Reduction of hydroelastic responses of a very-long floating structure by a floating oscillating-water-column breakwater system

The hydroelastic responses of a very-long floating structure (VLFS) placed behind a reverse T-shape freely floating breakwater with a built-in oscillating water column (OWC) chamber are analyzed in two dimensions. The Bernoulli–Euler beam equation is coupled with the equations of rigid and elastic motions of the breakwater and the VLFS. The interaction of waves between the floating rigid breakwater and the elastic VLFS is formulated in a consistent manner. It has been shown numerically that the structural deflections of the VLFS can be reduced significantly by a suitably designed reverse T-shape floating breakwater.     

Numerical study of the motions and drift force of a floating OWC device

The motion and the drift force of a floating OWC (oscillating water column) wave energy device in regular waves are studied taking account of the oscillating surface-pressure due to the pressure drop across the duct of the air chamber. The potential problem inside the chamber is formulated by making use of the Green integral equation associated with the Rankine-type Green function while the outer problem with the Kelvin-type Green function. The added mass, wave damping and excitation coefficients as well as the motion and drift force of the OWC device are calculated for various values of parameter related to the pressure drop.     

Numerical simulation of undersea cable dynamics

A fully three-dimensional code has been written to compute the motion of a towed cable. The code is based on a robust and stable finite difference approximation to the differential equations derived from basic dynamics. A 3500-ft (1.07 km) cable pulled at 18.5 knots (34.3 km hr⁻¹) through a circular turn of 700 yd (0.64 km) radius has been computed in about half of the real time of the maneuver. The computed displacements are close to the measured ones; the changes in depth are within 2%.     

Lagrangian diffusion equation and its application to oceanic dispersion

The Lagrangian diffusion equation appropriate for the dispersion of current followers (e. g., floats, drogues, drifters) is proposed. The analytical solution to the equation is obtained for a uniform deformation field, characterized by Lagrangian deformations and anisotropic eddy diffusivities both varying with time. Expressions are derived for the patch area and its elongation and rotation. For small values of elapsed time after the initial release the patch area can be accounted for by the exponential of the cumulative value of the horizontal divergence; the relative rate of change of the patch area can be accounted for by the horizontal divergence.     

Lethal and sublethal effects of short term acute doses of Kuwait Crude Oil and a dispersant Corexit 9527 on bay scallops, Argopecten irradians (Lamarck) and two predators at different temperatures

Investigations of short term acute exposure of bay scallops, Argopecten irradians and two scallop predators, the oyster drill Urosalpinx cinerea and the common starfish Asterias forbesi, to oil, dispersant, and oil-dispersant mixtures (Kuwait Crude Oil and Corexit 9527) suggested that predator and prey have different lethal susceptibilities. Scallops were most sensitive to dispersant and dispersant mixed with oil, starfish were only sensitive to dispersant while the oyster drill seemed unaffected even though all were exposed to dilutions of identically prepared stock solutions. Scallops were least susceptible during winter months and most susceptible at summer temperatures. Treatment had less effect on predators than on scallops at summer temperatures. Sublethal concentrations of dispersant and oil-dispersant mixtures diminished the behavioural ability of scallops to recognise drills and starfish. The degree of effect increased with temperature. Predator detection of prey at the same concentrations was more complex. The feeding response or posturing reflex of starfish was significantly slowed by all treatments. In contrast, drills were unaffected in their recognition of scallop effluent in a choice chamber after treatment.     

The estimation of acid dissociation constants in seawater media from potentionmetric titrations with strong base. I. The ionic product of water — Kw

The various assumptions implicit in the calculation of acid dissociation constants (based on ionic medium standard states) from potentiometric titrations using a cell with liquid junction (i.e. a pH measuring cell) have been examined. It was concluded that results can be obtained having an accuracy commensurate with the experimental precision. It has been shown that although the precise composition of the medium is a function of the hydrogen ion concentration (because of the protolytic nature of some of the ions in the media, e.g., sulphate and fluoride), the effect of such variations in the medium composition can be compensated for when defining the activity of hydrogen ion on an ionic medium standard state by defining the concentration of hydrogen ion as:

where β_HSO4 and β_HF are the relevant association constants and S_T and F_T are the total concentrations of sulphate and fluoride, respectively.This approach was used to obtain values for the ionic product of water (K_W) in artificial seawater media at various temperatures and ionic strengths. These were fitted to give the equation (molal concentration units):

$\text{pK}{}_{\mathrm{w}}\text{=}\text{3441.0}\text{T}\text{+2.256-0.7091}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(}\text{rms deviation 0.01}\text{)}$

where I is the formal ionic strength of the artificial seawater medium and T is the absolute temperature. The values obtained are in reasonable agreement with those found by previous workers.     

Metabolism of perylene by monooxygenases of the skin and liver of Ambystoma tigrinum

The prevalence of dermal neoplasia among neotenic tiger salamanders (Ambystoma tigrinum) collected from the Reese Air Force Base sewage lagoon far exceeded that among salamanders from nearby uncontaminated lagoons. Perylene was the predominant pglycyclic aromatic hydrocarbon contaminant in this lagoon. Perylene was shown to be a substrate for monooxygenases in skin and liver homogenates and formed DNA-binding metabolites. Perylene exposure appeared to augment subsequent perylene metabolism by dermal enzymes but it was not a strong inducer of hepatic monooxygenases. Aroclor 1254 induced benzo(a)pyrene and perylene metabolism by both skin and liver enzymes. However, perylene apparently was not activated by salamander enzymes, as suggested by its lack of in vitro mutagenicity and failure to induce tumors.     

Incorporation,distribution and fate of saturated petroleum hydrocarbons in sediments from a controlled marine ecosystem

A simulation of a chronic input of petroleum into an estuarine environment was investigated using the facilities at the Marine Ecosystems Research Laboratory at the University of Rhode Island. An oil-water dispersion of No. 2 fuel oil was added to the system (twice weekly for 24 weeks) and the saturated hydrocarbons from this oil were measured in suspended material and sediments. After the initial chronic oil addition, trace amounts of hydrocarbons were detected in the sediments within two weeks, but substantial accumulation was not detected for approximately 135 days. The oil appeared to enter the sediment via the suspended material, with most of the saturated hydrocarbons associated with smaller size sediment particles (< 45 μm to > 0·3 μm). With time, the fuel oil saturated hydrocarbons in the sediments were mixed to a depth of 3 to 4 cm. Although only 12% of the total saturated hydrocarbons added to the system were found in the sediments, these hydrocarbons appear to be relatively stable and were still detectable in these sediments for at least six months after the last oil addition.     

Deep tow studies of the Tamayo transform fault

The Tamayo transform fault occurs at the north end of the East Pacific Rise where it enters the Gulf of California. The two deep-tow surveys reported here show that the transform fault zone changes significantly as a function of distance from the spreading center intersections. At site 1, near the intersection, one side of the fault is young and the fault zone is narrow and well-defined. Strike slip occurs in a zone approximately 1-km wide suggesting a correspondingly narrow zone of decoupling between the Pacific and North American plates. On the young side of the strike-slip zone, normal faults occur along shear zones which are 45°–50° oblique to the transform strike. They occur parallel to the short axis of the strain ellipse for transform fault strain here, i.e., perpendicular to the least compressive stress. The transform walls are formed by normal faulting as has been pointed out in previous detailed surveys. Here, however, the age contrast of 2.5 m.y. across the transform valley is apparent in the morphology of the normal fault scarps. While the scarps are steep and well-defined on the young side, the scarps on the older side have gradual 10°–30° slopes and appear to be primarily talus ramps. Apparently, the scarps have been tectonically eroded by continued strike slip activity after the initial stages of normal faulting. Thus, transform valleys should be quite asymmetric in cross-section where there is a significant age contrast and one side is less than approximately 0.5 m.y. old. Also, along older sections of the transform valley walls, normal faulting may not be at all obvious due to degradation of the scarps by tectonic erosion. This phenomenon makes the likelihood of transform faults providing windows into the oceanic crust most unlikely except in special cases.The picture of transform deformation is more complex at site 2 in the central portion of the fault where both sides of the fault are greater than 1 m.y. old. Here the transform valley is wider (25–30 km as opposed to 2–5 km). There is no clear simple zone of strike slip tectonics. In fact, the only clear evidence for deformation is the intrusion of magmatic or serpentinite diapirs through the sediments of the transform valley floor. The diapirs have deformed the turbidite layers flooring the valley and in one carefully studied case the turbidite sequence has been uplifted, perched atop the diapir. The pattern of deformation on this outcropping diapir shows radial and concentric fractures which can be modeled by a vertical intrusion circular in plan view. Magnetic studies limit the possible composition to basalt or serpentinite. A 60-km-long median ridge is also likely to be the product of intrusion along the transform fault. The survey at site 2 pointed out the importance of vertical tectonics in the transform valley floor and in particular the importance of diapiric intrusions of either basaltic or serpentinite composition.Based on initial boundary conditions and present tectonic elements in the Tamayo fault zone, a possible history of the mouth of the Gulf of California is outlined. The median ridge was emplaced starting approximately 0.8 m.y. ago by regional extension across the transform fault, the result of leaky transform faulting. The diapirs occur along a possible relay zone of extension midway along the fault which began approximately 0.15 m.y. ago. The extension in this case is parallel to the trend of the transform fault, is still occurring at present, and may evolve into a true spreading center.Contribution of the Scripps Institution of Oceanography, new series.