Temperature-dependence of exciton radiative recombination in (Al,Ga)N/GaN quantum wells grown on a-plane GaN substrates

This article presents the dynamics of excitons in a-plane (Al,Ga)N/GaN single quantum wells of various thicknesses grown on bulk GaN substrates. For all quantum well samples, recombination is observed to be predominantly radiative in the low-temperature range. At higher temperatures, the escape of charge carriers from the quantum well to the (Al,Ga)N barriers is accompanied by a reduction in internal quantum efficiency. Based on the temperature-dependence of time-resolved photoluminescence experiments, we also show how the local disorder affects the exciton radiative lifetime at low temperature and the exciton non-radiative lifetime at high temperature.We acknowledge financial support from the Swiss National Science Foundation through Project No. 129715 and from the Polish National Science Center (Project DEC-2011/ 03/B/ST3/02647). The work was partially supported by the European Union within European Regional Development Fund through Innovative Economy Grant No. POIG.01.01.02-00-008/08. P.C. also acknowledges financing from the European Union Seventh Framework Program under grant agreement No. 265073

Finite Fault Analysis and Near Field Dynamic Strains and Rotations due to the 11/05/2011 (Mw5.2) Lorca Earthquake, South-Eastern Spain

The 11/5/2011 Lorca, Spain earthquake (Mw5.2) and related seismicity produced extensive damage in the town of Lorca and vicinity. During these earthquakes, evidence of rotations and permanent deformations in structures were observed. To analyze these aspects and study the source properties from the near field, the displacement time histories were obtained including the static component at Lorca station. Displacement time histories were computed by an appropriate double time integration procedure of accelerograms. Using these data, the foreshock and mainshock slip distributions were calculated by means of a complete waveform kinematic inversion. To study the dynamic deformations, the 3D tensor of displacement gradients at Lorca station was first estimated by a single station method. Using the finite fault inversion results and by means of a first order finite difference approach, the dynamic deformations tensor at surface was calculated at the recording site. In order to estimate the distribution of the peak dynamic deformations, the calculation was extended to the close neighboring area of the town. The possible influence of the near-field deformations on the surface structures was analyzed.Comment: 29 pages, 8 figure

Magnetometry as a tool to evaluate the environmental pollution

This paper presents the use of magnetometry to study pollution of soil and air. The magnetic method consists in determining the magnetic properties of pollution floating in the air and deposited in the soil, the leaves of trees or household dust in apartments. The method based on the fact that the magnetic particles present in the pollution are associated with heavy metals and toxic trace elements harmful to human health. The study of traffic pollution was focused on the spatial distribution of pollution in soils along roads in relation to the distance from the edge of road, the area topography and the factors affecting the speed of motor transport (traffic lights, traffic jams, road narrowing, etc.). The study of air pollution allowed to determine the seasonal correlation between pollution deposited on filters and meteorological parameters such as temperature, humidity and precipitation. Detailed analysis of magnetic susceptibility as an indicator of pollution revealed increasing trend with temperature and absolute humidity in the cold months of the year and the decreasing trend in the warm months. Similar correlations were not observed between the magnetic susceptibility and the precipitation. The second part presents a study of indoor air pollution based on measurements of dust collected in apartments in different districts of Warsaw. It was found that floor on which dust was taken did not affect the amount and composition of pollution in opposite to vehicle traffic, housing density and way of ventilation. Study shows that the most polluted apartments are in the Center, in the district of Praga Południe, Mokotów and Ursynów located close to the narrow streets with the large vehicle traffic and poor ventilation. Correlation of the magnetic susceptibility with the concentration of heavy metals in household dust is the base for use of susceptibility for monitoring indoor air pollution