深层抽水试验的评价     

Tripp  DW 王伟礼 《国外煤田地质》1991,(3):38-45

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The dust distribution within the inner coma of comet P/Halley 1982i: encounter by Giotto's impact detectors     

McDonnell JA  Alexander WM  Burton WM  Bussoletti E  Evans GC  Evans ST  Firth JG  Grard RJ  Green SF  Grun E  Hanner MS  Hughes DW  Igenbergs E  Kissel J  Kuczera H  Lindblad BA  Langevin Y  Mandeville JC  Nappo S  Pankiewicz GS  Perry CH  Schwehm GH  Sekanina Z  Stevenson TJ  Zarnecki JC et AL 《Astronomy and Astrophysics》1987,187(1-2):719-741

Analysis of the data from Giotto's Dust Impact Detection System experiment (DIDSY) is presented. These data represent measurement of the size of dust grains incident on the Giotto dust shield along its trajectory through the coma of comet P/Halley on 1986 March 13/14. First detection occurred at some 287000 km distance from the nucleus on the inbound leg; the majority of the DIDSY subsystems remained operational after closest approach (604 km) yielding the last detection at about 202000 km from the nucleus. In order to improve the data coverage (and especially for the smallest grains, to approximately 10(-19) kg particle mass), data from the PIA instrument has been combined with DIDSY data. Flux profiles are presented for the various mass channels showing, to a first approximation, a 1/R2 flux dependence, where R is the distance of the detection point from the cometary nucleus, although significant differences are noted. Deviations from this dependence are observed, particularly close to the nucleus. From the flux profiles, mass and geometrical area distributions for the dust grains are derived for the trajectory through the coma. Groundbased CCD imaging of the dust continuum in the inner coma at the time of encounter is also used to derive the area of grains intercepted by Giotto. The results are consistent with the area functions derived by Giotto data and the low albedo of the grains deduced from infrared emission. For the close encounter period (-5 min to +5 min), the cumulative mass distribution function has been investigated, initially in 20 second periods; there is strong evidence from the data for a steepening of the index of the mass distribution for masses greater than 10(-13) kg during passage through dust jets which is not within the error limits of statistical uncertainty. The fluences for dust grains along the entire trajectory is calculated; it is found that extrapolation of the spectrum determined at intermediate masses (cumulative mass index alpha = 0.85) is not able to account for the spacecraft deceleration as observed by the Giotto Radio Science Experiment and by ESOC tracking operations. Data at large masses (>10(-8) kg) recently analysed from the DIDSY data set show clear evidence of a decrease in the mass distribution index at these masses within the coma, and it is shown that such a value of the mass index can provide sufficient mass for consistency with the observed deceleration. The total particulate mass output from the nucleus of comet P/Halley at the time of encounter would be dependent on the maximum mass emitted if this change in slope observed in the coma were also applicable to the emission from the nucleus; this matter is discussed in the text. The flux time profiles have been converted through a simple approach to modeling of the particle trajectories to yield an indication of nucleus surface activity. There is indication of an enhancement in flux at t approximately -29 s corresponding to crossing of the dawn terminator, but the flux detected prior to crossing of the dawn terminator is shown to be higher than predicted by simple modelling. Further enhancements corresponding to jet activity are detected around +190 s and +270 s.  相似文献   

Analysis of multiple enteric viral targets as sewage markers in coral reefs     

Lipp EK  Futch JC  Griffin DW 《Marine pollution bulletin》2007,54(12):1897-1902

Water and coral mucus samples were collected from throughout the Florida Keys National Marine Sanctuary and the Dry Tortugas for three years and were analyzed for human enteric viruses (enteroviruses, noroviruses, hepatitis A virus and adenoviruses) as conservative markers of human sewage using molecular methods. Of the 100 coral and water samples collected, 40 contained genetic material from one or more human enteric viruses. DNA-based adenoviruses were detected widely, in 37.8% of samples and at 91% of stations, including ‘pristine’ reefs in the Dry Tortugas; however, the detection rate was 12% for the RNA-based enteroviruses and noroviruses (hepatitis A virus was never detected). The disparity between the prevalence of RNA- and DNA-based viruses suggests the need for additional work to determine the utility of adenovirus as marker of human sewage.  相似文献   

Occurrence and seasonal variations of algal toxins in water, phytoplankton and shellfish from North Stradbroke Island, Queensland, Australia   总被引：4，自引：0，他引：4  

Takahashi E  Yu Q  Eaglesham G  Connell DW  McBroom J  Costanzo S  Shaw GR 《Marine environmental research》2007,64(4):429-442

A number of marine microalgae are known to produce toxins that can accumulate in shellfish and when eaten, lead to toxic and potentially fatal reactions in humans. This paper reports on the occurrence and seasonal variations of algal toxins in the waters, phytoplankton and shellfish of Southeast Queensland, Australia. These algal toxins include okadaic acid (OA), domoic acid (DA), gymnodimine (GD), pectenotoxin-2 (PTX-2) and pectenotoxin-2-seco acid (PTX-2-SA), which were detected in the sampled shellfish and phytoplankton, via HPLC-MS/MS. Dissolved OA, PTX-2 and GD were also detected in the samples collected from the water column. This was the first occasion that DA and GD have been reported in shellfish, phytoplankton and the water column in Queensland waters. Phytoplankton tows contained both the toxic Dinophysis and Pseudo-nitzschia algae species, and are suspected of being the most likely producers of the OA, PTX-2s and DA found in shellfish of this area. The number of cells, however, did not correlate with the amount of toxins present in either shellfish or phytoplankton. This indicates that toxin production by algae varies with time and the species present and that number of cells alone cannot be used as an indicator for the presence of toxins. The presence of OA and PTX-2s were more frequently seen in the summer, while DA and GD were detected throughout the year and without any obvious seasonal patterns.  相似文献   

大规模反演问题的广义子空间方法     

Olde.  DW 周子勇 《物探化探译丛》1995,(1):12-19

子空间方法比起传统的高效－牛顿方法的主要优点在于前者只需对一个维数等于子空间维的矩阵进行反演。方法的有效性则主要在于合适地选择基本矢量，用得较多的矢量是那些与数据拟合差的梯度、或目标函数的模型分量的梯度有关的矢量。  相似文献   

香港中生代火成岩U—Pb法年龄测定   总被引：1，自引：0，他引：1  

Davis  DW 《广东地质》1998,13(3):59-68

香港中生代侵入岩和火山岩２２个锆石和独居石新的Ｕ－Ｐｂ年龄,揭示了中侏罗世至早白垩世火山－深成作用分为４期,（１６４．６±０．２）×１０＾６～（１５９．３±０．３）×１０＾６ａ,（１４６．６±０．２）×１０＾６～（１４６．２±０．２）×１０＾６ａ,（１４３．７±０．３）×１０＾６～（１４２．５±０．３）×１０＾６ａ,（１４０．９±０．２）×１０＾６～（１４０．４±０．２）×１０＾６ａ。从最早知道的  相似文献   

地球物理反演在矿产勘查中的应用     

Olden  DW 戚巧俊 《物探化探译丛》1997,(A02):54-59

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Risks posed by trace organic contaminants in coastal sediments in the Pearl River Delta, China   总被引：8，自引：0，他引：8  

Fung CN  Zheng GJ  Connell DW  Zhang X  Wong HL  Giesy JP  Fang Z  Lam PK 《Marine pollution bulletin》2005,50(10):1036-1049

Local marine environments in China's Pearl River Delta (PRD), the most rapidly developing region in one of the world's fastest growing economies, have been experiencing significant environmental stress during the past decades. This investigation was conducted to determine the status and trends of persistence organic pollutants (POPs) such as polycyclic aromatic hydrocarbons (PAHs), petroleum hydrocarbons (PHCs), polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides and dioxin-related compounds in marine sediments collected from sixteen coastal stations in the Pearl River Delta (PRD) in March 2003. Elevated concentrations of PAHs (94-4300 ng/g), PCBs (6.0-290 ng/g), PHCs (14-150 microg/g), and DDTs (1.4-600 ng/g) were detected in sediment samples. In addition, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-like activities in the sediment samples were estimated to range from 0.3 to 440 pg TCDD-EQ/g. Sediments collected from Xiashan contained the greatest concentrations of trace organic contaminations amongst all the sampling stations in the present study. The degree of trace organic contamination was, in general, more severe at stations situated along the west shores of the PRD than their counterparts in the east. A preliminary assessment was performed to examine the probable risks to the marine ecosystem due to POPs. The results showed that OC pesticide contamination in the PRD was particularly serious and might pose a threat to the health of the marine inhabitants.  相似文献   

Analysis of recharge-induced geochemical change in a contaminated aquifer   总被引：1，自引：0，他引：1  

McGuire JT  Long DT  Hyndman DW 《Ground water》2005,43(4):518-530

Recharge events that deliver electron acceptors such as O2, NO3, SO4, and Fe3+ to anaerobic, contaminated aquifers are likely important for natural attenuation processes. However, the specific influence of recharge on (bio)geochemical processes in ground water systems is not well understood. The impact of a moderate-sized recharge event on ground water chemistry was evaluated at a shallow, sandy aquifer contaminated with waste fuels and chlorinated solvents. Multivariate statistical analyses coupled with three-dimensional visualization were used to analyze ground water chemistry data (including redox indicators, major ions, and physical parameters) to reveal associations between chemical parameters and to infer processes within the ground water plume. Factor analysis indicated that dominant chemical associations and their interpreted processes (anaerobic and aerobic microbial processes, mineral precipitation/dissolution, and temperature effects) did not change significantly after the spring recharge event of 2000. However, the relative importance of each of these processes within the plume changed. After the recharge event, the overall importance of aerobic processes increased from the fourth to the second most important factor, representing the variability within the data set. The anaerobic signatures became more complex, suggesting that zones with multiple terminal electron-accepting processes (TEAPs) likely occur in the same water mass. Three-dimensional visualization of well clusters showed that water samples with similar chemical associations occurred in distinct water masses within the aquifer. Water mass distinctions were not based on dominant TEAPs, suggesting that the recharge effects on TEAPs occurred primarily at the interface between infiltrating recharge water and the aquifer.  相似文献   

The Spectroscopic Orbit of the Planetary Companion Transiting HD 209458     

Mazeh T  Naef D  Torres G  Latham DW  Mayor M  Beuzit JL  Brown TM  Buchhave L  Burnet M  Carney BW  Charbonneau D  Drukier GA  Laird JB  Pepe F  Perrier C  Queloz D  Santos NC  Sivan JP  Udry S  Zucker S 《The Astrophysical journal》2000,536(1):L55-L58

Three new silicon-bearing radicals of astrophysical interest, SiCCH and the two nearly isoenergetic isomers SiCN and SiNC, were detected in a laboratory discharge in their X2Pi ground states by Fourier transform microwave and millimeter-wave absorption spectroscopy. Hyperfine structure was observed in the low rotational transitions of the (2)Pi(1/2) ladder, and well-resolved Lambda-doubling was observed in both fine-structure ladders. With the spectroscopic constants derived from the laboratory measurements, the spectra of all three can be calculated to an uncertainty of less than 0.1 km s(-1) in equivalent radial velocity over the entire range of interest to radio astronomers. SiCN, with a dipole moment of 2.9 D, is probably the most promising of the three for astronomical discovery.  相似文献