This paper presents the experience of a service-learning course which used community geography to study a proposed research and community center in DeKalb, IL. The center was proposed as a jointly-developed project by the Northern Illinois University and local governmental entities. The original goal of the course was to explore the viability of the proposed project and solicit feedback from the community through traditional engaged planning and public participation. As students began interacting with university and residential communities, it became clear that both communities had input for the center, and found similarities in their experiences and perceptions. While noted divisions in interest groups are known in DeKalb, both communities found themselves surprisingly interested in meaningful discussion to better understand each other through their shared experiences. In response, our theoretical approach shifted to community geography. Students, university employees, and local residents introduced and analyzed questions together as researchers and participants, and developed recommendations to address shared concern. Students then prepared a report advocating for those concerns to submit to university and community leaders. Following the evolution of this project, this paper presents lessons learned and areas for application of community geography as a pedagogical technique, as an important component of geography curriculum, and as a research framework for town-gown relationship inquiry.
The structural evolution of two columbites under pressure, one ferrocolumbite from Raode (Africa) and one manganocolumbite
from Kragero (Norway), has been determined by single-crystal X-ray diffraction. Structural investigations at high pressure
have been carried out on samples which were preliminarily annealed to attain the complete cation-ordered state. For each crystal,
five complete datasets have been collected from room pressure up to ca. 7 GPa. Structure refinements converged to final discrepancy
factors R ranging between 5.2 and 5.8% for both the crystals. Structure refinements of X-ray diffraction data at different pressures
allowed characterisation of the mechanisms by which the columbite structure accommodates variations in pressure. A and B octahedral
volumes in both samples decrease linearly as pressure increases, with a larger compression of the larger A site. The difference
in polyhedral bulk moduli of the A sites for the two samples does not appear to relate directly to the octahedral sizes, the
A site being more compressible in the Fe-rich sample than in the Mn-rich one. By far the most compressible direction in both
the analysed samples is along b. The cations are in fact free to move along this direction, thus allowing the octahedral chains to slide over each other;
this effect is particularly evident in the manganocolumbite sample which shows a steep shortening of interchain A–B distances
along b. 相似文献
The West O’Gorman Fracture Zone is an unusual feature that lies between the Mathematician Ridge and the East Pacific Rise
on crust generated on the East Pacific Rise between 4 and 9 million years ago. We made a reconnaissance gravity, magnetic
and Sea Beam study of the zone with particular emphasis on its eastern (youngest) portion. That region is characterized by
an elongate main trough, a prominent median ridge and other, smaller ridges and troughs. The structure has the appearance
of large-offset fracture zone, possibly in a slow spreading environment. However, magnetic anomalies indicate that the offset,
if any, is quite small, and the spreading rate during formation was fast. In addition, the magnetic profiles do not support
earlier models for a difference in spreading rate north and south of the fracture. The morphology of the fracture zone suggests
that flexure may be responsible for some of the topography; but gravity studies indicate some of the most prominent features
of the fracture zone are at least partially compensated. The main trough is underlain by a thin crust (or high density body),
similar to large-offset fracture zones in the Atlantic, while the median ridge is underlain by a thickened crust. Sea Beam
data does not unambiguously resolve between volcanism or serpentinization of the upper mantle as a mechanism for isostatic
compensation.
Why the West O’Gorman exists remains enigmatic, but we speculate that the topographic expression of a fracture zone does not
require a transform offset during formation. Perhaps the spreading ridge was magma starved for some reason, resulting in a
thin crust that allowed water to penetrate and serpentinize portions of the upper mantle. 相似文献
In marine wetlands, nitrogen fixation is a potentially important nutrient source for nitrogen‐limited primary producers, but interactions between nitrogen fixers and different vascular plant species are not fully understood. Nitrogen fixation activity was compared in sediments vegetated by three plant species, Spartina foliosa, Salicornia virginica, and Salicornia bigelovii in the Kendall Frost Reserve salt marsh in Mission Bay (CA). This study addressed the effects of plant type, day and night conditions, and sediment depths on nitrogen fixation. Higher rates of nitrogen fixation were associated with S. foliosa than with either of the two Salicornia spp., which are known to compete more effectively than Spartina for exogenous nitrogen in the salt marsh environment. Rates of nitrogen fixation, determined by acetylene reduction, in sediments vegetated by S. virginica were low during the day (7.7 ± 1.2 μmol C2H4 m−2 h−1) but averaged 13 ± 6.6 μmol C2H4 m−2 h−1 at night, with particularly high rates in samples from locations with visible cyanobacterial mats. The opposite diel pattern was found for sediments containing S. foliosa plants, in which average daytime and nighttime rates of nitrogen fixation were 62 ± 23 and 21 ± 15 μmol C2H4 m−2 h−1, respectively. For S. foliosa, nitrogenase activity of rinsed roots and different sediment sections (0–1, or 4–5 cm depths) were measured. Although nitrogen fixation rates in vegetated sediment samples were substantial, all but one of rinsed S. foliosa root samples (n = 12) and subsurface sediments at 4–5 cm depths failed to show nitrogen fixation activity after 2 h, suggesting that the most active nitrogen fixers in these systems likely reside in surface sediments. Further, nitrogenase activity in shaded and unshaded S. foliosa samples did not differ, suggesting that nitrogen fixers may not rapidly respond to changes in plant photosynthetic activity. Average nitrogen fixation rates in S. foliosa‐vegetated samples from the Mission Bay salt marsh were on the same order as those of highly productive Atlantic coast marshes, and this microbially‐mediated nitrogen source may be similarly substantial in other Mediterranean wetlands. Sediment abiotic variables seem to exert greater control upon nitrogen fixation activity than the effects of particular plant species. Nonetheless, dominant plant species may differ substantially in their reliance on nitrogen fixation as a nutrient source, with potentially important consequences for wetland conservation and restoration. 相似文献
The exploitation of fossil fuels in the Mediterranean Sea will likely lead to an increase in the number of offshore platforms, a recognized threat for marine biodiversity. To date, in this basin, few attempts have been made to assess the impact of offshore gas and oil platforms on the biodiversity of benthic assemblages. Here, we adopted a structured experimental design coupled with high taxonomic resolution to outline putative effects of gas platforms on soft-bottom macrofauna assemblages in the North Ionian Sea. The analysis was based on a total of 20,295 specimens of 405 taxa, almost entirely identified at species level. Multivariate and univariate analyses showed idiosyncratic patterns of assemblage change with increasing distance from the platforms. Potential reasons underlying such inconsistency are analyzed and the view that structured experimental monitoring is a crucial tool to quantify the extent and magnitude of potential threats and to provide sound baseline information on biodiversity patterns is supported. 相似文献
Soil-temperature measurements can provide information on the distribution of degassing fissures, their relationship to the
internal structure of the volcano, and the temporal evolution of the system. At Vulcano Island (Italy), heat flux from a <3
km-deep magma body drives a hydrothermal system which extends across the main Fossa crater. This heat flux is also associated
with variable magmatic gas flow. A high-density map of soil-temperatures was made in 1996 at a constant depth of 30 cm on
the central and southern inner flanks of the Fossa crater. These measurements extended over an area covering about 0.04 km2, across which the heat flux is predominantly associated with a shallow boiling aquifer. The map shows that hot zones relate
to structures of higher permeability, mainly associated with a fissure system dating from the last eruptive cycle (1888–1890).
From 1996 to January 2005, we studied the evolution of the heat flux for the high temperature part of the map, both by repeating
our measurements as part of 14 visits, during which temperatures were measured at a constant depth, and using data from permanent
stations which allowed soil-temperatures to be continuously measured for selected vertical profiles. These data allowed us
to calculate the heat flux, and its variation, with good precision for values lower than about 100 W m−2, which is generally the case in the study area. Above 100 W m−2, although the heat flux value is underestimated, its variations are recorded with an error less than 10%. During the period
1996–2004, two increases in the thermal flux were recorded. The first one was related to the seismic crisis of November 1998
which opened existing or new fissures. The second, in November 2004, was probably due to magma migration, and was associated
with minor seismic activity. 相似文献
Fungi are a highly complex group of organisms of the kingdom Eumycota (i.e. the true-fungi) and other fungus-like organisms
traditionally studied by mycologists, such as slime molds (Myxomycota) and oomycota (Straminopiles or Heterokonts). They constitute
a significant proportion of the as yet undiscovered biota that is crucial in ecological processes and human well-being, through
at least three main trophic modes: saprophytism, parasitism, or symbiosis. In addition to direct benefit (sources of antibiotics)
or adverse effects (agents of disease), fungi can impact many environmental processes, particularly those associated with
the decomposition of organic matter. They are present in almost all regions and climates, even under extreme conditions. However,
studies have focussed mostly on economically interesting species, and knowledge of their diversity and functions is mainly
restricted to soil, rhizosphere, mangrove, and lotic ecosystems. In this study, we review the diversity and potential functions
of microscopic fungi in aquatic ecosystems, with focus on the pelagic environments where they often are regarded as allochthonous
material, of low ecological significance for food-web processes. Recent environmental 18S rDNA surveys of microbial eukaryotes
have (1) unveiled a large reservoir of unexpected fungal diversity in pelagic systems, (2) emphasized their ecological potentials
for ecosystem functioning, and (3) opened new perspectives in the context of food-web dynamics. In spite of persisting methodological
difficulties, we conclude that a better documentation of the diversity and quantitative and functional importance of fungi
will improve our understanding of pelagic processes and biogeochemical cycling. 相似文献
We compare high-resolution infrared observations of the CO 2–0 bands in the 2.297–2.310 μm region of M dwarfs and one L dwarf with theoretical expectations. We find a good match between the observational and synthetic spectra throughout the 2000–3500 K temperature regime investigated. None the less, for the 2500–3500 K temperature range, the temperatures that we derive from synthetic spectral fits are higher than expected from more empirical methods by several hundred kelvin. In order to reconcile our findings with the empirical temperature scale, it is necessary to invoke warming of the model atmosphere used to construct the synthetic spectra. We consider that the most likely reason for the back-warming is missing high-temperature opacity due to water vapour. We compare the water vapour opacity of the Partridge–Schwenke line list used for the model atmosphere with the output from a preliminary calculation by Barber & Tennyson. While the Partridge–Schwenke line list is a reasonable spectroscopic match for the new line list at 2000 K, by 4000 K it is missing around 25 per cent of the water vapour opacity. We thus consider that the offset between empirical and synthetic temperature scales is explained by the lack of hot water vapour used for computation of the synthetic spectra. For our coolest objects with temperatures below 2500 K, we find best fits when using synthetic spectra which include dust emission. Our spectra also allow us to constrain the rotational velocities of our sources, and these velocities are consistent with the broad trend of rotational velocities increasing from M to L. 相似文献
Scientific study has generated a range of hypotheses about the ecological structure and function of seamounts. Interpretations of these ideas and data are vital to understanding how seamount communities will respond to anthropogenic impacts. Here, we examine how diversity and structure of seamount assemblages vary with depth and slope of the sea floor. We conducted ROV video transects on three seamounts of the Taney Seamount Chain in the Northeast Pacific Ocean. Depth and slope were both related to assemblage structure on the Taney seamounts. Depth differences were seen in alpha‐ and beta‐diversity but not density. Beta‐diversity and density but not alpha‐diversity varied with slope. Overall, slope and depth together explained 14–31% of beta‐diversity. The findings suggest that differences in beta‐diversity as related to depth gradients may differ among onshore and offshore and/or between shallow and deep summit seamounts. Specifically, we hypothesize that differences in productivity and depth gradients among seamounts may generate different patterns of beta‐diversity. 相似文献