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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Solid State Chemistry 113 (1994), S. 176-181 
    ISSN: 0022-4596
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Tetrahedron Letters 33 (1992), S. 1225-1226 
    ISSN: 0040-4039
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Solid State Communications 92 (1994), S. 185-187 
    ISSN: 0038-1098
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The international journal of advanced manufacturing technology 16 (2000), S. 413-423 
    ISSN: 1433-3015
    Keywords: Keywords:Computer-aided inspection; Coordinate measurement; Form deviation evaluation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A practical approach towards evaluating form deviations of 2D complex contour profiles from the coordinate measurement data of discrete points is proposed. In this approach, a 2D complex contour is represented approximately by the combination of straight line and circular arc segments under the condition of satisfying the prespecified interpolation accuracy. The form deviation of a measured point is calculated relative to the approximate contour and the form deviation of the whole contour is evaluated using either the minimum zone criterion (MZC) or the least squares criterion (LSC). It has been demonstrated that the difference between the deviation definitions, one relative to the original contour and the other to the approximate contour, is not larger than the prespecified accuracy value, i.e. the evaluation precision of the form deviation can be sufficiently guaranteed. The effectiveness and the efficiency of the approach are verified with a practical example of a planar cam contour. Moreover, a weighted LSC technique is proposed in order to obtain a rational evaluation result for the measured points with non-uniform length interval.
    Type of Medium: Electronic Resource
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  • 5
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    PANGAEA
    In:  Supplement to: Tortell, Philippe Daniel; Trimborn, Scarlett; Li, Y; Rost, Björn; Payne, Christopher D (2010): Inorganic carbon utilization by Ross Sea phytoplankton across natural and experimental CO2 gradients. Journal of Phycology, 46(3), 433-443, https://doi.org/10.1111/j.1529-8817.2010.00839.x
    Publication Date: 2023-12-12
    Description: We present results from a field study of inorganic carbon (C) acquisition by Ross Sea phytoplankton during Phaeocystis-dominated early season blooms. Isotope disequilibrium experiments revealed that HCO3- was the primary inorganic C source for photosynthesis in all phytoplankton assemblages. From these experiments, we also derived relative enhancement factors for HCO3-/CO2 interconversion as a measure of extracellular carbonic anhydrase activity (eCA). The enhancement factors ranged from 1.0 (no apparent eCA activity) to 6.4, with an overall mean of 2.9. Additional eCA measurements, made using membrane inlet mass spectrometry (MIMS), yielded activities ranging from 2.4 to 6.9 U/[mg chl a] (mean 4.1). Measurements of short-term C-fixation parameters revealed saturation kinetics with respect to external inorganic carbon, with a mean half-saturation constant for inorganic carbon uptake (K1/2) of ~380 mM. Comparison of our early springtime results with published data from late-season Ross Sea assemblages showed that neither HCO3- utilization nor eCA activity was significantly correlated to ambient CO2 levels or phytoplankton taxonomic composition. We did, however, observe a strong negative relationship between surface water pCO2 and short-term 14C-fixation rates for the early season survey. Direct incubation experiments showed no statistically significant effects of pCO2 (10 to 80 Pa) on relative HCO3- utilization or eCA activity. Our results provide insight into the seasonal regulation of C uptake by Ross Sea phytoplankton across a range of pCO2 and phytoplankton taxonomic composition.
    Keywords: Carbon dioxide, partial pressure; Chlorophyll a; CORSACS II; Depth, bottom/max; Depth, top/min; DEPTH, water; Dominant species of live fauna; Event label; Latitude of event; Longitude of event; Nathaniel B. Palmer; NBP0608; NBP0608_SW14; NBP0608_SW20; NBP0608_SW21; NBP0608_SW23; NBP0608_SW28; NBP0608_SW32; NBP0608_SW35; NBP0608_SW38; NBP0608_SW41; NBP0608_SW42; NBP0608_SW43; NBP0608_SW44; NBP0608_SW45; NBP0608_SW46; NBP0608_SW47; NBP0608_SW48; Nitrate; Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; Ross Sea; Silicon dioxide; Southern Ocean; SPP1158; Surface water sample; SWS
    Type: Dataset
    Format: text/tab-separated-values, 108 data points
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  • 6
  • 7
    Publication Date: 2016-11-15
    Description: Deciphering the molecular codes of dissolved organic matter (DOM) improves our understanding of its role in the global element cycles and its active involvement in ecosystem services. This study demonstrates comprehensive characterization of DOM by an initial polarity-based stepwise solid phase extraction (SPE) with single methanol elution of the cartridges, but separate collection of equal aliquots of eluate. The reduction of molecular complexity in the individual DOM fractions attenuates intermolecular interactions and substantially increases the disposable resolution of any structure selective characterization. Suwannee River DOM (SR DOM) was used to collect five distinct SPE fractions with overall 91% DOC recovery. Optical spectroscopy (UV and fluorescence spectroscopy), high-field Fourier transform ion cyclotron mass spectrometry (FTICR MS) and nuclear magnetic resonance (NMR) spectroscopy showed analogous hierarchical clustering among the five eluates corroborating the robustness of this approach. Two abundant moderately hydrophobic fractions contained most of the SR DOM compounds, with substantial proportions of aliphatics, carboxylic-rich alicyclic molecules, carbohydrates and aromatics. A minor early eluting hydrophilic fraction was highly aliphatic and presented a large diversity of alicyclic carboxylic acids, whereas the two late eluting, minor hydrophobic fractions appeared as a largely defunctionalized mixture of aliphatic molecules. Comparative mass analysis showed that fractionation of SR DOM was governed by multiple molecular interactions depending on O/C ratio, molecular weight and aromaticity. The traditional optical indices SUVA254 and fluorescence index (FI) indicated the relative aromaticity in agreement with FTICR mass and NMR spectra; the classical fluorescent peaks A and C were observed in all four latter eluates. This versatile approach can be easily expanded to preparative scale under field conditions, and transferred to different DOM sources and SPE conditions.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 8
    Publication Date: 2017-01-20
    Description: Abstract. The recycling of organic material through bacteria and microzooplankton to higher trophic levels, known as the “microbial loop”, is an important process in aquatic ecosystems. Here the significance of the microbial loop in influencing nutrient supply to phytoplankton has been investigated in Lake Kinneret (Israel) using a coupled hydrodynamic– ecosystem model. The model was designed to simulate the dynamic cycling of carbon, nitrogen and phosphorus through bacteria, phytoplankton and zooplankton functional groups, with each pool having unique C :N: P dynamics. Three microbial loop sub-model configurations were used to isolate mechanisms by which the microbial loop could influence phytoplankton biomass, considering (i) the role of bacterial mineralisation, (ii) the effect of micrograzer excretion, and (iii) bacterial ability to compete for dissolved inorganic nutrients. The nutrient flux pathways between the abiotic pools and biotic groups and the patterns of biomass and nutrient limitation of the different phytoplankton groups were quantified for the different model configurations. Considerable variation in phytoplankton biomass and dissolved organic matter demonstrated the sensitivity of predictions to assumptions about microbial loop operation and the specific mechanisms by which phytoplankton growth was affected. Comparison of the simulations identified that the microbial loop most significantly altered phytoplankton growth by periodically amplifying internal phosphorus limitation due to bacterial competition for phosphate to satisfy their own stoichiometric requirements. Importantly, each configuration led to a unique prediction of the overall community composition, and we conclude that the microbial loop plays an important role in nutrient recycling by regulating not only the quantity, but also the stoichiometry of available N and P that is available to primary producers. The results demonstrate how commonly employed simplifying assumptions about model structure can lead to large uncertainty in phytoplankton community predictions and highlight the need for aquatic ecosystem models to carefully resolve the variable stoichiometry dynamics of microbial interactions.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 9
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    In:  EPIC3The VIth International Symposium on Inorganic Carbon Utilization by Aquatic Photosynthetic Organisms, 16-20 July, Malaga, Spain..
    Publication Date: 2019-07-16
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 10
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    In:  EPIC3Gordon Research Conference 'CO2 assimilation in plants: Genome to biome. 17-22 August, University of New England, Biddeford, USA..
    Publication Date: 2019-07-16
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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