The dynamical balance, transport and circulation of the Antarctic Circumpolar Current

The physical ingredients of the ACC circulation are reviewed. A picture of thecirculation is sketched by means of recent observations of the WOCE decade. Wepresent and discuss the role of forcing functions (wind stress, surfacebuoyancy flux) in the balance of the (quasi)-zonal flow, the meridionalcirculation and their relation to the ACC transport. Emphasis will be on theinterrelation of the zonal momentum balance and the meridional circulation, theimportance of diapycnal mixing and eddy processes. Finally, new model conceptsare described: a model of the ACC transport dependence on wind stress andbuoyancy flux, based on linear wave theory; and a model of the meridionaloverturning of the Southern Ocean, based on zonally averaged dynamics with eddyparameterization

Deep Transfer Learning for Error Decoding from Non-Invasive EEG

We recorded high-density EEG in a flanker task experiment (31 subjects) and an online BCI control paradigm (4 subjects). On these datasets, we evaluated the use of transfer learning for error decoding with deep convolutional neural networks (deep ConvNets). In comparison with a regularized linear discriminant analysis (rLDA) classifier, ConvNets were significantly better in both intra- and inter-subject decoding, achieving an average accuracy of 84.1 % within subject and 81.7 % on unknown subjects (flanker task). Neither method was, however, able to generalize reliably between paradigms. Visualization of features the ConvNets learned from the data showed plausible patterns of brain activity, revealing both similarities and differences between the different kinds of errors. Our findings indicate that deep learning techniques are useful to infer information about the correctness of action in BCI applications, particularly for the transfer of pre-trained classifiers to new recording sessions or subjects.Comment: 6 pages, 9 figures, The 6th International Winter Conference on Brain-Computer Interface 201

A large-scale evaluation framework for EEG deep learning architectures

EEG is the most common signal source for noninvasive BCI applications. For such applications, the EEG signal needs to be decoded and translated into appropriate actions. A recently emerging EEG decoding approach is deep learning with Convolutional or Recurrent Neural Networks (CNNs, RNNs) with many different architectures already published. Here we present a novel framework for the large-scale evaluation of different deep-learning architectures on different EEG datasets. This framework comprises (i) a collection of EEG datasets currently including 100 examples (recording sessions) from six different classification problems, (ii) a collection of different EEG decoding algorithms, and (iii) a wrapper linking the decoders to the data as well as handling structured documentation of all settings and (hyper-) parameters and statistics, designed to ensure transparency and reproducibility. As an applications example we used our framework by comparing three publicly available CNN architectures: the Braindecode Deep4 ConvNet, Braindecode Shallow ConvNet, and two versions of EEGNet. We also show how our framework can be used to study similarities and differences in the performance of different decoding methods across tasks. We argue that the deep learning EEG framework as described here could help to tap the full potential of deep learning for BCI applications.Comment: 7 pages, 3 figures, final version accepted for presentation at IEEE SMC 2018 conferenc

Side-entrainment in a jet embedded in a sidewind

Numerical simulations of HH jets never show side-entrainment of environmental material into the jet beam. This is because the bow shock associated with the jet head pushes the surrounding environment into a dense shell, which is never in direct contact with the sides of the jet beam. We present 3D simulations in which a side-streaming motion (representing the motion of the outflow source through the surrounding medium) pushes the post-bow shock shell into direct contact with the jet beam. This is a possible mechanism for modelling well collimated "molecular jets" as an atomic/ionic flow which entrains molecules initially present only in the surrounding environment.Comment: 8 pages, 12 figures, 1 table, accepted for publication in Ap

Magnetic Soret effect: Application of the ferrofluid dynamics theory

The ferrofluid dynamics theory is applied to thermodiffusive problems in magnetic fluids in the presence of magnetic fields. The analytical form for the magnetic part of the chemical potential and the most general expression of the mass flux are given. By employing these results to experiments, global Soret coefficients in agreement with measurements are determined. Also an estimate for a hitherto unknown transport coefficient is made.Comment: 7 pages, 2 figure

Plastic flow of persistent currents in two dimensional strongly interacting systems

The local persistent current in two dimensional strongly interacting systems is investigated. As the interaction strength is enhanced the current in the sample undergoes a transition from diffusive to ordered flow. The strong interacting flow has the characteristics of a plastic flow through dislocations in the pinned charge density wave which develops in the system at low densities.Comment: 12 pages, 4 figures, accepted for publication in Phys. Rev. B (RC

Dephasing in Disordered Conductors due to Fluctuating Electric Fields

We develop a novel eikonal expansion for the Cooperon to study the effect of space- and time-dependent electric fields on the dephasing rate of disordered conductors. For randomly fluctuating fields with arbitrary covariance we derive a general expression for the dephasing rate which is free of infrared divergencies in reduced dimensions. For time-dependent external fields with finite wavelength and sufficiently small amplitude we show that the dephasing rate is proportional to the square root of the electromagnetic power coupled into the system, in agreement with data by Wang and Lindelof [Phys. Rev. Lett. {\bf{59}}, 1156 (1987)].Comment: 17 Latex-pages, one figure; we now give more technical details and discuss the screening problem more carefully; to appear in Phys. Rev.

Report and preliminary results of R/V POSEIDON cruise POS500, LISA, Ligurian Slope AUV mapping, gravity coring and seismic reflection, Catania (Italy) – Malaga (Spain), 25.05.2016 – 09.06.2016

Cruise POS500 “LISA” with R/V Poseidon studied the western Ligurian Margin off Southern France, an area in the northeastern part of the western Mediterranean Sea characterized by its active tectonism and frequent mass wasting. The region near the Var estuary close to the city of Nice is particularly suited for landslide research because it represents a natural laboratority where it is possible to study a series of trigger processes of geological and anthropogenic origin. The aim of this MARUM expedition was to: i. Study fresh water seepage in the marine Nice airport landslide and adjacent stable plateau in 15-50 m water depth using water sampling, CTD and geochemistry; ii. Recover and deploy a number of observatories that monitor, pressure, temperature, tilt and seismicity; iii. Run an AUV micro-bathymetric survey with MARUM AUV SEAL5000 to complement existing multibeam maps; and iv. Acquire additional high-resolution seismic reflection profiles to unravel the complex architecture of the Nice slope and Var delta. In a period of approximately two weeks, we acquired valuable geophysical information that helps to understand the evolution of this portion of the Ligurian Margin and further to support an active Amphibious Drilling proposal submitted to ICDP and IODP. We could also show that heavy spring rainfall plus melt water from the French Maritime Alps supplied sufficient hydraulic forcing to push Var aquifer groundwaters to seep into the marine deposits and water column. Freshening was strongest in the 1979 Nice landslide scar, but was also found at the outer edge of the shelf. Recovery and redeployment of various observatory prototypes worked well, both for the MARUM MeBo seafloor drillstring tolos and independent piezometers. Observatory data have yet to be evaluated. In addition, geochemical analyses of bottom waters and pore waters was deferred to shore-based laboratorios except for salinity estimates using a refractometer. Seismic processing was started onboard, but is largely taking place post-cruise at University Bremen