The Wide Field Spectrograph (WiFeS)     

Michael Dopita  John Hart  Peter McGregor  Patrick Oates  Gabe Bloxham  Damien Jones 《Astrophysics and Space Science》2007,310(3-4):255-268

This paper describes the Wide Field Spectrograph (WiFeS) under construction at the Research School of Astronomy and Astrophysics (RSAA) of the Australian National University (ANU) for the ANU 2.3 m telescope at the Siding Spring Observatory. WiFeS is a powerful integral field, double-beam, concentric, image-slicing spectrograph designed to deliver excellent throughput, wavelength stability, spectrophotometric performance and superb image quality along with wide spectral coverage throughout the 320–950 nm wavelength region. It provides a 25×38 arcsec field with 0.5 arcsec sampling along each of twenty five 38×1 arcsec slitlets. The output format is optimized to match the 4096×4096 pixel CCD detectors in each of two cameras individually optimized for the blue and the red ends of the spectrum, respectively. A process of “interleaved nod-and-shuffle” will be applied to permit quantum noise-limited sky subtraction. Using VPH gratings, spectral resolutions of 3000 and 7000 are provided. The full spectral range is covered in a single exposure at R=3000, and in two exposures in the R=7000 mode. The use of transmissive coated optics, VPH gratings and optimized mirror coatings ensures a throughput (including telescope atmosphere and detector) >30% over a wide spectral range. The concentric image-slicer design ensures an excellent and uniform image quality across the full field. To maximize scientific return, the whole instrument is configured for remote observing, pipeline data reduction, and the accumulation of calibration image libraries.  相似文献   

Holocene glacier and deep water dynamics,Adélie Land region,East Antarctica     

Delphine Denis  Xavier Crosta  Sabine Schmidt  Damien S. Carson  Raja S. Ganeshram  Hans Renssen  Viviane Bout-Roumazeilles  Sebastien Zaragosi  Bernard Martin  Michel Cremer  Jacques Giraudeau 《Quaternary Science Reviews》2009,28(13-14):1291-1303

This study presents a high-resolution multi-proxy investigation of sediment core MD03-2601 and documents major glacier oscillations and deep water activity during the Holocene in the Adélie Land region, East Antarctica. A comparison with surface ocean conditions reveals synchronous changes of glaciers, sea ice and deep water formation at Milankovitch and sub-Milankovitch time scales. We report (1) a deglaciation of the Adélie Land continental shelf from 11 to 8.5 cal ka BP, which occurred in two phases of effective glacier grounding-line retreat at 10.6 and 9 cal ka BP, associated with active deep water formation; (2) a rapid glacier and sea ice readvance centred around 7.7 cal ka BP; and (3) five rapid expansions of the glacier–sea ice systems, during the Mid to Late Holocene, associated to a long-term increase of deep water formation. At Milankovich time scales, we show that the precessionnal component of insolation at high and low latitudes explains the major trend of the glacier–sea ice–ocean system throughout the Holocene, in the Adélie Land region. In addition, the orbitally-forced seasonality seems to control the coastal deep water formation via the sea ice–ocean coupling, which could lead to opposite patterns between north and south high latitudes during the Mid to Late Holocene. At sub-Milankovitch time scales, there are eight events of glacier–sea ice retreat and expansion that occurred during atmospheric cooling events over East Antarctica. Comparisons of our results with other peri-Antarctic records and model simulations from high southern latitudes may suggest that our interpretation on glacier–sea ice–ocean interactions and their Holocene evolutions reflect a more global Antarctic Holocene pattern.  相似文献   

Practical versus absolute salinity measurements: New advances in high performance seawater salinity sensors     

Philippe Grosso  Marc Le Menn  Jean-Louis De Bougrenet De La Tocnaye  Zong Yan Wu  Damien Malardé 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(1):151-156

Optical salinity sensors described here measure directly the seawater refractive index and thus enable a measurement of the seawater density and composition variation. We detail the measurement dependence to environmental parameters (in particular temperature and pressure) compared to conductivity sensors, and demonstrate that it may be advantageous to directly measure refractive index rather than electrical conductivity and so obtain a more direct route to density and absolute salinity.  相似文献   

Fe‐Mg interdiffusion profiles in rimmed forsterite grains in the Allende matrix: Time–temperature constraints for the parent body metamorphism          下载免费PDF全文

Priscille Cuvillier  Hugues Leroux  Damien Jacob  Pierre Hirel 《Meteoritics & planetary science》2015,50(9):1529-1545

The Allende matrix is dominated by micron‐sized lath‐shaped fayalitic olivine grains with a narrow compositional range (Fa_40–50). Fayalitic olivines also occur as rims around forsterite grains in chondrules and isolated forsterite fragments in the matrix or as veins cross‐cutting the grains. Allende is a type 3 CV carbonaceous chondrite having experienced a moderate thermal metamorphism. There is therefore a strong chemical disequilibrium between the large forsterite grains and the fayalite‐rich fine‐grained matrix. Chemical gradients at interfaces are poorly developed and thus not accessible using conventional techniques. Here, we used analytical transmission electron microscopy to study the microstructure of the fayalite‐rich matrix grains and interfaces with forsterite fragments. We confirm that fayalitic grains in the matrix and fayalitic rims around forsterite fragments have the same properties, suggesting a common origin after the accretion of the parent body of Allende. Composition profiles at the rim/forsterite interfaces exhibit a plateau in the rim (typically Fa₄₅), a compositional jump of 10 Fa% at the interface, and a concentration gradient in the forsterite grain. Whatever the studied forsterite grain or whatever the nature of the interface, the Fe‐Mg profiles in forsterite grains have the same length of about 1.5 μm. This strongly suggests that the composition profiles were formed by solid‐state diffusion during the thermal metamorphism episode. Time–temperature couples associated with the diffusion process during thermal metamorphism are deduced from profile modeling. Considering the uncertainties on the diffusion coefficient value, we found that the peak temperature in Allende is ranging from 425 to 505 °C.  相似文献   

Zircon texture and chemical composition as a guide to magmatic processes and mixing in a granitic environment and coeval volcanic system   总被引：3，自引：0，他引：3  

Damien Gagnevin  J. Stephen Daly  Andreas Kronz 《Contributions to Mineralogy and Petrology》2010,159(4):579-596

This study documents the chemical and textural responses of zircon in the Elba igneous complex, with particular reference to the 7- to 7.8-Ma-old Monte Capanne pluton in relation to its coeval volcanic counterpart (Capraia), using BSE imaging and quantitative electron microprobe analyses. The Monte Capanne pluton displays multiple field and geochemical evidence for magma mixing. The samples we have investigated (including monzogranitic, mafic enclave and dyke samples) display similar zircon textures and are associated with an extremely large range of trace and minor element (Hf, Y, HREE, Th, U) compositions, which contrast with relatively simple textures and zoning patterns in zircons from a Capraia dacite. We have used a relatively simple textural classification (patchy zoning, homogenous cores, oscillatory zoning and unzoned zircon) as the basis for discussing the chemical composition and chemical variation within zircons from the Monte Capanne pluton. Based on these data and other works (Dini et al. 2004 in Lithos 78:101–118, 2004) , it is inferred that mixing between metaluminous and peraluminous melts occurred early in the evolution of the Monte Capanne magma chamber. In particular, mixing was responsible for the development of the patchy-zoning texture in the zircon cores, which was associated with reactions between other accessory phases (including monazite, apatite, allanite), which we infer to have significantly affected the Th distribution in zircon. Zircons from the MC pluton displaying “homogeneous cores” have chemical affinities with zircons in the coeval Capraia volcanic system, consistent with the participation of a Capraia-like mantle end-member during mixing. Further zircon growth in the MC pluton produced the oscillatory zoning texture, which records both long-term (crystal fractionation) and transient (recharge with both silicic and mafic magmas) events in a hybrid magma chamber. It is inferred that Hf and the Th/U ratio cannot be used alone to infer magmatic processes due to their dependency on temperature, nor are they a diagnostic feature of xenocrystic grains. This study shows that zircon chemistry coupled with detailed textural analysis can provide a powerful tool to elucidate the complex evolution of a magma system.  相似文献   

The impact and rotational light curves of Comet 9P/Tempel 1     

Jean Manfroid  Damien Hutsemékers  Anita L. Cochran  William M. Jackson  Rita Schulz 《Icarus》2007,187(1):144-155

UVES and HIRES high-resolution spectra of Comet 9P/Tempel 1 are used to investigate the impact and rotational light curves of various species with a view toward building a simple model of the distribution and activity of the sources. The emission by OH, NH, CN, C₃, CH, C₂, NH₂, and OI, are analyzed, as well as the light scattered by the dust. It is found that a simple model reproduces fairly well the impact light curves of all species combining the production of the observed molecules and the expansion of the material throughout the slit. The impact light curves are consistent with velocities of 400-600 m/s. Their modeling requires a three-step dissociation sequence “Grand-Parent → Parent → Daughter” to produce the observed molecules. The rotational light curve for each species is explained in terms of a single model with three sources. The dust component can however not easily be explained that way.  相似文献   

Holocene fire regime changes from multiple-site sedimentary charcoal analyses in the Lourdes basin (Pyrenees,France)     

Damien Rius  Boris Vannière  Didier Galop  Hervé Richard 《Quaternary Science Reviews》2011,30(13-14):1696-1709

One lake and three peat bogs from the Lourdes glacial basin (France) were used for macrocharcoal analyses and fire frequency reconstruction over the entire Holocene (11700 years). The chronology was based upon thirty-three 14C AMS dates. Comparison of the distribution of both CHarcoal Accumulation Rate (CHAR) and fire return intervals showed that charcoal accumulation significantly differs between the lake and the peat bogs, but that frequency calculation overcomes the disparity between these site types. A composite frequency was built from the four individual records to assess regional versus local variability and fire regime controls by comparisons with regional fire activity, Holocene climatic oscillations and vegetation history. The millennial variability can be depicted as follows: relatively high frequency between 8000 and 5000 cal a BP (up to 5 fires/500 yrs), relatively low frequency between 5000 and 3000 cal a BP (down to 0 fires/500 yrs), and an increase between 3000 and 500 cal a BP (up to 4 fires/500 yrs). From 8000 to 5000 cal a BP, fire frequency displays strong synchrony between sites and appears to be mostly driven by increased summer temperature characterizing the Holocene Thermal Maximum (HTM). On the contrary, during the last 3000 years fire frequency was heterogeneous between sites and most probably human-driven. However, higher frequency at the millennial scale during the mid-Holocene strongly suggests that the perception of human-driven fire regime depends on the strength of natural controls.  相似文献   

Plio-Quaternary extension in the Venezuelan Andes: Mapping from SAR JERS imagery     

Damien Dhont  Guillaume Back  Yves Hervouët 《Tectonophysics》2005,399(1-4):293

The geometry of extensional structures is described for the first time in the active setting of the Venezuelan Andes using remote sensing imagery. We favored the use of a mosaic of Synthetic Aperture Radar (SAR) scenes of the Japanese Earth Resources Satellite-1 (JERS-1) assisted by complementary remote sensing devices (Landsat TM, digital elevation models) and field observations to make a structural analysis at regional scale. Radar images are particularly efficient in the Venezuelan Andes where dense vegetation and frequent cloud covering earlier lent difficulties to remote sensing studies. We focused our analysis in the Valera–Rio Momboy and Bocono faults corner and in the Mucujun area. We show that, in an area where ongoing compression and strike–slip deformations occur, brittle extension can be detected independently from previous knowledge. Extensional structures correspond to elongated tilted blocks with dimension less than 10 km in width. Blocks are bounded by curved faults in plan view, the concavity being turned towards the axial part of the belt. The geometry and kinematics of such structures suggest that syn-orogenic extension started together with initiation of right-lateral strike–slip motion along the Bocono Fault in the Plio-Quaternary.  相似文献   

Structural control of sinkholes and subsidence hazards along the Jordanian Dead Sea coast     

Damien Closson 《Environmental Geology》2005,47(2):290-301

For about four decades, the Dead Sea (DS) level and the surrounding water table has been dropping dramatically. At least from the eighties, the direct vicinity of the Lisan Peninsula (LP), Jordan, has been facing high rates of subsidence and sinkhole hazards. Between 2000 and 2002, the Arab Potash Company (APC) lost two salt evaporation ponds resulting in a loss of $70 million. In the fertile plain of Ghor al Haditha (GAH), three deep and wide bowl-shaped subsidence areas threaten human activities and infrastructures. Over the part of the Lisan Peninsula that emerged before the 1960s, relict fossil sinkholes occurred everywhere, whereas new collapses constantly appear in the southern area only. In this paper, we have integrated 15 years of field observations related to sinkholes and subsidence with interpretation of space borne radar interferometric outputs, aerial photographs and satellite images. This has helped to place hazardous areas in their geological context and to clarify them within the framework of the general tectonic setting of the area.  相似文献   

Tracking past mining activity using trace metals,lead isotopes and compositional data analysis of a sediment core from Longemer Lake,Vosges Mountains,France     

Anne-Lise Mariet  Fabrice Monna  Frédéric Gimbert  Carole Bégeot  Christophe Cloquet  Simon Belle  Laurent Millet  Damien Rius  Anne-Véronique Walter-Simonnet 《Journal of Paleolimnology》2018,60(3):399-412

A 157-cm-long sediment core from Longemer Lake in the Vosges Mountains of France spans the past two millennia and was analyzed for trace metal content and lead isotope composition. Trace metal accumulation rates highlight three main input phases: Roman Times (cal. 100 BC–AD 400), the Middle Ages (cal. AD 1000–1500), and the twentieth century. Atmospheric contamination displays a pattern that is similar to that seen in peat bogs from the region, at least until the eighteenth century. Thereafter, the lake sediment record is more precise than peat records. Some regional mining activity, such as that in archaeologically identified eighteenth-century mining districts, was detected from the lead isotope composition of sediment samples. Compositional data analysis, using six trace metals (silver, arsenic, cadmium, copper, lead and zinc), enabled us to distinguish between background conditions, periods of mining, and of other anthropogenic trace metal emissions, such as the recent use of leaded gasoline.  相似文献