Coherent pion production in neutrino nucleus collision in the 1 GeV region

We calculate cross sections for coherent pion production in nuclei induced by neutrinos and antineutrinos of the electron and muon type. The analogies and differences between this process and the related ones of coherent pion production induced by photons, or the (p,n) and $(^3 He, t)$ reactions are discussed. The process is one of the several ones occurring for intermediate energy neutrinos, to be considered when detecting atmospheric neutrinos. For this purpose the results shown here can be easily extrapolated to other energies and other nuclei.Comment: 13 pages, LaTex, 8 post-script figures available at [email protected]

Toughening of complete solid solution cermets by graphite addition

(Ti0.95Ta0.05)(C0.5N0.5)-Co complete solid solution cermets (CSCs) were developed by a mechanochemical synthesis process and a pressureless sintering method. The effect of different percentages of graphite used as a sintering additive on the nature of the binder phase and the mechanical properties of the cermets was investigated. Microstructural and mechanical characterisations were carried out by X-ray diffraction, optical microscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Vickers hardness, indentation fracture toughness and nanoindentation. The addition of graphite modified the carbon activity during sintering, reducing the dissolution of carbonitride ceramic particles into the molten binder. The amount of Ti and Ta remaining in the binder after sintering gradually decreased as the amount of graphite added increased, which induced a change in the nature of the binder phase. When no graphite was added, the binder consisted of the brittle TixTa1-xCo2 intermetallic phase. With the increase in the amount of graphite added, the formation of more ductile phases, such as TixTa1-xCo3 and α-Co, was observed, causing a significant improvement in the toughness of the cermets.Peer reviewe

Lack of uniqueness for weak solutions of the incompressible porous media equation

In this work we consider weak solutions of the incompressible 2-D porous media equation. By using the approach of De Lellis-Sz\'ekelyhidi we prove non-uniqueness for solutions in $L^\infty$ in space and time.Comment: 23 pages, 2 fugure

Construcción participativa de estrategias de restauración ecológica en humedales del Magdalena Medio, Colombia: una herramienta para el ordenamiento ambiental territorial

The socioecological relevance of the Magdalena Medio (Colombia) region wetlands and the dynamics of their degradation reveal the need to develop restoration processes that guarantee the land's sustainability as a tool for the transformation of social realities. The study presents two examples for the development of ecological restoration participative experiences in dry and wet tropical forests and aquatic habitats of the region through the implementation of strategies that combine techniques such as nucleation, enrichment and succession facilitation. To date these experiences have allowed the identification of 32 species with potential for restoration, standing out among these Tabebuia rosea, Hura crepitans, Phyllanthus elsiae and Spondia mombin as strong agents for ecological succession processes in order to recover and generate local ecological knowledge, materialize decisions related to planning and environmental protection, and revamp the role of the artisanal fishermen in the conservation and governance of the region´s wetlands.La importancia socio-ecológica de los humedales del Magdalena Medio (Colombia) y su dinámica de degradación, ponen de manifiesto la necesidad de desarrollar procesos de restauración que garanticen la sostenibilidad de los territorios, como herramienta de transformación de las realidades sociales. A partir de una iniciativa conjunta con pescadores artesanales, se definieron dos ventanas de estudio para el desarrollo de experiencias participativas de restauración ecológica en bosques secos, húmedos y humedales del Magdalena Medio, mediante la implementación de estrategias que combinan técnicas como nucleación, enriquecimiento y facilitación sucesional. A la fecha las experiencias han permitido identificar 32 especies con potencial para la restauración, destacándose Tabebuia rosea, Hura crepitans, Phyllanthus elsiae y Spondias mombin como fuertes dinamizadoras de los procesos de sucesión ecológica. La recuperación y generación de conocimiento ecológico propios, así como la materialización de las decisiones de ordenamiento y protección ambiental de los territorios, han permitido dar un nuevo significado al papel de los pescadores artesanales en la conservación y gobernanza de los humedales de la región

Participative construction of ecological restoration strategies for wetlands of the middle Magdalena River drainage: a tool for environmental land management

The socioecological relevance of the Magdalena Medio (Colombia) region wetlands and the dynamics of their degradation reveal the need to develop restoration processes that guarantee the land's sustainability as a tool for the transformation of social realities. The study presents two examples for the development of ecological restoration participative experiences in dry and wet tropical forests and aquatic habitats of the region through the implementation of strategies that combine techniques such as nucleation, enrichment and succession facilitation. To date these experiences have allowed the identification of 32 species with potential for restoration, standing out among these Tabebuia rosea, Hura crepitans, Phyllanthus elsiae and Spondia mombin as strong agents for ecological succession processes in order to recover and generate local ecological knowledge, materialize decisions related to planning and environmental protection, and revamp the role of the artisanal fishermen in the conservation and governance of the region´s wetlands

Estudio cinético del sistema de molienda de una fábrica de cemento cubana

A kinetic study realized in a moulding system in a cement factory ("Palmarito de Cauto" Santiago de Cuba) is presented. This objective of this study is the production of a pozzolonic cement PZ-250 with an addition until 40% of pozzolan. The present paper confirms the satisfactory predictions and permits to recommend the utilization it as a available way of economical efficiency.Se presentan resultados obtenidos en el estudio cinético realizado al sistema de molienda de la fábrica de cemento de "Palmarito de Cauto", Santiago de Cuba, con vistas a la producción de cemento puzolánico PZ-250 con adición de hasta un 40 % de puzolanas. El presente trabajo avala satisfactoriamente las predicciones realizadas y permiten recomendar su utilización como un medio idóneo de eficiencia económica

Correlations between Background Radiation inside a Multilayer Interleaving Structure, Geomagnetic Activity, and Cosmic Radiation: A Fourth Order Cumulant-based Correlation Analysis

In this work, we analyzed time-series of background radiation inside a multilayer interleaving structure, geomagnetic activity and cosmic-ray activity using the Pearson correlation coefficient and a new correlation measure based on the one-dimensional component of the fourth order cumulant. The new method is proposed based on the fact that the cumulant of a random process is zero if it is of Gaussian nature. The results show that this methodology is useful for detecting correlations between the analyzed variables.Comment: 8 pages, 2 figures and 4 table

Pion Cloud Contribution to K+ Nucleus Scattering

A careful reanalysis is done of the contribution to $K^{+}$ nucleus scattering from the interaction of the kaon with the virtual pion cloud. The usual approximations made in the evaluation of the related kaon selfenergy are shown to fail badly. We also find new interaction mechanisms which provide appreciable corrections to the kaon selfenergy. Some of these contribute to the imaginary part below pion creation threshold. The inclusion of these new mechanisms in the inelastic part of the optical potential produces a significant improvement in the differential and total $K^{+}$ nuclear cross sections. Uncertainties remain in the dispersive part of the optical potential.Comment: 27 pages, 17 figures (not all of them included, please request them), report UG-DFM-2/9

Pure point diffraction and cut and project schemes for measures: The smooth case

We present cut and project formalism based on measures and continuous weight functions of sufficiently fast decay. The emerging measures are strongly almost periodic. The corresponding dynamical systems are compact groups and homomorphic images of the underlying torus. In particular, they are strictly ergodic with pure point spectrum and continuous eigenfunctions. Their diffraction can be calculated explicitly. Our results cover and extend corresponding earlier results on dense Dirac combs and continuous weight functions with compact support. They also mark a clear difference in terms of factor maps between the case of continuous and non-continuous weight functions.Comment: 30 page