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  • 551.9  (1)
  • Capillary electrophoresis  (1)
  • Diffuse reflectance spectrometry  (1)
  • Key words Chronoamperometry
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  • 1
    Electronic Resource
    Electronic Resource
    A model for the propagation of a redox reaction through microcrystals (1997)
    Springer
    Journal of solid state electrochemistry 1 (1997), S. 108-113 
    Details
    ISSN: 1433-0768
    Keywords: Key words Chronoamperometry ; Simulation ; Solid state electrochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Chronoamperometry of reversible redox reactions with the insertion of cations into solid particles immobilised at an electrode surface is analysed theoretically using a semiinfinite planar diffusion model. A coupled diffusion of electrons and ions within the crystal lattice is separated in two differential equations. The redox reaction is initiated by the polarisation of the three-phase boundary, where the crystal is in contact with both the electrode and the solution. From this contact line the redox reaction advances on the surface and into the crystal body by the diffusion of ions and conductance of electrons. The effects of the geometry and conductivity of the particles on the current are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100080050030
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Microscopic in situ diffuse reflectance spectroelectrochemistry of solid state electrochemical reactions of particles immobilized on electrodes (1997)
    Springer
    Journal of solid state electrochemistry 1 (1997), S. 62-67 
    Details
    ISSN: 1433-0768
    Keywords: Key wordsSpectroelectrochemistry ; Diffuse reflectance spectrometry ; Solid state electrochemistry ; Voltammetry ; Microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An instrumental setup is described which allows electrochemical measurements to be performed with solid particles immobilized on the surface of a graphite electrode with in situ recording of diffuse reflectance spectra under an incident light microscope. The instrument used includes a special electrochemical cell and a microscope which is interfaced by a light␣guide to a transputer-integrated photodiode-array spectrometer allowing measurements ranging from 320 to 950 nm with a resolution of 3.2 nm/pixel and a PC-interfaced potentiostat. The 0R0 geometry of the optical arrangement and the use of crossed polarization filters for blocking specular reflectance makes it possible to use the Kubelka-Munk function for quantifying the optical measurements. The above instrument has been used for the study of the electrochromic system of solid silver octacyanomolybdate(IV/V) adjacent to a silver nitrate solution. The in situ diffuse reflec tance spectroelectrochemical measurements prove that the electrochemical reaction starts at the graphite/sample interface and then advances into the bulk of the sample towards the sample/electrolyte interface. The ratios Red:Ox determined by spectrometry and chronocoulometry as a function of electrode potentials are identical.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100080050023
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The ionic hemolymph composition of the terrestrial isopod Porcellio scaber Latr. during molt (1997)
    Springer
    Journal of comparative physiology 167 (1997), S. 536-542 
    Details
    ISSN: 1432-136X
    Keywords: Key words Calcium ; Capillary electrophoresis ; Hemolymph ; Isopod ; Molting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We analyzed the ionic composition of the hemolymph of Porcellio scaber in four different stages of the molt cycle using capillary electrophoresis and calcium selective mini- and microelectrodes. The main ions in the hemolymph were K+, Ca2+, Na+, Mg+, and Cl−. The values for total calcium obtained by means of capillary electrophoresis and calcium selective minielectrodes did not differ significantly from each other. In situ measurements of the free Ca2+ concentration ([Ca2+]) by means of calcium-selective microelectrodes indicated that Ca2+ is not bound in the hemolymph. During molt the [Ca2+] is significantly larger than during intermolt. The [Ca2+] increased by 13%, 19% and 18% during premolt, intramolt, and postmolt, respectively. The concentration of the other cations and of Cl− decreased significantly between premolt and intramolt. Thus, the rise of the [Ca2+] in the hemolymph is not due to a general increase in all ions, but rather to the resorption of cuticular calcium. Furthermore, the results suggest that K+, Na+, Mg+, and Cl−are extruded from the hemolymph during and/or after posterior ecdysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600050106
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  • 4
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    Unknown
    Recycling and Burial of Biogenic Silica in an Open Margin Oxygen Minimum Zone (2021)
    Details
    Publication Date: 2021-07-21
    Description: An extensive data set of biogenic silica (BSi) fluxes is presented for the Peruvian oxygen minimum zone (OMZ) at 11°S and 12°S. Each transect extends from the shelf to the upper slope (∼1,000 m) and dissects the permanently anoxic waters between ∼200 and 500 m water depth. BSi burial (2,100 mmol m−2 yr−1) and recycling fluxes (3,300 mmol m−2 yr−1) were highest on the shelf with mean preservation efficiencies (34% ± 15%) that exceed the global mean of 10%–20%. BSi preservation was highest on the inner shelf (up to 56%), decreasing to 7% and 12% under anoxic waters and below the OMZ, respectively. The data suggest that the main control on BSi preservation is the rate at which reactive BSi is transported away from undersaturated surface sediments by burial and bioturbation to the underlying saturated sediment layers where BSi dissolution is thermodynamically and/or kinetically inhibited. BSi burial across the entire Peruvian margin between 3°S to 15°S and down to 1,000 m water depth is estimated to be 0.1–0.2 Tmol yr−1; equivalent to 2%–7% of total burial on continental margins. Existing global data permit a simple relationship between BSi rain rate to the seafloor and the accumulation of unaltered BSi, giving the possibility to reconstruct rain rates and primary production from the sediment archive in addition to benthic Si turnover in global models.
    Description: Key Points: Biogenic silica (BSi) preservation is high on the shelf and low under predominantly anoxic bottom waters BSi burial across the Peruvian margin down to 1,000 m water depth accounts for up to 7% of the global burial on continental margins Existing global data permit a simple relationship between BSi accumulation and rain rate
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Keywords: 551.9 ; burial ; flux ; oxygen minimum zone ; Peru ; sediment ; silica
    Type: article
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    CITATION GEO-LEO
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