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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
581

Tests of purchasing power parity

Speed, Preston Brooks 29 January 2009 (has links)
This paper examines the long-run relationship between exchange rates and prices in ten countries in Southwest Asia, Africa, and the Pacific Rim for the post-Bretton Woods period. It uses cointegration tests to investigate the thesis that relative purchasing power parity exists as a long-run equilibrium condition between country-pairs. It expands upon tests for relative purchasing power parity suggested by previous authors by pretesting price index time series for structural breaks, in addition to pretesting the price indices and exchange rates for compatible stochastic properties. It compares the results of conventional cointegration tests for parity with a weaker form of the relationship suggested by Pippenger (1993) and Patel (1990), and finally, examines purchasing power parity by testing real bilateral exchange rates for stationarity. / Master of Arts
582

Inflation targeting and inflation convergence: International evidence

Arestis, P., Chortareas, G., Magkonis, Georgios, Moschos, D. 04 1900 (has links)
Yes / We examine whether the inflation rates of the countries that pursueinflation targeting policies have converged as opposed to the expe-rience of the OECD non-inflation targeters. Using a methodologyintroduced by Pesaran (2007a), we examine the stationarity prop-erties of the inflation differentials. This approach has the advantageof avoiding setting arbitrarily a specific country as the benchmarkeconomy. Our results indicate that the inflation rates converge irre-spective of the monetary policy framework.
583

Repression der cytosolischen GS1 von Zuckerrüben (Beta vulgaris L. var. altissima) durch Antisense-DNA-Konstrukte / Repression of the cytosolic GS1 from sugar beet (Beta vulgaris L. cv. altissima) by using antisense DNA constructs

Hoffmann, Guido Wolf 21 June 2000 (has links)
No description available.
584

Root morphology of co-occurring African fruit tree species with contrasting strategies of exploration and exploitation. / Wurzelmorphologie koexistierender afrikanischer Obstbäume mit unterschiedlichen Strategien der Exploration und Exploitation

Oppelt, Armin L. 09 May 2003 (has links)
No description available.
585

Responses of Posidonia australis Hook.f. and Posidonia sinuosa Cambridge et Kuo transplants to nitrogen, phosphorus and iron additions in Oyster Harbour, Western Australia, with focus on root development

Hovey, Renae Kathleen January 2009 (has links)
[Truncated abstract] There is a well-documented global decline of seagrass meadows in response to anthropogenic pressures. Transplantation of rhizome fragments into denuded areas has been used to enhance natural recovery but nutrient limitation and poor root growth may contribute to low success rates. Addition of nutrients to sediments has been proposed as a means of enhancing growth and survival of seagrass transplants by alleviating nutrient limitation but there is limited information of the effects of nutrient additions to seagrass transplants, particularly root development and morphology. In addition to nutrient limitation, sulphide accumulation in sediments with high organic matter has been shown to reduce seagrass growth and experimental iron additions have been shown to enhance seagrass growth by buffering the development of reduced conditions in organic rich sediments. This thesis examines responses (growth, morphology and nutrient status) of Posidonia australis and Posidonia sinuosa transplants to nitrogen (N), phosphorus (P) and chelated iron (Fe EDTA) additions, and includes a detailed investigation of root growth and morphology in response to these additions. Experiments were carried out in underwater plots in Oyster Harbour, a sheltered estuarine inlet with seasonal river flow, located on the southern coast of Western Australia. In the first experiment, nutrients (N, P and N+P) and Fe EDTA were added to sediment underlying transplants at the end of summer (March 2005). ... Nitrogen (both N and N+P) addition also reduced overall biomass allocation to roots. Nitrogen concentrations increased with N addition in P. sinuosa only but both species had more negative d15N values with N and N+P addition indicating that added N had been taken up. In contrast, P addition had little effect on root growth, and P concentrations only increased in P. australis. However, tissue concentrations of Zn, Co, and Mo in both species increased with P addition. Roots showed limited morphological variation (total root length, mean root diameter, root fineness, specific root length, surface area) in response to nutrient addition. Combined N and P addition increased lateral root density (branches m-1) but had no effect on other morphological parameters of the root compartment. Iron addition had no effect on P. sinuosa but P. australis transplants significantly reduced root growth and productivity, particularly in spring/summer growth period, due to lower primary and lateral growth rates. Overall, N or P additions did not enhance growth although these nutrients were taken up. Iron additions also had little effect on transplant growth. Seagrass transplants had significant root growth although they appeared not to respond to nutrient or iron addition. Both species produced extensive root systems capable of taking up sediment nutrients, which suggests that root development was not a limiting factor in establishment and growth of transplants in the temperate estuary, Oyster Harbour.
586

Transcriptional regulation of wood formation in eucalyptus : Role of MYB transcription factors and protein-protein interactions / Régulation transcriptionnelle de la formation du bois chez l'eucalyptus : rôle des facteurs de transcription MYB et des interactions protéines-protéines

Plasencia Casadevall, Anna 15 December 2015 (has links)
Notre objectif était de mieux comprendre la régulation de la biosynthèse des parois secondaires lors de la formation du bois chez l'Eucalyptus, le feuillu le plus planté au monde et le deuxième dont le génome est séquencé. Nous avons caractérisé trois facteurs de transcription de la famille MYB-R2R3 et montré que EgMYB137 était un nouveau régulateur de la biosynthèse des parois secondaires. Nous avons aussi démontré que l'activité transcriptionnelle de EgMYB1, un répresseur de la biosynthèse des lignines, était régulée par une interaction protéine-protéine impliquant une histone linker (EgH1.3). Enfin, nous avons mis au point une méthode de transformation homologue chez l'Eucalyptus via A. rhizogenes. Les " hairy roots " transgéniques sont adaptées à la caractérisation fonctionnelle de gènes reliés à la formation du xylème. Nos résultats ont permis de découvrir de nouveaux acteurs impliqués dans la régulation des parois secondaires, mettant en lumière la complexité de ce processus mais aussi offrant de nouvelles perspectives pour l'amélioration du bois pour des applications industrielles comme la production de bioéthanol de deuxième génération. / Our objective was to better understand the regulation of the biosynthesis of the lignified secondary cell walls during wood formation in Eucalyptus, the most planted hardwood tree, and the second whose genome has been sequenced. We functionally characterized three Eucalyptus transcription factors of the R2R3-MYB family and identified EgMYB137 as a new regulator of secondary cell wall deposition. We also showed that the transcriptional activity of EgMYB1, a repressor of lignin biosynthesis was modulated by protein-protein interactions involving a linker histone (EgH1.3). Finally, we set up a homologous transformation system for Eucalyptus using Agrobacterium rhizogenes. The transgenic hairy roots are suitable for high throughput functional characterization of cell wall-related genes. Our findings not only allowed getting new insights into the complexity of the network regulating secondary cell walls but also open new avenues to improve wood quality for industrial applications such as second-generation bioethanol.
587

The root system of vines on a fertilization experiment with special reference to the phosphate status of the soil

Vink, J. De M. January 1955 (has links)
Thesis (MScAgric)--University of Stellenbosch, 1955. / No Abstract Available
588

Genetic diversity of root-infesting woolly apple aphid Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae) populations in the Western Cape

Timm, Alicia (Alicia Eva) 03 1900 (has links)
Thesis (MScAgric)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Characterizing the genetic structure of a pest population can provide an understanding of the factors influencing its evolution and assist in its ultimate control. The aim of the present study was to characterize the genetic structure of woolly apple aphid Eriosoma lanigerum (Hausmann) populations in the Western Cape Province in South Africa. Since this economically important apple pest has not previously been characterized at molecular level, it was necessary to evaluate methods for determining the genetic structure of E. lanigerum populations. Two different molecular techniques were evaluated viz. random amplification of polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP). This study represents the first application of the latter technique to members of the Aphididae. Aphids were sampled from four regions in the Western Cape in South Africa viz. Elgin, Ceres, Vyeboom and Villiersdorp. A spatially nested sampling design was used to establish the distribution of the genetic variance of aphids. A total of 192 individuals from 13 farms were analysed. Ten RAPD primers were chosen for analysis from an initial assay of 25 after fragment reproducibility had been confirmed. For AFLP analysis three different rare-cutting restriction enzymes were evaluated for AFLP analysis, viz. EcoRI, SseI and MluI. The latter yielded the best results in combination with the frequent-cutting enzyme MseI. Twenty-five AFLP selective primer pairs were evaluated, out of which five were chosen for analysis of the total population. Two hundred and fifty AFLP fragments and 47 RAPD fragments were scored for analysis. Both analyses indicated that a low level of genetic variation was apparent in E. lanigerum populations and that no differentiation resulted from geographic isolation. From RAPD analyses it was deduced that all variation could be attributed to differences between individuals. AFLP analysis indicated that, whereas genetic differences in E. lanigerum populations between orchards were negligible, a significant portion of genetic variation could be attributed to differences between farms and individuals within farms. Therefore, AFLP analysis allowed for finer discrimination of the genetic structure of E. lanigerum populations than RAPD analysis and is recommended for studies of other aphid species. The fact that most of the genetic variation present in E. lanigerum populations could be found on small spatial scales indicated that sampling individuals over a wide geographic area was an ineffective way of detecting the genetic diversity present in E. lanigerum populations. The low level of variation in populations is most likely due to the exclusive occurrence of parthenogenetic reproduction, founder effects (including distribution of infested plant material from a limited source) and selective factors such as the use of resistant rootstocks or pesticides. Furthermore, the low level of variation found indicated that the possibility of controlling E. lanigerum in the Western Cape using host plant resistance is favourable. Thus, plant breeders developing resistance to E. lanigerum can expect plant entries to be exposed to most of the genetic diversity present in Western Cape populations, regardless of location. / AFRIKAANSE OPSOMMING: Die bepaling van die genetiese struktuur van 'n landboukundige plaagpopulasie kan lei tot begrip van die faktore wat die populasie beïnvloed en kan uiteindelike beheer vergemaklik. Die doel van die huidige studie was om die genetiese struktuur van die appelbloedluis Eriosoma lanigerum (Hausmann) in die Wes-Kaap Provinsie van Suid-Afrika te bepaal. Aangesien hierdie belangrike appelplaag nie van tevore op molekulêre vlak bestudeer is nie, was dit nodig om metodes vir die bepaling van die genetiese struktuur van E. lanigerum populasies te evalueer. Twee molekulêre tegnieke is geëvalueer, nl. lukraak geamplifiseerde polimorfiese ONS (RAPD) en geamplifiseerde fragment-lengte polimorfismes (AFLP). Hierdie studie is die eerste om laasgenoemde tegniek te gebruik om lede van die Aphididae te bestudeer. Plantluise is verkry van vier verskillende gebiede in die Wes-Kaap Provinsie van Suid-Afrika nl. Elgin, Ceres, Vyeboom en Villiersdorp. 'n Hierargiese sisteem is gebruik om die verspreiding van die genetiese variasie van plantluise te bepaal. In totaal is 192 individue van 13 plase geanaliseer. Tien RAPD inleiers is gekies uit 'n analise van 25 verskillende inleiers nadat fragment reproduseerbaarheid bevestig is. Drie verskillende restriksie ensieme is geëvalueer vir AFLP analise nl. EcoRI, SseI en Mlul. Die beste resultate is verkry toe MluI saam met MseI gebruik is. Vyf-en-twintig AFLP selektiewe inleier pare is geëvalueer waarvan vyf gekies is vir analise van die totale populasie. Twee-honderd-en-vyftig AFLP fragmente en 47 RAPD fragmente is gedokumenteer vir analise. Beide RAPD en AFLP analises het getoon dat daar 'n lae vlak van genetiese variasie in E. lanigerum populasies is en dat geen differensiasie as gevolg van geografiese isolasie ontstaan het nie. Uit RAPD analise is daar afgelei dat al die variasie toegeskryf kon word aan verskille tussen individue. AFLP het aangetoon dat alhoewel verskille in E. lanigerum populasies tussen boorde laag was, kon 'n hoë persentasie van die variasie toegeskryf word aan verskille tussen plase en individue binne plase. AFLP analise het meer insig in die genetiese struktuur van E. lanigerum populasies verskaf, en word dus aanbeveel vir studies van ander plantluise. Omdat meeste van die genetiese variasie oor klein geografiese afstande verkry word, is steekproefueming oor groot gebiede 'n ondoeltreffende manier om die genetiese variasie binne 'n monster te meet. Die lae vlak van genetiese variasie is waarskynlik te wyte aan partenogenetiese vermeerdering, stigter gevolge (insluitend verspreiding van geïnfesteerde plantmateriaal vanaf 'n beperkte bron), sowel as selektiewe faktore soos die gebruik van bestande onderstokke en insekdoders. Verder dui die lae vlak van variasie aan dat die moontlikheid vir beheer deur gasheerplantbestandheid goed is in die Wes-Kaap. Planttelers kan verseker wees dat hulle plante blootgestel sal wees aan meeste van die genetiese variasie in die Wes-Kaap appelbloedluis populasies ongeag hulle ligging.
589

Determining the Germination Date of Woody Plants: A Proposed Method for Locating the Root/Shoot Interface

Telewski, Frank W. January 1993 (has links)
A method for determining the germination dates of trees is based on wood anatomical characteristics and dendrochronology. This procedure requires destructive sampling of the tree for an extensive analysis of the zone between the roots and the trunk of the tree (root/shoot interface). The method is applicable to forest ecology and woody plant life history studies.
590

Settlement Behavior of a Sandy Loam Due to Suction Changes Associated with Simulated Artificial Tree Roots

Areghan, Joseph I 19 November 2012 (has links)
Shallow foundations rested on Leda clay that are widely distributed in Eastern Canada exhibit shrinkage characteristics and are prone to differential settlements. Due to this reason, significant repairs are necessary to the foundations and basements of residential structures constructed in Leda clay deposits. Differential settlements are commonly attributed to the changes in the natural water content of soils associated with water infiltration, evaporation or plant transpiration (i.e., tree-roots-suction). Various research studies have been undertaken to estimate the possible settlements of shallow foundations associated with the water infiltration or evaporation. Several thumb rules have been proposed through research studies, providing recommendations with respect to the distance at which trees must be planted as a function of their heights at maturity such that differential settlements can be avoided. However, limited studies have been carried out to estimate or model the settlements of shallow foundations taking into account the influence of tree-roots-suction. In the present research program, a comprehensive experimental study regarding the deformation characteristics of a sandy loam soil from Ottawa due to tree-root-suction is undertaken, using specially designed equipment. The study has been undertaken using a sandy loam soil so that the testing program can be conducted in a shorter period of time. An artificial rooting system (ARS) was designed and placed in a specially designed tank at the University of Ottawa to simulate tree-roots-suction and measure soil surface settlements associated with a decrease in natural water content (or increase in soil suction) using particle image velocimetry (PIV) technique. The ARS consists of an artificial root, suction generator, matric suction and volumetric water content monitoring devices. The variation of matric suction and volumetric water content are monitored at various depths using the instrumentation of the ARS. Based on the results of the experimental studies, a methodology is proposed to model the settlement behaviour of sandy loam soils due to suction from ARS, using commercial finite element software, SEEP/W and SIGMA/W (i.e. software package of GeoStudio 2007). The study offers a reasonably good comparison between the measured surface settlements and those estimated using the finite element modelling analysis. The modelling methodology presented in this thesis is promising and may be extended for estimating the settlement behaviour associated with the tree roots suction of Leda clay deposits and to other soils.

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