AN OCCURRENCE OF CALCIUM HYDROXIDE GROUND WATER IN JORDAN     

Marvin Saines  Hydrogeologist  Peter Dickson  Engineering Geologist  Paul Lambert  Environmental Chemist 《Ground water》1980,18(5):503-503

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Editorial     

B. H. Walker  R. G. Dickson 《Climatic change》1991,18(2-3):115-119

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Low-Energy Cutoffs in Electron Spectra of Solar Flares: Statistical Survey     

E. P. Kontar  E. Dickson  J. Kašparová 《Solar physics》2008,252(1):139-147

The Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) X-ray data base (February 2002 – May 2006) has been searched to find solar flares with weak thermal components and flat photon spectra. Using a regularized inversion technique, we determine the mean electron flux distribution from count spectra for a selection of events with flat photon spectra in the 15 – 20 keV energy range. Such spectral behavior is expected for photon spectra either affected by photospheric albedo or produced by electron spectra with an absence of electrons in a given energy range (e.g., a low-energy cutoff in the mean electron spectra of nonthemal particles). We have found 18 cases that exhibit a statistically significant local minimum (a dip) in the range of 13 – 19 keV. The positions and spectral indices of events with low-energy cutoff indicate that such features are likely to be the result of photospheric albedo. It is shown that if the isotropic albedo correction is applied, all low-energy cutoffs in the mean electron spectrum are removed, and hence the low-energy cutoffs in the mean electron spectrum of solar flares above ∼ 12 keV cannot be viewed as real features. If low-energy cutoffs exist in the mean electron spectra, their energies should be less than ∼ 12 keV.  相似文献   

Multivariate Analysis of Ground Water and Soil Data from a Waste Disposal Site   总被引：1，自引：0，他引：1  

Kevin G. Mumford  John F. MacGregor  Sarah E. Dickson  Richard H. Frappa 《Ground Water Monitoring & Remediation》2007,27(1):92-102

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Stratigraphy and noncultural site formation at the Shurmai Rockshelter (GnJm1) in the Mukogodo Hills of North-Central Kenya     

David D. Kuehn  D. Bruce Dickson 《Geoarchaeology》1999,14(1):63-85

The Shurmai rockshelter (GnJm1) is located in the semiarid Mukogodo Hills region of north central Kenya. The rockshelter cavity is formed in Precambrian granite gneiss. The site contains a stratified sequence of sediments and archaeological materials that date from the end of the African Middle Stone Age (at or before ca. 45,000 yr B.P.) to modern times. The stratigraphic sequence at the Shurmai rockshelter is described and the principal noncultural formation processes responsible for its creation are reconstructed. Extant rockshelter sediments consist predominately of coarse angular rubble produced by rock fall, and additional sands and gravels produced by granular disintegration, slopewash, debris flow activity, and, to a lesser extent, human activity. The more identifiable aspects of the geologic history of the shelter include a number of episodes of rock fall deposition, in situ rock fall weathering, and erosional truncation. The reconstruction of the formation processes active at the Shurmai Rockshelter is used to illustrate how such geoarchaeological analysis clarifies understanding of prehistoric human occupation in rockshelter contexts in general, and in granitic terrane in particular. © 1999 John Wiley & Sons, Inc.  相似文献