In this paper we present results of structural studies of compacting experimental systems of ductile grains in two and three dimensions. The high precision of our two-dimensional experiments enables a detailed study of the evolution of coordination numbers and local crystalline arrangements as a function of the packing fraction. The structure in both dimensions deviates considerably from that of hard disks and spheres, although geometrically, crystalline arrangements dominate on a local scale ͑in two dimensions͒. In three dimensions, the evolution of the coordination number is compared to experimental packings of hard and ductile grains from the literature. This comparison shows that the evolution of coordination number with packing fraction is not unique for ductile systems in general, but must depend on rheology and grain size.

Ductile compaction is common in many natural systems, but the temporal evolution of such systems is rarely studied. We observe surprising oscillations in the weight measured at the bottom of a self-compacting ensemble of ductile grains. The oscillations develop during the first ten hours of the experiment, and usually persist through the length of an experiment (one week). The weight oscillations are connected to the grain-wall contacts, and are directly correlated with the observed strain evolution and the dynamics of grain-wall contacts during the compaction. Here, we present the experimental results and characteristic time constants of the system, and discuss possible reasons for the measured weight oscillations.

This abstract reviews the latest methods to optimize marine controlled-source electromagnetic (CSEM) data acquisition to ensure reliable interpretation in the presence of complex bathymetry. We specifically analyze how amplitude and phase of the recorded electric field are affected if the receiver is located at the slope within a seabed trench. The main trends observed on real data offshore Brazil can be reproduced by 3D forward modeling taking into account the precise bathymetry profile. Understanding these trends is very helpful for quality control (QC) and thus increases confidence in the acquired data. Applying error propagation analysis together with known accuracy of receiver positioning we can assess the limiting sensitivity of the CSEM data recorded within a trench with a given steepness.Remarkably, all the data points follow almost the same linear dependence implying that the effect of a trench on CSEM data is mainly determined by a single parameter -the ratio h/w. For example, for h/w = 0.1, whether it is a 600 m wide 60 m deep