The ensuing atomic interactions create a steady supply of c14 that rapidly diffuses throughout the atmosphere.Plants take up c14 along with other carbon isotopes during photosynthesis in the proportions that occur in the atmosphere; animals acquire c14 by eating the plants (or other animals). When diffusive isotope fractionation of Sr isotopes is repeated a sufficient number of times by within-mantle processes on isotopically-anomalous mantle xenoliths (each of which originally had low Sr ratios.When mixed with variable amounts of terrestrial nonradiogenic strontium, these remnants generate mixing lines indistinguishable from age-indicative Rb-Sr isochrons.Working with several collaboraters, Libby established the natural occurrence of radiocarbon by detecting its radioactivity in methane from the Baltimore sewer.In contrast, methane made from petroleum products had no measurable radioactivity.Using this method, we demonstrate a high-resolution separation of 0.5, 1, 2, 5, and 10 kbp DNA fragments within 2 min.
Libby, a Professor of Chemistry at the University of Chicago, predicted that a radioactive isotope of carbon, known as carbon-14, would be found to occur in nature.
Two decades ago, Volkmuth and Austin introduced a patterned micro-post array in a microfluidic electrophoresis platform, in which DNA fragments were separated by biased reptation under a DC electric field. separated large fragments in a range of 60–135 kbp in a microfabricated array using DNA reorientation—or the ‘switchback’ principle.
Although the switchback principle is similar to what is used in PFGE, the device yields much faster separations owing to its sparse and regular sieving array. studied a three-dimensional (3D) nanopost array as an optimal separation matrix for DNA fragments over a few kbps under a DC electric field, resulting in similarly fast separations due to the sparse matrix performed continuous flow PFGE in a micromachined post array by applying pulsed electric fields of slightly unequal strengths.
The possibility of isotopic fractionation as an explanation for differences in Sr has been proposed to both authors on many occasions.
It therefore seems worthwhile to point out that isotopic fractionation does occur during the mass spectrometric ratio measurement.