21 research outputs found
Calibration methodology for mapping within-field crop variability using remote sensing
No full textA successful method of mapping within-field crop variability of shoot populations in wheat (Triticum aestivum) and barley (Hordeum vulgare L.) is demonstrated. The approach is extended to include a measure of green area index (GAI). These crop parameters and airborne remote sensing measures of the normalised difference vegetation index (NDVI) are shown to be linearly correlated. Measurements were made at key agronomic growth stages up to the period of anthesis and correlated using statistical linear regression based on a series of field calibration sites. Spatial averaging improves the estimation of the regression parameters and is best achieved by sub-sampling at each calibration site using three 0·25 m2 quadrats. Using the NDVI image to target the location of calibration sites, eight sites are shown to be sufficient, but they must be representative of the range in NDVI present in the field, and have a representative spatial distribution. Sampling the NDVI range is achieved by stratifying the NDVI image and then randomly selecting within each of the strata; ensuring a good spatial distribution is determined by visual interpretation of the image. Similarly, a block of adjacent fields can be successfully calibrated to provide multiple maps of within-field variability in each field using only eight points per block representative of the NDVI range and constraining the sampling to one calibration site per field. Compared to using 30 or more calibration sites, restricting samples to eight does not affect the estimation of the regression parameters as long as the criteria for selection outlined in this paper is adhered to. In repeated tests, the technique provided regression results with a value for the coefficient of determination of 0·7 in over 85% of cases. At farm scale, the results indicate an 80–90% probability of producing a map of within crop field variability with an accuracy of 75–99%. This approach provides a rapid tool for providing accurate and valuable management information in near real-time to the grower for better management and for immediate adoption in precision farming practices, and for determining variable rates of nitrogen, fungicide or plant growth regulators
Risk Taking and Performance in Multistage Tournaments: Evidence from Weightlifting Competitions
No full textWe analyze the impact of interim ranking on the risk taking and performance behaviour of professional athletes participating in international weightlifting competitions. Weightlifting competitions are multistage tournaments with the unique characteristic that the athletes must announce in advance the amount they intend to lift at each stage, thus allowing quantification of the riskiness of their choices. We present two key findings. First, risk taking exhibits an inverted-U relationship with rank: risk taking increases up to rank six, but athletes then revert to safer strategies towards the bottom of the ranking. Second, athletes systematically underperform when ranked closer to the top, despite higher incentives to perform well. An athlete is more than 30 percent less likely to lift the announced weight when ranked first than tenth. Athletes also underperform in relatively more prestigious competitions, when the competition is more intense, and when the potential gain from a successful lift is higher. Taken together, these findings suggest that athletes may systematically "choke under pressure".Choking under pressure, incentives, performance, risk taking, tournaments
An investigation into the design of cultivation systems for inter- and intra-row weed control
No full textThe aim of this study was to investigate the factors that influence the design of soil
engaging systems to mechanically control weeds between plants within the crop row
in widely spaced field vegetables. A mass flow soil dynamics model based on particle
dynamics was developed to aid designers in determining the lateral and forward
displacement of soil as it is undercut by shallow working wide blades. The model was
validated in soil bin laboratory experiments and used to design a novel mechanical
inter- and intra-row weeding system. Cont/d
Whole-crop cereals in dairy production
No full textThe four studies summarised and discussed in this thesis evaluate the use of whole-crop cereal silage (WCCS) for cattle in dairy production. The dry matter (DM) yield, chemical composition, digestibility, feed intake and milk production for WCCS were evaluated for different cereal species and maturity stages at harvest. The DM yield increased from milk to dough stages of maturity and was higher in winter triticale and rye than in spring barley and oats. Delayed harvest until early dough stage decreased the crude protein (CP) and neutral detergent fibre (NDF) concentrations in barley, oats and triticale. The concentration of water soluble carbohydrates (WSC) of the fresh crop was highest at the early milk stage, but these carbohydrates were to a large extent polymerised to starch by the early dough stage of maturity. Both WSC and starch concentrations were lower in oats than in barley, triticale and rye. When fed to dairy heifers the DM intake (DMI) of six-rowed barley was reduced at early milk and early dough stages most likely due to the development of sharp awns on the crop. The DMI of six-rowed barley silage also decreased with delayed maturity stage when fed to dairy cows. The DMI of oats was reduced at the heading and early milk stages of maturity due to low DM content of the silages. The DM digestibilities and organic matter digestibilities (OMD) of oats and winter rye were lower than for barley and winter triticale, as a combined effect of higher NDF concentrations and lower NDF digestibilities in the two former crops. When six-rowed barley silage harvested at the early dough stage was fed to dairy cows in mid-late lactation the daily energy-corrected milk (ECM) yield was 3 kg lower than when barley silage at heading was fed, due to reductions in milk yield, and both protein and fat concentrations in the milk. This decrease in ECM yield was due to lower DMI and OMD of the ration containing barley silage at early dough stage than of the ration including barley silage at the heading stage of maturity. In conclusion, spring barley and winter triticale appear to have the best feed values when chemical composition and digestibility are considered. When WCCS harvested at early dough stage is fed to dairy cows, milk production may decrease
Diffraction and database analyses of photoactive biphenyl compounds and novel carbaborane structures
No full textThe research involved in this thesis is mainly concerned with crystallography and the analysis using crystallographic techniques and methods. The work in this thesis is centered mainly on two types of chemical compounds, photoactive compounds and carbaboranes. The first is the photoactive compounds of biphenyl, its derivatives and similar compounds; these compounds have been studied by diffraction and database analysis. The photochemistry and subsequent structural analysis of biphenyls has been studied in collaboration with Professor Peter Wan at the University of Victoria, Canada. In this study Professor Wan and his group conducted all synthesis and spectroscopic analysis, including the photochemical analysis. In a similar study although not with biphenyls, the a-azidocinnamates were investigated in collaboration with Professor Meth-Cohn of the University of Sunderland. Professor Meth-Cohn and his group conducted all synthesis and spectroscopic analysis. The biphenyl type compounds have also been studied using database analysis to examine the bond lengths, torsion angles, inter-/intra-molecular interactions and general packing conformations and interactions within these structures and this analysis was used to study several conformational anomalies that exist in biphenyl derivative compounds. The second chemical type is carbaboranes; these compounds have been examined in collaboration with Professor Wade's group at the University of Durham. The analysis of carbaboranes centers mainly on hydrogen bonding however also expands into several novel carbaborane structures. Professor Wade and his group carried out the synthesis and spectroscopic analysis
The Interwar Suburbs of North West London: Planning for regeneration
No full textRecent UK planning policy has concentrated on regenerating inner cities. For the past thirty years, the interwar suburbs of North West London have seen a changing population, rising levels of deprivation and a deteriorating built environment. Exploring these changes and the role of local centres as foci for regeneration and revitalisation, twelve centres are investigated and their suitability for development assessed in the context of the draft Spatial Development Strategy for London. A new approach to suburban planning is proposed linking the changing condition of centres and the character of the surrounding neighbourhoods to develop more effective sub-regional planning policies
Investigations into the Characteristics of Historic Barley Varieties with Reference to Fungal Diseases and Physiology
No full textThe aim of this study was to characterise modern and historic barley varieties for agronomic and growth characteristics and to assess their resistance to Fusarium and mildew diseases.
Barley is a major agricultural crop cultivated throughout the world providing an important source of energy and protein for humans and animals. To achieve its potential, however, it must be carefully managed to avoid diseases particularly those caused by fungi which can cause serious economic losses and affect food safety and quality.
Contemporary barley varieties have been selected for yield and disease resistance. However, long term resistance to disease is increasingly difficult to achieve as microorganisms mutate and maintain their virulence. Investigating the potential of historic barley varieties as a genetic resource for future developments is one approach to obtaining novel attributes which may have been overlooked when breeding focused on yield rather than character of barley and on disease resistance.
To examine the characteristics and disease resistance of historic barley varieties a series of investigations was conducted. Initially a screening was initiated by growing thirteen historic barley varieties and two modern barley varieties in a field trial in 2009. Growth features, yield and symptoms of mildew and Fusarium Head Blight (FHB) were scored and compared. This field experiment was repeated in 2010 with six of these varieties at the John Innes Centre by deliberately exposing the plants to F. culmorum Fu 42. A further experiment was conducted at the same time by growing seven varieties in glasshouse conditions at the University of Sunderland under inoculated and uninoculated conditions.
From both growing seasons clear differences were found for the level of F. culmorum infection between the different barley cultivars with infection levels in heads ranging from 16% for Chevalier and 86.4% for Tipple barley varieties respectively. Nitrogen increased the level of FHB in all varieties possibly because
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of increased plant leaf number, tillers and humidity within the environment around the plant.
Mycotoxin analysis showed that F. culmorum infection resulted in mycotoxin contamination of all varieties. However, levels of mycotoxin were significantly lower in Chevalier barley compared to other barley varieties including the two modern varieties, Tipple and Westminster. Observations using scanning electron microscopy indicated a different pattern of fungal growth in Chevalier barley with limited fungal development on both external and internal surfaces compared to other susceptible varieties.
In general resistance against FHB disease depends on variable responses including plant physiology and morphology, antifungal compounds or resistance genes. Different flowering dates or flowering periods could be also considered reasons for different infection levels. However, in this study the duration of anthesis was not assessed and could be an important factor. Further experiments to identify the flowering times of different varieties could be considered for further research.
The lower levels of disease associated with lower levels of mycotoxins and a reduced fungal development in Chevalier barley indicated that this variety has a strong resistance against FHB disease. This may be because of its late flowering and its tall height minimising colonisation from the soil. However, Chevalier barley was found to be very susceptible to powdery mildew disease, particularly in glasshouse studies.
The potential of Chevalier barley to produce good malt was indicated when compared to modern varieties suggesting that Chevalier may be a valuable breeding stock for future developments
The role of dispositional reinvestment in choking during decision-making tasks in sport
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This thesis examines the moderating effect of dispositional reinvestment upon ‘choking’ in cognitive based tasks such as decision-making. Study 1 tested sixty-three participants’ performances on low- and high-complexity tests of motor skill, psychomotor skill and working memory under low- and high-pressure conditions. The association between reinvestment and choking was shown to extend beyond the motor skill domain to cognitive tasks, particularly those that tax working memory, with task complexity moderating this relationship. Next, a psychometric scale to identify individuals more susceptible to impaired decision-making under pressure was developed. A 13-item decision-specific version of the Reinvestment Scale (Masters, Polman, & Hammond, 1993) measuring an individual’s propensity to engage in conscious control and manifestations of ruminative thoughts emerged following factor analysis. Initial assessment of the scale’s predictive validity showed scores were highly correlated with coaches’ ratings of players’ tendency to choke. The final two studies examined choking using sport specific decision-making tasks. Initial findings were inconclusive, as choking was not observed. It was suggested the task lacked the sufficient cognitive demands to induce reinvestment. The last study, manipulating task complexity, found dispositional reinvestment to be associated with choking in the high complexity condition. The Decision-Specific Reinvestment Scale was also shown to be a better predictor of choking than the original scale. Overall, support was found for the hypothesis that Reinvestment is detrimental to performance under pressure in cognitive based tasks; however may not be the sole cause of disrupted performance. Masters and Maxwell’s (2004) concept of a working memory based explanation and Mullen and Hardy (2000) attentional threshold hypothesis offer a potential explanation to the findings
