Dynamics of Cultural Value of Non-Pastoral Activities among the Daasanach in East Africa

Many studies have focused on livelihood diversification among pastoral people in East Africa. The central theme of research on livelihood diversification is to clarify the economic background, contribution and consequences of non-pastoral activities for each household. However, pastoralists diversify their livelihoods not only out of economic necessity, but also by considering the cultural value and social relations, and the diversification process itself might change the value and relations. In this paper, by analysing various economic and socio-cultural contexts, including the opening of commercial farms, I examine how Daasanach youth legitimise their choice to enter into fishing activities that have negative connotations in their cultural value, and how other people view their choice.

Radiocarbon Analysis of Methane at the NERC Radiocarbon Facility (East Kilbride)

ABSTRACTMethane is the second most important anthropogenically produced greenhouse gas, and radiocarbon (14C) analysis is extremely valuable in identifying its age and source in the environment. At the NERC Radiocarbon Facility (East Kilbride, UK) we have developed expertise in analysis of methane 14C concentration and methodological approaches to field sampling over the past 20 years. This has opened a wide range of applications, which have mainly focused on (1) the age and source of methane emitted by peatlands and organic soils (e.g. to quantify the release of ancient carbon), (2) the source of aquatic emissions of methane, and (3) the age of methane generated by amenity and illegal landfill. Many of these scientifically important applications involve challenging sampling and measurement considerations, which our development program has continually aimed to overcome. Here, we describe our current methods, and recent improvements to aid field collection of samples in remote locations. We present the results of tests which (1) show the effectiveness of our methods to remove contaminants, especially CO2, (2) quantify the 14C background contribution, and (3) demonstrate the reliability of metal gas storage canisters for sample storage.

Revisiting the differential freezing nucleus spectra derived from drop-freezing experiments: methods of calculation, applications, and confidence limits

The differential nucleus concentration defined in Vali (1971) is re-examined and methods are given for its application. The purpose of this document is to facilitate the use of differential spectra in describing the results of drop freezing, or similar, experiments and to thereby provide additional insights into the significance of the measurements. The additive nature of differential concentrations is used to show how the background contribution can be accounted for in the measurements. A method is presented to evaluate the confidence limits of the spectra derived from given sets of measurements.

Revisiting the differential freezing nucleus spectra derived from drop freezing experiments; methods of calculation, applications and confidence limits

The differential nucleus concentration defined in Vali (1971) is re-examined and methods are given for its calculation. The purpose of this document is to facilitate the use of the differential spectra in describing the results of drop freezing, or similar, experiments and thereby provide additional insights into the measurements. The additive nature of differential concentrations is used to show how the background contribution can be accounted for in the measurements. A method is presented to evaluate the confidence limits of the results at each temperature covered in the measurements.

Invalidation of the Intracavity Optogalvanic Method for Radiocarbon Detection

The intracavity optogalvanic spectroscopy (ICOGS) method has been reported to quantify radiocarbon at subambient levels (<1 part per trillion). ICOGS uses a gas sample that is ionized in a low-pressure glow discharge located inside a 14CO2 laser cavity to detect changes in the discharge current under periodic modulation of the laser power to determine the 14CO2 concentration of the sample. When claims of detection thresholds below ambient levels were not verified by other researchers, we constructed a theoretical analysis to resolve differences between these conflicting reports and built and tested an ICOGS system to establish a lower limit of detection. Using a linear absorbance model of the background contribution of 12CO2 and data from the HITRAN database, we estimate that the limit of detection (3σx) is close to 1.5×104 Modern. By measuring a 1.5×104 Modern enriched CO2 sample in a cavity modulation ICOGS system without a clear signal, we conclude that for this system the limit of detection for ICOGS must be above 1.5×104. The implications for previous ICOGS reports are discussed.