Plant Community Composition and Structure Monitoring for Agate Fossil Beds National Monument, 2013 Annual Report

Introduction During the last century, much of the prairie within the Northern Great Plains has been plowed for cropland, planted with non-natives to maximize livestock production, or otherwise developed, making it one of the most threatened ecosystems in the United States. Within Nebraska, greater than 77% of the area of native mixed-grass prairie has been lost since European settlement (Samson and Knopf 1994). The National Park Service (NPS) plays an important role in preserving and restoring some of the last pieces of intact prairies within its boundaries. The stewardship goal of the NPS is to “preserve ecological integrity and cultural and historical authenticity” (NPS 2012); however, resource managers struggle with the reality that there have been fundamental changes in the disturbance regimes, such as climate, fire, and large ungulate grazing, that have historically maintained prairies, and there is the continual pressure of exotic invasive species. Long-term monitoring in national parks is essential to sound management of prairie landscapes, because it can provide information on environmental quality and condition, benchmarks of ecological integrity, and early warning of declines in ecosystem health. Agate Fossil Beds National Monument (AGFO) was established in 1965 to protect and preserve a large concentration of ancient mammal fossils. The park contains 2, 270 acres of native mixed-grass prairie intersected by riparian vegetation along the Niobrara River. Vegetation monitoring began in AGFO in 1998 by the Heartland Inventory & Monitoring Program (James 2010) and the Northern Great Plains Fire Ecology Program (FireEP; Wienk et al. 2011). In 2010, AGFO was incorporated into the Northern Great Plains Inventory & Monitoring Network (NGPN). At this time, vegetation monitoring protocols and plot locations were shifted to better represent the entire park and to coordinate efforts with the FireEP (Symstad et al. 2012b), and sampling efforts began in 2011 (Ashton et al. 2011). The long-term objectives of the NGPN and FireEP plant community monitoring effort in AGFO are to: 1. Determine park-wide status and long-term trends in vegetation species composition (e.g. exotic vs. native) and structure (e.g. cover, height) of herbaceous and shrub species. 2. Improve our understanding of the effects of external drivers and management actions on plant community species composition and structure by correlating changes in vegetation composition and structure with changes in climate, landscape patterns, atmospheric chemical composition, fire, and invasive plant control. This report is intended to provide a timely release of basic data sets and data summaries from our sampling efforts at AGFO in 2013, our third year of sampling. We visited 6 plots, and it will take 2 more years to visit every plot in the park twice (Figure 1). In addition, we surveyed vegetation in 5 plots that were first installed in 1997 by the Heartland Inventory & Monitoring Network. These plots are concentrated in the southeast corner of the park to evaluate the effects of trail construction (Figure 1). We also sampled vegetation at 11 plots along the riparian corridor at AGFO for the second year in a pilot study to develop a long-term monitoring approach for this area. The riparian corridor is narrow and not adequately represented in our standard sampling, but is of great ecological and management importance to the park. We expect to produce reports with more in-depth data analysis and interpretation when we complete 5 years of sampling. In the interim, reports, spatial data, and data summaries can be provided for park management and interpretation upon request

Analysis of a PWM Resonant Buck Chopper for Use as a Ship Service Converter Module

The Navy's interest in implementing a DC Zonal Electric Distribution System (DC ZEDS) in the next generation of surface combatant has motivated considerable research work into dc-dc converters. The switching frequency of a hard-switched dc-dc converter is limited by the maximum admissible switching losses allowed by the switch, heat sink, and cooling process. Also, hard- switched converters contribute significant Electromagnetic Interference (EMI) concerns for the system. This study provides a background analysis into resonant converters which utilize zero-voltage-switching and zero-current-switching techniques to mitigate the aforementioned concerns and facilitate high-bandwidth control loops. In particular, one candidate circuit is identified which can be readily realized using existing hardware and a straightforward control. The report documents the modes of operation of the circuit, sets forth the governing differential equation and mode-transition conditions, examines an ACSL simulation representation of the circuit, formulates design criteria for component selection, identifies key fabrication nuances, and documents a PSpice simulation of the circuit. Both simulation models are used to explain the operating modes of the circuit, provide insight into parameter selection, and ultimately to design the proper control of the circuit.Prepared for: Naval Surface Warfare Center (NSWC) Annapolis Det.N00167-98-WR-80279Approved for public release; distribution is unlimited

Plant Community Composition and Structure Monitoring for Scotts Bluff National Monument, 2011-2015 Summary Report

Executive Summary The Northern Great Plains Inventory & Monitoring Program and Fire Effects Program have been monitoring vegetation in Scotts Bluff National Monument for over 18 years. While methods have changed slightly, this report summarizes data from over 80 locations from 1998-2015. Below, we list the questions we asked using these data and provide a summarized answer. For more details see the full report. A summary of the current condition (2011-2015) and trends (based on 1988-2015) in plant communities at Scotts Bluff is found in Table ES-1. 1. What is the current status of plant community composition and structure of SCBL grasslands (species richness, cover, and diversity) and how has this changed from 1998 to 2015? SCBL plays a vital role in protecting and managing some of the last remnants of native mixed-grass prairie in the area. Native plant diversity is at a moderate level compared to other grasslands in the region (Table 10), but diversity is spatially variable. We found no significant trends in native diversity or evenness from 1998 to 2015, but both are threatened by the increasing cover of annual bromes (Figure 9). There has been an increase in annual brome abundance since the 1990s and continued control efforts will be necessary to maintain native prairie within SCBL. 2. How do trends in grassland condition correlate with climate and fire history? The large variability in SCBL’s climate makes it difficult to discern strong patterns linking temperature, precipitation, and plant community structure (e.g. exotic cover, diversity). Native diversity increased in plots with longer times since burning. There is an adaptive management program planned for 2017 which should provide better guidance to the park on the role of prescribed fire in managing annual bromes. 3. What, if any, rare plants were found in SCBL long-term monitoring plots? We identified 35 rare plant species in SCBL between 1998 and 2015; eight of these are considered critically imperiled within Nebraska. These plants are found in such low abundance and in such few plots, it is unlikely that plant community monitoring will be able to detect any trends in rare plant abundance. We recommend more targeted surveys of rare plant species of concern be completed when funds are available. 4. Was the SCBL golf course restoration effective at creating a grassland community dominated by native species? The golf course restoration project had mixed results. While some native grasses were established in one of the monitoring plots, establishment was poor in the other. To improve the rates of success and the establishment of native species, future projects should include funds to cover invasive plant control for many years (~10) after planting. 5. What is the composition and structure of riparian forests at SCBL? The riparian forest in SCBL is a fairly diverse assemblage of cottonwood, willow species, green ash, and box elder. Exotic grasses and forbs are common in the understory of the riparian forest, viii and continuing control efforts will be necessary to prevent their spread. The large abundance of green ash and box elder seedlings suggests that a transition to ash-dominated forests is underway

A New Reality for US-China Trade? (with transcript)

In this episode of the Case in Point podcasts, Penn Law’s William Burke-White and Bloomberg Law’s Jerome Ashton discuss President-Elect Trump, trade, and the future of the Trans-Pacific Partnership (TPP). Produced by Penn Law in collaboration with Bloomberg Law

Depletion potentials in highly size-asymmetric binary hard-sphere mixtures: Comparison of accurate simulation results with theory

We report a detailed study, using state-of-the-art simulation and theoretical methods, of the depletion potential between a pair of big hard spheres immersed in a reservoir of much smaller hard spheres, the size disparity being measured by the ratio of diameters q=\sigma_s/\sigma_b. Small particles are treated grand canonically, their influence being parameterized in terms of their packing fraction in the reservoir, \eta_s^r. Two specialized Monte Carlo simulation schemes --the geometrical cluster algorithm, and staged particle insertion-- are deployed to obtain accurate depletion potentials for a number of combinations of q\leq 0.1 and \eta_s^r. After applying corrections for simulation finite-size effects, the depletion potentials are compared with the prediction of new density functional theory (DFT) calculations based on the insertion trick using the Rosenfeld functional and several subsequent modifications. While agreement between the DFT and simulation is generally good, significant discrepancies are evident at the largest reservoir packing fraction accessible to our simulation methods, namely \eta_s^r=0.35. These discrepancies are, however, small compared to those between simulation and the much poorer predictions of the Derjaguin approximation at this \eta_s^r. The recently proposed morphometric approximation performs better than Derjaguin but is somewhat poorer than DFT for the size ratios and small sphere packing fractions that we consider. The effective potentials from simulation, DFT and the morphometric approximation were used to compute the second virial coefficient B_2 as a function of \eta_s^r. Comparison of the results enables an assessment of the extent to which DFT can be expected to correctly predict the propensity towards fluid fluid phase separation in additive binary hard sphere mixtures with q\leq 0.1.Comment: 16 pages, 9 figures, revised treatment of morphometric approximation and reordered some materia

Microwave-assisted synthesis and electrochemical evaluation of VO2 (B) nanostructures

Understanding how intercalation materials change during electrochemical operation is paramount to optimizing their behaviour and function and in situ characterization methods allow us to observe these changes without sample destruction. Here we first report the improved intercalation properties of bronze phase vanadium dioxide VO2 (B) prepared by a microwave-assisted route which exhibits a larger electrochemical capacity (232 mAh g-1) compared with VO2 (B) prepared by a solvothermal route (197 mAh g-1). These electrochemical differences have also been followed using in situ X-ray absorption spectroscopy allowing us to follow oxidation state changes as they occur during battery operation