title: Application of new technology liquid scintillation spectrometry to radiocarbon dating of tephra deposits, New Zealand

authors: Lowe, David J.

abstract: Two major technological advances in the radiocarbon dating method have recently enhanced its potential application to tephra studies: the advent of accelerator mass spectrometry and the development of new technology liquid scintillation (LS) spectrometry. The new technology LS spectrometer represents a significant refinement of the conventional dating method based on liquid scintillation counting of benzene. It improves upon conventional LS counting by allowing spectral analysis, and by providing a high degree of counting stability and efficiency in an ultra low-level background radiation environment. These attributes enable radiocarbon dating with greater accuracy and statistical precision, and also allow the determination of both smaller and older samples than previously possible by conventional radiometric methods.
The new Wallac Oy ‘Quantulus’ LS spectrometer has been in operation at the University of Waikato Radiocarbon Dating Laboratory since 1988. The instrument achieves ultra-low background levels by both passive and active forms of shielding. The shielding comprises a massive asymmetric passive lead shield surrounding an aticoincident liquid scintillation guard. In addition, the Quantulus contains dual multichannel analyzers which allow spectral analysis and ‘windowless’ data acquisition.
The Quantulus LS spectrometers at the Waikato laboratory have been used to date a variety of carbonaceous materials associated with tephra deposits in New Zealand, ranging in age from ca. 0.1–55 ka. In particular, we have tested the capability of the Quantulus for determining ages of samples that are typically more difficult or impossible to date by conventional methods: (1) very young samples (e.g. Tarawera Tephra, erupted ca. 100 years ago); (2) older samples (e.g. Mangaone Tephra, erupted ca. 30 ka); and (3) samples containing only sparse carbon (e.g. lake sediments associated with tephra layers aged ca. 20 ka or less). The Quantulus LS spectrometer is both more accurate and precise (statistical counting errors are reduced) than conventional instruments, is capable of extending the limits of detection at both ends of the age scale, and has a smaller sample handling ability. Analyses can be obtained at comparatively low cost. Such advances are potentially beneficial to tephrochronology and volcanology and a wide range of applications in Quaternary research.

text: Application of new technology liquid scintillation spectrometry to radiocarbon dating of tephra deposits, New Zealand Two major technological advances in the radiocarbon dating method have recently enhanced its potential application to tephra studies: the advent of accelerator mass spectrometry and the development of new technology liquid scintillation (LS) spectrometry. The new technology LS spectrometer represents a significant refinement of the conventional dating method based on liquid scintillation counting of benzene. It improves upon conventional LS counting by allowing spectral analysis, and by providing a high degree of counting stability and efficiency in an ultra low-level background radiation environment. These attributes enable radiocarbon dating with greater accuracy and statistical precision, and also allow the determination of both smaller and older samples than previously possible by conventional radiometric methods.
The new Wallac Oy ‘Quantulus’ LS spectrometer has been in operation at the University of Waikato Radiocarbon Dating Laboratory since 1988. The instrument achieves ultra-low background levels by both passive and active forms of shielding. The shielding comprises a massive asymmetric passive lead shield surrounding an aticoincident liquid scintillation guard. In addition, the Quantulus contains dual multichannel analyzers which allow spectral analysis and ‘windowless’ data acquisition.
The Quantulus LS spectrometers at the Waikato laboratory have been used to date a variety of carbonaceous materials associated with tephra deposits in New Zealand, ranging in age from ca. 0.1–55 ka. In particular, we have tested the capability of the Quantulus for determining ages of samples that are typically more difficult or impossible to date by conventional methods: (1) very young samples (e.g. Tarawera Tephra, erupted ca. 100 years ago); (2) older samples (e.g. Mangaone Tephra, erupted ca. 30 ka); and (3) samples containing only sparse carbon (e.g. lake sediments associated with tephra layers aged ca. 20 ka or less). The Quantulus LS spectrometer is both more accurate and precise (statistical counting errors are reduced) than conventional instruments, is capable of extending the limits of detection at both ends of the age scale, and has a smaller sample handling ability. Analyses can be obtained at comparatively low cost. Such advances are potentially beneficial to tephrochronology and volcanology and a wide range of applications in Quaternary research.

year: 1992

title: Classifier chains: A review and perspectives

authors: Read, Jesse

subjects: computer science

abstract: The family of methods collectively known as classifier chains has become a popular approach to multi-label learning problems. This approach involves chaining together off-the-shelf binary classifiers in a directed structure, such that individual label predictions become features for other classifiers. Such methods have proved flexible and effective and have obtained state-of-the-art empirical performance across many datasets and multi-label evaluation metrics. This performance led to further studies of the underlying mechanism and efficacy, and investigation into how it could be improved. In the recent decade, numerous studies have explored the theoretical underpinnings of classifier chains, and many improvements have been made to the training and inference procedures, such that this method remains among the best options for multi-label learning. Given this past and ongoing interest, which covers a broad range of applications and research themes, the goal of this work is to provide a review of classifier chains, a survey of the techniques and extensions provided in the literature, as well as perspectives for this approach in the domain of multi-label classification in the future. We conclude positively, with a number of recommendations for researchers and practitioners, as well as outlining key issues for future research.

text: Classifier chains: A review and perspectives The family of methods collectively known as classifier chains has become a popular approach to multi-label learning problems. This approach involves chaining together off-the-shelf binary classifiers in a directed structure, such that individual label predictions become features for other classifiers. Such methods have proved flexible and effective and have obtained state-of-the-art empirical performance across many datasets and multi-label evaluation metrics. This performance led to further studies of the underlying mechanism and efficacy, and investigation into how it could be improved. In the recent decade, numerous studies have explored the theoretical underpinnings of classifier chains, and many improvements have been made to the training and inference procedures, such that this method remains among the best options for multi-label learning. Given this past and ongoing interest, which covers a broad range of applications and research themes, the goal of this work is to provide a review of classifier chains, a survey of the techniques and extensions provided in the literature, as well as perspectives for this approach in the domain of multi-label classification in the future. We conclude positively, with a number of recommendations for researchers and practitioners, as well as outlining key issues for future research.

year: 2021

title: Distributed agent-centric system for indigenous data sovereignty

authors: Noovao, Setephano

subjects: holochain

abstract: The sovereignty of indigenous data is a key issue facing indigenous communities. Holochain, a distributed ledger technology, has the potential to address some of the challenges indigenous communities face with respect to data sovereignty. The purpose of this thesis is to critically evaluate the feasibility of using holochain technology to support indigenous data sovereignty. This paper first explores the literature on holochain technology, examining its underlying architecture and features. The research employs a three-phase design science research methodology, conducting an experiment to explore the integration of a decentralized application, holochain, with a prominent cloud service provider. The first phase concentrates on emulating real data-sharing platforms that may utilize data at its disposal, following the principles of indigenous data sovereignty, where a centralized platform could be hosted on a cloud computing service with multiple services in operation. The second phase involves developing a holochain application guided by the principles of indigenous data sovereignty. The final phase seeks to combine the established centralized platform from the first phase with the outcomes of the holochain application from the second phase to experimentally assess whether both technologies can create a data sovereignty solution that aligns with the needs of indigenous data sovereignty. The results of the experiment will provide a solid foundation for understanding the current state of the field and identifying areas where holochain can potentially offer solutions. Furthermore, the results of our research indicate that holochain shows significant promise in tackling the issue of indigenous data sovereignty, although there are considerable limitations that must be addressed and resolved to achieve improved results.

text: Distributed agent-centric system for indigenous data sovereignty The sovereignty of indigenous data is a key issue facing indigenous communities. Holochain, a distributed ledger technology, has the potential to address some of the challenges indigenous communities face with respect to data sovereignty. The purpose of this thesis is to critically evaluate the feasibility of using holochain technology to support indigenous data sovereignty. This paper first explores the literature on holochain technology, examining its underlying architecture and features. The research employs a three-phase design science research methodology, conducting an experiment to explore the integration of a decentralized application, holochain, with a prominent cloud service provider. The first phase concentrates on emulating real data-sharing platforms that may utilize data at its disposal, following the principles of indigenous data sovereignty, where a centralized platform could be hosted on a cloud computing service with multiple services in operation. The second phase involves developing a holochain application guided by the principles of indigenous data sovereignty. The final phase seeks to combine the established centralized platform from the first phase with the outcomes of the holochain application from the second phase to experimentally assess whether both technologies can create a data sovereignty solution that aligns with the needs of indigenous data sovereignty. The results of the experiment will provide a solid foundation for understanding the current state of the field and identifying areas where holochain can potentially offer solutions. Furthermore, the results of our research indicate that holochain shows significant promise in tackling the issue of indigenous data sovereignty, although there are considerable limitations that must be addressed and resolved to achieve improved results.

year: 2024