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141.
Katja Etzel Artur Benisek Edgar Dachs Lado Cemič 《Physics and Chemistry of Minerals》2007,34(10):733-746
The unite cell parameters and heat capacities of a series of synthetic clinopyroxenes on the join Ca-Tschermak (CaTs)−diopside
(Di) were measured using X-ray powder diffraction and calorimetric methods, respectively. The volume of mixing at 298 K shows
a negative asymmetric deviation from ideality. A two-parameter Margules fit to the data yields W
CaTs−Di
V
= −0.29 ± 0.11 cm3 mol−1 and W
Di−CaTs
V
= −1.14 ± 0.14 cm3 mol−1. Heat capacities were determined between 5 and 923 K by heat-pulse at 5−302 K and differential-scanning calorimetry at 143−923 K.
The precision of the low and high temperature C
p
data is better than ±1%. Polynomials of the form C
p
= a + bT
−1/2 + cT
−2 + dT
−3 were fitted to the C
p
data in the temperature range between 250 and 925 K. Thermal entropy values [S
298 − S
0] and [S
900 −S
0] as well as enthalpies [H
298 − H
0] and [H
900 − H
0] were calculated for all members of the solid solution series. No significant deviation from ideal mixing behavior was observed. 相似文献
142.
Katja Henjes 《Boundary-Layer Meteorology》1998,88(2):161-180
The inertial dissipation technique has been successfully employed for many years to measure the wind stress, especially over the open ocean. This method is based on Kolmogorov's theoretical prediction of universality in the inertial wavenumber range. The theory was developed under the assumption of locally isotropic turbulence, and the dissipation technique has been criticized as lacking justification in a boundary-layer shear flow. In this paper, Kolmogorov's theory is explicitly applied to the anisotropic conditions prevailing in the atmosphere. It is shown that the inertial dissipation method relies on the homogeneity and isotropy of the spectrum ii(k) for k in the inertial range. This is a weaker condition than Kolmogorov's assumption of isotropy of the correlation function Bij(r). In high-Reynolds-number shear flows, isotropy of ii(k) is realized to a good approximation, whereas isotropy of Bij(r) is not. Some consequences for the experimental implementation are discussed; in particular, sampling times (block lengths) not exceeding the order of the eddy life time are recommended in the calculation of spectra. 相似文献
143.
Ohne Zusammenfassung 相似文献
144.
Katja Eder Laura M. Otter Limei Yang Dorrit E. Jacob Julie M. Cairney 《Geostandards and Geoanalytical Research》2019,43(3):385-395
In this study atom probe tomography was used to study nacre, an important biocomposite material that is challenging to prepare and analyse by atom probe and, when successful, yields data that is challenging to interpret. It was found that these challenges mainly arise from the insulating and heterogeneous nano‐scale properties of nacre. We outline our current best practice for preparing and running atom probe tips, such as using a low acceleration voltage (< 3 kV) and current (≤ 50 pA) to avoid damage to the microstructure, and using transmission electron microscopy to confirm that the region of interest is located close to the apex of the atom probe tip. Optimisation of the preparation parameters led to several successful atom probe experiments, with one of the data sets containing part of an organic membrane and others showing organic inclusions within the reconstruction. 相似文献
145.
R. Tousey J. D. F. Bartoe J. D. Bohlin G. E. Brueckner J. D. Purcell V. E. Scherrer N. R. Sheeley Jr. R. J. Schumacher M. E. Vanhoosier 《Solar physics》1973,33(2):265-280
Some of the first observations obtained with the Naval Research Laboratory's Extreme Ultraviolet Spectrograph (S082A) during the first Skylab mission are presented and compared with magnetograms and other ground-based data. The instrument is a slitless objective-type grating spectrograph covering 170–630 Å and described in Solar Phys.
27, 251 (1972). Chromospheric network, loop prominences, active regions, a flare, limb brightening, XUV bright points, and coronal holes are among the phenomena shown and discussed. 相似文献
146.
The models appearing in the COUPLEX benchmark are a set of simplified albeit realistic test cases aimed at simulating the transport of radionuclides around a nuclear waste repository. Three different models were used. The first test case is related to simulations based on a simplified 2D far-field model close to those used for safety assessments in nuclear waste management. It leads to a classical convection diffusion type problem, but with highly variable parameters in space, highly concentrated sources in space and time, very different time scales and accurate results expected even after millions of years. The second test case is a simplification of a typical 3D near-field computation, taking into account the glass dissolution of vitrified waste, and the congruent release of several radionuclides (including daughter products), with their migration through the geological barrier. The aim of the third test case is to use the results of the near-field computation (COUPLEX 2) to drive the behavior of the nuclide source term in the far-field computation (COUPLEX 1). The modeling of this last case was purposely left rather open, unlike the previous two, leaving the choice to participants of the way the coupling should be made. 相似文献
147.
Katja von Allmen Thomas F. Nägler Thomas Pettke Dorothee Hippler Erika Griesshaber Alan Logan Anton Eisenhauer Elias Samankassou 《Chemical Geology》2010,269(3-4):210-219
Brachiopod shells are widely used as an archive to reconstruct elemental and isotopic composition of seawater. Studies, focused on oxygen and carbon isotopes over the last decades, are increasingly extending to the emerging calcium isotope system. To date, only little attention has been paid to test the reliability of fossil brachiopods on their modern counterparts.In this context, the present study investigates two modern brachiopods, Terebratulina septentrionalis (eastern Canada, 5–30 m depth, 7.1 °C seasonal temperature variation, two-layer shell) and Gryphus vitreus (northern Mediterranean, 200 m depth, constant all-year round temperature, three-layer shell). Both species were sampled along the ontogenetic growth direction and calcium, oxygen, and carbon isotopes as well as elemental concentration were measured. Calcium isotopes were analyzed on TIMS. The elemental composition was analyzed by LA-ICP-MS and ICP-AES.The results indicate an intra-specimen δ44/40Ca variation ranging from 0.16 to 0.33‰, pointing to a fairly homogenous distribution of calcium isotopes in brachiopod shells. However, in the light of the suggested 0.7‰ increase in calcium isotopes over the Phanerozoic such intra-specimen variations constrain ocean reconstruction. δ44/40Ca values of T. septentrionalis do not seem to be affected by growth rate. Calcium isotopic values of G. vitreus are heavy in the central part of the shell and trend towards lighter values in peripheral areas approaching the maximum isotopic composition of T. septentrionalis. The maximum inter-species δ44/40Ca difference of 0.62‰ between T. septentrionalis and G. vitreus indicates that care should be taken when using different taxa, species with different strontium content or brachiopods with specialized shell structure, such as G. vitreus, for ocean water reconstruction in terms of Ca isotopic composition. T. septentrionalis may record Ca isotopic fractionation related to seasonal seawater temperature variations in its shell but this is difficult to resolve at the current analytical precision. Average δ18O-derived temperatures of the two investigated species are close to on-site measured temperatures. 相似文献