Single-pulse fiber Bragg gratings and specific coatings for use at elevated temperatures.

The technique of recording fiber Bragg gratings (FBGs) with single exposure pulses during the fiber drawing process allows production of such gratings in complex array structures, with high mechanical strength of the fiber and in a simple and cost-efficient way. This is of special interest for the growing field of fiber sensor applications with FBGs. A general advantage of fiber sensor systems is their ability to be used also at elevated temperatures compared with conventional electric or electronic sensors.

Controllable coupling of superconducting flux qubits.

We have realized controllable coupling between two three-junction flux qubits by inserting an additional coupler loop between them, containing three Josephson junctions. Two of these are shared with the qubit loops, providing strong qubit-coupler interaction. The third junction gives the coupler a nontrivial current-flux relation; its derivative (i.

A parallel approach for subwavelength molecular surgery using gene-specific positioned metal nanoparticles as laser light antennas.

An optical technique for the parallel manipulation of nanoscale structures with molecular resolution is presented. Bioconjugated metal nanoparticles are thereby positioned at the location of interest, such as, e.g.

Four-qubit device with mixed couplings.

We present the first experimental results on a device with more than two superconducting qubits. The circuit consists of four three-junction flux qubits, with simultaneous ferro- and antiferromagnetic coupling implemented using shared Josephson junctions. Its response, which is dominated by the ground state, is characterized using low-frequency impedance measurement with a superconducting tank circuit coupled to the qubits.

Chip-based electrical detection of DNA.

A variety of methods have been developed for the detection of the binding of the complementary strand of DNA to a gene chip using electrical rather than the established optical signal techniques. Chip-based DNA sensors offer sensitivity, specificity, parallelisation and miniaturisation for the detection of selected DNA sequences or mutated genes associated with human diseases. Problems associated with the established fluorescence-based optical detection technique include the high equipment costs and the need to use sophisticated numerical algorithms to interpret the data.

Enzymatic control of metal deposition as key step for a low-background electrical detection for DNA chips.

Electrical detection of DNA using nanoparticle labels in combination with metal enhancement represents an interesting alternative to fluorescence readout schemes. This electrical method is hampered by unspecific metal deposition, resulting in a lower sensitivity of the assay. A novel enhancement technique based on an enzymatic process is introduced.

Optimal transformations for optical multiplex measurements in the presence of photon noise.

Hadamard multiplexing is a measurement strategy that yields best sensitivity improvements over scanning measurements for signal-independent detector noise. The presence of photon noise degrades the performance of Hadamard multiplexing because of the increase of photon noise by the superposition of multiple signals. I derive the reduction of the sensitivity gain of a Hadamard measurement and an upper limit for the gain of any cyclic multiplexing strategy in the presence of photon noise.

Optimization of gold nanoparticle-based DNA detection for microarrays.

DNA microarrays are promising tools for fast and highly parallel DNA detection by means of fluorescence or gold nanoparticle labeling. However, substrate modification with silanes (as a prerequisite for capture DNA binding) often leads to inhomogeneous surfaces and/or nonspecific binding of the labeled DNA. We examined both different substrate cleaning and activating protocols and also different blocking strategies for optimizing the procedures, especially those for nanoparticle labeling.

Microstructured arrays with pre-synthesized capture probes for DNA detection based on metal nanoparticles and silver enhancement.

DNA microarrays exhibiting highly defined squared spot geometry and increased homogeneity in capture DNA distribution were prepared by a combination of microfabrication and DNA spotting. The microfabricated substrates were tested using metal nanoparticles as markers. The optical absorption signal is improved by a silver enhancement step.

Pearl chain formation of nanoparticles in microelectrode gaps by dielectrophoresis.

The integration of molecular structures into microscopic electrode arrays is achieved by dielectrophoresis of gold nanoparticles in electrode gaps. Using microelectrodes realized by photolithography, we demonstrate here the generation of pearl chain arrangements of nanoparticles in structures accessible for standard technologies. To preserve the individual particle structures in the final nanowire arrangement, various strategies were employed.

Evidence for entangled states of two coupled flux qubits.

We have studied the low-frequency magnetic susceptibility of two inductively coupled flux qubits using the impedance measurement technique (IMT), through their influence on the resonant properties of a weakly coupled high-quality tank circuit. In a single qubit, an IMT dip in the tank's current-voltage phase angle at the level anticrossing yields the amplitude of coherent flux tunneling. For two qubits, the difference (IMT deficit) between the sum of single-qubit dips and the dip amplitude when both qubits are at degeneracy shows that the system is in a mixture of entangled states (a necessary condition for entanglement).

Miniaturized flow-through PCR with different template types in a silicon chip thermocycler.

Flow-through chip thermocyclers can be used in miniaturized rapid polymerase chain reaction (PCR) despite their high surface to volume ratio of samples. We demonstrated that a thermocycler made of silicon and glass chips and containing thin film transducers for heating and temperature control can be adapted to the amplification of various DNA templates of different sources and properties. Therefore, the concept of serial flow in a liquid/liquid two-phase system was combined with a surface management of inner side walls of the microchannel and an adaptation of PCR mixture composition.

Characterisation of lithographically patterned organosilane monolayers by preferential adsorption of dye molecules.

A method for the visualisation of micropatterned spots of molecular organosilane monolayers by adsorption of dyes is presented. Therefore, microspot arrays consisting of different types of organosilane monolayers are exposed to dye solutions. After this immersion, the chips are rinsed in a solvent, resulting in a locally differentiated fluorescence intensity.

The optical detection of individual DNA-conjugated gold nanoparticle labels after metal enhancement.

The detection of DNA using nanoparticles as labels is an interesting alternative to the standard fluorescence technique. It requires simpler detection equipment, resulting in higher stability and lower costs. Besides easier detection, metal enhancement allows a higher sensitivity of detection.

Metal nanoparticles as labels for heterogeneous, chip-based DNA detection.

The last decade has witnessed the development of a variety of metal nanoparticle-based techniques for DNA detection. High sensitivity and specificity, miniaturization, and cost-efficient detection are problems addressed by the use of nanoparticle labels in heterogeneous DNA detection schemes. The small label size, established bioconjugation chemistry, and the unusual optical and electrical properties of metal nanoparticles make them unique tools for DNA detection.

Continuous monitoring of Rabi oscillations in a Josephson flux qubit.

Under resonant irradiation, a quantum system can undergo coherent (Rabi) oscillations in time. We report evidence for such oscillations in a continuously observed three-Josephson-junction flux qubit, coupled to a high-quality tank circuit tuned to the Rabi frequency. In addition to simplicity, this method of Rabi spectroscopy enabled a long coherence time of about 2.

[Remote controlled drug release in the alimentary tract by local power deposition in alternating magnetic fields].

Remote controlled release of agents in the alimentary tract is an important task of gastroenterology and pharmacy. We investigated two different methods of drug release by heating locally restricted parts in medical capsules: hysteresis losses of magnetite powder and eddy current losses of metals in alternating magnetic fields. The comparison of our experimental results with theoretically derived expectations show that both methods are suitable techniques if special technical conditions are met.

Development and characterization of temperature-controlled microreactors for protein crystallization.

Physico-chemical properties of the crystallization of biological macromolecules are of particular interest for an efficient way to get high-quality crystals. Concept and realization of a novel temperature-controlled microreactor to study these parameters is revealed. The characterization of the device is focussed on the temperature distribution across the reaction chamber, its long-term stability and accuracy as well as the regeneration of the surface inside the chamber after contamination with a hydrophilic protein (rGFP).

Diffractive optical isolator made of high-efficiency dielectric gratings only.

The working principle of an optical isolator made of two corrugated dielectric gratings is introduced. One grating acts as a polarizer, and the other acts as a quarter-wave plate used in conical incidence converting linearly polarized light into circularly polarized light. Global maxima of diffraction efficiency for surface-corrugated gratings with binary, sinusoidal, and pyramidal ridge shapes with dependence on the material index are identified.

DNA-gold conjugates for the detection of specific molecular interactions.

DNA chips are an emerging technology for parallel detection of DNA molecules, with applications ranging from medicine to environmental monitoring. The typical set-up includes fluorescence labeling for detection of binding events on the chip surface. Here another labeling technique based on gold nanoparticles is presented.

Gold nanoparticles as novel label for DNA diagnostics.

The growing interest in DNA diagnostics, especially in combination with the need for highly-paralleled and miniaturized hybridization assays, is today addressed by fluorescence DNA chips. Fluorescence detection is approved and highly developed, however, it has also problematic aspects, e.g.

Flow-through polymerase chain reactions in chip thermocyclers.

The miniaturization of analytical devices by micromachining technology is destined to have a major impact on medical and bioanalytical fields. To meet the current demands for rapid DNA amplification, various instruments and innovative technologies have been introduced by several groups in recent years. The development of the devices was extended in different directions and adapted to corresponding applications.

A Modified General Regression Neural Network (MGRNN) with new, efficient training algorithms as a robust 'black box'-tool for data analysis.

A Modified General Regression Neural Network (MGRNN) is presented as an easy-to-use 'black box'-tool to feed in available data and obtain a reasonable regression surface. The MGRNN is based on the General Regression Neural Network by D. Specht [Specht, D.

Evaluation of liquid handling conditions in microplates.

Liquid handling in higher density microplates (e.g., 1536-well microplates) for more efficient drug screening necessitates carefully selected and optimized parameters.