Experimental impact cratering: A summary of the major results of the MEMIN research unit     

Thomas Kenkmann  Alex Deutsch  Klaus Thoma  Matthias Ebert  Michael H. Poelchau  Elmar Buhl  Eva-Regine Carl  Andreas N. Danilewsky  Georg Dresen  Anja Dufresne  Nathanaël Durr  Lars Ehm  Christian Grosse  Max Gulde  Nicole Güldemeister  Christopher Hamann  Lutz Hecht  Stefan Hiermaier  Tobias Hoerth  Astrid Kowitz  Falko Langenhorst  Bernd Lexow  Hanns-Peter Liermann  Robert Luther  Ulrich Mansfeld  Dorothee Moser  Manuel Raith  Wolf Uwe Reimold  Martin Sauer  Frank Schäfer  Ralf Thomas Schmitt  Frank Sommer  Jakob Wilk  Rebecca Winkler  Kai Wünnemann 《Meteoritics & planetary science》2018,53(8):1543-1568

This paper reviews major findings of the Multidisciplinary Experimental and Modeling Impact Crater Research Network (MEMIN). MEMIN is a consortium, funded from 2009 till 2017 by the German Research Foundation, and is aimed at investigating impact cratering processes by experimental and modeling approaches. The vision of this network has been to comprehensively quantify impact processes by conducting a strictly controlled experimental campaign at the laboratory scale, together with a multidisciplinary analytical approach. Central to MEMIN has been the use of powerful two-stage light-gas accelerators capable of producing impact craters in the decimeter size range in solid rocks that allowed detailed spatial analyses of petrophysical, structural, and geochemical changes in target rocks and ejecta. In addition, explosive setups, membrane-driven diamond anvil cells, as well as laser irradiation and split Hopkinson pressure bar technologies have been used to study the response of minerals and rocks to shock and dynamic loading as well as high-temperature conditions. We used Seeberger sandstone, Taunus quartzite, Carrara marble, and Weibern tuff as major target rock types. In concert with the experiments we conducted mesoscale numerical simulations of shock wave propagation in heterogeneous rocks resolving the complex response of grains and pores to compressive, shear, and tensile loading and macroscale modeling of crater formation and fracturing. Major results comprise (1) projectile–target interaction, (2) various aspects of shock metamorphism with special focus on low shock pressures and effects of target porosity and water saturation, (3) crater morphologies and cratering efficiencies in various nonporous and porous lithologies, (4) in situ target damage, (5) ejecta dynamics, and (6) geophysical survey of experimental craters.  相似文献   

Benthic nutrient fluxes along the Laurentian Channel: Impacts on the N budget of the St. Lawrence marine system     

Benoît Thibodeau  Moritz F. Lehmann  Jacqueline Kowarzyk  Alfonso Mucci  Yves Gélinas  Denis Gilbert  Roxane Maranger  Mohammad Alkhatib 《Estuarine, Coastal and Shelf Science》2010

Water column concentrations and benthic fluxes of dissolved inorganic nitrogen (DIN) and oxygen (DO) were measured in the Gulf of St. Lawrence and the Upper and Lower St. Lawrence Estuary (USLE and LSLE, respectively) to assess the nitrogen (N) budget in the St. Lawrence (SL) system, as well as to elucidate the impact of bottom water hypoxia on fixed-N removal in the LSLE. A severe nitrate deficit, with respect to ambient phosphate concentrations (N*∼−10 μmol L⁻¹), was observed within and in the vicinity of the hypoxic bottom water of the LSLE. Given that DO concentrations in the water column have remained above 50 μmol L⁻¹, nitrate reduction in suboxic sediments, rather than in the water column, is most likely responsible for the removal of fixed N from the SL system. Net nitrate fluxes into the sediments, derived from pore water nitrate concentration gradients, ranged from 190 μmol m⁻² d⁻¹ in the hypoxic western LSLE to 100 μmol m⁻² d⁻¹ in the Gulf. The average total benthic nitrate reduction rate for the Laurentian Channel (LC) is on the order of 690 μmol m⁻² d⁻¹, with coupled nitrification-nitrate reduction accounting for more than 70%. Using average nitrate reduction rates derived from the observed water column nitrate deficit, the annual fixed-N elimination within the three main channels of the Gulf of St. Lawrence and LSLE was estimated at 411 × 10⁶ t N, yielding an almost balanced N budget for the SL marine system.  相似文献   

Variability and propagation of Labrador Sea Water in the southern subpolar North Atlantic     

Dagmar Kieke  Birgit Klein  Lothar Stramma  Monika Rhein  Klaus Peter Koltermann   《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1656-1674

The variability of two modes of Labrador Sea Water (LSW) (upper and deep Labrador Sea Water) and their respective spreading in the interior North Atlantic Ocean are investigated by means of repeated ship surveys carried out along the zonal WOCE line A2/AR19 located at 43–48°N (1993–2007) and along the GOOS line at about 48–51°N (1997–2002). Hydrographic section data are complemented by temperature, salinity, and velocity time series recorded by two moorings. They have been deployed at the western flank of the Mid-Atlantic Ridge (MAR) in the Newfoundland Basin during 1996–2004. The analysis of hydrographic anomalies at various longitudes points to a gradual eastward propagation of LSW-related signals, which happens on time scales of 3–6 years from the formation region towards the MAR. Interactions of the North Atlantic Current (NAC) with the Deep Western Boundary Current (DWBC) close to Flemish Cap point to the NAC being the main distributor of the different types of LSW into the interior of the Newfoundland Basin. Comparisons between the ship data and the mooring records revealed that the mooring sites are located in a region affected by highly variable flow. The mooring time series demonstrate an elevated level of variability with eddy activity and variability associated with the NAC considerably influencing the LSW signals in this region. Hydrographic data taken from Argo profiles from the vicinity of the mooring sites turned out to mimic quite well the temporal evolution captured by the moorings. There is some indication of occasional southward flow in the LSW layer near the MAR. If this can be considered as a hint to an interior LSW-route, it is at least of minor importance in comparison to the DWBC. It acts as an important supplier for the interior North Atlantic, distributing older and recently formed LSW modes southward along the MAR.  相似文献   

G. BURBIDGE,D. LAYZER,J. G. PHILLIPS (eds.): Annual Review of Astronomy and Astrophysics. Vol. 24. Annual Reviews Inc. Palo Alto,Calif., USA, 1986. 627 Seiten,Leinen, Preis: US$47. -. ISBN 0-8243-0924-3     

Klaus Fritze 《Astronomische Nachrichten》1988,309(5):326-326

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Geodetic reference system 1980     

H. Moritz 《Journal of Geodesy》1988,62(3):348-358

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Testing the Limits of ICP-MS: Determination of Trace Elements in Ground Water at the Part-Per-Trillion Level   总被引：3，自引：0，他引：3  

Klaus J. Stetzenbach  Megumi Amano  David K. Kreamer  Vernon F. Hodge 《Ground water》1994,32(6):976-985

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Polarized single-crystal FTIR-spectra of natural staurolite     

Monika Koch-Müller  Klaus Langer  Anton Beran 《Physics and Chemistry of Minerals》1995,22(2):108-114

Polarized infrared absorption spectra of thin single-crystal slabs parallel to (010) and (001) of a staurolite from Pizzo Forno, Ticino, with analyzed composition (Fe_2.9Mg_0.9Zn_0.1Mn_0.1)Al_17.5Ti_0.1(Si_7.7Al_0.3)O₄₈H₃ have been measured in the range of 3000–4000 cm^?1. From the pleochroitic behaviour of the OH-vibrations three groups of bands can be distinguished: the bands of group I, a strong band at 3445 cm^?1 plus a weak shoulder at 3358 cm^?1, and the bands of group II, a weak band centered at 3677 cm^?1 plus a shoulder at 3635 cm^?1, are assigned to the H1 and H2 protons, respectively. The bands of group III, a weak band at 3577 cm^?1 plus a shoulder, cannot be interpreted on the basis of the proton positions known so far. We assign them to an additional proton H3, which is bonded to O1 and shows a bifurcated hydrogen bridge to two O5 in a vacant T2 site.  相似文献   

Consequences of explosive eruptions on small Solar System bodies: the case of the missing basalts on the aubrite parent body     

Lionel Wilson  Klaus Keil 《Earth and Planetary Science Letters》1991,104(2-4)

Aubrite meteorites are composed of constituents which are almost certainly of igneous origin. If they were generated by the melting and fractionation of enstatite chondrite-like parental material, as seems very likely, then plagioclase-rich, basaltic complements to the aubrites should have formed. However, such materials are not known as individual meteorites, and the compositions of two plagioclase-silica clasts and one albite-silica-(diopside-anorthite) clast (probably an impact melt) in the Norton County aubrite breccia suggest that they are not the putative enstatite-plagioclase basalts. We propose a new mechanism that explains the absence of these materials, showing that the expansion of even very small amounts of volatiles present in a melt approaching the surface of a small, low-gravity body will be enough to disrupt the melt into a spray of droplets moving faster than the local escape velocity. This explosive volcanic process of melt removal requires larger melt volatile contents on larger bodies, and data on the solubility of volatiles in basaltic melts suggest that the process was limited to bodies smaller than about 100 km in radius.  相似文献   

Extremely low temperatures in the stratosphore and very low total ozone amount above northern and central Europe during winter 1989     

Klaus Wege 《Journal of Atmospheric Chemistry》1991,12(4):381-390

On 1 February 1989, -83.5°C was recorded in 27.8 hPa over Hohenpeißenberg, the lowest temperature in the 22-year series. This was measured together with a very low total ozone amount of 266 DU. This may be compared with nearly twice this amount on 27 February 1989. The situation was very unusual: following an extremely cold winter in the Arctic stratosphere, the stratospheric cold pole was located over southern Scandinavia on 1 February in a very southerly position. The analyzed temperatures of -92 °C in 30 hPa were also unusual. Even though the low ozone amounts over Hohenpeißenberg were probably dynamically caused, an additional very small ozone decrease due to heterogeneous reactions in altitudes from 23–28 km, where the temperatures lie below -80 °C, cannot be ruled out. Extinction measurements by the orbitting SAGE II instrument indeed show polar stratospheric clouds over Europe near 50° N during the period 31 January–2 February. Also, polar stratospheric clouds were previously observed over Kiruna at similarly low temperatures and signs of a corresponding small ozone decrease were noted there.  相似文献   

On looming during Alpine foehn     

Klaus P. Hoinka 《Boundary-Layer Meteorology》1991,57(3):289-294

The note deals with looming during foehn north of the Alps. The results show that there is a weak effect in stretching optically the orography. However, the increase in view angle is probably not detectable by human observers looking south from Munich towards the Alps. The impression that the orography seems to be stretched during a foehn is also due to psychological effects which might be a factor of greater importance.  相似文献