Дисертації з теми "NMR Measurements"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: NMR Measurements.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "NMR Measurements".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Di, Caro Domenico. "NMR measurements for hazelnuts classification." Doctoral thesis, Universita degli studi di Salerno, 2018. http://hdl.handle.net/10556/3113.
Повний текст джерелаАнотація:
2016 - 2017In this work, a method for the quality detection of the in-shell hazelnuts, based on the low field NMR, has been proposed. The aim of the work is to develop an in-line classification system able to detect the hidden defects of the hazelnuts. After an analysis of the hazelnut oil, carried out in order to verify the applicability of the NMR techniques and to determine some configuration parameters, the influence factors that affect these measurements in presence of solid sample instead of liquids have been analyzed. Then, the measurement algorithms were defined. The proposed classification procedure is based on the CPMG sequence and the analysis of the transverse relaxation decay. The procedure includes three different steps in which different features are detected: moisture content, kernel development and mold development. These quality parameters have been evaluated .analyzing the maximum amplitude and the second echo peak of the CPMG signal, and the T2 distribution of the relaxation decay. In order to assure high repeatability and low execution time, special attention has been put in the definition of the data processing. Finally, the realized measurement system has been characterized in terms of classification performance. In this phase, because of the reduced size of the test sample (especially for the hazelnuts with defects) a resampling method, the bootstrap, was used. [edited by Author]
XVI n.s. (XXX ciclo)
2
Stait-Gardner, Tim, Scott A. Willis, Nirbhay N. Yadav, Gang Zheng, and William S. Price. "NMR diffusion measurements of complex systems." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-189360.
Повний текст джерелаАнотація:
The pulsed gradient spin-echo nuclear magnetic resonance experiment is a powerful tool for studying the constitution and structure of complex systems (e.g., polydisperse systems and porous media). In applications to polydisperse systems, it is important to consider the effects of obstruction, exchange, entanglement, and diffusional averaging processes whereas in applications to porous samples, reliable structural information can only be extracted from the time-dependence of the apparent diffusion coefficient when the
deleterious effects of spatially and/or temporally inhomogeneous background (magnetic field) gradients can be suppressed. These issues are considered in this review.
3
Stait-Gardner, Tim, Scott A. Willis, Nirbhay N. Yadav, Gang Zheng, and William S. Price. "NMR diffusion measurements of complex systems." Diffusion fundamentals 11 (2009) 15, S. 1-22, 2009. https://ul.qucosa.de/id/qucosa%3A12901.
Повний текст джерелаАнотація:
The pulsed gradient spin-echo nuclear magnetic resonance experiment is a powerful tool for studying the constitution and structure of complex systems (e.g., polydisperse systems and porous media). In applications to polydisperse systems, it is important to consider the effects of obstruction, exchange, entanglement, and diffusional averaging processes whereas in applications to porous samples, reliable structural information can only be extracted from the time-dependence of the apparent diffusion coefficient when the
deleterious effects of spatially and/or temporally inhomogeneous background (magnetic field) gradients can be suppressed. These issues are considered in this review.
4
Khajeh, Maryam. "Kinetic measurements using time-resolved NMR spectroscopy." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/kinetic-measurements-using-timeresolved-nmr-spectroscopy(aae85bb3-de19-450a-96ab-50e2dfd89da7).html.
Повний текст джерелаАнотація:
Many thousands of pounds are spent every year by pharmaceutical companies on understanding the mechanisms and kinetics of chemical reactions involved in drug discovery and production. NMR spectroscopy is often at the core of these studies as it is a powerful, non-destructive method for structure elucidation. As such investigations can be time-consuming and cost-inefficient, AstraZeneca, the project sponsor, is interested in more efficient methods for studying the kinetics of pharmaceutical reactions. In this work a number of different techniques have been devised, studied, and implemented to study the kinetics of chemical reactions by time-resolved NMR spectroscopy, in which every species in a reaction can be monitored simultaneously. These novel techniques allow the study of reactions which are difficult or impossible to study by conventional NMR methods (such as heterogeneous reactions), or which are complicated by having overlapping signals. It is possible to monitor the kinetics of a reaction very simply by acquiring a series of 1H spectra, and obtaining the integrals of the signals by least squares fitting. This technique has been used for kinetic studies of static and on-flow reactions. In the static systems the reaction mixture was placed in the normal NMR tube in the magnet, while in the flow system the reaction mixture was placed outside of the magnet, and the solution flowed through an NMR tube placed in the magnet. The novel flow system designed, constructed and tested here has been used for kinetic studies of illustrative homogeneous and heterogeneous reactions, and is suitable for use in a wide range of NMR instrumentation. Kinetic studies have also been carried out by acquiring a series of DOSY datasets, analysing the results using the multi-way method PARAFAC (PARAllel FACtor analysis). A series of DOSY datasets contains multivariate information on spectrum, time evolution and diffusion. Without providing any predetermined model, the data can be decomposed by PARAFAC to yield the spectrum, kinetics, and diffusion profiles for each of the components. It has also been shown that PARAFAC is remarkably robust to low signal-to-noise ratio data, significantly below the level at which conventional methods would fail.
5
Ferrari, Maude, J. P. Mérel, Sébastien Leclerc, Christian Moyne, and Didier Stemmelen. "Study of dispersion by NMR: comparison between NMR measurements and stochastic simulation." Diffusion fundamentals 18 (2013) 11, S. 1-4, 2013. https://ul.qucosa.de/id/qucosa%3A13718.
Повний текст джерелаАнотація:
Dispersion remains, today, a highly topical subject. Our group has been interested in characterizing this phenomenon by pulsed-field-gradient NMR technique. Direct measurement of the dispersion coefficient can be done with a Pulsed Gradient Spin Echo (PGSE) sequence by assuming that the asymptotic regime is reached. In unsteady state, the propagator formalism is used. To better understand these measurements, the NMR experiment is modeled using a stochastic simulation (random walks) and compared with experimental results. The comparison is made for the simple case of Poiseuille flow in a circular tube (Taylor-Aris dispersion).
6
Unger, Philip Peter. "NMR-based microprobes for magnetic field measurements." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ62675.pdf.
Повний текст джерела
7
Liess, Carsten. "NMR spectroscopic measurements of diffusion in heart." Thesis, University of Oxford, 1999. http://ora.ox.ac.uk/objects/uuid:1ed27b71-578a-4558-950a-10ded28bc2b3.
Повний текст джерелаАнотація:
A decrease in the apparent diffusion coefficient (ADC) of water is becoming an important tool for the detection of acute and chronic brain disorders, yet it is not known whether changes in myocardial ADCs hold similar potential. Consequently, this work determined whether the ADCs of water or intracellular metabolites could be used to show ischaemia or cell swelling in the isolated rat heart. A modified STEAM pulse sequence was designed to measure the ADCs of the 1H-NMR detectable metabolites, taurine and creatine, with 4 min time resolution in a 3 mm myocardial slice. Experiments included the measurement of: a) metabolite diffusion coefficients and diffusion tensors in solutions, and ADCs and diffusion tensors in the isolated, KCl-arrested rat heart; b) taurine and creatine content during 32 min total, global ischaemia in the isolated rat heart; c) metabolite and water ADCs before, during and after ischaemia; and d) changes in average cardiomyocyte diameter during perfusion and ischaemia using the taurine ADC measurements. At a diffusion time of 50 ms, the myocardial ADCs were 1.06 x 10-3 mm2/s for water, 0.29 x 10-3 mm2/s for taurine and 0.26 x 10"3 mm 2 /s for creatine. Neither taurine nor creatine was lost from the heart during ischaemia, making either suitable for ischaemic diffusion measurements. Contrary to changes in the brain, myocardial water and taurine ADCs remained constant during ischaemia; however, the total creatine ADC increased by 35% which was shown to result from hydrolysis of PCr to creatine. Using the taurine ADC measurements at diffusion times between 50 ms and 1510 ms, the average myocyte diameter was calculated to be 40 μm during perfusion and 27 μm by the end of ischaemia. The decrease in myocyte diameter indicates that the buffer perfused heart is highly oedematous. This is the first time that: 1) metabolite ADCs have been measured in isolated heart, and 2) NMR spectroscopy has been used to determine the myocyte diameter. Thus ADC changes may not have potential for detecting ischaemia in the heart, although the measurement of myocyte diameter using taurine ADCs could indicate myocardial oedema.
8
Miah, Habeeba Khatun. "Solid-state NMR measurements of proton chemical shift anistropies." Thesis, University of Nottingham, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.716676.
Повний текст джерелаАнотація:
A new isotropic-anisotropic correlation experiment has been designed. This combines ultrafast magic angle spinning (MAS) at rates up to 80 kHz for good resolution of isotropic sites with a symmetry-based recoupling sequence to reintroduce the chemical shift anisotropy (CSA) in the indirect dimension. The experiment was implemented for protons at a Larmor frequency of 600 MHz, with some further development at a higher field corresponding to 850 MHz. The experiment was also successfully extended to the case of 19F CSAs. The CSA can be extracted by fitting the resulting lineshapes when the isotropic line is resolved in the direct dimension. The effects of couplings to abundant heteronuclei have also been investigated, since the sequences also recouple the heteronuclear dipolar coupling in certain circumstances. In this case both the dipolar coupling constant and the CSA can be extracted by fitting the resulting lineshapes. Alternatively, the dipolar coupling can be removed, using a dual-channel version of the experiment, to leave only the CSA. CASTEP has been used, in conjunction with experimental results, to refine the X- ray crystal structures of a variety of systems. The success of the refinement process depends on the presence of accurate heavy atom positions since this has a large effect on the calculated *H NMR parameters. A secondary aim was to investigate the correlation between proton CSAs and hydrogen bond lengths. Plotting the optimised hydrogen bond lengths and the corresponding calculated anisotropies revealed linear relationships dependent on the nature of the hydrogen bond acceptors and donors. In contrast, the relationship between the isotropic shifts and hydrogen bond lengths was found to be less linear than previously proposed.
9
Law, Susan. "The characterisation of microemulsions using NMR measurements of diffusion." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5983/.
Повний текст джерелаАнотація:
This thesis investigates how nuclear magnetic resonance (NMR) measurements of diffusion are used to characterise reverse micelles (RMs) in water-in-oil (w/o) microemulsions. The average droplet sizes were determined at varying water to surfactant ratios (ω) and droplet volume fractions (ød), by converting the diffusion coefficients from the surfactant molecules into hydrodynamic radii using the Stokes-Einstein equation. The size distributions of AOT/n-octane/water RMs were obtained by the application of a constrained form of the inverse Laplace transform. The AOT/iso-octane/water/pentanol and CTAB/hexanol/water systems were also studied, where the alcohols act as co-surfactants. Molecular exchange processes were observed between the RMs and the continuous phase, at varying NMR experimental parameters at different ω and ød. There was a decrease in droplet sizes with the addition of pentanol to the AOT/iso-octane/water system, which was observed with consideration to the changes in the viscosity of the continuous phase due to the partitioning and exchange of co-surfactant molecules. Molecular simulations of solvated RMs were set up at the same values of ω as the NMR experiments. The simulations, which were constructed with all-atom forcefields, displayed the interactions between the molecules in the continuous and dispersed phases and showed the RM shape fluctuations and development. The AOT/iso-octane/water/pentanol droplets formed split RMs and were smaller than RMs in the AOT/iso-octane/water system at values of ω < 20. These observations were reflected in the experimental results. The CTAB/hexanol/water droplets formed oblate RMs initially, which continued to fragment into smaller droplets, due to hexanol molecules penetrating the micelle interface.
10
Adem, Ziad, Tobias Titze, Cordula B. Krause, Christian Chmelik, Jens Kullmann, Dirk Enke, Petrik Galvosas, and Jörg Kärger. "Correlating PFG NMR and IR diffusion measurements in porous glasses." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-189411.
Повний текст джерела
11
Adem, Ziad, Tobias Titze, Cordula B. Krause, Christian Chmelik, Jens Kullmann, Dirk Enke, Petrik Galvosas, and Jörg Kärger. "Correlating PFG NMR and IR diffusion measurements in porous glasses." Diffusion fundamentals 11 (2009) 19, S. 1-2, 2009. https://ul.qucosa.de/id/qucosa%3A13958.
Повний текст джерела
12
Li, Liangmou, Igor Shikhov, Yong Zheng, and Christoph Hermann Arns. "Experiment and simulation on NMR and electrical measurements on Liège Chalk." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-178744.
Повний текст джерелаАнотація:
Liège Chalk is a limestone of considerable commercial interest to the petroleum industry and formation factor a quantity required in this context. In this work we compare the formation factors based on electrical conductivity and diffusional displacement in a long time
limit both experimentally and numerically. Measurements are performed on Liège Chalk samples while simulations are performed on two model structures represented by randomly packed ellipsoids and utilizing a Gaussian random field approach. We ensure similarity in petrophysical sense of modelled media to Liège Chalk by matching experimental and simulated NMR relaxation response, Mercury Injection Capillary Pressure curves and electrical resistivity. Following this, the diffusional-based formation factor is estimated from a set of apparent diffusion coefficients in the tortuosity limit obtained with PGSTE NMR. All measurements have been numerically-simulated and are in good agreement with experiment. We have shown that for Liège Chalk, the NMR diffusion and electrical resistivity based formation factors do agree.
13
Li, Liangmou, Igor Shikhov, Yong Zheng, and Christoph Hermann Arns. "Experiment and simulation on NMR and electrical measurements on Liège Chalk." Diffusion fundamentals 22 (2014) 6, S. 1-7, 2014. https://ul.qucosa.de/id/qucosa%3A13486.
Повний текст джерелаАнотація:
Liège Chalk is a limestone of considerable commercial interest to the petroleum industry and formation factor a quantity required in this context. In this work we compare the formation factors based on electrical conductivity and diffusional displacement in a long time
limit both experimentally and numerically. Measurements are performed on Liège Chalk samples while simulations are performed on two model structures represented by randomly packed ellipsoids and utilizing a Gaussian random field approach. We ensure similarity in petrophysical sense of modelled media to Liège Chalk by matching experimental and simulated NMR relaxation response, Mercury Injection Capillary Pressure curves and electrical resistivity. Following this, the diffusional-based formation factor is estimated from a set of apparent diffusion coefficients in the tortuosity limit obtained with PGSTE NMR. All measurements have been numerically-simulated and are in good agreement with experiment. We have shown that for Liège Chalk, the NMR diffusion and electrical resistivity based formation factors do agree.
14
Payne, Geoffrey. "NMR studies on the local distributions of sodium ions in living systems." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329930.
Повний текст джерела
15
Al-Mahrooqi, Sultan Hamed. "Laboratory and numerical investigation of NMR relaxation measurements to study reservoir wettability." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414436.
Повний текст джерела
16
Lai, Wai Cheu. "Spin-spin coupling measurements in solid-state NMR and applications to rhodopsin." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417982.
Повний текст джерела
17
Price, William S. "Applications of pulsed gradient spin-echo NMR diffusion measurements to solution dynamics and organization." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-196800.
Повний текст джерелаАнотація:
The study of solution dynamics is a very fundamental area of research with wide ranging importance from physical chemistry through
to the life sciences. A common theme is that the interactions which control the dynamics and organization of solutions are generally very
weak. Translational diffusion provides a non-invasive, direct and natural probe of the dynamics and pulsed gradient spin-echo (PGSE) NMR is a convenient means of measuring diffusion. This paper gives a brief introduction to translational diffusion as a probe of solution dynamics and of the PGSE NMR method before presenting some representative examples illustrating the power of diffusion measurements for elucidating the molecular behaviour. The use of PGSE NMR to study solution dynamics and organization is a very active area of research and a very large
literature already exists, consequently, the coverage of possible applications and the literature cited here is not comprehensive.
18
Price, William S. "Applications of pulsed gradient spin-echo NMR diffusion measurements to solution dynamics and organization." Diffusion fundamentals 2 (2005) 112, S. 1-19, 2005. https://ul.qucosa.de/id/qucosa%3A14451.
Повний текст джерелаАнотація:
The study of solution dynamics is a very fundamental area of research with wide ranging importance from physical chemistry through
to the life sciences. A common theme is that the interactions which control the dynamics and organization of solutions are generally very
weak. Translational diffusion provides a non-invasive, direct and natural probe of the dynamics and pulsed gradient spin-echo (PGSE) NMR is a convenient means of measuring diffusion. This paper gives a brief introduction to translational diffusion as a probe of solution dynamics and of the PGSE NMR method before presenting some representative examples illustrating the power of diffusion measurements for elucidating the molecular behaviour. The use of PGSE NMR to study solution dynamics and organization is a very active area of research and a very large
literature already exists, consequently, the coverage of possible applications and the literature cited here is not comprehensive.
19
Copeman, Kayla. "Evaluating Epoxy Cure And Adhesion Strength Through Single-Sided Nmr Measurements Of Molecular Mobility." W&M ScholarWorks, 2021. https://scholarworks.wm.edu/etd/1627047854.
Повний текст джерелаАнотація:
Commonly used in aerospace, automotive, marine, defense, electronic, and manufacturing industries, epoxy adhesives offer advantages over mechanical joints by providing stronger and/or more flexible bonds, more uniform stress distribution, low shrinkage, and lightweight connections between materials. Determination of curing kinetics and properties of interfaces between epoxy and inorganic substrates provides insight that is useful for quality control and defect detection for such applications. Single-sided NMR provides a nondestructive and inexpensive method for probing epoxy materials and spatially resolving the decay of spin-lattice and spin-spin relaxation times (T1 and T2) during and after curing of epoxy resins onto substrates. In this thesis, we report the use of single-sided NMR for both characterizing the strength of adhesion between epoxy and inorganic substrates and monitoring the cure of epoxy at various temperatures. Multi-dimensional T1 –T2 measurements were performed to correlate with changes in surface energies that provide insight on the chemical adhesion of various epoxy samples. Furthermore, we used NMR measurements to monitor in-situ room-temperature and heat curing of epoxy to probe reductions in molecular mobility throughout the curing process. NMR relaxation properties were correlated with DSC data for comparison of the cure extent and cure rates. Our results show the efficacy of single-sided NMR measurements for studying curing, the extent of cure, adhesion strength of epoxies, and interphase phenomena.
20
Melean, Y., Kathryn E. Washburn, P. T. Callaghan, and Christoph H. Arns. "A numerical analysis of NMR pore-pore exchange measurements using micro X-ray computed tomography." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192412.
Повний текст джерелаАнотація:
Pore-pore relaxation exchange experiments are a recent development and hold great promise to spectrally derive length scales and connectivity information relevant for transport in porous media. However, for large pores, NMR diffusion-relaxation techniques reach a limit because bulk relaxation becomes dominant. A combination of NMR and Xray-CT techniques could be beneficial and lead to better models for regions of unresolved porosity in CT images, increasing the accuracy of image based calculations of transport
properties. In this study we carry out numerical NMR pore-pore exchange experiments on selected Xray-CT images of sandstones and carbonate rock, while at the same time tracking information about the geometry and topology of the pore space. We use pore partitioning techniques and geometric distance fields to relate T2-T2 relaxation exchange spectra to underlying structural quantities. It is shown that T2-T2 pore-pore exchange measurements at room temperatures for the samples considered likely reflect exchange between pores and throats or pores and roughness.
21
Vasenkov, Sergey, and Pavel Kortunov. "PFG NMR measurements of tortuosity factors for diffusion in meso- and macropores of FCC catalysts." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-197145.
Повний текст джерелаАнотація:
Pulsed field gradient (PFG) NMR is applied to measure self-diffusion coefficients of 1,3,5 tri-isopropyl-benzene in the particles of several industrial FCC catalysts having different systems of meso- and macropores. Relating these diffusivities to the self-diffusion coefficient of 1,3,5 tri-isopropyl-benzene in the liquid phase, the tortuosity factors for diffusion in the meso- and macropores of the particles were obtained. The values of the tortuosity factors were found to increase with a increasing volumetric fraction of the small (< 20 nm) meso- and macropores in the total intraparticle volume.
22
D’Agostino, Carmine, Geoff D. Moggridge, Lynn F. Gladden, and Mick D. Mantl. "Prediction of mutual diffusion coefficients in non-ideal binary mixtures from PFG-NMR diffusion measurements." Diffusion fundamentals 20 (2013) 109, S. 1-2, 2013. https://ul.qucosa.de/id/qucosa%3A13698.
Повний текст джерела
23
Melean, Y., Kathryn E. Washburn, P. T. Callaghan, and Christoph H. Arns. "A numerical analysis of NMR pore-pore exchange measurements using micro X-ray computed tomography." Diffusion fundamentals 10 (2009) 30, S. 1-3, 2009. https://ul.qucosa.de/id/qucosa%3A14125.
Повний текст джерелаАнотація:
Pore-pore relaxation exchange experiments are a recent development and hold great promise to spectrally derive length scales and connectivity information relevant for transport in porous media. However, for large pores, NMR diffusion-relaxation techniques reach a limit because bulk relaxation becomes dominant. A combination of NMR and Xray-CT techniques could be beneficial and lead to better models for regions of unresolved porosity in CT images, increasing the accuracy of image based calculations of transport
properties. In this study we carry out numerical NMR pore-pore exchange experiments on selected Xray-CT images of sandstones and carbonate rock, while at the same time tracking information about the geometry and topology of the pore space. We use pore partitioning techniques and geometric distance fields to relate T2-T2 relaxation exchange spectra to underlying structural quantities. It is shown that T2-T2 pore-pore exchange measurements at room temperatures for the samples considered likely reflect exchange between pores and throats or pores and roughness.
24
Vasenkov, Sergey, and Pavel Kortunov. "PFG NMR measurements of tortuosity factors for diffusion in meso- and macropores of FCC catalysts." Diffusion fundamentals 1 (2005) 2, S. 1-11, 2005. https://ul.qucosa.de/id/qucosa%3A14484.
Повний текст джерелаАнотація:
Pulsed field gradient (PFG) NMR is applied to measure self-diffusion coefficients of 1,3,5 tri-isopropyl-benzene in the particles of several industrial FCC catalysts having different systems of meso- and macropores. Relating these diffusivities to the self-diffusion coefficient of 1,3,5 tri-isopropyl-benzene in the liquid phase, the tortuosity factors for diffusion in the meso- and macropores of the particles were obtained. The values of the tortuosity factors were found to increase with a increasing volumetric fraction of the small (< 20 nm) meso- and macropores in the total intraparticle volume.
25
D’Agostino, Carmine, Geoff D. Moggridge, Lynn F. Gladden, and Mick D. Mantl. "Prediction of mutual diffusion coefficients in non-ideal binary mixtures from PFG-NMR diffusion measurements." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184023.
Повний текст джерела
26
Musu, Junita Trivianty. "Relationship between reservoir properties and NMR measurements : examples from Tirrawarra sandstone, Cooper Basin, South Australia." Title page, abstract and contents only, 2000. http://web4.library.adelaide.edu.au/theses/09SM/09smm991.pdf.
Повний текст джерела
27
Bellomo, Giovanni. "MR spectroscopy in human prostate: in vitro and in vivo measurements to optimize new quantification algorithms." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9259/.
Повний текст джерелаАнотація:
Il cancro della prostata (PCa) è il tumore maligno non-cutaneo più diffuso tra gli uomini ed è il secondo tumore che miete più vittime nei paesi occidentali. La necessità di nuove tecniche non invasive per la diagnosi precoce del PCa è aumentata negli anni. 1H-MRS (proton magnetic resonance spectroscopy) e 1H-MRSI (proton magnetic resonance spectroscopy imaging) sono tecniche avanzate di spettroscopia in risonanza magnetica che permettono di individuare presenza di metaboliti come citrato, colina, creatina e in alcuni casi poliammine in uno o più voxel nel tessuto prostatico. L’abbondanza o l’assenza di uno di questi metaboliti rende possibile discriminare un tessuto sano da uno patologico. Le tecniche di spettroscopia RM sono correntemente utilizzate nella pratica clinica per cervello e fegato, con l’utilizzo di software dedicati per l’analisi degli spettri. La quantificazione di metaboliti nella prostata invece può risultare difficile a causa del basso rapporto segnale/rumore (SNR) degli spettri e del forte accoppiamento-j del citrato. Lo scopo principale di questo lavoro è di proporre un software prototipo per la quantificazione automatica di citrato, colina e creatina nella prostata. Lo sviluppo del programma e dei suoi algoritmi è stato portato avanti all’interno dell’IRST (Istituto Romagnolo per lo Studio e la cura dei Tumori) con l’aiuto dell’unità di fisica sanitaria. Il cuore del programma è un algoritmo iterativo per il fit degli spettri che fa uso di simulazioni MRS sviluppate con il pacchetto di librerie GAMMA in C++. L’accuratezza delle quantificazioni è stata testata con dei fantocci realizzati all’interno dei laboratori dell’istituto. Tutte le misure spettroscopiche sono state eseguite con il nuovo scanner Philips Ingenia 3T, una delle machine di risonanza magnetica più avanzate per applicazioni cliniche. Infine, dopo aver eseguito i test in vitro sui fantocci, sono stati acquisiti gli spettri delle prostate di alcuni volontari sani, per testare se il programma fosse in grado di lavorare in condizioni di basso SNR.
28
Smith, Andrew Christopher. "A study of phase separation in isotopic mixtures of solid helium using NMR and pressure measurements." Thesis, Royal Holloway, University of London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398224.
Повний текст джерела
29
Junker, Friedhelm. "Materialforschung an porösen Festkörpern mittels Xenon-Diffusionsmessungen: eine 129Xe-PFG-NMR-Studie - Material research in porous solids via xenon diffusion measurements: a 129 Xe PFG NMR study." Gerhard-Mercator-Universitaet Duisburg, 2001. http://www.ub.uni-duisburg.de/ETD-db/theses/available/duett-05212001-091949/.
Повний текст джерелаАнотація:
This thesis describes the measurement of xenon diffusion coefficients in porous media via Pulsed Field Gradient (PFG) NMR spectroscopy. The thesis includes the characterization of a phase seperated polymer blend (PP/EPDM) in comparison to the pure components, the characterization of a number of commercially available semi-crystalline polymers and the characterization of a new microporous solid catalyst (silconimidonitride) with three different pore sizes by the diffusional behaviour of xenon in these materials. In addition to that a new theory is described which correlates the chemical shift of 129Xe NMR adsorption resonances with the corresponding xenon diffusion coefficients.
30
de, Oliveira Fredi André Roberto. "New applications of covariance NMR and experimental development for measurements of homonuclear coupling constants in overlapping signals." Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/565884.
Повний текст джерелаАнотація:
Los resultados experimentales obtenidos en esta tesis están presentados en la forma de 3 artículos científicos publicados en revistas científicas especializadas na área de Resonancia Magnética Nuclear (RMN). Dos artículos con el uso de Covariancia de RMN como un general método para obtener espectros de pRMN. El último trabajo describe un nuevo experimento llamado de selTOCSY G-SERF para medir JHH en señales solapadas.
Publicación 1 describe un método general para generar espectros de psRMN por Covariancia de RMN. Este nuevo enfoque es único en la espectroscopia de RMN; dando una manera barata, rápida e fácil de reconstruir espectros de psRMN sin despender tiempo en el espectrómetro.
El concepto de Covariancia de psRMN ha sido extendido a la publicación 2 para añadir la información de Multiplicidad-Editada (ME) en experimentos 2D que son difíciles o mismo imposible de lograr experimentalmente. Se muestra cómo la información puede transferirse a un conjunto de espectros de RMN 2D homonucleares y heteronucleares por procesamiento de covarianza, reconstruyendo nuevos espectros de psME de una manera rápida.
Finalmente, G-SERF y los métodos relacionados solo funcionan para señales de 1H aisladas en las que se puede aplicar con éxito la excitación selectiva. Desafortunadamente, como sucede en otros experimentos selectivos de frecuencia, este enfoque falla para las señales solapadas. En la publicación 3 se presenta un esquema TOCSY G-SERF doblemente selectivo para eludir esta limitación, midiendo JHH de manera eficiente incluso para protones que resonantes en regiones atestadas.The experimental results obtained in this thesis are presented in the form of three papers published in NMR specialised scientific peer-reviewed journals. Two articles dela with the use of covariance NMR as a general method to generate novel psNMR spectra. The last work describes a new selTOCSY G-SERF experiment, for accurately measuring JHH in overlapped regions. Publication 1 describes a novel general protocol to generate psNMR spectra by Covariance NMR. This new approach is unique in NMR spectroscopy; giving a cheap, fast an easy way to reconstruct psNMR spectra without spending time in the spectrometer. This new strategy has been referenced to as psNMR Covariance. The concept of psNMR Covariance has been extended in Publication 2 by inserting Multiplicity-Edited (ME) information into 2D experiments that are difficult or even impossible to achieve experimentally. It is shown how the ME information can be efficiently transferred to a set of homonuclear and heteronuclear 2D NMR spectra by Covariance processing, reconstructing new psME spectra in a fast way. Finally, G-SERF and related methods only work for isolated 1H signals on which selective excitation can be successfully applied. Unfortunately, as it happens in other frequency-selective experiments, this approach fails for overlapped signals. A doubly-selective TOCSY G-SERF scheme is presented in the Publication 3 to circumvent this limitation, by measuring JHH efficiently even for protons resonating in crowded regions.
31
Harvey, Pierre Dominique. "Applications of vibrational spectroscopy and NMR spin-lattice relaxation time measurements to organometallic and organic molecular crystals." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=73986.
Повний текст джерела
32
Dunkhorst, Kirsten. "Diffusionsmessungen an Polyethylenglykolen mittels PFG-NMR-Spektroskopie und dynamischer Lichtstreuung / Diffusion measurements of poly(etylene glycol) in solution by Pulsed Field Gradient NMR spectroscopy and Dynamic Light Scattering." Gerhard-Mercator-Universitaet Duisburg, 2005. http://www.ub.uni-duisburg.de/ETD-db/theses/available/duett-05052005-170324/.
Повний текст джерелаАнотація:
The Pulsed Field Gradient (PFG) NMR spectroscopy was uesd to determine, via the diffusion coefficient, the molecular weights and the molecular weight distributions for sampels of poly(etylene glycol) (PEG) in D2O. Additional it was investigated, whether the components of mixtures of poly(ethylene glycol) with different molecular weights could be quantitatively determined by the differences in diffusion coefficient. The results of this study are compared with the result of the Dynamic Light Scattering (DLS) technique, the standard methode for the determination of molecular weights. The PFG NMR findings shows that the the molecular weights and the molecular weight distributions agreed well with values provided by the manufacturer. The mixtures could not be determined quantitativley, because of considerable overlaps in the molecular weight distributions. But it could be shown that the PFG NMR spectroscopy and the DLS technique complement one another.
33
Adriaensen, H. "Dynamic spatially resolved unilateral NMR measurements of liquid ingress and vapour adsorption and desorption in heterogeneous layered fabrics." Thesis, Nottingham Trent University, 2010. http://irep.ntu.ac.uk/id/eprint/193/.
Повний текст джерелаАнотація:
This thesis presents investigations of liquid ingress and vapour uptake in different porous media including textile fabrics and activated carbons, monitored by means of a unilateral NMR instrument. The aim of this work is to assess protective materials which prevent toxic liquid ingress and toxic vapour uptake from contaminating materials and personnel. A high performance fabric made of a combination of coated and not coated fibres can provide extremely high protection against toxic liquids. By incorporating an adsorbent layer between two highly repellent layers, an “intelligent” fabric that can prevent complete penetration through the composite system by toxic vapours can be constructed. This project was undertaken with a low-field unilateral profile NMR Mouse® (MObile Universal Surface Explorer) which can collect signal from a thin and flat sensitive volume (ca. 1.5 cm x 1.5 cm x 0.6 mm) up to 10 mm above it, and in a non-invasive manner. The instrument uses a strong inherent magnetic field gradient (11.38 T.m-1) in conjunction with pulsed radio frequency waves. The method makes use of Fourier Transformed NMR in order to spatially resolve 1D vertical profiles for each measurement over a field of view exceeding 500 µm and with a spatial resolution of 15 µm. One system investigated was a laminate heterogeneous layered fabric, made of a horizontal stack of three individual layers, each 70 μm thick, constructed from entangled fibres of 10 µm in diameter. The top and bottom layers are strongly repellent to the oil used as a model that represents a simulant for a toxic liquid, whilst the middle layer is non-repellent and allows oil to absorb inside. The ability of the liquid challenge (source of hydrogen-containing molecules in the form of a droplet) to penetrate the textile structure depends on the external pressure applied to the droplet; the effect of this pressure is extensively investigated in this work. In further experiments, the middle layer of the fabric was replaced by an activated carbon cloth textile layer (200 μm thick) made of woven fibres. Activated carbon is an extremely powerful adsorbent into which one or more challenge(s) can be adsorbed at a time and has therefore a great aptitude to contribute to the effectiveness of protective textiles. In this work it is demonstrated that the ingress of liquids as a function of pressure vertically applied to the top of the sample can be dynamically monitored via a vertical stack of 1D NMR profiles. It was possible to non-invasively and non-destructively quantify the amount of liquid penetrating into the middle non-repellent layer (or activated carbon cloth layer) as a function of pressure. The ability of unilateral NMR to monitor the adsorption process of vapours onto activated carbons cloths was also explored. The monitoring technique was extended to other types of activated carbons including monoliths and composites. Spatially resolved one dimensional profiles of both the transverse NMR relaxation rate (R2) and the absolute quantity of adsorbate present at a given position across the selected slice were obtained for three different activated carbons (monolith, composite and cloth) which are challenging samples from the point of view of their electrical conductivity. The NMR amplitude is shown to strongly correlate with T2 and, when calibrated, the NMR amplitude is shown to reveal the saturation level. The NMR relaxation rate reveals subtle information about pore filling, which allows quantitative assessment of the system’s saturation level, without the need for calibration, provided that the molecule under investigation is known. Differing dynamic variations in R2 are seen for one adsorbate to another. For the case of ingress into textile cloth layer, the data suggests that the bigger pores are filled before the smaller pores.
34
Tambio, Sacris Jeru. "Evaluation of electrochemical performance of lithium-ion batteries and measurements of their transport properties by high-field NMR." Thesis, Nantes, 2019. http://www.theses.fr/2019NANT4074.
Повний текст джерелаАнотація:
Les applications automobiles des batteries lithium-ion exigent deux caractéristiques principales : le kilométrage (énergie) et le couple (puissance). La demande en énergie peut être facilement obtenue en augmentant le grammage des électrodes. Cependant, la puissance souffre du fait que l'épaisseur accrue des électrodes augmente la longueur du trajet pour le transport des ions, ce qui constitue le principal facteur limitant pour un fonctionnement correct à des densités de courant élevées. Cette étude traite de l’influence des paramètres d'électrode sur les performances électrochimiques, en particulier à des densités de courant élevées. Des cyclages électrochimiques en conjonction avec la RMN PFG-SE ont été réalisés pour identifier les limitations de performances et pour étudier la diffusion des ions dans la porosité de l'électrode. Les mesures électrochimiques révèlent que la conductivité intrinsèque du matériau actif détermine les performances à faibles densités de courant et au début de la charge grâce via la résistance de polarisation. Aux fortes densités de courant, un grammage élevé et l'obstruction du réseau CB-PVdF entravent le transport des ions. Ceci est bien illustré par notre modèle analytique qui relie les différents paramètres de l’électrode à la densité de courant critique. Les mesures de RMN confortent l'hypothèse selon laquelle une teneur accrue en CB-PVdF augmente la tortuosité en raison de toutes les interactions de ces additifs avec les espèces de l’électrolyteAutomotive applications of Lithium ion batteries demand two key characteristics: mileage (energy) and torque (power). Energy demand can be simple achieved by increasing electrode mass loadings. However, power suffers due to that increased electrode thickness increases the path length for ion transport, which is the key limiting factor for proper functioning at high current densities. This study deals with how the different electrode parameters affect electrochemical performance especially at high current densities. Electrochemical cycling in conjunction PFG-SE NMR were done to pinpoint performance limitations and to study ion diffusion within the electrode porosity. Electrochemical measurements reveal that at low rates the intrinsic conductivity of the active material dicates performance through the polarization resistance. At high current densities, increased mass loading and obstruction from the CB-PVdF network hampers ion transport. This is best illustrated by our analytical model which relates the various electrode parameters with the maximum working rate. NMR measurements support the hypothesis that increased CB-PVdF content increases tortuosity due to any existing interactions between the electrolyte species and these additives
35
Markovic, Strahinja. "Application of LF-NMR measurements and supervised learning regression methods for improved characterization of heavy oils and bitumens." Thesis, Curtin University, 2022. http://hdl.handle.net/20.500.11937/89363.
Повний текст джерелаАнотація:
This work studies the physicochemical properties of unconventional hydrocarbon resources such as heavy oils and bitumens. The principal methods used in the research consisted of LF-NMR experiments, hypothesis testing, and statistical and data-driven modeling. The research output consists of several machine learning and analytical models capable of predicting heavy oil and bitumen viscosity and core sample water saturation with high accuracy. These results provide a strong case for in-situ LF-NMR applications in well logging.
36
Pahlke, Hannes, Burkhard Geil, Danuta Kruk, and Franz Fujara. "The working range of static field gradient NMR illustrated by measurements of the intracrystalline diffusion of water in NaA-zeolites." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194906.
Повний текст джерела
37
Pahlke, Hannes, Burkhard Geil, Danuta Kruk, and Franz Fujara. "The working range of static field gradient NMR illustrated by measurements of the intracrystalline diffusion of water in NaA-zeolites." Diffusion fundamentals 3 (2005) 26, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14317.
Повний текст джерела
38
Regan, David Gabriel. "NMR DIFFUSION MEASUREMENTS OF COMPARTMENTALIZED AND MULTICOMPONENT BIOLOGICAL SYSTEMS: Studies of Tropoelastin, the Self Association of N Methylacetamide, and q-Space Analysis of Real and Model Cell Suspensions." University of Sydney. School of Molecular and Microbial Biosciences, 2002. http://hdl.handle.net/2123/514.
Повний текст джерелаАнотація:
Molecular diffusion is an inherent feature of all fluid systems. The processes and interactions that characterize these systems are in some way dependent upon the mobility of the component molecules. Pulsed field-gradient spin-echo nuclear magnetic resonance (PGSE NMR) is a powerful tool for the study of molecular diffusion; for heterogeneous systems, such as those typically found in biology, this technique is unsurpassed in the diversity of systems that yield to its probing. The aim of the work presented in this thesis was to use an integrated NMR-based approach, in conjunction with computer modeling, for the study of molecular diffusion in compartmentalized and multicomponent biological systems. Erythrocyte suspensions provided an ideal experimental system for the study of compartmentalized diffusion in cells. Water exchanges rapidly between the intra- and extracellular regions and, as the major constituent of the cell, provides a strong and predominant proton NMR signal. In addition, the cells are known to align in the strong static magnetic field of the spectrometer. As a consequence of these two properties, the signal intensity from a suitably designed series of PGSE NMR experiments exhibits a series of maxima and minima when graphed as a function of the magnitude of the spatial wave number vector q. The apparently periodic phenomenon is mathematically analogous to optical diffraction and interference and is referred to here as diffusion-coherence. It is the characterization of this phenomenon, with the aid of computer-based models, which was the focus of a major section of the work described herein. Two quite distinct molecular systems formed the basis of the work in which I investigated diffusion in multicomponent systems. Both systems involved molecules that undergo self-association such that at equilibrium a population distribution of different oligomeric species is present. The first of these was tropoelastin, the monomeric subunit of elastin, which under certain conditions aggregates to form a coacervate. The second system was N-methylacetamide (NMA) which also undergoes extensive self-association. NMA oligomers have previously been studied as peptide analogues due to the presence in the monomer of a peptide linkage. In this work the aim was to use PGSE NMR diffusion measurements, in a manner that is in many ways analogous to analytical ultracentrifugation, to obtain estimates of hydrodynamic and thermodynamic parameters. Computer modeling was also used extensively in this section of work for the interpretation of the experimental data.
39
Kubásek, Ondřej. "Měření doběhu gradientních magnetických polí v MR tomografu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218551.
Повний текст джерелаАнотація:
The objective of my thesis is to measure magnetic field gradient decay in an MR tomograph, process and evaluate the data measured and analyse the issue. The theoretical section focuses on the reasons for the gradient distortion which has a negative impact on NMR measuring techniques and it also describes options to eliminate the negative effects, focusing mainly on pre-emphasis filtration. It also lists methods of gradient magnetic field measuring. The practical section contains results of magnetic field decay measurements taken with the tomograph in the Institute of scientific instruments of the Academy of sciences in Brno using the method of instantaneous frequency with and without pre-emphasis compensation. The data are processed with MAREVISI and MATLAB programmes. MATLAB is used to develop a modern method of filtration to eliminate noise in useful signal leading to more accurate measurements of MR magnetic fields. This filtration uses a method of time-dependent variable thresholds and two-channel filter banks. MATLAB is also used to design a programme for approximation of the measured gradient magnetic field decay. The decay must be approximated in order to obtain time constants and the degree of exponential decay, which serve to set up the pre-emphasis compensation.
40
Bowtell, R. W. "Spatially localised NMR parameter measurement." Thesis, University of Nottingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381096.
Повний текст джерела
41
Cawley, M. G. "Measurement of T1̲ in NMR imaging." Thesis, University of Nottingham, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379014.
Повний текст джерела
42
Does, Mark D. "Measurement of water-NMR relaxation in peripheral nerve." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq22976.pdf.
Повний текст джерела
43
Regan, David G., Konstantin I. Momot, Penny J. Martens, Philip W. Kuchel, and Laura Poole-Warren. "NMR measurement of small-molecule diffusion in PVA hydrogels." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194358.
Повний текст джерелаАнотація:
Hydrogels are biocompatible polymeric materials that are becoming increasingly important in biomedical applications, such as drug delivery and tissue engineering. Understanding of small-molecule diffusion in these systems is important in the contexts of controlled
drug release; transport of nutrients (e.g., O2 and growth factors) into the gel; and transport of cellular waste out of the gel. In this work, the diffusion coefficient of the aromatic amino acid phenylalanine (Phe) in non-crosslinked and crosslinked poly(vinyl alcohol) (PVA) hydrogels was measured using two NMR diffusion methods, CONVEX and the standard pulsed-gradient spin-echo (PGSE). Pulsed field-gradient (PFG) NMR measurements provide the advantage of measuring the molecular selfdiffusion coefficient directly and without having to rely on the physical release of the solute, but are often difficult to perform in tissues and hydrated polymers due to a large water signal. CONVEX is a recently proposed diffusion method that alleviates this problem by means of NMR excitation-sculpting water suppression. In the measurements presented here, CONVEX results were superior to those from PGSE measurements with respect to every test applied, and enabled a reliable comparison of the diffusion coefficients of Phe in crosslinked and
non-crosslinked hydrogels. The value of D(Phe) was smaller in the non-crosslinked hydrogel than in the crosslinked gel; this finding is discussed in the paper.
44
Mattila, S. (Sampo). "Measurement and minimization of field inhomogeneities in high resolution NMR." Doctoral thesis, University of Oulu, 2001. http://urn.fi/urn:isbn:9514264762.
Повний текст джерелаАнотація:
Abstract
In this work, the homogeneity of both the B0 and B1 fields was studied. Both B0 and B1 field homogeneities are the basic assumptions of high resolution liquid state NMR. Although some inhomogeneity of both of the fields is always present, the spectrometers can be operated, with the help of the developed spectral purging techniques, without giving any thought to the field inhomogeneities or the necessary actions to minimize their adverse effects. Although the effect of B0 inhomogeneity can occasionally be seen, the B1 fieldin a modern probe head is often assumed to be sufficiently homogenous for any practical purpose. By using the method used in this study the B1 field strength along one axis, typically the z-axis, can be easily mapped. Based on the information gathered from a single experiment, one can obtain reliable and valuable information about the B1 field distribution, e.g. homogeneity of the coil. From such information, the degree of required artifact suppressing methods for successful NMR experiments can be determined. Since normal pulse length calibration also requires the acquisition of several 1-D spectra, the required experimentation time is not increased.
Although the maximum amount of signal from an NMR experiment is obtained when the signal is acquired from a maximum number of resonating spins, the results presented show that significantly more homogenous B1 field along the active sample volume is achieved by rejection of the signal originating from the outer parts of the coil length. Although the total amount of signal obtained from the outer parts of the RF-coil is not very high, some loss of signal is associated with the spatially selective acquisition. The rejected signal, however, is a significant source of artifacts, and if no precautions were taken, the artifacts would severely decrease the quality of the acquired data. If the sample concentration can be increased, it would be advantageous to dissolve the amount of sample available in as small an amount of solvent as is possible and place the sample in the most B1 homogenous part of the probe-head RF-coil. With the same amount of nuclear spins concentrated into a smaller volume, the sensitivity of an NMR experiment can be increased manifold.
As an application of a spatially selective data acquisition, a versatile method capable of producing a map of the B0 field strength and its variation along the sample volume is presented.
45
Trempe, Jean-François. "Measurement and interpretation of residual anisotropic interactions in biomelecular NMR." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79148.
Повний текст джерелаАнотація:
Residual dipolar couplings have been introduced recently as a new type of experimental constraints in biomolecular structure determination by nuclear magnetic resonance (NMR). These interactions are obtained by imparting weak orientational ordering to a biomolecule in a dilute liquid crystal. This results in a partial cancellation of anisotropic interactions such as the chemical shift anisotropy (CSA), the quadrupolar coupling and the dipolar coupling. Because the alignment is weak, only strong interactions manifest. These measurements can be used to refine structure or to define folds in structural genomics projects. Here, I demonstrate the use of a new alignment medium that consists of a nematic Pf1 bacteriophage suspension embedded in an aqueous polyacrylamide gel matrix. In the absence of the gel, the phage particles align spontaneously in the NMR field.
46
Rath, Parthasarathi. "Structural and functional characterization of PorA and PorH : the two major porins from Corynebacterium glutamicum." Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1856/.
Повний текст джерелаАнотація:
PorA (5 kDa) et PorH (7kDa) sont les deux protéines membranaires majeures de la membrane externe de Corynebacterium glutamicum qui appartient au groupe supragénérique des bactéries Gram-positives contenant plusieurs agents pathogènes i. E. Mycobacterium tuberculosis, M. Leprae et C. Diphtheriae. Les deux protéines forment des canaux ioniques hétéromériques et présentent la particularité d'avoir une modification post-traductionnelle : estérification par l'acide mycolique. Les deux protéines ont été produites dans deux systèmes d'expression : chez C. Glutamicum et dans un système acellulaire utilisant des extraits de E. Coli. La présence ou l'absence de modification post-traductionnelle, sur les protéines produites in vivo et in vitro a été caractérisée par spectrométrie de masse MALDI-TOF. Les spectres de dichroïsme cellulaire et de RMN de PorA et PorH uniformément marquées et solubilisées en micelles de LDAO sont caractéristiques de protéines mono-disperses, partiellement structurées, et de qualité compatible avec une détermination de structure par RMN. Le test fonctionnel des protéines, par mesure de conductivité ionique après reconstitution dans une membrane lipidique (technique dite de BLM pour " black lipid membrane ") a montré que a) la modification post-traductionnelle de PorA par un acide mycolique est essentielle (contrairement à celle de PorH) b) la présence simultanée de PorA et de PorH est requise pour la formation d'un canal ionique voltage dépendant typique d'une porine. Afin de mieux comprendre l'importance de l'acide mycolique pour l'activité canal ionique, le complexe protéique PorA-PorH a été reconstitué dans son environnement naturel. Les principaux lipides de la membrane externe du C. Glutamicum [Tréhalose dimycolate (TDM), tréhalose monomycolate (TMM) et cardiolipide (CL)] ont été extraits et purifiés par chromatographie d'adsorption et échange d'ions, sous forme protonée et sous forme perdeutériée. Après formation de protéoliposomes les propriétés membranaires de TDM seul ou en mélange avec CL ont été étudiées RMN du deutérium, diffusion dynamique de la lumière et microscopie électronique. L'insertion de PorA et PorH dans des vésicules de TDM a permis de mettre en évidence la reconstitution de l'hétéro-oligomère (contrairement aux micelles de LDAO). Ceci ouvre la voie à la détermination de structure 3D du complexe PorA-PorH fonctionnel par RMN solide et/ou liquidePorA (5 kDa) and PorH (7 kDa) are two major membrane proteins from the outer membrane of Corynebacterium glutamicum which belongs to the suprageneric group of Gram-positive bacteria containing number of human pathogens such as Mycobacterium tuberculosis, M. Leprae and C. Diphtheriae. Both PorA and PorH have been shown to form heteromeric ion channels and to be post-translationally modified by mycolic acids (a-alkyl, beta-hydroxy fatty acids). Both proteins were produced in their natural host with mycolic acid modification, as well as in E. Coli based continuous exchange cell-free expression system and thus devoid of mycolic acid modification. The presence or absence of mycolic acid modification on in vivo and in vitro expressed proteins was confirmed by MALDI-TOF mass spectrometry. CD and NMR spectra of 15N/13C uniformly labeled PorA and PorH solubilized in LDAO micelles indicated mono-dispersed and partially folded proteins, compatible with structure determination by NMR. However, functional assays (via black lipid membrane ion-channel conductance measurements) confirmed that a complex associating both proteins is required for function and that the mycolic acid modification on PorA (but not PorH), is an absolute requirement for the formation of a voltage dependent ion-channel. To understand further the importance of covalent or non-covalent interaction of their natural lipid environment on the complex formation, the major C. Glutamicum outer membrane lipids [Trehalose dimycolate (TDM), Trehalose monomycolate (TMM) and Cardiolipin (CL)] were purified using adsorption and ion exchange chromatography, both in protonated and perdeuterated form. Prior to proteoliposome reconstitution, the membrane forming properties of TDM alone or in mixture with CL were studied by 2H-NMR, Dynamic Light Scattering and Electron Microscopy. Furthermore, after in vitro reconstitution of PorA and PorH in TDM vesicles (and not in LDAO micelles or DMPC vesicles), evidence for the formation of the hetero oligomeric complex was observed. The 3D structure determination, by liquid and/or solid state NMR, of a functional PorA-PorH complex in its natural lipid environment is now feasible
47
Boxerman, Jerrold L. (Jerrold Lee). "Non-invasive measurement of physiology using dynamic susceptibility contrast NMR imaging." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11906.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Whitaker College of Health Sciences and Technology, 1995.Includes bibliographical references (leaves 252-274).
by Jerrold Lee Boxerman.
Ph.D.
48
Nturambirwe, Jean Frederic Isingizwe. "Non-destructive measurement of internal fruit quality using SQUID-NMR techniques." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71801.
Повний текст джерелаАнотація:
Thesis(MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: The SQUID-NMR technique has been increasingly recommended by many researchers as holding a lot of potential, and it is believed it will become an invaluable tool for non-destructive evaluation in the future. Most of its potential is yet to be exploited. Non-destructive quality control of food products is one of the applications where such a system is being tried. Much of the progress that has been made in improving such a system to the present degree of user friendliness and cost effectiveness shows that, with more effort, it would be possible to implement the technology for on-line sorting, and possibly to reduce it down to hand-held devices. The goal was to investigate the feasibility of the internal fruit quality measurements using the NMR technique, and to develop a SQUID system suitable for SQUID-NMR application, intended for a later integration in a full SQUID-NMR system. A working dc SQUID was manufactured on an YBCO (Y Ba2Cu3O7 ) thin film deposited on a 10 mm x 10 mm MgO substrate. The SQUID was made of microbridge Josephson junctions, patterned by using the double resist laser lithography method, implemented during the course of this manufacturing process. The test of the SQUID showed a non-hysteretic current-voltage characteristic. Under the action of bringing a magnet closer to the SQUID under test, and then retracting it, the modulation of the I-V curve was observed. The critical current of the SQUID was 20 A and the resistance was 5.5 A series of experiments were performed on destructive measurements of the sugar content in table grapes using NMR, in order to evaluate the feasibility of this technique. The total sugars(TSS) measurements of the same samples were carried out by refractometry, chosen as a conventional method for validation. The NMR measurements were evaluated to be 5.4% precise and have an accuracy of 9.3% relative to the refractometry measurements. A further series of experiments were carried out on a high-Tc SQUID-NMR system. A high correlation coefficient (0.85) of the increasing values of the T1 and T2 relaxation times to the decreasing concentration of sugar (sucrose) in water was obtained. Non-destructive measurements T1 and T2 in table grapes suggested a possible prediction of sugar content in table grapes from the values of T1 or T2. This technique also presented many advantages compared to the conventional high field NMR technique, such as the fast measurements that do not require spectral processing, the ease of sample preparation, and its non-destructive nature.
AFRIKAANSE OPSOMMING: Die SQUID-NMR tegniek word al hoe meer aanbeveel deur navorsers oor die groot potensiaal, en dit beloof om in die toekoms van onskatbare waarde te wees in nie vernietigende evaluering. Die potensiaal moet grotendeels nog ontgin word, en die nie vernietigende kwaliteitsbeheer van voedselprodukte is een van die toepassings wat hier getoets word. Die vooruitgang tot dusver om die stelsel te verbeter wat die gebruikersvriendelikheid en koste-effektiwiteit betref, toon dat met effens meer moeite dit moontlik sal wees om die tegnologie aan te pas vir lynsortering van vrugte, en om dit dalk ook as handtoestel beskikbaar te stel. Die vooruitgang tot dusver om die stelsel te verbeter wat die gebruikersvriendelikheid en koste-effektiwiteit betref, toon dat met effens meer moeite dit moontlik sal wees om die tegnologie aan te pas vir lynsortering van vrugte, en om dit dalk ook as handtoestel beskikbaar te stel. Die doel is om die uitvoerbaarheid van interne vrugtekwaliteit metings deur hierdie tegniek te ondersoek en om ’n SQUID stelsel te ontwikkel wat gepas is vir SQUIDNMR toepassing, met die doel om dit later in ’n volledige SQUID-NMR stelsel te kan integreer. ’n Werkende GS-SQUID is vervaardig op ’n YBCO dunfilm wat op ’n 10 mm x 10 mm MgO substraat gedeponeer is. Die SQUID is van mikro-brug Josephson aansluitings/ voegvlakke, waarop in die loop van die vervaardigingsproses ’n patroon m et dubbelweerstand laser litografie neergelê is. Toets van die SQUID het ’n niehisterese stroom-spanning as kenmerkend getoon. Die nader bring en terugtrekking van ’n magneet het gelei tot waarneming van die modulasie van die I-V kurwe. Die kritieke stroom van die SQUID was 20 A en die weerstand was 5.5 ohm. ’n Reeks eksperimente is uitgevoer oor vernietigende metings van die suikerinhoud van tafeldruiwe met gebruik van NMR, om die gangbaarheid van hierdie tegniek te evalueer. Totale suikers (TSS) metings van dieselfde monsters is uitgevoer deur refraktometrie, wat gekies is as gebruiklike metode vir geldigheidsbepaling. Die NMR metings is as 5.4% presies/noukeurig evalueer, en met ’n akkuraatheid van 9.3% teenoor die refraktometrie metingsyfers. ’n Verdere reeks eksperimente is uitgevoer op ’n hoë-Tc SQID-NMR stelsel. ’n Hoë korrelasiekoëffisiënt van 0.85 van die toenemende waardes van T1 en T2 ontspantye teenoor die afname in konsentrasie van sukrose in water is waargeneem. Nie-vernietigende metings van T1 eb T2 in tafeldruiwe het gelei tot die moontlikheid van gebruik van hierdie tegniek om suikerinhoud van tafeldruiwe te voorspel. Die tegniek het ook baie voordele getoon in teenstelling met die gebruiklike hoëveld NMR tegniek, onder andere dat hierdie metings vinniger is, nie verdere verwerking van die spektrum benodig nie, die maklike voorbereiding van die monsters en die nie-vernietigende aard van die proses.
49
Jones, Brian George. "¹⁹F NMR sensors for the measurement of pH in biological systems." Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296327.
Повний текст джерела
50
Bayer, A. "The use of Tâ‚/Tâ‚‚-relaxation effects for NMR flow sensors in multiphase flow." Thesis, Cranfield University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359385.
Повний текст джерела