A High-Eccentricity Low-Mass Companion to HD 89744     

Korzennik SG  Brown TM  Fischer DA  Nisenson P  Noyes RW 《The Astrophysical journal》2000,534(2):L147-L150

We present deep Hubble Space Telescope (HST) imaging, as well as ground-based imaging and spectroscopy, of the optical afterglow associated with the long-duration gamma-ray burst GRB 990712 and its host galaxy. The data were obtained 48-123 days after the burst occurred. The magnitudes of the host (R=21.9, V=22.5) and optical afterglow (R=25.4, V=25.8, 47.7 days after the burst) favor a scenario in which the optical light follows a pure power-law decay with an index of alpha approximately -1.0. We find no evidence for a contribution from a supernova like SN 1998bw. This suggests that either there are multiple classes of long-duration gamma-ray bursts or that the peak luminosity of the supernova was more than 1.5 mag fainter than SN 1998bw. The HST images and EFOSC2 spectra indicate that the gamma-ray burst was located in a bright, extended feature (possibly a star-forming region) 1.4 kpc from the nucleus of a 0.2L*B galaxy at z=0.434, possibly a Seyfert 2 galaxy. The late-time afterglow and host galaxy of GRB 990712 bear some resemblance to those of GRB 970508.  相似文献   

Persistent organic pollutants and stable isotopes in biopsy samples (2004/2006) from Southern Resident killer whales     

Krahn MM  Hanson MB  Baird RW  Boyer RH  Burrows DG  Emmons CK  Ford JK  Jones LL  Noren DP  Ross PS  Schorr GS  Collier TK 《Marine pollution bulletin》2007,54(12):1903-1911

“Southern Resident” killer whales include three “pods” (J, K and L) that reside primarily in Puget Sound/Georgia Basin during the spring, summer and fall. This population was listed as “endangered” in the US and Canada following a 20% decline between 1996 and 2001. The current study, using blubber/epidermis biopsy samples, contributes contemporary information about potential factors (i.e., levels of pollutants or changes in diet) that could adversely affect Southern Residents. Carbon and nitrogen stable isotopes indicated J- and L-pod consumed prey from similar trophic levels in 2004/2006 and also showed no evidence for a large shift in the trophic level of prey consumed by L-pod between 1996 and 2004/2006. ∑PCBs decreased for Southern Residents biopsied in 2004/2006 compared to 1993–1995. Surprisingly, however, a three-year-old male whale (J39) had the highest concentrations of ∑PBDEs, ∑HCHs and HCB. POP ratio differences between J- and L-pod suggested that they occupy different ranges in winter.  相似文献   

中国典型煤的激光显微荧光特征及R—I—VRo相关模式图的建立   总被引：1，自引：0，他引：1  

刘祖发 Wil.  RW 《沉积学报》1999,17(12):687-690

利用激光显微荧光探针、ＭＰＶ－Ⅲ显微光度计等方法系统地研究了我国典型煤的激光显微荧光特征,并运用二项参数（Ｉ４００、Ｒ）与澳大利亚同期煤进行了对比,结果发现我国煤的Ｉ４００普遍比澳大利亚同期煤高,据此,建立了我国煤的Ｒ－Ｉ－ＶＲｏ相关模式图,该图对于正常评价我国烃源岩成熟度具有重要意义。  相似文献   

Air-based measurements of permeability in pebbly sands     

Conrad CM  Ritzi RW  Dominic DF 《Ground water》2008,46(1):103-112

We considered small-scale measurement of permeability in pebbly sands having coarser grains supported in a finer grained matrix (fine packing). Our central question was whether air-based measurements are representative if made with a permeameter tip seal pressed in the sand matrix. We created pebbly sands and variably sorted sands, with systematic variation in aspects of their fine packing. We made permeability measurements by inserting the tip seal of an air permeameter in the matrix of these samples and compared them to the permeability of the composite sample determined by both water-based methods and theory. The air-permeameter measurements made in this way represent the permeability of the composite mixtures of coarser and finer grains and allow for the discernment of permeability between samples with different matrix compositions, ranging from fine to coarse sand. Furthermore, the collective results show that permeability differences in the pebbly sands and variably sorted sands with fine packing, however measured, are primarily due to differences in matrix permeability and not due to differences in the size or the percentage of the coarser grains.  相似文献   

Methodology for comparing source and plume remediation alternatives   总被引：2，自引：0，他引：2  

Falta RW 《Ground water》2008,46(2):272-285

It is often difficult at contaminated sites to decide whether remediation effort should be focused on the contaminant source, the dissolved plume, or on both zones. The decision process at these sites is hampered by a lack of quantitative tools for comparing remediation alternatives. A new screening-level mass balance approach is developed for simulating the transient effects of simultaneous ground water source and plume remediation. The contaminant source model is based on a power function relationship between source mass and source discharge, and it can consider partial source remediation at any time after the initial release. The source model serves as a time-dependent mass flux boundary condition to a new analytical plume model, where flow is assumed to be one dimensional, with three-dimensional dispersion. The plume model simulates first-order sequential decay and production of several species, and the decay rates and parent/daughter yield coefficients are variable functions of time and distance. This new method allows for flexible simulation of natural attenuation or remediation efforts that enhance plume degradation. The plume remediation effort may be temporary or delayed in time, limited in space, and it may have different chemical effects on different contaminant species in the decay chain.  相似文献   

The overlooked role of the ocean in mercury cycling in the Arctic     

Macdonald RW  Wang F  Stern G  Outridge P 《Marine pollution bulletin》2008,56(12):1963-1965

The rapid and high bioaccumulation of mercury in marine mammals and its spatial and temporal variations have been a major puzzle in the Arctic. While extensive efforts have been focussed on the monitoring and chemistry of atmospheric mercury depletion events, a recent mass budget estimate of mercury in the Arctic suggests that we have overlooked the role of the ocean itself. Only through focussed studies on Hg dynamics in the Arctic Ocean under a changing climate are we going to understand what the risk of mercury is to those marine ecosystems and the people who rely on them.  相似文献   

花岗岩底辟构造的识别     

Engl.  RW  汤葵联 《国土资源信息化》1992,(1):12-14

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高分辨率折射法地震数据的采集与解释     

Lank.  RW 李文琦 《水文地质技术方法》1992,(25):22-44,77

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花岗岩底辟的识别     

Engl.  RW 汪雄武 《国外花岗岩类地质与矿产》1992,(2):14-18

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燧石和页岩中的稀土元素不同海相沉积环境...     

Murr.  RW 叶杰 《国外地质(北京)》1992,(5):41-46

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