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81.
82.
Gerardo J. M. Luna J. L. Sokoloski Roberto D. D. Costa 《Astrophysics and Space Science》2006,304(1-4):283-285
We describe X-ray and optical observations of the symbiotic star RX Pup. From low resolution optical spectra, we obtain a reddening for RX Pup of E(B−V)=0.79. We use the neutral column density corresponding to this reddening as a lower limit for the X-ray spectra fits. The X-ray spectra can be fitted with either a two-temperarure thermal plasma model or a single-temperature plasma plus a narrow line at ≈0.55 keV, each modified by interstellar absorption. The RX Pup X-ray flux is not variable within the observation exposure time, suggesting that unlike in most CVs, an accretion disk boundary layer does not contribute significantly to the X-ray flux. Instead, the X-ray emission may come from shock-heated gas further away from the compact object. 相似文献
83.
84.
Amy M. Gaffney Lars E. Borg James N. Connelly 《Geochimica et cosmochimica acta》2007,71(20):5016-5031
Uranium-lead ratios (commonly represented as 238U/204Pb = μ) calculated for the sources of martian basalts preserve a record of petrogenetic processes that were active during early planetary differentiation and formation of martian geochemical reservoirs. To better define the range of μ values represented by the source regions of martian basalts, we completed U-Pb elemental and isotopic analyses on whole rock, mineral and leachate fractions from the martian meteorite Queen Alexandra Range 94201 (QUE 94201). The whole rock and silicate mineral fractions have unradiogenic Pb isotopic compositions that define a narrow range (206Pb/204Pb = 11.16-11.61). In contrast, the Pb isotopic compositions of weak HCl leachates are more variable and radiogenic. The intersection of the QUE 94201 data array with terrestrial Pb in 206Pb/204Pb-207Pb/204Pb-208Pb/204Pb compositional space is consistent with varying amounts of terrestrial contamination in these fractions. We calculate that only 1-7% contamination is present in the purified silicate mineral and whole rock fractions, whereas the HCl leachates contain up to 86% terrestrial Pb. This terrestrial Pb contamination generated a 206Pb-207Pb array in the QUE fractions that appears to represent an ancient age, which contrasts with a much younger crystallization age of 327 ± 10 Ma derived from Rb-Sr and Sm-Nd isochrons (Borg L. E., Nyquist L. E., Taylor L. A., Wiesmann H. and Shih C. -Y. (1997) Constraints on Martian differentiation processes from Rb-Sr and Sm-Nd isotopic analyses of the basaltic shergottite QUE 94201. Geochim. Cosmochim. Acta61, 4915-4931). Despite the contamination, and accepting 327 ± 10 Ma as the crystallization age, we use the U-Pb data to determine the initial 206Pb/204Pb of QUE 94201 to be 11.086 ± 0.008 and to calculate the μ value of its mantle source to be 1.82 ± 0.01. The μ value calculated for the QUE 94201 source is the lowest determined for any martian basalt source, and, when compared to the highest values determined for martian basalt sources, indicates that μ values in martian source reservoirs vary by at least a factor of two. Additionally, the range of source μ values indicates that the μ value of bulk silicate Mars is approximately three. The amount of variation in the μ values of the mantle sources (μ ∼ 2-4) is greater than can be explained by igneous processes involving silicate phases alone. We suggest the possibility that a small amount of sulfide crystallization may generate greater extents of U-Pb fractionation during formation of the mantle sources of martian basalts. 相似文献
85.
Sorption and desorption behavior of residual antidepressants and caffeine in freshwater sediment and sewage sludge 总被引:1,自引:0,他引:1
Ismael Laurindo Costa Junior Christiane Schinneider Machado Adelmo Lowe Pletsch Yohandra Reyes Torres 《国际泥沙研究》2022,37(3):346-354
The use of antidepressants is widespread in modern times. Thus, they present a potential risk for ecosystems due to occurrence in domestic sewage containing unaltered metabolites and structures, even after the treatment plants have processed the sewage. The current research investigated the sorption and desorption of antidepressants(citalopram, venlafaxine, fluoxetine, sertraline, and amitriptyline) and caffeine from freshwater sediment and sewage sludge. The samples of freshwater sediment were ... 相似文献
86.
Natural Hazards - The central USA has experienced an increase in the frequency and magnitude of human-induced earthquakes. The earthquakes are caused by the deep-well injection of water produced... 相似文献
87.
Annemarie Christophersen Nicola Litchfield Kelvin Berryman Richard Thomas Roberto Basili Laura Wallace William Ries Gavin P. Hayes Kathleen M. Haller Toshikazu Yoshioka Richard D. Koehler Dan Clark Monica Wolfson-Schwehr Margaret S. Boettcher Pilar Villamor Nick Horspool Teraphan Ornthammarath Ramon Zuñiga Robert M. Langridge Mark W. Stirling Tatiana Goded Carlos Costa Robert Yeats 《Natural Hazards》2015,79(1):111-135
88.
This paper investigates the spatial distribution of cattle breeders in Texas to quantify how climate factors influence cattle breed selection. A multivariate probit model is employed to examine the county-level binary choices of Bos taurus, Bos indicus and composite breeds derived from cattle breed association membership data. The estimation results suggest that summer heat stress is a significant factor for breed selection: positive for Bos indicus and negative for Bos taurus and composite breeds, with the average marginal effects on breed membership probability being 9.7 %, ?26.5 % and ?7.9 %, respectively. The intensity of the summer heat impacts can lead to noteworthy changes in spatial distributions of Texas cattle breeds in the event of climate change. 相似文献
89.
Prakki Satyamurty Claudia Priscila Wanzeler da Costa Antonio Ocimar Manzi 《Theoretical and Applied Climatology》2013,111(1-2):195-209
The regions where the divergence of vertically integrated water vapor flux, averaged over a season or a year, is positive (negative) are sources (sinks) of moisture for the atmosphere. An aerial river is defined as a stream of strong water vapor flux connecting a source and a sink. Moisture flux, its divergence, and sources and sinks over the tropics of South and Central America and the adjoining Atlantic Ocean are obtained for dry years and for wet years in the Amazon Basin. Results show that the Amazon Basin is a sink region for atmospheric moisture in all seasons and that there are two source regions for the moisture in the basin, one situated in the South Atlantic and the other in the North Atlantic, both located equator-ward of the respective subtropical high-pressure centers. The convergence of moisture increases over the Amazon Basin in austral summer, and at the same time it decreases in the Pacific and Atlantic ITCZs. Box model calculations reveal that the wet years, on the average, present about 55 % more moisture convergence than the dry years in the Amazon Basin. A reduction in the moisture inflow across the eastern and northern boundaries of the basin (at 45°W and at the Equator, respectively) and an increase in the outflow across the southern boundary (at 15°S) lead to dry conditions. The annual mean contribution of moisture convergence to the precipitation over the Amazon Basin is estimated to be 70 %. In the dry years, it lowers to around 50 %. The net convergence of water vapor flux over the basin is a good indicator of the wet or dry condition. 相似文献
90.
Ken Kobayashi Jonathan Cirtain Amy R. Winebarger Kelly Korreck Leon Golub Robert W. Walsh Bart De Pontieu Craig DeForest Alan Title Sergey Kuzin Sabrina Savage Dyana Beabout Brent Beabout William Podgorski David Caldwell Kenneth McCracken Mark Ordway Henry Bergner Richard Gates Sean McKillop Peter Cheimets Simon Platt Nick Mitchell David Windt 《Solar physics》2014,289(11):4393-4412
The High-Resolution Coronal Imager (Hi-C) was flown on a NASA sounding rocket on 11 July 2012. The goal of the Hi-C mission was to obtain high-resolution (≈?0.3?–?0.4′′), high-cadence (≈?5 seconds) images of a solar active region to investigate the dynamics of solar coronal structures at small spatial scales. The instrument consists of a normal-incidence telescope with the optics coated with multilayers to reflect a narrow wavelength range around 19.3 nm (including the Fe xii 19.5-nm spectral line) and a 4096×4096 camera with a plate scale of 0.1′′?pixel?1. The target of the Hi-C rocket flight was Active Region 11520. Hi-C obtained 37 full-frame images and 86 partial-frame images during the rocket flight. Analysis of the Hi-C data indicates the corona is structured on scales smaller than currently resolved by existing satellite missions. 相似文献