Influence of relative sea level changes on the construction of the Mississippi Fan

A conceptual sea-level-driven depositional model for individual fanlobes (channel-overbank systems) of the Mississippi Fan does not permit direct application of the sequence stratigraphic principles of Vail and colleagues. Deep Sea Drilling Project Leg 96 results suggest that, during initial relative lowering of sea level, the canyon and upper fan channel were formed; excavated fine-grained slope sediments may have formed a debris flow deposit base for the fanlobe. Continued lowering produced constructional channel-levee-overbank deposits. Rising relative sea level inhibited input of coarse clastics, and channel depressions filled with muds. A blanket of (hemi)pelagics represents relative high sea level stand.     

Coupled dynamics of tethered buoy systems

The three-dimensional coupled behavior during the interaction of buoys with their mooring systems is numerically analyzed. A time-domain model was developed to predict the response of a tethered buoy subject to hydrodynamic loadings. External loadings include hydrodynamic forces, tethers tensions, wind loadings and weight. System nonlinearities include large rotational and translational motions, and non-conservative fluid loadings. The mooring problem is formulated as a combined nonlinear initial-value and two-point-boundary-value problem which is directly integrated both in time and space. Buoy equations of motion are derived using small Eulerian angles. Coupling between rotational and translational degrees of freedom is included and coupling between the buoy and cable is effected by adopting the buoy equations of motion as boundary conditions at one end for the mooring problem. Numerical examples are provided to validate the formulation and solution technique; predicted responses of three types of buoy (sphere, spar, and disc) are compared with experimental results.     

In-vitro metabolism of benzo[a]pyrene and benzo[a]pyrene-7,8-dihydrodiol by liver and intestinal mucosa homogenates from the winter flounder (Pseudopleuronectes americanus)

Freshly prepared homogenates were used to assess the relative ability of winter flounder (Pseudopleuronectes americanus) liver and intestinal mucosal cells to metabolize the polycyclic aromatic hydrocarbon (PAH) benzo[a]pyrene (BaP) and its proximate carcinogenic metabolite, BaP-7,8-dihydrodiol (7,8-Diol). Data obtained from homogenates prepared from fish previously fed β-naphthoflavone (BNF) indicated that both tissues had similar abilities to metabolize either BaP or 7,8-Diol on a per gram of protein basis. Metabolite profiles produced indicate that water-soluble metabolite formation is favored at low doses. These findings support the hypothesis that the intestine plays an important role in first-pass metabolism of dietary carcinogens in the winter flounder.     

An experimental study of elastohydrodynamics of towed flexible cylinders aided by video image processing

Experimental studies of the elastohydrodynamics of towed flexible cylinders aided by video image processing are reported. A scale model of a prototype hydrophone array has been designed, fabricated, and tested in a speed range of 1.0 to 4.5 m/sec. The experiments were conducted in a 67-m long towing tank. The instrumented flexible member, 12.7 mm in diameter and 13.55 m long, was fixed at the one end and free at the other and was slightly lighter than neutrally bouyant. Three tail drogue configurations were employed. An integral part of the physical model tests was the development and utilization of a microcomputer based video image processing system for model configuration reconstitution. Instability characteristics, tail acceleration spectral densities, lift force due to curvature, and drag coefficients are quantified and discussed.     

Relationship between hydrocarbons and bacterial activity in mediterranean sediments: Part 2—hydrocarbon degrading activity of bacteria from sediments

In marine sediments from the Mediterranean coast polluted by oil spills (Etang de Berre) high bacterial activity is responsible for self-purification, samples collected from these areas showing a bacterial density several orders of magnitude higher than samples from non-polluted areas (Isle des Embiez). Between 60 and 80 % of the heterotrophic bacteria in the polluted areas are hydrocarbon-degrading, compared with 0.01 % in the non-polluted area.Several strains of hydrocarbon utilisers were isolated, a mixture of strains from each biotope was taken to represent a ‘biotope population’ and their activity towards different types of hydrocarbons (n-alkanes, iso-alkanes, cycloalkanes, aromatics) was determined.With ammonia as the nitrogen source the ‘biotope population’ from the polluted area degraded hydrocarbons much more readily than the ‘biotope population’ from the non-polluted area. With nitrate as the nitrogen source the degradation was much reduced, and, for some hydrocarbons, ceased in both ‘populations’.Individual hydrocarbons encouraged the growth of individual strains in the ‘biotope population’. In natural mixtures of hydrocarbons all strains grew well and degraded aliphatics. There was a good correlation between the respiratory activity of the ‘biotope population’ and the ability of the ‘population’ to utilise hydrocarbons for growth.     

Breaking of a tidal internal wave on a steep shelf as inferred from temperature measurements

The structure, evolution, and breaking of a tidal internal wave on a steep shelf are discussed on the basis of the data of temperature measurements. The bottom slope at the measurement site is close to the critical slope for a tidal wave. The tidal wave and other waves are inclined coastward. The tidal-wave amplitude increases monotonically with increasing horizon depth. The tidal wave is nonlinear in amplitude and turns over on the outer shelf. On the inner shelf, the internal wave is close in shape to rectangular and generates harmonics of its own. The harmonics make the tidal wave steeper and form solitary rises similar to bilateral bores. All these features ensure a more rapid sink for the internal-tide energy.     

The Structure of A Turbulent Jet in A Crossflow-Effect of Jet-Crossflow Velocity

A comprehensive numerical study on the three-dimensional structure of a turbulent jet in crossflow is performed. The jet-to-crossflow velocity ratio (R) varies in the range of 2 - 16; both vertical jets and inclined jets without excess streamwise momentum are considered. The numerical results of the Standard two-equation k-ε model show that the turbulent structure can be broadly categorised according to the jet-to-crossflow velocity ratio. For strong to moderate jet discharges, i.e. R> 4, the jet is characterized by a longitudinal transition through a bent-over phase during which the jet becomes almost parallel with the main freestream, to a sectional vortex-pair flow with double concentration maxima; the computed flow details and scalar mixing characteristics can be described by self-similar relations beyond a dimensionless distance of around 20-60. The similarity coefficients are only weakly dependent on R. The cross-section scalar field is kidney-shaped and bifurcated, vvith distinct double concentr