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Effect of divalent cations on the potassium contracture of slow muscle fibers ofRana temporaria (1987)

Schmidt, H.

Springer

The journal of membrane biology 100 (1987), S. 215-220

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ISSN: 1432-1424

Keywords: slow muscle fiber ; K contracture ; divalent cations

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Summary K contractures of single slow muscle fibers ofRana temporaria were measured isometrically in the presence of normal, reduced, and increased Ca2+ concentrations at 18 to 20°C. At normal Ca2+ concentration (1.8mm) contracture tension decreased from its peak value of 35.4±8.2 N/cm2 to 59.4±23.9% within one minute, and to 48.3±27% within two minutes (30 fibers). Peak tension was virtually unaffected by changes of the Ca2+ concentration, but maintenance of tension was impaired by low (0.2mm), and improved by high (10mm) Ca2+ concentrations. When Ca2+ was added during the K contracture, there was practically no restoration of lost tension. Effects similar to those of Ca2+ were observed upon addition of foreign divalent cations to the medium. Co2+, Ni2+, and Cd2+ were slightly more effective than Ca2+ and Mn2+; the smallest effects were obtained with Mg2+, Sr2+, and Ba2+. The effects of foreign divalent cations were independent of the presence of Ca2+. It is concluded that in slow fibers ofRana temporaria maintenance of contracture tension is not due to an influx of Ca2+ ions. Instead, binding of divalent cations to superficial sites seems to be essential.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02209152

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High temperature sulfidation of Fe-Mn alloys and Mn in H2-H2SDedicated to Professor Dr. Alfred Rahmel on the occasion of his 60th birthday (1987)

Papaiacovou, P. ; Schmidt, H.-P. ; Grabke, H. J. ; [et al.]

Weinheim [u.a.] : Wiley-Blackwell

Materials and Corrosion/Werkstoffe und Korrosion 38 (1987), S. 498-506

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ISSN: 0947-5117

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Description / Table of Contents: Sulfidierung von Fe-Mn-Legierungen und Mn bei hohen TemperaturenDie Sulfidierung von Fe-Mn-Legierungen mit 20-50% Mn und von reinem Mn wurde bei 973 K, 1073 K und 1173 K in H2-H2S Atmosphären bei konstantem pS2 oder konstantem pH2S/pH2 untersucht, unter Bedingungen, bei denen nur MnS gebildet wird. Die Sulfidierungskinetik ist vorwiegend parabolisch, aber bedingt durch zwei verschiedene Diffusionsvorgänge. Bei der Sulfidierung der Fe-Mn-Legierungen bei 973 K und 1073 K ist die Diffusion der Mn-Atome in der Legierung der geschwindigkeitsbestimmende Vorgang, und es wird eine verzahnte Grenzfläche Sulfidschicht/Legierung beobachtet. Bei 1173 K erfolgt ein Übergang zur Kontrolle der Sulfidierungsgeschwindigkeit durch Diffusion des Mn in der Sulfidschicht und ein Übergang von der verzahnten Grenzfläche zur ebenen Grenzfläche.

Notes: The sulfidation behaviour of a range of Fe-Mn alloys and pure Mn were studied at 973 K, 1073 K, and 1173 K in H2-H2S atmospheres at constant pS2 or constant pH2S/pH2. The sulfidation kinetics were parabolic in most cases, but two different diffusion processes affect the kinetics. In the sulfidation of the Fe-Mn alloys at 973 K and 1073 K, the diffusion of manganese atoms in the alloy is the rate-determining step and an interlocked scale/alloy interface is observed. At 1173 K there is a transition to rate-control by the diffusion of manganese in the sulfide scale connected with transition from rugged to a planar scale/alloy interface.

Additional Material: 13 Ill.