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The core-logger has been designed for the high-resolution radiometric analysis of soil cores using multiple detectors. This device allows for the automation of the measuring process and eliminates the need to dissect the cores. The design is aimed at measuring soil-cores with a 10cm radius and a length of 1m and allows for up to 4 detectors to be mounted on the measuring platform. Currently a combination of Bismuth-German.te (BGO) and C.esiwn-Iodide (CsI) detectors are used. The core logger required a good spatial resolution of - 1 cm. This has been difficult to obtain and has required extensive investigation. The shielding configurations were varied and the effect of background radiation was looked at in detail to determine an optimal construction. A secondary objective has been the complete measurement of a single core in 24 hours. This has also been difficult to achieve because the low activity of natural radiation in the core samples needs longer measuring times. The BGO detectors were used as a more efficient detector (than, e.g. CsI) which helped to reduce the required measuring time. Measured spectra have been analysed to determine the activity concentrations of the specific radionuclides of interest: 232Th, 238U, 40K and 137Cs. These activity profiles of the measured cores provide information that can then be used to radiometrically fingerprint the sample to determine soil characteristics such as grain size and mineral content. However, because the actual resolution of the system ( ~3cm) is greater than the typical core slice (~ 2cm), the radiometric information in a specific core-slice contains contributions from its adjacent slices. This folding or convolution of the measured spectra can be undone using a deconvolution method. which was examined and commented on. / Thesis (M.Sc.)-University of Natal, Durban, 2001.

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Typescript. / Thesis (Ph. D.)--University of Hawaii, 1967. / Bibliography: leaves 228-238. / xviii, 252 leaves maps, graphs, tables

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O estudo do comportamento reológico relacionando a interação entre as partículas do solo com o fluido é de grande importância para o desempenho e aplicação em obras de engenharia A reologia é mais utilizada na Engenharia Civil para avaliar a interação entre as partículas sólidas e a água em pasta, argamassa e concreto. Saibro é um material incoerente, originado pelo intemperismo incipiente de rochas graníticas, contendo grande quantidade de fragmentos pequenos de feldspatos e quartzo, além de outros minerais acessórios da rocha e é utilizado em argamassa. A presente pesquisa tem por objetivo caracterizar e avaliar o comportamento reológico de cinco Solos com diferentes consistências e de nove Saibros da Região Metropolitana do Recife (RMR) usados em argamassas, através de métodos convencionais de avaliação da consistência dos solos, como limites de liquidez e plasticidade e comparar com o comportamento obtido em ensaio com o Squeeze-Flow. O ensaio para o estudo da reologia consiste na compressão da amostra por meio de duas placas paralelas, medindo-se, simultaneamente, a carga aplicada e o deslocamento resultante. Foram obtidos os valores dos limites de consistências obedecendo às recomendações da Associação Brasileira de Normas Técnicas. As amostras foram moldadas, no formato cilíndrico com diâmetro de 101 mm e altura de 10 mm, nas mesmas umidades utilizadas para a obtenção do limite de liquidez no aparelho de Casagrande e nas umidades correspondentes ao limite de liquidez e de plasticidade e posteriormente comprimidas com medidas de deslocamento e carga. Os resultados mostram que os materiais mais argilosos apresentam maiores valores dos limites de liquidez e dos índices de plasticidade. Os dados obtidos nos ensaios com o Squeeze-Flow mostram a influência da quantidade de água na mistura com o solo e a curva carga versus deslocamento que apresenta comportamento elástico, plástico e plástico com endurecimento dependendo da quantidade de água, de finos e da consistência dos materiais. O estudo da interação entre as partículas e a água utilizando o Squeeze-Flow mostrou que a técnica é capaz de aferir e avaliar, com sensibilidade a forma da curva carga versus deslocamento dos materiais estudados para análise do comportamento utilizado. / The study of the rheological behavior relating the interaction between the soil particles with the fluid is of great importance for the performance and application engineering works The rheology is most used in Civil Engineering to evaluate the interaction between the solid particles and water paste, mortar and concrete. Clay is a material inconsistency, caused by the incipient weathering of granitic rocks, containing large amounts of small fragments of feldspar and quartz, and other accessory minerals of the rock and is used in mortar. This research aims to characterize and evaluate the rheological behavior of five soils with different consistencies and nine grit of the Metropolitan Region of Recife (RMR) used in mortars, through conventional methods of assessing the consistency of the soil, such as limits on liquidity and plasticity and compare with the behavior obtained in the test with the Squeeze-Flow. The test for the study is the compression rheology of the sample by means of two parallel plates, measuring both the applied load and resultant displacement. We obtained the values of consistency limits of complying with recommendations of the Brazilian Association of Technical Standards. The samples were molded in a cylindrical shape with a diameter of 101 mm and height 10 mm, the same water content used to obtain the liquid limit of the apparatus Casagrande and moisture corresponding to the liquid limit and plasticity and subsequently compressed by measures load and displacement. The results show that the more clayey materials present higher liquidity limits and plasticity indexes. The data obtained in tests with the Squeeze Flow show the influence of the amount of water to mix with the ground and the load versus displacement curve which has elastic behavior, plastic and plastic hardness depending on the amount of water, and the consistency of fine material . The interaction between particles and water using the Squeeze-Flow showed that the technique is able to assess and evaluate, with sensitivity to the shape of load versus displacement curve of the studied materials used for the analysis of behavior.

CAPES / As brássicas possuem alto potencial de biofumigação, pois produzem gases tóxicos voláteis aos fitopatógenos habitantes do solo (FHS). Este trabalho objetivou testar três espécies de brássicas: Brassica juncea (mostarda), Brassica oleraceae (repolho) e Brassica napus (canola) no controle de três FHS: Sclerotium rolfsii, Rhizoctonia solani e Pythium aphanidermathum. Realizaram-se três ensaios, sendo o primeiro in vitro, constituído por doses: 0, 5, 10, 15, 20 e 25% de extrato de canola e mostarda. Cada Placa de Petri contendo meio de cultura recebeu um disco de BDA contendo micélio de um fitopatógeno. Na tampa foram colocados os extratos que serviram como base para a placa. Foram realizadas leituras do crescimento micelial. No segundo ensaio realizado em casa de vegetação, utilizou-se doses de 0, 30, 60, 90 e 120 t ha-1 de repolho triturado, em dois cultivos. Em sacos plásticos com sistema de vedamento foram colocados 500 g de solo e 10 g de substrato com P. aphanidermathum, recebendo em seguida as doses de repolho, com posterior fechamento e acondicionamento em BOD a 22ºC por 15 dias. Em seguida, o solo de cada saco foi distribuído em 16 células de bandejas de cultivo de mudas, semeandose uma semente de pepino por célula. O terceiro e último ensaio foi realizado a campo em dois cultivos, utilizando-se as doses de 0, 30, 60, 90 e 120 t há-1 de canola triturada. Em parcelas de 1 m2 incorporou-se substrato de areia e quirela de milho contendo P. aphanidermathum e a canola triturada 24 h após, com posterior cobertura com lonas dupla-face. Após a retirada das lonas foram coletadas amostras de solo para avaliar a sobrevivência do fitopatógeno e para a distribuição em bandejas, seguindo a mesma metodologia descrita no segundo ensaio. A sobrevivência foi realizada semeando-se cinco sementes de pepino em copinhos plásticos, com solo esterilizado, onde foi colocado 0,5 g de aveia e 15 g de solo retirado das parcelas. Foram realizadas avaliações de emergência e tombamento. Nas parcelas do campo, realizou-se a semeadura de 50 sementes de pepino. Para os três experimentos foram feitas avaliações de emergência, tombamento e peso seco das plântulas. Em todas as amostras de solo coletadas, foram realizadas avaliações da atividade microbiana, fertilidade do solo e condutividade elétrica. No primeiro ensaio todos os fitopatógenos reduziram o crescimento micelial pelo aumento das doses de canola e mostarda. No segundo e terceiro ensaios o repolho e a canola foram efetivos em todas as variáveis avaliadas. Estes substratos além de apresentarem efeito direto sobre o fitopatógeno, por meio da produção dos gases, o aumento da atividade microbiana e da condutividade elétrica,contribuindo de maneira indireta no controle do FHS testado. A concentração de potássio no solo aumentou com o aumento das doses de repolho e de canola, mostrando que os altos teores de potássio nos tecidos das brássicas contribuíram para o controle de P. aphanidermathum, além de servir como fertilizante orgânico para locais onde há deficiência de potássio. / The brassicas has high potential biofumigation and they produce toxic gases to volatile soilborne plant pathogens (SPP). This study intend to test three species of brassica: Brassica juncea (mustard), Brassica oleracea (cabbage) and Brassica napus (canola) in the control of three SPP: Sclerotium rolfsii, Rhizoctonia solani and Pythium aphanidermathum. We conducted three tests, the first in vitro, consisting of three treatments: 0, 5, 10, 15, 20 and 25% extract of canola and mustard. Each Petri dish containing culture medium received a disk of PDA containing mycelium of a pathogen. On the cover were placed extracts that were the basis for the board. Readings were taken of mycelial growth. In the second experiment conducted in a greenhouse, we used doses of 0, 30, 60, 90 and 120 t ha-1 cabbage shredded, in two crops. In plastic bags with sealing system were placed 500 g soil and 10 g of substrate with P. Aphanidermathum, then receiving doses of cabbage, with later closing and placing in chamber at 22 ° C for 15 days. Then the soil from each bag was distributed in 16-cell tray seedling cultivation, seeding a cucumber seed per cell. The third and final field test was carried out in two crops, using doses of 0, 30, 60, 90 and 120 t ha-1, canola crushed. In plots of 1m2 is incorporated in a sand and corn containing quirela P. Aphanidermathum and canola crushed after 24 h, with subsequent coverage with double-sided pads. After removing the pads we collected soil samples to assess the survival of the pathogen and for distribution in trays, using the same methodology described in the second test. The survival was performed sowing to five cucumber seeds in plastic cups with sterilized soil, where it was placed 0.5 g of oats and 15 g of soil taken from plots. We have made emergency and tip evaluations. At the plots of the field, we sow 50 seeds of cucumber. For the three experiments were made emergency evaluations, damping off and seedling dry weight. In all soil samples were evaluated microbial activity, soil fertility and electrical conductivity. In the first trial all pathogens reduced the mycelial growth by increasing doses of canola and mustard. In the second and third tests cabbage and canola were effective in all variables. Demonstrated that besides the direct effect on the pathogen through the production of gases, increased microbial activity and electrical conductivity contributed indirectly to control the SPP tested. The concentration of potassium in the soil increased with increasing doses, showing that high levels of potassium in the tissues of crucifers contributed to the control of P. Aphanidermathum, besides serving as an organic fertilizer to places where there is a deficiency of potassium.

Brown’s Method was found to be a very satisfactory technique for determining the exchange capacity of soils. It was simple, rapid and gave comparable results with Shollenberger’s technique for thirty soils from Vancouver Island. The Puri Method gave comparable results to Brown’s but was too lengthy. Considerable variation occurred at high percent base saturation levels when determined by Schollenberger, Brown and Purl Methods for these soils. It was concluded, however, that Brown’s Method as well as being rapid and simple gave satisfactory results. As much as twenty percent variation in percent base saturation was noted for soils having the same pH value. The percent base saturation of a soil cannot be estimated from its pH with a high degree of accuracy. The total titration curves produced by adding increments of calcium to hydrogen saturated soils showed that the exchange capacity and base saturation could be determined by this method. It was also concluded the position and shape of the curves, indicated the buffer capacity of the soil. In a greenhouse experiment where Virginian Stock was grown as the indicator crop on five levels of percent base and calcium saturation, the following conclusions were made: (1) That a relationship exists between calcium and base saturation of the soil and plant growth. (2) That the flex point for the growth saturation curves occurred at 30% calcium saturation and 60% base saturation for both soil types. (3) That response to lime in the greenhouse coincided with known response in the field. (4) That a relationship exists between base saturation in the soil and calcium content of the plant. (5) That 1200 gm. samples of soil were better suited for saturation studies than 300 gm. samples. (6) That below a certain percent base saturation calcium is not available to plants. (7) That base saturation studies should form a sound basis for estimating the lime requirement of soils. The lime requirement of six soil types was estimated by three methods: (1) Percent Base Saturation expressed on a Volume Weight Basis. (2) Percent Base Saturation expressed on a weight basis. (3) Titration Curves on a weight basis. It was concluded that the Percent Base Saturation Method expressed on a volume weight basis gave a good indication of the lime requirement for the six soil types studied. The latter two methods indicated that very large quantities of lime were required for soils with low apparent specific gravities. This may result in overliming of the surface horizons / Land and Food Systems, Faculty of / Graduate

Ph.D., Faculty of Science, University of the Witwatersrand, 1987