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  • 1
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Polychaetes belonging to the genus Capitella are often present in high numbers in organic-rich sediments polluted with, e.g., oil components, and Capitella spp. may have a great impact on the biogeochemistry of these sediments. We examined the influence of Capitella sp. I on microbial activity in an organic-rich marine sediment contaminated with the polycyclic aromatic hydrocarbon, fluoranthene. Capitella sp. I were added to microcosms (10 000 ind m−2) and the impact of a pulse-sedimentation of fluoranthene-contaminated sediment (3 mm layer) was studied for a period of 12 d after sedimentation. The sediment oxygen uptake and total sediment metabolism (TCO2 production) increased in cores with worms (71 to 131%), whereas the anaerobic activity, measured as sulfate reduction rate 12 d after sedimentation, was lower compared to cores without worms. The effect of fluoranthene on sulfate reduction was most pronounced in the presence of worms, with a 34% reduction versus 16% in cores without worms. The reduced sulfur pools in cores with worms were smaller than in cores without worms, suggesting that the reduced anaerobic activity was caused by increased oxidation of the sediment, which may favor O2 and other electron-acceptors (e.g. NO3 −, Fe3+, Mn4+) in organic matter decomposition. The sediment oxygen uptake and TCO2 production did not show significant changes due to fluoranthene treatment, indicating that these parameters were either less sensitive to fluoranthene stress or recovered more rapidly (i.e. within 48 h) than sulfate reduction rates. Bioturbation by Capitella sp. I altered the depth profile of fluoranthene such that fluoranthene was found in deeper sediment layers (down to 2 cm) where diffusional loss and microbial breakdown probably are reduced relative to surface layers. In cores without worms, fluoranthene was found down to 1 cm, with 75% remaining in the upper 5 mm.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of engineering mathematics 33 (1998), S. 1-14 
    ISSN: 1573-2703
    Keywords: Atmospheric interface ; eye radius ; perturbation expansion ; vortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract A fully mature tropical cyclone is a complicated phenomenon, in which effects such as boundary-layer friction, latent heat release, and so on, must be accounted for, in order to give a complete description of the flow. Nevertheless, it is demonstrated here that a two-layer compressible atmosphere model, with a sharp interface separating the layers, is capable of giving a non-linear vortex-type solution at the lowest order of approximation. The ‘eye’ of the cyclone is formed when the interface is drawn down to sea level. Heat energy from the ocean into the cyclone and secondary flow within the vortex are both incorporated. The model provides an approximate description of cyclone behaviour, in terms that are easily understood. More complete descriptions are apparently only possible numerically, however, with a corresponding loss of ease of comprehension.
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  • 3
    Publication Date: 2011-06-07
    Print ISSN: 0277-5212
    Electronic ISSN: 1943-6246
    Topics: Biology
    Published by Springer
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  • 4
    Publication Date: 1997-06-26
    Print ISSN: 0025-3162
    Electronic ISSN: 1432-1793
    Topics: Biology
    Published by Springer
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  • 5
    Publication Date: 2019-08-15
    Description: Chronic, low intensity herbivory by invertebrates, termed background herbivory, has been understudied in tundra, yet its impacts are likely to increase in a warmer Arctic. The magnitude of these changes is however hard to predict as we know little about the drivers of current levels of invertebrate herbivory in tundra. We assessed the intensity of invertebrate herbivory on a common tundra plant, the dwarf birch (Betula glandulosa-nana complex), and investigated its relationship to latitude and climate across the tundra biome. Leaf damage by defoliating, mining and gall-forming invertebrates was measured in samples collected from 192 sites at 56 locations. Our results indicate that invertebrate herbivory is nearly ubiquitous across the tundra biome but occurs at low intensity. On average, invertebrates damaged 11.2% of the leaves and removed 1.4% of total leaf area. The damage was mainly caused by external leaf feeders, and most damaged leaves were only slightly affected (12% leaf area lost). Foliar damage was consistently positively correlated with mid-summer (July) temperature and, to a lesser extent, precipitation in the year of data collection, irrespective of latitude. Our models predict that, on average, foliar losses to invertebrates on dwarf birch are likely to increase by 6–7% over the current levels with a 1 °C increase in summer temperatures. Our results show that invertebrate herbivory on dwarf birch is small in magnitude but given its prevalence and dependence on climatic variables, background invertebrate herbivory should be included in predictions of climate change impacts on tundra ecosystems.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 125 (1987), S. 183-189 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
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  • 7
    ISSN: 0992-7689
    Keywords: Meteorology and atmospheric dynamics ; Middle atmosphere dynamics ; Thermospheric dynamics ; Waves and tides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Meteor radar measurements of winds near 95 km in four azimuth directions from the geographic South Pole are analyzed to reveal characteristics of the 12-h oscillation with zonal wavenumber one (s = 1). The wind measurements are confined to the periods from 19 January 1995 through 26 January 1996 and from 21 November 1996 through 27 January 1997. The 12-h s = 1 oscillation is found to be a predominantly summertime phenomenon, and is replaced in winter by a spectrum of oscillations with periods between 6 and 11.5 h. Both summers are characterized by minimum amplitudes (5–10 ms−1) during early January and maxima (15–20 ms−1) in November and late January. For 10-day means of the 12-h oscillation, smooth evolutions of phase of order 4–6 h occur during the course of the summer. In addition, there is considerable day-to-day variability (±5–10 ms−1 in amplitude) with distinct periods (i.e., ∼5 days and ∼8 days) which suggests modulation by planetary-scale disturbances. A comparison of climatological data from Scott Base, Molodezhnaya, and Mawson stations suggests that the 12-h oscillation near 78°S is s = 1, but that at 68°S there is probably a mixture between s = 1 and other zonal wavenumber oscillations (most probably s = 2). The mechanism responsible for the existence of the 12-h s = 1 oscillation has not yet been identified. Possible origins discussed herein include in situ excitation, nonlinear interaction between the migrating semidiurnal tide and a stationary s = 1 feature, and thermal excitation in the troposphere.
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  • 8
    ISSN: 0992-7689
    Keywords: Meteorology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; waves and tides)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The first meteor radar measurements of meridional winds in the lower thermosphere (about 95 ± 5 km), along four azimuth directions: 0°, 90°E, 180° and 90°W; approximately 2° from the geographic South Pole were made during two observational campaigns: January 19, 1995-January 26, 1996, and November 21, 1996-January 27, 1997. Herein we report analyses of the measurement results, obtained during the first campaign, which cover the whole one-year period, with particular emphasis on the transient nature and seasonal behavior of the main parameters of the intradiurnal wind oscillations. To analyze the data, two complementary methods are used: the well-known periodogram (FFT) technique and the S-transform technique. The most characteristic periods of the intradiurnal oscillations are found to be rather uniformly spread between about 7 h and 12 h. All of these oscillations are westward-propagating with zonal wave number s = 1 and their usual duration is confined to several periods. During the austral winter season the oscillations with periods less than 12 h are the most intensive, while during summer season the 12-h oscillations dominate. Lamb waves and internal-gravity wave propagation, non-linear interaction of the short-period tides, excitation in situ of the short period waves may be considered as possible processes which are responsible for intradiurnal wind oscillations in the lower thermosphere over South Pole.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0992-7689
    Keywords: Meteorology and atmospheric dynamics (Middle atmospheric dynamics; waves and tides)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Observations of the horizontal wind field over the South Pole were made during 1995 using a meteor radar. These data have revealed the presence of a rich spectrum of waves over the South Pole with a distinct annual occurrence. Included in this spectrum are long-period waves, whose periods are greater than one solar day, which are propagating eastward. These waves exhibit a distinct seasonal occurrence where the envelope of wave periods decreases from a period of 10 days near the fall equinox to a minimum of 2 days near the winter solstice and then progresses towards a period near 10 days at the spring equinox. Computation of the meridional gradient of quasi-geostrophic potential vorticity has revealed a region in the high-latitude upper mesosphere which could support an instability and serve as a source for these waves. Estimation of the wave periods which would be generated from an instability in this region closely resembles the observed seasonal variation in wave periods over the South Pole. These results are consistent with the hypothesis that the observed eastward propagating long-period waves over the South Pole are generated by an instability in the polar upper mesosphere. However, given our limited data set we cannot rule out a stratospheric source. Embedded in this spectrum of eastward propagating waves during the austral winter are a number of distinct wave events. Eight such wave events have been identified and localized using a constant-Q filter bank. The periods of these wave events ranges from 1.7 to 9.8 days and all exist for at least 3 wave periods. Least squares analysis has revealed that a number of these events are inconsistent with a wave propagating zonally around the geographic pole and could be related to waves propagating around a dynamical pole which is offset from the geographic pole. Additionally, one event which was observed appears to be a standing oscillation.
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  • 10
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Description anatomique et histologique des organes du tube digestif deCamponotus pennsylvanicus mâles pris dans leurs nids durant le mois de mai ou saisis pendant l'essaimage nuptial en juillet. La position des organes et leur histologie sont semblables à celles qui ont été déjà décrites pour lesCamponotus ouvrières. Dans le ventriculus du mâle, pourtant, les cellules épithéliales sont plus longues et leur forme est quelque peu différente de celles de l'ouvrière. Tous les organes digestifs gastriques du mâle contiennent de la nourriture. La plupart des mâles disséqués avaient 18 tubes de Malpighi; d'autres en avaient 20, un en avait 23; dans ce dernier, il y avait des tubulibranches. Chez les mâles essaimants, la plupart des organes digestifs gastriques sont affaissés ou réduits en diamètre. Le jabot, le gésier et le ventriculus reposent pratiquement sur le fond des trois premiers segments gastriques; cette position libère de grands espaces dans la partie antéro-dorsale de l'abdomen. Le système digestif est vide de nourriture. Les cellules épithéliales du ventriculus sont en dégénérescence et la cavité de cet organe est remplie de grains intensément colorables par l'hématoxyline. Il y a des différences entre le ventriculus deC. pennsylvanicus, décrit ici, et celui deAnergates atrautulus, décrit parMeyer (1955).
    Abstract: Zusammenfassung Die Anatomie und Histologie der Verdauungsorgane im Gaster des männlichenCamponotus pennsylvanicus werden beschrieben auf Grund von Exemplaren, die im Mai aus dem Nest genommen und im Juli während der Hochzeitsflug gefangen wurden. Die Verteilung der Organe und ihre Histologie sind ähnlich denen der Arbeiter vonCamponotus, die schon früher beschrieben wurden. Im männlichen Mitteldarm sind allerdings die Epithelzellen höher und ihre Form ist etwas anders als im Mitteldarm des Arbeiters. Nahrung ist vorhanden in allen männlichen Verdauungsorganen des Gasters. Die meisten untersuchten Männchen hatten 18 Malpighische Gefässe, einige hatten 20 und eines hatte 23; in letzterem Falle war einer der Gefässe verzweigt. In den Männchen in Hochzeitsflug sind die meisten Verdauungsorgane des Gasters zusammengefallen, oder ihr Durchmesser ist reduziert. Der Kropf, der Vormagen und der Mitteldarm liegen praktisch am Boden der drei ersten gastralen Segmente. Dieser Zustand läßt große Räume in der dorsalen Vorderende des Gasters frei. Das System enthält keine Nahrung. Die Epithelzellen des Mitteldarms degenerieren und das Lumen dieses Organs ist voll mit basophilen Körnchen. Es bestehen Unterschiede zwischen dem hier beschriebenen Mitteldarm vonC. pennsylvanicus und dem vonAnergates atratulus, welcher vonMeyer (1955) beschrieben wurde.
    Notes: Summary The anatomy and histology of the digestive organs in the gaster ofCamponotus pennsylvanicus males are described for those taken from nests during the month of May and for those captured when they were swarning for the nuptial flight in July. The arrangement of the organs and their histology are similar to that which has already been described for theCamponotous workers. In the male ventriculus, however, the epithelial cells are taller and their shapes somewhat different from those in the worker. There is food in all themale gastral digestive organs. Most males dissected had 18 Malpighian tubules, some had 20, and one had 23; in this latter case, one was branched. In the swarming males most of the gastral digestive organs are collapsed or reduced in diameter. The crop, proventriculus, and ventriculus are practically lying on the floor of the first three gastral segments; this condition leaves large spaces in the dorsal anterior end of the gaster. The system is empty of food. The epithelial cells of the ventriculus are degenerating, and the lumen of this organ is filled with basophilic-staining granules. There are differences between the midguts ofC. pennsylvanicus, here described, and ofAnergates atratulus, described byMeyer (1955).
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