ALBERT

Beschreibung: Many of the difficulties of staining plastic embedded tissues for light and electron microscopy derive from physical exclusion of hydrophilic staining reagents by hydrophobic embedding media. Structures which stain most intensely with hydrophilic reagents usually contain less hydrophobic plastic than do non-staining structures. Such incomplete infiltration is apparently caused by exclusion of viscous, hydrophobic monomers by physically dense and/or well hydrated tissue elements. In keeping with this, generalized staining of tissues embedded in hydrophobic media does occur when hydrophobic reagents are used. Staining of plastic-free structures with single hydrophilic reagents or with sequences of such reagents, is, however, largely rate-controlled. The surprising similarity of hydrophilic and hydrophobic plastic embedding media is discussed. Limits of this simple model are explored, with a consideration of the roles of fixative and of monomer-tissue reactions

Beschreibung: The boundaries of the mud area of the inner German Bight have been mapped w1th a subbottom echo sounder. The echo profiles reveal a uniform sediment body which is chararterized by the occurrence of mud (clayey silt) in separate layers. The western part of the area is dominated by mud showing fine-sand intercalations, the well-known storm sand layers. The eastern part consists of fine-sand /mud alternate bedding. Primary stratification may be altered by bioturbation, particularly in the western part. However, the echographic uniformity of the mud area is almost independent of the regional variations of facies. At the southern, western, and northern boundaries the mud-area sediment body wedges out above the adjacent, more sandy sedimems. The eastern boundary is a system of sand tongues and channels with fine-sand/mud alternate bedding. Here, interfingering of sand and sand/mud facies may be a typical pattern in the depositional sequence due to occasional shifting of both sand tongues and channels. Based on hydrographic data from the German Bight the origin of the mud was ascribed mainly to the suspension load of the river Elbe. The suspended matter is transported towards north by the "Elbe water mass" which is a particular water body with lower salinity, as compared with surrounding North Sea waters. Main part of the suspension load is, however, deposited in the inner German Bight. The limits of mud deposition are given by the western and eastern boundaries of the "Elbe water" body as well as by shallower sand ridges surrounding the mud area in the south, east, and west.

Beschreibung: The oligochaete fauna (mainly tubificids and naidids) of a freshwater tidal flat, the "Fiihrmannssand", in the freshwater part of the Elbe Estuary was investigated. The distribution patterns in relation to sediment structure and food availability are discussed. The population dynamics of tubificids and naidids differ significantly. The standing stock of tubificids remains fairly constant throughout the year. Breeding activities take place during the whole year. These data are discussed and compared with those of other surveys where seasonal reproduction activities of tubificids were reported. The naidid population fluctuates considerably in size throughout the year. Abundance maxima are mainly found in spring (Nais spp., Paranais frio). Two annual maxima, in early spring and autumn, are exhibited by Amphichaeta leydigii. Some data are presented on oligochaete endoparasites, especially on Caryophyllaeus laticeps (Cestoda).

Beschreibung: Die "Siegener" und die "Mayener Hauptüberschiebung", die in der Umgebung des Laacher Sees von mächtigem Bims überdeckt sind, gehören zu einer steil einfallenden, ca. 120 km langen Aufschiebung, die als "Siegener Hauptaufschiebung" bezeichnet wird. An ihr sind hier Hunsrückschiefer s.l. auf Serien der sandigen Siegener Normalfazies aufgeschoben worden. Ihr Verlauf wurde rekonstruiert anhand einer gezielten Analyse von Einzelaufschlüssen des paläozoischen Sockels und von Xenolithen der jungquartären Laacher Bimstuffe. Diese enthalten Auswürflinge von Gesteinen der sandigen Siegener Normalfazies einerseits und der Hunsrückschiefer andererseits. Daraus ergibt sich, daß die Bimstuffe aus mehreren Eruptionszentren nördlich und südlich der Hauptaufschiebung und nicht nur aus dem Laacher Vulkan gefördert wurden.

Beschreibung: Three arrays of ocean bottom seismographs have been deployed to study the seismicity at the northern end of the Juan de Fuca ridge system off western Canada. Nearly 100 events were located with estimated accuracies generally better than ±10 km, all lying on or near the en echalon ridge-transform fault plate boundaries as defined in this area by the magnetic anomalies, the seafloor morphology and by other geophysical data. The depths of 12 events were determined to lie between 2 and 6 km below the top of the crust. The seismograms exhibit clear P and S wave arrivals along with phases that involve P to S and sometimes S to P conversion probably at the base of the sediments beneath the instruments. The event magnitudes have been estimated from signal duration using four calibration events that were well recorded by a land station. The magnitude estimates permit the determination of rough magnitude-frequency of occurrence relations over the magnitude range of 1 to 3 that are in surprisingly good agreement with the recurrence relations for the area at larger magnitudes from 75 years of land station data. The mean P wave velocity in the uppermost mantle from the earthquake data recorded by the sea floor arrays is 7.6 km s-1 and the mean Vp/Vs ratio is 1.71 or a Poisson's ratio of 0.24.