Henry Polach

Bio: Henry Polach is an academic researcher from Australian National University. The author has contributed to research in topics: Radiocarbon dating & Liquid scintillation counting. The author has an hindex of 23, co-authored 42 publications receiving 6979 citations. Previous affiliations of Henry Polach include University of Arizona.

Characterizing aquatic dissolved organic matter.

Abstract: Standards for reporting C-14 age determinations are discussed. All dates should be related either directly or indirectly to the NBS oxalic acid standard. Corrections for isotopic fractionation are also desirable. For some materials, particularly marine shell, corrections for reservoir effect are necessary, but these should always be reported separately from the conventional radiocarbon age. The statistical uncertainty (plus or minus one standard deviation) expresses counting errors, inaccuracies in voltage, pressure, temperature, dilution, and should include errors in C-13 ratios. Errors can be significant when isotope ratios are estimated rather than measured directly. The error in the conventional C-14 half life is not included. The article includes tables indicating what data should be reported.

Post-glacial sea-level rise from a coral record at Huon Peninsula, Papua New Guinea

Abstract: DATING of coral reef terraces can provide a record of changes in sea level, which should be pronounced during the transition between glacial and interglacial periods. Cores drilled from coral reefs at Barbados in the equatorial west Atlantic1have revealed the sea-level changes that occurred during the Younger Dry as event at the end of the Last Glacial Maximum (∼11,000 yr BP). It has not been known, however, whether Pacific coral reefs can grow at a rate sufficient to keep up with the rise in sea level during such a transition. Here we report results obtained from a 52-m drill core from the post-glacial reef at Huon Peninsula, Papua New Guinea, spanning the interval from 7,000 to 11,000 14C yr BP, which show that coral growth kept pace while the relative sea level rose by 50m. Although the tectonic environment is very different from that at Barbados, the two records compare well when corrections are made for local tectonic uplift, showing that sea-level rise was similar at both locations. The rate of rise was greatest between 9,000 and 10,00014C yr BP, corresponding to the time of the Younger Dryas.

Pleistocene man in Australia: age and significance of the Mungo skeleton.

Abstract: THE Late Pleistocene human cremation found at Lake Mungo in western New South Wales is among the most significant recent discoveries in Australian prehistory1. The fragmented skeleton of this young, adult female2 was recovered from a buried soil on the Lake Mungo shoreline dune (lunette) known as “The Walls of China” (see accompanying paper, site 1). This paper records new radiocarbon data providing a precise age for these remains.

IntCal13 and Marine13 radiocarbon age calibration curves 0-50,000 years cal BP

Abstract: Additional co-authors: TJ Heaton, AG Hogg, KA Hughen, KF Kaiser, B Kromer, SW Manning, RW Reimer, DA Richards, JR Southon, S Talamo, CSM Turney, J van der Plicht, CE Weyhenmeyer

Extended 14C Data Base and Revised Calib 3.0 14C Age Calibration Program

Abstract: The age calibration program, CALIB (Stuiver & Reimer 1986), first made available in 1986 and subsequently modified in 1987 (revision 2.0 and 2.1), has been amended anew. The 1993 program (revision 3.0) incorporates further refinements and a new calibration data set covering nearly 22,000 cal yr (≈18,400 14C yr). The new data, and corrections to the previously used data set, derive from a 6-yr (1986–1992) time-scale calibration effort of several laboratories.

Bayesian analysis of radiocarbon dates

Abstract: If radiocarbon measurements are to be used at all for chronological purposes, we have to use statistical methods for calibration. The most widely used method of calibration can be seen as a simple application of Bayesian statistics, which uses both the information from the new measurement and information from the 14C calibration curve. In most dating applications, however, we have larger numbers of 14C measurements and we wish to relate those to events in the past. Bayesian statistics provides a coherent framework in which such analysis can be performed and is becoming a core element in many 14C dating projects. This article gives an overview of the main model components used in chronological analysis, their mathematical formulation, and examples of how such analyses can be performed using the latest version of the OxCal software (v4). Many such models can be put together, in a modular fashion, from simple elements, with defined constraints and groupings. In other cases, the commonly used "uniform phase" models might not be appropriate, and ramped, exponential, or normal distributions of events might be more useful. When considering analyses of these kinds, it is useful to be able run simulations on synthetic data. Methods for performing such tests are discussed here along with other methods of diagnosing possible problems with statistical models of this kind.

INTCAL98 Radiocarbon Age Calibration, 24,000-0 cal BP

Abstract: The focus of this paper is the conversion of radiocarbon ages to calibrated (cal) ages for the interval 24,000-0 cal BP (Before Present, 0 cal BP = AD 1950), based upon a sample set of dendrochronologically dated tree rings, uranium-thorium dated corals, and varve-counted marine sediment. The 14C age-cal age information, produced by many laboratories, is converted to 14C profiles and calibration curves, for the atmosphere as well as the oceans. We discuss offsets in measured 14C ages and the errors therein, regional 14C age differences, tree-coral 14C age comparisons and the time dependence of marine reservoir ages, and evaluate decadal vs. single-year 14C results. Changes in oceanic deepwater circulation, especially for the 16,000-11,000 cal BP interval, are reflected in the Δ 14C values of INTCAL98.

Dynamics of fat cell turnover in humans

Abstract: Obesity is increasing in an epidemic manner in most countries and constitutes a public health problem by enhancing the risk for cardiovascular disease and metabolic disorders such as type 2 diabetes. Owing to the increase in obesity, life expectancy may start to decrease in developed countries for the first time in recent history. The factors determining fat mass in adult humans are not fully understood, but increased lipid storage in already developed fat cells (adipocytes) is thought to be most important. Here we show that adipocyte number is a major determinant for the fat mass in adults. However, the number of fat cells stays constant in adulthood in lean and obese individuals, even after marked weight loss, indicating that the number of adipocytes is set during childhood and adolescence. To establish the dynamics within the stable population of adipocytes in adults, we have measured adipocyte turnover by analysing the integration of 14C derived from nuclear bomb tests in genomic DNA. Approximately 10% of fat cells are renewed annually at all adult ages and levels of body mass index. Neither adipocyte death nor generation rate is altered in early onset obesity, suggesting a tight regulation of fat cell number in this condition during adulthood. The high turnover of adipocytes establishes a new therapeutic target for pharmacological intervention in obesity.