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  • 1
    ISSN: 1871-4528
    Keywords: nitrite ; nitrosamines ; acceptable daily intake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Zusammenfassung Der Einfluss von Stickstoffdüngung (50, 100 und 150 kg/ha) und Lagerungsdauer auf die Nitratkonzentration in Kartoffeln wurde im Feldversuch untersucht. Fünf Genotypen wurden in 5 ausgewählten Gebieten angebaut, die im Hinblick auf Tageslänge, Temperatur und Niederschläge grosse Unterschiede aufwiesen. Mit steigender Stickstoffzufuhr wurde eine signifikante Erhöhung der Nitratkonzentration nachgewiesen, wobei sowohl zwischen den verschiedenen Genotypen (Tab. 1) als auch Anbaugebieten (Tab. 3) die Unterschiede gesichert waren. Die höchste Nitratkonzentration wurde in Kartoffeln nachgewiesen die im kältesten Anbaugebiet geerntet wurden, die geringste Nitratkonzentration in Kartoffeln aus Anbaugebieten mit verhältnismässig hoher Sommertemperatur. Die Nitratkonzentration der Knollen verringerte sich während der Lagerungsdauer von 90–180 Tagen signifikant (Tab. 2). Durchschnittlich wurden selbst bei der höchsten Stickstoffdüngung verhältnismässig niedrige Nitratkonzentrationen in den Kartoffelknollen gemessen. Daher bestehen gegen die Verwendung der Kartoffeln für den menschlichen Verzehr keine gesundheitlichen Bedenken.
    Abstract: Résumé L'influence de la fertilisation azotée (50, 100 et 150 kg/ha) et de la durée de conservation sur la teneur en nitrate dans les pommes de terre a été étudiée en expérimentations de plein champ. Cinq génotypes de pommes de terre ont été cultivés dans cinq localités qui diffèrent, entre elles, par la longueur de jour, la température et l'humidité. La teneur en nitrate dans les tubercules augmente de façon significative avec l'apport d'azote, mais en moindre proportion pour certains génotypes (tabl. 1). La différence entre les localités est également significative (tabl. 3). La plus forte teneur est observée dans la localité ayant la période de végétation la plus froide, tandis que la plus faible teneur correspond à une température estivale relativement élevéc. La teneur en nitrate dans les tubercules diminue de façon significative pendant les périodes de conservation de 90 à 180 jours (tabl. 2). La teneur moyenne en nitrate demeure faible dans les tubercules, même pour la fertilisation la plus élevée. C'est pourquoi, les tubercules ne présentent aucun risque pour la consommation humaine.
    Notes: Summary The effect of nitrogen fertilizer at levels of 50, 100 and 150 kg per ha, and of the length of storage on the nitrate content of potatoes was studied in field experiments. Five genotypes were grown at five sites differing widely in day length, temperature and precipitation. The nitrate concentration of the tubers increased significantly with increasing nitrogen supply, but less in some genotypes than in others and there were significant differences between localities. The highest nitrate concentration was found at the locality with the coolest growing season, the lowest at one with a relatively high summer temperature. Nitrate in tubers decreased significantly during storage periods of 90 and 180 days. The overall concentration of nitrate in the tubers was low event at the highest N dressing, and the tubers can safely be recommended for human consumption.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Numerical Methods for Partial Differential Equations 6 (1990), S. 279-309 
    ISSN: 0749-159X
    Keywords: Mathematics and Statistics ; Numerical Methods
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The simulation of multiphase and multicomponent fluid flows often requires the solution of large, coupled systems of nonlinear partial differential equations of convection-advection type. The equations are usually advection dominated with small but important local diffusive effects. An operator-splitting technique is used to address these different phenomena. A modified method of characteristics is used to try to eliminate the nonsymmetry in the operators due to advection. Although this method does not completely symmetrize the problem with nonlinear, nonconvex flux functions, the remaining operator is almost symmetric and can be stabilized via Petrov-Galerkin techniques with optimal or near optimal test functions. Effective localized test functions are descrbed. A coarse grid is defined to treat the slow variation of the fluid velocity away from fronts. A substructuring of this grid gives a proper frontal resolution via local patch grid refinement. Preconditioning techniques are presented to efficiently solve the resulting composite-grid problem. Error estimates for the total approximation procedure are presented. Finally, certain two-dimensional computations are described.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2019-02-01
    Description: Rock and fluid samples were collected from three hydrothermal chimneys at the Endeavour Segment, Juan de Fuca Ridge to evaluate linkages among mineralogy, fluid chemistry, and microbial community composition within the chimneys. Mössbauer, midinfrared thermal emission, and visible-near infrared spectroscopies were utilized for the first time to characterize vent mineralogy, in addition to thin-section petrography, X-ray diffraction, and elemental analyses. A 282°C venting chimney from the Bastille edifice was composed primarily of sulfide minerals such as chalcopyrite, marcasite, and sphalerite. In contrast, samples from a 300°C venting chimney from the Dante edifice and a 321°C venting chimney from the Hot Harold edifice contained a high abundance of the sulfate mineral anhydrite. Geochemical modeling of mixed vent fluids suggested the oxic-anoxic transition zone was above 100°C at all three vents, and that the thermodynamic energy available for autotrophic microbial redox reactions favored aerobic sulfide and methane oxidation. As predicted, microbes within the Dante and Hot Harold chimneys were most closely related to mesophilic and thermophilic aerobes of the Betaproteobacteria and Gammaproteobacteria and sulfide-oxidizing autotrophic Epsilonproteobacteria. However, most of the microbes within the Bastille chimney were most closely related to mesophilic and thermophilic anaerobes of the Deltaproteobacteria, especially sulfate reducers, and anaerobic hyperthermophilic archaea. The predominance of anaerobes in the Bastille chimney indicated that other environmental factors promote anoxic conditions. Possibilities include the maturity or fluid flow characteristics of the chimney, abiotic Fe2+ and S2− oxidation in the vent fluids, or O2 depletion by aerobic respiration on the chimney outer wall.
    Type: Article , PeerReviewed
    Format: text
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  • 4
    Publication Date: 2015-09-09
    Description: We present ultraviolet (UV) observations of six nearby Type Ia supernovae (SNe Ia) obtained with the Hubble Space Telescope , three of which were also observed in the near-IR (NIR) with Wide-Field Camera 3. UV observations with the Swift satellite, as well as ground-based optical and NIR data provide complementary information. The combined data set covers the wavelength range 0.2–2 μm. By also including archival data of SN 2014J, we analyse a sample spanning observed colour excesses up to E ( B – V ) = 1.4 mag. We study the wavelength-dependent extinction of each individual SN and find a diversity of reddening laws when characterized by the total-to-selective extinction R V . In particular, we note that for the two SNe with E ( B – V )  1 mag, for which the colour excess is dominated by dust extinction, we find R V  = 1.4 ± 0.1 and R V  = 2.8 ± 0.1. Adding UV photometry reduces the uncertainty of fitted R V by ~50 per cent allowing us to also measure R V of individual low-extinction objects which point to a similar diversity, currently not accounted for in the analyses when SNe Ia are used for studying the expansion history of the Universe.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 5
    Publication Date: 2016-12-04
    Description: We present the results of work involving a statistically complete sample of 34 galaxy clusters, in the redshift range 0.15 ≤ z ≤ 0.3 observed with Chandra . We investigate the luminosity–mass ( LM ) relation for the cluster sample, with the masses obtained via a full hydrostatic mass analysis. We utilize a method to fully account for selection biases when modelling the LM relation, and find that the LM relation is significantly different from the relation modelled when not account for selection effects. We find that the luminosity of our clusters is 2.2 ± 0.4 times higher (when accounting for selection effects) than the average for a given mass and its mass is 30 per cent lower than the population average for a given luminosity. Equivalently, using the LM relation measured from this sample without correcting for selection biases would lead to the underestimation by 40 per cent of the average mass of a cluster with a given luminosity. Comparing the hydrostatic masses to mass estimates determined from the Y X parameter, we find that they are entirely consistent, irrespective of the dynamical state of the cluster.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 6
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
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  • 7
    Publication Date: 2020-02-12
    Description: Practical simulation of CO2 storage in geological formations inherently involves decisions concerning relevant physics, upscaling, and numerical modeling. These decisions are unavoidable, since the full problem cannot be resolved by existing numerical approaches. Here, we report on the impact of three distinct approaches to make the problem computationally tractable: reduced physics, upscaling, and non-converged discretizations. Compounding these different strategies, we have used a benchmark study to try to assess the impact of an expert group on the results of the numerical simulations. In order to restrict the scope of the investigation, the geometric and geological description of the storage aquifer was simplified to the greatest extent possible. The different strategies applied to simplify the problem, lead to significantly deviating answers when addressing relevant storage questions. Furthermore, there is room for interpretation when complex simulation results are simplified to the type of higher-level information sought in decision making processes. Our experience leads us to conclude that, important questions relating to CO2 storage cannot be predicted convincingly to satisfactory accuracy with numerical simulation tools, even for highly idealized problems. This emphasizes the need for real-time monitoring and history matching during injection operations.
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
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