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111.
Michael Pearlman Carey Noll Peter Dunn Julie Horvath Van Husson Paul Stevens Mark Torrence Hoai Vo Scott Wetzel 《Journal of Geodynamics》2005,40(4-5):470
The International Laser Ranging Service (ILRS) was established in September 1998 as a service within the IAG to support programs in geodetic, geophysical, and lunar research activities and to provide data products to the International Earth Rotation Service (IERS) in support of its prime objectives. Now in operation for 5 years, the ILRS develops: (1) the standards and specifications necessary for product consistency and (2) the priorities and tracking strategies required to maximize network efficiency. The service collects, merges, analyzes, archives and distributes satellite and lunar laser ranging data to satisfy a variety of scientific, engineering, and operational needs and encourages the application of new technologies to enhance the quality, quantity, and cost effectiveness of its data products. The ILRS works with: (1) the global network to improve station performance; (2) new satellite missions in the design and building of retroreflector targets to maximize data quality and quantity and (3) science programs to optimize scientific data yield. The ILRS Central Bureau maintains a comprehensive web site as the primary vehicle for the distribution of information within the ILRS community. The site, which can be accessed at: http://ilrs.gsfc.nasa.gov is also available at mirrored sites at the Communications Research Laboratory (CRL) in Tokyo and the European Data Center (EDC) in Munich.During the last 2 years, the ILRS has addressed very important challenges: (1) data from the field stations are now submitted hourly and made available immediately through the data centers for access by the user community; (2) tracking on low satellites has been significantly improved through the sub-daily issue of predictions, drag functions, and the real-time exchange of time biases; (3) analysis products are now submitted in SINEX format for compatibility with the other space geodesy techniques; (4) the Analysis Working Group is heavily engaged in Pilot Projects as it works toward an ILRS “standard” global solution and (5) SLR has significantly increased its participation in the International Terrestrial Reference Frame (ITRF) activity, which is important to the success of IGGOS. 相似文献
112.
Stable isotope data on humid tropical hydrology are scarce and, at present, no such data exist for Borneo. Delta18O, δ2H and δ13C were analysed on 22 water samples from different parts of the Sungai (river) Niah basin (rain, cave drip, rainforest pool, tributary stream, river, estuary, sea) in north‐central Sarawak, Malaysian Borneo. This was done to improve understanding of the modern stable isotope systematics of the Sungai Niah basin, essential for the palaeoenvironmental interpretation of the Late Quaternary stable isotope proxies preserved in the Great Cave of Niah. The Niah hydrology data are put into a regional context using the meteoric water line for Southeast Asia, as derived from International Atomic Energy Agency/World Meteorological Organization isotopes in precipitation network data. Although the Niah hydrological data‐set is relatively small, spatial isotopic variability was found for the different subenvironments of the Sungai Niah basin. A progressive enrichment occurs towards the South China Sea (δ18O ?4·6‰; δ2H ?29·3‰; δ13C ?4·8‰) from the tributary stream (δ18O ?8·4‰; δ2H ?54·7‰; δ13C ?14·5‰) to up‐river (δ18O c. ?8‰; δ2H c. ?51‰; δ13C c. ?12‰) and down‐river values (δ18O c. ?7·5‰; δ2H c. ?45‰; δ13C c. ?11‰). This is thought to reflect differential evaporation and mixing of different components of the water cycle and a combination of depleted biogenic δ13C (plant respiration and decay) with enriched δ13C values (due to photosynthesis, atmospheric exchange, mixing with limestone and marine waters) downstream. Cave drip waters are relatively enriched in δ13C as compared to the surface waters. This may indicate rapid degassing of the cave drips as they enter the cave atmosphere. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
113.
The 1998 eruption of Volcán Cerro Azul in the Galápagos Islands produced two intra-caldera vents and a flank vent that erupted more than 1.0×108 m3 of lava. Lava compositions changed notably during the 5-week eruption, and contemporaneous eruptions in the caldera and on the flank produced different compositions. Lavas erupted from the flank vent range from 6.3 to 14.1% MgO, nearly the entire range of MgO contents previously reported from the volcano. On-site monitoring of eruptive activity is linked with petrogenetic processes such that geochemical variations are evaluated in a temporal context. Lavas from the 1998 eruption record two petrogenetic stages characterized by progressively more mafic lavas as the eruption proceeded. Crystal compositions, whole rock major and trace element compositions, and isotope ratios indicate that early lavas are the product of mixing between 1998 magma and remnant magma of the 1979 eruption. Intra-caldera lavas and later lavas have no 1979 signature, but were produced by the 1998 magma incorporating olivine and clinopyroxene xenocrysts. Thus, early magma petrogenesis is characterized by mixing with the 1979 magma, followed by the magma progressively entraining wehrlite cumulate mush.Editorial Responsibility: M.R. Carroll 相似文献
114.
Mark Cleary 《Singapore journal of tropical geography》2005,26(3):359-374
The paper examines how land and forest management policies were elaborated in French Indochina circa 1900–40. It places their development in the context of a scientific and economic discourse about the value of land and forest resources, the most appropriate ways in which they might be exploited and the relationship between colonial science and indigenous knowledge. By focusing on debates and laws relating to the development of small‐scale and plantation farming systems (Land Code legislations) and forest management and exploitation (Forest Code legislations) the paper seeks to ground arguments about Western conceptions of the “tropics” within a discussion of national policy development and impacts. Focusing primarily on Cochinchina and Annam (southern and central Vietnam) and drawing on materials from French archives, the paper shows how changes in both attitudes and legislation have had lasting consequences on systems of property rights in forest management and on the place and status of indigenous peoples in Indochina. 相似文献
115.
Recent research has highlighted the value of employing the idea of networks to describe the interrelatedness of today's globalizing economy. Networks facilitate flows of knowledge, ideas, managerial techniques and capital between firms both within and across political borders. This paper argues that the reconstruction of social connections through which information is created, given value and exchanged is fundamental to an understanding of not only contemporary but also historical patterns of economic globalization. We focus on the networks of the capitalist elite running 12 major multinational enterprises, active across British imperial territories, between c .1900 and c .1930. An examination is made of the economic and spatial interlocks between firms created by board members who were multiple directors. Social underpinnings of multiple directorates are examined by exploring the common, overlapping social spheres within which individuals engaged. A clearer grasp of the ways in which corporate activity operated in the early 1900s can provide a better understanding of the social context of global economic operations. 相似文献
116.
Kelly Addy Arthur Gold Barbara Nowicki James McKenna Mark Stolt Peter Groffman 《Estuaries and Coasts》2005,28(6):896-908
Coastal waters are severely threatened by nitrogen (N) loading from direct groundwater discharge. The subterranean estuary,
the mixing zone of fresh groundwater and sea water in a coastal aquifer, has a high potential to remove substantial N. A network
of piezometers was used to characterize the denitrification capacity and groundwater flow paths in the subterranean estuary
below a Rhode Island fringing salt marsh.15N-enriched nitrate was injected into the subterranean estuary (in situ push-pull method) to evaluate the denitrification capacity
of the saturated zone at multiple depths (125–300 cm) below different zones (upland-marsh transition zone, high marsh, and
low marsh). From the upland to low marsh, the water table became shallower, groundwater dissolved oxygen decreased, and groundwater
pH, soil organic carbon, and total root biomass increased. As groundwater approached the high and low marsh, the hydraulic
gradient increased and deep groundwater upwelled. In the warm season (groundwater temperature >12 °C), elevated groundwater
denitrification capacity within each zone was observed. The warm season low marsh groundwater denitrification capacity was
significantly higher than all other zones and depths. In the cool season (groundwater temperature <10.5 °C), elevated groundwater
denitrification capacity was only found in the low marsh. Additions of dissolved organic carbon did not alter groundwater
denitrification capacity suggesting that an alternative electron donor, possibly transported by tidal inundation from the
root zone, may be limiting. Combining flow paths with denitrification capacity and saturated porewater residence time, we
estimated that as much as 29–60 mg N could be removed from 11 of water flowing through the subterranean estuary below the
low marsh, arguing for the significance of subterranean estuaries in annual watershed scale N budgets. 相似文献
117.
The Clementine spacecraft orbited the Moon and acquired science data for 10 weeks in the Spring of 1994. During this time
it collected global 11-band multispectral images and near global altimetry. Select areas of the Moon were imaged at 25 m/pixel
in visible light and 60 m/pixel in thermal wavelengths. From these datasets a new paradigm for the evolution of the lunar
crust emerged. The Moon is no longer viewed as a two-terrane planet, the Apollo samples were found not to represent the lunar
crust as a whole, and the complexity of lunar crustal stratigraphy was further revealed. More than ten years later the Clementine
datasets continue to significantly advance lunar science and will continue to do so as new measurements are returned from
planned missions such as Chandrayaan, SELENE, and Lunar Reconnaissance Orbiter. This paper highlights the scientific research
conducted over the last decade using Clementine data and summarizes the influence of Clementine on our understanding of the
Moon. 相似文献
118.
Gold partitioning in melt-vapor-brine systems 总被引:5,自引:0,他引:5
Adam C. Simon Mark R. Frank Philip A. Candela Christoph A. Heinrich 《Geochimica et cosmochimica acta》2005,69(13):3321-3335
We used laser-ablation inductively coupled plasma mass spectrometry to measure the solubility of gold in synthetic sulfur-free vapor and brine fluid inclusions in a vapor + brine + haplogranite + magnetite + gold metal assemblage. Experiments were conducted at 800°C, oxygen fugacity buffered at Ni-NiO (NNO), and pressures ranging from 110 to 145 MPa. The wt% NaCl eq. of vapor increases from 2.3 to 19 and that of brine decreases from 57 to 35 with increasing pressure. The composition of the vapors and brines are dominated by NaCl + KCl + FeCl2 + H2O. Gold concentrations in vapor and brine decrease from 36 to 5 and 50 to 28 μg/g, respectively, and the calculated vapor:brine partition coefficients for gold decrease from 0.72 to 0.17 as pressure decreases from 145 to 110 MPa. These data are consistent with the thermodynamic boundary condition that the concentration of gold in the vapor and brine must approach a common value as the critical pressure is approached along the 800°C isotherm in the NaCl-KCl-FeCl2-HCl-H2O system.We use the equilibrium constant for gold dissolution as AuOH0, extrapolated from lower temperature and overlapping pressure range, to calculate expected concentrations of AuOH0 in our experimental vapors. These calculations suggest that a significant quantity of gold in our experimental vapors is present as a non-hydroxide species. Possible chloridogold(I) species are hypothesized based on the positively correlated gold and chloride concentrations in our experimental vapors. The absolute concentration of gold in our synthetic vapor, brine, and melt and calculated mass partition coefficients for gold between these physicochemically distinct magmatic phases suggests that gold solubility in aqueous fluids is a function of aqueous phase salinity, specifically total chloride concentration, at magmatic conditions. However, though we highlight here the effect of salinity, the combination of our data with data sets from lower temperatures evinces a significant decrease in gold solubility as temperature drops from 800°C to 600°C. This decrease in solubility has implications for gold deposition from ascending magmatic fluids. 相似文献
119.
Maria Schönbächler Mark Rehkämper Manuela A. Fehr Alex N. Halliday Bodo Hattendorf 《Geochimica et cosmochimica acta》2005,69(21):5113-5122
Stepwise dissolutions of the carbonaceous chondrites Orgueil (CI), Murchison (CM) and Allende (CV) reveal large nucleosynthetic anomalies for Zr isotopes that contrast with the uniform compositions found in bulk meteorites. Two complementary nucleosynthetic components are observed: one enriched and one depleted in s-process nuclides. The latter component, characterized by excess 96Zr, is most distinctive in the acetic acid leachate (up to ε96Zr ≈ 50). The excess decreases with increasing acid strength and the final leaching steps of the experiment are depleted in 96Zr and thus enriched in s-process nuclides. Presolar silicon carbide grains are likely host phases for part of the anomalous Zr released during these later stages. However, by mass balance they cannot account for the 96Zr excesses observed in the early leaching steps and this therefore hints at the presence of at least one additional carrier phase with significant amounts of anomalous Zr. The data provide evidence that average solar system material consists of a homogenized mixture of different nucleosynthetic components, which can be partly resolved by leaching experiments of carbonaceous chondrites. 相似文献
120.
Jean-Jacques Peucat Johildo Salomão Figueiredo Barbosa Ivana Conceição de Araújo Pinho Jean-Louis Paquette Hervé Martin C. Mark Fanning Angela Beatriz de Menezes Leal Simone Cruz 《Journal of South American Earth Sciences》2011,31(4):397-413
This work provides five new U–Pb zircon dating and the corresponding Nd isotope data for felsic granulites from the south Itabuna-Salvador-Curaçá Block (ISCB), in the São Francisco Craton, Brazil. Three major sets of felsic granulites can be recognised. The oldest set is tonalitic in composition and of TTG affinity. It is Archaean in age with magmatic zircon cores dated at 2675 ± 11 Ma by LA-ICPMS and up to ca 2.7–2.9 Ga by SHRIMP on an other sample. It exhibits epsilon Nd values between ?8 and ?11 at 2.1 Ga. This Nd signature is similar to that of granulites found in the western Archaean Jequié Block. Cartographically, this set of Archaean terrains represents at least 50% of the granulites in the studied area. The second set corresponds to a Palaeoproterozoic calc-alkaline tonalitic suite with zircon ages from 2019 ± 19 Ma to 2191 ± 10 Ma and epsilon Nd values between ?3 and ?4 at 2.1 Ga, corresponding partially to a newly formed crust. The third set of granulites is also Palaeoproterozoic. It is shoshonitic to monzonitic in composition and synchronous with the high grade metamorphism dated by metamorphic zircons at 2086 ± 7 Ma (average of five samples). The Nd isotope signature for this alkaline set is similar to that of the Palaeoproterozoic calc-alkaline one. Nd isotopes appear to be a very efficient tool to distinguish Archaean from Palaeoproterozoic felsic protoliths in granulitic suites of the Itabuna-Salvador-Curaçá Block (ISCB). Finally, the southern part of the ISCB is composed of a mixture of Archaean and Palaeoproterozoic protoliths, in similar amounts, suggesting that it was probably an active margin between 2.1 and 2.2 Ga located on the eastern border of the Archaean Jequié Block. A major crustal thickening process occurred at ca 2.09 Ga in the ISCB and seems significantly younger towards the west, in the Jequié granulites, where an average of 2056 ± 9 Ma is determined for the high grade event. 相似文献