Uptake rate and efficiency of uptake of hexachlorobenzene from water and sediment by tellinid clam, Macoma nasuta     

B.L. Boese  H. Lee II  D.T. Specht  R.C. Randall 《Marine environmental research》1988,24(1-4)

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Subglacial to proglacial sediment transition in a shallow ice-contact lake   总被引：1，自引：0，他引：1  

CHARLES W. ROVEY II  MARK K. BORUCKI 《Boreas: An International Journal of Quaternary Research》1995,24(2):117-127

A complete subglacial to glacial-lacustrine facies transition is described from a temporary exposure in the Lake Michigan bluffs of southeastern Wisconsin. This transition occurs where a Late Woodfordian terminal moraine intersects the bluff line and grades from basal meltout till to chaotic diamicton to rhythmites over an abrupt 90 m lateral distance. The boundary of the subglacial meltout deposits is marked by an abrupt increase in pebbles and cobbles, which cluster at specific horizons, producing an incipient stratification. Thereafter, the diamicton develops contorted flow structures with progressive segregation into coarse and fine-grained fractions, ultimately into well-stratified rhythmites.  相似文献   

Technical note: Estimating water shed S-graphs using a diffusion flow model     

T.V. Hromadka II  A.J. Nestlinger 《Advances in water resources》1985,8(4):214-218

A simplification of the two-dimensional (2-D) continuity and momentum equations is the diffusion equation. This simpler dynamic model of two-dimensional hydraulics affords the hydrologist a means to quickly estimate floodflow effects for overland flow. To investigate its capability, a numerical model using the diffusion approach is applied to a set of hypothetical watersheds in order to develop unit hydrographs. The model is based on an explicit, integrated finite-difference scheme, and the floodplain is simulated by use of topographic elevation and geometric data. Synthetic unit hydrographs (S-graphs) developed from use of the simple 2-D model show interesting correlations to the well-known S.C.S. unit hydrograph (S-graph).  相似文献   

Experimental deformation of a synthetic dunite at high temperature and pressure. I. Mechanical behavior, optical microstructure and deformation mechanism     

David H. Zeuch  H.W. Green II 《Tectonophysics》1984,110(3-4):233-262

We have performed a series of 27 deformation experiments on a very dry synthetic dunite, using the Griggs solid medium apparatus. Strain rates ranged from 1 × 10 ⁴ to 1 × 10 ⁷ sec ¹, temperatures varied from 1100° to 1300 °C, and the confining pressure was maintained at 10 or (more usually) 15 kbar. MACOR^IM, a commercially available, anhydrous, machinable glass ceramic with a low melting point, was used in many of the experiments. We find that strength measurements performed using macor as a confining medium are similar to results obtained using sodium chloride as the confining solid. Tests performed in undried sample assemblies using air-dried dunite specimens resulted in creep strengths greater than those found in any earlier studies except those of Post (1973. 1977). A single test on a sample for which both sample and assembly were dried at a temperature sufficiently high to drive off any adsorbed water resulted in a creep strength comparable to that determined by Post (1973, 1977) for very dry Mt. Burnett dunite. Despite our experimental difficulties, we are led to believe that our synthetic dunite exhibits mechanical behavior consistent with that determined in other experimental studies in which natural dunites and peridotites were used. Furthermore, we conclude that dry dunite is very probably as strong as the oft-disputed results of Post earlier indicated. Finally, we show that the optical textures of our highly recrystallized experimental specimens are essentially identical to naturally produced porphyroclastic textures and that the deformation mechanism in both the experimental and natural specimens is probably dislocation creep with recovery by dynamic recrystallization.  相似文献   

Comments on paper by A. Olsen and T. Birkeland: “electron microscope study of peridotite xenoliths in kimberlites”     

H. W. Green II 《Contributions to Mineralogy and Petrology》1974,46(1):69-72

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Continental drift and the global pattern of sedimentation     

President Dr. William W. Hay  Eric J. Barron  James L. Sloan II  John R. Southam 《International Journal of Earth Sciences》1981,70(1):302-315

The breakup of Pangaea through rifting and separation of the continents has special implications for the global pattern of sedimentation. The important initial conditions of Pangaea are area, elevation, the nature of the drainage and climate. The development of interior uplifts associated with rifting caused significant reorganization of drainage systems. Rifting and continental breakup result in unique sediment sequences on passive margins.The initial rift valleys were probably occupied by stratified fresh water lakes due to the equable Mesozoic climate, and during this phase might have accumulated about 7.5×10²¹ g of organic carbon; this would be 14% of the earth's total organic carbon concentrated on only 0.3% of the earth's surface. The sediments rich in organic carbon are expected to be typically overlain by evaporites.Sedimentation on the continental shelf is a complex interplay of thermal subsidence, sea level changes, sediment supply and isostatic adjustment.Beyond the shelf break, sedimentation rates in the world ocean appear to change significantly with time; during the Aptian-Albian, Campanian-Maastrichtian, Middle Eocene and Late Miocene-Quaternary overall sedimentation rates were about an order of magnitude higher than during the intervening periods. This variation is likely to be related to changing sediment supply responding to changes in sea level.

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Zusammenfassung Das Aufbrechen Pangaeas durch Spaltung und Separation der Kontinente hat spezielle Auswirkungen auf die globale Sedimentationsverteilung. Die bedeutenden Anfangsbedingungen Pangaeas sind Größe, Höhe, Abfluß- und Klimasituation. Die Entwicklung innerer Aufwölbungen, zusammen mit Spaltenbildung, hat eine entscheidende Reorganisation der Abflußsysteme bewirkt. Spaltung und Aufbrechen des Kontinents resultieren in einer einzigartigen Sedimentationsfolge an den passiven Rändern.Die anfänglichen Spaltungstäler waren wahrscheinlich von geschichteten Süßwasserseen eingenommen, hervorgerufen vom ausgeglichenen mesozoischen Klima. Während dieser Zeit können sich dort etwa 7,5 · 10²¹ g organischer Kohlenstoffe angesammelt haben, d. h. 14 % der weltweiten organischen Kohlenstoffe auf nur 0,3 % der Erdoberfläche. Die kohlenstoffreichen Sedimente sind typischerweise von Evaporiten überlagert.Sedimentation auf dem kontinentalen Schelf ist ein komplexes Zusammenspiel von Temperatursenkung, Wasserspiegelschwankungen, Sedimentsangebot und isostatischem Gleichgewicht.Jenseits des Schelfabhanges scheinen die Sedimentationsraten im Weltmeer signifikant mit der Zeit zu schwanken. Während des Aptiums-Albs, des Campaniums-Maastrichts, des Mittleren Eozäns und des Späten Miozän-Quartärs lagen die gesamten Sedimentationsraten um eine Größenordnung höher als in den dazwischenliegenden Zeiträumen. Diese Variation hängt wahrscheinlich mit einem geänderten Sedimentsangebot zusammen, das von Wasserspiegelschwankungen hervorgerufen wird.

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Résumé La dislocation de la Pangée, par fracturation (rifting) et séparation des continents, entraîne des implications particulières en ce qui concerne les modèles de sédimentation à l'échelle du globe. Les conditions initiales importantes de la Pangée sont la surface, l'altitude, la nature du drainage et le climat. Le développement de soulèvements intérieurs en association avec les processus de fracturation (rifting) fut la cause d'une importante réorganisation du système de drainage. Sur les marges continentales passives, des séquences sédimentaires uniqes résultent de ces processus de caussure (rifting), et de dislocation.Les vallées médianes (rifts) initiales ont été probablement occupées par des lacs à eaux douces stratifiées, dues au climat égal du Mésozoique, et ont pu durant cette période accumuler environ 7.5×20²¹ g. de carbone organique; cette quantité serait l'équivalent de 14% du carbone organique total du globe, concentrés sur 0.3% de sa surface. Les sédiments riches en carbone organique sont supposés être typiquement recouverts par des dépôts évaporitiques.La sédimentation sur le plateau continental se trouve en interaction complexe avec la subsidence thermique, les fluctuations du niveau des océans, les apports en sédiments et les ajustements isostatiques.Au delà de la limite externe du plateau continental, les taux de sédimentation dans les océans semblent varier de manière importante dans le temps; durant l'Aptien-Albien, le Campanien-Maastrichtien, L'Eocène moyen et le Miocène supérieur-Quaternaire, les taux d'ensemble de sédimentation ont été environ d'un ordre de grandeur plus élevé que durant les périodes intermédiaires. Cette variation est vraisemblablement liée aux changements des apports en sédiments, en réponse aux fluctuations du niveau océanique.

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(—1972 —1977) - . , 7,7 /. . . 10–15 , 7,0–7,4 /. . , , 30 7,5–7,7 /. 50 . 12–18 , . , .

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Dichlorobenzene in Ground Water: Evidence for Long-Term Persistence   总被引：1，自引：0，他引：1  

Larry B. Barber  II 《Ground water》1988,26(6):696-702

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Largescale ripples of the lower Wabash River     

ROSCOE G. JACKSON II 《Sedimentology》1976,23(5):593-623

Largescale ripples in the meandering lower Wabash River of Illinois and Indiana, U.S.A., include scroll bars and three dunelike bed forms (dunes, sand waves, and transverse bars). Scroll bars are lobate crested, asymmetrical in stream-wise vertical profile, usually solitary, and oriented approximately normal to local channel strike. They form by passive flow expansion downchannel from locally emergent topographic highs, face and lie near inner banks of meander bends, enjoy a high preservation potential as leveelike ridges of ridge-and-swale topography, and migrate only during relatively low stream discharges, when water depth over bar crests is less than 0·5 m. Dunes correspond to dunes of the flow-regime classification and rarely are solitary or superimposed. Sand waves may be symmetrical or asymmetrical, are always superimposed by dunes, occur in depths greater than 4 m and in bed material coarser than 1 mm mean size, and develop at bankfull and flood flows. Transverse bars migrate in depths less than 5 m in straight reaches and near inner banks of bends, display crestal dunes, and correspond to the bars of Costello (1974) and to the sand waves of Boothroyd (1969). Hydrodynamic regimes of scroll bars and transverse bars differ from that of dunes. The omnipresence of dunes upon stoss-sides of sand waves confirms the existence of an equilibrium superimposition of dunelike largescale ripples. Depth-velocity-size diagrams appear to be a valid representation of empirical stability fields of dunelike largescale ripples in deep unsteady nonuniform aqueous flows. Stability fields of dunes and sand waves overlap greatly. Velocity profiles demonstrate an absence of leeside flow separation over dunes and an appearance (rare) over transverse bars only when the ratio of trough depth to crest depth exceeds two. Dune stratification displays (1) largescale trough cross-strata, (2) thinning of sets as bed-material size increases, and (3) an orientation within 20° of local channel strike. Transverse bars show avalanche sets up to 2 m thick, with reactivation surfaces. Scroll bars display thick avalanche sets separated by reactivation structures consisting of erratically oriented smallscale trough cross-strata. Avalanche sets of scroll bars and of transverse bars are oriented 50–150° from and within 50° of, respectively, local channel strike.  相似文献   

A critique of homeostatis: Season and metabolism     

F. Sargent II 《Theoretical and Applied Climatology》1951,3(1):289-296

Summary Bioclimatologic investigation has shown that the fluid bathing the body cells—the internal environment—exhibits definite seasonal variations with regard to the concentration of substances in that fluid. Physiologic theory, on the other hand, maintains that the concentration of substances in the internal environment is kept relatively constant by means of a complex homeostatic (neuro-endocrine) mechanism. As a consequence physiology teaches that man is free and independent of the cosmic environment. This conflict is examined in the case of calcium and phosphorus metabolism. It is concluded that the internal environment isnot constant. It follows then that man is not free and independent of the changes in the cosmic environment.

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Zusammenfassung Die bioklimatologische Forschung hat festgestellt, daß die Flüssigkeit, die die Körperzellen umgibt—das innere Milieu—hinsichtlich der Konzentration der in ihr enthaltenen Substanzen bestimmte jahreszeitliche Schwankungen zeigt. Anderseits steht die physiologische Theorie auf dem Standpunkt, daß die Konzentration der Substanzen im Körperinnern durch einen komplexen homöostatischen (neuro-endokrinen) Mechanismus relativ konstant gehalten wird; infolgedessen lehrt die Physiologie, daß der Mensch frei und unabhängig von kosmischen Umwelteinflüssen sei. Dieser Widespruch wird in bezug auf den Calcium- und den Phosphor-Stoffwechsel geprüft und dabei festgestellt, daß das innere Milieunicht konstant ist. Der Mensch ist somit nicht frei und unabhängig von den Vorgängen des äußeren Milieus.

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Résumé Les recherches bioclimatologiques ont montré que le liquide entourant les cellules corporelles—le «milieu interne»—est soumis à certaines variations saisonnières quant à la concentration des substances qui'il renferme. Par contre la physiologie admet que la concentration de ces substances est maintenue relativement constante par un mécanisme homéstatique complexe (neuro-endocrinien); elle enseigne par conséquent que l'homme ne dépend pas des influences cosmiques. On examine cette contradiction à l'endroit du métabolisme du calcium et du phosphore et on constate que le milieu interne n'est pas constant. L'homme n'est doncpas indépendant des phénomènes du milieu extérieur.

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Based on a paper presented at the 30th Anniversary Meeting of the American Meteorological Society, St. Louis, Mo., January 3–6, 1950.  相似文献   

Nepheline--Alkali Feldspar Equilibria: I. Experimental Data and Thermodynamic Calculations     

ZYRIANOV  V. N.; PERCHUK  L. L.; PODLESSK  K. K.  II 《Journal of Petrology》1978,19(1):1-44

Nepheline-alkali feldspar equilibria with alkali chloride aqueoussolutions have been determined for the temperature range 400to 700 °C at 1000 bars pressure. Nepheline-alkali feldsparequilibria with alkali chloride melts have been determined forthe temperature range 800 to 1100 °C at approximately 6bars pressure. (1) NaAlSiO₄ + KCl(aq) = NaCl(aq) + KAlSiO₄ (2) NaAlSiO₄ + KCl(melt) = NaCl(melt) + KAlSiO₄ (3) NaAlSi₃O₈(high) + KCl(aq) = NaCl(aq) + KAlSi₃O₈(San) (4) NaAlSi₃O₈(low) + KCl(aq) = NaCl(aq) + KAlSi₃O₈(Mic) (5) NaAlSi₃O₈(high) + KCl(melt) = NaCl(melt) + KAlSi₃O₄(San) (6) NaAlSi₃O₈(low) + KCl(melt) = NaCl(melt) + KAlSi₃O₈(Mic) From these, two diagrams of phase relationships were derivedfor the following exchange equilibria: (7) NaAlSiO₄ + KAlSi₃O₈(San) = NaAlSi₃O₈(high) + KAlSiO₄; (8) NaAlSiO₄ + KAlSi₃O₈(Mic) = NaAlSi₃O₈(low) + KAlSiO₄. The effect of pressure on these equilibria has been determinedby comparing the experimental data for 1000 and 5000 bars (t= 500 °C) and thermodynamic calculations. It has also beenshown that the effect of excess silica in nepheline solid solutionon the K—Na distribution between nepheline and alkalifeldspar is substantial and opposite to that of temperature.In the high temperature region an increase in silica contentin nepheline of 2 wt. per cent eliminates the effect on theredistribution of a temperature increase of 100 °C. Thesecation exchange data and unit cell data for the crystal phasesare used to calculate thermodynamic mixing properties of nephelinesolid solution and alkali feldspar solid solution for a widerange of temperature and pressure.  相似文献