The impact of subhalos on the gamma-ray signal from dark matter annihilation

Assuming the lightest neutralino in the minimal supersymmetric extension to the Standard Model (MSSM) as the main dark matter (DM) component, we estimate the cumulative enhancement of the neutralino-induced gamma-ray signal in the Galactic halo due to the presence of subhalos. A realistic semi-analytical model for the spatial mass function of subhalos is implemented, incorporating effects that may influence the distribution and the evolution of substructures, such as the mass loss due to the tidal stripping and the orbital decay due to the dynamical friction.     

Macrophyte Abundance in Waquoit Bay: Effects of Land-Derived Nitrogen Loads on Seasonal and Multi-Year Biomass Patterns

Anthropogenic inputs of nutrients to coastal waters have rapidly restructured coastal ecosystems. To examine the response of macrophyte communities to land-derived nitrogen loading, we measured macrophyte biomass monthly for 6 years in three estuaries subject to different nitrogen loads owing to different land uses on the watersheds. The set of estuaries sampled had nitrogen loads over the broad range of 12 to 601 kg N ha⁻¹ year⁻¹. Macrophyte biomass increased as nitrogen loads increased, but the response of individual taxa varied. Specifically, biomass of Cladophora vagabunda and Gracilaria tikvahiae increased significantly as nitrogen loads increased. The biomass of other macroalgal taxa tended to decrease with increasing load, and the relative proportion of these taxa to total macrophyte biomass also decreased. The seagrass, Zostera marina, disappeared from the higher loaded estuaries but remained abundant in the estuary with the lowest load. Seasonal changes in macroalgal standing stock were also affected by nitrogen load, with larger fluctuations in biomass across the year and higher minimum biomass of macroalgae in the higher loaded estuaries. There were no significant changes in macrophyte biomass over the 6 years of this study, but there was a slight trend of increasing macroalgal biomass in the latter years. Macroalgal biomass was not related to irradiance or temperature, but Z. marina biomass was highest during the summer months when light and temperatures peak. Irradiance might, however, be a secondary limiting factor controlling macroalgal biomass in the higher loaded estuaries by restricting the depth of the macroalgal canopy. The relationship between the bloom-forming macroalgal species, C. vagabunda and G. tikvahiae, and nitrogen loads suggested a strong connection between development on watersheds and macroalgal blooms and loss of seagrasses. The influence of watershed land uses largely overwhelmed seasonal and inter-annual differences in standing stock of macrophytes in these temperate estuaries.     

Interactive Videos Enhance Learning about Socio-Ecological Systems

Two forms of interactive video were assessed in an online course focused on conservation. The hypothesis was that interactive video enhances student perceptions about learning and improves mental models of social-ecological systems. Results showed that students reported greater learning and attitudes toward the subject following interactive video. Moreover, metrics of network complexity applied to students' concept maps of socio-ecological systems increased longitudinally through the course highlighting greater awareness of socio-ecological linkages. We conclude that interactive video can increase awareness of interdisciplinary connections in socio-ecological systems and should be more widely employed in general education geography courses.     

Quantifying bank erosion on the South River from 1937 to 2005, and its importance in assessing Hg contamination

Bank sediments along a 40 km reach of the South River, downstream of Waynesboro, VA, store mercury from historical contamination as a result of textile manufacturing. Knowledge of the rate at which contaminated sediment is released to the stream channel through bank erosion is required to implement restoration programs designed, for example, to minimize its ecological impact and to reduce risk to human health. Digitized stream channel boundaries based on visual interpretations of georeferenced aerial imagery from 1937 and 2005 were compared to calculate a minimum estimate of the total area of bank sediment eroded between Waynesboro and Port Republic, Virginia. Estimates of riverbank height were extracted from aerial LIDAR data, allowing areal estimates of bank retreat to be converted to volumes. Nominal annual rates of bank retreat, averaged over the 68-year period, for several example locales along the study reach are very low, ranging from 3 to 15 cm per year. Bank erosion occurs at the outside banks of bends, through the development of islands, where deposition on confluence bars pushes the main flow into the opposite bank, and in small areas along the channel that are difficult to classify or explain. A minimum estimate of the total volume eroded for the study reach is approximately 161,000 m³; the corresponding annual mass of mercury supplied to the channel by bank erosion is 109.6 kg/year. Our work demonstrates that a careful analysis of aerial imagery and LIDAR data can provide detailed, spatially explicit estimates of mercury loading from bank erosion, even when rates of riverbank erosion are unusually low.     

Distribution and abundance of anthropogenic marine debris along the shelf and slope of the US West Coast

As marine debris levels continue to grow worldwide, defining sources, composition, and distribution of debris, as well as potential effects, becomes increasingly important. We investigated composition and abundance of man-made, benthic marine debris at 1347 randomly selected stations along the US West Coast during Groundfish Bottom Trawl Surveys in 2007 and 2008. Anthropogenic debris was observed in 469 tows at depths of 55-1280 m. Plastic and metallic debris occurred in the greatest number of hauls followed by fabric and glass. Mean density was 67.1 items km⁻² throughout the study area but was significantly higher south of 36°00′N latitude. Mean density significantly increased with depth, ranging from 30 items km⁻² in shallow (55-183 m) water to 128 items km⁻² in the deepest depth stratum (550-1280 m). Debris densities observed along the US West Coast were comparable to those seen elsewhere and provide a valuable backdrop for future comparisons.     

Field research to application: a study of human response to the 2011, Joplin tornado and its impact on alerts and warnings in the USA

Natural Hazards - An EF-5 tornado occurred on May 22, 2011, in the populated area of Joplin, Missouri, causing 161 fatalities and over 1000 injuries. A conceptual model of protective action...     

Hurricane trend detection

Natural Hazards - Because a change in the frequency (number/year) of hurricanes could be a result of climate change, we analyzed the historical record of Atlantic basin and US landfalling...     

Factors Controlling In Situ Biogeochemical Transformation of Trichloroethene: Field Survey

We have previously defined in situ biogeochemical transformation as the biogenic formation of reactive minerals that are capable of abiotically degrading chlorinated solvents such as trichloroethene without accumulation of degradation products such as vinyl chloride (AFCEE et al. 2008 ). This process has been implemented in biowalls used to intercept contaminated groundwater. Abiotic patterns of contaminant degradation were observed at Altus Air Force Base (AFB) and in an associated column study, but not at other sites including Dover AFB. These abiotic patterns were associated with biogenic formation of reactive iron sulfide minerals. Iron sulfides in the form of small individual grains, coatings on magnetite, and sulfur‐deficient pyrite framboids were observed in samples collected from the Altus AFB biowalls and one of the EPA columns. Larger iron sulfide grains coated with oxide layers were observed in samples collected from Dover AFB. Altus AFB and the EPA column differed from Dover AFB in that groundwater flow at Dover AFB was relatively slow and potentially reversing. High volumetric sulfate consumption rates, an abiotic pattern of trichloroethene (TCE) degradation, and the formation of small, high surface area iron sulfide particles were associated with relatively high rates of TCE removal via an abiotic pattern. Geochemical modeling demonstrated that iron monosulfides such as mackinawite were near saturation, and iron disulfides such as pyrite were supersaturated at all sites. This environmental condition can be supportive of nucleation of small particles rather than crystal growth leading to larger particles. When nucleation is dominant, small, high surface area, and reactive particles result. When crystal growth dominates the crystals are larger and have lower specific surface area and reactivity. These results taken together suggest that creation of a dynamic environment can promote biogeochemical transformation based on generation of reactive iron sulfides.     

Changes in biomass structure and trophic status of the plankton communities in a highly dynamic ecosystem (Gulf of Venice,Northern Adriatic Sea)

The changes in the plankton biomass structure in relation to nutrient inputs were studied in the Gulf of Venice (Northern Adriatic Sea), an area characterized by a very marked trophic state variability. The investigation was carried out at two stations, in March, May and July 2005 and 2006, considering the whole water column. The size structure (from picoplankton to mesozooplankton) of both autotrophs and heterotrophs was analysed. Signals of diluted waters and nutrient inputs were more marked in 2005 than in 2006. In 2005, the total plankton biomass was almost double (87 ± 37 μg·C·l^?1) that in 2006 (44 ± 26 μg·C·l^?1). The variations were determined mainly by phytoplankton, with a 70% decrease, and a shift from a community dominated by microphytoplankton (49 ± 12%) in 2005 to one dominated by bacteria (43 ± 11%) in 2006 was observed. The relationship between the heterotrophic (H) and autotrophic (A) biomass indicated a rapid decline of the H/A ratio with increasing phytoplankton biomass. This study, although temporally limited, is consistent with the results reported for other marine environments and it seems to confirm the importance of nutrient inputs in structuring the biomass of plankton community.