Keeping watch over Colombia’s slumbering volcanoes

The Volcanological and Seismological Observatories of Manizales, Pasto and Popayan (Colombian Geological Survey) monitor and study the active volcanoes of Colombia using seismological, geodetic, geochemical and other techniques. Since 2009, permanent GNSS stations have been installed to complement classical geodetic measurements (e.g., tilt, EDM). At the moment, there are a total of 20 GNSS stations installed at Nevado del Ruiz, Cerro Machín, Puracé and Galeras volcanoes. Nevado del Ruiz has remained the most dynamic of the active Colombian volcanoes since its tragic eruption of 13 November 1985. The most significant deformation occurred between 2007 and 2012, when inflation, associated with magma migration and several small to moderate explosive eruptions in 2012 (VEI less or equal to 3), was observed. Galeras has experienced more than 25 moderate Vulcanian eruptions (VEI less or equal to 3) since 1989. In particular, the deformation network detected significant signals associated with magma migration and the extrusion of lava domes in 1991, 2005, 2008 and 2012. Puracé volcano has been the site of more than 10 minor eruptive episodes (VEI=2) in the past century, most recently in 1977. Monitoring of this volcano started in 1994. Unrest at Puracé since that time has been characterized by significant increases in seismic activity but with little or no deformation. We employ GAMIT/GLOBK to process GPS data from the monitoring network with support from the Volcano Disaster Assistance Program (U.S. Geological Survey). Additionally, differential processing is carried out using the commercial package Trimble 4D Control. Preliminary results for 2012 show no significant deformation at Puracé and Galeras volcanoes. On the other hand, the time series from Nevado del Ruiz shows a minor inflation (2-4 cm/yr) associated with the eruptive activity of 2012

Numerical optimization of passive chaotic micromixers

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.Due to the lack of turbulence in micromixers diffusion is the main process contributing to microfluidic mixing. Especially mixing of uids with low diffusivity is a difficult task. The recently discovered mechanism of "chaotic-advection" enhances the diffusion process by stretching and folding the fluid interfaces in order to provide a larger interface. Certain passive micromixers like the staggered herringbone mixer (SHM) apply this concept and succeed in enhancing the mixing process considerably. The optimization of such micromixers is a time consuming and often expensive process. We demonstrate that the application of the lattice Boltzmann (LB) method to study advection and diffusion processes can be an efficient tool to optimize micromixers. By combining finite time Lyapunov exponents to study chaotic advection and Danckwert's intensity of segregation to study the diffusion, we demonstrate how optimal geometrical parameters for the SHM can be found and how diffusion is improved by the complex ow pattern inside the mixer. The current article provides a review of our results published in [1] together with additional studies on modelling diffusive mixing with the LB method.This work was financed within the DFG priority program "nano- and microfluidics", the DFG collaborative research center 716, and by the NWO/STW VIDI grant of J. Harting

Evaluation of Bacterial Resistance to Antibiotics in Stool Samples Obtained from Guinea Pigs (Cavia porcellus) in Family and Family-commercial Farms

The inappropriate use of antimicrobial agents in guinea pigs to control enteric pathogens affects the nutritional sustainability of the rural population. Therefore, it is important to identify the pathogen, its resistance, and the appropriate antimicrobial agent for its control. The present investigation was carried out in family and family-commercial guinea pig farms, in eight rural parishes of the Gualaceo canton, Azuay province, Ecuador, from which 384 samples were obtained by rectal swabbing of guinea pigs from production units with enteric problems (diarrhea), the same ones that were transferred to the laboratory of the Faculty of Agricultural Sciences of the University of Cuenca, in order to identify the bacterial agents present in fecal samples of guinea pigs. There the isolation of culture media and identification of pathogens were carried out, they were subsequently exposed to an antibiogram, in order to qualitatively assess their bacterial resistance. The data were tabulated and analyzed in SPSS, finding the presence of Escherichia coli (49.4%), Salmonella typhimurium (24.6%), Shigella flexneri (14.3%), and Klebsiella pneumoniae (11.7%). The Chi-square test determined that of the five antimicrobials used, only tetracycline had a relationship between bacterial presence and resistance. It was also found that Escherichia coli presented a higher percentage of resistance, for enrofloxacin 22.5%, neomycin 14.2%, sulfamethoxazole - trimethoprim 33.3%, tetracyclines 29.2%. Data were analyzed at a confidence level of 95% with a 5% error, concluding that the identified pathogens have low resistance to the antimicrobials used, but are still susceptible. Keywords: bacterial resistance, antibiogram, enteric infection, antibiotics. Resumen El uso inadecuado de agentes antimicrobianos en cobayos para controlar patógenos entéricos, afectan la sustentabilidad alimenticia de la población rural, por ello es importante identificar el patógeno, su resistencia y el agente antimicrobiano adecuado para su control. La presente investigación se realizó en explotaciones de cobayos de tipo familiar y familiar – comercial, en ocho parroquias rurales del cantón Gualaceo provincia del Azuay, Ecuador de donde se obtuvo 384 muestras mediante hisopado rectal de cobayos provenientes de unidades productoras con problemas entéricos (diarrea), las mismas que fueron trasladadas al laboratorio de la Facultad de Ciencias Agropecuarias de la Universidad de Cuenca, con el fin de identificar los agentes bacterianos presentes en muestras fecales de cobayos, ahí se realizó la infección de medios de cultivo e identificación de agentes patógenos, mismos que posteriormente fueron expuestos a un antibiograma, con la finalidad de evaluar cualitativamente su resistencia bacteriana. Los datos fueron tabulados y analizados en SPSS, encontrándose la presencia de Escherichia coli (49,4%), Salmonella typhimurium (24,6%), Shigella flexneri (14,3%) y Klebsiella pneumoniae (11,7%). En la prueba de chi 2, se determinó que de los cinco antimicrobianos usados, solamente la Tetraciclina tiene relación entre la presencia bacteriana y la resistencia; también se encontró que Escherichia coli presentó mayor porcentaje de resistencia, para Enrofloxacina 22,5%, Neomicina 14,2%, Sulfametoxazol – trimetoprim 33,3%, Tetraciclinas 29,2%, datos que fueron analizados a un nivel de confianza del 95% con un 5% de error, concluyendo que los patógenos identificados presentan baja resistencia a los antimicrobianos utilizados, pero aún son susceptibles. Palabras Clave: resistencia bacteriana, antibiograma, infección entérica, antibióticos

The Caterpillar Gallery: Quadric Surface Theorems, Parametric Design and Digital Fabrication

The use of certain quadratic surface theorems has mainly been associated in architecture with the design of classical vaults, domes and piping. The work presented by the authors is intended to explore the potential of these theorems to be used in the generation law for more complex shapes in contemporary architecture. The paper shows the case study of a built full-scale prototype, The Caterpillar gallery, a project stemming from the combination of geometric research and teaching innovation. Formal and structural experimentation take place in this project where, by starting from geometrical considerations, an efficient way of generating longitudinal spaces is proposed. One of the mentioned theorems applied to rotational cones provides the starting point for the generation of a set of concatenated surfaces that, once assembled, constitute a very stable self-supporting structure with a variety of possible applications

Quantitative analysis of numerical estimates for the permeability of porous media from lattice-Boltzmann simulations

During the last decade, lattice-Boltzmann (LB) simulations have been improved to become an efficient tool for determining the permeability of porous media samples. However, well known improvements of the original algorithm are often not implemented. These include for example multirelaxation time schemes or improved boundary conditions, as well as different possibilities to impose a pressure gradient. This paper shows that a significant difference of the calculated permeabilities can be found unless one uses a carefully selected setup. We present a detailed discussion of possible simulation setups and quantitative studies of the influence of simulation parameters. We illustrate our results by applying the algorithm to a Fontainebleau sandstone and by comparing our benchmark studies to other numerical permeability measurements in the literature.Comment: 14 pages, 11 figure

Spatial and temporal analysis of the seasonal and interannual variability in the tropical Pacific simulated with a coupled GCM

In the first part of this work, the dominant time scales that explain the tropical variability of the first SINTEX simulation (ECHAM4(T30)-ORCA) are identified through a spectral analysis. Higher order spectral analysis is used to examine the interactions among these time scales. The time series analyzed are an average of sea surface temperature over the Niño3 region. The time scales obtained are compared with those identified in another coupled GCM simulation (ECHAM4(T42)-OPYC3). The higher importance of the biannual time scale in this last is explained partly by the strength of the coupling between the annual and the biannual time scales. There is no such strong coupling in the SINTEX simulation. Important differences among the generation of the simulated warm (or cold) event suggest the need of a systematic classification to isolate their relevant features. Therefore in the second part of this work, we address this problem. A space-time cluster analysis is performed on a data set built by collecting the values of the heat content anomalies in the tropical Pacific region, in the fifteen months previous to a peak in the Niño3 Index that has been identified as a ‘warm’ (or ‘cold’) event. In the case of the warm events, three types of generation schemes are found. In two of them, there are anomalies of heat content in the west, north and south of the equator, more than nine months before the events start. In the third case, the anomalies appear and grow in the central equatorial Pacific. Only two types are needed to classify the generation of cold events. Negative sea level height anomalies appear six months before the Niño3 Index reaches the (local) minimum. They are located north of the equator in one of the groups, and south of it in the other. Some of these characteristic traits also appear in observations of warm and cold events

Cádiz, una economía por descubrir

Este trabajo intenta avanzar en el análisis de la economía de la provincia de Cádiz desde el siglo XIX hasta el XXI, poniendo en evidencia la función de los factores de desarrollo provinciales y la débil integración de las medidas de política económica de localización industrial en el entorno económico existente.This work tries to make advance the analysis of the evolution of the economy in the province of Cadiz, from the XIXth century to the XXIst century, putting forth the role of the factors of provincial development and the low integration of the measures oftheeconomical policyof industrial localisation in the existent economical environement

Characterizing SL2S galaxy groups using the Einstein radius

We analyzed the Einstein radius, $\theta_E$, in our sample of SL2S galaxy groups, and compared it with $R_A$ (the distance from the arcs to the center of the lens), using three different approaches: 1.- the velocity dispersion obtained from weak lensing assuming a Singular Isothermal Sphere profile ($\theta_{E,I}$), 2.- a strong lensing analytical method ($\theta_{E,II}$) combined with a velocity dispersion-concentration relation derived from numerical simulations designed to mimic our group sample, 3.- strong lensing modeling ($\theta_{E,III}$) of eleven groups (with four new models presented in this work) using HST and CFHT images. Finally, $R_A$ was analyzed as a function of redshift $z$ to investigate possible correlations with L, N, and the richness-to-luminosity ratio (N/L). We found a correlation between $\theta_{E}$ and $R_A$, but with large scatter. We estimate $\theta_{E,I}$ = (2.2 $\pm$ 0.9) + (0.7 $\pm$ 0.2)$R_A$, $\theta_{E,II}$ = (0.4 $\pm$ 1.5) + (1.1 $\pm$ 0.4)$R_A$, and $\theta_{E,III}$ = (0.4 $\pm$ 1.5) + (0.9 $\pm$ 0.3)$R_A$ for each method respectively. We found a weak evidence of anti-correlation between $R_A$ and $z$, with Log$R_A$ = (0.58$\pm$0.06) - (0.04$\pm$0.1)$z$, suggesting a possible evolution of the Einstein radius with $z$, as reported previously by other authors. Our results also show that $R_A$ is correlated with L and N (more luminous and richer groups have greater $R_A$), and a possible correlation between $R_A$ and the N/L ratio. Our analysis indicates that $R_A$ is correlated with $\theta_E$ in our sample, making $R_A$ useful to characterize properties like L and N (and possible N/L) in galaxy groups. Additionally, we present evidence suggesting that the Einstein radius evolves with $z$.Comment: Accepted for publication in Astronomy & Astrophysics. Typos correcte