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  • Solid state electrochemistry  (2)
  • Capillary electrophoresis  (1)
  • 1995-1999  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 167 (1997), S. 536-542 
    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
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of solid state electrochemistry 1 (1997), S. 108-113 
    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
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of solid state electrochemistry 1 (1997), S. 62-67 
    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
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