Monitoring Networks in Fractured Rocks: A Decision Analysis Approach   总被引：1，自引：0，他引：1  

Karen Jardine  Leslie Smith  Tom Clemo 《Ground water》1996,34(3):504-518

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Teaching GIS in Geography*   总被引：2，自引：0，他引：2  

Karen K. Kemp  Michael F. Goodchild  Rustin F. Dodson 《The Professional geographer》1992,44(2):181-191

Although numerous courses in geographic information systems (GIS) have been introduced into the geography curriculum over the past few years, there has been remarkably little debate over the issues involved. This paper first discusses the arguments for geography as an appropriate disciplinary setting for GIS teaching at the undergraduate level. This is followed by a discussion of the nature of GIS courses and their appropriate place in the undergraduate geography curriculum. The final section of the paper describes the NCGIA Core Curriculum project and examines its significance in this broader context.  相似文献   

Miscellaneous information 1989 (Addendum)     

Joseph Arditti  Adisheshappa Nagaraja Rao  Helen Nair 《Bulletin of Volcanology》1993,55(Z1):128

Miscellaneous information 1989 (Addendum)  相似文献   

Manual of planktonic foraminifera: J.A. Postuma. Elsevier,Amsterdam-London-New York, 1971, 420 pp., 1153 illustrations, 3 charts,Dfl. 75.00 (U.S.$ 20.75).     

Helen Tappan 《Sedimentary Geology》1972

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Major and trace elements in igneous rocks from apollo 15     

Philip A. Helmke  Douglas P. Blanchard  Larry A. Haskin  Karen Telander  Charles Weiss  Jeffrey W. Jacobs 《Earth, Moon, and Planets》1973,8(1-2):129-148

The concentrations of major and trace elements have been determined in igneous rocks from Apollo 15. All materials analyzed have typical depletions of Eu except for minerals separated from sample 15085. Four samples have concentrations of trace elements that are similar to those of KREEP. The samples of mare basalt from Apollo 15 have higher concentrations of FeO, MgO, Mn, and Cr and lower concentrations of CaO, Na₂O, K₂O, and rare-earth elements (REE) as compared to the samples of mare basalt from Apollos 11, 12, and 14. The samples can be divided into two groups on the basis of their normative compositions. One group is quartz normative and has low concentrations of FeO while the other is olivine normative and has high concentrations of FeO. The trace element data indicate that the samples of olivine normative basalt could be from different portions of a single lava flow. At least two and possible three parent magmas can be identified from the samples of the quartz normative group on the basis of their concentration ratios of Sm to Eu. Within each group, the compositions of the samples appear to be related by crystallization of olivine or pyroxene. Significant variations of the ratio of concentration of Sm to Eu cannot be produced without plagioclase-liquid equilibrium. The source material of mare basalt may be depleted in Eu. Alternatively, the magmas may have assimilated a small volume of material similar to KREEP.Paper dedicated to Prof. Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.  相似文献   

Quantifying Organization of Atmospheric Turbulent Eddy Motion Using Nonlinear Time Series Analysis   总被引：3，自引：0，他引：3  

Karen H. Wesson  Gabriel G. Katul  Mario Siqueira 《Boundary-Layer Meteorology》2003,106(3):507-525

Using three methods from nonlinear dynamics, we contrast the level of organization inthe vertical wind velocity (w) time series collected in the atmospheric surface layer(ASL) and the canopy sublayer (CSL) for a wide range of atmospheric stability ()conditions. The nonlinear methods applied include a modified Shannon entropy, waveletthresholding, and mutual information content. Time series measurements collected overa pine forest, a hardwood forest, a grass-covered forest clearing, and a bare soil, desertsurface were used for this purpose. The results from applying all three nonlinear timeseries measures suggest that w in the CSL is more organized than that in the ASL, and that as the flows in both layers evolve from near-neutral to near-convective conditions, the level of organization increases. Furthermore, we found that the degree of organization in w associated with changes in is more significant than the transition from CSL to ASL.  相似文献   

Mapping of Ozone and Water in the Atmosphere of Mars near the 1997 Aphelion     

Robert E. NovakMichael J. Mumma  Michael A. DiSanti  Neil Dello Russo  Karen Magee-Sauer 《Icarus》2002,158(1):14-23

We present absolute abundances and latitudinal variations of ozone and water in the atmosphere of Mars during its late northern spring (L_s=67.3°) shortly before aphelion. Long-slit maps of the a¹Δ_g state of molecular oxygen (O₂) and HDO, an isotopic form of water, were acquired on UT January 21.6 1997 using a high-resolution infrared spectrometer (CSHELL) at the NASA Infrared Telescope Facility. O₂(a¹Δ_g) is produced by ozone photolysis, and the ensuing dayglow emission at 1.27 μm is used as a tracer for ozone. Retrieved vertical column densities for ozone above ∼20 km ranged between 1.5 and 2.8 μm-atm at mid- to low latitudes (30°S-60°N) and decreased outside that region. A significant decrease in ozone density is seen near 30°N (close to the subsolar latitude of 23.5°N). The rotational temperatures retrieved from O₂(a-X) emissions show a mean of 172±2.5 K, confirming that the sensed ozone lies in the middle atmosphere (∼24 km). The ν₁ fundamental band of HDO near 3.67 μm was used as a proxy for H₂O. The retrieved vertical column abundance of water varies from 3 precipitable microns (pr-μm) at ∼30°S to 24 pr-μm at ∼60°N. We compare these results with current photochemical models and with measurements obtained by other methods.  相似文献   

Were Greek temples oriented towards aurorae?     

Ioannis Liritzis  Helen Vassiliou 《Astronomy& Geophysics》2006,47(1):1.14-1.18

Ioannis Liritzis and Helen Vassiliou assess the evidence that the Ancient Greeks saw the aurora borealis, and that it was a rare and special event, strongly enough associated with particular gods to build temples of unusual orientation.  相似文献   

Atmospheric Electrification in the Solar System     

Karen L. Aplin 《Surveys in Geophysics》2006,27(1):63-108

Atmospheric electrification is not a purely terrestrial phenomenon: all Solar System planetary atmospheres become slightly electrified by cosmic ray ionisation. There is evidence for lightning on Jupiter, Saturn, Uranus and Neptune, and it is possible on Mars, Venus and Titan. Controversy surrounds the role of atmospheric electricity in physical climate processes on Earth; here, a comparative approach is employed to review the role of electrification in the atmospheres of other planets and their moons. This paper reviews the theory, and, where available, measurements, of planetary atmospheric electricity which is taken to include ion production and ion–aerosol interactions. The conditions necessary for a planetary atmospheric electric circuit similar to Earth’s, and the likelihood of meeting these conditions in other planetary atmospheres, are briefly discussed. Atmospheric electrification could be important throughout the solar system, particularly at the outer planets which receive little solar radiation, increasing the relative significance of electrical forces. Nucleation onto atmospheric ions has been predicted to affect the evolution and lifetime of haze layers on Titan, Neptune and Triton. Atmospheric electrical processes on Titan, before the arrival of the Huygens probe, are summarised. For planets closer to Earth, heating from solar radiation dominates atmospheric circulations. However, Mars may have a global circuit analogous to the terrestrial model, but based on electrical discharges from dust storms. There is an increasing need for direct measurements of planetary atmospheric electrification, in particular on Mars, to assess the risk for future unmanned and manned missions. Theoretical understanding could be increased by cross-disciplinary work to modify and update models and parameterisations initially developed for a specific atmosphere, to make them more broadly applicable to other planetary atmospheres.  相似文献   

Microbial ecology of the stratified water column of the Black Sea as revealed by a comprehensive biomarker study   总被引：2，自引：0，他引：2  

Stuart G. Wakeham  Rudi Amann  Katherine H. Freeman  Ellen C. Hopmans  Bo Barker Jrgensen  Isabell F. Putnam  Stefan Schouten  Jaap S. Sinninghe Damst  Helen M. Talbot  Dagmar Woebken 《Organic Geochemistry》2007,38(12):2070-2097

The stratified water column of the Black Sea is partitioned into oxic, suboxic, and euxinic zones, each characterized by different biogeochemical processes and by distinct microbial communities. In 2003, we collected particulate matter by large volume in situ filtration at the highest resolution to date for lipid biomarker analysis and bacterioplankton for enumeration of major prokaryotic groups. Abundances of several prokaryotic groups were estimated using CARD-FISH probes specific for Bacteria, Archaea (Crenarchaeota and Euryarchaeota), epsilonproteobacteria (mainly sulfide oxidizers) and sulfate reducing bacteria. We also measured a wide range of bacterial and archaeal lipid biomarkers. Depth distributions of diagnostic biomarkers are matched with zonation of microbial processes, including aerobic bacterial oxidation of methane, oxidation of ammonium by bacteria and archaea, metal reduction, and sulfide oxidation at the chemocline, and bacterial sulfate reduction and anaerobic oxidation of methane by archaea in the anoxic zone. Cell densities for archaea and sulfate reducing bacteria are estimated based on water column biomarker concentrations and compared with CARD-FISH results.  相似文献