title: SHCal20 Southern Hemisphere Calibration, 0–55,000 Years cal BP

authors: Hogg, Alan G.

subjects: carbon cycle

abstract: Early researchers of radiocarbon levels in Southern Hemisphere tree rings identified a variable North-South hemispheric offset, necessitating construction of a separate radiocarbon calibration curve for the South. We present here SHCal20, a revised calibration curve from 0–55,000 cal BP, based upon SHCal13 and fortified by the addition of 14 new tree-ring data sets in the 2140–0, 3520–3453, 3608–3590 and 13,140–11,375 cal BP time intervals. We detail the statistical approaches used for curve construction and present recommendations for the use of the Northern Hemisphere curve (IntCal20), the Southern Hemisphere curve (SHCal20) and suggest where application of an equal mixture of the curves might be more appropriate. Using our Bayesian spline with errors-in-variables methodology, and based upon a comparison of Southern Hemisphere tree-ring data compared with contemporaneous Northern Hemisphere data, we estimate the mean Southern Hemisphere offset to be 36 ± 27 ¹⁴C yrs older.

text: SHCal20 Southern Hemisphere Calibration, 0–55,000 Years cal BP Early researchers of radiocarbon levels in Southern Hemisphere tree rings identified a variable North-South hemispheric offset, necessitating construction of a separate radiocarbon calibration curve for the South. We present here SHCal20, a revised calibration curve from 0–55,000 cal BP, based upon SHCal13 and fortified by the addition of 14 new tree-ring data sets in the 2140–0, 3520–3453, 3608–3590 and 13,140–11,375 cal BP time intervals. We detail the statistical approaches used for curve construction and present recommendations for the use of the Northern Hemisphere curve (IntCal20), the Southern Hemisphere curve (SHCal20) and suggest where application of an equal mixture of the curves might be more appropriate. Using our Bayesian spline with errors-in-variables methodology, and based upon a comparison of Southern Hemisphere tree-ring data compared with contemporaneous Northern Hemisphere data, we estimate the mean Southern Hemisphere offset to be 36 ± 27 ¹⁴C yrs older.

year: 2020

title: Towards achieving low background levels in routine dating by liquid scintillation spectrometry

authors: Hogg, Alan G.

subjects: liquid scintillation

abstract: International radiocarbon intercalibration studies have revealed that radiometric laboratories using liquid scintillation (LS) spectrometry of benzene reported, on average, younger ages for near-background standards than either gas proportional counter (GPC) or accelerator mass spectrometry (AMS) laboratories. These studies suggested that the younger LS ages are probably related to the use of spectrophotometric benzene as a background standard. An analysis of successive
110-ka subfossil wood (Airedale Reef Ancient Wood: ARAW) standards shows that vacuum line memory effects occur in LS spectrometry and, consequently, must be corrected to obtain accurate ¹⁴C dates. ARAW standards, measured at monthly intervals in the Waikato laboratory, are used to provide blank corrections for both research and routine dating applications. The strong correlation between the ARAW Δ¹⁴C data and the sample activities that preceded the standards may provide an opportunity to obtain sample-specific blank corrections. Lithium carbide synthesis is likely to prove a source of contamination. This work suggests that reproducible background levels for routine dating of less than 0.1 pMC (55 ka ¹⁴C yr) are achievable.

text: Towards achieving low background levels in routine dating by liquid scintillation spectrometry International radiocarbon intercalibration studies have revealed that radiometric laboratories using liquid scintillation (LS) spectrometry of benzene reported, on average, younger ages for near-background standards than either gas proportional counter (GPC) or accelerator mass spectrometry (AMS) laboratories. These studies suggested that the younger LS ages are probably related to the use of spectrophotometric benzene as a background standard. An analysis of successive
110-ka subfossil wood (Airedale Reef Ancient Wood: ARAW) standards shows that vacuum line memory effects occur in LS spectrometry and, consequently, must be corrected to obtain accurate ¹⁴C dates. ARAW standards, measured at monthly intervals in the Waikato laboratory, are used to provide blank corrections for both research and routine dating applications. The strong correlation between the ARAW Δ¹⁴C data and the sample activities that preceded the standards may provide an opportunity to obtain sample-specific blank corrections. Lithium carbide synthesis is likely to prove a source of contamination. This work suggests that reproducible background levels for routine dating of less than 0.1 pMC (55 ka ¹⁴C yr) are achievable.

year: 2004

title: Inter-propositional semantic relations and semantic relational encoding in written discourse in Maori: an investigation

authors: Houia, Waldo

subjects: Maori

abstract: This thesis is an investigation of the various ways in which relationships of meaning between propositions (such as reason-result and temporal overlap) are encoded (as clauses, sentences and groups of sentences) and signalled in Maori.
In Chapter 1, the overall research topic and research questions are outlined.
Chapter 2 locates the research on inter-propositional semantic relations with reference to the concept of cohesion which is central to inter-propositional relational signalling and encoding. Here, reference is made to a number of relevant publications in the area.
Chapter 3 provides an introductory examination of the role of cohesion in the encoding and signalling of inter-propositional semantic relations in Maori.
Chapter 4 introduces a corpus of written texts and examines that corpus in terms of the ways in which inter-propositional semantic relations are encoded.
Chapter 5 examines a number of textbooks designed for learners of both English and Maori in terms of the extent to which they draw upon insights relating to the operation of inter-propositional semantic relations.
In Chapter 6, the research findings are summarised and their implications for aspects of the teaching and learning of Maori are discussed. In addition, suggestions are made in relation to future research possibilities.
Overall, the conclusion reached is that the study of semantic relational encoding and signalling in Maori texts reveals a number of aspects of language that appear not to be commonly taught and suggests the need for further studies of this type.

text: Inter-propositional semantic relations and semantic relational encoding in written discourse in Maori: an investigation This thesis is an investigation of the various ways in which relationships of meaning between propositions (such as reason-result and temporal overlap) are encoded (as clauses, sentences and groups of sentences) and signalled in Maori.
In Chapter 1, the overall research topic and research questions are outlined.
Chapter 2 locates the research on inter-propositional semantic relations with reference to the concept of cohesion which is central to inter-propositional relational signalling and encoding. Here, reference is made to a number of relevant publications in the area.
Chapter 3 provides an introductory examination of the role of cohesion in the encoding and signalling of inter-propositional semantic relations in Maori.
Chapter 4 introduces a corpus of written texts and examines that corpus in terms of the ways in which inter-propositional semantic relations are encoded.
Chapter 5 examines a number of textbooks designed for learners of both English and Maori in terms of the extent to which they draw upon insights relating to the operation of inter-propositional semantic relations.
In Chapter 6, the research findings are summarised and their implications for aspects of the teaching and learning of Maori are discussed. In addition, suggestions are made in relation to future research possibilities.
Overall, the conclusion reached is that the study of semantic relational encoding and signalling in Maori texts reveals a number of aspects of language that appear not to be commonly taught and suggests the need for further studies of this type.

year: 2001