Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter

Data collected by the Pierre Auger Observatory through 31 August 2007 showed evidence for anisotropy in the arrival directions of cosmic rays above the Greisen-Zatsepin-Kuz'min energy threshold, 6 x 10(19) eV. The anisotropy was measured by the fraction of arrival directions that are less than 3.1 degrees from the position of an active galactic nucleus within 75 Mpc (using the Veron-Cetty and Veron 12th catalog). An updated measurement of this fraction is reported here using the arrival directions of cosmic rays recorded above the same energy threshold through 31 December 2009. The number of arrival directions has increased from 27 to 69, allowing a more precise measurement. The correlating fraction is (38(-6)(+7))%, compared with 21% expected for isotropic cosmic rays. This is down from the early estimate of (69-(+11)(13))%. The enlarged set of arrival directions is examined also in relation to other populations of nearby extragalactic objects: galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in hard X-rays by the Swift Burst Alert Telescope. A celestial region around the position of the radiogalaxy Cen A has the largest excess of arrival directions relative to isotropic expectations. The 2-point autocorrelation function is shown for the enlarged set of arrival directions and compared to the isotropic expectation. (C) 2010 Elsevier B.V. All rights reserved.

Empirical correlation of shear wave velocity (Vs) with spt of soils in Madrid

Empirical correlations are usually used as a predictive tool in geotechnical engineering. However, equations calculated for soils very different to the ones to be characterized are frequently used, and so they are not representative of their mechanical properties. This fact, added to the increasing interest of civil engineering in knowing the shear wave velocity (Vs) of the ground, has led to the calculation of different empirical equations to predict the Vs value of the soils of Madrid. In this study this has been achieved by calculating the empirical correlations between the Vs value obtained through the ReMi (Refraction Microtremor) technique and the Standard Penetration Test (500 NSPT values). The empirical correlations proposed are applicable to the whole metropolitan area of Madrid, and have an excellent predictive capability owing to the incorporation of the measurement depth to the equations, which has an important influence in the resistance properties of soils.