Megaflooding on Earth and Mars by Devon M. Burr,Paul A. Carling & Victor R. Baker     

Alexander Gershunov 《水文科学杂志》2013,58(7):1246-1247

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4829923 Sewage disposal     

Alexander G Copson  Mirza N Baig 《Marine pollution bulletin》1989,20(12):639

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European Environmental Research Organization (EERO)     

Alexander J. B. Zehnder 《GeoJournal》1990,22(4):438-438

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Hydrophobic and electrostatic parameters in bacterial adhesion   总被引：5，自引：0，他引：5  

Mark C. M. van Loosdrecht  Willem Norde  Johannes Lyklema  Alexander J. B. Zehnder 《Aquatic Sciences - Research Across Boundaries》1990,52(1):103-114

Recently it has been shown that the initial stages of bacterial adhesion to a model-surface of sulphated polystyrene can best be described using hydrophobic and electrostatic parameters. In the present study it is tested whether these parameters can generally be applied to predict bacterial adhesion by using (i) glass, as a model for hydrophilic and natural surfaces of silicates and oxides, (ii) polystyrene coated with proteins, as a model for a surface coated with an organic layer, and (iii) river Rhine sediment, as an example of a natural surface. Adhesion to glass was dominated by electrostatic interaction, whereas adhesion to polystyrene coated with various types of proteins depended on the surface characteristics of the bacteria and the type of protein. By relating Van der Waals interactions to hydrophobicity of the interacting species, the adhesion of bacteria to the various surfaces including the river Rhine sediments could be interpreted in terms of the DLVO-theory. It is therefore concluded that the conceptual principles of the DLVO-theory (interplay of Van der Waals and electrostatic interactions) are suitable to describe, at least qualitatively, the initial processes of bacterial adhesion to a wide range of surfaces.  相似文献   

Die Entwicklung der Tethystrias und Herkunft ihrer Fauna     

Doz. Dr. Edith Kristan-Tollmann  Prof. Dr. Alexander Tollmann 《International Journal of Earth Sciences》1982,71(3):987-1019

Zusammenfassung Es wird zunächst ein kurzer Überblick über die stratigraphische und fazielle Entwicklung der Trias im Gesamtraum der Tethys zwischen Betischer Kordillere in Spanien und Timor gegeben. Hierbei zeigt sich, daß im Westabschnitt, besonders im mediterranen Raum, eine mio- und aristogeosynklinale und nur untergeordnet eugeosynklinale Entwicklung der Trias vorliegt, in Ostasien (Himalaya, China) auch eugeosynklinal entwickelte Trias vermehrt auftritt. Die europäische Entwicklung der Tethystrias ist durch ihre vielfältige Individualisierung von der asiatischen Trias, die in ihrem Oberteil weiträumig durch eine detritische Fazies beherrscht ist, unterschieden, was besonders auf den Einfluß der indosinischen Faltung in Ostasien zurückgeht. Nord- und Südast der Tethys aber deshalb und auf Grund eines verschiedenartigen Erbes als Paläo- und Neotethys zu bezeichnen, geht zu weit, da die Einheit der gesamten Tethys hierdurch begrifflich zerrissen werden würde.Besonders hervorzuheben ist die Tatsache, daß zahlreiche typische Triasschichtglieder in verschiedenen Abschnitten des Gesamtraumes der Tethys auftreten, nach Litho- und Biofazies und Altersstellung eindeutig als gleichartig identifiziert werden können und demnach im gesamten Raum mit gleichen Namen belegt werden sollen. Das gilt besonders für Reichenhaller Rauhwacke, Gutensteiner Kalk, Reiflinger Kalk, Wettersteinkalk, Hallstätter Kalk, Dachsteinkalk, Kössener Schichten, Rhätoliaskalk — um nur einige Glieder zu nennen, die vom gesamten Raum vom mediterranen Gebiet bis über China hinaus, und zwar z. T. bis Timor — und im Falle des Hallstätter Kalkes bis Südamerika -, verfolgt werden können. Die Ursache liegt im gleichen Schicksal der Kontinentrandgebiete, teils durch Eustatik, teils durch die Mobilität des Schelfs, teils durch die gleichartigen Gesteinsbildner in Fauna und Flora bewirkt.Die Gemeinsamkeit von entscheidenden Faunenelementen über den gesamten Raum der Tethys hin ist ein nächstes, besonders ins Auge stechendes Merkmal. Sie bezieht sich nicht nur auf planktonische und pelagische Elemente, sondern auch auf vagil-benthonische, ja sessile Organismen und umfaßt überraschend viele Arten der Makro- und Mikrofauna, darunter viele Leitfossilien. Zahlreiche Formen sind bisher unter verschiedenen Lokalnamen beschrieben worden, deren Nachuntersuchung nun die Gleichartigkeit über den gesamten Raum der Tethys bestätigt hat. Natürlich bezieht sich diese Feststellung nur auf einen Teil der Fauna, daneben erscheinen auch an Faunenprovinzen gebundene Elemente.Schließlich werden Überlegungen über die Herkunft der Tethysfauna angestellt. Als Heimat eines wesentlichen überregional verbreiteten Anteils wird der ostpazifische Raum am amerikanischen Kontinentalrand, besonders der Raum von Britisch-Kolumbien abgeleitet. Als Gründe sprechen dafür: 1. Reichliche Beteiligung von Tethyselementen an der Fauna dieser ostpazifischen Provinz, 2. Fehlen eines Meeresweges quer durch (Mittel-) Amerika nach Osten zur Tethys in der Zeit der Trias, 3. Rekonstruktion eines Paläowind- und Meeresströmungssystems auf Grund der Triaspaläogeographie und aktualistischer Prinzipien, das eine Drift von Osten nach Westen durch Pazifik und Tethys bewirkt haben muß, 4. Die Möglichkeit dieser Wanderung von Faunenelementen über den Pazifik auch für vagiles und sessiles Benthos mit Hilfe von Larvenstadien und in pseudoplanktonischer Form auf Tang und Treibholz. Abgesehen von diesem über den gesamten tropischen bis tropennahen Raum von Pazifik und Tethys verbreiteten Anteil kommt naturgemäß noch ein autochthoner Anteil der Fauna hinzu, der sich in den einzelnen Faunenprovinzen jeweils autonom entwickelt hat — besonders begünstigt im asiatischen Teil der Tethys. Schließlich liegt nach der Verbreitung bestimmter Arten und Artgruppen noch die Möglichkeit der Wanderung eurasiatischer Formen in höheren Breiten mit den ostgerichteten Gegenströmungen von Tethys und Pazifik nahe.

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The development of the Triassic within the Tethys realm and the origin of its fauna

Summary This paper gives at first a survey about the stratigraphy and facies of the Triassic within the Tethys realm between Betic Cordillera in Spain and Timor in Indonesia. This review shows that the western part of the Tethys in the Mediterranean region comprises a mio-, (eu-)and aristogeosynclinal facies of the Triassic and prooves that the eugeosynclinal facies is more significant for the central- and eastasiatic part of the Tethys realm.The European development is characterized by an extreme individualisation of faciestypes and a hight specification of Triassic formations, whilst the Asiatic region is dominated by an extensive spreading of immense masses of detritus in the Upper Triassic — particularly in the northern branch of Tethys -, in dependence on the Indosinic orogenesis at the end of the Middle Triassic. The distinction of a northern Paleotethys and a southern Neotethys during the Mesozoic era with regard to this event can't be sanctioned, respecting the integrity of the Tethys as a whole.The following chapter stresses the fact that many alpine formations are spreaded whole over the Tethys realm, identic in lithofacies, biofacies, fauna, flora and stratigraphic position, so that one must not hesitate denominating the same formations with the same name (Lugeon/Andrusov-principle). Those formations and members, identical all over the Tethys region, are e. g. Reichenhaller cellular dolomite, Gutenstein Wurstel-limestone, Reifling-, Wetterstein-, Hallstatt- and Dachstein-limestone, which can be observed from the Mediterranean region up to China and Timor — the Hallstatt limestone as fare as Southern America. The reason of this surprisingly fact is caused by the same conditions of the plate margins during the Triassic tectonic history, moreover by the same conditions for the formation of organogeneous limestone by time-specific organismes and in some cases also in eustatic movements of the sea level.The next fact shown in this paper is the result that a lot of characteristic alpin fauna elements are spreaded all over the Tethys area, from the Alps to Indonesia. This statement concerns not only planctonic and pseudoplanctonic taxa, but also many bentonic elements living in a vagil or sessil manner within the macro- and microfauna — comprisingly also many index-fossils. Hitherto a lot of those species have been described under local names. The revision of the fossil material, collected directly by the authors in many sectors of the Tethys has confirmed this result of widespread species whole over the Tethys ocean.Finally some reflections are made about the origin of the Tethys fauna. A part of the Tethys fauna which is common with the fauna of the Eastern Pacific region, is regarded as originally developed in Western America, particularly in the territory of British Columbia, and transported by the Pacific ocean currents westwards into the Tethys. A short connection between Eastern Pacific and Western Tethys by a Protoatlantic (Poseidon) did not existe in consequence of the existence of Pangea during the Triassic time. Therefore the communication of the identic faunistic elements of Eastern Pacific and Tethys must have be realized by transpacific way: New observations about the longevity of larval stages, also of recent benthic organisms and reflections about the Triassic paleocurrent system in the Panthalassa established on actualistic principles (Fig. 2) proove the feasibility of such a theory. By the counter-current in high latitudes the transport of Tethyal elements to eastern areas along the shore of America could be effected.

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Résumé Cet article donne premièrement un résumé de la stratigraphie et du faciès du Trias de la région mesogéenne entre la Cordillère Bétique et Timor en Indonésie. Il apparaît ainsi qu'on trouve dans les régions méditerranéennes notamment un faciès mio- et aristogéosynclinal, tandis que le faciès eugéosynclinal est plus fréquent dans la partie centrale et orientale de la Téthys asiatique.La partie européenne de la Téthys est caractérisée par une individualisation extrême des types de faciès et des formations. Au contraire, le faciès de la région asiatique est dominé par des masses détritiques dans le Trias supérieur, comme conséquence de la phase orogénique indosinienne dans l'Asie orientale.Par la suite on démontre que bien des formations alpines sont répandues dans toute la région de la Téthys, identiques en lithofaciès, biofaciès, faunes, flores et dans leur position stratigraphique — en conséquence, il ne faut pas hésiter d'employer les mêmes désignations pour les mêmes formations dans tout le territoire en question. On retrouve par exemple les cargnieules de Reichenhall, les calcaires vermiculés de Gutenstein, les calcaires de Reifling, du Wetterstein, de Hallstatt et du Dachstein etc. à partir de la région méditerranéenne jusqu' en Chine et à Timor; d'autre part, les calcaires de Hallstatt se retrouvent jusqu' en Amérique méridionale. Ce fait étonnant tient à des conditions identiques valables pour les bords des plaques continentales pendant le Triassique, ainsi qu'à une formation identique des calcaires organogènes provoquée par l'existence simultanée des mêmes organismes et aussi par des oscillations eustatiques de l'océan.Un autre résultat que nous aimerions mentionner dans cet article est le fait qu' un nombre assez grand des éléments de la faune alpine est répandu dans tout le territoire de la Téthys. Cette constatation ne concerne pas seulement les éléments (pseudo-)planctoniques, mais aussi beaucoup d'organismes bentoniques (vagiles et sessiles) de la macroet microfaune. Jusqu' à présent, beaucoup de ces espèces sont décrites sous des noms locaux. La révision des suites des fossiles, collectionnées par les auteurs eux-mêmes dans les différents secteurs de la Téthys, a confirmé ce fait.Enfin des réflexions sont faites sur l'origine de la faune téthysienne. Une partie de cette faune de la Téthys, celle qui correspond à la faune de la région pacifique orientale, se serait développée d'abord en Amérique septentrionale, notamment en Colombie britannique, et aurait été transportée par le courant pacifique central vers l'ouest, dans la Téthys. Une communication directe, pendant le Trias, entre le Pacifique et la Téthys occidentale, par un Protoatlantique («Poseidon») n'existait pas du fait que la Pangéa était intacte. La migration des éléments faunistiques dans le Pacifique oriental et dans la Téthys n'était possible que le long de la route transpacifique. Des observations nouvelles sur la longue durée des stades larvales des organismes bentoniques ainsi que des réflexions concernant les paléocourants de la Panthalassa (Fig. 2) prouvent le bien-fondé de cette théorie. Par des contre-courants dans des latitudes supérieures, le transport des éléments faunistiques de la Téthys dans des régions arctiques et antarctiques de l'Amérique était possible.

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Arbeit im Rahmen des Int. Geol. Correl. Programme, Projekt 73/I/4, Triassic of the Tethys Realm, durchgeführt.  相似文献   

Anthropogenic nitrogen deposition induces rapid ecological changes in alpine lakes of the Colorado Front Range (USA)   总被引：10，自引：3，他引：7  

Alexander P. Wolfe  Jill S. Baron  R. Jack Cornett 《Journal of Paleolimnology》2001,25(1):1-7

Recent sediments from two alpine lakes (> 3300 m asl) in the Colorado Front Range (USA) register marked and near-synchronous changes that are believed to represent ecological responses to enhanced atmospheric deposition of fixed nitrogen from anthropogenic sources. Directional shifts in sediment proxies include greater representations of mesotrophic diatoms and increasingly depleted ¹⁵N values. These trends are particularly pronounced since ~ 1950, and appear to chronicle lake responses to excess N derived from agricultural and industrial sources to the east. The rate and magnitude of recent ecological changes far exceed the context of natural variability, as inferred from comparative analyses of a long core capturingthe entire 14,000-year postglacial history of one of the lakes. Nitrogen deposition to these seemingly pristine natural areas has resulted in subtle but detectable limnological changes that likely represent the beginning of a stronger response to nitrogen enrichment.  相似文献   

Improved magnetic anomalies of the Antarctic lithosphere from satellite and near-surface data     

Hyung Rae Kim  Ralph R. B. von Frese  Patrick T. Taylor  Alexander V. Golynsky  Luis R. Gaya-Piqué  Fausto Ferraccioli 《Geophysical Journal International》2007,171(1):119-126

The Antarctic magnetic anomaly map compiled marine and airborne surveys collected south of 60°S through 1999 and used Magsat data to help fill in the regional gaps between the surveys. Ørsted and CHAMP satellite magnetic observations with greatly improved measurement accuracies and temporal and spatial coverage of the Antarctic, have now supplanted the Magsat data. We combined the new satellite observations with the near-surface survey data for an improved magnetic anomaly map of the Antarctic lithosphere. Specifically, we separated the crustal from the core and external field components in the satellite data using crustal thickness variations estimated from the terrain and the satellite-derived free-air gravity observations. Regional gaps in the near-surface surveys were then filled with predictions from crustal magnetization models that jointly satisfied the near-surface and satellite crustal anomalies. Comparisons in some of the regional gaps that also considered newly acquired aeromagnetic data demonstrated the enhanced anomaly estimation capabilities of the predictions over those from conventional minimum curvature and spherical harmonic geomagnetic field models. We also noted that the growing number of regional and world magnetic survey compilations involve coverage gaps where these procedures can contribute effective near-surface crustal anomaly estimates.  相似文献   

Seismic,petrologic, and geodetic analyses of the 1999 dome-forming eruption of Guagua Pichincha volcano,Ecuador     

Alexander Garcia-Aristizabal  Hiroyuki Kumagai  Pablo Samaniego  Patricia Mothes  Hugo Yepes  Michel Monzier 《Journal of Volcanology and Geothermal Research》2007

Guagua Pichincha, located 14 km west of Quito, Ecuador, is a stratovolcano bisected by a horseshoe-shaped caldera. In 1999, after some months of phreatic activity, Guagua Pichincha entered into an eruptive period characterized by the extrusion of several dacitic domes, vulcanian eruptions, and pyroclastic flows. We estimated the three-dimensional (3-D) P-wave velocity structure beneath Guagua Pichincha using a tomographic inversion method based on finite-difference calculations of first-arrival times. Hypocenters of volcano-tectonic (VT) earthquakes and long-period (LP) events were relocated using the 3-D P-wave velocity model. A low-velocity anomaly exists beneath the caldera and may represent an active volcanic conduit. Petrologic analysis of eruptive products indicates a magma storage region beneath the caldera, having a vertical extent of 7–8 km with the upper boundary at about sea level. This zone coincides with the source region of deeper VT earthquakes, indicating that a primary magma body exists in this region. LP swarms occurred in a cyclic pattern synchronous with ground deformation during magma extrusions. The correlation between seismicity and ground deformation suggests that both respond to pressure changes caused by the cyclic eruptive behavior of lava domes.  相似文献   

GPS radio holography as a tool for remote sensing of the atmosphere, mesosphere, and terrestrial surface from space     

Alexander Pavelyev  Yuei-An Liou  Christoph Reigber  Jens Wickert  Kiyoshi Igarashi  Klemens Hocke  Cheng-Yung Huang 《GPS Solutions》2002,6(1-2):100-108

GPS radio occultation (RO) signals are highly coherent and precise, and thus sufficient for holographic investigation of the atmosphere, ionosphere, and the Earth's surface from space. In principle, three-dimensional radio-holographic remote sensing is possible by using new radio holographic equations to retrieve the radio field within the atmosphere from a radio field known at some interface outside the atmosphere. A simplified two-dimensional form of the radio-holographic equations which are developed under an assumption of local spherical symmetry can be used to obtain two-dimensional radio images of the atmosphere and terrestrial surface. To achieve this, radio holograms recorded by a GPS receiver onboard a low earth orbit (LEO) satellite at two GPS frequencies can be used and focused synthetic aperture principle applied. Analysis of GPS/MET RO data is presented to show the effectiveness of a radio-holographic approach. It is shown that the amplitude of GPS radio signals (in addition to phase data) can be used to obtain detailed altitude profiles of the vertical gradient of refractivity in the atmosphere and electron density in the mesosphere. The results demonstrate the applicability of GPS radio holography for a detailed global study of the natural processes in the atmosphere and mesosphere. Electronic Publication  相似文献   

The development of computer networks: First results from a microeconomic model     

Gunther Maier  Alexander Kaufmann 《Journal of Geographical Systems》2001,3(2):155-166

 Computer networks like the Internet are gaining importance in social and economic life. The accelerating pace of the adoption of network technologies for business purposes is a rather recent phenomenon. Many applications are still in the early, sometimes even experimental, phase. Nevertheless, it seems to be certain that networks will change the socioeconomic structures we know today. This is the background for our special interest in the development of networks, in the role of spatial factors influencing the formation of networks, and consequences of networks on spatial structures, and in the role of externalities. This paper discusses a simple economic model – based on a microeconomic calculus – that incorporates the main factors that generate the growth of computer networks. The paper provides analytic results about the generation of computer networks. The paper discusses (1) under what conditions economic factors will initiate the process of network formation, (2) the relationship between individual and social evaluation, and (3) the efficiency of a network that is generated based on economic mechanisms. Received: 5 July 2000 / Accepted: 28 November 2000  相似文献