This study is an attempt to explore the multifarious aspects of Karl Friedrich Schinkel

The purpose of the work is to employ molecular simulation to further extend the understanding of Self-Assembled Monolayers (SAMs), especially as it relates to three particular applications: organic-inorganic composite membranes, surface treatments in Micro-Electro-Mechanical Systems (MEMS) and organic-surface-modified Ordered Mesoporous Materials (OMMs). The first focus area for the work is the use of SAMS in organic-inorganic composite membranes for gas separations. These composite membranes, recently proposed in the literature, are based on the chemical derivatization of porous inorganic surfaces with organic oligomers. Our simulations achieve good qualitative agreement with experiment in several respects, including the improvement in the overall selectivity of the membrane and decrease in the permeance when increasing the chain length. The best improvement in the overall solubility selectivity is reached when the chains span throughout the pore. The second application focus is on the use of SAMs as coatings in MEMS devices. The work focuses on the modeling of adhesion issues for SAM coatings at the molecular level. It is shown that as the chain length is increased from 4 to 18 carbon atoms, the adhesion forces between two monolayers at the same separations decreases. The third application focus is on the use of SAMs for tailoring surface and structural properties of OMMs, in particular, porous silicas. A molecular study of structural and surface properties of a silica material with a 5 nm pore size, modified via chemical bonding of organosilanes with a range of sizes (C4, C8 and C18) is presented. Grand canonical MC simulations are employed to obtain nitrogen adsorption isotherms for unmodified and modified MCM-41 material models. Furthermore, the density profiles of alkyl chains and nitrogen molecules are analyzed to clarify the differences in the adsorption mechanisms in unmodified and modified materials. The position of the capillary condensation steps gradually shifted to lower pressure values with the increase in size of the bonded ligands, and this shift was accompanied by a gradual disappearance of the hysteresis loop. As the length of the bonded ligands is increased, a systematic decrease in the pore diameter is observed and the multi-layer adsorption mechanism in modified model materials diminishes.

Mon travail de thèse concerne l'étude de la matière interstellaire, notamment l'émission submillimétrique des grains de poussière mais aussi l'évolution de leurs propriétés, des milieux diffus vers les milieux denses, aussi bien dans notre Galaxie que dans le Grand Nuage de Magellan.<br /> J'ai participé au développement d'un modèle d'émission submillimétrique des poussières, et j'ai ajusté ses paramètres de manière à ce qu'il soit capable de reproduire les faits observationnels. Ce modèle prend en compte la nature amorphe des grains. Il considère une distribution désordonnée de charges à l'échelle macroscopique, et une distribution de systèmes à deux niveaux à l'échelle microscopique.<br /> J'ai comparé l'émissivité des grains dans des régions atomiques (HI) et moléculaires (CO) de notre Galaxie. J'ai montré que la pente et le niveau des émissivités des grains augmentent notablement dans la majorité des régions denses de notre Galaxie, dans la gamme 100-550 Μm. Les conclusions de ce travail confortent l'idée de coagulation des grains.<br />Enfin, je me suis concentrée sur l'étude de la poussière dans le Grand Nuage de Magellan (LMC). J'ai pu mettre en évidence pour la première fois une sous-abondance de la poussière dans le LMC. De plus mes résultats montrent que les variations spatiales des différentes compositions de la poussière et du champ de rayonnement à travers cette galaxie, sont gouvernées par l'activité de formation stellaire, présente et passée. Pour finir je me suis interrogée sur les interprétations possibles concernant les différences observées entre les phases atomiques et moléculaires du LMC.

Ce manuscrit décrit douze ans d'activités de recherche au Centre de Recherche en Automatique de Nancy dans le domaine de la compression d'images (grand public mais aussi médicales), ainsi que dans celui du tatouage d'images dans un contexte de compression.<br />Nous avons mis l'accent sur l'étape de quantification de la chaîne de compression pour laquelle nous avons proposé une méthode dite de « quantification vectorielle algébrique avec zone morte »<br />(QVAZM) associée à une analyse multirésolution par ondelettes, permettant d'améliorer sensiblement, par rapport au nouveau standard JPEG2000 ainsi qu'à l'algorithme de référence SPIHT, les performances en termes de compromis débit-distorsion, et ainsi la qualité visuelle de l'image reconstruite.<br />Nous avons travaillé sur trois points essentiels et proposé à chaque fois des solutions afin de rendre l'utilisation de la QVAZM réaliste dans une chaîne de compression : l'indexage des vecteurs du dictionnaire, le réglage des paramètres du dictionnaire (facteur d'échelle et zone morte) et l'allocation des ressources binaires.<br />La contribution majeure de nos travaux dans le domaine de l'imagerie médicale 3D a consisté à tenter d'ouvrir une voie à la compression avec perte, encore inenvisageable il y a quelques années pour des raisons évidentes de diagnostic. Nous avons pour cela étendu avec succès notre algorithme<br />QVAZM au cas des images médicales volumiques. Parallèlement à ces travaux, nous avons étudié l'impact de la compression avec perte sur certaines applications de traitement d'images médicales, en particulier sur un outil d'aide à la détection de nodules pulmonaires pour lequel nous avons pu montrer une robustesse à la compression avec perte, même à fort taux de compression (jusqu'à 96 :1).<br />Enfin, la contribution principale de nos travaux dans le domaine du tatouage concerne le développement d'approches combinées compression/tatouage et ont abouti à la proposition de deux méthodes de tatouage reposant sur la QVAZM, associée à une analyse multirésolution par transformée en ondelettes. Elles sont particulièrement attractives pour les applications où la compression constitue la principale attaque (ou le principal traitement).

Cette thèse concerne la modélisation d'ouvrages maçonnés tridimensionnels en grand appareil, précontraints ou comportant un grand nombre de blocs. Ces structures sont des constructions en gros blocs de pierre, éventuellement liés par des joints de mortier, dont les géométries tridimensionnelles ne permettent généralement pas la définition d'un volume élémentaire représentatif. Le comportement mécanique de ces édifices ou structures, peut être étudié par des méthodes qui considèrent le comportement des blocs et leurs interactions avec des blocs voisins, par frottement sec ou en présence de mortier cohésif. Nous avons donc choisi de les modéliser par la méthode des éléments discrets Non Smooth Contact Dynamics. Les monuments étudiés sont des structures en pierres massives, simple appareil régulier (mur) ou irrégulier (pont Julien) et structures précontraintes (escalier, coupôle). D'une part, un nouvel algorithme de détection des contacts a été développé pour gérer les contacts surfaciques, spécifiques aux maçonneries. Diverses applications sur des cas réels, et des comparaisons avec des expériences issues de la littérature, ont montré la robustesse de l'algorithme. Les résultats obtenus par l'analyse des descentes de charges sont cohérents avec les caractères physiques et géométriques des ouvrages considérés. D'autre part, les liaisons de contact conduisent souvent à un problème statiquement indéterminé au niveau local. Nous avons proposé une méthode de résolution qui traite simulatnément tous les noeuds d'une liaison plane. L'étude sur des cas académiques a permis de tester la pertinence de la méthode. Une comparaison a été faite avec la méthode de résolution existante, implémentée dans le code LMGC90.

Thesis (Ph. D.)--Lehigh University, 2001. / Includes vita. Includes bibliographical references (leaves 225-235).

Metal--organic frameworks (MOFs) are porous crystalline materials that are synthesized from rigid organic ligands and metal-containing clusters. They are highly tunable as a number of different structures can be made by simply changing the organic ligand and/or metal ion. MOFs are a promising class of materials for many energy-related applications, including H2 storage and CO2 capture and sequestration. Computational studies can provide insights into MOFs and the mechanism of gas sorption and separation. Theoretical studies on existing MOFs are performed to determine what structural characteristics leads to favorable gas sorption mechanisms. The results from these studies can provide insights into designing new MOFs that are tailored for specific applications. In this work, grand canonical Monte Carlo (GCMC) simulations were performed in various MOFs to understand the gas sorption mechanisms and identify the favorable sorption sites in the respective materials. Experimental observables such as sorption isotherms and associated isosteric heat of adsorption, Qst, values can be generated using this method. Outstanding agreement with experimental measurements engenders confidence in a variety of molecular level predictions. Explicit many-body polarization effects were shown to be important for the modeling of gas sorption in highly charged/polar MOFs that contain open-metal sites. Indeed, this was demonstrated through a series of simulation studies in various MOFs with rht topology that contain such sites. Specifically, the inclusion of many-body polarization interactions was essential to reproduce the experimentally observed sorption isotherms and Qst values and capture the binding of sorbate molecules onto the open-metal sites in these MOFs. This work also presents computational studies on a family of pillared square grid that are water-stable and display high CO2 sorption and selectivity. These MOFs are deemed promising for industrial applications and CO2 separations. Simulations in these materials revealed favorable interactions between the CO2 molecules and the SiF62- pillars. Further, the compound with the smallest pore size exhibits the highest selectivity for CO2 as demonstrated through both experimental and theoretical studies. Many other MOFs with intriguing sorption properties are investigated in this work and their sorption mechanisms have been discerned through molecular simulation.

Which grand strategies do Great Powers adopt towards rising challengers? When do Great Powers conciliate their potential rivals, and when do they opt for strategies of containment? In this master’s report, I outline an argument to answer these and related questions. I add to the existing literatures on grand strategy and power transitions in several key respects. First, I model power shifts between Great Powers as contests over access to externally located benefits rather than as contests over power for its own sake. Second, I emphasize the weight of domestic politics in shaping states’ preferences over the apportionment of these benefits. Third, I highlight the role of diplomacy in determining whether established Great Powers choose to conciliate or else contain potential rivals. Empirically, I provide four vignettes of Great Power responses to rising states: the United States’ strategy towards Japan during the Cold War; Britain’s appeasement of the United States, 1890-1914; the United States’ containment of the Soviet Union under Ronald Reagan; and Britain’s containment of Wilhelmine Germany. / text

Debris flows in at least 529 Grand Canyon tributaries transport poorly-sorted clayto boulder-sized sediment into the Colorado River, and are initiated by failures in weathered bedrock, the "fire-hose effect," and classic soil-slips often following periods of intense rainfall coincident with multi-day storms. Recent debris flows had peak-discharges from about 100-300 m3/s. Twentieth-century debris flows occurred from once every 10-15 years in eastern tributaries, to once in over a century in western drainage areas. Systemwide, debris flows likely recur about every 30-50 years, and the largest recent flows were initiated during Pacific-Ocean storms in autumn and winter. Three idealized hydrographs are inferred for recent debris flows based on deposits and flow evidence: Type I, has a single debris-flow peak followed by a decayed recessional streamflow; Type II, has multiple, decreasing debris-flow peaks with intervening flow transformations between debris flow and non-debris flow phases; and Type III, may have either a simple or complex debris-flow phase (begin as either Type I or II), followed by a larger streamflow peak that reworks or buries debris-flow deposits under streamflow gravel deposits. From 1987 through 1995, at least 25 debris flows constricted the Colorado River, creating 2 rapids and enlarging at least 9 riffles or rapids. In March-April, 1996, reworking effects of a 7-day controlled flood release (peak = 1,300 m³/s) on 18 aggraded debris fans in Grand Canyon were studied. Large changes occurred at the most-recent deposits (1994-1995), but several other older deposits (1987-1993) changed little. On the most-recent fan deposits, distal margins became armored with cobbles and boulders, while river constriction, flow velocity, and streampower were decreased. Partial armoring of fan margins by relatively-low mainstem flows since the debris flows occurred, was an important factor limiting fan reworking because particles became interlocked and imbricated, allowing them to resist transport during the flood. Similar future floods will accomplish variable degrees of fan reworking, depending on the extent that matrix-supported sediments are winnowed by preceding mainstem flows.

The Bureau of Reclamation (BOR) is interested in understanding the human and environmental consequences of past Glen Canyon Dam water release policies and using these data to inform future water release and land management policies. One step in this direction is to understand how American Indian people have used the Colorado River and adjoining lands in Glen Canyon and Grand Canyon. The BOR, through its Glen Canyon Environmental Studies (GCES) office, has provided funds for various American Indian groups to identify places and things of cultural significance in the 300 mile long river and canyon ecosystem that has come to be called the Colorado River Corridor. This study is the second to report on the cultural resources of the Southern Paiute people found in this riverine ecosystem. The rock art study funded by the BOR and managed by the Glen Canyon Environmental Studies (GCES) office is the basis of this report. This study is unique in the history of rock art studies and is unusual when compared with other American Indian cultural resource assessments. There are five unique features of this study. First, all funds for conducting the research were contracted to the Southern Paiute Consortium. Second, the Southern Paiute people decided during the previous studies that their next study would be about rock art. Third, the GCES /BOR permitted research to be conducted in terms of Paiute perceptions of the study area rather than specifically in terms of the scientifically established study area for the project. Thus, it was possible to conduct the Kanab Creek side canyon study. Fourth, all interviews were guided by a ten -page survey instrument, so Southern Paiute responses could be systematically compared. Fifth, both all-male and all- female research trips were conducted, thus producing the first gender - specific interviews of rock art sites. The resulting study is both interdisciplinary and multivocal.