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971.
Alan Latham 《Area》1999,31(2):161-168
Summary This paper explores the dynamics of engagement and disengagement within urban space. It argues that a certain capacity to encounter the world around the self in an active, creative way is central to the self's ability to recognize and care about the places it inhabits and the people encountered within those places. Drawing on the work of Donald Winnicott and Jessica Benjamin, it outlines a framework of self-other psycho-dynamics through which this active, creative encountering may be understood, and examines the violence of indifference that occurs when this everyday creativity is absent. 相似文献
972.
973.
Alan F. Arbogast 《The Professional geographer》2000,52(4):594-606
The Nodaway dune field is perched along Lake Superior in Upper Michigan. This study uses absolute and relative‐age dating methods to test the hypothesis that the dune field finally stabilized after the Nipissing high stand, about 4,000 years ago. Surface soils on snouts of all dunes are moderately developed Spodosols, indicating that dunes stabilized within a few hundred years of each other. One thermoluminescence date provided an age of 8 ka from soil parent material, but is probably overestimated due to residual thermoluminescence. Subsequent optical stimulated luminescence and accelerator mass spectrometry age estimates indicate that the most recent accumulation of sand occurred between ?3.7 and 3.0 ka. This interval suggests one of three possibilities: 1) that the dune field was reactivated during the Algoma high stand and then stabilized; 2) that the dune field stabilized gradually, probably as sand supply diminished after the Nipissing high stand; and 3) that a combination of these two processes occurred. 相似文献
974.
975.
The circulation patterns in St. Andrew Bay, Florida are revealed through the application of a well-tested, extensively used three-dimensional hydrodynamic model. A high resolution grid resolving both the horizontal and vertical directions is used with a systematically developed set of forcing functions to simulate conditions over a full year. Water levels at the three open boundaries are deduced from a year-long deployment of pressure gauges, and freshwater loadings are based upon drainage basin characteristics and precipitation measurements. Model validation involves comparisons with hydrographic casts taken at twelve stations distributed throughout the bay at monthly intervals. The relative average error between the observed and model-predicted salinity is 15% for the surface of the water column and 4% for the bottom. The annual net flow balance consists of an influx of water at the two Intracoastal Waterway open boundaries, with that water exiting to the Gulf of Mexico. An average of about 100 m3 s−1 enters from East Bay and about 40 m3 s−1 enters through West Bay. On shorter time scales, the flow balance is quite variable both in terms of magnitude and direction. This study also presents methods to overcome the paucity of data that is usually available for the development of such a model. These include techniques to take bottom pressure data sets with short gaps and create reliable sea surface elevation boundary conditions and to take precipitation data and drainage basin characteristics and produce estimates of freshwater inflows. 相似文献
976.
Richard Dame Merryl Alber Dennis Allen Michael Mallin Clay Montague Alan Lewitus Alice Chalmers Robert Gardner Craig Gilman Björn Kjerfve Jay Pinckney Ned Smith 《Estuaries and Coasts》2000,23(6):793-819
Estuaries of the southeastern Atlantic coastal plain are dominated by shallow meso-tidal bar-built systems interspersed with shallow sounds and both low flow coastal plain and high flow piedmont riverine systems. Three general geographical areas can be discriminated: the sounds of North Carolina; the alternating series of riverine and ocean dominated bar-built systems of South Carolina, Georgia, and northeast Florida, and the subtropical bar-built estuaries of the Florida southeast coast. The regional climate ranges from temperate to subtropical with sea level rise and hurricanes having a major impact on the region's estuaries because of its low and relatively flat geomorphology. Primary production is highest in the central region. Seagrasses are common in the northern and southern most systems, while intertidal salt marshes composed ofSpartina alterniflora reach their greatest extent and productivity in South Carolina and Georgia. Nuisance blooms (cyanobacteria, dinoflagellates, and cryptomonads) occur more frequently in the northern and extreme southern parts of the region. Fishery catches are highest in the North Carolina and Florida areas. Human population growth with its associated urbanization reaches a maximum in Florida and it is thought that the long-term sustainability of the Florida coast for human habitation will be lost within the next 25 years. Tidal flushing appears to play an important role in mitigating anthropogenic inputs in systems of moderate to high tidal range, i.e., the South Carolina and Georgia coasts. The most pressing environmental problems for the estuaries of the southeastern Atlantic coast seem to be nutrient loading and poor land use in North Carolina and high human population density and growth in Florida. The future utilization of these estuarine systems and their services will depend on the development of improved management strategies based on improved data quality. 相似文献
977.
Andy Thean Alan Pedlar Marek J. Kukula Stefi A. Baum Christopher P. O'Dea 《Monthly notices of the Royal Astronomical Society》2000,314(3):573-588
We present 8.4-GHz VLA A-configuration observations of 87 sources from the mid-infrared-selected AGN sample of Rush et al. These 0.25-arcsec-resolution observations allow elongated radio structures tens of pc in size to be resolved, and enable radio components smaller than 3.5 arcsec to be isolated from diffuse galactic disc emission. When combined with previous data, matched radio observations covering 90 per cent of the sample have been collected, and these represent the largest subarcsecond–resolution radio imaging survey of a homogeneously selected sample of Seyfert galaxies to date.
We use our observations to identify five radio-loud AGN in the sample. The nature of the radio emission from Seyfert nuclei will be discussed in subsequent papers. 相似文献
We use our observations to identify five radio-loud AGN in the sample. The nature of the radio emission from Seyfert nuclei will be discussed in subsequent papers. 相似文献
978.
Tony O. Henninger P. William FronemanNicole B. Richoux Alan N. Hodgson 《Estuarine, Coastal and Shelf Science》2009
The role of submerged macrophytes as refugia from fish predation and as possible food sources for the estuarine isopod Exosphaeroma hylocoetes ( Barnard, K.H., 1940) was investigated. Laboratory experiments tested the effectiveness of artificial vegetation, replicating submerged vegetation, in enabling isopods to elude selected fish predators Rhabdosargus holubi, Glossogobius callidus, Monodactylus falciformis and Clinus cottoides. Isopods preferentially hid in the vegetation (>90%), even in absence of fish. The predatory fish had varying success in finding isopods within the vegetation. Isopod mortality ranged from 2% (R. holubi) to a maximum of 87% (C. cottoides) within vegetation, depending on the fish predator present. Stable isotope and fatty acid analyses ruled out the submerged macrophyte Ruppia maritima and inundated fringing grasses as direct food sources, but highlighted the epiphytic biota (mainly diatoms) found on the submerged vegetation and sediments as more likely food sources. These findings are consistent with gut content analyses. The results suggest that the close association of E. hylocoetes with R. maritima is the result of the vegetation providing the isopod with a refuge against fish predation as well as areas of increased food availability. 相似文献
979.
Previous observations in the Gareloch, a Scottish silled fjord, have identified yet failed to explain the baroclinic circulation pattern. Additional fieldwork was carried out in April 2005, showing the loch to be stratified with two distinct layers and currents in each layer 180° out of phase at the M2 frequency. The currents did not display the expected sinusoidal signal that is characteristic of the tide and instead were pulsated and stronger than predicted by barotropic forcing. Fourier analysis showed that the flow was dominated by short period non-linear oscillations that were harmonics of the semi-diurnal tide. Two hydrostatic estuarine models were applied to the Gareloch: a 2D vertical model (SLICE) and a 3D model (ECOMSED). Both models were capable of reproducing the observed (2005) baroclinic circulation at the M2 time scale but failed to simulate the higher frequency, non-linear oscillations. However, each model generated higher harmonics in idealised scenarios. Because lateral motion was negligible and SLICE was an order of magnitude more efficient than ECOMSED, the 2D model was used to simulate the higher harmonics and showed that their generation was attributed to the non-linear distortion of the internal tide. When the internal Froude number (determined by barotropic velocity, stratification and water depth) was increased from a sub-critical value, non-linear advection became more important and higher harmonics were generated. The internal tide was further modified by wave reflection and interaction off steep boundaries, and by flow over the sill. 相似文献
980.
Cristina Ferretti Simone Vacca Chiara De Ciucis Barbara Marengo Alan R. Duckworth Renata Manconi Roberto Pronzato & Cinzia Domenicotti 《Marine Ecology》2009,30(3):327-336
Growth dynamics and bioactivity variation of the Mediterranean demosponges Agelas oroides and Petrosia ficiformis were investigated over 15 months at Paraggi and Colombara within the Marine Reserve of Portofino Promontory (Mediterranean Sea, Ligurian Sea, Italy). For both species, growth rates varied between individuals and were unaffected by initial sponge size. The two species showed a different trend in growth pattern: A. oroides did not vary significantly between seasons, sites and depths; in contrast, some individuals of P. ficiformis showed a seasonal pattern, shrinking during winter as water temperature decreased and growing during summer when water temperature increased. Differences in growth between the two species may result from different reproductive cycles, food availability, species-specific thermophily and patterns of spatial competition. Moreover, spatial competition probably induced sponges to produce bioactive secondary molecules. Spatial and temporal variation of bioactivity of both species was examined for the first time by studying its effect on human neuroblastoma cells. The bioactivity of A. oroides extracts differed significantly between seasons, sites and depths, whereas the cytotoxicity of P. ficiformis differed significantly between seasons and depths (differences for sites were not determined). These results suggest the possible influence of environmental factors on bioactive metabolite biosynthesis. 相似文献