An in vitro study of the replication, morphology and DNA base composition of Mycoplasma ovipneumoniae : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Microbiology at Massey University, New Zealand

Mycoplasma ovipneumoniae can almost invariably be isolated from the lungs of sheep with chronic pneumonia, which is a prevalent disease in New Zealand hoggets. At Massey University, a study is in progress to establish the part, if any, played by M. ovipneumoniae in the patho­genesis of the disease. This thesis represents an in vitro investigation of some properties of M. ovipneu­moniae. It was undertaken as part of the larger study, and is presented in that context. To establish a method for the production of high titre exponential phase inocula for use in disease transmission experiments, the growth of M. ovipneumoniae in FM4 broth was studied. It was found that a maximum titre of 1.0 to 3.0 x 109 CFU/ml was produced regardless of the inoculum size or degree of aeration. The organism had a minimum division time of 1.7 hr; had no stationary phase and in the late death phase was inactivated with a half-life of about 0.5 hr. The organism was stored at -70° with little loss in titre (less than two-fold) over an 18 month period. Shaking cultures became sufficiently turbid during growth to allow meaningful measurements to be made using an SP20 spectrophotometer. In defined conditions, viz. when a shaking culture is in the exponential phase and contains 2.0 to 10.0 x 108 CFU/ml, the viable cell count can be estimated from turbidity measurements. Electron microscopy of M. ovipneumoniae showed that the cells are roughly spherical, 400 to 700nm in diameter, probably replicate by binary fission, contain ribosomes and fibrils of deoxyribonucleic acid, and are bounded by a trilaminar membrane bearing projections 12nm long. No specialized structural feature such as the attachment sites found in M. pneumoniae was detected. The New Zealand isolate of M. ovipneumoniae was morphologically indistinguishable from the standard M. ovipneumoniae strain isolated in Australia. Although the above description could be applied to many mycoplasma species, it should be noted that the average cell diameter of M. ovipneumoniae (about 550nm) is larger than that found for most but not all species of mycoplasma. The base composition of the DNA of M. ovipneumoniae determined by the thermal denaturation and buoyant density studies was 28.1% GC and 28.0% GC respectively. This relatively low GC content falls within the accepted range for mycoplasma species (23 - 40% GC) and within the much narrower range (26.8 - 28.5% GC) of glycolytic mycoplasmas causing respiratory disease in domestic animals

Trends in New Zealand climate change policy 1988 - 2006 : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Public Policy at Massey University

Since 1988 the New Zealand government has participated in an international effort to limit climate change. This study focuses on the domestic policies to reduce greenhouse gas emissions pursued over the period 1988 - 2006, using information drawn from public sources and obtained under the Official Information Act. The science of climate change, international legal framework, and New Zealand's emissions are briefly described to provide the context for policy. The history of domestic climate change policy between 1988 and 2005 is reviewed, and the policies released over the course of 2006 examined. The long-term trends in policy are analysed, and the 2006 policy assessed against them to determine whether it represents a continuation or departure from those trends. Finally, some brief policy recommendations are made. The analysis of long-term trends shows that the New Zealand government has consistently preferred economic instruments over regulatory ones in the effort to reduce emissions, and that it has consistently excluded agriculture from policy. There has also been a heavy reliance on forest sinks at the expense of emissions reductions. Finally, there has been a repeated failure to implement policy, particularly in the area of putting a price on carbon. The 2006 policies broadly followed these trends, although with some important differences: there was a greater willingness to use regulation and the first steps towards incorporating agriculture were taken. Overall, the approach was more pragmatic than that taken previously

Singlet Fermionic Dark Matter and the Electroweak Phase Transition

We consider a model with a gauge singlet Dirac fermion as a cold dark matter candidate. The dark matter particle communicates with the Standard Model via a gauge singlet scalar mediator that couples to the Higgs. The scalar mediator also serves to create a tree-level barrier in the scalar potential which leads to a strongly first order electroweak phase transition as required for Electroweak Baryogenesis. We find a large number of models that can account for all the dark matter and provide a strong phase transition while avoiding constraints from dark matter direct detection, electroweak precision data, and the latest Higgs data from the LHC. The next generation of direct detection experiments could rule out a large region of the parameter space but can be evaded in some regions when the Higgs-singlet mixing is very small.Comment: 9 pages, 6 figures. v2: figure captions updated, colour confusion fixed, no other changes. v3: references added, some clarification, now matches version published in JHE

Electroweak Vacuum Stability in light of BICEP2

We consider the effect of a period of inflation with a high energy density upon the stability of the Higgs potential in the early universe. The recent measurement of a large tensor-to-scalar ratio, $r_T \sim 0.16$, by the BICEP-2 experiment possibly implies that the energy density during inflation was very high, comparable with the GUT scale. Given that the standard model Higgs potential is known to develop an instability at $\Lambda \sim 10^{10}$ GeV this means that the resulting large quantum fluctuations of the Higgs field could destabilize the vacuum during inflation, even if the Higgs field starts at zero expectation value. We estimate the probability of such a catastrophic destabilisation given such an inflationary scenario and calculate that for a Higgs mass of $m_h=125.5$ GeV that the top mass must be less than $m_t\sim 172$ GeV. We present two possible cures: a direct coupling between the Higgs and the inflaton and a non-zero temperature from dissipation during inflation.Comment: 5 pages, 4 figures. Typos corrected, results unchanged, matches version submitted to journa

A novel approach to hybrid propulsion transfers

This paper introduces a hybrid propulsion transfer termed a Hohmann Spiral, incorporating low and high-thrust technologies, analogous to the high-thrust bi-elliptic transfer. To understand this transfer fully it is compared to a standard high thrust Hohmann and a bi-elliptic transfer. Two critical specific impulse ratios are derived independent of time that determine the point this novel transfer consumes the exact amount of fuel as the two compared transfer types. It is found that these ratios are valid for both a circular and elliptical starting orbit so long as the apogee of the elliptical orbit coincides with the target orbit radius. An expression representing the fuel mass fraction is derived dependent of time in order to allow a bound solution space. The final part of this paper investigates two orbit transfer case studies, one is a Geostationary Transfer Orbit to Geostationary Earth Orbit based on the Alphabus platform specification and the other is from Low Earth Orbit to an orbit near the Moon. It is found the thrust required to complete the former transfer in a specified duration of 90 days exceeds current technology and as such provides a technology requirement for future spacecraft. It is found however, for spacecraft of significantly smaller mass, in the region of 1000kg, compared to Alphabus (Max. mass at Launch =8100kg), the transfer consumes the same fuel mass as a standard high-thrust Hohmann transfer with realistic low-thrust propulsion values (150mN, 300mN and 450mN) within the set duration of 90 days. In addition, it is shown that utilising uprated thrusters (210mN, 420mN and 630mN) a fuel mass saving can be made. This could provide a potential transfer alternative for future smaller spacecraft. The second case study is bound to a maximum thrust of 150mN, but the mission duration is not specified to highlight the variation. It is found that the HST offers fuel mass savings of roughly 5% compared to a standard high-thrust transfer and approximately 1.5% compared to a bi-elliptic transfer for different scenarios

Novel numerical optimisation of the Hohmann Spiral Transfer

As the revenue of commercial spacecraft platforms is generated by its payload, of which the capacity is maximised when fuel-mass is minimised, there is great interest in ensuring the fuel required for the trajectory to deliver the satellite to its working orbit is minimum. This paper presents an optimisation study of a novel orbit transfer, recently introduced by the authors through an analytical analysis, known as the Hohmann Spiral Transfer . The transfer is analogous to the bi-elliptic transfer but incorporating high and low-thrust propulsion. This paper has shown that substantial fuel mass savings are possible when utilizing the HST. For a transfer to Geostationary Earth Orbit it is shown that a fuel mass saving of approximately 320 kg (~ 5 - 10% of mwet ) is possible for a wet mass of 3000-6000 kg – whilst satisfying a time constraint of 90 days. Several trends in the gathered data are also identified that determine when the HST with high or low-thrust plane change should be used to offer the greatest fuel mass benefit

Hohmann spiral transfer with inclination change performed by low-thrust system

This paper investigates the Hohmann Spiral Transfer (HST), an orbit transfer method previously developed by the authors incorporating both high and low-thrust propulsion systems, using the low-thrust system to perform an inclination change as well as orbit transfer. The HST is similar to the bi-elliptic transfer as the high-thrust system is first used to propel the spacecraft beyond the target where it is used again to circularize at an intermediate orbit. The low-thrust system is then activated and, while maintaining this orbit altitude, used to change the orbit inclination to suit the mission specification. The low-thrust system is then used again to reduce the spacecraft altitude by spiraling in-toward the target orbit. An analytical analysis of the HST utilizing the low-thrust system for the inclination change is performed which allows a critical specific impulse ratio to be derived determining the point at which the HST consumes the same amount of fuel as the Hohmann transfer. A critical ratio is found for both a circular and elliptical initial orbit. These equations are validated by a numerical approach before being compared to the HST utilizing the high-thrust system to perform the inclination change. An additional critical ratio comparing the HST utilizing the low-thrust system for the inclination change with its high-thrust counterpart is derived and by using these three critical ratios together, it can be determined when each transfer offers the lowest fuel mass consumption. Initial analyses have shown the HST utilizing low-thrust inclination change to offer the greatest benefit at low R2 (R2 - R1) and large AI (AI > 30º). A novel numerical optimization process which could be used to optimize the trajectory is also introduced

An extension and numerical analysis of the Hohmann spiral transfer

This paper extends previous work on the Hohmann Transfer Spiral (HST) by introducing a plane change into the analysis. An analytical expression determining the critical specific impulse incorporating a plane change is derived for both a circular and elliptical initial orbit. This expression determines the point at which the HST is equivalent in terms of fuel mass fraction to the compared Hohmann transfer. The expression assumes that the inclination change is performed by the high-thrust system. The numerical approach uses a blending method coupled with optimised weighting constants to deliver a locally optimal low-thrust trajectory. By comparing the analytical and numerical approaches, it is shown that the analytical can deliver a good estimation of the HST characteristics so long as little orbit eccentricity control is required. In the cases where orbit eccentricity control is required, the numerical approach should be used. A case study from an inclined Geostationary Transfer Orbit, equivalent to a high-latitude launch site, to Geostationary Earth Orbit has shown that the HST can offer a fuel mass saving approximately 5% of the launch mass. This equates to the mass penalty associated with this high-latitude launch site and therefore mimics the advantages of a low-latitude launch site at the expense of a longer transfer duration

Learning from the learners' experience: e-Learning@greenwich post-conference reflections

This publication comprises papers from presenters who, having made a conference presentation, were invited to author an academic paper about their work