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May Jadallah Alycia M. Hund Jonathan Thayn Joel Garth Studebaker Zachary J. Roman Elizabeth Kirby 《The Journal of geography》2017,116(4):139-151
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. 相似文献
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Trond H. Torsvik Elizabeth A. Eide Joe G. Meert Mark A. Smethurst & Harald J. Walderhaug 《Geophysical Journal International》1998,135(3):1045-1059
The Bøverbru and Lunner dyke ages are statistically concordant. However, the palaeomagnetic signature of the Bøverbru dyke is complex, and directions from the margins and the interior of the dyke differ in polarity. Therefore, the new Early Triassic palaeomagnetic pole for Baltica (Eurasia) is exclusively based on the less complex Lunner dykes and contacts (palaeomagnetic pole: latitude=52.9°N, longitude=164.4°E, dp / dm =4.5 ° /7.3°). The early Triassic palaeomagnetic pole [mean age: 243±5 Ma (2 σ )] is slightly different from the Upper Carboniferous–Permian (294–274 Ma) and Kiaman-aged poles from the Oslo Rift. 相似文献
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Information regarding climatic conditions during plant growth is preserved by the oxygen-isotope composition of biogenic silica (phytoliths) deposited in grasses. The O-isotope compositions of phytoliths and the plant water from which they precipitate are dependent on soil-water δ18O values, relative humidity, evapotranspiration rates, and temperature. Plant water and phytoliths from two grass species, Ammophila breviligulata (C3) and Calamovilfa longifolia (C4) at Pinery Provincial Park in southwestern Ontario, Canada, were examined to determine the variability in their δ18O values. Stem water was unfractionated from soil-water in oxygen isotopic composition and the δ18O values of stem silica provide a good proxy for the soil water available to roots during the growing season. Greater spatial and temporal variation in the δ18O values of water in the top 5 cm of the soil, and their enhanced sensitivity to evaporative 18O enrichment, are reflected in the generally higher δ18O values of water in the shallow roots and rhizomes of these grasses. Water within the sheath and lower and upper leaf tissues experiences continual evaporation, becoming progressively enriched in 18O as it moves towards the tip of the leaf. However, the water from which leaf silica precipitates has not acquired the extreme 18O enrichment predicted using steady-state models, or measured for midday or average daily leaf water. Possible explanations for this behaviour include preferential deposition of silica at night; the existence of a secluded water fraction within the leaf, which experiences smaller diurnal variations in isotopic composition than leaf water at sites of evaporation; kinetic isotope effects during rapid precipitation of leaf silica; and incomplete exchange between the oxygen in the silicic acid and the leaf water. 相似文献
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