Submillimeter Wave Astronomy Satellite observations of Comet 9P/Tempel 1 and Deep Impact     

Frank Bensch  Gary J. Melnick  Martin Harwit  Ronald L. Snell  Volker Tolls 《Icarus》2006,184(2):602-610

On 4 July 2005 at 5:52 UT the Deep Impact mission successfully completed its goal to hit the nucleus of 9P/Tempel 1 with an impactor, forming a crater on the nucleus and ejecting material into the coma of the comet. NASA's Submillimeter Wave Astronomy Satellite (SWAS) observed the ₁₁₀-₁₀₁ ortho-water ground-state rotational transition in Comet 9P/Tempel 1 before, during, and after the impact. No excess emission from the impact was detected by SWAS and we derive an upper limit of 1.8×¹⁰⁷ kg on the water ice evaporated by the impact. However, the water production rate of the comet showed large natural variations of more than a factor of three during the weeks before and after the impact. Episodes of increased activity with alternated with periods with low outgassing (). We estimate that 9P/Tempel 1 vaporized a total of N∼4.5×¹⁰³⁴ water molecules (∼1.3×¹⁰⁹ kg) during June-September 2005. Our observations indicate that only a small fraction of the nucleus of Tempel 1 appears to be covered with active areas. Water vapor is expected to emanate predominantly from topographic features periodically facing the Sun as the comet rotates. We calculate that appreciable asymmetries of these features could lead to a spin-down or spin-up of the nucleus at observable rates.  相似文献   

Resolving cosmic structure formation with the Millennium-II Simulation     

Michael Boylan-Kolchin  Volker Springel  Simon D. M. White  Adrian Jenkins  Gerard Lemson 《Monthly notices of the Royal Astronomical Society》2009,398(3):1150-1164

We present the Millennium-II Simulation (MS-II), a very large N -body simulation of dark matter evolution in the concordance Λ cold dark matter (ΛCDM) cosmology. The MS-II assumes the same cosmological parameters and uses the same particle number and output data structure as the original Millennium Simulation (MS), but was carried out in a periodic cube one-fifth the size  (100  h ⁻¹ Mpc)  with five times better spatial resolution (a Plummer equivalent softening of  1.0  h ⁻¹ kpc  ) and with 125 times better mass resolution (a particle mass of  6.9 × 10⁶  h ⁻¹ M_⊙  ). By comparing results at MS and MS-II resolution, we demonstrate excellent convergence in dark matter statistics such as the halo mass function, the subhalo abundance distribution, the mass dependence of halo formation times, the linear and non-linear autocorrelations and power spectra, and halo assembly bias. Together, the two simulations provide precise results for such statistics over an unprecedented range of scales, from haloes similar to those hosting Local Group dwarf spheroidal galaxies to haloes corresponding to the richest galaxy clusters. The 'Milky Way' haloes of the Aquarius Project were selected from a lower resolution version of the MS-II and were then resimulated at much higher resolution. As a result, they are present in the MS-II along with thousands of other similar mass haloes. A comparison of their assembly histories in the MS-II and in resimulations of 1000 times better resolution shows detailed agreement over a factor of 100 in mass growth. We publicly release halo catalogues and assembly trees for the MS-II in the same format within the same archive as those already released for the MS.  相似文献   

Nitrogen recycling in subducted oceanic lithosphere: The record in high- and ultrahigh-pressure metabasaltic rocks     

Ralf Halama  Gray E. Bebout  Volker Schenk 《Geochimica et cosmochimica acta》2010,74(5):1636-7521

This paper provides the first measurements of the nitrogen (N) concentrations and isotopic compositions of high- and ultrahigh-pressure mafic eclogites, aimed at characterizing the subduction input flux of N in deeply subducting altered oceanic crust (AOC). The samples that were studied are from the Raspas Complex (Ecuador), Lago di Cignana (Italy), the Zambezi Belt (Zambia) and Cabo Ortegal (Spain), together representing subduction to 50-90 km depths. The eclogites contain 2-20 ppm N with δ¹⁵N_air values ranging from −1 to +8‰. These values overlap those of altered oceanic crust, but are distinct from values for fresh MORB (for the latter, ∼1.1 ppm N and δ¹⁵N_air ∼ −4‰). Based on N data in combination with other trace element data, the eclogite suites can be subdivided into those that are indistinguishable from their likely protolith, AOC, with or without superimposed effects of devolatilization (Lago di Cignana, Cabo Ortegal), and those that have experienced metasomatic additions during subduction-zone metamorphism (Zambezi Belt, Raspas). For the former group, the lack of a detectable loss of N in the eclogites, compared to various altered MORB compositions, suggests the retention of N in deeply subducted oceanic crust. The metasomatic effects affecting the latter group can be best explained by mixing with a (meta)sedimentary component, resulting in correlated enrichments of N and other trace elements (in particular, Ba and Pb) thought to be mobilized during HP/UHP metamorphism. Serpentinized and high-pressure metamorphosed peridotites, associated with the eclogites at Raspas and Cabo Ortegal, contain 3-15 ppm N with δ¹⁵N_air values ranging from +3 to +6‰, significantly higher than the generally accepted values for the MORB mantle (δ¹⁵N_air ∼ −5‰). Based on their relatively high N contents and their homogeneous and positive δ¹⁵N values, admixing of sedimentary N is also indicated for the serpentinized peridotites.One possible pathway for the addition of sediment-derived N into eclogites and peridotites involves mixing with fluids along the slab-mantle wedge interface. Alternatively, sedimentary N could be incorporated into peridotites during serpentinization at bending-related faults at the outer rise and, during later deserpentinization, released into fluids that then infiltrate overlying rocks. Deep retention of N in subducting oceanic crust should be considered in any attempt to balance subduction inputs with outputs in the form of arc volcanic gases. If materials such as these eclogites and serpentinized peridotites are eventually subducted to beyond sub-arc depths into the deeper mantle, containing some fraction of their forearc-subarc N inventory (documented here), they could deliver isotopically heavy N into the mantle to potentially be sampled by plume-related magmas.  相似文献   

Eckfeld Maar: Window into an Eocene Terrestrial Habitat in Central Europe   总被引：1，自引：1，他引：0  

Herbert Lutz  Uwe KaulfuSS  Torsten Wappler  Werner L?hnertz  Volker Wilde  Dieter F. Mertz  Jens Mingram  Jens L. Franzen  Herbert Frankenh?user  Martin Koziol 《《地质学报》英文版》2010,84(4):984-1009

<正>To mark the occasion of the 175th anniversary of the Rheinische Naturforschende Gesellschaft in 2009 and of the centennial of the Mainz Natural History Museum in 2010,we present a short account of our present knowledge of the Eckfeld Maar after 20 years of continuous research.This paper does not attempt to include all of the detailed results on the geology of the Eckfeld site or its biota.To date,nearly 250 papers and books have been published since the start of our project.An up-to-date list of these publications can be found at www.eckfeldermaar. de.  相似文献   

Predicting metal detector performance for landmine clearance: soil magnetic map of Angola     

Holger Preetz  Volker Hennings 《Environmental Earth Sciences》2010,60(7):1499-1508

A map depicting predicted classes of soil magnetic susceptibility in Angola was produced. The map is based on a classification system for the susceptibility of tropical soils set up by the authors and a 1:2,000,000 scale FAO soil map. Statistical data of two large groups of parent rock—ultrabasic, basic and intermediate igneous rocks on the one hand and acid igneous rocks and some slightly metamorphosed rocks and clastic sediments on the other—had been linked to three associated degrees of weathering. These determining factors were used to classify Angolan soils, and the overall method is semi-quantitative. The resulting map shows that easily available pedological information as given by FAO soil maps is generally appropriate to predict soil magnetic susceptibility. Potential metal detector performance failures may be predicted. The resulting information is a useful tool for planning the use of appropriate techniques in landmine clearance operations.  相似文献   

Determinants of corporate adaptation to climate change in winter tourism: An econometric analysis     

Volker H. Hoffmann  David C. Sprengel  Andreas Ziegler  Matthias Kolb  Bruno Abegg 《Global Environmental Change》2009,19(2):256-264

While corporate adaptation strategies in response to climate change have been characterized, the determinants of adaptation have not been comprehensively analyzed. Knowledge of these determinants is particularly useful for policy makers to provide favorable conditions in support of corporate adaptation measures. Based on unique data from a survey of Swiss ski lift operators, this paper empirically examines such determinants at the business level. Our econometric analysis with linear regression and count data models finds a positive influence of the awareness of possible climate change effects on the scope of corporate adaptation. Surprisingly, no significant influence of the vulnerability to climate change effects on the scope of adaptation could be found. Finally, the dependency on the affected business and the ability to adapt influence the specific strategic directions of corporate adaptation.  相似文献   

A computer simulation study of Al/Si ordering in gehlenite and the paradox of the low transition temperature     

S. Thayaparam  Martin T. Dove  Volker Heine 《Physics and Chemistry of Minerals》1994,21(1-2):110-116

The ordering of Al and Si in gehlenite is considered using computer simulation. The enthalpy of ordering ΔH per 2Al+2Si atoms is found to be 0.52 eV. It is dominated by the nearest neighbour interaction, but the analysis is carried out to fifth neighbours. The nearest neighbour interaction differs significantly from that for other materials. The structure does not have a connected network of ordering sites, which mainly accounts for the unobservably low transition temperature for Al/Si ordering. Two alternatives are given for the likely ordering pattern.  相似文献   

Geoelektrische Tiefsondierungen und ihre Übereinstimmung mit Bohrbefunden     

Volker Fritsch 《Pure and Applied Geophysics》1959,44(1):144-153

Zusammenfassung Es werden Messanordnungen beschrieben, die für geoelektrische Tiefsondierungen bis ungefähr 4000 m geeignet sind. Anschliessend werden die erzielten Messergebnisse besprochen. Die Übereinstimmung zwischen der geoelektrischen Prognose und dem Ergebnis der Bohrung ist eine sehr gute. Die Abweichung schwankt im Mittel um ungefähr 8–13%.

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Summary Some measurement methods are described for geoelectrical deepinvestigations down to a depth of 4000 m. Then the obtained results are discussed. The results of the geoelectrical deep-investigations were confirmed in a very satisfactory manner by deep drillings. The average limit of error of the geoelectrical predictions was ±8–13%.

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Aus einem Vortrag gehalten am 4. April 1959 auf der 7. Allgem. Versammlung der Società Italiana di Geofisica e Meteorologia (Genova: 3.–5. April 1959).  相似文献   

DIE GEOELEKTRISCHE ÜBERPRÜFUNG DER BAUGRUNDVERFESTIGUNG DURCH ZEMENTINJEKTIONEN     

Volker Fritsch 《Pure and Applied Geophysics》1953,24(1):207-213

Summary The observations of ten Aprils (1941–50) at Blue Hill have been analyzed, and it has been found that frost (night minimum temperature 32° F) (T) can be predicted on the basis of the 19h wet-bulb temperature (ti) by the formula:T=ti–k, in whichk is found to be 1.8 F deg. in clear weather and 2.1 F deg. in cloudy. The results of a test on an independent set of Aprils (1936–40), are satisfactory especially with clear skies at 19h.  相似文献   

Influenza delle condizioni geoelettriche sulla caduta del fulmine     

Dipl.-Ing. Dr. Volker Fritsch 《Pure and Applied Geophysics》1939,1(1):175-216

Riassunto Richiamate le più importanti nozioni fondamentali sulla fisica del fulmine, si desume che i conduttori geologici da esso attraversati si comportano come se fossero percorsi da corrente alternata ad alta frequenza con una lunghezza d'onda dell'ordine di mille metri. Tenendo presente che le leggi della radiogeologia costituiscono le basi di ogni indagine relativa alla conduzione del fulmine nel sottosuolo, si giustifica il pericolo di caduta del fulmine per azione geoelettrica spiegandolo alla stregua dei dati d'osservazione. In pari tempo si dà ragione dell'esistenza dei cosidetti nidi di fulmini. Rilevato come i dati statistici sinora raccolti risultino spesso non soddisfacenti, viene messa in luce l'utilità di una statistica organica e completa su tali fenomeni, illustrando l'opportunità dell'istituzione di appositi campi sperimentali per tutte le indagini riferentesi ai fulmini nei rapporti con le caratteristiche geoelettriche del sottosuolo.

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Zusammenfassung Der Blitz beansprucht durchflossene geologische Leiter ähnlich wie ein hochfrequenter Wechselstrom, dessen Wellenlänge ungefähr im Tausendmeterbande liegt. Die Beurteilung der Blitzstromleitung im Untergrunde hat nach den Gesichtspunkten der Funkgeologie zu erfolge n.Die geoelektrische Blitzgefährdung ist theoretisch verständlich und durch zahlreiche Beobachtungen nachgewiesen. Auch die Frage nach der Existenz der sog. Blitznester ist positiv zu beantworten. Die bisherigen statistischen Ergebnisse sind vielfach unbefriedigend und es wäre daher eine einheitliche und befriedigende Statistik unbedingt anzustreben. Für die Entwicklung der weiteren Forschung wäre es sehr vorteilhaft, wenn besondere Blitzversuchsfelder errichtet würden. Diese wären dann auch nach funkgeologischen Gesichtspunkten zu untersuchen.

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