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

Torsion and Gravitation: A new view

According to the teleparallel equivalent of general relativity, curvature and torsion are two equivalent ways of describing the same gravitational field. Despite equivalent, however, they act differently: whereas curvature yields a geometric description, in which the concept of gravitational force is absent, torsion acts as a true gravitational force, quite similar to the Lorentz force of electrodynamics. As a consequence, the right-hand side of a spinless-particle equation of motion (which would represent a gravitational force) is always zero in the geometric description, but not in the teleparallel case. This means essentially that the gravitational coupling prescription can be minimal only in the geometric case. Relying on this property, a new gravitational coupling prescription in the presence of curvature and torsion is proposed. It is constructed in such a way to preserve the equivalence between curvature and torsion, and its basic property is to be equivalent with the usual coupling prescription of general relativity. According to this view, no new physics is connected with torsion, which appears as a mere alternative to curvature in the description of gravitation. An application of this formulation to the equations of motion of both a spinless and a spinning particle is madeComment: To appear on IJMP

A latent genetic subtype of major depression identified by whole-exome genotyping data in a Mexican-American cohort

Published online 16 May 2017Identifying data-driven subtypes of major depressive disorder (MDD) is an important topic of psychiatric research. Currently, MDD subtypes are based on clinically defined depression symptom patterns. Although a few data-driven attempts have been made to identify more homogenous subgroups within MDD, other studies have not focused on using human genetic data for MDD subtyping. Here we used a computational strategy to identify MDD subtypes based on single-nucleotide polymorphism genotyping data from MDD cases and controls using Hamming distance and cluster analysis. We examined a cohort of Mexican-American participants from Los Angeles, including MDD patients (n=203) and healthy controls (n=196). The results in cluster trees indicate that a significant latent subtype exists in the Mexican-American MDD group. The individuals in this hidden subtype have increased common genetic substrates related to major depression and they also have more anxiety and less middle insomnia, depersonalization and derealisation, and paranoid symptoms. Advances in this line of research to validate this strategy in other patient groups of different ethnicities will have the potential to eventually be translated to clinical practice, with the tantalising possibility that in the future it may be possible to refine MDD diagnosis based on genetic data.C Yu, M Arcos-Burgos, J Licinio and M-L Won

Determination of pulsation periods and other parameters of 2875 stars classified as MIRA in the All Sky Automated Survey (ASAS)

We have developed an interactive PYTHON code and derived crucial ephemeris data of 99.4% of all stars classified as 'Mira' in the ASAS data base, referring to pulsation periods, mean maximum magnitudes and, whenever possible, the amplitudes among others. We present a statistical comparison between our results and those given by the AAVSO International Variable Star Index (VSX), as well as those determined with the machine learning automatic procedure of Richards et al. 2012. Our periods are in good agreement with those of the VSX in more than 95% of the stars. However, when comparing our periods with those of Richards et al, the coincidence rate is only 76% and most of the remaining cases refer to aliases. We conclude that automatic codes require still more refinements in order to provide reliable period values. Period distributions of the target stars show three local maxima around 215, 275 and 330 d, apparently of universal validity, their relative strength seems to depend on galactic longitude. Our visual amplitude distribution turns out to be bimodal, however 1/3 of the targets have rather small amplitudes (A $<$ 2.5$^{m}$) and could refer to semi-regular variables (SR). We estimate that about 20% of our targets belong to the SR class. We also provide a list of 63 candidates for period variations and a sample of 35 multiperiodic stars which seem to confirm the universal validity of typical sequences in the double period and in the Petersen diagramsComment: 14 pages, 14 figures, and 8 tables. Accepted to The Astrophysical Journal Supplement Series, September 201

Effects of different contextual interference programs in agility (Efectos producidos por diferentes programas de interferencia contextual en la agilidad)

En este estudio participaron 76 alumnos de 9-10 años de edad de un colegio público de educación primaria (44 chicos y 32 chicas). Los participantes fueron randomizados en función del resultado del pretest en cuatro grupos: interferencia contextual baja (ICB, n=19), interferencia contextual moderada (ICM, n=19) interferencia contextual alta (ICA, n=19) y Grupo Control (GC, n=19). El objetivo de este estudio fue conocer que método de entrenamiento de la agilidad en función de la interferencia contextual baja, moderada o alta (ICB, ICM e ICA) es más efectivo en escolares de cuarto curso de educación primaria, con el fin de dilucidar qué método de desarrollo de esta capacidad resultó el idóneo en esta etapa de escolarización. La agilidad fue evaluada mediante el test MAT2. Salvo en el grupo control (CG), se obtuvieron diferencias significativas en la agilidad (test MAT2), en todos los grupos después de un programa de intervención de 4 semanas de duración en alumnos del cuarto curso de primaria. Estas diferencias han sido superiores en el grupo de ICM (p<0,01, ES=1,12). Se encontraron diferencias significativas (p<0,05, ES=0,79) en el postest entre el grupo de ICM e ICB. This study involved 76 students from 9-10 years old in a public elementary school (44 boys and 32 girls). Participants were randomized to the outcome of the pretest into four groups: low contextual interference (ICB, n = 19), moderate contextual interference (ICM, n = 19) high contextual interference (ICA, n = 19) and Control Group (GC, n = 19). The aim of this study was to determine which method of agility training (ICB, ICM or ICA) is more effective in primary school children (9-10 years), in order to figure out what method of development of this capacity was the appropriate at this stage of schooling. The agility was evaluated by MAT2 test. Except in the control group (GC), there were significant differences in agility (MAT2 test) in all groups (ICB, ICM and ICA) after an intervention program of 4-week fourth-year students of elementary school. These differences have been higher in the ICM group (p<0.01, ES=1.12). We found significant differences (p<0.05, ES=0.79) in the posttest between the ICM and ICB group

Summing Feynman diagrams in the worldline formalism

The worldline formalism shares with string theory the property that it allows one to write down master integrals that effectively combine the contributions of many Feynman diagrams. While at the one-loop level these diagrams differ only by the position of the external legs along a fixed line or loop, at multiloop they generally involve different topologies. Here we summarize various efforts that have been made over the years to exploit this property in a computationally meaningful way. As a first example, we show how to generalize the Landau-Khalatnikov-Fradkin formula for the non-perturbative gauge transformation of the fermion propagator in QED to the general 2n - point case by pure manipulations at the path-integral level. At the parameter-integral level, we show how to integrate out individual photons in the low-energy expansion, and then sketch a recently introduced general framework for the analytical evaluation of such worldline integrals involving a reduction to quantum mechanics on the circle and the relation between inverse derivatives and Bernoulli polynomials