Change in the Magnetic Domain Alignment Process at the Onset of a Frustrated Magnetic State in Ferrimagnetic La2Ni(Ni1/3Sb2/3)O6 Double Perovskite

We have performed a combined study of magnetization hysteresis loops and time dependence of the magnetization in a broad temperature range for the ferrimagnetic La2Ni(Ni1/3Sb2/3)O6 double perovskite. This material has a ferrimagnetic order transition at ~100 K and at lower temperatures (~ 20 K) shows the signature of a frustrated state due to the presence of two competing magnetic exchange interactions. The temperature dependence of the coercive field shows an important upturn below the point where the frustrated state sets in. The use of the magnetization vs. applied magnetic field hysteresis data, together with the magnetization vs. time data provides a unique opportunity to distinguish between different scenarios for the low temperature regime. From our analysis, a strong domain wall pinning results the best scenario for the low temperature regime. For temperatures larger than 20K the adequate scenario seems to correspond to a weak domain wall pinning.Comment: 4 pages, 5 figures included. Manuscript submitted to IEEE Transactions on Magnetics, proceedings of the LAW3M 2013 conferenc

Spatial effects in real networks: measures, null models, and applications

Spatially embedded networks are shaped by a combination of purely topological (space-independent) and space-dependent formation rules. While it is quite easy to artificially generate networks where the relative importance of these two factors can be varied arbitrarily, it is much more difficult to disentangle these two architectural effects in real networks. Here we propose a solution to the problem by introducing global and local measures of spatial effects that, through a comparison with adequate null models, effectively filter out the spurious contribution of non-spatial constraints. Our filtering allows us to consistently compare different embedded networks or different historical snapshots of the same network. As a challenging application we analyse the World Trade Web, whose topology is expected to depend on geographic distances but is also strongly determined by non-spatial constraints (degree sequence or GDP). Remarkably, we are able to detect weak but significant spatial effects both locally and globally in the network, showing that our method succeeds in retrieving spatial information even when non-spatial factors dominate. We finally relate our results to the economic literature on gravity models and trade globalization

p-wave Holographic Superconductors and five-dimensional gauged Supergravity

We explore five-dimensional ${\cal N}=4$ $SU(2)\times U(1)$ and ${\cal N}=8$ SO(6) gauged supergravities as frameworks for condensed matter applications. These theories contain charged (dilatonic) black holes and 2-forms which have non-trivial quantum numbers with respect to U(1) subgroups of SO(6). A question of interest is whether they also contain black holes with two-form hair with the required asymptotic to give rise to holographic superconductivity. We first consider the ${\cal N}=4$ case, which contains a complex two-form potential $A_{\mu\nu}$ which has U(1) charge $\pm 1$. We find that a slight generalization, where the two-form potential has an arbitrary charge $q$, leads to a five-dimensional model that exhibits second-order superconducting transitions of p-wave type where the role of order parameter is played by $A_{\mu\nu}$, provided $q \gtrsim 5.6$. We identify the operator that condenses in the dual CFT, which is closely related to ${\cal N}=4$ Super Yang-Mills theory with chemical potentials. Similar phase transitions between R-charged black holes and black holes with 2-form hair are found in a generalized version of the ${\cal N}=8$ gauged supergravity Lagrangian where the two-forms have charge $q\gtrsim 1.8$.Comment: 35 pages, 14 figure

Atomic and molecular interstellar absorption lines toward the high galactic latitude stars HD~141569 and HD~157841 at ultra-high resolution

We present ultra-high resolution (0.32 km/s) spectra obtained with the 3.9m Anglo-Australian Telescope (AAT) and Ultra-High-Resolution Facility (UHRF), of interstellar NaI D1, D2, Ca II K, K I and CH absorption toward two high galactic latitude stars HD141569 and HD157841. We have compared our data with 21-cm observations obtained from the Leiden/Dwingeloo HI survey. We derive the velocity structure, column densities of the clouds represented by the various components and identify the clouds with ISM structures seen in the region at other wavelengths. We further derive abundances, linear depletions and H2 fractional abundances for these clouds, wherever possible. Toward HD141569, we detect two components in our UHRF spectra : a weak, broad component at - 15 km/s, seen only in CaII K absorption and another component at 0 km/s, seen in NaI D1, D2, Ca II K, KI and CH absorption. In the case of the HD157841 sightline, a total of 6 components are seen on our UHRF spectra in NaI D1, D2 Ca II K, K I and CH absorption. 2 of these 6 components are seen only in a single species.Comment: 16 pages, Latex, 4 figures, ps files Astrophysical Journal (in press

Estimación mediante rapd's de la diversidad genética en guadua en el departamento del cauca, colombia

Mediante RAPD's se analizaron 120 muestras foliares de 12 biotipos de Guadua angustifolia Kunth clasificados morfológicamente, procedentes de la cuenca del río Cauca, en el departamento del Cauca, Colombia, para determinar diversidad genética. El ADN se extrajo mediante el protocolo modificado de Dellaporta (1983). Se emplearon los cebadores; OPF-12, OPG-19, OPN-19 y OPP-16 con mayor número de bandas polimórficas. El índice de Shannon (HT = 0.4556 ± 0.1849) señaló diversidad genética total alta y diversidad entre los biotipos y al interior de ellos. El Índice de estructura genética (Gst = 0.5200) e Indice de migración efectiva (Nm = 0.4615) definieron biotipos bien diferenciados. El análisis de similaridad conformó tres grupos a un coeficiente de 0.64. El grupo G1 incluyó los biotipos Curvado, Rayada frecuente, Amarilla Playón, Rayada ancha, Rayada escasa, Convexa, Amarilla, Hembra, Verde irregular y algunos individuos de verde alta. El grupo G2, Verde alta y Macho. El grupo G3, Rayada negra. El estudio molecular agrupó los individuos de forma similar al estudio morfológico, con excepción de los individuos del biotipo Hembra. Palabras claves: Guadua angustifolia, caracterización molecular, variación genética

Intensive monitoring of conventional and surrogate quality parameters in a highly urbanized river affected by multiple combined sewer overflows

Abstract The paper reports results of four intensive campaigns carried out on the Seveso River (Milan metropolitan area, Italy) between 2014 and 2016, during intense precipitation events. Laboratory analyses were coupled with on-site, continuous measurements to assess the impact of pollutants on water quality based on both conventional and surrogate parameters. Laboratory data included total suspended solids, caffeine, total phosphorus and nitrogen, and their dissolved forms. Screening of trace metals (Cr, Cu, Pb, Ni, Cd) and PBDEs (polybromodiphenylethers) was carried out. Continuous measurements included water level, physico-chemical variables and turbidity. Nutrient concentrations were generally high (e.g. average total phosphorus > 1,000 μg/L) indicating strong sewage contributions. Among monitored pollutants Cr, Cu, Pb, and Cd concentrations were well correlated to TSS, turbidity and discharge, being bound mostly to suspended particulate matter. A different behavior was found for Ni, that showed an early peak occurring before the flow peak, as a result of first flush events. PBDEs correlated well to nutrient concentrations, showing the highest peaks soon after activation of the combined sewer overflows, likely because of its accumulation in sewers. In addition to showing the existing correlations between quality parameters, the paper highlights the importance of surrogate parameters as indicators of anthropic pollution inputs

Experiencias educacionales conjuntas entre las cátedras de Cálculo Avanzado e Hidráulica General y Aplicada

En el presente trabajo se propone mostrar los resultados alcanzados al desarrollar una experiencia innovadora en la enseñanza de Métodos Numéricos en carreras de Ingeniería, denominada “Experiencia Educacional Conjunta”, en la que participaron las cátedras de “Calculo Avanzado” e “Hidráulica General y Aplicada”. La experiencia consistió en la aplicación de métodos numéricos para modelar el comportamiento del movimiento del agua en un medio permeable. Para su implementación los alumnos recibieron la explicación en forma conjunta de los docentes de las cátedras involucradas, ocasión en la que se suministró la información necesaria para interpretar la física del fenómeno. Se proporcionaron los datos del problema y la ecuación en derivadas parciales que representa el comportamiento hidráulico. En base a la información brindada y a los objetivos propuestos, se procedió a explicar el método de diferencias finitas para el tratamiento numérico de la ecuación de Laplace acompañando una grilla discreta y los valores en la frontera. Con los resultados obtenidos se determinaron parámetros hidráulicos de interés a fin de interpretar el problema planteado. Se analizó la calidad de los resultados obtenidos y el alcance de las técnicas numéricas en la problemática hidráulica. Finalmente, en función de una encuesta realizada, se pudo apreciar la impresión provocada en los alumnos con este tipo de experiencia educacional, y se elaboraron pautas de mejora en la metodología de la enseñanza para un mayor aprovechamiento de las temáticas abordadas por ambas cátedras.Publicado en: Mecánica Computacional vol. XXXV, no.14Facultad de Ingenierí

Experiencias educacionales conjuntas entre las cátedras de Cálculo Avanzado e Hidráulica General y Aplicada

En el presente trabajo se propone mostrar los resultados alcanzados al desarrollar una experiencia innovadora en la enseñanza de Métodos Numéricos en carreras de Ingeniería, denominada “Experiencia Educacional Conjunta”, en la que participaron las cátedras de “Calculo Avanzado” e “Hidráulica General y Aplicada”. La experiencia consistió en la aplicación de métodos numéricos para modelar el comportamiento del movimiento del agua en un medio permeable. Para su implementación los alumnos recibieron la explicación en forma conjunta de los docentes de las cátedras involucradas, ocasión en la que se suministró la información necesaria para interpretar la física del fenómeno. Se proporcionaron los datos del problema y la ecuación en derivadas parciales que representa el comportamiento hidráulico. En base a la información brindada y a los objetivos propuestos, se procedió a explicar el método de diferencias finitas para el tratamiento numérico de la ecuación de Laplace acompañando una grilla discreta y los valores en la frontera. Con los resultados obtenidos se determinaron parámetros hidráulicos de interés a fin de interpretar el problema planteado. Se analizó la calidad de los resultados obtenidos y el alcance de las técnicas numéricas en la problemática hidráulica. Finalmente, en función de una encuesta realizada, se pudo apreciar la impresión provocada en los alumnos con este tipo de experiencia educacional, y se elaboraron pautas de mejora en la metodología de la enseñanza para un mayor aprovechamiento de las temáticas abordadas por ambas cátedras.Publicado en: Mecánica Computacional vol. XXXV, no.14Facultad de Ingenierí

Baryonic symmetries and M5 branes in the AdS_4/CFT_3 correspondence

We study U(1) symmetries dual to Betti multiplets in the AdS_4/CFT_3 correspondence for M2 branes at Calabi-Yau four-fold singularities. Analysis of the boundary conditions for vector fields in AdS_4 allows for a choice where wrapped M5 brane states carrying non-zero charge under such symmetries can be considered. We begin by focusing on isolated toric singularities without vanishing six-cycles, and study in detail the cone over Q^{111}. The boundary conditions considered are dual to a CFT where the gauge group is U(1)^2 x SU(N)^4. We find agreement between the spectrum of gauge-invariant baryonic-type operators in this theory and wrapped M5 brane states. Moreover, the physics of vacua in which these symmetries are spontaneously broken precisely matches a dual gravity analysis involving resolutions of the singularity, where we are able to match condensates of the baryonic operators, Goldstone bosons and global strings. We also argue more generally that theories where the resolutions have six-cycles are expected to receive non-perturbative corrections from M5 brane instantons. We give a general formula relating the instanton action to normalizable harmonic two-forms, and compute it explicitly for the Q^{222} example. The holographic interpretation of such instantons is currently unclear.Comment: 92 pages, 10 figure