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  • 2020-2024  (3)
  • 2005-2009  (62)
  • 1985-1989  (27)
  • 1
    Publication Date: 2023-02-01
    Description: Geomagnetic excursions represent the dynamic nature of the geodynamo. Accumulated palaeomagnetic records indicate that such excursions are dominated by dipolar-fields, but exhibit different structures. Here we report a palaeomagnetic record from the varved sediments of Lake Suigetsu, central Japan, which reveals fine structures in the Laschamp Excursion and a new post-Laschamp excursion that coincides with the Δ14C maxima. The record’s high-resolution chronology provides IntCal20 mid-ages and varve-counted durations. Both excursions comprise multiple subcentennial directional-swings. Simulations of filtering effects on sediment-magnetisations demonstrate that this high-resolution record replicates most of the features in existing, lower-resolution Laschamp excursion records, including the apparent clockwise open-loop of the virtual geomagnetic pole pass. The virtual geomagnetic poles during the ‘swing’ phases make four clusters centred in hemispherically-symmetric regions, three of which encompass the virtual geomagnetic poles associated with the Laschamp Excursion recorded in lavas at various locations. The stationary dipolar-field sources under each cluster should have intermittently dominated one after another during the excursions.
    Type: info:eu-repo/semantics/article
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  • 2
    Publication Date: 2024-04-22
    Description: The Campi Flegrei (CF) caldera, in southern Italy, is the source of some of the most powerful Late Pleistocene eruptions of the European sub-continent (e.g., Campanian Ignimbrite, Neapolitan Yellow Tuff eruptions). Although the CF caldera has been continuously and intensively investigated for decades, relatively little is known regarding its earliest volcanic activity. In this work, integrating existing and new tephrostratigraphic data, we provide a comprehensive and updated framework for the CF volcanic activity which has occurred at ∼160 ka and between ∼110 ka and ∼90 ka. The new tephrostratigraphic, geochemical (EMPA + LA-ICP-MS), chronological (40Ar/39Ar dating) and grain-size distribution data relate to CF tephra deposits preserved in mid-proximal (Campanian Plain), distal (Tyrrhenian Sea) and ultra-distal (Lower Danube area) sedimentary archives. Our results allowed us to recognize the presence of at least 13 CF eruptions covering the investigated time frame, with 12 eruptions occurring between 110 and 90 ka. Our high-resolution stratigraphic and chronological investigation also allowed us to recognize that the Triflisco/C-22 tephra, previously considered as a single marker layer, can be actually separated into three different events, sourced from within the CF area in the short time interval of ∼93-90 ka, suggesting a more complex and intense volcanic history than previously thought. Moreover, a Bayesian age-depth model, constrained by previous and new high precision 40Ar/39Ar ages, has led to a reliable estimate of the ages of those undated CF eruptions. Overall, the updated framework on the stratigraphy, chronology, dispersion, and geochemistry of the CF tephra of ∼160 ka and between 110 ka and 90 ka consolidates the notion that the Middle-Late Pleistocene activity in theCF area represents a significant stage of its volcanic evolution, characterised by intense and frequent explosive eruptions.
    Type: info:eu-repo/semantics/article
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  • 3
    Publication Date: 2024-03-21
    Description: Understanding the temporal and spatial environmental response to past climate change during the Last Glacial-Interglacial Transition (LGIT, 16-8 ka) across Europe relies on precise chronologies for palaeoenvironmental records. Tephra layers (volcanic ash) are a powerful chronological tool to synchronise disparate records across the continent. Yet, some regions remain overlooked in terms of cryptotephra investigations. Building on earlier work at the same sites, we present the first complete LGIT high-resolution cryptotephra investigation of two lake records in the Carpathian Mountains in Romania, Lake Brazi and Lake Lia. Numerous volcanic glass shards have been recognised as originating from various volcanic regions, including: Iceland (Katla, Askja, and Torfajokull), Italy (Campi Flegrei, Ischia, Lipari, and Pantelleria), and central Anatolia (Acigol and Ericyes). In total, four distinct tephra horizons have now been identified in these records: 1) an LGIT Lipari tephra (11,515–12,885 cal BP, 95.4% range); 2) Askja-S (11,070–10,720 cal BP, 95.4% range); 3) an Early Holocene Lipari tephra,(12,590–10,845 cal BP, 95.4% range) and; 4) an Early Holocene Ischia tephra (11,120–10,740 cal BP, 95.4% range). The use of trace element analysis on selected cryptotephra layers provided additional important information in identifying volcanic source and facilitating correlations. These tephra layers, along with numerous other discrete cryptotephra layers, offer promise as significant future isochrons for comprehending the spatial and temporal fluctuations in past climate change throughout Europe and the Mediterranean area. This research has emphasized the significance of the Carpathian region in expanding the European and Mediterranean tephra lattice and establishing it as a keystone area within the framework.
    Type: info:eu-repo/semantics/article
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 4876-4884 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The radiative lifetime of nitrogen atoms in the 3p 4D0 state is determined to be 43±3 ns, and the total removal rate constants from the excited 3p 4D0 state of nitrogen atoms are measured for collisions with He, Ne, Ar, Kr, Xe, and N2. In a low pressure discharge flow reactor, the 3p 4D0 state is prepared by two-photon excitation from the 4S0 ground state of atomic nitrogen. Time-resolved fluorescence from the 3p 4D0→3s 4P transition monitors the temporal evolution of the population in the 3p 4D0 state. As the rare gases become heavier with a more complex electron cloud, the quenching rate constants increase from less than 0.6×10−11 cm3 s−1 for He to a value of 66±12×10−11 cm3 s−1 for Xe. Collision mechanisms which might account for such a dramatic increase are discussed.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1572-8889
    Keywords: eastern spruce budworm ; Choristoneura fumiferana ; white spruce ; balsam fir ; epicuticular wax
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fourth-instar larvae of the eastern spruce bud-worm Choristoneura fumiferanaClem. (Lepidoptera: Tortricidae) were shown in two-choice feeding tests to respond differently to epicuticular waxes from different white spruce and balsam fir trees. Larvae also showed different preferences for various wax fractions obtained by separation on silicic acid.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 38 (1985), S. 221-225 
    ISSN: 1570-7458
    Keywords: Eastern spruce budworm ; Choristoneura fumiferana ; Tortricidae ; feeding behaviour ; host plant extracts ; sugars/glycosides ; amino acids/bases ; organic acids ; two-choice feeding tests ; fir ; Abies ; spruce ; Picea spp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Trois extraits ont été obtenus de chacune de quatre plantes-hôtes: sucres/glycosides; acides aminées/bases organiques; acides organiques. Les quatre plantes-hôtes étudiées furent le sapin baumier, et les épinettes blanc, noir, et rouge. Le comportement gustatoire des larves a été étudié en raison de l'effet de combinaisons d'extraits de chaque plantehôte. Les résultats comparent la préférence des larves ainsi que leur consommation totale envers ces extraits.
    Notes: Abstract Three extracts were obtained from each of four host plants: sugars/glycosides; amino acids/bases; and organic acids. The four hosts studied were balsam fir, black spruce, red spruce, and white spuce. The effects of recombined host plant extracts on the feeding behaviour of eastern spruce budworm larvae were examined in two-choice tests. Results compare feeding preferences as well as feeding rates between combinations of extracts. The importance of each class of polar compounds is discussed.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Chimaeric genes can be constructed which fuse the transit peptide of a small subunit of the chloroplast-located ribulose l,5-bisphosphate carboxylase with a bacterial protein. The fusion protein is translocated into chloroplasts and cleaved in a similar way to the small subunit polypeptide ...
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  • 8
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chromosomes of the brooding species Lasaea consanguinea were studied as part of a general invertigation of evolutionary genetics of antarctic bivalve species. Laseid species are of particular interest because they are widely distributed geographically, they inhabit the high intertidal zone, and they may reproduce apomictically. The diploid number of chromosomes for Lasaea consanguinea ranges from 100 to 120, 110 to 112 being most frequent. Karyological data (2n=108) show 6 groups of chromosomes. Group I includes 8 metacentric (m), 3 submetacentric (sm), 2 subtelocentric (st) and 4 telocentric (t) pairs. Group II has 11 t to st pairs; group III, 9 sm to m pairs; group IV, 8 m to sm pairs; group V, 6 st and group VI, 3 m pairs. Within each of the Groups II to VI chromosome pairs are of about the same size and morphology. The chromosomes of Lasaea consanguinea are unusual because of their abundance, their large size and their numerical variability. We suggest that Lasaea consanguinea has had a hermaphroditic ancestor where abnormal reproduction such as inbreeding, lack of males, and apomixy gave rise to genetic instability, the high number of chromosomes being related to the genetic instability with evolutionary polyploidy or/and supernumerary chromosomes.
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  • 9
    ISSN: 1573-1561
    Keywords: Eastern spruce budworm ; Choristoneura fumiferana ; Lepidoptera ; Tortricidae ; conifers ; Picea sp. ; Abies sp. ; host volatiles ; attraction ; larval olfaction ; olfactometer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A two-choice, wind-tunnel olfactometer was designed and contructed to determine whether second-instar eastern spruce budworm larvae,Christoneura fumiferana (Clem.), could detect and discriminate among host-plant volatiles. Volatiles of current year's growth ofPicea glauca were preferred over those ofP. rubens, P. mariana, or air.Abies balsamea was preferred overP. mariana or air.P. rubens andP. mariana were both preferred over air. Two-year-old growth ofP. glauca, A. balsamea, P. rubens, andP. mariana were all preferred over air. Current year's growth of these host evergreen species was usually preferred over former year's growth of the same species in each case.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 11 (1985), S. 809-817 
    ISSN: 1573-1561
    Keywords: Eastern spruce budworm ; Lepidoptera ; Tortricidae ; Choristoneura fumiferana ; host preference ; deterrence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Feeding preferences to extracts from three host plants were determined for sixth-instar eastern spruce budworm larvae reared on one of three hosts or on artificial diet. Preferences of foliage-reared larvae were compared to those of diet-reared, or naive, larvae. No effect of plant induction was found using amino acids and bases and chloroform extracts on test disks in three-choice experiments. Possible effects of habituation for sugars and glycosides from white spruce were shown. Organic acids contributed to a phenomenon of avoidance learning in larvae reared on all three hosts, showing that this fraction from balsam fir was the least deterrent, while that from black spruce was the most deterrent.
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