The distribution of titanium on the lunar surface     

Albert E. Metzger  Richard E. Parker 《Earth and Planetary Science Letters》1979,45(1):155-171

Titanium concentrations have been derived from measurements with the lunar-orbiting gamma-ray experiment on Apollo 15 and 16 by analyzing a spectral interval in which the titanium signal is relatively enhanced. Landing site soil values provide the reference for a regression curve from which Ti concentrations in 137 regions of adequate counting statistics are calculated. Among the mare regions overflown, the southern portion of Mare Tranquillitatis contains the highest Ti concentration (4.4%), Mare Serenitatis, Mare Fecunditatis, and Mare Smythii have intermediate values corresponding to low-Ti basalts, and Mare Crisium is conspicuously low in Ti (0.9%). Regional values in the western maria range from 1.1% to 4.1%, somewhat higher in the north than in the south, with the highest values seen south and west of Aristarchus. The Aristarchus Plateau appears chemically distinct from the surrounding mare. The younger western basalts mapped by the experiment do not appear to be identical to the Apollo 11 and Apollo 17 high-Ti basalts. Low-Ti basalts predominate in the observed mare regions. Highland Ti concentrations range from undetectable to 1.5% with several exceptions; accuracy is limited by the relatively large uncertainty. Highland results suggest a north-south asymmetry which is not consistent with previously reported results for Fe and Th. Comparisons with telescopic spectral reflectance studies of the maria do not show complete agreement and suggest that effects due to Fe may not have been fully removed from the reflectance data.  相似文献   

Combining Ring Width, Density and Stable Carbon Isotope Proxies to Enhance the Climate Signal in Tree-Rings: An Example from the Southern French Alps   总被引：1，自引：0，他引：1  

Mary Gagen  Danny McCarroll  Jean-Louis Edouard 《Climatic change》2006,78(2-4):363-379

At present the most powerful tree-ring based climate reconstructions use high numbers of growth proxy series (ring width and density) to produce spatially smoothed estimates, such as average Northern Hemisphere summer temperatures. These single parameter reconstructions might be supplemented with regional climate reconstructions capable of capturing variability in more than one climate variable without lower replication compromising statistical quality, if multiple tree ring proxies were used. Pinus sylvestris and Pinus uncinata latewood density, width and δ¹³C series are presented from two sites in the French subalpine zone, east of Briançon. Where two proxies have the same dominant climate control their combination enhances that signal. Where proxies differ in dominant controlling climate variable, combining series allows access to bi-variable calibrations. Using this approach, multi-proxy reconstructions of both temperature and precipitation would better reflect complex synoptic variability in climate on spatially useful scales.  相似文献   

Comparing impacts to shallow-water habitas through time and space     

Karim A. Abood  Susan G. Metzger 《Estuaries and Coasts》1996,19(2):220-228

Impacts to shallow-water estuarine habitats should be assessed in a holistic context reflecting both the interrelatedness of habitats that characterize these environments and the history of impacts, human and natural, that have shaped their present ecology. In a holistic context these habitats are considered to be dynamic associations of macrohabitats and micro-habitats, interacting through time to affect the quantity (Q₁), quality (Q₂), and timing (T) of material and energy transfer within the system. Where data are available, this holistic approach (Q₁, Q₂ and T or Q₂T) allows impacts to be evaluated in a multidimensional framework of time and space. Unfortunately, few data are available to evaluate the long-term implications of timing, the T factor. Recorded observations of most estuarine systems cover tens of years, periods not extensive enough to assess long-term changes to the environment or to distinguish man's impacts from those of nature. Sustained droughts, for example, can cause massive disruption in estuaries, altering habitats and species composition. When these changes occur over periods of 5–10 yr, the changes are difficult to identify and may be attributed to man's activities rather than nature's Using the Hudson River estuary as an example, we have knowledge of historical impacts extending back to the 1700s, ranging from dredging to major droughts. For the Hudson River, recorded observations of rainfall and river flow extend back about 70 yr; however, tree rings provide a more extensive record since tree growth increments are directly dependent upon rainfall. The Hudson River drought record was extended back to 1694 using tree rings. Using the reconstructed record, the relationship between today's conditions—flow and average location of the ocean-derived salt front—can be placed in a historical context. This historical perspective allows us to place present-day human impacts into the contex of long-term natural impacts and to discriminate among these effects. The drought example is particularly relevant to shallow-water habitats because these habitats provide an interface between fresh and marine waters. *** DIRECT SUPPORT *** A01BY074 00008  相似文献   

Hydrological conditions over the western Mediterranean basin during the deposition of the cold Sapropel 6 (ca. 175 kyr BP)     

Edouard Bard  Gilles Delaygue  Frauke Rostek  Fabrizio AntonioliSergio Silenzi  Daniel P. Schrag 《Earth and Planetary Science Letters》2002,202(2):481-494

A new oxygen isotope record is reported from a stalagmite collected in the Argentarola Cave located on the Tyrrhenian coast of Italy. As shown from observations and numerical modeling of δ¹⁸O in modern precipitation, the recorded δ¹⁸O variability for this zone is dominated by the amount of precipitation (so-called ‘amount effect’). The δ¹⁸O profile measured in the stalagmite is characterized by a prominent negative excursion (ca. 2-3‰) between 180 and 170 kyr BP. This paleoclimatic feature is interpreted as being due to a relatively wet period which occurred during the penultimate glacial period, more precisely, during Marine Isotope Stage 6.5. This pluvial phase is shown to correspond chronologically to the deposition of the sapropel event 6 (S6). Although this particular sapropel event occurred during a cold phase, the δ¹⁸O excursion is similar to those corresponding to other sapropels (S4, S3 and S2). The evidence for humid conditions during S6 in the western Mediterranean basin agrees with previous studies based on deep-sea sediment cores. Taken collectively, the data suggest that during sapropel events dilution of ocean surface waters was not restricted to the output of the river Nile but was rather widespread over the entire Mediterranean Sea due to increased rainfall.  相似文献   

To Bury or to Burn: Optimum Use of Crop Residues to Reduce Atmospheric CO2   总被引：1，自引：0，他引：1  

Robert A. Metzger  Gregory Benford  Martin I. Hoffert 《Climatic change》2002,54(3):369-374

We argue that sequestering of carbon waste is inherently more efficient andwill probably cost less than using the carbon for biomass burning. The ratioof carbon emitted per unit of primary energy released through combustion, C/E,favors sequestration for fundamental reasons of chemistry and engineering,strongly suggesting a low C/E strategy. This is a more direct way of analysisthan assigning dollar estimates to technologies of which we have as yet littleor no direct experience.  相似文献   

Asymptotic transport parameters in a heterogeneous porous medium: Comparison of two ensemble-averaging procedures     

D. Metzger  H. Kinzelbach  I. Neuweiler  W. Kinzelbach 《Stochastic Environmental Research and Risk Assessment (SERRA)》1999,13(6):396-415

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Magnetar-driven bubbles and the origin of collimated outflows in gamma-ray bursts     

N. Bucciantini  E. Quataert  J. Arons  B. D. Metzger  T. A. Thompson 《Monthly notices of the Royal Astronomical Society》2007,380(4):1541-1553

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A balloon-borne observation of the X-ray source Cygnus XR-1     

Albert E. Metzger  Joseph F. Dolan 《Astrophysics and Space Science》1972,17(2):482-488

An observation of the variable X-ray source Cygnus XR-1 was made with a balloon-borne proportional counter in the energy region 22–70 keV. The resultant spectrum indicates that the source was in a state of maximum flux during the time period 1915–2005 UT, 15 January, 1968. This paper presents results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS7-100, sponsored by the National Aeronautics and Space Administration.  相似文献   

Apollo 15 and 16 results of the integrated geochemical experiment     

I. Adler  J. I. Trombka  P. Lowman  R. Schmadebeck  H. Blodget  E. Eller  L. Yin  R. Lamothe  G. Osswald  J. Gerard  P. Gorenstein  P. Bjorkholm  H. Gursky  B. Harris  J. Arnold  A. Metzger  R. Reedy 《Earth, Moon, and Planets》1973,7(3-4):487-504

A number of experiments carried in orbit on the Apollo 15 and 16 spacecraft were used in the compositional mapping of the lunar surface. The observations involved measurements of secondary (fluorescent) X-rays, gamma rays and alpha particle emissions. A large scale compositional map of over 20% of the lunar surface was obtained for the first time. It was possible to demonstrate significant chemical differences between the mare and the highlands, to find specific areas of high radioactivity and to learn something about the composition of the Moon's hidden side.Paper dedicated to Professor Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.  相似文献   

Stakeholder integrated research (STIR): a new approach tested in climate change adaptation research     

Marc Gramberger  Katharina Zellmer  Kasper Kok  Marc J. Metzger 《Climatic change》2015,128(3-4):201-214

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