Thematische Bibliographien / CPMG echoes

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Auswahl der wissenschaftlichen Literatur zum Thema „CPMG echoes“

Autor: Grafiati

Veröffentlicht am 25. Mai 2024

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Zeitschriftenartikel zum Thema "CPMG echoes"

Malone, M. W., und K. L. Sauer. „Homonuclear Dipolar Coupling and CPMG Spin-Echoes in NQR“. Applied Magnetic Resonance 43, Nr. 4 (29.03.2012): 541–46. http://dx.doi.org/10.1007/s00723-012-0324-y.

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Oshio, Koichi, und Ferenc A. Jolesz. „Fast MRI by creating multiple spin echoes in a CPMG sequence“. Magnetic Resonance in Medicine 30, Nr. 2 (August 1993): 251–54. http://dx.doi.org/10.1002/mrm.1910300216.

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Grebenkov, D. S. „Multiexponential attenuation of the CPMG spin echoes due to a geometrical confinement“. Journal of Magnetic Resonance 180, Nr. 1 (Mai 2006): 118–26. http://dx.doi.org/10.1016/j.jmr.2006.01.014.

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Zaripov, Ruslan, Evgeniya Vavilova, Iskander Khairuzhdinov, Kev Salikhov, Violeta Voronkova, Mohammad A. Abdulmalic, Francois E. Meva et al. „Tuning the spin coherence time of Cu(II)−(bis)oxamato and Cu(II)−(bis)oxamidato complexes by advanced ESR pulse protocols“. Beilstein Journal of Nanotechnology 8 (27.04.2017): 943–55. http://dx.doi.org/10.3762/bjnano.8.96.

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We have investigated with the pulsed ESR technique at X- and Q-band frequencies the coherence and relaxation of Cu spins S = 1/2 in single crystals of diamagnetically diluted mononuclear [n-Bu4N]2[Cu(opba)] (1%) in the host lattice of [n-Bu4N]2[Ni(opba)] (99%, opba = o-phenylenebis(oxamato)) and of diamagnetically diluted mononuclear [n-Bu4N]2[Cu(opbon-Pr2)] (1%) in the host lattice of [n-Bu4N]2[Ni(opbon-Pr2)] (99%, opbon-Pr2 = o-phenylenebis(N(propyl)oxamidato)). For that we have measured the electron spin dephasing time T m at different temperatures with the two-pulse primary echo and with the special Carr–Purcell–Meiboom–Gill (CPMG) multiple microwave pulse sequence. Application of the CPMG protocol has led to a substantial increase of the spin coherence lifetime in both complexes as compared to the primary echo results. It shows the efficiency of the suppression of the electron spin decoherence channel in the studied complexes arising due to spectral diffusion induced by a random modulation of the hyperfine interaction with the nuclear spins. We argue that this method can be used as a test for the relevance of the spectral diffusion for the electron spin decoherence. Our results have revealed a prominent role of the opba4– and opbon-Pr2 4– ligands for the dephasing of the Cu spins. The presence of additional 14N nuclei and protons in [Cu(opbon-Pr2)]2– as compared to [Cu(opba)]2– yields significantly shorter T m times. Such a detrimental effect of the opbon-Pr2 4− ligands has to be considered when discussing a potential application of the Cu(II)−(bis)oxamato and Cu(II)−(bis)oxamidato complexes as building blocks of more complex molecular structures in prototype spintronic devices. Furthermore, in our work we propose an improved CPMG pulse protocol that enables elimination of unwanted echoes that inevitably appear in the case of inhomogeneously broadened ESR spectra due to the selective excitation of electron spins.

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Mao, Kanmi, Jennifer L. Rapp, Jerzy W. Wiench und Marek Pruski. „Characterization of Nanostructured Organic-Inorganic Hybrid Materials Using Advanced Solid-State NMR Spectroscopy“. MRS Proceedings 1184 (2009). http://dx.doi.org/10.1557/proc-1184-hh07-01.

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AbstractWe demonstrate the applications of several novel techniques in solid-state nuclear magnetic resonance spectroscopy (SSNMR) to the structural studies of mesoporous organic-inorganic hybrid catalytic materials. Most of these latest capabilities of solid-state NMR were made possible by combining fast magic angle spinning (at ≥ 40 kHz) with new multiple RF pulse sequences. Remarkable gains in sensitivity have been achieved in heteronuclear correlation (HETCOR) spectroscopy through the detection of high-λ (1H) rather than low-λ (e.g., 13C, 15N) nuclei. This so-called indirect detection technique can yield through-space 2D 13C-1H HETCOR spectra of surface species under natural abundance within minutes, a result that earlier has been out of reach. The 15N-1H correlation spectra of species bound to a surface can now be acquired, also without isotope enrichment. The first indirectly detected through-bond 2D 13C-1H spectra of solid samples are shown, as well. In the case of 1D and 2D 29Si NMR, the possibility of generating multiple Carr-Purcell-Meiboom-Gill (CPMG) echoes during data acquisition offered time savings by a factor of ten to one hundred. Examples of the studied materials involve mesoporous silica and mixed oxide nanoparticles functionalized with various types of organic groups, where solid-state NMR provides the definitive characterization.

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Dissertationen zum Thema "CPMG echoes"

Whitaker, Chastity Diane Shaffer. „Evaluation of Hahn, CPMG, and combined spin echo analysis at 8 Tesla MRI“. Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1092788422.

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Thesis (Ph. D.)--Ohio State University, 2004.
Title from first page of PDF file. Document formatted into pages; contains xxvi, 265 p. : ill. (some col.). Advisor: Petra Schmalbrock, Department of Radiology. Includes bibliographical references (p. 244-265).

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Walder, Brennan J. „Separating, correlating, and exploiting anisotropic lineshapes for NMR structure determination in solids“. The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429846088.

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Tongning, Robert-christopher. „Ralentir le déphasage des états de superposition atomiques dans un cristal de Tm3+ : YAG“. Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01011160.

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Ce travail se place dans le contexte des recherches sur les mémoires quantiques pour la lumière. L'information quantique est stockée dans un état de superposition atomique, dont la durée de vie détermine le temps maximum de stockage.On s'intéresse particulièrement aux matériaux capables de capturer la lumière par excitation résonnante d'une raie d'absorption, puis de conserver l'information quantique dans un état de superposition du fondamental électronique.Dans Tm3+:YAG, l'information est enregistrée dans un état de spin nucléaire. Cependant le champ magnétique qui lève la dégénérescence nucléaire entraîne les différents spins à des vitesses de précession différentes, ce qui tend à détruire l'aimantation initiale, porteuse de l'information.Une étude quantique du cristal est réalisée lors du premier chapitre de ce manuscrit. Les trois chapitres suivants traitent des différents mécanismes conduisant au déphasage des spins nucléaires. On y trouvera différente analyses théoriques qui seront confirmées par un ensemble de résultats expérimentaux, ainsi qu'une description détaillée du dispositif expérimental. Enfin le dernier chapitre, prospectif, exploite les outils développés au cours de la thèse pour préserver les cohérences optiques. Il présente quelques résultats expérimentaux prometteurs sur l'allongement du temps de vie de ces cohérences optiques.

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Bussandri, Mattia Santiago. „Trenes de ecos libres de oscilaciones en RMN de sistemas de espines-1/2 con acoplamiento espín-espín indirecto“. Bachelor's thesis, 2017. http://hdl.handle.net/11086/5827.

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Tesis (Lic. en Física)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, 2017.
Las secuencias multipulsos se utilizan a diario desde los comienzos de la Resonancia Magnética Nuclear. Quizás la más popular de las secuencias, conocida como CPMG por las iniciales de sus creadores, produce un tren de ecos de espín utilizada normalmente para refocalizar las inhomogeneidades del campo magnético externo. Aplicado a muestras con espines desacoplados, la secuencia produce un tren de ecos modulados por un decaimiento exponencial, o multiexponencial, dependiendo del entorno físico del sistema en estudio. Sin embargo, cuando el sistema incluye espines acoplados, en particular en muestras líquidas, los trenes de ecos presentan una modulación producto de las interacciones espín-espín indirecta entre los núcleos. Éste trabajo se centra en la eliminación de dichas oscilaciones, con el objetivo de obtener trenes de ecos libres de interacciones que puedan ser de utilidad para, por ejemplo, la implementación de secuencias de imágenes ultrarrápidas. Se presentarán resultados experimentales obtenidos en sistemas de espines de distinta complejidad, tanto en número de espines como en intensidad de interacción entre núcleos.

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Buchteile zum Thema "CPMG echoes"

„Fundamentals of Borehole NMR Data Processing and Inversion“. In Practical NMR for Oil and Gas Exploration, 245–312. Royal Society of Chemistry, 2023. http://dx.doi.org/10.1039/9781782622253-00245.

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Borehole NMR tools usually acquire basic Carr–Purcell–Meiboom–Gill (CPMG) echo trains consisting of several hundred to a few thousand echoes. Echo train data should be converted to a 1D distribution (T1 and T2), 2D distribution (D–T2 and T1–T2) or 3D distribution (T1–D–T2) through Inverse Laplace Transformation (ILT) to further obtain petrophysical parameters and identify the fluid properties of the reservoir. Meanwhile, data compression is normally employed in multidimensional (2D and 3D) NMR inversion procedures to avoid huge memory usage and slow computational speeds. Furthermore, highly resolved solutions of inverted echo data related to signal-to-noise ratios can be significantly improved using proper inversion methods and denoising techniques. A better understanding of the data processing and corresponding inversion methods will be very helpful for the data interpretation and application.

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„Fundamentals of NMR Physics“. In Practical NMR for Oil and Gas Exploration, 57–86. Royal Society of Chemistry, 2023. http://dx.doi.org/10.1039/9781782622253-00057.

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The physical principles on which downhole NMR is based are complex. The magnetic resonance phenomena and the pulse sequences, for example, are related to quantum mechanics. NMR logging measurements and NMR log interpretation, however, may be understood with the knowledge of a few basic NMR concepts. These concepts include nuclear magnetism, polarization, T1 relaxation time, T2 relaxation time, pulse tipping, free induction decay, spin echoes, and CPMG and inverse-recovery pulse sequences for one-, two-, and three-dimensional NMR measurements. This chapter is devoted to a discussion of these concepts. More complete and advanced discussions of the basics of NMR physics are found in many fine textbooks referenced at the end of the book.

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Konferenzberichte zum Thema "CPMG echoes"

Wang Quanmin, Chen Bin, Guo Gang und Huang Kedi. „Simulation of UWB echoes from ground based on CPML-FDTD“. In 2010 3rd IEEE International Conference on Computer Science and Information Technology (ICCSIT 2010). IEEE, 2010. http://dx.doi.org/10.1109/iccsit.2010.5564658.

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Xie, Z. Harry, Thomas Gentzis und Humberto Carvajal-Ortiz. „MEASURING KEROGEN, SOLID ORGANICS, AND OIL PRODUCTION POTENTIALS OF UNCONVENTIONAL SOURCE ROCKS USING SOLID TYPE 20-MHZ NMR TECHNIQUES“. In 2021 SPWLA 62nd Annual Logging Symposium Online. Society of Petrophysicists and Well Log Analysts, 2021. http://dx.doi.org/10.30632/spwla-2021-0094.

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It is well known that the NMR relaxation time T2 is proportional to the molecular mobility of water or hydrocarbons in rocks. In unconventional tight rocks, water and hydrocarbons are trapped in small pores of nanometer sizes, and their molecular mobility is severely restricted, causing the NMR T2 to be much shorter than that of conventional cases where pore sizes are in micrometer ranges. There are demands for advanced NMR techniques to study those solid-like bound hydrocarbons. In the meantime, it is of great interest for petrophysicists and geochemists to understand kerogen models in order to determine thermal maturity and hydrocarbon potential of organic-rich source rocks, and always attractive to have practical techniques that are nondestructive and less time consuming. In this study, a series of NMR 1D and 2D experiments have been performed on various types of source rocks with emphasis on short NMR T2 components, from sub-milliseconds down to a few microseconds, which are associated with kerogen, heavy hydrocarbons, and small hydrocarbon molecules bound in nanopores. The results show that the NMR CPMG pulse sequence used for the T2 data acquisition is (1) not capable of detecting and measuring the very rigid solid component of the T2 shorter than 30 microseconds, which is thought from kerogen, and (2) uncertain for the NMR components with T2 between 30 microseconds and 0.1 ms, which is dependent on the inter-echo spacing time (TE). Instead, the solid echo-pulse sequence was used to acquire the early time NMR signals that represent rigid solid matters, such as kerogen, in rock samples that have short relaxation times of less than 20 microseconds. The NMR solid echo signals were fitted into a composition of a Gaussian plus exponential functions to better describe NMR responses of source rocks with the shortest relaxation time of a few microseconds. The Gaussian component in the NMR signal is the measure of rigid solids associated with kerogen in the source rock. Model rock samples of thermally immature outcrops of the Upper Jurassic Kimmeridge Clay Formation in the UK and the Green River Shale Formation in the USA were used for comparison studies between the low field solid NMR techniques and geochemical analytical methods. The thermal maturities of the samples were artificially altered through the hydrous pyrolysis method at selected temperatures. The comparison results show that the amplitude of the Gaussian component measurement by NMR strongly correlated with the S2 of pyrolysis. The NMR relaxation times of the solid portion are directly proportional to the thermal maturity determined by organic petrography. This study concludes that the nondestructive solid NMR method provides an alternative and rapid way to study solid organic matters. The combined techniques enable us to further study kerogen models and hydrocarbon-generating potentials in organic-rich source rocks.

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Ni, Qingwen, und Shuo Chen. „Assessing the Effect of Matrix Metalloproteinase-9 on the Growth of Mice Teeth“. In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53708.

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Dentin and bone are formed when odontoblasts and osteoblasts synthesize and secrete collagen type I-rich extracellular matrix that mineralizes in a highly controlled manner. A wide spectrum of mouse and human disorders affecting tooth and bone biomineralization shows that dentin and bone formation are under strict genetic control. Although the controlling mechanisms of dentinogenesis and osteogenesis require further study, a large body of evidence points to the importance of the matrix metalloproteinases (MMPs) participate in a wide variety of extracellular matrix degradation. Detailed knowledge of MMPs may be important for understanding the pathogenesis of tooth development. Some researchers have pointed MMP-9 is an extracelluar proteinase that is highly expressed in osteoclasts and has been postulated to play an important role in their resorptive activity. Although MMP-9 has been reported to play a role in bone resorption, the association of this enzyme during deciduous tooth resorption has not yet been clarified. Based on accumulating evidence, we hypothesized that MMP-9 should play a role in teeth attrition. In this study, we have applied NMR relaxation technique to assess age-related MMP-9 KO tooth quality in vitro by quantifying changes in dentin and pulp simultaneously. The major hypothesis in this paper was that whether noninvasive NMR relaxation time measurements could be used to characterize MMP-9 KO changes in dentin and pulp, and to predict tooth quality. Specifically, we tested that age-related MMP-9 KO tooth changes result in an alteration of the NMR spin-spin (T2) relaxation time signal due to the structural changes in the tooth matrix. This signal can be further processed to produce a T2 relaxation distribution spectrum related to dentin and pulp, and their derived parameters can be used as descriptors of age-related MMP-9 KO tooth changes. In this study, the proton liquid-like NMR spin-spin (T2) relaxation decay signal was obtained from the Carr-Purcell-Meiboom-Gill (CPMG) NMR spin echo train method [1,2], then the relaxation decay signal was converted to T2 relaxation distribution spectra describing the size domain of dentin and pulp. Therefore, we can calibrate the intensities in NMR inversion T2 relaxation distribution spectra corresponding to the amount of dentin and pulp related to the structural changes. Here, we propose an NMR calibration method “NMR standard estimation” — the ratio of the amount of pulp to the amount of dentin obtained from NMR T2 distribution spectra that can be used to measure the age-related MMP-9 KO structural changes in teeth [3]. We are cognizant of the biological and physiological variability manifest in teeth size variations, but feel that this kind of NMR standard estimation — the ratio of amount of dentin to amount of pulp from the NMR T2 inversion spectrum can be used to determine age-related MMP-9 KO structural changes in teeth and eliminate any variations in size of teeth.

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