Combined numerical model of currents, waves, and sediment transport in Lake Donuzlav

We present a numerical model of the dynamics of Lake Donuzlav, which enables one to perform simultaneous numerical analyses of the currents, sea level, waves, and sediment transport. The model is based on the hydrodynamic block and the spectral wave model. For typical storm situations, we study the specific features of the integral circulation of waters and the three-dimensional structure of currents, investigate the wind-induced wave fields, and evaluate the flows of sediments and deformations of the bottom. The presence of intense eddy structures is revealed in the field of currents caused by the bottom topography. A significant intensification of waves in the south part of the lake is established in the case of penetration of storm waves through the strait. It is shown that the account of waves leads to qualitative changes in the structure of circulation in the lake and to the formation of well-pronounced areas of wave-induced elevations and lowerings of the sea level. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 43–65, March–April, 2006.     

Effects of polynuclear aromatic hydrocarbons on lysosomal membranes in molluscs

Lysosomal sequestration of polynuclear aromatic hydrocarbons (PNAHs), a major class of environmental contaminant, is a well-established phenomenon;¹ considerably less is known about their pathological effects on lysosomes. Marine molluscs contain a number of lysosome-rich tissues and PNAHs are known to induce deleterious alterations in lysosomal structure and latency of lysosomal enzymes.² The latter are presumed to involve destabilisation of the lysosomal membrane, resulting in increased permeability and reduced enzyme latency. If lysosomal injury involves derangement of membrane-lipid structure due to the interaction of PNAHs then it would be expected that membrane damage would be closely linked to the structural characteristics of the intruding molecule. Our results show that the effects of the isomeric PNAHs phenanthrene and anthracene on digestive cell lysosomal stability were markedly different in the marine mussel (Mytilus edulis) over the same range of tissue concentrations. Lysosomal membrane stability was determined using a cytochemical test for enzyme latency.³     

An analysis of 3.5 kHz acoustic reflections and sediment physical properties

Near-bottom normal incidence acoustic reflection data and sediment physical property data are used to study the relationships between acoustic reflections and sediment physical properties. A pinger-hydrophone experiment was performed to obtain the necessary acoustic reflection data. In addition, a standard piston core was retrieved in the acoustic survey area for physical property analysis. The piston core was sampled and 13 properties were measured at 55 locations within the top 12 m of the core. Correlation studies amongst the sediment physical properties resulted in the following strong correlations: acoustic impedance ($\text{Z}$) and porosity ($\text{N}$), (0.96); water content ($\text{WC}$) and $\text{Z}$, (0.95); bulk density ($\text{BD}$) and $\text{Z}$, (0.99).The empirical orthonormal function (EOF) method was employed for acoustic signal analysis. This method assumes no a-priori models of the sediment or causality. The EOF method reduced the acoustic data to 8 functions that contained 97.6% of the sample variance. The EOFs were subsequently analysed by using cepstrum analysis which reveals time delay information and enhances detecting zones of reflectivity. The result of the sediment physical property and cepstrum analysis indicates that zones of reflectivity are essentially zones of relatively high acoustic impedance, low porosity, and low phi (high mean grain size).     

The statistics of second order wave forces

A starting point in the statistical analysis of the slow drift motions of moored offshore structures is the determination of the statistical distribution of the second order exciting forces. In the past^2,6 an exponential probability density function has been used, this being the limiting case as the incident seastate becomes infinitely narrow banded. In the present note the second order force distribution is found for a general seastate and a significant deviation from an exponential distribution is found for those seastates which are likely to occur in practice. The statistical theory is based on a heuristic approximation to the second order force, which is shown to be consistent with a frequently used frequency domain approximation which has been suggested by Newman.⁸ Although Roberts² has shown that for very lightly damped systems the response statistics are independent of those of the exciting force, the present results may have a significant effect on the response statistics for higher levels of damping.     

Self-noise measurements using a moored sonobuoy with a suspended hydrophone

Moored sonobuoys are used for refraction seismic measurements at sea, although the range of operation is limited by the self noise caused by the hydrophone suspension.In this paper the main causes of self noise are discussed and a useful deployment scheme of a moored sonobuoy with suspended hydrophone is described.Some design criteria, in particular an equation for calculation of the optimal length of the expandable rubber band-which is situated between the surface float and the damping-body-are discussed.Finally, it is shown from noise measurements during the F. S. Valdivia cruise in 1975, that self noise level in the band 2 Hz to 20 Hz is 180 mPa to 280 mPa at a fully developed windsea with a characteristic wave height of more than 4 meters and a waterstream velocity about 0.5 m s¹.During these measurements the hydrophone was attached to the cable without rubber band. It is concluded that at a normal seastate the self noise level can be reduced to the order of ocean floor noise.     

A Pull-Up Shallow Water Seismometer

An inexpensive Pull-Up Shallow Water Seismometer (PUSS) has been designed and built to conduct long range seismic refraction experiments in the North Sea and the continental shelf around Britain, with the particular goal of studying the crustal and lithospheric structure under the epeirogenic basin of the North Sea. Signals from a gimbal-mounted 3-component geophone and a hydrophone are frequency modulated and mixed with clock and flutter correction signals before being recorded on a standard speed cassette tape recorder, with one hour of recording time. A 100 hour programmable timer allows the interval between the time of reset of the clock and each shot window of optional 5 or 10 min duration, to be preselected. The PUSS is launched and recovered using a pull-up technique originally developed for current meters. The replay system is also described.In May 1976 sea trials of 5 PUSSes were conducted along a 200 km refraction line in the North Sea. The encouraging performance of the equipment resulted in the decision to build a further 10 units and to proceed with a 400 km refraction line planned for the summer of 1977.     

An experimental facility for testing loaded structures in a high hydrostatic pressure environment and an application to axially loaded columns

An experimental facility is described for the testing of structures under a combined axial load and hydrostatic pressure load. This facility was used to determine the effects of hydrostatic pressure (up to 6000 psi) on the load-carrying capacity of slender metal columns. There appeared to be no significant effect in this case.     

Response of data from numerical modelling of the Equatorial Atlantic circulation to fluctuations of turbulence coefficients

A numerical model for ocean thermohydrodynamics is considered whose difference scheme permits a number of linear and quadratic invariants to be retained. The model is used as the basis for adaptive computations in the Equatorial Atlantic ocean. Model equations were integrated using different values of the coefficients of diffusion and momentum turbulent exchange. It has been shown that variations of these coefficients strongly influence the intensity of jet streams and the structure of the thermocline.Translated by Vladimir A. Puchkin.