Decay of a highly eccentric satellite     

G. Janin  E. A. Roth 《Celestial Mechanics and Dynamical Astronomy》1976,14(1):141-149

The re-entry phase of a highly eccentric satellite is discussed. Numerical simulations allowing the prediction of the exact date of re-entry of a highly eccentric satellite are exposed.It is shown that under very particular circumstances the life of the satellite can be extended by a few days. The number of final revolutions of the rapidly contracting orbit depends critically on the air density between 70 km and 100 km.Re-entry of the European scientific satellite HEOS-1 predicted for 28 October, 1975 is near such a situation.  相似文献   

Rock Damage and Fluid Transport, Part I     

Georg Dresen  Ove Stephansson  Arno Zang 《Pure and Applied Geophysics》2006,163(5-6):915-916

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Monitoring of atmospheric deposition in European forests and an overview on its implication on forest condition     

Richard Fischer  Volker Mues  Erwin Ulrich  Georg Becher  Martin Lorenz 《Applied Geochemistry》2007

Forest conditions in Europe have been monitored over 20 years jointly by the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) and the European Union (EU). Maps for mean bulk SO₄, NO₃ and NH₄ deposition at around 400 intensive monitoring plots in the years 1999–2001, as well as time trends for the period 1996–2001, are presented. Mean bulk SO₄ deposition at 169 plots mostly located in central Europe decreased from 7.4 to 5.8 kgS ha⁻¹ a⁻¹. Mean NH₄ bulk deposition decreased from 6.2 to 5.3 kgN ha⁻¹ a⁻¹. Nitrate bulk deposition fluctuated around 5 kgN ha⁻¹ a⁻¹. On average, throughfall deposition was considerably higher than bulk deposition. Time trends for mean tree crown defoliation as an overall indicator for forest condition show a peak in the mid 1990s for most of the monitored main tree species and a recent increase for the years 2003 and 2004. Multivariate linear regression analyses show some significant relations between deposition and defoliation. These relations depend on the tree species and site characteristics. Effects of deposition are moderated by the influence of biotic stress factors such as insects and fungi and by abiotic stress factors, such as weather.  相似文献   

Two-dimensional maps in multi-dimensional worlds: A case of community-based mapping in Northern Thailand     

Robin Roth 《Geoforum》2007,38(1):49-59

Community-based mapping has become a necessary tool for development work worldwide - its adoption is near hegemonic. Mapping community land, however, can have unforeseen consequences in part due to its tendency to render what are complex configurations of social-ecological relationships into two-dimensional form. I argue that one of the key limitations to commonly practiced community-based mapping is the assumption that the spatial organization of resource use and management is an abstract entity that can be mapped independent of the social relations that produce it. This paper uses a case study from Northern Thailand to show how mapping techniques that fix and simplify fluid and complex associations can inadvertently prescribe changes to how residents manage their land, effectively becoming not only a tool for securing land tenure but also a tool for the spatial re-organization of land-use and management.  相似文献   

A comparison of estimated and calculated effective porosity   总被引：1，自引：1，他引：0  

Daniel B. Stephens  Kuo-Chin Hsu  Mark A. Prieksat  Mark D. Ankeny  Neil Blandford  Tracy L. Roth  James A. Kelsey  Julia R. Whitworth 《Hydrogeology Journal》1998,6(1):156-165

 Effective porosity in solute-transport analyses is usually estimated rather than calculated from tracer tests in the field or laboratory. Calculated values of effective porosity in the laboratory on three different textured samples were compared to estimates derived from particle-size distributions and soil–water characteristic curves. The agreement was poor and it seems that no clear relationships exist between effective porosity calculated from laboratory tracer tests and effective porosity estimated from particle-size distributions and soil–water characteristic curves. A field tracer test in a sand-and-gravel aquifer produced a calculated effective porosity of approximately 0.17. By comparison, estimates of effective porosity from textural data, moisture retention, and published values were approximately 50–90% greater than the field calibrated value. Thus, estimation of effective porosity for chemical transport is highly dependent on the chosen transport model and is best obtained by laboratory or field tracer tests. Received, March 1997 · Revised, August 1997 · Accepted, August 1997  相似文献   

Zur chemischen Variabilität regionalmetamorph gebildeter Plagioklase,Epidote und Granate     

Eckart Braun  Georg Müller 《Contributions to Mineralogy and Petrology》1975,52(3):193-211

Plagioclases, Fe-rich epidotes and garnets coexisting in metamorphic rocks of basaltoid and granitoid substrata have been analyzed by standard microprobe techniques. The results presented are based on 34000 data on plagioclases, nearly 24400 on coexisting epidotes as well as of 5000 garnet data. The chemical variations within the singular plagioclase grain and in the range of a thin section are very comprehensive. Adjoining microfields (10–20 μm distance) exhibit differences in the An-contents between 30 and 80% rel. These observations are valid for nearly 78% of the examined plagioclases. Only in the higher amphibolite facies the An-variations are reduced to an average value of 32% rel. Merely the high temperature plagioclases with a compositional range of An 68-An 79 coexisting with clinopyroxene are largely homogeneous. Their variation is amounting to 6,5% An rel. The epidote chemisms reveal a dependance on both of the different substrata and their oxidation status. The maximum value of the Fe (III) substitution on the M₁ position in the epidote structure is reaching 97 molar per cent at the higher oxidized meta-granitoids and merely 87% at the metabasaltoids. The variations of the Fe/Al-proportions in the microfields are amounting to 5–20% as to the granitoid substrata and to 5–47% rel. as to the basaltoid substrata. In both of the substrata the garnets are very rich of almandine (40–70%). Besides variable amounts of grossularite and pyrope components they also contain 10–20% (basaltoids) and 1–20% (granitoids) spessartine. The most significant element variations are observed for the element Mn in garnets of granitoid origin. These variations attain 46% within the garnet grains. Only for the garnets of the basic substrata from the amphibolite facies one can state a homogenization. The reaction inertia in achieving metamorphic equilibrium is demonstrated by a selected metabasite sample of the amphibolite facies. It seems that only at temperature >600°C a homogenization of the plagioclases and garnets is initiated so that at low temperature a thermometry by means of An-contents in the plagioclases or Mn/Fe-relations in the garnets is not possible.  相似文献   

Die Bedeutung des Rückstandes von Druck-Lösungsvorgängen für stratigraphische Abfolgen,Wechsellagerung und Lagerstättenbildung     

Dr. Peter Trurnit  Prof. Dr. Georg Christian Amstutz 《International Journal of Earth Sciences》1979,68(3):1107-1124

Zusammenfassung Druck-Lösungserscheinungen sind nicht auf stylolithische Kontakte beschränkt. Die Mehrzahl der Druck-Lösungsflächen ist glatt und nicht als solche erkennbar. Bei Abwesenheit von Stylolithisierung wird Druck-Lösungsrückstand meistens fälschlich als primäres Sediment angesprochen.Druckgelöstes Material wandert von Becken aus. Auf Schwellen führt es zu erhöhtem Stoffangebot für chemische und organische Ablagerung. Druckunlösliches Material konzentriert sich passiv in den Becken.Die Unterschiede zwischen benachbarten lithologischen Horizonten werden in stratigraphischen Abfolgen während der Diagenese über Druck-Lösungstätigkeit verstärkt. Wechsellagerungen können entstehen, indem relativ reine, fast monomineralische Horizonte (Kalkspat, Dolomit, Quarz) von Druck-Lösung kaum betroffen werden, während etwas mehr verunreinigte Schichten, besonders bei Gegenwart von Tonmineralien, bis auf ihren Lösungsrückstand zusammenschrumpfen können.Die während Faltung und Schieferung fortdauernde Druck-Lösungstätigkeit bewirkt weiteren Gesteinsschwund.Hauptsächlich synsedimentäre Lagerstätten können über Druck-Lösungsvorgänge während Diagenese und Orogenese eine weitere Anreicherung erfahren, indem Wertmineralien im Lösungsrückstand zurückbleiben. Verstärkte Anreicherungen sind in Richtung der Becken und Faltenschenkel zu erwarten.

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Pressure solution phenomena are not restricted to stylolitic contacts. The majority of pressure solution planes is smooth and not recognizable as such. Pressure solution residue in the absence of stylolitization is often misinterpreted as a primary sediment.Material dissolved under nonuniform pressure migrates from basins to ridges, where it leads to increased precipitation and organic deposition. The material that is insoluble under unilateral pressure thus becomes more concentrated in the basins.The differences between neighbouring lithological units in stratigraphic series are increased during diagenesis by pressure solution activity. Intercalations may result from relatively pure, almost monomineralic layers (e. g. calcite, dolomite, quartz) remaining relatively unaffected by pressure solution processes, while more impure layers, especially those containing clay minerals, may shrink to its solution residue.During folding and cleavage, continuing pressure solution activity results in further loss of rock matter.Mainly synsedimentary ore deposits may be further concentrated by pressure solution processes, both during diagenesis and orogenesis, leaving valuable minerals as part of the solution residue. Elevated concentrations are to be expected towards the basins and limbs of folds.

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Résumé Les phénomènes de dissolution par pression inégale ne sont pas limités aux contacts stylolithiques. La plupart des surfaces de dissolution par pression linéaire est lisse et sans caractères particuliers. En l'absence de stylolithisation, les résidus sont considérés souvent à tort comme des sédiments primaires.Le matériel dissous par pression linéaire migre du centre des bassins vers ses bords; cela conduit à un accroissement des dépÔts chimiques et organiques sur les seuils. Le matériel insoluble se concentre passivement au centre des bassins.Les différences entre horizons lithologiques voisins dans les séries stratigraphiques sont accentuées pendant la diagénèse par l'activité de dissolution par pression inégale. Il peut se former des alternances ou des horizons relativement »purs«, presque monominéraux (calcite, dolomite, quartz), qui ne sont pas touchés par la dissolution par pression inégale, tandis que des couches moins »pures« en raison de la présence en particulier de minéraux argileux, peuvent Être réduites à des résidus de dissolution.L'activité persistante de la dissolution par pression linéaire au cours du plissement et de la schistosité entraÎne une nouvelle diminution de matière dans la roche.Ce sont surtout les gisements synsédimentaires qui peuvent subir un enrichissement supplémentaire pendant la diagénèse et l'orogénèse, puisque ce sont les minéraux de valeur qui s'accumulent dans les résidus de dissolution. Ces enrichissements peuvent Être particulièrement renforcés en direction du centre des bassins et des flancs des plis.

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Der Einfluß verschiedener Substitutionen auf die Gitterkonstanten von koexistierenden Biotiten und Muskowiten     

Georg Müller 《Contributions to Mineralogy and Petrology》1966,13(1):59-74

Structural formulas were calculated for 8 analysed coexisting biotite-muscovitepairs from granitic rocks. Characteristic components of these structural formulas were plotted against the unit cell dimensions of these micas.In accordance with the results of Gower (1957) the substitution of OH^– by F^– in trioctahedral micas was found to reduce c ₀ · . However, in contrast to his statements, octahedral alumina was found to reduce c ₀ · sin also and to an even larger extent than fluorine. This observation is in agreement with the commonly encountered compacting of the mica structure through replacement of 3 large cations (Fe²⁺, Mg²⁺, Mn²⁺) by two smaller ones (Al³⁺, Fe³⁺).Concerning b ₀ the combined amounts of octahedral Al and tetrahedral Si cause a reduction of this value, which means indirectly that tetrahedral Al alone would increase b ₀.Reductions of b ₀ and c ₀ · sin by Al in synthetic micas were also found by Crowley and Roy (1964) and Seifert (1966) for the substitution Mg + Si by two Al in trioctahedral micas.In an earlier paper the author (Müller, 1966) has already shown with the same mica samples that the substitutions of M²⁺ by Al³⁺ and of OH^– by F^– also have the strongest effects of all substitutions on the refractive indices, densities, and specific refractive energies of these micas. Therefore it is evident that the latter effects as well as the changes of lattice constants described in this paper are interrelated.

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Mein Dank gilt den Herren Dr.W. Harre und Dr. H. Gundlach, Bundesanstalt für Bodenforschung, Hannover, für die Ausführung der chemischen Glimmeranalysen, sowie der Deutschen Forschungsgemeinschaft, Bad Godesberg, für ihre finanzielle Beihilfe. Herrn Dr. F. Seifert, Kiel, danke ich für zahlreiche sachliche Diskussionen und Hinweise und für die Überlassung seines Algol-Rechenprogramms, mit welchem 4 der 16 Strukturformeln elektronisch berechnet wurden. Herrn Prof. Dr. F. Liebau, Kiel, verdanke ich einige freundliche Ratschläge.  相似文献   

über ein Struktur-Experiment an einer Kugel und Beziehungen zwischen Gross-Lineamenten und Pol-Lagen in der Erdgeschichte     

Prof. Dr. Georg Knetsch 《International Journal of Earth Sciences》1964,54(1):523-548

Zusammenfassung Ein Versuch mit einer rotierenden Schaumgummi- und Tonkugel wird beschrieben. Strukturelle Analogien zwischen dem beim Experiment auftretenden Schwächeflächen-Netz und gro\tektonischen Lineamenten werden besprochen; die Beziehungen solcher Lineamentmuster zur Lage des gleichalten Pols werden versuchsweise diskutiert.

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Summary An experiment with a rotating clay ball is being described. Comparisons between resulting ball-modell-structures and geological lineaments are tried and conclusions are discussed concerning relations between lineament-patterns and former situations of the poles of the Earth.

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Planetary,solar and astrophysical relativistic electrons: Common energization mechanisms?     

Ilan Roth   《Planetary and Space Science》2007,55(15):2319-2323

Direct observations or deduced analysis indicate clearly that formation of intense fluxes of relativistic electrons is an important ingredient in the evolution of numerous active magnetized plasma systems. Examples of relativistic electron energization include the recovery phase of a planetary magnetic storm, post solar flare coronal activity and the afterglow of gamma ray bursts. It is suggested that there exists a universal mechanism, which may explain electron energization at the vastly different magnetized plasma environments. The favorite configuration consists of an inhomogeneous magnetic field anchored at a given magnetic structure and excitation of whistler waves due to external injection of low-energy non-isotropic electrons. The energization proceeds as a bootstrap process due to interaction with the propagating whistler waves along the inhomogeneous magnetic field.  相似文献