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161.
Robert Mendelsohn Alan Basist Ariel Dinar Pradeep Kurukulasuriya Claude Williams 《Climatic change》2007,81(1):85-99
This paper measures the influence of climate normals (average long-term surface wetness and temperature) and interannual climate
variance on farms in the United States and Brazil using satellite data. The paper finds that just climate normals or just
climate variance variables can explain both net revenues and how much land is used for cropland. However, because they are
correlated with each other, it is important to include both normals and variance in the same statistical model to get accurate
measures of their individual contribution to farm outcomes. In general, higher climate variance increases the probability
that land is used for cropland in both countries and higher temperatures reduce both cropland and land values. Other annual
effects were not consistent across the two countries. 相似文献
162.
Gérard Thuillier Michel Hersé Paul C. Simon Dietrich Labs Holger Mandel Didier Gillotay Thomas Foujols 《Solar physics》1998,177(1-2):41-61
The SOLSPEC instrument has been built to carry out solar spectral irradiance measurements from 200 to 3000 nm. It consists of three spectrometers designed to measure the solar spectral irradiance in ultraviolet, visible, and infrared domains. It flew with the ATLAS I mission in March 1992. This paper is dedicated to the visible part of the solar spectrum. Comparisons with recent data are shown and differences below 450 nm are discussed. 相似文献
163.
Michel Westphal Evgueni L. Gurevitch Boris V. Samsonov Hugues Feinberg & Jean Pierre Pozzi 《Geophysical Journal International》1998,134(1):254-266
The deep drill hole SG6 in western Siberia (66°N, 78.5°E) penetrated 1.1 km of lower Triassic basalts, which are possibly an extension of the central Siberian Permo– Triassic flood basalt province. About 300 samples of these basalts were progressively demagnetized and measured. Principal component analysis often shows multiple magnetizations carried by haematite and magnetite. The corrected mean inclinations are +77° and −77° for the haematite component. A magnetostratigraphic scale was derived and showed a N–R–N–R–N succession. This is quite different from the Noril'sk and Taimyr typical polarity scale, R–N.
The basalts found in the SG6 deep drill hole are slightly younger than those of central Siberia and Taimyr. They correspond to middle–upper Induan age, whereas the Noril'sk and Taimyr sections correspond to an uppermost Permian and lower Induan age. Altogether they indicate that, after a high output rate of volcanic material near the Permo–Triassic boundary, this activity slowed down drastically on the Siberian platform and Taimyr, but persisted for several million years in western Siberia. 相似文献
The basalts found in the SG6 deep drill hole are slightly younger than those of central Siberia and Taimyr. They correspond to middle–upper Induan age, whereas the Noril'sk and Taimyr sections correspond to an uppermost Permian and lower Induan age. Altogether they indicate that, after a high output rate of volcanic material near the Permo–Triassic boundary, this activity slowed down drastically on the Siberian platform and Taimyr, but persisted for several million years in western Siberia. 相似文献
164.
165.
Cosmogenic nuclides in extraterrestrial matter provide a wealth of information on the exposure and collision histories of
small objects in space and on the history of the solar and galactic cosmic radiation. The interpretation of the observed abundances
of cosmogenic nuclides requires detailed and accurate knowledge of their production rates. Accelerator experiments provide
a quantitative basis and the ground truth for modeling cosmogenic nuclide production by measurements of the relevant cross
sections and by realistic simulations of the interaction of galactic protons with meteoroids under completely controlled conditions,
respectively. We review the establishment of physical model calculations of cosmogenic nuclide production in extraterrestrial
matter on the basis of such accelerator experiments and exemplify this approach by presenting new experimental and theoretical
results for the cosmogenic nuclide44Ti. The model calculations describe all aspects of cosmogenic nuclide production and allow the determination of long-term
solar and galactic cosmic ray spectra and a consistent interpretation of cosmogenic nuclides in extraterrestrial matter. 相似文献
166.
Matheron (1971) proposed an approximation of the extension variance in IR. We propose in this note an extension of this formula in IR 2 , based on a MacLaurin formula. Its application is shown in an example, the estimation of the maximum depressional storage of a soil surface. 相似文献
167.
Using the standard map as a model problem and in the spirit of cluster analysis we have studied the invariance of the distributions of different indicators introduced to detect and measure weak chaos. We show that the problem is less straightforward than expected and that, except for very strong chaotic dynamical systems, all the complexities (islands, sticking phenomena, cantori) of mixed Hamiltonian systems are reflected into the indicators of convergence towards invariant distributions. 相似文献
168.
Michel Pichavant 《Contributions to Mineralogy and Petrology》1981,76(4):430-439
An experimental study of the effect of boron in the water saturated Q-Or-Ab-B2O3-H2O system has been performed at P=1 Kbar to provide experimental data and explain the role of boron in some late magmatic and early hydrothermal events. Experiments were conducted between 500° C and 800° starting from a gel, or a previously crystallized gel, and variable amounts of boron (0 to 18% B2O3) added to water. The phases obtained were: quartz, sanidine, albite, silicate liquid quenched to glass, and aqueous vapour phase. Boric acids, borates and isotropic low index materials were found in the quenched vapour phase. An aluminium silicate-like mineral, not yet fully identified, is also present.The solidus temperature of the Q-Or-Ab composition is lowered by 60° C when 5 wt. % B2O3 is added and by more than 130° C when 17wt. % B2O3 is added. Compositions of equilibrated silicate melts and vapours were obtained between 780° C and 750° C for various B2O3 concentrations. The vapour phase is B and Si rich. It is also enriched in Na with respect to K, and in alkalis with respect to Al. Its silicate solute content is higher than in experiments with pure water. The solubility of water is increased by the addition of boron in Q-Or-Ab melts. Microprobe data show that the melts equilibrated with vapour phases become hyperaluminous and more potassic than sodic. The partition coefficient of boron is in favour of the vapour (k
D=B2O3% in melt/B2O3% in vapour=0.33±0.02). The effect of the interaction between the silicate phases and the vapour is discussed. Comparison is made between the behaviour of boron and that of chlorine and fluorine. Geological applications are also provided, which concern the influence of boron on minimum melting, on muscovite stability and on the hypersolvus-subsolvus transition. 相似文献
169.
Structure,diversity and stability of two oligochaete communities according to sedimentary inputs in Lake Geneva (Switzerland) 总被引:3,自引:1,他引:3
Two oligochaete communities were sampled monthly during one year in two 35 m deep locations of Lake Geneva (Switzerland).
Organic sedimentation was lower and less variable in station 1 than in station 2 (157 versus 214 g C m−2yr−1). The oligochaete community in station 1 was more diverse and more stable (persistent over time) than in station 2, as long
as the organic sedimentation was low. Diversity and stability decreased in station 1 when the organic sedimentation increased,
and during anOscillatoria bloom. The less diverse community in station 2 was more resistent to these changes. Diversity was associated with environmental
stability, but resistance to perturbation was greater in the simpler community which is adapted to changing environmental
conditions. The value of oligochaete communities as an indicator of the level of eutrophication was reassessed according to
our present data. Changes in the structure of oligochaete communities were related to changes in sedimentation processes. 相似文献
170.
Willard S. Moore Kenneth W. Bruland Jacqueline Michel 《Earth and Planetary Science Letters》1981,53(3):391-399
Samples from the MANOP Santa Barbara Basin sediment trap intercomparison were analyzed for the isotopes of uranium, thorium, radium, lead, and polonium. All of the traps showed approximately the same compositions and isotopic ratios, indicating that they trapped similar materials. The234Th flux via falling particles was very close to the flux predicted from the production and scavenging rates of234Th from the water column. The210Pb content of the trapped particles and the surface sediments were the same, however, the measured flux of210Pb was seven times greater than the predicted flux. Predicted and measured fluxes of228Th and210Po were similarly out of balance. To explain this apparent inconsistency, we suggest (as others have done) that the Santa Barbara Basin is an area where scavenging from the water column is intensified and where sediments deposited initially on the margins may be physically remobilized on a short time scale. These two effects increase the apparent area from which the basin derives the longer-lived isotopes but does not increase significantly the supply of the short-lived234Th. 相似文献