Preliminary studies of food habits of juvenile fish,China Poot Marsh and Potter Marsh,Alaska, 1978

During the year 1978, juvenile salmonids were collected from coastal streams running through China Poot Marsh and the stomach contents analyzed. Stomach contents of threespine stickleback (Gasterosteus aculeatus) and staghorn sculpin (Leptocottus armatus) from China Poot and of threespine stickleback from Potter Marsh were also analyzed; these two species were generally caught in tidal pools on the marshes. The juvenile coho salmon (Oncorhynchus kisutch) had the most varied diet; 37 different prey items were identified in the stomachs. By comparison, 25, 26, and 33 prey taxa were identified in the stomach contents of Dolly Varden char (Salvelinus malma), threespine stickleback, and staghorn sculpin, respectively. Amphipods were the dominant prey of all fish collected from China Poot Marsh; chironomidae larvae were the most common item in the stomach contents of threespine stickleback from Potter Marsh. The diets of all species changed over the course of the study period; the change was most dramatic for juvenile salmonids and sculpins.     

Bindungsverhalten ausgewählter Elemente in Sedimenten eines sauren Tagebaurestsees/FNR>

Binding Character of Selected Elements in Acidic Mining Lake Sediments To investigate the vertical element distribution in an acidic mining lake the concentrations of selected elements were measured by ICP‐MS and ICP‐OES. By knowing the metal concentrations in different depths it is possible to divide these metals into three groups. While the concentrations of iron, manganese, and zinc decline with decreasing depth, those of aluminium, copper, and nickel rise up. For lead and cobalt no distinct tendency could be determined. The limit value for all measured elements was not exceeded in any sampling location. The binding character of the metals is, besides the seasonal conditions of the lake (circulation in spring and stagnation in summer), influenced by the sediment depth. The addition of Carbokalk® for lake water neutralization had no significant effect on binding character of the analyzed metals. The application of a sequential extraction procedure enabled a classification of the available metal binding forms. All analyzed metals occurred mainly in compounds which are difficult to mobilize and for environment only slightly available.     

Chemistry, small-scale inhomogeneity, and formation of moldavites as condensates from sands vaporized by the Ries impact

The formation of the Ries impact and the moldavites have identical radiogenic ages of 14.3 Ma. According to this conformity in age moldavites are generally regarded as products of the Ries impact. This paper, which is divided into two sections, deals with two aspects of the moldavite-forming process: the formation of moldavite bodies by accretion of small precursors, and the physical and chemical conditions under which these primary units originated from sands which covered the Ries impact site.First, the chemical inhomogeneity of moldavite glasses is investigated in sections of 11 moldavites, using back scattered electron (BSE) images and electron microprobe analyses on 0.4-2.7 mm long traverses. Schlieren and lechatelierite particles are interpreted as relics of small, chemically different precursors, which accumulated to larger moldavite bodies at temperatures too low to be efficient for mixing. The patterns of schlieren and lechatelierite inclusions represent two successive rheological regimes: Small agglomerating primary melt units were extended into thin lamellae and threads under conditions of laminar flow. As evidenced by folded textures, these fluidal arrays were later plastically deformed under conditions of compressional stress.To elucidate the production of the primary melt units by the Ries impact, in the second section the geologic situation of the Ries area is considered with regard to possible source materials. The site of the Ries impact, situated at the northern border of the pre-Alpine Molasse basin, was covered at the time of the impact by fluviatile sediments of the lower sequence of the Obere Süßwasser-Molasse (OSM) Formation of Middle Miocene age, consisting of sands, marly sands and clays. Chemical analyses for major and trace elements of 38 moldavites from Bohemia and Moravia, and of 28 samples of the OSM Formation, collected from outcrops and drill holes, immediately south of the Ries crater and south of the Danube, show chemical conformity of moldavites and sand samples with regard to the major parameters SiO_2,Al₂O₃+ FeO, and MgO + CaO, indicating that these sands were the essential source material of moldavites. But, differences in contents of individual major and trace elements between moldavites and sands show that the formation of moldavites from sands involved a specific chemical differentiation which can not be explained by selective vaporization or melting, nor by selective condensation from melt or vapeur. Because large ions were enriched and small ones depleted in moldavites, the ionic radius has controlled the distribution of elements between sands and moldavites. We assume that moldavites originated from a plasma that the impact produced at its encounter with the surficial sand formation at the impact site, and that the primary units formed as early condensates in which large ions were preferentially trapped.     

Arch Filament Systems Associated with X-Ray Loops

Using multi-wavelength observations obtained with the Tenerife telescopes (VTT and GCT) and with the Yohkoh satellite, we observed new emerging flux with an associated arch filament system (AFS) in the chromosphere and bright X-ray loops in the corona. We observed the change of connectivity of the X-ray loop footpoints which may be at the origin of the occurrence of a subflare. Densities, gas and magnetic pressures of cold AFS and hot loops were derived and discussed. The extrapolation of the photospheric magnetic field observed with the GCT in a linear force-free field assumption (constant ) shows that this region, in spite of having roughly a global potential configuration, consists of two systems of arch filaments. We found these two systems best fitted with two sheared magnetic topologies of opposite values of ± 0.1 Mm^-1     

Recursive evaluation of interaction forces of unbounded soil in the time domain from dynamic-stiffness coefficients in the frequency domain

The interaction forces of the linear unbounded soil in a non-linear soil-structure-interaction analysis can be calculated recursively, starting directly from the dynamic-stiffness coefficients in the frequency domain. Two possibilities of choosing a recursive equation are discussed.

• (i) The recursive equation in the frequency domain. For each frequency, the interaction force at a specific time station is expressed as a function of the corresponding interaction force at the previous time station and of the displacements at the current time station and at the two most recent past time stations. This recursive evaluation of the convolution integral. which can be derived using the z-transformation, is rigorous. By using interpolation in the frequency domain, an approximate procedure results, which leads to a significant reduction in computational effort.
• (ii) The recursive equation in the time domain. By approximating the dynamic-stiffness coefficients as the ratios of two polynomials in frequency using a curve-fitting technique based on the least-squares method and by applying the partial-fraction expansion and using the z-transformation, the recursive coefficients can be determined explicitly. Alternatively, the ratio of two polynomials can also be transformed to an ordinary differential equation together with the initial conditions.

The recursive equations using interpolation in the frequency domain and based on a ratio of two polynomials lead to a reduction in the computational effort of one and up to three orders of magnitude, respectively.     

Time-domain boundary element method in viscoelasticity with application to a spherical cavity

The weighted-residual technique, the indirect boundary element method, the truncated indirect boundary element method and the direct boundary element method can be used to analyse nonlinear soil-structure interaction in the time domain. They are illustrated and compared by using the one-dimensional dynamic problem of the spherical cavity in an infinite space. For realistic time steps, all formulations lead to accurate results, but the weighted-residual technique and the truncated indirect boundary element method are much more efficient than the direct boundary element method in the time domain. Hysteretic damping leads to noncausal behaviour, which can, however, be neglected from a practical point of view.     

Non-linear soil–structure interaction analysis based on the boundary-element method in time domain with application to embedded foundation

The various boundary-element methods, well established in the frequency domain, are developed in the time domain for a foundation embedded in a layered halfspace. They are the weighted-residual technique and the indirect boundary-element method, based on a weighted-residual equation, and the direct boundary-element method based on a reciprocity equation, both equations involving time and space. In the indirect approach, formulating the weighted-residual equation over the last time step only results in the truncated indirect boundary-element formulation which requires a reduced computational effort. In all cases, convolution integrals occur. The truncated indirect boundary-element method leads to a highly reliable algorithm, as is verified when a linear analysis in the time domain is compared to the corresponding one in the frequency domain. This boundary-element formulation, which is non-local in space and time, represents a rigorous generally applicable method taking into account a layered halfspace in a non-linear soil-structure interaction analysis. As an example, the non-linear soil-structure interaction analysis of a structure embedded in a halfspace with partial uplift of the basemat and separation of the side wall is investigated.     

On causality in dynamic response analysis by time-dependent boundary element methods

The ramifications of a particular type of causality constraint, namely so-called shadow-zones, are explored in the context of time-dependent boundary element methods. In particular, wave propagation problems in 2-D elastic soil media with a non-convex shape are analysed.