Using the Internet to Integrate Thematic and Regional Approaches in Geographic Education

Geographers have long debated the superiority of regional versus thematic approaches to geographical analysis and geographic education. While most acknowledge that these two approaches are complementary, the task of implementing both approaches in a single introductory course remains challenging. “Global Change, Local Places,” an Internet–based course offered at Florida State University, attempts to fuse thematic and regional approaches using methodological and pedagogical techniques that emphasize student–centered learning and Internet technologies. Results of a student survey and analysis of student assignments suggest that this format was successful. Students expressed a high level of satisfaction with course content, and, although attainment of skills and knowledge was particularly hard to measure given the structure and goals of the course, students appear to have gained country–specific knowledge as well as skills in critical analysis using thematic concepts.     

Visualization of wave-induced suspension patterns over two-dimensional bedforms

High spatial and temporal resolution measurements of suspended sand concentration ( c ) over vortex ripples were collected with a three-transducer acoustic backscatter sensor (ABS) array, under irregular `natural' waves in a multidirectional wave basin. These measurements permit two-dimensional visualization of the movement of sediment-laden vortices over an individual vortex ripple under a series of waves. Patterns of sediment motion were tracked through consecutive zero-crossings in the horizontal velocity ( U ) record measured at 0·05 m above the ripple crest elevation. It was possible to trace the advection of individual sediment-laden vortices at the zero-crossings. During 73% of these events, shedding and advection of coherent suspension events occurred before the flow reversal associated with the zero-crossing. This may be caused by the bedforms retarding the near-bed flow inducing the eddy shedding before the zero-crossing. While at maxima in U , secondary suspension events with low c were observed to pass over the ripple crest moving with U measured at 0·05 m. This pattern is attributed to vortex shedding from adjacent bedforms and/or antecedent suspension events. The most energetic events appeared to persist for several wave cycles and reached heights of ≈0·20 m. These suspension events appeared to be more persistent when smaller waves follow larger waves, possibly as a result of weaker reversals in vorticity. Although the events appeared to be vertically coherent in the time series from the individual transducers, it is apparent through visualization that these events are associated with the pairing of antecedent and developing vortices.     

The Mackenzie Delta: sedimentary processes and facies of a high-latitude, fine-grained delta

The Mackenzie Delta is a large fine‐grained delta deposited in a cold arctic setting. The delta has been constructed upon a flooding surface developed on a previous shelf‐phase delta. There are three principal depositional zones: the subaerial delta plain, the distributary channel mouth region and the subaqeous delta. The subaerial delta plain is characterized by an anastomosing system of high‐sinuosity channels and extensive thermokarst lake development. This region is greatly influenced by the annual cycle of seasonal processes including winter freezing of sediments and channels, ice‐jamming and flooding in the early spring and declining river stage during the summer and autumn. Deposition occurs on channel levees and in thermokarst lakes during flood events and is commonly rhythmic in nature with discrete annual beds being distinguishable. In the channel mouth environment, deposition is dominated by landward accretion and aggradation of mouth bars during river‐ and storm surge‐induced flood events. The subaqeous delta is characterized by a shallow water platform and a gentle offshore slope. Sediment bypassing of the shallow‐water platform is efficient as a result of the presence of incised submarine channels and the predominance of suspension transport of fine‐grained sediments. Facies of the shallow platform include silty sand with climbing ripple lamination. Offshore facies are dominated by seaward‐fining fine sand to silt tempestites. Sea‐ice scouring and sediment deformation are common beyond 10 m water depth where bioturbated muds are the predominant facies. The low angle profile of the shallow‐water platform is interpreted to be the combined response of a fine‐grained delta to (1) storm sediment dispersal; (2) autoretreat as a result of the increasing subaerial and subaqeous area of deposition as the delta progrades out of its glacial valley; (3) limited water depth above the underlying flooding surface; and (4) efficient nearshore bypassing of sediment through subice channels at the peak of spring discharge. Several indicators of the cold climate can be used as criteria for the interpretation of ancient successions, including thermokarst lake development, submarine channel scours, freeze–thaw deformation and ice‐scour deformation structures. Permafrost inhibits compaction subsidence and, together with the shallow‐water setting, also limits autocyclic lobe switching. The cold climate can thus influence stratal architecture by favouring the development of regional‐scale clinoform sets rather than multiple, smaller scale lobes separated by autocyclic flooding surfaces.     

1994 REPORT ON WHIN SILL DOLERITE WS-E FROM ENGLAND AND PITSCURRIE MICROGABBRO PM-S FROM SCOTLAND: ASSESSMENT BY ONE HUNDRED AND FOUR INTERNATIONAL LABORATORIES

This compilation report describes the field location, mineralogy, preparation and homogeneity testing of two new GIT-IWG reference materials: Whin Sill dolerite (WS-E) from England and Pitscurrie microgabbro (PM-S) from Scotland. The elemental composition of these two new reference materials has been established by an international cooperative analysis programme involving participation by 104 laboratories. A full assessment of these analytical results is presented, from which working values have been derived for the major elements as well as for 45 trace elements in WS-E and 44 trace elements in PM-S. Furthermore, isotopic ratios are presented for both samples, particularly for ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd.     

Hepato Toxicity of Malathion on the Protein Metabolism in Cyprinus carpio

Freshwater fish were exposed to sublethal concentration of commercial grade malathion (50 E. C.) (2 ppm) for 7,15 and 30 days. After each exposure period, certain biochemical parameters were studied. A decrease in total, structural and soluble proteins and an increase in free amino acid and protease activity levels in contrast to protein decrement were observed in 7 and 15 days of exposure, but on 30 days of exposure all the values got nearer to normalcy. The restoration of different protein fractions to normalcy implies that after 15 days of exposure there seems to exist an oscillatory phase in protein turnover towards a more synthetic phase leading to the establishment of recovery and adaptation phenomena.     

Zirconium Determination by ED-XRF: a Critical Evaluation of Silicate Reference Materials as Calibration Standards

An assessment of the difficulties in determining zirconium by various techniques indicates that X-ray fluorescence analysis has several favourable characteristics, provided the technique can be calibrated reliably. After critical evaluation, a group of silicate reference materials was selected to calibrate energy dispersive X-ray fluorescence instrumentation. The accuracy of the resultant calibration was verified by a standards addition procedure. New zirconium data were obtained on a wide range of reference samples and compared with values from recent compilations.