Direct examination of natural and engineered environments has revealed that the majority of microorganisms in these systems live in structured communities termed biofilms. To gain a better understanding for how biofilms function and interact with their local environment, fundamental capabilities for enhanced visualization, compositional analysis, and functional characterization of biofilms are needed. For pore-scale and community-scale analysis (100’s of nm to 10’s of microns), a variety of surface tools are available. However, understanding biofilm structure in complex three-dimensional (3-D) environments is considerably more difficult. X-ray microtomography can reveal a biofilm’s internal structure, but obtaining sufficient contrast to image low atomic number (Z) biological material against a higher-Z substrate makes detecting biofilms difficult. Here we present results imaging Shewanella oneidensis biofilms on a Hollow-fiber Membrane Biofilm Reactor (HfMBR), using the x-ray microtomography system at sector 2-BM of the Advanced Photon Source (APS), at energies ranging from 12.9-15.4 keV and pixel sizes of 0.7 and 1.3 μm/pixel. We examine the use of osmium (Os) as a contrast agent to enhance biofilm visibility and demonstrate that staining improves imaging of hydrated biofilms. We also present results using a Talbot interferometer to provide phase and scatter contrast information in addition to absorption. Talbot interferometry allows imaging of unstained hydrated biofilms with phase contrast, while absorption contrast primarily highlights edges and scatter contrast provides little information. However, the gratings used here limit the spatial resolution to no finer than 2 μm, which hinders the ability to detect small features. Future studies at higher resolution or higher Talbot order for greater sensitivity to density variations may improve imaging.
Pacific Northwest National Laboratory (PNNL) is performing a computational assessment of the impact of several
important gamma-ray detector material properties (e.g. energy resolution and intrinsic detection efficiency) on the
scenario-specific spectroscopic performance of these materials. The research approach combines 3D radiation transport
calculations, detector response modeling, and spectroscopic analysis of simulated energy deposition spectra to map the
functional dependence of detection performance on the underlying material properties. This assessment is intended to
help guide formulation of performance goals for new detector materials within the context of materials discovery
programs, with an emphasis on applications in the threat reduction, nonproliferation, and safeguards/ verification user
communities. The research results will also provide guidance to the gamma-ray sensor design community in estimating
relative spectroscopic performance merits of candidate materials for novel or notional detectors.
We report the results of Differential Aperture X-ray Microscopy (DAXM) measurements near Te precipitates in CdZnTe
grown via low-pressure Bridgman. White-beam Laue patterns were acquired with 3-D spatial resolution (with 0.25 μm
resolution in the scanning directions and 1 μm resolution in depth) at depths of up to 35 μm deep normal to the surface.
We find very little crystal strain (< 10-3) or rotation (<0.05 degrees) near Te precipitates. We also examine local
deformations in the vicinity of a microhardness indent, and find that although significant rotations exist, the spatial
extent is limited to a few tens of microns. Furthermore, observed crystal strains are limited to 5 x 10-3 or less in regions
near the microhardness indent.