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31.
Auger electron spectroscopy has been used to study K-feldspar that has been reacted with both aqueous 10% HF and a 50% mixture of a 10% HF/0.1 N H2SO4 solution. In the feldspar/HF system, the resulting feldspar surface was shown to have been fluorinated; depth profiling, using argon ion sputtering, showed the fluorination to have occurred substantially into the mineral bulk. In the feldspar/ system, the resulting surface contained both fluorine and sulfur. The fluorination had again penetrated into the bulk, but the sulfur could be removed with mild argon ion sputtering. The signal ratio was much lower on the feldspar surface treated with the 10% HF/0.1 N H2SO4 solution than the feldspar surface treated with the weaker 10% HF acid solution. 相似文献
32.
R. S. Mcmillan T. L. Moore M. L. Perry P. H. Smith 《Astrophysics and Space Science》1994,212(1-2):271-280
We have been measuring changes in the radial velocities (RV's) of solar-type stars to search for gravitational perturbations by planets. We transmit violet starlight through a Fabry-Perot etalon interferometer and sense changes in Doppler shift from changes in the fluxes of light on the slopes of stellar absorption lines. Our data now span 6 years. Our observations of the Sun showed earlier that both our technique and the profiles of solar photospheric violet absorption lines can be stable enough to reveal planetary perturbations. We now carry this validation to the spectra of other near-solar-type stars. Annual averages of our RV's of Draconis and Virginis are stable to ±6 m s–1. The slope of our five-year series of RV's of Bootis A is consistent with the star's well-determined visual astrometric orbit about Bootis B. The Fabry-Perot technique of Doppler shift measurement is fully capable of detecting perturbations due to planets with masses and orbits similar to those of Jupiter.Paper presented at the Conference onPlanetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A. 相似文献
33.
Sublethal abnormalities were examined in developing embryos of the winter flounder,Pseudopleuronectes americanus, as part of a study of its early reproductive success in Long Island Sound and two sites in Boston Harbor. These sites represented varying levels of anthropogenic contamination that were possibly affecting reproduction, as ascertained by chromosomal abnormalities and lowered developmental rates in the embryos. Effort was focused on examination of blastula and tail-bund embryos from field-captured females spawned at the laboratory. Abnormalities observed included evidence of cytotoxicity and chromosome damage. Embryos of fish from New Haven were usually the most aberrant, while embryos from other sites, notably Hempstead, Shoreham, and both Boston Harbor stations, showed subtle indications of abnormality. 相似文献
34.
35.
Nearest neighbor classifiers have not been widely used by remote sensing practitioners. The lack of acceptance of these classifiers may be partially due to their notoriously slow speed of execution which makes them impractical for the classification of mega-pixel images. However, training data reduction, distance measure optimization, and neighbor searching algorithms based on the modified k-d tree can speed nearest neighbor classification substantially. 相似文献
36.
N. G. J. Gazey M. Lockwood M. Grande C. H. Perry P. N. Smith S. Coles A. D. Aylward R. J. Bunting H. Opgenoorth B. Wilken 《Annales Geophysicae》1997,14(10):1032-1043
We present combined observations made near midnight by the EISCAT radar, all-sky cameras and the combined released and radiation efects satellite (CRRES) shortly before and during a substorm. In particular, we study a discrete, equatorward-drifting auroral arc, seen several degrees poleward of the onset region. The arc passes through the field-aligned beam of the EISCAT radar and is seen to be associated with a considerable upflow of ionospheric plasma. During the substorm, the CRRES satellite observed two major injections, 17 min apart, the second of which was dominated by O+ ions. We show that the observed are was in a suitable location in both latitude and MLT to have fed O+ ions into the second injection and that the upward flux of ions associated with it was sufficient to explain the observed injection. We interpret these data as showing that arcs in the nightside plasma-sheet boundary layer could be the source of O+ ions energised by a dipolarisation of the mid- and near-Earth tail, as opposed to ions ejected from the dayside ionosphere in the cleft ion fountain. 相似文献
37.
Radovan Pipík Anne-Marie Bodergat Danielle Briot Michal Ková? Ján Král’ Grzegorz Zielinski 《Journal of Paleolimnology》2012,47(2):233-249
The Turiec Basin (TB) of Slovakia formed in the Miocene when the West Carpathians escaped from the Alpine region. The 1,250-m-thick
sedimentary Neogene fill of the basin preserved fossil leaves as well as endemic bivalves, gastropods, and ostracodes. The
paleolimnologic changes recorded in the TB infill were derived from the most abundant fossils, the ostracodes. Five contemporaneous
ostracode assemblages within the Late Miocene lacustrine system were distinguished through statistical analysis. These assemblages
have low species similarity, between 2.1 and 24.1%, and are recognized by shape differences among the Candoninae. The ostracode
assemblages, mollusca fossils, and Sr-isotope ratios suggest a low-salinity environment at the beginning of the Late Miocene,
during a brief connection with the Central Paratethys. When the connection ceased, the basin became an isolated freshwater
lake, with five zones differentiated ecologically and bathymetrically using the ostracode assemblages. Taxonomic comparison
of the faunas of the TB and the freshwater to brackish Neogene basins of Europe demonstrates the endemic character of the
TB ostracode fauna. The biologic characteristics of the ostracode families, along with the geology of the lake basin, suggest
that the longevity of the Late Miocene lake probably exceeded 1 Ma. 相似文献
38.
39.
The Marshall Space Flight Center (MSFC) Meteoroid Stream Model simulates particle ejection and subsequent evolution from comets
in order to provide meteor shower forecasts to spacecraft operators for hazard mitigation and planning purposes. The model,
previously detailed in Moser and Cooke (Earth Moon Planets 95, 141 (2004)), has recently been updated; the changes include the implementation of the RADAU integrator, an improved planetary
treatment, and the inclusion of general relativistic effects in the force function. The results of these updates are investigated
with respect to various meteoroid streams and the outcome presented. 相似文献
40.
Natural Hazards - Collapse of residential buildings is the major cause of death during earthquakes. Seismic retrofitting of residential buildings is a cost-effective way to reduce injury and death.... 相似文献