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Dissertations / Theses on the topic 'Two dimensional NMR'
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Kraft, Robert A. (Robert Arthur) 1970. "In vivo two-dimensional NMR correlation spectroscopy." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85271.
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Robyr, Pierre Stéphane. "Two-dimensional polarization-transfer NMR spectroscopy for studying ordered and disordered solids /." [S.l.] : [s.n.], 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10968.
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Smith, K. I. "The two-dimensional nuclear magnetic resonance spectroscopy analysis of peptides in solution." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377720.
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Feng, Yi. "One- and two-dimensional high-resolution solid-state NMR investigation of zeolite structures." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30806.
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The work reported in this thesis describes for the first time the application of two-dimensional ²⁹Si high-resolution solid state NMR experiments to the investigation of the three-dimensional Si-O-Si bonding connectivities in zeolites. 2D COSY type, INADEQUATE type and spin-diffusion experiments are discussed and evaluated, the INADEQUATE experiments being particularly successful in this work. By preparing highly crystalline, highly siliceous samples of zeolites and careful optimization of all experimental parameters, it is possible to directly observe ²⁹Si-O-²⁹Si J couplings in these experiments.
The three-dimensional lattice connectivities obtained from this work for ²⁹Si enriched zeolite ZSM-39 and natural abundance ZSM-12 and ZSM-22 are in excellent agreement with the lattice structures determined by XRD techniques. In the case of a ²⁹Si enriched sample of zeolite DD3R, the ²⁹Si 2D NMR results indicate that the structure is of lower symmetry than has been postulated from diffraction studies.
Zeolite ZSM-5, which has the most complex three-dimensional framework of all the known zeolites, was extensively studied in its room temperature phase by 2D NMR spectroscopy. In addition, the effects of temperature and the presence of sorbed p-xylene and p-dichlorobenzene on the phase behavior of ZSM-5 were also investigated.
The ²⁹Si 2D NMR data on ZSM-11 at high temperature are in good agreement with the known structure, I4m2. Low temperature 2D experiments on
ZSM-11 gave the assignment of space group symmetry 14 to the structure which was previous unknown.
Finally, ²⁹Si 2D NMR results on ZSM-23 reveal that there are 12 independent T-sites in the structure which is not consistent with the space groups proposed in the literature which have 7 crystallographically inequivalent T-sites.Science, Faculty of
Chemistry, Department of
Graduate
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Ziouzia, Fanoula. "The capacity and NMR investigation of two dimensional helium mixtures adsorbed on grafoil." Thesis, Royal Holloway, University of London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405286.
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The subject of this thesis is the investigation of two dimensional helium mixtures adsorbed on Grafoil. Heat capacity and Nuclear Magnetic Resonance (NMR) measurements were used in the temperature range of 1 mK to 90 mK. This work represents the first systematic study of monolayer fluid helium mixtures adsorbed in Grafoil at low mK temperatures, extends previous experimental observations on solid helium mixtures and explores the ground state of 3He on top of three layers of 4He. The experimental setup consists of a dilution refrigerator with a nuclear de magnetisation stage with the possibility to achieve ultra low temperatures of 0.3 mK. An NMR setup was constructed to perform continuous wave NMR measurements and was satisfactorily used to obtain data for this thesis. A series of automated, computer controlled data acquisition programmes was also developed to measure and analyse the signals. The study involved the investigation of three different types of mixtures on the second and third layer of Grafoil. The study of fluid mixtures lead for the first time, to evidence of finite solubility of 2D 3He in fluid 4He. It was also possible to explore, within the data collected, the phenomenon of phase separation within a monolayer mixture. Furthermore, the possibility of 3He condensation and stratification effects in this system were also argued as an alternative scenario. A study of solid helium mixtures supported previous observations of delocalised 3He tunnelling excitations and a model was constructed to interpret the data. Additional data in this mixture at various 3He concentrations provided evidence of finite solubility of 3He in 2D solid 4He. Finally, additional measurements were undertaken on 3He on top of three layers of 4He. A number of new and interesting features were observed. The new data suggest the possibility of a phase transition below 10 mK
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Lee, Daniel. "Development of high-resolution two-dimensional correlation spectroscopy in solid-state NMR : applications to nanocomposites and fullerides." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/11864/.
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Two-dimensional correlation spectroscopy in solid-state NMR is an immensely important tool for the analysis of materials, such as technologically interesting nano-materials or bio-materials. After detailing one method that returns high-resolution one-dimensional solid-state proton NMR spectra, high-resolution proton-proton two-dimensional correlation experiments are described and demonstrated. Subsequently, a new two-dimensional NMR experiment is described which is suitable for obtaining a high-resolution proton dimension in heteronuclear dipolar correlation spectra of solids. This new experiment has been used to characterise the interface between the organic and inorganic components of "coreshell" colloidal nanocomposite particles. In addition, a new two-dimensional NMR experiment is described which is suitable for obtaining homonuclear scalar correlation spectra in solids. This new experiment has several advantages, including increased cross peak intensities coupled with good suppression of the diagonal. Its utility is demonstrated via carbon-13 spectra of natural abundance samples as well as the polymer phase of caesium fulleride.
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Pedrazzini, Filippo. "Two-dimensional relaxation-diffusion analysis to study water compartmentalization in cells by a single-sided NMR device." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10368/.
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In questo lavoro di tesi è presentato un metodo per lo studio della compartimentalizzazione dell’acqua in cellule biologiche, mediante lo studio dell’autodiffusione delle molecole d’acqua tramite uno strumento NMR single-sided.
Le misure sono state eseguite nel laboratorio NMR all’interno del DIFA di Bologna.
Sono stati misurati i coefficienti di autodiffusione di tre campioni in condizione bulk, ottenendo risultati consistenti con la letteratura. È stato poi analizzato un sistema cellulare modello, Saccharomyces cerevisiae, allo stato solido, ottimizzando le procedure per l’ottenimento di mappe di correlazione 2D, aventi come assi il coefficiente di autodiffusione D e il tempo di rilassamento trasversale T2. In questo sistema l’acqua è confinata e l’autodiffusione è ristretta dalle pareti cellulari, si parla quindi di coefficiente di autodiffusione apparente, Dapp. Mediante le mappe sono state individuate due famiglie di nuclei 1H.
Il campione è stato poi analizzato in diluizione in acqua distillata, confermando la separazione del segnale in due distinte famiglie.
L’utilizzo di un composto chelato, il CuEDTA, ha permesso di affermare che la famiglia con il Dapp maggiore corrisponde all’acqua esterna alle cellule. L’analisi dei dati ottenuti sulle due famiglie al variare del tempo lasciato alle molecole d’acqua per la diffusione hanno portato alla stima del raggio dei due compartimenti: r=2.3±0.2µm per l’acqua extracellulare, r=0.9±0.1µm per quella intracellulare, che è probabilmente acqua scambiata tra gli organelli e il citoplasma. L’incertezza associata a tali stime tiene conto soltanto dell’errore nel calcolo dei parametri liberi del fit dei dati, è pertanto una sottostima, dovuta alle approssimazioni connesse all’utilizzo di equazioni valide per un sistema poroso costituito da pori sferici connessi non permeabili. Gli ordini di grandezza dei raggi calcolati sono invece consistenti con quelli osservabili dalle immagini ottenute con il microscopio ottico.
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Pannell, Daniel K. (Daniel Kirk). "A Study of Intra- and Interaggregate Exchange Processes of Alkyllithium Compounds Using One- and Two- Dimensional NMR Spectroscopy." Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc278360/.
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One- and two-dimensional NMR spectroscopy, including 13C{6Li}{1H} triple resonance techniques, were used to characterize a series of mixed alkyllithium aggregates and to study their exchange processes.
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Moldovan, Daniel, Radu Fechete, Dan Eugen Demco, Eugen Culea, and Bernhard Blümich. "Monte-Carlo simulations of the two-dimensional NMR T 2 - T 2 exchange of fluids in porous media." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192252.
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The effects of molecular exchange processes on the two-dimensional (2D) NMR T2-T2 distributions obtained by Laplace inversion were studied by numerical simulations. The Monte–Carlo technique is used to generate free random walks of a large number of
molecules within space regions characterized by different relaxation times. Molecular exchange processes are considered during CPMG encoding periods as well as during the storage period, τstore. Systematic simulations were performed as function of NMR parameters like the storage period, τstore and geometric or physical system properties.
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Titman, Jeremy Joseph. "Restriction of magnetization transfer and methods for the measurement of scalar coupling constants in two dimensional NMR spectroscopy." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358849.
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Moldovan, Daniel, Radu Fechete, Dan Eugen Demco, Eugen Culea, and Bernhard Blümich. "Monte-Carlo simulations of the two-dimensional NMR T 2 - T 2 exchange of fluids in porous media." Diffusion fundamentals 10 (2009) 20, S. 1-3, 2009. https://ul.qucosa.de/id/qucosa%3A14111.
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The effects of molecular exchange processes on the two-dimensional (2D) NMR T2-T2 distributions obtained by Laplace inversion were studied by numerical simulations. The Monte–Carlo technique is used to generate free random walks of a large number of
molecules within space regions characterized by different relaxation times. Molecular exchange processes are considered during CPMG encoding periods as well as during the storage period, τstore. Systematic simulations were performed as function of NMR parameters like the storage period, τstore and geometric or physical system properties.
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Lu, Shao-Po. "Syntheses and Structures of Substituted Polycyclic Molecules and Analysis of the Two-Dimensional NMR Spectrum of Thiele's Ester." Thesis, University of North Texas, 1990. https://digital.library.unt.edu/ark:/67531/metadc500745/.
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Diels-Alder cycloaddition of methylcyclopentadienes to 2,5-dibromo-p-benzoquinone was performed. A single, isomerically pure cycloadduct was isolated, whose structure was assigned via analysis of its 1-D and 2-D NMR spectra. Diels-Alder cycloaddition of methylcyclopentadienes to 2 -methoxy-p-benzoquinone was performed. A single, isomerically pure cycloadduct was isolated, whose structure was assigned via analysis of the 1-D and 2-D NMR spectra of this cycloadduct and its reduction product obtained via stereo-specific reduction with sodium borohydride in the presence of cerous chloride. The structure of Thiele's ester was assigned via analysis of its 1-D and 2-D NMR spectra.
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Johnson, Garrett. "Structure Elucidation of a Pyrrolobenzodiazepine Alkaloid and a Biologically Active Polyketide Produced by Rhodococcus sp. MTM3W5.2 via Two-Dimensional NMR Spectroscopy." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etd/3681.
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As the battle against ever-increasing drug resistence bacteria rages on, novel and sometimes more complex natural products can be used to combat this. In this study, two-dimensional NMR techniques were utilized to collect a complete spectral data set for two natural products. The first structure, a synthesized Pyrrolobenzodiazepine alkaloid natural product was confirmed through these methods. The second, a strain of Rhodococcus, MTM3W5.2, produces a novel antibacterial molecule in broth cultures and the active compound was fractionated using a Sephedex LH-20 column. Chromatographic purification yielded a pure sample at 58.90 minutes, RT.58. HRMS data deduced an exact mass of 911.5490 Da, equivalent to a molecular formula of C52H78O13. Several major spin systems were constructed from the 2D-NMR spectra. However, due to limited sample quantity in compound with a large molecular weight and product instability, the long range HMBC signals needed to connect these fragments have not yet been obtained.
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Liu, Xiaoran. "Elucidation of Stabilization Pathways of Polyacrylonitrile by 13C-13C and 1H-13C Two Dimensional Solid-State NMR." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1427750353.
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Chen, Kan. "Applications of Mass Spectrometry to Analysis of Prodiginines, Bioactivated Methylenedianiline Intermediates, and Hypoxia Induced Changes in the Zebrafish Skeletal Muscle Proteome." ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/899.
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Mass spectrometry coupled with liquid chromatography and gel electrophoresis enables separation and detection of components in a complex mixture. During the last two decades, its applications were dramatically extended and remarkable progress has been made in many fields, in particular, environmental and biological analyses. This dissertation focuses on identification and characterization of biologically active compounds and comparative analysis of protein expression changes. The first two projects (Chapters 2 and 3) focus on the application of LC/MS approach to profile the bioactivated intermediates of 4, 4'-methylenedianiline (DAPM) from rat vascular smooth muscle cells (VSMCs) and bile. In our study, several DAPM metabolites were detected and characterized in detail by liquid chromatography-electrospray tandem mass spectrometry. The structural assignments of these metabolites from VSMCs and rat bile significantly improve our understanding of DAPM biotransformations and toxicity. The third project described in Chapter 4 focuses on using electrospray tandem mass spectrometry (ES-MS/MS) and theoretical calculation (GAUSSIAN 03 program) to investigate the unusual methyl radical loss and consecutive fragment ions that dominate the low-energy collision induced dissociation (CID) mass spectra of prodiginine compounds. Structures of the fragment ions are proposed and explanations are given to rationalize the observed competition between the formation of even-electron ions and radical ions. Our study shows that the lower apparent threshold associated with methyl radical loss points to a lower kinetic barrier. In Chapter 5, hypoxia-induced changes of zebrafish skeletal muscle were studied using two-dimensional difference in-gel electrophoresis (2D-DIGE) in vivo after 48 h in hypoxia vs. normoxia. The results showed that proteins involved in mitochondrial oxidative metabolism are down-regulated, whereas glycolytic enzymes are up-regulated to compensate for the loss of ATP synthesis in aerobic metabolism. The up-regulation of two spots identified as hemoglobin variants was also observed. These protein expression changes are consistent with a hypoxic response that enhances anaerobic metabolism or O2 transport to tissues.
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Bäuerle, Christopher. "L'Hélium 3 adsorbé sur du graphite : un système modèle pour la physique des fermions en interaction à deux dimensions." Université Joseph Fourier (Grenoble ; 1971-2015), 1996. http://www.theses.fr/1996GRE10221.
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Dans ce memoire nous presentons des mesures des films d'helium 3 adsorbe sur du graphite etudies par rmn a tres basse temperature. Des mesures systematiques realisees pour la deuxieme couche d'helium 3 adsorbe sur du graphite avec une tres grille de taux de couverture nous permettent une determination tres precise du diagramme de phases. Nous avons pu montrer que la region de coexistence liquide-solide est caracterisee par une dependance lineaire de la quantite du solide (ou du liquide) en fonction de la densite totale du film et par l'invariance des proprietes magnetiques du liquide et du solide. Nos mesures montrent que la phase 4/7#e#m#e est stable dans une certaine plage de densites. Par contre, nos resultats infirment l'hypothese de l'existence d'une phase 2/3, avancee par greywall. Nous presentons pour la premiere fois des resultats pour le solide antiferromagnetique dans un regime ou la temperature est inferieure a l'energie d'echange. Nos mesures montrent que l'aimantation ne peut pas etre decrite par une serie htaf pour des temperatures au-dessous de 2mk. Nous avons effectue des mesures de l'aimantation du solide ferromagnetique en fonction du champ magnetique a une densite correspondant a l'anomalie ferromagnetique. L'utilisation d'un nouveau substrat de graphite exfolie (papyex) nous permet d'etudier l'influence des effets de taille sur l'aimantation. Nos resultats sont bien decrits par la theorie des ondes de spin de kopietz et al. . Ces mesures constituent une premiere exploration du regime pour lequel le gap du spectre des ondes de spin est domine par le champ magnetique. Nous observons des liquides de fermi bidimensionnels extremement correles. Des facteurs de renforcement de 45 sont obtenus, soit 2 fois plus grands que pour l'helium 3 liquide massif. Nous montrons pour la premiere fois que l'helium 3 liquide a deux dimensions a des densites elevees est decrit semi-quantitativement par le modele des fermions presque localises. A tres basse temperature nous observons une augmentation de l'aimantation assez surprenante. Cette augmentation est en accord qualitatif avec une localisation faible du type anderson a deux dimensions. Nous avons realise une experience sur l'helium 3 superfluide massif qui permet de tester experimentalement la theorie de kibble sur la creation des cordes cosmiques lors de transitions de phases rapides. Nous avons observe que l'energie deposee par une reaction nucleaire entre un atome d'helium 3 et un neutron n'est pas entierement convertie en quasiparticules. Le deficit en energie peut etre explique par la creation de defauts topologiques (vortex) pendant une transition rapide entre l'helium 3 normal et l'helium 3 superfluide. En utilisant un modele simple pour le processus refroidissement, nous obtenons des valeurs pour la densite des vortex qui sont en bon accord avec les predictions de zurek pour la creation de cordes cosmiques par le mecanisme de kibble. Ces mesures ont permis de tester pour la premiere fois de maniere quantitative le mecanisme propose theoriquement pour la creation de cordes cosmiques dans l'univers primordial
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Tissandié, Loïc. "Analyse et valorisation des matières premières à odeur boisée : ciblage des composés odorants." Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4244.
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Ce mémoire de doctorat rassemble les travaux réalisés dans le cadre d’une étude analytique approfondie et systématique des substances à odeur boisée. Ces substances définissent une famille d’ingrédients unanimement appréciés pour leurs notes puissantes et recherchés par les parfumeurs pour composer les accords parmi les plus emblématiques de la profession. Les matières premières inscrites au programme de cette étude sont les essences de Gaïac, d’Araucaria, de Patchouli, de Cyprès Jaune d’Alaska, de Vétiver et d’Agarwood, ainsi que certains de leurs produits dérivés. La plupart de ces matières premières sont couramment utilisées par l’industrie du parfum. Leur spécificité provient de leur composition chimique très largement dominée par les dérivés sesquiterpéniques, conférant ainsi à ces extraits une complexité moléculaire indéniable. Les principaux objectifs de cette thèse de doctorat ont consisté à améliorer la connaissance de ces matières premières en termes de composition chimique, à déterminer autant que possible les composés odorants contribuant à leur odeur, et enfin d’explorer d’éventuelles voies de valorisation pour ces mêmes ingrédients à l’échelle industrielle.La méthodologie analytique développée tout au long de l’étude a nécessité l’utilisation combinée d’un large éventail de techniques chromatographiques, spectrométriques et spectroscopiques pour parvenir à caractériser ces matières premières au plus près et à réaliser l’isolement de leurs constituants inconnus. Ainsi, ces travaux s’articulent autour de quatre outils centraux : la chromatographie gazeuse bidimensionnelle intégrale couplée à la spectrométrie de masse (GC × GC–MS), la chromatographie gazeuse couplée à l’olfactométrie (GC–O), la chromatographie gazeuse semi-préparative (GC prép.) et la résonance magnétique nucléaire (RMN). Près de 190 composés ont été isolés et caractérisés dont 107 sont décrits pour la première fois comme constituants d’extraits naturelsThis Ph.D. dissertation sums up the work carried out as part of a thorough and systematic analytical study of woody-scented substances. These substances define a family of ingredients unanimously appreciated for their powerful notes, and sought by perfumers to compose some of the most emblematic accords in perfumery. The raw materials included in the frame of this study are the oils of Guaiac, Araucaria, Patchouli, Alaska Yellow Cypress, Vetiver, and Agarwood, as well as some of their by-products. Most of these raw materials are ingredients commonly used by the perfume industry. Their chemical specificity comes from their composition largely dominated by sesquiterpene derivatives, giving these extracts an undeniable molecular complexity. The main objectives of this Ph.D. thesis were to improve the knowledge of these raw materials in terms of chemical composition, to determine as much as possible the odorous compounds contributing to their odor, and finally to explore possible ways of valorization for these products on an industrial scale.The analytical methodology developed throughout this study required the combined use of a wide range of chromatographic, spectrometric, and spectroscopic techniques in order to characterize these raw materials as precisely as possible and achieve the isolation of their unknown constituents. Thus, our work revolved around four central tools: comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC-MS), gas chromatography-olfactometry (GC–O), preparative capillary-gas chromatography (pc-GC) and nuclear magnetic resonance (NMR). Almost 190 compounds have been isolated and characterized, 107 of which are described for the first time as constituents of natural extracts
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Del, Tenno Ivan. "Thick points of two dimensional Brownian motion." Zürich : ETH Zürich, Department of Mathematics, 2004. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=200.
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Di, Ventra Massimiliano. "Atomic-scale study of the electronic properties of two-dimensional semiconducting systems /." [S.l.] : [s.n.], 1997. http://library.epfl.ch/theses/?nr=1703.
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Botta, Nicola. "Numerical investigations of two-dimensional Euler flows : cylinder at transonic speed /." [S.l.] : [s.n.], 1995. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10852.
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Ferrari, Christian. "Aspects of two dimensional magnetic Schrödinger operators : quantum hall systems and magnetic Stark resonances /." [S.l.] : [s.n.], 2003. http://library.epfl.ch/theses/?display=detail&nr=2769.
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Schmithüsen, Bernhard. "Grid adaptation for the stationary two-dimensional drift-diffusion model in semiconductor device simulation /." Zürich : [s.n.], 2002. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=14449.
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Schulz-Rinne, Carsten Werner. "The Riemann problem for two-dimensional gas dynamics and new limiters for high-order schemes /." [S.l.] : [s.n.], 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10297.
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Kivala, Milan. "Two-dimensional acetylenic scaffolding : extended donor-substituted perethynylated dehydroannulenes, charge-transfer chromophores, and cascade reactions /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17593.
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Eichel, Rüdiger-Albert. "New concepts in two-dimensional pulse electron paramagnetic resonance spectroscopy : resolution enhancement by magnetic field modulation /." Zürich : [s.n.], 2001. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=14394.
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Nickbon, Parisa. "Vänster, höger, upp eller ner? : En kvalitativ studie om var Sverigedemokraterna kan placeras på det politiska spektrumet." Thesis, Mittuniversitetet, Avdelningen för samhällsvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-34800.
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Throughout the years there has been rise to extensive debate in the media and in the research world about the Swedish Democrats being labeled as a populist radical right-winged party or even leaning towards a centrist position with authoritarian values. With a general election coming up soon this year the aim of this study is with the help of a two-dimensional approach, combining the traditional left/right dimension and the GAL-TAL dimension, to find out where the SD place themselves on the political spectrum. The left/right dimension focuses on socioeconomic interests – the relationship between the state and the market while GAL-TAN considers socio-cultural issues such as independence and the degree of individual freedom. By conducting a qualitative content analysis and an ideal-type analysis in this study, several statements from the party's manifestos from the year 2010, 2014 and 2018 have been analyzed to find out where the party can be placed on the political spectrum. The study shows that the SD can be placed on the two-dimensional scale, where the party combines elements of TAN, some libertarian elements (GAL), where SD positions itself as a centrist-right party in some issues of the economic dimension. In addition, results show that social conservatism has been a prominent ideology in the SD:s manifestos over the years.2018-06-07.
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Pereira, Claudete Fernandes. "Uso da espectroscopia de correlação bidimensional (2D) e construção e avaliação de um espectropolarímetro para a região do infravermelho próximo (NIR)." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249974.
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Orientador: Celio PasquiniTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-08-06T07:12:46Z (GMT). No. of bitstreams: 1 Pereira_ClaudeteFernandes_D.pdf: 2102754 bytes, checksum: 94aabfeb5b023dd70dc648a8f2343f52 (MD5) Previous issue date: 2006
Resumo: A espectroscopia de correlação bidimensional (2D) foi utilizada neste trabalho como ferramenta de seleção de variáveis espectrais na região do infravermelho próximo (NIR) para a determinação dos seguintes parâmetros de qualidade de gasolinas: teor de etanol, MON e RON. Para tanto, foi sugerido um sistema de perturbação de concentração em fluxo. Tal sistema apresenta algumas vantagens em relação aos sistemas de perturbação em batelada: os experimentos são realizados em sistema fechado; uma maior velocidade na aplicação da perturbação é obtida, além de se trabalhar em micro-escala. Em outra etapa do trabalho, sugeriu-se a construção de um espectropolarímetro baseado em Filtro Óptico Acústico Sintonizável (AOTF) que opera na região do Infravermelho próximo (800 ¿ 1600 nm). A medida de rotação óptica no instrumento proposto é feita utilizando-se a razão entre os dois feixes difratados pelo AOTF (espectro de rotação óptica), a qual é proporcional ao ângulo de rotação da luz polarizada imposto pela amostra. O instrumento foi empregado na obtenção de espectros de rotação óptica na região NIR de sacarose, glicose, frutose e cânfora. Esses espectros são proporcionais às concentrações das espécies estudadas e curvas analíticas com bons coeficientes de correlação foram obtidas
Abstract: The two-dimensional correlation spectroscopy was used in this work as a tool for spectral variable selection in the near-infrared (NIR) region aiming the determination of the following quality parameters of gasoline: ethanol content, MON (Motor Octane Number) and RON (Research Octane Number). To achieve this objective, it was developed a flow system to automated the perturbation by concentration. This system presents some advantages in relation to batch systems employed to the same purpose: the experiments are accomplished in a closed system; a greater velocity in the application perturbation can be obtained and the experiments are made in micro-scale. In another part, this work presents the construction of a spectropolarimeter based on the acousto-optic tunable filter (AOTF), which works on the near-infrared region (800 ¿ 1600 nm). The measure of optical rotation on the instrument is made using the ratio between two diffracted beams by the AOTF (optical rotation spectrum), which is proportional to the rotation angle of the polarized light imposed by the sample. The instrument was applied in the investigation of NIR optical rotation spectra of sucrose, glucose, fructose and camphor. These spectra are proportional to the concentration of species studied and analytical curves with good correlation coefficients were obtained.
Doutorado
Quimica Analitica
Doutor em Ciências
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Piras, Antioco. "Etude par résonnance magnétique nucléaire haute résolution en solution de la structure des polyesters insaturés." Paris 6, 1988. http://www.theses.fr/1988PA066483.
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Preparation et caracterisation par rmn a haute resolution d'alpha -omega -dihydroxy polyesters insatures modeles par rmn bidimensionnelle: mise en evidence de 3 types de branchements: cours, longs, cycliques. Preparation de polyesters lineaires par synthese en solution ou a partir de diacetates, reactions non adaptables industriellement sans modification des procedes; mise au point d'une technique de dosage de la reaction de saturation des produits industriels et etude des parametres influant sur cette reaction
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Bensaci, Abderrahmane. "Etude par RMN du sélénium 77 et du tellure 125 de la cinétique d'échange de dichalcogénures aromatiques." Rouen, 1987. http://www.theses.fr/1987ROUES008.
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Ashoka, Sahadevan Suchithra. "Anilate-based molecular building blocks for metal-organic frameworks and molecular conductors Conducting Anilate-Based Mixed-Valence Fe(II)Fe(III) Coordination Polymer: Small-Polaron Hopping Model for Oxalate-Type Fe(II)Fe(III) 2D Networks Nanosheets of Two-Dimensional Neutral Coordination Polymers Based on Near-Infrared-Emitting Lanthanides and a Chlorocyananilate Ligand." Thesis, Angers, 2019. http://bu.univ-angers.fr/Contact.
Full textAbstract:
Ce travail porte sur la synthèse et la caractérisation de matériaux moléculaires fonctionnels basés sur la molécule anilate et présentant des propriétés de conductivité, de magnétisme et de luminescence. Les anilates sont des dérivés de la 2,5-dihydroxy-1,4-benzoquinone substitués en positions 3 et 6 par une variété d’éléments (H, F, Cl, Br, I, CN, etc). Parmi eux, le seul composé hétérosubstitué ClCNAn2- a été choisi pour préparer une nouvelle famille de polymères de coordination bidimensionnels (PC 2D) avec des métaux de transition ou des ions lanthanides : i) un PC à valence mixte FeIIFeIII, de formule [TAG][FeIIFeIII(ClCNAn)3], contient pour la première fois le cation triaminoguanidinium dans un réseau de coordination.ii) Des PC basés sur le ligand ClCNAn2- et des ions lanthanides émettant dans le proche infrarouge (YbIII, NdIII, ErIII). Ces composés ont été exfoliés en monocouches, et des études de photoluminescence ont été menées à la fois sur les cristaux et les monocouches. iii) Une famille de PC hétéroleptiques basés sur des ions lanthanides et sur deux types de ligands pontants, le ligand ClCNAn2- et des ligands de type carboxylates (DOBDC et F4-BDC). iv) Une famille de PC basés sur des ions DyIII ont été préparés afin d’étudier leur propriétés magnétiques. v) Finalement, la capacité des ligands anilates à se combiner à des conducteurs moléculaires basés sur le BEDT-TTF a été démontrée à travers la synthèse et l’électrocristallisation de semiconducteurs organiques et de conducteurs magnétiques hybrides avec l’anion [Fe(ClCNAn)3]3-This work reports on the design, synthesis and characterization of novel anilate-based functional molecular materials showing luminescent, magnetic and/or conducting properties. The family of anilate ligands comprises several derivatives obtained by introducing various substituents (H, F, Cl, Br, I, CN, etc.) at the 3 and 6 positions of the common 2,5-dihydroxy-1,4-benzoquinone framework. Among the anilate ligands, the only known heterosubstituted anilate with Cl/CN substituents at the 3,6 positions, ClCNAn2-, have been selected for preparing a novel family of 2D layered coordination polymers (2D CP) with both 3d metal ions and 4f lanthanide ions, through a general and straightforward synthetic strategy. i) Mixed-valence FeIIFeIII 2D CP, formulated as [TAG][FeIIFeIII(ClCNAn)3], containing, the tris(amino)-guanidinium (TAG) cation for the first time in such 2D networks has been synthesized and thoroughly characterized. ii) 2D CPs based on NIR-emitting lanthanides (YbIII, NdIII, ErIII) and the ClCNAn2- ligand, have been prepared and characterized. These layered compounds were exfoliated to nanosheets, by sonication-assisted solution synthesis. Time-resolved photoluminescence studies performed on both the bulk and nanosheets are also highlighted. iii) Novel family of heteroleptic 2D CPs based on NIR-emitting lanthanides and mixed ligands (ClCNAn2- and carboxylate ligands (DOBDC and F4-BDC)), were prepared and characterized. vi) Novel family of 2D CPs based on DyIII and ClCNAn2- were prepared in order to investigate their magnetic properties. v) Furthermore, the ability of anilate ligands to work as components of BEDT-TTF- based molecular conductors have been demonstrated through the synthesis, via electrocrystallization technique. vi) П-d hybrid multifunctional paramagnetic molecular conductors BEDT-TTF and [Fe(ClCNAn)3]3-) were also studied
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Baudrillard, Vincent. "Etude structurale par résonance magnétique nucléaire mono- et bidimensionnelle haut-champ de carbanions vinyliques à fonction carbonyle masquée." Rouen, 1996. http://www.theses.fr/1996ROUES024.
Full textAbstract:
Les caractéristiques spectrales en résonance magnétique nucléaire du proton, du carbone et du silicium des éthers d'énol silylés β-silylés ont été déterminées via un certain nombre d'expériences de résonance magnétique nucléaire spécifiquement mises au point et optimisées pour ces composés. Les produits secondaires obtenus lors de la synthèse des éthers d'énol silylés β-silylés ont été identifiés grâce à ces techniques résonance magnétique nucléaire mono- et bidimensionnelles et grâce à la spectrométrie de masse couplée à la chromatographie en phase gazeuse. Ces analyses montrent que l'addition de t-butyllithium sur les éthers d'énol silylés β-bromés entraîne une compétition entre une réaction d'échange halogène-métal (majoritaire), une réaction de désilylation de la fonction éther d'énol silylé et une réaction de métallation. Les espèces réactives formées lors de l'addition de t-butyllithium sur les éthers d'énol silylés beta bromés ont été analysées par résonance magnétique nucléaire du proton, du carbone et du silicium à basse température entraînant exclusivement une réaction d'échange halogène-métal avec une formation d'espèces purement carbanioniques et que l'addition de tétrahydrofurane à ces espèces carbanioniques entraînait leur transposition en espèces énoliques avec un rendement satisfaisant (r>30%) si la température du milieu est convenablement contrôlée (élévation lente).
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Izquierdo, Marguerite. "Caractérisation spectrale en spectroscopie RMN in vivo : contribution au développement de méthodes physiques d'investigation." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10153.
Full textAbstract:
Ce travail a pour objectif de contribuer a l'identification des resonances obtenues in vivo par spectroscopie rmn proton 1d et 2d, globale et localisee. Les techniques d'edition spectrale et de caracterisation developpees ont ete appliquees en particulier a l'etude des tumeurs intracerebrales du cerveau de rat in vivo. Un travail preliminaire a consiste a elaborer une methode rapide de correction des imperfections introduites par un modulateur de phase et d'amplitude, qui permet d'obtenir des impulsions de bonne qualite. Plusieurs axes de recherche ont ensuite ete suivis afin d'apporter des informations complementaires contribuant a l'identification moleculaire. Un de ces axes a concerne les techniques de rmn a deux dimensions, en examinant plus particulierement les fonctions d'apodisation utilisees pour le traitement des spectres 2d obtenus in vivo, afin d'optimiser le rapport signal sur bruit. La spectroscopie 2d de correlation combinee a l'imagerie spectroscopique a permis d'acceder a la repartition spatiale des acides amines et des carbohydrates presents dans une plante in vivo. D'autre part, les techniques d'observation localisees (imagerie et imagerie spectroscopique) des coherences a multiples quanta ont ete proposees afin d'observer simultanement les differents ordres de coherence des systemes de spins couples et non-couples. Enfin, dans un autre contexte, la mesure localisee du coefficient de diffusion a conduit a l'edition et a la caracterisation des metabolites presents dans les tumeurs intracerebrales in vivo en fonction de leur degre de mobilite translationnelle
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Aroca, Patricia Paulina. "One and two-dimensional NMR characterization of organofunctionalized silica gels." Thesis, 1995. http://hdl.handle.net/2429/8744.
Full textAbstract:
An alternative preparation is proposed in this thesis for the synthesis of
organofunctionalized silica gels based on the copolymerization of tetraethoxysilane (TEOS)
and an organofunctionalized triethoxysilane. The principal analytical techniques used to
determine the integrity and distribution of the functionality in the copolymer matrix were
solution and solid state NMR.
The model copolymer chosen for these studies is methyltriethoxysilane (MTES)/TEOS.
One-dimensional 29Si solid state NMR was used to establish the integrity of the system and
relative proportions of the different silicon environments present. Two-dimensional ¹H-29Si
heteronuclear correlation NMR experiments unambiguously demonstrated that the monomers
in the copolymer were “mixed and not phase-separated.
To quantify the extent of mixing of the two monomers in the copolymer, kinetic
studies were undertaken with the objective of determining reactivity ratios for each monomer.
The acid catalyzed hydrolysis and dimer formation reactions of the TEOS and MTES
monomers were characterized at a number of catalyst concentrations in order to determine the
pH independent kinetic rate constants. With both homopolymers well characterized, the
hydrolysis and dimer formation kinetic rate constants were determined for the copolymer.
From these kinetic data reactivity ratios were calculated which suggest that the MTES/TEOS
system tends to form a random copolymer.
One interesting possible application of organofunctionalized silica gels is in the
manufacturing of low temperature functionalized glasses. The synthesis of large pieces of
glasses from the copolymerization of TEOS and MTES requires the usage of a drying
chemical control agent (DCCA) to prevent cracking. The most commonly used DCCA is
formamide. Solution NMR was used to determine the integrity and interaction of formamide
in the polymerization process. Another step taken to characterize the suitability of these
compounds for the manufacturing of low temperature functionalized glasses was to
characterize the thermal stability of numerous organic functionalities by thermal analysis
techniques and NMR. Of all the functionalities studied the methyl group had the highest
thermal stability, up to 700°C when thermally treated under nitrogen, showing promise for the
synthesis of methyl functionalized glasses.
The cross polarization (CP) dynamics of a number of MTES/TEOS copolymers were
then studied, to determine the distance range between the methyl group and the fully
condensed unfunctionalized silane (Si(OSi)4). These results further support the conclusion
that the functionality in the MTES/TEOS copolymer is quite evenly distributed throughout the
copolymer matrix. [Scientific formulae used in this abstract could not be reproduced.]
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Prabhu, Uday Ramesh. "Development Of Two Dimensional Correlation And Resolved Methodologies For NMR Spectroscopic Discrimination Of Enantiomers." Thesis, 2010. http://hdl.handle.net/2005/1890.
Full textAbstract:
The research work reported in this thesis deals with the development of novel NMR experimental techniques for the spectroscopic discrimination of enantiomers dissolved in a chiral liquid crystalline medium. The information on the chemical shifts and coupling constants pertaining to each enantiomer has been derived on the investigated chiral molecules. The enantiomeric excess (ee), a parameter which is of profound importance in pharmaceutical industry and in asymmetric synthesis, has also been measured. A special attention is paid to the use of high sensitivity of H NMR for chiral discrimination. Typical analyses of H NMR spectra are severely hindered due to enormous spectral inhomogeneous broadening arising from too many unresolved transitions, in addition to superposition of spectra from both the enantiomers. Therefore, the major part of the work is focused on the design and application of pulse sequences to overcome many of these drawbacks. This helps to achieve very high resolution, discerning of overlapped transitions, identification of resonances pertaining to each enantiomer and simplification of the spectrum for easy extraction of spectral parameters, in addition to the accurate measurement of ee.
Initially a brief discussion is provided on enantiomers, diastereomers, basic principles of NMR spectroscopy, the several interaction Hamiltonians responsible for yielding the NMR spectra, introduction to product and polarization operator formalisms that gives insight into the spin dynamics for designing appropriate two-dimensional (2D) NMR experiments. This sets the foundation to understand the complex multiplet structures of the diagonal peaks and cross peaks in the resulting 2D spectrum. Subsequently, a brief introduction is given for the available techniques for NMR spectroscopic discrimination of enantiomers in isotropic medium, where only chemical shifts are employed as a measurable parameter. The limitations of these techniques are circumvented by the introduction of other anisotropic NMR parameters, such as homo-and hetero-nuclear dipolar couplings, quadrupolar couplings and chemical shift anisotropies. To achieve this goal the enantiomers are dissolved in weakly aligning chiral liquid crystalline (CLC) medium. To understand this, a general introduction to liquid crystals and their utility as an alignment medium in NMR spectroscopy and the anisotropic interactions affecting the NMR spectrum has also been provided. The preparation of the CLC phase of Poly-γ-Benzyl-L-Glutamate (PBLG) employed in the present study and its orientational behaviour has been discussed. The detection of NMR spectra of various nuclei and the interaction parameters utilized for chiral discrimination will be enumerated. A brief summary of the experiments employed for the spectral analyses of the enantiomers dissolved in PBLG will also be presented.
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Soltero, Luis Ruben. "Investigation of multiple quantum coherence transfer in two-dimensional NMR spectroscopy." Thesis, 1990. http://hdl.handle.net/1911/16391.
Full textAbstract:
The limitations of zero quantum NMR pulse sequences reported in the literature are discussed. Several new pulse sequences which improve and extend the scope of the currently available pulse sequences are described.
A modified double quantum filtered proton zero quantum 2D-NMR pulse sequence which employs a potentially more efficient and chemical shift independent excitation scheme is described. Results obtained with the modified experiment are illustrated using the complex alkaloid gelsemine.
Two new pulse sequences which provide $F\sb1$ homonuclear decoupling double quantum filtered zero quantum 2D-NMR spectra are introduced. One of the pulse sequences uses a chemical shift dependent excitation scheme while the second uses a chemical shift independent sequence. The effects of composite 180$\sbsp{y}{o}$ pulses during the excitation and evolution of zero quantum coherences are explored. The effectiveness of a magnetic field homogeneity spoiling pulses on the signal intensity of zero quantum resonances is investigated as is the effect of the tip angle of the radio frequency conversion pulse, $\alpha$.
Double quantum filtered, $F\sb1$ proton homodecoupled zero quantum relayed coherence transfer is discussed and a new pulse sequence described. The pulse sequence provides a mechanism for exploring remote proton-proton connectivities. The mapping of the two four spin systems of the helicene derived phenanthro (3$\sp\prime$,4$\sp\prime$:3,4) phenanthro (2,1-b) thiophene is discussed in the context of zero quantum relay. A remote 5-bond "W" connectivity is observed for phenanthro (4,3-a) dibenzothiophene.
Heteronuclear $\sp{13}$C-$\sp{31}$P chemical shift correlation via heteronuclear multiple quantum coherence is described. Enhanced sensitivity is afforded by the inverse detection of $\sp{31}$P rather than detection of the much less abundant $\sp{13}$C spin. Correlations via $\sp1J\sb{CP}$ and $\sp{n}J\sb{CP}$ where n = 2, 3, are observed with minor variations in the pulse sequence. A description of the laboratory built probes and X-band decoupler is also presented.
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Tseng, Yu-Yu, and 曾瑜玉. "Structural Determination of Unusual DNA Motifs Using Two-Dimensional NMR Technology." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/80889343353215753421.
Full textAbstract:
博士國立中興大學
化學系
89
Several unusual DNA structures containing special motifs are recently solved by the combination of 2D homo-, and hetero-nuclear NMR spectra at natural abundance. The exchangeable protons were systematically assigned from the H2O-NOESY spectrum(1). Such spectrum can provide direct evidence for some unusual base-pairing(2). The unusual structural features could also be detected from the D2O-NOESY that reveals the internucleotide NOE between the non-exchangeable protons. Besides the NOE distance constraints, dihedral angle constraints are also essential for structural calculation. The high resolution natural abundance 1H-13C HSQC can not only be utilized for assigning the chemical shifts of 13C with directly-bonded protons, but also for extracting 3JH3'-P, 2JC3'-P, 3J(n)C4'-(n+1)P, 3J(n+1)C4'-(n+1)P, and 4J(n+1)H4'-(n+1)P coupling constants. These coupling constants are useful in locating backbone beta and epthlone torsion angles(3) through the modified Karplus equation. Besides, the natural abundance 1H-13C HMBC can be utilized for the stereospecific assignment(3) of H5'(Pro-R) and H5'(Pro-S), which is of critical importance in determining nucleic acid structure. Combination of NOE distance constraints and beta、gamma、epthlone and kai torsion angles constraints allow for a more detailed picture of the unusual DNA motifs. We have used the NMR methodology described above to solve several unusual DNA structures; 1) we have found a novel cross- strand purine-pyrimidine (A-C) and hetero purine-purine (G-A) stacks in the 5'-CTCCTAAACACAGTGCAGGAC-3' 21-mer(4), which is a HIV-1 reverse transcriptase inhibitors selected through oligo- nucleotide libraries. These mixed base-base stacks are caused by a sheared A˙C pair adjacent to a sheared G˙A pair in the 5'-AA/GC-3' sequences; 2) we have found that single-residue d(PuNPy) hairpin loops can be stably closed by a sheared purine˙pyrimidine (A˙C) pair at a neutral pH condition(5); 3) we have determined the solution structure of a TCC-loop hairpin(6) in a cruciform promoter for the bacteriophage (N4 vRNAP). All three pyrimidines in the TCC-loop are unpaired. The first loop nucleotide T base was found to fold into the minor groove, and form three H-bonds with the juxtaposed stem G˙C base-pairs. The central loop cytosine base stacks upon the 3'-end cytosine base of the closing base-pair. The last loop cytosine base extrudes outward, with its deoxyribose/phosphodiester backbone stacking upon the 5'-end guanine base of the closing base-pair; 4) a DNA hairpin containing a T3 loop, as occurs in the terminal repeat of a popular gene therapy vector (Adenoassociated Virus 2, AAV2), was found to adopt the same motif as TCC3.
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Lin, Chiong-chi, and 林瓊琪. "Hydration of Amino Acid Studied with One-and Two- Dimensional NMR Spectroscopy." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/66878583181463360573.
Full text
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Jerath, Kanay. "Reconciliation of two-dimensional NMR measurements with the process of mud-filtrate invasion : synthetic and field examples." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-12-4410.
Full textAbstract:
Nuclear magnetic resonance (NMR) has become an effective borehole measurement option to assess petrophysical and fluid properties of porous and permeable rocks. In the case of fluid typing, two-dimensional (2D) NMR interpretation techniques have advantages over conventional one-dimensional (1D) interpretation as they provide additional discriminatory information about saturating fluids and their properties. However, often there is ambiguity as to whether fluids detected with NMR measurements are mobile or residual. In some instances, rapid vertical variations of rock properties (e.g. across thinly-bedded formations) can make it difficult to separate NMR fluid signatures from those due to pore-size distributions. There are also cases where conventional fluid identification methods based on resistivity and nuclear logs indicate dominant presence of water while NMR measurements indicate presence of water, hydrocarbon, and mud filtrate. In such cases, it is important to ascertain whether existing hydrocarbons are residual or mobile. The radial lengths of investigation of resistivity, nuclear, and NMR measurements are very different, with NMR measurements being the shallowest sensing. Even in the case of several radial zones of NMR response attributed to different acquisition frequencies and DC magnetic field gradients, the measured signal originates from a fairly shallow radial zone compared to that of nuclear and resistivity logs. Depending on drilling mud being used and the radial extent of mud-filtrate invasion, the NMR response of virgin reservoir fluids can be masked by mud filtrate because of fluid displacement and mixing. In order to separate those effects, it is important to reconcile NMR measurements with electrical and nuclear logs for improved assessment of porosity and mobile hydrocarbon saturation. Previously, Voss et al. (2009) and Gandhi et al. (2010) introduced the concept of Common Stratigraphic Framework (CSF) to construct and validate multi-layer static and dynamic petrophysical models based on the numerical simulation of well logs. In this thesis, the concept of CSF is implemented to reconcile 2D NMR interpretations with multi-layer static and dynamic petrophysical models. It is found that quantifying the exact radial zone of response and corresponding fluid saturations can only be accomplished with studies of mud-filtrate invasion that honor available resistivity and nuclear logs. This thesis indicates that the two interpretation methods complement each other and when applied in conjunction, improve and refine the overall petrophysical understanding of permeable rock formations. Examples of successful application include field data acquired in thinly-bedded gas formations invaded with water-base mud, where bed-boundary effects are significant and residual hydrocarbon saturation is relatively high. In such cases, numerical simulation of mud-filtrate invasion and well logs acquired after invasion enables reliable interpretations of petrophysical and fluid properties. The interpretation procedure introduced in this thesis also provides an explicit way to determine the uncertainty of petrophysical and fluid interpretations.text
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Chien, Yao-Ying. "One-dimensional and two-dimensional NMR studies of atrazine and simple organic compounds sorbed by humic acid micelles." 1999. http://catalog.hathitrust.org/api/volumes/oclc/44724877.html.
Full textAbstract:
Thesis (Ph. D.)--University of Wisconsin--Madison, 1999.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 115-124).
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Mishra, Sandeep Kumar. "Study of Diverse Chemical Problems by NMR and the Design of Novel Two Dimensional Techniques." Thesis, 2017. http://etd.iisc.ernet.in/2005/3558.
Full textAbstract:
The research work reported in this thesis is focused on the chiral analysis, quantification of enantiomeric composition, assignment of absolute configuration of molecules with chosen functional groups. The weak intra-molecular hydrogen bonding interactions are detected by exploiting several multinuclear and multi-dimensional techniques. Pulse sequences have been designed to manipulate the spin dynamics to derive specific information from the complex NMR spectra encountered in diverse situations. Broadly, the thesis can be classified in to three sections. The section I containing two chapters reports the introduction of new chiral auxiliaries and protocols developed for enantiomeric discrimination, measurement of enantiomeric contents, assignment of absolute configuration for molecules possessing specific functional groups using chiral solvating and derivatizing agents. The section II, reports NMR experimental evidence for the observation of the rare type of intramolecular hydrogen bonds involving organic fluorine in biologically important organic molecules, that are corroborated by extensive DFT based theoretical calculations. The section II also discusses the H/D exchange mechanism as a tool for quantification of HB strengths in organic building blocks. The section III reports the two different novel NMR methodologies designed for deriving information on the scalar interaction strengths in an orchestrated manner. The designed sequences are able to completely eradicate the axial peaks, prevents the evolution of unwanted couplings and also yields ultrahigh resolution in the direct dimension, permitting the accurate measurement of scalar couplings for a particular spin. The brief summary about each chapter is given below.
Chapter 1 provides a general introduction to one and two dimensional NMR spectroscopy. The pedagogical approach has been followed to discuss the conceptual understanding of spin physics and the NMR spectral parameters. The basic introduction to chirality, existing approaches in the literature for discrimination of enantiomers and the assignment of absolute configuration of molecules with chosen functional groups and their limitations are briefly discussed. The brief introduction to hydrogen bond, experimental methods to obtain the qualitative information about the strengths of hydrogen bonds, and the theoretical approaches employed in the thesis to corroborate the NMR experimental findings have been provided. The mechanism of H/D exchange, the utilization of exchange rates to derive strengths of intra-molecular hydrogen bond in small molecules have also been discussed. This chapter builds the bridge for the rest of the chapters. Each of these topics are discussed at length in the corresponding chapters.
Part I: NMR Chiral Analysis: Novel Protocols
Chapter 2 discusses a simple mix and shake method for testing the enantiopurity of primary, secondary and tertiary chiral amines and their derivatives, amino alcohols. The protocol involves the in-situ formation of chiral ammonium borate salt from a mixture of C2 symmetric chiral BINOL, trialkoxyborane and chiral amines. The proposed concept has been convincingly demonstrated for the visualization of enantiomers of a large number of chiral and pro-chiral amines and amino alcohols. The protocol also permits the precise measurement of enantiomeric composition. The significant advantage of the protocol is that it can be performed directly in the NMR tube, without any physical purification. The structure of the borate complex responsible for the enantiodifferentiation of amines has also been established by employing multinuclear NMR techniques and DFT calculations. From DOSY and 11B NMR experiments it has been ascertained that there are only two possible complexes or entities which are responsible for differentiating enantiomers. From the combined utility of DFT calculations and the 11B NMR chemical shifts, the structure of the borate complex has been determined to be an amine-coordinated complex with the N atom of the amine.
Chapter 3 discusses a simple chiral derivatizing protocol involving the coupling of 2-formylphenylboronic acid and an optically pure [1,1-binaphthalene]-2,2-diamine for the rapid and accurate determination of the enantiopurity of hydroxy acids and their derivatives, possessing one or two optically active centers. It is established that this protocol is not only rapid method for discrimination of enantiomers but also highly effective for assigning the absolute configuration of various chiral hydroxy acids and their derivatives. The developed protocol involves the coupling of 2-formylphenylboronic acid with (R)-[1,1-binaphthalene]-2,2-diamine, and 2-formylphenylboronic acid with (S)-[1,1-binaphthalene]-2,2-diamine as
chiral derivatizing agents. The absence of aliphatic peaks from the derivatizing agent, large chemical shift separation between the discriminated peaks of diastereomers, and the systematic change in the direction of displacement of peaks for an enantiomer in a particular diastereomeric complex, permitted the unambiguous assignment of absolute configuration.
Part II : Rare Type of Intramolecular Hydrogen Bonding
In chapter 4 The rare occurrence of intramolecular hydrogen bonds of the type N–H˖˖˖F–C, in the derivatives of imides and hydrazides in a low polarity solvent, is convincingly established by employing multi-dimensional and multinuclear solution state NMR experiments. The observation of 1hJFH, 2hJFN, and 2hJFF of significant strengths, where the spin polarization is transmitted through space among the interacting NMR active nuclei, provided strong and conclusive evidence for the existence of intra-molecular hydrogen bonds. Solvent induced perturbations and the variable temperature NMR experiments unambiguously supported the presence of intramolecular hydrogen bond. The two dimensional HOESY and 15N–1H HSQC experiments reveals the existence of multiple conformers in some of the investigated molecules. The 1H DOSY experimental results discarded any possibility of self or cross-dimerization of the molecules. The results of DFT based calculations, viz., Quantum Theory of Atoms In Molecules (QTAIM) and Non Covalent Interaction (NCI), are in close agreement with the NMR experimental findings.
In chapter 5 the rates of hydrogen/deuterium (H/D) exchange determined by 1H NMR spectra have been utilized to derive the strength of hydrogen bonds and to monitor the electronic effects in the site-specific halogen substituted benzamides and anilines. The theoretical fitting of the time dependent variation in the integral areas of 1H NMR resonances to the first order decay function permitted the determination of H/D exchange rate constants (k) and their precise half-lives (t1/2) with high degree of reproducibility. The comparative study also permitted the determination of relative strengths of hydrogen bonds and the contribution from electronic effects on the H/D exchange rates.
Part III: Novel NMR Methodologies for the Precise Measurement of 1H-1H Couplings
Chapter 6 describes two novel NMR methodologies developed for the precise measurement of 1H-1H couplings. Poor chemical shift dispersion and the pairwise interaction among the entire coupled network of protons results in the severely complex and overcrowded one dimensional 1H NMR spectra, hampering both the resonance assignments and the accurate determination of nJHH. The available two-dimensional selective refocusing (SERF) based experiments suffer from the evolution of magnetization from uncoupled protons as intense uninformative axial peaks. This creates ambiguity in the identification of peaks belonging to the coupled partners of a selectively excited proton, hindering the extraction of their interaction strengths. This challenge has been circumvented by designing two novel experimental technique, cited as “Clean-G-SERF” and “PS-Clean-G-SERF”. The Clean-G-SERF technique completely eradicates the axial peaks and suppresses the evolution of unwanted couplings while retaining only the couplings to the selectively excited proton. The method permits the accurate determination of spin-spin couplings even from a complex proton NMR spectrum in an orchestrated manner. The PS-Clean-G-SERF technique has been designed for the complete elimination of axial peaks and undesired couplings, with a blend of ultra-high resolution achieved by real time broad band homonuclear decoupling has been discussed in this chapter. The spin dynamics involved in both these pulse sequences have been discussed. The diverse applications of both these novel experiments have been demonstrated.
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Huang, Hou-Ju, and 黃厚儒. "Microstructure of Poly(Acrylamide-co-N-Vinylformamide)/SDS complexes Studied by Two-Dimensional NOESY NMR." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/56519354302747733204.
Full textAbstract:
碩士國立成功大學
化學工程學系碩博士班
96
The main purpose of the study is to explore the extremely different behaviors toward SDS shown by poly(acrylamide) (PAAm) and poly(N-vinylformamide) (PNVF), in the present study we have synthesized statistical PAAm-co-PNVF copolymers and PAAm-b-PNVF block copolymers with different AAm/NVF ratios. The part I of this study, we have initiated an investigation of the PAAm-co-PNVF/SDS system by pyrene fluorescence and 2D NOESY NMR. PAAm-co-PNVF is a good model copolymer suitable for the NOESY experiment, because the proton chemical shits of AAm, NVF, and SDS are well separated. We know that the SDS molecules can closely contact (<5Å) with PNVF, so the question arisen here is: could the SDS molecules be close (<5Å) to the AAm unit in the PAAm-co-PNVF copolymer with the aid of the strong interaction between NVF and SDS? Our answer based on the results from 2D NOESY NMR is “No!”. It suggests that the AAm unit (CH2CHCONH2) really dislike SDS, even the SDS molecules close by locate only several nanometers apart. In the part II of the study, we focus on the PAAm-b-PNVF/SDS system by pyrene fluorescence and compared with PAAm/PNVF/SDS blending system. The polymer-surfactant interaction in the PAAm-b-PNVF/SDS system was weaker than PAAm/PNVF/SDS blending system. Viscosity measurements confirmed the presence of three behaviors: no change of the polymer coil shape in region I, contraction of polymer coils in region II, and expansion in the region III.
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Flaum, Mark. "Fluid and rock characterization using new NMR diffusion-editing pulse sequences and two dimensional diffusivity-T2 maps." Thesis, 2007. http://hdl.handle.net/1911/20607.
Full textAbstract:
New down-hole nuclear magnetic resonance (NMR) measurement and interpretation techniques have substantially improved fluid and reservoir characterization. These techniques take advantage of the magnetic field gradient of the logging tools to make diffusion sensitive NMR measurements. In this work, new NMR pulse sequences called "diffusion-editing" (DE) are used to measure diffusivity and relaxation times for a variety of samples. We use a new inversion technique to obtain two-dimensional maps of diffusivity and relaxation times, and propose new interpretation approaches for these maps.
Two DE NMR pulse sequences are of particular interest. First is the CPMG-DE Pulse sequence, based on the Carr-Purcell-Meiboom-Gill pulse sequence in a magnetic field gradient. Results presented here demonstrate that CPMG-DE measurements can be used to determine the saturation of partially saturated samples, detect wettability change, and observe the presence of internal field gradients or restricted diffusion.
The second DE sequence of interest is PFG-SE DE, based on the pulse field gradient stimulated echo (PFG-SE) sequence. The PFG-SE DE sequence is particularly well suited for analyzing restricted diffusion, which occurs when the spins are prevented from diffusing freely by the presence of confinement such as pore walls.
The interpretation of pore-size distributions from PFG-SE DE measurements can be simplified by approximating the pore network as a system of spheres of varying sizes. A procedure is developed for determining the optimal parameters for measuring spheres of a selected size. A technique for combining the sensitive portions of multiple measurements using masks is also developed. Experiments are performed on grain packs, vuggy carbonates, and emulsions. In most cases, the range of length scales the system is sensitive to is too narrow using the available range of gradients to provide interesting information about the systems, but in the case of emulsions the results are positive when evaluating droplet size distributions.
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Li, Kun-ta, and 李昆達. "Multi-nuclear One and Two Dimensional Solid State NMR Studies of Bis(2-Methyl-8-Quinolinolato)-(2,6-Dimethylphenolate)Aluminum." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/67040846401575400411.
Full textAbstract:
碩士國立中山大學
化學系研究所
92
Bis(2-methyl-8-quinolinolato)-(2,6-dimethylphenolate)aluminum is a newly synthesized material suitable for manufacturing organic light-emitting devices (OLED). NMR parameters such as chemical shift, dipolar and quadrupolar tensors are intimately related to the electronic and geometric structures which are important for understanding its physical and chemical properties. In this work, we report the solid state NMR studies of this material. By using two-field (corresponding to proton resonance frequencies of 200 MHz, 500 MHz , respectively) 1D 1H MAS, 27Al MAS, 1H/13C CP/MAS and 2D 13C nutation MAS techniques, the chemical shift tensors of 13C and quadrupolar coupling constant of 27Al have been obtained. The relationship between these values and the light-emitting properties of this material is discussed.
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Liu, Su-Chin, and 劉素琴. "One and Two Dimensional NMR Studies of the Dependence of Chemical Shift and Dynamics of ADP and AMP on pH Value and Temperature." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/59816586327712976091.
Full textAbstract:
碩士國立中山大學
化學系研究所
91
Recently years NMR technique plays an important role in investigation of structures of biochemistry molecules. Especially two-dimension NMR experiments are powerful evidences of the relation of intramolecule of biochemistry. Further more we design a series of experiments about studies of chemical shift and dynamics under different pH values and at different temperature.
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"Elasto-plastic adaptative analysis for modeling fracture processes of two-dimensional structures." Tese, MAXWELL, 1999. http://www.maxwell.lambda.ele.puc-rio.br/cgi-bin/db2www/PRG_0991.D2W/SHOW?Cont=1885:pt&Mat=&Sys=&Nr=&Fun=&CdLinPrg=pt.
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"A geometric modeler for generation of two - and three - dimensional finite element meshes." Tese, MAXWELL, 1999. http://www.maxwell.lambda.ele.puc-rio.br/cgi-bin/db2www/PRG_0991.D2W/SHOW?Cont=1258:pt&Mat=&Sys=&Nr=&Fun=&CdLinPrg=pt.
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