Unique Neoproterozoic carbon isotope excursions sustained by coupled evaporite dissolution and pyrite burial

The Neoproterozoic era witnessed a succession of biological innovations that culminated in diverse animal body plans and behaviours during the Ediacaran–Cambrian radiations. Intriguingly, this interval is also marked by perturbations to the global carbon cycle, as evidenced by extreme fluctuations in climate and carbon isotopes. The Neoproterozoic isotope record has defied parsimonious explanation because sustained 12C-enrichment (low δ13C) in seawater seems to imply that substantially more oxygen was consumed by organic carbon oxidation than could possibly have been available. We propose a solution to this problem, in which carbon and oxygen cycles can maintain dynamic equilibrium during negative δ13C excursions when surplus oxidant is generated through bacterial reduction of sulfate that originates from evaporite weathering. Coupling of evaporite dissolution with pyrite burial drives a positive feedback loop whereby net oxidation of marine organic carbon can sustain greenhouse forcing of chemical weathering, nutrient input and ocean margin euxinia. Our proposed framework is particularly applicable to the late Ediacaran ‘Shuram’ isotope excursion that directly preceded the emergence of energetic metazoan metabolisms during the Ediacaran–Cambrian transition. Here we show that non-steady-state sulfate dynamics contributed to climate change, episodic ocean oxygenation and opportunistic radiations of aerobic life during the Neoproterozoic era

Costs associated with fire blight incursion management and predicted costs of future incursions

The Erwinia amylovora incursion in the Royal Botanic Gardens, Melbourne (RBGM) in autumn 1997 cost the Australian pome fruit and nursery industries an estimated A$20 million in lost revenue. The cost of the national orchard and urban surveys, eradication programs, diagnostics, and media management was estimated at A$2.2 million and involved some 250 people. As a result of the E. amylovora incursion in the RBGM, an imposition of interstate trade on the movement of host plants and related produce was enforced. These restrictions cost the Victorian pome fruit and nursery industries around A$7 million in lost sales and depressed prices. International trade was also suspended in some instances and the Tasmanian industry application for access to the Japanese apple market was delayed for two years and cost an estimated A$10 million in lost sales. Prior to and since the RBGM incursion a number of research projects have been commissioned, at a cost of A$0.5 million, to formulate detailed contingency plans and diagnostic protocols and improve awareness and Australia’s preparedness for the next E. amylovora incident. The economic impact of a fire blight outbreak in Australia’s largest pome fruit growing district (Goulburn Valley, Victoria) was calculated using a dynamic multi-regional computable general equilibrium program of Australia called TERM (The Enormous Regional Model) (Horridge et al., 2003). Two separate scenarios were considered. In the first scenario an outbreak with 30$260 million. In the second scenario an outbreak is not eradicated and pome fruit output in the Goulburn Valley declines by 50% for pears and 20% for apples and results in losses of A$870 million in net present value

Forward and Inverse Processing in Electromagnetic NDE Using Squids

Electromagnetic NDE has been successfully applied to the detection of surface cracks and is routinely used to locate flaws in airframes, pipelines and in steel offshore oil platforms. However, there are still many problems to be solved, particularly in the aviation industry, which require the detection of deeper flaws such as corrosion in multi-layered structures and cracks around rivet holes which are obscured by the head of the rivet. Most systems use coils as detectors (though Hall probes are occasionally used), which have low sensitivity at low frequencies due to the fact that the induced voltage is proportional to the rate of change of magnetic flux through the coil. Unfortunately it is necessary to use low frequencies to detect deep subsurface flaws on account of the skin-depth effect, otherwise the electromagnetic field cannot propagate down to the depth of the flaw. SQUID (Superconducting Quantum Interference Device) sensors are ideally suited to overcome the deficiencies of coils, because they are primarily detectors of magnetic flux which, together with their high sensitivity, makes the detection of deep flaws more likely. SQUIDs have been successfully used for measuring very low magnetic fields, particularly in the field of biomagnetism, and it is hoped to exploit this sensitivity to detect flaws at large stand-off distances for example in pipelines which are surrounded by thick layers of cladding