Karl F von Reden
Dados Biográficos
| ID | 5597846 |
|---|---|
| NOME | Karl F von Reden |
| PRENOMES | Karl F |
| SOBRENOME | von Reden |
| ASSINATURA | VON REDEN K F |
| VERIFICADO | Não |
| TOTAL DE OBRAS | 9 |
| TOTAL DE CITAÇÕES | 71 |
| TOTAL COMO AUTOR | 9 |
| TOTAL COMO EDITOR | 0 |
| PRIMEIRO ANO DE PUBLICAÇÃO | 1997 |
| ANO MAIS RECENTE DE PUBLICAÇÃO | 2013 |
| ÍNDICE H | 4 |
Improved Precision of Radiocarbon Measurements for CH 4 and CO 2 Using GC and Continuous-Flow AMS Achieved by Summation of Repeated Injections
Compound specific radiocarbon measurements can be made instantaneously using a gas chromatograph (GC) combustion system coupled to a 14 C AMS system fitted with a gas ion source. Samples below 10 μg C can be analyzed but the precision is reduced to 5–10% because of lower source efficiency. We modified our GC for CH 4 and CO 2 analysis and injected samples multiple times to sum data and increase precision. We attained a maximum precision of 0.6% f…
Fire History of a Giant African Baobab Evinced by Radiocarbon Dating
The article reports the first radiocarbon dating of a live African baobab ( Adansonia digitata L.), by investigating wood samples collected from 2 inner cavities of the very large 2-stemmed Platland tree of South Africa. Some 16 segments extracted from determined positions of the samples, which correspond to a depth of up to 15–20 cm in the wood, were processed and analyzed by accelerator mass spectrometry (AMS). Calibrated ages of segments are n…
A Continuous-Flow Gas Chromatography 14 C Accelerator Mass Spectrometry System
Gas-accepting ion sources for radiocarbon accelerator mass spectrometry (AMS) have permitted the direct analysis of CO 2 gas, eliminating the need to graphitize samples. As a result, a variety of analytical instruments can be interfaced to an AMS system, processing time is decreased, and smaller samples can be analyzed (albeit with lower precision). We have coupled a gas chromatograph to a compact 14 C AMS system fitted with a microwave ion sourc…
Age and Growth Rate Dynamics of an Old African Baobab Determined by Radiocarbon Dating
In 2008, a large African baobab ( Adansonia digitata L.) from Makulu Makete, South Africa, split vertically into 2 sections, revealing a large enclosed cavity. Several wood samples collected from the cavity were processed and radiocarbon dated by accelerator mass spectrometry (AMS) for determining the age and growth rate dynamics of the tree. The 14 C date of the oldest sample was found to be of 1016 ± 22 BP, which corresponds to a calibrated age…
The Keck Carbon Cycle AMS Laboratory, University of California, Irvine
We present a status report of the accelerator mass spectrometry (AMS) facility at the University of California, Irvine, USA. Recent spectrometer upgrades and repairs are discussed. Modifications to preparation laboratory procedures designed to improve sample throughput efficiency while maintaining precision of 2–3‰ for 1-mg samples (Santos et al. 2007c) are presented
Developments in Radiocarbon Technologies
We review developments in radiocarbon measuring techniques from the Libby counter through proportional gas counters and liquid scintillation spectrometers to the more recent developments of accelerator mass spectrometry (AMS), followed by a coupling of gas chromatography with AMS for compound-specific 14 C analyses. While during the first 60 yr of 14 C measurements beta counting, specifically gas counting, was the dominant technique, in the futur…
Target Preparation for Continuous Flow Accelerator Mass Spectrometry
For very small samples, it is difficult to prepare graphitic targets that will yield a useful and steady sputtered ion beam. Working with materials separated by preparative capillary gas chromatography, we have succeeded with amounts as small as 20 μg C. This seems to be a practical limit, as it involves 1) multiple chromatographic runs with trapping of effluent fractions, 2) recovery and combustion of the fractions, 3) graphitization and 4) comp…
Microscale AMS 14 C Measurement at Nosams
Techniques for making precise and accurate radiocarbon accelerator mass spectrometry (AMS) measurements on samples containing less than a few hundred micrograms of carbon are being developed at the NOSAMS facility. A detailed examination of all aspects of the sample preparation and data analysis process shows encouraging results. Small quantities of CO 2 are reduced to graphite over cobalt catalyst at an optimal temperature of 605°. Measured 14 C…
C AMS Measurements of <100 μG Samples with a High-Current System
The NOSAMS facility at Woods Hole Oceanographic Institution has started to develop and apply techniques for measuring very small samples on a standard Tandetron accelerator mass spectrometry (AMS) system with high-current hemispherical Cs sputter ion sources. Over the past year, results on samples ranging from 7 to 160 μg C showed both the feasibility of such analyses and the present limitations on reducing the size of solid carbon samples. One o…
Microscale AMS 14 C Measurement at Nosams
Techniques for making precise and accurate radiocarbon accelerator mass spectrometry (AMS) measurements on samples containing less than a few hundred micrograms of carbon are being developed at the NOSAMS facility. A detailed examination of all aspects of the sample preparation and data analysis process shows encouraging results. Small quantities of CO 2 are reduced to graphite over cobalt catalyst at an optimal temperature of 605°. Measured 14 C…
The Keck Carbon Cycle AMS Laboratory, University of California, Irvine
We present a status report of the accelerator mass spectrometry (AMS) facility at the University of California, Irvine, USA. Recent spectrometer upgrades and repairs are discussed. Modifications to preparation laboratory procedures designed to improve sample throughput efficiency while maintaining precision of 2–3‰ for 1-mg samples (Santos et al. 2007c) are presented
Developments in Radiocarbon Technologies
We review developments in radiocarbon measuring techniques from the Libby counter through proportional gas counters and liquid scintillation spectrometers to the more recent developments of accelerator mass spectrometry (AMS), followed by a coupling of gas chromatography with AMS for compound-specific 14 C analyses. While during the first 60 yr of 14 C measurements beta counting, specifically gas counting, was the dominant technique, in the futur…
Age and Growth Rate Dynamics of an Old African Baobab Determined by Radiocarbon Dating
In 2008, a large African baobab ( Adansonia digitata L.) from Makulu Makete, South Africa, split vertically into 2 sections, revealing a large enclosed cavity. Several wood samples collected from the cavity were processed and radiocarbon dated by accelerator mass spectrometry (AMS) for determining the age and growth rate dynamics of the tree. The 14 C date of the oldest sample was found to be of 1016 ± 22 BP, which corresponds to a calibrated age…
Fire History of a Giant African Baobab Evinced by Radiocarbon Dating
The article reports the first radiocarbon dating of a live African baobab ( Adansonia digitata L.), by investigating wood samples collected from 2 inner cavities of the very large 2-stemmed Platland tree of South Africa. Some 16 segments extracted from determined positions of the samples, which correspond to a depth of up to 15–20 cm in the wood, were processed and analyzed by accelerator mass spectrometry (AMS). Calibrated ages of segments are n…
C AMS Measurements of <100 μG Samples with a High-Current System
The NOSAMS facility at Woods Hole Oceanographic Institution has started to develop and apply techniques for measuring very small samples on a standard Tandetron accelerator mass spectrometry (AMS) system with high-current hemispherical Cs sputter ion sources. Over the past year, results on samples ranging from 7 to 160 μg C showed both the feasibility of such analyses and the present limitations on reducing the size of solid carbon samples. One o…
Improved Precision of Radiocarbon Measurements for CH 4 and CO 2 Using GC and Continuous-Flow AMS Achieved by Summation of Repeated Injections
Compound specific radiocarbon measurements can be made instantaneously using a gas chromatograph (GC) combustion system coupled to a 14 C AMS system fitted with a gas ion source. Samples below 10 μg C can be analyzed but the precision is reduced to 5–10% because of lower source efficiency. We modified our GC for CH 4 and CO 2 analysis and injected samples multiple times to sum data and increase precision. We attained a maximum precision of 0.6% f…
A Continuous-Flow Gas Chromatography 14 C Accelerator Mass Spectrometry System
Gas-accepting ion sources for radiocarbon accelerator mass spectrometry (AMS) have permitted the direct analysis of CO 2 gas, eliminating the need to graphitize samples. As a result, a variety of analytical instruments can be interfaced to an AMS system, processing time is decreased, and smaller samples can be analyzed (albeit with lower precision). We have coupled a gas chromatograph to a compact 14 C AMS system fitted with a microwave ion sourc…
Target Preparation for Continuous Flow Accelerator Mass Spectrometry
For very small samples, it is difficult to prepare graphitic targets that will yield a useful and steady sputtered ion beam. Working with materials separated by preparative capillary gas chromatography, we have succeeded with amounts as small as 20 μg C. This seems to be a practical limit, as it involves 1) multiple chromatographic runs with trapping of effluent fractions, 2) recovery and combustion of the fractions, 3) graphitization and 4) comp…
Target Preparation for Continuous Flow Accelerator Mass Spectrometry
For very small samples, it is difficult to prepare graphitic targets that will yield a useful and steady sputtered ion beam. Working with materials separated by preparative capillary gas chromatography, we have succeeded with amounts as small as 20 μg C. This seems to be a practical limit, as it involves 1) multiple chromatographic runs with trapping of effluent fractions, 2) recovery and combustion of the fractions, 3) graphitization and 4) comp…
Microscale AMS 14 C Measurement at Nosams
Techniques for making precise and accurate radiocarbon accelerator mass spectrometry (AMS) measurements on samples containing less than a few hundred micrograms of carbon are being developed at the NOSAMS facility. A detailed examination of all aspects of the sample preparation and data analysis process shows encouraging results. Small quantities of CO 2 are reduced to graphite over cobalt catalyst at an optimal temperature of 605°. Measured 14 C…
C AMS Measurements of <100 μG Samples with a High-Current System
The NOSAMS facility at Woods Hole Oceanographic Institution has started to develop and apply techniques for measuring very small samples on a standard Tandetron accelerator mass spectrometry (AMS) system with high-current hemispherical Cs sputter ion sources. Over the past year, results on samples ranging from 7 to 160 μg C showed both the feasibility of such analyses and the present limitations on reducing the size of solid carbon samples. One o…
Developments in Radiocarbon Technologies
We review developments in radiocarbon measuring techniques from the Libby counter through proportional gas counters and liquid scintillation spectrometers to the more recent developments of accelerator mass spectrometry (AMS), followed by a coupling of gas chromatography with AMS for compound-specific 14 C analyses. While during the first 60 yr of 14 C measurements beta counting, specifically gas counting, was the dominant technique, in the futur…
Fire History of a Giant African Baobab Evinced by Radiocarbon Dating
The article reports the first radiocarbon dating of a live African baobab ( Adansonia digitata L.), by investigating wood samples collected from 2 inner cavities of the very large 2-stemmed Platland tree of South Africa. Some 16 segments extracted from determined positions of the samples, which correspond to a depth of up to 15–20 cm in the wood, were processed and analyzed by accelerator mass spectrometry (AMS). Calibrated ages of segments are n…
A Continuous-Flow Gas Chromatography 14 C Accelerator Mass Spectrometry System
Gas-accepting ion sources for radiocarbon accelerator mass spectrometry (AMS) have permitted the direct analysis of CO 2 gas, eliminating the need to graphitize samples. As a result, a variety of analytical instruments can be interfaced to an AMS system, processing time is decreased, and smaller samples can be analyzed (albeit with lower precision). We have coupled a gas chromatograph to a compact 14 C AMS system fitted with a microwave ion sourc…
Age and Growth Rate Dynamics of an Old African Baobab Determined by Radiocarbon Dating
In 2008, a large African baobab ( Adansonia digitata L.) from Makulu Makete, South Africa, split vertically into 2 sections, revealing a large enclosed cavity. Several wood samples collected from the cavity were processed and radiocarbon dated by accelerator mass spectrometry (AMS) for determining the age and growth rate dynamics of the tree. The 14 C date of the oldest sample was found to be of 1016 ± 22 BP, which corresponds to a calibrated age…
The Keck Carbon Cycle AMS Laboratory, University of California, Irvine
We present a status report of the accelerator mass spectrometry (AMS) facility at the University of California, Irvine, USA. Recent spectrometer upgrades and repairs are discussed. Modifications to preparation laboratory procedures designed to improve sample throughput efficiency while maintaining precision of 2–3‰ for 1-mg samples (Santos et al. 2007c) are presented
Improved Precision of Radiocarbon Measurements for CH 4 and CO 2 Using GC and Continuous-Flow AMS Achieved by Summation of Repeated Injections
Compound specific radiocarbon measurements can be made instantaneously using a gas chromatograph (GC) combustion system coupled to a 14 C AMS system fitted with a gas ion source. Samples below 10 μg C can be analyzed but the precision is reduced to 5–10% because of lower source efficiency. We modified our GC for CH 4 and CO 2 analysis and injected samples multiple times to sum data and increase precision. We attained a maximum precision of 0.6% f…
Accelerator mass spectrometry (9 obras) · Chemistry (7 obras) · Chromatography (6 obras) · Mass spectrometry (6 obras) · Radiocarbon dating (6 obras) · Isotope Analysis in Ecology (5 obras) · Archaeology (4 obras) · Geography (4 obras) · Geology (4 obras) · Materials Science (4 obras)