Dissertations / Theses: 'Magnetic and spectroscopic investigations'

1

Sharma, Manju. "Magnetic and spectroscopic investigations of pristine and cation-substituted barium hexaferrites." Thesis, IIT Delhi, 2019. http://eprint.iitd.ac.in:80//handle/2074/8041.

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Fischer, Håkon. "Magnetic and spectroscopic investigations of mineral transformations in mixed-valence oxides and magnesium silicates /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17774.

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3

Zhang, Rui. "Nuclear Magnetic Resonance Spectroscopic and Computational Investigations of Chloroperoxidase Catalyzed Regio- and Enantio-Selective Transformations." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/855.

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Chloroperoxidase (CPO) is the most versatile heme-containing enzyme that catalyzes a broad spectrum of reactions. The remarkable feature of this enzyme is the high regio- and enantio-selectivity exhibited in CPO-catalyzed oxidation reactions. The aim of this dissertation is to elucidate the structural basis for regio- and enantio-selective transformations and investigate the application of CPO in biodegradation of synthetic dyes. To unravel the mechanism of CPO-catalyzed regioselective oxidation of indole, the dissertation explored the structure of CPO-indole complex using paramagnetic relaxation and molecular modeling. The distances between the protons of indole and the heme iron revealed that the pyrrole ring of indole is oriented toward the heme with its 2-H pointing directly at the heme iron. This provides the first experimental and theoretical explanation for the "unexpected" regioselectivity of CPO-catalyzed indole oxidation. Furthermore, the residues including Leu 70, Phe 103, Ile 179, Val 182, Glu 183, and Phe 186 were found essential to the substrate binding to CPO. These results will serve as a lighthouse in guiding the design of CPO mutants with tailor-made activities for biotechnological applications. To understand the origin of the enantioselectivity of CPO-catalyzed oxidation reactions, the interactions of CPO with substrates such as 2-(methylthio)thiophene were investigated by nuclear magnetic resonance spectroscopy (NMR) and computational techniques. In particular, the enantioselectivity is partly explained by the binding orientation of substrates. In third facet of this dissertation, a green and efficient system for degradation of synthetic dyes was developed. Several commercial dyes such as orange G were tested in the CPO-H2O2-Cl- system, where degradation of these dyes was found very efficient. The presence of halide ions and acidic pH were found necessary to the decomposition of dyes. Significantly, the results revealed that this degradation of azo dyes involves a ferric hypochlorite intermediate of CPO (Fe-OCl), compound X.

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Paramananthan, Navaneethan. "Investigations of brain perturbation by magnetic resonance spectroscopy." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282328.

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5

Worthington, Lara Angharad. "Investigation of compressed-sensing for acceleration of magnetic resonance spectroscopic imaging." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6128/.

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Magnetic Resonance Spectroscopic Imaging (MRSI) is a functional MRI technique allowing non-invasive biochemical mapping of the brain. MRSI is advantageous for characterising many neurological conditions; however, its clinical application is limited by lengthy scan time and low spatial resolution, which are intrinsically linked. This research investigated the potential of Compressed Sensing (CS) to speed-up MRSI or enhance spatial resolution. CS allows accelerated acquisition by reducing the data sampling requirements, whilst preserving image quality. The focus of this work was the effect of CS-MRSI at different acceleration factors upon spatial integrity. CS reconstruction software was developed and applied to retrospective MRSI data. Imaging test objects and software simulations were developed to assess MRSI spatial resolution via metabolite edge response measurements. CS-MRSI was also investigated in realistic scenarios using data from healthy volunteers and a child with Optic Pathway Glioma (OPG). The potential of CS-MRSI to enable high-resolution MRSI in feasible scan times was investigated using simulations of focal and infiltrative OPG. Results suggest that CS-MRSI can reduce scan duration by up to a factor of 5 whilst simultaneously eliminating ringing artefacts and increasing spatial resolution compared with conventionally filtered MRSI. Therefore, CS could greatly increase the clinical utility of MRSI.

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Rechkemmer, Yvonne [Verfasser], and Joris van [Akademischer Betreuer] Slageren. "Spectroscopic investigations of the magnetic anisotropy of lanthanide- and cobalt-based molecular nanomagnets / Yvonne Rechkemmer ; Betreuer: Joris van Slageren." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2016. http://d-nb.info/1118369777/34.

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7

Wang, Yue. "Investigations of RNA pseudoknot structures and dynamics by nuclear magnetic resonance spectroscopy /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p9992935.

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8

Thomas, Elizabeth Louise. "Investigations of lipid metabolism by #in vivo' 13C magnetic resonance spectroscopy." Thesis, Queen Mary, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363063.

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9

Grunhut, J., G. Wade, J. Sundqvist, A. ud-Doula, C. Neiner, Richard Ignace, W. Marcolino, et al. "Investigating the Spectroscopic, Magnetic and Circumstellar Variability of the O9 Subgiant Star HD 57682." Digital Commons @ East Tennessee State University, 2013. https://dc.etsu.edu/etsu-works/6236.

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The O9IV star HD 57682, discovered to be magnetic within the context of the Magnetism in Massive Stars (MiMeS) survey in 2009, is one of only eight convincingly detected magnetic O-type stars. Among this select group, it stands out due to its sharp-lined photospheric spectrum. Since its discovery, the MiMeS Collaboration has continued to obtain spectroscopic and magnetic observations in order to refine our knowledge of its magnetic field strength and geometry, rotational period and spectral properties and variability. In this paper we report new Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) spectropolarimetric observations of HD 57682, which are combined with previously published ESPaDOnS data and archival Hα spectroscopy. This data set is used to determine the rotational period (63.5708 ± 0.0057 d), refine the longitudinal magnetic field variation and magnetic geometry (dipole surface field strength of 880 ± 50 G and magnetic obliquity of 79° ± 4° as measured from the magnetic longitudinal field variations, assuming an inclination of 60°) and examine the phase variation of various lines. In particular, we demonstrate that the Hα equivalent width undergoes a double-wave variation during a single rotation of the star, consistent with the derived magnetic geometry. We group the variable lines into two classes: those that, like Hα, exhibit non-sinusoidal variability, often with multiple maxima during the rotation cycle, and those that vary essentially sinusoidally. Based on our modelling of the Hα emission, we show that the variability is consistent with emission being generated from an optically thick, flattened distribution of magnetically confined plasma that is roughly distributed about the magnetic equator. Finally, we discuss our findings in the magnetospheric framework proposed in our earlier study.

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10

Khokhar, Shahan. "Chemical Investigations of Australian Marine Sponges Using Experimental and Theoretical NMR Spectroscopy." Thesis, Griffith University, 2015. http://hdl.handle.net/10072/367252.

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This thesis is divided into two parts (A and B). Our overall aim was to isolate and characterize natural products from Australian marine sponges. The uniqueness of this thesis arises from the application of Density Functional Theory (DFT), a quantum mechanical modelling method, which can be used to help elucidate and confirm molecular structures. DFT calculations, and in particular, DFT-NMR (Nuclear Magnetic Resonance) calculations, are still in their relative infancy. The research presented in Part A exemplifies DFT-NMR as a powerful technique, which can be added to a natural product chemist’s “structure-elucidation toolkit”.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Natural Sciences
Science, Environment, Engineering and Technology
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11

Karthik, G. "Investigations Of Spin-Dynamics And Steady-States Under Coherent And Relaxation Processes In Nuclear Magnetic Resonance Spectroscopy." Thesis, Indian Institute of Science, 2001. https://etd.iisc.ac.in/handle/2005/259.

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The existence of bulk magnetism in matter can be attributed to the magnetic properties of the sub-atomic particles that constitute the former. The fact that the origin of these microscopic magnetic moments cannot be related to the existence of microscopic currents became apparent when this assumption predicted completely featureless bulk magnetic properties in contradiction to the observation of various bulk magnetic properties [1]. This microscopic magnetic moment, independent of other motions, hints at the existence of a hitherto unknown degree of freedom that a particle can possess. This property has come to be known as the "spin" of the particle. The atomic nucleus is comprised of the protons and the neutrons which possess a spin each. The composite object- the atomic nucleus is therefore a tiny magnet itself. In the presence of an external bias like a magnetic field, the nucleus therefore evolves like a magnetic moment and attains a characteristic frequency in its evolution called the Larmor frequency given by, (formula) where η is the magnetogyric ratio of the particle and B is the applied magnetic field. The existence of a natural frequency presents the possibility of a resonance behaviour in the response of the system when probed with a driving field. This is the basic principle of magnetic resonance, which in the context of the atomic nucleus, was discovered independently by Purcell [2] and Bloch [3]. From its conception, the technique and the associated understanding of the involved phenomena have come a long way. In its original form the technique involved the study of the steady-state response of the nuclear magnetic moment to a driving field. This continuous wave NMR had the basic limitation of exciting resonances in a given sample, serially. In due course of time, this technique was replaced by the Fourier transform NMR (FTNMR) [4]. This technique differed from the continuous wave NMR in its study of the transient response of the system in contrast to the steady-state response in the former. The advantage of this method is the parallel observation of all the resonances present in the system ( within the band-width of the excitation). In addition to the bias created by the external field, other internal molecular fields produce additional bias which in turn produce interesting signatures on the spectrum of the system, which are potential carriers of information about the molecular state. The fact that the spins are not isolated from the molecular environment, produces a striking effect on the ideal spectrum of the system. These effects contain in them, the signatures of the molecular local environment and are hence of immense interest to physicists, chemists and biologists.

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12

Karthik, G. "Investigations Of Spin-Dynamics And Steady-States Under Coherent And Relaxation Processes In Nuclear Magnetic Resonance Spectroscopy." Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/259.

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Abstract:

The existence of bulk magnetism in matter can be attributed to the magnetic properties of the sub-atomic particles that constitute the former. The fact that the origin of these microscopic magnetic moments cannot be related to the existence of microscopic currents became apparent when this assumption predicted completely featureless bulk magnetic properties in contradiction to the observation of various bulk magnetic properties [1]. This microscopic magnetic moment, independent of other motions, hints at the existence of a hitherto unknown degree of freedom that a particle can possess. This property has come to be known as the "spin" of the particle. The atomic nucleus is comprised of the protons and the neutrons which possess a spin each. The composite object- the atomic nucleus is therefore a tiny magnet itself. In the presence of an external bias like a magnetic field, the nucleus therefore evolves like a magnetic moment and attains a characteristic frequency in its evolution called the Larmor frequency given by, (formula) where η is the magnetogyric ratio of the particle and B is the applied magnetic field. The existence of a natural frequency presents the possibility of a resonance behaviour in the response of the system when probed with a driving field. This is the basic principle of magnetic resonance, which in the context of the atomic nucleus, was discovered independently by Purcell [2] and Bloch [3]. From its conception, the technique and the associated understanding of the involved phenomena have come a long way. In its original form the technique involved the study of the steady-state response of the nuclear magnetic moment to a driving field. This continuous wave NMR had the basic limitation of exciting resonances in a given sample, serially. In due course of time, this technique was replaced by the Fourier transform NMR (FTNMR) [4]. This technique differed from the continuous wave NMR in its study of the transient response of the system in contrast to the steady-state response in the former. The advantage of this method is the parallel observation of all the resonances present in the system ( within the band-width of the excitation). In addition to the bias created by the external field, other internal molecular fields produce additional bias which in turn produce interesting signatures on the spectrum of the system, which are potential carriers of information about the molecular state. The fact that the spins are not isolated from the molecular environment, produces a striking effect on the ideal spectrum of the system. These effects contain in them, the signatures of the molecular local environment and are hence of immense interest to physicists, chemists and biologists.

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13

Thornton, Sheila. "Investigations into the diving response of northern elephant seals (Mirounga angustirostris) using magnetic resonance imaging and spectroscopy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0020/NQ56633.pdf.

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14

Siow, Bernard Marshall Chia Wang. "Investigating single- and intermolecular zero- quantum spectroscopic magnetic resonance imaging as a method for detection of superparamagnetic contrast agents." Thesis, University of Newcastle Upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519477.

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15

Zöllner, Helge [Verfasser], and Thomas [Gutachter] Heinzel. "Metabolic investigations in patients with hepatic encephalopathy by magnetic resonance imaging and spectroscopy / Helge Zöllner ; Gutachter: Thomas Heinzel." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2020. http://d-nb.info/1203370008/34.

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16

Griffin, Joanna Louise. "Investigations of the metal fluoride transition state and ground state analogue complexes of HAD superfamily proteins by nuclear magnetic resonance spectroscopy." Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.574570.

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Metal fluorides (MgF3-, AIF4 - and BeF3-) have been used to mimic the transition state and ground state of phosphate transfer enzymes. The aim of this thesis is to study how phosphate transfer enzymes are able to achieve rate enhancements of 1021 over the uncatalysed reaction, using the full complement of metal fluoride analogues. NMR and X-ray crystallography have been used synchronically to extend the current knowledge of phosphate transfer in β-phosphoglucomutase (βPGM) and phosphoserine phosphatase (PSP). The charge balance theory proposes that the active site of phosphate transfer enzymes is set-up to neutralise the negative charge on the substrate and has been proposed in the literature using phosphoglycerate kinase. Chapter 3 of this thesis shows that the charge balance hypothesis holds true for ~PGM and highlights the importance of local charge in the active site. Chapters 4 and 5 establish the use of BeF3- as a ground state analogue in ~PGM. Complexes in the absence and presence of substrate, have been fully characterised by 19F NMR, IH and 15N chemical shift analysis including backbone assignment and X-ray crystallography. Key residues involved in cap and core domain closure have been recognised through this analysis. A minor conformer of the βPGM:MgF3-:G6P TSA complex was observed in the 19F NMR spectrum. Chapter 6 establishes the nature of this complex as arising from a change in geometry from trigonal bipyramidal to octahedral geometry around the central magnesium ion in the metal fluoride moiety. The full complement of metal fluoride complexes of PSP have been formed and characterised by 19F NMR in chapter 7. The 19F chemical shift and sum isotope shift for each fluoride has been recorded in each complex and has been compared to the available X-ray crystal structures to establish that the NMR and crystallography data report on the same structures.

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17

Turner, Jeffrey W. "High resolution nuclear magnetic resonance investigations of polymethylenic plant biopolymers structural determinations and post-depositional ammonia nitrogen incorporation /." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1189438308.

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18

Wegrzyk, Jennifer. "Wide-pulse, high-frequency electrical stimulation" in humans : Combined investigations of neural and muscular function using electrophysiological and nuclear magnetic resonance techniques." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4080.

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L'ectrostimulation dite conventionnelle (CONV) est délivrée par des impulsions électriques de basse fréquence (≤ 50 Hz), de courte durée (< 400 μs) et de haute intensité. Ce type d'ESNM permet ainsi d'évoquer une contraction musculaire grâce à l'activation directe des axones moteurs et est associé à une fatigue musculaire exagérée par rapport aux contractions volontaires (VOL). Au contraire, lors de l'utilisation d'impulsions de longues durées (1 ms), de hautes fréquences (≥ 80 Hz) et de faibles intensités (i.e. protocole « Wide-Pulse, High-Frequency » (WPHF)), une partie de la force musculaire évoquée aurait pour origine des mécanismes centraux. En effet, une augmentation de la force produite en réponse à WPHF a été rapportée alors que l'intensité de stimulation était constante. Cette « extra force » (EF) refléterait le recrutement par voie réflexe des motoneurones spinaux. L'objectif de ce travail de thèse était de mieux appréhender les mécanismes neurophysiologiques à l'origine de l'EF et d'évaluer les conséquences métaboliques et corticales du protocole WPHF (1 ms - 100 Hz) par rapport à des protocoles d'exercices VOL et de type CONV (50 μs - 25 Hz). Les réponses musculaires des fléchisseurs plantaires et les réponses cérébrales ont été évalué par résonance magnétique nucléaire (la spectroscopie par résonance magnétique du phosphore 31 du muscle et l'imagerie par résonance magnétique fonctionnelle du cerveau) et électrophysiologie (EMG). Ces résultats constituent une première étape importante vers une meilleure prise en charge des pathologies liées à des atteintes du neuromusculaire
Conventional neuromuscular electrical stimulation (CONV) is delivered via surface electrodes at short pulse duration (< 400 μs), low frequencies (≤ 50 Hz) and high current intensities. The motor unit recruitment pattern of CONV, however, is different from the pattern of voluntary contractions (VOL) and leads to a hastened onset of muscle fatigue. The use of wide-pulses (1ms), high frequencies (100 Hz) (WPHF) and low current intensities might approach the natural activation pattern of VOL by enhancing the neural contribution to force production. Previous studies investigating WPHF reported progressive and unexpected force increments ("Extra Forces") despite a constant stimulation intensity which might reflect the more pronounced activation of sensory pathways within the central nervous system. The objective of this thesis was to investigate this "Extra Force" (EF) phenomenon and to evaluate the efficiency of WPHF (1 ms pulse duration at 100 Hz) in terms of metabolic demand and neural contribution to force production in comparison to CONV NMES (0.05 ms pulse duration at 25 Hz) and VOL. Our experiments comprised electrophysiological (EMG) and nuclear magnetic resonance techniques (31P spectroscopy of the muscle, functional imaging of the brain). The findings should be considered in future studies investigating the potential of NMES in a clinical context as a treatment for neuromuscular pathologies

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Liu, Qiang. "Synthesis, characterization and investigation on the magnetic and electronic structure of strontium iron oxides." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14772/document.

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Les diverses perovskites de strontium-fer présentent de très fortes corrélations entre la structurecristalline et les phénomènes d’ordre de lacunes d’oxygènes, de charge, de spin et d’orbitales. Danscette thèse, nous avons réalisé une étude systématique des relations entre les ordres de charges etles ordres de spins selon les différents environnements cristallographiques rencontrés pour lescations Fe3+ et Fe4+ dans la phase Sr4Fe4O11, pour le cation Fe3+ dans les phases Sr3Fe2O6 et Sr2Fe2O10et pour le cation Fe2+ dans la phase SrFeO2. Les synthèses des phases polycristallines furent réaliséesvia des voies « solide » ou « sol-gel » en complément de la synthèse de cristaux préparés à l’aide d’unfour à image à fusion de zone verticale pour les phases Sr4Fe4O11 et Sr2Fe2O10. La qualité cristalline etchimique des oxydes fut contrôlée par diffraction de rayons X sur poudre et spectroscopieMössbauer alors que l’étude de la structure électronique de chaque phase a été réalisée à l’aide despectroscopie d’absorption de rayons X. Finalement, les structures magnétiques des phases Sr3Fe2O6et Sr4Fe4O11 sont aussi présentées
The relationship of the crystallographic, magnetic, and electronic structure have long been of highinterest in research. Strontium iron oxides have structural, charge, spin, and orbital degrees offreedom, and thus give rich information to study for the condensed matter scientists. In this thesis,we have systematically studied the strontium iron oxides based on the freedom of the iron charge:Fe3+ and Fe4+ mixed valence compound SrFeO2,75 , Fe3+ compound Sr3Fe2O6 and SrFeO2,5 with differentcoordination around Fe3+ and Fe2+ compound SrFeO2. The synthesis of the polycrystalline compoundsare through either solid state reaction or sol-gel method. Single crystals of SrFeO2,75 and SrFeO2,5have been prepared by floating zone furnace. The purity of all the compounds is checked by lab x-raydiffraction and Mössbauer spectroscopy. Electronic structures have been studied by x-ray absorptionspectroscopy for all these compounds. Special efforts have been used to investigate the magneticstructure of SrFeO2,75 and Sr3Fe2O6

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20

McKenna, Paul. "Spectroscopic investigations of C-nitrosocompounds." Thesis, Heriot-Watt University, 1986. http://hdl.handle.net/10399/1062.

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21

Nichols, R. J. "Infrared spectroscopic investigations of electrocatalysis." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233925.

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22

Bell, Andrew John. "Spectroscopic investigations of molecular dynamics." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280858.

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23

Woodruff, Nicholas D. "Investigation of protein structure and folding by NMR spectroscopy." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302124.

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24

Friedrich, Frank. "Spectroscopic investigations of delaminated and intercalated phyllosilicates." Karlsruhe : Univ.-Verl, 2005. http://deposit.d-nb.de/cgi-bin/dokserv?idn=976439301.

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25

Anwar, M. "Spectroscopic investigations of amorphous complex dielectric materials." Thesis, Brunel University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234036.

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Lawson, Michael Alan. "Spectroscopic investigations of thermally induced polyphosphazene decomposition." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607701.

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27

Schmidt, Emily Ann. "Spectroscopic investigations of the beta-amyloid peptide." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5668.

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Thesis (M.S.)--University of Missouri-Columbia, 2008.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 14, 2009) Includes bibliographical references.

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Lee, Joonsup. "Spectroscopic Investigations into Disease Diagnosis and Pathogensis." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/10094.

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Spectroscopic investigations into disease can be divided into the different modes of analysis and sample forms. Modern instruments are capable of analysing biological samples, cells and tissues. Software can be integrated into the data analysis, providing a means to extract hidden information. Spectroscopic techniques can collect information on multiple analytes, resulting in a wealth of information collected in a short period of time. Therefore spectroscopic techniques were exploited to investigate disease, with a range of analysis techniques. A spectral, humidity artefact was observed. As these studies were undertaken to explore potential diagnostic applications, an investigation into the cause of the artefact was undertaken. Further studies into artefacts were initiated after the observation of creatine deposits on thin tissue sections of murine brains. The mechanisms behind the formation of these deposits were investigated. The diagnostic applications of spectroscopy of human blood fractions were investigated. A proof-of-concept study was applied to a number of diseases with promising preliminary results. The very first spectroscopic investigation of microparticles (MPs) was undertaken. MPs are sub-micron vesicles that bud from the surface of cells and platelets and are released carrying surface proteins and receptors and a cargo of DNA/RNA. In a murine model of cerebral malaria (CM), if mice are treated with an anti-malarial during the early stages of the infection, they are protected from CM. The mechanism behind this protection was investigated via FTIR imaging of mice brain samples. Particle-induced X-ray spectroscopy routinely uses protons as a beam particle, with an energy of three mega-electron volts. The use of heavier particles is possible, with the potential to increase the yields that are achievable. This effect was applied to investigate the changes that occur when analysing thin brain sections.

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Meng, Jiqun J. "Line scan proton magnetic resonance spectroscopic imaging." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36963.

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30

Newbury, Angela Lois. "An investigation into the applicability of NMR for cure monitoring of composites." Thesis, University of Plymouth, 1994. http://hdl.handle.net/10026.1/2005.

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Fibre-reinforced polymer-matrix composite materials have highly attractive physical properties which justify the present rapid increase in applications within industry. However, composite materials suffer, like every structural material, from a failure to achieve their design properties. Therefore this research project has investigated the processing of resin used in composite materials. Initially the research programme has been concerned with the cure of epoxy resins (specifically Araldite MY750 epoxy resin system), the behaviour of the resin as it cures and how the extent of cure can affect the mechanical properties of components. Therefore, investigations have been carried out into how resin cure can be monitored by the NMR spectra and the relaxation time properties. There were four methods of analysing the data investigated, overall transverse relaxation time (T2) and free induction decay data (FID) data using the Oxford QP NMR analyser, transverse relaxation time data and spectral changes for the individual chemical environments using the Jeol EX270 NMR spectrometer, curemeter investigations using the vibrating needle curemeter (VNC) and finally Barcol hardness investigations during the later part of the cure cycle. Both the Jeol NMR spectrometer and the Oxford QP NMR analyser are designed for use primarily with liquid-state experimentation, however for the spectral, relaxation time, and FID investigations results were obtained far longer in the cure than expected. Also for the T2 investigations a transition period was noticed in the data obtained that corresponded to the gel of the resin as determined by known viscosity data for that resin mix at that cure temperature. The use of NMR as a curemeter technique was verified by repeating the analysis of the resin cure at 40, 60, 80 and 100°C. This data was then compared to known viscosity data and cure profiles obtained by the VNC curemeter and Barcol hardness readings on similar sized samples.

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Campbell, Susan Christina. "Pharmaceutical polymorphism : an investigation using solid-state nuclear magnetic resonance spectroscopy." Thesis, Durham University, 1998. http://etheses.dur.ac.uk/5021/.

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The study of two pharmaceutically active systems that each display polymorphism has provided a platform upon which to develop and apply solid-state NMR techniques in order to increase the understanding of the solid-state structure of small organic molecules. The multidisciplinary approach adopted has highlighted the advantages of solid-state NMR as a non-invasive probe of molecular conformation and crystallographic packing.Carbon-13 CP/MAS spectra of the two polymorphs of BRL55834 - a fluorinated benzopyran derivative - immediately suggest the presence of one and three molecules in the asymmetric unit. A lack of crystals suitable for single-crystal XRD has catalysed the application of high-power powder X-ray diffraction studies. Subsequent attempts at structure solution using Genetic Algorithm techniques are showing preliminary results that reinforce predictions made from solid-state NMR. Novel triple-channel techniques have aided assignment and resolution of die complex (^13)C CP/MAS spectra. Enrichment of the (^15)N site appears to have resulted in the formation of a new polymorph. Techniques for the analysis of detection Units have been developed using solid-state Raman spectroscopy and chemometric analysis. The aminoxanthine derivative, BRL61063, provides interesting inter-form variations in molecular disorder, solid-state packing, and hydrogen bonding. A previously basic understanding of the single-crystal XRD data has been further evaluated through the course of this Ph.D. and solid-state NMR spectral editing techniques have been developed and applied to identify these phenomena. Recrystallisation studies have produced two samples that appear to exist in an intermediate state between the rigid and mobile structural limits. Temperature variation causes interesting changes in the relaxation characteristics and natural abundance (^15)N and (^13)C CP/MAS spectra. Residual dipolar coupling effects vary in their manifestation within the (^13)C CP/MAS spectra of the polymorphic systems studied and comparison with the literature yields important information regarding molecular conformation. Nitrogen-15 enrichment and operation at higher magnetic field have been applied to reduce these second order effects. Finally, some distance has been travelled along the path towards decoupling (^14)N. Future development of this technique holds potential for resolution enhancement in the solid state spectra of most naturally occurring, nitrogen-containing molecules.

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32

Brown, Stephen J. C. "Analytical investigations in magnetic recording." Thesis, University of Plymouth, 2003. http://hdl.handle.net/10026.1/2741.

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The Fourier method is used to provide new analytic solutions for idealized mathematical models of double-element shielded magnetoresistive (MR) recording heads. The general two-dimensional model allows analysis of various recording head configurations; a single pole head, a ring head, a dual stripe head and a differential head. The analysis accommodates both longitudinal recording (with no soft magnetic underlayer present) and perpendicular recording (in the presence of a soft underlayer). Typical field, spectral response function and output voltage pulse plots for double-element MR heads are given and compared to published, approximate solutions. The integrals arising in the determination of the Fourier series coefficients, magnetic potential and magnetic field components are expressed either as rapidly convergent infinite series or in terms of special functions to provide a more efficient means of evaluation than numerical integration. It is shown that, in many situations, it is only necessary to take the first Fourier coefficient in the calculation of output voltage pulse shapes in order to achieve sufficiently accurate results. Bi-variate regression techniques are used to provide a convenient method to approximate the first Fourier series coefficient for a broad range of typical head dimensions. The thesis goes on to examine high speed switching behaviour in two classes of recording media by considering two different particle orientation distributions; 2D random media - intended to simulate a modern thin film rigid disk, and 3D oriented media- simulating a single domain particulate tape media. The gyromagnetic switching constant of a medium is calculated directly from the Landau - Lifshitz - Gilbert (L-L-G) equation of motion, which is solved numerically. The switching constants produced are discussed and compared with published experimental values for different media.

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33

Norton, Lisa K. "Spectroscopic investigations of dendritic polymers as molecular containers." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/6102.

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Thesis (M.S.)--University of Missouri-Columbia, 2008.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on September 22, 2008) Includes bibliographical references.

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34

Knutson, Barbara Lynn. "Spectroscopic and kinetic investigations in supercritical fluid solutions." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/11685.

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35

Wittmann, Hermann Felix. "Spectroscopic investigations of platinum and palladium poly-ynes." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319905.

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36

Snow, Mark Stephen. "Spectroscopic investigations of chiral and induced chiral interactions." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432277.

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37

Blaza, James Nicholas. "Spectroscopic investigations of catalysis by respiratory complex I." Thesis, University of Cambridge, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708587.

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38

Jin, Yigang. "Spectroscopic investigations of new glass-ionomer dental cements." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1535.

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Thesis (M.S.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains xii, 63 p. : ill. (some col.) Includes abstract. Includes bibliographical references.

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39

Nagapudi, Karthik. "Solid-state NMR investigation of structure and dynamics of polyrotaxanes." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/8638.

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40

Walton, Sarah Ann. "MoÌˆssbauer spectroscopic studies of novel nanophase magnetic systems." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243255.

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41

Case, Simon. "Moessbauer spectroscopic and structural studies of magnetic multilayers." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343621.

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42

Chatnuntawech, Itthi. "Model-based reconstruction of magnetic resonance spectroscopic imaging." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82376.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 77-80).
Magnetic resonance imaging (MRI) is a medical imaging technique that is used to obtain images of soft tissue throughout the body. Since its development in the 1970s, MRI has gained tremendous importance in clinical practice because it can produce high quality images of diagnostic value in an ever expanding range of applications from neuroimaging to body imaging to cancer. By far the dominant signal source in MRI is hydrogen nuclei in water. The presence of water at high concentration (-50M) in body tissue, combined with signal contrast modulation induced by the local environment of water molecules, accounts for the success of MRI as a medical imaging modality. As opposed to conventional MRI, which derives its signal from the water component, magnetic resonance spectroscopy (MRS) acquires the magnetic resonance signal from other chemical components, most frequently various metabolites in the brain, but also signals from tumors in breast and prostate. The spectroscopic signal arises from low concentration (-1 - 10mM) compounds, but in spite of the challenges posed by the resulting low signal-to-noise ratio (SNR), the development of MRS is motivated by the desire to directly observe signal sources other than water. The combination of MRS with spatial encoding is called magnetic resonance spectroscopic imaging (MRSI). MRSI captures not only the relative intensities of metabolite signals at each voxel, but also their spatial distributions. While MRSI has been proven to be clinically useful, it suffers from fundamental tradeoffs due to the inherently low SNR, such as long acquisition time and low spatial resolution. In this thesis, techniques that combine benefits from both model-based reconstruction methods and regularized reconstructions with prior knowledge are proposed and demonstrated for MRSI. These methods address constraints on acquisition time in MRSI by undersampling data during acquisition in combination with improved image reconstruction methods.
by Itthi Chatnuntawech.
S.M.

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43

Gu, Meng. "High-speed volumetric ¹H magnetic resonance spectroscopic imaging /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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44

Xu, Jingwei. "Vibrational spectroscopic investigations of calcium phosphates and dental materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0021/NQ30421.pdf.

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45

Pouillot, Frederic. "Thermodynamic and spectroscopic investigations of solid-supercritical fluid equilibrium." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/11120.

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46

Hardy, Sonja [Verfasser]. "Spectroscopic investigations of high pressure multiphase systems / Sonja Hardy." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2014. http://d-nb.info/1049572645/34.

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47

Foxall, Peta Jane Dunckley. "High resolution NMR spectroscopic investigations into renal allograft function." Thesis, Birkbeck (University of London), 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488683.

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48

Conlon, Elizabeth Sarah. "Spectroscopic investigations of hot stars in the galactic halo." Thesis, Queen's University Belfast, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335339.

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Nicholls, Andrew William. "NMR spectroscopic and computational chemical investigations into drug reactivity." Thesis, Birkbeck (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244102.

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50

So, Po Wah. "'1H NMR spectroscopic investigations into experimentally-induced hepatotoxic processes." Thesis, Birkbeck (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363065.

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Dissertations / Theses on the topic 'Magnetic and spectroscopic investigations'

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