The PERCIVAL detector: first user experiments.

The PERCIVAL detector is a CMOS imager designed for the soft X-ray regime at photon sources. Although still in its final development phase, it has recently seen its first user experiments: ptychography at a free-electron laser, holographic imaging at a storage ring and preliminary tests on X-ray photon correlation spectroscopy. The detector performed remarkably well in terms of spatial resolution achievable in the sample plane, owing to its small pixel size, large active area and very large dynamic range; but also in terms of its frame rate, which is significantly faster than traditional CCDs. In particular, it is the combination of these features which makes PERCIVAL an attractive option for soft X-ray science.

Experimental 3D coherent diffractive imaging from photon-sparse random projections.

The routine atomic resolution structure determination of single particles is expected to have profound implications for probing structure-function relationships in systems ranging from energy-storage materials to biological molecules. Extremely bright ultrashort-pulse X-ray sources - X-ray free-electron lasers (XFELs) - provide X-rays that can be used to probe ensembles of nearly identical nanoscale particles. When combined with coherent diffractive imaging, these objects can be imaged; however, as the resolution of the images approaches the atomic scale, the measured data are increasingly difficult to obtain and, during an X-ray pulse, the number of photons incident on the 2D detector is much smaller than the number of pixels. This latter concern, the signal 'sparsity', materially impedes the application of the method. An experimental analog using a conventional X-ray source is demonstrated and yields signal levels comparable with those expected from single biomolecules illuminated by focused XFEL pulses. The analog experiment provides an invaluable cross check on the fidelity of the reconstructed data that is not available during XFEL experiments. Using these experimental data, it is established that a sparsity of order 1.3 × 10-3 photons per pixel per frame can be overcome, lending vital insight to the solution of the atomic resolution XFEL single-particle imaging problem by experimentally demonstrating 3D coherent diffractive imaging from photon-sparse random projections.

Effect of electrolyte concentration on microstructure and properties of micro arc oxidized hydroxyapatite/titania nanostructured composite.

Micro arc oxidation was employed to grow TiO2/hydroxyapatite composite layer on titanium substrate. The correlation between electrolyte concentration, diameter and density of the pores in fabricated layers was investigated. Therefore, the effect of electrolyte concentration on composition and morphology of grown layers was studied using SEM, EDX, XRD and XPS techniques. Samples were coated in electrolytes containing 5, 10 and 15 g/l calcium acetate and 1, 3 and 5 g/l ß-glycerophosphate, at optimized voltage for 3 min. Pore size variations obey a similar pattern by the addition of both calcium acetate and ß-glycerophosphatein various concentrations based on SEM observations. However, completely different volume fraction of porosities in as-obtained coatings was obtained as a result of these two components addition. Indeed, size and volume fraction of porosities in fabricated layers are directly affected by electrolyte concentration. The average crystallite size of TiO2 and hydroxyapatite was determined as 45 nm and 48.5 nm, respectively. Moreover, the biocompatibility of selected specimens has been proved by MTT test.