A comparison of cytochrome P4501A (CYP1A) mRNA inducibility in four species of Atlantic coast anadromous fishes     

Isaac Wirgin  Blake Konkle  Mark Pedersen  Cheryl Grunwald  Jim Williams  Simon C. Courtenay 《Estuaries and Coasts》1996,19(4):913-922

Quantification of levels of cytochrome P4501A (CYP1A) gene expression in sentinel species of fishes has been proposed as a management tool to evaluate contamination of aquatic systems. Based on preliminary studies, we hypothesized that differences in CYP1A mRNA inducibility among individuals, populations, or species might lead to spurious conclusions when using this approach in environmental monitoring programs. To address this possibility, we quantitated and compared CYP1A mRNA induction levels in four species of common Atlantic Coast estuarine fish: smooth flounder, hogchoker, striped bass, and Atlantic tomcod, which were treated with model chemicals (beta naphthoflavone (β-NF), or benzo[a]pyrene at 10 ppm) known to induce CYP1A mRNA, or were exposed to contaminated environments. Species-specific CYP1A DNA probes were generated from PCR (polymerase chain reaction) amplification of genomic DNA using conserved oligonucleotide primers, and, along with cloned rainbow trout and Atlantic tomcod CYP1A cDNA probes were used to quantify CYP1A mRNA levels in northern blot analyses. Successful PCR amplification of CYP1A hybridizable DNA fragments was observed for all four species. Results from northern blot analyses showed large differences in CYP1A mRNA induction among species; only Atlantic tomcod exhibited significant induction of CYP1A mRNA for both chemically treated (97-fold) and environmentally exposed fish (34-fold). Significant, although lower, levels of induction were observed in β-NF treated (14-fold) smooth flounder, but not in environmentally exposed smooth flounder. Only low levels (not significant) of CYP1A gene induction were detected in hogchokers and striped bass. We conclude that CYP1A mRNA inducibility differed significantly among fish taxa perhaps due to differences in regulation of gene expression, suggesting that careful selection of sentinel species should be exercised prior to the use of CYP1A mRNA induction in environmental monitoring programs. However, the significance of differences in CYP1A mRNA inducibility in relation to higher level biological endpoints has yet to be determined.  相似文献   

Controlled-source tensor magnetotelluric responses of a layered earth with azimuthal anisotropy   总被引：2，自引：0，他引：2  

Xiaobo Li  Laust B. Pedersen 《Geophysical Journal International》1992,111(1):91-103

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Simulation of the Ku-band Radar altimeter sea ice effective scattering surface     

Tonboe  R. Andersen  S. Pedersen  L.T. 《Geoscience and Remote Sensing Letters, IEEE》2006,3(2):237-240

A radiative transfer model is used to simulate the sea ice radar altimeter effective scattering surface variability as a function of snow depth and density. Under dry snow conditions without layering these are the primary snow parameters affecting the scattering surface variability. The model is initialized with in situ data collected during the May 2004 GreenIce ice camp in the Lincoln Sea (73/spl deg/W; 85/spl deg/N). Our results show that the snow cover is important for the effective scattering surface depth in sea ice and thus for the range measurement, ice freeboard, and ice thickness estimation.  相似文献   

Volcanic plume simulation on large scales     

Josef M. Oberhuber  Michael Herzog  Hans-F. Graf  Karsten Schwanke 《Journal of Volcanology and Geothermal Research》1998,87(1-4)

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Armalcolite-bearing Fe-Ti oxide assemblages in graphite-equilibrated salic volcanic rocks with native iron from Disko,central West Greenland     

A. K. Pedersen 《Contributions to Mineralogy and Petrology》1981,77(4):307-324

Native iron-bearing strongly sediment-contaminated andesitic to dacitic lavas from the Maligât Formation on Disko contain an early phenocryst assemblage of plagioclase, low-Ca pyroxene(s) and ilmenite. The phenocrystic ilmenite has reacted to form complex Fe-Ti oxide-metal-sulphide aggregates, which contain one or more of the oxides ilmenite, armalcolite and rutile. The armalcolite is very similar to the lunar type 1 armalcolite of Haggerty (1973) and approximate compositionally the ternary system FeTi₂O₅-MgTi₂O₅-Ti₃O₅ (92 to 97 mol.%). When evidence from several salic rocks is combined the Fe-Ti oxide-metal-sulphide aggregates display reactions which may represent one isobaric invariant assemblage (ilmenite-armalcolite-rutile-iron) and the 3 boundary univariant reactions in the system Fe-Ti-O. The compositional and textural features of ferro-magnesian silicates, oxides and metals show that most rocks were affected by a rapidly declining f _{O 2} during magma ascent and cooling, as displayed in the Fe-Ti oxide-metal-sulphide aggregates by the cross-cutting of one or several T—f _{O 2} buffer curves in the system Fe-Ti-O. Prominent sulphidation reactions are observed in the oxide aggregates and are always of the type where FeO in oxide is replaced by FeS while the liberated oxygen is consumed in a reduction process. Carbon, bound as graphite or cohenite, occurs throughout the rocks and is mostly enclosed in phenocrysts and xenocrysts. When the salic magmas ascended from pre-eruption reservoirs at 1 to 1.5 kb the reduction was largely controlled by strongly pressure-dependent carbon-oxygen equilibria resulting in rapidly declining T—f _{O 2} paths recorded by the oxide assemblages. In the simplified C-O gas system carbon-barometry (Sato 1979) applied to the selected rocks would indicate final equilibrium pressures of between 10 and 100 bars. The scarcity of preserved graphite in the lavas would suggest that the carbon-controlled reductions were terminated when available carbon was exhausted during the magma ascent and solidification.  相似文献   

Exploration for scheelite in East Greenland — A case study     

C.P. Hallenstein  J.L. Pedersen  H. Stendal 《Journal of Geochemical Exploration》1981,15(1-3)

An intensive scheelite exploration program was carried out in Precambrian crystalline and sedimentary rocks intruded by granites of Precambrian and Caledonian ages in East Greenland (70–74°30′N). Previous heavy-mineral panning (2100 samples within an area of 100,000 km²) formed the basis for selection of scheelite-anomalous subregions (1550 km²)In the subregions, pan-concentrate samples were taken from first- and second-order rivers and from mid and side moraines of active glaciers. All samples were studied in the field under UV light, and scheelite grains were counted. A consideration of the distribution of scheelite in the samples together with the river and glacial drainage systems, led to definition of the potential source areas of the scheelite within localities of 2–5 km².Within the localities, panning of scree fines (samples every 100–200 m along talus slopes) and UV-light traverses at night led to the finding of outcropping or sub-outcropping scheelite mineralisation. Scheelite was observed associated with granite-carbonate contact zones, quartz vein stockworks, and fault zones in limestones, at nine localities within the 300-km-long zone of investigation.The heavy-mineral panning method with the counting of scheelite grains in the field and the subsequent definition of potential scheelite-bearing areas has the advantage that it is possible to execute a program from the subregional to the outcropping mineralisation stage in one field season. The investigation in this case was performed by five geologists during the 1979 2.5-month field season.  相似文献   

Rb/1bSr isochrons for the granitic plutons around Farsund,southern Norway     

Svend Pedersen  Torgeir Falkum 《Chemical Geology》1975,15(2):97-101

The granitic and charnockitic intrusions in the Precambrian migmatites around Farsund in southern Norway have previously been shown to be successively intruded as well as being geochemically different. Rb- and Sr-isotope data support the conclusion that they are intruded with a separate time interval and that the Farsund charnockite is younger (852±41 m.y.) than the Lyngdal hornblende granite (932±38 m.y.). Furthermore, the different initial ratios (0.7128 and 0.7054, respectively) disprove a comagmatic origin unless large-scale contamination has occurred.  相似文献   

Geology and mineralogy of the Sarfartôq carbonatite complex,southern West Greenland     

Karsten Secher  Lotte Melchior Larsen 《Lithos》1980,13(2):199-212

The Sarfartôq carbonatite complex was emplaced in lower Palaeozoic time in a weakness zone within the Precambrian shield. Dolomitic magma intruded in two major stages of activity. In the first stage a steeply dipping conical body of concentric sheets of rauhaugite was formed, while in the second stage several batches of magma were emplaced into the surrounding marginal shock-zone as concentric and radial beforsite dykes and agglomerates. Hydrothermal activity gave rise to several phases of mineralisation in veins and shear zones. The accompanying fenitisation was of the Na-type. The whole complex covers about 90 km². The main rock-forming minerals are dolomite-ankerite, apatite, orange reversely pleochroic phlogopite, richterite-arfvedsonite and magnetite. Important accessories are pyrochlore, zircon and niobian rutile. A complete mineral list is given, together with microprobe data on mineral chemistry. The dolomitic magmas were poor in SiO₂, Al₂O₃ and K₂O in relation to other carbonatites. Nb, U and LREEs are strongly enriched in pyrochloremineralised zones where the Nb content may be up to 40%. Some shear zones are strongly enriched in Th and HREEs (specifically Eu) and lesser Pb and Zn. Niobium, uranium, rare earth elements and phosphorus occur in economically interesting concentrations.  相似文献   

Ar/Ar geochronology of the West Greenland Tertiary volcanic province     

M. Storey  R. A. Duncan  A. K. Pedersen  L. M. Larsen  H. C. Larsen 《Earth and Planetary Science Letters》1998,160(3-4):569-586

Paleocene volcanic rocks in West Greenland and Baffin Island were among the first products of the Iceland mantle plume, forming part of a larger igneous province that is now submerged beneath the northern Labrador Sea. A ⁴⁰Ar/³⁹Ar dating study shows that volcanism commenced in West Greenland between 60.9 and 61.3 Ma and that 80% of the Paleocene lava pile was erupted in 1 million years or less (weighted mean age of 60.5±0.4 Ma). Minimum estimates of magma production rates (1.3×10⁻⁴ km³ year⁻¹ km⁻¹) are similar to the present Iceland rift, except for the uppermost part of the Paleocene volcanic succession where the rate decreases to <0.7×10⁻⁴ km³ year⁻¹ km⁻¹ (rift). The timing of onset of volcanism in West Greenland coincides with the opening of the northern Labrador Sea and is also strikingly similar to the age of the oldest Tertiary volcanic rocks from offshore SE Greenland and the British–Irish province. This is interpreted as manifesting the impact and rapid (>1 m/year) lateral spreading of the Iceland plume head at the base of the Greenland lithosphere at 62 Ma. We suggest that the arrival, or at least a major increase in the flux, of the Iceland mantle plume beneath Greenland was a contributing factor in the initiation of seafloor spreading in the northern Labrador Sea. Our study has also revealed a previously unrecognised Early Eocene volcanic episode in West Greenland. This magmatism may be related to movement on the transform Ungava Fault System which transferred drifting from the Labrador Sea to Baffin Bay. A regional change in plate kinematics at 55 Ma, associated with the opening of the North Atlantic, would have caused net extension along parts of this fault. This would have resulted in decompression and partial melting of the underlying asthenosphere. The source of the melts for the Eocene magmatism may have been remnants of still anomalously hot Iceland plume mantle which were left stranded beneath the West Greenland lithosphere in the Early Paleocene.  相似文献   

Elastic Kirchhoff-Helmholtz Synthetic Seismograms     

A. Druzhinin  H. Pedersen  M. Campillo  W. Kim 《Pure and Applied Geophysics》1998,151(1):17-45

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