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排序方式: 共有210条查询结果,搜索用时 31 毫秒
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Natural Hazards - In crisis situations, illiterates and people with other linguistic challenges are unable to understand text messages to inform or be informed of a situation. Pictographic... 相似文献
23.
P. Majewski F. Aschauer S. Aschauer A. Bähr B. Bergbauer M. Hilchenbach M. Krumrey C. Laubis T. Lauf P. Lechner G. Lutz F. Scholze H. Soltau A. Stefanescu L. Strüder J. Treis 《Experimental Astronomy》2014,37(3):525-538
The Mercury Imaging X-ray Spectrometer (MIXS) will be launched on board of the 5th ESA cornerstone mission BepiColombo. The two channel instrument MIXS is dedicated to the exploration of the elemental composition of the mercurian surface by imaging x-ray spectroscopy of the elemental fluorescence lines. One of the main scientific goals of MIXS is to provide spatially resolved elemental abundance maps of key rock-forming elements. MIXS will be the successor of the XRS instrument, which is currently orbiting Mercury on board of NASAs satellite MESSENGER. MIXS will provide unprecedented spectral and spatial resolution due to its innovative detector and optics concepts. The MIXS target energy band ranges from 0.5 to 7 keV and allows to directly access the Fe-L line at 0.7 keV, which was not accessible to previous missions. In addition, the high spectroscopic resolution of FWHM ≤ 200 eV at the reference energy of 1 keV after one year in Mercury orbit, allows to separate the x-ray fluorescence emission lines of important elements like Mg (1.25 keV) and Al (1.49 keV) without the need for any filter. The detectors for the energy and spatially resolved detection of x-rays for both channels are identical DEPFET (DEpleted P-channel FET) active pixel detectors. We report on the calibration of the MIXS flight and flight spare detector modules at the PTB (Physikalisch-Technische Bundesanstalt) beamlines at the BESSY II synchrotron radiation facility. Each detector was calibrated at least at 10 discrete energies in the energy range from 0.5 to 10 keV. The excellent spectroscopic performance of all three detector modules was verified. 相似文献
24.
Sebastian?WetterichEmail author Lutz?Schirrmeister Erika?Pietrzeniuk 《Journal of Paleolimnology》2005,34(3):363-376
Ostracode analysis was carried out on samples from ice-rich permafrost deposits obtained on the Bykovsky Peninsula (Laptev Sea). A composite profile was investigated that covers most of a 38-m thick permafrost sequence and corresponds to the last ca. 60 kyr of the Late Quaternary. The ostracode assemblages are similar to those known from European Quaternary lake deposits during cold stages. The ostracode habitats were small, shallow, cold, oligotrophic pools located in low centred ice wedge polygons or in small thermokarst depressions. In total, 15 taxa, representing 7 genera, were identified from 65 samples. The studied section is subdivided into six ostracode zones that correspond to Late Quaternary climatic and environmental stadial-interstadial variations established by other paleoenvironmental proxies: (1) cold and dry Zyrianian stadial (58–53 kyr BP); (2) warm and dry Karginian interstadial (48–34 kyr BP); (3) transition from the Karginian interstadial to the cold and dry Sartanian stadial (34–21 kyr BP); (4) transition from the Sartanian stadial to the warm and dry Late Pleistocene period, the Allerød (21–14 kyr BP); (5) transition from the Allerød to the warm and wet Middle Holocene (14–7 kyr BP); and (6) cool and wet Late Holocene (ca. 3 kyr BP). The abundance and diversity of the ostracodes will be used as an additional bioindicator for paleoenvironmental reconstructions of the Siberian Arctic. 相似文献
25.
Impact of Earth radiation pressure on GPS position estimates 总被引:10,自引:8,他引:2
C. J. Rodriguez-Solano U. Hugentobler P. Steigenberger S. Lutz 《Journal of Geodesy》2012,86(5):309-317
GPS satellite orbits available from the International GNSS Service (IGS) show a consistent radial bias of up to several cm
and a particular pattern in the Satellite Laser Ranging (SLR) residuals, which are suggested to be related to radiation pressure
mismodeling. In addition, orbit-related frequencies were identified in geodetic time series such as apparent geocenter motion
and station displacements derived from GPS tracking data. A potential solution to these discrepancies is the inclusion of
Earth radiation pressure (visible and infrared) modeling in the orbit determination process. This is currently not yet considered
by all analysis centers contributing to the IGS final orbits. The acceleration, accounting for Earth radiation and satellite
models, is introduced in this paper in the computation of a global GPS network (around 200 IGS sites) adopting the analysis
strategies from the Center for Orbit Determination in Europe (CODE). Two solutions covering 9 years (2000–2008) with and without
Earth radiation pressure were computed and form the basis for this study. In previous studies, it has been shown that Earth
radiation pressure has a non-negligible effect on the GPS orbits, mainly in the radial component. In this paper, the effect
on the along-track and cross-track components is studied in more detail. Also in this paper, it is shown that Earth radiation
pressure leads to a change in the estimates of GPS ground station positions, which is systematic over large regions of the
Earth. This observed “deformation” of the Earth is towards North–South and with large scale patterns that repeat six times
per GPS draconitic year (350 days), reaching a magnitude of up to 1 mm. The impact of Earth radiation pressure on the geocenter
and length of day estimates was also investigated, but the effect is found to be less significant as compared to the orbits
and position estimates. 相似文献
26.
Christian Wolf Alfonso Aragón-Salamanca Michael Balogh Marco Barden Eric F. Bell Meghan E. Gray Chien Y. Peng David Bacon Fabio D. Barazza Asmus Böhm John A. R. Caldwell Anna Gallazzi Boris Häußler Catherine Heymans Knud Jahnke Shardha Jogee Eelco van Kampen Kyle Lane Daniel H. McIntosh Klaus Meisenheimer Casey Papovich Sebastian F. Sánchez y Taylor Lutz Wisotzki Xianzhong Zheng 《Monthly notices of the Royal Astronomical Society》2009,393(4):1302-1323
We investigate the properties of optically passive spirals and dusty red galaxies in the A901/2 cluster complex at redshift ∼0.17 using rest-frame near-ultraviolet–optical spectral energy distributions, 24-μm infrared data and Hubble Space Telescope morphologies from the STAGES data set. The cluster sample is based on COMBO-17 redshifts with an rms precision of σ cz ≈ 2000 km s−1 . We find that 'dusty red galaxies' and 'optically passive spirals' in A901/2 are largely the same phenomenon, and that they form stars at a substantial rate, which is only four times lower than that in blue spirals at fixed mass. This star formation is more obscured than in blue galaxies and its optical signatures are weak. They appear predominantly in the stellar mass range of log M * /M⊙ =[10, 11] where they constitute over half of the star-forming galaxies in the cluster; they are thus a vital ingredient for understanding the overall picture of star formation quenching in clusters. We find that the mean specific star formation rate (SFR) of star-forming galaxies in the cluster is clearly lower than in the field, in contrast to the specific SFR properties of blue galaxies alone, which appear similar in cluster and field. Such a rich red spiral population is best explained if quenching is a slow process and morphological transformation is delayed even more. At log M * /M⊙ < 10 , such galaxies are rare, suggesting that their quenching is fast and accompanied by morphological change. We note that edge-on spirals play a minor role; despite being dust reddened they form only a small fraction of spirals independent of environment. 相似文献
27.
Catherine Heymans Meghan E. Gray Chien Y. Peng Ludovic Van Waerbeke Eric F. Bell Christian Wolf David Bacon Michael Balogh Fabio D. Barazza Marco Barden Asmus Böhm John A. R. Caldwell Boris Häußler Knud Jahnke Shardha Jogee Eelco van Kampen Kyle Lane Daniel H. McIntosh Klaus Meisenheimer Yannick Mellier Sebastian F. Sánchez y N. Taylor Lutz Wisotzki Xianzhong Zheng 《Monthly notices of the Royal Astronomical Society》2008,385(3):1431-1442
We present a high-resolution dark matter reconstruction of the z = 0.165 Abell 901/902 supercluster from a weak lensing analysis of the Hubble Space Telescope STAGES survey. We detect the four main structures of the supercluster at high significance, resolving substructure within and between the clusters. We find that the distribution of dark matter is well traced by the cluster galaxies, with the brightest cluster galaxies marking out the strongest peaks in the dark matter distribution. We also find a significant extension of the dark matter distribution of Abell 901a in the direction of an infalling X-ray group Abell 901α. We present mass, mass-to-light and mass-to-stellar mass ratio measurements of the structures and substructures that we detect. We find no evidence for variation of the mass-to-light and mass-to-stellar mass ratio between the different clusters. We compare our space-based lensing analysis with an earlier ground-based lensing analysis of the supercluster to demonstrate the importance of space-based imaging for future weak lensing dark matter 'observations'. 相似文献
28.
29.
Peter Koenraad Swart Genevieve Healy Lisa Greer Michael Lutz Amel Saied Daniel Anderegg Richard E. Dodge David Rudnick 《Estuaries and Coasts》1999,22(2):384-397
This paper will discuss the use of chemical proxies in coral skeletons to reconstruct the history of salinity (from the δ18O of the skeleton) and nutrients in the water (from the δ13C) in Florida Bay between 1824 and 1994. Monthly salinity and water temperature data collected since 1989 were used to establish a correlation between salinity, temperature, and the δ18O of the skeleton of the coralSolenastrea bournoni from Lignumvitae Basin in Florida Bay. This relationship explains over 50% of the variance in the δ18O of the skeleton. Assuming that interannual variations in the temperature of the water are small, we have applied this relationship to the δ18O measured in the coral skeleton collected from Lignumvitae Basin which has a record between 1824 and 1993. These data provide a revised estimate of salinity variation in Lignumvitae Basin for the period when historical records for salinity were not available, and show that the highest salinity events occurred in the past 30 yr. Using the relationships between the salinity in Lignumvitate Basin and other basins, obtained using a modern dataset, we are able to estimate ranges in salinity for other portions of Florida Bay. Skeletons of specimens of the coral speciesSiderastrea radians collected from other areas of Florida Bay show similar patterns in the δ18O over the past 10 yr, indicating that corals in most portions of Florida Bay are recording salinity variations in their skeletons and therefore support the idea that salinity variations in different portions of Florida Bay can be related. Fluorescence analysis of the coral from Lignumvitae Basin shows a large change in the magnitude of the 10-yr signal coincident with the construction of the railway, confirming that this event had a significant impact upon Florida Bay. The δ13C of the coral skeletons reveals a long-term history of the oxidation of organic material, fixation of carbon by photosynthesis (algal blooms), and the intrusion of marine water into the bay. Since the construction of the railway from Miami to Key West there has been a long-term decrease in the δ13C of the coral skeleton from Lignumvitae Basin, suggesting the increased oxidation of organic material in this area. This decrease in δ13C appears to have reached a minimum value around 1984 and has increased since this time in the western portions of Florida Bay. The increase may be related to the algal blooms prevalent in the area or alternatively could result from intrusion of more marine water. In the eastern areas, a small increase in the δ18C between 1984 and 1988 was followed by further decline suggesting more oxidation of organic material. We have also attempted to use the concentration of barium in the coral skeleton as a proxy indicator of the nutrient status in Florida Bay. 相似文献
30.
Santiago Hernández-León Lutz Postel Javier Arístegui May Gómez María Fernanda Montero Santiago Torres Carlos Almeida Eugen Kühner Ullrich Brenning Eberhard Hagen 《Journal of Oceanography》1999,55(4):471-482
Plankton biomass and indices of metabolism and growth [electron transport system (ETS), glutamate dehydrogenase (GDH) and aspartate transcarbamylase (ATC) activities] were studied over a 2,800 km east-west section of the tropical North Atlantic Ocean (21°N) in <200, 200–500 and >;500 µm size classes. On the large-scale, zooplankton (>;200 µm) enzymatic activities increased westward in the study section, where large cyanobacteria chains (Trichodesmium spp.) were observed. Parallel to it, an increase in medium calanoids (1–2 mm length) was observed towards the western part of the transect, whereas small calanoids (<1 mm) were dominant throughout the boundary area of the subtropical gyre. Microplankton ETS and mesoplankton ETS and ATC activities seemed to match the wave length of low frequency waves. Our results suggest that such waves are related to the observed enhancement of metabolic activity of micro- and mesoplankton. The large-scale and mesoscale variability observed give evidence of the inadequacy of assuming a steady-state picture of the euphotic zone of tropical and subtropical waters. 相似文献