排序方式： 共有24条查询结果，搜索用时 15 毫秒
1.
The phenol-degrading system which can be induced in Rhodococcus spec. P 1 brings about the metabolization of phenol via the β-ketoadipate path (ortho-cleavage of catechol). For the more precise characterization of the degradation performance investigations were made into the influences of different carbon sources: glucose, galactose, ribose, arabinose, xylose, acetate, citricacid, mandelic acid, protocatechoic acid, glycerol, tryptophane, phenylalanine and the complex substrate of nutrient broth as well as succinate, catechol and benzoate. Only the three last-named substances show an influence: succinate inhibits only the synthesis of phenol hydroxylase, catechol and benzoate inhibit the synthesis and activity of phenol hydroxylase. As a comparison of the results with literature shows, even at the same path of degradation there are different regulating mechanismus in the different microorganisms. 相似文献
2.
3.
Short-term sedimentation patterns were evaluated from August 1992 to May 1993 in different wetland habitats characteristic of the Rhône Delta, including impounded and seasonally-dry saline Arthrocnemum marshes, brackish Juncus, Phragmites, and Scirpus riverine wetlands directly connected to the Rhône River, and Arthrocnemum-dominated marine marshes influenced by the Mediterranean. Short-term sedimentation was measured as sediment accumulation on paper filters which had been placed on the soil surface for several weeks. Total sedimentation and material lost on ignition was significantly related to individual sampling periods, reflecting the importance of short-term processes. High sedimentation at riverine sites (up to 22 g m?2 d?1) was related to a combination of river stage and wind events. Marine and impounded wetlands of the Rhône Delta experienced low sedimentation throughout the period of study. Sedimentation rates averaged over the study period were 0.8 g m?2 d?1, 1.8 g m?2 d?1, and 5.4 g m?2 d?1 for marine, impounded, and riverine sites, respectively. Percent material lost on ignition was low in all habitats (average 15%) and followed a seasonal trend with a minimum in late fall and winter (1%). Soil percent organic matter was also low in the top several centimeters (13%), suggesting that inorganic sedimentation is very important for accretion on these wetland surfaces. Coastal flooding was not a significant mechanism for sedimentation in the marine sites during the period of study. Sedimentation is an important factor in elevation change, and this study shows that impounded habitats, the most common “natural environment“ left in the delta, may become vulnerable to sea-level rise in the future if management practices continue to isolate these wetlands from riverine sources of sediment. 相似文献
4.
Marieke van Erp Robert Hensel Davide Ceolin Marian van der Meij 《Transactions in GIS》2015,19(4):563-581
For biodiversity research, the field of study that is concerned with the richness of species of our planet, it is of the utmost importance that the location of an animal specimen find is known with high precision. Due to specimens often having been collected over the course of many years, their accompanying geographical data is often ambiguous or may be very imprecise. In this article, we detail an approach that utilizes reasoning and external sources to improve the geographical information of animal finds. Our main contribution is to show that adding external domain knowledge improves the ability to georeference locations over traditional methods that focus solely on analyzing geographical information. Additionally, our system is able to output the confidence it has in its decisions through a confidence measure based on the difficulty of the instance and the steps undertaken to disambiguate it. Our results show that adding domain knowledge to the georeferencing process increases the accuracy @5km from 38.9% to 61.7% and from 47.0% to 74.5% @25km. Furthermore, we reduce the mean distance by more than half, from 251.1km to 114.5km, and decrease the number of records for which no reference can be found from 26.2% to 7.4%. 相似文献
5.
A 115-year-old railroad levee bisecting a tidal freshwater marsh perpendicular to the Patuxent River (Maryland) channel has created a northern, upstream marsh and a southern, downstream marsh. The main purpose of this study was to determine how this levee may affect the ability of the marsh system to gain elevation and to determine the levee’s impact on the marsh’s long-term sustainability to local relative sea level rise (RSLR). Previously unpublished data from 1989 to 1992 showed that suspended solids and short-term sediment deposition were greater in the south marsh compared to the north marsh; wetland surface elevation change data (1999 to 2009) showed significantly higher elevation gain in the south marsh compared to the north (6?±?2 vs. 0?±?2 mm year?1, respectively). However, marsh surface accretion (2007 to 2009) showed no significant differences between north and south marshes (23?±?8 and 26?±?7 mm year?1, respectively), and showed that shallow subsidence was an important process in both marshes. A strong seasonal effect was evident for both accretion and elevation change, with significant gains during the growing season and elevation loss during the non-growing season. Sediment transport, deposition and accretion decreased along the intertidal gradient, although no clear patterns in elevation change were recorded. Given the range in local RSLR rates in the Chesapeake Bay (2.9 to 5.8 mm year?1), only the south marsh is keeping pace with sea level at the present time. Although one would expect the north marsh to benefit from high accretion of abundant riverine sediments, these results suggest that long-term elevation gain is a more nuanced process involving more than riverine sediments. Overall, other factors such as infrequent episodic coastal events may be important in allowing the south marsh to keep pace with sea level rise. Finally, caution should be exercised when using data sets spanning only a couple of years to estimate wetland sustainability as they may not be representative of long-term cumulative effects. Two years of data do not seem to be enough to establish long-term elevation change rates at Jug Bay, but instead a decadal time frame is more appropriate. 相似文献
6.
Jean-Paul Deroin Jean Chorowicz Thierry Deroin Phillippe Dutarte Jean-Yves Scanvic Andr Simonin 《ISPRS Journal of Photogrammetry and Remote Sensing》1990,45(5-6)
Classification image processing is based mainly upon spectral features but this information alone is inadequate for drawing comprehensive maps or reliably distinguishing lithological or structural targets, especially in vegetation-covered areas. It is therefore of interest to explore an approach in which subtle features of the image are matched with field data in a variety of parameters either measured or assessed qualitatively. This approach is necessarily multidisciplinary, the three basic aspects being geomorphological, botanical and geological.The Cévennes massif, in southern France, with its sedimentary margins was selected as a test area, having both varied geology, giving a variety of landscapes, and a range of climatic zones, from Mediterranean to sub-Alpine.The present work is distinguished by its use of the landscape unit, which is rarely considered in geology. Landscapes units are recognized and defined, and the spectral homogeneity of the units is then assessed. They are combined with satellite and other data in order to improve the digital processing for geological purposes.The parameters characterising each landscape unit define the various elements contributing to the landscape, the most important of which are morphology, vegetation and geology, and their interactions. Our results using these parameters show the interest of the management of both the satellite (SPOT in this case) and non-satellite (exogenous) data. 相似文献
7.
An analcime-rich mugearite near Spring Mount in north-eastern New South Wales contains dominant kaersutite, lesser anorthoclase and rare Ti-rich mica megacrysts, and also rare Group I peridotite xenoliths and granitoid inclusions. Mineralogical, experimental and Sr and Nd isotopic data are interpreted to indicate that the megacrysts are cognate with their host and that megacryst precipitation occurred at pressures in the vicinity of 1 GPa. Isotopic and other data indicate minimal crystal contamination of the melt. The generation of this evolved lava (100 Mg/(Mg+Fe2+), M55; differentiation index DI52–56) by high-pressure amphiboledominated fractionation of a mantle-derived hydrous alkali basaltic parent (M70) is inconsistent with observed megacryst abundances (<3%) and absence of Group II cumulates, and with the magnitude of the crystal extracts (45% crystals) indicated by crystal fractionation models. These data suggest the mugearite is not a high-pressure differentiate of a hypothetical primary parental magma (M70). Alternatively, its composition might approximate that of a primary magma derived from a relatively Fe-rich amphibole lherzolite mantle source. 相似文献
8.
9.
Tidal freshwater marshes around the world face an uncertain future with increasing water levels, salinity intrusion, and temperature and precipitation shifts associated with climate change. Due to the characteristic abundance of both annual and perennial species in these habitats, even small increases in early growing season water levels may reduce seed germination, seedling establishment, and late-season plant cover, decreasing overall species abundance and productivity. This study looks at the distribution of tidal freshwater marsh plant species at Jug Bay, Patuxent River (Chesapeake Bay, USA), with respect to intertidal elevation, and the relationship between inundation early in the growing season and peak plant cover to better understand the potential impacts and marsh responses to increased inundation. Results show that 62% of marsh plant species are distributed at elevations around mean high water and are characterized by narrow elevation ranges in contrast with species growing at lower elevations. In addition, the frequency and duration of inundation and water depth to which the marsh was exposed to, prior to the growing season (March 15–May 15), negatively affected peak plant cover (measured in end-June to mid-July) after a threshold value was reached. For example, 36 and 55% decreases in peak plant cover were observed after duration of inundation threshold values of 25 and 36% was reached for annual and perennial species, respectively. Overall, this study suggests that plant communities of tidal freshwater marshes are sensitive to even small systematic changes in inundation, which may affect species abundance and richness as well as overall wetland resiliency to climate change. 相似文献
10.
Ryoga Maeda Steven Goderis Akira Yamaguchi Thibaut Van Acker Frank Vanhaecke Vinciane Debaille Phillippe Claeys 《Meteoritics & planetary science》2023,58(7):1018-1038
The chemical effects of terrestrial alteration, with a particular focus on lithophile trace elements, were studied for a set of H chondrites displaying various degrees of weathering from fresh falls to altered finds collected from hot deserts. According to their trace element distributions, a considerable fraction of rare earth elements (REEs), Th, and U resides within cracks observed in weathered meteorite specimens. These cracks appear to accumulate unbound REEs locally accompanied by Th and U relative to the major element abundances, especially P and Si. The deposition of Ce is observed in cracks in the case of most of the weathered samples. Trace element maps visually confirm the accumulation of these elements in such cracks, as previously inferred based on chemical leaching experiments. Because the positive Ce anomalies and unbound REE depositions in cracks occur in all weathered samples studied here while none of such features are observed in less altered samples including falls (except for altered fall sample Nuevo Mercurio), these features are interpreted to have been caused by terrestrial weathering following chemical leaching. However, the overall effects on the bulk chemical composition remain limited as the data for all Antarctic meteorites studied in this work (except for heavily weathered sample A 09516, H6) are in good agreement with published data for unaltered meteorites. 相似文献