Gold and palladium as indicators of an extraterrestrial component in the Cetaceous/Tertiary boundary layer at Woodside Creek and Chancet Quarry, Marlborough, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Earth Sciences at Massey University

It is widely believed that a large meteorite approximately 10 km in diameter impacted Earth at the termination of the Cretaceous Period with cosmic velocity, vaporising itself, along with a greater mass of the terrestrial target rocks into a cloud of hot rock vapour. The vapour cloud condensed into particles of sand to clay size at high altitude before returning to Earth to form a worldwide layer marking the Cretaceous/Tertiary boundary. Chemical evidence from this boundary layer suggests that the impactor was a chondritic meteorite, enriched in the platinum group elements compared to the Earth's crust. An enrichment of these elements above their background crustal abundances to approximately 0.1 of the chondritic abundance has been observed in a number of Cretaceous/Tertiary boundary layers worldwide. Iridium is the platinum group element traditionally used as an indicator of the extraterrestrial component (ETC) in likely impact layers due to its rarity in the Earth's crust and low detection limits possible using neutron activation analysis methods. Neutron activation analysis is however expensive and requires specialist facilities, this thesis proposes that the elements gold and palladium can also be used to indicate the ETC in the Cretaceous/Tertiary boundary layer. Samples from two Cretaceous/Tertiary boundary sites, Woodside Creek and Chancet Quarry, were analysed for gold and palladium using graphite furnace atomic absorption spectrometry. A strong correlation was found between iridium, gold, and palladium abundances at these sites, with all showing enrichment at precisely the Cretaceous/Tertiary boundary in proportion to iridium, indicating a common origin for all three elements. Gold showed almost precisely the expected 0.1 of its chondritic abundance in the clay size fraction at both Woodside Creek and Chancet Quarry (15 ng/g). Palladium showed exactly 0.1 of its chondritic abundance at the Chancet Quarry boundary with 53 ng/g. Gold abundances on the boundary at Woodside Creek (55 ng/g) and Chancet Quarry (44 ng/g) showed excellent agreement with published values as did the palladium result for Woodside Creek (22 ng/g)

Theory and Techniques for Synthesizing a Family of Graph Algorithms

Although Breadth-First Search (BFS) has several advantages over Depth-First Search (DFS) its prohibitive space requirements have meant that algorithm designers often pass it over in favor of DFS. To address this shortcoming, we introduce a theory of Efficient BFS (EBFS) along with a simple recursive program schema for carrying out the search. The theory is based on dominance relations, a long standing technique from the field of search algorithms. We show how the theory can be used to systematically derive solutions to two graph algorithms, namely the Single Source Shortest Path problem and the Minimum Spanning Tree problem. The solutions are found by making small systematic changes to the derivation, revealing the connections between the two problems which are often obscured in textbook presentations of them.Comment: In Proceedings SYNT 2012, arXiv:1207.055

The impact of COVID-19 school disruption on learning outcomes: the 2001 Foot and Mouth Disease experience gives reason for optimism

The COVID-19 crisis has led to disruption to schooling across the world. Though it is recognised that pupils are suffering immediate learning loss, there exists a lack of understanding as to how this disruption might affect longer-term educational outcomes. William Cook considers this question by examining the effect of school disruption in England as a result of restrictions put in place to manage the Foot and Mouth Disease epidemic in 2001. He finds that primary schools that had been significantly disrupted by the measures exhibited achievement falls in the year immediately after the outbreak, driven by sizeable falls in maths performance in particular. The negative effects weaken in subsequent years, suggesting that the effects of school disruption may fade out as cohorts progress through schooling

Reconstructed Wavefronts: Comparative Quality of Several Systems

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Low Frequency Gravitational Waves from Black Hole MACHO Binaries

Nakamura, Sasaki, Tanaka, and Thorne have recently estimated the initial distribution of binary MACHOs in the galactic halo assuming that the MACHOs are primordial half solar mass black holes, and considered their coalescence as a possible source for ground-based interferometer gravitational wave detectors such as LIGO. Evolving their binary distribution forward in time to the present, the low-frequency (10^{-5} < f < 10^{-1} Hz) spectrum of gravitational waves associated with such a population of compact binaries is calculated. The resulting gravitational waves would form a strong stochastic background in proposed space interferometers such as LISA and OMEGA. Low frequency gravitational waves are likely to become a key tool for determining the properties of binaries within the dark MACHO population.Comment: 8 pages + 2 ps figures; AASTe