Magnetic anomaly map for Northern,Western, and Eastern Europe*     

Thomas Wonik  Klaus Trippler  Helmut Geipel  Siegfried Greinwald  Inna Pashkevitch 《地学学报》2001,13(3):203-213

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Monte-Carlo simulation of Mercury's exosphere     

Peter Wurz  Helmut Lammer 《Icarus》2003,164(1):1-13

Because of its proximity to the Sun and its small size, Mercury has not been able to retain its atmosphere and only a thin exosphere surrounds the planet. The exospheric pressure at the planetary surface is approximately 10⁻¹⁰ mbar, set by the Mariner 10 occultation experiment. The existence of gaseous species H, He, and O has been established by Mariner 10. In addition Na, K, and Ca have been observed by ground based instrumentation. Other elements are expected to be found in Mercury's exosphere since the total pressure of the known species is almost two orders of magnitude less than the exospheric pressure.It is intended to measure these exospheric particle densities in situ with an instrument on board of ESA's BepiColombo Mercury Planetary Orbiter (MPO) spacecraft. Since the expected exospheric densities are very small we developed a Monte-Carlo computer model to investigate if such a measurement is feasible along the MPO spacecraft orbit. We model energy and ejection angle distributions of the particles at the surface, with the emission process determining the actual distribution functions. Our model follows the trajectory of each particle by numerical integration until the particle hits Mercury's surface again or escapes from the calculation domain. Using a large set of these trajectories bulk parameters of the exospheric gas are derived, e.g., particle densities for various atomic and molecular species. Our study suggests that a mass spectrometric measurement is feasible and, at least at MPO's periherm, all species that are released from the surface will be observed.  相似文献   

Preparation,collisional decay and transfer of alignment in C2H2 21     

J. B. Halpern  Ralf Dopheide  Helmut Zacharias 《Astrophysics and Space Science》1996,236(1):19-27

Stimulated Raman scattering is used to prepare ensembles of aligned acetylene molecules in thev ₂=1 excited vibrational level. Decay and transfer of the alignment is followed by laser induced fluorescence. Measurements of the initially excited alignment agree well with theoretical calculations. The rate constants for decay decrease as the rotational quantum numberJ of the excited level increases.  相似文献   

The responses of different ethnic groups in the Sudan to rural-urban migration     

Ruppert H 《GeoJournal》1991,25(1):7-12

The ethnic identities of the various population groups in the Sudan are a product of their specific natural and social environments. The migration of these groups to the towns, especially to Greater Khartoum, involves a drastic change of cultural norms and values. However, the capability of change and the subsequent results are strongly conditioned by the specific background of each ethnic group and by the conditions in its area of origin. This is being proved by a comparative study on three ethnic groups in the Sudan: the Nuba, the Zaghawa and the Hadandawa.  相似文献   

Effects of natural attenuation processes on groundwater contamination caused by abandoned waste sites in Berlin     

Helmut Kerndorff  Stephan Kühn  Thomas Minden  Dagmar Orlikowski  Thomas Struppe 《Environmental Geology》2008,55(2):291-301

The aim of this research project is to identify, characterize and quantify natural attenuation (NA) processes in groundwater affected by emissions of abandoned waste disposal sites in Berlin-Kladow/Gatow, Germany. It is part of the funding priority called KORA established by the Federal Ministry for Education and Research (BMBF) to explore the extent to which NA can be used for remedial purposes for varied forms of soil and groundwater contamination. Information on the emission behaviour of individual parameters is generated on the basis of hydrogeochemical comparison of 20 years old and new data. Using groundwater-modelling and CFC-analysis, information on the transport and retention of pollutants in groundwater is compiled. The microbial colonization of contaminated aquifers is characterized by molecular biological methods [polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE)] to differentiate between contaminated and not contaminated zones.  相似文献   

Zur Theorie einfacher und mehrfacher räumlicher Mittelbildungen     

Helmut Pichler 《Meteorology and Atmospheric Physics》1962,13(2):207-217

Zusammenfassung Die Arbeit stellt einen Beitrag zur Theorie der einfachen und mehrfachen räumlichen Mittelbildung einer Feldfunktion dar. Es werden Formeln für die verschiedenen Mittelbildungen angegeben. Ferner wird gezeigt, daß eine zweifache räumliche Mittelbildung durch eine einfache mit einer entsprechend anderen Gitterdistanz ersetzt werden kann. Weiter wird die Genauigkeit der Approximation des Differentialoperators der Mittelung durch einen Differenzenoperator an Hand von Rossby-Wellen diskutiert. Dabei wird nachgewiesen, daß nur, wenn die Gitterdistanz der räumlichen Mittelbildung gegenüber der Wellenlänge von Rossby-Wellen klein verbleibt, eine hinreichend genaue Näherung erzielt werden kann.

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Summary The paper is a contribution to the theory of single and multiple space means of a field function. Formulae for the derivation of various types of means are given. It is shown that a double space mean can be replaced by a single one, provided an appropriate grid distance is used. For the case ofRossby waves, the degree of approximation of the mean attained by using an operator with finite increments and the accurate differential operator is discussed. Sufficient approximation can only be obtained when the grid distance is small compared to the length of theRossby waves.

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Résumé Ce mémoire est une contribution à la théorie de l'établissement dans l'espace des moyennes simples et multiples d'une fonction de champ. On y indique des formules pour l'établissement des diverses moyennes. On montre ensuite qu'une moyenne spaciale double peut être remplacée par une moyenne simple par la seule modification de la distance séparant les mailles du réseau. On discute au moyen d'ondes deRossby la précision de l'approximation obtenue par les moyennes issues d'un opérateur différentiel et d'un opérateur de différences. On démontre ainsi que l'approximation ne peut être suffisante que si la grandeur des mailles du réseau servant à l'établissement des moyennes reste petite par rapport à la longueur des ondes deRossby.

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Kriterien für die anwendung des ertelschen erhaltungssatzes in ionisierten bzw. viskosen medien     

Helmut Pichler 《Pure and Applied Geophysics》1966,65(1):180-184

Zusammenfassung Es wird gezeigt, dass für ein Gasgemisch, das geladene Komponenten enthält und von einem divergenzfreien und stationären Magnetfeld durchsetzt wird, für eine geladene Komponente (Ionen oder freie Elektronen) näherungsweise der Ertelsche Erhaltungssatz gilt, falls unter bestimmten Voraussetzungen das Verhältnis der Reibungskraft (innere) zur magnetischen Feldkraft sehr klein verbleibt. Weiter wurde nachgewiesen, dass derselbe Erhaltungssatz näherungsweise auch für ein viskoses Medium gilt, falls die Reynoldszahl (Verhältnis der Trägheitskraft zur Reibungskraft (innere)) sehr gross ist. Dies ist bei einem turbulenten Medium der Fall.

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Summary It is shown that in a gas mixture containing charged constituents (ions and free electrons) the conservation theorem of Ertel is valid on certain conditions for one of the charged constituent if the ratio of the friction force between the neutral and charged constituents to the magnetic force is small. The same conservation theorem is also valid for a viscous fluid if the Reynoldsnumber (ratio of inertial force to the viscous force) is large.

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A New Genus and Species of Rhynchonellid (Brachiopoda, Recent) from Submarine Caves in the Mediterranean Sea   总被引：1，自引：0，他引：1  

Alan  Logan Helmut  Zibrowius 《Marine Ecology》1994,15(1):77-88

Abstract. A new rhynchonellid brachiopod genus Tethyrhynchia , with type species Tethyrhynchia mediterranea n. sp., is described from specimens discovered in dark zones of submarine caves along the Mediterranean coast of France between Marseille and La Ciotat, and also at Zembra Island, off the Gulf of Tunis, Tunisia. Other brachiopods occurring with this diminutive rhynchonellid are also small and include the megathyridids Argyrotheca cistellula and Megathiris detruncata . This is the first recorded occurrence of a rhynchonellid from the Mediterranean Sea. The new form is apparently neotenous, in that the lophophore in adults never develops beyond the trocholophous stage. A new type of rhynchonellid crus, crescentic in profile and here named the lunifer type, is described. The new genus is assigned to the new family Tethyrhynchiidae , and comparisons are made with other extant rhynchonellid genera.  相似文献   

On the propulsion quality of ships operating at restricted water depth     

Helmut Schwanecke 《Ocean Engineering》1979,6(6):571-580

The propulsive efficiency of marine vehicles has been investigated from the point of view of the effect of restricted waters of the propulsion characteristics. Model tests have been performed for both single-screw and twin-screw vessels. Also optimum propulsion data for modern sea-going single-screw merchant ships operating in unrestricted waters are presented for the sake of general comparison.  相似文献   

Seasonal Changes in Soluble Carbohydrates, Starch, and Energy Content in Mediterranean Seagrasses   总被引：2，自引：0，他引：2  

Helmut Pirc 《Marine Ecology》1989,10(2):97-105

Abstract. In all scagrass species investigated, rhizomes were the main storage organs for soluble carbohydrate reserves, and the highest levels were found in Cymodocea nodosa (U cria ) A scherson . Sucrose was the primary soluble carbohydrate identified in Posidonia oceanica (L.) D elile , and Zostera noltii H ornem . This disaccharide was dominant in Cymodocea nodosa roots, as well as in its rhizome in winter. Myo-inositol was the main cyclitol in Zostera noltii. In Cymodocea nodosa leaves 1-chiro-inositol was the main sugar component; it was also present to a lesser extent in the roots and rhizomes. The amounts of glucose and fructose were correlated with growth to a certain extent in all species. Higher amounts of starch were stored in the rhizomes of Posidonia oceanica and Zostera noltii. The energy content of Mediterranean scagrasses was significantly higher than in tropical species. No distinct seasonal trend in energy content could be observed.  相似文献