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排序方式: 共有470条查询结果,搜索用时 15 毫秒
1.
Sarah Church Peter Ade James Bock Melanie Bowden John Carlstrom Ken Ganga Walter Gear James Hinderks Wayne Hu Brian Keating John Kovac Andrew Lange Eric Leitch Olivier Mallie Simon Melhuish Anthony Murphy Ben Rusholme Creidhe OSullivan Lucio Piccirillo Clem Pryke Andy Taylor Keith Thompson 《New Astronomy Reviews》2003,47(11-12):1083
QUEST on DASI is a ground-based, high-sensitivity, high-resolution (ℓmax2500) experiment designed to map CMB polarization at 100 and 150 GHz and to measure the power spectra from E-modes, B-modes from lensing of the CMB, and B-modes from primordial gravitational waves. The experiment comprises a 2.6 m Cassegrain optical system, equipped with an array of 62 polarization-sensitive bolometers (PSBs), located at the South Pole. The instrument is designed to minimize systematic effects; features include differencing of pairs of orthogonal PSBs within a single feed, a rotatable achromatic waveplate, and axisymmetric rotatable optics. In addition the South Pole location allows both repeatable and highly controlled observations. QUEST on DASI will commence operation in early 2005. 相似文献
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M. Marengo M. Karovska D.D. Sasselov C. Papaliolios J.T. Armstrong T.E. Nordgren 《Astrophysics and Space Science》2003,286(1-2):185-190
We present a new method to compute wavelength- and phase-dependent limb darkening corrections for classical Cepheids. These
corrections are derived from hydrodynamic simulations and radiative transfer modeling with a full set of atomic and molecular
opacities. Comparison with hydrostatic models having the same stellar parameters show a larger limb darkening for most phases
in our models, and temporal variations related to the hydrodynamics of the stellar pulsation. Weassess the implications of
our results with respect to the geometric Baade-Wesselink method, which uses interferometric measurements of Cepheid angular
diameters to determine their distances and radii. The relevance of the hydrodynamic effects predicted by our model on the
limb darkening of pulsating Cepheids is finally discussed in terms of the predicted capabilities of the VLTI.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Maggie Cusack Yannicke Dauphin Jean-Pierre Cuif Murielle Salom Andy Freer Huabing Yin 《Chemical Geology》2008,253(3-4):172-179
Biominerals are natural composite materials comprising organic and inorganic components. Detailed knowledge of the nature and distribution of both components is a crucial requirement in order to advance our understanding of biomineral formation, their material properties and preservation potential as well as the interpretation of environmental data. Detailed chemical data are essential for our understanding of the nature and distribution of such components. Micro-XANES mapping at the sulphur K-edge reveals that, in the brachiopod Terebratulina retusa, the sulphate concentration is higher in the outer (primary) layer than in the calcite fibres of the secondary layer. This is co-incident with a higher magnesium concentration. In contrast, the sheaths surrounding the calcite fibres contain sulphur as thiol, confirming the presence of protein while, the sulphur within the fibres themselves, occurs as sulphate. Micro-XANES analysis of the insoluble organic extract from T. retusa indicates the presence of organic sulphate while Micro-Raman spectroscopy confirms that structurally substituted sulphate (SSS) is also present although semi-quantitative Raman spectroscopy carried out in this spectral region (wavenumbers 900–1200) indicates that the sulphate present is at the threshold of detection by Raman spectroscopy. The distribution of phosphorus in the shell of T. retusa correlates well with that of protein indicating the presence of phosphorylated proteins in the periostracum, the sheaths surrounding the calcite fibres and the interface between the primary and secondary layer. 相似文献
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T. P. Armstrong S. M. Krimigis D. Hovestadt B. Klecker G. Gloeckler 《Solar physics》1976,49(2):395-407
Comprehensive measurements of the temporal variations of the Z 6 charge composition in the 4 July 1974 solar event made with experiments aboard IMP-7 and 8 show that large variations in the charge composition occur in three-hour-averaged intensities. Hourly averaged fluxes show variations as large as factors of 3 to 4 from one hour to the next and 3 hour averages show nearly a factor of 10 peak to minimum over the event. The precision of the measurements are limited by counting statistics of the Fe-group channel. Iron to oxygen variations are established by both rate channel and pulse height analysis techniques. Comparison of measurements from IMP-7 and 8, separated by about 70 R
E shows that, while significant differences in composition and intensity exist for brief periods, the gross compositional variations are reproduced well at both spacecraft. These observations provide particularly stringent conditions for theories of the acceleration, release, and propagation of solar energetic particles. 相似文献
9.
N. Kosheleva E. Karabanov A. Kositskiy D. Williams S. Armstrong 《Journal of Geochemical Exploration》2006,88(1-3):118
A channel account approach is proposed to estimate longitudinal changes in runoff along large river systems. This new method provides a quantitative basis for describing the fluvial transport of suspended particulate material and dissolved substances. This method includes an evaluation of basic elements of water balance in separate sections of the river network and subsequent correction of channel accounting equations for the entire system using a maximum likelihood principle. To calculate water discharges of tributaries that have no hydrological information, structural analysis of river network is performed. This approach provides less error in comparison with traditional methods of estimating lateral inflow. The method is used to trace water discharge with increasing distance along the Lena river basin and to evaluate the contribution of geologically and lithologically uneven sub-basins in water discharge formation during a summer low water period. 相似文献
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