive in a wide region of parameter space. For large bare quark masses, instead, it is possible to obtain more sensible results; problems are still present but restricted to a small region. We present evidence for a saturation transition independent from the gauge coupling $\beta$ and for a transition line that, starting from the temperature critical point at $\mu=0$, moves towards smaller $\beta$ with increasing $\mu$ as expected from simplified phenomenological arguments.Comment: 14 pages, 10 figure

Study of isospin violating ϕ\phi excitation in e+e−→ωπ0e^+e^- \to \omega\pi^0

We study the reaction $e^+ e^-\to \omega\pi^0$ in the vicinity of $\phi$ mass region. The isospin-violating $\phi$ excitation is accounted for by two major mechanisms. One is electromagnetic (EM) transition and the other is strong isospin violations. For the latter, we consider contributions from the intermediate hadronic meson loops and $\phi$-$\rho^0$ mixing as the major mechanisms via the $t$ and s-channel transitions, respectively. By fitting the recent KLOE data, we succeed in constraining the model parameters and extracting the $\phi\to\omega\pi^0$ branching ratio. It shows that the branching ratio is sensitive to the $\phi$ excitation line shape and background contributions. Some crucial insights into the correlation between isospin violation and Okubo-Zweig-Iizuka (OZI) rule evading transitions are also learned.Comment: Revised version to appear in J. Phys.

Constructability-based design approach for steel structures: From truss beams to real-world inspired industrial buildings

This paper presents an optimization framework for steel trusses. The authors implemented a penalty-based approach to optimise the size, shape, and topology based on a dynamic grouping strategy to address the constructability challenges. The main contribution of the paper is the use of damped exponential constructability penalties. This approach ensures optimal designs by balancing structural complexity, through standardization in design, and minimizing the total number of members and variety of sections, with the overall structural cost. The paper also presents a detailed analysis that underscores the sensitivity of the optimization convergence to the algorithmic hyperparameters, emphasizing the role of cross-section assignments and stabilization of truss piece counts. The optimization framework is validated on a trussed roof structure based on the findings from the single truss optimization. The best truss topology proved to be the Howe truss configuration, highlighting its efficiency in meeting the defined objective function