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  • Dielectric measurements  (4)
  • Central American Seaway  (1)
  • 1
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    High Precision Femtosecond Laser Ablation ICP‐MS Measurement of Benthic Foraminiferal Mn‐Incorporation for Paleoenvironmental Reconstruction: A Case Study From the Plio‐Pleistocene Caribbean Sea (2022)
    Details
    Publication Date: 2023-01-21
    Description: Closure of the Central American Seaway (CAS) and hydrology of the Caribbean Sea triggered Northern Hemisphere Glaciation and played an important role in the Pliocene to modern‐day climate re‐establishing the deep and surface ocean currents. New data on Mn/Ca obtained with femtosecond laser ablation inductively coupled plasma mass spectrometry on well‐preserved tests of the epibenthic foraminifer Cibicidoides wuellerstorfi and infaunal C. mundulus contribute to the interpretation of paleoenvironmental conditions of the Caribbean Sea between 5.2 and 2.2 Ma (million years) across the closure of the CAS. Hydrothermal activity at the Lesser Antilles may be a primary source of Mn in the well‐oxygenated Plio‐Pleistocene Caribbean Sea. Incorporation of Mn in the benthic foraminifer shell carbonate is assumed to be affected by surface ocean nutrient cycling, and may hence be an indicator of paleoproductivity.
    Description: Plain Language Summary: The closure of the Panama Isthmus caused the expansion of ice sheets in the Northern Hemisphere and changed the water current dynamics and climate in the Caribbean Sea since the Pliocene (∼5.3 million years ago). New Mn/Ca data measured using femtosecond laser ablation inductively coupled plasma mass spectrometry on the deep‐sea benthic foraminifer species Cibicidoides wuellerstorfi and Cibicidoides mundulus help us understand past environmental conditions of the Caribbean Sea prevailed between 5.2 and 2.2 million years ago. While manganese might be sourced from the surrounding hydrothermal vents, its incorporation in the foraminifer shell carbonate might be related to nutrient cycling and may indicate past biological productivity in the ocean.
    Description: Key Points: Femtosecond‐laser ablation inductively coupled plasma mass spectrometry provides a new approach on distinguishing Mn of the ontogenetic shell calcite from Mn of the authigenic coatings. Ontogenetic Mn within the foraminifer shell calcite may result from the regional nutrient cycle. Mn in the deep eastern Caribbean Sea may mainly derive from hydrothermal sources along the Antilles Island Arc.
    Description: MPIC
    Description: https://doi.org/10.17632/bps7nw7922.1
    Keywords: ddc:560 ; manganese ; Cibicidoides wuellerstorfi ; Cibicidoides mundulus ; Central American Seaway ; trace elements ; hydrothermal ; paleoproductivity
    Language: English
    Type: doc-type:article
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  • 2
    Electronic Resource
    Electronic Resource
    Dielectric investigation of the glass relaxation in poly(vinyl acetate) and poly(vinyl chloride) under high hydrostatic pressure (1985)
    Springer
    Colloid & polymer science 263 (1985), S. 873-878 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric measurements ; high pressure ; glass relaxation ; poly(vinyl acetate) ; poly(vinyl chloride)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Measurements of the complex relative permittivity of poly(vinyl acetate) from 35 °C to 190 °C and poly(vinyl chloride) from 90 °C to 150 °C in the frequency range 10−2 −107 Hz and the pressure range 1–5000 bar are reported. Details of the pressure generating system and of the dielectric equipment are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01469623
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  • 3
    Electronic Resource
    Electronic Resource
    Dielectric relaxation of ball-like labels in polyisoprene (1994)
    Springer
    Colloid & polymer science 272 (1994), S. 17-24 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric measurements ; label ; polyisoprene ; ball-like molecules ; glass process ; local process ; voids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Ball-like molecules with strong dipoles (labels) were mixed with synthetic polyisoprene (IR305) in low concentrations (〈1%) and measured dielectrically in the frequency range 10−2–107 Hz and the temperature range −70–0°C (glass relaxation region). Calorimetric measurements showed that this type of label has a plasticizing effect on the polymeric matrix. The dielectric measurements showed that these ball-like molecules relax through cooperative rotations with the polymeric segments and at the same relaxation frequency. In addition, the label molecules showed a high-frequency local relaxation process. The relaxation strength ratio of the local process (X local) to the total relaxation strength of the label was found to be dependent on the volume as well as on the shape of the label. A comparison between the relaxation behaviors of the ball-and rod-like molecules, having the same volume, showed that the length of the label is also an important parameter for the determination of the local contribution as well as of the cooperative relaxation mechanism of the label. The label relaxation process is discussed in relation to the molecular packing of the host polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00653306
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  • 4
    Electronic Resource
    Electronic Resource
    Dielectric relaxation of rod-like labels in polyisoprene (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 219-228 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric measurements ; label ; polyisoprene ; glass process ; rod-likemolecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Rod-like molecules with a strong dipole in the long axis were mixed with synthetic polyisoprene (IR305) in low concentrations (0.1–5 wt%) and measured dielectrically in the frequency range 10−2–106 Hz and the temperature range −60°–0°C (glass relaxation range). The measurements showed an additional symmetrical relaxation process slower than the glass process by a factor ranging from 10 to 100 times, depending on the length and structure of the label. The label relaxation process was characterized by a narrow distribution of relaxation times and its strong coupling with the segmental motion. For the labels with only a longitudinal dipole moment, no relevant part of the label relaxation was observed in the relaxation frequencies of the glass process; this may be attributed to the parallelism and compactness of the polyisoprene chains. In contrast, the labels with an additional vertical dipole component showed an additional relaxation process superimposed on the glass relaxation with also almost the same distribution of relaxation times. The slow label relaxation could be attributed to a diffusion or rotational diffusion relaxation process through a multistep relaxation mechanism determined by the segmental motion of the matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655473
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  • 5
    Electronic Resource
    Electronic Resource
    Method of determination of dielectric relaxation characteristics of plasticized polystyrenes on the basis of calorimetric glass temperature (1993)
    Springer
    Colloid & polymer science 271 (1993), S. 834-842 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric measurements ; calorimetric glass transition temperature ; glass relaxation process ; polystyrene ; oligostyrene ; polystyrene blends
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The dielectric loss measurements of different polystyrenes (fractions and blends) with different molecular weights (M n 2000–125000 g/mol) were carried out in the frequency range 10−2–106 Hz and the temperature range of the glass process (60°–135°C, depending on the molecular weight). The measurements of the pure fractions showed that the half-width of the glass relaxation process of the different polystyrenes can be correlated by a straight line, if they are plotted versus the relaxation frequency maxima of the glass process, regardless of the difference in both their molecular weight and glass transition temperature. Moreover, the fine structure of the shape of the glass process of polystyrenes with different molecular weights was found to be the same when the glass process appears at the same relaxation frequency range. The addition of oligostyrenes or low molecular 〈10% wt additives to the high molecular weight polystyrene did not influence the shape of the glass process. The calorimetric glass transition temperature of polystyrene was found to be only dependent on the number average molecular weight as well as on the number of end groups, but not on the molecular weight distribution. The obtained experimental results were correlated to develop a method for the estimation of the dielectric relaxation characteristics (relaxation frequency as well as the shape parameters) of the glass process of plasticized polystyrenes based on the calorimetric glass transition temperature. A method for the analysis of the dielectric relaxation curves of mixtures of label and polymer is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652765
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