Pour comprendre l'origine de la torsion lamellaire dans le poly(triméthylène téréphtalate), PTT, une étude a été entrepris sur la structure des sphérolites à bandes de PTT en utilisant la micro-diffraction des rayons-X sur une source synchrotrone. Nous avons démontré que les pics de diffraction de la maille triclinique de PTT révèlent une variation périodique de l'intensité en fonction de la distance jusqu'au centre sphérolitique lorsque nous effectuons un balayage avec un micro-faisceau de rayons X. Cela indique que la torsion lamellaire est strictement uniforme et régulière. Celte derrière observation est plus compatible avec le modèle expliquant la torsion comme résultat de contraintes surfaciques que des dislocations-vis géantes. En outre, les données expérimentales montrent que les polymères achiraux ne sont pas indifférents par rapport à l'inversion de la chiralité lamellaire, et que le changement de la chiralité est nécessairement accompagné d'un changement de signe du vecteur de croissance. En plus, nous avons observé que l'inclinaison globale de la chaîne (c'est à dire, l'inclinaison du paramètre c de la maille dans le plan perpendiculaire à la direction de la croissance rapide) n'affecte pas la vitesse et le sens de la torsion. Cela remet en question la seconde hypothèse du modèle de Keith et Padden. Par contre, l'inclinaison des segments de la chaine à l'interface du cristal lamellaire peut être identifiée comme le facteur clé déterminant les contraintes superficielles qui provoquent la torsion lamellaire. Avec la variation de l'épaisseur du cristal la chiralité lamellaire change, ce qui dû au changement de l'angle des segments polymères à l'interface. / To address the origin of the lamellar twisting in polytrimethylene terephthalate (PTT) an in-depth micro-focus X-ray scattering study was correlated to the data derived using conventional polarized optical microscopy to study the banded spherulite texture for PTT. It is shown that the diffraction peaks of the triclinic lattice of PTT show a periodical pattern as a function of the distance from the spherulite center when scanned with the micro focus X-ray beam. This indicates that the lamellar twist has a strictly uniform and regular nature. The latter observation is more compatible with the model explaining the twist as a result of unbalanced surface stresses than the giant screw dislocations. Moreover, the data shows that achiral polymers are in fact not indifferent to the inversion of the lamellar handedness, and that a change in handedness is necessarily accompanied by a change in the sign of the growth vector. At the same time, we show that the overall chain tilt (i.e., the inclination of the c-parameter of the unit cell in the plane perpendicular to the fast growth direction) does not affect the rate and sense of twisting. This calls into question the second premise of the KP-mod el. Instead, the local inclination of the terminal segment of the crystalline stem protruding the lamellar surface can be identified as the origin of the surface stresses and forcing the lamellar ribbon to twist. With the variation of the crystal thickness as a function of crystallization temperature the angle and direction of this segment is changed, resulting in a change of the lamellar ribbon chirality.

The Pilbara region of Western Australia hosts the Hamersley Province, an area of abundant iron ore resources located in the lower Hamersley Groups, Brockman and Marra Mamba Iron Formations. This study consists of a geotechnical and a geochemical and mineralogical investigation into the Banded Iron Formation (BIF) and shale deposits of the lower Hamersley Group that reside in the pit walls of RTIO mines in Western Australia. Areas throughout Tom Price, Paraburdoo, Marandoo and West Angelas iron ore mines are geotechnically investigated for rock mass conditions through the use of the Slope Mass Rating (SMR) classification system and through point load and slake durability testing. Selected samples from these areas were then geochemically and mineralogically tested by X-ray Fluorescence (XRF), X-ray Diffraction (XRD) and microscopic analysis, to determine the geochemical and mineralogical changes of BIF and shale as they alter and weather through hypogene and supergene alteration and Recent weathering. It was found that the most efficient method for determining the alteration and/or weathering of lower Hamersley Group BIF and shale deposits was by the use of a chemical alteration index, calculated from enriched and depleted major elements in the BIF and shale as they alter and weather. It has been suggested here that this Pilbara Iron alteration index can be calculated efficiently and effectively from geochemical testing in intervals down boreholes throughout future or developing open pit mines to assist in estimating slope stability conditions. It is also suggested that many boreholes should be analysed in section or in 3D space to create cross sections or block models showing the varying extent of alteration and weathering throughout the area being studied. From the geotechnical investigation, it was found that the weakest region, in terms of pit slope stability, were the highly and extremely altered and/or weathered regions with Pilbara Iron alteration indices of between 61 and 80, and 81 and 100, respectively. If these zones are identified, slope stability analysis can be focused on these geotechnically vulnerable areas. Slope stability analysis should be completed by using a suitable technique, such as by the use of SMR, which, along with other risk identification measures, will identify potentially unstable areas and suggest the required course of action. Further hazard and risk analysis should be undertaken in potentially unstable areas and remedial measures undertaken as appropriate. Thereby, the Pilbara Iron alteration index can be used in the Hamersley Province as a predictive tool for pit slope stability.

Made available in DSpace on 2016-12-23T13:56:01Z (GMT). No. of bitstreams: 1 Tese Final JM PDF.pdf: 1085003 bytes, checksum: 2192e6e7be6853aaf003ec8f29976338 (MD5) Previous issue date: 2007-11-05 / Introdução: Mycobacterium leprae foi a primeira bactéria a ser indicada como agente etiológico de uma doença infecciosa. A hanseníase permanece até os dias de hoje uma doença enigmática e que não é completamente entendida. A identificação do M. leprae é difícil, particularmente por sua inabilidade de cultivo in vitro. Pacientes multibacilares são as principais fontes do bacilo. A transmissão natural da hanseníase entre tatus foi descrita pela primeira vez em 1975, no sudeste dos EUA. Esta descoberta sugeriu a possibilidade do tatu-galinha desenvolver uma função na transmissão da hanseníase em humanos. A procura dos reservatórios da hanseníase é a principal estratégia para eliminação da doença, tal como os pacientes multibacilares e as fontes ambientais. Então, realizou-se um estudo de prevalência em 69 tatus selvagens da espécie Dasypus novemcinctus, capturados no estado do Espírito Santo, no período de julho de 2004 a julho de 2005. Objetivos: Procurou-se avaliar a presença do M. leprae nos tatus da espécie D. novemcinctus no estado do Espírito Santo, através de achados de sinais clínicos de infecção na necropsia e na técnica de PCR, utilizando dois pares de primers: 18 kDa e ML1/ML2, bem como avaliar e comparar os dois pares de primers utilizados para a detecção da infecção. Métodos: Após anestesiados, os tatus foram pesados, definidos os sexos, submetidos ao exame clínico e coleta de fragmento de tecidos para a técnica de PCR. Sessenta e cinco tatus foram necropsiados e fragmentos de fígado, baço, cérebro e linfonodos foram analizados pela técnica de PCR. Resultados e Conclusões: Em 95% dos animais estudados foi evidenciado pelo menos um sinal clínico da hanseníase. Através da técnica de PCR foi detectada 6% (4 animais) de positividade na pesquisa de DNA de M. leprae, utilizando os primers ML1/ML2. Dos 4 animais positivos no PCR convencional, somente dois permaneceram positivos pela técnica de Real Time PCR e confirmados pelo seqüenciamento. O método diagnóstico mais sensível para detecção de M. leprae foi o PCR, utilizando os pares de primers ML1/ML2. Estes resultados sugerem a infecção adquirida naturalmente nos tatus da espécie D. novemcinctus no estado do Espírito Santo, Brasil. / Introduction: Mycobacterium leprae, was the first agent to be linked to an infectious disease, and leprosy still today an enigmatic disease which is not fully understood. Multibacillary patients are thought to be the main source of M. leprae. Identification of M. leprae is difficult, partly due to the inability of the bacillus to grow in vitro. The natural transmission among nine-banded armadillos in the southern parts of the United States has been described since 1975. This discovery suggested the possibility that the nine-banded armadillo plays a role in the transmission of human leprosy. The search of M. leprae sources is the main point of strategy for leprosy elimination, such as multibacillary patients and environmental sources. It was realized a prevalence study in 69 nine-banded armadillos, Dasypus novemcinctus, from state of Espírito Santo, Brazil, during 2004 to 2005. Objectives: Assess the M. leprae infection in armadillos from D. novemcinctus from state of Espírito Santo through the clinical signs of leprosy found in the necropsy and PCR technique using two set of primers, ML1/ML2 and 18 kDa, such as compare the set of primers. Methods: After anesthesia, the armadillos were weighed, sex was determined, clinical exam was made and samples were collected for PCR. Tissue samples (liver, spleen, brain and lymph nodes) from 65 nine-banded armadillos were collected to looking for natural infection of M. leprae by PCR technique. Results and Conclusion: 95% of the armadillos had at least one clinical sign for leprosy in wild armadillos. Four (6%) animals were positive in conventional PCR. Two animals that were positive in conventional PCR remained positive in Real Time PCR, and confirmed by sequencing. The best method to detect M. leprae was the PCR using the ML1/ML2 set of primers. These results suggest the infection acquired naturally in D. novemcinctus from state of Espírito Santo, Brazil.

The external silicon cycle during the Precambrian (4.5-0.5 Ga) is not well understood despite its key significance to apprehend ancient dynamics at the surface of the Earth. In the absence of silicifying organisms, external silicon cycle dramatically differs from nowadays. Our current understanding of Precambrian oceans is limited to the assumption that silicon concentrations were close to saturation of amorphous silica. This thesis aims to bring new insights to different processes that controlled the geochemical silicon cycle during the Archaean (3.8-2.5 Ga). Bulk rock Ge/Si ratio and Si isotopes (δ30Si) offer ideal tracers to unravel different processes that control the Si cycle given their sensitivity to fractionation under near-surface conditions. <p>First, this study focuses on Si inputs and outputs to ocean over a limited time period (~2.95 Ga Pongola Supergroup, South Africa) through the study of a palaeosol sequence and a contemporaneous banded iron formation. The palaeosol study offers precious clues in the comprehension of Archaean weathering processes and Si transfer from continent to ocean. Desilication and iron leaching were shown to be the major Archaean weathering processes. The occurrence of weathering residues issued of these processes as major component in fine-grained detrital sedimentary mass (shales) attests that identified weathering processes are widely developed and suggest an important dissolved Si flux from continent to the ocean. In parallel, banded iron formations (BIFs), typically characterised by alternation of iron-rich and silica-rich layers, represent an extraordinary record of the ocean-derived silica precipitation throughout the Precambrian. A detailed study of a 2.95 Ga BIF with excellent stratigraphic constraints identifies a seawater reservoir mixed with significant freshwater and very limited amount of high temperature hydrothermal fluids as the parental water mass from which BIFs precipitated. In addition, the export of silicon promoted by the silicon adsorption onto Fe-oxyhydroxides is evidenced. Then, both Si- and Fe-rich layers of BIFs have a common source water mass and a common siliceous ferric oxyhydroxides precursor. Thus, both palaeosols and BIFs highlight the significance of continental inputs to ocean, generally under- estimated or neglected, as well as the close link between Fe and Si cycles. <p>In a second time, this study explores secular changes in the Si cycle along the Precambrian. During this timespan, the world ocean underwent a progressive decrease in hydrothermal inputs and a long-term cooling. Effects of declining temperature over the oceanic Si cycle are highlighted by increasing δ30Si signatures of both chemically precipitated chert and BIF through time within the 3.8-2.5 Ga time interval. Interestingly, Si isotope compositions of BIF are shown to be kept systematically lighter of about 1.5‰ than contemporaneous cherts suggesting that both depositions occurred through different mechanisms. Along with the progressive increase of δ30Si signature, a decrease in Ge/Si ratios is attributed to a decrease in hydrothermal inputs along with the development of large and widespread desilication during continental weathering.<p><p><p>Le cycle externe du silicium au précambrien (4.5-0.5 Ga) reste mal compris malgré sa position clé dans la compréhension des processus opérant à la surface de la Terre primitive. En l’absence d’organismes sécrétant un squelette externe en silice, le cycle précambrien du silicium était vraisemblablement très différent de celui que nous connaissons à l’heure actuelle. Notre conception de l’océan archéen est limitée à l’hypothèse d’une concentration en silicium proche de la saturation en silice amorphe. Cette thèse vise à une meilleure compréhension des processus qui contrôlaient le cycle géochimique externe du silicium à l’archéen (3.8-2.5 Ga). Dans cette optique, le rapport germanium/silicium (Ge/Si) et les isotopes stables du silicium (δ30Si) représentent des traceurs idéaux pour démêler les différents processus contrôlant le cycle du Si. <p>Dans un premier temps, cette étude se focalise sur les apports et les exports de silicium à l’océan sur une période de temps restreinte (~2.95 Ga Pongola Supergroup, Afrique du Sud) via l’étude d’un paléosol et d’un dépôt sédimentaire de précipitation chimique quasi-contemporain. L’étude du paléosol apporte de précieux indices quant aux processus d’altération archéens et aux transferts de silicium des continents vers l’océan. Ainsi, la désilicification et le lessivage du fer apparaissent comme des processus majeurs de l’altération archéenne. La présence de résidus issus de ces processus d’altération en tant que composants majeurs de dépôts détritiques (shales) atteste de la globalité de ces processus et suggère des flux significatifs en silicium dissout des continents vers l’océan. En parallèle, les « banded iron formations » (BIFs), caractérisés par une alternance de niveaux riches en fer et en silice, représentent un enregistrement extraordinaire et caractéristique du précambrien de précipitation de silice à partir de l’océan. Une étude détaillée d’un dépôt de BIFs permet d’identifier une contribution importante des eaux douces dans la masse d’eau à partir de laquelle ces roches sont précipitées. Par ailleurs, un mécanisme d’export de silicium via absorption sur des oxyhydroxydes de fer est mis en évidence. Ainsi, les niveaux riches en fer et riche en silice constituant les BIFs auraient une même origine, un réservoir d’eau de mer mélangée avec des eaux douces et une contribution minime de fluides hydrothermaux de haute température, et un même précurseur commun. Dès lors, tant les paléosols que les BIFs mettent en évidence l’importance des apports continentaux à l’océan, souvent négligés ou sous estimés, ainsi que le lien étroit entre les cycles du fer et du silicium.<p>Dans un second temps, cette étude explore l’évolution du cycle du silicium au cours du précambrien. Durant cette période, l’océan voit les apports hydrothermaux ainsi que sa température diminuer. Dans l’intervalle de temps 3.8-2.5 Ga, les effets de tels changements sur le cycle du silicium sont marqués par un alourdissement progressif des signatures isotopiques des cherts et des BIFs. Le fort parallélisme entre l’évolution temporelle des compositions isotopiques des deux précipités met en évidence leur origine commune, l’océan. Cependant, les compositions isotopiques des BIFs sont systématiquement plus légères d’environ 1.5‰ que les signatures enregistrées pas les cherts. Cette différence est interprétée comme le reflet de mécanismes de dépôts différents. L’alourdissement progressif des compositions isotopiques concomitant à une diminution des rapports Ge/Si reflètent une diminution des apports hydrothermaux ainsi que la mise en place d’une désilicification de plus en plus importante et/ou généralisée lors de l’altération des continents.<p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Noteworthy species endemic to the Galapagos Islands off Ecuador are two flightless birds, the Galapagos Penguin (Spheniscus mendiculus) and Flightless Cormorant (Phalacrocrax harrisi). Both adapted increased swimming ability at the cost of flight. This however has limited their ability to find richer feeding grounds in times of low resource availability, or to escape potential predators. Their population numbers, though small, were stable. Stress on this stability has increased since human arrival. Various invasive species from pets, farm animals and rats to even mosquito vectors of avian disease accompanied humans. . El Nino Southern Oscillation or ENSO cycles of warm waters in the Pacific Ocean south of the Equator cause drastic drops in food sources for all Galapagos seabirds. Serious ENSO events in 1983 and 1998 caused some species’ populations to drop by as much as 77%. Periodic less severe cycles may help explain how population recovery has not rebounded to earlier numbers. Reduced chick survival and adult fecundity seem to occur in concert with mild events. With available data and use of a modeling approach, this study focuses and explores their situations. Restoring population stability may include use of models, species monitoring, conservation and limiting invasive species. Usher matrices based on different climate conditions were produced using data combined from current and past census counts and weather. Models are used to compare available census data and test reliable predictors. Climate data from National Oceanic and Atmospheric Administration and the University of Florida provides for testing predictions of current and probable future climate change. Life histories of both species are regarded. Results suggest the current Cormorant population is still stable. The Penguin, however, faces a 20% probability of extinction in 100 years if current conditions remain. Extinction probability rises to 60% if climate change continues to worsen. Interventions such as captive breeding could be suitable for population recovery.

<p>The production of insects for protein is projected to reach a market share of 1.33 billion USD, a rapid increase from the estimated 144 million USD share of 2019 market. The isolation of insect protein produces by-products, including chitin. Currently chitin is extracted from aquaculture by-products, such as shrimp and crab shells, and used to produce chitosan for various applications in the supplement and food industry. With the insect market expected to continue its growth, the feasibility of sourcing commercial chitin and chitosan from reared crickets’, and the application properties of its counterpart, chitosan, was investigated in this dissertation. In the first part of this dissertation, chitin from two commonly reared crickets in the Unites States, <i>Acheta domesticus</i> and <i>Gryllodes sigillatus</i>, was successfully extracted, purified, and identified as a commercially viable option for chitin and chitosan. Extensive crustacean chitin studies served as the foundation of purification steps, however durations were adjusted to account for intrinsic differences between insects and crustacean exoskeletons. Furthermore, cricket chitosan was prepared and optimized with varying degrees of deacetylation. As expected, cricket chitosan had lower molecular but did not have a detectable effect on the bioactive properties tested. All cricket chitosan produced had similar lipid binding capacity <i>in vitro</i>. Additionally, the microbial inhibition of cricket chitosan and commercial chitosan (~70% DDA) were not significantly different when evaluated against <i>L. innocua</i> and <i>E. coli</i>. High DDA cricket chitosan showed greatest bacterial inhibition as expected. In the second part of this dissertation, cricket derived chitosan showed similar and improved food packaging properties, when evaluated against commercial shrimp chitosan. microstructure analysis provided by scanning electron microscopy showed greater compaction and agglomeration of cricket chitosan films. The change in microstructure may be attributed to the increased complexity generally attributed to insect chitosan materials, a result of remaining melanin and protein in close association with insect exoskeleton chitosan. As a result, cricket films had similar or increased tensile strengths but decreased elongation percentages when compared to shrimp films. Water vapor permeability of cricket films was decreased due to tortuosity. Residual melanin likely played an important role in increasing cricket film surface hydrophobicity and providing enhanced light barrier properties. Overall, this dissertation successfully shows the potential of crickets as insect derived chitin and chitosan, and its effectiveness as a lipid binding and antibacterial agent, as well as its potential use in biobased food packaging. </p>

By counting 1's in the "right half" of 2w consecutive rows, we locate the main diagonal of any doubly infinite permutation matrix with bandwidth w. Then the matrix can be correctly centered and factored into block-diagonal permutation matrices. Part II of the paper discusses the same questions for the much larger class of band-dominated matrices. The main diagonal is determined by the Fredholm index of a singly infinite submatrix. Thus the main diagonal is determined "at infinity" in general, but from only 2w rows for banded permutations.

No description available.

Les conditions oxydantes de la surface terrestre actuelle sont dues à la teneur élevée en dioxygène de l’atmosphère. Au début de l’histoire de la Terre il y a 4.54 milliards d'années (Ga), l’oxygène n’était pas stable dans l’atmosphère. Il a fallu deux épisodes d’augmentation brutale de ce gaz atmosphérique pour qu’il atteigne son niveau actuel : l’un vers 2.4 Ga, nommé le Grand Evènement Oxydant (GOE) qui fait l’objet de ce projet, l’autre 2 milliards d’années plus tard, nommé l’Evènement Oxydant Néo-protérozoïque (NOE). Le GOE est vraisemblablement le résultat de l’émersion généralisée de larges continents dont l’érosion libère le phosphate dans l’océan, un nutriment nécessaire à la production biologique, qui a donc permis l’explosion de la photosynthèse oxygénée. Ces deux hausses d’oxygène atmosphérique coïncident avec deux évolutions majeures dans l’histoire de la vie : (i) peu après le GOE, les eucaryotes sont apparus, alors que (ii) le NOE correspond à l’apparition des métazoaires et à l’explosion cambrienne. L’étude de ces phénomènes atmosphériques primitifs peut avoir d’importantes répercussions sur notre compréhension de l’origine et de l’évolution de la vie, qu’on estime principalement marine à cet âge. Les seules archives de ces temps primitifs sur Terre sont les roches sédimentaires. Pour savoir comment l’oxygénation de l’atmosphère a pu être reliée à cette vie marine, il faut tout d’abord comprendre comment l’océan a interagi avec l’atmosphère lors de cet évènement d’oxygénation. Cette question est au coeur de ce projet : comment le GOE a-t-il affecté les cycles biogéochimiques océaniques dont la vie est dépendante ? Nous nous sommes intéressés aux formations ferrifères litées ou BIFs (Banded Iron Formations). La chimie de ces roches marines fait écho à celle de l’océan contemporain à leur formation. Déterminer quantitativement la composition de l’océan à partir de celles des sédiments, même chimiques, est un défi quasiment impossible à relever y compris dans l’océan moderne. C’est pourquoi nous avons proposé de déterminer le temps de résidence d’éléments sensibles aux conditions redox de la surface, le soufre, le fer et le cuivre dans l’océan pré-GOE. Nous avons obtenu, par des séries temporelles, le spectre des fluctuations isotopiques de ces éléments enregistrées dans des carottes de formations ferrifères litées. La limite inférieure du spectre donne le temps de résidence de ces éléments dans l’eau de mer et fournit donc une indication solide sur la teneur de ces éléments dans l’océan à cette période. Nous avons analysé des échantillons protérozoïques proches de la limite Archéen-Protérozoïque du Transvaal (Afrique du Sud) et d’Hamersley (Australie). Des échantillons eoarchéens de Nuvvuagittuq (Canada) ont été récoltés mais n'ont pas pu être analysés faute de temps. / The present-day oxidizing conditions at Earth's surface are due to the high oxygen content of the atmosphere. However, oxygen was not always stable in the terrestrial atmosphere. Two distinct periods during which oxygen increased in a step-like manner were required to reach the current atmospheric oxygen level. The first, at about 2.4 Ga, is known as the Great Oxidation Event (GOE) and is at the core of this Ph.D. thesis. The other, occurring almost two billion years later, is called the Neo-Proterozoic Oxidation Event (NOE). The GOE likely is the result of the beginning widespread emergence of large continental expanses whose subsequent erosion gradually released phosphate into the ocean. Phosphate, a nutrient essential to organic production, in turn allowed the explosion of oxygenated photosynthesis. The GOE and NOE coincide with two major changes in the history of life. Shortly after the GOE, eukaryotes appeared, while the NOE corresponds to the appearance of metazoans and the Cambrian explosion. A better grasp of the GOE hence may have important implications for the understanding of the origin and evolution of life, which is thought to have been mainly marine at this stage in Earth history. The only records of the oxygen level during these ancient times are found in terrestrial sedimentary rocks. To understand how oxygenation of the atmosphere relates to marine life, we must first understand how the ocean was connected to the atmosphere during the GOE and how the GOE affected life-dependent ocean biogeochemical cycles. To this end we focused on banded iron formations (BIF). The chemistry of these sedimentary marine rocks directly reflects the chemistry of the contemporary ocean. Deriving quantitatively the composition of the ocean from a hydrogenous sediment is a challenge almost impossible to meet, even for the modern ocean. This is why we instead determined the residence time of redox-sensitive elements (in this case sulfur, iron, and copper) in the pre-GOE ocean. We specifically targeted the periods of isotopic fluctuations in these elements as recorded in BIF cores. The lower limit of the spectrum provides the residence time of these elements in seawater, hence giving a robust indication of their contents in the pre-GOE ocean. We sampled early Proterozoic BIF near the Archean-Proterozoic boundary in Transvaal (South Africa) and Hamersley (Australia), as well as Archean BIF from Nuvvuagittuq (Canada), though the latter were not analyzed during this thesis due to shortage of time.

One purpose of breeding programs is the selection of the better test lines. The accuracy of selection can be improved by using optimal design and using models that fit the data well. Finding this is not easy, especially in large experiments which assess more than one hundred lines without the possibility of replication due to the limited material, area and high costs. Thus, the large number of parameters in the complex variance structure that needs to be fitted relies on the limited number of replicated check varieties. The main objectives of this thesis were to model 21 trials of sugarcane provided by \"Centro de Tecnologia Canavieira\" (CTC - Brazilian company of sugarcane) and to evaluate the design employed, which uses a large number of unreplicated test lines (new varieties) and systematic replicated check (commercial) lines. The mixed linear model was used to identify the three major components of spatial variation in the plot errors and the competition effects at the genetic and residual levels. The test lines were assumed as random effects and check lines as fixed, because they came from different processes. The single and joint analyses were developed because the trials could be grouped into two types: (i) one longitudinal data set (two cuts) and (ii) five regional groups of experiment (each group was a region which had three sites). In a study of alternative designs, a fixed size trial was assumed to evaluate the efficiency of the type of unreplicated design employed in these 21 trials comparing to spatially optimized unreplicated and p-rep designs with checks and a spatially optimized p-rep design. To investigate models and design there were four simulation studies to assess mainly the i) fitted model, under conditions of competition effects at the genetic level, ii) accuracy of estimation in the separate versus joint analysis; iii) relation between the sugarcane lodging and the negative residual correlation, and iv) design efficiency. To conclude, the main information obtained from the simulation studies was: the convergence number of the algorithm model analyzed; the variance parameter estimates; the correlations between the direct genetic EBLUPs and the true direct genetic effects; the assertiveness of selection or the average similarity, where similarity was measured as the percentage of the 30 test lines with the highest direct genetic EBLUPs that are in the true 30 best test lines (generated); and the heritability estimates or the genetic gain. / Um dos propósitos dos programas de melhoramento genético é a seleção de novos clones melhores (novos materiais). A acurácia de seleção pode ser melhorada usando delineamentos ótimos e modelos bem ajustados. Porém, descobrir isso não é fácil, especialmente, em experimentos grandes que possuem mais de cem clones sem a possibilidade de repetição devido à limitação de material, área e custos elevados, dadas as poucas repetições de parcelas com variedades comerciais (testemunhas) e o número de parâmetros de complexa variância estrutural que necessitam ser assumidos. Os principais objetivos desta tese foram modelar 21 experimentos de cana de açúcar fornecidos pelo Centro de Tecnologia Canavieira (CTC - empresa brasileira de cana de açúcar) e avaliar o delineamento empregado, o qual usa um número grande de clones não repetidos e testemunhas sistematicamente repetidas. O modelo linear misto foi usado, identificando três principais componentes de variação espacial nos erros de parcelas e efeitos de competição, em nível genético e residual. Os clones foram assumidos de efeitos aleatórios e as testemunhas de efeitos fixos, pois vieram de processos diferentes. As análises individuais e conjuntas foram desenvolvidas neste material pois os experimentos puderam ser agrupados em dois tipos: (i) um delineamento longitudinal (duas colheitas) e (ii) cinco grupos de experimentos (cada grupo uma região com três locais). Para os estudos de delineamentos, um tamanho fixo de experimento foi assumido para se avaliar a eficiência do delineamento não replicado (empregado nesses 21 experimentos) com os não replicados otimizado espacialmente, os parcialmente replicados com testemunhas e os parcialmente replicados otimizado espacialmente. Quatro estudos de simulação foram feitos para avaliar i) os modelos ajustados, sob condições de efeito de competição em nível genético, ii) a acurácia das estimativas vindas dos modelos de análise individual e conjunta; iii) a relação entre tombamento da cana e a correlação residual negativa, e iv) a eficiência dos delineamentos. Para concluir, as principais informações utilizadas nos estudos de simulação foram: o número de vezes que o algoritmo convergiu; a variância na estimativa dos parâmetros; a correlação entre os EBLUPs genético direto e os efeitos genéticos reais; a assertividade de seleção ou a semelhança média, sendo semelhança medida como a porcentagem dos 30 clones com os maiores EBLUPS genético e os 30 melhores verdadeiros clones; e a estimativa da herdabilidade ou do ganho genético.