Bart Johnson

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We have imaged a 2D buried Ni nanostructure at 8 nm resolution using coherent x-ray diffraction and the oversampling phasing method. By employing a 3D imaging reconstruction algorithm, for the first time we have experimentally determined the 3D structure of a noncrystalline nanostructured material at 50 nm resolution. The 2D and 3D imaging resolution is(More)
Due to the special contents of this issue, the 2007 subject and author indexes, which usually would appear in the December issue, will be in our January 2008 issue. Also, the second part of the article, " Program Evaluations: Improving Operational Effectiveness and Organizational Effi ciency, " will be moved to our January issue. This issue includes our(More)
The respiratory release of carbon dioxide (CO2) from soil is a major yet poorly understood flux in the global carbon cycle. Climatic warming is hypothesized to increase rates of soil respiration, potentially fueling further increases in global temperatures. However, despite considerable scientific attention in recent decades, the overall response of soil(More)
BACKGROUND Arbuscular mycorrhizal fungi (AMF) provide numerous services to their plant symbionts. Understanding climate change effects on AMF, and the resulting plant responses, is crucial for predicting ecosystem responses at regional and global scales. We investigated how the effects of climate change on AMF-plant symbioses are mediated by soil water(More)
Wetland restoration is a pressing conservation priority, but there are few replicated field studies that provide a scientific foundation for these activities. We conducted a 3-year, replicated field experiment to examine the effectiveness of initial site preparation techniques (combinations of solarization, herbicide, tilling, and thermal weed control) in(More)
Oak savanna was once a major ecosystem of Oregon's Willamette Valley. Changing land-use patterns, urbanization and fire suppression have contributed to the loss of oak savanna throughout its former range, and it is estimated that less than 1% remains. Using tree distribution, tree-age and environmental data, historical savanna structure and recent forest(More)
Plants are typically infected by a consortium of internal fungal associates, including endophytes in their leaves, as well as arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) in their roots. It is logical that these organisms will interact with each other and the abiotic environment in addition to their host, but there has been little(More)
Agent-based modeling provides a means for addressing the way human and natural systems interact to change landscapes over time. Until recently, evaluation of simulation models has focused on map comparison techniques that evaluate the degree to which predictions match real-world observations. However, methods that change the focus of evaluation from(More)