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排序方式: 共有84条查询结果,搜索用时 46 毫秒
1.
Organic pollutants associated with macromolecular soil organic matter: Mode of binding 总被引:2,自引:0,他引:2
H. H. Richnow R. Seifert J. Hefter M. Link W. Francke G. Schaefer W. Michaelis 《Organic Geochemistry》1997,26(11-12)
A study of ether-linked moieties in macromolecular bound residues of polycyclic aromatic hydrocarbons (PAH) generated in bioremediation experiments was performed using high temperature hydrolysis degradation with subsequent analysis of the products by GC-MS. This hydrolysis reaction was specifically designed to cleave ether bonds including relatively stable diarylether structures. Among the reaction products, aromatic alcohols representing typical microbiologically derived metabolites of PAH were found in addition to natural compounds. Thus, parts of the bound residues appeared to be linked within the macromolecular material by ether bonds. Model experiments with an oxidoreductase enzyme and aromatic alcohols indicate the formation of these ether bonds to be an enzyme-catalysed process. 相似文献
2.
Alexander Pavelyev Yuei-An Liou Christoph Reigber Jens Wickert Kiyoshi Igarashi Klemens Hocke Cheng-Yung Huang 《GPS Solutions》2002,6(1-2):100-108
GPS radio occultation (RO) signals are highly coherent and precise, and thus sufficient for holographic investigation of
the atmosphere, ionosphere, and the Earth's surface from space. In principle, three-dimensional radio-holographic remote sensing
is possible by using new radio holographic equations to retrieve the radio field within the atmosphere from a radio field
known at some interface outside the atmosphere. A simplified two-dimensional form of the radio-holographic equations which
are developed under an assumption of local spherical symmetry can be used to obtain two-dimensional radio images of the atmosphere
and terrestrial surface. To achieve this, radio holograms recorded by a GPS receiver onboard a low earth orbit (LEO) satellite
at two GPS frequencies can be used and focused synthetic aperture principle applied. Analysis of GPS/MET RO data is presented
to show the effectiveness of a radio-holographic approach. It is shown that the amplitude of GPS radio signals (in addition
to phase data) can be used to obtain detailed altitude profiles of the vertical gradient of refractivity in the atmosphere
and electron density in the mesosphere. The results demonstrate the applicability of GPS radio holography for a detailed global
study of the natural processes in the atmosphere and mesosphere.
Electronic Publication 相似文献
3.
Klemens Hocke 《Annales Geophysicae》1996,14(2):201-210
During the MLTCS (Mesosphere-Lower Thermosphere Coupling Study) campaign the EISCAT UHF radar was continuously operated over 7 days (30 July-5 August 1992) in the CP-1 mode. The long time series obtained of the fundamental ionospheric parameters field-aligned ion velocity (Vi), ion and electron temperature (T and Te), and electron density (Ne) are useful in investigating tidal variations in the E- and F-region since the geomagnetic activity was particularly low during the time of measurement. Maximum entropy spectra of the parameters were calculated for the relatively quiet interval from 1 August to 4 August 1992 and indicated dominant variations with harmonics of 24 hours. In the electron density spectrum especially, harmonics up to the sixth order (4-h period) are clearly visible. The phase and amplitude height profiles (100-450 km) of the diurnal, semidiurnal, and terdiurnal variations were determined by Fourier transform for a 24-h data set beginning at 12:00 UT on 3 August 1992 when the contaminating influences of electric fields were negligible. The tidal variations of the ion temperatures are compared with the corresponding variations of the neutral temperature predicted by the MSISE-90 model. A remarkable result is the dominance of terdiurnal temperature oscillations at E-region heights on 3–4 August 1992, while the measured diurnal and semidiurnal variations were negligible. The finding was confirmed by the analysis of further EISCAT data (2-3 August 1989, 2–3 July 1990, 31 March- 1 April 1992) which also showed a dominant terdiurnal temperature tide in the E-region. This is different from numerous observations of tides in the E-region at mid-latitudes where the diurnal and especially the semidiurnal temperature oscillations were dominant. 相似文献
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Zusammenfassung und Folgerungen Es darf als gesichert gelten, dass die 1961 im Auftrag der Internationalen Gew?sserschutzkommission für den Bodensee ermittelte
Jahresfracht von 806 t Gesamtphosphor des Alpenrheins in bezug auf den gel?sten Gesamtphosphor viel zu hoch, in bezug auf
die Summe von gel?stem und ungel?stem Gesamtphosphor aber wesentlich zu niedrig liegt.
Die aus den Ergebnissen der 1961 er Untersuchung für den Alpenrhein gezogenen Schlussfolgerungen k?nnen daher nur zum Teil
richtig sein.
Kann durch die andernorts bereits durchgeführten Untersuchungen oder durch neue Abkl?rungen festgestellt werden, dass die
aus der adsorptiven Bindung an die Rheinsedimente im Bodensee freigesetzte P-Menge kleiner oder gleich der gel?sten P-Fracht
des Alpenrheins ist, so hat, die Forderung auf zus?tzliche Einrichtungen zur P-Elimination (3. Reinigungsstufe oder Simultanf?llung)
bei den geplanten oder erstellten mechanisch-biologischen Kl?ranlagen im Einzugsgebiet des Bodensees ihre volle Berechtigung.
Summary and Conclusions It can be considered an established fact that the yearly load of 806 tons of total phosphorus for the Alpine reaches of the Rhine, determined in 1961 on behalf of the International Commission for the Protection of the Lake of Constance against Pollution, is much too high for the dissolved total phosphorus and significantly too low for the sum of the dissolved and undissolved total phosphorus. The conclusions drawn from the 1961 study of the Alpine regions of the Rhine can therefore be only partially correct. If it can be proven that the amount of phosphorus released from the sediments in the Lake of Constance is smaller or equal to the dissolved phosphorus load of the Alpine part of the Rhine, the demand for additional installations for phosphorus elimination (tertiary treatment of sewage or simultaneous precipitation) for the mechanical-biological sewage treatment plants in the catchment area of the Lake of Constance is fully justified.相似文献
7.
A cross-ecosystem comparison of spatial and temporal patterns of covariation in the recruitment of functionally analogous fish stocks 总被引:2,自引:1,他引:1
Bernard A. Megrey Jonathan A. Hare William T. Stockhausen Are Dommasnes Harald Gjster William Overholtz Sarah Gaichas Georg Skaret Jannike Falk-Petersen Jason S. Link Kevin D. Friedland 《Progress in Oceanography》2009,81(1-4):63
Temporal and spatial patterns of recruitment (R) and spawning stock biomass (S) variability were compared among functionally analogous species and similar feeding guilds from six marine ecosystems. Data were aggregated into four regions including the Gulf of Maine/Georges Bank, the Norwegian/Barents Seas, the eastern Bering Sea, and the Gulf of Alaska. Variability was characterized by calculating coefficients of variation and anomalies for three response variables: ln(R), ln(R/S), and stock–recruit model residuals. Patterns of synchrony and asynchrony in the response variables were examined among and between ecosystems, between- and within-ocean basins and among functionally analogous species groups using pair-wise correlation analysis corrected for within-time series autocorrelation, multivariate cross-correlation analyses and regime shift detectors. Time series trends in response variables showed consistent within basin similarities and consistent and coherent differences between the Atlantic and Pacific basin ecosystems. Regime shift detection algorithms identified two broad-scale regime shift time periods for the pelagic feeding guild (1972–1976 and 1999–2002) and possibly one for the benthic feeding guild (1999–2002). No spatial patterns in response variable coefficients of variation were observed. Results from multivariate cross-correlation analysis showed similar trends. The data suggest common external factors act in synchrony on stocks within ocean basins but temporal stock patterns, often of the same species or functional group, between basins change in opposition to each other. Basin-scale results (similar within but different between) suggest that the two geographically broad areas are connected by unknown mechanisms that, depending on the year, may influence the two basins in opposite ways. This work demonstrates that commonalities and synchronies in recruitment fluctuations can be found across geographically distant ecosystems but biophysical causes of the fluctuations remain difficult to identify. 相似文献
8.
A logarithmic transformation may be used to improve the efficiency of estimates of the mean when observations follow the lognormal distribution. But if this transformation is applied to observations that follow another distribution, bias may be introduced. We consider some consequences of erroneously applying lognormal estimation theory and demonstrate that biased estimates may be obtained for certain classes of distributions. Illustrations of bias obtained in gold sampling are given. 相似文献
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