Groundwater flow and contaminant transport modelling at an air weapons range     

Geneviève Bordeleau  Richard Martel  Dirk Schäfer  Guy Ampleman  Sonia Thiboutot 《Environmental Geology》2008,55(2):385-396

Numerical modelling was done at the Cold Lake Air Weapons Range, Canada, to test whether the dissolved RDX and nitrate detected in groundwater come from the same sources, and to predict whether contamination poses a threat to the surface water receptors near the site. Military live fire training activities may indeed pose a risk of contamination to groundwater resources, however field investigations on military bases are quite recent, and little information is available on the long-term behaviour of munition residues related contaminants. Very limited information was available about the contaminant source zones, which were assigned based on our knowledge of current training activities. The RDX plume was well represented with the model, but the heterogeneous distribution of nitrate concentrations was more difficult to reproduce. It was nonetheless determined that both contaminants originate from the same areas. According to the model, both contaminants should reach the nearby river, but concentrations in the river should remain very low if the source zone concentration does not change. Finally, the model allowed the recommendation of a new location for the main bombing target, which would offer added protection to the river and the lake into which it flows.  相似文献   

Close binary systems before and after mass transfer: A comparison of observations and theory     

J. P. De Grève  D. Vanbeveren 《Astrophysics and Space Science》1980,68(2):433-457

From a search through the literature 174 close binaries with known absolute dimensions have been sampled. Distinction is made between systems before and after mass exchange. Mass, period and mass ratio distributions and relations of the group of unevolved binaries (i.e., prior to mass exchange) are transformed into corresponding distributions and relations of evolved binaries. The transformations are based upon theM _1f=g(M _1f) relation derived from an extended set of published theoretical computations of the evolution of close binaries. From this relation the following characteristics of the system after mass exchange are computed:M _1f,M _2f (andq _f),P _f. Five different modes of mass transfer were applied for the computation of the values ofP _f andM _2f. The variation of the period was calculated using the formalism given by Vanbeverenet al. (1979). The results are compared to the observations of binary systems after mass exchange, and are discussed together with an analysis of the effect of several selection effects present in the distributions. The main conclusion is that, during mass exchange in close binaries, more than 50% of the mass is lost to the system in the process of transfer, removing a large amount of angular momentum.This research is supported by the National Foundation of Collective Fundamental Research of Belgium (F.K.F.O.) under No. 2.9009.79.  相似文献   

Bifurcation points in close binary evolution: Medium-mass binaries     

J. P. De Grève 《Astrophysics and Space Science》1982,84(2):447-456

The remaining core hydrogen burning lifetime after case B of mass transfer of the secondary (mass gaining) component in a medium mass close binary star is estimated, for mediummass binaries with primaries in the mass range 5M to 9M . From the comparison of this quantity with the helium burning time-scale of the remnant primary a critical mass ratioq _c is derived such that for larger values ofq, mass transfer from the secondary towards the primary starts before the latter has evolved into a white dwarf. Consequences for the advanced stages of medium mass binaries are discussed.  相似文献   

Synchronous aperture synthesis observations of pulsars     

R. G. Strom  H. W. Van Someren Gréve 《Astrophysics and Space Science》1990,171(1-2):351-355

By modifying the online software of the Westerbork Synthesis Radio Telescope it is possible to sample the radio emission from a field containing a pulsar synchronously with the pulsed signal. Recording the emission from eight separate temporal windows, we can simultaneously observe both the on-pulse and off-pulse signals. We are using this technique for three different kinds of pulsar investigation: (a) to check and improve the positions of some pulsars; (b) to look for unpulsed components; and (c) to search for weak extended emission around pulsars. Observations have been carried out at 6, 21, 49, and 92 cm. Examples of results from all three types of investigation are given.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.  相似文献   

The evolution of massive close binaries     

De Grève  J. P.  De Loore  C.  Van Dessel  E. L. 《Astrophysics and Space Science》1978,53(1):105-130

The results of evolutionary computations for massive binary systems (initial masses of the primary 10M ) with mass ratios between 0.3 and 0.8 are summarized and compared with observations in order to verify how far one can go with the conservative assumption of mass exchange. It is found that conservative mass exchange leads to acceptable first-order models of W-R and massive X-ray binaries. However, the comparison between this theory and observation reveals that for the observed systems (W-R and X-ray binaries) a preference exists for low intial mass ratios; moreover, the X-ray luminosities of the theoretical models are systematically too low, though this may be due to the adopted wind model. In addition, the influences of several parameters (distance between the components, chemical composition, primary mass, mass ratio and atmosphere) are examined. These parameters influence the remnant mass and any further evolution only marginally. Attention is also given to the effect on the system parameters of a supernova explosion of the remnant of the mass-losing component. For a large range of systems a disruption probability smaller than 25% is found.  相似文献   

Dating the onset of Lower Tagus River terrace formation using electron spin resonance          下载免费PDF全文

PIERLUIGI ROSINA  PIERRE VOINCHET  JEAN‐JACQUES BAHAIN  JORGE CRISTOVÃO  CHRISTOPHE FALGUÈRES 《第四纪科学杂志》2014,29(2):153-162

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Le Bassin Cambrien de Tisrouima (Haut-Atlas Occidental,Maroc)     

Henri Termier  Geneviève Termier 《International Journal of Earth Sciences》1971,60(2):656-665

Résumé Dans le Haut-Atlas marocain, entre l'oued Sous au Sud, Asif AÏt Moussa à l'Ouest, le bled Seksaoua au Nord et Tizi n'Test à l'Est, plus exactement dans la partie sud-ouest du Massif du Tichka et au Nord-Ouest de ce massif affleurent en de nombreux endroits des roches charbonneuses: grès, arkoses, pélites, schistes, cipolins et coméennes dont la principale est la tisrouimite (7). Cette dernière s'est déposée un peu avant les calcaires àArchaeocyatha du Cambrien inférieur, puis en mÊme temps que leurs couches de base. Les autres roches charbonneuses sont sensiblement contemporaines de la tisrouimite. On peut en conclure qu'il a existé un bassin sédimentaire riche en matière organique à une époque correspondant, en première approximation, a l'Assadasien.

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The area of study in the moroccan High-Atlas area is included between wady Sous to the South, Asif AÏt Moussa to the West, bled Seksaoua to the North and Tizi n'Test to the East; more exactly it is located in the south-western and nordwestern Tichka. In this area we have noticed numerous outcrops of carbonaceous rocks, such as sandstones, arkoses, mudstones, shales, cipolins and hornfels, the principal variety of which is tisrouimite (7). Tisroumite first was deposited shortly before the Lower Cambrian Archaeocyathid limestones, and again later contemporaneously with the basal layers of these limestones. The other carbonaceous rocks are more or less contemporaneous with the tisrouimite. Therefore we conclude approximately at the time of the Assedasian (early Cambrian II) a sedimentary basin existed the sediments of which were rich in organic matter

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Zusammenfassung Im marokkanischen Hoch-Atlas, zwischen Wadi Sous im Süden, Asif AÏt Moussa im Westen, der Gegend um Seksoua im Norden und Tizi n'Test im Osten, sind im SW-Teil und NE-Teil des Tichka-Gebirgsstockes dunkle, kohlenstoffreiche Gesteine aufgeschlossen: Sandstein, Arkose, Pelit, Schiefer, grüner Marmor und Homfels, dessen Hauptvariante tisrouimite genannt wird. Die Hornfelse sind etwas älter als die Archaeocyathiden-Kalke des Unterkambriums und bilden ihre Basis Die übrigen Gesteine sind etwa gleich alt wie die Hornfelse. Wir schließen daraus, daß hier zur Zeit des Assadassien (tieferes Kambrium II) ein Sedimentationsbecken lag, dessen Sedimente reich an organischen Substanzen waren.

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Reply to comments by E. Grüger     

Geneviève Woillard 《Quaternary Research》1979,12(1):154-155

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La Notion de Migration en Paléontologie     

Henri  Geneviève Termier 《International Journal of Earth Sciences》1956,45(1):26-42

Zusammenfassung Gemessen mit dem Maßstab der geologischen Zeiten, dauern die Wanderungen, wie sie die Biologen studieren, nur fast einen Augenblick; demgegenüber aber erstrecken sich die Verschiebungen der Fauna und Flora, wie sie die geologischen Studien festlegen, über Millionen von Jahren. Diese Verschiebungen sind statistische Erscheinungen aus dem Gebiet der Biogeographie und stellen das Ergebnis von zahlreichen biologischen Bewegungen dar. Die Verfasser untersuchen die Wanderungen der Säugetiere (stete Entwicklung durch erwachsene Typen), die Wanderungen der Pflanzen (unstete Entwicklung durch Keime), die Wanderungen der wirbellosen Seetiere, die man in die eine oder in die andere der vorhergehenden Abteilungen einreihen kann. Einige neue Ausdrücke werden vorgeschlagen.  相似文献   

Garnet re‐equilibration by coupled dissolution–reprecipitation: evidence from textural,major element and oxygen isotope zoning of ‘cloudy’ garnet     

L. A. J. MARTIN  M. BALLÈVRE  P. BOULVAIS  A. HALFPENNY  O. VANDERHAEGHE  S. DUCHÊNE  E. DELOULE 《Journal of Metamorphic Geology》2011,29(2):213-231

The analysis of texture, major element and oxygen isotope compositions of cloudy garnet crystals from a metapelite sampled on Ikaria Island (Greece) is used to assess the model of growth and re‐equilibration of these garnet crystals and to reconstruct the pressure–temperature–fluid history of the sample. Garnet crystals show complex textural and chemical zoning. Garnet cores (100–200 μm) are devoid of fluid inclusions. They are characterized by growth zoning demonstrated by a bell‐shaped profile of spessartine component (7–3 mol.%), an increase in grossular from 14 to 22 mol.% and δ¹⁸O values between 9.5 ± 0.3‰ and 10.4 ± 0.2‰. Garnet inner rims (90–130 μm) are fluid inclusion‐rich and show a decreasing grossular component from 22 to 5 mol.%. The trend of the spessartine component observed in the inner rim allows two domains to be distinguished. In contrast to domain I, where the spessartine content shows the same trend as in the core, the spessartine content of domain II increases outwards from 2 to 14 mol.%. The δ¹⁸O values decrease towards the margins of the crystals to a lowest value of 7.4 ± 0.2‰. The outer rims (<10 μm) are devoid of fluid inclusions and have the same chemical composition as the outermost part of domain II of the inner rim. Garnet crystals underwent a four‐stage history. Stage 1: garnet growth during the prograde path in a closed system for oxygen. Garnet cores are remnants of this growth stage. Stage 2: garnet re‐equilibration by coupled dissolution–reprecipitation at the temperature peak (630 < T < 650 °C). This causes the creation of porosity as the coupled dissolution–reprecipitation process allows chemical (Ca) and isotopic (O) exchange between garnet inner rims and the matrix. The formation of the outer rim is related to the closure of porosity. Stage 3: garnet mode decreases during the early retrograde path, but garnet is still a stable phase. The resulting garnet composition is characterized by an increasing Mn content in the inner rim’s domain II caused by intracrystalline diffusion. Stage 4: dissolution of garnet during the late retrograde path as garnet is not a stable phase anymore. This last stage forms corroded garnet. This study shows that coupled dissolution–reprecipitation is a possible re‐equilibration process for garnet in metamorphic rocks and that intra‐mineral porosity is an efficient pathway for chemical and isotopic exchange between garnet and the matrix, even for otherwise slow diffusing elements.  相似文献