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131.
Yuki Shibazaki Eiji Ohtani Hiroshi Fukui Takeshi Sakai Seiji Kamada Daisuke Ishikawa Satoshi Tsutsui Alfred Q.R. Baron Naoya Nishitani Naohisa Hirao Kenichi Takemura 《Earth and Planetary Science Letters》2012
We have determined the density evolution of the sound velocity of dhcp-FeHx (x ≈ 1) up to 70 GPa at room temperature, by inelastic X-ray scattering and by X-ray diffraction. We find that the variation of VP with density is different for the ferromagnetic and nonmagnetic dhcp-FeHx, and that only nonmagnetic dhcp-FeHx follows Birch's law. Combining our results with Birch's law for iron and assuming an ideal two-component mixing model, we obtain an upper bound of the hydrogen content in the Earth's inner core, 0.23(6) wt.% H, corresponding to FeH0.13(3). The iron alloy with 0.23(6) wt.% H can satisfy the density, and compressional and shear sound velocities of the PREM inner core, assuming that there are no other light elements in the inner core. 相似文献
132.
Anozie Ebigbo Rainer Helmig Alfred B. Cunningham Holger Class Robin Gerlach 《Advances in water resources》2010
The concentration of greenhouse gases – particularly carbon dioxide (CO2) – in the atmosphere has been on the rise in the past decades. One of the methods which have been proposed to help reduce anthropogenic CO2 emissions is the capture of CO2from large, stationary point sources and storage in deep geological formations. The caprock is an impermeable geological layer which prevents the leakage of stored CO2, and its integrity is of utmost importance for storage security. Due to the high pressure build-up during injection, the caprock in the vicinity of the well is particularly at risk of fracturing. Biofilms could be used as biobarriers which help prevent the leakage of CO2 through the caprock in injection well vicinity by blocking leakage pathways. The biofilm could also protect well cement from corrosion by CO2-rich brine. 相似文献
133.
134.
Urban social vulnerability assessment with physical proxies and spatial metrics derived from air- and spaceborne imagery and GIS data 总被引:2,自引:0,他引:2
Risk management in urban planning is of increasing importance to mitigate the growing amount of damage and the increasing
number of casualties caused by natural disasters. Risk assessment to support management requires knowledge about present and
future hazards, elements at risk and different types of vulnerability. This article deals with the assessment of social vulnerability
(SV). In the past this has frequently been neglected due to lack of data and assessment difficulties. Existing approaches
for SV assessment, primarily based on community-based methods or on census data, have limited efficiency and transferability.
In this article a new method based on contextual analysis of image and GIS data is presented. An approach based on proxy variables
that were derived from high-resolution optical and laser scanning data was applied, in combination with elevation information
and existing hazard data. Object-oriented image analysis was applied for the definition and estimation of those variables,
focusing on SV indicators with physical characteristics. A reference Social Vulnerability Index (SVI) was created from census
data available for the study area on a neighbourhood level and tested for parts of Tegucigalpa, Honduras. For the evaluation
of the proxy-variables, a stepwise regression model to select the best explanatory variables for changes in the SVI was applied.
Eight out of 47 variables explained almost 60% of the variance, whereby the slope position and the proportion of built-up
area in a neighbourhood were found to be the most valuable proxies. This work shows that contextual segmentation-based analysis
of geospatial data can substantially aid in SV assessment and, when combined with field-based information, leads to optimization
in terms of assessment frequency and cost. 相似文献
135.
136.
137.
Oxygen isotope systematics of gem corundum deposits in Madagascar: relevance for their geological origin 总被引:1,自引:1,他引:1
Gaston Giuliani Anthony Fallick Michel Rakotondrazafy Daniel Ohnenstetter Alfred Andriamamonjy Théogène Ralantoarison Saholy Rakotosamizanany Marie Razanatseheno Yohann Offant Virginie Garnier Christian Dunaigre Dietmar Schwarz Alain Mercier Voahangy Ratrimo Bruno Ralison 《Mineralium Deposita》2007,42(3):251-270
The oxygen isotopic composition of gem corundum was measured from 22 deposits and occurrences in Madagascar to provide a gemstone
geological identification and characterization. Primary corundum deposits in Madagascar are hosted in magmatic (syenite and
alkali basalt) and metamorphic rocks (gneiss, cordieritite, mafic and ultramafic rocks, marble, and calc-silicate rocks).
In both domains the circulation of fluids, especially along shear zones for metamorphic deposits, provoked in situ transformation
of the corundum host rocks with the formation of metasomatites such as phlogopite, sakenite, and corundumite. Secondary deposits
(placers) are the most important economically and are contained in detrital basins and karsts. The oxygen isotopic ratios
(18O/16O) of ruby and sapphire from primary deposits are a good indicator of their geological origin and reveal a wide range of δ18O (Vienna Standard Mean Ocean Water) between 1.3 and 15.6‰. Metamorphic rubies are defined by two groups of δ18O values in the range of 1.7 to 2.9‰ (cordieritite) and 3.8 to 6.1‰ (amphibolite). “Magmatic” rubies from pyroxenitic xenoliths
contained in the alkali basalt of Soamiakatra have δ18O values ranging between 1.3 and 4.7‰. Sapphires are classified into two main groups with δ18O in the range of 4.7 to 9.0‰ (pyroxenite and feldspathic gneiss) and 10.7 to 15.6‰ (skarn in marble from Andranondambo).
The δ18O values for gem corundum from secondary deposits have a wide spread between −0.3 and 16.5‰. The ruby and sapphire found in
placers linked to alkali basalt environments in the northern and central regions of Madagascar have consistent δ18O values between 3.5 and 6.9‰. Ruby from the placers of Vatomandry and Andilamena has δ18O values of 5.9‰, and between 0.5 and 4.0‰, respectively. The placers of the Ilakaka area are characterized by a huge variety
of colored sapphires and rubies, with δ18O values between −0.3 and 16.5‰, and their origin is debated. A comparison with oxygen isotope data obtained on gem corundum
from Eastern Africa, India, and Sri Lanka is presented. Giant placer deposits from Sri Lanka, Madagascar, and Tanzania have
a large variety of colored sapphires and rubies with a large variation in δ18O due to mingling of corundum of different origin: mafic and ultramafic rocks for ruby, desilicated pegmatites for blue sapphire,
syenite for yellow, green, and blue sapphire, and skarn in marbles for blue sapphire. 相似文献
138.
Most iron meteorites presumably formed from the cores of parent bodies having more or less chondritic bulk compositions. Consideration of the behavior of S during condensation and core formation indicates that these cores, at least in the case of groups having high or moderate volatile contents (IIAB, IIIAB), contained a substantial amount of S. When elemental fractionations observed in these iron meteorite groups are compared to model calculations of fractional crystallization it becomes evident that at least the IIAB parent melt, and very likely the IIIAB parent melt as well, did not contain the full S complement of the parent body. We consider three possible scenarios to account for the S depletion: (1) Outgassing of S during parent body differentiation; this was probably only possible if the parent body contained organic material, which is improbable for IIIAB. (2) Liquid immiscibility. Our fractional crystallization model would predict curved log Xvs. log Ni relationships in this case, which for many elements are not observed. (3) Formation of metastable liquid layers by episodic melting during core formation. This is based on the fact that the difference in melting temperature between a FeFeS eutectic and FeNi metals is ~500 K. Two melting episodes would tend to form distinct liquid layers that maintain their identities over the crystallization lifetime of the core.Solidification of the cores parental to the main iron meteorite groups should also produce a significant number of sulfide meteorites. The scarcity of sulfide-rich meteorites can be attributed to their lower mechanical resistance to space attrition, higher ablation during atmospheric passage, and faster weathering on earth. 相似文献
139.
We present an analysis of images of Saturn's moon Titan, obtained by the Voyager 1 spacecraft on November 8-12, 1980. Orange filter (590-640 nm) images were photometrically corrected and a longitudinal average removed from them, leaving residual images with up to 5% contrast, and dominated by surface reflectivity. The resultant map shows the same regions observed at 673 nm by the Hubble Space Telescope (HST). Many of the same albedo features are present in both datasets, despite the short wavelength (600 nm) of the Voyager 1 images. A very small apparent longitudinal offset over the 14 year observation interval places tight constraints on Titan's rotation, which appears essentially synchronous at 15.9458±0.0016 days (orbital period =15.945421±0.000005 days). The detectability of the surface at such short wavelengths puts constraints on the optical depth, which may be overestimated by some fractal models. 相似文献
140.
Alfred Xin Yu 《Astrophysics and Space Science》1993,202(2):237-246
Further exploration of the -field theory as first proposed by Yu (1989) is here presented to cover the equation of motion of a test particle which induces gravitational radiation. The same theory is shown to contain an exact gravitational radiation equation derived as a logical consequence of field equations without extra postulates. In this general dynamic context the theory is renamed The (,A
µ
)-field Theory. 相似文献