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91.
Zoltn Vci Carl B. Agee Christopher D. K. Herd Erin Walton Oliver Tschauner Karen Ziegler Vitali B. Prakapenka Eran Greenberg Sylvia Monique‐Thomas 《Meteoritics & planetary science》2020,55(5):1011-1030
Hydrous alteration of olivine macrocrysts in a Martian olivine phyric basalt, NWA 10416, and a terrestrial basalt from southern Colorado are examined using SEM, EPMA, TEM, and µXRD techniques. The olivines in the meteorite contain linear nanotubes of hydrous material, amorphous areas, and fluid dissolution textures quite distinct from alteration identified in other Martian meteorites. Instead, they bear resemblance to terrestrial deuteric alteration features. The presence of the hydrous alteration phase Mg‐laihunite within the olivines has been confirmed by µXRD analysis. The cores of the olivines in both Martian and terrestrial samples are overgrown by unaltered rims whose compositions match those of a separate population of groundmass olivines, suggesting that the core olivines are xenocrysts whose alteration preceded crystallization of the groundmass. The terrestrial sample is linked to deep crustal metasomatism and the “ignimbrite flare‐up” of the Oligocene epoch. The comparison of the two samples suggests the existence of an analogous relatively water‐rich magmatic reservoir on Mars. 相似文献
92.
S. J. Warren D. J. Mortlock S. K. Leggett D. J. Pinfield D. Homeier S. Dye R. F. Jameson N. Lodieu P. W. Lucas A. J. Adamson F. Allard D. Barrado y Navascués M. Casali K. Chiu N. C. Hambly P. C. Hewett P. Hirst M. J. Irwin A. Lawrence M. C. Liu † E. L. Martín R. L. Smart L. Valdivielso B. P. Venemans 《Monthly notices of the Royal Astronomical Society》2007,381(4):1400-1412
93.
John H. Trefry Robert P. Trocine Michelle L. McElvaine Robert D. Rember Lucas T. Hawkins 《Environmental Geology》2007,53(2):375-385
Concentrations of total Hg in sediments near six drilling sites in the Gulf of Mexico were elevated well above average background
values of 40–80 ng/g. The excess Hg was associated with barite from discharged drilling mud. In contrast with total Hg, concentrations
of methylmercury (MeHg) in these sediments did not vary significantly at nearfield (<100 m) versus farfield (>3 km) distances
from the drilling sites. Observed variability in concentrations of MeHg were related to local differences in redox state in
the top 10 cm of sediment. Low to non-detectable concentrations of MeHg were found in nearfield sediments that were anoxic,
highly reducing and contained abundant H2S. At most drilling sites, nearfield samples with high concentrations of total Hg (>200 ng/g) had similar or lower amounts
of MeHg than found at background (farfield) stations. Higher values of MeHg were found in a few nearfield sediments at one
site where concentrations of TOC were higher and where sediments were anoxic and moderately reducing. Overall, results from
this study support the conclusion that elevated concentrations of MeHg in sediments around drilling sites are not a common
phenomenon in the Gulf of Mexico. 相似文献
94.
Using structured telephone interviews this research focuses on how Canadian migrants living in the United States experience
and describe home. We argue that the globalisation of peoples’ lives, transnationalism and the concomitant creation of transnational
social spaces have greatly affected the meaning of home for migrants. The understandings of home that result reflect the reality
of living in social worlds that span two countries and the development of decentred multiple attachments and feelings of belonging
in more than one place. In response to these circumstances Canadian migrants experience home as multi-dimensional, pluri-local,
and characterized by regular movement across the U.S.–Canada border. When asked specifically about feeling at home upon re-entry
to the U.S. many respondents answered yes. However, many interviewees qualified their answers by describing home in different
ways and associating different aspects of their lives with each country. Canada as home was most often described in terms
of family, while home in the U.S. was associated with work. Respondents also differentiated between feeling at home once they
reached their residence as opposed to feeling unwelcome at the U.S. border. 相似文献
95.
Research interest in speciation of arsenic stems from its species dependent behavior in the environment and in living organisms. The complexity of the matrix to be analyzed and low concentrations of target arsenic species that may be labile or difficult to chromatogram, indicate that a suitable pre‐treatment methodology is required. This study investigated the usefulness of chelation solvent extraction – high performance liquid chromatography (CSE‐HPLC) for the speciation of arsenic in water. It involved reacting arsenic with the chelant known for its affinity towards arsenic, followed by extraction, separation, and identification of the arsenic‐chelant‐arsenic complex. Arsenic species having different physicochemical properties were investigated. Species, such as, As2O3, As3O5, KH2AsO4, Na2HAsO4, and NaAsO2 were detected as a group of closely eluted peaks with different retention times and spectral properties, whereas, the organic arsenic species CH3Na2AsO3, o‐arsanilic acid, roxarson and triphenyl arsine separated quite well on the EnviroseP‐CM HPLC column. Key method parameters, such as, type of HPLC column, composition of mobile phase and organic solvents affecting peak resolution and sensitivity were optimized. Real environmental matrices contaminated with arsenic were analyzed under varying wavelengths (λmax = 190, 210, 220, 234, 244, and 282 nm), with good precision. Different arsenic species were detected in these samples with excellent background and signal‐to‐noise ratios demonstrating the robustness of the method. The detection limit, reproducibility, selectivity, accuracy, and dynamic range of the calibration curves were evaluated. 相似文献
96.
Nowadays many telescopes around the world are automated and some networks of robotic telescopes are active or planned. Such equipment could be used for thetraining of students and for science in the Universities of DCs and of newastronomical countries, by sending them observational data via Internetor through remotely controlled telescope. It seems that it is thetime to open up for discussion with UN and ESA organizations and also withIAU, how to implement links between robotic telescopes and suchUniversities applying for collaborations. Many scientific fields couldthus be accessible to them, for example on stellar variability, near-earthobject follow-up, -ray burst counterpart tracking, and so on. 相似文献
97.
A camera network with hourly resolution was used to monitor the complex snow processes in montane forest environments. We developed a semi‐automatic procedure to interpret snow depths from the digital images, which exhibited high consistency with manual measurements and station‐based recordings. To extract snow interception dynamics, six binary classification methods were compared. The MaxEntropy classifier demonstrated better performance than the other methods under conditions of varying illumination and was therefore selected as the method used for quantifying snow in tree canopies. Snow accumulation and ablation on the ground, as well as snow loading and unloading in the forest canopies, were investigated using snow parameters derived from the time‐lapse photography monitoring. The influences of meteorologic conditions, forest cover, and elevation on the snow processes were also considered. Time‐lapse photography proved to be an effective and low‐cost approach for collecting useful information on snow processes and facilitating the set‐up of hydrological models. 相似文献
98.
99.
Research presented here explores the feasibility of leveraging vegetation data derived from airborne light detection and ranging (LiDAR) and terrestrial laser scanning (TLS) for visibility modeling. Using LiDAR and TLS datasets of a lodgepole pine (Pinus contorta) dominant ecosystem, tree canopy and trunk obstructions were isolated relevant to a discrete visibility beam in a short‐range line‐of‐sight model. Cumulative obstruction factors from vegetation were compared with reference visibility values from digital photographs along sightline paths. LiDAR‐derived tree factors were augmented with single‐scan TLS data for obstruction prediction. Good correlation between datasets was found up to 10 m from the terrestrial scanner, but fine scale visibility modeling was problematic at longer distances. Analysis of correlation and regression results reveal the influence of obstruction shadowing inherent to discrete LiDAR and TLS, potentially limiting the feasibility of modeling visibility over large areas with similar technology. However, the results support the potential for TLS‐derived subcanopy metrics for augmenting large amounts of aerial LiDAR data to significantly improve models of forest structure. Subtle LiDAR processing improvements, including more accurate tree delineation through higher point density aerial data, combined with better vegetation quantification processes for TLS data, will advance the feasibility and accuracy of data integration. 相似文献
100.
Zintl化合物是以Edward Zintl命名的化合物,是一类由电正性的碱金属或碱土金属与电负性的13族或14族元素形成的特殊金属间化合物。其价键模式可以是离子键、金属键和共价键共存,其中的准金属可以共价键的形式形成各种形式的离子簇,因而其结构复杂多样。这类化合物的部分阴离子簇不仅具有稳定的笼状、层状和链状结构,并且具有特殊的光、电、磁等性能,使得在半导体、催化、电极材料等方面都有应用的前景和发展潜力。介绍了几个特殊Zintl化合物体系,盐湖丰产元素在Zintl化合物中的作用,指出了含有盐湖丰产元素的Zintl化合物的应用前景和方向。 相似文献