Long term prediction of non-linear vertical bending moments on a fast monohull

An assessment is made of the maximum wave induced bending moment expected to occur during the operational lifetime of a fast monohull, based on long term distribution calculations of the non-linear vertical bending moment at mid-ship. The ship is assumed to operate in the Northern North Sea, with an operational life of 25 years. A succession of short-term stationary ship responses represented by Rayleigh distributions of peaks results in the long-term distribution of the structural loads. Non-linear pseudo transfer functions are used in the procedure to calculate the variances of the short-term responses. The amplitudes of these transfer functions are calculated by a non-linear time domain seakeeping program. The results are compared with rules minimum required values and also with results from simpler calculation procedures such as adopting design sea states.     

Geology of the Continental Margin of Enderby and Mac. Robertson Lands, East Antarctica: Insights from a Regional Data Set

In 2001 and 2002, Australia acquired an integrated geophysical data set over the deep-water continental margin of East Antarctica from west of Enderby Land to offshore from Prydz Bay. The data include approximately 7700 km of high-quality, deep-seismic data with coincident gravity, magnetic and bathymetry data, and 37 non-reversed refraction stations using expendable sonobuoys. Integration of these data with similar quality data recorded by Japan in 1999 allows a new regional interpretation of this sector of the Antarctic margin. This part of the Antarctic continental margin formed during the breakup of the eastern margin of India and East Antarctica, which culminated with the onset of seafloor spreading in the Valanginian. The geology of the Antarctic margin and the adjacent oceanic crust can be divided into distinct east and west sectors by an interpreted crustal boundary at approximately 58° E. Across this boundary, the continent–ocean boundary (COB), defined as the inboard edge of unequivocal oceanic crust, steps outboard from west to east by about 100 km. Structure in the sector west of 58° E is largely controlled by the mixed rift-transform setting. The edge of the onshore Archaean–Proterozoic Napier Complex is downfaulted oceanwards near the shelf edge by at least 6 km and these rocks are interpreted to underlie a rift basin beneath the continental slope. The thickness of rift and pre-rift rocks cannot be accurately determined with the available data, but they appear to be relatively thin. The margin is overlain by a blanket of post-rift sedimentary rocks that are up to 6 km thick beneath the lower continental slope. The COB in this sector is interpreted from the seismic reflection data and potential field modelling to coincide with the base of a basement depression at 8.0–8.5 s two-way time, approximately 170 km oceanwards of the shelf-edge bounding fault system. Oceanic crust in this sector is highly variable in character, from rugged with a relief of more than 1 km over distances of 10–20 km, to rugose with low-amplitude relief set on a long-wavelength undulating basement. The crustal velocity profile appears unusual, with velocities of 7.6–7.95 km s⁻¹ being recorded at several stations at a depth that gives a thickness of crust of only 4 km. If these velocities are from mantle, then the thin crust may be due to the presence of fracture zones. Alternatively, the velocities may be coming from a lower crust that has been heavily altered by the intrusion of mantle rocks. The sector east of 58° E has formed in a normal rifted margin setting, with complexities in the east from the underlying structure of the N–S trending Palaeozoic Lambert Graben. The Napier Complex is downfaulted to depths of 8–10 km beneath the upper continental slope, and the margin rift basin is more than 300 km wide. As in the western sector, the rift-stage rocks are probably relatively thin. This part of the margin is blanketed by post-rift sediments that are up to about 8 km thick. The interpreted COB in the eastern sector is the most prominent boundary in deep water, and typically coincides with a prominent oceanwards step-up in the basement level of up to 1 km. As in the west, the interpretation of this boundary is supported by potential field modelling. The oceanic crust adjacent to the COB in this sector has a highly distinctive character, commonly with (1) a smooth upper surface underlain by short, seaward-dipping flows; (2) a transparent upper crustal layer; (3) a lower crust dominated by dipping high-amplitude reflections that probably reflect intruded or altered shears; (4) a strong reflection Moho, confirmed by seismic refraction modelling; and (5) prominent landward-dipping upper mantle reflections on several adjacent lines. A similar style of oceanic crust is also found in contemporaneous ocean basins that developed between Greater India and Australia–Antarctica west of Bruce Rise on the Antarctic margin, and along the Cuvier margin of northwest Australia.     

Input of atmospheric lead to marine sediments in a south-east Pacific coastal area (approximately 36 degrees S)

Atmospheric input of Pb to coastal sediments in the south-east Pacific (approximately 36 degrees S) was estimated using: (1) a salt marsh (non-local emission sources) as a natural collector of atmospheric fluxes and (2) Pb concentrations in rain and air samples, both considered to be representative of the atmospheric input in the study area. A radioisotopic geochronology technique ((210)Pb) was used to estimate the total Pb atmospheric supply to the sediments. The results show that atmospheric input to Concepción Bay accounts for 13-68% of Pb in near shore sediments, evaluated through salt marsh and rain, both showing comparable results. Consequently, there are other relevant Pb sources to explain the higher concentrations in this area. Sediments in the shelf are subject to important influence of upwelling waters, estimated by Salamanca [Sources and sinks of (210)Pb in Concepción Bay, Chile (1993) PhD thesis, Marine Science Research Center, State University of New York at Stony Brook, USA] using (210)Pb. The atmospheric input, however, is mainly responsible for the total Pb input, since the salt marsh (natural atmospheric collector) shows similar Pb(xs) inventories than the shelf, corresponding to a regional-scale Pb emissions.     

Evidence for methane and hydrogen sulfide venting imprinted on a Quaternary eolianite from southern Israel

Two different and physically separated chemosynthetic communities of bacteria are responsible for the formation of the Beeri native sulfur deposit hosted in a Late Quaternary sandstone on the southern coastal plain of Israel. The enriched concentrations are distributed over an area of about 1 km², within a zone 2–3 m thick at 1–13 m below surface. Two hundred fifty meters below the sulfur deposit, sulfur-reducing bacteria, thriving on methane generated in Neogene marls, reduced the Messinian gypsum to generate hydrogen sulfide, which subaqueously vented together with methane into the siliciclastic Quaternary sequence. Another, different chemosynthetic community ofBeggiatoa-like and unidentified bacteria oxidized the hydrogen sulfide into native sulfur and secondary gypsum, alunite, and iron sulfates. The coupled chemical and bacterial processes attributed to the formation of the sulfur deposit at Beeri are strikingly similar to the processes occurring today in the context of submarine hydrocarbon vents associated with the salt diapirs in the Gulf of Mexico.     

Nature and composition of shore-zone sediments between Jeddah and Yanbu, eastern Red Sea

The shore-zone sediments between Jeddah and Yanbu, west coast of Saudi Arabia, are composed mostly of skeletal carbonate sands. The nearshore sediments containing benthic foraminifera, algal fragments and molluscs are multimodal, the mean grain size varying between 0.76 and 2.35 ø. The beach sediments, except samples dominated by cerithid gastropods in some localities, are relatively finer than the nearshore sediments. Although the beaches to a great extent comprise sand-sized material, fine lime muds and coarse clastic gravels occur in certain areas. The dune sediments comprising mostly algal grains and ooids are very fine with 50 percent of the material in the 0.25–0.18 mm size grade. Except a general northward decrease in mean grain size, regional trends in the textural parameters of the sediments between Jeddah and Yanbu are not quite apparent. Lateral variations in the textural characteristics suggest a landward migration of the sediments in the shore zone under the influence of northerly and northwesterly winds. The carbon and oxygen (δ ¹³C + 4.80 to 4.84‰ PDB) (δ ¹³O − 0.04 to + 0.53‰ PDB) isotopic ratios of the lime muds occurring in certain shallow margins in the shore-zone, which are much higher than those of the green algae, indicate that the fine carbonates are at least in part inorganic in origin.

Like the shallow-water carbonates in tropical seas, aragonite and high Mg-calcite are the dominant carbonate minerals in the shore-zone sediments. There is a landward increase in aragonite contents caused by the landward migration of fine material from the nearshore. The dominant clay mineral in the nearshore sediments is kaolinite with subordinate swelling chlorite and little illite. Kaolinite is contributed by the coastal regions under the sub-tropical humid climate. Swelling chlorite is considered to have been formed in the nearshore by mechanical mixture of chlorite and montmorillonite derived from the metamorphic and igneous terrains of the Tertiary mountains bordering the coastal plain.     

Gravity field analysis of Sio Guyot: An isostatically compensated seamount in the Mid-Pacific Mountains

Positive gravity anomalies indicate two dense conduits or eruptive centers beneath the northern summit of Sio Guyot, western Mid-Pacific Mountains. The low amplitude of the positive anomalies and the gravity lows flanking the guyot can be explained by crust 2.5 times the normal Pacific Ocean crustal thickness extending to a depth of 22 ± 2 km. The excess mass of the seamount is 100% locally isostatically compensated by the mass deficit below; this compensation may result from flexural loading and voluminous sill injection near a former ridge-crest transform fault system trending roughly ENE and NNW.     

Effects of beta-naphthoflavone on hepatic biotransformation and glutathione biosynthesis in largemouth bass (Micropterus salmoides)

We are investigating the effects of in vivo exposure of prototypical enzyme inducing agents on hepatic biotransformation enzyme expression in largemouth bass (Micropterus salmoides), a predatory game fish found throughout the United States and Canada. The current study targeted those genes involved in biotransformation and oxidative stress that may be regulated by Ah-receptor-dependent pathways. Exposure of bass to beta-naphthoflavone (beta-NF, 66 mg/kg, i.p.) elicited a 7-9-fold increase in hepatic microsomal cytochrome P4501A-dependent ethoxyresorufin O-deethylase (EROD) activities, but did not affect cytosolic GST catalytic activities toward 1-chloro-2,4-dinitrobenzene (CDNB) or 5-androstene-3,17-dione (ADI). Glutathione S-transferase A (GST-A) mRNA expression exhibited a transient, but non-significant increase following exposure to beta-NF, and generally tracked the minimal changes observed in GST-CDNB activities. Expression of the mRNA encoding glutamate-cysteine ligase catalytic subunit (GCLC), the rate-limiting enzyme in glutathione (GSH) biosynthesis, was increased 1.7-fold by beta-NF. Changes in GCLC mRNA expression were paralleled by increases in intracellular GSH. In summary, largemouth bass hepatic CYP1A-dependent and GSH biosynthetic pathways, and to a lesser extent GST, are responsive to exposure to beta-NF.     

Model estimates for the mean gas exchange between the ocean and the atmosphere under the conditions of the present-day climate and its changes expected in the 21st century

Annual mean fluxes of CO₂ and oxygen across the sea surface are estimated with the use of numerical modeling for several regions located in the Gulf Stream and Kuroshio zones. The present-day climatic conditions and the climatic conditions expected in the middle and at the end of the 21st century are considered. Specific features of gas exchange under a strong wind that are associated with gas exchange by bubbles and with changes in the air-water difference of the gas concentrations were taken into account in the calculations. The estimates obtained differ substantially from the results based on the traditional approach, which disregards the above features. A considerable increase in the absorption of CO₂ by the ocean, which is mainly caused by the continuing increase in the CO₂ concentration in the air during its small changes in the ocean, is expected in the 21st century. At the same time, no trends are revealed in the annual mean fluxes of oxygen across the ocean surface. The conclusion is made that, in calculations of CO₂ absorption by the world ocean, it is necessary to take into account both specific features of gas transfer under a strong wind and an increase in the atmospheric concentration of CO₂.