Preface     

Theodore A. Fritz  Shing F. Fung 《Surveys in Geophysics》2005,26(1-3):1-3

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The sedimentation history of Lake Huron and Georgian Bay: results from analysis of seismic reflection profiles     

David M. Dobson  Theodore C. Moore Jr.  David K. Rea 《Journal of Paleolimnology》1995,13(3):231-249

An extensive seismic reflection profile survey conducted concurrently with a sediment coring program in northern Lake Huron, Georgian Bay, and the North Channel revealed a detailed Holocene lake level history. Seven acoustic sequences were identified in the seismic stratigraphy, and these sequences show great variation in both the character and the spatial distribution of sediment deposition through time. The depths to the acoustically-defined sequence boundaries were digitized from the analog seismic records and merged with Loran-C navigation records from the cruise, yielding a three-dimensional record of the location of each sequence boundary. Thicknesses of the sequences were calculated from these depths, and a minimum-curvature spline surface was fit to the thickness data. These surfaces were used to construct isopach maps which show the trends in thickness of sediment accumulation throughout the lake basins for each of the sequences. ¹⁴C-AMS dates of materials from the cores fixed the dates of the sediment sequence boundaries, allowing sediment accumulation rates to be calculated. The distribution of sedimentation in the basins as shown on the isopach maps allowed assessment of sediment transport and water flow through the basins over time, which when combined with the work of Lewis & Anderson (1989), provides a detailed record of the transport and drainage of water through these basins as the Wisconsinan ice sheet retreated and isostatic rebound opened and closed outlets. Reversals of flow direction through the Straits of Mackinac and through the channels connecting Lake Huron and Georgian Bay and the North Channel are indicated by changes in sediment thickness distributions.  相似文献   

A decade of change in nets and plastic litter from fisheries off Alaska     

Theodore R. Merrell 《Marine pollution bulletin》1984,15(10):378-384

Ten 1 km beaches on Amchitka Island, Alaska, were surveyed once annually in 1972–1974 and in 1982 to determine weights and numbers of fish-net fragments and other plastic litter items. Most litter was from Japanese and Soviet fishing vessels. Litter rapidly increased during 1972–74 (from 122 to 345 kg km^?1 of beach) but decreased 26% by 1982 to 255 kg km^?1. There was a 37% reduction in weight of trawl web on Amchitka beaches, and the number of gill-net floats declined 47%. The decrease in litter between 1974 and 1982, attributed to fewer trawlers and gill-netters fishing off Alaska, shows that marine litter could be rapidly reduced if disposal of litter at sea were restricted.  相似文献   

Ultraviolet observations of interstellar molecules and grains fromSpacelab     

Theodore P. Snow Jr. 《Astrophysics and Space Science》1979,66(2):453-466

Observational results obtained to date on interstellar grains and molecules are briefly reviewed, and several promising areas for further research withSpacelab are suggested. Regarding grains, useful data can be expected on the shape of the ultraviolet extinction curve for new interstellar regions; the nature of UV extinction at short wavelengths, down to the Lyman limit; the presence or absence of structure in the UV extinction curve comparable to the visible-wavelength diffuse bands; the scattering properties of grains in new kinds of clouds and nebulae; and the polarization properties of grains in UV wavelengths. The principal advances which may be expected in observations of molecules will include the ability to probe more heavily-obscured regions, where molecular species are more abundant than in the diffuse clouds observed to date; coverage of wavelength regions (such as 1400–3200) not well-studied with previous instruments such asCopernicus; and the capability of observing in optical absorption species detected in the same line of sight in radio emission, which provides unique information on cloud geometry and physical conditions.  相似文献   

Metabolic and physiological regulation of Chlorella sp.(Trebouxiophyceae,Chlorophyta) under nitrogen deprivation     

YONG Wai-Kuan  LIM Phaik-Eem  VELLO Vejeysri  SIM Kae-Shin  ABDUL MAJID Nazia  MUSTAFA Emienour Muzalina  NIK SULAIMAN Nik Meriam  LIEW Kan-Ern  CHEN Brenna Jia-Tian  PHANG Siew-Moi 《海洋湖沼学报（英文）》2019,(1):186-198

A freshwater green microalgae Chlorella sp., UMACC344 was shown to produce high lipid content and has the potential to be used as feedstock for biofuel production. In this study, photosynthetic effciency, biochemical pro?les and non-targeted metabolic pro?ling were studied to compare between the nitrogen-replete and deplete conditions. Slowed growth, change in photosynthetic pigments and lowered photosynthetic effciency were observed in response to nitrogen deprivation. Biochemical pro?les of the cultures showed an increased level of carbohydrate, lipids and total fatty acids, while the total soluble protein content was lowered. A trend of fatty acid saturation was observed in the nitrogen-deplete culture with an increase in the level of saturated fatty acids especially C16:0 and C18:0, accompanied by a decrease in proportions of monounsaturated and polyunsaturated fatty acids. Fifty-nine metabolites, including amino acids, lipids, phytochemical compounds, vitamins and cofactors were signi?cantly dysregulated and annotated in this study. Pathway mapping analysis revealed a rewiring of metabolic pathways in the cells, particularly purine, carotenoid, nicotinate and nicotinamide, and amino acid metabolisms. Within the treatment period of nitrogen deprivation, the key processes involved were reshu ? ing of nitrogen from proteins and photosynthetic machinery, together with carbon repartitioning in carbohydrates and lipids.  相似文献   

Positioning fisheries in a changing world   总被引：1，自引：1，他引：0  

R. Quentin Grafton  Ray Hilborn  Lori Ridgeway  Dale Squires  Meryl Williams  Serge Garcia  Theodore Groves  James Joseph  Kieran Kelleher  Tom Kompas  Gary Libecap  Carl Gustaf Lundin  Mitsutaku Makino  Thorolfur Matthiasson  Richard McLoughlin  Ana Parma  Gustavo San Martin  Ben Satia  Carl-Christian Schmidt  Maree Tait  Lin Xiu Zhang 《Marine Policy》2008,32(4):630-634

Marine capture fisheries face major and complex challenges: habitat degradation, poor economic returns, social hardships from depleted stocks, illegal fishing, and climate change, among others. The key factors that prevent the transition to sustainable fisheries are information failures, transition costs, use and non-use conflicts and capacity constraints. Using the experiences of fisheries successes and failures it is argued only through better governance and institutional change that encompasses the public good of the oceans (biodiversity, ecosystem integrity, sustainability) and societal values (existence, aesthetic and amenity) will fisheries be made sustainable.  相似文献   

Long-term trends in water clarity revealed by Secchi-disk measurements in lower Narragansett Bay   总被引：3，自引：0，他引：3  

Borkman  David G.; Smayda  Theodore J. 《ICES Journal of Marine Science》1998,55(4):668-679

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Steady-state observations of geomagnetically trapped energetic heavy ions and their implications for theory     

Theodore A. Fritz  Walther N. Spjeldvik 《Planetary and Space Science》1981,29(11):1169-1193

Measurements of energetic heavy ions using the Explorer 45 and ATS-6 satellites are reviewed and the resulting implications for theory are evaluated. The measured ions are basically protons and helium ions in the energy range from 0.1 to 1 MeV/nucleon. The equatorial energetic ion distributions inside L = 4.5 are found to be very stable for extended periods of time. These ions are very closely confined to the equatorial plane and are sharply peaked as a function of L around a value designated as L_max. Beyond L = 5.0 the fluxes of these ions are more variable with order of magnitude variations being observed at L = 6.6 on the time scales of minutes, hours, or days. The region inside L = 4.5 appears to be well described by radial diffusive transport driven by fluctuations in the geomagnetic field coupled with losses due to charge exchange and Coulomb interactions with ambient hydrogen geocorona and terrestrial plasma environment. From an analysis relating the position in L-value of the maximum intensity, L_max, observed for a given ion species and energy, it is argued that the influence of fluctuations in the convection electric field as discussed by Cornwall (1972) are not effective in radially diffusing in L ions with energies greater than a few hundred kiloelectron volts per nucleon. The source of these ions remains basically undetermined and its determination must await further measurements.  相似文献   

Field observations of fronts and high-frequency temperature fluctuations in a thermal plume     

Theodore Green  Stephen Roffler 《Advances in water resources》1981,4(3):137-145

High-frequency temperature variations were measured at seven depths, at a point 130 m from the cooling-water outfall of a power plant. The data are studied using spectra, correlation functions and probability distributions. The sharp thermal fronts observed in the data are related to the surface thermal fronts seen using airborne infra-red scanning, and to laboratory studies of instabilities in mixing layers between uniformly flowing and quiescent fluids.  相似文献   

Spectrophotometry of Jupiter     

Willem Wamsteker  Theodore D. Fay  Bill J. Duncan 《Icarus》1976,29(2):315-319

Spectrophotometric maps of Jupiter were made between 24 and 27(UT) November 1974 on the McMath Solar Telescope at Kitt Peak National Observatory. We report a comparison between observed scaled reflectivities of the Jovian North Tropical Zone and the North Equatorial Belt at System II longitudes between 195 and 205 degrees. The belt/zone reflectivity ratios between 430 and 740nm are related to the optical transmission curves of the organic and/or sulfur polymers synthesized by Khare and Sagan in a simulated Jovian atmosphere.  相似文献