A small-scale physical modelling system was developed and employed to investigate the effects of tube sampling. Amorphous silica and an oil blend of matching refractive index were mixed to form a transparent soil. Black glass beads were embedded within the soil body on the vertical central plane. After consolidation in a Perspex box, a glass model sampler was pushed into the transparent soil. Movements within the soil body were recorded using digital photography; these images were later analysed by Particle Image Velocimetry. The centreline strain path (CSP) of the sample during tube penetration was calculated and compared to existing analytical and numerical models’ strain predictions, and some degree of correlation was observed. However, it is shown that the CSP is not constant throughout the sample, but varies with depth below the base of the borehole. It was also noticed that after tube penetration, significant residual extensive strains remain for soil on the centreline of the specimen. Different tube geometries were tested and a correlation was found between strain magnitudes and the Area Ratio, Inside Clearance Ratio and the Outer Cutting Edge Taper Angle. It was also found that samples taken in normally consolidated soils were more heavily disturbed than those in lightly overconsolidated soils. After removal from the soil model, samples were stored for six months and volumetric strains within them, set up by a redistribution of pore fluid pressures, were found to be small, typically less than 1%. Soil at the edge of the sampler wall reduced in volume, while the centre swelled. Specimens were thereafter extruded from the sampling tube and the strain path created by this step was quantified. It was found that extrusion compresses the soil while still inside the tube, with soil closest to the extruder more significantly affected. All of these parts of the sampling process contribute to the overall sample disturbance and can therefore have an effect on the sample’s measured properties.

Wheat yields need to rise to meet growing demands due to population growth and changing diets. Additionally, the resilience of crop yields to climate change and rising temperatures needs to be improved. Inhibition of photosynthesis under sub-optimal environmental conditions decreases carbon fixation, reducing crop yields. Heat stress inhibits photosynthesis, in part due to a decrease in the activation state of Rubisco. Rubisco activase (Rca) is required to restore and maintain the catalytic activity of Rubisco. Rca has a relatively low temperature optimum; improving its thermal tolerance would maintain Rubisco activity and enhance photosynthesis at higher temperatures, with predicted positive impacts on grain yields under moderate heat stress. Two approaches were taken to improve the thermal tolerance of Rca in wheat. Firstly, natural variation in the thermal tolerance of Rca in wheat was investigated. Cultivars exhibiting differences in their photosynthetic performance were identified, but the complexity in breeding for increased thermal tolerance was highlighted, with both advantageous and disadvantageous characteristics being identified. The second approach was to introduce the more thermally stable Rca from cotton into wheat in an attempt to broaden the range of temperatures at which photosynthesis operates. Transgenic plants were produced but the cotton Rca protein was undetectable in the wheat lines investigated. Two genes encoding Rca in wheat were identified; one gene is alternatively spliced to produce α and β isoforms. Virus-Induced Gene Silencing of the Rca isoforms in wheat indicated that the Rca genes in wheat may be co-regulated. A non-radioactive activity assay was developed for use in Rubisco and Rca research, allowing high-throughput of samples and avoiding the difficulties some labs may have in completing radioactive assays. The information gained in this study will guide future approaches to optimise the thermal stability of Rca and generate temperature-resilient crops.

Plastics have become an integral part of our lives. However, the disposal of plastic waste poses an enormous problem to society. An ideal solution would be to break down a polymer into its monomer, which could then be used as the building-blocks to recreate the polymer. Unfortunately, the majority of plastics do not degrade readily into their monomer units. Thermal degradation of polymers usually follows a radical mechanism (which is of high energy and requires high temperatures) and produces a large proportion of straight chain alkanes, which have low relative octane number (RON) and so cannot be used in internal combustion engines. However, a suitable catalyst can help to branch straight alkane chains and so give high RON fuels that can be blended into commercial fuels. An extensive thermogravimetric study of polymer-catalyst mixtures was undertaken and produced dramatic reductions in the onset temperature of degradation and significant changes in the activation energy, suggesting a change to a desirable Brønsted- or Lewis-acid catalysed degradation mechanism in many cases. For example, GC-MS analysis of low-density polyethylene (LDPE) degraded with Fulcat 435 clay showed the polymer forming a large number of C6-C7 single-branched alkanes of intermediate RON value. In comparison, degradation of LDPE in the presence of a ZSM-5 zeolite (280z) resulted in the production of a large aromatic content (41% of Total Mass at 450ºC) together with branched C6-C8 hydrocarbons (40%). This formation of a large proportion of high RON components from polyethylene and other polymers could move us one step closer to tackling the enormous problem of plastic waste disposal that the world faces today.

The purpose of this study was to determine the county extension agents' perceptions of institutional constraints to the performance of their duties within the Arizona Cooperative Extension System. Study population was 66 county extension agents in the state of Arizona. They were surveyed by mailed questionnaire. Study results indicated, on the average, most of the institutional constraints affect slightly on the county extension agents' work performance. Considerable variation observed among respondents in their perceptions of severity of the constraints. Some of the other important findings include; (1) 4-H agents perceived constraints more severe than Agriculture or Home Economic Agents. (2) County agents perceived more constraints in salary and promotion more severe than county directors. (3) County agents with more than 5 years of service perceived more of the constraints in the area of Personnel Evaluation more severe than agents with 5 years or less service.

The purpose of this study was to appraise the attitudes of agricultural instructors providing village extension services in the northern province of Sri Lanka toward their job in the agriculture extension service. Major findings indicate in the aggregate, agricultural instructors like their job and have a good attitude toward their job. The job factors offering the agricultural instructors the positive attitudes are the communication established between agricultural instructors and various layers of administration, the intrinsic reward of the job itself, and the relationship with co-workers and the working conditions. The job factors offering the negative attitudes was the pay and its adequacy for a comfortable living. Attitudes of agricultural instructors toward the job and its relationship with service were not significantly varied with service.

Germination responses of P.I. 237110 and 'Ganada' yellow bluestem (Bothriochloa ischaemum (L.) Keng.) were compared in four experiments. P.I. 237110 had the highest total germination for all seed conditioning treatments. At the lowest temperature (15.6°C) P.I. 237110 did not germinate and Ganada had a low total germination. P.I. 237110 and Ganada require high (>20°C) incubation temperatures for optimum germination. Seed conditioning treatments did not significantly increase total germination for P.I. 237110 or Ganada. The caryopsis treatment gave the highest percent germination for all germplasm except Ganada. P.I. 237110 had the fastest time to 50% germination for all seed conditioning treatments. Seed conditioning did not significantly affect time to 50% germination for P.I. 237110 or Ganada. Ganada had significantly higher respiration rates than P.I. 237110 at 0 and -0.4 MPa but not at -0.8 and -1.2 MPa. Respiration rates for both germplasm decreased as osmotic concentrations became more negative.

The effects of subjection of 15-day-old plants of tomato (Lycopersicon esculentum L. 'Contessa') to low night temperature (LNT) of 4°C for up to 21 nights and pre-chilling application of 10% sucrose solution on vegetative, reproductive and yield responses were examined under greenhouse conditions. Chilled seedlings exhibited severe inhibition of growth, with the degree of inhibition increasing with length of chilling. While sucrose treatment (ST) reduced such inhibition and promoted subsequent recovery, it transiently inhibited growth of the unchilled controls. In the long-term, inhibition of growth was observed only for the 0%-sucrose-treated plants cooled for 21 nights. Although LNT lowered the position of the first inflorescence in a direct relation to duration of exposure, this effect was reduced by ST. LNT had no lasting effects on the reproductive and productivity responses of the first two inflorescence (FTI), earliness of flowering, or potential yield and quality. ST promoted flowering of only the 21-day-cooled plants as well as numbers of flowers, fruit set and large fruit responses of FTI. The results indicate that, although early chilling stunts seedling growth, plants may recover at a later favorable temperature without loss to their reproductive capacity or yielding potential.

Livestock production characteristics on the Navajo Reservation were studied to quantify and characterize herd demographics, feeding practices, management practices, marketing practices, and attitudinal orientations of producers. A stratified random (by grazing Agency) sample of the population (n = 10,000) yielded 125 possible respondents from each Agency. Face to face interviews were conducted by Navajo district grazing committeemen in the fall of 1997 for a total of 257 completed surveys. Navajo livestock producers were subsistence-level producers, who battled low birthing rates, slightly elevated mortality rates, diminished resource capacity, and challenges to economical feeding regimes. Most Navajos believed that livestock were an important part of their family's financial well-being; the Reservation was overgrazed; and that Navajos should be allowed to fence their land over their neighbors' objections. Navajo livestock production can be improved through education and greater articulation of the resource base. More detailed data collection is warranted to provide greater insight into production characteristics.

Plants can vary in their mating systems from completely inbreeding to completely outcrossing, with intermediate forms referred to as mixed mating systems. Arabidopsis lyrata is a strongly outcrossing perennial due to a sporophytic self incompatibility (SI) system. The species occurs in temperate regions of the Northern hemisphere where in Europe its SI system is fully working but around the Great Lakes of North America some populations of A. lyrata show a breakdown in SI. Consequently these North American populations are inbreeding or have a mixed mating system next to outcrossing populations with a working SI system. In this thesis I used North American A. lyrata to investigate the evolutionary consequences involving variation in mating systems. First of all I was interested in the time that populations had been isolated from each other in the past that could explain differences in mating systems. In order to determine whether populations experienced a breakdown of SI independently or whether this originated from a single event I used chloroplast DNA (cpDNA) markers to reveal deep phylogeny and microsatellite markers to determine recent population genetic patterns. The results showed a loss of SI in populations from all three detected cpDNA haplotypes. Microsatellite data showed that predominantly inbreeding populations sharing one of these haplotypes showed high levels of homozygosity and that in all three haplotype lineages self-compatible individuals always had reduced heterozygosity compared to self-incompatible individuals. The data further showed that there had likely been at least two independent postglacial colonization routes to the north of the great lakes. This was consistent with phylogeographic studies of other organisms with limited dispersal such as reptiles and amphibians. The next question was the role of inbreeding depression in the loss of SI. Inbreeding depression is defined as the decline of fitness after an inbreeding event. Inbreeding causes an increase in homozygosity that exposes recessive deleterious mutations, which would normally be sheltered in a heterozygous state, and causes a fitness decline. Individuals experiencing a loss of SI will have higher inbreeding levels and can result in inbreeding depression, which is thought to maintain the SI system. To gain more insight into the role of inbreeding depression in the shift from self-incompatibility to self-compatibility, I conducted an experiment in which I created outcrossed and selfed offspring from self-compatible and self-incompatible mothers from populations with different outcrossing histories. I monitored the offspring for early- and late acting fitness traits like germination rate, growth and time to flowering. I found inbreeding depression in only one late acting fitness trait, the increase in leaves 5 weeks after germination, to be significantly higher for self-incompatible than self-compatible individuals. I also conducted a regression analysis where relative fitness (the ratio of the fitness trait values of selfed and outcrossed offspring) per mother was regressed against population heterozygosity and found a significantly negative regression. This result suggested that individuals from a population with a relatively high heterozygosity suffered more from inbreeding depression than individuals from populations with a relatively low heterozygosity. This indicated that the history of outcrossing of a population, or purging, played an important role in the shift from outcrossing to inbreeding. The detection of inbreeding depression could not be evident by only looking at life history traits under greenhouse conditions. But stressful environmental conditions like a pathogen infection could magnify inbreeding depression. I would expect that predominantly outcrossing populations would have a higher heterozygosity than predominantly inbreeding populations and therefore be able to show a higher fitness when exposed to a pathogen. To test this hypothesis I used four outcrossing and four inbreeding populations, which I infected with the crucifer pathogen Albugo candida and measured relative growth rates (RGR) and monitored resistance rates. The results showed that there were three infection phenotypes: resistant (no signs of infection), partially resistant (only the initially infected parts showed symptoms) and susceptible (symptoms present on the whole plant). The inbreeding populations showed a bimodal distribution of resistance as two populations showed a high rate of resistance and two showed a low rate of resistance. The outcrossing populations showed a much more uniform distribution of resistant individuals with a higher rate of partially infected individuals across populations than inbreeding populations. Resistant and partially resistant individuals did not differ significantly in their RGR from each other but both had a significantly lower RGR than the untreated control group and a significantly higher RGR than the susceptible individuals. This suggested a cost of resistance that was lower than a cost of being susceptible in the presence of a pathogen. There was no effect of mating system on RGR, which was primarily caused by the fact that two inbreeding populations contained a high amount of resistant individuals and an outcrossing population that showed a very low amount of partially resistant and resistant individuals. The difference in resistance to A. candida in A. lyrata differed much more between inbreeding than between outcrossing populations. This suggested that alleles responsible for resistance were concentrated in homozygous form in inbreeding populations and both homozygous and heterozygous form in outcrossing populations. This would mean that mating system plays a role in susceptibility, as resistance genes would be concentrated in certain individuals in inbreeding populations as opposed to a more modal distribution in outcrossing populations. A shift in mating system often has an effect on floral traits, as there is a lack of necessity to attract pollinators. I wanted to test whether these changes were apparent in A. lyrata by comparing pollinator attractants and sexual floral traits between strongly outcrossing and strongly inbreeding populations. I hypothesized that individuals depending on pollinators for outcrossing would show a higher emission of volatiles and floral traits that had evolved to optimize pollen transmission to conspecifics. Autonomously selfing individuals would be independent of pollinators so should show a reduced volatile emission pattern, a floral trait composition that evolved to transmit pollen to their own stigma, and a reduction in floral display compared to outcrossers. My results showed a somewhat contradicting pattern as self-compatible individuals showed higher volatile emission than self-incompatible individuals but self-incompatible individuals showed larger petal size than self-compatible individuals. Pistil height and stamen length were strongly correlated but petal size seemed to co-vary relatively independent from pistil and stamen length. I found no effect of mating system on the evolvement of floral traits to optimize pollen to the stigma and contradicting patterns for pollinator attractant traits. Due to low sample sizes this study turned out to be a pilot study for further research so the results in this study were not conclusive at this stage. Finally I conclude that SI has been lost independently several times and the low observed genetic load in the North American populations compared to the European populations could be responsible for that. There have probably been two independent colonization routes to the North of the Great Lakes following the last glaciation in which a Northern distributed cpDNA haplotype lineage seems to have a lower frequency of SC individuals than a southern cpDNA haplotype lineage.

The work described in this thesis was designed to investigate the current impact of parasitic gastroenteritis on organic and conventional dairy farms in first season grazing youngstock in Scotland, and to elucidate a marker of significant parasite challenge within individual calves, in order to target these calves with an anthelmintic treatment. It was felt particularly that any recommendations should be practical and easily implemented on-farm, and optimise anthelmintic usage, with regard to animal health, welfare and performance on both organic and conventional farms. There is world-wide recognition that nematode parasite infections are one of the greatest causes of lost productivity of grazing livestock. In the UK, the single most important cause of parasitic gastroenteritis in cattle is infection with the abomasal nematode, Ostertagia ostertagi, although concomitant infection with the less pathogenic intestinal nematode, Cooperia oncophora is common. Often, non-organic (conventional) producers use anthelmintic treatment programmes that prevent disease or treat all animals in a group without necessarily considering the basic epidemiological information needed for an optimal strategic control. Organic producers are encouraged to avoid this approach, thus it may be hypothesised that organic livestock harbour higher parasite burdens compared to livestock in conventional systems. However, little information is available on current UK organic dairy anthelmintic use and subsequent parasite challenge to youngstock. This thesis aimed to investigate current management practices on three Scottish organic farms compared to three Scottish conventional farms and examine different ways of assessing parasite challenge (including novel markers) with a view to the implementation of a targeted selective treatment (TST) programme. Liveweight gain assessment by means of weigh-bands as a tool to investigate the effect of parasitism on the host was also examined. In year one of the study, the six farms were visited on four occasions throughout the grazing season where fifteen first season grazers on each farm had their liveweight measured (weigh-band or weigh-scale), a faecal egg count (FEC) recorded and plasma pepsinogen, plasma fructosamine and Ostertagia ostertagi antibody concentrations measured. Knowledge of the epidemiology and pathophysiology of gastrointestinal nematode infestation has led to the identification of parasitic biomarkers for use either as a diagnostic tool or for providing a threshold for anthelmintic treatment. Faecal egg counts (FEC) are the most widely used parameter, both clinically and in studies on gastrointestinal nematode infections of ruminants, because of their relative convenience and low cost. Organic producers are encouraged to use faecal egg counts in order to direct anthelmintic treatment to calves, or groups of calves, that have counts of 200 eggs per gram or more (Soil Association, 2010). The recent launch of COWS (Control of Worms Sustainably in Cattle) in May 2010 - an initiative to prevent widespread anthelmintic resistance and to use anthelmintics appropriately in cattle in the UK - has also seen conventional farmers encouraged to use faecal egg counts in the same manner as their organic counterparts (Taylor, 2010i). None of the biomarkers, including FEC, investigated in the study reflected liveweight gain adequately to use in a targeted selective anthelmintic treatment programme. An ideal biomarker would give indication of calves that would most benefit from anthelmintic treatment before liveweight gain was affected. The biomarkers in this study indicated presence of gastrointestinal parasitism but could not target the animals that had poor liveweight gains. The emphasis on FEC in advice to farmers regarding the need for anthelmintic treatment requires re-evaluation. The data from year one showed that the conventionally farmed first season grazers (FSG) had significantly higher liveweight gains than the organically farmed calves. Anthelmintic treatment was applied to the organic calves in the study when the calves were known to be harbouring gastrointestinal parasite infection from positive faecal egg counts. The organically farmed first season grazers in this study had high gastrointestinal parasite challenge, indicated by parasite-based markers such as FEC and plasma pepsinogen concentration. The conventional producers in this study exposed FSG to 652% more days of anthelmintic than the organic producers and gained superior liveweight gains over the grazing season. Essentially, the organic producers fulfilled the ethos of organic production, reducing anthelmintic usage and showing necessity of anthelmintic treatment. However, subclinical and clinical parasitic gastroenteritis reduces animal welfare, the essence of the organic ethos. The organic industry needs to investigate whether there is a superior alternative to FEC that still promotes the organic ethos and reduces subclinical and clinical parasitic gastroenteritis. The possibility of using liveweight gain as a marker for anthelmintic treatment was investigated. An accurate assessment of liveweight is necessary if calf liveweight gain is to be calculated accurately and used as a threshold for anthelmintic treatment. Cattle weigh-scales are expensive and often not available on farm, particularly where youngstock may be grazing at pasture and gathered in the field for handling. With this in mind, cattle weigh-bands, which measure heart girth and relate this to liveweight, have been devised and used in practice in order to estimate cattle liveweight. Realistically, if a liveweight gain threshold were to be recommended for use on farms in the UK, the weigh-band must estimate liveweight and hence liveweight gain accurately. Given that many farmers do not possess weigh-scales on farm, use of heart-girth measurements to estimate liveweight gain is the best option available to farmers currently. Year two involved the implementation of a targeted selective anthelmintic treatment (TST) programme on two organic farms and one conventional farm; all were previously involved in the year one study. Anthelmintic treatment was applied only to FSG calves growing at <0.75kg/day at two points in the grazing season. Organic Farm 1 (O1) and Organic Farm 2 (O2) increased the liveweight gain of the FSG in year two by 50% and 44% respectively. Farm O2 exposed the FSG to 1160% more days of anthelmintic than in 2009; however, approximately 10% of the group were left untreated. Conventional FSG showed reduced liveweight gain from the previous year by 19%. However, respiratory disease was present on-farm also and may have confounded findings. Applying a performance-based targeted anthelmintic regime treatment in the field is possible and using it on farms where anthelmintic treatment was already minimal, such as organic farms, increased liveweight gain in first season grazers without significantly increasing anthelmintic treatment. Applying a TST regime to a conventional farm where previously a suppressive anthelmintic treatment had been applied may have reduced liveweight gain in the first season grazers (FSG) but maintained it at an acceptable level. The acceptance by farmers of TST strategies, and their implementation, may require a high level of input and education to the farming community.