Ionospheric signature of surface mine blasts from Global Positioning System measurements     

Eric Calais  J. Bernard Minster  Michelle Hofton  & Michael Hedlin 《Geophysical Journal International》1998,132(1):191-202

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Remediating Ground Water with Zero-Valent Metals: Chemical Considerations in Barrier Design   总被引：2，自引：0，他引：2  

Paul G. Tratnyek  Timothy L. Johnson  Michelle M. Scherer  Gerald R. Eykholt 《Ground Water Monitoring & Remediation》1997,17(4):108-114

To gain perspective and insight into the performance of permeable reactive barriers containing granular iron metal, it is useful to compare the degradation kinetics of individual chlorinated solvents over a range of operating conditions. Pseudo first-order disappearance rate constants normalized to iron surface area concentration (k_SA) recently have been reported for this purpose. This paper presents the results of further exploratory data analysis showing the extent to which variation in k_SA is due to initial halocarbon concentration, iron type, and other factors. To aid in preliminary design calculations, representative values of k_SA and a reactive transport model have been used to calculate the minimum barrier width needed for different ground water flow velocities and degrees of halocarbon conversion. Complete dechlorination of all degradation intermediates requires a wider treatment zone, but the effect is not simply additive because degradation occurs by sequential and parallel reaction pathways.  相似文献   

Planetary perturbations of the Moon in ELP 2000     

Jean Chapront  Michelle Chapront-Touze 《Celestial Mechanics and Dynamical Astronomy》1982,26(1):83-94

A new solution for the planetary perturbations of the Moon is being built in the frame of ELP 2000, using Bretagnon's planetary theories, and achieved at the first order. It contains the two actions commonly distinguished: direct and indirect. The internal precision of computation is 2×10^–6 arcsec. First-order planetary perturbations, in the direct case (Venus & Mars), have been compared to Standaert's solution. The major discrepancy reaches 70 cm in the longitude of Venus. Perturbations of the second order with respect to planetary masses, have been undertaken and illustrations are given. Finally, new values for the perigee and node motions are proposed.Proceedings of the Conference on Analytical Methods and Ephemerides: Theory and Observations of the Moon and Planets. Facultés universitaires Notre Dame de la Paix, Namur, Belgium, 28–31 July, 1980.  相似文献   

Nitrogen microanalysis of glass inclusions in chondritic olivines by nuclear reaction     

Maria Eugenia Varela  Michelle Bonnin- Mosbah  Jean Paul Gallien 《Geochimica et cosmochimica acta》2003,67(6):1255-1265

Measured were the abundance and distribution of nitrogen in glasses of glass inclusions in olivines of CV3, CO3, CR, C4, CH3, and LL chondritic meteorites by means of the ¹⁴N(d, p)¹⁵N nuclear reaction. Similar to what was observed with carbon, nitrogen is present in low concentrations (<20 ppm) in the structure of olivines but can by stored in variable amounts in glasses of glass inclusions. These primitive glasses, characterized by a Si-Al-Ca-rich composition, have highly variable nitrogen contents (30 to 1500 ppm) and highly inhomogeneous nitrogen distribution. Nitrogen contents are independent of the chemical composition of the glasses. The heterogeneous distribution is a common feature of all studied inclusions, as is evidenced by the variable contents of nitrogen in glass inclusions occurring in the same olivine grain. Nitrogen heterogeneity is suggestive of trapping of solid nitrogen carrier phases during formation of the constituents of chondrules. However, part of the originally trapped nitrogen appears to have been lost, possibly, by ulterior oxidation and subsequent transformation into volatile species.  相似文献   

Total mercury and methylmercury in sediments near offshore drilling sites in the Gulf of Mexico     

John H. Trefry  Robert P. Trocine  Michelle L. McElvaine  Robert D. Rember  Lucas T. Hawkins 《Environmental Geology》2007,53(2):375-385

Concentrations of total Hg in sediments near six drilling sites in the Gulf of Mexico were elevated well above average background values of 40–80 ng/g. The excess Hg was associated with barite from discharged drilling mud. In contrast with total Hg, concentrations of methylmercury (MeHg) in these sediments did not vary significantly at nearfield (<100 m) versus farfield (>3 km) distances from the drilling sites. Observed variability in concentrations of MeHg were related to local differences in redox state in the top 10 cm of sediment. Low to non-detectable concentrations of MeHg were found in nearfield sediments that were anoxic, highly reducing and contained abundant H₂S. At most drilling sites, nearfield samples with high concentrations of total Hg (>200 ng/g) had similar or lower amounts of MeHg than found at background (farfield) stations. Higher values of MeHg were found in a few nearfield sediments at one site where concentrations of TOC were higher and where sediments were anoxic and moderately reducing. Overall, results from this study support the conclusion that elevated concentrations of MeHg in sediments around drilling sites are not a common phenomenon in the Gulf of Mexico.  相似文献   

A portable rainfall simulator for field assessment of splash and slopewash in remote locations   总被引：1，自引：0，他引：1  

Michelle A. Clarke  Rory P. D. Walsh 《地球表面变化过程与地形》2007,32(13):2052-2069

This paper describes the design, operation and performance of a field‐portable ‘drip‐type’ simulator and erosion measurement system. The system was constructed specifically for soil erosion research in the humid tropics and has been used extensively in Malaysian Borneo. The simulator is capable of producing replicable storms of up to 200 mm h^?1 intensity and 20–30 minutes duration with a drop‐size distribution close to that of natural storms of such intensity (D₅₀ of simulated rainfall is 4·15 mm at 200 mm h^?1 and 3·65 mm at 160 mm h^?1, D⁵⁰ measured during natural rainfall = 3·25 mm). The simulator is portable and simply constructed and operates without a motor or electronics, thus making it particularly useful in remote, mountainous areas. The erosion measurement system allows assessment of: (1) rainsplash detachment and net downslope transport from the erosion plot; (2) slopewash (erosion transported by overland flow); and (3) infiltration capacity and overland flow. The performance of the simulator–erosion system compared with previous systems is assessed with reference to experiments carried out in primary and regenerating tropical rainforest at Danum Valley (Malaysian Borneo). The system was found to compare favourably with previous field simulators, producing a total storm kinetic energy of 727 J m^?2 (over a 20‐minute storm event) and a kinetic energy rate of 0·61 J m^?2 s^?1, approximately half that experienced on the ground during a natural rainfall event of similar intensity, despite the shorter distance to the ground. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Comment on “Holocene aridity and storm phases, Gulf and Atlantic coasts, USA” by Ervin G. Otvos, 2005, Quaternary Research 63, 368-373     

Michelle Goman 《Quaternary Research》2006,66(1):182-184

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Land, ethnic, and gender change: Transnational migration and its effects on Guatemalan lives and landscapes   总被引：1，自引：0，他引：1  

Matthew J. Taylor  Michelle J. Moran-Taylor 《Geoforum》2006,37(1):41-61

Migration to the United States of America from Guatemala effects many aspects of Guatemalan life. We document, through extensive ethnographic fieldwork, how migrants and their remittances effect gender relations, ethnicity, land use, and land distribution. Our evidence is drawn from research in four communities. San Pedro Pinula and Gualán represent communities of eastern Guatemala. San Cristóbal Totonicapán is an Indigenous town in Guatemala’s western highlands, and San Lucas is a lowland frontier community in the Guatemalan department of Ixcán, which borders Chiapas, Mexico. Our results reveal that migrants and their remittances, both social and tangible, result in significant changes in land use and land distribution in Ixcán. Migrant money permits the conversion of rainforest into cattle pasture and also results in the accumulation of land in the hands of migrants. In terms of land use, we see in San Pedro Pinula that migrant money also allows the Pokoman Maya to make small entries into the Ladino (non-indigenous) dominated cattle business. In San Pedro Pinula, the migration and return of Maya residents also permits them to slowly challenge ethnic roles that have developed over the last five centuries. When we look at how migration effects gender roles in Gualán and San Cristóbal we also note that migration and social remittances permit a gradual challenge and erosion of traditional gender roles in Guatemala. We point out, however, that migration-related changes to traditional gender and ethnic roles is gradual because migrants, despite their increased earnings and awareness, run into a social structure that resists rapid change. This is not the case when we examine land transformations in Ixcán. Here, migrants encounter few barriers when they attempt to put their new money and ideas to work. Despite the advantages that migration brings to many families, especially in the face of a faltering national economy and state inactivity regarding national development, we conclude that migration and remittances do not result in community or nation-wide development. At this stage migrant remittances are used for personal advancement and very little money and effort is invested in works that benefit communities or neighborhoods. We call for continued studies of the effects of international migration on Guatemalan hometowns that build on our initial studies to better understand the longer-term ramifications of migration in a country where no community is without migrants.  相似文献   

Excess Xenon-128 in meteorites     

M. N. Rao  R. S. Clark  P. K. Kuroda 《Astrophysics and Space Science》1968,1(4):513-518

Using known compositions of primordial and spallation xenon components in several meteorites, the neutron produced Xe¹²⁸ⁿ has been resolved. For obtaining the value for spallation produced (Xe¹²⁸/Xe¹³⁰)_c, the meteorites with low iodine content and high spallation contribution are considered. Using these data, the neutron densities in several meteorites due to cosmic-ray exposure are calculated and their significance is qualitatively discussed.  相似文献   

Effect of Bioremediation on the Microbial Community in Oiled Mangrove Sediments   总被引：10，自引：0，他引：10  

Michelle A Ramsay  Richard P.J Swannell  Warren A Shipton  Norman C Duke  Russell T Hill   《Marine pollution bulletin》2000,41(7-12):413-419

Bioremediation was conducted in the field on a mature Rhizophora stylosa mangrove stand on land to be reclaimed near Fisherman’s Landing Wharf, Gladstone Australia. Gippsland crude oil was added to six large plots (>40 m²) and three plots were left untreated as controls. Bioremediation was used to treat three oiled plots and the remaining three were maintained as oiled only plots. The bioremediation strategy consisted of actively aerating the sediment and adding a slow-release fertilizer in order to promote oil biodegradation by indigenous micro-organisms. Oil addition stimulated the numbers of alkane-degrading bacteria slightly to levels of 10⁴–10⁵/g sediment. Bioremediation of the oiled sediment had a marked effect on the alkane-degrading population, increasing the population size by three orders of magnitude from 10⁵ to 10⁸ cells/g of sediment. An effect of bioremediation on the growth of aromatic-degraders was detected with numbers of aromatic-degraders increasing from 10⁴ to 10⁶ cells/g of sediment. Active aeration and nutrient addition significantly stimulated the growth of hydrocarbon-degraders in oiled mangrove sediment in the field.  相似文献