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71.
Marie-Pierre Isaure Géraldine Sarret Yong-Eui Choi Sirine C. Fakra Sébastien Pairis Stephan Clemens Alain Manceau 《Geochimica et cosmochimica acta》2010,74(20):5817-5834
In tobacco plants, elimination of Zn and Cd via the production of Ca-containing grains at the top of leaf hairs, called trichomes, is a potent detoxification mechanism. This study examines how Cd is incorporated in these biominerals, and how calcium growth supplement modifies their nature. Scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDX), microfocused X-ray diffraction (μ-XRD), and microfocused X-ray absorption near edge structure (μ-XANES) spectroscopy were used to image the morphology of the grains, identify the crystallized mineral phases, and speciate Cd, respectively. The mineralogy of the grains and chemical form of Cd varied with the amount of Ca. When tobacco plants were grown in a nutrient solution containing 25 μM Cd and low Ca supplement (Ca/Cd = 11 mol ratio), most of the grains were oblong-shaped and low-Cd-substituted calcite. When exposed to the same amount of Cd and high Ca supplement (Ca/Cd = 131 mol ratio), grains were more abundant and diverse in compositions, and in total more Cd was eliminated. Most grains in the high Ca/Cd experiment were round-shaped and composed predominantly of Cd-substituted vaterite, a usually metastable calcium carbonate polymorph, and subordinate calcite. Calcium oxalate and a Ca amorphous phase were detected occasionally in the two treatments, but were devoid of Cd. The biomineralization of cadmium and implications of results for Cd exposure of smokers and phytoremediation are discussed. 相似文献
72.
Bojan Nikolic Paul Alexander Garret Cotter Malcolm Longair Marcel Clemens 《Astrophysics and Space Science》2003,284(2):573-576
We present preliminary results of recent spatially resolved mid infrared (Mid-IR) spectroscopy with the MICHELLE instrument
on UKIRT of NGC 7469, observed as part of a larger programme to study a sample of starburst and AGN in the Mid-IR.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
73.
H. C.Thomas L.Dunne M. S.Clemens P.Alexander S.Eales D. A.Green A.James 《Monthly notices of the Royal Astronomical Society》2002,331(4):853-864
We present SCUBA 850-μm, JCMT CO( J =2→1) , B -band imaging and VLA H i observations of the NGC 7465/4/3 group of galaxies. The 850-μm emission associated with NGC 7465 extends to at least ∼2 R 25 and is well correlated with the H i . We investigate a range of possible mechanisms by which dust beyond R 25 may be heated to give the observed extended submillimetre emission. By modelling the dust heating by stars in two extreme geometries, we fail to find any reasonable star formation scenario that is consistent with both the 850-μm and optical data. Furthermore, we do not detect any CO( J =2→1) emission coincident with the extended dust and atomic gas as would be expected if significant star formation were occurring. We show that shock-heating of dust via cloud–cloud collisions in the stripped interstellar medium of NGC 7465 could be sufficient to explain the extended 850-μm emission and lack of optical emission in the stripped gas, and suggest that cloud–cloud collisions may be an important dust heating mechanism in gas-rich systems. 相似文献
74.
Stefan Kneifel Maximilian Maahn Gerhard Peters Clemens Simmer 《Meteorology and Atmospheric Physics》2011,113(1-2):75-87
Quantifying snowfall intensity especially under arctic conditions is a challenge because wind and snow drift deteriorate estimates obtained from both ground-based gauges and disdrometers. Ground-based remote sensing with active instruments might be a solution because they can measure well above drifting snow and do not suffer from flow distortions by the instrument. Clear disadvantages are, however, the dependency of e.g. radar returns on snow habit which might lead to similar large uncertainties. Moreover, high sensitivity radars are still far too costly to operate in a network and under harsh conditions. In this paper we compare returns from a low-cost, low-power vertically pointing FM-CW radar (Micro Rain Radar, MRR) operating at 24.1?GHz with returns from a 35.5?GHz cloud radar (MIRA36) for dry snowfall during a 6-month observation period at an Alpine station (Environmental Research Station Schneefernerhaus, UFS) at 2,650?m height above sea level. The goal was to quantify the potential and limitations of the MRR in relation to what is achievable by a cloud radar. The operational MRR procedures to derive standard radar variables like effective reflectivity factor (Z e) or the mean Doppler velocity (W) had to be modified for snowfall since the MRR was originally designed for rain observations. Since the radar returns from snowfall are weaker than from comparable rainfall, the behavior of the MRR close to its detection threshold has been analyzed and a method is proposed to quantify the noise level of the MRR based on clear sky observations. By converting the resulting MRR-Z e into 35.5?GHz equivalent Z e values, a remaining difference below 1?dBz with slightly higher values close to the noise threshold could be obtained. Due to the much higher sensitivity of MIRA36, the transition of the MRR from the true signal to noise can be observed, which agrees well with the independent clear sky noise estimate. The mean Doppler velocity differences between both radars are below 0.3?ms?1. The distribution of Z e values from MIRA36 are finally used to estimate the uncertainty of retrieved snowfall and snow accumulation with the MRR. At UFS low snowfall rates missed by the MRR are negligible when comparing snow accumulation, which were mainly caused by intensities between 0.1 and 0.8 mm?h?1. The MRR overestimates the total snow accumulation by about 7%. This error is much smaller than the error caused by uncertain Z e?Csnowfall rate relations, which would affect the MIRA36 estimated to a similar degree. 相似文献
75.
76.
S-type ignimbrites with polybaric crystallisation histories: the Tolmie Igneous Complex,Central Victoria,Australia 总被引:1,自引:1,他引:0
J. D. Clemens W. D. Birch R. A. Dudley 《Contributions to Mineralogy and Petrology》2011,162(6):1315-1337
The Late Devonian Tolmie Igneous Complex (in north-eastern Victoria, Australia) contains S-type, intracaldera, rhyolitic ignimbrites
with multiple generations of phenocrysts of biotite, garnet, cordierite and orthopyroxene; one unit also contains fayalitic
olivine. Geothermometry and calculated phase relations indicate high-T deep- to mid-crustal origins for the magmas, with crystallisation at several levels. At least four separate magma groups
make up the complex. Compositional variations within and between ignimbrites are adequately modelled by selective entrainment
of peritectic garnet, ilmenite, orthopyroxene and plagioclase into the magmas. Neither crystal fractionation nor mafic-felsic
magma mixing played a role. Chemical and isotope data suggest that the magma sources were once variably Ba-enriched arc greywackes
with different proportions of clay. The deep origin of some of the Tolmie Complex magmas means that supracrustal rocks underlie
parts of north-eastern Victoria at depths of around 35 km. This has important implications for understanding the region’s
tectonic development. 相似文献
77.
78.
Romed Ruggenthaler Gertraud Meißl Clemens Geitner Georg Leitinger Nikolaus Endstrasser Friedrich Schöberl 《水文科学杂志》2013,58(7):1263-1279
ABSTRACTThis study presents an adaptation of the double-ring infiltrometer (DRI) device, which allows several infiltration experiments to be conducted at the same location. Hence, it becomes possible to use the DRI method to investigate infiltration behaviour under different initial soil moisture conditions. The main feature is the splitting of the inner ring into two parts. While the lower part remains in the soil throughout the investigation period, the upper part is attached to the lower one just before the infiltration experiment. This method was applied to eight test sites in an Alpine catchment, covering different land-use/cover types. The results demonstrated the applicability of the adapted system and showed correlations between total water infiltration and initial soil moisture conditions on pastures, independent of the underlying soil type. In contrast, no correlation was found at forest sites or wetlands. Thus, the study emphasizes the importance of paying special attention to the impact of initial soil moisture conditions on the infiltration—and consequently the runoff behaviour—at managed areas. Given the differences in the total infiltrated water of between 30 and 1306 mm, consideration of the interplay between initial soil moisture conditions, land-use/cover type, and soil properties in rainfall–runoff models is a prerequisite to predict runoff production accurately.
EDITOR Z.W. Kundzewicz; ASSOCIATE EDITOR not assigned 相似文献
79.
AbstractIn Australian stratigraphic nomenclature, the concept of granitic rock suites has been in formal use for over a decade. The basis for this suite classification of granitic rocks is inconsistent and, in eastern Australian usage, unsound on several levels. We also note that the approach used in Western Australia is different. Granitic intrusions are probably not truly amenable to any strict, comprehensive, lithostratigraphic classification. If these rocks are integrated into such a scheme, group- and supergroup-level units (i.e. formal suites and supersuites) should not be incorporated. For the present, mappable units should be recognised at the levels of formation and member. The use of granite suites and supersuites in formal stratigraphic hierarchies is not recommended. Instead, granitic bodies could be grouped into individual plutons, which may or may not form parts of larger batholiths.
- KEY POINTS
The suite-based classification of granitic bodies, as currently used in the Australian Stratigraphic Units Database, is based on unsound principles, and is not employed in a consistent manner.
Granitic intrusive rocks probably cannot be grouped using lithostratigraphic principles that are consistent with either the local or international codes.
Granitic bodies can be grouped into batholiths, plutons and members, but the names of these units should, for the moment, remain informal.
80.
Martin B. Kalinowski Anders Axelsson Marc Bean Xavier Blanchard Theodore W. Bowyer Guy Brachet Simon Hebel Justin I. McIntyre Jana Peters Christoph Pistner Maria Raith Anders Ringbom Paul R. J. Saey Clemens Schlosser Trevor J. Stocki Thomas Taffary R. Kurt Ungar 《Pure and Applied Geophysics》2010,167(4-5):517-539
A global monitoring system for atmospheric xenon radioactivity is being established as part of the International Monitoring System that will verify compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) once the treaty has entered into force. This paper studies isotopic activity ratios to support the interpretation of observed atmospheric concentrations of 135Xe, 133mXe, 133Xe and 131mXe. The goal is to distinguish nuclear explosion sources from civilian releases. Simulations of nuclear explosions and reactors, empirical data for both test and reactor releases as well as observations by measurement stations of the International Noble Gas Experiment (INGE) are used to provide a proof of concept for the isotopic ratio based method for source discrimination. 相似文献