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A comprehensive investigation of polar stratospheric clouds was performed on 25 January 2000 with instruments onboard a balloon gondola flown from Kiruna, Sweden. Cloud layers were repeatedly encountered at altitudes between 20 and 24 kilometers over a wide range of atmospheric temperatures (185 to 197 kelvin). Particle composition analysis showed that a(More)
Graded distributions of ephrin ligands are involved in the formation of topographic maps. However, it is still poorly understood how growth cones read gradients of membrane-bound guidance molecules. We used microcontact printing to produce discontinuous gradients of substrate-bound ephrinA5. These consist of submicron-sized protein-covered spots, which vary(More)
Coherent diffractive imaging (CDI) and scanning transmission x-ray microscopy (STXM) are two popular microscopy techniques that have evolved quite independently. CDI promises to reach resolutions below 10 nanometers, but the reconstruction procedures put stringent requirements on data quality and sample preparation. In contrast, STXM features(More)
Microcontact printing (microCP) of proteins has been successfully used for patterning surfaces in various contexts. Here we describe a simple 'lift-off' method to print precise patterns of axon guidance molecules, which are used as substrate for growing chick retinal ganglion cell (RGC) axons. Briefly, the etched pattern of a silicon master is transferred(More)
We report on significant advances and new results concerning a recently developed method for grating-based hard x-ray phase tomography. We demonstrate how the soft tissue sensitivity of the technique is increased and show in vitro tomographic images of a tumor bearing rat brain sample, without use of contrast agents. In particular, we observe that the brain(More)
A growing number of X-ray sources based on the free-electron laser (XFEL) principle are presently under construction or have recently started operation. The intense, ultrashort pulses of these sources will enable new insights in many different fields of science. A key problem is to provide x-ray optical elements capable of collecting the largest possible(More)
Imaging modalities including magnetic resonance imaging and X-ray computed tomography are established methods in daily clinical diagnosis of human brain. Clinical equipment does not provide sufficient spatial resolution to obtain morphological information on the cellular level, essential for applying minimally or non-invasive surgical interventions.(More)
We combined grating-based phase contrast imaging with projection magnification using a high-brilliance microfocus x-ray source. This geometry offers increased detection efficiency even at higher energies for quantitative high-resolution phase contrast imaging. By systematic methodical investigations, it is shown, how the primary measurement signal is(More)
The fabrication and characterization of Fresnel zone plates (FZPs) for hard X-ray microscopy applications are reported. High-quality 500 nm- and 1 µm-thick Au FZPs with outermost zone widths down to 50 nm and 70 nm, respectively, and with diameters up to 600 µm were fabricated. The diffraction efficiencies of the fabricated FZPs were measured for a wide(More)