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181.
Ana I. Gómez de Castro Willem Wamsteker Martin Barstow Noah Brosch Norbert Kappelmann Wollfram Kollatchny Domitilla de Martino Isabella Pagano Alain Lecavelier des Étangs David Ehenreich Dieter Reimers Rosa González Delgado Francisco Najarro Jeff Linsky 《Astrophysics and Space Science》2006,303(1-4):133-145
Progress of modern astrophysics requires the access to the electromagnetic spectrum in the broadest energy range. The Ultraviolet is a fundamental energy domain since it is one of the most powerful tool to study plasmas at temperatures in the 3,000–300,000 K range as well as electronic transitions of the most abundant molecules in the Universe. Moreover, the UV radiation field is a powerful astrochemical and photoionizing agent.The objective of this review is to describe the crucial issues that require access to the UV range. A summary has been added to the end with a more classic view of UV needs by astronomical object type; this approach is followed at length in the rest of the contributions of this issue. 相似文献
182.
Detrital input and early diagenesis in sediments from Lake Baikal revealed by rock magnetism 总被引:3,自引:0,他引:3
Franois Demory Hedi Oberhnsli Norbert R. Nowaczyk Matthias Gottschalk Richard Wirth Rudolf Naumann 《Global and Planetary Change》2005,46(1-4):145
A rock magnetic study was performed on sediment cores from six locations in Lake Baikal. For a comprehensive approach of the processes influencing the rock magnetic signal, additional data are presented such as total organic carbon (TOC), total sulphur (TS), opal, water content and relative variations in iron and titanium measured on selected intervals. In glacial sediments, the magnetic signal is dominated by magnetite, which is considered to be of detrital origin. This predominance of magnetite is interrupted by distinct horizons of authigenic greigite, probably confined to reductive microenvironments. In interglacial stages, besides dilution by biogenic silica and a decreasing detrital input, the weakness of the rock magnetic signal is also due to a reductive dissolution of magnetic particles. The magnetic assemblage is strongly linked to the redox history of interglacial sediment. In the oxidised bottom sediments of Lake Baikal, a biogenic magnetite is observed [Peck, J.A., King, J.W., 1996. Magnetofossils in the sediments of lake Baikal, Siberia. Earth Planet. Sci. Lett. 140 (1–4), 159–172]. After burial under the redox front, the magnetite is preferentially dissolved, and detrital hematite remains dominant when the sedimentation rate is low and when the residence time of the magnetite close to the redox boundary is long. During these low sedimentation rate conditions, the redox front is preserved [Granina, L., Müller, B. and Wehrli, B., 2004. Origin and dynamics of Fe and Mn sedimentary layers in Lake Baikal. Chem. Geol. 205 (1-2), 55-72]. At constant sedimentation rate and fast burial, the magnetite is preserved or transformed into greigite when sulphate-reducing conditions are reached in the sediment. In interglacial sediments, the magnetic assemblages depict changes in the sedimentation rate, which are traced using the ratio of magnetite over hematite (S-ratio). At the beginning of interglacials, the sedimentation rate is constant with an assemblage magnetite+greigite (high S-ratio), and at the end of some interglacials, the sedimentation rate decreases with a predominance of hematite (low S-ratio). 相似文献
183.
184.
Scott Altmann Christophe Tournassat Florence Goutelard Jean-Claude Parneix Thomas Gimmi Norbert Maes 《Applied Geochemistry》2012
Clay mineral-rich sedimentary formations are currently under investigation to evaluate their potential use as host formations for installation of deep underground disposal facilities for radioactive waste (e.g. Boom Clay (BE), Opalinus Clay (CH), Callovo–Oxfordian argillite (FR)). The ultimate safety of the corresponding repository concepts depends largely on the capacity of the host formation to limit the flux towards the biosphere of radionuclides (RN) contained in the waste to acceptably low levels. Data for diffusion-driven transfer in these formations shows extreme differences in the measured or modelled behaviour for various radionuclides, e.g. between halogen RN (36Cl, 129I) and actinides (238,235U, 237Np, 232Th, etc.), which result from major differences between RN of the effects on transport of two phenomena: diffusion and sorption. This paper describes recent research aimed at improving understanding of these two phenomena, focusing on the results of studies carried out during the EC Funmig IP on clayrocks from the above three formations and from the Boda formation (HU). 相似文献
185.
Inge Bischoff-Gauß Norbert Kalthoff Samiro Khodayar Melitta Fiebig-Wittmaack Sonia Montecinos 《Boundary-Layer Meteorology》2008,128(3):357-379
The boundary layer of the Elqui valley in the arid north of Chile exhibits several interesting phenomena, such as a very shallow
convective boundary layer (CBL) during the day. In the morning, warming is observed in and above the CBL, while the humidity
decreases in the CBL. At midday, in and above the CBL of the valley, the temperature stagnates. In the afternoon in the CBL
the temperature decreases and humidity increases, although the latent heat flux is very low. Because the characteristic features
of the valley atmosphere are hard to interpret from observations alone, model simulations were applied. The simulations indicate
that all components of the budget equations, i.e. the turbulent flux divergences, advection via the sea breeze, the upvalley
and upslope wind systems, as well as subsidence, contribute to the evolution of the valley atmosphere. 相似文献
186.
Conventional methods of palaeoclimate reconstruction provide estimates of climatic parameters using proxy data which have
originated from individual sites. These reconstructions yield information on the local environment but only limited information
on spatial scales that are required for model-data intercomparisons. We present here a new approach that connects these different
scales by an upscaling of the local palaeoinformation together with a dynamically consistent spatial smoothing. A probabilistic
data-based method for local reconstructions is combined with a dynamic constraint on the reconstructed climate parameter which
stabilises the reconstruction on the target scale. The variational analysis leads to climatological fields being optimised
with respect to the proxy data and to the prescribed dynamics in a statistically consistent way. This method allows a probabilistic
approach of quality control of the palaeodata in terms of their spatial consistency and homogeneity and for an estimation
of reconstruction errors. The method was applied to palaeobotanical data to reconstruct near-surface temperature fields constrained
by simple linear dynamics. An approximate approach was used to estimate the magnitude of reconstruction errors in terms of
standard deviations. Reconstructed January and July mean temperature of the early Eemian (∼ 125,000 years bp) have errors with a median value of about 1.8°C in January and about 1.1°C in July. Reconstructions across Europe show positive
temperature anomalies for Scandinavia and near the East coast of the Baltic Sea. In contrast, early Eemian temperatures were
apparently quite similar to those found today in Central Europe, as no drastic differences were reconstructed between the
Eemian and modern (1961–1990) climate. This implies somewhat stronger temperature gradients in the Eemian than are observed
today.
Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
187.
Steven L. Finkelstein Sangeeta Malhotra James E. Rhoads Nimish P. Hathi Norbert Pirzkal 《Monthly notices of the Royal Astronomical Society》2009,393(4):1174-1182
Recent results have shown that a substantial fraction of high-redshift Lyman α (Lyα) galaxies contain considerable amounts of dust. This implies that Lyα galaxies are not primordial, as has been thought in the past. However, this dust has not been directly detected in emission; rather it has been inferred based on extinction estimates from rest-frame ultraviolet (UV) and optical observations. This can be tricky, as both dust and old stars redden galactic spectra at the wavelengths used to infer dust. Measuring dust emission directly from these galaxies is thus a more accurate way to estimate the total dust mass, giving us real physical information on the stellar populations and interstellar medium enrichment. New generation instruments, such as the Atacama Large Millimeter Array and Sub-Millimeter Array, should be able to detect dust emission from some of these galaxies in the submillimeter. Using measurements of the UV spectral slopes, we derive far-infrared flux predictions for of a sample of 23 z ≥ 4 Lyα galaxies. We find that in only a few hours, we can detect dust emission from 39 ± 22 per cent of our Lyα galaxies. Comparing these results to those found from a sample of 21 Lyman break galaxies (LBGs), we find that LBGs are on average 60 per cent more likely to be detected than Lyα galaxies, implying that they are more dusty, and thus indicating an evolutionary difference between these objects. These observations will provide better constraints on dust in these galaxies than those derived from their UV and optical fluxes alone. Undeniable proof of dust in these galaxies could explain the larger than expected Lyα equivalent widths seen in many Lyα galaxies today. 相似文献
188.
Joydeep Bagchi Joe Jacob Gopal-Krishna Norbert Werner Nitin Wadnerkar Jaydeep Belapure A. C. Kumbharkhane 《Monthly notices of the Royal Astronomical Society》2009,399(2):601-614
We present detailed observations of MRC 0116+111, revealing a luminous, miniradio halo of ∼240-kpc diameter located at the centre of a cluster of galaxies at redshift z = 0.131 . Our optical and multiwavelength Giant Metrewave Radio Telescope and Very Large Array radio observations reveal a highly unusual radio source: showing a pair of giant (∼100-kpc diameter) bubble-like diffuse structures, that are about three times larger than the analogous extended radio emission observed in M87 – the dominant central radio galaxy in the Virgo cluster. However, in MRC 0116+111 we do not detect any ongoing active galactic nucleus (AGN) activity, such as a compact core or active radio jets feeding the plasma bubbles. The radio emitting relativistic particles and magnetic fields were probably seeded in the past by a pair of radio jets originating in the AGN of the central cD galaxy. The extremely steep high-frequency radio spectrum of the north-western bubble, located ∼100 kpc from cluster centre, indicates radiation losses, possibly because having detached, it is rising buoyantly and moving away into the putative hot intracluster medium. The other bubble, closer to the cluster centre, shows signs of ongoing particle re-acceleration. We estimate that the radio jets which inflated these two bubbles might have also fed enough energy into the intracluster medium to create an enormous system of cavities and shock fronts, and to drive a massive outflow from the AGN, which could counter-balance and even quench a cooling flow. Therefore, this source presents an excellent opportunity to understand the energetics and the dynamical evolution of radio jet inflated plasma bubbles in the hot cluster atmosphere. 相似文献
189.
Ralf Srama Thomas Stephan Eberhard Grün Norbert Pailer Anton Kearsley Amara Graps Rene Laufer Pascale Ehrenfreund Nicolas Altobelli Kathrin Altwegg Siegfried Auer Jack Baggaley Mark J. Burchell James Carpenter Luigi Colangeli Francesca Esposito Simon F. Green Hartmut Henkel Mihaly Horanyi Annette Jäckel Sascha Kempf Neil McBride Georg Moragas-Klostermeyer Harald Krüger Pasquale Palumbo Andre Srowig Mario Trieloff Peter Tsou Zoltan Sternovsky Oliver Zeile Hans-Peter Röser 《Experimental Astronomy》2009,23(1):303-328
The scientific community has expressed strong interest to re-fly Stardust-like missions with improved instrumentation. We
propose a new mission concept, SARIM, that collects interstellar and interplanetary dust particles and returns them to Earth.
SARIM is optimised for the collection and discrimination of interstellar dust grains. Improved active dust collectors on-board
allow us to perform in-situ determination of individual dust impacts and their impact location. This will provide important
constraints for subsequent laboratory analysis.
The SARIM spacecraft will be placed at the L2 libration point of the Sun–Earth system, outside the Earth’s debris belts and
inside the solar-wind charging environment. SARIM is three-axes stabilised and collects interstellar grains between July and
October when the relative encounter speeds with interstellar dust grains are lowest (4 to 20 km/s). During a 3-year dust collection
period several hundred interstellar and several thousand interplanetary grains will be collected by a total sensitive area
of 1 m2. At the end of the collection phase seven collector modules are stored and sealed in a MIRKA-type sample return capsule.
SARIM will return the capsule containing the stardust to Earth to allow for an extraction and investigation of interstellar
samples by latest laboratory technologies. 相似文献
190.
Geological mapping of an unexposed area can be supported by indirect methods. Among these, the use of mushrooms as geobotanical indicators and the shallow-penetration electromagnetic VLF method proved to be useful in the Bükk Mountains. Mushrooms have not been applied to geological mapping before. Common species like Boletus edulis and Leccinum aurantiacum are correlated with siliciclastic and magmatic formations while Calocybe gambosa is correlated with limestone. The validity of this correlation observed in the eastern part of the Bükk Mts. was controlled on a site where there was an indicated (by the mushrooms only) but unexposed occurrence of siliciclastic rocks not mapped before. The extent and structure of this occurrence were explored with the VLF survey and a trial-and-error method was applied for the interpretation. This case study presented here demonstrates the effectiveness of the combination of these relatively simple and inexpensive methods. 相似文献