BACKGROUND: Orthodontists rely heavily on cephalometric analysis to assess growth potential and direction. Geometric morphometrics examines shape and can help the clinician reach more accurate diagnoses and predict future growth. PURPOSE: The aims of this study are: 1) Determine principle components describing craniofacial shape changes; 2) Assess shape changes in growing subjects; 3) Develop a model for craniofacial growth prediction using geometric morphometrics. RESEARCH DESIGN: The Cranial base, maxilla and mandible were digitized on 330 lateral cephalograms from ages 6-16 (n=33). Generalized Procrustes analysis was performed on the longitudinal data sample. Principle Component, Discriminant Function and Two-Block Partial Least Squares analysis were assessed against changes in individual structures to determine if changes in the maxillary, mandibular or cranial base are related to changes in shape of the overall craniofacial form. RESULTS: PCA shows that the first six principle components account for 67.7 – 77.0% of the observed shape variance in each region and 56.0% of the whole form. Multivariate regression analysis predicts the shape of the entire craniofacial complex at 16 years old based on the shape observed at 6 years old with 94% certainty. An intraclass correlation coefficient of 0.98 confirms reliability. CONCLUSION: Morphometric analyses indicate that changes in maxillofacial morphology during skeletal maturation are linear. The shape of the craniofacial complex does not change significantly and growth pattern is maintained. Our model can predict the craniofacial shape at 16 years of age based on the shape observed at 6 years of age.

La dystocie représente une des causes principales de la mortalité maternelle et fœtale lors de l’accouchement. Une relation trop étroite entre les dimensions maternelles et fœtales résultent souvent en une césarienne d’urgence. Les manuels obstétricaux actuels proposent qu’une forme gynoïde de la cavité obstétricale est normale car elle favorise une descente fœtale sans difficulté lors de la parturition parce qu’elle est arrondie. Ce mémoire de maîtrise porte sur l’étude de la variation inter-populationnelle de la forme du canal obstétrique chez trois populations génétiquement différentes pour tester si ces populations ont toutes une forme gynoïde ou si elles sont variables morphologiquement. Les cavités pelviennes analysées sont constituées de 59 bassins d’Américaines d’origine européenne, 74 bassins d’Américaines d’origine africaine et 19 bassins de Sadlermiuts. Vingt points anatomiques sur la cavité pelvienne ont été digitalisés à partir du bassin articulé pour permettre une visualisation tridimensionnelle de la forme du canal obstétrique. Une analyse Procrustes suivie d’une analyse en composantes principales ont été faites pour faire ressortir les composantes qui permettent de faire des distinctions entre les trois populations. L’existence d’une relation d’une part entre la taille et/ou la masse et d’autre part la morphologie du canal obstétrique a aussi été explorée. Résultats : La morphologie qui décrit les Sadlermiuts est la forme platypelloïde, soit un diamètre médio-latéral plus grand que le diamètre antéro-postérieur, et ce à tous les détroits. Les Américaines africaines présentent une morphologie qui tend vers une forme gynoïde aux détroits supérieur et moyen, et les Américaines européennes démontrent une morphologie intermédiaire entre les formes gynoïde et androïde au détroit supérieur. Seule la taille du bassin (taille centroïde) est corrélée à des changements de la forme du canal obstétrique pour les détroits supérieur et moyen. Discussion: La forme gynoïde n’est pas représentative de la cavité obstétricale chez les trois populations. Il est possible que la forme platypelloïde des Sadlermiuts soit une conséquence de comportements induisant des changements morphologiques lors du développement squelettique. D’autres études sont requises pour évaluer cette hypothèse. / Dystocia, the tightness of fit between the maternal and fetal dimensions within the birth canal, is one of the main causes of mortality during birthing. A majority of obstetrical manuals postulate that a gynecoid (round) form of the pelvic inlet is generally associated with birthing ease and that it is the normal form of the obstetrical canal. This memoir focuses on the analysis of the variation of the obstetrical canal within three genetically different populations and their possible relationship with size. The skeletal sample consists of the pelves of 74 African Americans, 59 Americans of European descent, and 19 Sadlermiuts. Twenty anatomical points have been digitized in three dimensions on the articulated pelvis defining the birth canal. A Generalized Procrustes Analysis followed by a Principal Component Analysis allowed the visualization of the morphological variations of the birth canal among the three populations. The possible relationship between size and canal form have been explored. Results: The Sadlermiuts have a birth canal that is platypelloid, i.e. wide mediolateraly and contracted anteroposteriorly, at all pelvic planes. The African Americans demonstrate a tendency for a gynecoid (round) pelvic inlet and the European Americans seem to possess an intermediate form between a gynecoid and an android morphology of the pelvic inlet. Only pelvic size (centroid size) was correlated with changes in the pelvic morphology of the pelvic inlet and midplane. Discussion: The gynecoid morphology is not the most common shape in the populations included in this study. One possible explanation for the platypelloid shape of the Sadlermiut population may be a result of behavioral activities that induce morphological changes during growth. Further studies are needed to confirm this hypothesis.

La dystocie représente une des causes principales de la mortalité maternelle et fœtale lors de l’accouchement. Une relation trop étroite entre les dimensions maternelles et fœtales résultent souvent en une césarienne d’urgence. Les manuels obstétricaux actuels proposent qu’une forme gynoïde de la cavité obstétricale est normale car elle favorise une descente fœtale sans difficulté lors de la parturition parce qu’elle est arrondie. Ce mémoire de maîtrise porte sur l’étude de la variation inter-populationnelle de la forme du canal obstétrique chez trois populations génétiquement différentes pour tester si ces populations ont toutes une forme gynoïde ou si elles sont variables morphologiquement. Les cavités pelviennes analysées sont constituées de 59 bassins d’Américaines d’origine européenne, 74 bassins d’Américaines d’origine africaine et 19 bassins de Sadlermiuts. Vingt points anatomiques sur la cavité pelvienne ont été digitalisés à partir du bassin articulé pour permettre une visualisation tridimensionnelle de la forme du canal obstétrique. Une analyse Procrustes suivie d’une analyse en composantes principales ont été faites pour faire ressortir les composantes qui permettent de faire des distinctions entre les trois populations. L’existence d’une relation d’une part entre la taille et/ou la masse et d’autre part la morphologie du canal obstétrique a aussi été explorée. Résultats : La morphologie qui décrit les Sadlermiuts est la forme platypelloïde, soit un diamètre médio-latéral plus grand que le diamètre antéro-postérieur, et ce à tous les détroits. Les Américaines africaines présentent une morphologie qui tend vers une forme gynoïde aux détroits supérieur et moyen, et les Américaines européennes démontrent une morphologie intermédiaire entre les formes gynoïde et androïde au détroit supérieur. Seule la taille du bassin (taille centroïde) est corrélée à des changements de la forme du canal obstétrique pour les détroits supérieur et moyen. Discussion: La forme gynoïde n’est pas représentative de la cavité obstétricale chez les trois populations. Il est possible que la forme platypelloïde des Sadlermiuts soit une conséquence de comportements induisant des changements morphologiques lors du développement squelettique. D’autres études sont requises pour évaluer cette hypothèse. / Dystocia, the tightness of fit between the maternal and fetal dimensions within the birth canal, is one of the main causes of mortality during birthing. A majority of obstetrical manuals postulate that a gynecoid (round) form of the pelvic inlet is generally associated with birthing ease and that it is the normal form of the obstetrical canal. This memoir focuses on the analysis of the variation of the obstetrical canal within three genetically different populations and their possible relationship with size. The skeletal sample consists of the pelves of 74 African Americans, 59 Americans of European descent, and 19 Sadlermiuts. Twenty anatomical points have been digitized in three dimensions on the articulated pelvis defining the birth canal. A Generalized Procrustes Analysis followed by a Principal Component Analysis allowed the visualization of the morphological variations of the birth canal among the three populations. The possible relationship between size and canal form have been explored. Results: The Sadlermiuts have a birth canal that is platypelloid, i.e. wide mediolateraly and contracted anteroposteriorly, at all pelvic planes. The African Americans demonstrate a tendency for a gynecoid (round) pelvic inlet and the European Americans seem to possess an intermediate form between a gynecoid and an android morphology of the pelvic inlet. Only pelvic size (centroid size) was correlated with changes in the pelvic morphology of the pelvic inlet and midplane. Discussion: The gynecoid morphology is not the most common shape in the populations included in this study. One possible explanation for the platypelloid shape of the Sadlermiut population may be a result of behavioral activities that induce morphological changes during growth. Further studies are needed to confirm this hypothesis.

Objective The goal of this project was to define and measure human volumetric airway dimensions with radiographic volumetric three-dimensional imaging and digital reconstruction of the pharynx using cone beam computed tomography to directly correlate these measurements with both normal and developmentally deficient jaw joints and their positions. The volume of the oropharynx was measured by creating a superior border connecting the 3-D midpoint of sella turcica and the posterior nasal spine and extending inferiorly to the level connecting the most infero-anterior point of C3 and the anterior hyoid bone as seen in the multi-planar views of the cone beam computed tomography image. The calculations were accomplished by using 3dMD software. Further extrapolation of this study'a data may be useful to establish the direct association of obstructive sleep apnea and deficiencies of jaw growth and airway development. Design In this retrospective study, 250 subjects were randomly selected from a pool of 800 referred for dental imaging at ddi Imaging Center in Sacramento, California. Digital images were captured using a low-radiation, rapid scanning cone beam computed tomography system (iCAT). Results A total of 250 subjects, 163 females and 87 males, were included in this study. Descriptive statistics were applied to the following variables: 1. Assessment of the relationship between total airway volume and several categorically independent variables: * For total airway volume, no significant difference was found between males and females; between the right temporomandibular positions; between right temporomandibular integrity; or between the left temporomandibular integrity. * There was a significant difference found between the left temporomandibular positions for total airway volume. 2. Assessment of the relationship between total airway volume and each cephalometric measurement: * Based on the Spearman correlation test, there were significant increasing relationships between total airway volume and several of the cephalometric measurements (p<0.05). * Correlation coefficients ranged from 0.13 to 0.22 indicating there were weak correlations between the two variables. 3. Assessment of the relationship between total airway volume and age: * Based on the Spearman correlation test, there was no significant relationship between total airway volume and age (p=0.8304). In addition, Spearman correlation showed no correlation between total airway volume and sex and skeletal growth pattern tendencies. Conclusions Three dimensional images of the airway offer the opportunity to serially examine individuals, acquire airway patency information, and improve the evaluation of sites of airway obstruction. Further studies to determine the effects of pharyngeal stenosis and other regional changes to the oropharynx upon physiologic response may be key to understanding the effects of biomechanical influences upon craniofacial form. Comprehension of structural inter-relationships will also help develop an understanding of how and why adaptive changes in airway shape and volume occur. Airway patency is related to many variables: head posture, the direction of mandibular rotation during growth and development, and hyoid bone position. Further studies may offer an increased understanding of these structural and positional interrelationships.

The temporal and spatial variability in wind speed and direction was investigated in a study of the mesoscale wind fields in the Canberra region. The statistical description of the winds was based on twelve months of three-hourly data at seventeen sites obtained in a joint program carried out by the Division of Land Use Research, CSIRO, the National Capital Development Commission, and the Bureau of Meteorology. The statistical analysis proceeded in stages. The first two stages were concerned with the determination and examination of averages and measures of dipersion. Information on the temporal variability in regional wind, defined as the average of the winds at the seventeen collection sites, provided the first insight into the important determinants of winds in the region. The data were then categorized on the basis of the information thus obtained, and the averages over time for each site were analysed in each category. The variation between sites revealed the extent of the spatial variability in the region. For each category, for each site, there were perturbations around the average state, and in the last stage of the study, the analysis examined how the perturbations were related across sites using correlation coefficients. Generalized Procrustes Analysis was used, followed by the extensive use of cluster analysis. Linear modelling techniques were used at all stages of the study, not only for wind speed, but also for wind direction which is an angular variate and thus required different modelling procedures. The models related the variables of interest to terrain features such as position, elevation and surface roughness. These models allowed an informed judgement to be made on the likelihood of accurately estimating the winds at other locations in the region using interpolation techniques.

La morphologie des os humains varie en fonction du sexe, de l'âge et de l'ethnie. Cette variabilité de l'anatomie humaine peut aider à déterminer le sexe, l'âge et l'ethnie. Les outils utilisés pour de telles analyses sont classiquement des méthodes ostéométriques (longueur, angle, rapport de longueur) qui peuvent être sujettes à des biais d'analyse ou d'interprétation. L'analyse morphométrique géométrique 3D (MG) permet de limiter ces biais. Elle étudie et compare la forme d'un ou plusieurs objets en éliminant les effets liés à la taille de celui-ci. Nous n'avons pas retrouvé d'analyse du dimorphisme sexuel, ethnique et lié à l'âge de l'extrémité distale du fémur à l'aide de cette méthode. Le fémur est pourtant un des plus gros os du corps et il est souvent bien conservé dans les restes humains. L'objectif de ce travail était de montrer qu'il existe une différence de forme du fémur distal en fonction de l'âge, du sexe et de l'ethnie visualisable grâce à MG. Nous avons réalisé une MG de 482 scanners d'extrémité distale de fémur de sujets vivant dans le sud de la France et dans la région de Chongqing (chine). Les sujets présentant une pathologie osseuse ou articulaires ont été exclus. Dix landmarks ont été positionnés sur des reconstructions tridimentionelles. Nous avons également réalisé une analyse ostéométrique " classique " en plus de MG afin d'évaluer la vraisemblance de nos résultats. Les données ont été analysées par deux observateurs à deux temps différents. Nous avons calculé pour chaque landmark la variabilité inter et intraobservateur. Les landmarks choisis permettaient de caractériser la forme de l'extrémité distale du fémur. La première étape a consisté en la réalisation d'une analyse généralisée procrustre (GPA). Les coordonnées dans l'espace des landmarks ont été analysées en utilisant une analyse en composant principal (PCA). Une analyse discriminante a permis de vérifier le pourcentage de cas dans lequel le sexe, l'âge ou l'ethnie estimés étaient les bons. GPA retrouve une différence de forme statistiquement significative entre les sexes, en fonction de l'âge et entre les ethnies. PCA retrouve une différence de forme en fonction de l'âge, du sexe ou de l'ethnie qui représente respectivement 54,4 ;58,6 et 61,9% de la variabilité observée. Les taux d'assignement correct avec cette méthode étaient de 80% (âge) ; 77,3% (sexe) et 82 % (l'ethnie). L'analyse ostéométrique " classique " retrouvait des valeurs comparables à celles retrouvées dans la littérature. Le pourcentage d'erreur intra et inter observateur pour l'ensemble des landmarks n'excédait jamais 2%. Nous avons démontré que l'analyse MG du fémur distal permettait de mettre en évidence une variabilité en fonction du sexe, de l'âge et de l'ethnie de ce segment osseux. La reproductibilité élevée et la vraisemblance des résultats valident notre méthodologie. Cette différence de forme a des retombées directes en anthropobiologie mais aussi en orthopédie. Cette méthode d'assignation ne donne pas de résultats suffisamment précis pour être utilisée seule. Cependant, elle a l'avantage de pouvoir être utilisée dans des contextes d'autopsie virtuelle ou in vivo. Par ailleurs, par la présente étude nous réactualisons les données morphométriques de population contemporaine du sud de la France et aussi de la région de Chongqing en chine. Cette méthodologie adéquate et reproductible va permettre de réaliser des comparaisons diachroniques ainsi qu'inter ethnique. La validation de l'utilisation d'examen d'imagerie médicaux ouvre un champ nouveau en anthropologie physique. En ce qui concerne l'aspect orthopédique, cette variabilité questionne sur la nécessité ou non d'implant spécifique et surtout sur la nécessité de réévaluer de manière régulière la forme des prothèses de genou. / The shape of human bones varies based on age, sex and ethnicity. This variability in human anatomy can be used to determine a person's age, sex and ethnicity. Historically, the tools used for such analyses are osteometric methods (length, angle, length ratio) that can be plagued by analysis or interpretation biases. Three-dimensional geometric morphometric analysis (3D GM) can limit the impact of these biases. It is used to describe and compare the general shape of one or more objects by eliminating any size-related effects. To the best of our knowledge, this method has never been used to analyse the sexual dimorphism, ethnicity-related and age-related differences in the distal femur. The femur is one of the longest human bones and is often well preserved in human remains. The goal of this study was to demonstrate differences in the shape of the distal femur according to age, sex and ethnicity using GM. We carried out 3D GM on 482 CT scans of the distal femur of adults living in the South of France and in the Chongqing region of China. Subjects with bone or joint pathologies were excluded. Ten landmarks were defined on 3D reconstructions of the distal femur. A standard osteometric analysis was performed in addition to the GM analysis to evaluate the plausibility of our results. The data were analysed by two observers at two different times. This allowed us to calculate the inter- and intra-observer variability for each landmark. The chosen landmarks were used to characterise the shape of the distal femur. The first step consisted of a generalized Procrustes analysis (GPA). The landmarks' coordinates in space were analysed using a principal component analysis (PCA). A discriminant analysis was performed to determine the percentage of cases in which the sex, age or ethnicity was correctly estimated. The GPA found a statistically significant difference in the distal femur shape between different sexes, ethnicity groups and age groups. The PCA found that age, sex and ethnicity accounted for 54.4%, 58.6% and 61.9% of the observed variability in distal femur shape, respectively. Using this method, 80% of cases were assigned the correct age, 77.3% the correct sex and 82% the correct ethnic group. The results of the osteometric analysis were comparable to published values. The percentage error for the intra- and interobserver comparisons for all the landmarks was always less than 2%. In this study, MG analysis of the distal femur revealed age-related, sex-related and ethnicity-related variability in the distal femur. The high reproducibility and plausibility of our results validate our methodology. These shape differences have direct implications for anthropobiology and also orthopaedics. Although this method is not sufficiently accurate to be used alone, it has the advantage of being usable in the context of virtual or in vivo autopsy cases. Moreover, this study has updated the morphometric data for a modern population in the south of France and the Chongqing region of China. This reliable and accurate methodology can be used to perform diachronic and interethnic comparisons. Validation of this medical imaging modality opens new avenues in physical anthropology research. In the orthopaedics field, this variability means that the shape of implants used for knee arthroplasty should be re-assessed regularly and brings into question the need for gender-specific or ethnicity-specific implants.

Geralmente, nos experimentos genótipo por ambiente (G × E) é comum observar o comportamento dos genótipos em relação a distintos atributos nos ambientes considerados. A análise deste tipo de experimentos tem sido abordada amplamente para o caso de um único atributo. Nesta tese são apresentadas algumas alternativas de análise considerando genótipos, ambientes e atributos simultaneamente. A primeira, é baseada no método de mistura de máxima verossimilhança de agrupamento - Mixclus e a análise de componentes principais de 3 modos - 3MPCA, que permitem a análise de tabelas de tripla entrada, estes dois métodos têm sido muito usados na área da psicologia e da química, mas pouco na agricultura. A segunda, é uma metodologia que combina, o modelo de efeitos aditivos com interação multiplicativa - AMMI, modelo eficiente para a análise de experimentos (G × E) com um atributo e a análise de procrustes generalizada, que permite comparar configurações de pontos e proporcionar uma medida numérica de quanto elas diferem. Finalmente, é apresentada uma alternativa para realizar imputação de dados nos experimentos (G × E), pois, uma situação muito frequente nestes experimentos, é a presença de dados faltantes. Conclui-se que as metodologias propostas constituem ferramentas úteis para a análise de experimentos (G × E) multiatributo. / Usually, in the experiments genotype by environment (G×E) it is common to observe the behaviour of genotypes in relation to different attributes in the environments considered. The analysis of such experiments have been widely discussed for the case of a single attribute. This thesis presents some alternatives of analysis, considering genotypes, environments and attributes simultaneously. The first, is based on the mixture maximum likelihood method - Mixclus and the three-mode principal component analysis, these two methods have been very used in the psychology and chemistry, but little in agriculture. The second, is a methodology that combines the additive main effects and multiplicative interaction models - AMMI, efficient model for the analysis of experiments (G×E) with one attribute, and the generalised procrustes analysis, which allows compare configurations of points and provide a numerical measure of how much they differ. Finally, an alternative to perform data imputation in the experiments (G×E) is presented, because, a very frequent situation in these experiments, is the presence of missing values. It is concluded that the proposed methodologies are useful tools for the analysis of experiments (G×E) multi-attribute.

Geralmente, nos experimentos genótipo por ambiente (G × E) é comum observar o comportamento dos genótipos em relação a distintos atributos nos ambientes considerados. A análise deste tipo de experimentos tem sido abordada amplamente para o caso de um único atributo. Nesta tese são apresentadas algumas alternativas de análise considerando genótipos, ambientes e atributos simultaneamente. A primeira, é baseada no método de mistura de máxima verossimilhança de agrupamento - Mixclus e a análise de componentes principais de 3 modos - 3MPCA, que permitem a análise de tabelas de tripla entrada, estes dois métodos têm sido muito usados na área da psicologia e da química, mas pouco na agricultura. A segunda, é uma metodologia que combina, o modelo de efeitos aditivos com interação multiplicativa - AMMI, modelo eficiente para a análise de experimentos (G × E) com um atributo e a análise de procrustes generalizada, que permite comparar configurações de pontos e proporcionar uma medida numérica de quanto elas diferem. Finalmente, é apresentada uma alternativa para realizar imputação de dados nos experimentos (G × E), pois, uma situação muito frequente nestes experimentos, é a presença de dados faltantes. Conclui-se que as metodologias propostas constituem ferramentas úteis para a análise de experimentos (G × E) multiatributo. / Usually, in the experiments genotype by environment (G×E) it is common to observe the behaviour of genotypes in relation to different attributes in the environments considered. The analysis of such experiments have been widely discussed for the case of a single attribute. This thesis presents some alternatives of analysis, considering genotypes, environments and attributes simultaneously. The first, is based on the mixture maximum likelihood method - Mixclus and the three-mode principal component analysis, these two methods have been very used in the psychology and chemistry, but little in agriculture. The second, is a methodology that combines the additive main effects and multiplicative interaction models - AMMI, efficient model for the analysis of experiments (G×E) with one attribute, and the generalised procrustes analysis, which allows compare configurations of points and provide a numerical measure of how much they differ. Finally, an alternative to perform data imputation in the experiments (G×E) is presented, because, a very frequent situation in these experiments, is the presence of missing values. It is concluded that the proposed methodologies are useful tools for the analysis of experiments (G×E) multi-attribute.

Spatial and temporal temperature and moisture patterns across the Tibetan Plateau are very complex. The onset and magnitude of the Holocene climate optimum in the Asian monsoon realm, in particular, is a subject of considerable debate as this time period is often used as an analogue for recent global warming. In the light of contradictory inferences regarding past climate and environmental change on the Tibetan Plateau, I have attempted to explain mismatches in the timing and magnitude of change. Therefore, I analysed the temporal variation of fossil pollen and diatom spectra and the geochemical record from palaeo-ecological records covering different time scales (late Quaternary and the last 200 years) from two core regions in the NE and SE Tibetan Plateau. For interpretation purposes I combined my data with other available palaeo-ecological data to set up corresponding aquatic and terrestrial proxy data sets of two lake pairs and two sets of sites. I focused on the direct comparison of proxies representing lacustrine response to climate signals (e.g., diatoms, ostracods, geochemical record) and proxies representing changes in the terrestrial environment (i.e., terrestrial pollen), in order to asses whether the lake and its catchments respond at similar times and magnitudes to environmental changes. Therefore, I introduced the established numerical technique procrustes rotation as a new approach in palaeoecology to quantitatively compare raw data of any two sedimentary records of interest in order to assess their degree of concordance. Focusing on the late Quaternary, sediment cores from two lakes (Kuhai Lake 35.3°N; 99.2°E; 4150 m asl; and Koucha Lake 34.0°N; 97.2°E; 4540 m asl) on the semi-arid northeastern Tibetan Plateau were analysed to identify post-glacial vegetation and environmental changes, and to investigate the responses of lake ecosystems to such changes. Based on the pollen record, five major vegetation and climate changes could be identified: (1) A shift from alpine desert to alpine steppe indicates a change from cold, dry conditions to warmer and more moist conditions at 14.8 cal. ka BP, (2) alpine steppe with tundra elements points to conditions of higher effective moisture and a stepwise warming climate at 13.6 cal. ka BP, (3) the appearance of high-alpine meadow vegetation indicates a further change towards increased moisture, but with colder temperatures, at 7.0 cal. ka BP, (4) the reoccurrence of alpine steppe with desert elements suggests a return to a significantly colder and drier phase at 6.3 cal. ka BP, and (5) the establishment of alpine steppe-meadow vegetation indicates a change back to relatively moist conditions at 2.2 cal. ka BP. To place the reconstructed climate inferences from the NE Tibetan Plateau into the context of Holocene moisture evolution across the Tibetan Plateau, I applied a five-scale moisture index and average link clustering to all available continuous pollen and non-pollen palaeoclimate records from the Tibetan Plateau, in an attempt to detect coherent regional and temporal patterns of moisture evolution on the Plateau. However, no common temporal or spatial pattern of moisture evolution during the Holocene could be detected, which can be assigned to the complex responses of different proxies to environmental changes in an already very heterogeneous mountain landscape, where minor differences in elevation can result in marked variations in microenvironments. Focusing on the past 200 years, I analysed the sedimentary records (LC6 Lake 29.5°N, 94.3°E, 4132 m asl; and Wuxu Lake 29.9°N, 101.1°E, 3705 m asl) from the southeastern Tibetan Plateau. I found that despite presumed significant temperature increases over that period, pollen and diatom records from the SE Tibetan Plateau reveal only very subtle changes throughout their profiles. The compositional species turnover investigated over the last 200 years appears relatively low in comparison to the species reorganisations during the Holocene. The results indicate that climatically induced ecological thresholds are not yet crossed, but that human activity has an increasing influence, particularly on the terrestrial ecosystem. Forest clearances and reforestation have not caused forest decline in our study area, but a conversion of natural forests to semi-natural secondary forests. The results from the numerical proxy comparison of the two sets of two pairs of Tibetan lakes indicate that the use of different proxies and the work with palaeo-ecological records from different lake types can cause deviant stories of inferred change. Irrespective of the timescale (Holocene or last 200 years) or region (SE or NE Tibetan Plateau) analysed, the agreement in terms of the direction, timing, and magnitude of change between the corresponding terrestrial data sets is generally better than the match between the corresponding lacustrine data sets, suggesting that lacustrine proxies may partly be influenced by in-lake or local catchment processes whereas the terrestrial proxy reflects a more regional climatic signal. The current disaccord on coherent temporal and spatial climate patterns on the Tibetan Plateau can partly be ascribed to the complexity of proxy response and lake systems on the Tibetan Plateau. Therefore, a multi-proxy, multi-site approach is important in order to gain a reliable climate interpretation for the complex mountain landscape of the Tibetan Plateau. / Die räumlichen und zeitlichen Temperatur- und Feuchtigkeitsmuster auf dem Tibet-Plateau sind sehr komplex. Im Einzugsbereich der asiatischen Monsune sind insbesondere der Beginn und das Ausmaß des Klimaoptimums während des Holozäns von wissenschaftlichem Interesse, da diese Periode oft als Analogie für die derzeitige globale Klimaerwärmung herangezogen wird. In Hinblick auf sich teilweise widersprechende Paläoklima- und Umweltrekonstruktionen für das Tibet-Plateau, ist es mein Ziel, die bestehenden Unstimmigkeiten bezüglich des Zeitpunktes und des Ausmaßes des Umweltwandels zu erklären. Dafür wurden von mir zeitliche Variationen fossiler Pollen- und Diatomeenspektren und geochemische Untersuchungen an Seesedimenten unterschiedlicher Zeitskalen (Spätquartär und die letzten 200 Jahre) aus zwei Kernregionen auf dem NO und SO Tibet-Plateau analysiert. Zur Unterstützung der Interpretation wurden die hier erhobenen Daten mit bereits vorhandenen paläoökologischen Aufzeichnungen der Lokalitäten kombiniert, um Datensätze der entsprechenden aquatischen und terrestrischen Proxy-Daten (Stellvertreterdaten) zweier Seenpaare aus den beiden Regionen gegenüberstellen zu können. Hierbei konzentrierte ich mich auf den direkten Vergleich von Proxies, die die Seenentwicklung reflektieren (z.B. Diatomeen, Ostracoden, geochemische Eigenschaften), mit Proxies, die Veränderungen der terrestrischen Umgebung des Sees beschreiben (terrestrische Pollen). Durch diesen Vergleich lässt sich beurteilen, ob Veränderungen im See selbst mit Umweltveränderungen in dem jeweiligen Einzugsgebiet zeitlich übereinstimmen. Dafür habe ich die bereits etablierte numerische Methode Procrustes-Rotation als neuen Ansatz in der Paläoökologie eingeführt. Damit ist ein quantitativer Vergleich von Rohdaten zweier beliebiger sedimentärer Datensätze möglich, um den Grad der Übereinstimmung zu prüfen. Um die in dieser Arbeit rekonstruierten Umwelt- und Klimaereignisse des nordöstlichen Tibet-Plateaus in einen größeren Zusammenhang hinsichtlich holozäner Klimaentwicklung des gesamten Plateaus setzen zu können, und um schlüssige zeitliche und räumliche Klimatrends auf dem Plateau erkennen zu können, habe ich auf alle vorhandenen Paläoklimadatensätze einen Fünf-Skalen Feuchtigkeitsindex und eine Clusteranalyse angewandt. Es konnten jedoch keine einheitlichen zeitlichen und räumlichen Trends der holozänen Klimaentwicklung nachgewiesen werden, was meiner Analyse entsprechend, auf die komplexen Reaktionen verschiedener Proxies auf Umweltveränderungen in einer ohnehin sehr heterogen Berglandschaft, zurückgeführt werden kann. Die Ergebnisse des numerischen Proxy-Vergleichs beider Seenpaare zeigen, dass die Verwendung von verschiedenen Proxies und die Arbeit mit paläo-ökologischen Datensätzen unterschiedlicher See-Typen zu abweichenden Klimaableitungen führen können. Unabhängig vom untersuchten Zeitraum (Holozän oder die letzten 200 Jahren) oder der Region (SO oder NO Tibet-Plateau), ist die Übereinstimmung zweier Datensätze hinsichtlich der Richtung, des Zeitpunktes und des Ausmaßes der abgeleiteten Paläo-Umweltverhältnisse in der Regel zwischen den entsprechenden terrestrischen Datensätzen besser als zwischen den entsprechenden lakustrinen Datensätzen. Die derzeitige Uneinigkeit über stimmige zeitliche und räumliche Klimatrends auf dem Tibet-Plateau kann daher teilweise der Komplexität der verschieden Proxies und ihrer individuellen Empfindlichkeiten gegenüber Umweltveränderungen sowie der unterschiedlichen Reaktionsweise verschiedenartiger See-Systeme auf dem Plateau zugeschrieben werden. Meine Ergebnisse zeigen, dass ein „Multi-Proxy-Multi-Site-Ansatz“ für zuverlässige Paläoklimaableitungen für das Tibet-Plateau von zentraler Bedeutung ist.

Το αντικείμενο της εργασίας αυτής είναι η μελέτη των μετανευτώνειων προσεγγίσεων στο πλαίσιο της Γενικής Σχετικότητας, με έμφαση στους αστέρες νετρονίων. Λόγω του οτι, η μελέτη των αστέρων νετρονίων βασίζεται στην υδροδυναμική περιγραφή της ύλης, το κύριο ενδιαφέρον μας αφορά στον τρόπο που εισάγονται οι μετανευτώνειες προσεγγίσεις στις υδροδυναμικές εξισώσεις της Γενικής Σχετικότητας. Στο πρώτο κεφάλαιο παρουσιάζονται ορισμένα θεωρητικά στοιχεία γύρω απο φυσικά χαρακτηριστικά και τις ιδιότητες των συμπαγών αστέρων. Στο δεύτερο κεφάλαιο παρουσιάζονται τα γενικά χαρακτηριστικά των καταστατικών εξισώσεων των συμπαγών αστέρων, με έμφαση στην πολυτροπική καταστατική εξίσωση. Στο τρίτο κεφάλαιο παρουσιάζεται η θεωρία των μετανευτώνειων προσεγγίσεων, καθώς και οι μετανευτώνειες εξισώσεις πρώτης τάξης της υδροδυναμικής, στη Γενική Σχετικότητα όπως εισήχθησαν απο τον Chandrasekhar. Στο τέταρτο κεφάλαιο παρουσιάζεται η διαταρακτική μέθοδος που χρησιμοποιείται απο τους Fahlman και Anand, για την μελέτη των περιστρεφόμενων πολυτρόπων στο πλαίσιο της πρώτης μετανευτώνειας προσέγγισης στη Γενική Σχετικότητα. Στο πέμπτο κεφάλαιο παρουσιάζεται η μετανευτώνεια προσέγγιση δεύτερης τάξης όπως διατυπώθηκε απο τους Chandrasekhar και Nutku. Στο έκτο, και τελευταίο, κεφάλαιο παρουσιάζεται ένα υπολογιστικό αλγεβρικό πακέτο για μετανευτώνειους υπολογισμούς στη Γενική Σχετικότητα, το PROCRUSTES. Με την βοήθεια του πακέτου αυτού υπολογίσαμε διάφορες ποσότητες στη δεύτερη μετανευτώνεια προσέγγιση, όπως τον τανυστή ενέργειας - ορμής, 𝑇𝑖𝑗, τον τανυστή Ricci, 𝑅𝑖𝑗, τις εξισώσεις κίνησης, Τ𝑖𝑗;𝑗 = 0, και άλλες. Το PROCRUSTES είναι ένα πολύ χρήσιμο εργαλείο στη μετανευτώνεια μελέτη καθώς μπορεί κανείς να παράξει τις περίπλοκες εκφράσεις διαφόρων ποσοτήτων σε ελάχιστο χρόνο και χωρίς την πιθανότητα λάθους. Επίσης, με την βοήθεια του πακέτου αυτού, υπολογίσαμε τις αναλυτικές εκφράσεις των εξισώσεως κίνησης, Τ𝑖𝑗;𝑗 = 0, στην δεύτερη μετανευτώνεια προσέγγιση. Με κατάλληλη μετατροπή των εκφράσεων αυτών, μπορούμε να εφαρμόσουμε την μέθοδο των Fahlman και Anand, με σκοπό την μελέτη των περιστερόμενων πολυτρόπων στη μετανευτώνεια προσέγγιση δεύτερης τάξης. Στο τέλος της εργασίας παρατίθεται ένα συμπλήρωμα με τη δομή του προγράμματος και ορισμένες απο τις ποσότητες που υπολογίστηκαν στο πλαίσιο της εργασίας. / The main subject of my master thesis is the study of,the post-Newtonian approximations (PNA) in General Relativity (G-R), mainly those that concern the neutron stars. Owing to the study of neutron stars is on the hydrodynamic description of matter, our main interest lies uponthe way the PNA affects the hydrodynamic equations of G-R. In the first chapter there is presented the main theory around the physical attributes of compact stars. The second chapter reffers to the general features of the equations of state (EoS) of compact stars, giving emphasis to the polytropic EoS. In the yhird chapter, there is presented the theory of the PNA. There are also presented the the hydrodynamic equations in the PNA as the were introduced by Chandrasekhar. The fourth chapter is dedicated to the presentation of the method that was introduced by Fahlman and Anand, on the study of rotating polytropes in the PNA to G-R. The fifth chapter focuses on the second PNA as it formulated by Chandrasekhar and Nutku. During the sixth and final chapter there is presented a computer algebra package for post-Newtonian calculations in G-R, the PROCRUSTES. Whith the aid of thiw package, we calculated several quantities in the second PNA, as for example the E-M tensor 𝑇𝑖𝑗„ the Ricci tensor 𝑅𝑖𝑗 and the equations of motion (EoM) Τ𝑖𝑗 ;𝑗 = 0. PROCRUSTES is a very useful tool for the post-Newtonian study, as someone can produce the compicated equations of several quantities in no time and eliminating the possibility of making some mistake during the calculation. Moreover, using PROCRUSTES we calculated the expressions of the EoM’s in the second PNA. Under appropriate transformation of these expressions, we are able to apply the method of Fahlman and Anand onto these equations with a view to the study of rotating polytropes in the second PNA. At the end of this work there is quoted a supplement with the structure of the programm we used, along with some of the quantities that were calculated during this work.