Cadmium sorption in estuarine mud-type sediment and the accumulation of cadmium in the soft-shell clam,Mya arenaria     

Harriette Longacre Phelps 《Estuaries and Coasts》1979,2(1):40-44

YoungMya arenaria were exposed to cadmium-109 sorbed to humic acid, bentonite, protein (albumin), mud-type sediment and filtered estuarine water in a 24-hour static assay. After 31/2 hours, shells had sorbed twice as much as cadmium as tissues. Cadmium-109 was linearly accumulated over 24 hours byMya exposed to cadmium in estuarine water and bentonite-sorbed cadmium. Protein (albumin)-sorbed cadmium was not accumulated byMya. Final 24-hour average accumulation levels of sorbed cadmium compared to cadmium in estuarine water were: bentonite-cadmium, 100%; humic acidcadmium, 60%; mud sediment-cadmium, 33%; albumin-cadmium, 12%.  相似文献   

Petrogenesis of the mafic feldspathoidal lavas of the Raton-Clayton volcanic field,New Mexico     

David W. Phelps  David A. Gust  Joseph L. Wooden 《Contributions to Mineralogy and Petrology》1983,84(2-3):182-190

Major and trace-element whole rock data, Nd and Sr isotopic data, and microprobe data have been collected from a suite of basanites, olivine nephelinites, and olivine melilite nephelinites from the Raton-Clayton volcanic field, New Mexico. Most of the lavas have geochemical characteristics that suggest they are primary upper mantle derived melts. The previously unreported occurrence of Type I and Type II ultramafic xenoliths in some of the lava flows supports this conclusion. All the lavas are strongly enriched in light REE, Sr, Ba, U, Th, and P₂O₅. ⁸⁷Sr/⁸⁶Sr ratios are 0.70394 to 0.70412 and ¹⁴³Nd/¹⁴⁴Nd ratios are equal to an epsilon value of +1.4; the data fall within the Nd-Sr correlation field. Trace-element modeling indicates that the lavas were last in equilibrium with a light-REE enriched mantle with a (La/Yb)_N of two to nine. However, the Nd isotopic data indicate a source with a time integrated, chondritic normalized, Sm/Nd ratio of 1.01. To account for this discrepancy a metasomatic enrichment of the source is proposed. The timing of the enrichment event can only be constrained to less than 1 AE ago, and the isotopic composition of the premetasomatized source and the metasomatizing agent cannot be specified. However, geochemical constraints suggest a CO₂-rich fluid enriched in incompatible elements as the likely metasomatizing agent  相似文献   

Associated middle to late Jurassic volcanism and extension in southern South America     

D.A. Gust  K.T. Biddle  D.W. Phelps  M.A. Uliana   《Tectonophysics》1985,116(3-4)

The extrusive products of a Middle to Late Jurassic volcanic event occur throughout a wide area of southern South America. These volcanic rocks are associated in time and space with a series of NNW-trending grabens. The extension that produced the grabens began perhaps in the latest Triassic and continued throughout most of the Jurassic. The Middle to Late Jurassic volcanic rocks represent the culminating event of this period of extension.The Jurassic volcanic rocks described here are dominantly rhyolites and basalts, but flows of intermediate composition are also present. Major element geochemistry on a suite of samples taken from a west-east transect near 44°S latitude shows that these rocks are not related directly to convergent arc volcanism along the margin of South America, but are the products of a separate tectonic/magmatic event that involved significant crustal anatexis.The extension and related volcanism directly preceded the opening of the Rocas Verdes marginal basin along the western margin of Chile and may have led to the initial separation of South America and South Africa. As such, the Middle-to-Late Jurassic extension and volcanism heralded the breakup of part of Gondwanaland.  相似文献   

Determination of the deformation properties of bedrock under turbine foundations     

Rudolf Hiltscher  Anders Carlsson  Tommy Olsson 《Rock Mechanics and Rock Engineering》1984,17(1):37-49

Summary This paper presents an improved investigation technique for in-situ determination of the deformation properties of rock masses, which are important parameters in the desing of foundations. This technique permits testing on a circular, one square metre area of the rock. In order to obtain reproducible loading conditions when testing, an equipment was introduced that gave almost uniformly distributed loading of the rock surface. This device is described in this paper. Displacement measurements are made in a central measuring hole, since a point of zero displacement, located equidistant between the loaded surface and the upward-pointing anchoring forces, offered a suitable reference point. In this way, the measuring device is also well protected against disturbing variations in temperature. During cyclic loading and unloading, charateristic load/deflection graphs are recorded, which directly demonstrate the deformation properties of the rock, such as the modulus of deformation at different loads, linearity deviation from linearity, as well as hysteresis effects and creep. It is clear that the results of the investigation apply only to the measuring point—the place at which the investigation was carried out. The properties of the rock nearby may vary considerably. The procedure for using this method of investigation for testing improvement measures for turbine foundations is shown in some examples.  相似文献   

On Modelling Discrete Geological Structures as Markov Random Fields   总被引：1，自引：0，他引：1  

Tommy Norberg  Lars Rosén  Ágnes Baran  Sándor Baran 《Mathematical Geology》2002,34(1):63-77

The purpose of this paper is to extend the locally based prediction methodology of BayMar to a global one by modelling discrete spatial structures as Markov random fields. BayMar uses one-dimensional Markov-properties for estimating spatial correlation and Bayesian updating for locally integrating prior and additional information. The methodology of this paper introduces a new estimator of the field parameters based on the maximum likelihood technique for one-dimensional Markov chains. This makes the estimator straightforward to calculate also when there is a large amount of missing observations, which often is the case in geological applications. We make simulations (both unconditional and conditional on the observed data) and maximum a posteriori predictions (restorations) of the non-observed data using Markov chain Monte Carlo methods, in the restoration case by employing simulated annealing. The described method gives satisfactory predictions, while more work is needed in order to simulate, since it appears to have a tendency to overestimate strong spatial dependence. It provides an important development compared to the BayMar-methodology by facilitating global predictions and improved use of sparse data.  相似文献   

基于遗传算法的多光谱影像非监督训练分类系统     

HUNG Chih-Cheng  XIANG Mei  Minh Pham  KUO Bor-Chen  Tommy L. Coleman 《遥感学报》2007,11(5):702-709

本文将遗传算法（GA）应用于非监督训练,提高了遥感数据的分类精度。遗传竞争学习算法（GA-CL）综合了遗传算法和简单的竞争学习算法,可用于改进非监督训练的结果。遗传算法在典型样本聚类的过程中可以避免得到局部最优值。Jeffries-Matusita（J-M）距离法是通过统计测量两个训练类别之间的分离度,可用于评价这种算法。将此算法应用于TM数据的结果显示,遗传算法改进了简单的竞争学习算法,与其他非监督训练算法相比,其提供了K-均值,GA-K-均值和简单的竞争学习算法。  相似文献   

Geostatistical analysis of the effects of stage and roughness on reach-scale spatial patterns of velocity and turbulence intensity     

Carl J. Legleiter  Tracy L. Phelps  Ellen E. Wohl 《Geomorphology》2007,83(3-4):322-345

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Water environment early warning index system in Tongzhou District     

Xiu-ju Zhang  Ning Qiu  Wen-Rong Zhao  Huan An  Julius Lissa Tommy 《Natural Hazards》2015,75(3):2699-2714

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Post-disaster economic development in Aceh: Neoliberalization and other economic-geographical imaginaries     

Nicholas A. Phelps  Michelle Ann Miller 《Geoforum》2011,42(4):418-426

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J. Neilson and B. Pritchard,Value Chain Struggles: Institutions and Governance in the Plantation Districts of South India     

Nicholas A. Phelps 《Singapore journal of tropical geography》2011,32(2):272-273

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