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Schmid, Günter Maximilian. "Dynamical symmetry breaking in molecules and molecular aggregates." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/17393.
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Bone, Richard George Andrew. "New applications of the molecular symmetry group." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239761.
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Aghaei, Amin. "Symmetry-Adapted Molecular Modeling of Nanostructures and Biomembranes." Research Showcase @ CMU, 2013. http://repository.cmu.edu/dissertations/295.
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Tremendous advances in nanoscience during the past decades have drawn a new horizon for the future of science. Many biological and structural elements such as DNA, bio-membranes, nanotubes, nanowires and thin films have been studied carefully in the past decades. In this work we target to speed up the computational methods by incorporating the structural symmetries that nanostructures have. In particular, we use the Objective Structures (OS) framework to speed up molecular dynamics (MD), lattice dynamics (phonon analysis) and multiscale methods. OS framework is a generalization of the standard idea for crystal lattices of assuming periodicity of atomic positions with a large supercell. OS not only considers the translational periodicity of the structure, but also other symmetries such as rotational and screw symmetries. In addition to the computational efficiency afforded by Objective Structures, OS provides us with more flexibility in the shape of the unit cell and the form of the external deformation and loading, comparing to using the translational periodicity. This is because the deformation and loading should be consistent in all cells and not all deformations keep the periodicity of the structures. For instance, bending and twisting cannot be modeled with methods using the structure's periodicity. Using OS framework we then carefully studied carbon nanotubes under non-equilibrium deformations. We also studied the failure mechanism of pristine and twisted nanotubes under tensile loading. We found a range of failure mechanisms, including the formation of Stone-Wales defects, the opening of voids, and the motion of atoms out of the cross-section. We also used the OS framework to make concrete analogies between crystalline phonons and normal modes of vibration in non-crystalline but highly symmetric nanostructures.
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Hohenstein, Edward G. "Implementation and applications of density-fitted symmetry-adapted perturbation theory." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42699.
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Noncovalent interactions play a vital role throughout much of chemistry. The understanding and characterization of these interactions is an area where theoretical chemistry can provide unique insight. While many methods have been developed to study noncovalent interactions, symmetry-adapted perturbation theory (SAPT) stands out as one of the most robust. In addition to providing energetic information about an interaction, it provides insight into the underlying physics of the interaction by decomposing the energy into electrostatics, exchange, induction and dispersion. Therefore, SAPT is capable of not only answering questions about how strongly a complex is bound, but also why it is bound. This proves to be an invaluable tool for the understanding of noncovalent interactions in complex systems.
The wavefunction-based formulation of SAPT can provide qualitative results for large systems as well as quantitative results for smaller systems. In order to extend the applicability of this method, approximations to the two-electron integrals must be introduced. At low-order, the introduction of density fitting approximations allows SAPT computations to be performed on systems with up to 220 atoms and 2850 basis functions. Higher-orders of SAPT, which boasts accuracy rivaling the best theoretical methods, can be applied to systems with over 40 atoms. Higher-order SAPT also benefits from approximations that attempt to truncate unneccesary unoccupied orbitals.
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Wiggers, Greg A. "Molecular Design for Nonpolar Chiral-axial Quadratic Nonlinear Optics." Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1220713451.
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Santos, José Guilherme Pereira de Almeida. "Molecular tools to dissect the role of Dmrt2a and Dmrt2b in the left-right axis formation in zebrafish." Master's thesis, Faculdade de Ciências e Tecnologia, 2013. http://hdl.handle.net/10362/10902.
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Dissertação para obtenção do Grau de Mestre em Genética Molecular
e BiomedicinaWe tend to view the vertebrate body as bilaterally symmetric, but in fact, this only happens from the outside. Internally, most of the organs from heart to liver are asymmetrically positioned. Skeleton and its associated muscles, symmetric structures of the vertebrate body, have its origins in the transient symmetric blocks of mesoderm called somites whereas the asymmetric morphogenesis of the internal organs is due to asymmetric gene expression in the lateral plate mesoderm (LPM). Previous studies using Morpholino (MO) technology have shown that dmrt2a is involved in these two processes in zebrafish. When Dmrt2a levels are reduced, asymmetric gene expression in the LPM becomes randomized and symmetric gene expression in the presomitic mesoderm (PSM) is disrupted. The paralogous of dmrt2a, the fish specific dmrt2b has been shown to be involved in regulating asymmetric gene expression in the LPM as well. Here we used the recent Transcription activator-like effector nucleases (TALENs) technology to generate dmrt2a and dmrt2b mutant alleles that will allow us in the future to uncover the downstream effectors of these transcription factors using high-throughput experiments. In addition, we overexpressed dmrt2a at the one-cell stage to characterize asymmetry versus symmetry phenotypes. The results show clearly the ability of TALEN technology to generate mutant alleles in zebrafish. Nevertheless, dmrt2a and dmrt2b homozygous mutants developed so far fail to recapitulate their previously described MO phenotypes which raise the question on what molecular mechanism(s) allow(s) zebrafish to cope with frameshift mutations. The overexpression of dmrt2a shows that a time window of opportunity during which symmetric embryonic territories are able to respond to asymmetric signals does exist during embryonic development.
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Liljegren, Tor. "Utveckling av en matematiklaboration på Vetenskapens hus : En tillämpning av gruppteori på molekylär symmetri." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-31785.
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This master thesis is the documented work of the construction process and testing of a three hour laboratory session in mathematics aimed at high school level students. The purpose of the thesis was to create an interesting laboratory session for the science education center ”The House of Science” that could be used as a part of their regular program directed to schools. The thesis explores the possibilities for how one can construct a laboratory session on the topic ”molecular symmetry” as well as the underlying pedagogical theories used to describe learning processes in creative contexts. A model for such a session is proposed, an evaluation is conducted and its results and implications are appropriately discussed. An important review of the mathematical background of symmetries, group theory and linear representations of finite groups was written and can be found in the appendices.
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Liao, Chen-Ting, Xuan Li, Daniel J. Haxton, Thomas N. Rescigno, Robert R. Lucchese, C. William McCurdy, and Arvinder Sandhu. "Probing autoionizing states of molecular oxygen with XUV transient absorption: Electronic-symmetry-dependent line shapes and laser-induced modifications." AMER PHYSICAL SOC, 2017. http://hdl.handle.net/10150/624049.
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We used extreme ultraviolet (XUV) transient absorption spectroscopy to study the autoionizing Rydberg states of oxygen in an electronically- and vibrationally-resolved fashion. XUVpulse initiates molecular polarization and near-infrared pulse perturbs its evolution. Transient absorption spectra show positive optical-density (OD) change in the case of ns sigma(g) and nd pi(g) autoionizing states of oxygen and negative OD change for nd sigma(g) states. Multiconfiguration time-dependent Hartree-Fock (MCTDHF) calculations are used to simulate the transient absorption and the resulting spectra and temporal evolution agree with experimental observations. We model the effect of nearinfrared perturbation on molecular polarization and find that the laser-induced phase-shift model agrees with the experimental andMCTDHF results, while the laser-induced attenuation model does not. We relate the electronicstate- symmetry-dependent sign of the OD change to the Fano parameters of the static absorption line shapes.
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Tauer, Anthony Philip. "Theoretical Investigations of Pi-Pi and Sulfur-Pi Interactions and their Roles in Biomolecular Systems." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7573.
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The study of noncovalent interactions between aromatic rings and various functional groups is a very popular topic in current computational chemistry. The research presented in this thesis takes steps to bridge the gap between theoretical prototypes and real-world systems.
The non-additive contributions to the interaction energy in stacked aromatic systems are measured by expanding the prototype benzene dimer into trimeric and tetrameric systems. We show that the three- and four-body interaction terms generally do not contribute significantly to the overall interaction energy, and that the two-body terms are essentially the same as in the isolated dimer.
The sulfur-pi interaction is then studied by using the hydrogen sufide-benzene dimer as a prototype system for theoretical predictions. We obtain higly-accurate potential energy curves, as well as an interaction energy extrapolated to the complete basis set limit. Energy decomposition analysis using symmetry-adapted perturbation theory shows that the sulfur-pi interaction is primarily electrostatic in nature.
These theoretical results are then compared to an analysis of real sulfur-pi contacts found by searching protein structures in the Brookhaven Protein DataBank. We find that the most frequently seen configuration does not correspond to the theoretically predicted equilibrium for sydrogen sulfide-benzene, but instead to a configuration that suggests an alkyl-pi interaction involving the carbon adjacent to the sulfur atom. We believe our findings indicate that environmental effects within proteins are altering the energetics of the sulfur-pi interaction so that other functional groups are preferred for interacting with the aromatic ring.
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Bukhari, Ghadeer, and Wenheng Zhang. "INDEPENDENT ORIGINATION OF FLORAL ZYGOMORPHY, A PREDICTED ADAPTIVE RESPONSE TO POLLINATORS: DEVELOPMENTAL AND GENETIC MECHANISMS." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4482.
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Observations of floral development indicate that floral organ initiation in pentapetalous flowers more commonly results in a medially positioned abaxial petal (MAB) than in a medially positioned adaxial petal (MAD), where the medial plane is defined by the stem and the bract during early floral development. It was proposed that the dominant MAB petal initiation might impose a developmental constraint that leads to the evolution of limited patterns of floral zygomorphy in Asteridae, a family in which the floral zygomorphy develops along the medial plane and results in a central ventral (CV) petal in mature flowers. Here, I investigate whether the pattern of floral organ initiation may limit patterns of floral zygomorphy to evolve in pentapetalous angiosperms. I analyzed floral diagrams representing 405 species in 330 genera of pentapetalous angiosperms to reconstruct the evolution of floral organ initiation and the evolution of developmental processes that give rise to floral zygomorphy on a phylogenetic framework. Results indicate that MAB petal initiation is the most common; it occupies 86.2% of diversity and represents the ancestral state of floral organ initiation in pentapetalous angiosperms. The MAD petal initiation evolved 28 times independently from the ancestral MAB petal initiation. Among the 34 independent originations of floral zygomorphy, 76.5% of these clades represent MAB petal initiation, among which only 47% of the clades result a CV petal in mature flowers. The discrepancy is explained by the existence of developmental processes that result in floral zygomorphy along oblique planes of floral symmetry in addition to along the medial plane. Findings suggest that although the early floral organ initiation plays a constraining role to the evolution of patterns of floral zygomorphy, the constraint diverges along phylogenetically distantly related groups that allow the independent originations of floral zygomorphy through distinct development processes in pentapetalous angiosperms. In additional study, the butterfly-like flowers of Schizanthus are adapted to pollination by bees, hummingbirds, and moths. I investigated the genetic basis of the zygomorphic corolla, for which development is key to the explosive pollen release mechanism found in the species of Schizanthus adapted to bee pollinators. I examined differential gene expression profiles across the zygomorphic corolla of Schizanthus pinnatus, a bee-pollinated species, by analyzing RNA transcriptome sequencing (RNA- seq). Data indicated that CYC2 is not expressed in the zygomorphic corolla of Sc. pinnatus, suggesting CYC2 is not involved in the development of floral zygomorphy in Schizanthus (Solanaceae). The data also indicated that a number of genes are differentially expressed across the corolla.
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Mifsud, Richard William. "An exploration of some aspects of molecular replacement in macromolecular crystallography." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/282871.
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This thesis reports work in three areas of X-ray crystallography. An initial chapter describes the structure of a protein, the methods based on the use of X-rays and computer analysis of diffraction patterns to determine crystal structure, and the subsequent derivation of the structure of part or all of a protein molecule. Work to determine the structure of the protein cytokine receptor-like factor 3 (CRLF3) leading to the successful generation of a structural model of a significant part of this molecule is then described in Chapter 2. A variety of techniques had to be deployed to complete this work, and the steps undertaken are described. Analysis was performed principally using phaser, using maximum likelihood methods. Areas for improvement in generating non-crystallographic symmetry (NCS) operators in existing programmes were identified and new and modified algorithms implemented and tested. Searches based on improved single sphere algorithms, and a new two-sphere approach, are reported. These methods showed improvements in many cases and are available for future use. In Chapter 4, work on determining the relative importance of low resolution and high intensity data in molecular replacement solutions is described. This work has shown that high intensity data are more important than the low resolution data, dispelling a common perception and helping in experimental design.
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Schmiedt, Hanno [Verfasser], Stephan [Gutachter] Schlemmer, and Per [Gutachter] Jensen. "Molecular symmetry, super-rotation, and semi-classical motion. New ideas for old problems / Hanno Schmiedt ; Gutachter: Stephan Schlemmer, Per Jensen." Köln : Universitäts- und Stadtbibliothek Köln, 2017. http://d-nb.info/1132248299/34.
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Morita, Hiroyuki. "Gamow-Teller transitions in the light N = Z odd-odd nuclei:Proton-neutron correlation and SU(4) symmetry with clusters." Kyoto University, 2019. http://hdl.handle.net/2433/242608.
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Douguet, Nicolas. "Symmetry in the dissociative recombination of polyatomic ions and in ultra-cold few body collisions." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4654.
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We discuss the role of symmetries in the dissociative recombinations (DR) of three polyatomic ions, namely the linear HCO+ (formyl) ion and the two highly symmetric H+3 and H3O+ (hydronium) molecular ions. Regarding the HCO+ ion, we apply a quantum mechanical treatment using the Multi-channel Quantum Defect Theory (MQDT) formalism to describe the ion-electron scattering process. Our study takes into account the Renner-Teller effect in order to model the non Born-Oppenheimer vibronic coupling in linear polyatomic ions. The coupling has shown to represent the main mechanism responsible for electronic capturing in highly excited Rydberg states associated with excited vibrational levels of the ionic core. We consider all internal degrees of freedom of HCO+ and obtain the dissociative cross section as a function of the incident electron kinetic energy. We have also improved the theoretical approach by including the large permanent dipole moment of HCO+ using a generalization of the MQDT formalism. To our knowledge, this is the rst time the permanent dipole moment of an ion is included in a DR study. The obtained results are in good agreement with experimental data. We also study the DR of H+3 and H3O+ symmetric ions using a simpli ed theoretical treatment, which focuses on the key ingredient of the DR process, the electron capture in the rst excited degenerate vibrational normal mode of the ions through non Born-Oppenheimer Jahn-Teller coupling. For both ions the obtained cross sections are in very good agreement with the available experimental data. Moreover, in the case of H+3 , the results reproduce previous calculations from two independent theoretical studies. Finally, we investigate the role of symmetries in few body ultra-cold collisions by considering both three and four identical atoms systems. We derive allowed rearrangements of different fragments of the system, satisfying the complete symmetry of the molecular Hamiltonian. For that purpose we establish a correspondence between constants of motion of the system in di erent large-distance con gurations and irreducible representations of the total symmetry group. Selection rules (forbidden transitions) and allowed states, which depend on the fermionic or bosonic nature of the atoms, can be derived from these results.ID: 029050862; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2010.; Includes bibliographical references (p. 226-232).
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Shimozawa, Masaaki. "Superconducting properties of heavy fermion thin films and superlattices." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188463.
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Marino, Andrea. "Ultrafast investigation of electronic and structural dynamics in photomagnetic molecular solids." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S037/document.
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La capacité de photo-commuter les propriétés physico-chimiques des matériaux fonctionnels grâce à des transitions de phase induites par la lumière, ouvre des perspectives fascinantes pour diriger un matériau vers un nouvel état hors équilibre thermique. Cependant, il est fondamental de comprendre tous les phénomènes élémentaires, habituellement cachés dans une moyenne statistique lors des transformations à l'équilibre. Les études résolues en temps représentent une approche unique pour accéder à l'évolution des différents degrés de liberté du système et connaître les processus élémentaires mis en jeu lors de la commutation macroscopique. Les matériaux à transition de spin (SCO) sont d'un intérêt particulier car ce sont des systèmes photo-réversibles. Ces matériaux sont aussi des prototypes photomagnétiques et photochromiques qui commutent entre deux états de différente multiplicité de spin, nommés bas spin (LS) et haut spin (HS). Dans ce travail de thèse, nous étudions les dynamique ultrarapides électroniques et structurales de cette classe de solides moléculaires, en soulignant l'importance d'utiliser des sondes complémentaires sensibles à différents degrés de liberté. Les commutation photo-induite entre états de spin est ultra-rapide et initialement localisée à l'échelle moléculaire, où le couplage électron-phonon active des vibrations cohérentes intramoléculaires. Un transfert d'énergie ultra-rapide de la molécule au réseau, via un couplage phonon-phonon, permet de piéger efficacement le système dans le nouvel état photo-induit. Cependant, dans les solides moléculaires, l'excès d'énergie libérée de la molécule excitée résulte dans un aspect complexe multi-échelle impliquant plusieurs degrés de liberté à des échelles de temps différentes. Dans ce travail de thèse, nous avons étudié la dynamique multi-étape hors équilibre d'un système SCO présentant une brisure de symétrie entre la phase HS et la phase intermédiaire (IP) où une mise en ordre à longue distance des états HS et LS des molécules résulte en la formation d'une onde de concentration de spin (SSCW). La diffraction des rayons X résolue en temps combinée avec des études de spectroscopie optique donnent une description complète de la dynamique hors-équilibre de la SSCW hors-équilibre en mesurant l'évolution temporelle des deux paramètres d'ordre décrivant le systèmeThe ability to photo-switch physical/chemical properties of functional materials through photo induced phase transition opens fascinating perspectives for driving the material towards new state out of thermal equilibrium. However, it is fundamental to disentangle and understand all the dynamical phenomena, otherwise hidden in statistically averaged macroscopic transformations. Arguably, time-resolved studies are unique approach to access the necessary information on the multiple degrees of freedom and elementary processes involved during the macroscopic switching. As photo-reversible molecular switches, spin crossover (SCO) materials are of particular interest. These photomagnetic and photochromic prototype materials undergo metastable photoinduced phase transition between two states of different spin multiplicity, namely low-spin (LS) and high-spin (HS). In this PhD work it will be presented the ultrafast electronic and structural dynamics of SCO molecular solids emphasizing the importance of using complementary probes sensitive to different degrees of freedom. The photoinduced spin state switching concerns initially only an ultrafast, but localized, molecular response which through strong electron-phonon coupling activates coherent intra-molecular vibrations. An ultrafast energy transfer from the molecule to the lattice, via phonon-phonon coupling, allows an efficient trapping of the system in the new photoinduced state. However in molecular solids, the excess of energy released from the absorber molecule results in a complex multi-scale aspect involving several degrees of freedom at different time scales. In this contest, we investigated the multi-step out-of equilibrium dynamics of a SCO system undergoing symmetry breaking between the HS phase and the intermediate (IP) phase where a long range ordering of HS and LS molecules results in a spin state concentration wave (SSCW), analogous to charge or spin density waves. Combined time-resolved X-ray diffraction and optical spectroscopy studies provide a complete overview of the out-of-equilibrium thermodynamics of the SSCW, investigating how the two order parameters describing the system evolve in time
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Câmara, Amanda Souza. "Uma transição assimétrica entre estados simétricos: o alosterismo da Glucosamina 6-fosfato Desaminase." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-18042013-101101/.
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Sistemas alostéricos são característicos de proteínas com um ou mais estados de equilíbrio. Nesse sentido, uma enzima passa por modificações de sua atividade quando um substrato cooperativo se liga a um estado ou outro (1). Estes estados são reconhecidos por possuírem uma conformação mais estável e coexistirem num ensemble. Este trabalho sustenta que tais proteínas oscilem naturalmente entre esses estados. Experimentos de difração de raios-X e RMN, que proporcionam parâmetros de deslocamento anisotrópicos e tempos de relaxação de spin nuclear, já demonstram a coexistência de ambos estados em solução e descrevem o movimento como uma mudança de equilíbrio populacional dos confórmeros (2). Também é possível desenvolver métodos numéricos, como o cálculo de modos normais e a simulação de dinâmica molecular, para associar a geometria proteica a um movimento sobre determinado potencial de campos de força. O sistema adotado para o desenvolvimento desses estudos é a enzima alostérica Glucosamina-6-fosfato Desaminase. Características que defendem seu uso são sua reversibilidade catalítica, rápido equilíbrio cinético e muito baixa afinidade do estado T por ligantes. Sua estrutura também já foi resolvida por experimentos de cristalografia, identificando ambos estados alostéricos. E a caracterização das mudanças estruturais entre os estados T e R está bem estabelecida, identificando diferentes subunidades a distintos graus de rotação e prevendo uma oscilação de baixa frequência entre eles (3). Resultados obtidos neste projeto constituem: (a) uma dinâmica de 100ns partindo do estado T de toda a proteína (hexamérica) solvatada explicitamente, formando um ensemble NVT de 92000 átomos através do programa NAMD, usando o campo de forças CHARMM; (b) análise de componentes principais aproveitando esta dinâmica e usando algoritmos do programa Gromacs; (c) e análise de modos normais, em que os cálculos de minimização de energia foram feitos pelo programa Gromacs sob o campo de forças ENCADV, no vácuo. Análises desses resultados envolvem cálculos de RMSDs e flutuações, trajetórias calculadas para os autovetores oriundos de NMA ou de PCA, fatores de Debye-Waller e a confirmação visual (e gráficos de distância entre resíduos) de aproximação a um estado ou outro. Como a prévia caracterização da movimentação alostérica, identificava duas regiões para cada monômero como representativas de corpos rígidos, também é desenvolvida uma análise por tensores de inércia. Espera-se que, ao longo do tempo, essas subunidades se comportem como corpos quase rígidos e os movimentos destas regiões rígidas correspondam a uma maior representatividade da transição alostérica. Assim, a caracterização dos tensores seria capaz de filtrar movimentos de mais alta frequência que constituem ruído em relação a movimentos funcionais da proteína. - Algoritmos para cálculos matriciais dos tensores foram escritos em Fortran e em TCl.Allosteric systems are characteristic of proteins with one or more equilibrium states. Such an enzyme experiences a modification of its activity when a cooperative substrate binds to a state or another, thus, establishing a change in population equilibrium (1). These states are recognized by having a more stable conformation, and they coexist in an ensemble. X-ray diffraction and NMR experiments already demonstrated this dynamic equilibrium, and simulation methods, as molecular dynamics and normal mode analysis, generally provide a more complete proof (2).The allosteric enzyme Glucosamine-6-Phosphate Deaminase appeared to be a good model to better understand the equilibrium dynamics as essential to the protein function, given its reversibility of the catalysis and rapid-equilibrium kinetic mechanism. It also has the structure elucidated for both its conformers (3). A computational approach would now give better perspective on how the conformational changes occur. A set of results of this latter kind were obtained: (a) a 100ns dynamic starting at the hexameric T conformer, explicitly solvated, building a NVT ensemble using NAMD program and CHARMM force field; (b) a principal components analysis making use of the calculated dynamic and of the Gromacs algorithms; (c) and normal mode analysis of the T conformer structure (pdb code 1fsf) minimized with Gromacs program using ENCADV vacuum force field. Not only the conventional analyses for these results (fluctuations and projections) were taken, but also an inertia tensor analysis was developed. As the allosteric conformational change, for this protein, was described by the displacement of only two rigid body subunits³, its description by inertia tensors should act as a filter for the high frequency and functionally uninteresting motions, which normally constitute only noise.
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Khojayori, Farahnoz N. "Floral symmetry genes elucidate the development and evolution of oil-bee pollinated flowers of Malpighiaceae and Krameriaceae." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5585.
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Specialization on insect and animal pollinators is thought to be the driving force for the evolution of floral traits. Specifically in the New World (NW), the oil-bee pollination syndrome has led to the convergence of floral characters in two distantly related families of core eudicots, Malpighiaceae and Krameriaceae. Both families display a flag-like structure that establishes a zygomorphic flower and floral oil rewards in epithelial elaiophores. These traits work concomitantly to attract and reward female oil-bees that help fertilize these flowers and in return receive oils. The underlying genetics of floral zygomorphy were studied in several clades of core eudicots, which implicated CYCLOIDEA2-(CYC2-)like genes of the TCP gene family to play a role in the establishment and maintenance of this trait. In Malpighiaceae, previous work demonstrated that two CYC2-like genes, CYC2A and CYC2B, are expressed during development correlated with establishing zygomorphy in flowers of NW Malpighiaceae. In this thesis work, I investigated the underlying developmental and genetic basis for the establishment of non-homologous and yet functionally similar traits in the oil-bee pollinated flowers of Malpighiaceae and Krameriaceae. In Chapter 1, I investigated the modification of a conserved CYC2 genetic program in the Old World (OW) acridocarpoids of Malpighiaceae following a major biogeographic disjunction. And in Chapter 2, I studied the floral ontogeny and genetic basis of floral zygomorphy development in Krameria lanceolata Torrey of Krameriaceae. This thesis work sheds light on the significance of the interdisciplinary study of floral symmetry evolution through comparative pollination ecology, development, and genetics.
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Fidalgo, Felipe Delfini Caetano 1987. "Dividindo e conquistando com simetrias em geometria de distâncias." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/306799.
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Orientador: Carlile Campos LavorTese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica
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Resumo: Motivado por estudos em estruturas 3D de proteínas, biomoléculas imprescindíveis no estudo da vida, surgiu um problema chamado Discretizable Molecular Distance Geometry Problem (DMDGP) que provou ser NP-Difícil. Para resolvê-lo, existe um algoritmo da literatura, Branch & Prune (BP), que utiliza uma estratégia combinatória de exploração de uma árvore binária de soluções associada ao problema. Além disso, foram descobertas relações de simetria que permitem obter uma solução, a partir de outra, através de reflexões nos chamados vértices de simetria. Alguns pesquisadores passaram a realizar este trabalho em paralelo (ParallelBP), dividindo uma instância em sub-instâncias, resolvendo localmente com o BP (o que pode ser feito em duas direções) e unindo as sub-soluções com movimentos rígidos, com o intuito de determinar as soluções em menor tempo. Nossa proposta é fornecer uma estratégia Dividir-e-Conquistar para resolver o DMDGP, de modo a melhorar a abordagem em paralelo. Ela possui três estágios. Inicialmente, dividimos uma instância em sub-instâncias duas-a-duas sobrepostas através dos vértices de simetria. Depois, utiliza-se os chamados gaps para decidir a direção em que o BP deve fornecer a solução local. Por fim, utilizamos rotações baseadas na Álgebra de Quatérnios para combinar as sub-soluções em soluções factíveis
Abstract: Motived by studies in 3D structures of proteins, essential biomolecules for Life, arised a problem called Discretizable Molecular Distance Geometry Problem (DMDGP) which proved to be NP-Hard. Aiming to solve it, there is an algorithm in the literature, Branch & Prune (BP), which uses a combinatorial strategy of exploring a binary tree of solutions that is associated to the problem. Moreover, some symmetry relations have been discovered which allows the obtainance of one solution from the other one by means of reflections in the so-called symmetry vertices. Some researchers started to do this work using parallel computing (ParallelBP), dividing one instance into sub-instances, solving the problem locally with the BP (what can be done in two directions) and joining the sub-solutions with rigid movements, with the objective of determining the solutions in a smaller time. Our purpose, thus, is to provide a Divide-and-Conquer strategy to solve the DMDGP in order to improve the parallel version. It has three stages. Initially, the instance is divided into sub-instances two-by-two overlapping by means of the symmetry vertices. After, the so-called gaps are used to decide the direction that the BP ought to provide the local solution. Finally, we propose to use Quaternion Rotations to combine sub-solutions into feasible solutions
Doutorado
Matematica Aplicada
Doutor em Matemática Aplicada
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Jüstel, Dominik [Verfasser], Gero [Akademischer Betreuer] Friesecke, Richard D. [Akademischer Betreuer] James, and Rupert [Akademischer Betreuer] Lasser. "Radiation for the Analysis of Molecular Structures with Non-Crystalline Symmetry: Modelling and Representation Theoretic Design / Dominik Jüstel. Gutachter: Richard D. James ; Rupert Lasser ; Gero Friesecke. Betreuer: Gero Friesecke." München : Universitätsbibliothek der TU München, 2014. http://d-nb.info/1060193884/34.
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Jüstel, Dominik Verfasser], Gero [Akademischer Betreuer] [Friesecke, Richard D. [Akademischer Betreuer] James, and Rupert [Akademischer Betreuer] Lasser. "Radiation for the Analysis of Molecular Structures with Non-Crystalline Symmetry: Modelling and Representation Theoretic Design / Dominik Jüstel. Gutachter: Richard D. James ; Rupert Lasser ; Gero Friesecke. Betreuer: Gero Friesecke." München : Universitätsbibliothek der TU München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:91-diss-20141015-1222032-0-2.
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Brennecke, Julian Tim [Verfasser], Bert de [Akademischer Betreuer] Groot, Bert de [Gutachter] Groot, Marcus [Gutachter] Müller, Luis A. [Gutachter] Pardo, Andreas [Gutachter] Janshoff, Sarah [Gutachter] Köster, and Johannes [Gutachter] Söding. "Mechanosensing and Symmetry of Potassium Channels Studied by Molecular Dynamics Simulations / Julian Tim Brennecke ; Gutachter: Bert de Groot, Marcus Müller, Luis A. Pardo, Andreas Janshoff, Sarah Köster, Johannes Söding ; Betreuer: Bert de Groot." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://d-nb.info/1168473489/34.
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Pakalidou, Nikoletta. "Self-assembly of two-dimensional convex and nonconvex colloidal platelets." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/selfassembly-of-twodimensional-convex-and-nonconvex-colloidal-platelets(072e9fad-3e34-4803-b3df-6aed3ce756c7).html.
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One of the most promising routes to create advanced materials is self-assembly. Self-assembly refers to the self-organisation of building blocks to form ordered structures. As the properties of the self-assembled materials will inherit the properties of the basic building blocks, it is then possible to engineer the properties of the materials by tailoring the properties of the building blocks. In order to create mesoscale materials, the self-assembly of molecular building blocks of different sizes and interactions is important. Mesoscopic materials can be obtained by using larger building blocks such as nano and colloidal particles. Colloidal particles are particularly attractive as building blocks because it is possible to design interparticle interactions by controlling both the chemistry of the particles' surface and the properties of the solvent in which the particles are immersed. The self-assembly of spherical colloidal particles has been widely reported in the literature. However, advances in experimental techniques to produce particles with different shapes and sizes have opened new opportunities to create more complex structures that cannot be formed using spherical particles. Indeed, the particles' shape and effective interactions between them dictate the spatial arrangement and micro-structure of the system, which can be engineered to produce functional materials for a wide range of applications. The driving forces determining the self-assembly of colloidal particles can be modified by the use of external influences such as geometrical confinement and electromagnetic forces. Geometrical confinement, for example, has been used to design quasi two-dimensional materials such as multi-layered structures of spheres, dimers, rods, spherical caps, and monolayers of platelets with various geometries and symmetries. In this dissertation, we present three computer simulations studies using Monte Carlo and Molecular Dynamics simulations determining the self-assembly of monolayer colloidal platelets with different shapes confined in two dimensions. These particles have been selected due to recent experiments in colloidal particles with similar shapes. All the particles' models are represented by planar polygons, and three different effects affecting their self-assembly have been analysed: (a) the curvature of the particles' vertices; (b) the curvature of the particles' edges; and finally (c) the addition of functional groups on the particles' surface. These studies aim to demonstrate that the subtle changes on the particle's shape can be used to engineer complex patterns for the fabrication of advanced materials. Monte Carlo simulations are performed to study the self-assembly of colloidal platelets with rounded corners with 4, 5, and 6-fold symmetries. Square platelets provide a rich phase behaviour that ranges between disorder-order and order-order phase transitions. Suprisingly, the disk-like shape of pentagons and hexagons prevents the total crystallisation of these systems, even at a high pressure state. A hysteresis gap is observed by the analysis of compression and expansion runs for the case of square platelets and the thermodynamic method known as direct coexistence method is used to be accurately determined the point of the order-order transition. Further, unexpected results are obtained by performing Molecular Dynamics simulations in systems with platelets with 3, 4, 5, and 6-fold symmetries when all the sides of each polygon are curved. Macroscopic chiral symmetry breaking is observed for platelets with 4 and 6-fold symmetries, and for the first time a rule is promoted to explain when these chiral structures can be formed driven only by packing effects. This unique rule is verified also for platelets with the same curved sides as previously when functional chains tethered to either vertices or sides. Indeed, square platelets with curved sides confined in two dimensions can form chiral structures at medium densities when flexible chains tethered to either vertices or sides. Triangular platelets with curved sides can form chiral structures only when the chains are tethered to the corners, since the chains experience an one-hand rotation to sterically protect one side. When the chains are symmetrically tethered to the sides, local chiral symmetry breaking is observed as both left-hand and right-hand sides on each vertex are sterically protected allowing the same probability for rotation either in clockwise or anticlockwise direction.
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Erlekam, Undine. "Sterically flexible molecules in the gas phase." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2008. http://dx.doi.org/10.18452/15833.
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Für die makroskopischen Eigenschaften und Funktionen biologisch relevanter Materie spielen schwache, intra- und intermolekulare Wechselwirkungen dispersiver und elektrostatischer Natur auf molekularem Niveau eine große Rolle. Um diese schwachen Wechselwirkungen zu untersuchen, können Modellsysteme, isoliert in der Gasphase, herangezogen werden. Benzoldimer, ein schwach gebundener Van der Waals Komplex, kann beispielsweise als Modellsystem für dispersive Wechselwirkungen dienen. In der vorliegenden Arbeit werden die strukturellen Eigenschaften und die (interne) Dynamik des Benzoldimers mit Hilfe spektroskopischer Methoden in den Energiebereichen der Rotationen, Vibrationen und elektronischen Übergänge untersucht und im Kontext der Symmetrie diskutiert. Die in dieser Arbeit vorgestellten Experimente tragen zu einem tieferen Verständnis des Benzoldimers bei, jedoch zeigt das Experiment zur internen Dynamik auch, dass eine ausreichende theoretische Beschreibung des Benzoldimers nach wie vor eine Herausforderung darstellt. Schwingungsübergänge hochsymmetrischer Moleküle sind oft optisch inaktiv, können jedoch mit der hier vorgestellten Methode der Symmetrieerniedrigung durch Komplexierung zugänglich gemacht werden, wie am Beispiel des Benzols demonstriert wird. Außerdem wird ein Mechanismus vorgstellt, der kollisionsinduzierte Konformationsänderungen in einem Molekularstrahl beschreibt. Dieses Modell kann generell für Molekularstrahlexperimente an flexiblen Molekülen hilfreich sein, einerseits um die beobachtete Konformationsverteilung zu verstehen, andererseits um die experimentellen Parameter gezielt zu verändern und somit Konformerpopulationen zu manipulieren. Die in dieser Dissertation vorgestellten spektroskopischen Experimente liefern einerseits molekülspezifische Informationen und ermöglichen andererseits, Modelle, die von allgemeiner Bedeutung sind, zu entwickeln.The macroscopically observable properties and functionalities of biological matter are often determined by weak intra- and intermolecular interactions on the microscopic level. Such weak interactions are for example hydrogen bonding and van der Waals interactions and can be investigated best on isolated model systems in the gas phase. The benzene dimer, for example, is a prototype system to investgate dispersive interactions. The spectroscopic experiments, covering the energy ranges of rotations, vibrations and electronic transitions, presented in this thesis, contribute to a deeper understanding of the benzene dimer. However, from the experiments investigating the internal dynamics it becomes clear that an appropriate theoretical description of the benzene dimer is still a challenge. Vibrational transitions of highly symmetric molecules, as for example of the benzene, are often optically inactive. Here, a method is presented, which exploits symmetry reduction upon complexation and thus allows one to access such modes. Furthermore, a model is proposed describing collision induced conformational interconversion in a molecular beam. This model can be helpful for molecular beam experiments of flexible molecules to understand the observed relative conformational population and to adapt the experimental conditions allowing for the manipulation of the relative conformer abundances. In this thesis, results are presented that allow one on the one hand to deduce molecular specific information and that on the other hand also give a broader insight into phenomena of general importance.
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Coulaud, Esther. "Analyse théorique de l'interaction d'échange magnétique : effets de solvant et décomposition." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4740.
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La Théorie de la Fonctionnelle de la Densité (DFT) combinée avec le formalisme de la Symétrie Brisée (BS) est aujourd'hui très utilisée dans le domaine du magnétisme moléculaire pour le calcul des constantes d'échange magnétique. Dans le but d'améliorer la compréhension des contributions qui participe à l'interaction d'échange caractérisant les systèmes magnétiques, nous avons mené une étude théorique systématique basée sur l'étude de deux types de modèles. Ces complexes binucléaires de cuivre(II) reliés par divers groupements pontant de type hydroxo, azoture, et chloro, ainsi que des bis-nitroxydes modèles constitués de deux groupements nitroxydes reliés par un système conjugué sont caractérisés par des couplages ferro- et anti-ferromagnétiques variés. Nous avons développé une approche théorique basée sur l'utilisation d'orbitales gelées permettant d'étudier la décomposition de l'interaction d'échange magnétique en différentes contributions telles que l'échange direct, l'échange cinétique et le mécanisme de polarisation de spin. Dans un second temps, nous avons étendu ce travail de rationalisation aux effets de solvant à l'aide de modèles implicites ou explicites. Grâce à une analyse basée sur l'approche de Hoffmann, nous avons pu déterminer les paramètres caractérisant dans les mécanismes d'échange direct et d'échange cinétiqueDensity Functional Theory (DFT) combined with the Broken Symmetry (BS) method is today widely used in the field of molecular magnetism for the computation of magnetic exchange coupling constants. In order to improve the understanding of the contributions involved in the exchange phenomena characterizing some magnetic systems, we propose a study based on two types of models. Copper(II) binuclear complexes connected with various bridging groups like hydroxo, azide, and chlorine, as well as small bis-nitroxide composed of two nitroxide moieties linked by a conjugated system show various ferro- and anti-ferromagnetic couplings. We have developed a theoretical approach based on the use of frozen orbitals to decompose the magnetic exchange interaction in different contributions such as the direct exchange, the kinetic exchange and mechanism of spin polarization. In a second part, we have extended this work to rationalize the solvent effects using implicit or explicit models. Through an analysis based on the Hoffmann's approach, we have determined some parameters characterizing the mechanisms of direct exchange and kinetic exchange
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Rakotoarimalala, Stephan. "Etude par microscopie non linéaire et modélisaion de la dynamique induite par la lumière des systèmes moléculaires complexes : application aux systèmes moléculaires et aux tissus biologiques." Thesis, Angers, 2017. http://www.theses.fr/2017ANGE0097.
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La symétrie spatiale d’un milieu matériel influe fortement sur le mécanisme de son interaction avec un champ électromagnétique extérieur. C’est ce qu’on observe de manière évidente en optique non linéaire. Il est bien établi théoriquement que pour les cristaux dont le groupe d’espace est muni d’une symétrie d’inversion - cristaux dits centrosymétriques -la génération d’harmonique paire est impossibleThe spatial symmetry of a material environment strongly influences the mechanism of its interaction with an external electromagnetic field. This is evident in non-linear optics. It is well established the oretically that for crystals the space group is provided with an inversion symmetry - so-called centrosymmetrical crystals -Paired harmonic generation is impossible
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Alanko, S. (Seppo). "High resolution infrared spectroscopy on the fundamental bands of 13CH3I." Doctoral thesis, University of Oulu, 1999. http://urn.fi/urn:isbn:9514251857.
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This thesis deals with the rotation-vibration theory and high resolution infrared spectroscopy of semirigid C3 molecules. Semirigid molecules form a class of molecules which are strongly bound with one well defined structure, and without low frequency internal motions. The theory, as well as the experimental studies of semirigid molecules are of special importance in the field of rotation-vibration spectroscopy. They provide a good starting point for interpreting and analyzing the spectra of practically all types of molecules.
In this work, the theory is reviewed fromthe standpoint of one particular molecule, 13CH3I, which is a prolate symmetric top with C3 symmetry. The origin and the properties of the rotation-vibration Hamiltonian are discussed in detail. Molecular symmetry plays an important role in these studies. The expansion of the Hamiltonian for nuclear motion in powers of the vibrational operators converges rapidly as numerical examples thoughout the treatment indicate. The molecule is thus a good subject for the perturbation calculations, also reviewed here in detail. 13CH3I can be considered as a model example of semirigid molecules.
From the spectroscopic point of view, this thesis is a study of the six fundamental bands of 13CH3I. The rotational analysis of the vibrational ground state is first given. Special attention is paid to obtaining the axial rotational constants which are problematic for symmetric top molecules. The relatively high energy level density of 13CH3I leads to several resonances. The fundamental bands, especially the higher ones, must therefore be treated as parts of band systems. Care is paid to properly take into account the effects of the near-lying vibrational levels on the constants of the fundamentals. Certain ambiguities in the rotation-vibration Hamiltonian of 13CH3I are also discussed.
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Dale, Aaron Grainger. "Elucidating the molecular target of symmetric bis-benzimidazoles." Thesis, University of London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543260.
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Lin, Zhou. "Theoretical Studies on the Spectroscopy and Dynamics of Astrochemically Significant Species." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429633299.
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Tkac, Ondrej. "Inelastic scattering of symmetric top molecules." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627964.
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Rotationally inelastic scattering of symmetric top molecules is examined by crossed molecular beam and velocity map imaging experiments using a newly constructed instrument. The systems studied are collisions of methyl radicals and ammonia molecules with rare gases and diatomic molecules. Resonance-enhanced multi-photon ionization detection provides velocity map images for ND3 molecules in a single n't, level, and for methyl radicals in levels corresponding to a single rotational angular momentum quantum number (n'), but averaged over a subset of the projection quantum number k'. Product level-resolved angular scattering distributions are extracted from measured images, and for CD3, CH3 and ND3 + He systems are compared with full close-coupling quantum-mechanical scattering calculations that used ab initio potential energy surfaces. These calculations were performed by collaborating groups at Radboud University Nijmegen (ND3 + He), and Johns Hopkins University and the University of Maryland (CD3 / CH3 + He). The experimental measurements provide rigorous tests of the accuracy of the potential energy surfaces and computed quantum scattering dynamics, and agreement between experiment and theory is excellent. For the experimental studies of ND3, a hexapole electrostatic lens was used for the 11 initial state-selection of ND3 molecules in their electronic and vibrational ground states in a molecular beam. For selected final quantum states, the effect of collision energy on the differential cross section for the ND3 + He system was explored in the range 230 - 720 cm-I. For methyl radical scattering experiments, this initial state selection was not possible, but colling in a supersonic expansion restricted the radicals to n = 0 and 1 rotational angular momentum levels prior to the collisions of interest. The inelastic scattering of methyl radicals and ammonia molecules with He and H2 (and D2 in the case of methyl radicals) is predominantly forward scattered for small changes in the n quantum number, but the scattering shifts to the sideways and backward directions as I'!.n increases. The comparison of experimental differential cross sections with theoretical calculations also reveals the dependence of scattering on the k' - projection quantum number and on further features of the scattering dynamics such as the impact parameter. The inelastic scattering ofND3 with Ar and methyl radical with Ar and N2 is dominated by forward scattering for all final levels probed. Common features of the scattering dynamics of these two symmetric top molecules, one closed shell and the other an open-shell radical, are identified and discussed.
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Schroderus, J. (Jyrki). "Internal rotation in symmetric top molecules." Doctoral thesis, University of Oulu, 2004. http://urn.fi/urn:isbn:9514275675.
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Abstract
Internal rotation in symmetric top molecules offers an excellent opportunity to investigate large amplitude motion in a relatively simple intramolecular environment. Due to specific symmetry characteristics of a symmetric top molecular frame, the internal rotation degree of freedom is in the zeroth order approximation separable from the small amplitude vibrations and the overall rotation, thus enabling to characterize the vibrational-torsional-rotational energy structure with a relatively simple Hamiltonian. Lessons from symmetric internal rotor studies may be applied to more complex systems, such as asymmetric internal rotors and macromolecules.
This thesis deals with internal rotation in CH3SiH3, CH3SiD3, CH3CF3 which have become a prototype of symmetric internal rotors. The thesis presents high resolution vibration-torsion-rotation spectra and detailed analysis of these molecules. Particular attention is focused on torsion-mediated interactions, such as Coriolis-type interactions and Fermi-type interactions, coupling the internal rotation and the small amplitude vibrational motion.
The studies show that the expansion of the data to the small amplitude vibrations and inclusion of the torsion-mediated interactions play a crucial role in order to obtain an appropriate characterization of the vibrational-torsional-rotational energy level structure and physically meaningful molecular parameters.
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Pangerl, Michael [Verfasser], and Dirk [Akademischer Betreuer] Trauner. "Towards the total synthesis of oldhamine A : a symmetry-based approach towards new ion channel blockers ; self-assembly of highly symmetric molecules / Michael Pangerl. Betreuer: Dirk Trauner." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2013. http://d-nb.info/1073121232/34.
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Paso, Risto. "Rotation-vibration spectroscopy of certain symmetric top molecules." Oulu : University of Oulu, 1985. http://catalog.hathitrust.org/api/volumes/oclc/12672901.html.
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Clunas, Scott. "The synthesis of chiral Câ†3-symmetric systems." Thesis, University of Aberdeen, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310643.
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Chapter one is an overall introduction reviewing the applications of compounds possessing rotational symmetry, in particular their role as asymmetric reagents/catalysts in various reactions. The attempted syntheses of two different types of C3-symmetric homochiral triols are described in chapter two. Unfunctionalised and functionalised triamides were synthesised from the corresponding amine and 1,3,5-benzenetricarbonyl trichloride. Unfunctionalised N-substituted 1,3,5-triazacychlohexanes (triazines) were synthesised from the corresponding amine and formaldehyde, however reactions between chiral amino alcohols and formaldehyde failed to give the desired trihydroxy triazines. Chapter three describes the syntheses of a range of unfunctionalised chiral C3-symmetric compounds, as well as a review of C3-symmetric systems as host molecules. The successful synthesis of a range of unfunctionalised triethrs was carried out by reacting 1,3,5-tris(bromomehyl)mesitylene with some selected terpenes and other alcohols. Their role as host molecules was investigated, however they failed to bind with any of the various metals that were used. Their asymmetric induction capabilities were also tested when one of the triethers was used as a catalyst in the Et2Zn/aldehyde reaction. The desired alcohol was indeed isolated, however it was found by 1H nmr of the Mosher's ester to be a reacemic mixture. In chapter four the synthesis of the unfunctionalised triethers that was described in chapter three was extended to the synthesis of C3-symmetric triethers containing functional groups. A range of tridentate ligands were synthesised containing either amino, ester, keto or hydroxyl terminal groups. In addition to these, trihydroxy ligands containing amino linkages in place of ethereal linkages were also synthesised. From these compounds three of the trihydroxy ligands were used in complexation reactions with Sn, Ti, Si, Ni, and Cu. The reactions using Si, Ni and Cu failed to give the desired complexes. However, strong evidence was obtained for the existence of the desired Sn and Ti complexes. Once again using the Et2Zn/aldehyde reaction preliminary asymmetric induction studies were carried out using one of the Ti complexes. The reaction showed some selectivity in favour of the R enantiomer. Chapter four also describes the syntheses of some hexadentate ligands, in particular the synthesis of a chiral C3-symmetric hexol, a C3-symmetric ligand containing three β keto-ester groups, and also a 1,3-diketo derivative.
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Liu, Chunmei [Verfasser]. "Attosecond Coherent Control of Symmetry Breaking and Restoration in Atoms and Molecules / Chunmei Liu." Berlin : Freie Universität Berlin, 2019. http://d-nb.info/1190645157/34.
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Tam, Hungsze. "Microwave Spectra of ¹³C Isotopic Species of Methyl Cyanide in the Ground, v₈=1 and v₈=2 Vibrational States." Thesis, North Texas State University, 1988. https://digital.library.unt.edu/ark:/67531/metadc332039/.
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The problem of the quadrupole interaction occurring in a vibrating-rotating C₃v symmetric top molecule has been studied in detail. The quadrupole interaction has been treated as another perturbation term to a general frequency expression accounting for the vibrating-rotating interaction of the molecule so that a complete frequency formula is obtained for both interactions, and from which hyperfine spectral components are predicted and measured. The hyperfine transitions in the ground, and v₈=1 and v₈=2 excited vibrational states of the ¹³C isotopes of methyl cyanide have been investigated in the frequency range 17-72 GHz, primarily in the low J transitions (0≤J≤3). The study of the ground state of isotope i3CH3i3CN, and the v₈=1, v₈=2 excited vibrational states for all the isotopes have been conducted here for the first time. A substantial perturbation has been discovered and discussed at the ΔJ=3→4 transitions within the Kl=1 sets in the v₈=1 mode for isotopes ¹³CH₃CN and CH₃¹³CN. A total of 716 hyperfine transitions have been assigned from measurements, only 7 of which have been measured previously. A total of 84 molecular constants have been reported; 70 of these constants are derived for the first time from microwave data.
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Castaldi, Maria Paola. "Introduction of multiple chiral centres into symmetric small molecules." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425000.
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Ferreira, Luiz Agostinho. "Non compact symmetric spaces and the Toda molecule equations." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37691.
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Smyth, Edward. "Raman optical activity of proteins and glycoproteins." Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312130.
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Uwaha, Makio. "Simple Models for Chirality Conversion of Crystals and Molecules by Grinding." The Physical Society of Japan, 2008. http://hdl.handle.net/2237/13865.
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Bringuier, Stefan. "Mechanical Properties of Symmetric Tilt Grain Boundaries in Silicon and Silicon Carbide: A Molecular Dynamics Study." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/560748.
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The mechanical properties of polycrystalline materials are governed by the underlying microstructure. In this context, in this dissertation, the role of grain boundaries on the mechanical response of two technologically important materials namely silicon and silicon carbide are examined. In particular, the dynamics of silicon carbide and silicon symmetric tilt bicrystals under shear load are characterized via molecular dynamics simulations. Cubic silicon carbide bicrystals with low-angle grain boundaries exhibit stick-slip behavior due to athermal climb of edge dislocations along the grain boundary at low temperatures. With increasing temperature, stick-slip becomes less pronounced due to competing dislocation glide, and at high-temperatures, structural disordering of the low-angle grain boundary inhibits stick-slip. In contrast, structural disordering of the high-angle grain boundary is induced under shear even at low temperatures, resulting in a significantly dampened stick-slip behavior. When a single layer graphene sheet is introduced at the grain boundary of the symmetric tilt silicon-carbide bicrystals, the resultant shear response is dictated by the orientation of the graphene sheet. Specifically, when the graphene layer is oriented perpendicular to the gain boundary, stick-slip behavior displayed by the low-angle grain boundaries is inhibited, though both low-angle and high-angle grain boundaries exhibit displacement along crystallographic planes parallel with the applied shear direction. On the other hand, when the graphene sheet is parallel to the grain boundary, shear deformation at the grain boundary for both low-angle and high-angle bicrystals is diminished. In silicon bicrystals, high-angle grain boundaries demonstrate coupled motion, characterized by an additional normal motion of the grain boundary. Interestingly, this phenomenon was observed previously in metallic materials. Further, the grain boundary coupling factor, which is ratio of the grain boundary normal velocity to the grain translation velocity, matches the predicted geometric value. The underlying atomic scale mechanisms that govern the grain boundary coupled motion consists of concerted rotations of silicon tetrahedra within the grain boundary. For low-angle grain boundaries in silicon, the activation of dislocation glide along the predicted slip-plane takes precedence and no grain boundary coupling is observed. This behavior is similar to that of silicon carbide seen at high-temperatures but for silicon it occurs for a large temperature window.
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Kameda, Minoru. "Molecular design of N-spiro C2-symmetric chiral phase-transfer catalysts for practical asymmetric synthesis of α-amino acids." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147838.
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Wang, Wei. "Computational Spectroscopic Analysis of Orbital Hybridization and Crystal Field Interaction for Trivalent Uranium Ion in Crystals of Hexagonal Symmetry." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1258479110.
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Tsai, Mei-Hsuan. "Boron containing molecular imprinted polymer (MIP) templates from symmetric and asymmetric diboration of olefins and other boron containing functional polymers." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608235.
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Mei, Shan. "Novel Three Dimensional C3v Symmetric Nano-molecules Based on Polyhedral Oligomeric Silsesquioxanes (POSS) Nano-atoms." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1367361671.
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Neacsu, Corneliu Cātālin Verfasser], Thomas [Akademischer Betreuer] Elsässer, Markus B. [Akademischer Betreuer] Raschke, and Oliver [Akademischer Betreuer] [Benson. "Tip-enhanced near-field optical microscopy : from symmetry selectivity to single molecule sensitivity / Corneliu Catalin Neacsu. Gutachter: Thomas Elsässer ; Markus B. Raschke ; Oliver Benson." Berlin : Humboldt Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://d-nb.info/1015016847/34.
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Landinez, Borda Edgar Josué 1984. "Simulações atomísticas de eventos raros através do método super-simétrico." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278445.
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Orientador: Maurice de KoningDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Nesta dissertação abordamos o problema da escala temporal nas simulações atomísticas, focando no problema de eventos raros. A solução deste problema so e possível com o desenvolvimento de técnicas especiais. Especificamente, estudamos o método super-simétrico para encontrar caminhos de reação. Este metodo não apresenta as limitições comuns de outros metodos para eventos raros. Aplicamos o método a três problemas padrão e encontramos que o método permite estudar as transições raras sem precisar de um conhecimento detalhado do sistema. Além disso permite observar qualitativamente os mecanismos de transição
Abstract: This thesis deals with the problem of time scale in atomistic simulations, focusing on the problem of rare events. The solution to this problem is only possible with the development of special techniques. Specifically, we studied the super-symmetric method to find reaction pathways. This method does not have the usual limitations of other methods for rare events. We apply the method to three standard problems and find that the method allows to study the rare transitions without a detailed knowledge of the system. In addition, it allows us to observe qualitatively the transition mechanisms
Mestrado
Física Estatistica e Termodinamica
Mestre em Física
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Duluard, Amandine. "Transport polarisé en spin à travers une barrière de MgO (001) : magnétorésistance et couplage magnétique." Phd thesis, Université de Lorraine, 2012. http://tel.archives-ouvertes.fr/tel-00769754.
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Les jonctions tunnel magnétiques épitaxiées Fe/MgO/Fe(001) présentent des comportements remarquables dans la limite des faibles ou des fortes épaisseurs de MgO. Ainsi, dans le premier cas, une interaction antiferromagnétique entre les deux couches de fer est observée ; dans le second, des effets de filtrage en symétrie conduisent à l'obtention de fortes valeurs de magnétorésistance. Les expériences réalisées au cours de cette thèse visent à étudier et mettre en relation ces deux régimes de propriétés extrêmes. Des analyses en tension et en température nous permettent d'étudier les conséquences d'une modulation de la structure cristalline des électrodes et/ou de l'interface sur le transport polarisé en spin. Dans ce cadre, nous nous intéressons à trois systèmes : des jonctions hybrides Fe/MgO(001)/CoFeB, où l'électrode de CoFeB est déposée par pulvérisation cathodique puis cristallisée in situ, des jonctions Fe/MgO/Fe à texture (001), ainsi que des jonctions Fe/MgO/Fe monocristallines présentant une rugosité artificielle à l'interface barrière/électrode. Le couplage antiferromagnétique dans des systèmes Fe/MgO/Fe(001) à barrière fine est étudié grâce à des mesures de magnétométrie sur la gamme de température [5 K ; 500 K]. Nous considérons aussi l'effet de modifications structurales et/ou chimiques de l'interface par le biais de l'introduction d'une rugosité contrôlée ou d'un contaminant. Les résultats les plus originaux de cette thèse sont obtenus grâce à l'introduction d'une rugosité artificielle à l'interface Fe/MgO ; contre toute attente, ce désordre contrôlé peut en effet augmenter l'effet de magnétorésistance ou l'intensité du couplage antiferromagnétique.
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Breymann, Wolfgang. "Phases plastiques, theorie des groupes et dynamique moleculaire : deux applications." Paris 6, 1987. http://www.theses.fr/1987PA066150.
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Etude theorique des phases plastiques des cristaux moleculaires. La premiere partie se propose d'expliquer le profil spectral raman de certains modes de vibrations internes en utilisant la technique des fonctions rotateurs symetriques pour exprimer d'une facon generale, l'interaction vibrationnelle entre modes appartenant a diverses molecules. Les resultats sont ensuite appliques aux modes internes detectables par diffusion raman et qui sont, simultanement, fortement actifs en absorption ir. La seconde partie contient une simulation par dynamique moleculaire d'un modele realiste d'un cristal de neopentane dans sa phase plastique
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Simler, Thomas. "New transition metal complexes with functional N-heterocyclic carbene ligands for molecular activation." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAF005.
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Le sujet de cette thèse porte sur l’étude de ligands hybrides incorporant un donneur carbène N-hétérocyclique (NHC). Les ligands phosphine-NHC construits sur le motif m-phénylène ont conduit à des complexes di- ou tétranucléaires d’Ag, Cu, Au et Ir, et à des complexes bimétalliques Ag/Cu et Ag/Ir par transmétallation sélective du site NHC. Dans le cas des ligands phosphino-picoline-NHC (PNC), la transmétallation des sels de Li ou K correspondants a permis d’isoler des complexes « pinceurs » dé-aromatisés du Cr, Fe et Co. La déprotonation du ligand bis(phosphinométhyl)pyridine (PNP) a été examinée, et les ligands dé-aromatisés mono- et bis-anioniques correspondants ont été utilisés dans des réactions de transmétallation vers le Cr(II) et Zr(IV). Différents modes de coordination des ligands dé-aromatisés, notamment une métallation de la position alpha-CHP, ont été observés. La substitution de la phosphine dans PNC par une fonction imine conduit à un ligand hybride « rédox non-innocent »The purpose of this work is the synthesis and study of hybrid and potentially “pincer” ligands featuring an N-heterocyclic carbene (NHC) donor. The phosphine-NHC ligands based on the m-phenylene framework led to di- or tetranuclear Ag, Cu, Au and Ir complexes, and to bimetallic Ag/Cu and Ag/Ir complexes by selective transmetallation of the NHC. With the phosphino-picoline-NHC (PNC) ligands, transmetallation from the corresponding Li or K salts led to dearomatised Cr, Fe and Co “pincer” complexes. Deprotonation of the bis(phosphinomethyl)pyridine (PNP) ligand was also examined. The corresponding dearomatised mono- and bis-anionic ligands were isolated as Li or K salts and further used in transmetallation reactions towards Cr(II) and Zr(IV). Different coordination modes of the dearomatised ligands, including side-arm metallation, were observed. Substitution of the phosphine group in PNC by an imine donor led to a hybrid and “redox non-innocent” ligand