Mineralogical characterization of potential targets for the ASTEX mission scenario     

Vishnu Reddy  Andreas Nathues  Michael J. Gaffey  Sven Schaeff 《Planetary and Space Science》2011,59(8):772-778

In-situ investigation of asteroids is the next logical step in understanding their exact surface mineralogy, petrology, elemental abundances, particle size distribution, internal structure, and collisional evolution. Near-Earth asteroids (NEAs) provide us with ample opportunities for in-situ scientific exploration with lower Δv requirements and subsequently lower costs than their main belt counterparts. The ASTEX mission concept aims at surface characterization of two compositionally diverse NEAs, one with primitive and the other with a strong thermally evolved surface mineralogy. Here we present the first results of our ground-based characterization of potential ASTEX mission targets using the SpeX instrument on the NASA IRTF. Of the four potential targets we characterized, two (1991 JW and 1998 PA) have compositions similar to ordinary chondrite mineralogy. The other two targets (1994 CC and 1999 TA10) are thermally evolved objects with igneous formation histories. While 1994 CC is a triplet system and thus very challenging to orbit the V-type NEA, 1999 TA10 is the most interesting scientific ASTEX target identified so far.  相似文献   

Shallow Drilling of Seafloor Hydrothermal Systems Using the BGS Rockdrill: Conical Seamount (New Ireland Fore-Arc) and PACMANUS (Eastern Manus Basin), Papua New Guinea     

Sven Petersen  Peter M. Herzig  Thomas Kuhn  Leander Franz  Mark D. Hannington  Thomas Monecke 《Marine Georesources & Geotechnology》2013,31(3):175-193

ABSTRACT

From September to October 2002, shallow drilling, using the submersible (5 m) Rockdrill of the British Geological Survey and the German R/V Sonne revealed critical information on the subsurface nature of two distinct hydrothermal systems in the New Ireland fore-arc and the Manus Basin of Papua New Guinea. Drilling at Conical Seamount significantly extends the known surface extent of the previously discovered vein-style gold mineralization (up to 230 g/t Au) at this site. Drilling the conventional PACMANUS volcanic-hosted massive sulfide deposit recovered complexly textured massive sulfide with spectacular concentrations of gold in several core sections including 0.5 m @ 28 g/t Au, 0.35 m @ 30 g/t Au, and 0.20 m @ 57 g/t Au. Shallow drilling is a fast and cost efficient method that bridges the gap between surface sampling and deep (ODP) drilling and will become a standard practice in the future study of seafloor hydrothermal systems and massive sulfide deposits.  相似文献   

Parrotfish mediation in coral mortality and bioerosion by the encrusting,excavating sponge Cliona tenuis     

Juan Carlos Márquez  Sven Zea 《Marine Ecology》2012,33(4):417-426

The parrotfish Sparisoma viride often grazes live coral from edges undermined by the Caribbean encrusting and excavating sponge Cliona tenuis. To test whether parrotfish biting action has an effect on the dynamics of the sponge–coral interaction, we manipulated access of parrotfishes to the sponge–coral border in two species of massive corals. When parrotfish had access to the border, C. tenuis advanced significantly more slowly into the coral Siderastrea siderea than into the coral Diploria strigosa. When fish bites were prevented, sponge spread into S. siderea was further slowed down but remained the same for D. strigosa. Additionally, a thinner layer of the outer coral skeleton was removed by bioerosion when fish were excluded, a condition more pronounced in D. strigosa than in S. siderea. Thus, the speed of sponge‐spread and the extent of bioerosion by parrotfish was coral species‐dependent. It is hypothesized that coral skeleton architecture is the main variable associated with such dependency. Cliona tenuis spread is slow when undermining live S. siderea owing to the coral’s compact skeleton. The coral’s smooth and hard surface promotes a wide and shallow parrotfish bite morphology, which allows the sponge to overgrow the denuded area and thus advance slightly faster. On the less compact skeleton of the brain coral, D. strigosa, sponge spread is more rapid. This coral’s rather uneven surface sustains narrower and deeper parrotfish bites which do not facilitate the already fast sponge progress. Parrotfish corallivory thus acts synergistically with C. tenuis to further harm corals whose skeletal architecture slows sponge lateral spread. In addition, C. tenuis also appears to mediate the predator–prey fish–coral interaction by attracting parrotfish biting.  相似文献   

Seagrass ecophysiology meets ecological genomics: are we ready?     

Gabriele Procaccini  Sven Beer  Mats Björk  Jeanine Olsen  Silvia Mazzuca  Rui Santos 《Marine Ecology》2012,33(4):522-527

In March 2011, the Ecophysiology and Genetics Working Groups of the European Science Foundation COST Action ES 0906, entitled Seagrass Productivity: From Genes to Ecosystem Management, organized an exploratory workshop entitled “Linking Ecophysiology and Ecogenomics in Seagrass Systems”. The goal of the workshop was to discuss how to integrate comparative gene expression studies with physiological processes such as photosynthetic performance, carbon and nitrogen utilization and environmental adaptation. The main questions discussed for integrative research related to mechanisms of carbon utilization, light requirements, temperature effects and natural variation in pH and ocean acidification. It was concluded that the seagrass research community is still in the nascent stages of linking ecophysiology with genomic responses, as carbon and nitrogen metabolism of seagrasses have not been sufficiently well studied. Likewise, genomic approaches have only been able to assign meaningful interpretations to a handful of differentially expressed genes. Nevertheless, the way forward has been established.  相似文献   

Adaptive growth reduction in response to fish kairomones allows mosquito larvae (Culex pipiens) to reduce predation risk     

Jonas Jourdan  Jasmin Baier  Rüdiger Riesch  Sven Klimpel  Bruno Streit  Ruth Müller  Martin Plath 《Aquatic Sciences - Research Across Boundaries》2016,78(2):303-314

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Using subsurface metazoan fauna to indicate groundwater–surface water interactions in the Nakdong River floodplain, South Korea     

Jörg Bork  Sven E. Berkhoff  Sabine Bork  Hans Jürgen Hahn 《Hydrogeology Journal》2009,17(1):61-75

Hydrological interactions between surface water and groundwater (GW) can be described using hydrochemical and biological methods. Surface water–groundwater interactions and their effects on groundwater invertebrate communities were studied in the Nakdong River floodplain in South Korea. Furthermore, the GW-Fauna-Index, a promising new index for assessing the strength of surface-water influence on groundwater, was tested. The influence of surface water on groundwater decreased with increasing depth and distance from the river. While hydrochemistry prevailingly reflected the origin of the waters in the study area (i.e. whether alluvial or from adjacent rock), faunal communities seemed to display an affinity to surface-water intrusion. Fauna reacted quickly to changes in hydrology, and temporal changes in faunal community structure were significantly linked to the hydrological situation in the floodplain. The metazoan faunal community and the GW-Fauna-Index allow a distinction between surface and subsurface waters with varying degrees of exchange. The results indicate that hydrological conditions are reflected by faunal assemblages on a high spatiotemporal resolution, and that surface-water intrusion can be estimated using the GW-Fauna-Index.  相似文献   

Spatial scan statistics in vulnerability assessment: an application to mountain hazards   总被引：4，自引：2，他引：2  

Sven Fuchs  Christine Ornetsmüller  Reinhold Totschnig 《Natural Hazards》2012,64(3):2129-2151

In the European Alps, the concept of risk has increasingly been applied in order to reduce the susceptibility of society to mountain hazards. Risk is defined as a function of the magnitude and frequency of a hazard process times consequences; the latter being quantified by the value of elements at risk exposed and their vulnerability. Vulnerability is defined by the degree of loss to a given element at risk resulting from the impact of a natural hazard. Recent empirical studies suggested a dependency of the degree of loss on the hazard impact, and respective vulnerability (or damage-loss) functions were developed. However, until now, only little information is available on the spatial characteristics of vulnerability on a local scale; considerable ranges in the loss ratio for medium process intensities only provide a hint that there might be mutual reasons for lower or higher loss rates. In this paper, we therefore focus on the spatial dimension of vulnerability by searching for spatial clusters in the damage ratio of elements at risk exposed. By using the software SaTScan, we applied an ordinal data model and a normal data model in order to detect spatial distribution patterns of five individual torrent events in Austria. For both models, we detected some significant clusters of high damage ratios, and consequently high vulnerability. Moreover, secondary clusters of high and low values were found. Based on our results, the assumption that lower process intensities result in lower damage ratios, and therefore in lower vulnerability, and vice versa, has to be partly rejected. The spatial distribution of vulnerability is not only dependent on the process intensities but also on the overall land use pattern and the individual constructive characteristics of the buildings exposed. Generally, we suggest the use of a normal data model for test sites exceeding a minimum of 30 elements at risk exposed. As such, the study enhanced our understanding of spatial vulnerability patterns on a local scale.  相似文献   

Vulnerability assessment in natural hazard and risk analysis: current approaches and future challenges   总被引：10，自引：9，他引：1  

Sven Fuchs  J?rn Birkmann  Thomas Glade 《Natural Hazards》2012,64(3):1969-1975

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Eutrephoceras subplicatum (Steinmann, 1895) is a junior synonym of Eutrephoceras dorbignyanum (Forbes in Darwin, 1846) (Cephalopoda, Nautiloidea) from the Maastrichtian Quiriquina Formation of Chile     

Sven N. Nielsen  Christian Salazar 《Cretaceous Research》2011,32(6):833-840

Nautilus subplicatusSteinmann, 1895 is a latest Cretaceous species of nautiloid which is common in southern South America (Chile, Argentina) and the Antarctic Peninsula and which is best assigned to the genus EutrephocerasHyatt, 1894. Nautilus dorbignyanusForbes in Darwin, 1846 and Nautilus valenciennii Hupé in Gay, 1854 are here considered to be senior synonyms which later authors have apparently overlooked. The type material of these two taxa is reillustrated. On the basis of this and additional material it is demonstrated that only a single nautiloid species occurs in the Quiriquina Formation of late Maastrichtian age. For this we propose to use N. dorbignyanus as the oldest available name.  相似文献   

Editorial for the special issue: vulnerability to natural hazards—the challenge of integration   总被引：8，自引：6，他引：2  

Sven Fuchs  Christian Kuhlicke  Volker Meyer 《Natural Hazards》2011,58(2):609-619

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