منابع مشابه
r-Process Abundance Universality and Actinide Cosmochronology
We review recent observational and theoretical results concerning the presence of actinide nuclei on the surfaces of old halo stars and their use as an age determinant. We present model calculations which show that the observed universality of abundances for 56 < Z < 75 elements in these stars does not necessarily imply a unique astrophysical site for the r-process. Neither does it imply a univ...
متن کاملHope and Inquietudes in Nucleo-cosmochronology
Critical views are presented on some nucleo-cosmochronological questions. Progress has been made recently in the development of the 187 Re-187 Os cosmochronometry. From this, there is good hope for this clock to become of the highest quality for the nuclear dating of the Universe. The simultaneous observation of Th and U in ultra-metal-poor stars would also be a most interesting prospect. In co...
متن کاملCosmochronology and the universality of the r-process abundances
We review recent observational and theoretical results concerning the presence of actinide nuclei on the surfaces of old halo stars and their use as an age determinant. We present evidence that the observed universality of abundances for 56 < Z < 75 elements in these stars does not imply a unique astrophysical site for the r-process. Neither does it imply a universality of abundances of nuclei ...
متن کاملBeryllium in turnoff stars of NGC 6397 : early Galaxy spallation , cosmochronology and cluster formation ⋆
We present the first detection of beryllium in two turnoff stars of the old, metal-poor globular cluster NGC 6397. The beryllium lines are clearly detected and we determine a mean beryllium abundance of log(Be/H)= −12.35± 0.2. The beryllium abundance is very similar to that of field stars of similar Fe content. We interpret the beryllium abundance observed as the result of primary spallation of...
متن کاملI-12: Nuclear Reprogramming in Bovin Somatic Cell Nuclear Transfer
Somatic cell nuclear transfer (SCNT or cloning) returns a differentiated cell to a totipotent status; a process termed nuclear reprogramming. Reproductive cloning has potential applications in both agriculture and biomedicine, but is limited by low efficiency. To understand the deficiencies of nuclear reprogramming, our research has focused on both candidate genes and global gene expression pat...
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ژورنال
عنوان ژورنال: The Astronomical Journal
سال: 1960
ISSN: 0004-6256
DOI: 10.1086/108117