Aging determinant

An understanding of the concept of secular equilibrium is also important for such age determinations using U-Th series radionuclides. Owing to the longevity of Th, and the number of parent atoms remains essentially... 

W. F. Libby (Los Angeles) use of carbon-14 for age determination in archeology, geology, geophysics, and other branches of science. 

Elster, H. 1990 Age determination offossil bone by amino add racemization. Ph.D. dissertation, Weizmann Institute, Rehovot. 

While a new tire may have excellent resistance to crack initiation and propagation between the steel belts, an aged tire of the exact same construction can exhibit dramatically reduced crack growth resistance, which in some cases may contribute to tire failure. To further underscore the point, the United States National Highway Traffic Safety Administration (NHTSA) determined that tire aging was a main contributor to the Firestone Wilderness AT tire recall [1]. Figure 34.1 shows the failure rate of Wilderness AT tires as a function of tire age (determined from date of tire manufacture). 

C22-0114. The amount of radioactive carbon in any once-living sample eventually drops too low for accurate dating. This detection limit is about 0.03/g min, whereas fresh samples exhibit a count rate of 15.3/g min. What is the upper limit for age determinations using carbon dating ... 

The Kishu deposit, located at middle Honshu, is associated with Kumano acidic rocks intruded into the Shimanto and Kumano formations. K-Ar age determination indicates that the activity of Kumano acidic rocks occurred at middle Miocene (14 1... 

Ku TL (1976) The uranium-series methods of age determination. Arm Rev Earth Planet Sci 4 347-380... 

Age determinations are consistent with their stratigraphic position, either within the sample itself or in the context of the surrounding deposits and sample location. 

Agreement is found for ages determined on the same material by independent dating methods... 

Demand for high-resolution records of environmental change from speleothems has led to a dramatic increase in the number of sub-samples required from individual samples to define the distance-age relationships along the axis of growth. Twenty years ago, the age determination of top and bottom sub-samples was generally considered adequate to... 

Reliable chronologies should be based on multiple °Th age determinations at a sampling interval that is appropriate for the spatial resolution of geochemical analysis along the axis of growth and accounts for the possibility of non-linear or discontinuous growth. 

Smith PE, Farquhar RM Hancock RG (1991) Direct radiometric age determination of carbonate diagenesis using U-Pb in secondary calcite. Earth Planet Sci Lett 105 474-491 Spalding RF, Mathews TD (1972) Submerged stalagmites from caves in the Bahamas Indicators of low sea level stand. Quat Res 2 470-472... 

Ra in the water sample and fm is the fraction of the endmember remaining in the sample. Age determinations calculated in such a manner reflect the time elapsed since the water sample became enriched in Ra by the discharge of groundwater. " Ra is regenerated on the order of days. The fraction /em can be estimated either from salinity signal or from the distribution of isotopes, but this term can be difficult to... 

The discovery of the decay chain, of course, started with the seminal work of Marie Curie in identifying and separating Ra. Through the work of the Curies and others, all the members of the decay chain were identified. An important milestone for geochronometrists was the discovery of °Th (called Ionium) by Bertram Boltwood, the Yale scientist who also made the first age determinations on minerals using the U-Pb dating method (Boltwood in 1906 established the antiquity of rocks and even identified a mineral from Sri Lanka-then Ceylon as having an age of 2.1 billion years )... 

The element revealed itself through spectacular violet-colored flames and several red spectral lines. The metal melts at 38 °C, is very soft, and extremely reactive (burns in air and reacts violently with water). Rubidium is stored under mineral oil. It is suitable as a scavenger (oxygen capture) in vacuum tubes, where it is deposited on the glass as a mirror. It can also be found in photocells and phosphors for screens (for example, for air-traffic controllers. Not physiologically important. The radioactive rubidium-87 is useful for age determination in geochronology (half-life ca. 50 billion years). 

There is, however, a drawback to this method of dating. The half-life (see Textbox 14) of the racemization process is greatly affected by temperature it is shorter at higher temperatures and slows down as the temperature decreases. An uncertainty of 2°C in the temperature history of dead remains can lead to an error of about 50% in the age determined. For the racemization of amino acids to be applicable for dating, therefore, it is crucial that the temperature history of the environment where the amino acids (that is, skin or bone) have been deposited should be well known. 

Geyh, M. A. and H. Schleicher (1990), Absolute Age Determination Physical and Chemical Dating Methods and Their Application, Springer, New York. 

Wagner, G. A. (1999), Age Determination of Young Rocks and Artifacts, Physical and Chemical Clocks in Quaternary Geology and Archaeology, Springer, New York. 

Rude CS University of Vermont, Burlington, VT Determine the prevalence of lead poisoning among children less than six years of age determine the predictive ability of a prescreening lead questionnaire National Center for Research Resources... 

The best sealed-in minerals are zircons, zirconium silicate minerals which are formed when melted lava on the flanks of volcanoes solidifies. When the zircons crystallize out, they incorporate radioactive uranium (in particular 238U), which decays in several steps, leading Anally to the lead isotope 208Pb. The rate of decay is very low, as the half-life of uranium-238 is 4.5 x 109 years. Thus, the U-Pb-zircon method for age determination of Precambrian rock is very important. The fossils studied by Schopf were sandwiched between two lava layers (Schopf, 1999). The volcanic layers were dated to 3.458 0.0019 x 109 years and 3.471 0.005 x 109 years the age of the fossil layer (Apex chert) was thus determined to be about 3.465xlO9 years. 

Based on currently available elemental abundance data and age determinations, the thick disk could have formed either through a violent, heating merger or through accretion of (substantial) satellites in a hierarchical galaxy formation scenario. The fast monolithic-like collapse is getting more and more problematic as data are gathered. It would be especially crucial to establish if there is an age-metallicity relation in the thick disk or not as in that case the thick disk could not have formed in that way (since the models indicate that the formation time-scale for the stars in the thick disk would be very short, see [7]). 

The case of Oetzi (or the Iceman), the frozen mummy found in 1991 on the Alps on the border between Austria and Italy and now kept at the Archaeological Museum of Bolzano (Italy), is also well known. AMS radiocarbon measurements from the laboratories of Zurich[78] and Oxford[79] on tissue and bone samples from the Iceman dated him to 4550 19 years BP. When calibrated, this radiocarbon age corresponds to three probable calendar time intervals between 3350 BC and 3100 BC. Consistent measurements were obtained by dating some of his equipment and also botanic remains from the discovery site. [80] In this context, it is important to note that dating of Oetzi represents a good example of the relevance of the behaviour of the calibration curve in the final precision of a radiocarbon measurement. Actually, in this case, despite a very high precision of the radiocarbon age ( 19 years), the special trend in the calibration curve around the dated period, i.e. in particular the so-called wiggles, prevents a more exact and unambiguous absolute age determination. 

J.R. Arnold and W.F. Libby, Age determination by radiocarbon content check with samples of known age, Science 110, 678 680 (1949). 

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