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911.
Natalie C. Williams Karen A. Bjorndal Margaret M. Lamont Raymond R. Carthy 《Estuaries and Coasts》2014,37(4):986-994
The foraging ecology and diet of the green turtle, Chelonia mydas, remain understudied, particularly in peripheral areas of its distribution. We assessed the diet of an aggregation of juvenile green turtles at the northern edge of its range during winter months using two approaches. Stomach content analyses provide a single time sample, and stable isotope analyses integrate diet over a several-month period. We evaluated diet consistency in prey choice over time by comparing the results of these two approaches. We examined stomach contents from 43 juvenile green turtles that died during cold stunning events in St. Joseph Bay, Florida, in 2008 and 2011. Stomach contents were evaluated for volume, dry mass, percent frequency of occurrence, and index of relative importance of individual diet items. Juvenile green turtles were omnivorous, feeding primarily on seagrasses and tunicates. Diet characterizations from stomach contents differed from those based on stable isotope analyses, indicating the turtles are not feeding consistently during winter months. Evaluation of diets during warm months is needed. 相似文献
912.
I. P. Williams 《Astrophysics and Space Science》1972,18(1):223-225
The accumulation of floccules into protoplanets is discussed, and it is pointed out that the simplifications which have been introduced into recent numerical models may result in the incorrect conclusion being reached. 相似文献
913.
914.
V. A. Williams 《The Photogrammetric Record》1961,3(18):551-552
915.
K. Stephan R. Jaumann R. Wagner M. C. De Sanctis E. Palomba A. Longobardo D. A. Williams K. Krohn F. Tosi L. A. McFadden F. G. Carrozzo F. Zambon E. Ammannito J.‐P. Combe K.‐D. Matz F. Schulzeck I. von der Gathen T. Roatsch C. A. Raymond C. T. Russell 《Meteoritics & planetary science》2018,53(9):1866-1883
Impact crater Dantu not only exhibits a very complex geological history but also shows an exceptional heterogeneity of its surface composition. Because of its location within a low‐lying region named Vendimia Planitia, which has been proposed to represent an ancient impact basin, Dantu possibly offers a window into the composition of Ceres’s deeper crust, which apparently is enriched in ammonia. Local concentration of carbonates within Dantu or its ejecta blanket may be either exposed or their emplacement induced by the Dantu impact event. Because carbonates can be seen along Dantu's crater walls, exposed due to recent slumping, but also as fresh spots or clusters of spots scattered across the surface, the deposition/formation of carbonates took place over a long time period. The association of several bright spots enriched in carbonates with sets of fractures on Dantu's floor might be accidental. Nevertheless, its morphological and compositional similarity to the faculae in Ceres’s prominent impact crater Occator including its hydrated state does not exclude a cryo‐volcanic origin, i.e., upwelling of carbonate‐enriched brines influenced by H2O ice in the subsurface. Indeed, an isolated H2O ice spot can be identified near Dantu, which shows that ice still exists in Ceres’s subsurface at midlatitudes and that it can exist on the surface for a longer period of time. 相似文献
916.
On the ejection velocity of meteoroids from comets 总被引:1,自引:0,他引:1
Yuehua Ma I. P. Williams Wenping Chen 《Monthly notices of the Royal Astronomical Society》2002,337(3):1081-1086
917.
Michael R. Helfert Kamlesh P. Lulla Victor S. Whitehead M. Justin Wilkinson Donald E. Williams Michael J.. McCulley 《国际地球制图》2013,28(3):65-79
Abstract Although high‐resolution microwave synthetic aperture radar (SAR) sensors possess all‐weather capability for mapping soil moisture from spaceborne platforms, continuous temporal and spatial monitoring of this important hydrological parameter has been relatively limited. However, the recent launch of operational SAR sensors aboard various satellites have made possible synoptic soil moisture monitoring a reality. Such systems operate over a wide range of frequencies, look angles, and polarization combinations, and thus show synergistic advantages when combined for estimating soil moisture patterns. Two soil moisture inversion algorithms have been developed using as inputs radar backscattering data at L, S, and C bands in the microwave frequency range. These models have been tested using radar image simulation with speckle added. It is observed that the neural network algorithm yields superior results in mapping actual soil moisture patterns over the linear statistical inversion technique, although both models show comparable errors in soil moisture estimation. We infer that using statistical estimation errors alone for comparison purposes may lead to erroneous conclusions regarding the advantages of one soil moisture inversion algorithm over another. 相似文献
918.
C. Winkler K. Bennett L. O. Hanlon K. S. O'Flaherty O. R. Williams R. M. Kippen J. Ryan W. Collmar V. Schönfelder H. Steinle W. Hermsen 《Astrophysics and Space Science》1995,231(1-2):153-156
COMPTEL on board CGRO has observed a very strong (S[> 0.3 MeV] = 2.03 × 10–4 erg cm–2), complex, and long lasting (162 s) gamma-ray burst on February 17, 1994 (GRB 940217). Temporal fluctuations occur on timescales as short as 100 ms. Hard-to-soft spectral evolution has been observed during the burst emission and also within individual peaks. The photon spectra obtained within the 6 peaks can be modelled by single power law spectra and by broken power laws with break energies at around 1 MeV. The best-fit power law slopes vary between 1.1 and 3.5 throughout the event. The burst is located at [
2000,
2000] = [29.5°, 3.8°] with a 3 error radius of 0.9°. COMPTEL does not detect any significant post-burst emission (as reported by EGRET) at low energies (< 30 MeV), and our upper limits are marginally consistent with the EGRET detections. Using high energy spectral and temporal information, distance limits to GRB 940217 have been derived. 相似文献
919.
920.
Stuart Corbridge Glyn Williams Manoj Srivastava René Véron 《Singapore journal of tropical geography》2003,24(2):242-257
This paper considers some practical problems associated with organising large‐scale comparative field research in eastern India. The focus of the paper is on the use of brainstorming and “modified logframes” as two means by which hypotheses about the working of the local state from the point of view of the rural poor could be turned into concrete field questions. The paper is less concerned with ethical and positional issues relating to team‐based research in “the tropics” (on this, see Williams et al., 2003a) than with the equally important if apparently more prosaic issues relating to the flawed but necessary search for objectivity and rigour in comparative field studies. 相似文献