PEPSI: The high‐resolution échelle spectrograph and polarimeter for the Large Binocular Telescope     

K.G. Strassmeier  I. Ilyin  A. Jrvinen  M. Weber  M. Woche  S. I. Barnes  S.‐M. Bauer  E. Beckert  W. Bittner  R. Bredthauer  T. A. Carroll  C. Denker  F. Dionies  I. DiVarano  D. Dscher  T. Fechner  D. Feuerstein  T. Granzer  T. Hahn  G. Harnisch  A. Hofmann  M. Lesser  J. Paschke  S. Pankratow  V. Plank  D. Plüschke  E. Popow  D. Sablowski  J. Storm 《Astronomische Nachrichten》2015,336(4):324-361

PEPSI is the bench‐mounted, two‐arm, fibre‐fed and stabilized Potsdam Echelle Polarimetric and Spectroscopic Instrument for the 2×8.4 m Large Binocular Telescope (LBT). Three spectral resolutions of either 43 000, 120 000 or 270 000 can cover the entire optical/red wavelength range from 383 to 907 nm in three exposures. Two 10.3k×10.3k CCDs with 9‐µm pixels and peak quantum efficiencies of 94–96 % record a total of 92 échelle orders. We introduce a new variant of a wave‐guide image slicer with 3, 5, and 7 slices and peak efficiencies between 92–96 %. A total of six cross dispersers cover the six wavelength settings of the spectrograph, two of them always simultaneously. These are made of a VPH‐grating sandwiched by two prisms. The peak efficiency of the system, including the telescope, is 15 % at 650 nm, and still 11 % and 10 % at 390 nm and 900 nm, respectively. In combination with the 110 m² light‐collecting capability of the LBT, we expect a limiting magnitude of ≈20th mag in V in the low‐resolution mode. The R = 120 000 mode can also be used with two, dual‐beam Stokes IQUV polarimeters. The 270 000‐mode is made possible with the 7‐slice image slicer and a 100‐µm fibre through a projected sky aperture of 0.74″, comparable to the median seeing of the LBT site. The 43 000‐mode with 12‐pixel sampling per resolution element is our bad seeing or faint‐object mode. Any of the three resolution modes can either be used with sky fibers for simultaneous sky exposures or with light from a stabilized Fabry‐Pérot étalon for ultra‐precise radial velocities. CCD‐image processing is performed with the dedicated data‐reduction and analysis package PEPSI‐S4S. Its full error propagation through all image‐processing steps allows an adaptive selection of parameters by using statistical inferences and robust estimators. A solar feed makes use of PEPSI during day time and a 500‐m feed from the 1.8 m VATT can be used when the LBT is busy otherwise. In this paper, we present the basic instrument design, its realization, and its characteristics. Some pre‐commissioning first‐light spectra shall demonstrate the basic functionality. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Langzeitige Änderung des Salzgehaltes in der Unterweser     

Dr. Iris Grabemann  Gunther Krause  Gerold Siedler 《Ocean Dynamics》1983,36(2):61-77

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Isotopic and hydrochemical studies of groundwater flow and salinity in the Southern Upper Rhine Graben     

Michael Bauer  Lorenz Eichinger  Philippe Elsass  Wolfram Kloppmann  Gunther Wirsing 《International Journal of Earth Sciences》2005,94(4):565-579

In order to determine the origin and the propagation mechanisms of highly concentrated chloride brines within the Quaternary aquifer system in the southern part of the Upper Rhine Graben, a combined isotope (H, O, C) and hydrochemical analysis was carried out. Groundwater recharge in this area is a complex system, consisting of local precipitation, river bank filtration, lateral flow from the Graben borders and, to a minor extent, an old Pleistocene component. In some areas, groundwater consists of up to 90% of recent bank filtrate, reaching depths down to at least 100 m. The isotopic and hydrochemical results show, that the elevated chloride concentrations in the Quaternary aquifer mainly result from leaky settling basins charged by the French potash mines until the mid 1970s. Input of natural brines coming from tertiary salt diapirs is of only minor importance. While infiltrating, the anthropogenic brines were strongly diluted by local river bank filtrate of the Rhine. Nevertheless, maximum chloride concentrations nowadays still reach some 10,000 mg/l at the base of the aquifer at a depth of more than 100 m below surface. The main volume of the brines is stored in the less permeable lower part of the quaternary sediments (Breisgau-Formation) whereas only a minor part is transported northwards with the rapid convective groundwater flow. Brines undergoing only dilution preserve their hydrochemical characteristics (NaCl-type). In contrast, brines recirculated from the Breisgau-Formation show a northwards increasing alteration through ion exchange processes. Potassium and sodium may be fixed in the fine grained aquifer material while calcium is set free into the groundwater. After a flow distance of about 12 km, complex hydraulic interactions between groundwater and surface waters lead to the rise of strongly diluted and hydrochemically altered brines with chloride contents up to maximum 700 mg/l. The presented case study is an example for a detailed analysis of a multi-component groundwater mixing system using combined isotope and hydrochemical methods. Furthermore, cation exchange is shown as a major process affecting the hydrochemical evolution of the young groundwater in the southern Upper Rhine Graben which is locally strongly polluted by chloride as a consequence of former potash mining.  相似文献   

Comment on a paper “The origin of high magnetic remanence in fault pseudotachylites: Theoretical considerations and implication for coseismic electrical currents” by E.C. Ferré, M.S. Zechmeister, J.W. Geissman, N. Mathana Sekaran, and K. Kocak     

Gunther Kletetschka   《Tectonophysics》2006,419(1-4)

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Diagenesis of organic matter and fine clay minerals: a comparative study     

T.G. Powell  A.E. Foscolos  P.R. Gunther  L.R. Snowdon 《Geochimica et cosmochimica acta》1978,42(8):1181-1197

A geochemical study has been made of fine clay minerals and organic matter in subsurface shale samples from the Canadian Northwest Territories. The mixed layer clays comprise smectite-vermiculite-illite but are transformed during thermal diagenesis to a pseudo-quaternary system (smectitevermiculite-illite-chlorite) by incorporation of amorphous inorganic material. The first clay dehydration occurs prior to hydrocarbon generation and is accompanied by adsorption of K⁺ and substitution of Al³⁺ for Si⁴⁺ in the clay lattice. Vermiculite is an intermediary in the transformation of smectite to illite and in the presence of Ca²⁺ ions delays the second dehydration step to the zone where cracking of liquid hydrocarbons to gas occurs.Hydrocarbon generation commences at a vitrinite reflectance level of ? 0.5% R₀ maximum in both amorphous and woody-herbaceous organic matter but does not reach a significant level in the latter case until reflectance levels of 0.7% R₀ maximum. The pristane to phytane ratio and proportion of n-alkanes and acyclic isoprenoids increase during hydrocarbon generation from woody-herbaceous organic matter. Anomalous hydrocarbon yields from certain samples are attributed to high concentrations of plant resins. Destructions of liquid hydrocarbons by cracking commences at a reflectance level of 1.0% R₀ maximum and is essentially complete by a reflectance level of 1.4% R₀ maximum. The proportion of n-alkanes in the saturates decreases during cracking of the liquid hydrocarbons.  相似文献   

Presolar nanodiamonds: faster, cleaner, and limits on platinum-HL     

Silke Merchel  Ulrich Ott  Siegfried Herrmann  Thomas Faestermann  Gunther Korschinek  Anton Wallner 《Geochimica et cosmochimica acta》2003,67(24):4949-4960

We have developed a procedure that allows extraction of clean nanodiamond samples from primitive meteorites for isotopic analyses of trace elements on a timescale of just a week. This procedure includes microwave digestion and optimization of existing isolation techniques for further purification. Abundances of trace elements that are difficult to dissolve using standard procedures (e.g., Ir) are lower in the diamond residues prepared using the new technique. Accelerator mass spectrometry (AMS) was explored as a means for isotopic measurements. Results obtained on diamond fractions from Allende and Murchison show the need for suitable matrix-adjusted standards to correct for fractionation effects; nevertheless they allow putting an upper limit on the abundance of ¹⁹⁸Pt-H in nanodiamonds of ∼1 × 10¹⁴ atoms/g. This limit is on the order of what can be expected from predictions of competing nucleosynthesis models and extrapolation of the apparently mass dependent abundance trend of the associated noble gases.Unfortunately, and unexpectedly, presolar silicon carbide is almost quantitatively dissolved during microwave digestion with HCl/HF/HNO₃. Re-evaluation of the standard extraction technique, however, shows that it also may lead to severe loss of fine-grained SiC, a fact not commonly appreciated. A lower limit to SiC abundance in Murchison is 20 ppm, and previous conclusions that Murchison SiC is unusually coarse-grained compared to SiC in other primitive meteorites seem not to be warranted. Graphite and silicon nitride may survive and possibly can be separated after this step as suggested by a simulation experiment using terrestrial analog material, but the detailed behavior of meteoritic graphite requires further study.  相似文献   

Critical tissue copper residues for marine bivalve (Mytilus galloprovincialis) and echinoderm (Strongylocentrotus purpuratus) embryonic development: conceptual, regulatory and environmental implications     

Rosen G  Rivera-Duarte I  Chadwick DB  Ryan A  Santore RC  Paquin PR 《Marine environmental research》2008,66(3):327-336

Critical tissue copper (Cu) residues associated with adverse effects on embryo-larval development were determined for the Mediterranean mussel (Mytilus galloprovincialis) and purple sea urchin (Strongylocentrotus purpuratus) following laboratory exposure to Cu-spiked seawater collected from San Diego Bay, California, USA. Whole body no-observed-effect-residues (NOER) were similar, with means of 21 and 23mugg(-1)dw, for M. galloprovincialis and S. purpuratus, respectively. Mean whole body median effect residues (ER50) were 49 and 142mugg(-1)dw for M. galloprovincialis and S. purpuratus, respectively. The difference in ER50s between species was reduced to a factor of <2 when expressed as soft tissue residues. Coefficients of variation among whole body-ER50s were 3-fold lower than median waterborne effect concentrations (EC50) for both species exposed to samples varying in water quality characteristics. This suggests that tissue concentrations were a better predictor of toxicity than water concentrations. The CBRs described herein do not differentiate between the internal Cu concentrations that are metabolically available and those that are accumulated and then detoxified. They do appear, however, to be well enough related to the level of accumulation at the site of action of toxicity that they serve as useful surrogates for the copper concentration that affects embryonic development of the species tested. Results presented have potentially important implications for a variety of monitoring and assessment strategies. These include regulatory approaches for deriving saltwater ambient water quality criteria for Cu, contributions towards the development of a saltwater biotic ligand model, the conceptual approach of using CBRs, and ecological risk assessment.  相似文献   

Magnetic record associated with tree ring density: Possible climate proxy     

Gunther Kletetschka  Petr Pruner  Daniela Venhodova  Jaroslav Kadlec 《Geochemical transactions》2007,8(1):2

A magnetic signature of tree rings was tested as a potential paleo-climatic indicator. We examined wood from sequoia tree, located in Mountain Home State Forest, California, whose tree ring record spans over the period 600 – 1700 A.D. We measured low and high-field magnetic susceptibility, the natural remanent magnetization (NRM), saturation isothermal remanent magnetization (SIRM), and stability against thermal and alternating field (AF) demagnetization. Magnetic investigation of the 200 mm long sequoia material suggests that magnetic efficiency of natural remanence may be a sensitive paleoclimate indicator because it is substantially higher (in average >1%) during the Medieval Warm Epoch (700–1300 A.D.) than during the Little Ice Age (1300–1850 A.D.) where it is <1%. Diamagnetic behavior has been noted to be prevalent in regions with higher tree ring density. The mineralogical nature of the remanence carrier was not directly detected but maghemite is suggested due to low coercivity and absence of Verwey transition. Tree ring density, along with the wood's magnetic remanence efficiency, records the Little Ice Age (LIA) well documented in Europe. Such a record suggests that the European LIA was a global phenomenon. Magnetic analysis of the thermal stability reveals the blocking temperatures near 200 degree C. This phenomenon suggests that the remanent component in this tree may be thermal in origin and was controlled by local thermal condition.  相似文献   

Cross sections from 5 to 35 MeV for the reactions natMg(3He,x)26Al, 27Al(3He,x)26Al,natCa(3He,x)41Ca,and natCa(3He,x)36Cl: Implications for early irradiation in the solar system     

Gregory F. HERZOG  Marc W. CAFFEE  Thomas FAESTERMANN  R. HERTENBERGER  Gunther KORSCHINEK  Ingo LEYA  Robert C. REEDY  J. M. SISTERSON 《Meteoritics & planetary science》2011,46(10):1427-1446

Abstract– Cross sections were measured for the nuclear reactions ^natMg(³He,x)²⁶Al, ²⁷Al(³He,x)²⁶Al, ^natCa(³He,x)⁴¹Ca, and ^natCa(³He,x)³⁶Cl in the energy region from approximately 5–35 MeV. The rates of these reactions are important for studies of early solar system irradiation scenarios. The ²⁶Al, ³⁶Cl, and ⁴¹Ca were separated chemically, and the numbers of atoms produced in each reaction channel were measured using accelerator mass spectrometry (AMS). From these results, 26 cross sections were determined and compared with predictions of the TALYS code. Agreement is within 40% for most cross sections. Our measurements were used to model the production of ⁷Be, ¹⁰Be, ²⁶Al, and ⁴¹Ca in the early solar system. For projectiles ¹H, ³He, and ⁴He, we assumed energy spectra of the general form E^?α. For a wide range of parameterizations, the modeled ratios of ⁷Be/Be and ¹⁰Be/Be on the one hand and of ²⁶Al/²⁷Al and ⁴¹Ca/Ca on the other are coupled because the excitation functions for the relevant nuclear reactions have similar shapes. Modeling of a closed system with the constraint that ¹⁰Be/⁹Be = 0.001 fails to reproduce simultaneously the range of ⁷Be/⁹Be, ²⁶Al/²⁷Al, and ⁴¹Ca/Ca ratios inferred for the early solar system from studies of meteorites.  相似文献   

Acoustic backscatter and sediment textural properties of inner shelf sands,northeastern Gulf of Mexico     

Kenneth S. Davis  Niall C. Slowey  Ingo H. Stender  Hannelore Fiedler  William R. Bryant  Gunther Fechner 《Geo-Marine Letters》1996,16(3):273-278

The relationship between spatial variations of the properties of sea-floor sediments and acoustic backscatter from the surface of the sea floor on the continental shelf off of Panama City, Florida, USA, is investigated using surficial sediment grab samples and digital side-scan sonar data. Acoustic backscatter strength has a high, direct correlation with the mean grain size of the sediments. Acoustic backscatter strength also correlates directly with the carbonate content of the sediments, particularly in medium-and coarse-sand facies, because large, irregularly shaped, carbonate particles affect both the mean grain size of the sediments and the roughness of the surface of the sea floor.  相似文献