Global distribution of neutrons from Mars: results from Mars odyssey     

Feldman WC  Boynton WV  Tokar RL  Prettyman TH  Gasnault O  Squyres SW  Elphic RC  Lawrence DJ  Lawson SL  Maurice S  McKinney GW  Moore KR  Reedy RC 《Science (New York, N.Y.)》2002,297(5578):75-78

Global distributions of thermal, epithermal, and fast neutron fluxes have been mapped during late southern summer/northern winter using the Mars Odyssey Neutron Spectrometer. These fluxes are selectively sensitive to the vertical and lateral spatial distributions of H and CO2 in the uppermost meter of the martian surface. Poleward of +/-60 degrees latitude is terrain rich in hydrogen, probably H2O ice buried beneath tens of centimeter-thick hydrogen-poor soil. The central portion of the north polar cap is covered by a thick CO2 layer, as is the residual south polar cap. Portions of the low to middle latitudes indicate subsurface deposits of chemically and/or physically bound H2O and/or OH.  相似文献   

Detecting energy emissions from a rotating black hole     

van Putten MH  Levinson A 《Science (New York, N.Y.)》2002,295(5561):1874-1877

The rotational energy of a black hole surrounded by a torus is released through several channels. We have determined that a minor fraction of the energy is released in baryon-poor outflows from a differentially rotating open magnetic flux tube, and a major fraction of about eta/2 is released in gravitational radiation by the torus with angular velocity eta similar 0.2 to 0.5 relative to that of the black hole. We associate the energy emitted in baryon-poor outflows with gamma-ray bursts. The remaining fraction is released in torus winds, thermal emissions, and (conceivably) megaelectron-volt neutrino emissions. The emitted gravitational radiation can be detected by gravitational wave experiments and provides a method for identifying Kerr black holes in the Universe.  相似文献   

Irrigation scheduling for potatoes in Michigan     

Maurice L. Vitosh 《American Journal of Potato Research》1984,61(4):205-213

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Grazing as a management tool in dune grasslands: Evidence of soil and scale dependence of the effect of large herbivores on plant diversity     

Pejman Tahmasebi Kohyani  Beatrijs Bossuyt  Maurice Hoffmann 《Biological conservation》2008,141(6):1687-1694

In nature management, the introduction of large herbivores into human-influenced grasslands is thought to be effective to maintain or enhance plant diversity. In order to test the validity of this assumption, we studied the effect of grazing by large herbivores on plant species richness and community heterogeneity across a soil acidity gradient at different spatial scales in dry coastal dune grasslands in western Belgium and north-western France. The effect of grazing on plant richness varied with scale and soil acidity. Grazing had a predominantly positive effect on plant species richness in all habitats at the small scale (0.25 × 0.25 m). However, at site scale (8 × 8 m) it had only positive effects in grasslands with higher soil pH (6-7.4). Similarly, grazing resulted in a homogenization of grassland vegetation at lower pH, while heterogeneity increased with grazing on soil with higher pH. In general, grazing increased the number of rare species, independent of soil pH. The results confirm that the impact of grazing on plant diversity depends on the scale considered and that the effects further depend on soil acidity which was correlated to biomass production at the given soil pH range in this study. Although grazing seems an appropriate management tool to maintain and even enhance plant biodiversity under many circumstances, it may negatively affect plant species richness, where soil resources limit plant biomass production.  相似文献   

Molecular Characterisation of 18 Pratylenchus Species Using rDNA Restriction Fragment Length Polymorphism     

LievenWaeyenberge  AlexanderRyss  MauriceMoens  JorgePinochet  ThierryC.Vrain 《云南农业大学学报(自然科学版)》1999,14(Z1):128-128

 rDNA RFLP is a reliable method for identification purposes, and a powerful tool to analyse genetic variation in nematodes.  相似文献   

Effects of Leachate Irrigation on Landfill Vegetation and Subsequent Methane Emissions     

Maurice  C.  Ettala  M.  Lagerkvist  A. 《Water, air, and soil pollution》1999,113(1-4):203-216

Short-rotation tree forests are irrigated with landfill leachate to reduce both leachate volume and nutrient content. It is of interest both for leachate treatment and energy recovery to optimise the productivity of such plantations. This study's aim was to investigate the effects of irrigation on soil quality, tree growth and on emissions of landfill gas (LFG) produced in the wastes. Soils irrigated with leachate had a higher average nutrient and organic matter contents, and a lower dry solids content. Larger trees occur on plots irrigated with leachate, presumably due to the positive effect of water and nutrient supply. The willows used in this experiment seemed to be tolerant of high carbon dioxide concentrations, as no statistically effect arising from LFG emissions could be linked to tree growth. Methane oxidation levels between 50 and 950 mol m^-2 yr^-1 were observed. The positive correlation between soil methane oxidation capacity and tree presence is an interesting perspective on reduction of methane emissions by landfill's top cover vegetation type. Optimising methane oxidation using vegetation as a ‘cover crop’ could reduce the amount of methane discharged into the atmosphere.  相似文献