| 1. |
- Eilers, Gerriet, et al.
(författare)
-
The Radiocarbon Intracavity Optogalvanic Spectroscopy Setup at Uppsala
- 2013
-
Ingår i: Radiocarbon. - : Cambridge University Press (CUP). - 0033-8222 .- 1945-5755. ; 55:3-4, s. 237-250
-
Tidskriftsartikel (refereegranskat)abstract
- Accelerator mass spectrometry (AMS) is by far the predominant technology deployed for radiocarbon tracer studies. Applications are widespread from archaeology to biological, environmental, and pharmaceutical sciences. In spite of its excellent performance, AMS is expensive and complicated to operate. Consequently, alternative detection techniques for 14C are of great interest, with the vision of a compact, user-friendly, and inexpensive analytical method. Here, we report on the use of intracavity optogalvanic spectroscopy (ICOGS) for measurements of the 14C/12C ratio. This new detection technique was developed by Murnick et al. (2008). In the infrared (IR) region, CO2 molecules have strong absorption coefficients. The IR-absorption lines are narrow in line width and shifted for different carbon isotopes. These properties can potentially be exploited to detect 14CO2, 13CO2, or 12CO2 molecules unambiguously. In ICOGS, the sample is in the form of CO2 gas, eliminating the graphitization step that h is required in most AMS labs. The status of the ICOGS setup in Uppsala is presented. The system is operational but not yet fully developed. Data are presented for initial results that illustrate the dependence of the optogalvanic signal on various parameters, such as background and plasma-induced changes in the sample gas composition.
|
|
| 2. |
- Mellström, Anette, et al.
(författare)
-
Radiocarbon wiggle-matching of bulk sediments - how accurate can it be?
- 2013
-
Ingår i: Radiocarbon. - : Cambridge University Press (CUP). - 0033-8222 .- 1945-5755. ; 55:2-3, s. 1173-1186
-
Tidskriftsartikel (refereegranskat)abstract
- We used the radiocarbon wiggle-match dating technique to date the varved sediments of Lake Gyltigesjön in southern Sweden with the main aim to construct an accurate chronology covering the period between about 3000 and 2000 cal BP. Wiggle-match dating was applied to bulk sediments to evaluate the possibility of constructing accurate chronologies in the absence of terrestrial plant macrofossils and when the amount of old carbon in the sediments is unknown. Facilitated by a floating varve chronology and relatively stable 14C reservoir ages, the results show the possibility to assess the contribution of old carbon solely based on the 14C wiggle-matching of bulk sediments. We confirm the wiggle-matched chronology and the 14C reservoir age of approximately 260 yr by cross-checking the results with 14C dating of macrofossils. The obtained calibrated ages based on bulk sediments have an uncertainty range of about 60–65 yr (95.4% confidence interval). This study confirms that 14C wiggle-match dating of bulk sediments is a viable tool when constructing high-resolution chronologies. The method is especially useful in Sun-climate studies since the timing between solar activity variations (expressed as 14C variations) and climate changes can be accurately determined.
|
|
| 3. |
- Salehpour, Mehran, 1960-, et al.
(författare)
-
Life science applications utilizing radiocarbon tracing
- 2013
-
Ingår i: Radiocarbon. - Tucson, Arizona, USA : Cambridge University Press (CUP). - 0033-8222 .- 1945-5755. ; 55:2-3, s. 865-873
-
Tidskriftsartikel (refereegranskat)abstract
- Radiocarbon-based accelerator mass spectrometry (AMS) facilities at Uppsala University include a measurement center for archaeological applications and a separate entity dedicated to life science research. This paper addresses the latter, with the intention of giving a brief description of the biomedical activities at our laboratory, as well as presenting new data. The ultra-small sample preparation method, which can be used down to a few μg C samples, is outlined and complemented with new results. Furthermore, it is shown that the average secondary ion current performance for small samples can be improved by increasing the distance between the cathode surface and the pressed graphite surface. Finally, data is presented for a new application: Amyloidoses are a group of diseases where the conformational changes in specific proteins’ structure lead to the formation of extracellular deposits that spread and increase in mass and eventually may lead to total organ failure and death. The formation timeframe is unknown and yet it is an important clue for the elucidation of the mechanism. We present results on bomb-peak dating of 4 different types of purified amyloid proteins from human postmortem heart and spleen samples. The data indicates that the average measured age of the carbon originating from the systemic amyloid types studied here correspond to a few years before the death of the subject. This suggests that a major part of the fibril formation takes place during the last few years before death, rather than as an accumulation of amyloid deposits over decades.
|
|
| 4. |
- Szidat, S., et al.
(författare)
-
Intercomparison of 14C Analysis of Carbonaceous Aerosols : Exercise 2009
- 2013
-
Ingår i: Radiocarbon. - : Cambridge University Press (CUP). - 0033-8222 .- 1945-5755. ; 55:2-3, s. 1496-1509
-
Tidskriftsartikel (refereegranskat)abstract
- Radiocarbon analysis of the carbonaceous aerosol allows an apportionment of fossil and non-fossil sources of airborne particulate matter (PM). A chemical separation of total carbon (TC) into its subfractions organic carbon (OC) and elemental carbon (EC) refines this powerful technique, as OC and EC originate from different sources and undergo different processes in the atmosphere. Although C-14 analysis of TC, EC, and OC has recently gained increasing attention, interlaboratory quality assurance measures have largely been missing, especially for the isolation of EC and OC. In this work, we present results from an intercomparison of 9 laboratories for C-14 analysis of carbonaceous aerosol samples on quartz fiber filters. Two ambient PM samples and 1 reference material (RM 8785) were provided with representative filter blanks. All laboratories performed C-14 determinations of TC and a subset of isolated EC and OC for isotopic measurement. In general, C-14 measurements of TC and OC agreed acceptably well between the laboratories, i.e. for TC within 0.015-0.025 (FC)-C-14 for the ambient filters and within 0.041 (FC)-C-14 for RM 8785. Due to inhomogeneous filter loading, RM 8785 demonstrated only limited applicability as a reference material for C-14 analysis of carbonaceous aerosols. C-14 analysis of EC revealed a large deviation between the laboratories of 28-79% as a consequence of different separation techniques. This result indicates a need for further discussion on optimal methods of EC isolation for C-14 analysis and a second stage of this intercomparison.
|
|
| 5. |
- Vybornov, A., et al.
(författare)
-
Chronological problems with neolithization of the northern caspian sea area and the forest-steppe povolzhye region
- 2012
-
Ingår i: Radiocarbon. - 0033-8222 .- 1945-5755. ; 54:3-4, s. 795-799
-
Tidskriftsartikel (refereegranskat)abstract
- Steppe and forest-steppe areas of the Povolzhye area (Caucasus and central Asia) bear much interest for the Neolithic in connection with the productive economy of the region at the time. Recent data have allowed correction of the region's chronology. A number of C-14 dates denote the existence of the Neolithic in this territory as early as the 5th to 6th millennium BP. However, some questions are still under debate and require further data to clarify.
|
|
| 6. |
- Adolphi, Florian, et al.
(författare)
-
Intercomparison of C-14 Dating of Wood Samples at Lund University and Eth-Zurich Ams Facilities: Extraction, Graphitization, and Measurement
- 2013
-
Ingår i: Radiocarbon. - 0033-8222. ; 55:2-3, s. 391-400
-
Tidskriftsartikel (refereegranskat)abstract
- We conducted an interlaboratory comparison between our radiocarbon-related research group at Lund University and the established ETH-Zurich facility to test the quality of the results obtained in Lund and to identify sources of potential background differences and scatter. We did find differences between the 2 laboratories in the contributions of chemical preparation, graphitization, and measurements to the overall background. The resulting overall background is, however, almost similar. Multiple measurements on 2 wood samples of known calendar age yield consistent and accurate C-14 ages in both laboratories. However, one of our known samples indicates that IntCal09 is similar to 38 +/- 16 C-14 BP too young at 7020 calendar yr BP, which is consistent with one of the raw data sets contributing to IntCal09. Overall, our results show that a systematic approach to compare the different steps involved in C-14 age determination is a useful exercise to pinpoint targets for improvement of lab routines and assess interlaboratory differences. These effects do not necessarily become apparent when comparing C-14 measurements that integrate over the whole process of preparation and measurement of different laboratories.
|
|
| 7. |
- Genberg, Johan, et al.
(författare)
-
Development of graphitization of μg-sized samples at Lund University
- 2010
-
Ingår i: Radiocarbon. - 0033-8222. ; 52:3, s. 1270-1276
-
Konferensbidrag (refereegranskat)abstract
- To be able to successfully measure radiocarbon with accelerator mass spectrometry (AMS) in atmospheric aerosol samples, graphitization of small sample sizes (< 50 µg carbon) must provide reproducible results. At Lund University, a graphitization line optimized for small samples has been constructed. Attention has been given to minimize the reduction reactor volume and each reactor is equipped with a very small pressure transducer that enables constant monitoring of the reaction. Samples as small as 25 µg of carbon have been successfully analyzed, and the mass detection limit of the system has probably not been reached.
|
|
| 8. |
- Genberg, Johan, et al.
(författare)
-
Sealed Glass Tube Combustion of mu g-Sized Aerosol Samples
- 2013
-
Ingår i: Radiocarbon. - 0033-8222. ; 55:2-3, s. 617-623
-
Tidskriftsartikel (refereegranskat)abstract
- It is important to evaluate each step in radiocarbon analysis to ensure that the whole process is as efficient and accurate as possible. Aerosol filter samples contain a myriad of carbonaceous compounds with varying resistance to oxidation. Complete combustion of the sample is thus of great importance to ensure that the graphitized sample is representative of the original filter sample. We have evaluated sealed tube combustion of mu g-sized aerosol samples using different types and amounts of reagents. Successful analysis of aerosol samples as small as 20 mu g C was possible following small changes to our standard on-line method. The sealed tube combustion method performs well for standard samples containing 11 mu g C.
|
|
| 9. |
- Georgiadou, Elisavet, et al.
(författare)
-
Bomb-pulse dating of human material – modelling the influence of diet
- 2010
-
Ingår i: Radiocarbon. - 0033-8222. ; 52:2, s. 800-807
-
Konferensbidrag (refereegranskat)abstract
- The atmospheric testing of nuclear weapons during the 1950s and early 1960s produced large amounts of radiocarbon. This 14C bomb pulse provides useful age information in numerous scientific fields, e.g. in geosciences and environmental sciences. Bomb-pulse dating can also be used to date human material (e.g. in forensics and medical science). Bombpulse dating relies on precise measurements of the declining 14C concentration in atmospheric carbon dioxide collected at clean-air sites. However, local variations in the 14C specific activity of air and foodstuffs occur, which are caused by natural processes as well as by various human activities. As 14C enters the human body mainly through the diet, variations of 14C concentration in foodstuffs need to be considered. The marine component of the diet is believed to be of particular importance due to the non-equilibrium in 14C specific activity between the atmosphere and aquatic reservoirs during the bomb pulse. This article reviews the 14C concentration in marine foodstuffs during the bomb-pulse era, and models how the marine component in one’s diet can affect the precision of bomb-pulse dating of human material.
|
|
| 10. |
- Georgiadou, Elisavet, et al.
(författare)
-
Potential Influence of Diet on Bomb-Pulse Dating of Human Plaque Samples
- 2013
-
Ingår i: Radiocarbon. - : Cambridge University Press (CUP). - 0033-8222. ; 55:2-3, s. 874-884
-
Tidskriftsartikel (refereegranskat)abstract
- The radiocarbon concentration of different atherosclerotic plaque fragments obtained from 20 patients in Portugal, operated in 2000-2001, has been measured in order to define the year of plaque formation. A difference of 1.8-15 yr was observed, with the mean and median both 9 yr, between the bomb-pulse date estimated with the CALIBomb software and the operation date. Stable isotope (delta C-13 and delta N-15) analysis was also performed and provides insight to the diet of the subjects. The wide range of measured stable isotope values could indicate that the subjects' diet varied, including an abundance of marine foodstuffs. It could also mean a different isotope fractionation process for the different plaque fragments (cap, core, interface to media) and a possible difference in tissues in which the various fragments are formed. Analysis of delta C-13 and delta N-15 values of each patient separately revealed subjects considered more influenced by marine foodstuffs consumption.
|
|
| 11. |
- Sydoff, Marie, et al.
(författare)
-
Experiences from the production and homogeneity analysis of an AMS 14C sucrose standard for high-activity measurements
- 2010
-
Ingår i: Radiocarbon. - 0033-8222. ; 52:3, s. 1351-1357
-
Konferensbidrag (refereegranskat)abstract
- Accurate accelerator mass spectrometry (AMS) measurements rely on standards with well-known isotopic ratios. For radiocarbon measurements, a number of standards with different properties are commercially available, of which the IAEA-C6 sucrose standard with a 14C value of 150.61 pMC is the most active. When analyzing biological samples resulting from studies using 14C-labeled substances, the activity content can be up to 100 times this value. Thus, there is a need for a standard material with higher activity content than IAEA-C6 for making accurate AMS measurements on this type of sample. This paper describes the attempts of producing a standard with an activity content of about 10 times modern carbon. The material chosen has to be chemically inert, preferably non-toxic, commercially available in 14C-labeled form, and the activity must be homogeneously distributed within the material. Two different standard materials were considered: urea and sucrose. Sucrose was chosen for the new standard, since it is non-toxic, inexpensive, and organic and on combustion, forms only carbon dioxide (CO2) and water (H2O). In this paper, we discuss our experience in the production and homogeneity analysis of this material, from the crystallization of the sucrose solution to the graphitization of the samples. When using an online combustion method and a septa-sealed vial reduction method, the AMS measurements indicated that the activity was not homogeneously distributed throughout the material. Contrary to this, measurements of the sucrose solution prior to recrystallization indicated that the activity was more homogeneously distributed before than after the recrystallization. In order to determine whether the inhomogeneity depended on the graphitization method (i.e. the combustion or the reduction method) or on the material itself, 3 different graphitization methods and 2 different methods of recrystallization were tested.
|
|
| 12. |
- Wild, E. M., et al.
(författare)
-
C-14 DATING OF HUMIC ACIDS FROM BRONZE AND IRON AGE PLANT REMAINS FROM THE EASTERN MEDITERRANEAN
- 2013
-
Ingår i: Radiocarbon. - : Cambridge University Press (CUP). - 0033-8222. ; 55:2-3, s. 599-607
-
Tidskriftsartikel (refereegranskat)abstract
- Radiocarbon dating of plant remains is often difficult due to the complete dissolution of the samples in the alkaline step of the ABA pretreatment. At the VERA laboratory, this problem was encountered frequently when numerous Bronze and Early Iron Age samples from the eastern Mediterranean were dated in the course of the special research program SCIEM2000 and in other collaborations with archaeologists focused on that area and time period. For these samples, only a C-14 age determination of the humic acid fraction was possible. Humic acids from archaeological samples are always assessed as a second-choice material for C-14 dating. It is assumed that the C-14 ages may be affected by the presence of humic acids originating from other (younger) organic material, e. g. from soil horizons located above a sample. Therefore, when humic acids are dated a verification of the dates is crucial. To address this basic requirement, we started some time ago to date both fractions of charred seeds, wood, and charcoal samples whenever available, i. e. the residue after the ABA treatment and the humic acids extracted from the samples in the alkaline step. The results of this comparison showed that for the investigated eastern Mediterranean archaeological sites, 50 (out of 52) humic acid dates were in agreement with the C-14 dates of the respective ABA-treated samples. Statistical analysis of the age differences leads to the conclusion that the extracted humic acids originated from the samples themselves or from contemporaneous material and were not appreciably contaminated by extraneous material of different age.
|
|
