scholarly journals A Computer Program for Radiocarbon Age Calibration

Radiocarbon ◽  
1986 ◽  
Vol 28 (2B) ◽  
pp. 1022-1030 ◽  
Author(s):  
Minze Stuiver ◽  
Paula J Reimer
Keyword(s):  
Standard Deviation ◽  
Computer Program ◽  
Data Base ◽  
Calibration Curve ◽  
Radiocarbon Age ◽  
Calibration Curves

The calibration curves and tables given in this issue of RADIOCARBON form a data base ideally suited for a computerized operation. The program listed below converts a radiocarbon age and its age error os (one standard deviation) into calibrated ages (intercepts with the calibration curve), and ranges of calibrated ages that correspond to the age error. The standard deviation oC in the calibration curve is taken into account using (see Stuiver and Pearson, this issue, for details).

scholarly journals The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP)

Radiocarbon ◽  
2020 ◽  
Vol 62 (4) ◽  
pp. 725-757 ◽  
Author(s):  
Paula J Reimer ◽  
William E N Austin ◽  
Edouard Bard ◽  
Alex Bayliss ◽  
Paul G Blackwell ◽  
...  
Keyword(s):  
Tree Ring ◽  
Ocean Circulation ◽  
Calibration Curve ◽  
Three Dimensional ◽  
Circulation Model ◽  
Radiocarbon Age ◽  
Calibration Curves ◽  
Tree Ring Data ◽  
Ocean Surface Layer ◽  
Reservoir Age

ABSTRACTRadiocarbon (14C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals.

How to cope with calibration

Antiquity ◽  
1987 ◽  
Vol 61 (231) ◽  
pp. 98-103 ◽  
Author(s):  
Gordon W. Pearson
Keyword(s):  
Computer Program ◽  
Statistical Methods ◽  
Calibration Curve ◽  
Large Format ◽  
University Of Washington ◽  
Calibration Curves ◽  
Anglo American ◽  
The University ◽  
Radiocarbon Calibration

The first calibration curve, published by Suess in 1967 (Suess 1967), was a wiggly thing arrived at by a process Suess called ‘cosmic schwung’. Later curves used more formal statistical methods, including Clark's published in ANTIQUITY (Clark 1975), which came to be one of the most used. It would be good to have the new standard curves available in ANTIQUITY, but they are far too bulky. We recommend the now-indispensable calibration issue of Radiocarbon (Stuiver & Kra 1986), which takes 230 large-format pages to set them out as tables, graphs and a computer program.Gordon Pearson is the British end of the Anglo-American axis, with Minze Stuiver at the University of Washington, largely responsible for the new calibration. He summarizes what the calibration does and how best to work with it.This paper is a guide to working with the Radiocarbon calibration issue in particular, as well as calibration curves in general. It therefore follows the conventions for calibrated and uncalibrated dates that are presented there, rather than ANTIQUITY's normal convention.

scholarly journals Determination of Sodium Cromoglycate by a New Kinetic Spectrophotometric Method in Biological Samples

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
Mohsen Keyvanfard ◽  
Khadijeh Alizad ◽  
Razieh Shakeri
Keyword(s):  
Standard Deviation ◽  
Sodium Cromoglycate ◽  
Spectrophotometric Method ◽  
Calibration Curve ◽  
Biological Samples ◽  
Limit Of Detection ◽  
Micellar Medium ◽  
Relative Standard ◽  
Kinetic Spectrophotometric

A new kinetic spectrophotometric method is described for the determination of ultratrace amounts of sodium cromoglycate (SCG). The method based on catalytic action of SCG on the oxidation of amaranth with periodate in acidic and micellar medium. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of the amaranth at 518 nm, for the first 4 min from initiation of the reaction. Calibration curve was linear in the range of 4.0−36.0 ng mL−1SCG. The limit of detection is 2.7 ng mL−1SCG. The relative standard deviation (RSD) for ten replicate analyses of 12, 20, and 28 ng mL−1SCG was 0.40%, 0.32%, and 0.53%, respectively. The proposed method was used for the determination of SCG in biological samples.

scholarly journals Validation of an LC-MS/MS Method for the Quantification of Caffeine and Theobromine Using Non-Matched Matrix Calibration Curve

Molecules ◽  
2019 ◽  
Vol 24 (16) ◽  
pp. 2863 ◽  
Author(s):  
Vera M. Mendes ◽  
Margarida Coelho ◽  
Angelo R. Tomé ◽  
Rodrigo A. Cunha ◽  
Bruno Manadas
Keyword(s):  
Human Plasma ◽  
Calibration Curve ◽  
Considerable Effort ◽  
Caffeine Consumption ◽  
Internal Standards ◽  
Beneficial Effects ◽  
Calibration Curves ◽  
Accuracy And Precision ◽  
Precise Quantification ◽  
Surrogate Matrix

Caffeine is one of the most widely consumed psycho-stimulants. The study of the beneficial effects of caffeine consumption to decrease the risk of developing several neuropsychiatric pathologies is receiving increasing attention. Thus, accurate and sensitive methods have been developed, mainly by LC-MS/MS, in order to quantify caffeine and its metabolites. These quantifications of caffeine and its metabolites by LC-MS/MS require a considerable effort to select or find a surrogate matrix, without the compounds of interest, to be used in the calibration curves. Thus, we evaluated the possibility of using calibration curves prepared in solvent instead of calibration curves prepared in human plasma. Results show that the calibration curves prepared in solvent and in human plasma were similar by comparing their slopes and interceptions, and the accuracy and precision were within the limits of acceptance for both calibration curves. This work demonstrates that, by using internal standards, it is possible to use a calibration curve in solvent instead of a calibration curve in plasma to perform an accurate and precise quantification of caffeine and theobromine.

Chemical Method for the Determination of Vitamin D in Evaporated Milk With Elimination of Cholesterol by Digitonin Precipitation

1969 ◽  
Vol 52 (6) ◽  
pp. 1189-1195 ◽  
Author(s):  
J Eisses ◽  
H Dk Vries
Keyword(s):  
Vitamin D ◽  
Standard Deviation ◽  
Calibration Curve ◽  
Chemical Method ◽  
Colorimetric Method ◽  
Sterol Content ◽  
Alumina Column ◽  
Decomposition Products ◽  
Colorimetric Measurement

Abstract The colorimetric method of Jones et al. for the determination of vitamin D in evaporated milk, based on theUSPXVI method, was modified to obtain a simpler colorimetric measurement and more accurate results. The main modification is the elimination of nearly all cholesterol, according to the procedure of Den Herder for the determination of the sterol content of fats, by precipitation with digitonin in the saponified mass. The Florex column, used in the procedure of Jones et al. for the elimination of decomposition products of vitamin A, was omitted since it gave high blank values; an alumina column was substituted. The resulting method, when applied to samples of evaporated milk to which a known quantity of vitamin D had been added, showed a recovery of 78% with a standard deviation of 6%, using a calibration curve based on crystalline vitamin D. Data from these measurements, as well as data from vitamin D determination on several brands of fortified and unfortified evaporated milk, are presented.

Validation of Liquid Chromatographic Method for Assay of Calcitriol and Alfacalcidol in Capsule Formulations

1986 ◽  
Vol 69 (6) ◽  
pp. 1026-1030
Author(s):  
Bruce C Flann ◽  
Bruce A Lodge
Keyword(s):  
Standard Deviation ◽  
Calibration Curve ◽  
Mobile Phase ◽  
Chromatographic Method ◽  
Liquid Chromatographic Method ◽  
Chromatographic Procedure ◽  
Liquid Chromatographic ◽  
Better Than

Abstract The validation of a liquid chromatographic procedure suitable for the determination of calcitriol and alfacalcidol in their respective formulations labeled to contain at least 0.25 μ.g drug per unit is described. The capsule content is diluted and chromatographed in 15-20 min on silica columns (5 μm) with a mobile phase of hexane-tetrahydrofuranmethylene dichloride-isopropanol (72 + 12 + 12 + 4, v/v) with detection at 254 nm. The calibration curve is linear. Recoveries of “spikes” averaged 101% with a standard deviation of 2%. Precision was better than 1.5%.

scholarly journals Radiocarbon Variations from Tasmanian Conifers: Results from Three Early Holocene Logs

Radiocarbon ◽  
1995 ◽  
Vol 37 (2) ◽  
pp. 361-369 ◽  
Author(s):  
Mike Barbetti ◽  
Trevor Bird ◽  
George Dolezal ◽  
Gillian Taylor ◽  
Roger Francey ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Calibration Curve ◽  
The Other ◽  
Early Holocene ◽  
Conifer Species ◽  
Middle Holocene ◽  
Calibration Curves ◽  
Lagarostrobos Franklinii ◽  
Floodplain Sediments ◽  
Good Coverage

Dendrochronological studies are being carried out on two conifer species in the Stanley River area of western Tasmania. The chronology for Huon pine (Lagarostrobos franklinii), with living trees up to 1400 yr old, extends back to 571 bc. Living celery-top pine (Phyllocladus aspleniifolius) trees are up to 500 yr old. Apart from living or recently felled trees, sections have been taken from 350 subfossil logs preserved in floodplain sediments. They range in age from >38 ka to modern, with good coverage for the periods 9–3.5 ka and from 2.5 ka to the present. We report here on 14C measurements of decadal samples from three early Holocene logs, between 10 and 9 ka bp, providing short (ca. 300-yr) records of atmospheric 14C variations when plotted against ring numbers. The southern hemisphere data from Tasmania can be compared and wiggle-matched with published 14C calibration curves from German oak and pine. One set of measurements covers the period, ca. 9280–8990 cal bp, overlapping the link between the Hohenheim “Main 9” and middle Holocene master oak chronologies. The other sets of measurements from Tasmania coincide; they span the period, ca. 9840–9480 cal bp, overlapping the end of the German Preboreal pine and the beginning of the oak chronologies. Our measurements confirm that this part of the calibration curve is a gently sloping 14C-age plateau (ca. 8900–8700 bp, between 10,000 and 9500 cal bp), and suggest interhemispheric 14C differences close to zero.

Spectrographic Calculations with Computerized Emulsion Calibration and Programmable Calculator Computations

1976 ◽  
Vol 30 (2) ◽  
pp. 190-195 ◽  
Author(s):  
D. R. Blevins ◽  
W. R. O'Neill
Keyword(s):  
Computer Program ◽  
Linear Equation ◽  
Calibration Curve ◽  
Graphical Methods ◽  
Calibration Data ◽  
Programmable Calculator ◽  
Element Concentrations ◽  
Program Strategy ◽  
Desk Calculator ◽  
Intensity Ratios

Photographic spectrographic calculations of intensity ratios and the corresponding element concentrations are performed faster and more accurately with programmable desk calculators than by graphical methods. These calculations are facilitated by applying a transform to microphotometer transmittance readings to make them linear with respect to intensity. This transform has the form log [{(100 – T)/ T} {(a + T)/ T}] where a is the transform constant and T is percent transmittance. A FORTRAN computer program strategy is given for calculating the transform constant from emulsion calibration data and obtaining a linear equation for the emulsion calibration curve. This equation is used to program a desk calculator to convert transmittance readings to intensity ratios corrected for background. A second calculator program computes element concentrations from the intensity ratios.

scholarly journals Selection and Treatment of Data for Radiocarbon Calibration: An Update to the International Calibration (IntCal) Criteria

Radiocarbon ◽  
2013 ◽  
Vol 55 (4) ◽  
pp. 1923-1945 ◽  
Author(s):  
Paula J Reimer ◽  
Edouard Bard ◽  
Alex Bayliss ◽  
J Warren Beck ◽  
Paul G Blackwell ◽  
...  
Keyword(s):  
Calibration Curve ◽  
Quality Data ◽  
Calibration Data ◽  
High Quality ◽  
High Quality Data ◽  
Surface Ocean ◽  
Basic Assumptions ◽  
Calibration Curves ◽  
Curve Model ◽  
Radiocarbon Calibration

High-quality data from appropriate archives are needed for the continuing improvement of radiocarbon calibration curves. We discuss here the basic assumptions behind 14C dating that necessitate calibration and the relative strengths and weaknesses of archives from which calibration data are obtained. We also highlight the procedures, problems, and uncertainties involved in determining atmospheric and surface ocean 14C/12C in these archives, including a discussion of the various methods used to derive an independent absolute timescale and uncertainty. The types of data required for the current IntCal database and calibration curve model are tabulated with examples.

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