Hadron spectra from a non-relativistic model with confining harmonic potential

Hadron spectra and other properties of quark systems are studied in the framework of a non-relativistic spin-independent phenomenological model. The chosen confining potential is harmonic, which allowed us to obtain analytical solutions for both meson and baryon (of equal constituent quarks) spectra. The introduced parameters are fixed from the low-lying levels of heavy quark mesons. The requirement of flavor independence is imposed, and it restricts the possible choices of inter-quark potentials. The hyper-spherical coordinates are considered for the solution of the three-body problem.Comment: Revtex file, 8 figures, 18 pages. Content and references added, some tables changed by figure

EuCo2P2: A Model Molecular-Field Helical Heisenberg Antiferromagnet

The metallic compound EuCo2P2 with the body-centered tetragonal ThCr2Si2 structure containing Eu spins 7/2 was previously shown from single-crystal neutron diffraction measurements to exhibit a helical antiferromagnetic (AFM) structure below TN = 66.5 K with the helix axis along the c axis and with the ordered moments aligned within the ab-plane. Here we report crystallography, electrical resistivity, heat capacity, magnetization and magnetic susceptibility measurements on single crystals of this compound. We demonstrate that EuCo2P2 is a model molecular-field helical Heisenberg antiferromagnet from comparisons of the anisotropic magnetic susceptibility chi, high-field magnetization and magnetic heat capacity of EuCo2P2 single crystals at temperature T < TN with the predictions of our recent formulation of molecular field theory. Values of the Heisenberg exchange interactions between the Eu spins are derived from the data. The low-T magnetic heat capacity ~ T^3 arising from spin-wave excitations with no anisotropy gap is calculated and found to be comparable to the lattice heat capacity. The density of states at the Fermi energy of EuCo2P2 and the related compound BaCo2P2 are found from the heat capacity data to be large, 10 and 16 states/eV per formula unit for EuCo2P2 and BaCo2P2, respectively. These values are enhanced by a factor of ~2.5 above those found from DFT electronic structure calculations for the two compounds. The calculations also find ferromagnetic Eu-Eu exchange interactions within the ab-plane and AFM interactions between nearest- and next-nearest planes, in agreement with the MFT analysis of chi{ab}(T < TN).Comment: 20 pages, 17 figures, 3 tables, 46 references. This is an extended replacement of arXiv:1512.02958 with an additional coautho

Non-affine geometrization can lead to nonphysical instabilities

Geometrization of dynamics consists of representing trajectories by geodesics on a configuration space with a suitably defined metric. Previously, efforts were made to show that the analysis of dynamical stability can also be carried out within geometrical frameworks, by measuring the broadening rate of a bundle of geodesics. Two known formalisms are via Jacobi and Eisenhart metrics. We find that this geometrical analysis measures the actual stability when the length of any geodesic is proportional to the corresponding time interval. We prove that the Jacobi metric is not always an appropriate parametrization by showing that it predicts chaotic behavior for a system of harmonic oscillators. Furthermore, we show, by explicit calculation, that the correspondence between dynamical- and geometrical-spread is ill-defined for the Jacobi metric. We find that the Eisenhart dynamics corresponds to the actual tangent dynamics and is therefore an appropriate geometrization scheme.Comment: Featured on the Cover of the Journal. 9 pages, 6 figures: http://iopscience.iop.org/1751-8121/48/7/07510

A facile synthetic strategy to polysiloxanes containing sulfonyl side groups with high dielectric permittivity

The chemical modification of polymers with lateral polar groups increases their dielectric permittivity above the glass transition temperature, making them attractive materials for dielectric elastomer actuators. Despite the large dipole moment of the sulfonyl moiety, its usefulness as a substituent in high permittivity polysiloxanes has not been explored so far. This work explores two post-polymerization synthetic strategies to reach such a goal, namely the oxidation of the thioether groups present in polysiloxanes which carry thioether side groups at every repeat unit and the modification of the vinyl groups of poly(methyl-vinylsiloxanes) with sulfonyl groups via thiol-ene chemistry. While both strategies in principle work, the oxidation of the thioether groups results in an undesired shortening of the polysiloxane chains. In contrast, the thiol-ene reactions give the target polymer in a clean and highly efficient process. For this reason the access to two sulfonyl containing thiols, to be employed in the thiol-ene reaction, was improved to the degree that they are now available on the 50 g scale as pure compounds. The sulfonyl content of the polysiloxanes was systematically varied by the use of two different thiols in the thiol-ene post-polymerization modification, one of which carried the sulfonyl group, the other a (dummy) butyl group instead. The prepared polymers were characterized by NMR, DSC, TGA, GPC, and impedance spectroscopy. All polymers show glass transition temperatures below room temperature. Dielectric permittivity measurements at room temperature show that the permittivity of the polymers at the frequency with minimal losses can be fine-tuned from about 5 up to 22.7. Because of their high dielectric permittivity, low glass transition temperatures, and easy and scalable synthesis from cheap materials, these novel polymers are attractive components for high permittivity elastomers to be employed in actuators, capacitors, and flexible electronics

Determinação das frações de carbono orgânico no solo do Páramo La Cortadera – Boyacá

Páramos are considered strategic ecosystems because of their supply of environmental services, the accumulation of carbon being among those worth highlighting. This study aimed to determine the fractions of organic carbon present in the ground of the Páramo La Cortadera, employing the technique of organic matter characterization and the wet digestion method (Walkley – Black). The results showed that the native vegetation has a higher concentration of carbon compared to the coverings of farms and pastures; being that the carbon is extractable, the fraction that had the highest values, followed by humic and fulvic acids. The study concludes that the páramo “La Cortadera” is a very vulnerable ecosystem due to high anthropogenic impact, therefore, it is preferable to preserve and protect it, due to the fact that it contains labile carbon fractions that can be returned directly to the atmosphere, favoring climate change and the greenhouse effect.Los páramos son considerados ecosistemas estratégicos por su oferta de servicios ambientales, entre los que cabe resaltar la acumulación de carbono. Esta investigación tuvo como objetivo determinar las fracciones de carbono orgánico presentes en el suelo del páramo La Cortadera, mediante la técnica de caracterización de materia orgánica y el método de digestión vía húmeda (Walkley-Black). Los resultados mostraron que la vegetación nativa tiene mayor concentración de carbono en comparación con las coberturas de cultivos y pastizales. El carbono extractable fue la fracción que presentó los valores más altos, seguido por los ácidos húmicos y fúlvicos. Se concluye que el páramo La Cortadera es un ecosistema muy vulnerable por el alto impacto antrópico; por lo tanto, se debe propender a su conservación y protección, por cuanto contiene fracciones lábiles de carbono que pueden ser devueltas directamente a la atmósfera y favorecer el cambio climático y el efecto invernadero.Os páramos são considerados ecossistemas estratégicos pela oferta de serviços ambientais, entre os quais cabe destacar a acumulação de carbono. Esta pesquisa teve como objetivo determinar as frações de carbono orgânico presente no solo do páramo “La Cortadera”, empregando a técnica de caracterização de matéria orgânica e o método de digestão por via úmida (Walkley – Black). Os resultados mostraram que a vegetação nativa tem maior concentração de carbono em comparação com as coberturas das culturas e as pastagens, sendo o carbono extraível, a fração que apresentou os valores mais elevados, seguido pelos ácidos húmicos e fúlvicos. Concluise que o páramo La Cortadera é um ecossistema muito vulnerável pelo alto impacto antrópico, portanto, deve promove-lo e protegê-lo, devido às frações lábeis de carbono que podem ser retornadas diretamente para a atmosfera, favorecendo mudanças climáticas e o efeito estufa

Now, the part of intuition. Research, Art and Creation, 2018

Catálogo de Exposición del Máster en Investigación en Arte y Creación de la UCM. Muestra celebrada del 25 de septiembre al 10 de octubre de 2018 en la Sala de Exposiciones de la Facultad de Bellas Artes. C / Pintor el Greco 2, Ciudad Universitaria. 28040 Madrid. Comisariado de Javier Mañero Rodicio.Exhibition catalog of the Master in Art and Creation Research of the UCM. September 25 to October 10, 2018 in the Exhibition Hall of the Faculty of Fine Arts. C / Pintor El Greco 2, University City. 28040 Madrid. Curated by Javier Mañero Rodicio.Fac. de Bellas ArtesFALSEFacultad de Bellas Artes. Universidad Complutense de Madrid.pu