Der Umgitterungsmechanismus der Phasenumwandlung kub.‐flz. γ → kub.‐rz. α hängt von der Stapelfehlerenergie (SFE) ab. Bei großer SFE ist eine Verschiebung von (111)γ‐Ebenen durch Shockleysche Halbversetzungen vom Typ b = 1/6 [211]γ nicht möglich, und die direkte Umgitterung γ → α erfolgt durch zwei homogene Scherungen um 19°28′ bzw. 10°32′. Bei einer SFE unterhalb von etwa 15 bis 20 erg/cm2 findet diese Abgleitung jedoch statt, wobei sich die ϵ‐Phase bildet. Abhängig von der thermodynamischen Stabilität kann durch eine weitere Scherung die ϵ → α‐Umwandlung erfolgen. Die Umwandlung γ → α erfolgt vorzugsweise durch äußere elastische Spannungen, der γ → ϵ → α‐Übergang ebenso, aber auch durch plastische Deformation auf Grund von gleitfähigen Teilversetzungen.

On guinea-pig heart we investigated whether cyclic AMP serves as a messenger for H1 - and/or H2-mediated responses to histamine. (1) On papillary muscle histamine elicited positive inotropic responses which were antagonized by burimamide but not by promethazine. The stimulation of H2-receptors was not only associated with an increase in contractility but also with an increase in cAMP. As shown by the time course of effects for 10(-5) M histamine, the maximal increase in cAMP preceded the maximum in contractility. The mechanical and biochemical responses to histamine were potentiated by the phosphodiesterase inhibitor papaverine, but antagonized by burimamide. (2) On the left guinea-pig atrium containing H1-receptors the inotropic response to histamine (10(-5) M) was not accompanied by increases in cAMP at stimulation frequencies of 0.5 and 2 Hz, respectively. In addition, in the presence of papaverine (3 X 10 (-5) M) no change in the cyclic AMP level occurred after application of histamine. Papaverine by itself, however, concomitantly increased contractility and cyclic AMP at a stimulation frequency of 0.5 Hz. In contrast, at 2 Hz papaverine increased only cAMP leaving the contractility unchanged. At this frequency the well-known Ca2+-antagonistic effect comes into prominence, thus masking the positive inotropic effect attributable to the inhibition of the phosphodiesterase. (3) On the right guinea-pig atrium the mediation of the positive chronotropic response to histamine by H2-receptors which is partly involved in the inotropic effect via the frequency-force relationship does not lead to a concomitant increase in cAMP. Also, in the presence of papaverine, histamine had no influence on the cAMP. However, papaverine potentiated the cardioacceleration produced by histamine. Although it is very likely that the cAMP in the sinus node rises, we were not able to detect an increase in cAMP in the whole atrial tissue. From the present results the conclusion can be drawn that the mediation of the inotropic effect due to stimulation of H2-receptors by histamine is associated with an increase of cyclic AMP, whereas that of H1-receptors is not. The view that cAMP may be the second messenger in the chronotropic action of histamine needs further elucidation by experiments on sino-atrial cells.

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Dilatometrische, magnetometrische und röntgenographische sowie metallographische Untersuchungen mit Gefügeaufnahmen über die Austenit‐Martensit‐Umwandlung von Manganstählen mit rd. 0,035 bis 0,06% C, 2,25 bis 31,1% Mn und geringen Gehalten an den üblichen Begleitelementen von Stahl. Einfluß einer Kaltverformung. Besprechung der Ergebnisse mit Folgerungen vor allem über die Konzentrationsbereiche und Morphologie der Umwandlung zu α‐Martensit und ε‐Martensit und über die Weiterumwandlung von ε‐Martensit in α‐Martensit.

Die Menge an verformungsinduziertem a -Martensit hangt bei mctastabilen austenitischcn Stiihlen von der Stapelfehlerenergie ab. Liegt diese oberhalb von etwa 100 erg/cm2, so findet eine direkte y -+ a-Umwandlung statt, die wegen des komplizierten Schermechanismus bei der Umgitterung durch iiuRere Spannungen bzw. Deformationen quantitativ nicht oder nur geringfugig beeinflufit w-ird. In dem Mafie, wie durch Zugabe bestimmter The volume of strain induced a-martensite in metastable steels depends on the stacking fault energy. If its value makes more than -100 ergs/cm*, a direct y -a transformation occurs, this being not or little quantitatively influenced because of the complicated shearing mechanism of lattice change by external stresses or strains. Tho tendency to form extended stacking faults or hexagonal e-martensite increases to the ciegrcc as by adding of certain alloying elements, as e. g. Cr + Ni, Cr + Mn or Mn + C, the stacking fault energy is lowered. The indirect y -E -a or y -SF -a-transformation occurs, where &-martensite and stacking faults only gradually differ from eachother. Because of the simple shearing mechanism of the y / & and y/SF transformation external stresses are strongly favouring the indirect transformation. Especially in crossing regions o f &-plates or stacking faults, but also in their internal parts, shearings are generated which are prestages or nuclei of a-crystals. If the SFE is below -20 ergs/cm2 a complete strain induced a-martensite formation becomes possible, if this is in accordance with the thermodynamic stability relations.

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4-triazole interact with methaemoglobin from Chironomus plumosus. In a weakly acidic environment all complexes show light absorption spectra of the parahaematin type with maxima near 535 and 415 mp. 2. The affinity of these ligands to Chironomus-methaemoglobin rises with increasing basic strength, with the exception of 3-amino-l,2,4-triazole. 3. The spectra of the N-alkylated imidazoleor triazole-complexes are pH-invariant, while those of the complexes with ligands containing a free NH-group shift their maxima to longer wavelengths in alkaline medium (about 542 and 417 mp). 4. This spectral change is attributed to the deprotonation of the NH-group of the bound ligands. The ionization constants of this reaction have been estimated. They demostrate a strong increase of the acidity of these ligands as a result of their interaction with the haemoprotein. 5. Furthermore, the ligands influence the ionization constants of some haemin-linked protein groups. 6. The results are an example of the changes of the electronic properties of low-molecular compounds (drugs etc.) interacting with specific receptors of biomacromolecules and vice versa.

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