U-Th-Pb and Th/U disequilibrium isotope systematics: Precise accessory mineral chronology and melt evolution tracing in the Alpine Bergell intrusion     

Felix Oberli  Martin Meier  Claudio L. Rosenberg 《Geochimica et cosmochimica acta》2004,68(11):2543-2560

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Assessing streams in Germany with benthic invertebrates: selection of candidate metrics   总被引：3，自引：0，他引：3  

Daniel Hering  Carolin Meier  Claudia Rawer-Jost  Christian K. Feld  Regina Biss  Armin Zenker  Andrea Sundermann  Susanne Lohse  Jürgen Bhmer 《Limnologica》2004,34(4):398-415

The process of selecting invertebrate-based candidate metrics for the German stream assessment system is described. The aim was to identify metrics indicating degradation types other than organic pollution and acidification (“general degradation”). For 18 out of 24 German stream types a data base of roughly 2,000 benthic invertebrate samples was generated; for each sample 79 metrics were calculated. Data on land use in the catchment were compiled for all sampling sites, together with data on hydromorphology for many sampling sites. Hydromorphological and land use parameters, which describe a clear gradient in the data sets were identified by Non-metric Multidimensional Scaling (NMS). Correlation analyses between land use/hydromorphological parameters and metric results were calculated separately for the individual stream types. Among those metrics best indicating catchment- and hydromorphological degradation in the majority of stream types are: proportion of Ephemeroptera, Plecoptera and Trichoptera; proportion of Plecoptera (mainly suited for mountain streams); number of Plecoptera taxa; proportion of xenosaprobic taxa; proportion of epirhithral preferring taxa. Differences of metric correlations between stream types and between degradation types are discussed, leading to a list of candidate metrics for assessing German streams.  相似文献   

Flameless atomic-absorption determination of gold in geological materials     

A.L. Meier 《Journal of Geochemical Exploration》1980,13(1):77-85

Gold in geologic material is dissolved using a solution of hydrobromic acid and bromine, extracted with methyl isobutyl ketone, and determined using an atomic-absorption spectrophotometer equipped with a graphite furnace atomizer. A comparison of results obtained by this flameless atomic-absorption method on U.S. Geological Survey reference rocks and geochemical samples with reported values and with results obtained by flame atomic-absorption shows that reasonable accuracy is achieved with improved precision. The sensitivity, accuracy, and precision of the method allows acquisition of data on the distribution of gold at or below its crustal abundance.  相似文献   

A theoretical study of the electronic structure of disiloxane [(SiH3)2O] and its relation to silicates     

Rahel Meier  Tae-Kyu Ha 《Physics and Chemistry of Minerals》1980,6(1):37-46

Ab initio selfconsistent field calculations have been carried out for disiloxane, (SiH₃)₂O, and the equilibrium structure determined. The Slater-type orbital STO-3G* basis set including d-functions on Si gave the equilibrium structure of r _e(Si-O)=1.58 Å and θ_e(Si-O-Si)=140.0° for the most stable C_ss conformer, in reasonable agreement with the experimental values of 1.634 Å and 144.1°, respectively. The barrier of internal rotation of the silyl-group has been found to be rather small. The influence of the d-function to the electronic structure is discussed and the calculated results are related to the silicates, especially to the sorosilicates.  相似文献   

A comparison of lead-isotope measurements on exploration-type samples using inductively coupled plasma and thermal ionization mass spectrometry     

Brian L. Gulson  Allen L. Meier  Stanley E. Church  Karen J. Mizon 《Journal of Geochemical Exploration》1989,32(1-3)

Thermal ionization mass spectrometry (TI-MS) has long been the method of choice for Pb-isotope determinations. More recently, however, inductively coupled plasma mass spectrometry (ICP-MS) has been used to determine Pb-isotope ratios for mineral exploration. The ICP-MS technique, although not as precise as TI-MS, may promote a wider application of Ph-isotope ratio methods because it allows individual isotopes to be determined more rapidly, generally without need for chemical separation (e.g., Smith et al., 1984; Hinners et al., 1987). To demonstrate the utility of the ICP-MS method, we have conducted a series of Pb-isotope measurements on several suites of samples using both TI-MS and ICP-MS.  相似文献   

Methane consumption in aerated soils of the temperate zone   总被引：10，自引：0，他引：10  

MATTHIAS BORN  HELMUT DÖRR  INGEBORG LEVIN 《Tellus. Series B, Chemical and physical meteorology》1990,42(1):2-8

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Geospace imaging using Thomson scattering     

R.R. Meier  C. Englert  D. Chua  D. Socker  J.M. Picone  T. Carter  J. Huba  S. Slinker  J. Krall  W. Vincent 《Journal of Atmospheric and Solar》2009,71(1):132-142

We evaluate the potential of imaging for the first time, the near-earth space plasma environment seamlessly from the ionosphere through the magnetosphere by remotely sensing Thomson scattering of solar visible light by geospace electrons. Using state of the art first principles models of the magnetosphere/ionosphere system, we show that the column emission rates are weak, generally less than 10 Rayleighs, but detectable with currently available instrument technology recently deployed for heliospheric imaging. We demonstrate that distinct features such as the bow shock, magnetosheath and magnetopause are detectable in synthetic images simulated using modified solar coronagraphs and white light imagers, providing that the large background signals are properly quantified. The availability of global geospace images of the electron concentration will enable major advances in our understanding of how Earth's near-space environment responds as a coupled system to changing solar forcings. Such images are expected to play a central role in space weather assessment and forecasting, from which significant capabilities will accrue, much as the imaging of the Earth's surface and lower atmosphere has advanced understanding and forecasting of tropospheric weather.  相似文献   

European climate in the late twenty-first century: regional simulations with two driving global models and two forcing scenarios   总被引：15，自引：2，他引：13  

J.?R?is?nenEmail author  U.?Hansson  A.?Ullerstig  R.?D?scher  L.?P.?Graham  C.?Jones  H.?E.?M.?Meier  P.?Samuelsson  U.?Willén 《Climate Dynamics》2004,22(1):13-31

A basic analysis is presented for a series of regional climate change simulations that were conducted by the Swedish Rossby Centre and contribute to the PRUDENCE (Prediction of Regional scenarios and Uncertainties for Defining EuropeaN Climate change risks and Effects) project. For each of the two driving global models HadAM3H and ECHAM4/OPYC3, a 30-year control run and two 30-year scenario runs (based on the SRES A2 and B2 emission scenarios) were made with the regional model. In this way, four realizations of climate change from 1961–1990 to 2071–2100 were obtained. The simulated changes are larger for the A2 than the B2 scenario (although with few qualitative differences) and in most cases in the ECHAM4/OPYC3-driven (RE) than in the HadAM3H-driven (RH) regional simulations. In all the scenario runs, the warming in northern Europe is largest in winter or late autumn. In central and southern Europe, the warming peaks in summer when it locally reaches 10 °C in the RE-A2 simulation and 6–7 °C in the RH-A2 and RE-B2 simulations. The four simulations agree on a general increase in precipitation in northern Europe especially in winter and on a general decrease in precipitation in southern and central Europe in summer, but the magnitude and the geographical patterns of the change differ markedly between RH and RE. This reflects very different changes in the atmospheric circulation during the winter half-year, which also lead to quite different simulated changes in windiness. All four simulations show a large increase in the lowest minimum temperatures in northern, central and eastern Europe, most likely due to reduced snow cover. Extreme daily precipitation increases even in most of those areas where the mean annual precipitation decreases.  相似文献