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1.
Faith Vilas David J. Tholen Larry A. Lebofsky Humberto Campins Glenn J. Veeder Richard P. Binzel Alan T. Tokunaga 《Icarus》1985,63(2):201-205
Visual and infrared observations were made of Amor asteroid 1982 DV during its discovery apparition. Broadband visual and near-infrared photometry shows that it is an S-class asteroid. Narrowband spectrophotometry shows an absorption feature due to olivine or pyroxene or both centered at 0.93 μm. Applying a nonrotating thermal model to 10-μm photometry, the geometric albedo is calculated to be approximately 0.27. The geometric albedo for a slowly rotating, rocky surface was calculated for 1 night to be 0.15, consistent with S-class asteroid albedos. Thus, 1982 DV is either one of the most reflective S-class asteroids known, or a significant amount of bare rock is exposed on the asteroid's surface. For the nonrotating model, ellipsoidal dimensions for 1982 DV are 3.5 × 1.4 × 1.4 km. 相似文献
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Jennifer M. Galloway Christine T. Doherty R. Timothy Patterson Helen M. Roe 《第四纪科学杂志》2009,24(4):322-335
A pollen‐based study from Tiny Lake in the Seymour‐Belize Inlet Complex of central coastal British Columbia, Canada, permits an evaluation of the dynamic response of coastal temperate rainforests to postglacial climate change. Open Pinus parklands grew at the site during the early Lateglacial when the climate was cool and dry, but more humid conditions in the later phases of the Lateglacial permitted mesophytic conifers to colonise the region. Early Holocene conditions were warmer than present and a successional mosaic of Tsuga heterophylla and Alnus occurred at Tiny Lake. Climate cooling and moistening at 8740 ± 70 14C a BP initiated the development of closed, late successional T. heterophylla–Cupressaceae forests, which achieved modern character after 6860 ± 50 14C a BP, when a temperate and very wet climate became established. The onset of early Holocene climate cooling and moistening at Tiny Lake may have preceded change at more southern locations, including within the Seymour‐Belize Inlet Complex, on a meso‐ to synoptic scale. This would suggest that an early Holocene intensification of the Aleutian Low pressure system was an important influence on forest dynamics in the Seymour‐Belize Inlet Complex and that the study region was located near the southern extent of immediate influence of this semi‐permanent air mass. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
6.
Ashley Gerard Davies Dennis L. Matson Glenn J. Veeder Torrence V. Johnson Diana L. Blaney 《Icarus》2005,176(1):123-137
The modeling of thermal emission from active lava flows must account for the cooling of the lava after solidification. Models of lava cooling applied to data collected by the Galileo spacecraft have, until now, not taken this into consideration. This is a flaw as lava flows on Io are thought to be relatively thin with a range in thickness from ∼1 to 13 m. Once a flow is completely solidified (a rapid process on a geological time scale), the surface cools faster than the surface of a partially molten flow. Cooling via the base of the lava flow is also important and accelerates the solidification of the flow compared to the rate for the ‘semi-infinite’ approximation (which is only valid for very deep lava bodies). We introduce a new model which incorporates the solidification and basal cooling features. This model gives a superior reproduction of the cooling of the 1997 Pillan lava flows on Io observed by the Galileo spacecraft. We also use the new model to determine what observations are necessary to constrain lava emplacement style at Loki Patera. Flows exhibit different cooling profiles from that expected from a lava lake. We model cooling with a finite-element code and make quantitative predictions for the behavior of lava flows and other lava bodies that can be tested against observations both on Io and Earth. For example, a 10-m-thick ultramafic flow, like those emplaced at Pillan Patera in 1997, solidifies in ∼450 days (at which point the surface temperature has cooled to ∼280 K) and takes another 390 days to cool to 249 K. Observations over a sufficient period of time reveal divergent cooling trends for different lava bodies [examples: lava flows and lava lakes have different cooling trends after the flow has solidified (flows cool faster)]. Thin flows solidify and cool faster than flows of greater thickness. The model can therefore be used as a diagnostic tool for constraining possible emplacement mechanisms and compositions of bodies of lava in remote-sensing data. 相似文献
7.
Charles H. Nelson Douglas S. Hall Francis C. Fekel Robert E. Fried Richard E. Lines Helen C. Lines 《Astrophysics and Space Science》1991,182(1):1-17
Photometry of HD 155638=V792 Her has been analyzed to determine the elements of this totally eclipsing RS CVn binary. The light variation outside eclipse was found to have a period of 27d.07±0d.07, which is slightly different from the 27d.5384±0d.0045 orbital period. Analysis of the eclipses was achieved by a modification of the Russell-Merrill technique. With the aid of radial velocity measures, absolute elements were obtained for the hot and cool stars, respectively;R
h=2.58R
,R
c=12.28R
,M
h=1.40M
,M
c=1.46M
,i=80o.61 and velocity semi-amplitudesK
c=48.36 km s–1±0.79 km s–1, andK
h=50.50 km s–1±0.33 km s–1. The apparent magnitudes areV
h=9
m
.73 andV
c=8
m
.48. The distance to HD 155638 was estimated to be 310 parsecs. 相似文献
8.
Glenn M. Frye Jr. Philip P. Dunphy Edward L. Chupp Paul Evenson 《Solar physics》1988,118(1-2):321-346
9.
Detailed field sampling and analyses and laboratory-based diffusion-cell experiments were used in conjunction with 3-D reactive transport modeling (MODFLOW and MT3D99) to quantify the fate and long-term (10 ka) transport of As in the Rabbit Lake In-pit Tailings Management Facility (RLITMF), northern Saskatchewan, Canada. The RLITMF (300 m × 425 m × 90 m thick) was engineered to ensure solute transport within the RLITMF is dominated by diffusion. Concentrations of As in the tailings pore fluids ranged from 0.24 to 140 mg/L (n = 43). Arsenic speciation analyses indicate 90% of this arsenic exists as As5+. This observation is supported by pH–Eh measurements of pore fluids (n = 135). Geochemical analyses yielded a strong inverse correlation between the Fe/As molar ratio in the tailings solids and the corresponding concentration of dissolved As, which is attributed to the adsorption of As to secondary 2-line ferrihydrite present in the tailings. Diffusion-cell testing yielded values for the effective diffusion coefficient, sorption coefficient, and effective porosity of As in the tailings of 4.5 × 10−10 m2/s, 2–4 cm3/g and 0.36, respectively. Reactive transport simulations using the field and laboratory data show adsorption of As to the tailings and diffusive transport of dissolved As in the tailings should reduce the source term concentration of As to between 40% and 70% of the initial concentrations over the 10 ka simulation period. Based on these simulations, the As concentrations in the regional groundwater, 50 m down gradient of the tailings facility, should be maintained at background concentrations of 0.001 mg/L over the 10 ka period. These findings suggest the engineered in-pit disposal of U mine tailings can provide long-term protection for the local groundwater regime from As contamination. 相似文献
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