Ni pattern electrodes with well-defined triple phase boundary ͑TPB͒ lengths were prepared in order to investigate the reaction mechanisms at solid oxide fuel cell ͑SOFC͒ anodes. The anode microstructures were stable during thermal treatment and electrochemical measurements. Electrochemical impedance spectroscopy was used to study the influence of the overpotential, of the gas atmosphere, of the temperature, and of the pattern geometry on the electrochemical behavior of SOFC anodes. It is found that the reaction kinetics are dominated by one main process. This process is thermally activated with an activation of energy of E A ϭ 0.88 Ϯ 0.04 eV. At overpotentials higher than 300 mV, a second process becomes relevant. The partial pressure of water in the fuel gas atmosphere has a catalytic effect on the anode performance, whereas variations of the patrial pressure of hydrogen in the fuel gas atmosphere have no significant influence on the electrode behavior. A model was established in order to explain the catalytic effect of water. The direct proportionality between the relaxation frequency and the TPB length suggests a TPB limitation of the anode kinetics.

Spin-orbit coupling is a manifestation of special relativity. In the reference frame of a moving electron, electric fields transform into magnetic fields, which interact with the electron spin and lift the degeneracy of spin-up and spin-down states. In solid-state systems, the resulting spin-orbit fields are referred to as Dresselhaus or Rashba fields, depending on whether the electric fields originate from bulk or structure inversion asymmetry, respectively. Yet, it remains a challenge to determine the absolute value of both contributions in a single sample. Here we show that both fields can be measured by optically monitoring the angular dependence of the electrons' spin precession on their direction of movement with respect to the crystal lattice. Furthermore, we demonstrate spin resonance induced by the spin-orbit fields. We apply our method to GaAs/InGaAs quantum-well electrons, but it can be used universally to characterise spin-orbit interactions in semiconductors, facilitating the design of spintronic devices.Symmetry-breaking electric fields in semiconductors induce a spin splitting, because electric fields appear to a moving electron as magnetic fields, which interact with the electron spin and couple it with the electron momentum, or wave vector, k. In zinc-blende-type crystals, such as GaAs, the electric fields resulting from the lack of an inversion centre lead to bulk inversion asymmetry (BIA) and to the Dresselhaus term in the Hamiltonian [1]. In the conduction band, its coupling is linear or cubic in k with proportionality constants β and γ, respectively. In heterostructures, additional electric fields are introduced owing to structure inversion asymmetry (SIA), giving rise to the Rashba term [2], which for conduction-band electrons is linear in k with coupling constant α. Both contributions have been extensively studied [3], since a potential use of electron spins in future devices (e.g. a spin transistor [4]) requires precise control of the spin's environment and of the Dresselhaus and Rashba fields [5]. Spin-orbit fields also contribute to spin decoherence [6].In two-dimensional systems, such as quantum wells (QWs), usually α β and γ ≈ 0 [7,8,9,10]. Therefore, measurements of the spin-orbit coupling initially focused on the Rashba term in QWs and concentrated on the study of beatings in Shubnikov-de-Haas oscillations [8,10,11,12,13], whose interpretation, however, is debated [14,15]. More recent experiments include the investigation of antilocalization in magnetotransport [16] or the analysis of photocurrents [17]. In the latter experiment, the ratio α/β could be determined. A gateinduced transition from weak localization to antilocalization allowed the discrimination between Rashba, as well as linear and cubic Dresselhaus contributions to the spinorbit field [18]. Tuning of the Rashba coupling has been achieved by introducing additional electric fields from gates [9,19] or by changing the electron density [20,21].The influence of effective spin-orbit magnetic fields on optical measurements in ...

We investigated the adsorption of bovine serum albumin (BSA) on colloidal Al2O3 particles in an aqueous environment. Changes in the zeta potential of the Al2O3 particles upon the adsorption of BSA were measured using an electro-acoustic technique. The mass of protein adsorbed was determined by using UV-vis spectroscopy. The change of the isoelectric point of the Al2O3 powder-protein suspension was found to be a function of adsorbed protein mass. It was shown that approximately one monolayer of BSA was needed to fully mask the surface and to compromise the charge of Al2O3. From titration experiments it follows that about 30-36% of the negatively charged groups of the protein form bonds with the protonated and charged Al2O3 surface. On the basis of our observations we introduced a new adsorption model for BSA on Al2O3 particles.

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We describe a novel quadrotor Micro Air Vehicle (MAV) system that is designed to use computer vision algorithms within the flight control loop. The main contribution is a MAV system that is able to run both the visionbased flight control and stereo-vision-based obstacle detection parallelly on an embedded computer onboard the MAV. The system design features the integration of a powerful onboard computer and the synchronization of IMU-Vision measurements by hardware timestamping which allows tight integration of IMU measurements into the computer vision pipeline. We evaluate the accuracy of marker-based visual pose estimation for flight control and demonstrate markerbased autonomous flight including obstacle detection using stereo vision. We also show the benefits of our IMU-Vision synchronization for egomotion estimation in additional experiments where we use the synchronized measurements for pose estimation using the 2pt+gravity formulation of the PnP problem.

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