Compression of witherite to 8 GPa and the crystal structure of BaCO3II     

C. M. Holl  J. R. Smyth  H. M. S. Laustsen  S. D. Jacobsen  R. T. Downs 《Physics and Chemistry of Minerals》2000,27(7):467-473

Natural witherite (Ba_0.99Sr_0.01CO₃) has been studied by single-crystal X-ray diffraction in the diamond anvil cell at eight pressures up to 8 GPa. At ambient pressure, cell dimensions are a?=?5.3164(12) Å, b?=?8.8921(19) Å, c?=?6.4279(16) Å, and the structure was refined in space group Pmcn to R(F)?=?0.020 from 2972 intensity data. The unit cell and atom position parameters for the orthorhombic cell were refined at pressures of 1.2, 2.0, 2.9, 3.9, 4.6, 5.5, 6.2, and 7.0 GPa. The volume-pressure data are used to calculate equation of state parameters K _T0?=?50.4(12) GPa and K′?=?1.9(4). At approximately 7.2 GPa, a first-order transformation to space group P3¯1c was observed. Cell dimensions of the high-pressure phase at 7.2 GPa are a?=?5.258(6) Å, c?=?5.64(1) Å. The high pressure structure was determined and refined to R(F)?=?0.06 using 83 intensity data, of which 15 were unique. This high-pressure phase appears to be more compressible than the orthorhombic phase with an estimated initial bulk modulus (K _7.2GPa) of 10 GPa.  相似文献   

Documentation of Istanbul Historic Peninsula by Kinematic Terrestrial Laser Scanning     

Thomas P.  Kersten  Gürcan  Büyüksal&#;h  &#;brah&#;m  Baz  Karsten  Jacobsen 《The Photogrammetric Record》2009,24(126):122-138

Although the Historic Peninsula of old Istanbul was added to the UNESCO World Heritage List in 1985, complete documentation of this important area has not yet been carried out. In 2006 the Istanbul Metropolitan Municipality's Historical Environment Protection Directorate initiated the "Historic Peninsula Project", which covers an area of 1500 ha and includes approximately 48 000 buildings in crowded and frequently narrow streets. BİMTAŞ, a company owned by the Municipality, immediately started the documentation of all buildings in the project area using terrestrial laser scanning. This created the challenge of building up an efficient production environment with new high-end technology to fulfil the requirements of this project in a very short timeframe of 2 years. This paper describes the entire production environment for documentation of all buildings, detailing the frequent adaptations of the process resulting from learning on the job. Although the data acquisition and mapping environment was established in the course of production, it was always essential to optimise the technical solutions in order to meet the requirements for data quality and delivery deadlines. Only 80 ha of the required 1500 ha was completed using static scanning during the first 6 months, thus requiring a change from static to mobile terrestrial laser scanning in order to accelerate the work and to conclude the scanning phase for the remaining major area within 3 months.  相似文献   

Global Change and Regional Landscape Response and Desertification in Siberia     

V.M.PLYUSNIN  L.V.DANKO 《资源与生态学报(英文版)》2011,(3):277-279

Climate changes and associated natural and anthropogenic processes have manifested themselves particularly clearly during the last two decades. The study of consequences of these changes has become one of the central scientific, social and political issues of our time (Pilot 2000; UNEP 2007).  相似文献   

Leaching of Salmonella enterica in clay columns comparing two manure application methods     

Bech T  Dalsgaard A  Jacobsen OS  Jacobsen CS 《Ground water》2011,49(1):32-42

Transfer of zoonotic bacterial pathogens through intact soil columns was monitored in an outdoor lysimeter over 36 d. Manure spiked with Salmonella enterica serovar Senftenberg was applied to either the soil surface or injected 0.08 m into the soil to compare leaching associated with the two manure application methods. The highest concentrations of S. enterica (up to 60,000 S. enterica CFU/mL) were detected on Day 1 in the first drainage samples, with measurable but declining concentrations persisting for 10 to 36 d depending on replicate columns. The total recovery of leached S. enterica in drainage samples ranged from 0.08% to 13.8%. When comparing the two application methods, there was no statistically significant difference in the leaching concentration of S. enterica at each sampling time during the study period. In addition, comparison of enumerations by selective plating and real-time polymerase chain reaction yielded similar concentrations of S. enterica, indicating that mainly viable and culturable cells were leached from the columns. When the experiment was terminated, the fluorescent dye Acid Yellow was applied to four selected columns and the distribution of dye and size of active (dye-stained) pores were measured with a digital camera and visualization software. The profiles showed that the area covered by active pores ranged from 0.1% to 3.6%. The relatively small fraction of active pores in the soil profile was consistent with the evidence of rapid transport of S. enterica and chloride in the columns.  相似文献   

Nd isotopic variations of Phanerozoic paleoceans     

Lisette S. Keto  Stein B. Jacobsen 《Earth and Planetary Science Letters》1988,90(4):395-410

The size of various Phanerozoic paleoceans, determined from paleogeographic maps, provides a framework for assigningε_Nd measurements of primary authigenic marine minerals to individual paleoceans and for establishing theirε_Nd versus age curves. We report newε_Nd data (in the range from 80 to 750 Ma) for the largest Phanerozoic and Late Precambrian paleocean, the Pacific/Panthalassa Ocean (PPO), and limited data on some small Paleozoic paleoceans. These new data and all other published data on paleoceanε_Nd values are used to determine the trends through time ofε_Nd in seven Phanerozoic paleoceans. The variations in paleoceanε_Nd curves are due to changes in the rate of crustal additions and in paleoceanic geometry. From these data we can calculate a meanε_Nd curve and a mean Nd model age curve for Phanerozoic seawater. These curves show large variations with age and reflect the variations ofε_Nd in erosion products from the continents as a function of age. The high erosion rates of young, uplifted areas enhanceε_Nd and Nd model age variations of Phanerozoic seawater. This makes it difficult to quantitatively recover crustal addition rates from these curves; however, it makes the episodic nature of continental additions more evident.  相似文献   

Crystal chemistry, thermal expansion, and Raman spectra of hydroxyl-clinohumite: implications for water in Earth’s interior     

Yu Ye  Joseph R. Smyth  Steven D. Jacobsen  Céline Goujon 《Contributions to Mineralogy and Petrology》2013,165(3):563-574

Two samples of hydroxyl-clinohumite, sample SZ0407B with approximate composition Mg_8.674(14)Fe_0.374(4)(Si_0.99(1)O₄)₄(OH)₂ and sample SZ0411B with composition Mg₉(SiO₄)₄(OH)₂, were synthesized at 12 GPa and 1,250 °C coexisting with olivine. Unit-cell parameters determined by single-crystal X-ray diffraction are given as follows: a = 4.7525(4) Å, b = 10.2935(12) Å, c = 13.7077(10) Å, α = 100.645(9)°, V = 659.04(9) Å³ for SZ0407B, and a = 4.7518(6) Å, b = 10.2861(12) Å, c = 13.7008(9) Å, α = 100.638(9)°, V = 658.15(9) Å³ for SZ0411B. Single-crystal X-ray intensity data were collected for crystal structure refinements of both samples. Relative to the pure-Mg sample, Fe decreases M3–OH bond lengths by ~0.010(3) Å, consistent with some ferric iron ordering into M3. Raman spectroscopy shows two strong bands in the lattice-mode region at 650 and 690 cm^?1 in the Fe-bearing sample, which are not observed in the pure-Mg sample. Spectra in the H₂O region show at least five bands, which are deconvolved into seven distinct O–H-stretching modes. Thermal expansion measurements were carried out for both samples from 153 to 787 K by single-crystal X-ray diffraction. The average a-, b-, c-axial and volumetric thermal expansion coefficients (10^?6 K^?1) are 10.5(1), 12.3(2), 12.5(2) and 34.9(5) for SZ0407B, respectively, and 11.1(1), 12.6(3), 13.7(3), 36.8(6) for SZ0411B, respectively. After heating, the unit-cell parameters were refined again for each sample at ambient condition, and no significant changes were observed, indicating no significant oxidation or dehydration during the experiment. For the DHMS phases along the brucite–forsterite join, linear regression gives a systematic linear decrease in expansivity with increasing density. Further, substitution of ferrous iron into these structures decreases thermal expansivity, making the Fe-bearing varieties slightly stiffer.  相似文献   

Monitoring Spatial and Temporal Land Use/Cover Changes; a Case Study in Western Black Sea Region of Turkey     

M. Alkan  M. Oruc  Y. Yildirim  D. Z. Seker  K. Jacobsen 《Journal of the Indian Society of Remote Sensing》2013,41(3):587-596

Rapid land use/land cover changes have taken place in many cities of Turkey. Land use and land cover changes are essential for wide range of applications. In this study, Landsat TM satellite imageries date from 1987, 1993, 2000 and 2010 were used to analyse temporal and spatial changes in the Western Black Sea Region of Turkey. Zonguldak and Eregli two largest and economic important cities which have been active coal mining and iron fabric areas. Maximum Likelihood Classification technique was implemented and the results were represented in classes of open area, forest, agricultural, water, mining, urban and pollution in the sea. Urban areas on both cities increased from 1987 to 2010. The agricultural and open areas from 1987 to 2010 decreased in parallel to land use and land cover change in both cities. Meanwhile, forest areas increased continuously with about 20 % from 1987 to 2010 in both cities. As industrial activity, the coal fields doubled from 1987 to 2010.  相似文献   

An integrated laser anemometer and dust accumulator for studying wind-induced dust transport on Mars     

J.P. Merrison  H.P. Gunnlaugsson  K. Kinch  T.L. Jacobsen  A.E. Jensen  P. Nørnberg  H. Wahlgreen 《Planetary and Space Science》2006,54(11):1065-1072

Windborne dust is one of the most important and dynamic factors affecting the Martian surface and its atmosphere, yet there lacks a detailed physical understanding how it is transported. We present a miniature laser-based optoelectronic instrument for use on a Mars lander. It integrates sensors capable of quantifying important parameters needed for the understanding and modeling of dust transport on Mars, these include wind speed, wind direction, suspended dust concentration, dust deposition and removal rates as well as the electrification of the Martian dust. Dust electrification has been seen from experimental simulations to be of considerable importance to the processes of adhesion and cohesion, specifically prompting the formation of low mass density dust aggregates. Testing of this prototype instrument has been performed under simulated Martian conditions in a wind tunnel facility. The results and analysis of its functionality will be presented.  相似文献   

Technogenic hydrogeochemical anomalies of tungsten deposits in Kykylbey ore region     

LeonidV.Zamana LarisaP.Chechel 《东北亚地学研究》2004,7(1):52-57

Peculiarities of the tungsten deposits drainage flow chemical composition formation, the development of which was ceased almost 40 years ago, have been considered. Migration peculiarities of ore components have been covered, and forms of their migration have been calculated. Inertial characteristics of the surface flow contamination are shown.  相似文献   

Geodynamics and ore content of basite-ultrabasite complexes ofSiberian Platform southern framing rocks （Kodaro-Udokan and Muja zones of North Transbaikalye）     

BairN.Abramov 《东北亚地学研究》2004,7(1):15-19

In southern framing of Siberian Platform, basite-ultrabasite intrusive complexes were forming over a long period of time (Early Proterozoic-Paleozoic Era) as a result of collisional and post-collisional processes. In Muja zone they formed mainly in island-arch geodynamic conditions, in Kodaro-Udokan zone-in continental. Most productive toward noble metals in Muja zones are basite-ultrabasites of the Dovyrensk complex‘, in Kodaro-Udokan basites of the Chiney complex. Gold in these formations has both mantle and crustal springs.  相似文献