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Solar Physics - New observations of solar oscillations are reported. Power density spectra derived from these observations reveal narrow-band oscillations that are spatially global, have spatial... 相似文献
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Biogenic carbonates spawned from microbial activities are common occurrences in soils. Here, we investigate the carbonate biomineralization mediated by the bacterium Bacillus megaterium, a dominant strain separated from a loess profile in China. Upon completing bacterial cultivation, the ensuring products are centrifuged, and the resultant supernatant and the concentrated bacterial sludge as well as the un-separated culture are added separately into a Ca-CO3 containing solution for crystallization experiments. Results of XRD and SEM analysis indicate that calcite is the dominant mineral phase formed when the bacteria are present. When the supernatant alone is used, however, a significant portion of vaterite is also precipitated. Experimental results further reveal that the bacteria have a strong tendency to colonize the center area of the calcite {1 0 4} faces. Observed crystal morphology suggests that the bacterial colony may promote the growth normal to each individual {1 0 4} face of calcite when the cell concentration is high, but may retard it or even cause dissolution of the immediate substrate surfaces when the concentration is low. SEM images taken at earlier stages of the crystallization experiments demonstrate the nucleation of calcite on the bacterial cell walls but do not show obvious morphological changes on the nanometer- to submicron-sized nuclei. δ13C measurements unveil that the crystals grown in the presence of bacteria are further enriched in the heavy carbon isotope, implying that the bacterial metabolism may not be the carbon sources for the mineralization. Based upon these findings, we propose a mechanism for the B. megaterium mediated calcite mineralization and conclude that the whole process involves epi- and inter-cellular growth in the local microenvironments whose conditions may be controlled by cell sequestration and proton pumping during bacterial respiration. 相似文献
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Linking Inuit knowledge and meteorological station observations to understand changing wind patterns at Clyde River,Nunavut 总被引:1,自引:1,他引:0
Shari Gearheard Matthew Pocernich Ronald Stewart Joelie Sanguya Henry P. Huntington 《Climatic change》2010,100(2):267-294
Connecting indigenous and scientific observations and knowledge has received much attention in the Arctic, not least in the
area of climate change. On some levels, this connection can be established relatively easily, linking observations of similar
phenomena or of various effects stemming from the same cause. Closer examinations of specific environmental parameters, however,
can lead to far more complex and difficult attempts to make those connections. In this paper we examine observations of wind
at Clyde River, Nunavut, Canada. For Inuit, many activities are governed by environmental conditions. Wind, in particular,
is identified by Inuit as one of the most important environmental variables, playing a key role in driving sea ice, ocean,
and weather conditions that can either enable or constrain hunting, travel, or other important activities. Inuit observe wind
patterns closely, and through many means, as a result of their close connection to the land and sea. Inuit in many parts of
Nunavut are reporting changes in wind patterns in recent years. At Clyde River, a community on the eastern coast of Baffin
Island, Inuit have observed that at least three key aspects of wind have changed over the last few decades: wind variability,
wind speed, and wind direction. At the same time, wind observations are also available from an operational weather station
located at Clyde River. An analysis of this information shows little change in wind parameters since the mid-1970s. Though
the station data and Inuit observations correspond in some instances, overall, there is limited agreement. Although the differences
in the two perspectives may point to possible biases that may exist from both sources—the weather station data may not be
representative of the region, Inuit observations or explanations may be inaccurate, or the instrumental and Inuit observations
may not be of the same phenomena—they also raise interesting questions about methods for observing wind and the nature of
Arctic winds. 相似文献
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Ocean Dynamics - Loop Current Eddies (LCEs) are warm-core, anticyclonic rings that shed from the Loop Current and migrate westward providing kinetic and potential energy to the Gulf of... 相似文献
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