D. J. Braun

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Standing modes of light in front of the reflecting surface of silicon modulate the excitation and emission of fluorescent dyes. This effect was used to determine the distance of a biomembrane from an oxidized silicon chip. The membrane of a red blood cell (ghost) was stained with a cya-nine dye and attached with poly-lysine to a surface structured with(More)
The electrical sheet resistance between living cells grown on planar electronic contacts of semiconductors or metals is a crucial parameter for bioelectronic devices. It determines the strength of electrical signal transduction from cells to chips and from chips to cells. We measured the sheet resistance by applying AC voltage to oxidized silicon chips and(More)
The Thouless conjecture states that the average conductance of a disordered metallic sample in the diffusive regime can be related to the sensitivity of the sample's spectrum to a change in the boundary conditions. Here we present results of a direct numerical study of the conjecture for the Anderson model. They were obtained by calculating the(More)
A long standing goal is the direct optical control of biomolecules and water for applications ranging from microfluidics over biomolecule detection to non-equilibrium biophysics. Thermal forces originating from optically applied, dynamic microscale temperature gradients have shown to possess great potential to reach this goal. It was demonstrated that laser(More)
We implement a simple computer-based photon-counting lock-in that combines the signal-to-noise benefits of photon counting with lock-in detection. We experimentally specify the flatness and the noise characteristics of a flexible software implementation. The noise of amplitude and phase of the small signal is at the limit of photonic shot noise; from 1000(More)
The cell is the structural and functional unit of all known living organisms. The inside of cells consists of an aqueous solution, containing all kind of interacting molecules and complex molecular machineries. Precise methods to control properties of fluids, like flow fields or the concentration of solutes would be a powerful tool for the controlled(More)
The light-driven proton pump current generated by bacteriorhodopsin reconstituted in asymmetric planar bilayer membranes was investigated. The current-voltage dependence was found to be nonlinear and can be approximated by an exponential at least below +50 mV. The current changed e-fold when the membrane potential was changed by 80 mV. The voltage(More)
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