Effects of Irregular Wave Groups on Pile Forces

The wave forces on 1, 2 and 4 vertical circular piles under the action of several wave trains of the same wave parameters, such as Hs,Tp and Mo, but different wave group factor GF are measured in the laboratory. After comparing these forces, it may be concluded that the mean and significant wave forces are almost of no difference for the wave trains with different GF. When GF is larger, the one-tenth of the wave froce extreme is slightly increased and the maximum wave force is much larger than the ones with smaller GF, to which attention must be paid in engineering practice.     

A new concept of a hull form to improve wave response characteristics for marine construction barges

The object of the new hull form is to provide a single hull which possesses long natural periods of roll and heave and has substantially reduced motion response amplitudes in very high sea states. Model tests and preliminary estimates indicated that the new hull form can be designed for roll and heave motions nearly equivalent to those of much larger semisubmersible units.All existing conventional marine construction barges have rectangular cross section hull. The new hull form consists of a system of upper side tanks and lower side tanks added onto a rectangular cross section hull. The upper tanks and lower tanks form longitudinal troughs on the port and starboard sides. Structural grillage of any open type is to connect the upper and lower tanks at the side of the vessel. Figure 1 indicates a profile and a typical transverse section of the new hull form. The new hull comprises the concept of reduced water plane area which is turn results in low transverse metacentric height and low tons per in. immersion. The novel features of combining low GM_T and low TPI with extremely heavy damping and added mass of the entrained water characteristics result in very long natural periods of roll and heave and considerably small rolling and heaving amplitudes in high sea states. The open side shell plating on the side of the vessel functions to dissipate wave energy at the side of the vessel which would have otherwise been transmitted to the vessel and caused the vessel to respond. This paper presents the conceptual foundation and outline of the new hull form. Model test results are presented and implemented. Also presented is the design philosophy.     

藓羽藻(Bryopsis hypnoides)核酮糖-1，5-二磷酸羧化酶／加氧酶的分离与活性测定

采用硫酸铵分部沉淀与凝胶过滤的方法，进行藓羽藻Rubisco的分离研究。结果表明，分离的藓羽藻Rubisco经SDS-聚丙烯酰胺凝胶电泳检测呈两条清晰条带，分别为Rubisco大亚基与小亚基；与菠菜相比，藓羽藻Rubisco大亚基分子量与菠菜基本相同，而小亚基较之稍大一些。藓羽藻Rubisco活力测定结果表明，Rubisco分离过程中用硫酸铵分部沉淀后活力降低许多，分离后活力有所上升，但仍比粗提液活力弱；在Rubisco活力测定过程中，藓羽藻Rubisco的活化温度与其它物种Rubisco活化的温度不同，在低温下活化效果较好。这些结果说明Rubisco的酶活力受硫酸铵的影响而且藓羽藻Rubisco相对陆地高等植物结构不稳定。     

Environmental change and oyster colonization within the Hudson River estuary linked to Holocene climate

Geophysical mapping and sampling data provide a record of changing environmental and faunal conditions within the Hudson River estuary during the mid- to late Holocene. On the shallow, broad marginal flats of the mesohaline Hudson, fossil oyster beds (Crassostrea virginica) are found exposed on the river bottom and buried by sediment. The shallowest beds are well imaged in chirp sub-bottom and side-scan sonar data and form discrete flow-perpendicular bands, 0.6–1.0 km wide and up to 3 km long, which cover 30% of the river bottom. Radiocarbon-dated sediment cores indicate oysters thrived within two time periods from ~500–2,400 and ~5,600–6,100 cal. years b.p. Sediment and physical property data indicate a changing depositional regime consistent with the oyster chronology. Similar changes in oyster presence are found in local shell midden sites of the Lower Hudson Valley as well as elsewhere along the Atlantic coast, and may reflect climatic controls associated with warm–cool cycles during the Holocene. Oysters flourished during the mid-Holocene warm period, disappeared with the onset of cooler climate at 4,000–5,000 cal. years b.p., and returned during warmer conditions of the late Holocene. The most recent demise of oysters within the Hudson at 500–900 cal. years b.p. may have accompanied the Little Ice Age.     

Patterns and controls of surface sediment distribution: west-central Florida inner shelf

The west-central Florida inner shelf represents a transition between the quartz-dominated barrier-island system and the carbonate-dominated mid-outer shelf. Surface sediments exhibit a complex distribution pattern that can be attributed to multiple sediment sources and the ineffectiveness of physical processes for large-scale sediment redistribution. The west Florida shelf is the submerged extension of the Florida carbonate platform, consisting of a limestone karst surface veneered with a thin unconsolidated sediment cover. A total of 498 surface sediment samples were collected on the inner shelf and analyzed for texture and composition. Results show that sediment consists of a combination of fine quartz sand and coarse, biogenic carbonate sand and gravel, with variable but subordinate amounts of black, phosphorite-rich sand. The carbonate component consists primarily of molluskan fragments. The distribution is patchy and discontinuous with no discernible pattern, and the transition between sediment types is generally abrupt. Quartz-rich sediment dominates the inner 15 km north of the entrance into Tampa Bay, but south of the Bay is common only along the inner 3 km. Elsewhere, carbonate-rich sediment is the predominate sediment type, except where there is little sediment cover, in which cases black, phosphorite-rich sand dominates. Sediment sources are likely within, or around the periphery of the basin. Fine quartz sand is likely reworked from coastal units deposited during Pleistocene sea-level high stands. Carbonate sand and gravel is produced by marine organisms within the depositional basin. The black, phosphorite-rich sand likely originates from the bioerosion and reworking of the underlying strata that irregularly crop out within the study area. The distribution pattern contains elements of both storm- and tide-dominated siliciclastic shelves, but it is dictated primarily by the sediment source, similar to some carbonate systems. Other systems with similar sediment attributes include cool-water carbonate, sediment-starved, and mixed carbonate/siliciclastic systems. This study suggests a possible genetic link among the three systems.     

Marine mammals from northeast Atlantic: relationship between their trophic status as determined by delta13C and delta15N measurements and their trace metal concentrations

The relationship between trophic position through delta13C and delta15N and trace metal concentrations (Zn, Cd, Cu and Hg) was investigated in the tissues of six marine mammal species from the Northeast Atlantic: striped dolphin Stenella coeruleoalba, common dolphin, Delphinus delphis, Atlantic white-sided dolphin Lagenorhynchus acutus, harbour porpoise Phocoena phocoena, white beaked-dolphin Lagenorhynchus albirostris, grey seal Halichoerus grypus stranded on French Channel and Irish coasts. White-beaked dolphins, harbour porpoises, white-sided dolphins, common and striped dolphins display the same relative and decreasing trophic position, as measured by delta15N values, along both the Irish and French channel coasts, reflecting conservative trophic habits between these two places. Hepatic and renal Cd concentrations were significantly correlated to muscle delta13C and delta15N values while Hg, Zn and Cu did not. These results suggest that Cd accumulation is partly linked to the diet while other factors such as age or body condition might explain Hg, Zn or Cu variability in marine mammals. Combined stable isotope and trace metal analyses appear to be useful tools for the study of marine mammal ecology.     

Expression of P-glycoprotein in southeastern oysters, Crassostrea virginica

These studies provide important fundamental information regarding the expression of P-glycoprotein (p-gp) in southeastern oysters (Crassostrea virginica). Using rhodamine transport studies, p-gp activity was detected in newly fertilized embryos. A monoclonal antibody (C219) was used to evaluate p-gp expression in oyster tissues. On the basis of laboratory studies, p-gp expression tended to be higher in gill tissues than mantle tissues, and was generally not related to salinity differences. Seasonal studies were conducted with oysters collected monthly for 1 year from Lighthouse Creek, an unpolluted site. There was a general pattern of higher p-gp expression in the warmer months and lower expression in the colder months. In contrast, total gill protein concentrations decreased during the warmer months and increased during the colder months. These studies indicate that there are seasonal patterns in p-gp expression which may represent an adaptive response to natural stressors associated with summer conditions.     

Structural monitoring of offshore platforms using impulse and relaxation response

Monitoring offshore platforms, long span bridges, high rise buildings, TV towers and other similar structures is essential for ensuring their safety in service. Continuous monitoring assumes even greater significance in the case of offshore platforms, which are highly susceptible to damage due to the corrosive environment and the continuous action of waves. Also, since a major part of the structure is under water and covered by marine growth, even a trained diver cannot easily detect damage in the structure. In the present work, vibration criterion is adopted for structural monitoring of jacket platforms. Artificial excitation of these structures is not always practicable and ambient excitation due to wind and waves may not be sufficient for collecting the required vibration data. Alternate methods can be adopted for the same purpose, for example, the application of an impact or a sudden relaxation of an applied force for exciting the structure. For jacket platforms, impact can be applied by gently pushing the structure at the fender while relaxation can be accomplished by pulling the structure and then suddenly releasing it using a tug or a supply vessel in both cases. The present study is an experimental investigation on a laboratory model of a jacket platform, for exploring the feasibility of adapting vibration responses due to impulse and relaxation, for structural monitoring. Effects of damage in six members of the platform as well as changes in deck masses were studied. A finite element model of the structure was used to analyze all the cases for comparison of the results as well as system identification. A data acquisition and analysis procedure for obtaining the response signatures of the platform due to the impulse and relaxation procedure was also developed for possible adoption in on-line monitoring of offshore platforms. From the study, it has been concluded that both impulse and relaxation responses are useful tools for monitoring offshore jacket platforms. The present work forms the basis for the development of an automated, on-line monitoring system for offshore platforms, using neural networks.     

Relative microbial activity and mineralization associated with water masses in the lower Cook Inlet,Alaska

A study of the microbial uptake and respiration (mineralization) of radioactive glutamic acid was made in 141 surface water samples in the Cook Inlet, Alaska during three sampling periods (October, 1976; April, 1977; and November, 1977). The rate at which the test substrate was incorporated into cell material plus that respired as CO₂ was used to calculate the relative microbial activity. A northern water mass with salinities less than 31 showed high rates of relative microbial activity but low mineralization rates as indicated by respiration of¹⁴CO₂. The reverse pattern was seen in the water mass (salinity higher than 31) to the south which was more typical of coastal water. These data suggest that the organic nutrients in these two water masses are quite different either qualitatively or quantitatively. This study illustrates how the observed measurement of relative microbial activity might be helpful in defining specific water masses.(The publication of this article was unintentionally delayed owing to a fault in secretarial routine.)Published as Technical Paper No. 6009, Oregon Agricultural Experiment Station.     

Vertical migration and mortality of benthos in dredged material: Part II—crustacea

Benthic invertebrates have many characteristics which make them prime candidates for burial studies in dredged material. A major concern in dredging and disposal projects is the effect of burial on the survival of benthic invertebrates. The purpose of the research reported in this paper was to determine the ability of estuarine benthos—in particular three species of molluscs (Mercenaria mercenaria, Nucula proxima and Ilyanassa obsoleta)—to migrate vertically in natural and exotic sediments and to determine the survival of benthos when exposed to particular amounts of simulated dredged material.Mortalities generally increased with increased sediment depth, with increased burial time and with overlying sediments whose particle size distribution differed from that of the species native sediment. Temperature affected mortalities and vertical migration. It was concluded that vertical migration is a viable process which can significantly affect rehabilitation of a dredged disposal area. Under certain conditions, vertical migration should be considered, together with larval settling and immigration from outside impacted areas, as a mechanism of recruiting a dredgedump site.