Unitarized pion-nucleon scattering amplitude from inverse amplitude method

In a recent work on low energy pion-nucleon scattering, instead of using chiral perturbation theory (ChPT) amplitude, we started from a pion-nucleon {\it soft-pion} result and used elastic unitarity directly as a dynamical constraint to construct first-order unitarity corrected amplitudes. The resulting amplitudes are crossing symmetric but, as the ChPT ones, satisfy only approximate unitarity relation. In the present work, we reconsider our approach and we apply the inverse amplitude method (IAM) in order to access the energy resonance region. We present the resulting S- and P-wave phase shifts that are shown to be in qualitative agreement with experimental data.Comment: 6 pages, 3 figure

Neighbour transitivity on codes in Hamming graphs

We consider a \emph{code} to be a subset of the vertex set of a \emph{Hamming graph}. In this setting a \emph{neighbour} of the code is a vertex which differs in exactly one entry from some codeword. This paper examines codes with the property that some group of automorphisms acts transitively on the \emph{set of neighbours} of the code. We call these codes \emph{neighbour transitive}. We obtain sufficient conditions for a neighbour transitive group to fix the code setwise. Moreover, we construct an infinite family of neighbour transitive codes, with \emph{minimum distance} $\delta=4$, where this is not the case. That is to say, knowledge of even the complete set of code neighbours does not determine the code

Pion-Pion Phase-Shifts and the Value of Quark-Antiquark Condensate in the Chiral Limit

We use low energy pion-pion phase-shifts in order to make distinction between the alternatives for the value of the quark-antiquark condensate $B_0$ in the chiral limit. We will consider the amplitude up to and including ${\cal O}(p^4)$ contributions within the Standard and Generalized Chiral Perturbation Theory frameworks. They are unitarized by means of Pad\'e approximants in order to fit experimental phase-shifts in the resonance region. As the best fits correspond to $\alpha = \beta = 1$, we conclude that pion-pion phase-shift analysis favors the standard ChPT scenario, which assumes just one, large leading order parameter $_{_0}$.Comment: 5 pages, 3 figures and 1 tabl

Two Superconducting Phases in CeRh_1-xIr_xIn_5

Pressure studies of CeRh_1-xIr_xIn_5 indicate two superconducting phases as a function of x, one with T_c >= 2 K for x < 0.9 and the other with T_c < 1.2 K for x > 0.9. The higher T_c phase, phase-1, emerges in proximity to an antiferromagnetic quantum-critical point; whereas, Cooper pairing in the lower T_c phase-2 is inferred to arise from fluctuations of a yet to be found magnetic state. The T-x-P phase diagram of CeRh_1-xIr_xIn_5, though qualitatively similar, is distinctly different from that of CeCu_2(Si_1-xGe_x)_2.Comment: 5 pages, 3 figure

The Collins-Roscoe mechanism and D-spaces

We prove that if a space X is well ordered $(\alpha A)$, or linearly semi-stratifiable, or elastic then X is a D-space

Modeling electrodialysis and a photochemical process for their integration in saline wastewater treatment.

Oxidation processes can be used to treat industrial wastewater containing non-biodegradable organic compounds. However, the presence of dissolved salts may inhibit or retard the treatment process. In this study, wastewater desalination by electrodialysis (ED) associated with an advanced oxidation process (photo-Fenton) was applied to an aqueous NaCl solution containing phenol. The influence of process variables on the demineralization factor was investigated for ED in pilot scale and a correlation was obtained between the phenol, salt and water fluxes with the driving force. The oxidation process was investigated in a laboratory batch reactor and a model based on artificial neural networks was developed by fitting the experimental data describing the reaction rate as a function of the input variables. With the experimental parameters of both processes, a dynamic model was developed for ED and a continuous model, using a plug flow reactor approach, for the oxidation process. Finally, the hybrid model simulation could validate different scenarios of the integrated system and can be used for process optimization

Development of polymeric anepectic meshes: Auxetic metamaterials with negative thermal expansion

This paper reports the application of additive manufacturing technology to fabricate bi-dimensional lightweight composite meshes capable of demonstrating auxetic properties (negative Poisson's ratio (NPR)) in combination with negative thermal expansion (NTE) behaviour, using as constituent materials polymers that do not exhibit NTE behaviour. To describe the combination of NPR and NTE characteristics, the designation of 'anepectic' is being proposed. Each mesh, obtained from varying either the material combination or the design parameters, was tested on a heated silicone bath to study the effects of the different combinations on the coefficient of thermal expansion (CTE). It was found that all meshes studied demonstrated a successful combination of NPR and NTE behaviours, and it was revealed that there is a possibility to tailor the meshes to activate the NTE behaviour within a chosen range of temperatures. For an extreme case, a Poisson's ratio of-0.056, along with a CTE of-1568 × 10 -6 K -1 has been achieved.authorsversionpublishe

Diffraction and an infrared finite gluon propagator

We discuss some phenomenological applications of an infrared finite gluon propagator characterized by a dynamically generated gluon mass. In particular we compute the effect of the dynamical gluon mass on $pp$ and ${\bar{p}}p$ diffractive scattering. We also show how the data on $\gamma p$ photoproduction and hadronic $\gamma \gamma$ reactions can be derived from the $pp$ and $\bar{p}p$ forward scattering amplitudes by assuming vector meson dominance and the additive quark model.Comment: 4 pages, 7 figures, added references and figures, changed structure. Contribution to Proceedings of XVIIIth Reuniao de Trabalho sobre Interacoes Hadronicas, Sao Paulo, Brazil, 22-24 May, 200

Improving the Knowledge on Seismogenic Sources in the Lower Tagus Valley for Seismic Hazard Purposes

The Lower Tagus Valley, that includes the metropolitan area of Lisbon, has been struck by several earthquakes which produced significant material damage and loss of lives. Their exact location remains unknown. Our goal is to shed some light into the seismogenic sources in the area using seismic reflection and geological data. In areas with no seismic coverage, potential-field data interpretation was carried out. Seismicity was overlaid to the potential seismogenic structures and high-resolution data was acquired in order to confirm which structures have been active into the Quaternary. Three major fault-zones affecting the Neogene were identified: V. F. Xira, Samora-Alcochete and Pinhal Novo. For the first fault, strong evidences suggest it is active. The other two fault-zones and other structures previously unknown can be correlated with several epicentres. Empirical relationships between maximum moment magnitude and fault area indicate that MW > 6.5 earthquakes can be expected for the larger structures