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101.
The concentrations of copper, zinc, cadmium, selenium and mercury were determined in eggs, muscle, liver, kidney and stomach content of nestilings and adults of the Antarctic petrel, Thalassoica antarctica, and its predator, the south polar skua, Chataracta maccormicki, from Svarthamaren, Dronning Maud Land, Antarctica. The dominant food of the petrels is krill, Euphausia superba. The results show relatively high levels of cadmium in krill, which is assumed to be the main reason for the high levels of cadmium in petrels and skuas. Cadmium is almost absent in eggs, but accumulates very rapidly with age in nestlings. The copper concentrations in livers of nestling petrels reach very high levels during growth. This may be seen in connection with physiological development processes. Mercury seems to be accumulated with age and between trophic levels. Among the nestlings, the mercury levels decrease with increasing age, which may be accomplished by the excretion of mercury through the growth of feathers and as a dilution effect during growth. Selenium and mercury are inversely correlated in nestlings. The levels of zinc were similar for different nestling stages and between nestlings and adults in skuas and petrels. 相似文献
102.
H.P. Gunnlaugsson H. Rasmussen M.B. Madsen P. Nørnberg 《Planetary and Space Science》2009,57(5-6):640-645
The Mars Exploration Rover, Spirit, landed on 4 January 2004, in a lava field in Gusev crater on Mars. Samples interpreted as olivine basalt have been investigated with Mössbauer spectroscopy and chemically with Alpha-particle-X-ray spectrometry (APXS).In this contribution we present the results of a new analysis of the Mössbauer spectra of selected rock targets in Gusev crater. The results show that the rock surfaces investigated are inhomogeneous, and show strong enhancement of olivine in the surface layer. By subtraction of the surface signal to obtain the spectrum of the true interior of the rock samples, the measurements show the usual correlation between olivine and iron oxides of olivine basalt.It is argued that the compositional changes observed are related to high temperature oxidation of the rocks, probably during solidification, a process known to lead to anomalously magnetic rocks. The rock Mazatzal is discussed in some detail, and it is suggested that the surface is covered with deposits rich in ferric iron rather than these ferric phases being due to oxidation of the rock. The fact that all the surfaces in this investigation show this same pattern, suggests that the dominating erosion of the surface layer of basaltic rocks at Gusev crater has been mechanical rather than chemical. 相似文献
103.
Erik Høg 《Experimental Astronomy》2009,25(1-3):225-240
Galileo Galilei’s use of the newly invented telescope for astronomical observation resulted immediately in epochal discoveries about the physical nature of celestial bodies, but the advantage for astrometry came much later. The quadrant and sextant were pre-telescopic instruments for measurement of large angles between stars, improved by Tycho Brahe in the years 1570–1590. Fitted with telescopic sights after 1660, such instruments were quite successful, especially in the hands of John Flamsteed. The meridian circle was a new type of astrometric instrument, already invented and used by Ole Rømer in about 1705, but it took a hundred years before it could fully take over. The centuries-long evolution of techniques is reviewed, including the use of photoelectric astrometry and space technology in the first astrometry satellite, Hipparcos, launched by ESA in 1989. Hipparcos made accurate measurement of large angles a million times more efficiently than could be done in about 1950 from the ground, and it will soon be followed by Gaia which is expected to be another one million times more efficient for optical astrometry. 相似文献
104.
Fluid-assisted zircon and monazite growth within a shear zone: a case study from Finnmark,Arctic Norway 总被引:1,自引:0,他引:1
Christopher L. Kirkland Martin J. Whitehouse Trond Slagstad 《Contributions to Mineralogy and Petrology》2009,158(5):637-657
The U–Pb ages, REE content, and oxygen isotopic composition of zircon rims developed within a major shear zone in the Kalak
Nappe Complex (KNC), Arctic Norway have been determined along with the age of monazite crystals. Different generations of
granitic veins have been distinguished based on both field criteria and monazite ages of 446 ± 3 and 424 ± 3 Ma. Within each
of these veins, inherited zircon cores are mantled by homogeneous low CL-response zircon rims which yield a range of concordant
U–Pb dates of ca. 470–360 Ma. Significant numbers of zircon rims coincide with the timing of monazite crystallization. The
zircon rims have moderate light REE enrichment compared to cores, distinctive (Sm/La)
n
values of less than 12, and La between 0.3 and 10 ppm. This indicates free elemental exchange between newly formed zircon
rims and the surrounding matrix. The rims have calculated accumulated alpha-radiation dosages corresponding with a crystalline
structure and δ18O values of 1‰. This implies rim crystallization directly from a zirconium-saturated hydrothermal fluid which was modified
by some silicate melt. Growth of the zircon rims was prolonged and locally variable due to preferential fluid flow. A third
type of zircon can be recognized, forming both rims and cores, with high alpha-radiation doses, and significant enrichment
in La, Pr, and Eu. These are interpreted as low-temperature hydrothermally altered metamict zircons. The high volatile input
and partial melting in the shear zone favoured prolonged zircon rim growth due to its ability to easily nucleate on inherited
seeds. On the other hand, monazite, susceptible to dissolution and re-growth, crystallized in brief episodes, as has been
predicted from theoretical phase diagrams. From a regional perspective, these results elucidate cryptic Ar–Ar cooling ages,
providing the first record of a Late Ordovician heating and cooling phase within the KNC prior to the climactic Scandian collision. 相似文献
105.
106.
Anthony G. Patt Detlef P. van Vuuren Frans Berkhout Asbjørn Aaheim Andries F. Hof Morna Isaac Reinhard Mechler 《Climatic change》2010,99(3-4):383-402
Adaptation is an important element on the climate change policy agenda. Integrated assessment models, which are key tools to assess climate change policies, have begun to address adaptation, either by including it implicitly in damage cost estimates, or by making it an explicit control variable. We analyze how modelers have chosen to describe adaptation within an integrated framework, and suggest many ways they could improve the treatment of adaptation by considering more of its bottom-up characteristics. Until this happens, we suggest, models may be too optimistic about the net benefits adaptation can provide, and therefore may underestimate the amount of mitigation they judge to be socially optimal. Under some conditions, better modeling of adaptation costs and benefits could have important implications for defining mitigation targets. 相似文献
107.
A novel downscaling approach of the ERA40 (ECMWF 40-years reanalysis) data set has been taken and results for comparison with
observations in Norway are shown. The method applies a nudging technique in a stretched global model, focused in the Norwegian
Sea (67°N, 5°W). The effective resolution is three times the one of the ERA40, equivalent to about 30 km grid spacing in the
area of focus. Longer waves (<T42) in the downscaled solution are nudged towards the ERA40 solution, and thus the large-scale
circulation is similar in the two data sets. The shorter waves are free to evolve, and produce high intensities of winds and
precipitation. The comparison to observations incorporate numerous station data points of (1) precipitation (#357), (2) temperature
(#98) and (3) wind (#10), and for the period 1961–1990, the downscaled data set shows large improvements over ERA40. The daily
precipitation shows considerable reduction in bias (from 50 to 11%), and twofold reduction at the 99.9 percentile (from −59
to −29%). The daily temperature showed a bias reduction of about a degree in most areas, and relative large RMSE reduction
(from 7.5 to 5.0°C except winter). The wind comparison showed a slight improvement in bias, and significant improvements in
RMSE. 相似文献
108.
109.
We consider numerical identification of the piecewise constant permeability function in a nonlinear parabolic equation, with the augmented Lagrangian method. By studying this problem, we aim at also gaining some insight into the potential ability of the augmented Lagrangian method to handle permeability estimation within the full two-phase porous-media flow setting. The identification is formulated as a constrained minimization problem. The parameter estimation problem is reduced to a coupled nonlinear algebraic system, which can be solved efficiently with the conjugate gradient method. The methodology is developed and numerical experiments with the proposed method are presented. 相似文献
110.