title: Spectroscopic and synthetic studies of lichen metabolites

authors: Ronaldson, Kathlyn Joy

abstract: Lichen metabolites from various Nephroma and Pseudocyphellaria species have been subjected to a number of spectroscopic and synthetic investigations. Hypoiodite reaction of 15α-acetoxyhopan-17(21)-en-24-ol yielded a complex mixture of products, while similar reaction of 7-oxohopan-22-ol resulted in cleavage of the side-chain. Preparation of an α-sulphenylated 15-ketone was achieved as the first step in a carbonyl transposition sequence. Complete assignment of the ¹³C nmr spectra of four pentacyclic and two ring A-cleaved stictane derivatives provided evidence of the boat-ring B. The low frequency infrared spectra of a number of stictane and hopane triterpenoids yielded structurally significant correlations. Two depsidonal constituents of N. australe were demonstrated to be hypostictic acid and hyposalazinic acid. The reactions of mercuric acetate with unsaturated compounds are reviewed and anomalous products of Jones reagent oxidation investigated.

text: Spectroscopic and synthetic studies of lichen metabolites Lichen metabolites from various Nephroma and Pseudocyphellaria species have been subjected to a number of spectroscopic and synthetic investigations. Hypoiodite reaction of 15α-acetoxyhopan-17(21)-en-24-ol yielded a complex mixture of products, while similar reaction of 7-oxohopan-22-ol resulted in cleavage of the side-chain. Preparation of an α-sulphenylated 15-ketone was achieved as the first step in a carbonyl transposition sequence. Complete assignment of the ¹³C nmr spectra of four pentacyclic and two ring A-cleaved stictane derivatives provided evidence of the boat-ring B. The low frequency infrared spectra of a number of stictane and hopane triterpenoids yielded structurally significant correlations. Two depsidonal constituents of N. australe were demonstrated to be hypostictic acid and hyposalazinic acid. The reactions of mercuric acetate with unsaturated compounds are reviewed and anomalous products of Jones reagent oxidation investigated.

year: 1980

title: Fast Monte Carlo Simulation of ⁹⁰Y Bremsstrahlung using a Kernel-based Photon Source

authors: Zakariah, Suhaili

subjects: Monte Carlo

abstract: In targeted radionuclide therapy using ⁹⁰Y, bremsstrahlung photons can be used for imaging and subsequently for absorbed dose estimation. Monte Carlo simulation is a reliable method to study bremsstrahlung imaging but it takes a long computation time as not all ⁹⁰Y disintegrations result in emission of a bremsstrahlung photon. Furthermore the electron transport simulation is particularly time consuming. This research proposes that bremsstrahlung photons produced from the decay of a ⁹⁰Y point source are replaced with a kernel-based photon source for faster Monte Carlo simulation.
This study is divided into three main parts. First, a ⁹⁰Y point source in a spherical water phantom is fully simulated using Monte Carlo simulation. The characteristics of the bremsstrahlung photons produced from the ⁹⁰Y decay are investigated. The full Monte Carlo simulation of ⁹⁰Y point source provides the relationships between the emission position, energy and emission angle of the bremsstrahlung photon. These are recorded as probability distribution functions (PDFs).
Then, a kernel-based photon source which comprises of an array of photon-emitting concentric spherical shells is developed. The energy spectrum and angular distributions of the emitted photons are defined for each shell using the PDFs obtained previously from the full ⁹⁰Y Monte Carlo simulation. The kernel-based photon source shows a very close approximation to the distribution of bremsstrahlung photons generated by the full Monte Carlo simulation of ⁹⁰Y point source if the shells are sufficiently closely spaced.
Finally, the accuracy and speed of the kernel-based photon source are evaluated. A simplified gamma camera model, which consists of a collimator and NaI(Tl) detector is simulated to obtain the point spread function (PSF) of the point source ‘image’. The PSF can be represented as a Gaussian function. Estimation of σ of the Gaussian function and thus the full-width half-maximum (FWHM) is used to compare the different kernel-based photon source models to represent a ‘real’ source generated by a full Monte Carlo ⁹⁰Y simulation. The results show that the FWHMs of the photon source with kernels are comparable to full Monte Carlo simulation of ⁹⁰Y point source. The FWHM determined for a photon point source with the spectrum of ⁹⁰Y bremsstrahlung underestimates the full Monte Carlo simulation of the true ⁹⁰Y point source. This demonstrates that it is important to account for the photons being emitted at a distance away from the source and all of the photons cannot be assumed to come from a single point. It is more computationally efficient to use this source model than the kernel-based photon sources as it has the shortest computation time, however it is quite inaccurate. Simplifying the kernel-based source by assuming the photon emission as isotropic reduces the accuracy of the model slightly, though the reduction in simulation time is sufficiently small that the more accurate anisotropic kernel should be preferred.
The kernel-based photon source proposed in this study can be used to accurately represent the bremsstrahlung photons produced from the beta decay of a ⁹⁰Y point source. This approach greatly improves the simulation speed by almost 30 times.

text: Fast Monte Carlo Simulation of ⁹⁰Y Bremsstrahlung using a Kernel-based Photon Source In targeted radionuclide therapy using ⁹⁰Y, bremsstrahlung photons can be used for imaging and subsequently for absorbed dose estimation. Monte Carlo simulation is a reliable method to study bremsstrahlung imaging but it takes a long computation time as not all ⁹⁰Y disintegrations result in emission of a bremsstrahlung photon. Furthermore the electron transport simulation is particularly time consuming. This research proposes that bremsstrahlung photons produced from the decay of a ⁹⁰Y point source are replaced with a kernel-based photon source for faster Monte Carlo simulation.
This study is divided into three main parts. First, a ⁹⁰Y point source in a spherical water phantom is fully simulated using Monte Carlo simulation. The characteristics of the bremsstrahlung photons produced from the ⁹⁰Y decay are investigated. The full Monte Carlo simulation of ⁹⁰Y point source provides the relationships between the emission position, energy and emission angle of the bremsstrahlung photon. These are recorded as probability distribution functions (PDFs).
Then, a kernel-based photon source which comprises of an array of photon-emitting concentric spherical shells is developed. The energy spectrum and angular distributions of the emitted photons are defined for each shell using the PDFs obtained previously from the full ⁹⁰Y Monte Carlo simulation. The kernel-based photon source shows a very close approximation to the distribution of bremsstrahlung photons generated by the full Monte Carlo simulation of ⁹⁰Y point source if the shells are sufficiently closely spaced.
Finally, the accuracy and speed of the kernel-based photon source are evaluated. A simplified gamma camera model, which consists of a collimator and NaI(Tl) detector is simulated to obtain the point spread function (PSF) of the point source ‘image’. The PSF can be represented as a Gaussian function. Estimation of σ of the Gaussian function and thus the full-width half-maximum (FWHM) is used to compare the different kernel-based photon source models to represent a ‘real’ source generated by a full Monte Carlo ⁹⁰Y simulation. The results show that the FWHMs of the photon source with kernels are comparable to full Monte Carlo simulation of ⁹⁰Y point source. The FWHM determined for a photon point source with the spectrum of ⁹⁰Y bremsstrahlung underestimates the full Monte Carlo simulation of the true ⁹⁰Y point source. This demonstrates that it is important to account for the photons being emitted at a distance away from the source and all of the photons cannot be assumed to come from a single point. It is more computationally efficient to use this source model than the kernel-based photon sources as it has the shortest computation time, however it is quite inaccurate. Simplifying the kernel-based source by assuming the photon emission as isotropic reduces the accuracy of the model slightly, though the reduction in simulation time is sufficiently small that the more accurate anisotropic kernel should be preferred.
The kernel-based photon source proposed in this study can be used to accurately represent the bremsstrahlung photons produced from the beta decay of a ⁹⁰Y point source. This approach greatly improves the simulation speed by almost 30 times.

year: 2011

title: Te ao hurihuri : iwi identification in the census

authors: Kukutai, Tahu

abstract: As the flagship of official statistics, the national population census is an important forum for the recognition of indigenous peoples in their homelands and territories (United Nations, 2008). While most governments worldwide count and classify their populations by ethnicity, New Zealand is rare in enabling multiple expressions of indigenous identity in the census. Since 1991, it has been possible to identify as Māori in three ways: by descent, ethnicity and iwi (tribal) affiliation (see Figure 1). The Māori descent population is the largest— in 2013, just under 669,000 individuals ticked the Māori descent box. The number identifying as Māori by ethnicity - intended as a measure of cultural belonging - was substantially lower at just under 600,000. Most of the remaining 69,000 Māori descendants identified solely as NZ European. In 2013 nearly 83 per cent of Māori descendants (n=535,941) reported belonging to at least one iwi. Of those that did not report an iwi affiliation, 40 per cent did not identify as Māori by ethnicity either.

text: Te ao hurihuri : iwi identification in the census As the flagship of official statistics, the national population census is an important forum for the recognition of indigenous peoples in their homelands and territories (United Nations, 2008). While most governments worldwide count and classify their populations by ethnicity, New Zealand is rare in enabling multiple expressions of indigenous identity in the census. Since 1991, it has been possible to identify as Māori in three ways: by descent, ethnicity and iwi (tribal) affiliation (see Figure 1). The Māori descent population is the largest— in 2013, just under 669,000 individuals ticked the Māori descent box. The number identifying as Māori by ethnicity - intended as a measure of cultural belonging - was substantially lower at just under 600,000. Most of the remaining 69,000 Māori descendants identified solely as NZ European. In 2013 nearly 83 per cent of Māori descendants (n=535,941) reported belonging to at least one iwi. Of those that did not report an iwi affiliation, 40 per cent did not identify as Māori by ethnicity either.

year: 2015