Dans cette thèse je m'intéresse à des propriétés de rigidité de certaines constructions d'algèbres de von Neumann. Ces constructions relient la théorie des groupes et la théorie ergodique au monde des algèbres d'opérateurs. Il est donc naturel de s'interroger sur la force de ce lien et sur la possibilité d'un enrichissement mutuel dans ces différents domaines. Le Chapitre II traite des actions Gaussiennes. Ce sont des actions de groupes discrets préservant une mesure de probabilité qui généralisent les actions de Bernoulli. Dans un premier temps, j'étudie les propriétés d'ergodicité de ces actions à partir d'une analyse de leurs algèbres de von Neumann (voir Theorem II.1.22 et Corollary II.2.16). Ensuite, je classifie les algèbres de von Neumann associées à certaines actions Gaussiennes, à isomorphisme près, en montrant un résultat de W*-Superrigidité (Theorem II.4.5). Ces résultats généralisent des travaux analogues sur les actions de Bernoulli ([KT08,CI10,Io11,IPV13]).Dans le Chapitre III, j'étudie les produits libres amalgamés d'algèbres de von Neumann. Ce chapitre résulte d'une collaboration avec C. Houdayer et S. Raum. Nous analysons les sous-Algèbres de Cartan de tels produits libres amalgamés. Nous déduisons notamment de notre analyse que le produit libre de deux algèbres de von Neumann n'est jamais obtenu à partir d'une action d'un groupe sur un espace mesuré.Enfin, le Chapitre IV porte sur les algèbres de von Neumann associées à des groupes hyperboliques. Ce chapitre est obtenu en collaboration avec A. Carderi. Nous utilisons la géométrie des groupes hyperboliques pour fournir de nouveaux exemples de sous-Algèbres maximales moyennables (mais de type I) dans des facteurs II_1. / The purpose of this dissertation is to put on light rigidity properties of several constructions of von Neumann algebras. These constructions relate group theory and ergodic theory to operator algebras.In Chapter II, we study von Neumann algebras associated with measure-Preserving actions of discrete groups: Gaussian actions. These actions are somehow a generalization of Bernoulli actions. We have two goals in this chapter. The first goal is to use the von Neumann algebra associated with an action as a tool to deduce properties of the initial action (see Corollary II.2.16). The second aim is to prove structural results and classification results for von Neumann algebras associated with Gaussian actions. The most striking rigidity result of the chapter is Theorem II.4.5, which states that in some cases the von Neumann algebra associated with a Gaussian action entirely remembers the action, up to conjugacy. Our results generalize similar results for Bernoulli actions ([KT08,CI10,Io11,IPV13]).In Chapter III, we study amalgamated free products of von Neumann algebras. The content of this chapter is obtained in collaboration with C. Houdayer and S. Raum. We investigate Cartan subalgebras in such amalgamated free products. In particular, we deduce that the free product of two von Neumann algebras is never obtained as a group-Measure space construction of a non-Singular action of a discrete countable group on a measured space.Finally, Chapter IV is concerned with von Neumann algebras associated with hyperbolic groups. The content of this chapter is obtained in collaboration with A. Carderi. We use the geometry of hyperbolic groups to provide new examples of maximal amenable (and yet type I) subalgebras in type II_1 factors.

Dans cette thèse, on s'intéresse à la théorie mesurée des groupes, à l'entropie sofique et aux algèbres d'opérateurs ; plus précisément, on étudie les actions des groupes sur des espaces de probabilités, des propriétés fondamentales de leur entropie sofique (pour des groupes discrets), leurs groupes pleins (pour des groupes Polonais), et les algèbres de von Neumann et leurs sous-algèbres moyennables (pour des groupes à caractère hyperbolique et des réseaux de groupes de Lie). Cette thèse est constituée de trois parties.Dans une première partie j'étudie l'entropie sofique des actions profinies. L'entropie sofique est un invariant des actions mesurées des groupes sofiques défini par L. Bowen qui généralise la notion d'entropie introduite par Kolmogorov. La définition d'entropie sofique nécessite de fixer une approximation sofique du groupe. Nous montrons que l'entropie sofique des actions profinies est effectivement dépendante de l'approximation sofique choisie dans le cas des groupes libres et certains réseaux de groupes de Lie.La deuxième partie est un travail en collaboration avec François Le Maître. Elle est constituée d'un article prépublié dans lequel nous généralisons la notion de groupe plein aux actions préservant une mesure de probabilité des groupes polonais, et en particulier, des groupes localement compacts. On définit une topologie polonaise sur ces groupes pleins et on étudie leurs propriétés topologiques fondamentales, notamment leur rang topologique et la densité des éléments apériodiques.La troisième partie est un travail en collaboration avec Rémi Boutonnet. Elle est constituée de deux articles prépubliés dans lesquels nous considérons la question de la maximalité de la sous-algèbre de von Neumann d'un sous-groupe moyennable maximal, dans celle du groupe ambiant. Nous résolvons la question dans le cas des groupes à caractère hyperbolique en utilisant les techniques de Sorin Popa. Puis, nous introduisons un critère dynamique à la Furstenberg, permettant de résoudre la question pour des sous-groupes moyennables de réseaux des groupes de Lie en rang supérieur. / This dissertation is about measured group theory, sofic entropy and operator algebras. More precisely, we will study actions of groups on probability spaces, some fundamental properties of their sofic entropy (for countable groups), their full groups (for Polish groups) and the amenable subalgebras of von Neumann algebras associated with hyperbolic groups and lattices of Lie groups. This dissertation is composed of three parts.The first part is devoted to the study of sofic entropy of profinite actions. Sofic entropy is an invariant for actions of sofic groups defined by L. Bowen that generalize Kolmogorov's entropy. The definition of sofic entropy makes use of a fixed sofic approximation of the group. We will show that the sofic entropy of profinite actions does depend on the chosen sofic approximation for free groups and some lattices of Lie groups. The second part is based on a joint work with François Le Maître. The content of this part is based on a prepublication in which we generalize the notion of full group to probability measure preserving actions of Polish groups, and in particular, of locally compact groups. We define a Polish topology on these full groups and we study their basic topological properties, such as the topological rank and the density of aperiodic elements. The third part is based on a joint work with Rémi Boutonnet. The content of this part is based on two prepublications in which we try to understand when the von Neumann algebra of a maximal amenable subgroup of a countable group is itself maximal amenable. We solve the question for hyperbolic and relatively hyperbolic groups using techniques due to Popa. With different techniques, we will then present a dynamical criterion which allow us to answer the question for some amenable subgroups of lattices of Lie groups of higher rank.

O objetivo desse estudo foi verificar a relação da aptidão aeróbia e de fatores neuromusculares com o desempenho em SR em tenistas com diferentes níveis de jogo. Um grupo de dez tenistas profissionais (GP) e um grupo de dez tenistas amadores (GA) foram submetidos a quatro sessões experimentais, a saber: 1) medidas antropométricas, familiarização com o teste de drop jump (DJ) e com o teste de contração voluntária isométrica máxima (CVIM) para membros inferiores, e um teste progressivo até a exaustão; 2) um teste de DJ e um teste de carga constante para avaliar a cinética on e off do consumo de oxigênio (VO2); 3) um teste de CVIM para membros inferiores, outro teste de carga constante para avaliar a cinética on e off do VO2 e familiarização com o teste de SR; 4) um teste composto por dez SR. O GP apresentou valores significativamente menores para o tempo do melhor sprint (SRmelhor) e para a média dos tempos de todos os sprints (SRmédio) em relação ao GA (p < 0,05). O percentual de aumento do tempo ao longo dos sprints (SR%aumento) do GP não foi significativamente menor em comparação ao GA (p = 0,102), porém a chance dessa variável ser menor para o GP foi considerada \"provável\". Para o GP, a única correlação significativa observada foi entre o SRmédio e o tempo de contato obtido no teste de DJ (r = 0,641, p < 0,05). Em relação ao GA, foram observadas correlações significativas da velocidade pico obtida no teste progressivo até a exaustão com o SRmelhor (r = -0,680, p < 0,05) e SRmédio (r = -0,744, p < 0,05), assim como da amplitude da fase lenta da cinética off do VO2 com o SRmelhor (r = -0,756, p < 0,05) e SRmédio (r = -0,794, p < 0,05). Portanto, esses dados sugerem que tenistas profissionais possuem um melhor desempenho em SR em comparação aos tenistas amadores. Entretanto, não está clara a importância de fatores da aptidão aeróbia e neuromusculares no desempenho dessa atividade / The objective of this study was to verify the relationship of aerobic fitness and neuromuscular factors with RS performance in tennis players with different playing level. A group of ten professional (PG) and ten amateur (AG) tennis players were submitted to four experimental sessions, to know: 1) anthropometric measurements, familiarization with the drop jump (DJ) test and the maximal voluntary isometric contraction (MVIC) test for the lower limbs, and a progressive test until exhaustion; 2) a DJ test and a constant load test for on and off oxygen consumption (VO2) kinetics measurement; 3) a MVIC test for the lower limbs, another constant load test for on and off VO2 kinetics measurement, and familiarization with the RS test; 4) a test of ten RS. The PG presented significant lower values for the best sprint time (RSbest) and mean time of all sprints (RSmean) in relation to the AG (p < 0.05). The percentage increase in time over all sprints (RSincrease) of the PG was not significantly lower in comparison to the AG (p = 0.102), however the chance of this variable to be lower for the PG was considered \"probable\". For the PG the only significant correlation observed was between RSmean and the contact time obtained in the DJ test (r = 0.641, p < 0.05). In relation to the AG, significant correlations were observed for the peak speed obtained on the progressive test until exhaustion with the RSbest (r = -0.680, p < 0.05) and RSmean (r = -0.744, p < 0.05), likewise for the amplitude of the slow phase in oxygen uptake off-kinetics with the RSbest (r = -0.756, p < 0.05) and RSmean (r = -0.794, p < 0.05). Thus, these data suggest that professional tennis players have a better performance in RS compared to amateur tennis players. However, it is not clear the importance of aerobic fitness and neuromuscular factors in the performance of this activity

Se por um lado a estimação das vazões máximas pelos métodos tradicionais, estatístico (Análise de Frequência Local - AFL) e determinístico (Cheia Máxima Provável - CMP), vem sendo alvo de críticas, por outro, a Análise de Frequência Conjugada (AFC) e o método do Hidrograma Máximo Mais Provável (HMMP), mais recentemente proposto, evidenciam-se como ferramentas promissoras. A AFC consiste da combinação entre técnicas probabilísticas e determinísticas e o HMMP utiliza os conceitos do Hidrograma Unitário Curvilíneo (HUC) de Mockus e da distribuição temporal de chuvas dada por Huff. Este trabalho tem o intuito de aplicar os métodos AFL, AFC e HMMP de maneira a avaliar os procedimentos e peculiaridades de cada método e assim possibilitar uma análise comparativa. Os referidos métodos foram aplicados para as séries de vazões dos aproveitamentos hidrelétricos UHE Sobradinho e UHE Três Marias, localizados na bacia do rio São Francisco, e a estação fluviométrica Paso de Los Libres localizada na bacia hidrográfica do rio Uruguai. Foram avaliadas a estabilidade e a sensibilidade dos métodos à extensão da série, à variação da magnitude das menores vazões das séries de valores máximos e a influência da presença de outliers, nos valores máximos determinados. As análises da estabilidade e sensibilidade apresentam diferenças máximas entre as estimativas de vazões decamilenares de 321% para a Análise de Frequência Local, 64% para a Análise de Frequência Conjugada e 82% para o Hidrograma Máximo Mais Provável. Conclusões importantes foram obtidas, dentre as quais o fato dos métodos AFC e HMMP apresentarem vantagens em relação ao método AFL para todas as análises realizadas. O método do HMMP apresentou variação pouco significativa quanto à presença de outliers e influência da presença dos menores valores, sendo considerado o mais promissor dentre os três métodos e para as séries analisadas no presente trabalho. / If, on one hand, the estimation of peak flows by traditional statistical analysis (Local Frequency Analysis - AFL) and deterministic methods (Probable Maximum Flood - PMF) has been criticized, on the other, the Conjugated Frequency Analysis (AFC) and the method of Hydrograph Maximum Most Probable (HMMP), recently proposed, are highlighted as promising tools. The AFC consists of a combination of deterministic and probabilistic techniques and HMMP uses the concepts of Curvilinear Unit Hydrograph (HUC) by Mockus and temporal distribution of rainfall given by Huff. This paper aims to apply the AFL, AFC and HMMP methods in order to assess the procedures and peculiarities of each method and thus provide a comparative analysis. The methods were applied to the series of flows of hydroelectric Sobradinho and Três Marias, located in the São Francisco basin, and Paso de Los Libres fluviometric station located in the basin of the River Uruguay. Stability and sensitivity of the methods to extend the series, the variation of the magnitude of lower flows series of maxima and the influence of the presence of outliers in certain maximums were evaluated. The stability and sensitivity analyzes presented maximum differences between estimated decamilenares flow of 321% for the Analysis of Local Frequency, 64% for the Analysis of Combined frequency and 82% for Hydrograph Maximum Most Probable. The method presented HMMP negligible variation for the presence of outliers and influence of the presence of minor amounts, and it is considered the most promising among the three methods and for the series analyzed in this work.

Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-08-11T12:24:29Z No. of bitstreams: 1 cristianodasilvabrum.pdf: 18446282 bytes, checksum: 7310bb73832b9312a18b83babb7d931d (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-08-11T13:00:25Z (GMT) No. of bitstreams: 1 cristianodasilvabrum.pdf: 18446282 bytes, checksum: 7310bb73832b9312a18b83babb7d931d (MD5) / Made available in DSpace on 2017-08-11T13:00:25Z (GMT). No. of bitstreams: 1 cristianodasilvabrum.pdf: 18446282 bytes, checksum: 7310bb73832b9312a18b83babb7d931d (MD5) Previous issue date: 2012-11-23 / FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais / INTRODUÇÃO. Os sintomas do trato urinário inferior (LUTS) têm alta prevalência, ocorrendo em 50 % dos homens com mais de 50 anos e em 90% após 80 anos e está associado à hiperplasia prostática benigna (HPB) em 50% das vezes. LUTS e HPB têm sido associados mais recentemente à síndrome metabólica, a fatores de risco cardiovascular e ao baixo nível de atividade física, porém estas associações são complexas e nãe estão bem esclarecidas. A atividade física para ser adequada deve gerar melhora da aptidão cardiorrespiratória, sendo esta avaliada pelo volume máximo de oxigênio (Vo2max). O objetivo deste trabalho é avaliar a associação do LUTS com Vo2max, flexibilidade, o nível de atividade física e variáveis antropométricas em homens com 50 a 59 anos. PACIENTES E MÉTODOS. Foi realizado um estudo caso-controle no qual o LUTS foi considerado como o desfecho e o Vo2max, a flexibilidade, o nível de atividade física e variáveis antropométricas como a exposição. Foram avaliados 100 homens com idade entre 50 e 59 anos provenientes do ambulatório de especialidades clínicas do Hospital Universitário (HU-CAS) da Universidade Federal de Juiz de Fora, sendo alocados 49 pacientes no grupo caso (com LUTS) e 51 no grupo controle (sem LUTS). Os pacientes passaram pelo seguinte protocolo experimental: anamnese, avaliação do nível de atividade física pelo Questionário Internacional de Atividade Física (IPAQ) em sua versão curta, avaliação do LUTS pelo Questionário Internacional de Sintomas Prostáticos (IPSS), avaliação antropométrica com a medida do índice de massa corpórea (IMC), relação cintura quadril (RCQ) e circunferência abdominal. Para a avaliação do Vo2max foi realizado o Polar Fitness Test e para avaliar a flexibilidade foi utilizado o teste de Sentar e Alcançar. RESULTADOS: na análise bi-variada foi identificada associação estatisticamente significativa do LUTS com o nível de atividade física (OR = 0,37, IC95% = 0,16 a 0,84, p= 0,02); com o Vo2max (OR = 0,206, IC95% = 0,086 a 0,495, p<0,001) e com a flexibilidade (OR = 0,309, IC95% = 0,130 a 0,337, p= 0,01). Porém, o modelo multivariado adotado indicou que controlando o efeito da flexibilidade e do nível de atividade física, o Vo2max foi a única variável associada de forma estatisticamente significativa com o LUTS, com Odds ratio ajustada de 0,30 ( IC95% = 0,105 a 0,875, p= 0,027). CONCLUSÃO: Homens com idade entre 50 a 59 anos com Vo2max adequado, têm aproximadamente 70% a menos de chance de desenvolver LUTS. / INTRODUCTION. Lower urinary tract symptoms (LUTS) are highly prevalent, occurring in 50% of men over 50 years old and in 90% of men over 80, and is associated with benign prostatic hyperplasia (BPH) in 50% of the cases. LUTS and BPH have more recently been associated with metabolic syndrome, cardiovascular risk factors, and low physical activity level, but these associations are complex and not well understood. Physical activity, to be considered adequate, should generate improved cardiorespiratory fitness, which is assessed by maximal oxygen uptake (VO2max). The objective of this study is to evaluate the association of LUTS with VO2max, flexibility, physical activity level, and anthropometric variables in men aged 50 to 59 years. PATIENTS AND METHODS. We conducted a case-control study in which LUTS was considered as the outcome and VO2max, flexibility, physical activity level, and anthropometric variables as the exposure variables. We evaluated 100 men aged between 50 and 59 years from the outpatient specialty clinics of the University Hospital (HU-CAS), Federal University of Juiz de Fora, assigning 49 patients to the case group (with LUTS) and 51 to the control group (without LUTS). The patients underwent the following experimental protocol: anamnesis, physical activity level assessment using the International Physical Activity Questionnaire (IPAQ) in its short version, LUTS assessment using the International Prostate Symptom Score (IPSS) Questionnaire, anthropometric assessment measuring body mass index (BMI), waist-to-hip ratio (WHR), and waist circumference. For the assessment of VO2max, the Polar Fitness Test was performed, and to assess flexibility, the Sit and Reach test was used. RESULTS: In bivariate analysis a statistically significant association was identified for LUTS with physical activity level (OR = 0.37, 95% CI = 0.16 to 0.84, p = 0.02); with VO2max (OR = 0.206, 95% CI = 0.086 to 0.495, p <0.001); and with flexibility (OR = 0.309, 95% CI = 0.130 to 0.337, p = 0.01). However, the multivariate model adopted indicated that, controlling for the effect of flexibility and of physical activity level, VO2max was the only statistically significant variable associated with LUTS, with an adjusted odds ratio of 0.30 (95% CI = 0.105 to 0.875 , p = 0.027). CONCLUSION: Men aged 50 to 59 years, with adequate VO2max, have approximately a 70% less chance of developing LUTS.

Background: Physiologic functional capacity through maximal oxygen uptake (V̇O2max) can be measured in many different ways depending on sport and qualities needed to be assessed.In handball a demanding 3000 meter (m) running test is used to evaluate V̇O2max. If this test is sport specific or if it could be replaced by a less strenuous test is unknown. Aim: The aim ofthis study was to compare performance on 3000-meter running with predicted V̇O2max from a submaximal treadmill jogging test (SMTJ) and performance of the Yo-Yo intermittentrecovery test 1 (IR1). Methods: Male handball players (n = 12) performed the 3000 m running test, the Submaximal Treadmill Jogging test and the Yo-Yo Intermittent Recovery test level 1. Measurements in seconds (s), ml ∙ kg-1 ∙ min-1 and meters where collected and correlated using Pearson r, interclass correlation. Results: A strong significant linear correlation (p &lt; 0.01) was found between performance in 3000 m running (s) and Yo-Yo IR1 performance (m), r = - 0.724 (r2 = 0.524). A weak, not significant linear correlation (p &gt; 0.05)was found between performance in 3000 m running (s) and predicted V̇O2max from submaximal treadmill test (ml ∙ kg-1 ∙ min-1), r = - 0.309 (r2 = 0.095). Conclusion: According to this study the 3000 m running test could be replaced by the Yo-Yo IR1 test or vice versa in adolescent male handball players. The submaximal treadmill test used in this study had several potential errors in estimating V̇O2max, this is probably the reason why only a weak correlation was found between the SMTJ and the 3000 m running test.

Syfte och frågeställningar: Syftet med studien var att undersöka hos vältränade om det fanns något samband mellan maximal styrka, effektutveckling och snabbhet, dvs tester som till stor del speglar anaerob kapacitet. Syftet var också att undersöka om det här fanns någon skillnad och/eller likhet mellan kvinnor och män. (1) Hur ser det eventuella sambandet ut mellan effektutveckling och maximal styrka? (2) Hur ser det eventuella sambandet ut mellan effektutveckling och snabbhet? (3) Hur ser det eventuella sambandet ut mellan maximal styrka och snabbhet? (4) Hur ser det eventuella sambandet ut, på ovanstående frågeställningar, hos kvinnor och män? Metod: Metoden var kvantitativ och laborativ, utformad för att undersöka det eventuella sambandet mellan snabbhet, maximal styrka och effektutveckling – Detta testades genom tre olika fysiologiska tester. Testerna genomfördes på en grupp bestående av 10 män (ålder 24,4±2,8 år, kroppsvikt 78,9±9,7 kg och längd 175,6±7,5 cm) och 10 kvinnor (ålder 24,1±1,7 år, kroppsvikt 65±8,0 kg och längd 167±5,7 cm) som var vältränade men hade olika idrottsbakgrund. Målet var att, utifrån den undersökta gruppen, kunna göra uttalanden om en större population. Testerna som genomfördes var 1 RM knäböj (maximal styrka), sprint 5 m, 10 m och 30 m (snabbhet) samt ett Wingate-test (effektutveckling). Med hjälp av statistikprogrammet Statistica 12.0 och beräkningsmetoden Pearson korrelationskoefficient, har rådata från testerna beräknats för att redovisa det eventuella sambandet. Resultat: Resultatet visade att det fanns, antingen ett medelstarkt samband eller ett starkt samband mellan alla tre testerna, för hela gruppen. Majoriteten av testerna visade ett starkt samband, endast mellan effektutveckling och snabbhet 5 m och 30 m var det ett medelstarkt samband, inga svaga samband hittades. De starkaste sambanden som hittades, för hela gruppen, var mellan effektutveckling och maximal styrka (r 0,90 i absoluta tal och r 0,78 i relativa tal). Män hade, totalt sett, många fler starka samband mellan de olika testerna än kvinnor, kvinnor hade endast ett enda starkt samband, vilket var mellan effektutveckling och maximal styrka. Män å andra sidan hade, med majoritet (8 av 14), ett starkt samband mellan de olika testerna, de starkaste sambanden hittades mellan effektutveckling och övriga tester. Slutsats: Det fanns ett tydligt samband mellan de olika anaeroba kapaciteterna, för hela gruppen. När resultatet redovisas för kvinnor och män enskilt, så var slutsatsen inte densamma – Kvinnor visade både svagare och färre förekommande samband mellan alla kapaciteter än män. / <p>Ämneslärarprogrammet, Specialidrott</p>

Abstract Today, the diagnosis of osteoporosis and assessment of fracture risk is based on estimation of bone mineral density (BMD) determined by dual-energy X-ray absorptiometry (DXA). A lack has been shown in the prediction of individual fracture risk using DXA-based BMD (BMDDXA). Digital radiography (DR) has eased the application of dual-energy techniques for separating bone and soft tissue, but the direct application of dual-energy digital radiography (DEDR) to determine BMD has not been investigated. Additionally, with BMD and bone mass, bone geometry affects strongly the mechanical strength of bone. Geometrical parameters can also be determined from the DR images. This study aimed to investigate the ability of DEDR to determine BMD and whether the combination of DEDR-based BMD and geometry improves the prediction of maximal load. Fracture and osteoporosis diagnoses could thus be done with one examination, i.e. with DEDR, whereas in the current routine both DR imaging and DXA examination are needed for diagnoses. Reindeer femora were imaged by DR with two different energies (79 and 100 kVp). The different geometrical parameters were also determined from the 79 kVp images. The BMD measured by DEDR (BMDDEDR) were calculated using the calculation principle of DXA. The ability of BMDDEDR to predict BMDDXA was investigated. The femora were mechanically tested in an axial loading configuration with the shaft in a vertical position to determine mechanical parameters. The best combination of BMDDEDR and geometrical parameters to predict bone maximal load was explored. BMDDXA was used for comparison. Significant moderate to high linear correlations were observed in all regions of the upper femur (femoral neck, Ward’s triangle, trochanter and inter-trochanter) between BMDDEDR and BMDDXA. BMDDEDR of the femoral neck and BMDDXA of the femoral neck predicted maximal load similarly. The best combination of parameters to predict maximal load was BMDDEDR at Ward’s triangle, femoral shaft diameter (FSD) and femoral shaft axis length (FNAL) (r = 0.79, p &lt; 0.05). The study shows that DEDR is a suitable method to determine BMD in vitro and the combination of BMD and geometry improves the prediction of bone maximal load when compared to BMDDEDR of femoral neck or trochanter only. The thesis also includes unpublished data from a preliminary human study. / Tiivistelmä Osteoporoosin diagnosointi ja murtumariskin määrittäminen perustuvat kaksienergisellä röntgenabsorptiometrialla (DXA) mitattavaan luun mineraalitiheyden (BMD) arviointiin. DXA:lla määritetyn luun mineraalitiheyden (BMDDXA) on kuitenkin osoitettu olevan puutteellinen murtumariskin yksilöllisessä ennustamisessa. Digitaalinen röntgenkuvaus (DR) on helpottanut sellaisten kaksienergisten tekniikoiden toteuttamista, joissa luu ja pehmytkudos on eroteltu toisistaan. Kaksienergisen digitaalisen röntgenkuvausmenetelmän (DEDR) soveltamista BMD:n määrittämiseen ei ole tutkittu. BMD:n ja luun massan lisäksi on luun geometrialla vahva vaikutus luun mekaaniseen lujuuteen. Geometriset parametrit voidaan määrittää niin ikään digitaalisista röntgenkuvista. Tässä työssä tutkittiin, pystytäänkö DEDR:llä määrittämään BMD sekä parantaako DEDR:llä mitattujen BMD:n ja geometrian yhdistelmä luun maksimikuormituksen ennustetta. Näin ollen murtuma- ja osteoporoosidiagnoosit voitaisiin tehdä yhdellä tutkimuksella (DEDR), kun nykyisin diagnoosit vaativat sekä digitaalisen röntgenkuvauksen että DXA-tutkimuksen. Poron reisiluut kuvattiin digitaalisen röntgenlaitteen kahdella eri kuvausjännitteellä (79 ja 100 kVp). 79 kVp -kuvista määritettiin myös erilaiset geometriaparametrit. BMD laskettiin DEDR-kuvista (BMDDEDR) DXA:n laskentaperiaatetta käyttäen. BMDDEDR:n kyky ennustaa BMDDXA:a tutkittiin. Maksimikuormituksen selvittämiseksi reisiluut testattiin mekaanisesti aksiaalisuunnassa varren ollessa pystysuorassa asennossa. BMDDEDR- ja geometriaparametreista määritettiin paras yhdistelmä maksimikuorman ennustamiseen. BMDDXA-arvoja käytettiin analysoinnissa vertailun vuoksi. BMDDEDR- ja BMDDXA-arvojen välillä havaittiin merkitsevä keskinkertainen tai korkea korrelaatio kaikissa mielenkiintoalueissa (reisiluun kaula, Wardin kolmio, sarvennoisen alue ja reisiluun varren alue). Wardin kolmiosta mitatun BMD:n (WABMDDEDR), reisiluun varren halkaisijan (FSD) ja reisiluun kaulan kautta kulkevan akselin (FNAL) yhdistelmä ennusti parhaiten luun haurautta (r = 0.79, p &lt; 0.05). Tutkimus osoittaa, että DEDR on sopiva menetelmä BMD:n määrittämiseen tutkimusolosuhteissa ja että BMD:n ja geometrian yhdistelmä parantaa maksimikuormituksen ennustetta pelkästään reisiluun kaulasta tai sarvennoisesta mitattuun BMDDEDR:iin verrattuna. Väitöskirja sisältää myös julkaisemattomia tuloksia alustavista ihmistutkimuksista.

On s'intéresse, dans cette thèse, à des questions concernant le nombre maximum de points rationnels d'une courbe singulière définie sur un corps fini, sujet qui, depuis Weil, a été amplement abordé dans le cas lisse. Cette étude se déroule en deux temps. Tout d'abord on présente une construction de courbes singulières de genres et corps de base donnés, possédant un grand nombre de points rationnels : cette construction, qui repose sur des notions et outils de géométrie algébrique et d'algèbre commutative, permet de construire, en partant d'une courbe lisse X, une courbe à singularités X', de telle sorte que X soit la normalisée de X', et que les singularités ajoutées soient rationnelles sur le corps de base et de degré de singularité prescrit. Ensuite, en utilisant une approche euclidienne, on prouve une nouvelle borne sur le nombre de points fermés de degré deux d'une courbe lisse définie sur un corps fini.La combinaison de ces résultats, à priori indépendants, permet notamment d'étudier le problème de savoir quand la borne d'Aubry-Perret, analogue de la borne de Weil dans le cas singulier, est atteinte. Cela nous amène de façon naturelle à l'étude des propriétés des courbes maximales et, lorsque la cardinalité du corps de base est un carré, à l'analyse du spectre des genres de ces dernières. / In this PhD thesis, we focus on some issues about the maximum number of rational points on a singular curve defined over a finite field. This topic has been extensively discussed in the smooth case since Weil's works. We have split our study into two stages. First, we provide a construction of singular curves of prescribed genera and base field and with many rational points: such a construction, based on some notions and tools from algebraic geometry and commutative algebra, yields a method for constructing, given a smooth curve X, another curve X' with singularities, such that X is the normalization of X', and the added singularities are rational on the base field and with the prescribed singularity degree. Then, using a Euclidian approach, we prove a new bound for the number of closed points of degree two on a smooth curve defined over a finite field.Combining these two a priori independent results, we can study the following question: when is the Aubry-Perret bound (the analogue of the Weil bound in the singular case) reached? This leads naturally to the study of the properties of maximal curves and, when the cardinality of the base field is a square, to the analysis of the spectrum of their genera.

In this thesis we have investigated two different types of problems in multivariable operator theory. The first one deals with the defect sequence for contractive tuples and maximal con-tractive tuples. These condone deals with the wandering subspaces of the Bergman space and the Dirichlet space over the polydisc. These are described in thefollowing two sections. (I) The Defect Sequence for ContractiveTuples LetT=(T1,...,Td)bead-tuple of bounded linear operators on some Hilbert space H. We say that T is a row contraction, or, acontractive tuplei f the row operator (Pl refer the abstract pdf file)