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21.
The effect of cadmium on the growth of an intertidal marine gastropod, Nassarius festivus, was investigated using a number of biomarkers namely conventional measurements in terms of increase in shell length or body weight, scope for growth (SfG) and RNA/DNA ratio. After eight days of cadmium exposure, the no observable effect concentration (NOEC) and lowest observable effect concentration (LOEC) for the rate of increase in wet weight were 1.00 and 1.38 mg/l, respectively, while those for shell length did not show any significant difference from the control until day 16. After 16 days of cadmium exposure, the LOEC for both shell length and wet weight measurements was 0.22 mg/l. The 8-day SfG test was sensitive to cadmium stress, showing a significant decrease at 0.16 mg/l cadmium when compared to the control. The NOEC and LOEC of RNA/DNA ratio determination were 0.52 and 0.93 mg/l, respectively. An assessment based on sensitivity and technical complexity suggests that Scope for Growth is the most sensitive growth biomarker, followed by the RNA/DNA ratio, and then the conventional growth measurement based on shell size and body weight. 相似文献
22.
The Significance of Multiple Saturation Points in the Context of Polybaric Near-fractional Melting 总被引:1,自引:0,他引:1
Experimental petrologists have successfully located basalticliquid compositions parental to mid-ocean ridge basalt thatare, within experimental resolution, multiply saturated withthree-phase harzburgite or four-phase lherzolite assemblageson their liquidus at some elevated pressure. Such an experimentalresult is a necessary consequence of any paradigm in which eruptedbasalts derive from single-batch primary liquids that equilibratewith a mantle residue and undergo no subsequent magma mixingbefore differentiation and eruption. Here we investigate whether,conversely, such evidence of multiple saturation is sufficientto exclude dynamic melting models wherein increments of meltare mixed after segregation from residues, during melt transportor in magma chambers. Using two independent models of crystalliquidequilibria to simulate polybaric near-fractional peridotitemelting, we find that aggregate liquids from such melting processescan display near-intersections of liquidus surfaces too closeto distinguish experimentally from exact multiple saturationpoints. Given uncertainties in glass compositions, fractionationcorrections, experimental temperature and pressure conditions,and achievement of equilibrium, these results suggest that polybaricmixtures can in fact masquerade as mantle-equilibrated single-batchprimary liquids. Multiple saturation points on the liquidussurfaces of primitive basalts do, however, preserve informationabout the average pressure of extraction of their constituentincrements of liquid. KEY WORDS: mantle melting; basaltic volcanism; experimental igneous petrology; thermodynamic modelling; inverse method 相似文献
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24.
Kongsbreen, a tide-water glacier located in Kongsfjorden, is the most active calving glacier in Svalbard. Three SPOT images are used to determine its flow speed and calving rate. The position of fourteen reference points was determined on the coast or mountain sides, and the changes in position of 144 characteristic features on the glacier surface were calculated. The obtained speed profiles arc consistent with the findings from previous works from 1962-64 and 1983-86. When comparing the obtained longitudinal profile to the data from 1962–64. it is found that the flow velocity at a given distance from the front has been nearly constant.
The results from the SPOT images analysis are completed by using existing topographic works. The present study shows that SPOT images (panchromatic as well as multichannel), recorded with a periodicity of one year, can be used to determine precisely the annual flow speed and calving rate of active glaciers such as Kongsbreen. Images recorded with a periodicity of two, three or four weeks can allow identical determination on tide-water glaciers during a surging active phase. 相似文献
The results from the SPOT images analysis are completed by using existing topographic works. The present study shows that SPOT images (panchromatic as well as multichannel), recorded with a periodicity of one year, can be used to determine precisely the annual flow speed and calving rate of active glaciers such as Kongsbreen. Images recorded with a periodicity of two, three or four weeks can allow identical determination on tide-water glaciers during a surging active phase. 相似文献
25.
The hierarchid tessellation model belongs to a class of spatial data models based on the recursive decomposition of space. The quadtree is one such tessellation and is characterized by square cells and a 1:4 decomposition ratio. To relax these constraints in the tessellation, a generalized hierarchical tessellation data model, called Adaptive Recursive Tessellations (ART), has been proposed. ART increases flexibility in the tessellation by the use of rectangular cells and variable decomposition ratios. In ART, users can specify cell sizes which are intuitively meaningful to their applications, or which can reflect the scales of data. ART is implemented in a data structure called Adaptive Recursive Run-Encoding (ARRE), which is a variant of two-dimensional run-encoding whose running path can vary with the different tessellation structures incorporated in an ART model. Given the recognition of the benefits of implementing statistical spatial analysis in GIS, the use of hierarchical tessellation models such as ART in spatial analysis is discussed. Three examples are introduced to show how ART can: (1) be applied to solve the quadrat size problem in quadrat analysis of point patterns; (2) act as the data model in the variable resolution block kriging technique for geostatistical data to reduce variation in kriging error; and (3) facilitate the evaluation of spatial autocorrelation for area data at multiple map resolutions via the construction of a connectivity matrix for calculating spatial autocorrelation indices based on ARRE. 相似文献
26.
KROON NORRIS KLAUS IAN T. ALEXANDER LEON PAUL BARDOT CHARLES E. BARKER JEAN-PIERRE BELLIER CHARLES D. BLOME LEON J. CLARKE JOCHEN ERBACHER KRISTINA L. FAUL MARY ANNE HOLMES BRIAN T. HUBER MIRIAM E. KATZ KENNETH G. MACLEOD SANDRA MARCA FRANCISA C. MARTINEZ-RUIZ ISAO MITA MUTSUMI NAKAI JAMES G. OGG DOROTHY K. PAK THOMAS K. PLETSCH JEAN M. SELF-TRIAL NICHOLAS J. SHACKLETON JAN SMIT WILLIAM USSLERIII DAVID K. WATKINS JOEN WIDMARK & PAUL A. WILSON 《Geology Today》1998,14(6):222-226
27.
PETER JENNISKENS PAUL WERCINSKI JOE OLEJNICZAK GARY ALLEN PRASUN N. DESAI GEORGE RAICHE DEAN KONTINOS DOUG REVELLE JASON HATTON RICHARD L. BAKER RAY W. RUSSELL MIKE TAYLOR FRANS RIETMEIJER 《Earth, Moon, and Planets》2004,95(1-4):339-360
The imminent return of the Genesis Sample Return Capsule (SRC) from the Earth’s L1 point on September 8, 2004, represents
the first opportunity since the Apollo era to study the atmospheric entry of a meter-sized body at or above the Earth’s escape
speed. Until now, reentry heating models are based on only one successful reentry with an instrumented vehicle at higher than
escape speed, the 22 May 1965 NASA “FIRE 2” experiment. In preparation of an instrumented airborne and ground-based observing
campaign, we examined the expected bolide radiation for the reentry of the Genesis SRC. We find that the expected emission
spectrum consists mostly of blackbody emission from the SRC surface (T∼
∼2630 K@peak heating), slightly skewed in shape because of a range of surface temperatures. At high enough spectral resolution,
shock emission from nitrogen and oxygen atoms, as well as the first positive and first negative bands of N2+, will stand out above this continuum. Carbon atom lines and the 389-nm CN band emission may also be detected, as well as
the mid-IR 4.6-μm CO band. The ablation rate can be studied from the signature of trace sodium in the heat shield material,
calibrated by the total amount of matter lost from the recovered shield. A pristine collection of the heat shield would also
permit the sampling of products of ablation. 相似文献
28.
29.
Submarine pillow basalts (34 Ma) recovered from the NorthernKerguelen Plateau at ODP Site 1140 contain abundant unalteredglass, providing the first opportunity to measure the volatilecontents of tholeiitic basaltic magmas related to the Kerguelenmantle plume. The glasses have La/Sm and Nb/Zr ratios that varyfrom values similar to Southeast Indian Ridge (SEIR) MORB (Unit1), to slightly more enriched (Unit 6), to values transitionalbetween SEIR MORB and basaltic magmas formed by melting of theKerguelen plume (Units 2 and 3). Volatile contents for glassesin Units 1 and 6 are similar to depleted mid-ocean ridge basalt(MORB) values (0·250·27 wt % H2O, 12401450ppm S, 4254 ppm Cl). In contrast, H2O contents are higherfor the enriched glasses (Unit 2, 0·44 wt % H2O; Unit3, 0·69 wt %), as are S (1500 ppm) and Cl (146206ppm). Cl/K ratios for all glasses are relatively low (0·030·04),indicating that assimilation of hydrothermally altered materialdid not occur during shallow-level crystallization. H2O/Ce forthe enriched glasses (Units 2 and 3) is significantly lowerthan Pacific and South Atlantic MORB values, suggesting thatlow H2O/Ce may be an inherent characteristic of the Kerguelenplume source. Vapor saturation pressures calculated using theH2O and CO2 contents of the glasses indicate that 相似文献
30.
PAUL C. BUCKLAND DAVID W. PERRY GÍSLI M. GISLASON REW J. DUGMORE 《Boreas: An International Journal of Quaternary Research》1986,15(2):173-184
The origins of the Icelandic biota are discussed with particular reference to recent work on Coleopteran (beetle) and Trichopteran (caddis fly) fossils from deposits which are earlier than the arrival of man (Landnám) in the country. The hypothesis of survival through Pleistocene glaciations in refugia is discounted in favour of immigration on ice floes during Late Glacial/Early Holocene deglaciation. Consideration of the nature of the insect fauna and the extent of Late Glacial ice sheets, with the evidence from ocean circulation patterns, suggests a source area in the fjords of south-west Norway. The model is applicable to the origins of the biota on all the North Atlantic islands, east of the Davis Strait. 相似文献