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Near Infra-red (NIR) reflectance spectroscopy is an instrumental technique to analyse the chemical composition (eg. nitrogen content) of organic materials. As an approach it is rapid, accurate and hence cost effective. Composition is currently determined by calibration equations which relate traditional wet chemical measurements to NIR spectral measurements for the same sample. This thesis examines statistical methods of estimating composition from the NIR spectra and suggests new methods. The relative merits of each of the methods is described. Variation within the spectra is also affected by physical attributes like particle size. Several transformations are examined for their ability to reduce non-chemical differences. These include some transformations previously found to be useful and also some new approaches. Methods of calibration are then investigated. Of the 'standard* methods, stepwise multiple linear regression, principal component regression, latent root regression and partial least squares are discussed. In addition, some new methods are considered. Firstly, three new calibration models are derived which, like some of the 'standard' methods, use information from the whole spectra. Next is a slightly different approach, whereby only the information from informative areas of the spectra, called 'windows', are used for calibration. Finally, hierarchical models for combining information from different sample sets in a flexible way are considered and adapted for NIR data types.

Abstract Propolis has been used by man for millennia for its antimicrobial and pharmaceutical properties. However, its use as an agricultural antimicrobial agent has only recently been assessed. This study assessed the use of an ethanolic extract of propolis (EEP) for the control of avocado fruit fungal pathogens. Qualitative analyses of EEP indicated flavonoids as the main antimicrobial constituents. Quantitative analyses detected 16.35 mg ml-1 total flavonoids and 3.28 mg ml-1 total phenolics. The Minimum Inhibitory Concentration (MIC) of EEP was determined as 5 mg ml-1 against Colletotrichum gloeosporioides, Pestalotiopsis guipinii, a complex of Colletotrichum gloeosporioides and Pseudocercospora sp. (CgP complex), Verticillium sp., Fusarium sp. and Monilia sp., isolated from avocado fruits, using the agar dilution method, at a concentration gradient from 1 to 10 mg ml-1. Electron micrographs of Pestalotiopsis guipinii, Colletotrichum sp. and Colletotrichum gloeosporioides/Pseudocercospora sp. (CgP complex) incubated on agar media containing EEP clearly indicated signs of cell wall damage with large pores within the hyphae. Conidial germination of Colletortichum sp. and P. guipinii was inhibited by 98.95 % and 40.41 % respectively by EEP. Trees infected with Colletotrichum sp., P. guipinii or CgP complex conidia were incubated within greenhouse conditions and treated with 5 mg ml-1 EEP at weekly intervals from once every week to once every six weeks. Disease indices from experimental and control trees were similar but noticeable control of CgP disease symptoms was observed from treatment with EEP. ‘Fuerte’ avocado trees were treated with copper hydroxide, borehole water or 5 mg ml-1 EEP during the 2006-2007 growing season. All fruit were similar after harvesting with respect to pre-harvest disease. The occurrence of post-harvest diseases was analysed after simulations of import and export markets. EEP treated fruit were similar to bore-hole treated fruits (control). Similar results were observed after trials to assess the use of EEP as a post-harvest dip. The stem-end of prematurely harvested ‘Fuerte’ fruit were dipped into 5 mg ml-1 EEP, and incubated until ripe, to assess control of stem-end rot (SER). EEP reduced the occurrence of SER by 30 %. EEP was further assessed to inhibit infection or disease spread by Colletotrichum conidia. Fruits were inoculated with Colletotrichum conidia and either treated with 5 mg ml-1 or 10 mg ml-1 EEP either after or before infection. The fruits were incubated until ripe. Both treatments reduced the occurrence of disease (P < 0.001). In conclusion, EEP did not efficiently control disease in the field, but showed high potential as a future fungicide for avocado fruit. Optimisation of EEP includes higher concentrations, the addition of stickers, and/or more frequent spraying of trees.

Nitrate determination and ion-selective electrodes, with particular emphasis on the nitrate selective electrode, are reviewed. A new electrode for nitrate has been developed, by covalent attachment of appropriate sensor groups to a robust polymer matrix, with a view to improving the lifetime and the applications of the electrode to include hostile environments. The QAS (I) were prepared as sensor materials.(1) R' = R" = R''' = ethyl(2) R' = allylR" = R''' = methyl, ethyl, propyl(3) R' = R" = allylR''' = methyl, ethyl, propyl, butyl(4) R' = R" = R''' = allylX- = Cl, Br. (I) [diagram]. The production of membranes by cross-linking the sensors (I) with styrene-b-butadiene-b-styrene triblock elastomer (SBS) using a free radical initiated cyclopolymerisation is described. Various methods of membrane preparation have been investigated, and a convenient one-step solvent casting procedure identified and optimised. A range of membranes has been prepared and their physical and electroanalytical properties evaluated. The cross-linked density of the polymers was calculated from swelling measurements and the Flory-Rehner equation, the extent of covalent attachment has been derived from Kjeldahl analyses. The performance of the membranes as ion-selective electrodes is presented and discussed. Several electrodes showed fast response, long lifetime and Nernstian behaviour in the range 10-1 - 10-4 mol dm-3, but their selectivity was inferior to present commercial electrodes. A number of materials were introduced as mediators in order to improve the selectivity of the membranes. A possible mediator (O-nitrophenyloctyl ether) was identified and an analogue (O-nitrophenyl-w-undecylenyl ether) prepared which had suitable functionality for covalent attachment to the polymer. Unfortunately the inclusion of this material did not improvethe selectivity to chloride and the reasons for this are discussed.

The test - retest reliability coefficients of the values of measurements made on the pH, the Pco₂, the standard bicarbonate, the base excess, and the buffer base, of arterial whole blood were estimated for a group of 30 male subjects with the use of the Astrup Micro-equipment, the Siggaard-Andersen revised Nomogram, and a testing program on three successive mornings. Reliability coefficients were estimated for these parameters in both the resting and the post-exercise conditions, and the intra-indivldual and the inter-individual variances were estimated for each reliability coefficient. It was found that the standard bicarbonate and the base excess had the more reliable values, and that the pH and PC0₂ had less reliable values. It was shown that the values of measurements of pH, standard bicarbonate and base excess were significantly different on Day 1 from those values on Days 2 and 3. This effect was attributed to apprehension towards the testing experience and to the strangeness of the testing environment. The measurement errors of the Astrup Micro-equipment and the Siggaard-Andersen revised Nomogram were estimated for the individual parameters. It was found that the buffer base was the only parameter in which the pH meter measurement error variance was large enough to have a decided effect upon the value of the reliability coefficient. The Nomogram measurement error variances were so small that they could be considered negligible. The temporal measurement error of the collection of blood - the error inherent in the time difference between the collection of successive tubes of blood - was investigated for the pH parameter. This temporal measurement error was shown to be practically negligible although statistically significant in the resting condition, but was shown to have both practical importance and statistical significance in the post-exercise condition. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

Dentre as características que definem um fruto maduro, o adoçamento é um dos mais importantes. Porém, no que concerne à manga, os dados existentes são escassos e pouco esclarecedores. Neste trabalho foi estudada a síntese e a degradação do amido da manga \'Keitt\', nos aspectos químicos (teores de amido, de amilose e de açúcares solúveis), nos aspectos bioquímicos (atividade de enzimas relacionadas à degradação do amido, perfil de enzimas ligadas ao grânulo de amido) e aspecto morfológico do grânulo de amido (preliminar), e o amadurecimento do fruto. A manga \'Keitt\' teve um padrão atípico de fruto climatérico, com a produção de pequenas quantidades de etileno e C02, culminando em picos após o processo de amadurecimento ter sido iniciado. Todo o amido acumulado (cerca de 8 %) durante o desenvolvimento até os 3 dias após a colheita (dpc), foi totalmente degradado a partir dos 5 dpc chegando ao final do amadurecimento com apenas traços do seu conteúdo inicial. Ao mesmo tempo acumulou cerca de 10 % de açúcares solúveis, com predominância da sacarose. As enzimas que potencialmente podem degradar o amido, tiveram perfil de atividade compatível com a sua atuação. Houve um aumento bastante significativo de atividade da &#945;-amilase durante a formação do fruto e da &#946;--amilase durante o amadurecimento do fruto. As fosforilases e isoamilases, embora tivessem atividade suficiente para atuar durante a degradação do amido, demonstraram pelo perfil de atividade terem bastante importância durante a síntese do amido. Os grânulos de amido, como observados por microscopia eletrônica de varredura, tem grânulos redondos, lisos e pequenos (até 20 &#181;m), que diminuem de tamanho durante o amadurecimento da manga. As proteínas ligadas ao grânulo, como visto por eletroforese em condições dissociantes, aumentaram em número e quantidade depois da colheita da manga, mostrando que várias proteínas de alto e baixo peso molecular, aderiram ao grânulo antes do início da degradação. / Sweetening is one of the most important characteristics concerning ripe fruit. However, physiological and biochemical changes associated to mango fruit ripening process, including mango sweetening, is still poor understood. In this work the synthesis and breakdown of the starch were studied focusing starch, amylose, and soluble sugars content. Also the activities of some enzymes that participate in starch metabolism were evaluated during development and ripening of mango \'Keitt\'. Thought Scanning Electron Microscopy, granule starch shape and superficial changes related to the degree of mango ripening, were investigated. Results shown that mango fruit (cv. Keitt) has not a typical profile of ethylene and respiration during the ripening process, with very low leveis of both parameters. There was a massive conversion of the starch accumulated (~8 % )during fruit development to soluble sugar (~10 %), with a predominance of sucrose. The activity of &#945;-amylase increased at least 20 times during fruit development while &#946:-amylase showed detectable activity after fruit harvesting. Starchphosphorylases and isoamylases activities can be linked with both starch synthesis and degradation. Granule starch isolated from mango, showed spherical shape and small size (~20 &#181;m) when the mango achieve full starch content (~3 days after harvest), with about 25 % of amylose. During fruit ripening, granule size suffered superficial corrosion and decreased in size (~6 &#181;m). SDS-PAGE gels showed that after harvesting increased the number of starch bounded proteins with low and high molecular weight, inclusive inside the granule. These proteins can be associated with starch degradation process.