Magnetic properties of the low-dimensional spin-1/2 magnet \alpha-Cu_2As_2O_7

In this work we study the interplay between the crystal structure and magnetism of the pyroarsenate \alpha-Cu_2As_2O_7 by means of magnetization, heat capacity, electron spin resonance and nuclear magnetic resonance measurements as well as density functional theory (DFT) calculations and quantum Monte Carlo (QMC) simulations. The data reveal that the magnetic Cu-O chains in the crystal structure represent a realization of a quasi-one dimensional (1D) coupled alternating spin-1/2 Heisenberg chain model with relevant pathways through non-magnetic AsO_4 tetrahedra. Owing to residual 3D interactions antiferromagnetic long range ordering at T_N\simeq10K takes place. Application of external magnetic field B along the magnetically easy axis induces the transition to a spin-flop phase at B_{SF}~1.7T (2K). The experimental data suggest that substantial quantum spin fluctuations take place at low magnetic fields in the ordered state. DFT calculations confirm the quasi-one-dimensional nature of the spin lattice, with the leading coupling J_1 within the structural dimers. QMC fits to the magnetic susceptibility evaluate J_1=164K, the weaker intrachain coupling J'_1/J_1 = 0.55, and the effective interchain coupling J_{ic1}/J_1 = 0.20.Comment: Accepted for publication in Physical Review

Fatal, superb and rough tango: The brave compadrito and the cult to the knife in Borges

Este documento es de carácter reflexivo no derivado de procesos de investigación y presenta un recorrido parcial por la relación entre el tango y el contexto de los compadritos argentinos en la escritura narrativa y poética de Jorge Luis Borges desde la perspectiva del análisis textual y búsqueda de relaciones semióticas. Es un ejercicio escrito en el marco del curso introducción a los estudios literarios de la Universidad Autónoma de Bucaramanga y expresa las búsquedas de sentido iniciales en el proceso de identificación de elementos de interés en la literatura latinoamericana.This document is of a reflexive nature not derived from research processes and presents a partial journey through the relationship between tango and the context of Argentine compadritos in the narrative and poetic writing of Jorge Luis Borges from the perspective of textual analysis and relationship search semiotics It is a written exercise within the framework of the introductory course to literary studies of the Universidad Autónoma de Bucaramanga and expresses the search for initial meaning in the process of identifying elements of interest in Latin American literature

Estimation of the Primary Net Production above Ground through Remote Sensing in a Pastoral System of the Colombian Altillanura.

The primary net production above ground (ANPP) represents the main forage resource that supports the bovine production systems and its valuation is essential to help in the decision making on the management of the pastures. The ANPP has been estimated by periodic biomass courtesy, but with the use of the remote sensor integrated into the efficiency model formulated by Monteih (1972), it has been possible to estimate this biophysical parameter more efficiently at different scales and at low cost. The objective of this study was to estimate the PPNA based on a model of efficiency in the use of light for pastoral coverage in the Colombian Altillanura. The work is in the Carimagua Research Center of the Colombian Agricultural Research Corporation –AGROSAVIA– located in the municipality of Puerto Gaitán - Meta, Colombia. The pasture was monitored through forage supply gaps, in 14 paddocks with an approximate area of 2.6 ha each, established with Urochloa humidicola CIAT 6133 c.v Llanero under grazing of cattle with rest periods of 28 to 30 days. The spectral information was obtained from the on-board Sentinel 2 sensor and the global radiation data was obtained from a field weather station. A PPNA observed in the field and estimated by the efficiency model of 603.79 ±189kgDM/ha ± 188 and de 589.22 ±104 kgDM/ha was found, with a coefficient of determination R2 (0.79) and a significant correlation p \u3c 0.01 of 0.89. This methodology would quantify the supply of fodder on a larger scale under the same type of pastures

Probing the Timescale of the 1.4 GHz Radio emissions as a Star formation tracer

Radio used as a star formation rate (SFR) tracer presents enormous advantages by being unaffected by dust and radio sources being pinpointed at the sub-arc-second level. The interpretation of the low frequency 1.4 GHz luminosity is hampered by the difficulty in modeling the cosmic ray paths in the interstellar medium, and their interactions with the magnetic field. In this work, we compare the SFR derived from radio observations, and the ones derived from spectral energy distribution (SED) modeling. We aim at better understand the behavior of the SFR radio tracer, with a specific emphasis on the link with star-formation histories. We used the SED modeling code Code Investigating GALaxy Emission, CIGALE, with a non-parametric star formation history model (SFH) and fit the data over the wavelength range from the ultraviolet (UV) up to the mid-infrared (mid-IR). We interpret the difference between radio and SED-based SFR tracers in the light of recent gradients in the derived SFH. To validate the robustness of the results, we checked for any remaining active galaxy nuclei (AGN) contribution and tested the impact of our SFH modeling approach. Approximately 27% our galaxies present a radio SFR (SFR$_{\rm radio}$) at least ten times larger than the instantaneous SFR from SED-fitting (SFR$_{\rm SED}$). This trend affects primarily the galaxies that show a declining SFH activity over the last 300 Myr. Both SFR indicators converge toward a consistent value, when the SFHs are averaged over a period larger than 150 Myr to derive SFR$_{\rm SED}$. Although the radio at low frequency 1.4 GHz is a good tracer of the star formation activity of galaxies with constant or increasing SFH, our results indicate that this is not the case for galaxies that are quenching. Our analysis suggests that the star formation time sensitivity of the radio low frequency could be longer than 150 Myr.Comment: 10 pages, 10 figure

Estudio microbiológico durante el faenado, transporte, almacenamiento y procesamiento de canales bovinas.

Se estudian microbiológicamente 10 canales bovinas tomadas al azar durante el faenado, almacenamiento, transporte y deshuese a cortes mayoristas de un total de 35 animales sacrificados en Villavicencio, Colombia y transportados 126 km en cuartos de canal en carros aislados no refrigerados para su deshuese y consumo en Bogotá. Fueron recolectadas muestras de los equipos utilizados para conocer su importancia como contaminantes. De cada canal se tomaron 4 muestras, 2 de los cuartos posteriores y 2 de los anteriores. Todas las muestras recolectadas se analizaron para recuento total de bacterias mesofílicas aerobias, coliformes y psicrofílicas/cm2. El análisis estadístico demuestra coeficientes de regresión simple altamente significativos entre tiempo y bacterias mesófilicas totales y coliformes y entre tiempo y bacterias psicrofílicas. No hubo diferencias significativas entre la temperatura y los recuentos en las diferentes clases de bacterias estudiadas. Los equipos utilizados durante el proceso fueron altamente contaminantes (paredes y pisos de carros, mesas y cuchillos de deshuese, bancos). Se encontró mayor contaminación en los cuartos anteriores que en los posterioresGanado de leche-Ganadería lech

Carcinoma de pene y liquen escleroso: dos entidades estrechamente relacionadas

El liquen escleroatrófico (LS) o Balanitis xerótica obliterans es un transtorno crónico de la piel de causa desconocida que puede aparecer en la región genital sobre todo en varones de mediana edad no circuncidados y que se relaciona con el cáncer de pene. Su incidencia varía en función de las serie

Mortality due to malnutrition among children aged five and younger: five years before and after the implementation of the mana program. Antioquia, 1998-2007

ABSTRACT: To evaluate the mortality trends among children aged five and younger in the department of Antioquia (Colombia), where deaths are due to or associated with malnutrition. The time period studied was before and after the implementation of the mana program, from 1998 to 2007. Methodology: an ecological study was conducted to analyze the mortality trends in children under five in the regions of Antioquia before and after the implementation of the mana program. Data was analyzed using the Chi Square association and trend test. The Jointpoint regression was applied to analyze the mortality trend, and a factorial analysis was conducted by extracting the principal components. Results: a decreasing trend in mortality was observed during the time frame of the study. A statistically significant inflexion was observed in the general analysis of the Antioquia department in the year 2000, with an annual variation of -8.30% and a decreasing trend. Analysis revealed the inflexion points for the different regions of Antioquia: the year 2000 for the regions called Valle de Aburrá, Nordeste, Occidente, Oriente, and Suroeste, 2001 for Bajo Cauca, 2005 for Urabá, 2003 for Norte and 2004 for Magdalena Medio. Conclusion: A decreasing trend in mortality due to and associated with malnutrition was observed in each of the Antioquia regions during the time frame studied. This trend started before the implementation of the mana program.RESUMEN: Analizar el comportamiento de la mortalidad por y asociada a la desnutrición, en menores de cinco años; cinco años antes y cinco años después de la implementación del programa mana en las regiones del departamento de Antioquia entre 1998 a 2007. Metodología: estudio ecológico para el análisis del comportamiento de la mortalidad en menores de cinco años ocurridas en las regiones de Antioquia, antes y después de la creación del programa mana. Se calculó chi cuadrado de asociación y tendencia; así como el análisis de tendencia con la regresión de Jointpoint y se realizó análisis factorial a través de la extracción de componentes principales. Resultados: se observó tendencia a la disminución de la mortalidad a través de los años de estudio. En el análisis general de Antioquia, se identificó un punto de inflexión en el año 2000, el cual fue estadísticamente significativo con una variación de -8,30 con tendencia al descenso. En las regiones se identificó que Valle de Aburrá, Nordeste, Occidente, Oriente, Suroeste el punto de inflexión fue en 2000, Bajo Cauca 2001, Urabá 2002, Norte 2003 y Magdalena Medio, 2004. Conclusión: se observó tendencia en disminución de la mortalidad por desnutrición en las regiones de Antioquia en el período analizado, descenso que se presenta desde años anteriores a la implementación de mana

Whole Genome Association Analysis of Idiopathic Eosinophilic Enteritis in Brown Egg Layers

Idiopathic Eosinophilic Enteritis (IEE) is an intestine disease that affects absorption of nutrients and performance. Hens of a commercial breeding layer line and its two reciprocal crosses with another line were recorded for IEE related traits and genotyped for over 40,000 genetic markers across the genome. Whole genome association analysis was performed on 288 daughters from high and low incidence sire families. Single marker association analyses of IEE incidence in separate lines showed consistent significant regions on chromosomes 4 and 5 (p\u3c0.001). Simultaneous analyses of all SNPs in all 3 lines using Bayesian whole genome selection methods indicated evidence of associations on chromosomes 1, 2 and 4 for additive effects and on chromosome 5 for dominance effects. Line specific regions also appeared on chromosome Z. With further investigation, these results can be used to develop genetic markers to select against this disease and to understand its genetic basis

Frustrated magnet Li2ZrCuO4 - Paramagnetism meets paraelectricity

By measuring 7Li nuclear magnetic resonance, Cu2+ electron spin resonance and a complex dielectric constant in the frustrated spin-1/2 chain compound γ-Li2ZrCuO4 we find that the electric sublattice of mobile Li+ ions orders glass-like at T g ∼ 100 K. This yields the emergence of non-equivalent spin sites in the spin-1/2 CuO2 chains. We suggest that such a remarkable interplay between electrical and spin degrees of freedom may influence the properties of the spiral spin state in Li2ZrCuO4 which develops in this material at low temperatures. © 2010 IOP Publishing Ltd

Incidencia de liquen escleroso en 617 circuncisiones

El liquen escleroatrófico es un transtorno crónico de la piel de causa desconocida que puede aparecer en la región genital sobre todo en varones de mediana edad no circuncidados y que se relaciona con el cáncer de pene. Su incidencia varía en función de las series