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Evans Curry Shelby Hildebrand Mark Kunkei Ann Pittman Derald Walling 《International Journal of Mathematical Education in Science & Technology》2013,44(6):997-1001
Completion and performance data from 92 high ability seventh and eighth grade students in an eight‐week summer programme conducted in 1989 and sponsored by the GTE Service Corporation are examined. 相似文献
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A. Navas D. E. Walling T. Quine J. Machín J. Soto S. Domenech M. López-Vicente 《Journal of Radioanalytical and Nuclear Chemistry》2007,274(2):331-339
The extent of soil erosion in some Spanish semiarid regions has caused great concern regarding the sustainability of soil resources. Accelerated soil erosion, particularly in some Mediterranean areas, is likely to be one of the main environmental problems associated with climate change. Fallout 137Cs has been shown to provide a reliable basis for assessing soil erosion rates in different environments around the world. However, existing information concerning the spatial variation of 137Cs inventories at reference sites has identified a need for further investigation of the factors affecting their spatial variability in semiarid environments, where stony and skeletal soils are predominant. Reference sites at three locations in the central Ebro valley were selected to investigate the 137Cs content of several grain size fractions. Each site included both natural vegetated conditions and cultivated land and the three sites were characterized by different values of mean annual rainfall. The results obtained demonstrate the influence of lithology, land use and climate on the spatial variability of 137Cs inventories that increase from 1190, to 1500 and 1710 Bq·m?2 with increasing annual rainfall values from 300 to 500 mm at the study sites. The soils on marls at the Valareña site had the highest proportion of 137Cs in the coarse fractions of cultivated soils (12%) in comparison with soils developed on limestones at Loma Negra (5%), whereas no 137Cs content was found in the coarse fractions of soils on glacis-terrace materials at Peñaflor. The 137Cs reference inventories are higher in soils on marls and sands at cultivated locations at Valareña and Peñaflor, but have similar values in soils at cultivated and uncultivated locations on limestones at Loma Negra. Therefore, in absence of level undisturbed soils with natural vegetation cover, cultivated flat soils on hard rocks could provide reliable reference inventories. 相似文献
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基于湖库沉积剖面137Cs变化的流域表层侵蚀速率计算模型 总被引:6,自引:0,他引:6
根据湖库沉积剖面中1970年以后的137Cs浓度递减速率,推导出农耕和非农耕流域平均表层侵蚀速率的理论模型.选择了国内外的一些湖泊和水库,利用实测数据和已有的研究资料对模型计算结果进行了验证.证明了该计算模型的在小流域尺度上有较高的精确度,为流域侵蚀产沙估算,特别是对无常规观测数据地区水土流失的评价提供了便捷的替代性技术方法和途径. 相似文献
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Maureen A. Walling Shengchun Wang Hua Shi Jason R. E. Shepard 《Analytical and bioanalytical chemistry》2010,398(3):1263-1271
For a better understanding of complex biological processes, it is desirable to simultaneously follow the dynamics of multiple components in living cells or organisms in real time. An encoding scheme was developed that enables the observation of multiple cell populations with single-cell resolution. Specifically, different yeast cell types were labeled with quantum dots and added to an array of microwells, where they randomly self-assemble into the complementary-sized cavities. Quantum dots conjugated to cells externally, internally, or in combination generated unique optical patterns to differentiate various cell types in the array. For the model system described herein, cells were monitored for their lacZ expression levels through the processing of a fluorescent precursor by ß-galactosidase. The encoding schemes employed were independent of the reporter emission and had no affect on the cellular activity. The live cell array platform allowed analysis of hundreds of individual cells simultaneously and continuously in real time. By coupling this platform with quantum dot cell labeling, the utility of this array format is extended to mixed cellular populations. Figure
Three images of individual cells localized on a microarray: (left) white light image. (center) false color image of the quantum dot-encoded cells, and (right) an overlay image of the white light and encoding images. 相似文献
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Rosemary Cogan Evans Curry Derald Walling 《International Journal of Mathematical Education in Science & Technology》2013,44(4):619-632
Virtually from its inception psychophysics has been caught on the horns of the dilemma as to the proper form of the fundamental psychophysical law. This paper illustrates an integration of two competing theories. 相似文献
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By comparison of volumes and 137Cs contents of the deposited sediments before and after 1993, changes of specific sediment yields and relative sediment contributions
from the gully area and from the inter gully area after closing cultivation on the later area on a small catchment of Zhaojia
Gully, in the Rolling Loess Plateau, are analyzed in this paper. Closing cultivation in a large scale has not resulted in
decrease but increase of specific sediment yield of the catchment, in sharp decrease of the sediment yield and the relative
sediment contribution of the inter-gully area, and in increase of the sediment yield and the contribution of the gully area,
for a short term. The mean specific sediment yield of 29650 t km−2 a−1 of 1994–1996 in the catchment was 2.2 times the average value of 13413 t km−2 a−1 for a long term. The specific sediment yield of the inter-gully area decreased from the 14335 t km−2 a−1 in 1994 to 7034 t km−2 a−1 in 1995 and 3517 t km−2 a−1 in 1996, while the yield of the gully area varied between 44944 and 62136 t km−2 a−1 during the period of 1994–1996 which was much greater than the value of 21118 t km−2 a−1 before 1993. The relative sediment contribution from the inter-gully area decreased from 23% in 1994 to 15% in 1995 and 6%
in 1996, while the contribution from the gully area increased from 77% in 1994 to 85% in 1995 and 94% in 1996. It is suggested
that compacting of ploughed soils resulted in increasing of the erosion resistance but in decreasing of the precipitation
infiltration, therefore, the soil erosion reduced but the runoff amount increased on the inter-gully area. Increase of delivering
runoff from the inter-gully area to the gully area should result in activeness of gully erosion and mass movements, consequently,
in increase of the total sediment yield from the catchment. 相似文献
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Lynne H. Walling 《The Ramanujan Journal》2018,47(3):475-499
We find nice representatives for the 0-dimensional cusps of the degree n Siegel upper half-space under the action of \(\Gamma _0(\mathcal N )\). To each of these, we attach a Siegel Eisenstein series, and then we make explicit a result of Siegel, realizing any integral weight average Siegel theta series of arbitrary level \(\mathcal N \) and Dirichlet character \(\chi _{_L}\) modulo \(\mathcal N \) as a linear combination of Siegel Eisenstein series. 相似文献