Nuclear history enrichment

Much of the impetus for the awakened interest and utilization of inorganic membranes recently came hom a history of about forty or fifty years of some large scale successes of porous ceramic membranes for gaseous diffusion to enrich uranium in the military weapons and nuclear power reactor applications. In the gaseous diffusion literature, the porous membranes are referred to as the porous barriers. For nuclear power generation, uranium enrichment can account for approximately 10% of the operating costs (Charpin and Rigny, 1989]. 

Whatever the site, we now know from astronomical observations of very old stars in our Galaxy that the r process occurred early. In particular, these stars are so old that they formed from Galactic gas that was enriched with matter from only one or a few r-process events. Remarkably, for r-process nuclei in the nuclear mass range from about A = 130 to A = 195, the abundance pattern in these stars is almost identical to that inferred in the Solar System, for which millions of r-process events have contributed. The rather astonishing implication is that the r-process mechanism is robust in the sense that its operation seems to have been fairly constant throughout the history of the Galaxy. 

Our Galaxy is a collection of gas and stars nearly 13 billion years in age. Throughout its history, gas has condensed into stars. These stars live their lives in stable configurations by burning nuclear fuel which creates new nuclei (7). Once the usable nuclear fuel is exhausted, the star dies and expels its outer layers, thereby enriching the gas between the stars in new isotopes. This gas then can form into new stars, and the cycle repeats. One of the new stars that formed in the Galaxy 4.5 billion years ago is our Sun, and the chemical elements and their isotopes in our Solar System are thus the result of billions of years of Galactic history. 

This procedure has been used with success on a wide variety of plant groups and even some animals. The method is used to isolate total genomic DNA (nuclear, chloroplast, and mitochondrial). It is a rapid, inexpensive method that is suitabie for use in conjunction with other protocois, such as isolation of DNA enriched for cpDNA. it is also easy to scale down for use in population sampling, using 0.01 g or less of fresh tissue. Other applications include isolation of DNA from herbarium specimens (Doyle Dickson, 1987. Taxon 36 715-722), and isolation of RNA. A brief word on the history of the protocol is in order. This procedure was modified by us (Doyle and Doyle, 1987. Phytochemical Bulletin 19 11-15) for use with fresh piant tissue from a method of Saghai-Maroof et al. (1984, PNAS USA 81 8014-8019) who used lyophilized tissue. They in turn had developed their procedure from earlier protocols. We were recently asked to publish a slightly modified version of our procedure (Doyle and Doyle, 1990 Focus 12 13-15). We recently learned from Brian Taylor (Texas A M University, USA) that he had published a virtually identical procedure for fresh tissue, also in Focus, in 1982 (Taylor Powell, Focus 4 4-6) of which we (and apparently the editors of Focus ) were entirely unaware. It is indeed a useful procedure, thus independently confirmed. 

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