Articles you may be interested inIn situ near-edge x-ray absorption fine structure spectroscopy investigation of the thermal defunctionalization of graphene oxide J. Vac. Sci. Technol. B 30, 061206 (2012); 10.1116/1.4766325 Predicting in-plane distortion from electron-beam lithography on x-ray mask membranesWe have observed the chemical changes in PMMA irradiated by x rays in situ. The chemical changes are monitored by micro-x-ray absorption near edge structure spectra at the carbon absorption edge. The loss of the ester group ͑CvO͒ and formation of CvC bonds have been determined quantitatively from changes in the intensities of the respective * resonant peaks as a function of dose. Samples prepared under different conditions were examined. From the dose dependence of bond formation, scission and linking, the performance of the resist can be predicted, so that the preparation strategy, dose, and development can be optimized.

with energies between the carbon and oxygen K-edges Radiation damage to Vicia faba chromosome structure, as measured by the mass loss, was determined in the scanning transmission X-ray microscope for unstained specimens in both the wet and dry states. Dried specimens remain undamaged after either single or multiple images at doses up to 2400 Mrad at wavelengths of 3.15 or 3.64nm. In contrast, wet specimens are damaged irrespective of the imaging protocol. The damage induced by multiple exposures is greater than that seen in a single exposure of the same total dose. Thus, the rate of data collection is greater than or equal to the rate of damage. The damage during multiple exposures of wet chromosomes is influenced by several factors. First, the fixative used influences the extent of radiation damage. Wet chromosomes fixed with glutaraldehyde are more resistant than those fixed with formaldehyde or osmium tetroxide. A second factor is ionic strength. Damage to wet chromosomes increases if the ionic strength decreases below that at which chromatin undergoes a conformational transition. The mass of wet and dry chromosomes is the same, and consequently quantitative measurements can be made on wet specimens. Such measurements give a DNA mass fraction of 39 f 8% for V . faba chromosomes.(

We have reconstructed in-line (or Gabor) x-ray holograms at 40-50-nm resolution from a complex biological specimen. The holograms were recorded as a relief pattern on photoresist with use of 1.89-nm, soft x rays from the X1A undulator beam line at the National Synchrotron Light Source at Brookhaven National Laboratory. We have improved the resolution and the fidelity and simplified the experiment compared with earlier work by employing a special atomic-force microscope to examine and digitize the holograms. Following digitization the holograms were reconstructed numerically, allowing both the absorptive and phase-shifting properties of the reconstructed object to be mapped. A comparison of the reconstructed images with images obtained from visible light and transmission electron microscopes has been made to confirm the validity of the x-ray holographic technique. The method offers promise as a technique for soft-x-ray microscopy and diffraction tomography of dry and frozen hydrated specimens and for microscopy with pulsed x-ray sources.

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Scanning luminescence X-ray microscopy is based on the use of the very small focused probe of a scanning X-ray microscope to stimulate visible light emission from phosphors and dyes. Using an undulator X-ray source and a Fresnel zone plate to produce a focused X-ray probe, images of P31 phosphor grains with a resolution of 50-75 nm have been obtained, and luminescence from polystyrene spheres loaded with 50-100 pmol/g of fluorescent dye has been imaged. The resolution was not limited by the focused X-ray probe (the microscope has imaged features at 3 6-nm spacing in transmission mode) but by dark noise and the low net efficiency of the luminescence detection system used for this investigation. This technique may make it possible to image dye-tagged sites of biochemical activity at the resolution of the X-ray microscope in wet, unsectioned, and unfixed cells, especially with soft X-ray optimized dyes. Because the image is formed from the detection of signal against a dark background, calculations suggest that the radiation dose for luminescence imaging of dye-tagged features should be 2-22 times lower than it is in transmission X-ray microscopy. A possible extension of the technique for three-dimensional imaging at the transverse resolution of the X-ray microscope is described, where visible light collection optics might be used to obtain submicrometre axial resolution. ('1 1993 The Royal Microscopical Society 121 122 C . JACOBSEN E T AL.