Integrating Geospatial Technologies in Fifth-Grade Curriculum: Impact on Spatial Ability and Map-Analysis Skills

This study explores the effects of geographic information systems (GIS) curriculum on fifth-grade students' spatial ability and map-analysis skills. A total of 174 students from an urban public school district and their teachers participated in a quasi-experimental design study. Four teachers implemented a GIS curriculum in experimental classes over six weeks while three teachers continued with regular teaching in control classes. Both groups completed pre- and post-tests measuring spatial ability and map-analysis skills. Students in the GIS classes demonstrated more growth over time in spatial ability and map-analysis skills than did their peers in the control classes.     

Electron-beam induced amorphization of stishovite: Silicon-coordination change observed using Si K-edge extended electron energy-loss fine structure

The analysis of the extended energy-loss fine structure (EXELFS) of the Si K-edge for sixfold-coordinated Si in synthetic stishovite and fourfold-coordinated Si in natural α-quartz is reported by using electron energy-loss spectroscopy (EELS) in combination with transmission electron microscopy (TEM). The stishovite Si K-edge EXELFS spectra were measured as a time-dependent series to document irradiation-induced amorphization. The amorphization was also investigated through the change in Si K- and O K-edge energy-loss near edge structure (ELNES). For α-quartz, in contrast to stishovite, electron irradiation-induced vitrification, verified by selected area electron diffraction (SAED), produced no detectable changes of the EXELFS. The Si K-edge EXELFS were analysed with the classical extended X-ray absorption fine structure (EXAFS) treatment and compared to ab initio curve-waved multiple-scattering (MS) calculations of EXAFS spectra for stishovite and α-quartz. Highly accurate information on the local atomic environment of the silicon atoms during the irradiation-induced amorphization of stishovite is obtained from the EXELFS structure parameters (Si−O bond distances, coordination numbers and Debye-Waller factors). The mean Si−O bond distance R and mean Si coordination number N changes from R=0.1775 nm and N=6 for stishovite through a disordered intermediate state (R≈0.172 nm and N≈5) to R≈0.167 nm and N≈4.5 for a nearly amorphous state similar to α-quartz (R=0.1609 nm and N=4). During the amorphization process, the Debye-Waller factor (DWF) passes through a maximum value of as it changes from for sixfold to for fourfold coordination of Si. This increase in Debye-Waller factor indicates an increase in mean-square relative displacement (MSRD) between the central silicon atom and its oxygen neighbours that is consistent with the presence of an intermediate structural state with fivefold coordination of Si. The distribution of coordination states can be estimated by modelling the amorphization as a decay process. Using the EXELFS data for amorphization, a new method is developed to derive the relative amounts of Si coordinations in high-pressure minerals with mixed coordination. For the radiation-induced amorphization process of stishovite the formation of a transitory structure with Si largely in fivefold coordination is deduced. Received: 18 December 1996 / Revised, accepted: 20 June 1997     

Ultra-high temperatures from oxygen isotope thermometry of a coesite-sanidine grospydite

The oxygen isotope compositions of coesite, sanidine, kyanite, clinopyroxene and garnet were measured in an ultra-high pressure-temperature grospydite from the Roberts Victor kimberlite, South Africa. The ¹⁸O values (per mil v. SMOW) of each phase and (1 ) are as follows: coesite, 8.62 (0.31); sanidine, 8.31 (0.02); kyanite, 7.98 (0.08); pyroxene, 7.63 (0.11); garnet, 7.53 (0.03). In situ analyses of the coesite with the laser extraction system are ¹⁸O=9.35 (0.08), n=4, demonstrating that the coesite is homogeneous. The coesite has partially inverted to polycrystalline quartz and the pyroxene is extensively altered during uplift. The larger scatter for the mineral separate coesite and pyroxene data may be due to partial reequilibration between the decompression-related breakdown products of these two phases. The anomalously high ¹⁸O value of the grospydite (¹⁸O_wholerock=7.7) is consistent with altered oceanic crust as a source rock. Temperature estimates from a linear regression of all the data to three different published calibrations correspond to an equilibrium temperature of 1310±80°C. The calculated isotopic pressure effect is to lower these estimates by about 40°C at 40 kb. The estimated temperature based on Al–Si disorder in sanidine is 1200±100°C and that from Fe–Mg exchange thermometry between garnet and clinopyroxene is 1100±50°C. Given the large errors associated with thermometry at such high temperatures, it is concluded that the xenolith equilibrated that 1200±100°C. Pressure estimates are 45±5 kb, based on dilution of the univariant equilibria albite = jadeite + coesite and 2 kyanite + 3 diopside = grossular + pyrope + 2coesite. Zoning in the outer 20 m of the feldspar from Ab_0.8 to Ab₁₆ indicates rapid decompression to 25 kb or less. The isotopic temperature estimates are the highest ever obtained and combined with the high degree of Al–Si disorder in sanidine require rapid cooling from ultra-high temperatures. It is inferred that the xenolith was sampled at the time of equilibration, providing a point on the upper Cretaceous geotherm in the mantle below South Africa.     

From regulated access to transferable harvesting rights: Policy insights from New Zealand

The dramatic decline in yields from many of the world's fisheries has prompted an assessment of traditional regulatory approaches to management. Transferable harvesting rights provide an alternative institutional structure in fisheries management. This paper has two aims. First, it links outcomes in the fishery with institutional structure. Second, the paper identifies several important institutional variables if a transition is to be made to from command-and-control management to tradeable rights. In particular, the transition phase must deal with the expectations that attach to the status quo structure of rights in the fishery. The paper's empirical content is drawn from New Zealand's experience with the introduction of transferable harvesting rights.     

A Model For the Effects Of Point-Source Emission Of Aerosols On Groundwater Systems

The effect of natural aerosols on groundwater chemistry is widely accepted, but the effects of anthropogenic aerosol emissions have received relatively little study. This sensitivity analysis examines the factors most significantly influencing the concentration of aerosols in groundwater. Processes include aerosol dispersion from a point source, deposition on the land surface , transport through the unsaturated zone, and mixing with underlying groundwater. The composite simulation model integrates well-documented models for the atmospheric, unsaturated-zone, and saturated-zone systems; models were chosen which could use the most readily obtainable or estimated input parameters. The analysis indicates that point-source aerosol contaminants possess a significant potential to affect aquifer water quality adversely. Furthermore, aerosols may have an impact on background concentrations on a regional scale. The key parameters are the source concentration, net infiltration, transport-velocity distributions in the unsaturated zone, and depth of the water table. We surmise that instances where groundwater contaminant dispersal greatly exceeds predicted travel times could be the result of aerosol contamination and not underestimations of seepage velocities or hydrodynamic dispersion. Aerosol contamination of groundwater should not be dismissed a priori. Résumé: L'impact des aérosols naturels sur la chimie des eaux souterraines est bien connu; mais celui provoqué par les émissions d'aérosols produits par l'homme a été bien peu étudié. Dans ce travail, les facteurs qui influencent de manière significative la concentration en aérosols des eaux souterraines ont été examinés en détail. Les processus en cause comprennent la dispersion de l'aérosol à partir d'une source ponctuelle, le dépôt à la surface du sol, le transport dans la zone non saturée et le mélange avec l'eau de la nappe. Le modèle composite de simulation intègre des modèles bien connu pour l'atmosphère, la zone non saturée et la zone saturée; les modèles choisis sont ceux qui utilisent les paramètres d'entrée les plus faciles à obtenir ou à estimer. L'analyse indique que les contaminants produits par une source ponctuelle peuvent affecter significativement de façon défavorable la qualité des eaux souterraines. En outre, les aérosols peuvent avoir un impact sur les concentrations originelles à l'échelle régionale. Les paramètres-clés sont la concentration à la source, l'infiltration nette et la profondeur de la surface piézométrique. Nous soupçonnons que dans les cas où la dispersion de polluants dans un aquifère dépasse largement les temps de transit prédits par les modèles, il se pourrait que cela soit dû à une contamination par des aérosols et non à une surestimation des vitesses d'infiltration ou de la dispersion hydrodynamique. La contamination des eaux souterraines par des aérosols ne doit pas être rejectée a priori.     

Electron precipitation and ionospheric radio absorption in the auroral zones

Auroral absorption, measured with riometers at various stations, has been compared with the fluxes of energetic particles detected simultaneously by a satellite passing overhead. The absorption and the particle flux are found to be correlated, the relation depending on the time of day. The observed relationship is discussed in the light of computations of the absorption, based on the rates of ion production previously given by Rees and on reasonable atmospheric models. A case is presented for more prolonged comparisons of this kind, the combination of a polar orbit with ground-based observations at the South Pole station being particularly fruitful in this type of experiment.     

Investigation of drainage basin geometry near an anomalously straight reach of the Big Black River,Mississippi, USA

Drainage basin geometry was analyzed in the lower portion of the Big Black River, Mississippi. The study was centered on a reach of the Big Black River that encompasses an anomalous straight reach (ASR) and has morphometric characteristics that differ from those of upstream and downstream reaches. The study area was divided into three reaches, defined by alluvial valley and active floodplain width, sinuosity, and slope. Tributary streams with confluences in the three study reaches were investigated for evidence of surface tilting, and channel and valley slopes and sinuosity were measured. The average stream channel and valley slopes within the middle reach are nearly double those of the upper and lower reaches. Lateral stream migration within the tributary basins was quantitatively analyzed by measuring the asymmetry factor (AF) and transverse topographic symmetry factor (T) indices. While AF results suggest minimal to no lateral migration within the tributaries, the T results show some shifting. The results are inconclusive regarding the possible effect of neotectonic activity in the study area near the ASR. The mean southward migration may indicate a preferred migration direction relative to the general dip of the coastal plain and plunge of the Mississippi Embayment.