Dirac quasinormal modes for a 4-dimensional Lifshitz Black Hole

We study the quasinormal modes of fermionic perturbations for an asymptotically Lifshitz black hole in 4-dimensions with dynamical exponent z=2 and plane topology for the transverse section, and we find analytically and numerically the quasinormal modes for massless fermionic fields by using the improved asymptotic iteration method and the Horowitz-Hubeny method. The quasinormal frequencies are purely imaginary and negative, which guarantees the stability of these black holes under massless fermionic field perturbations. Remarkably, both numerical methods yield consistent results; i.e., both methods converge to the exact quasinormal frequencies; however, the improved asymptotic iteration method converges in a fewer number of iterations. Also, we find analytically the quasinormal modes for massive fermionic fields for the mode with lowest angular momentum. In this case, the quasinormal frequencies are purely imaginary and negative, which guarantees the stability of these black holes under fermionic field perturbations. Moreover, we show that the lowest quasinormal frequencies have real and imaginary parts for the mode with higher angular momentum by using the improved asymptotic iteration method.Comment: Version accepted for publication in EPJC. arXiv admin note: text overlap with arXiv:1306.597

Moir\'e patterns on STM images of graphite from surface and subsurface rotated layer

We have observed with STM moir\'e patterns corresponding to the rotation of one graphene layer on HOPG surface. The moir\'e patterns were characterized by rotation angle and extension in the plane. Additionally, by identifying border domains and defects we can discriminate between moir\'e patterns due to rotation on the surface or subsurface layer. For a better understanding of moir\'e patterns formation we have studied by first principles an array of three graphene layers where the top or the middle layer appears rotated around the stacking axis. We compare the experimental and theoretical results and we show the strong influence of rotations both in surface and subsurface layers for moir\'e patterns formation in corresponding STM images.Comment: 5 pages, 6 figure

Reconstructing paleoseismic deformation, 2: 1000 years of great earthquakes at Chucalén, south central Chile

In this paper we adopt a quantitative biostratigraphic approach to establish a 1000-year-long coastal record of megathrust earthquake and tsunami occurrence in south central Chile. Our investigations focus on a site in the centre of the rupture segment of the largest instrumentally recorded earthquake, the AD 1960 magnitude 9.5 Chile earthquake. At Chucalén coseismic subsidence in 1960 is recorded in the lithostratigraphy and biostratigraphy of coastal marshes, with peat overlain by minerogenic sediment and changes in the assemblages of diatoms (unicellular algae) indicating an abrupt increase in relative sea level. In addition to the 1960 earthquake, the stratigraphy at Chucalén records three earlier earthquakes, the historically documented earthquake of 1575 and two prehistoric earthquakes, radiocarbon dated to AD 1270–1450 and 1070–1220. Laterally extensive sand sheets containing marine or brackish diatom assemblages suggest tsunami deposition associated with at least two of the three pre-1960 earthquakes. The record presented here suggests a longer earthquake recurrence interval, averaging 270 years, than the historical recurrence interval, which averages 128 years. The lack of geologic evidence at Chucalén of two historically documented earthquakes, in 1737 and 1837, supports the previously suggested hypothesis of variability in historical earthquake characteristics. Our estimates of coseismic land-level change for the four earthquakes range from meter-scale subsidence to no subsidence or slight uplift, suggesting earthquakes completing each ∼270 year cycle may not share a common, characteristic slip distribution. The presence of buried soils at elevations below their modern equivalents implies net relative sea-level rise over the course of the Chucalén paleoseismic record, in contrast to relative sea-level fall over preceding millennia inferred from sites on the mainland. Sea-level rise may contribute to the preservation of evidence for multiple earthquakes during the last millennium, while net relative sea-level fall over the last 2000–5000 years may explain the lack of evidence for older earthquakes

On a Conjecture of Goriely for the Speed of Fronts of the Reaction--Diffusion Equation

In a recent paper Goriely considers the one--dimensional scalar reaction--diffusion equation $u_t = u_{xx} + f(u)$ with a polynomial reaction term $f(u)$ and conjectures the existence of a relation between a global resonance of the hamiltonian system $u_{xx} + f(u) = 0$ and the asymptotic speed of propagation of fronts of the reaction diffusion equation. Based on this conjecture an explicit expression for the speed of the front is given. We give a counterexample to this conjecture and conclude that additional restrictions should be placed on the reaction terms for which it may hold.Comment: 9 pages Revtex plus 4 postcript figure

Tectonic deformation of the Andes and the configuration of the subducted slab in central Peru: Results from a micro-seismic experiment

The vast majority of the microearthquakes recorded occurred to the east: on the Huaytapallana fault in the Eastern Cordillera or in the western margin of the sub-Andes. The sub-Andes appear to be the physiographic province subjected to the most intense seismic deformation. Focal depths for the crustal events here are as deep as 50 km, and the fault plane solutions, show thrust faulting on steep planes oriented roughly north-south. The Huaytapallana fault in the Cordillera Oriental also shows relatively high seismicity along a northeast-southwest trend that agrees with the fault scarp and the east dipping nodal plane of two large earthquakes that occurred on this fault in 1969. The recorded microearthquakes of intermediate depth show a flat seismic zone about 25 km thick at a depth of about 100 km. This agrees with the suggestion that beneath Peru the slab first dips at an angle of 30 deg to a depth of 100 km and then flattens following a quasi-horizontal trajectory. Fault plane solutions of intermediate depth microearthquakes have horizontal T axes oriented east-west

Soil Water Movement in a Watershed in the Chilean Patagonia

Magallanes region, located southern Chile, contains about 1.9 million sheep heads, in about 5 million hectares of rangelands. However, forage production is concentrated in small wetlands meadows called locally “Vegas” that only represent about 300.000 hectares. Those ecosystems that sustain patagonian ranches, produce 20 times more forage biomass than the surrounding natural rangelands. Patagonian vegas have concave topography with a hydrophyte (wet) center, and mesic slopes and xeric highlands of Festuca gracillima. Although the moisture content is controled by topography, there is scarce information about the movement of water through this concave topography. Also, the spatial variability of the soil between the Xeric to the Hydrophyte parts must be taking in account. It is essential to evaluate the movement of water inside the soil, to define agronomic managements to promote the storage and conduction of water. The study was conducted in a watershed dominated by vegas at the Kampenaike Experimental Station in Magallanes region, in Chilean Patagonia (-52,7 ° Lat.; -70.97° Long). Soil was monitored by instruments in five pits, two at East and West of Xeric side; two at East and West of mesic side; and the last at the middle of the vega. Soil moisture sensors (n = 2) and water tension (n = 1) were placed in three soil horizons (5, 30 and 80 cm deep). A weather station was set up in the middle of the vega. Differences in the physical properties that govern the storage and conduction of water between all the sectors were founded. The differences were due to the great spatial variability of the type of soil, because the topography and the genesis

Contribution of Collaborative Work to Teacher Reflection and the Transformation of Pedagogical Practices of School and University Science Teachers // Contribución del trabajo colaborativo en la reflexión docente y en la transformación de las prácticas pedagógicas de profesores de ciencia escolares y universitarios

Poor results of science learning, both at school and university, have led us to acknowledge the need to transform our teaching. Currently, reflection and collaborative work with colleagues are conceived as being key factors in the process of the transformation of practices. Based on the experiences of a group of school and university science teachers working on action-research, we describe the contribution that collaborative work has on reflection for the transformation of practices. The main aspects are the recognition of strengths and weaknesses, listening to and learning from the experience of others, and the discussion of specific classroom practices. On the other hand, these reflections contribute to the transformation at different levels: the teacher, classroom teaching practices, and the school community. The fact that it is a diverse group that includes both school and university teachers generate enriching reflections that help to transform practices in both areas. These reflections not only benefit the school system, but also science teachers education, and provide insights on a new University-School relationship // Los deficientes resultados de aprendizaje en el área de las ciencias, tanto en el ámbito escolar como universitario, nos han llevado a la necesidad de transformar nuestra enseñanza. En la actualidad, la reflexión y el trabajo colaborativo con colegas se conciben como claves en el proceso de transformación de las prácticas. A partir de la experiencia de un grupo de docentes escolares y universitarios de ciencia que realiza una investigación-acción, describimos la contribución que tiene el trabajo colaborativo sobre la reflexión para la transformación de las prácticas. Destacan aspectos como el reconocimiento de debilidades y fortalezas, el escuchar y aprender de la experiencia de otros y la discusión de prácticas concretas de aula. Por otra parte, estas reflexiones contribuyen a la transformación en diferentes niveles: del profesor, de las prácticas del docente en el aula y de la comunidad escolar. El hecho de que sea un grupo diverso, que incluye a profesores tanto del sistema escolar como universitario, genera reflexiones enriquecedoras, que ayudan a transformar las prácticas en estos dos ámbitos, beneficiando no solo al sistema escolar, sino también a la formación de profesores de ciencia, y dando luces acerca de una nueva relación universidad-escuela

Principios de Desarrollo Profesional Docente construidos por y para Profesores de Ciencia: una propuesta sustentable que emerge desde la indagación de las propias prácticas / Principles of Teacher Professional Development built by and for Science Teachers: a sustainable proposal that emerges from the inquiry of self-practices

La transformación de las prácticas de los docentes en el área de ciencias, tanto a nivel escolar como universitario (incluida la formación inicial), constituye una necesidad urgente si pretendemos alfabetizar científicamente a la población. Este estudio muestra una propuesta de cinco principios para el desarrollo profesional docente en ciencias, que emergen desde la indagación colaborativa de las propias prácticas de un conjunto de docentes de educación primaria, secundaria y universitaria, quienes trabajan hace cuatro años en un proceso de desarrollo profesional conjunto. Estos principios incluyen la construcción de una visión común acerca del para qué enseñar ciencias, la indagación de las prácticas a partir de las particularidades de la educación científica, la reflexión individual y colectiva sobre las prácticas, la valoración de la autoridad de la experiencia para el aprendizaje docente y la promoción de un ambiente de desarrollo profesional que involucre diversidad de contextos y niveles de enseñanza. // The transformation of teaching practices in the area of sciences, both at school and university levels (including initial training), is an urgent need if we intend to achieve scientific literacy in the population. This study shows a proposal of five principles for teacher professional development in sciences, emerged from the collaborative inquiry of self-practices in a group of primary, secondary and university teachers, who have been working together for four years in a professional development process. These principles include the construction of a common vision on the purpose for teaching sciences; the inquiry of practices starting from the distinctive features of scientific education; individual and collective reflection on practices; the valuation of the authority of experience for teacher learning; and the promotion of an environment of professional development involving diverse contexts and teaching levels. Implications for professional development are discussed

(Correcting) misdiagnoses of asthma: A cost effectiveness analysis

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Background: The prevalence of physician-diagnosed-asthma has risen over the past three decades and misdiagnosis of asthma is potentially common. Objective: to determine whether a secondary-screening-program to establish a correct diagnosis of asthma in those who report a physician diagnosis of asthma is cost effective.Method: Randomly selected physician-diagnosed-asthmatic subjects from 8 Canadian cities were studied with an extensive diagnostic algorithm to rule-in, or rule-out, a correct diagnosis of asthma. Subjects in whom the diagnosis of asthma was excluded were followed up for 6-months and data on asthma medications and heath care utilization was obtained. Economic analysis was performed to estimate the incremental lifetime costs associated with secondary screening of previously diagnosed asthmatic subjects. Analysis was from the perspective of the Canadian healthcare system and is reported in Canadian dollars.Results: Of 540 randomly selected patients with physician diagnosed asthma 150 (28%; 95%CI 19-37%) did not have asthma when objectively studied. 71% of these misdiagnosed patients were on some asthma medications. Incorporating the incremental cost of secondary-screening for the diagnosis of asthma, we found that the average cost savings per 100 individuals screened was $35,141 (95$4,588-$69,278).Conclusion: Cost savings primarily resulted from lifetime costs of medication use averted in those who had been misdiagnosed.This work was funded by the Canadian Institute of Health Research, Canada and the University Of Ottawa Division Of Respiratory Medicine