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Possible effects of internal rotation in low-mass stars (1976)

Mengel, John G. ; Gross, Peter G.

Springer

Astrophysics and space science 41 (1976), S. 407-415

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ISSN: 1572-946X

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract The influence of internal rotation on the evolution of a 0.85M ⊙ star is investigated by the construction of model sequences. Rotation is treated by a simple one-dimensional approximation. The calculations assume solid-body rotation on the zero-age Main Sequence, followed by conservation of angular momentum in shells. The 4 cases considered have the initial angular velocities 0,2×10−4, 6×10−4, and 8×10−4/sec. All cases but the last are followed to helium ignition. Compared with the non-rotating case, the rotating models are older at Main-Sequence turnoff, develop fast-spinning central regions on the red-giant branch, and ignite helium at higher surface luminosities and at larger helium-core masses. The increases in the last two quantities are roughly proportional to the square of the initial angular velocity. The 6×10−4 case is followed through the helium core flash to the zero-age horizontal branch. Under the assumption of spherical symmetry, the non-central ignition of helium leads to a sequence of flashes of decreasing amplitude occurring progressively closer to the center. The flashes are weaker than those encountered in previous studies and do not produce mixing.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00646189

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Acetalisierungen mit N,N-Dimethylformamid-Dialkylsulfat-Addukten (1979)

Kantlehner, Willi ; Gutbrod, Heinz-Dieter ; Groß, Peter

Weinheim : Wiley-Blackwell

Liebigs Annalen 1979 (1979), S. 522-527

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ISSN: 0170-2041

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Description / Table of Contents: Acetalization Reactions with N,N-Dimethylformamide-Dialkyl Sulfate AdductsHern Professor Dr. Hellmut Bredereck zum 75. Geburtstag gewidmet.The adducts 2 and 3 from N,N-dimethylformamide and dialkyl sulfate adducts react in the presence of alcohols with aromatic aldehydes, α, β-unsaturated aldehydes, and ketones to form acetals and ketals, respectively. The influence of the nature of the carbonyl compound on acetalization is considered.

Notes: Die Addukte 2 und 3 aus N,N-Dimethylformamid und Dialkylsulfaten setzen sich in Gegenwart von Alkoholen mit aromatischen Aldehyden, α, β-ungesättigten Aldehyden oder Ketonen zu Acetalen bzw. Ketalen um. Der Einfluß der Art der Carbonylverbindung auf den Verlauf der Acetalisierung wird untersucht.

Additional Material: 2 Tab.