Étude des grands bancs de sable du Sud-est de la mer Celtique     

Philippe Bouysse  Robert Horn  Francis Lapierre  François Le Lann 《Marine Geology》1976,20(3):251-275

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Some results of biogeographic research on meadows in the Dyje-Svratka basin in the Czech Republic     

Stanislav Horník 《GeoJournal》1993,31(4):379-382

Some results of biogeographic research on meadows in the Dyje-Svratka basin in the Czech Republic. The paper shows one example of biogeographic inventory of natural ecosystems in an unflooded meadow in the Dyje-Svratka basin. It is part of the complex physio-geographic research of the Geographic Department of the Masaryk University in Brno aimed at gaining a basis for territorial interpretation of ecological regularities and territorial application of general ecological optimizing principles. A segment of biocenosis of Ulmi-fraxineta carpini has been analyzed (Zlatník 1956).The endeavour of Czech geographers to study geosystems of various dimensions completely gets in the limelight. In question is the understanding of mutual relationship of components of geosystems based on the exchange of mass and energy. There are two ways of studying them: spatial relations or approaches concentrated on processes. In contrast to the above unilateral concept, the endeavour to make the approaches compatible appears rarely. This complex view is made possible by geobiocenologically taken biogeography in papers of Zlatník and Rauer, their students and successors. This paper shows only one example of the results of biogeographic stock-taking of meadows in the Dyje-Svratka basin, indicating relations of eco- and geosystems which confirm the necessity of ecological orientation of the present biogeography and its potential contribution to ecology.  相似文献   

High-density CO2−N2 inclusions in eclogite-facies metasediments of the Münchberg gneiss complex,SE Germany     

R. Klemd  A. M. van den Kerkhof  E. E. Horn 《Contributions to Mineralogy and Petrology》1992,111(3):409-419

The eclogite-facies metasedimentary rocks in the Münchberg gneiss complex (T=630±30° C/P17–24 kbar) locally contain CO₂–N₂-rich fluid inclusions of extremely low molar volumes (32 cm³/mol) in quartz. These fluid compositions are mainly found in rocks intercalated with calcsilicate bands. Densities were determined from low-temperature phase transitions like stable or metastable homogenization (L+VL), partial homogenization (S+L+VS+L) and the transition S+LL (L = liquid, V = vapour, S = solid). The high fluid densities are in agreement with eclogite-facies pressure and temperature and subsequent amphibolite facies. CO₂–N₂ inclusions were not observed in adjacent eclogites nor in non-calcareous metasediments. These rock types contain predominantly H₂O-rich inclusions correlating with amphibolite-facies conditions. The variation of fluid composition with lithological differences indicates local fluid gradients and speaks against a pervasive fluid flow during eclogite-facies metamorphism.  相似文献   

Diatom assemblages from Costa Rican lakes: an initial ecological assessment     

Kurt A. Haberyan  Sally P. Horn  Brian F. Cumming 《Journal of Paleolimnology》1997,17(3):263-274

We compared the distributions of 59 diatom species in surface sediments of 25 Costa Rican lakes with 21 environmental variables using canonical correspondence analysis (CCA). The distribution of taxa was related to the chemical and physical characteristics of the lakes. The most influential chemical variables were cation concentrations (especially magnesium) and related variables such as water hardness, pH, and temperature. Lake area and lake depth were among the most important physical variables.A number of taxa were identified as potential environmental indicators. The diatoms Brachysira serians var. brachysira and Frustulia rhomboides seem to be associated with low values of alkalinity, hardness, Ca, Mg, and SiO2. Cymbella minuta var. silesiaca is associated with low to moderate values of alkalinity, hardness, Ca, and Mg. Nitzschia cf. amphibia may be an indicator of moderate-to-high concentrations of Mg. Pinnularia braunii var. amphicephala seems to prefer low values of hardness, Ca, Mg, and SiO2.In many closed lakes, these environmental variables (Mg/Ca/hardness/alkalinity) increase with effective evaporation. Consequently, these diatoms may be indirectly tracking P:E ratios. Results from this initial, small data set indicate the potential of diatoms for inferring lake paleochemistry, and perhaps P:E ratios, in Costa Rica.  相似文献   

‘Gendered spaces’ in urban and rural contexts: An introduction     

Joos Droogleever Fortuijn  Andre Horn  Wim Ostendorf 《GeoJournal》2004,61(3):215-217

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K-Ar dating of ring complexes and fault systems in Northern Kordofan,Sudan: evidence for independent magmatic and tectonic activity     

D. Müller-Sohnius  P. Horn 《International Journal of Earth Sciences》1994,83(3):604-613

From an area of brittle shearing and ring complexes in Northern Kordofan, Sudan 28 K-Ar ages were calculated to determine the geochronology of tectonic and magmatic events. The age results for deformational episodes are 560, 340 and 255 Ma, whereas alkaline magma was intruded at 280, 220 and 165 Ma. The incompatibility of age marks leads to the conclusion that magmatic and tectonic activity in this area have to be regarded as independent events. This holds true even when all dated intrusions from the entire region are compared with post-Pan-African continental tectonic features.  相似文献   

Ed.: G. D. Grive and M. R. Reeve: Marine Mesocosms. Biological and Chemical Research in Experimental Ecosystem. New York – Heidelberg – Berlin,Springer Verlag, 136 Abb., 430 S., ISBN 0-387-90579-0, ISBN 3-540-90579     

W. Horn 《洁净——土壤、空气、水》1983,11(3):308-308

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The relative performance of various cup anemometers in a gusty wind     

Lyle H. Horn 《Theoretical and Applied Climatology》1958,9(2):231-237

Summary Wind data collected during the Great Plains Turbulence Field Experiment of 1953 are used to study the relative performances of various types of cup anemometers subjected to air flow of known gustiness. Scatter diagrams which relate differences in the indicated mean speeds of two anemometers to gustiness are prepared. Although the instruments compared represent a wide range of moments of inertia, no relationship between gustiness and anemometer performance is noted. This result is examined in light of Schrenk's parameter which describes anemometer performance.

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Zusammenfassung Windbeobachtungen, welche während des Great Plains Turbulence Field Program im Jahre 1953 gewonnen wurden, werden zu einem Vergleich verschiedener Typen von Schalenkreuzanemometern in einem Windfeld von bekannter Böigkeit verwendet. Die Ergebnisse werden in Form von Streubildern veranschaulicht, in denen die Geschwindigkeits-unterschiede von verschiedenen Anemometern als Funktion des Böigkeitsgrades aufgetragen sind. Obgleich die verglichenen Anemometer erheblich verschiedene Trägheitsmomente besitzen, ergibt sich keine Abhängigkeit der Anzeigedifferenzen von der Böigkeit des Windes. Dieser Befund wird mit Hilfe des Schrenkschen Parameters näher beleuchtet.

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Résumé Les observations anémométriques effectuées dans le cadre du Great Plains Turbulence Field Program en 1953 sont utilisées ici dans le but de comparer différents types d'anémomètres à cupules placés dans un champ de mouvement de turbulence connue. Les résultats sont donnés sous forme d'essaims de points dans un système de référence: écarts individuels de l'indication et degré de turbulence. Bien que les instruments comparés présentent des moments d'inertie notablement différents, les écarts observés ne dépendent pas de la turbulence du vent. Ce résultat est encore examiné à l'aide du paramètre de Schrenk.

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With 4 Figures  相似文献   

Effects of lava flows on lunar crater populations     

Gerhard Neukum  Peter Horn 《Earth, Moon, and Planets》1976,15(3-4):205-222

It is shown that endogenic lava flow processes can be identified by their characteristic effects on lunar crater size distributions without necessarily being able to recognise individual flows on the photographs studied. The thickness of lava flows or a series of flows can be estimated from these crater size distribution characteristics. The lava flow histories of the Apollo landing sites 11, 12 and 15 are discussed in detail. The thicknesses of the most recent (3–3.4 × 10⁹ years ago) flows there and of the youngest flows in an area in south-west Mare Imbrium (3 × 10⁹ years) are found to range between 30 and 60 m. The subsequent flow episodes at the landing sites showing up in the crater size distributions can be related to differences in the radiometric ages of the respective lunar rocks.  相似文献   

Supernova Sources and the 92Nb-92Zr p-Process Chronometer     

Yin QZ  Jacobsen SB  McDonough WF  Horn I  Petaev MI  Zipfel J 《The Astrophysical journal》2000,536(1):L49-L53

We report new Zr isotope evidence for live (92)Nb (mean life: tau&d1;92Nb=52 Myr) within the early solar system resulting in &parl0;92Nb&solm0;93Nb&parr0;initial approximately 10-3. The meteoritic minerals rutile and zircon have, respectively, very high and very low Nb/Zr ratios and are ideal for exploring the (92)Nb-(92)Zr chronometer. Rutiles exhibit high positive straightepsilon92Zr ( approximately 14-36) while a zircon has a negative straightepsilon92Zr ( approximately -4), as would be expected if (92)Nb was live in the early solar system. The meteoritic rutiles appear to be young, with apparent times of formation of approximately 80-220 Myr subsequent to the origin of the solar system. The initial (92)Nb/(92)Mo for the solar system is broadly compatible with a model of uniform production if the (92)Nb/(92)Mo production ratio for Type II supernova (SNII) sources with neutrino-driven winds is used. Data for all the now extinct p-process nuclides ((92)Nb, (97)Tc, and (146)Sm) are consistent with these isotopes being derived by uniform production from SNII sources and a free decay interval of approximately 10 Myr. Consideration of a range of models indicates that the average p-process production ratio of (92)Nb/(92)Mo needs to be at least in the range of 0.06-0.25.  相似文献