Evidence for a meteoritic origin of the September 15, 2007, Carancas crater

On September 15th, 2007, around 11:45 local time in Peru, near the Bolivian border, the atmospheric entry of a meteoroid produced bright lights in the sky and intense detonations. Soon after, a crater was discovered south of Lake Titicaca. These events have been detected by the Bolivian seismic network and two infrasound arrays operating for the Comprehensive Nuclear-Test-Ban Treaty Organization, situated at about 80 and 1620 km from the crater. The localization and origin time computed with the seismic records are consistent with the reported impact. The entry elevation and azimuthal angles of the trajectory are estimated from the observed signal time sequences and backazimuths. From the crater diameter and the airwave amplitudes, the kinetic energy, mass and explosive energy are calculated. Using the estimated velocity of the meteoroid and similarity criteria between orbital elements, an association with possible parent asteroids is attempted. The favorable setting of this event provides a unique opportunity to evaluate physical and kinematic parameters of the object that generated the first actual terrestrial meteorite impact seismically recorded

Giant magnetoimpedance of FeNi-based nanostructures deposited onto glass and flexible substrates

This work was supported in part by the Basque Government through the Actimat Project under Grant IE13-380

Flexible magnetoelectronics: some aspects of the development of hibrid thin film structures

This work was developed under support of the “Laboratory of Physical Sensoric” project of Ural Federal University and ACTIMAT-ETORTEK grant of UPV-EHU and The Basque Country Government

Simulations of a mortality plateau in the sexual Penna model for biological ageing

The Penna model is a strategy to simulate the genetic dynamics of age-structured populations, in which the individuals genomes are represented by bit-strings. It provides a simple metaphor for the evolutionary process in terms of the mutation accumulation theory. In its original version, an individual dies due to inherited diseases when its current number of accumulated mutations, n, reaches a threshold value, T. Since the number of accumulated diseases increases with age, the probability to die is zero for very young ages (n = T). Here, instead of using a step function to determine the genetic death age, we test several other functions that may or may not slightly increase the death probability at young ages (n < T), but that decreases this probability at old ones. Our purpose is to study the oldest old effect, that is, a plateau in the mortality curves at advanced ages. Imposing certain conditions, it has been possible to obtain a clear plateau using the Penna model. However, a more realistic one appears when a modified version, that keeps the population size fixed without fluctuations, is used. We also find a relation between the birth rate, the age-structure of the population and the death probability.Comment: submitted to Phys. Rev.

Estimación de la variabilidad mecánica de placas de roca por ensayos no-destructivos: métodos de análisis

En este artículo se emplean mayores y complementarios métodos de análisis para estimar la variabilidad mecánica de placas de material rocoso por ensayos no-destructivos, inicialmente presentado en esta misma revista. Esto con el propósito de generalizar y mejorar la aplicabilidad de este método alternativo, basado en la geoestadística, para que pueda ser utilizado en procesos de control de calidad de placas de material rocoso destinadas al revestimiento de pisos. Se ha hecho énfasis en los métodos de análisis geoestadísticos, en lo que respecta al análisis exploratorio de los datos, análisis de anisotropía, verificación del modelo geoestadístico, verificación de la estructura espacial, verificación del tamaño de muestra y modelación de la distribución espacial de la resistencia mecánica.

Monte carlo simulations of parapatric speciation

Parapatric speciation is studied using an individual--based model with sexual reproduction. We combine the theory of mutation accumulation for biological ageing with an environmental selection pressure that varies according to the individuals geographical positions and phenotypic traits. Fluctuations and genetic diversity of large populations are crucial ingredients to model the features of evolutionary branching and are intrinsic properties of the model. Its implementation on a spatial lattice gives interesting insights into the population dynamics of speciation on a geographical landscape and the disruptive selection that leads to the divergence of phenotypes. Our results suggest that assortative mating is not an obligatory ingredient to obtain speciation in large populations at low gene flow.Comment: submitted to Phys.Rev.

Present experiment of BASJE group at Mt. Chacaltaya

A compact air shower array to observe primary cosmic rays above a few TeV has been installed at Mt. Chacaltaya in Bolivia since 1996. This array is available to observe the air showers above 6 TeV and the longitudinal development curves above 50 TeV. The purpose of the observations is to study the chemical composition and the energy spectrum of cosmic rays in the energy region including the “knee” of the energy spectrum. First, the consistency between direct measurements (balloon-borne experiments) and air shower observations in the energy region from 50 TeV to 80 TeV is examined and confirmed. Next, the chemical composition and the energy spectrum are derived from the air shower observations. In the study, the longitudinal developments of shower particles are calculated by Monte Carlo simulations, assuming different chemical compositions above 80 TeV. The characteristics of the present air shower array and the comparison of the preliminary observed results with that of the simulations are presented

Measurement of cosmic ray chemical composition at Mt. Chacaltaya

BASJE grouphas measured the chemical composition of primary cosmic rays with energies around the “knee” with several methods. These measurements show that the averaged mass number of cosmic ray particles increases with energy upto the knee. In order to measure the chemical composition in much wider energy range, we have started a new experiment at Mt. Chacaltaya in 2000

Galactic-disk enhancement of cosmic rays at E > 1012eV

We observed an enhancement of cosmic rays from the Vela region with SAS array at Mt. Chacaltaya in Bolivia. It is not possible to conclude that this enhancement is caused by primary gamma-rays, since the observed events not limited with the less muons in the air showers show the same enhancement. In order to confirm this result with improved statistics and to investigate the energy dependence of this enhancement, we have installed a new array, called MAS array. All the data with much higher statistics show the enhancement along the Whole galactic disk