Core-log-seismic integration as a framework for determining the basin-wide significance of regional reflectors in the eastern equatorial Pacific

ODP Leg 138 in the eastern equatorial Pacific (EEP) provided a unique opportunity to understand the paleoceanographic significance of seismic reflectors in this climatically sensitive region. Carefully offset multiple cores were spliced into a complete stratigraphic section for the upper 250 m at each site and accurate, astronomically tuned time scales were generated from these composites. Well log data provided a means to correct composite depths to true depths as well as density and velocity data for the generation of synthetic seismograms. These synthetic seismograms were used to determine the paleoceanographic significance of regionally traceable reflectors by linking variations in the core record to the seismic record. The EEP reflectors are due to changes in carbonate content, primarily due to variations in surface productivity, as indicated by the presence of mats of the upwelling diatom Thalassiothrix longissima. The EEP composite GRAPE records were successfully used as a tuning target for GRAPE records in the central equatorial Pacific (CEP), as a means to detelxnine the basin-wide extent of EEP reflectors, and as a guide to the further interpretation of the CEP seismic record. It was found that EEP reflectors R3-t, R5, R6, R8-b, and Site 844 reflectors R 10, R 12-b and R 13, correspond to reflectors i n the CEP. However, some of the CEP reflectors, which were postulated to be due to periods of enhanced dissolution, also con\u27espond to diatom mats, and hence the origin of these reflectors must be reconsidered

Proposal for the establishment of a maritime training centre (MTC) for the training of ratings in Sierra Leone

This paper is specifically directed towards the establishment of a Maritime Training Centre in Sierra Leone for the training of ratings and port marine and engineering personnel in accordance with the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers, 1978. It is also anticipated that spare capacity and future expansion would facilitate training of oil terminal employees, operators of ferries, coastal and fishing vessels personnel in the offshore industry and other personnel in the marine related industry. The proposed establishment of a Maritime Training Centre is not one of prestige, but of economic and training necessity. While regional maritime academies are laudable, they are basically meant for officers and not ratings. The training of engine and deck ratings should be given great attention. It is my veiw that it will be futile to concentrate solely on the training and upgrading of officers alone with little attention to the training of ratings. Ratings play an equally important role as the officers in the efficient and safe operation of ships. Futhermore the cost of training ratings abroad with the problem of scarce foreign exchange is not attractive even when the cost of training is met under United Nations Development Programme (U.N.D.P.) country programme funds. Governments of developing countries don\u27t think the cost involved is justified when there are other areas of national development requiring urgent attention and scarce foreign exchange expenditure e.g food, medicine, healthcare, general education, education in medicine and dentistry etc. This however does not exempt the governments from it\u27s obligations as a coastal state and a member of the International Maritime Organisation (I.M.O.) from maritime education and training, nor to abandon the mass of Sierra Leonean seamen who by virtue of new regulations have found it impossible to maintain their jobs on foreigngoing merchant ships. The entire maritime industry is going through a new technological era. This fact has to be taken seriously, so much so by developing countries. Appropiate training is the only key left if our seafarers are to compete and secure jobs and catch up on advancing technology

Seismic Stratigraphy of the Eastern Equatorial Pacific Ocean: Paleoceanographic Implications

The collection of Leg 138 well-log and shipboard physical-property data, in conjunction with high-resolution seismic profiles, provides an opportunity to understand the paleoceanographic significance of seismic reflectors and to gain insight into the paleoceanographic evolution of the eastern equatorial Pacific Ocean. A series of eight reflectors or reflector packages were traced between two transects connecting five Leg 138 sites. By generating synthetic seismograms at each of these sites and comparing these to the field records, the origin of these seismic reflectors was determined in terms of physical-property variations and other core measurements. In particular, these reflectors were usually associated with sharp variations in density, which in turn, are related to variations in carbonate content. Intervals with moderate or poor nannofossil preservation indices were generally restricted to intervals below the reflectors traced in this study, suggesting that dissolution played little role in producing these reflectors. However, intervals with T. longissima mats were associated with many of the reflectors (R3-b, R4, R5-t, R5-b, R6) at the three sites (847, 849, and 850) where this diatom was encountered. This suggests that the reflectors found in this study are related to productivity events, although these events manifested themselves in a different way at the sites in which T. longissima mats were not observed. Interpreted seismic stratigraphic sections were compiled from the reflector horizon data for the two transects. Along the western transect, the section between reflectors R3 and R8 thins abruptly north of l°40\u27 to l°50\u27N, suggesting that this marks the northern limit of high equatorial productivity at that time (3.9-9.5 Ma), because the seafloor is reasonably constant in depth along this transect. Unfortunately, statements about sharp productivity gradients cannot be made for the eastern transect where sediment thinning corresponds to a deepening of the seafloor and thus may be related to variations in dissolution. Finally, six reflectors were found to be associated with major paleoceanographic events; three of these reflectors correspond to those found by Mayer et al. (1985,1986) in the central equatorial Pacific Ocean, suggesting that these correspond to Pacific-wide Oceanographic events. One of these reflectors (R8-b) is caused by a pervasive dissolution event as is its central equatorial counterpart. The others (R3-b and R5-t), however, appear to be the result of productivity events in the eastern equatorial Pacific that are synchronous with dissolution events in the central equatorial Pacific. We suggest that while localized high productivity creates low carbonate intervals (and thus reflectors) in the eastern equatorial Pacific, steep gradients in the CCD result in enhanced dissolution and low carbonate intervals (and thus reflectors) in the deeper central equatorial Pacifi

Reliability Assessment Of Conceptual Launch Vehicles

Planning is underway for new NASA missions to the moon and to MARS. These missions carry a great deal of risk, as the Challenger and Columbia accidents demonstrate. In order to minimize the risks to the crew and the mission, risk reduction must be done at every stage, not only in quality manufacturing, but also in design. It is necessary, therefore, to be able to compare the risks posed in different launch vehicle designs. Further, these designs have not yet been implemented, so it is necessary to compare these risks without being able to test the vehicles themselves. This paper will discuss some of the issues involved in this type of comparison. It will start with a general discussion of reliability estimation. It will continue with a short look at some software designed to make this estimation easier and faster. It will conclude with a few recommendations for future tools

Downhole Logging as a Paeoceanographic Tool on Ocean Drilling Program Leg 138: Interface Between High-Resolution Stratigraphy and Regional Syntheses

On Ocean Drilling Program (ODP) Leg 138, standard shipboard procedures were modified to allow for the real-time monitoring of several laboratory core-scanning systems that provide centimeter-scale measurements of saturated bulk density, magnetic susceptibility and digital color reflectance. These continuous, high-resolution data sets were used to ensure the proper offset of multiple holes and to splice together complete sedimentary sections. Typically, the spliced, continuous sediment sections were found to be about 10% longer than the section drilled, as measured by the length of the drill string. While the source of this elongation is not yet fully understood, it must be compensated for in order to property determine sediment fluxes and mass accumulation rates. Downhole logging, in conjunction with inverse correlation techniques provided a means to determine where the distortion occurred and to correct back to true in situ depths. Downhole logging also provides a means, through the generation of synthetic seismograms, of precisely relating the paleoceanographic events found in the core record to the high-resolution seismic record. Once correlated to the seismic record, the spatial and temporal extent of paleoceanographic events can be traced well beyond the borehole. Most seismic events in the equatorial Pacific are related to rapid changes in carbonate content that, in turn, are related to both productivity events (often expressed as monospecific laminated diatom oozes) and times of enhanced dissolution. While many of these events may have oceanwide extent, others, like the absence of carbonate in the late-Miocene to Recent in the Guatemala Basin have been shown to be regional and confined to only the deeper portions of the Guatemala Basin. As we identify and trace specific paleoceanographic events in the seismic record, we can begin to explore the response of the ocean through gradients of latitude, productivity, and depth

Downhole logging as a paeoceanographic tool on ocean drilling program leg 138: Interface between high-resolution stratigraphy and regional syntheses

On Ocean Drilling Program (ODP) Leg 138, standard shipboard procedures were modified to allow for the real-time monitoring of several laboratory core-scanning systems that provide centimeter-scale measurements of saturated bulk density, magnetic susceptibility and digital color reflectance. These continuous, high-resolution data sets were used to ensure the proper offset of multiple holes and to splice together complete sedimentary sections. Typically, the spliced, continuousediment sections were found to be about 10% longer than the section drilled, as measured by the length of the drill string. While the source of this elongation is not yet fully understood, it must be compensated for in order to property determine sediment fluxes and mass accumulation rates. Downhole logging, in conjunction with inverse correlation techniques provided a means to determine where the distortion occurred and to correct back to true in sire depths. Downhole logging also provides a means, through the generation of synthetic seismograms, of precisely relating the paleoceanographic events found in the core record to the high-resolution seismic record. Once correlated to the seismic record, the spatial and temporal extent of paleoceanographic events can be traced well beyond the borehole. Most seismic events in the equatorial Pacific are related to rapid changes in carbonate contenthat, in turn, are related to both productivity events (often expressed as monospecific laminated diatom oozes) and times of enhanced dissolution. While many of these events may have oceanwide extent, others, like the absence of carbonate in the late-Miocene to Recent in the Guatemala Basin have been shown to be regional and confined to only the deeper portions of the Guatemala Basin. As we identify and trace specific paleoceanographic events in the seismic record, we can begin to explore the response of the ocean through gradients of latitude, productivity, and depth

Prior exercise and antioxidant supplementation: effect on oxidative stress and muscle injury

<p>Abstract</p> <p>Background</p> <p>Both acute bouts of prior exercise (preconditioning) and antioxidant nutrients have been used in an attempt to attenuate muscle injury or oxidative stress in response to resistance exercise. However, most studies have focused on untrained participants rather than on athletes. The purpose of this work was to determine the independent and combined effects of antioxidant supplementation (vitamin C + mixed tocopherols/tocotrienols) and prior eccentric exercise in attenuating markers of skeletal muscle injury and oxidative stress in resistance trained men.</p> <p>Methods</p> <p>Thirty-six men were randomly assigned to: no prior exercise + placebo; no prior exercise + antioxidant; prior exercise + placebo; prior exercise + antioxidant. Markers of muscle/cell injury (muscle performance, muscle soreness, C-reactive protein, and creatine kinase activity), as well as oxidative stress (blood protein carbonyls and peroxides), were measured before and through 48 hours of exercise recovery.</p> <p>Results</p> <p>No group by time interactions were noted for any variable (P > 0.05). Time main effects were noted for creatine kinase activity, muscle soreness, maximal isometric force and peak velocity (P < 0.0001). Protein carbonyls and peroxides were relatively unaffected by exercise.</p> <p>Conclusion</p> <p>There appears to be no independent or combined effect of a prior bout of eccentric exercise or antioxidant supplementation as used here on markers of muscle injury in resistance trained men. Moreover, eccentric exercise as used in the present study results in minimal blood oxidative stress in resistance trained men. Hence, antioxidant supplementation for the purpose of minimizing blood oxidative stress in relation to eccentric exercise appears unnecessary in this population.</p

The effects of oxygen depletion due to upwelling groundwater on the post-hatch fitness of Atlantic salmon (Salmo salar)

The conditions experienced by incubating Atlantic salmon (Salmo salar) eggs are strongly influenced by hyporheic exchange. In some rivers, periods of intense groundwater upwelling can reduce oxygen levels in the incubation zone to 0% saturation. The present study investigated the effect of oxygen sags on the post-hatch fitness of Atlantic salmon. A laboratory experiment allowed fine-scale control of oxygen concentrations to replicate those induced by low oxygen groundwater in rivers. Extreme oxygen sags in the earlier stages of embryo development resulted in a developmental lag with alevin hatching later and at an underdeveloped state. At the latest stages of development, oxygen sags caused premature hatching of severely underdeveloped alevin. These findings combined with a review of the literature suggest post-hatch survival of embryos exposed to groundwater induced hypoxia will be lower due to predation and poor competitiveness