Дисертації з теми "Field Cycling NMR"
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1
Pine, Kerrin J. "Localized fast field-cycling NMR relaxometry." Thesis, University of Aberdeen, 2014. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=215228.
Повний текст джерелаАнотація:
Conventional MRI relies on a strong fixed magnetic field B0 which is stable during the imaging process. By contrast, field-cycling MRI switches the strength of B0 up or down during an experiment. In this way, field-cycling provides access to endogenous information not accessible to standard MRI, such as enhanced T1 relaxation at certain NMR frequencies due to interactions between hydrogen and nitrogen nuclei in proteins. However, biomedical research of T1 dispersion is limited by the unavailability of equipment and rapid software methods. Strategies are presented to address these deficiencies. A removable electromagnet was designed and implemented for use with a 59-mT vertical-field, permanent-magnet based imager. The resistive magnet locally offsets the primary field over a small projected region to enable field-cycling relaxometry on an otherwise-conventional imager. Radiofrequency coils were constructed to suit the electromagnet’s configuration. T1 dispersion measurements were demonstrated for, separately, the finger joints and forearm of a human volunteer. Prior to this work, producing graphs of T1 dispersion from a volume of interest required lengthy T1 mapping at each field strength step. A new pulse sequence combining SR/IR T1 determination with field-cycling and point-resolved spectroscopy localization enables the measurement of dispersion curves of a volume selected from a pilot image. Its advantages include less partial voluming than whole-sample relaxometry, as well as better SNR and faster acquisition times than image-based techniques. The sequence’s sensitivity is sufficient to reveal distinctive ‘quadrupole dips’ in dispersion curves. To the author’s knowledge, it is the first pulse sequence to enable the relationship between T1 and field strength to be examined in times which are feasible for clinical investigations. Used together as presented in this thesis, the hardware and software developed represent a step towards field-cycling being used to reveal useful diagnostic information inaccessible to conventional MRI.
2
Zampetoulas, Vasileios. "Fast field-cycling NMR relaxometry on biological samples extended to ultra-low magnetic fields." Thesis, University of Aberdeen, 2018. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=237833.
Повний текст джерела
3
Miesel, Karsten [Verfasser]. "Field cycling NMR experiments with hyperpolarized multi-spin-systems / Karsten Miesel." Berlin : Freie Universität Berlin, 2008. http://d-nb.info/1023401371/34.
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4
Wu, Weimin. "Field-cycling NMR investigations of nuclear spin relaxation and proton tunnelling." Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/10155/.
Повний текст джерелаАнотація:
A current-switched superconducting field-cycling NMR spectrometer has been designed and built for studying the role of quantum tunnelling in molecular dynamics. The instrument is designed for work in the solid state with sample temperatures extending from 4K up to 300K. The maximum field-switching rate is 10Ts-1. Among the samples studied in this thesis is the nuclear spin-relaxation and proton tunnelling. Concerted double proton transfer in the hydrogen bonds of carboxylic acid dimers is well established as the model system for translational quantum tunnelling. The model system has been chosen to illustrate the smooth quantum-to-classical transition and at all temperatures the proton transfer is characterised by a single correlation time. Quadrupolar interactions introduce an additional relaxation to the proton spin polarisation. The enhanced relaxation of the proton spin appears as a dip in the proton magnetisation curve. This technique is employed to measure the quadrupolar transition frequency of 14N and 35Cl and determine the structure of heroin hydrochloride. The introduction of a second spin species has a significant effect on the spin-lattice relaxation. Compared with homonuclear systems, the spectral density acquires additional components characterised by the sum and difference Larmor frequencies of the two nuclei. Further, instead of a single relaxation time, there are four elements of a relaxation matrix. Therefore, the magnetisation recovery becomes bi-exponential and the initial polarisation state of the second nucleus strongly affects the magnetisation recovery of the nucleus which is being observed. We shall report on the results of spin-lattice relaxation investigations on 1H-13C, 1H-19F systems. The role of heteronuclear interactions in spin-lattice relaxation and the newly developed methodology of field-cycling relaxometry will be discussed. This represents the first 13C field-cycling NMR experiment and the first to measure the field dependence of the off-diagonal element of the relaxation matrix.
5
Noble, Daniel Leigh. "Field-cycling NMR investigations of proton tunnelling and nuclear spin relaxation." Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438354.
Повний текст джерела
6
Freiman, Gabriel, Jean-Pierre Korb, Benjamin Nicot, and Patrice Ligneul. "Microscopic wettability of carbonate rocks: a proton field cycling NMR approach." Diffusion fundamentals 10 (2009) 25, S. 1-3, 2009. https://ul.qucosa.de/id/qucosa%3A14116.
Повний текст джерелаАнотація:
Nuclear Magnetic Relaxation Dispersion (NMRD) is strongly sensitive to the microscopic wettability of oil and brine bearing carbonate rocks. Exploring a very large range of low frequency enables isolating the typical NMRD dispersion features, 1/T1Surf, associated to
the different processes of molecular surface dynamics. This allows a separation of the surface and bulk microdynamics of oil and water even for a biphasic saturation of petroleum rocks. Several surface dynamical parameters were determined and related to the concept of microscopic wettability of oil and water in porous media.
7
Sun, Cheng. "Quantum dynamics and tunnelling of methyl rotors studied by field-cycling NMR." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10751/.
Повний текст джерелаАнотація:
Quantum dynamics and tunnelling of methyl rotors has been studied using field-cycling nuclear magnetic resonance (NMR) spectrometer, in a variety of samples. The characteristic frequency of the tunnelling motion of methyl groups has been investigated using both low-field dipole-dipole driven experiments and tunnel resonance level-crossing experiments. The classical hopping and quantum tunnelling of methyl groups have been studied by making temperature-dependent and field-dependent measurements of the spin-lattice relaxation time T1. The spectral density functions of the dipolar interaction, mediated by the rotation of methyl groups, have been directly plotted, and the correlation times characteristic of the rotational motion have been determined. Electron spin resonance (ESR) tunnel resonance spectra have been studied in samples with unpaired electrons by making resonant contact between the methyl tunnelling reservoir and the electron spins. The phenomenon of dynamic proton polarisation (DNP) has also been investigated in these samples. Experiments demonstrating the cooling of methyl tunnelling reservoir and the diffusion of energy amongst tunnelling reservoirs are presented. In low-field dipole-dipole driven experiments, in order to avoid the tunnelling transition saturation problem, the sideband stirring radiofrequency (rf) irradiation technique has been utilised and the low-field NMR spectra have been observed with enhanced sideband peaks. The rf irradiation time-dependence of the low-field spectra has been investigated. The experimental data is supported by numerical simulations, using appropriate theoretical models.
8
McGloin, C. J. "Hydrogen bond dynamics : an investigation using NMR field-cycling and QENS techniques." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298074.
Повний текст джерела
9
Volgmann, K., B. Kresse, A. F. Privalov, F. Fujara, and P. Heitjans. "7Li Field-Cycling NMR as Powerful Tool for Investigating Li Ion Conductors." Diffusion fundamentals 21 (2014) 25, S.1, 2014. https://ul.qucosa.de/id/qucosa%3A32435.
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10
Hofmann, Marius [Verfasser], and Ernst [Akademischer Betreuer] RößLer. "Field-Cycling NMR as a Tool of Molecular Rheology / Marius Hofmann ; Betreuer: Ernst Rößler." Bayreuth : Universität Bayreuth, 2016. http://d-nb.info/1116426382/34.
Повний текст джерела
11
Abu-Khumra, Sabah. "Quantum rotor tunnelling in methyl ethyl ketone and acetophenone studied using field-cycling NMR techniques." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/14032/.
Повний текст джерелаАнотація:
In the solid state the rotation of a methyl group is hindered by a potential barrier and at low temperature the rotational motion is characterised by quantum tunnelling. The Pauli Exclusion Principle imposes constraints on the allowable eigenstates of the methyl rotor and leads to a combination of spatial and spin variables. The characteristics of these quantum tunnelling states, labelled A and E, are explored experimentally and methods are investigated for creating prescribed non-equilibrium states. We will investigate and explore the tunnelling polarization associated with the A and E tunnelling-magnetic levels by means of field-cycling NMR. Secondary rf irradiation is used to drive A-E and E-A transitions associated with NMR tunnelling sidebands. This polarization is then transferred to the 1H Zeeman system at a field-dependent level-crossing where the methyl tunnelling frequency equals one or two times the 1H Larmor frequency. The level-crossing contact is a necessary step since the tunnel temperature cannot be measured directly with a pulse. A new pulse sequence is described and the resulting spectra are analogous to the solid effect and dynamic nuclear polarization. Therefore we assign the phrase ‘dynamic tunnelling polarization’ to describe the experiments. Two samples are studied in depth, methyl ethyl ketone and acetophenone which have tunnel frequencies of 495 and 1435 kHz respectively. The experiments investigate the phenomena as a function of a variety of physical parameters in order to determine the fundamental physics.
12
Grinberg, Farida. "Reorientations mediated by translational displacements in confined liquid crystals studied by field cycling NMR relaxometry and Monte Carlo simulations: Reorientations mediated by translational displacements in confinedliquid crystals studied by field cycling NMR relaxometry and Monte Carlo simulations." Diffusion fundamentals 6 (2007) 73, S. 1-9, 2007. https://ul.qucosa.de/id/qucosa%3A14253.
Повний текст джерелаАнотація:
Ordering effects and low-frequency molecular dynamics in the nematic liquid crystals confined in mesoscopic pores was studied with the help of field cycling (FC) Nuclear Magnetic Resonance (NMR) relaxometry and Monte Carlo simulations. Proton relaxation rates were measured above the bulk isotropisation temperature in the broad frequency range between 2 kHz and 7 MHz. The average pore radii of confinements were between 1.5 and 15 nanometers. The relaxation dispersion curves in the confined materials exhibited strong deviations from the behaviour in bulk. In a few kHz range, a dramatic enhancement of the relaxation rates exceeding two
orders of magnitude compared to the bulk sample was observed. The low-frequency value of the relaxation rate exhibited a strong dependence on the pore size. Experimental findings were interpreted in terms of the surface induced orientational order and diffusion between the sites with different orientations of local directors. The analysis was supported by Monte Carlo simulations of the reorientations mediated by translational displacements (RMTD) in spherical cavities.
13
Ardelean, Ioan, Sergiu Muncaci, Codruta Badea, Alexandra Pop, Carlos Mattea, and Siegfried Stapf. "Translational diffusion at the surface of porous media with magnetic impurities via Fast Field Cycling NMR relaxometry." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-182881.
Повний текст джерела
14
Ardelean, Ioan, Sergiu Muncaci, Codruta Badea, Alexandra Pop, Carlos Mattea, and Siegfried Stapf. "Translational diffusion at the surface of porous media with magnetic impurities via Fast Field Cycling NMR relaxometry." Diffusion fundamentals 20 (2013) 41, S. 1-2, 2013. https://ul.qucosa.de/id/qucosa%3A13609.
Повний текст джерела
15
Kresse, Holger Benjamin [Verfasser], Franz [Akademischer Betreuer] Fujara, and Ernst [Akademischer Betreuer] RößLer. "Field-Cycling NMR bei extrem kleinen Larmor-Frequenzen – Entwicklung und Anwendung / Holger Benjamin Kresse ; Franz Fujara, Ernst Rößler." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2016. http://d-nb.info/1121781705/34.
Повний текст джерела
16
Flämig, Max [Verfasser], and Ernst [Akademischer Betreuer] Rössler. "A Field Cycling NMR Relaxometry Study on Molecular Liquids and Plastically Crystalline Phases / Max Flämig ; Betreuer: Ernst Rössler." Bayreuth : Universität Bayreuth, 2020. http://d-nb.info/1222101726/34.
Повний текст джерела
17
Herrmann, Axel [Verfasser], and Ernst [Akademischer Betreuer] RößLer. "Polymer Melts Investigated by Field Cycling NMR Relaxometry: From Simple Liquid to Reptation Dynamics / Axel Herrmann. Betreuer: Ernst Rößler." Bayreuth : Universität Bayreuth, 2012. http://d-nb.info/1059412667/34.
Повний текст джерела
18
Grinberg, Farida. "Reorientations mediated by translational displacements in confined liquid crystals studied by field cycling NMR relaxometry and Monte Carlo simulations." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194134.
Повний текст джерелаАнотація:
Ordering effects and low-frequency molecular dynamics in the nematic liquid crystals confined in mesoscopic pores was studied with the help of field cycling (FC) Nuclear Magnetic Resonance (NMR) relaxometry and Monte Carlo simulations. Proton relaxation rates were measured above the bulk isotropisation temperature in the broad frequency range between 2 kHz and 7 MHz. The average pore radii of confinements were between 1.5 and 15 nanometers. The relaxation dispersion curves in the confined materials exhibited strong deviations from the behaviour in bulk. In a few kHz range, a dramatic enhancement of the relaxation rates exceeding two
orders of magnitude compared to the bulk sample was observed. The low-frequency value of the relaxation rate exhibited a strong dependence on the pore size. Experimental findings were interpreted in terms of the surface induced orientational order and diffusion between the sites with different orientations of local directors. The analysis was supported by Monte Carlo simulations of the reorientations mediated by translational displacements (RMTD) in spherical cavities.
19
TACKE, CHRISTIAN [Verfasser], Franz [Akademischer Betreuer] Fujara, and Danuta [Akademischer Betreuer] Kruk. "Resonanzen in Field-Cycling-NMR an Molekülkristallen: (reversible) Spindynamik oder (irreversible) Relaxation? / Christian Tacke. Betreuer: Franz Fujara ; Danuta Kruk." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2015. http://d-nb.info/1110980833/34.
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20
Gizatullin, Bulat [Verfasser], Jörg [Akademischer Betreuer] Kröger, Esteban Akademischer Betreuer] Anoardo, and Siegfried [Gutachter] [Stapf. "Dynamic nuclear polarization NMR fast field cycling study complex systems / Bulat Gizatullin ; Gutachter: Siegfried Stapf ; Jörg Kröger, Esteban Anoardo." Ilmenau : TU Ilmenau, 2020. http://d-nb.info/1218465778/34.
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21
Meier, Roman [Verfasser], and Ernst [Akademischer Betreuer] RößLer. "Molecular Liquids and Polymers Investigated by Field Cycling 1H NMR Relaxometry: Impact of Rotational and Translational Dynamics on Relaxation / Roman Meier. Betreuer: Ernst Rößler." Bayreuth : Universität Bayreuth, 2014. http://d-nb.info/1060009676/34.
Повний текст джерела
22
Pu, Mingming. "Investigations of the Mechanism for Activation of Bacillus Thuringiensis Phosphatidylinositol-specific Phospholipase C." Thesis, Boston College, 2009. http://hdl.handle.net/2345/1179.
Повний текст джерелаАнотація:
Thesis advisor: Mary F. RobertsThesis advisor: Steven D. Bruner
The bacterial phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis is specifically activated by low concentrations of a non-substrate lipid, phosphatidylcholine (PC), presented as an interface. However, if the PC concentration in the interface is too high relative to substrate, the enzyme exhibits surface dilution inhibition. Understanding this bacterial enzyme, which shares many kinetic features with the larger and more complex mammalian PI-PLC enzymes, requires elucidating the mechanism for PC activation and inhibition. Various techniques were applied to study the interaction of the protein with vesicles composed of both the activator lipid PC and the substrate lipid (or a nonhydrolyzable analogue). Fluorescence correlation spectroscopy (FCS), used to monitor bulk partitioning of the enzyme on vesicles, revealed that both the PC and the substrate analogue are required for the tightest binding of the PI-PLC to vesicles. Furthermore, the tightest binding occurred at low mole fractions of substrate-like phospholipids. Field cycling 31P NMR (fc-P-NMR) spin-lattice relaxation studies provided information on how bound protein affects the lipid dynamics in mixed substrate analogue/PC vesicles. The combination of the two techniques could explain the enzyme kinetic profile for the PC activation and surface dilution inhibition: small amounts of PC in an interface enhanced PI-PLC binding to substrate-rich vesicles while high fractions of PC tended to sequester the enzyme from the bulk of its substrate leading to reduced specific activity. FCS binding profiles of mutant proteins were particularly useful in determining if a specific mutation affected a single or both phospholipid binding modes. In addition, an allosteric PC binding site was identified by fc-P-NMR and site directed spin labeling. A proposed model for PC activation suggested surface-induced dimerization of the protein. Experiments in support of the model used cysteine mutations to create covalent dimers of this PI-PLC. Two of these disulfide linked dimers, formed from W242C or S250C, exhibited higher specific activities and tighter binding to PC surfaces. In addition, single molecule total internal reflection fluorescence microscopy was used to monitor the off-rate of PI-PLC from surface tethered vesicles, providing us with a direct measure of off-rates of the protein from different composition vesicles
Thesis (PhD) — Boston College, 2009
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
23
Ducroix, Alice. "Multi-scale dynamics of water inside boehmite : a NMR approach." Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS575.pdf.
Повний текст джерелаАнотація:
Dans plusieurs domaines de la chimie, les catalyseurs occupent une place importante puisqu’ils assurent une réaction plus rapide, une meilleure sélectivité et réduisent l’utilisation de matières premières. L’industrie s’est récemment tournée vers les catalyseurs hétérogènes dont la récupération est plus facile. Ces catalyseurs sont constitués d’un support poreux et de sites actifs répartis en surface à travers la porosité du support. Pour optimiser pleinement le support, de récentes études ont abordé la question de l’accessibilité des molécules aux sites réactionnels. Cela passe notamment par la compréhension de la mobilité des solvants et du trafic moléculaire dans le milieu poreux. Le support catalytique hétérogène par excellence est l’alumine γ, obtenue par calcination topotactique de la boehmite. La texture et les propriétés poreuses sont principalement héritées de la boehmite, en particulier de l’organisation des agglomérats et des agrégats. Cette organisation est principalement obtenue lors des étapes de mise en forme (peptisation) et d’extrusion lors du procédé d’obtention de l’alumine. Le transport et la dynamique multi-échelle à l’intérieur de la boehmite seront étudiés au cours de ces deux étapes, notamment comment les molécules de solvant (ici l’eau) se déplacent à l’intérieur de ce matériau et quels mécanismes pilotent la dynamique. Afin d’étudier cette dynamique, des suspensions de boehmite avec différentes textures initiales seront obtenues par dialyse et stress osmotique et les extrudés par une voie industrielle usuelle. Le transport autour de l’interface des agrégats et des parois des pores (échelle nanométrique) sera étudié par Résonance Magnétique Nucléaire à champ cyclé sur une échelle de temps de la nanoseconde à la microseconde. La diffusion a été suivie à la surface de ces objets et s’est avérée être régie par une forte interaction avec la surface, en particulier la courbure de surface. Il a notamment été trouvé un temps de séjour important (≈ 8μs) des molécules d’eau à la surface et un coefficient de diffusion de surface lent (< 3. 10-10 m2/s). À l’échelle du micron, la dynamique est étudiée par RMN à gradient de champ pulsé sur une échelle de temps de la milliseconde à la seconde. La diffusion semble être gouvernée par la structure topologique résultant de l’organisation complexe des agrégats et des agglomérats (connectivité des pores, anisotropie, etc.)For several domains of chemistry, catalyst take up a significant place since they ensure a quicker reaction, a better selectivity and reduce the use of raw material. Industry has recently turned to heterogeneous catalyst whose recovery is easier. These catalysts consist of a porous support and active sites distributed on the surface through the support porosity. To fully optimized the support, recent studies have tackled the issue of accessibility of molecules to the reaction sites. This one includes the comprehension of solvent mobility and molecular traffic in the porous medium. The heterogeneous catalytic support par excellence is γ-alumina, obtained by a topotactic calcination of boehmite. Texture and porous properties are then mostly inherited from boehmite, especially from the organization of agglomerates and aggregates. This organization is mostly obtained during the kneading, (peptization) and the extrusion steps of the boehmite-to-alumina process. Transport and multi-scale dynamics inside boehmite will then be investigated during these two steps particularly how solvent molecules (here water) move inside this material and what mechanisms drive the dynamics . To study this dynamics, boehmite suspensions with different initial textures will be obtained through dialysis and osmotic stress and extrudates from the traditional industrial route. Transport around the interface of aggregates and pore walls (nanometric scale) will be studied by Field Cycling Nuclear Magnetic Resonance on a ns-µs time scale. Diffusion was followed at the surface of such objects and was found to be governed by a strong interaction with the surface and especially the surface curvature. A consequent residence time (≈ 8µs) of water molecules at the surface and a rather slow surface diffusion coefficient (< 3. 10-10 m2/s) was exhibited. At the micron scale, dynamics is investigated by Pulsed Field Gradient NMR on a millisecond to second time scale. Diffusion seems to be driven by the topological structure imposed by the complex organization of aggregates and agglomerates (connected pore, anisotropy, etc.)
24
Ascona, Christian Rivera. "Manipulação de coerências de múltiplo quantum em materiais magnéticos via RMN em campo externo nulo." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-15092011-153626/.
Повний текст джерелаАнотація:
Neste trabalho desenvolvemos metodologias para o estudo de materiais magnéticos usando Ressonância Magnética Nuclear em campo magnético externo nulo (RMNz), via a análise e manipulação das transições entre os estados de energia nucleares. Na primeira etapa, revisamos e complementamos os modelos teóricos, encontrados na literatura, que são utilizados para prever a formação dos múltiplos ecos. Concluímos deste estudo, que o aparecimento destes múltiplos ecos está associado com as transições entre os níveis de energia nuclear que são chamadas de transições de múltiplo quantum (MQ). Adicionalmente, concluímos que os instantes nos quais surgem os ecos de múltiplo quantum e os tipos de coerências que contribuem para cada eco estão diretamente relacionados com as distribuições dos acoplamentos Zeeman e/ou quadrupolar ao longo da amostra. Na segunda etapa deste projeto estudamos a seleção de coerências mediante a aplicação de ciclagem das fases dos pulsos de radiofrequências. Além de permitir o estudo individual de cada eco, a seleção de coerências permitiu a realização de medidas com tempos ao eco muito mais curtos e, consequentemente, a medida de sinais com maiores relações sinal/ruído. O que permitiu o estudo seletivo de cada eco, em detrimento dos outros, e assim pudemos inferir que coerências contribuem para formação do eco selecionado. Os compostos usados para o estudo experimental foram o GdAl2 e GdCo2. Os sinais de RMN dos núcleos 155,157Gd, 27Al e 59Co apresentaram ecos de múltiplo quantum. Posteriormente realizamos a seleção de coerências para estes núcleos.This study we developed methodologies for the study of magnetic materials using nuclear magnetic resonance without the application of external magnetic field (RMNz), by manipulating transitions between the nuclear energy states. In the first step, we revised and complemented the theoretical models found in the literature, which were proposed to predict the formation of multiple echoes. We concluded from this study that the appearance of multiple echoes is associated with transitions between the levels of nuclear transitions that are called multiple-quantum (MQ). Moreover, we understood that the instants in which the multiple quantum echoes appear and the types of coherences that contribute to each echo are directly associated with the Zeeman and electric quadrupolar coupling heterogeneities along the sample. In the second step of this project, we studied the selection of coherences by phase cycling the radiofrequency pulses. This allowed the individual study of each echo, enabling us to infer which coherences contribute to the formation of the selected echo. Besides the individual study of each echo, the coherence selection allowed measuring them with the smallest echo time and, consequently, observing signals with much higher signal-to-noise ratios. The compounds used for the experimental study were the GdAl2 and GdCo2. The NMR signals of nuclei 155,157Gd, 27Al and 59Co showed multiple quantum echoes. Later we performed the selection of coherences for these nuclei.
25
Loganathan, D. "Field cycling NMR studies of molecular dynamics in liquid crystals." Thesis, 2000. http://hdl.handle.net/2009/958.
Повний текст джерела
26
Kresse, Holger Benjamin. "Field-Cycling NMR bei extrem kleinen Larmor-Frequenzen – Entwicklung und Anwendung." Phd thesis, 2016. http://tuprints.ulb.tu-darmstadt.de/5824/1/Dissertation_Kresse_2016_.pdf.
Повний текст джерелаАнотація:
In dieser Arbeit wird die Weiterentwicklung des in Darmstadt vorhandenen Field-Cycling (FC) NMR-Magneten zu extrem kleinen Larmor-Frequenzen beschrieben. Das Magnetfeld wird je nach benötigter Stärke von verschiedenen Spulen erzeugt. Dabei werden äußere statische Felder durch drei senkrecht angeordnete, mit konstantem Strom betriebene Spulen kompensiert. Unterhalb von einem Kilohertz 1H Larmor-Frequenz wird das Magnetfeld über einen dreiachsigen Fluxgate-Sensor mit einer weiteren dreidimensionalen Anordnung von Spulen geregelt.
Für Messungen in kleinen Magnetfeldern ist eine direkte Kalibrierung mittels FC NMR nötig, dazu werden verschiedene Methoden vorgestellt: (i) Larmor-Präzession im schräg stehenden Evolutionsfeld, (ii) simultane Messung von Relaxation und Larmor-Frequenz im schräg stehenden Evolutionsfeld sowie (iii) Quermessungen mit und ohne Einstrahlung zusätzlicher magnetischer Wechselfelder.
Das kleinste stabile Feld im Magneten, das mit der FC NMR nachgewiesen werden konnte, hat eine 1H Larmor-Frequenz von 3,4 Hz, was einer Stärke von weniger als 100 nT entspricht. Eine simultane Messung der Spin-Gitter-Relaxation und des Evolutionsfeldes konnte noch bei einer Larmor-Frequenz von 7,2 Hz durchgeführt werden. In Quermessungen unter Einstrahlung zusätzlicher magnetischer Wechselfelder wurden Strukturen des Anregungsprofils der Einstrahlung nachgewiesen, dies weist auf eine hohe Stabilität und Homogenität des Feldes hin.
Die Flüssigkeit Tetradekan bei Raumtemperatur zeigt wie erwartet keine Dispersion der Spin-Gitter-Relaxation bis hinunter zu Larmor-Frequenzen von etwa 7 Hz. Bei Wasser hingegen wurde unterhalb von ungefähr einem Kilohertz eine Frequenzabhängigkeit der Relaxation gemessen, welche auf Protonenaustausch zwischen Wassermolekülen mit verschiedenen Sauerstoffisotopen zurückzuführen ist.
Bei Verwendung einer weiteren Stromquelle von Siemens können Magnetfelder von bis zu zwei Tesla kurzzeitig erzeugt werden. Der Messbereich des FC-Magneten erstreckt sich damit über mehr als sieben Dekaden: Von etwa 7 Hz bis zu 85 MHz.
In Kooperation mit der Arbeitsgruppe von Ernst Rößler, Universität Bayreuth, wurde die Dynamik linearer Polymerschmelzen unter anderen von Polybutadien und Polydimethylsiloxan molekulargewichtsabhängig mit der FC NMR untersucht. Mithilfe von Isotopenverdünnungsexperimenten konnte die intra- und die intermolekulare Relaxation getrennt werden. Aus Letzterer wurde das zeitabhängige segmentale mittlere Verschiebungsquadrat berechnet, welches mit dem vorhergesagten Verhalten in den Regimen I und II des Tube-Reptation-Modells gut übereinstimmt. Durch Ergänzung des mittleren Verschiebungsquadrats auf längerer Zeitskala mithilfe der Feldgradienten NMR konnten alle vier Regime dieses Modells experimentell bestätigt werden.
Zusätzlich wurde die Ionendynamik in metallischem Lithium als Modellsystem mit der 7Li FC NMR untersucht. Durch die Auswertung der Relaxationsraten mit verschiedenen, möglichst einfachen Modellen konnte die Temperaturabhängigkeit der Korrelationszeit bzw. des Diffusionskoeffizienten bestimmt werden. Eine gute Übereinstimmung mit Literaturdaten anderer Messmethoden bestätigt die 7Li FC NMR als geeignetes Verfahren zur Untersuchung von Lithium-Ionendynamik in einem großen Frequenzbereich.
27
Hsu, Chia-Wei, and 許珈瑋. "Dynamic of Water in H-ZSM-5 by Fast Field Cycling NMR." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/9a8hr8.
Повний текст джерелаАнотація:
碩士國立中正大學
化學暨生物化學研究所
102
FFC (Fast Field Cycling)NMR relaxometry is a very powerful tool to investigate the molecular dynamic at low frequency (0.01-40MHz) and study the slow molecular motions.Relaxation used in this present study has more advantages over mechanical field cycling.The important applications of FFC NMR includes proteins ,liquids which confined in porous materials ,and polymers. The relaxation rate of bulk and confined sample are different at low frequency region (0.01-40MHz). In this study ,nuclear magnetic relaxation dispersion (NMRD) is utilized to investigate the H2O molecular dynamic with 5% , 10% and 20% content in H-ZSM-5 at the temperature range of 208K and 298K. We got some molecular dynamic parameters by molecular dynamic fitting. According to NMRD profile , We found that the relaxation rate increases gradually with the decreasing frequencies and then increases with the decreaseing temperature. According to the fitting data ,we can get some message about dynamic and distribution of water which confined in the pore material .In addition , we found that phase transition temperature has something to do with water where in big or small pore.
28
Chou, Ching-Yu, and 周靜瑜. "Probing protein dynamics by field cycling nuclear magnetic resonance (NMR) relaxation technique." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/67516712581967958725.
Повний текст джерелаАнотація:
博士國立臺灣師範大學
物理學系
100
Spectral density function analysis is a direct description of protein dynamics and can be extracted from NMR relaxation measurements, such as spin-lattice relaxation (R1) dispersion. Toward that goal, we have built a field cycling device for measuring R1 field dispersion curves over the field range of 0-14.1T. The device permit the shuttling of solution protein samples in regular NMR tube to be shuttled up-and-down the 1 meter superconducting magnet bore stably and reproducibly in ~ 100 ms. Using this compact field cycling device, we have obtained the first set of 15N-R1 dispersion curve of a protein, ubiquitin from 0.9 T to 20 T. Surprisingly, the field-dependent 15N-R1 curves of many residues cannot be fit with conventional Lorentzian functions and new spectral density functions based on motions subjected to harmonic potential have to be derived. The backbone dynamic information derived accordingly showed that ubiquitin contains a rigid β-strands core and mobile termini. However, the most novel finding of this thesis work is our ability to determine the harmonic potential energy for each residue from analysis of the R1 dispersion curve. The results showed that potential energy can be correlated to conformational exchange and residues having large potential energy are those exhibiting slow conformational exchange. The discovery could be a further evidence of conformational selection for ubiquitin binding mechanism.
29
Tacke, Christian. "Resonanzen in Field-Cycling-NMR an Molekülkristallen: (reversible) Spindynamik oder (irreversible) Relaxation?" Phd thesis, 2015. https://tuprints.ulb.tu-darmstadt.de/4379/1/main.pdf.
Повний текст джерелаАнотація:
In Mehrspinsystemen mit Kernen vom Spin 1/2 und Kernen mit einer quadrupolaren Wechselwirkung, die über die Dipol-Dipol-Wechselwirkung gekoppelt sind, können sogenannte „Quadrupolare Dipps“ auftreten. Es gibt zwei Haupterklärungen für diesen Effekt: Polarisationstransfer und Relaxation. Die entsprechenden Messdaten ähneln sich sehr und ohne weitere Untersuchungen können diese in vielen Fällen nicht leicht unterschieden werden.
Der physikalische und theoretische Hintergrund dieser beiden Phänomene unterscheidet sich sehr stark. Im Falle von keiner oder sehr langsamer Dynamik findet Polarisationstransfer statt. Dieser ist energieerhaltend im Spinsystem und kann vollständig mit Quantenmechanik auf dem Spinsystem beschrieben werden. Eine genaue Kenntnis der Kristallographie wird hierfür benötigt, da diese die relevanten Hamiltonians direkt beeinflußt. Für Systeme mit genügend schneller Dynamik tritt Relaxation auf und Energie fließt vom Spinsystem zum Gitter. Es ist also eine detailliertere theoretische Beschreibung nötig. Diese muss ein Modell der Dynamik beinhalten, meist in Form einer spektralen Dichte. Beide theoretischen Modelle sollten eine detaillierte Beschreibung des gesamten Spinsystems beinhalten.
Eine Softwarebibliothek wurde entwickelt, um komplexe Spinsysteme modellieren zu können. Sie erlaubt die Simulation von Polarisationstransfer und Relaxation.
Am Protonenleiter K3H(SO4)2 wurden NMR-Messungen durchgeführt. Ein Einkristall zeigt scharfe quadrupolare Dipps bei Raumtemperatur. Dynamik konnte mit Hilfe von Relaxationsmessungen und Literaturwerten ausgeschlossen werden. Eine Polarisationstransferanalyse wurde genutzt um die Effekte mit einer guten Übereinstimmung zu beschreiben. Als zweites System wurden Imidazolium-Molekülkristalle untersucht. Es wurde erwartet, daß die quadrupolaren Dipps durch Polarisationstransfer hervorgerufen wurden. Diese Annahme wurde eingehend analysiert und stellte sich als unwahr heraus. Eine Relaxationsanalyse zeigt eine gute Übereinstimmung mit den Messdaten bei hohen Temperaturen. Hierbei wird eine zweistufige spektrale Dichte genutzt, was darauf hindeutet, daß es zwei getrennte dynamische Prozesse in diesem System gibt.
30
Hsieh, Chu-Jung, and 謝渠蓉. "Effects of Cholesterol on Membrane Molecular Dynamics by Fast Field-Cycling NMR Relaxometry." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/37917877191909869820.
Повний текст джерелаАнотація:
碩士國立中正大學
化學暨生物化學研究所
101
Biological membranes are complex structures are composed of a variety of lipids and proteins. The different membrane compositions affect viscoelastic and hydrodynamic properties of membranes which are critical to their functions. Lipid bilayer vesicles inserted by cholesterol not only increase membrane surface motional behavior also strengthen vesicles stability. Cholesterol-rich vesicles are similar to cell membranes in structure and composition. Therefore, cholesterol-rich vesicles can be a typical model for studying membrane dynamic and function. In this study, nuclear magnetic relaxation dispersion (NMRD) was utilized to investigate the detailed molecular dynamic of membrane difference between vesicles and cholesterol vesicles at the temperature range of 278 K and 298 K. Two different vesicles size were prepared. According to the activation energy of diffusion coefficient, the 30% mol cholesterol vesicles happened phase transitions. The effect of cholesterol is mainly on the order fluctuation of membrane and diffusion motion of lipid molecules. In addition, the distance between lipid molecules become closer when the ratio of cholesterol increases.
31
董軒俐. "Dynamics of CD3OH and CH3OD in H-ZSM-5 by Fast Field Cycling NMR." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/9u5cgv.
Повний текст джерелаАнотація:
碩士國立中正大學
化學暨生物化學研究所
104
The conversion of methanol to hydrocarbons using zeolite catalysts is one of the most investigated reactions in the field of industrial chemistry since its discovery in 1977. In this study, fast field-cycling (FFC) NMR was utilized to investigate the molecular dynamics of CH3OD and CD3OH with 10 %, 20 % and 30 % content in H-ZSM-5 at the temperature range of 218 K and 298 K. Three model-free curves were used for fitting NMRD profiles, corresponding to three different states of methanol or the product molecules in H-ZSM-5. The molecular motions at two of these states becomes faster with increasing methanol amount. The methanol amount dependent molecular motions reflect the adsorption condition of methanol. In additional, the mechanism of methylation in H-ZSM-5 was also discussed by different deuterium substituted methanol. According to NMRD profile, the relaxation rate increases with the decreasing frequencies and also increases with the decreasing temperature. The dynamics and distribution of methanol and its products confined in the pore material were also investigated. Two products, methyl group and water molecules, were found in accordance of temperature dependent molecular motions. In addition, it shows phase transition temperature correlates with pore sizes.
32
Chang, Chia-Hao, and 張嘉豪. "Effect of Melittin and Pardaxin on Phospholipids Membrane by Fast Field-Cycling NMR Relaxometry." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/69835481756852603318.
Повний текст джерелаАнотація:
碩士國立中正大學
化學暨生物化學研究所
104
Antimicrobial peptides are small amphiphilic molecules with antibacterial activity, generally between 5 and over a hundred amino acids. Until now, over 5000 kinds of antimicrobial peptides are found. Antimicrobial peptides can be divided mainly into four groups according to its secondary structure: (1) β-sheet, (2)α-helix, (3)extended, and (4)loop. Among these mentioned above, the β-sheet and α-helix are the most common structure. The antimicrobial peptides perform the antibacterial activity by attacking the membrane, which can be divided into the following three attacking modes: (1) Toroidal mode, (2) Barrel-stave mode, and (3) Carpet mode. Two antimicrobial peptides, melittin and pardaxin, has been widely studied over the past two decades. The attacking mechanism are toroidal mode and barrel-stave mode for melittin and pardaxin, respectively. The difference between them is melittin leads to bending formation of the annular hole connecting the inner and outer lipid bilayer membrane while pardaxin directly penetrates the lipid bilayer to form a cylindrical hole. In addition, two attacking modes make membrane rupture due to the different osmotic pressure between inner and outer. The study of lipid bilayer dynamics is performed by fast field cycling nuclear magnetic resonance relaxometry. The spin-lattice relaxation rate of system consisting 1-Palmitoyl-2-oleoyl-sn-glycerol-3-phosphoglycerol,sodium salt (POPG) and antimicrobial peptides are investigated by varing P/L ratio and temperatures. By using simulation, the detailed molecular dynamics is obtained. Furthermore, the 31P NMR spectroscopy is a powerful tool to inspect the pore-formation by observing the disappearance of the signal intensity.
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YU, JIA-RU, and 余佳儒. "Effects of Calcium on Membrane Molecular Dynamics Studied by Fast Field-Cycling NMR Relaxometry." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/88267465574102336531.
Повний текст джерелаАнотація:
碩士國立中正大學
化學暨生物化學研究所
101
Biomembranes, mostly composed of phospholipid molecules and proteins, forms a barrier between the intra- and extra-cellular environments and be able to control the material enters and exits the cell. Phospholipids can form bilayer structure (Lamellar phase, Lα phase) and nonbilayer structures (Inverted hexagonal phase, HII phase) in many bio-systems, particularly in regard to membrane fusion and exocytosis. HII phase are involved to destabilize membrane structures and membrane destabilization both in vivo and in vitro usually can be induced by external agents, such as metal ions (Ca2+ and K+ ) and biomolecules (protein and peptide). In this study, the effects of calcium on the lamellar-to-inverted hexagonal (Lα/HII) phase transition and the dynamics for phospholipids on liposome were investigated. The samples of POPC/cholesterol and POPC liposome were prepared with various concentration of Ca2+. The states of Lα/HII phase transition were verified by variable temperature 31P NMR spectroscopy. Zeta potential was also measured to investigate surface potential of liposome. The detailed molecular dynamics on membrane were explored by fast field-cycling nuclear magnetic resonance relaxometry (FFC NMR). The results of R1 relaxation measured by FFC NMR we got some molecular dynamic parameters by molecular dynamic fitting. For POPC liposomes, Ca2+ can reduce bending elastic modulus (κ) and repulsion force. For POPC/cholesterol liposome, although the effects of liposome from Ca2+ just like POPC liposome, cholesterol cause phospholipids tightly packed and make membrane more rigid. Consequently, the Lα/HII phase transition temperature is affected and shifts from 293 K-303 K in POPC liposome system to 303 K-313 K in POPC/cholesterol liposome system.
34
Kariyo, Sobiroh [Verfasser]. "Molecular dynamics of polymers by means of NMR field cycling relaxometry / vorgelegt von Sobiroh Kariyo." 2005. http://d-nb.info/975064592/34.
Повний текст джерела
35
Chen, Tsai-Chen, and 陳采榛. "Effects of Antimicrobial Peptides on Phospholipids Membrane Molecular Dynamics Studied by Fast-Field-Cycling NMR Relaxometry." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/44k2j4.
Повний текст джерелаАнотація:
碩士國立中正大學
化學暨生物化學研究所
102
Antimicrobial peptides are small molecules with antibacterial activity, generally between 12 and 50 amino acids that are broadly effective components of innate immunity. Until now, antimicrobial peptides found have reached more than 2000 kinds. Antimicrobial peptides are usually acting on the cell membrane of bacteria, forming a channel in the cell membrane, which can be divided into the following three attack modes: (1) Toroidal model; (2) Barrel stave model; (3) Carpet model. There two antimicrobial peptides over the past two decades has been widely studied are melittin and pardaxin. The widely accepted mechanism for melittin and pardaxin are “toroidal” and “barrel-stave”, respectively. Different between the two is melittin will lead lipid bilayer to bending, forming the annular hole connecting the inner and outer membrane, and pardaxin directly through the lipid bilayer to form a cylindrical hole. Let the inner and outer cell membrane osmotic imbalance rupture. In our article, we studied dynamics in lipid bilayers by fast field cycling nuclear magnetic resonance relaxometry. Spin-lattice relaxation rate recorded for liposomes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt) (POPG) at different temperature and different antimicrobial peptides. We got some molecular dynamic parameters by molecular dynamic fitting.
36
Wojciechowski, Miłosz. "Dynamika cieczy w ograniczonej geometrii : zastosowanie relaksometrii Magnetycznego Rezonansu Jądrowego." Praca doktorska, 2019. https://ruj.uj.edu.pl/xmlui/handle/item/148751.
Повний текст джерелаАнотація:
Praca "Dynamika cieczy w ograniczonej geometrii - zastosowanie relaksometrii Magnetycznego Rezonansu Jądrowego" opisuje szczegółowo analizę i interpretację dyspersji szybkości relaksacji spin-sieć jonożeli opartych na dwóch cieczy jonowych: Tiocyjanianie 1-etylo-3-metyloimidazoliowym ([EMIM][SCN]) oraz l-butylo-3-metyloimidazoliowym siarczanie oktylu ([BMIM][0cS04]). Mianem jonożeli określa się układy, w których ciecz jonowa została unieruchomiona w stałych matrycach. Dzięki takiemu zabiegowi można je w bezpieczniejszy sposób wykorzystać jak o elektrolity w urządzeniach elektronicznych, bateriach itp. Z perspektywy potencjalnych zastosowań istotna jest jednak znajomość tego, jak fakt uwięzienia cieczy w ograniczeniu geometrycznym wpływa na dynamikę, a pośrednio na przewodnictwo jonowe finalnego produktu. W badaniach zastosowano metodę relaksometrii Magnetycznego Rezonansu Jądrowego (MRJ) typu FFC ("Fast Field Cycling") - tzw. szybkiego przemiatania pola. Technika ta jest unikalną metodą eksperymentalną umożliwiająca zidentyfikowanie mechanizmów i skali czasowej procesów dynamicznych zachodzących w układach molekularnych i jonowych, zarówno stałych, jak i ciekłych. Obserwacja relaksacji jądrowej 'H cieczy jonowych w warunkach swobodnych (czysta ciecz) i warunkach uwięzienia geometrycznego (ciecz umieszczona w matrycy krzemowej) wykazała zmiany dynamiki molekularnej w zależności od rodzaju cieczy jonowej i jej względnej zawartości w porach matrycy. Analiza profili dyspersji szybkości relaksacji spin-sieć 'H w szerokich zakresach częstości Larmora (4 kFlz - 40 MFIz) oraz dla szerokiego zakresu temperatur (223 - 253 K dla [EMIM][SCN] oraz 243 - 303 K dla [BMIMJIOCSO4]) pozwoliła na rozróżnienie i charakterystykę różnych mechanizmów dyfuzji jonów cieczy jonowych w szerokiej skali czasowej. Dogłębna analiza zależności dyspersyjnych szybkości relaksacji spin-sieć opierała się na dopasowaniu modelu zawierającego przyczynki do całkowitej relaksacji wynikające z fluktuacji oddziaływań dipol-dipol modulowanych przez dynamikę translacyjną i rotacyjną jonów. Dzięki różnej zależności funkcyjnej od częstotliwości Larmora, wkłady te można jednoznacznie rozdzielić i określić czasy korelacji charakteryzujące dany proces. Parametry opisujące procesy dyfuzji translacyjnej i rotacyjnej otrzymane dla cieczy w postaci swobodnej wykorzystano jak o punkt odniesienia do opisu zmienionej dynamiki jonów w warunkach ograniczenia geometrycznego. Wyróżniono dwie główne frakcje cieczy jonowej: znajdującą się w centrum poru, której dynamika była zbliżona do dynamiki czystej cieczy, oraz znajdującą się bliżej powierzchni matrycy krzemowej. Wyznaczono parametry charakteryzujące dynamikę: czasy korelacji oraz względne współczynniki dyfuzji, a ich zmienność z temperaturą opisano zależnością Vogel-Fulcher-Tammann. Jednym z istotniejszych wniosków pracy jest to, że pomimo oddziaływania z powierzchnią krzemową i efektów sterycznych dynamika translacyjna dla wszystkich badanych układów zachowuje trójwymiarowy charakter.The thesis "Dynamics of liquids in confinement - the application of Nuclear Magnetic Resonance Relaxometry" describes in detail the analysis and interpretation of the spin-lattice relaxation rate dispersion of ionogels based on two ionic liquids: l-ethyl-3-methyIimidazolium thiocyanate ([EMIM][SCN]) and I-butyl-3-methylimidazolium octyl sulphate ([BMIM][0 cS0 4 ]).The ionogel is a solid system within which the ionic liquid has been immobilized. Thanks to such solidification, they can be used in a safer way as electrolytes in electronic devices, batteries, etc. From the applicational point of view, it is important to know how the confinement affects the liquid dynamics and, indirectly, the ionic conductivity of the final product. The technique used for the research was Fast Field Cycling Nuclear Magnetic Resonance (FFC NMR) Relaxometry. This is a unique experimental method that allows to identify the mechanisms and time scale of dynamic processes in molecular and ionic systems, both solid and liquid. Observation of 1H nuclear relaxation of ionic liquids in free state (bulk liquid) and in confinement (liquid entrapped in silica matrices) revealed changes in molecular dynamics depending on the type of ionic liquid and its relative content within the pores of the matrix. Analysis of 1H NMR spinlattice relaxation rate dispersion profiles in broad Larmor frequency range (4 kHz - 40 MHz) and temperature range (223 - 253 K for [EMIM][SCN] and 243 - 303 K for [BMIM][0 cS0 4 ]) allowed to distinguish and characterize different mechanisms of ion diffusion taking place in different timescales. An in-depth analysis of the frequency dependence of spin-lattice relaxation rate was based on the model with the total relaxation rate decomposed into contributions that stem from the fluctuation of the dipole-dipole interactions modulated by the translational and rotational dynamics of the ions. Due to different functional dependence on the Larmor frequency, these contributions can be separated and the correlation times characterizing the given process can be determined. Parameters describing the translational and rotational diffusion processes obtained for liquids in a free form were used as a reference point to describe the dynamics of ions altered due to geometric confinement. Two main fractions of the ionic liquid were distinguished: first one located in the center of the pore, the dynamics of which was similar to the dynamics of the pure liquid, and the fraction of liquid closer to the surface of the silica matrix. Correlation times and relative diffusion coefficients have been determined, as well as their temperature dependence according to the Vogel-Fulcher-Tammann relationship. One of the most important conclusions of the work is that despite the interaction with the silica surface and the steric effects, the translational dynamics for all studied systems retains its three-dimensional character.
37
Liu, Wei-Ting, and 劉威廷. "Effects of Calcium on Lipid/Cholesterol Mixed Membrane Molecular Dynamics Studied by Fast Field-Cycling NMR Relaxometry." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/4d68e9.
Повний текст джерелаАнотація:
碩士國立中正大學
化學暨生物化學研究所
102
Biological membranes, mostly composed of phospholipid molecules and proteins, form a barrier between intra- and extra-cellular environments and allow to control the material enters and exits the cell. The changes of stability of the biological membranes are closely related to many physiological mechanisms, e.g., membrane fusion and exocytosis. The process can also be induced by adding external agents, such as calcium ions and sodium ions to the membrane surroundings, and investigated via analysis of the motion of the phospholipid molecules. In this study, the samples, POPC and POPC containing of 30 % cholesterol, were prepared with various concentration of calcium ions. The detailed molecular dynamics on membrane were investigated by fast-field cycling nuclear magnetic resonance (FFC-NMR) and relaxation theory in the temperature range of 293-343 K. The results showed that the incorporating of cholesterol and calcium ion to POPC result in the tightly packed phospholipid and the rigidity of the membrane. The membrane bending elastic modulus (κ) increases more significant in cholesterol contained samples. The distance between the phospholipid molecules was found to become much closer when cholesterol and calcium ions were added. It also leads to the decrease of the translational diffusion coefficient (D). The incorporating of cholesterol and calcium ion also raised the rotational correlation time (τR) by the shielding effect of surface charge on membrane and resulting in the increase of interaction between liposomes.
38
Ayalur-Karunakaran, Santhosh Kumar [Verfasser]. "Molecular dynamics of adsorbed polymer thin films using NMR field cycling relaxometry / vorgelegt von Santhosh Kumar Ayalur-Karunakaran." 2010. http://d-nb.info/1010970704/34.
Повний текст джерела
39
Manalu, Marison Sudianto. "Effects of the Peptide Bacitracin and Calcium on Phospholipids Membrane Molecular Dynamics Studied byFast-Field-Cycling NMR Relaxometry." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/77794200468964355001.
Повний текст джерелаАнотація:
碩士國立中正大學
化學暨生物化學研究所
105
Biological membranes mostly composed of phospholipid molecules and proteins form a barrier between intra and extra-cellular environments and be able to control the material enters and exit the cell. Both in vivo and in vitro membrane destabilization can usually be induced by external agents such as bio molecules (i.e., proteins and peptides). Fast field cycling nuclear magnetic resonance relaxometry can provide valuable information because of it is sensitivity to dynamic process that occur over a broad time scale. Recorded the data for the large unilamellar liposome which compose of POPG (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol) and POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) with addition of bacitracin and Ca2+. By analysis of the data recorded, the result shown that the influence of the bacitracin depends on its concentration. Bacitracin mainly affected the order fluctuation of the membrane, diffusional motion and rotational correlation time liposome. Moreover, the P/L ratio with higher concentration caused weaker surface charge and less shielding effect of the liposome. Key word : NMRD, bacitracin, phospholipid membrane.
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Sailaja, Sesha A. "Proton magnetic relaxation investigations of correlation among molecular structure and dynamics in liquid crystals and fabrication of field cycling NMR spectrometer." Thesis, 1994. http://hdl.handle.net/2009/912.
Повний текст джерела
41
Kruber, Stephan. "Electroimanes de estructura variable para resonancia magnética nuclear con ciclado rápido de campo magnético." Doctoral thesis, 2015. http://hdl.handle.net/11086/5785.
Повний текст джерелаАнотація:
en este trabajo de tesis se proponen nuevos conceptos y métodos para el diseño de electroimanes ffc, con lo cual se define el estado actual del arte en la materia. se consideran sistemas basados en bobinados múltiples controlados individualmente y sistemas de electroimanes con geometría variable (siendo ésta la principal innovación que se aporta, definiendo el concepto de electroimán activo). ambos conceptos fueron a su vez desarrollados para eliminar los complejos procesos de maquinado necesarios en los electroimanes actualmente en uso a nivel global, lográndose otras ventajas que serían expuestas oportunamente. se implementas un prototipo de sistema de geometría variable, el cual fue probado y verificado utilizando un aparato existente en el laboratorio.