Search for second and third generation leptoquarks including production via technicolor interactions in p(p)over-bar collisions at root s=1.8 TeV

We report the results of a search for second and third generation leptoquarks using 88 ph(-1) of data recorded by the Collider Detector at Fermilab. Color tripler technipions, which play the role of scalar leptoquarks, are investigated due to their potential production in decays of strongly coupled color octet technirhos. Events with a signature of two heavy flavor jets and missing energy may indicate the decay of a second (third) generation leptoquark to a charm (bottom) quark and a neutrino. As the data are found to be consistent with standard model expectations, mass limits are determined

Demography and population models for Hieracium Pilosella in New Zealand

Hieracium pilosella has become a major concern in the high country grasslands of New Zealand. This thesis provides an understanding of the population dynamics of H. pilosella in an area which has supported the weed as a major component of the vegetation for more than 30 years. The study uses a combined modelling and experimental approach to determine vital rates and regulatory mechanisms. It then uses these to predict the rate of spatial spread, change in density, and the likely impact of biological control. Mature populations of H pilosella at Mt. John were found to be regulated by the interaction between density-dependent mortality and density-independent reproduction. The addition of water and/or fertiliser caused an increase in the reproductive vigour of the plant and a decrease in density while simulated grazing (i.e. mowing) had little effect on the population. A link was found between reproductive vigour and rosette size or age (50% of first year rosettes reproduced while only 11 % of older rosettes did), although the reproductive threshold size (23 mm diameter) appeared to be independent of age. Rosettes grown on soil which had previously supported H pilosella had lower growth and reproductive rates and produced fewer stolons of shorter length. However, there was little support for either the allelopathic or aluminium toxicity hypotheses for these lower growth rates. Spatial population models suggested that in the early stages of colonisation, H pilosella vital rates are such that it has the potential to occupy 100% of available space but as the population matures, vital rates change and it is unable to occupy all available space, probably because of intraspecific competition and a limit on plant size. Spread of patches was predicted to be 0.5 - 0.8 cm/yr by both explicit spatial simulation models and analytical diffusion models. Both spatial and non-spatial models predicted that the most effective agent for biological control would be one which caused an increase in mortality rather than a decrease in fecundity; to reduce a population by more than 50% a control agent would have to either increase mortality by 10 - 15 % or decrease daughter production by 80%

Activation of MEK1 through Chemical Methods - a redox trigger for evaluating the effects of phosphorylation

Protein phosphorylation plays a key role in regulating protein function and has been linked to such diseases as cancer, inflammation, and neurological disorders. The introduction of the negatively charged phosphate group can alter the protein's function through the induction of conformational changes or by inhibiting or promoting protein-protein interactions. Given that many upstream kinases of phosphorylated proteins are unknown, and that mutation of phosphorylated sites to negatively charged residues have shown variable results, another method for evaluating the effects of phosphorylation is needed. Previously, phosphotyrosine had been shown to be an effective mimic for sulfotyrosine in hirudin; therefore, we expected that sulfonation of cysteine may serve as an alternative approach to make mimics of phosphorylated serine (and possibly threonine) proteins. Sulfonation of cysteine is rapidly reversed in the presence of reducing agents; therefore, this modification can be potentially used as a redox trigger for evaluating the effects of phosphorylation. In this dissertation MEK1 - which is enzymatically activated through phosphorylation of serine 218 and 222 - was evaluated for its ability to be chemically activated by sulfonation of cysteine 218 and / or 222 through the reaction with sodium tetrathionate and sodium sulfite. Sulfonation of cysteine 218 was shown to not only mimic phosphoserine's ability to trigger activation in MEK1, but was also demonstrated to mediate phosphorylation-dependent protein-protein interactions with the polyclonal antibody anti-MEK1 [pSpS218/222]. However, in the presence of the reducing agent DTT, the sulfonated protein's enzymatic activity was reduced to its respective basal level and it was no longer able to be recognized by anti-MEK1 [pSpS218/222]. Since many upstream kinases of phosphorylated proteins are unknown, the introduction of the thiosulfate moiety by chemical means offers endless opportunities to study the effects of phosphorylation

<i>Ranunculus acris</i> control in dairy pasture – a comparison of herbicides, plant growth promoters, a bioherbicide and pregraze mowing

<p>The efficacy of control tactics for <i>Ranunculus acris</i> was quantified on poorly- and well-drained soils in a factorial experiment conducted over three years in 18 dairy pastures. Soil drainage, gibberellic acid and nitrogenous fertiliser (growth promoters), and a bioherbicide utilising <i>Sclerotinia sclerotiorum</i> had no effect on the cover of <i>R. acris</i>. The herbicides aminopyralid and aminopyralid+triclopyr, by contrast, gave long-lasting reductions in the cover of the weed and substantial temporary reductions in the clovers. Flumetsulam, thifensulfuron methyl, MCPA, MCPB and MCPB+bentazone were less effective overall. Pregraze mowing reduced <i>R. acris</i> as the frequency of mowing increased. For all herbicides, there was a 1:1 replacement of <i>R. acris</i> by grasses and clovers. The efficacy of the treatments varied greatly between pastures, possibly due to genetic differences between the <i>R. acris</i> populations and their historical exposure to the herbicides.</p

Modelling Tradescantia fluminensis to assess long term survival

We present a simple Poisson process model for the growth of Tradescantia fluminensis, an invasive plant species that inhibits the regeneration of native forest remnants in New Zealand. The model was parameterised with data derived from field experiments in New Zealand and then verified with independent data. The model gave good predictions which showed that its underlying assumptions are sound. However, this simple model had less predictive power for outputs based on variance suggesting that some assumptions were lacking. Therefore, we extended the model to include higher variability between plants thereby improving its predictions. This high variance model suggests that control measures that promote node death at the base of the plant or restrict the main stem growth rate will be more effective than those that reduce the number of branching events. The extended model forms a good basis for assessing the efficacy of various forms of control of this weed, including the recently-released leaf-feeding tradescantia leaf beetle (Neolema ogloblini)