19 research outputs found
The calculation method of interaction between metal atoms under influence of the radiation
A method of calculation of interatomic interaction potentials in the presence of ionized states has been developed. They have been obtained for the atoms with different ionization degree on example of aluminum. The Heine-Abarenkov-Animalu model potential form factors was employed. The form factor parameters of ionized atoms was determined on the base of the quantum defect method using the atomic-spectroscopy data. The potential of interatomic interaction for different charged states with different degree of ionization were determined
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A new model to simulate climate-change impacts on forest succession for local land management
We developed a new climate-sensitive vegetation state-and-transition simulation model (CV-STSM) to simulate future vegetation at a fine spatial grain commensurate with the scales of human land-use decisions, and under the joint influences of changing climate, site productivity, and disturbance. CV-STSM integrates outputs from four different modeling systems. Successional changes in tree species composition and stand structure were represented as transition probabilities and organized into a state-and-transition simulation model. States were characterized based on assessments of both current vegetation and of projected future vegetation from a dynamic global vegetation model (DGVM). State definitions included sufficient detail to support the integration of CV-STSM with an agent-based model of land-use decisions and a mechanistic model of fire behavior and spread. Transition probabilities were parameterized using output from a stand biometric model run across a wide range of site productivities. Biogeographic and biogeochemical projections from the DGVM were used to adjust the transition probabilities to account for the impacts of climate change on site productivity and potential vegetation type. We conducted experimental simulations in the Willamette Valley, Oregon, USA. Our simulation landscape incorporated detailed new assessments of critically imperiled Oregon white oak (Quercus garryana) savanna and prairie habitats among the suite of existing and future vegetation types. The experimental design fully crossed four future climate scenarios with three disturbance scenarios. CV-STSM showed strong interactions between climate and disturbance scenarios. All disturbance scenarios increased the abundance of oak savanna habitat, but an interaction between the most intense disturbance and climate-change scenarios also increased the abundance of subtropical tree species. Even so, subtropical tree species were far less abundant at the end of simulations in CV-STSM than in the dynamic global vegetation model simulations. Our results indicate that dynamic global vegetation models may overestimate future rates of vegetation change, especially in the absence of stand-replacing disturbances. Modeling tools such as CV-STSM that simulate rates and direction of vegetation change affected by interactions and feedbacks between climate and land-use change can help policy makers, land managers, and society as a whole develop effective plans to adapt to rapidly changing climate.This is the publisher’s final pdf. The published article is copyrighted by the Ecological Society of America and can be found at: http://www.esajournals.org/loi/ecapKeywords: Envision, Agent-based model, Disturbance, Dynamic global vegetation model, MC1, State-and-transition simulation model, Oregon, Fire, Willamette Valle
A Landscape Plan Based on Historical Fire Regimes for a Managed Forest Ecosystem: the Augusta Creek Study
The Augusta Creek project was initiated to establish and integrate landscape and watershed objectives into a landscape plan to guide management activities within a 7600-hectare (19,000-acre) planning area in western Oregon. Primary objectives included the maintenance of native species, ecosystem processes and structures, and long-term ecosystem productivity in a federally managed landscape where substantial acreage was allocated to timber harvest. Landscape and watershed management objectives and prescriptions were based on an interpreted range of natural variability of landscape conditions and disturbance processes. A dendrochronological study characterized fire patterns and regimes over the last 500 years. Changes in landscape conditions throughout the larger surrounding watershed due to human uses (e.g., roads in riparian areas, widespread clearcutting, a major dam, and portions of a designated wilderness and an unroaded area) also were factored into the landscape plan. Landscape prescriptions include an aquatic reserve system comprised of small watersheds distributed throughout the planning area and major valley-bottom corridor reserves that connect the small-watershed reserves. Where timber harvest was allocated, prescriptions derived from interpretations of fire regimes differ in rotation ages (100 to 300 years), green-tree retention levels (15- to 50-percent canopy cover), and spatial patterns of residual trees. General prescriptions for fire management also were based on interpretations of past fire regimes. All these prescriptions were linked to specific blocks of land to provide an efficient transition to site-level planning and project implementation. Landscape and watershed conditions were projected 200 years into the future and compared with conditions that would result from application of standards, guidelines, and assumptions in the Northwest Forest Plan prior to adjustments resulting from watershed analyses. The contrasting prescriptions for aquatic reserves and timber harvest (rotation lengths, green-tree retention levels, and spatial patterns) in these two approaches resulted in strikingly different potential future landscapes. These differences have significant implications for some ecosystem processes and habitats. We view this management approach as a potential post watershed analysis implementation of the Northwest Forest Plan and offer it as an example of how ecosystem management could be applied in a particular landscape by using the results of watershed analysis
ALD Functionalized Nanoporous Gold: Thermal Stability, Mechanical Properties, and Catalytic Activity
Nanoporous metals have many technologically promising applications but their tendency to coarsen limits their long-term stability and excludes high temperature applications. Here, we demonstrate that atomic layer deposition (ALD) can be used to stabilize and functionalize nanoporous metals. Specifically, we studied the effect of nanometer-thick alumina and titania ALD films on thermal stability, mechanical properties, and catalytic activity of nanoporous gold (np-Au). Our results demonstrate that even only one-nm-thick oxide films can stabilize the nanoscale morphology of np-Au up to 1000 C, while simultaneously making the material stronger and stiffer. The catalytic activity of np-Au can be drastically increased by TiO{sub 2} ALD coatings. Our results open the door to high temperature sensor, actuator, and catalysis applications and functionalized electrodes for energy storage and harvesting applications