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71.
Influence of internal loading on phosphorus concentration in shallow lakes before and after reduction of the external loading 总被引:2,自引:1,他引:1
An analysis of data from 49 shallow lakes showed, that the parameters of empirical models between phosphorus loading and concentration in the lake (e.g. Vollenweider type of relations) differ significantly for lakes without or with a reduced external loading. For lakes without a reduction of the external loading the summer phosphorus concentration is determined by the external phosphorus loading and the hydraulic loading. For these lakes the classical models suffice; deviations between calculations and measurements are partly due to errors made in the determination of the loading.In contrast, for lakes where the external loading was reduced, the measured internal loading explains most of the variation in the summer lake concentration. The external loading is of minor importance and the classical models cannot be applied. The internal loading measured before reduction of the external loading is not useful in predicting the concentration afterwards. Instead of the internal loading, the sediment composition can be used. The advantage of using sediment composition is that these variables are easier to determine and vary less in time. The most promising variable is the ratio between total P and total Fe in the sediment.Abbreviations: Qs
hydraulic loading (m y-1)
-
hydraulic retention time (y)
- Lext
external phosphorus loading (gP m-2 y-1)
- Lint
internal phosphorus loading (gP m-2 y-1)
- Plake
phosphorus concentration in the lake (gP m-3)
- Pinlet
phosphorus concentration in the inlet water (gP m-3)
- Psed
phosphorus content on the sediment (gP kg-1 d.w.)
- Fesed
iron content of the sediment (gFe kg-1 d.w.)
-
Y
dependent variable multiple regression calculations
-
X1, X2
independent variables multiple regressions calculations
-
a, a1
constants
-
a2, b
constants 相似文献
72.
Dominik?A.?Nachtsheim Claude?R.?JoirisEmail author Diederik?D’Hert 《Polar Biology》2016,39(4):755-758
The ivory gull Pagophila eburnea is an Arctic seabird species whose distribution is tightly coupled to the availability of sea ice. During the last decades, strong declines have been reported for breeding colonies in Canada and Greenland, which are usually located on nunataks or remote coastal islands. Here, we report the observation of a colony of ivory gulls breeding on a gravel-covered iceberg 70 km off Northeast Greenland in August 2014. It concerned approximately 60 adults, including two ringed individuals, and many chicks. This represents an unusual breeding site for the species, to be compared with a few cases of colonies on gravel-covered sea ice. Breeding on an offshore iceberg may be advantageous since it provides ultimate protection from predators. Furthermore, the proximity to the productive North East Water polynya may have been attractive to these gulls. As a consequence of this and previous observations, colony surveys should not solely focus on inland and coastal breeding habitats, but should be extended towards the ocean. 相似文献
73.
Christiaan Sybesma Diederik Schowanek Luit Slooten Nadia Walravens 《Photosynthesis research》1986,9(1-2):149-158
The induction of anoxygenic photosynthesis in the cyanobacterium Oscillatoria limnetica by sulfide was shown to involve the synthesis of a sulfide oxidizing factor; this factor, partly adsorbed on the thylakoid membrane, can be recovered in the soluble phase and is active also on membranes from oxygenically grown cells. The factor is required for sulfide dependent light-induced hydrogen evolution. It accelerates electron transport from sulfide to the electron donor of photosystem I, P700, in membranes from cells in which anoxygenic photosynthesis is induced. The plastiquinone analogue DBMIB does not inhibit electron transport to P700 but accelerates it. The analogue might promote cyclic electron transport involving P700, thus preventing electrons to reach hydrogenase.Abbrevlations chl
chlorophyll
- DBMIB
3,5-dibromo-3-methyl-6-isopropyl-8-benzoquinone
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- EDTA
ethylenediamine tetraacetate
- FAD
flavin adenine dinucleotide
- HEPES
N-2-hydroxyethyl-piperazine N-2-ethane sulfonic acid
- PS
photosystem
Dedicated to Prof. L.N.M. Duysens on the occasion of his retirement 相似文献
74.
Aimée Little Benjamin Elliott Chantal Conneller Diederik Pomstra Adrian A. Evans Laura C. Fitton Andrew Holland Robert Davis Rachel Kershaw Sonia O’Connor Terry O’Connor Thomas Sparrow Andrew S. Wilson Peter Jordan Matthew J. Collins André Carlo Colonese Oliver E. Craig Rebecca Knight Alexandre J. A. Lucquin Barry Taylor Nicky Milner 《PloS one》2016,11(4)
Shamanic belief systems represent the first form of religious practice visible within the global archaeological record. Here we report on the earliest known evidence of shamanic costume: modified red deer crania headdresses from the Early Holocene site of Star Carr (c. 11 kya). More than 90% of the examples from prehistoric Europe come from this one site, establishing it as a place of outstanding shamanistic/cosmological significance. Our work, involving a programme of experimental replication, analysis of macroscopic traces, organic residue analysis and 3D image acquisition, metrology and visualisation, represents the first attempt to understand the manufacturing processes used to create these artefacts. The results produced were unexpected—rather than being carefully crafted objects, elements of their production can only be described as expedient. 相似文献
75.
Nicolas Capelli Francisco Barja Diederik Van Tuinen Jean Monnat Gilbert Turian Ruben Ortega Perez 《FEMS microbiology letters》1997,147(2):215-220
We have enriched a 47-kDa polypeptide (p47) from Neurospora crassa on the basis of its affinity to calmodulin. The p47 was purified to homogeneity by chromatography on a Mono S cation exchange column and evidence is presented that the polypeptide co-sediments specifically with F-actin. The intracellular distribution of p47 and actin was also examined using indirect double immunofluorescence staining of cells at different stages of development. Our results suggest that by altering the conformation binding site of actin to p47, calmodulin could play a regulatory role in the polarized hyphal growth of N. crassa. 相似文献
76.
Aim Invasive alien species are a growing threat to biodiversity, and identifying the mechanisms that enable these species to establish viable populations in their new environment is paramount for management of the problems they pose. Using an unusually large number of both failed and successful documented introductions of parakeets (Aves: Psittacidae) in Europe, we test two of the major hypotheses on the establishment success of invading species, namely the climate‐matching and the human‐activity hypothesis. Location European human population centres where ring‐necked parakeet (Psittacula krameri) and/or monk parakeet (Myiopsitta monachus) introductions have occurred. Methods Data on ring‐necked and monk parakeet introductions in Europe were gathered from various sources, including published books and articles, but also from unpublished reports and local grey literature. Information was verified with experts from the region under consideration. In order to test the climate‐matching hypothesis, we verified whether the climatic factors that determine the parakeets’ native ranges also explain establishment success in Europe. Parakeet occurrence data from the native ranges were analysed using the presence‐only modelling method Maxent , and correlations between parakeet establishment and climatic and anthropogenic variables in Europe were assessed using both stepwise logistic regression and the information‐theoretic model selection approach. Results The establishment success of ring‐necked and monk parakeets was found to be positively associated with human population density, and, both in the native and in the introduced regions, parakeet occurrence was negatively correlated with the number of frost days. Thus, parakeets are more likely to establish in warmer and human‐dominated areas. Main conclusions The large number of independent parakeet introductions in Europe allows us to test the often‐used climate‐matching and human‐activity hypotheses at the species level. We show that both hypotheses offer insight into the invasion process of monk and ring‐necked parakeets. Our results suggest that, in the future, parakeet establishment probability may increase even further because global warming is likely to cause a decrease in the number of frost days and because urbanization and human populations are still increasing. 相似文献
77.
78.
Summary An improved auto-analyzer method for the quantitative determination of phosphonate-phosphorus was developed. Its advantages are of three sorts: 1) phosphonates can be determined in a variety of media, even with high levels of organic compounds, 2) viscous bacterial broths can be analysed directly on the auto-analyzer, 3) the method has an increased sensitivity. 相似文献
79.
Patrick Verschueren Diederik De Cock Luk Corluy Rik Joos Christine Langenaken Veerle Taelman Frank Raeman Isabelle Ravelingien Klaas Vandevyvere Jan Lenaerts Elke Geens Piet Geusens Johan Vanhoof Anne Durnez Jan Remans Bert Vander Cruyssen Els Van Essche An Sileghem Griet De Brabanter Johan Joly Kristien Van der Elst Sabrina Meyfroidt Rene Westhovens 《Arthritis research & therapy》2015,17(1)
IntroductionConsidering a lack of efficacy data in patients with early rheumatoid arthritis (eRA) presenting without classical markers of poor prognosis, we compared methotrexate (MTX) with or without step-down glucocorticoids in the CareRA trial.MethodsDisease-modifying antirheumatic drug–naïve patients with eRA were stratified into a low-risk group based on prognostic markers that included non-erosiveness, anti–citrullinated protein antibodies and rheumatoid factor negativity and low disease activity (Disease Activity Score in 28 joints based on C-reactive protein (DAS28(CRP)) ≤3.2). Patients were randomized to 15 mg of MTX weekly (MTX with tight step-up (MTX-TSU)) or 15 mg of MTX weekly with prednisone bridging, starting at 30 mg and tapered to 5 mg daily from week 6 (COmbinatie therapie bij Reumatoïde Artritis (COBRA Slim)). A TSU approach was applied. Outcomes assessed were DAS28(CRP)-determined remission, cumulative disease activity, Health Assessment Questionnaire (HAQ) scores and adverse events (AEs) after 16 treatment weeks.ResultsWe analyzed 43 COBRA Slim and 47 MTX-TSU patients and found that 65.1% in the COBRA Slim group and 46.8% in the MTX-TSU group reached remission (P = 0.081). Mean ± standard deviation area under the curve values of DAS28(CRP) were 13.84 ± 4.58 and 11.18 ± 4.25 for the MTX-TSU and COBRA Slim patients, respectively (P = 0.006). More COBRA Slim patients had an HAQ score of 0 (51.2% versus 23.4%, P = 0.006) at week 16. Therapy-related AEs between groups did not differ.ConclusionIn patients with low-risk eRA, MTX with step-down glucocorticoid bridging seems more efficacious than MTX step-up monotherapy, with a comparable number of AEs observed over the first 16 treatment weeks.
Trial registration
EU Clinical Trials Register Identifier: EudraCT number 2008-007225-39. Registered 5 November 2008.Electronic supplementary material
The online version of this article (doi:10.1186/s13075-015-0611-8) contains supplementary material, which is available to authorized users. 相似文献80.
Ralph R. E. G. Geuskens Jordi Borst Marit Lucas A. M. Merel Boers Olvert A. Berkhemer Yvo B. W. E. M. Roos Marianne A. A. van Walderveen Sjoerd F. M. Jenniskens Wim H. van Zwam Diederik W. J. Dippel Charles B. L. M. Majoie Henk A. Marquering MR CLEAN trial investigators 《PloS one》2015,10(11)