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311.
Matt Hilton Chris Collins Roberto De Propris Ivan K. Baldry Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Matthew Colless Warrick J. Couch Gavin B. Dalton Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Carole A. Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve J. Maddox Darren Madgwick Peder Norberg John A. Peacock Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2005,363(2):661-674
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R. Maas R. D. Loss K. J. R. Rosman J. R. De Laeter R. S. Lewis G. R. Huss G. W. Lugmair 《Meteoritics & planetary science》2001,36(6):849-858
Abstract— ‐The elemental and isotopic abundances of Te and Pd have been measured by thermal ionization mass spectrometry in a purified sample of interstellar nanodiamonds from the Allende meteorite, after combustion of the diamonds in an oxygen plasma. Small positive anomalies were found in 128Te (4.0 ± 1.5 %0) and 130Te (9.3 ± 2.8 %0) from three analyses of the Allende nanodiamond sample EB, and in 110Pd (9.4 ± 5.7 %0) from two analyses of the same sample. No other anomalies of a significant nature were found in either Te or Pd. These results are consistent with the neutron burst model (Meyer et al., 2000), and the r‐process based rapid separation model of Ott (1996) in that 128, 130Te and 110Pd are enhanced relative to their solar abundances. However, in the framework of the neutron burst model, some separation between stable products and radioactive precursors may be required in order to be consistent with the full data set of Te isotopes. In the framework of the rapid separation scenario, our data suggests a separation time of approximately 4000 s, based on the magnitudes of the precursor life‐times for 128Te and 130Te. The elemental abundance ratio Te‐H/Xe‐H agrees with the prediction of the rapid separation model, provided little fractionation occurred during trapping of the exotic components by the diamonds, but differs significantly from expectations based on the neutron burst model. Differences in the inferred 128Te/130Te ratio between our work and that of Richter et al. (1998) point to the need for further investigations. 相似文献
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V. R. Eke Carlton M. Baugh Shaun Cole Carlos S. Frenk Peder Norberg John A. Peacock Ivan K. Baldry Joss Bland-Hawthorn Terry Bridges Russell Cannon Matthew Colless Chris Collins Warrick Couch Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Karl Glazebrook Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Darren Madgwick Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,348(3):866-878
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Timothy S. Collett Myung W. LeeWarren F. Agena John J. MillerKristen A. Lewis Margarita V. ZyrianovaRay Boswell Tanya L. Inks 《Marine and Petroleum Geology》2011,28(2):279-294
In the 1960s Russian scientists made what was then a bold assertion that gas hydrates should occur in abundance in nature. Since this early start, the scientific foundation has been built for the realization that gas hydrates are a global phenomenon, occurring in permafrost regions of the arctic and in deep water portions of most continental margins worldwide. In 1995, the U.S. Geological Survey made the first systematic assessment of the in-place natural gas hydrate resources of the United States. That study suggested that the amount of gas in the gas hydrate accumulations of northern Alaska probably exceeds the volume of known conventional gas resources on the North Slope. Researchers have long speculated that gas hydrates could eventually become a producible energy resource, yet technical and economic hurdles have historically made gas hydrate development a distant goal. This view began to change in recent years with the realization that this unconventional resource could be developed with existing conventional oil and gas production technology. One of the most significant developments was the completion of the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well on the Alaska North Slope, which along with the Mallik project in Canada, have for the first time allowed the rational assessment of gas hydrate production technology and concepts. Almost 40 years of gas hydrate research in northern Alaska has confirmed the occurrence of at least two large gas hydrate accumulations on the North Slope. We have also seen in Alaska the first ever assessment of how much gas could be technically recovered from gas hydrates. However, significant technical concerns need to be further resolved in order to assess the ultimate impact of gas hydrate energy resource development in northern Alaska. 相似文献
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Randall B. Wayth Stephen J. Warren Geraint F. Lewis Paul C. Hewett 《Monthly notices of the Royal Astronomical Society》2005,360(4):1333-1344
We perform a detailed analysis of the optical gravitational lens ER 0047–2808 imaged with the Wide Field Planetary Camera 2 on the Hubble Space Telescope . Using software specifically designed for the analysis of resolved gravitational lens systems, we focus on how the image alone can constrain the mass distribution in the lens galaxy. We find that the data are of sufficient quality to strongly constrain the lens model with no a priori assumptions about the source. Using a variety of mass models, we find statistically acceptable results for elliptical isothermal-like models with an Einstein radius of 1.17 arcsec. An elliptical power-law model (Σ∝ R −β ) for the surface mass density favours a slope slightly steeper than isothermal with β= 1.08 ± 0.03 . Other models including a constant mass-to-light ratio (M/L), pure Navarro, Frenk & White halo and (surprisingly) an isothermal sphere with external shear are ruled out by the data. We find the galaxy light profile can only be fit with a Sérsic plus point-source model. The resulting total M/L B contained within the images is 4.7 h 65 ± 0.3 . In addition, we find the luminous matter is aligned with the total mass distribution within a few degrees. This is the first time a resolved optical gravitational lens image has been quantitatively reproduced using a non-parametric source.
The source, reconstructed by the software, is revealed to have two bright regions, with an unresolved component inside the caustic and a resolved component straddling a fold caustic. The angular size of the entire source is ∼0.1 arcsec and its (unlensed) Lyα flux is 3 × 10−17 erg s−1 cm−2 . 相似文献
The source, reconstructed by the software, is revealed to have two bright regions, with an unresolved component inside the caustic and a resolved component straddling a fold caustic. The angular size of the entire source is ∼0.1 arcsec and its (unlensed) Lyα flux is 3 × 10
320.