Influence of a cyclic and dynamic loading history on dynamic properties of dry sand, part I: cyclic and dynamic torsional prestraining

Initial fabric of a soil induced by its cyclic strain history is an important parameter together with the void ratio, state of stress and amplitude in respect to further accumulation of deformations under drained cyclic loading. It is of importance for the further deformation prediction to determine the initial fabric of the grain skeleton or the cyclic loading history of the soil. An attempt is made within this paper to correlate small strain stiffness of non-cohesive soil with its cyclic loading history. The results of performed cyclic and dynamic torsional tests show that small strain shear modulus is only moderately affected by cyclic prestraining even if high amplitudes are applied. A signature of prestraining history is observed in the tests since the sand memorizes its prestraining amplitude and the number of applied cycles.     

Winter air pollution episodes over Cape Town

Episodes of air pollution over Cape Town are identified using multi-year time series of SO₂ and NO_x concentrations. The associated meteorological conditions are studied both from synoptic and meso-scale perspectives using detailed observations, statistical analyses and numerical model simulations. Atmospheric conditions are most conducive to poor dispersion in the winter months, April to August. Episodes are initiated by the eastward passage of an intense, synoptic anticyclone over the Cape Town area. The 850 hPa geopotential height typically rises to 1600 gpm a day before the episode. Northeasterly berg winds are common and act to dry out the boundary layer. A nocturnal radiation inversion forms with a mean strength of 11 °C and extends from the surface to 953 hPa (500m). Gradient and thermal winds tend to cancel out providing for low net transport rates for near-surface emissions. Acoustic sounder profiles for two episodes illustrate a reduction of winds and turbulence within the boundary layer. The episode surface circulation is simulated using a two-layer model. Hills which lie upstream of Cape Town obstruct the northeasterly flow during the morning.     

Seismic evidence of increased tectonothermal activity near the Oberpfalz deep continental drilling location (SE Germany)

The success of ultradeep drilling projects, as e.g. within the German Continental Deep Drilling Programme (Kontinentales Tiefbohrprogramm, KTB) in the Oberpfalz strongly depends on the thermal and geological-tectonic environment of the well. In the present paper we apply the correlation of elevated temperatures and seismic reflectivity of the lower continental crust to the deep seismic network of the Oberpfalz. The results together with the correlation to other geoscientific data indicate increased temperatures in the area of the KTB location. These temperatures are most probably related to influences of the Eger graben and possibly are not yet measured at the surface using heat flow determinations.

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Zusammenfassung Der Erfolg ultratiefer Bohrungen, wie etwa in der Oberpfalz im Rahmen des deutschen Kontinentalen Tiefbohrprogramms (KTB), hängt sehr stark vom thermischen und geologisch-tektonischen Umfeld der Bohrung ab. In der vorliegenden Arbeit wird die Korrelation von erhöhten Temperaturen und guter Reflektivität der kontinentalen Unterkruste angewandt auf das seismische Netz der DEKORP 4 und KTB Linien in der Oberpfalz. Aufgrund der Ergebnisse und anderer geowissenschaftlicher Resultate sind höhere Temperaturen als vorher berechnet im Bereich der Tiefbohrung zu erwarten. Diese dürften im Zusammenhang mit dem westlichen Ende des Eger Grabens stehen.

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Résumé Le succès de sondages très profonds, comme celui qui est envisagé dans le Haut Palatinat dans le cadre du programme allemand de sondages profonds continentaux (Kontinental Tiefbohrprogramm: KTB) est étroitement lié à l'environnement thermique et tectono-géologique des forages. Dans cette note, la corrélation entre les hautes températures et la réflectivité sismique est appliquée au réseau sismique fourni par les profils DEKORP 4 et KTB dans le Haut Palatinat. Les résultats obtenus, joints à d'autres données géologiques, laissent prévoir dans la région du KTB des températures plus élevées que celles qui étaient envisagées jusqu'ici. Ces températures élevées sont probablement en relation avec l'extrémité ouest du graben d'Eger et n'ont pas encore été repérées en surface par les mesures du flux de chaleur.

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170- - / / . , . 18% , : KTst 0=950 (Stefan A), KTst 1=700 (Westfal D), KTst 3=400 (Westfal C), KTst 4a=330 (Westfal ), KTst 4a=322 (Westfal C), KTst 4=320 (Westfal C), KTst 5=300 (Westfal C), KTst 6=270 (Westfal C). . , . , . . , , , - . , 43 - 8,2 ³, — 20,5 ³. , , - ; , .

     

The physical properties of the Hα-emission line stars: CD-42°11721, KK Oph and XX Oph

By use of the data found in the literature, observed at the ESO and taken from the IRAS point source catalogue, the physical properties of the H-emission stars: CD-42°11721, KK Oph and XX Oph were studied photometrically and spectroscopically. The results can be summarized as follows: (a) Feii and [Feii] emission lines show that these stars have a gaseous envelope of which part is of low density. (b) P Cygni profiles in the spectral lines of XX Oph indicate the existence of rapid gaseous motions in its atmosphere. The presence of P Cygni profiles in the spectra of the other two stars is not certain. (c) In the outer atmosphere of CD-42°11721 and KK Oph at least two circumstellar concentrations of dust grains seems to be present; the temperatures of these dust shells are, for both stars, about 1200 and 250 K. (d) XX Oph has an M6III companion causing the infrared excess. Furthermore, we have studied the physical properties of the dust shells. The distances to the central star, the chemical composition and the masses of each shell were estimated. It is recommended to study above stars further with high dispersion spectroscopy and simultaneous long-term photometry.Based partly on data obtained at the ESO, La Silla, Chile and with the Infrared Astronomical Satellite (IRAS).     

Die Paläogeographie des Nillandes in Kreide und Tertiär

Ohne Zusammenfassung     

Die Paläogeographie des Nillandes in Kreide und Tertiär

Ohne Zusammenfassung     

Fluid mud dynamics in the Weser estuary turbidity zone tracked by high-resolution side-scan sonar and parametric sub-bottom profiler

Fluid mud in estuarine turbidity maximum zones (TMZ) can pose considerable navigation risks due to potentially substantial reductions in nautical depth, coupled with an inherent difficulty of detection by conventional echo-sounders. Despite intensive research efforts, however, our knowledge about the spatial and temporal dynamics of fluid mud is still not sufficient. In this study, the combined use of a side-scan sonar (Sportscan®, Imagenex) and a parametric sub-bottom profiler (SES-2000®, Innomar Technology GmbH) has proved successful for high-resolution fluid mud detection and volumetric quantification in an estuarine environment. In 2004 and 2005, repeated surveys were conducted in the navigation channel of the upper meso- to lower macrotidal Weser estuary TMZ (German North Sea coast) at different tidal stages and river discharges. Current velocity data were simultaneously collected by 1,200-kHz broadband ADCP (RDInstruments) measurements. Ground-truthing was carried out by means of grab sampling and gravity coring, adapted to fluid mud conditions. It was found that fluid mud occurrence in the Weser estuary is highly variable on time scales of a few hours and spatial scales of several metres. The riverbed is characterised by sand and mud deposits, and a complex morphology including subaqueous dunes and smooth bed deposits intermittently overlain by fluid mud. Thus, a continuous, coherent fluid mud body covering the entire TMZ riverbed was not observed. Rather, spatial distribution was patchy and highly dependent on suspended particulate matter (SPM) concentrations in the water column, as a result of which local fluid mud deposits varied in thickness from centimetres to metres. The formation of fluid mud was largely restricted to slack water, although slack-water conditions were not necessarily associated with large-scale fluid mud appearance. Advective SPM transport of resuspended fluid mud seems to be the most plausible explanation for the high spatial variability observed, even between two successive tides. The amount of fluid mud deposited and resuspended in the course of a tidal cycle can reach several 10s of tons even in small riverbed depressions.     

Boundary current-controlled turbidite deposition: A sedimentation model for the Southern Nares Abyssal Plain,Western North Atlantic

Examination of 38 sediment cores, bottom photographs, 7,000 km of 3.5 kHz reflection profiles and other seismic data from the southern part of the Nares Abyssal Plain suggests that complex sedimentary patterns and high sedimentation rates can be largely attributed to effects of a deep boundary current flowing eastward along the north flank of the Greater Antilles Outer Ridge. It is concluded that the areal dispersal pattern of turbidites on the plain results mainly from Quaternary climatically-induced fluctuations of the boundary current intensity.     

Cadmium-binding proteins in the blue crab, callinectes sapidus: laboratory-field comparison

The blue crab, Callinectes sapidus, is distributed along the east coast of the United States from Cape Cod, Mass., through the Gulf of Mexico, including both relatively unpolluted coastal areas and estuaries contaminated with trace metals. Cadmium is of particular concern because it is concentrated in the digestive glands of blue crabs and can be passed on to consumer organisms. Tissue concentrations and partitioning of trace metals from crabs exposed in the laboratory to 10 ppb dissolved cadmium for 40 days were compared with blue crabs collected from two locations on the Hudson River, NY, Foundry Cove and Haverstraw Bay, Foundry Cove and Haverstraw Bay, both of which have elevated trace metal levels relative to estuarine areas near Beaufort, NC. Crab digestive glands, gills and muscle were removed and analyzed for total cadmium, copper, zinc and nickel concentrations using acid digestion and atomic absorption spectrophotometry, and metal-binding (metallothionein-like) proteins were determined by gel-filtration chromatography. In crabs exposed to cadmium in the laboratory, the cytosolic partitioning was similar to previous investigations at our laboratory where higher levels of cadmium (100 ppb) and shorter exposure times (14 days) were used. The similarity in cadmium partitioning from these two separate experiments indicates dose independence. In crabs from polluted environments the digestive glands contained the highest concentrations of trace metals. Chromatograms of the cytosol from the digestive glands and gills from both field and laboratory exposed crabs showed similar distributions of cadmium, copper and zinc. The gills of both field and laboratory-exposed crabs had metal-binding proteins that contained mostly cadmium, and the digestive glands had metallothionein-like proteins that contained cadmium, copper and zinc. Estimated molecular weights for these proteins were similar to the metallothioneins found in other crustaceans and mammals.