Experiments on the growth and food conversion efficiency of the spat of Ostrea edulis L in a recirculation system     

Walne  P. R.; Spencer  B. E. 《ICES Journal of Marine Science》1974,35(3):303-318

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The Thornton Beach Mammoth: Consistency of Numerical Age and Morphology     

Spencer G. Lucas 《Quaternary Research》1996,45(3):332-333

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The distribution of particulate matter in the Atlantic Ocean     

Peter G. Brewer  Derek W. Spencer  Pierre E. Biscaye  Adele Hanley  Peter L. Sachs  Clarence L. Smith  Susan Kadar  Janet Fredericks 《Earth and Planetary Science Letters》1976,32(2):393-402

We have determined the dry weight of suspended particulate matter in seawater in a section through the western Atlantic Ocean from 75°N to 52°S. The concentrations, operationally defined as that weight retained on 0.6-μm and 0.4-μm pore size Nuclepore filters, contained in 1 kg of seawater, range from 5 to 300 μg/kg and show readily explainable regional features. High concentrations are found in surface waters and in association with radpidly moving bottom waters in the Denmark Straits overflow and in Antarctic bottom waters to 15°S. Low concentrations, <12 μg/kg, characterize the mid-water regions of the sub-tropical gyres. High concentrations are seen in sinking Labrador Sea water and in a plume extending at least a kilometer off the bottom at 35°N–40°N where the cruise track intersects the North Atlantic gyre. It is doubtful whether this important phenomenon could be observed by any means other than through particulate observations, either optical or gravimetric, and this provides a unique insight into the scale of vertical turbulent processes.  相似文献   

An oceanic calcium problem?     

Peter G. Brewer  George T.F. Wong  Michael P. Bacon  Derek W. Spencer 《Earth and Planetary Science Letters》1975,26(1):81-87

Recent published data on dissolved calcium in seawater reveal an apparent excess of calcium over that predicted from the changes in alkalinity. In the South Pacific this excess calcium is approximately 40 μmoles/kg. We suggest that this arises from an in-situ titration of some of the alkalinity by protons derived from the redox changes associated with oxidative decomposition of organic matter. This postulates an effective flux of nitric and phosphoric acids into the deep water. Other redox changes, such as in the oxidation of reduced sulfur, may also contribute protons, but these are more difficult to evaluate. This concept changes current thinking on the oceanic CO₂-carbonate system. It increases the amount of calcium carbonate believed to have dissolved in the ocean by ca. 25%; and alters the proportions of abyssal CO₂ believed to be derived from respiration versus carbonate dissolution by about 10%.  相似文献   

Ground-Water Contaminant Plume Differentiation and Source Determination Using BTEX Concentration Ratios     

Y. Jeffrey Yang  Rick D. Spencer  Mark A. Mersmann  Todd M. Gates 《Ground water》1995,33(6):927-935

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加拿大阿尔伯达省西部上泥盆统凯恩组白云岩的成因   总被引：1，自引：0，他引：1  

金振奎 Spen.  RJ 《地质论评》1993,39(6):529-534

加拿大阿尔伯达省西部上泥盆统凯恩组主要由粉晶白云岩和细晶白云岩组成，另外还常见一种充填溶蚀孔洞的亮晶白云石。粉晶白云岩纹理、泥裂和鸟眼等构造发育，其δ＾１３Ｃ为＋１．０‰－＋３．０‰，δ＾１８Ｏ为－６．０‰－－４．３‰，为潮坪上混合水白云化形成。细晶白云岩分布于假整合面之下，其δ＾１３Ｃ为＋０．２‰－＋２．９‰，δ＾１８Ｏ为－６．９‰－－４．６‰，也是混合水白云化的产物。亮晶白云石洁净明亮、晶粒粗  相似文献   

Conditions of metamorphism in an early Paleozoic blueschist,schist of Skookum Gulch,northern California     

Spencer J. Cotkin 《Contributions to Mineralogy and Petrology》1987,96(2):192-200

The Late Ordovician schist of Skookum Gulch, northern California, is one of only a few pre-Mesozoic blueschist localities in North America. Among these, the Skookum Gulch occurrence is noteworthy because it contains lawsonite and has had a relatively simple metamorphic and structural history.Numerous assemblages and a wide variation in the modal proportion of minerals are present due to a spectrum of bulk compositions. This is reflected in the composition of Na-amphibole, which varies from ferro-glaucophane, glaucophane, and crossite (±magnetite) to magnesio-riebeckite (+hematite). Application of the available experiments and empirically calibrated equilibria to the assemblages glaucophane+lawsonite+chlorite+quartz+albite and glaucophane+actinolite+epidote+chlorite+quartz+albite yield estimates of temperature and pressure near T= 275° C and P=7.0 kbar. Estimates of uncertainty are difficult to assess, but are no more than ±100° C and ±3.0 kbar, and are probably considerably smaller. Calcite +quartz+sphene and calcite+quartz+actinolite indicate an extremely H₂O-rich fluid (X(CO₂)<0.003).The absence of a greenschist facies overprint indicates that the schist of Skookum Gulch was uplifted soon after metamorphism. However, it was not exposed until the recent geologic past, having resided at shallow crustal levels for approximately 400 Ma.  相似文献   

First passage of a sliding rigid structure on a frictional foundation     

L. A. Bergman  B. F. Spencer 《地震工程与结构动力学》1985,13(3):281-291

The first passage problem for a sliding rigid block on a frictional foundation, subjected to Gaussian white noise through the foundation, is studied. A well-posed boundary value problem is formulated from Markov process theory and solved for the ordinary moments of time to first passage by the finite element method. A range of parameters is studied representing a simple seismic base isolation system. Results of Monte Carlo simulation are given for comparison.  相似文献   

Geochemistry of great Salt Lake,Utah II: Pleistocene-Holocene evolution     

R.J. Spencer  H.P. Eugster  B.F. Jones 《Geochimica et cosmochimica acta》1985,49(3):739-747

Sedimentologic and biostratigraphic evidence is used to develop a geochemical model for Great Salt Lake, Utah, extending back some 30,000 yrs. B.P. Hydrologie conditions as defined by the water budget equation are characterized by a lake initially at a low, saline stage, rising by about 17,000 yrs. B.P. to fresh water basin-full conditions (Bonneville level) and then, after about 15,000 yrs. B.P., dropping rapidly to a saline stage again, as exemplified by the present situation.Inflow composition has changed through time in response to the hydrologie history. During fresh-water periods high discharge inflow is dominated by calcium bicarbonate-type river waters; during saline stages, low discharge, NaCl-rich hydrothermal springs are significant solute sources. This evolution in lake composition to NaCl domination is illustrated by the massive mirabilite deposition, free of halite, following the rapid drawdown until about 8,000 years ago, while historic droughts have yielded principally halite.Hydrologic history can be combined with inferred inflow composition to derive concentration curves with time for each major solute in the lake. Calcium concentrations before the drawdown were controlled by calcite solubility, and afterwards by aragonite. Significant amounts of solutes are removed from the lake by diffusion into the sediments. Na⁺, Cl^? and SO₄^2? are also involved in salt precipitation. By including pore fluid data, a surprisingly good fit has been obtained between solute input over the time period considered and the amounts actually found in lake brines, pore fluids, salt beds and sediments. Excess amounts are present for calcium, carbonate and silica, indicating detrital input.  相似文献   

The composition,structure, temperature and dynamics of the upper thermosphere in the polar regions during October to December 1981     

D. Rees  R. Gordon  T.J. Fuller-Rowell  M. Smith  G.R. Carignan  T.L. Killeen  P.B. Hays  N.W. Spencer 《Planetary and Space Science》1985,33(6):617-666

During the period October to December 1981, the Dynamics Explorer-2 (DE-2) spacecraft successively observed the South polar and the North polar regions, and recorded the temperature, composition and dynamical structure of the upper thermosphere. In October 1981, perigee was about 310 km altitude, in the vicinity of the South Pole, with the satellite orbit in the 09.00–21.00 L.T. plane. During late November and December, the perigee had precessed to the region of the North Pole, with the spacecraft sampling the upper thermosphere in the 06.00 18.00 L.T. plane. DE-2 observed the meridional wind with a Fabry-Perot interferometer (FPI), the zonal wind with the wind and temperature spectrometer (WATS), the neutral temperature with the FPI, and the neutral atmosphere composition and density with the neutral atmosphere composition spectrometer (NACS). A comparison between the South (summer) Pole and the North (winter) Pole data shows considerable seasonal differences in all neutral atmosphere parameters. The region of the summer pole, under similar geomagnetic and solar activity conditions, and at a level of about 300 km, is about 300 K warmer than that of the winter pole, and the density of atomic oxygen is strongly depleted (and nitrogen enhanced) around the summer pole (compared with the winter pole). Only part of the differences in temperature and composition structure can be related to the seasonal variation of solar insolation, however, and both polar regions display structural variations (with latitude and Universal Time) which are unmistakeable characteristics of strong magnetospheric forcing. The magnitude of the neutral atmosphere perturbations in winds, temperature, density and composition within both summer and winter polar regions all increase with increasing levels of geomagnetic activity.The UCL 3-dimensional time dependent global model has been used to simulate the diurnal, seasonal and geomagnetic response of the neutral thermosphere, attempting to follow the major features of the solar and geomagnetic inputs to the thermosphere which were present during the late 1981 period.In the UCL model, geomagnetic forcing is characterized by semi-empirical models of the polar electric field which show a dependence on the Y component of the Interplanetary Magnetic Field, due to Heppner and Maynard (1983), It is possible to obtain an overall agreement, in both summer and winter hemispheres, with the thermospheric wind structure at high latitudes, and to explain the geomagnetic control of the combined thermal and compositional structure both qualitatively and quantitatively. To obtain such agreement, however, it is essential to enhance the polar ionosphere as a consequence of magnetospheric particle precipitation, reflecting both widespread auroral (kilovolt) electrons, and “soft” cusp and polar cap sources. Geomagnetic forcing of the high latitude thermosphere cannot be explained purely by a polar convective electric field, and the thermal as well as ionising properties of these polar and auroral electron sources are crucial components of the total geomagnetic input.  相似文献