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121.
122.
We provide a new way of constraining the relative scintillation efficiency Leff for liquid xenon. Using a simple estimate for the electronic and nuclear stopping powers together with an analysis of recombination processes we predict both the ionization and the scintillation yields. Using presently available data for the ionization yield, we can use the correlation between these two quantities to constrain Leff from below. Moreover, we argue that more reliable data on the ionization yield would allow to verify our assumptions on the atomic cross sections and to predict the value of Leff. We conclude that the relative scintillation efficiency should not decrease at low nuclear recoil energies, which has important consequences for the robustness of exclusion limits for low WIMP masses in liquid xenon Dark Matter searches. 相似文献
123.
Felix Kaminsky 《Earth》2012,110(1-4):127-147
Starting from the late 1980s, several groups of lower-mantle mineral inclusions in diamond have been found. Three associations were established among them: juvenile ultramafic, analogous to eclogitic, and carbonatitic. The juvenile ultramafic association strongly predominates, and it is composed of ferropericlase, MgSi-, CaSi- and CaTi-perovskites, stishovite, tetragonal almandine-pyrope phase (TAPP), and some others. The association analogous to the upper-mantle eclogitic association, formed from subducting lithosphere, comprises: majorite, CaSi-perovskite bearing compositional Eu anomalies, phase ‘Egg’ with a tetragonal structure, and stishovite. The carbonatitic association is represented by various carbonates, halides, and associated minerals. Some mineral associations (wüstite + periclase and native iron + iron carbides) are, possibly, related to the D″ layer at the core/mantle boundary. The mineralogical composition of the lower mantle is now understood to be more complex than had been suggested in theoretic and experimental works. The proportion of ferropericlase in the lower mantle is higher than it was suggested before, and its composition is more iron-rich (mg = 0.36–0.90) as compared to experimental and theoretical data. Free silica (stishovite) is always present in lower-mantle associations, and a separate aluminous phase (TAPP) has been identified in several areas. These discrepancies suggest that the composition of the lower mantle differs to that of the upper-mantle, and experiments based solely on ‘pyrolitic’ compositions are not, therefore, applicable to the lower mantle. These data indicate a probability of an alternative to the CI-chondrite model of the Earth's formation, for example, an enstatite-chondrite model. 相似文献
124.
Ocean Dynamics - Third-generation models employ a host of parameterization schemes to consider the input wind forcing and the wave energy dissipation under different physical settings and... 相似文献
125.
Felix Bilek 《Environmental Geology》2006,49(5):674-683
Dump groundwaters in the former East-German lignite-mining district are characterized by high amounts of ferrous iron and
sulphate. Both the pyrite weathering products endanger the surface water quality when discharged into lakes. Only the precipitation
of both contaminants in the subsurface can prevent the further contamination of surface waters. The two-step process of microbial
catalyzed sulphate reduction and iron sulphide precipitation is limited by the low availability of natural organic substances
as electron donators. Therefore, a new remediation technique is developed based on the injection of a liquid organic electron
donator (methanol) into the contaminated aquifer. The saturated aquifer is used as a bioreactor, where iron monosulphides
are precipitated in the groundwater-filled pore space. Column experiments were performed under natural pressure and temperature
conditions with natural anoxic groundwater and original sediments to test the remediation technology. The test showed that
a complete iron removal (4 mmol/l), even under rather acid conditions (pH 3.8), is possible after having established an active
sulphate reducer population. The turnover of the added organic substance with sulphate is complete and the amount of the resulting
sulphide controls the effluent pH. In addition, intensified microbial activity triggers the turnover of natural organic substances.
Also, natural Fe(III) hydroxides react with the sulphide produced. Considering the long natural retention times (decades),
artificially enhanced FeS precipitation is spontaneous, although it shows kinetic behaviour in the range of days. In light
of the promising results, the development of a field scale application of this technique is considered to be necessary. It
will have to focus on the improved precipitation control of the FeS in the subsurface. 相似文献
126.
Guido Meinhold Dimitrios Kostopoulos Dirk Frei Felix Himmerkus Thomas Reischmann 《International Journal of Earth Sciences》2010,99(4):813-832
The Pirgadikia Terrane in northern Greece forms tectonic inliers within the Vardar suture zone bordering the Serbo-Macedonian
Massif to the southwest. It comprises Cadomian basement rocks of volcanic-arc origin and very mature quartz-rich metasedimentary
rocks. U–Pb laser ablation sector-field inductively-coupled plasma mass spectrometry analyses of detrital zircons from the
latter reveal a marked input from a Cadomian–Pan-African source with minor contribution from Mesoproterozoic, Palaeoproterozoic
and Archaean sources. The metasedimentary rocks are correlated with Ordovician overlap sequences at the northern margin of
Gondwana on the basis of their maturity and zircon age spectra. The Pirgadikia Terrane can be best interpreted as a peri-Gondwana
terrane of Avalonian origin, which was situated close to the Cadomian terranes in the Late Neoproterozoic–Early Palaeozoic,
very much like the Istanbul Terrane. The second unit investigated is the Vertiskos Terrane, which constitutes the major part
of the Serbo-Macedonian Massif in Greece. It comprises predominantly igneous rocks of Silurian age and minor metasedimentary
rocks of unknown age and provenance. U–Pb analyses of detrital zircons from a garnetiferous mica schist of the Vertiskos Terrane
indicate derivation from 550 to 1,150 Ma-old source rocks with a major Cadomian peak. This, combined with minor input of >1,950 Ma-old
zircons and the absence of ages between ca. 1.2 and 1.7 Ga suggests a NW Africa source. The protolith age of the garnetiferous
mica schist is presumably Early Ordovician. One sample of garnet-bearing biotite gneiss, interpreted as meta-igneous rock,
comprises predominantly subhedral zircons of igneous origin with late Middle Ordovician to Silurian ages. We suggest that
the rock association of the Vertiskos Terrane is part of an ancient active-margin succession of the Hun superterrane, comparable
to successions of the Austro- and Intra-Alpine Terranes. The new data of this study provide evidence of occurrences of Avalonia-
and Armorica-derived terranes in the Eastern Mediterranean and moreover help to clarify palaeogeographic reconstructions for
the peri-Gondwana realm in the Early Palaeozoic. 相似文献
127.
Felix V. Kaminsky Sergei M. Sablukov Ludmila I. Sablukova Dominic M.DeR. Channer 《Lithos》2004,76(1-4):565-590
In Venezuela, kimberlites have so far only been found in the Guaniamo region, where they occur as high diamond grade sheets in massive to steeply foliated Paleoproterozoic granitoid rocks. The emplacement age of the Guaniamo kimberlites is 712±6 Ma, i.e., Neoproterozoic. The Guaniamo kimberlites contain a high abundance of mantle minerals, with greater than 30% olivine macrocrysts. The principal kimberlite indicator minerals found are pyrope garnet and chromian spinel, with the overwhelming majority of the garnets being of the peridotite association. Chrome-diopside is rare, and picroilmenite is uncommon. Chemically, the Guaniamo kimberlites are characterized by high MgO contents, with low Al2O3 and TiO2 contents and higher than average FeO and K2O contents. These rocks have above average Ni, Cr, Co, Th, Nb, Ta, Sr and LREE concentrations and very low P, Y and, particularly, Zr and Hf contents. The Nb/Zr ratio is very distinctive and is similar to that of the Aries, Australia kimberlite. The Guaniamo kimberlites are similar in petrography, mineralogy and mantle mineral content to ilmenite-free Group 2 mica kimberlites of South Africa. The Nd-Sr isotopic characteristics of Guaniamo kimberlites are distinct from both kimberlite Group 1 and Group 2, being more similar to transitional type kimberlites, and in particular to diamondiferous kimberlites of the Arkhangelsk Diamond Province, Russia. The Guaniamo kimberlites form part of a compositional spectrum between other standard kimberlite reference groups. They formed from metasomatised subcontinental lithospheric mantle and it is likely that subduction of oceanic crust was the source of this metasomatised material, and also of the eclogitic component, which is dominant in Guaniamo diamonds. 相似文献
128.
Geomagnetic pulsations in the frequency range of Pc1 pearl waves with the dynamic spectra having a very narrow spectrum width
at the beginning of the event and a very broad spectrum width (Δf/f0 ∼ 1) in the later part of the event are analyzed. One of the observed events shown by the dynamic spectrum resembles a goose
with the beak at the beginning of the event and with the wing in the later part of the event. Various interpretations of these
geomagnetic pulsations are presented taking into account nonlinear effects, quasilinear interaction of electromagnetic ion-cyclotron
waves with energetic, anisotropic protons and modulation of plasma parameters in the magnetosphere by Pc3–5 hydromagnetic
waves. The ionospheric effect in the signal formation is determined by the ionospheric Alfvén resonator. It can control the
frequency range of the dynamic spectra, but not the internal structure of the signal. 相似文献
129.
The Baikal is a deep long and narrow basin in East Siberia which follows a huge fault zone adjoining the Siberian Platform. The basin was formed by rapid subsidence of continental crust during the pas 3–4 Ma. It is bounded by normal faults which indicate extension of the crust during the subsidence. According to seismic reflection profiling data, the intensity of extension is not large (3–7%). It is much smaller than the thinning of the crystalline crust under the basin (up to 38%). The thinning and crustal subsidence can be explained by the transformation of gabbro in the lower crust into dense garnet granulites. The latter rocks (with Vp 7.7−7.8 km/sec) are still located under the remnant part of the crust. Rapid transformation took place due to an inflow of catalyzing fluid along the fault zone from the asthenospheric upwelling. This upwelling, which is at a depth of 80–90 km, caused a general uplift of a broad area in the south of East Siberia. 相似文献
130.
Sandrine Bony Bjorn Stevens Felix Ament Sebastien Bigorre Patrick Chazette Susanne Crewell Julien Delanoë Kerry Emanuel David Farrell Cyrille Flamant Silke Gross Lutz Hirsch Johannes Karstensen Bernhard Mayer Louise Nuijens James H. RuppertJr. Irina Sandu Pier Siebesma Sabrina Speich Frédéric Szczap Julien Totems Raphaela Vogel Manfred Wendisch Martin Wirth 《Surveys in Geophysics》2017,38(6):1529-1568
Trade-wind cumuli constitute the cloud type with the highest frequency of occurrence on Earth, and it has been shown that their sensitivity to changing environmental conditions will critically influence the magnitude and pace of future global warming. Research over the last decade has pointed out the importance of the interplay between clouds, convection and circulation in controling this sensitivity. Numerical models represent this interplay in diverse ways, which translates into different responses of trade-cumuli to climate perturbations. Climate models predict that the area covered by shallow cumuli at cloud base is very sensitive to changes in environmental conditions, while process models suggest the opposite. To understand and resolve this contradiction, we propose to organize a field campaign aimed at quantifying the physical properties of trade-cumuli (e.g., cloud fraction and water content) as a function of the large-scale environment. Beyond a better understanding of clouds-circulation coupling processes, the campaign will provide a reference data set that may be used as a benchmark for advancing the modelling and the satellite remote sensing of clouds and circulation. It will also be an opportunity for complementary investigations such as evaluating model convective parameterizations or studying the role of ocean mesoscale eddies in air–sea interactions and convective organization. 相似文献