Flexural strengthening by means of a arc overlay in the tension zone

Dissertação para obtenção do Grau de Mestre em Engenharia Civil – Perfil de Estruturas

Transfer zone of prestressed CFRP reinforcement applied according to NSM technique for strengthening of RC structures

This study presents an experimental program to assess the tensile strain distribution along prestressed carbon fiber reinforced polymer (CFRP) reinforcement flexurally applied on the tensile surface of RC beams according to near surface mounted (NSM) technique. Moreover, the current study aims to propose an analytical formulation, with a design framework, for the prediction of distribution of CFRP tensile strain and bond shear stress and, additionally, the prestress transfer length. After demonstration the good predictive performance of the proposed analytical approach, parametric studies were carried out to analytically evaluate the influence of the main material properties, and CFRP and groove cross section on the distribution of the CFRP tensile strain and bond shear stress, and on the prestress transfer length. The proposed analytical approach can also predict the evolution of the prestress transfer length during the curing time of the adhesive by considering the variation of its elasticity modulus during this period.

Shear strengthening of reinforced concrete beams with SHCC-FRP panels

Tese de Doutoramento em Engenharia Civil

Population dynamics of the pea crab Austinixa aidae (Brachyura, Pinnotheridae): a symbiotic of the ghost shrimp Callichirus major (Thalassinidea, Callianassidae) from the southwestern Atlantic

The Pinnotheridae family is one of the most diverse and complex groups of brachyuran crabs, many of them symbionts of a wide variety of invertebrates. The present study describes the population dynamics of the pea crab Austinixa aidae (Righi, 1967), a symbiont associated with the burrows of the ghost shrimp Callichirus major (Say, 1818). Individuals (n = 588) were collected bimonthly from May, 2005 to September, 2006 along a sandy beach in the southwestern Atlantic, state of São Paulo, Brazil. Our data indicated that the population demography of A. aidae was characterized by a bimodal size-frequency distribution (between 2.0 and 4.0 mm and between 8.0 and 9.0 mm CW) that remained similar throughout the study period. Sex ratio does not differ significantly from 1:1 (p > 0.05), which confirms the pattern observed in other symbiontic pinnotherids. Density values (1.72 ± 1.34 ind. • ap.-1) are in agreement with those found for other species of the genus. The mean symbiosis incidence (75.6%) was one of the highest among species of the Pinnotheridae family, but it was the lowest among the three studied species of the genus. Recruitment pattern was annual, beginning in May and peaking in July, in both years, after the peak of ovigerous females in the population (from March to May). Our findings describe ecological and biological aspects of A. aidae similar to those of other species of this genus, even from different geographic localities.

The tectonically controlled emplacement of a vertically sheeted gabbro-pyroxenite intrusion: Feeder-zone of an ocean-island volcano (Fuerteventura, Canary Islands)

The Miocene PX1 gabbro-pyroxenite pluton, Fuerteventura, Canary Islands, is a 3.5 x 5.5 km shallow-level intrusion (0.15-0.2 GPa and 1100-1120 degrees C), interpreted as the feeder-zone to an ocean-island volcano. It displays a vertical magmatic banding expressed in five 50 to 100 metre-wide NNE-SSW trending alkaline gabbro sequences alternating with pyroxenites. This emplacement geometry was controlled by brittle to ductile shear zones, generated by a regional E-W extensional tectonic setting that affected Fuerteventura during the Miocene. At a smaller scale, the PX1 gabbro and pyroxenite bands consist of metre-thick differentiation units, which suggest emplacement by periodic injection of magma pulses as vertical dykes that amalgamated, similarly to a sub-volcanic sheeted dyke complex. Individual dykes underwent internal differentiation following a solidification front parallel to the dyke edges. This solidification front may have been favoured by a significant lateral/horizontal thermal gradient, expressed by the vertical banding in the gabbros, the fractionation asymmetry within individual dykes and the migmatisation of the wall rocks. Pyroxenitic layers result from the fractionation and accumulation of clinopyroxene +/- olivine +/- plagioclase crystals from a mildly alkaline basaltic liquid. They are interpreted as truncated differentiation sequences, from which residual melts were extracted at various stages of their chemical evolution by subsequent dyke intrusions, either next to or within the crystallising unit. Compaction and squeezing of the crystal mush is ascribed to the incoming and inflating magma pulses. The expelled interstitial liquid was likely collected and erupted along with the magma flowing through the newly injected dykes. Clinopyroxene mineral orientation - as evidenced by EBSD and micro X-ray tomography investigations - displays a marked pure-shear component, supporting the interpretation of the role of compaction in the generation of the pyroxenites. Conversely, gabbro sequences underwent minor melt extraction and are believed to represent crystallised coalesced magma batches emplaced at lower rates at the end of eruptive cycles. Clinopyroxene orientations in gabbros record a simple shear component suggesting syn-magmatic deformation parallel to observed NNE-SSW trending shear zones induced by the regional tensional stress field. This emplacement model implies a crystallisation time of 1 to 5 years for individual dykes, consistent with PX1 emplacement over less than 0.5 My. A minimum amount of approximately 150 km(3) of magma is needed to generate the pluton, part of it having been erupted through the Central Volcanic Centre of Fuerteventura. If the regional extensional tectonic regime controls the PX1 feeder-zone initiation and overall geometry, rates and volumes of magma depend on other, source-related factors. High injection rates are likely to induce intrusion growth rates larger than could be accommodated by the regional extension. In this case, dyke intrusion by propagation of a weak tip, combined with the inability of magma to circulate through previously emplaced and crystallised dykes could result in an increase of non-lithostatic pressure on previously emplaced mushy dyke walls; thus generating strong pure-shear compaction within the pluton feeder-zone and interstitial melt expulsion. These compaction-dominated processes are recorded by the cumulitic pyroxenite bands. (C) 2010 Elsevier B.V. All rights reserved.

A study of the cambial zone and conductive phloem of common beech (Fagus sylvatica L.) using an image analysis method. I. Influence of tree age on the structure

Quantification is a major problem when using histology to study the influence of ecological factors on tree structure. This paper presents a method to prepare and to analyse transverse sections of cambial zone and of conductive phloem in bark samples. The following paper (II) presents the automated measurement procedure. Part I here describes and discusses the preparation method, and the influence of tree age on the observed structure. Highly contrasted images of samples extracted at breast height during dormancy were analysed with an automatic image analyser. Between three young (38 years) and three old (147 years) trees, age-related differences were identified by size and shape parameters, at both cell and tissue levels. In the cambial zone, older trees had larger and more rectangular fusiform initials. In the phloem, sieve tubes were also larger, but their shape did not change and the area for sap conduction was similar in both categories. Nevertheless, alterations were limited, and demanded statistical analysis to be identified and ascertained. The physiological implications of the structural changes are discussed.

Reliability of current estimates of schistosomiasis prevalence in the Rainforest Zone of the state of Pernambuco, Northeastern Brazil

The Program for Schistosomiasis Control within the Unified Health System (PCE-SUS) was implemented by 1999 in the Rainforest Zone or "Zona da Mata" of Pernambuco (ZMP) aiming to carry out biennial stool surveys of whole populations through municipal health organs followed by treatment of the positives through the local units of the Family Health Program (PSF). Yearly reports from the Health Department of Pernambuco State (SES/PE) from 2002 to 2004 on the PCE-SUS surveys were assessed to evaluate whether the current estimates of prevalence in the municipalities of the ZMP are based on reliable samples so as to allow considerations on the real situation of schistosomiasis in that area. The surveys carried out in that period did not follow the major principles underlying sampling design, thus posing problems in both precision and validity of the estimates. Only 12 out of 43 municipalities had minimally reliable estimates: five with moderate prevalence (10-50%) and seven with low prevalence (< 10%). Surveys with appropriate sampling procedures aimed either at representative target groups (school-aged children) or communities are recommended for the ZMP and other endemic areas not only to provide reliable information on the current situation of schistosomiasis but also to plan adequate control strategies.

Melt topology and chemistry during partial melting in contact aureoles : an experimental study and field example

This study was initiated to investigate partial melting within the high-grade metamorphic rocks beneath the Little Cottonwood contact aureole (Utah, USA), in order to understand the melt generation, melt migration, and geometry of initial melt distribution on grain scale during crustal anatexis. The emplacement of the Little Cottonwood stock produced a contact aureole in the pelitic host rocks of the Big Cottonwood formation (BC). Metamorphic isogrades in pelitic rocks range form biotite to 2nd sillimanite grade as a function of distance from the contact. Migmatites are restricted to the highest grade and resulted form partial melting of the BC formation rocks. First melt was produced by a combined muscovite/biotite dehydration reaction in the sillimanite + k-feldspar stability field. Melt extraction from the pelites resulted in restites (magnetite + cordierite + alumosilicate ± biotite) surrounded by feldspar enriched quartzite zones. This texture is the result of gradual infiltration of partial melts into the quartzite. Larger, discrete melt accumulation occurred in extensional or transpressional domains such as boudin necks, veins, and ductile shear zones. Melt composition are Si02- rich, crystallized as pegmatites, and apparently were very mobile. They were able to infiltrate the quartzite pervaisivly. These melts are similar in composition to first melts produced in the hydrothermal partial melt experiments at 2kbar between 700 - 800°C on fine grained high metamorphic rocks (andalusite-cordierited-biotite-zone) of the BC formation. The experimental melts are water rich and in disequilibrium with the melting rock. Initial melt composition is heterogeneous for short run duration, reflective a lack of chemical equilibrium between individual melt pools. Rock core scale heterogeneity decreased with time indicating partial homogenization of melt compositions. A simultaneous shift of melt composition to higher silica content with time was observed. The silica content of the melt increased due to local melt/mineral reactions. Melt textures indicate that reactive melt transport is most efficient along grain boundaries rimmed by dissimilar grains. Melt heterogeneity resulted in chemical potential gradients which are major driving forces for initial melt migration and govern melt distribution during initial melting. An additional subject of the thesis is the crystal size distributions of opaque minerals in a fine-grained, high-grade meta-pelite of the Big Cottonwood which were obtained from 3D X-ray tomography (uCT) and 2D thin section analysis. µCT delivers accurate size distributions within a restricted range (~ a factor of 20 in size in a single 3D image), while the absolute number of crystals is difficult to obtain from these sparsely distributed, small crystals on the basis of 2D images. Crystal size distributions obtained from both methods are otherwise similar. - Ce travail de recherche a été entrepris dans le but d'étudier les processus de fusion partielle dans les roches fortement métamorphiques de l'auréole de contact de Little Cottonwood (Utah, USA) et ceci afin de comprendre la génération de liquide de fusion, la migration de ces liquides et la géométrie de la distribution initiale des liquides de fusion à l'échelle du grain durant l'anatexie de la croûte. L'emplacement du petit massif intrusif de Little Cottonwood a produit une auréole de contact dans les roches pélitiques encaissantes appartenant à la Foimation du Big Cottonwood (BC). Les isogrades métamorphiques dans les roches pélitiques varient de l'isograde de la biotite à la deuxième isograde de la sillimanite en fonction de la distance par rapport au massif intrusif. Les migmatites sont restreintes aux zones montrant le plus haut degré métamorphique et résultent de la fusion partielle des roches de la Formation de BC. Le premier liquide de fusion a été produit par la réaction de déshydratation combinée de la muscovite et de la biotite dans le champ de stabilité du feldspath potassique Pt de la sillimanite. L'extraction du liquide de fusion des pélites forme des restites (magnétites + cordiérite + aluminosilicate ± biotite) entourées par des zones de quartzites enrichies en feldspath. Cette texture est le résultat de l'infiltration graduelle du liquide de fusion partielle dans les quartzites. Des accumulations distinctes et plus larges de liquide de fusion ont lieu dans des domaines d'extension ou de transpression tels que les boudins, les veines, et les zones de cisaillement ductile. La composition des liquides de fusion est similaire à celle des liquides pegmatoïdes, et ces liquides sont apparemment très mobiles et capables d'infiltrer les quartzites. Ces liquides de fusion ont la même composition que les premiers liquides produits dans les expériences hydrotheunales de fusion partielle à 2kbar et entre 700-800° C sur les roches finement grenues et hautement métamorphiques (andalousite-cordiérite-biotite zone) de la Formation de BC. Les liquides de fusion obtenus expérimentalement sont riches en eau et sont en déséquilibre avec la roche en fusion. La composition initiale des liquides de fusion est hétérogène pour les expériences de courte durée et reflète l'absence d'équilibre chimique entre les différentes zones d'accumulation des liquides de fusion. L'hétérogénéité à l'échelle du noyau s'estompe avec le temps et témoigne de l'homogénéisation de la composition des liquides de fusion. Par ailleurs, on observe parallèlement un décalage de la composition des liquides vers des compositions plus riches en silice au cours du temps. Le contenu en silice des liquides de fusion évolue vers un liquide pegmatitique en raison des réactions liquides/minéraux. Les textures des liquides de fusion indiquent que le transport des liquides est plus efficace le long des bordures de grains bordés par des grains différents. Aucun changement apparent du volume total n'est visible. L'hétérogénéité des liquides s'accompagne d'un gradient de potentiel chimique qui sert de moteur principal à la migration des liquides et à la distribution des liquides durant la fusion. Un sujet complémentaire de ce travail de thèse réside dans l'étude de la distribution de la taille des cristaux opaques dans les pélites finement grenues et fortement métamorphiques de la Formation de Big Cottonwood. Les distributions de taille ont été obtenues suite à l'analyse d'images 3D acquise par tomographie ainsi que par analyse de lames minces. La microtomographie par rayon X fournit une distribution de taille précise sur une marge restreinte (- un facteur de taille 20 dans une seule image 3D), alors que le nombre absolu de cristaux est difficile à obtenir sur la base d'image 2D en raison de la petite taille et de la faible abondance de ces cristaux. Les distributions de taille obtenues par les deux méthodes sont sinon similaire. Abstact: Chemical differentiation of the primitive Earth was due to melting and separation of melts. Today, melt generation and emplacement is still the dominant process for the growth of the crust. Most granite formation is due to partial melting of the lower crust, followed by transport of magma through the crust to the shallow crust where it is emplaced. Partial melting and melt segregation are essential steps before such a granitic magma can ascent through the crust. The chemistry and physics of partial melting and segregation is complex. Hence detailed studies, in which field observations yield critical information that can be compared to experimental observations, are crucial to the understanding of these fundamental processes that lead and are leading to the chemical stratification of the Earth. The research presented in this thesis is a combined field and experimental study of partial melting of high-grade meta-pelitic rocks of the Little Cottonwood contact aureole (Utah, USA). Contact metamorphic rocks are ideal for textural studies of melt generation, since the relatively short times of the metamorphic event prevents much of the recrystallization which plagues textural studies of lower crustal rocks. The purpose of the study is to characterize melt generation, identify melting reactions, and to constrain melt formation, segregation and migration mechanisms. In parallel an experimental study was undertaken to investigate melt in the high grade meta pelitic rocks, to confirm melt composition, and to compare textures of the partial molten rock cores in the absence of deformation. Results show that a pegmatoidal melt is produced by partial melting of the pelitic rocks. This melt is highly mobile. It is capable of pervasive infiltration of the adjacent quartzite. Infiltration results in rounded quartz grains bordered by a thin feldspar rim. Using computed micro X-ray tomography these melt networks can be imaged. The infiltrated melt leads to rheological weakening and to a decompaction of the solid quartzite. Such decompaction can explain the recent discovery of abundant xenocrysts in many magmas, since it favors the isolation of mineral grains. Pervasive infiltration is apparently strongly influenced by melt viscosity and melt-crystal wetting behavior, both of which depend on the water content of melt and the temperature. In all experiments the first melt is produced on grain boundaries, dominantly by the local minerals. Grain scale heterogeneity of a melting rock leads thus to chemical concentration gradients in the melt, which are the driving force for initial melt migration. Pervasive melt films along grain boundaries leading to an interconnected network are immediately established. The initial chemical heterogeneities in the melt diminish with time. Résumé large public: La différenciation chimique de la Terre primitive est la conséquence de la fusion des roches et de la séparation des liquides qui en résultent. Aujourd'hui, la production de liquide magmatique est toujours le mécanisme dominant pour la croissance de la croûte terrestre. Ainsi la formation de la plupart des granites est un processus qui implique la production de magma par fusion partielle de la croûte inférieure, la migration de ces magmas à travers la croûte et finalement son emplacement dans les niveaux superficielle de la croûte terrestre. Au cours de cette évolution, les processus de fusion partielle et de ségrégation sont des étapes indispensables à l'ascension des granites à travers la croûte. Les conditions physico-chimiques nécessaires à la fusion partielle et à l'extraction de ces liquides sont complexes. C'est pourquoi des études détaillées des processus de fusion partielle sont cruciales pour la compréhension de ces mécanismes fondamentaux responsables de la stratification chimique de la Terre. Parmi ces études, les observations de terrain apportent notamment des informations déterminantes qui peuvent être comparées aux données expérimentales. Le travail de recherche présenté dans ce mémoire de thèse associe études de terrain et données expérimentales sur la fusion partielle des roches pélitiques de haut degré métamorphiques provenant de l'auréole de contact de Little Cottonwood (Utah, USA). Les roches du métamorphisme de contact sont idéales pour l'étude de la folination de liquide de fusion. En effet, la durée relativement courte de ce type d'événement métamorphique prévient en grande partie la recristallisation qui perturbe les études de texture des roches dans la croûte inférieure. Le but de cette étude est de caractériser la génération des liquides de fusion, d'identifier les réactions responsables de la fusion de ces roches et de contraindre la formation de ces liquides et leur mécanisme de ségrégation et de migration. Parallèlement, des travaux expérimentaux ont été entrepris pour reproduire la fusion partielle de ces roches en laboratoire. Cette étude a été effectuée dans le but de confirmer la composition chimique des liquides, et de comparer les textures obtenues en l'absence de déformation. Les résultats montrent qu'un liquide de fusion pegmatoïde est produit par fusion partielle des roches pélitiques. La grande mobilité de ce liquide permet une infiltration pénétrative dans les quarzites. Ces infiltrations se manifestent par des grains de quartz arrondis entourés par une fine bordure de feldspath. L'utilisation de la tomography à rayons X a permis d'obtenir des images de ce réseau de liquide de fusion. L'infiltration de liquide de fusion entraîne un affaiblissement de la rhéologie de la roche ainsi qu'une décompaction des quartzites massifs. Une telle décompaction peut expliquer la découverte récente d'abondants xénocristaux dans beaucoup de magmas, puisque elle favorise l'isolation des minéraux. L'infiltration pénétrative est apparemment fortement influencée par la viscosité du fluide de fusion et le comportement de la tension superficielle entre les cristaux et le liquide, les deux étant dépendant du contenu en eau dans le liquide de fusion et de la température. Dans toutes les expériences, le premier liquide est produit sur les bordures de grains, principalement par les minéraux locaux. L'hétérogénéité à l'échelle des grains d'une roche en fusion conduit donc à un gradient de concentration chimique dans le liquide, qui sert de moteur à l'initiation de la migration du liquide. Des fines couches de liquide de fusion le long de bordures de grains formant un réseau enchevêtré s'établit immédiatement. Les hétérogénéités chimiques initiales dans le liquide s'estompent avec le temps.

Detailed 3D seismic imaging of a fault zone beneath Lake Geneva, Switzerland

An efficient high-resolution (HR) three-dimensional (3D) seismic reflection system for small-scale targets in lacustrine settings was developed. In Lake Geneva, near the city of Lausanne, Switzerland, the offshore extension of a complex fault zone well mapped on land was chosen for testing our system. A preliminary two-dimensional seismic survey indicated structures that include a thin (<40 m) layer of subhorizontal Quaternary sediments that unconformably overlie south-east-dipping Tertiary Molasse beds and a major fault zone (Paudeze Fault Zone) that separates Plateau and Subalpine Molasse (SM) units. A 3D survey was conducted over this test site using a newly developed three-streamer system. It provided high-quality data with a penetration to depths of 300 m below the water bottom of non-aliased signal for dips up to 30degrees and with a maximum vertical resolution of 1.1 m. The data were subjected to a conventional 3D processing sequence that included post-stack time migration. Tests with 3D pre-stack depth migration showed that such techniques can be applied to HR seismic surveys. Delineation of several horizons and fault surfaces reveals the potential for small-scale geologic and tectonic interpretation in three dimensions. Five major seismic facies and their detailed 3D geometries can be distinguished. Three fault surfaces and the top of a molasse surface were mapped in 3D. Analysis of the geometry of these surfaces and their relative orientation suggests that pre-existing structures within the Plateau Molasse (PM) unit influenced later faulting between the Plateau and SM. In particular, a change in strike of the PM bed dip may indicate a fold formed by a regional stress regime, the orientation of which was different from the one responsible for the creation of the Paudeze Fault Zone. This structure might have later influenced the local stress regime and caused the curved shape of the Paudeze Fault in our surveyed area.

Formation of chlorite during thrust fault reactivation. Record of fluid origin and P-T conditions in the Monte Perdido thrust fault (southern Pyrenees)

The chemical and isotopic compositions of clay minerals such as illite and chlorite are commonly used to quantify diagenetic and low-grade metamorphic conditions, an approach that is also used in the present study of the Monte Perdido thrust fault from the South Pyrenean fold-and-thrust belt. The Monte Perdido thrust fault is a shallow thrust juxtaposing upper Cretaceous-Paleocene platform carbonates and Lower Eocene marls and turbidites from the Jaca basin. The core zone of the fault, about 6 m thick, consists of intensely deformed clay-bearing rocks bounded by major shear surfaces. Illite and chlorite are the main hydrous minerals in the fault zone. Illite is oriented along cleavage planes while chlorite formed along shear veins (< 50 mu m in thickness). Authigenic chlorite provides essential information about the origin of fluids and their temperature. delta O-18 and delta D values of newly formed chlorite support equilibration with sedimentary interstitial water, directly derived from the local hanging wall and footwall during deformation. Given the absence of large-scale fluid flow, the mineralization observed in the thrust faults records the P-T conditions of thrust activity. Temperatures of chlorite formation of about 240A degrees C are obtained via two independent methods: chlorite compositional thermometers and oxygen isotope fractionation between cogenetic chlorite and quartz. Burial depth conditions of 7 km are determined for the Monte Perdido thrust reactivation, coupling calculated temperature and fluid inclusion isochores. The present study demonstrates that both isotopic and thermodynamic methods applied to clay minerals formed in thrust fault are useful to help constrain diagenetic and low-grade metamorphic conditions.

Kinetics of crystal growth and equilibrium domains in eclogite of the Sesia Zone, Western Alps

Kinetics of crystal growth and equilibrium domains in eclogite of the Sesia Zone, Western Alps Darbellay Bastien Institut de Minéralogie et Géochimie Résumé grand public Comme toute matière, la roche est sensible à son environnement et cherche à s'adapter pour acquérir un état stable (état d'équilibre). Les changements des conditions physiques (température et pression) vont ainsi impliquer des modifications dans la roche. Le métamorphisme est l'étude de ces changements. Les minéraux qui constituent la roche peuvent modifier, leur structure, leur chimie ou être remplacer par d'autres minéraux plus stables. Il est ainsi crucial de déterminer les processus responsables et limitant de la croissance minérale. Trois processus permettent la croissance ; (1) la dissolution des éléments du réactant, (2) le transport de ces éléments vers le site de croissance, (3) l'incorporation de ces éléments dans la nouvelle structure. Cette thèse se focalise sur les structures des minéraux de haute pression (forme, zonation chimique, structure interne) pour essayer de déterminer les facteurs importants à l'origine de leur état final. Les zones d'étude se situent dans la zone de Sésia. La première partie traite de la problématique liée à l'incorporation d'un élément dans une structure minérale. A l'image de la croissance humaine, les irrégularités minéralogiques permettent de mettre en lumière un dysfonctionnement de la croissance due à un excès ou à une carence d'un élément. Bien dosé, cet élément est cependant essentiel à la croissance. Les zoisites (épidotes) des métabasites de la région de Cima di Bonze montrent une zonation chimique en sablier. Dans cette zonation la teneur en fer excède la capacité maximum que peut contenir la structure orthorhombique de la zoisite. Des défauts de structure permettent l'accommodation de cet excès. La zoisite peut ainsi adapter sa structure pour permettre l'incorporation d'une relativement grande quantité de fer. Les études précédentes montraient, pour des conditions similaires, la formation de deux épidotes distinctes. La deuxième partie se penche sur la compétition entre le minéral qui fait sa croissance et les minéraux (réactants) qui l'entourent. Les métapélites de la région du Monte Mucrone contiennent des grenats atollaires. Des études détaillées de la texture et de la zonation chimique du grenat ainsi qu'une modélisation thermodynamique ont permis de mieux cerner les facteurs importants responsables de la forme atollaire. Cette structure est obtenue par un changement du comportement de la croissance du grenat le long d'un chemin P-T hercynien. Dans un premier stade, le grenat croît rapidement et consume peu le quartz de la matrice. La croissance se fait ainsi le long des jointures des grains de quartz. Dans un second temps, les changements de conditions PT donnent une croissance lente du grenat et une forte consommation du quartz. Le grenat peut ainsi développer sa forme dodécaédrale classique. La troisième partie s'intéresse aux distances de transport par diffusion d'un élément (ici l'argon) durant la haute pression. Pour ce faire, un profile d'âges 40Ar/39Ar sur biotite a été mesuré depuis un veine de haute pression riche en argon jusque dans son encaissant (granitoïd du Monte Mucrone). Le profile montre une répartition des âges suivant une courbe de diffusion. Le transport se fait sur une longueur de deux centimètre avec l'aide d'un fluide. Il est réduit à une échelle millimétrique quand la phase fluide disparaît. Cette étude montre ainsi les difficultés de transport des éléments durant la haute pression ne permettant pas un rééquilibrage de la roche à grande échelle. Kinetics of crystal growth and equilibrium domains in eclogite of the Sesia Zone, Western Alps Darbellay Bastien Institut de Minéralogie et Géochimie Résumé de thèse Les processus de croissance (diffusion des éléments et les réactions d'interface) et les conditions dans lesquelles les minéraux grandissent (température, pression, fluide, composition chimique de la roche), déterminent la texture ainsi que la zonation des minéraux. Cette thèse se focalise, par le biais de textures peu communes, sur trois différents processus impliqués dans la croissance minérale à haute pression (Zone de Sésia, Alpes de l'Ouest, Italie). L'incorporation d'un élément dans une structure minérale ne peut se faire que dans des sites en accord avec la taille et la charge ionique de l'élément. De plus, la balance de charge doit être maintenue dans le minéral. La régularité de la structure cristalline fixe ainsi une limite maximum de concentration d'un élément donné. Les zoisites provenant des métabasites de la région de Cima di Bonze montrent des zonations en sablier caractérisées par une concentration anormale en fer. La zonation se marque par une différente teinte de biréfringence et par un plus grand angle d'extinction que le reste de la zoisite. Une inter-croissance de clinozoisite à l'intérieur de la structure orthorhombique de la zoisite peut ainsi être suspectée. Les analyses XRD (diffraction des rayons x) ainsi que les analyses Raman ne confirment pas cette suspicion. Seules les analyses TEM (microscope à électrons transmis) montrent des défauts de structure pouvant être interprétés comme des modules de clinozoisite. Ils ne peuvent cependant pas être considérés comme une phase thermodynamique. Un nouveau trou d'immiscibilité entre deux zoisite (X ep= 0.1 and Xep = 0.15) a ainsi pu être établi. Dans les métapélites la région du Monte Mucrone, des grenats fortement zonés montrent une évolution texturale singulière. Ils présentent une forme initiale de `champignon' qui se développe pour former une structure atollaire finale. L'étude conjuguée de la structure 3D et des zonations, ainsi que l'établissement d'un model thermodynamique, indiquent que ces structures proviennent de deux épisodes de croissances : (1) La croissance du grenat durant un chemin prograde hercynien (de 525 °C et 6.2 kbar à 640 °C et 9 kbar) permet la formation des textures atollaires. Elles sont le résultat d'une croissance poecilitique initiale suivie d'une croissance idiomorphique du grenat. (2) La structure est rendue plus complexe par la cristallisation d'un grenat homogène tout autour ainsi qu'à l'intérieur du grenat hercynien durant la haute pression alpine (550 °C and 20 kbar). L'arrivée de l'eau durant la haute pression facilite le transport d'éléments et permet une cristallisation rapide du grenat. La diffusion peut être un facteur limitant de la croissance minéralogique. Elle a aussi une grande importance pour la géochronologie. Une veine de haute pression à l'intérieur du granitoïde du Monte Mucrone a été étudiée dans le but de déterminer la distance de diffusion de l'argon. Le profile d'âges 40Ar/39Ar sur biotites, établi de la veine vers le métagranitoïde, suit une courbe de diffusion. Les âges sont élevés proche de la veine (800 Ma) puis décroissent jusqu'à des âges homogènes (170-150 Ma) à deux centimètres de la veine. La présence de fluide, marqué par de hautes concentrations en chlore, permet une diffusion centimétrique. Cependant, la distance est réduite à une échelle millimétrique quand le fluide est absent. Les très faibles distances de diffusion préservent les âges pré-alpins et impliquent un événement géologique pour les âges de 170-150 Ma. Kinetics of crystal growth and equilibrium domains in eclogite of the Sesia Zone, Western Alps Darbellay Bastien Institut de Minéralogie et Géochimie Thesis abstract Rock textures and zonings are the consequence of growth processes (element diffusion and interface reaction) steered by the environment in which they grew (pressure, differential stress, temperature, fluid and rock composition). The thesis presented here focuses on three different topics, each of it dealing with aspects of mineral growth processes during subduction, in a high-pressure environment. All studies were conducted in the Sesia Zone of the Western European Alps, Italy. The first study addresses the crystallography and geochemistry of element incorporation in zoisite, one of the major hydrous minerals found in subduction zone rocks. Elements can be incorporated into a mineral structure only on crystallographic sites that offer enough space for the ion and the overall charge balance has to be maintained. Element concentrations are hence limited. Incorporation of some elements produces complex zoning, including hourglass like patterns, which are the focus of the first contribution. Zoisites from Cima di Bonze (Sesia Zone) show spectacular hourglass zoning defined by Fe-content variations. The hourglass zones have a distinct birefringence and a different extinction angle than the regular part of the zoisite. We show by detailed XRD (X-ray diffraction) and confocal Raman analyses that the high Fe-zones are nevertheless zoisite, and not clinozoisite as one might expect. High resolution TEM (transmission electron microscopy) analyses show planar defects on (100) that can be interpreted as small-scale clinozoisite modules. However, these clinozoisites cannot be interpreted as a distinctive thermodynamic phase and the entire mineral has to be considered as zoisite. The miscibility gap between two zoisites (Xep = 0.1 and Xep = 0.15) can be then definite at 550 ± 50°C and 14 to 20 Kbar. Strongly zoned garnets in quartz rich metapelite from the Monte Mucrone area (Sesia Zone) show evolution form 3D mushroom to atoll structure. The second contribution presents textural investigations, garnet zoning and thermodynamic modeling that demonstrate that atoll garnets are the result of two distinctive growth events. (1) Garnet atoll structure is already formed during a prograde Hercynian path from 525 °C and 6.2 kbar to 640 °C and 9 kbar. It results in an initial poikilitic growth followed by a final idiomorphic growth event. (2) Alpine HP garnet are homogenous (550 °C and 20 kbar) and grew around and also inside the Hercynian garnet. Lack of prograde Alpine garnet and fast growth of the HP garnet is explained by the absence of water during much of the prograde path. Water saturation was only observed towards the end, close towards the peak metamorphic conditions. Diffusion could be a limiting factor for crystal growth. It has also a great importance in geochronology. HP vein inside the metagranitoide of the Monte Mucrone (~300 Ma) was investigated to determine argon diffusion scales during high-pressure metamorphism. 40Ar/39Ar biotite ages profile from the vein toward the metagranodiorite show a diffusion curve: old ages (800 Ma) located close to the vein decrease until homogenous 170-150 Ma ages are obtained, two centimeter away from the vein. Centimeter-scale diffusion occurs with help of a fluid phase marked by high chlorine concentrations. Argon diffusion is reduced to a millimeter scale when free fluid is absent. Very short diffusion distance permits to preserve pre-Alpine ages. The 170-150 Ma ages are considered to be geologic meaningful, probably resulting from the extensional tectonics linked to opening of the Tethian ocean.

K-T transition in Deccan Traps of central India marks major marine Seaway across India

Deccan intertrappean sediments in central India are generally considered as terrestrial deposits of Maastrichtian age, but the Cretaceous-Tertiary (K-T) position is still unknown. Here we report the discovery of the K-T transition, a marine incursion and environmental changes preserved within the intertrappean sediments at Jhilmili, Chhindwara District, Madhya Pradesh. Integrative biostratigraphic, sedimentologic, mineralogic and chemostratigraphic analyses reveal the basal Danian in the intertrappean sediments between lower and upper trap basalts that regionally correspond to C29r and the C29R/C29N transition, respectively. Intertrappean deposition occurred in predominantly terrestrial semi-humid to and environments. But a short aquatic interval of fresh water ponds and lakes followed by shallow coastal marine conditions with brackish marine ostracods and early Danian zone P1a planktic foraminifera mark this interval very close to the K-T boundary. This marine incursion marks the existence of a nearby seaway, probably extending inland from the west through the Narmada and Tapti rift valleys. The Jhilmili results thus identify the K-T boundary near the end of the main phase of Deccan eruptions and indicate that a major seaway extended at least 800 km across India. (C) 2009 Elsevier B.V. All rights reserved.

Community Policing in Switzerland's Major Urban Areas: An Observational Study of the Implementation and Impact Using Geospatial Data Mining

La présente étude est à la fois une évaluation du processus de la mise en oeuvre et des impacts de la police de proximité dans les cinq plus grandes zones urbaines de Suisse - Bâle, Berne, Genève, Lausanne et Zurich. La police de proximité (community policing) est à la fois une philosophie et une stratégie organisationnelle qui favorise un partenariat renouvelé entre la police et les communautés locales dans le but de résoudre les problèmes relatifs à la sécurité et à l'ordre public. L'évaluation de processus a analysé des données relatives aux réformes internes de la police qui ont été obtenues par l'intermédiaire d'entretiens semi-structurés avec des administrateurs clés des cinq départements de police, ainsi que dans des documents écrits de la police et d'autres sources publiques. L'évaluation des impacts, quant à elle, s'est basée sur des variables contextuelles telles que des statistiques policières et des données de recensement, ainsi que sur des indicateurs d'impacts construit à partir des données du Swiss Crime Survey (SCS) relatives au sentiment d'insécurité, à la perception du désordre public et à la satisfaction de la population à l'égard de la police. Le SCS est un sondage régulier qui a permis d'interroger des habitants des cinq grandes zones urbaines à plusieurs reprises depuis le milieu des années 1980. L'évaluation de processus a abouti à un « Calendrier des activités » visant à créer des données de panel permettant de mesurer les progrès réalisés dans la mise en oeuvre de la police de proximité à l'aide d'une grille d'évaluation à six dimensions à des intervalles de cinq ans entre 1990 et 2010. L'évaluation des impacts, effectuée ex post facto, a utilisé un concept de recherche non-expérimental (observational design) dans le but d'analyser les impacts de différents modèles de police de proximité dans des zones comparables à travers les cinq villes étudiées. Les quartiers urbains, délimités par zone de code postal, ont ainsi été regroupés par l'intermédiaire d'une typologie réalisée à l'aide d'algorithmes d'apprentissage automatique (machine learning). Des algorithmes supervisés et non supervisés ont été utilisés sur les données à haute dimensionnalité relatives à la criminalité, à la structure socio-économique et démographique et au cadre bâti dans le but de regrouper les quartiers urbains les plus similaires dans des clusters. D'abord, les cartes auto-organisatrices (self-organizing maps) ont été utilisées dans le but de réduire la variance intra-cluster des variables contextuelles et de maximiser simultanément la variance inter-cluster des réponses au sondage. Ensuite, l'algorithme des forêts d'arbres décisionnels (random forests) a permis à la fois d'évaluer la pertinence de la typologie de quartier élaborée et de sélectionner les variables contextuelles clés afin de construire un modèle parcimonieux faisant un minimum d'erreurs de classification. Enfin, pour l'analyse des impacts, la méthode des appariements des coefficients de propension (propensity score matching) a été utilisée pour équilibrer les échantillons prétest-posttest en termes d'âge, de sexe et de niveau d'éducation des répondants au sein de chaque type de quartier ainsi identifié dans chacune des villes, avant d'effectuer un test statistique de la différence observée dans les indicateurs d'impacts. De plus, tous les résultats statistiquement significatifs ont été soumis à une analyse de sensibilité (sensitivity analysis) afin d'évaluer leur robustesse face à un biais potentiel dû à des covariables non observées. L'étude relève qu'au cours des quinze dernières années, les cinq services de police ont entamé des réformes majeures de leur organisation ainsi que de leurs stratégies opérationnelles et qu'ils ont noué des partenariats stratégiques afin de mettre en oeuvre la police de proximité. La typologie de quartier développée a abouti à une réduction de la variance intra-cluster des variables contextuelles et permet d'expliquer une partie significative de la variance inter-cluster des indicateurs d'impacts avant la mise en oeuvre du traitement. Ceci semble suggérer que les méthodes de géocomputation aident à équilibrer les covariables observées et donc à réduire les menaces relatives à la validité interne d'un concept de recherche non-expérimental. Enfin, l'analyse des impacts a révélé que le sentiment d'insécurité a diminué de manière significative pendant la période 2000-2005 dans les quartiers se trouvant à l'intérieur et autour des centres-villes de Berne et de Zurich. Ces améliorations sont assez robustes face à des biais dus à des covariables inobservées et covarient dans le temps et l'espace avec la mise en oeuvre de la police de proximité. L'hypothèse alternative envisageant que les diminutions observées dans le sentiment d'insécurité soient, partiellement, un résultat des interventions policières de proximité semble donc être aussi plausible que l'hypothèse nulle considérant l'absence absolue d'effet. Ceci, même si le concept de recherche non-expérimental mis en oeuvre ne peut pas complètement exclure la sélection et la régression à la moyenne comme explications alternatives. The current research project is both a process and impact evaluation of community policing in Switzerland's five major urban areas - Basel, Bern, Geneva, Lausanne, and Zurich. Community policing is both a philosophy and an organizational strategy that promotes a renewed partnership between the police and the community to solve problems of crime and disorder. The process evaluation data on police internal reforms were obtained through semi-structured interviews with key administrators from the five police departments as well as from police internal documents and additional public sources. The impact evaluation uses official crime records and census statistics as contextual variables as well as Swiss Crime Survey (SCS) data on fear of crime, perceptions of disorder, and public attitudes towards the police as outcome measures. The SCS is a standing survey instrument that has polled residents of the five urban areas repeatedly since the mid-1980s. The process evaluation produced a "Calendar of Action" to create panel data to measure community policing implementation progress over six evaluative dimensions in intervals of five years between 1990 and 2010. The impact evaluation, carried out ex post facto, uses an observational design that analyzes the impact of the different community policing models between matched comparison areas across the five cities. Using ZIP code districts as proxies for urban neighborhoods, geospatial data mining algorithms serve to develop a neighborhood typology in order to match the comparison areas. To this end, both unsupervised and supervised algorithms are used to analyze high-dimensional data on crime, the socio-economic and demographic structure, and the built environment in order to classify urban neighborhoods into clusters of similar type. In a first step, self-organizing maps serve as tools to develop a clustering algorithm that reduces the within-cluster variance in the contextual variables and simultaneously maximizes the between-cluster variance in survey responses. The random forests algorithm then serves to assess the appropriateness of the resulting neighborhood typology and to select the key contextual variables in order to build a parsimonious model that makes a minimum of classification errors. Finally, for the impact analysis, propensity score matching methods are used to match the survey respondents of the pretest and posttest samples on age, gender, and their level of education for each neighborhood type identified within each city, before conducting a statistical test of the observed difference in the outcome measures. Moreover, all significant results were subjected to a sensitivity analysis to assess the robustness of these findings in the face of potential bias due to some unobserved covariates. The study finds that over the last fifteen years, all five police departments have undertaken major reforms of their internal organization and operating strategies and forged strategic partnerships in order to implement community policing. The resulting neighborhood typology reduced the within-cluster variance of the contextual variables and accounted for a significant share of the between-cluster variance in the outcome measures prior to treatment, suggesting that geocomputational methods help to balance the observed covariates and hence to reduce threats to the internal validity of an observational design. Finally, the impact analysis revealed that fear of crime dropped significantly over the 2000-2005 period in the neighborhoods in and around the urban centers of Bern and Zurich. These improvements are fairly robust in the face of bias due to some unobserved covariate and covary temporally and spatially with the implementation of community policing. The alternative hypothesis that the observed reductions in fear of crime were at least in part a result of community policing interventions thus appears at least as plausible as the null hypothesis of absolutely no effect, even if the observational design cannot completely rule out selection and regression to the mean as alternative explanations.

Inverse metamorphic zonation in very low-grade Tibetan zone series of SE Zanskar and its tectonic consequences (NW India, Himalaya)

The metamorphism of the carbonate rocks of the SE Zanskar Tibetan zone has been studied by `'illite crystallinity'' and calcite-dolomite thermometry. The epizonal Zangla unit overlies the anchizonal Chumik unit. This discontinuous inverse zonation demonstrates a late to post-metamorphic thrust of the first unit over the second. The studied area underwent a complex tectonic history: - The tectonic units were stacked from the NE to the SW, generating recumbent folds, NE dipping thrusts and the regional metamorphism. The compressive movements were active under lower temperature conditions, resulting in late thrusts that disturbed the metamorphic zonation. The discontinuous inverse metamorphic zonation dates from this phase. - A NE vergent backfolding phase occurred at lower temperature conditions. It caused the uplift of more metamorphic levels. - A late extensional phase is revealed by the presence of NE dipping low angle normal faults, and a major high angle fault, the Sarchu fault. The low angle normal faults locally run along earlier thrusts (composite tectonic contacts). Their throw has been sufficient to reset a normal stratigraphic superposition (young layers overlying old ones), but insufficient to erase the inverse metamorphic relationship. However, the combined action of backfolding and normal faulting can locally lessen, or even cancel, the inverse metamorphic superposition. After deduction of the normal fault translation, the vertical component of the original thrust displacement through stratigraphy is 400 m, which is a value far too low to explain the temperature difference between the two units. The horizontal component of displacement is therefore far more important than the vertical one. The regional distribution of metamorphism within the Zangla unit points out to an anchizonal front and an epizonal inner part. This fact is in agreement with nappe tectonics.

Feasibility of Visualization and Simulation Applications to Improve Work Zone Safety and Mobility

Visualization is a relatively recent tool available to engineers for enhancing transportation project design through improved communication, decision making, and stakeholder feedback. Current visualization techniques include image composites, video composites, 2D drawings, drive-through or fly-through animations, 3D rendering models, virtual reality, and 4D CAD. These methods are used mainly to communicate within the design and construction team and between the team and external stakeholders. Use of visualization improves understanding of design intent and project concepts and facilitates effective decision making. However, visualization tools are typically used for presentation only in large-scale urban projects. Visualization is not widely accepted due to a lack of demonstrated engineering benefits for typical agency projects, such as small- and medium-sized projects, rural projects, and projects where external stakeholder communication is not a major issue. Furthermore, there is a perceived high cost of investment of both financial and human capital in adopting visualization tools. The most advanced visualization technique of virtual reality has only been used in academic research settings, and 4D CAD has been used on a very limited basis for highly complicated specialty projects. However, there are a number of less intensive visualization methods available which may provide some benefit to many agency projects. In this paper, we present the results of a feasibility study examining the use of visualization and simulation applications for improving highway planning, design, construction, and safety and mobility.