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Glossy Buckthorn Invasion Across Three Land-use Classes in Northern Michigan
No full textAgricultural lands that are left to revert to forests are frequently colonized by nonnative shrubs, such as the invasive Frangula alnus (glossy buckthorn). To better understand this phenomenon, we assessed a glossy buckthorn invasion across three land-use classes on a 6-ha site in Houghton County, Michigan. The site included a remnant northern hardwood woodlot, a Pinus sylvestris (Scotch pine) plantation, and an abandoned field colonized by Fraxinus americana (white ash), which is now declining from Agrilus planipennis (emerald ash borer). We examined the height structure and minimum age of the invasion spatially, as well as factors such as overstory and understory composition, light availability, soil characteristics, and proximity to edges. We used nonmetric multidimensional scaling ordination and comparative analysis to examine the height structure of the invasion by land-use category. We observed differential invasion success across land-use histories, which may be associated with soil and vegetation legacies of land clearing and subsequent agricultural abandonment. We observed the greatest densities of glossy buckthorn on plots associated with past agricultural use and abandonment, which also contained the greatest range in size classes and on average the oldest individuals. Our findings suggest that the impact of land-use legacies on soils warrants further investigation as a potential mechanism underlying invasion success. An improved understanding of legacy effects could help land managers target control efforts in areas that may be predisposed to land invasion because of prior land use
Deep Core Advocacy Coalitions
Get PDFAs one of the most established theoretical approaches to public policy, the Advocacy Coalition Framework (ACF) has moored most of its theoretical arguments around a textbook policy conflict consisting of two or more advocacy coalitions in a mature adversarial policy subsystem within an advanced polyarchy. This article steps beyond the textbook by introducing deep core coalitions marked by compounding intersectional identities operating at the macro-system. It offers two illustrations of deep core coalitions, one bound by their collective transgender identity and the other by their collective traditionalist identity. Finally, this article concludes with a discussion of what it means for a research program to embrace a diverse research agenda, such as through better linkages with other theoretical approaches, launching more comparative research designs, or, as done here, focusing on a new type of advocacy coalition operating at the macro-system
Testing and Analysis of a Passive Thermal Management System and Superconducting Data Transfer for Use in Lunar Permanently Shadowed Regions
No full textNASA’s future return to the moon as part of the Artemis program requires the development of infrastructure capable of operating on the harsh lunar surface as well as the cryogenic conditions of Permanently Shadowed Regions (PSRs). The Planetary Surface Technology Development Lab (PSTDL) at Michigan Technological University designed the Tethered Mechanism for Persistent Energy Storage and Transmission (TEMPEST) to operate in these harsh conditions while minimizing size, weight, and power constraints as part of the NASA’s Watts on the Moon challenge. The development of TEMPEST was a continuation of the Tethered-permanently shadowed Region EXplorer (T-REx) rover as part of NASA’s 2020 BIG idea challenge where the PSTDL developed an infrastructure deployment rover designed to operate in TEMPEST. PSRs is a stationary power infrastructure solution, designed to transmit power 3km from a periodic generation source to a customer load. The TEMPEST system is divided into three subsystems: Upstream TEMPEST, tether connection, and Downstream TEMPEST. Upstream TEMPEST receives power from a generation source and boosts the voltage level to the transmission voltage of 700 VDC. This power is then transmitted across an aluminum tether to Downstream TEMPSET via the tether connection. Downstream TEMPEST houses the energy storage component of the system, which is used to supply power to the customer’s load. Since the TEMPEST modules are exposed to the harsh thermal environment of the Lunar PSR, a thermal management system (TMS) for each subsystem must be designed and integrated to keep all critical components within their operating temperature limits. Due to the mission profile, TEMPEST has high power dissipation for 6 hours, followed by 18 hours of cold temperature survival. To address this challenge, a passive multi-component TMS was incorporated into the design. Most notably, the design contains a significant mass of Phase Change Material (PCM). Since there is little heat generation due to disconnection from the power source during the 18-hour discharging cycle, the primary function of the PCM is to store thermal energy from component inefficiencies and slowly release that heat with its low thermal conductivity over time to keep components within their minimum operating temperature limits. In addition to the TEMPEST thermal system, testing was performed on the communication characteristics of the tether. A benefit of a tethered system is the capability of non-line-of-sight communication between nodes, a major advantage inside of a PSR. TEMPEST’s tether takes advantage of the extreme thermal environment of the PSRs to enhance the resistive properties of the tether. Tether testing at cryogenic temperatures characterizes the transient properties of the tether and provides conclusions on how this impacts mission design
Inference of the Mass Composition of Cosmic Rays with Energies from 1018.5 to 1020 eV Using the Pierre Auger Observatory and Deep Learning
No full textWe present measurements of the atmospheric depth of the shower maximum Xmax, inferred for the first time on an event-by-event level using the surface detector of the Pierre Auger Observatory. Using deep learning, we were able to extend measurements of the Xmax distributions up to energies of 100 EeV (1020 eV), not yet revealed by current measurements, providing new insights into the mass composition of cosmic rays at extreme energies. Gaining a 10-fold increase in statistics compared to the fluorescence detector data, we find evidence that the rate of change of the average Xmax with the logarithm of energy features three breaks at 6.5±0.6(stat)±1(syst) EeV, 11±2(stat)±1(syst) EeV, and 31±5(stat)±3(syst) EeV, in the vicinity to the three prominent features (ankle, instep, suppression) of the cosmic-ray flux. The energy evolution of the mean and standard deviation of the measured Xmax distributions indicates that the mass composition becomes increasingly heavier and purer, thus being incompatible with a large fraction of light nuclei between 50 and 100 EeV
Land-use effects on soil organic matter and related soil properties in a mixed agricultural–forest landscape of central Wisconsin, USA
Get PDFSoil organic matter (SOM) influences a wide range of ecosystem processes, including nutrient cycling, water movement, plant productivity, and biodiversity. In agricultural landscapes, adjacent land uses often differ in SOM contents and related soil properties, such as soil organic carbon (SOC) stocks, but the direction and magnitude of these effects are inconsistent across studies. We assessed how land uses differed in SOM and related properties in a representative US Midwest agricultural–forest landscape to support land-use and management decisions by local landowners and producers. We measured SOM, bulk density (Db), root biomass, and pH, and estimated SOC stocks, in a Typic Hapludalf under four adjacent land uses (permanent forest, pasture, restored prairie on former pasture, and spruce plantation on former pasture). Surface SOM concentrations and stocks were higher under permanent forest (89 g kg−1 and 85 Mg ha−1, respectively) and pasture (63 g kg−1 and 81 Mg ha−1, respectively) than under restored prairie (49 g kg−1 and 58 Mg ha−1, respectively) and spruce plantation (46 g kg−1 and 46 Mg ha−1, respectively). Land uses also differed in Db, root biomass, and pH, with permanent forest and spruce plantation soils having generally lower Db, more root biomass, and more acidic pH than pasture and restored prairie soils. Specific statistically significant differences depended upon depth in the soil profile. Overall, our results suggest that each land use differentially impacts a unique set of soil properties, precluding any single explanation or management recommendation aimed at improving soil health as a whole
Evidence of pure ammonia clouds in Jupiter\u27s Northern Temperate domain from Juno/JIRAM infrared spectral data
Get PDFIn this work, we analyse data from the Jovian Infrared Auroral Mapper (JIRAM) imaging spectrometer on board the NASA mission Juno, to investigate the presence of spectrally identifiable ammonia clouds (SIACs). Focusing on the data from the first perijove passage, we found that a white vortex structure near 40°N provides the best candidate. Implementing atmospheric retrieval thanks to the planetary spectrum generator, we fit the JIRAM spectra (in the 2.5-3.1 μm range) inside and outside the vortex, varying the gaseous ammonia profiles, and the clouds and hazes properties and composition. We found that outside the vortex, the best fit is achieved using main clouds composed of tholins (approximation of an unknown contaminant material). Inside the vortex the best fit is achieved when main cloud decks are composed of pure ammonia ice, or ammonia-coated tholins. We therefore claim the detection of 38 SIACs, all detected over the white vortex structure. With respect to the external regions, the retrieved parameters distributions inside the vortex show: (i) higher altitude hazes and clouds, (ii) smaller haze\u27s effective radii, and (iii) higher gaseous ammonia relative humidity values. Both the detection of pure ammonia ice clouds and the retrieved physical parameters are consistent with the vortex being the result of a moist convection storm that uplifted fresh ammonia from the deep troposphere which in turn either condensed or became a possible source of coating material for existing cloud particles. This work confirms the trend established by space and ground-based observations, for which ammonia clouds on Jupiter are rare and connected to strong convective episodes
Arctic Energy Governance: Complexity, Transitions and the Oversized Role of Nation States
No full textThe Arctic region presents unique challenges and paradoxes for governance, particularly in the energy sector. The early 21st century has intensified interest in the Arctic, driven by its symbolic representation of climate change challenges and the allure of untapped oil and gas reserves. This juxtaposition of environmental vulnerability against the backdrop of significant energy potential sets the stage for complex governance issues, balancing the pressing need for climate mitigation with the economic incentives of resource exploitation. The inherent contradictions between pursuing sustainable energy transitions and the continuation of hydrocarbon extraction underline a multi-dimensional paradox involving sustainability, energy security and justice. This chapter delves into the governance challenges presented in the Arctic, including the production, transportation, conversion, utilization and decommissioning of energy resources. It critically examines the roles of various stakeholders, including nation-states. The analysis extends to the fragmentation of Arctic energy governance, highlighting both vertical and horizontal divides that complicate coherent policy formulation and implementation. This chapter argues for a balanced approach to Arctic energy governance that harmonizes security, sustainability and justice considerations, advocating for increased collaboration, regulatory alignment and stakeholder engagement to navigate the complexities of the Arctic energy landscape towards a sustainable and equitable future
Trophic Ecology and Mercury Bioaccumulation among Lake Superior lake charr (Salvelinus namaycush) Ecotypes
No full textThe Lake Superior lake charr population consists of siscowet, lean, humper and redfin ecological morphotypes or ecotypes. In addition to morphological and physiological differences, these fish occupy different habitats in Lake Superior and partition various invertebrate and fish prey resources. In this study, we measured the stable isotopes of carbon (δ13C) and nitrogen (δ15N) and mercury (Hg) concentrations among these ecotypes collected from the waters surrounding Lake Superior\u27s Isle Royale. Average Hg concentrations were highest for redfins (1386 ng/g dry wt) followed by siscowets (826 ng/g), humpers (799 ng/g) and leans (519 ng/g) and differed significantly among the ecotypes (p \u3c 0.05). This pattern in Hg concentrations was generally consistent following corrections for size differences among ecotypes but with length corrected Hg concentrations for humpers (1185 ng/g) being higher than redfins (1075 ng/g). δ13C and δ15N results demonstrated a high degree of overlap among ecotypes suggesting that none occupy a unique niche in the waters surrounding Isle Royale. Modeling efforts indicated that differences in growth efficiencies among ecotypes likely contribute to the observed differences in Hg bioaccumulation. Specifically, differences with respect to the extent of insectivorous foraging in the diet likely regulate growth efficiencies and the extent of Hg bioaccumulation realized among ecotypes
Molecular dynamics simulation on oxidation process and interfacial performance of foamed asphalt binders based on ReaxFF force field
No full textAsphalt can deteriorate and age due to exposure to environmental conditions. This ageing reduces pavement performance and recycling waste pavement is relevant for environmental protection. The oxidation process, properties and interfacial behaviour of asphalt binders and foamed asphalt binders were discussed with the classical molecular dynamics (MD) simulation and reactive force field molecular dynamics (ReaxFF MD) simulation, as well as mineral aggregate molecular systems. The oxidized models for each asphalt molecule were proposed, which closely matched actual experimental study results. The simulation results showed that sulfur atoms oxidized the fastest, followed by benzyl carbon. As the degree of oxidation increased, the viscosity and glass transition temperature of asphalt molecules also increased. The interfacial energies of various systems were analysed, such as foamed asphalt-aged asphalt, asphalt-aggregate and asphalt-recycled aggregate. It was found that the adhesion of asphalt-aged asphalt decreased due to the presence of water, but this phenomenon was not observed in the asphalt-recycled aggregate interface when the water content was less than 2%. The mean square displacement results showed that 3% or less water content facilitated the diffusion and movement of molecules in asphalt-recycled aggregate systems, whereas, in asphalt-aggregate systems, only 1% water content was sufficient