Tribute to John Wasson     

Ed Anders  Derek Sears 《Meteoritics & planetary science》1992,27(1):2-2

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Variations in the Rate of Anaerobic Succinate Accumulation within the Central and Marginal Regions of an Euryoxic Bivalve Mantle     

Ed  Greenfield Miles A.  Crenshaw 《Marine Ecology》1981,2(4):353-362

Abstract. Anaerobic metabolism in the central and marginal portions of the mantle of Mercenaria mercenaria was compared. Anaerobic succinate accumulation was more rapid in the central region. This difference may be due to higher phosphoenolpyruvate carboxykinase activity in the central region. Thus, the central region is more specialized for anaerobic metabolism and the marginal region more for net shell growth. The original rate of succinate accumulation in the mantle is similar in isolated mantles and intact clams, suggesting that mantle succinate production does not require translocation of precursors from other tissues. However, in intact clams, the rate of succinate accumulation in the central region of the mantle slows after four hours. The reduced rate is probably caused by reducing the metabolic rate. Succinate accumulation and shell dissolution are slower in freshly collected clams than in clams that had been stored anaerobically. The difference may be due to induction of PEPCK synthesis during storage. Shell derived calcium did not accumulate in the mantle and, therefore did not alter the intracellular calcium concentration in the mantle.  相似文献   

The Ah receptor in marine animals: phylogenetic distribution and relationship to cytochrome P4501A inducibility     

Mark E. Hahn  Alan Poland  Ed Glover  John J. Stegeman 《Marine environmental research》1992,34(1-4)

In mammals, the induction of cytochrome P4501A forms by chlorinated dibenzo-p-dioxins, chlorinated dibenzofurans, and halogenated biphenyls is under control of a soluble protein known as the Ah (aromatic hydrocarbon) receptor. Little is known about the presence and properties of the Ah receptor in other vertebrate and invertebrate species. In these studies, we sought evidence for an Ah receptor in the liver or liver-equivalent of 20 species of marine and freshwater animals, using the photoaffinity ligand 2-azido-3-[¹²⁵I] iodo-7,8-dibromodibenzo-p-dioxin (N₃[¹²⁵I]Br₂DD). Specific labeling of cytosolic proteins by N₃[¹²⁵I]Br₂DD was observed in seven species of teleost and elasmobranch fish, in PLHC-I fish hepatoma cells, and in beluga whales. No specifically labeled proteins were found in cytosol from two species of agnathan fish nor in any of nine invertebrate species representing eight classes of four phyla. The presence or absence of specifically labeled polypeptides corresponds with the inducibility of cytochrome P4501A and sensitivity to the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin and related planar halogenated aromatic hydrocarbons in many of these groups. Thus, Ah receptor function may have arisen early invertebrate evolution and has been conserved from elasmobranch and teleost fish to mammals.  相似文献   

The effects of sewage discharge on water quality and phytoplankton of Hawai'ian coastal waters     

Parnell PE 《Marine environmental research》2003,55(4):293-311

The effects of sewage discharge on algal populations and the quality of Hawai'ian coastal waters were investigated. Two outfalls were studied. One discharges primary treated sewage and the other discharges secondary treated sewage but are otherwise similar. This enabled comparisons of the effects of these different levels of treatment on the water quality and algal productivity of receiving waters. Plumes were followed and repeatedly sampled in a time-series manner. Rhodamine dye was used as a conservative tracer to compare the dilution behavior of the plume constituents MRP, NO(3)+NO(2), NH(4), Silicate, TDP, TDN, total bacteria, PC, and PN. Rates of initial dilution ranged from two to almost three orders of magnitude, and were in reasonable agreement with engineering model predictions. Dilution of plume constituents approximated that of Rhodamine until background concentrations were reached, typically within 10 min of discharge. Chl a concentrations did not increase through time in the primary sewage plume but did increase up to 30% in the secondary sewage plume. However, rates of far-field dilution were so rapid that the increase could not have been due to algal growth. The increase was attributed to the plume mixing with a water mass whose relative chl a concentrations were greater. Rates of secondary dilution ranged from 2 to 3 orders of magnitude resulting in total dilutions of 10(5)-10(6) within 3 h of discharge. These rates of secondary dilution were much greater than model predictions. From a nutrient standpoint, secondary treatment exhibited no advantages over primary treatment because dilutions were so rapid.  相似文献   

Beyond world cities: Central America in a global space of flows   总被引：1，自引：0，他引：1  

Ed Brown  Peter J. Taylor  & Gilda Catalano 《Area》2002,34(2):139-148

Central America is a region without a world city. Traditionally, the region's national projects have been based upon openness to the world economy: how do the region's contemporary transnational projects connect to the world economy under the new conditions of openness that is contemporary globalization? Focusing upon advanced producer services, three connections into the world city network are identified: global service firms operating directly in Central American cities, local service firms operating indirectly through extra-regional world cities and global service firms operating through Latin American regional offices. Miami is confirmed as the primary world city through which Central America connects into the world economy  相似文献   

Precambrian–Cambrian boundary interval deposition and the marginal platform of the Avalon microcontinent     

Ed Landing   《Journal of Geodynamics》2004,37(3-5):411

Thick terminal Proterozoic–lowest Cambrian successions allow reference of the Saint John, New Brunswick, and MacCodrum Brook, southern Cape Breton Island, areas to the marginal platform of the Avalon microcontinent. Marginal-platform siliciclastic-dominated sequences form a cover on Late Precambrian arc successions from southern New Brunswick to North Wales. Their deposition in fault-bounded basins began with the origin of the Avalon microcontinent and development of a persistent transtensional regime in the latest Precambrian. The terminal Proterozoic–lowest Cambrian on the Avalonian marginal platform consists of three successive lithofacies associations: lower subaerial rift to marginal-marine facies; overlying cool-water, wave-influenced, marine platform sandstones and shales; and higher macrotidal quartz arenites (=Avalonian depositional sequences 1–2). Only the Lower Cambrian macrotidal quartz arenites onlap southeast, where they form the oldest Cambrian unit on the inner platform. These major lithofacies are the Rencontre, Chapel Island, and Random formations, respectively, in Avalonian North America. Southwest thinning of the Rencontre–Chapel Island–Random interval in southern New Brunswick reflects slower subsidence of a fault-bounded area in the city of Saint John. The depositional sequence 1–2 unconformity, which falls in the sub-trilobitic Lower Cambrian Watsonella crosbyi Zone of the Chapel Island Formation, persists for 650 km along the marginal platform from southeastern Newfoundland to southern New Brunswick and, potentially, appears in Cape Breton Island. Latest Precambrian-earliest Cambrian epeirogenic and depositional history was very uniform along the marginal platform, and a unified lithostratigraphic nomenclature is appropriate.  相似文献   

Crustal observations beneath the southern North Sea and their tectonic and geological implications     

Richard H.B. Rijkers  Ed J.Th. Duin 《Tectonophysics》1994,240(1-4):215-224

In 1991, a deep seismic reflection line, MPNI-9101, was acquired in the southern North Sea from the Mesozoic Broad Fourteens Basin, across the West Netherlands Basin onto the London-Brabant Massif (LBM). The resultant section shows a strongly reflective lower crust beneath the area of Mesozoic basin development. This lower crustal reflectivity continues to be strong beneath the LBM. The travel time to the base of the reflective zone increases from approximately 11.0 s beneath the Mesozoic basins to 12.5 s beneath the LBM, suggesting a southward thickening of the crust (Rijkers et al., 1993). Based on these travel times and information from deep wells and refraction surveys. Moho depth is estimated to increase from about 31 km beneath the Mesozoic basins to about 38 km beneath the LBM. This difference in depth to the Moho can partly be explained by coaxial stretching of the crust beneath the Mesozoic basins. In comparison with the Mesozoic basins, the crust beneath the LBM was thickened during the Caledonian and Variscan orogenies.  相似文献   

Strombolian and phreatomagmatic deposits of Ohakune craters, Ruapehu, New Zealand: A complex interaction between external water and rising basaltic magma     

B.F. Houghton  W.R. Hackett 《Journal of Volcanology and Geothermal Research》1984,21(3-4)

The Ohakune Craters form one of several parasitic centres surrounding Ruapehu volcano, at the southern end of the Taupo Volcanic Zone. An inner scoria cone and an outer, probably older, tuff ring are the principal structures in a nested cluster of four vents.The scoria cone consists of alternating lava flows and coarse, welded and unwelded, strombolian block and bomb beds. The strombolian beds consist of principally two discrete types of essential clast, vesicular bombs and dense angular blocks. Rare finer-grained beds are unusually block-rich. The tuff ring consists of alternating strombolian and phreatomagmatic units. Strombolian beds have similar grain size characteristics to scoria cone units, but contain more highly vesicular unoxidised bombs and few blocks. Phreatomagmatic deposits, which contain clasts with variable degrees of palagonitisation, consist of less well-sorted airfall deposits and very poorly sorted, crystal-rich pyroclastic surge deposits.Disruption by expanding magmatic gas bubbles was a major but relatively constant influence on both strombolian and phreatomagmatic eruptions at Ohakune. Instead, the nature of deposits was principally controlled by two other variables, vent geometry and the relative influence of external water during volcanism. During tuff-ring construction, magma is considered to have risen rapidly to the surface, and to have been ejected without sufficient residence time in the vent for non-explosive degassing. Availability of external water principally governed the eruption mechanism and hence the nature of the deposits. Essentials clasts of the scoria cone are, by comparison, dense, degassed and oxidised. It is suggested that a change in vent geometry, possibly the construction of the tuff ring itself, permitted lava ponding and degassing during scoria cone growth. During strombolian eruptions, magma remaining in the vent probably became depleted in gas, leading to the formation of an inert zone, or crust, above actively degassing magma. Subsequent explosions had therefore to disrupt both this passive crust and underlying, vesiculating magma “driving” the eruption. Cycles of strombolian eruption are thought to have stopped when the thickness of the inert crust precluded explosive eruption and only recommenced when some of this material was removed, either as a lava flow or during phreatomagmatic explosions when external water entered the vent. Such explosions probably formed the unusually fine-grained and block-rich beds in the strombolian sequence.The Ohakune deposits are an excellent example of the products of explosive eruption of fluid, gas-rich basic magma vesiculating under very near-surface conditions. A complex interplay of rate of magma rise, rate and depth of formation of gas bubbles, vent geometry, abundance of shallow external water, wind velocity and accumulation rate of ejecta determines the nature of deposits of such eruptions.  相似文献   

Telecommunications Synchronization and GPS   总被引：1，自引：0，他引：1  

Ed Butterline  Sally L. Frodge 《GPS Solutions》2001,5(1):51-54

Today, the Global Positioning System (GPS) is the technology most frequently selected for use in digital communication networks to meet the requirement for precision timing synchronization. The technological evolution of the telecommunications industry over the past 30 years has driven this constantly growing demand for higher performance and timing accuracy. Increased timing accuracy provides overall improvements in system performance, quality, and efficiency. In the United States and in many parts of the world, the telecommunications infrastructure uses the GPS signal as an integral and basic part of the system. The stability of GPS, ongoing health of the GPS constellation, and GPS signal quality can mpact telecommunications systems. ? 2001 John Wiley & Sons, Inc.  相似文献   

R. E. (Ted) Munn — Founding editor; a mini-biography     

Peter Taylor  Morley Thomas  Ed Truhlar  Doug Whelpdale 《Boundary-Layer Meteorology》1996,78(1-2):3-8

Ted Munn founded Boundary-Layer Meteorology in 1970 and served as Editor for 75 volumes over a 25 year period. This short article briefly reviews Ted's scientific career with the Atmospheric Environment Service (of Canada), the International Institute for Applied Systems Analysis in Austria and with the Institute of Environmental Studies at the University of Toronto, and as editor of this journal.  相似文献