Average chemical composition of the lunar surface     

Anthony L. Turkevich 《Earth, Moon, and Planets》1973,8(3):365-367

The available data on the chemical composition of the lunar surface at eleven sites (3 Surveyor, 5 Apollo and 3 Luna) are used to estimate the amounts of principal chemical elements (those present in more than about 0.5% by atom) in average lunar surface material. The terrae of the Moon differ from the maria in having much less iron and titanium and appreciably more aluminum and calcium.Paper dedicated to Prof. Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.  相似文献   

Finite element models for rock fracture mechanics     

Anthony R. Ingraffea  Francois E. Heuze 《国际地质力学数值与分析法杂志》1980,4(1):25-43

A finite element model for the prediction of discrete fracture propagation in rock structures loaded in compression is presented. The model integrates any one of three theories for mixed-mode fracture initiation; it contains an energy balance algorithm for predicting crack increment length, and incorporates recent developments in finite element stress-intensity factor computation. The predictions of the model are compared with the observed fracture response of a real rock structure. Results show that the model accurately predicts both stable and unstable fracture progagations observed experimentally.  相似文献   

Comparison of the analytical results from the surveyor,Apollo, and Luna missions     

Anthony L. Turkevich 《Earth, Moon, and Planets》1972,5(3-4):411-421

The principal chemical element composition and inferred mineralogy of the powdered lunar surface material at seven mare and one terra sites on the Moon are compared. The mare compositions are all similar to one another and comparable to those of terrestrial ocean ridge basalts except in having higher titanium and much lower sodium contents than the latter. These analyses suggest that most, if not all, lunar maria have this chemical composition and are derived from rocks with an average density of 3.19 g cm^–3. Mare Tranquillitatis differs from the other maria in having twice the titanium content of the others.The chemical composition of the single highland site studied (Surveyor 7) is distinctly different from that of any of the maria in having much lower amounts of titanium and iron and larger amounts of aluminium and calcium. Confirmation of these general characteristics of lunar highland material has come from recent observations by the Apollo 15 Orbiter. The inferred mineralogy is 45 mole percent high anorthite plagioclase and the parent rocks have an estimated density of 2.94 g cm^–3. The Surveyor 7 chemical composition is the principal contributor to present estimates of the overall chemical composition of the lunar surface.Presented at the NATO Advanced Study Institute on Lunar Studies, Patras, Greece, September 14–25, 1971. This paper is an expanded and updated version of a paper presented at the Apollo 12 Lunar Science Conference, Houston, Texas, January 11–14, 1971, and published in the Proceedings of this Conference (Turkevich, 1971).  相似文献   

An evaluation of hemolymph cholinesterase activities in the tropical scallop,Euvola (Pecten) ziczac,for the rapid assessment of pesticide exposure     

Owen R  Buxton L  Sarkis S  Toaspern M  Knap A  Depledge M 《Marine pollution bulletin》2002,44(10):1010-1017

The use of sequential measurements of hemolymph cholinesterase activities as a non-invasive biomarker of seasonal organophosphate/carbamate exposure was investigated for the tropical scallop, Euvola (Pecten) ziczac. Overall activities of both acetylcholinesterase and butyrylcholinesterase were relatively high compared to studies with bivalve tissues. Acute in vivo experiments showed inhibition of hemolymph acetylcholinesterase activity at concentrations of the organophosphate insecticide chlorpyrifos of 0.1, 1 and 10 ng l(-1). Monthly sampling of hemolymph from scallops at two sites in Bermuda over a 15 month period showed seasonal acetylcholinesterase and butyrylcholinesterase inhibition. Direct and indirect evidence suggests that this inhibition did not relate to biochemical or physiological changes associated with gonad maturation and spawning, but rather reflected diffuse contamination of the marine environment by cholinesterase inhibitors or increased bioavailability of such inhibitors at these times. Repetitive sampling of scallop hemolymph for cholinesterase activities represents a rapid, sensitive and non-invasive method for assessing seasonal, sublethal pesticide exposure in these commercially important bivalves and suggests a wider use in marine pollution monitoring.  相似文献   

Is sediment delivery a fallacy?     

Anthony J. Parsons  John Wainwright  Richard E. Brazier  D. Mark Powell 《地球表面变化过程与地形》2006,31(10):1325-1328

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Two Supervised Neural Networks for Classification of Sedimentary Organic Matter Images from Palynological Preparations     

Andrew F. Weller  Anthony J. Harris  J. Andrew Ware 《Mathematical Geosciences》2007,39(7):657-671

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Ferrihydrite dissolution by pyridine-2,6-bis(monothiocarboxylic acid) and hydrolysis products     

Suraj Dhungana  Charles R. Anthony III  Larry E. Hersman 《Geochimica et cosmochimica acta》2007,71(23):5651-5660

Pyridine-2,6-bis(monothiocarboxylate) (pdtc), a metabolic product of microorganisms, including Pseudomonas putida and Pseudomonas stutzeri was investigated for its ability of dissolve Fe(III)(hydr)oxides at pH 7.5. Concentration dependent dissolution of ferrihydrite under anaerobic environment showed saturation of the dissolution rate at the higher concentration of pdtc. The surface controlled ferrihydrite dissolution rate was determined to be 1.2 × 10⁻⁶ mol m⁻² h⁻¹. Anaerobic dissolution of ferrihydrite by pyridine-2,6-dicarboxylic acid or dipicolinic acid (dpa), a hydrolysis product of pdtc, was investigated to study the mechanism(s) involved in the pdtc facilitated ferrihydrite dissolution. These studies suggest that pdtc dissolved ferrihydrite using a reduction step, where dpa chelates the Fe reduced by a second hydrolysis product, H₂S. Dpa facilitated dissolution of ferrihydrite showed very small increase in the Fe dissolution when the concentration of external reductant, ascorbate, was doubled, suggesting the surface dynamics being dominated by the interactions between dpa and ferrihydrite. Greater than stoichiometric amounts of Fe were mobilized during dpa dissolution of ferrihydrite assisted by ascorbate and cysteine. This is attributed to the catalytic dissolution of Fe(III)(hydr)oxides by the in situ generated Fe(II) in the presence of a complex former, dpa.  相似文献   

土地覆盖制图：基于最优化遥感数据的支撑向量机分类   总被引：1，自引：0，他引：1  

Gidudu Anthony  Heinz Ruther 《遥感学报》2007,11(5):694-701

遥感数据具有在不同空间、光谱和时间尺度上获取地表测量信息的能力,使其成为获取土地覆盖信息的一个主要数据源。影像分类即把卫星影像上的相关像元划分给某类已知的土地覆盖类型的过程。支撑向量机（SVMs）是一种土地覆盖分类的新技术。三种常用的SVMs是：基于线性和多项式的SVM以及具有高斯核函数的SVM分类器,分类能否成功地应用有赖于其各自选择的最佳参数。但是海量的遥感数据使得这些参数的确定速度十分缓慢。本文研究了一种新的基于最优化遥感数据压缩技术的SVM分类方法。研究显示用于获取SVM参数的数据量能够在不影响土地覆盖的分类精度的前提下进行压缩。数据压缩成功的应用于多项式和高斯核函数的SVM分类,而线性SVM的分类精度却非常低。  相似文献   

Hubble Space Telescope-WFPC2/Hα Observations of the Ejected Nebula M1-67     

Yves Grosdidier  Anthony F.J. Moffat  Agnès Acker 《Astrophysics and Space Science》1998,260(1-2):181-184

We present HST-WFPC2/Hα deep images of the ejected nebula M1-67. Our data suggest that M1-67 is the imprint of a previous, slow LBV wind ejected from the central star WR124, now a WN8 star. We find evidence that the LBV wind is highly variableand anisotropic. Some dense, persisting clumps have possibly been ejected directly from the stellar surface. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

A Ca ii H&K survey of γ Doradus candidates     

Anthony B. Kaye  & Klaus G. Strassmeier 《Monthly notices of the Royal Astronomical Society》1998,294(2):L35-L39

In an investigation of the starspot hypothesis as it applies to the 'slowly variable' F-type dwarfs, we spectroscopically observed eight promising γ Doradus candidates to search for Ca  ii H&K emission. We found that there are no significant emission reversals in the cores of these resonance lines. Based on the ceiling flux calculations of the Ca  ii K line and on calculations of the Rossby number, we conclude that there is no support for the presence of strong magnetic activity and the starspot hypothesis in these objects.  相似文献