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Let G be a finite undirected graph without loops and multiple edges. A graph is called “unterringfrei”, if there is no induced subgraph being a cycle of length⩾4. This note shows that the chromatic polynomial of such a graph does only have positive integers as its roots. Conversely all polynomials with only positive integral roots are the chromatic polynomials of such graphs under the slight restriction that M(G;α)=0 implies that M(G;β)=0 for α>β⩾0.

1. Cat ventricular muscle fibers were bathed in K-rich (13.7 mM) Tyrode solution so that action potentials were mediated by the slow Ca inward current. 2. Sucrose osmotically balanced Tyrode solutions with 50, 25 and 8.3% of normal Na concentration were used in all experiments. The basic effects of Na withdrawal are decrease of action potential upstroke velocity, overshoot and duration, and increase peak and resting tension. Threshold of stimulation also increased. 3. The time courses of these Na withdrawal effects were significantly related in that action potential impairment always closely followed the positive inotropy. Furthermore, this time-dependence on inotropic state resembled that of electrical and mechanical effects from experiments of Cae variation in K-rich Tyrode solution. 4. It was found that reduced frequency and rest periods enabled the muscles to recover from the electrical and mechanical effects of Na withdrawal. The reappearance of all full Na withdrawal effects after rest periods followed the same time courses, though slightly faster, as in Na withdrawal treatment of continuously stimulated muscles. If stimulation was stopped before Na withdrawal and not resumed until 10 or 25 min after, the initial action potentials were nearly full sized, there was no visible inotropic effect, and full effects required nearly as much time as in continuously stimulated muscles. 5. The evidence shows clearly that Na does not detectably contribute to the slow inward current. In addition, flux studies showing that increased intracellular free Ca results from Na withdrawal, when considered with the relationship between action potential impairment and positive inotropy, suggest as a necessary conclusion that it is a reduced transmembrane Ca gradient which is responsible for impairment of Ca-mediated action potentials.

Auf Grund der in § 2 der Abhandlung naher begrundeten Tatsache, das die Grose des Unterschiedes zwischen derK- Absorptionsgrenze und derKγ- Linie eines chemischen Elementes mit der Grose der Atomnummer des letzteren in gesetzmasigem Zusammenhang steht, werden in § 3 fur die Elemente mit einer Atomnummer zwischen 22 und 52 zunachst derv/R-Wert derK- Grenze aus demjenigen der genauer mesbarenKγ-Linie und daraus dann mit Hilfe derv/R-Werte der in Frage kommenden Emissionslinien unter Benutzung der bekannten Additionsbeziehungen auch diev/R-Werte der ubrigen Niveaus berechnet, so das sich also alle diese Zahlenwerte lediglich auf die Messungen der Wellenlangenwerte von Spektrallinien stutzen, die sich eben mit erheblich groserer Genauigkeit ausfuhren lassen als die der Absorptionsgrenzen selbst.

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(1889). LVI. On the relation between fluorescence and arrangement of molecules. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science: Vol. 28, No. 175, pp. 473-480.

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