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11.
S.E. Palmer E.W. Baker L.S. Charney J.W. Louda 《Geochimica et cosmochimica acta》1982,46(7):1233-1241
Analyses of forty-two United States humic coals have revealed a striking divergence between chlorophyll diagenesis in coals when compared to the more widely studied marine sediments, shales, asphalts and petroleums. Porphyrins of humic coals have been found to be dominated by the ETIO-series, to lack members above C-32, and, in lower ranked samples (e.g. Sub-bituminous-B, high volatile C) to exhibit mass spectral envelopes with unique even-carbon number predominances. The weighted average mass, as well as the carbon number maximum (viz. mode), of these coal porphyrin homologies has been found to decrease as rank increases. The generation of porphyrins of the ETIO-series is suggested as occurring both during early coal formation, including oxidative scission of the isocyclic ring at the phorbide stage, and later during the catagenic alteration of surviving DPEP-series porphyrins. A preliminary study of chlorophyll diagenesis in a South Florida peat partially substantiates this suggestion and has further shown that the coal porphyrins can be derived from bacterial, as well as higher plant, chlorophylls. 相似文献
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Natural Hazards - Risk and resilience assessments have been both widely, but separately, used as tools for guiding policymakers to formulate disaster-risk reduction policies. On the one hand, risk... 相似文献
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Coral branches partially block the flow of water through the colony, creating an inner zone of reduced water exchange where hypoxic conditions can develop during the night. Previous studies have shown that this oxygen deficiency is alleviated by the fanning behavior of mutualistic damselfish that spend the night between the coral branches, constantly moving their fins. Our findings show that fin‐stroking frequency during fanning by the damselfish Dascyllus marginatus is moderately plastic, with lower frequency under higher oxygen concentration, and vice versa. The inter‐play between oxygen concentration and fin motion maintains nearly steady oxygen concentration between the coral branches during the night. 相似文献
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M. L. Kaplan A. W. Huffman K. M. Lux J. J. Charney A. J. Riordan Y.-L. Lin 《Meteorology and Atmospheric Physics》2005,88(3-4):129-152
Summary In this paper, we describe the results of 44 case study analyses of synoptic scale data sets that define the atmospheric structure prior to the development of accident-producing turbulence. First, the 44 case studies are categorized as a function of the location, altitude, time of year, time of day, and turbulence environment, i.e., in clear air, cloudiness, convection, near mountains, or in the proximity of deep convection. It is noteworthy that this later category was much more ubiquitous than was anticipated. Second, NCEP Reanalysis data sets as well as both visible and infrared satellite imagery are employed to diagnose predictor fields associated with the synoptic-scale environment preceding severe turbulence. These predictor fields are calculated based on jet stream configuration, kinematic, dynamical, and thermodynamic analyses of the synoptic-scale atmosphere.The results of these analyses indicate a prevalence of severe accident-producing turbulence within the entrance region of the polar or subtropical jet stream at the synoptic-scale. Typically, there is a region of flow curvature located just upstream within the jet entrance region, convection is present within 100km of the accident, the vertical motion is upward typically within the curved entrance region, absolute vorticity is low, the vertical wind shear is increasing with time, and horizontal cold air advection is substantial. Not all of the 44-case studies conform to this entrance region paradigm. However, most do and the most consistent predictor of severe turbulence is upstream curvature in the synoptic-scale flow. Nearby convection is the second most ubiquitous predictor field. Upward vertical motion, low absolute vorticity, and horizontal cold air advection are all typical predictors in case studies occurring both within the entrance and exit regions of the polar or subtropical jet stream.Current affiliation: USDA/Forest Service, North Central Research Station, East Lansing, MI 48823. 相似文献
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Alexander Tsatskin Tatyana S.Gendler Friedrich Heller Igal Dekman Gitti L.Frey 《山地科学学报》2009,6(2):113-124
The paper addresses the controversial question of the role of clay-sized dust in the formation of paleosols in coastal eolianites, Israel. At the Habonim type section, the pedocomplex dated by archaeology and luminescence to 45-135 ka ago shows at least three paleosols, not separated by non-soil sediments. The oldest reddish paleosol （apparently related to MIS 5） is magnetically enhanced, leached from carbonates, with signs of bioturbation and strongly aged clay coatings. The reddening is due to very fine, -20 nm, poorly crystallized, superparamagnetic （SP） hematite, as determined by Mossbauer studies. In subsoil, lithorelics of eolianite are found. Over time, the soil surface aggraded due to accelerated fine dust accumulation alongside local slope wash. On younger materials formed magnetically depleted vertisols, dominated by smectite-type expandable paramagnetic clays. In thin sections, vertisols exhibit strong stipple-speckled and striated b-fabric due to shrink-swell processes, impregnative calcite nodules and Fe-Mn redistribution. The uppermost hydric vertisol shows the strongest expression of juxtaposed features of recurrent calcite and Fe precipitation. This paleosol developed on colluvial soil materials, as evidenced by mixing of clay coated and uncoated grains of quartz and calcite allochems. M6ssbauer spectra show high amounts of Fe（III） incorporated in the clay structure, low amounts of SP goethite and absence of SP hematite. Whilst magnetic susceptibility drops in vertisols to minimal values, increase. The latter along ferrimagnetie grain sizes with differences in the hierarchy of microfabric features is taken as indication for lithologic discontinuities which may have resulted from continuous, albeit variable and low-intensity, input of eolian clay from both remote Saharan and local sources, roughly dated to the earlier to middle part of the Last Glacial. 相似文献
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Oxytetracycline (OTC) is an antibiotic that is regularly added to fish ponds used in industrial- scale fish-farming along
the Mediterranean coast of Israel. It is not found in unpolluted water. The ponds are constructed upon porous sands that are
also the host rock of the local aquifer. These ponds leak. Monitoring for OTC was carried out in a fish pond and three surrounding
water wells that exploit the local aquifer. The local groundwater is composed of the native groundwater and the leakage additions.
Two wells, P-204 P-205 are used to insure that the water levels in the ponds are maintained. A frequently pumping well, M-2,
is located closest to the main source of OTC input at pond B. It is used to supply drinking water and OTC was found in it.
This contaminant is related to leakage from the nearby fish pond. OTC is generally assumed to be immobile and effectively
removed by soil and sediments. In this case, continuous leakage of the pond has created preferential saturated flow paths
that bring the contaminants directly to groundwater, bypassing the immobilizing sorption processes that usually take place
in the unsaturated zone. In the absence of such conduits OTC is effectively excluded from reaching other producing wells. 相似文献
18.
Igal Charney 《Area》2007,39(2):195-205
After 2000 a handful of very tall buildings were approved in central London, a circumstance that challenged well-established planning practices in that part of the city. Their promotion by Ken Livingstone, the mayor, but opposition to them by conservation groups, seemed to signal a fierce campaign ahead; in fact, it was all over in an instant. This article examines how this debate was framed to dismiss the arguments and concerns of those who oppose tall buildings. To make tall buildings acceptable, London's mayor drew on the merits associated with iconic architecture and high-profile architects. Under Livingstone's incumbency tall buildings were affirmed by the expertise and clout of global architects who provided legitimacy for mayoral ambitions to reach for the sky. Stressing the significance of high-quality design and iconic architecture helped to wear down deep-rooted antagonism and to channel the debate to improving the aesthetic qualities of London, a goal that enjoys wide consensus. 相似文献