Radioisotope dating with an accelerator: a blind measurement

The age of a sample of carbon dioxide has been determined by accelerating the carbon with a cyclotron and detecting the carbon-14 ions in the beam. Nitrogen-14 was eliminated as a background through the use of a range-separation technique. To avoid all possibility of experimenter bias, the measurement was conducted in a blind fashion.     

Beryllium-10 mass spectrometry with a cyclotron

The Grenoble cyclotron has been used as a mass spectrometer to measure ratios of beryllium-10 to beryllium-9 of 10(-8), 10(-9), and 10(-10) in standardized beryllium oxide samples. Similar measurements can be used to determine cosmogenic beryllium-10 (half-life, 1.5 x 10(6) years) profiles in various geophysical reservoirs such as sea sediments and polar ice. This procedure can be used either to date such samples or to give information about geophysical and astrophysical phenomena that have influenced the beryllium-10 production rate in the past.     

Radiocarbon dating with electrostatic accelerators: dating of milligram samples

The recently developed direct counting technique for radiocarbon atoms has been used to measure the relative numbers of such atoms in various geological samples which had earlier been dated by the beta-ray counting method. Sample weights ranged from 3.5 to 15 milligrams. The dates determined by the two methods are consistent with each other. Further experience with the new method is also reported.     

Radioisotope uptake as a measure of synthesis of messenger RNA

Exogenously supplied radioactive uracil (or guanine) enters the intracellular pools of RNA precursors in Escherichia coli only as nucleotides are removed from these pools by net synthesis of RNA. Consequently uptake of uracil over a short period does not measure the sum of the synthesis of all forms of RNA, unstable and stable, as is often supposed. Uptake of uracil during changing conditions of growth may be influenced by changes in types of RNA's being made; under such conditions that no stable RNA is being made, the synthesis of unstable forms may be greatly underestimated.     

Zinc-65 in cyclotron workers

Small but persistent body burdens of zinc-65 have been found in cyclotron workers. This radionuclide and others are produced by nuclear reactions with the construction materials of the cyclotron. Only zinc-65 has gained entry into the body, but in amounts of less than 1 percent of the maximum permissible amount.     

农药代谢试验放射性同位素示踪样品处理技术

本文根据相关文件和标准内容,综述了农药登记代谢试验核素选择原则、供试作物要求、示踪剂引入方法以及样品的提取、纯化技术要点。合理的预处理方法可以降低液闪测试的淬灭效应,提高登记代谢试验结果准确性,减少样品和试剂用量,减少放射性废物处理成本和不必要的污染。     

Obsidian hydration dating applied to dating of basaltic volcanic activity

Basalt flows and bombs that contain remelted rhyolite glass can be dated by obsidian hydration dating.     

Glass hydration: a method of dating glass objects

A new nondestructive method for dating or authenticating man-made glass is proposed, and the initial results of an exploration of the potential of this method are presented. The method is based on a relation between the age of a glass object and the thickness of the layer of hydrated glass on its surface, with the thickness of this hydrated surface layer being measured by means of the (15)N nuclear resonance depth profiling technique. A qualitative age scale is established for some common 19th- and 20th-century American glass.     

Ultrastrong coupling of the cyclotron transition of a 2D electron gas to a THz metamaterial

Artificial cavity photon resonators with ultrastrong light-matter interactions are attracting interest both in semiconductor and superconducting systems because of the possibility of manipulating the cavity quantum electrodynamic ground state with controllable physical properties. We report here experiments showing ultrastrong light-matter coupling in a terahertz (THz) metamaterial where the cyclotron transition of a high-mobility two-dimensional electron gas (2DEG) is coupled to the photonic modes of an array of electronic split-ring resonators. We observe a normalized coupling ratio, Ω/ω(c) = 0.58, between the vacuum Rabi frequency, ?, and the cyclotron frequency, ω(c). Our system appears to be scalable in frequency and could be brought to the microwave spectral range with the potential of strongly controlling the magnetotransport properties of a high-mobility 2DEG.     

Pottery dating from thermoluminescence

For pottery sherds from an arid region, the ratio of natural thermoluminescence to thermoluminescence induced by a standard dose of radiation corresponds closely to the independently assessed archeologic age. Difficulties in age determination, because of variations among sherds, are reduced by averaging results for samples from the same time period.     

Carbon-14 dating: a comparison of Beta and ion counting

Accelerator ion counting compares favorably with conventional beta counting. The major advantage of ion counting is that milligram samples can be analyzed. When sample size is not limiting, ion counting complements beta counting for the more routine carbon-14 determinations. Further development is needed before ion counting can achieve the same high precision as beta counting for large samples (+/- 2 per mil). A solution to the background variability has to be found before ion counting can be used to date samples back to the 75,000-year limit of beta counting.