Journal articles: 'NMR theory][High resolution NMR'

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Wong, Tuck C. "Book Reviews: High Resolution NMR: Theory and Chemical Applications." Applied Spectroscopy 54, no. 8 (August 2000): 279A. http://dx.doi.org/10.1366/0003702001950878.

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Alderman, Oliver L. G., Dinu Iuga, Andrew P. Howes, Kevin J. Pike, Diane Holland, and Ray Dupree. "Spectral assignments and NMR parameter–structure relationships in borates using high-resolution 11B NMR and density functional theory." Physical Chemistry Chemical Physics 15, no. 21 (2013): 8208. http://dx.doi.org/10.1039/c3cp50772f.

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Plainchont, Bertrand, Daisy Pitoux, Ghanem Hamdoun, Jean-Michel Ouvrard, Denis Merlet, Jonathan Farjon, and Nicolas Giraud. "Achieving high resolution and optimizing sensitivity in spatial frequency encoding NMR spectroscopy: from theory to practice." Physical Chemistry Chemical Physics 18, no. 33 (2016): 22827–39. http://dx.doi.org/10.1039/c6cp01054g.

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Plainchont, Bertrand, Daisy Pitoux, Ghanem Hamdoun, Jean-Michel Ouvrard, Denis Merlet, Jonathan Farjon, and Nicolas Giraud. "Correction: Achieving high resolution and optimizing sensitivity in spatial frequency encoding NMR spectroscopy: from theory to practice." Physical Chemistry Chemical Physics 18, no. 45 (2016): 31338. http://dx.doi.org/10.1039/c6cp90272c.

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Correction for ‘Achieving high resolution and optimizing sensitivity in spatial frequency encoding NMR spectroscopy: from theory to practice’ by Bertrand Plainchont et al., Phys. Chem. Chem. Phys., 2016, 18, 22827–22839.

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Roberts, John D. "Pople, Schneider, and Bernstein A truly seminal treatise of NMR." Canadian Journal of Chemistry 83, no. 9 (September 1, 2005): 1626–28. http://dx.doi.org/10.1139/v05-156.

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The appearance of the authoritative and comprehensive book, High-Resolution Nuclear Resonance Spectroscopy, by John A. Pople, William G. Schneider, and Harold J. Bernstein in 1959 came at just the right time for chemists and other scientists to develop a clear vision of the wide breadth of applications of this critical emerging field and, in addition, to have the opportunity to learn the underlying basic theory in substantial detail.Key words: Pople, Schneider, Bernstein, NMR theory, NMR applications.

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Pallister, Peter J., Igor L. Moudrakovski, and John A. Ripmeester. "High-field multinuclear solid-state nuclear magnetic resonance (NMR) and first principle calculations in MgSO4 polymorphs." Canadian Journal of Chemistry 89, no. 9 (September 2011): 1076–86. http://dx.doi.org/10.1139/v11-044.

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A combination of solid-state nuclear magnetic resonance (NMR) and first principles calculations was applied to obtain 17O, 25Mg, and 33S NMR parameters for two polymorphs of anhydrous magnesium sulfate. Working at the very high magnetic field of 21.14 T results in a dramatic improvement of resolution through a reduction of the effects of quadrupolar interactions and significant improvement in sensitivity. Experimental 25Mg and 33S spectra are dominated by quadrupolar interactions with quadrupolar parameters unique for each polymorph. In the case of 17O, there is a substantial contribution of the chemical shift anisotropy. The use of multiple-quantum magic-angle spinning (MQMAS) experiments allows the resolution of distinct oxygen species and assignment of signals in the experimental 17O spectrum. Chemical shielding constants and quadrupolar parameters for all three nuclei were calculated using plane wave pseudopotential density functional theory as implemented in the CASTEP computational package. The calculated NMR parameters are in very good agreement with the experimental results and help in signal assignment of the 17O spectrum. The results suggest applicability of such a combined computational and experimental solid-state NMR approach for the refinement of crystallographic data.

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Venianakis, Themistoklis, Christina Oikonomaki, Michael G. Siskos, Panayiotis C. Varras, Alexandra Primikyri, Eleni Alexandri, and Ioannis P. Gerothanassis. "DFT Calculations of 1H- and 13C-NMR Chemical Shifts of Geometric Isomers of Conjugated Linoleic Acid (18:2 ω-7) and Model Compounds in Solution." Molecules 25, no. 16 (August 11, 2020): 3660. http://dx.doi.org/10.3390/molecules25163660.

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A density functional theory (DFT) study of the 1H- and 13C-NMR chemical shifts of the geometric isomers of 18:2 ω-7 conjugated linoleic acid (CLA) and nine model compounds is presented, using five functionals and two basis sets. The results are compared with available experimental data from solution high resolution nuclear magnetic resonance (NMR). The experimental 1H chemical shifts exhibit highly diagnostic resonances due to the olefinic protons of the conjugated double bonds. The “inside” olefinic protons of the conjugated double bonds are deshielded than those of the “outside” protons. Furthermore, in the cis/trans isomers, the signals of the cis bonds are more deshielded than those of the trans bonds. These regularities of the experimental 1H chemical shifts of the olefinic protons of the conjugated double bonds are reproduced very accurately for the lowest energy DFT optimized single conformer, for all functionals and basis sets used. The other low energy conformers have negligible effects on the computational 1H-NMR chemical shifts. We conclude that proton NMR chemical shifts are more discriminating than carbon, and DFT calculations can provide a valuable tool for (i) the accurate prediction of 1H-NMR chemical shifts even with less demanding functionals and basis sets; (ii) the unequivocal identification of geometric isomerism of CLAs that occur in nature, and (iii) to derive high resolution structures in solution.

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Monti, J. P., P. Gallice, A. Crevat, M. el Mehdi, C. Durand, and A. Murisasco. "Intra-erythrocytic sodium in uremic patients, as determined by "high-resolution" 23Na nuclear magnetic resonance." Clinical Chemistry 32, no. 1 (January 1, 1986): 104–7. http://dx.doi.org/10.1093/clinchem/32.1.104.

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Abstract The use of 23Na nuclear magnetic resonance with aqueous shift reagent has made it possible to determine intracellular sodium concentrations in living erythrocytes. We applied this technique to samples from 16 healthy subjects and 41 uremic patients. The results seem to show distinct populations among the latter. Classically, two different relaxation times are obtained for intracellular sodium in biological media, according to relaxation NMR theory. Some patients, however, exhibit abnormal results that cannot be accounted for by this theory.

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Ahmed, Raheel, Panayiotis C. Varras, Michael G. Siskos, Hina Siddiqui, M. Iqbal Choudhary, and Ioannis P. Gerothanassis. "NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric Endo-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate." Molecules 25, no. 21 (October 23, 2020): 4902. http://dx.doi.org/10.3390/molecules25214902.

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A combination of selective 1D Total Correlation Spectroscopy (TOCSY) and 1H-13C Heteronuclear Multiple Bond Correlation (HMBC) NMR techniques has been employed for the identification of methyl linolenate primary oxidation products without the need for laborious isolation of the individual compounds. Complex hydroperoxides and diastereomeric endo-hydroperoxides were identified and quantified. Strongly deshielded C–O–O–H 1H-NMR resonances of diastereomeric endo-hydroperoxides in the region of 8.8 to 9.6 ppm were shown to be due to intramolecular hydrogen bonding interactions of the hydroperoxide proton with an oxygen atom of the five-member endo-peroxide ring. These strongly deshielded resonances were utilized as a new method to derive, for the first time, three-dimensional structures with an assignment of pairs of diastereomers in solution with the combined use of 1H-NMR chemical shifts, Density Functional Theory (DFT), and Our N-layered Integrated molecular Orbital and molecular Mechanics (ONIOM) calculations.

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Kanzari-Mnallah, Dorra, Med L. Efrit, Jiří Pavlíček, Frédéric Vellieux, Habib Boughzala, and Azaiez B. Akacha. "Synthesis, Conformational Analysis and Crystal Structure of New Thioxo, Oxo, Seleno Diastereomeric Cyclophosphamides Containing 1,3,2-dioxaphosphorinane." Current Organic Chemistry 23, no. 2 (April 23, 2019): 205–13. http://dx.doi.org/10.2174/1385272823666190213142748.

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Thioxo, Oxo and Seleno diastereomeric cyclophosphamides containing 1,3,2- dioxaphosphorinane are prepared by a one-step chemical reaction. Their structural determination is carried out by means of Nuclear Magnetic Resonance NMR (31P, 1 H, 13C) and High-Resolution Mass Spectroscopy (HRMS). The conformational study of diastereomeric products is described. Density Functional Theory (DFT) calculations allowed the identification of preferred conformations. Experimental and calculated 31P, 13C, 1H NMR chemical shifts are compared. The molecular structure of the 2-Benzylamino-5-methyl-5- propyl-2-oxo-1,3,2-dioxaphosphorinane (3d) has been determined by means of crystal Xray diffraction methods.

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Skinner, Thomas E., Timo O. Reiss, Burkhard Luy, Navin Khaneja, and Steffen J. Glaser. "Application of optimal control theory to the design of broadband excitation pulses for high-resolution NMR." Journal of Magnetic Resonance 163, no. 1 (July 2003): 8–15. http://dx.doi.org/10.1016/s1090-7807(03)00153-8.

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Schaefer, Ted, and Rudy Sebastian. "1H and 19F NMR conformational studies of the monofluorostyrenes in solution. Comparison with theory and vapor phase behavior." Canadian Journal of Chemistry 68, no. 8 (August 1, 1990): 1383–92. http://dx.doi.org/10.1139/v90-212.

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The parameters for the high resolution 1H and 19F NMR spectra of 2-, 3-, and 4-fluorostyrene are reported for solutions in CS2 and acetone-d6 at 300 K. The populations of the planar cis and trans conformers of 2- and 3-fluorostyrene are deduced from the long-range coupling constants involving the meta and α protons. These populations are insensitive to solvent and appear to be in reasonable agreement with previous 6-31G MO computations for the free molecule; they are also compared with populations deduced from recent rotational and vibronic spectra. The long-range coupling constants for the protons of 4-fluorostyrene imply an internal barrier to rotation about the exocyclic carbon–carbon bond very similar to that in styrene, in agreement with the 6-31G results. The signs of the coupling constants involving 19F and the protons in the side chain are reported and discussed in terms of coupling mechanisms for the three molecules. An earlier surmise, of a positive a electron contribution to the coupling constant over six bonds in an all-trans arrangement, is confirmed for the meta and trans-β protons in 3-fluorostyrene. Keywords: monofluorostyrenes, 1H and 19F NMR, conformations, long-range coupling mechanisms, MO calculations of internal barriers.

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Kim, Chul, Son-Jong Hwang, Robert C. Bowman, Joseph W. Reiter, Jason A. Zan, James G. Kulleck, Houria Kabbour, E. H. Majzoub, and V. Ozolins. "LiSc(BH4)4 as a Hydrogen Storage Material: Multinuclear High-Resolution Solid-State NMR and First-Principles Density Functional Theory Studies." Journal of Physical Chemistry C 113, no. 22 (May 7, 2009): 9956–68. http://dx.doi.org/10.1021/jp9011685.

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Shaw, Janet L., Samantha J. Doble, James Stewart, and Victor N. Nemykin. "Charged and confused: Meso-tetrakis(p-methoxycarbonyl-phenyl) N-confused porphyrin as a precursor to water soluble variants." Journal of Porphyrins and Phthalocyanines 21, no. 04-06 (April 2017): 287–94. http://dx.doi.org/10.1142/s1088424617500158.

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A metal-free meso-tetrakis([Formula: see text]-methoxycarbonylphenyl) N-confused porphyrin (1) was prepared as the precursor for water-soluble derivatives by the reaction between pyrrole, methyl-4-formylbenzoate, and MSA. Tautomeric behavior of the porphyrin 1 in polar and non-polar solvents was probed by [Formula: see text]H NMR, UV-vis, MCD, steady-state fluorescence, and high-resolution ESI methods and was found to be similar to the previously reported metal-free N-confused porphyrins. The electronic structure and the nature of the excited states in 1 were correlated with the results obtained by density functional theory (DFT) and time-dependent DFT (TDDFT) calculations.

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Dybowski, Michal P., Piotr Holowinski, Rafal Typek, and Andrzej L. Dawidowicz. "Comprehensive analytical and structural characteristics of methyl 3,3-dimethyl-2-(1-(pent-4-en-1-yl)-1H-indazole-3-carboxamido)butanoate (MDMB-4en-PINACA)." Forensic Toxicology 39, no. 2 (April 1, 2021): 481–92. http://dx.doi.org/10.1007/s11419-021-00573-y.

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Abstract Purpose The purpose of the study was to evaluate a complete analytical and structural characterization of methyl 3,3-dimethyl-2-(1-(pent-4-en-1-yl)-1H-indazole-3-carboxamido)butanoate (MDMB-4en-PINACA), a novel synthetic cannabinoid being the analogue of 5F-ADB. Methods The compound was analyzed by gas chromatography–mass spectrometry (GC–MS), high-resolution liquid chromatography–mass spectrometry (LC–MS), X-ray diffraction and spectroscopic methods, such as nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopies. To derive MDMB-4en-PINACA molecular geometry and to assign infrared absorption bands, quantum calculations with the employment of density functional theory were also used. Results We present a wide range of chromatographic and spectroscopic data supported with theoretical calculations allowing to identify MDMB-4en-PINACA. Conclusions To our knowledge, this is the first report presenting a comprehensive analytical and structural characterization of MDMB-4en-PINACA obtained by 1D and 2D NMR, GC–MS, LC–MS(/MS), attenuated total reflection-FTIR spectroscopy, powder X-ray diffraction and quantum chemical calculations. The presented results not only broaden the knowledge about this psychoactive substance but also are useful for forensic and clinical purposes.

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Cakmakci, Doruk, Emin Onur Karakaslar, Elisa Ruhland, Marie-Pierre Chenard, Francois Proust, Martial Piotto, Izzie Jacques Namer, and A. Ercument Cicek. "Machine learning assisted intraoperative assessment of brain tumor margins using HRMAS NMR spectroscopy." PLOS Computational Biology 16, no. 11 (November 11, 2020): e1008184. http://dx.doi.org/10.1371/journal.pcbi.1008184.

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Complete resection of the tumor is important for survival in glioma patients. Even if the gross total resection was achieved, left-over micro-scale tissue in the excision cavity risks recurrence. High Resolution Magic Angle Spinning Nuclear Magnetic Resonance (HRMAS NMR) technique can distinguish healthy and malign tissue efficiently using peak intensities of biomarker metabolites. The method is fast, sensitive and can work with small and unprocessed samples, which makes it a good fit for real-time analysis during surgery. However, only a targeted analysis for the existence of known tumor biomarkers can be made and this requires a technician with chemistry background, and a pathologist with knowledge on tumor metabolism to be present during surgery. Here, we show that we can accurately perform this analysis in real-time and can analyze the full spectrum in an untargeted fashion using machine learning. We work on a new and large HRMAS NMR dataset of glioma and control samples (n = 565), which are also labeled with a quantitative pathology analysis. Our results show that a random forest based approach can distinguish samples with tumor cells and controls accurately and effectively with a median AUC of 85.6% and AUPR of 93.4%. We also show that we can further distinguish benign and malignant samples with a median AUC of 87.1% and AUPR of 96.1%. We analyze the feature (peak) importance for classification to interpret the results of the classifier. We validate that known malignancy biomarkers such as creatine and 2-hydroxyglutarate play an important role in distinguishing tumor and normal cells and suggest new biomarker regions. The code is released at http://github.com/ciceklab/HRMAS_NC.

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Passadis, Stamatis S., Sofia Hadjithoma, Panagiota Siafarika, Angelos G. Kalampounias, Anastasios D. Keramidas, Haralampos N. Miras, and Themistoklis A. Kabanos. "Synthesis, Structural and Physicochemical Characterization of a Titanium(IV) Compound with the Hydroxamate Ligand N,2-Dihydroxybenzamide." Molecules 26, no. 18 (September 15, 2021): 5588. http://dx.doi.org/10.3390/molecules26185588.

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The siderophore organic ligand N,2-dihydroxybenzamide (H2dihybe) incorporates the hydroxamate group, in addition to the phenoxy group in the ortho-position and reveals a very rich coordination chemistry with potential applications in medicine, materials, and physical sciences. The reaction of H2dihybe with TiCl4 in methyl alcohol and KOH yielded the tetranuclear titanium oxo-cluster (TOC) [TiIV4(μ-O)2(HOCH3)4(μ-Hdihybe)4(Hdihybe)4]Cl4∙10H2O∙12CH3OH (1). The titanium compound was characterized by single-crystal X-ray structure analysis, ESI-MS, 13C, and 1H NMR spectroscopy, solid-state and solution UV–Vis, IR vibrational, and luminescence spectroscopies and molecular orbital calculations. The inorganic core Ti4(μ-O)2 of 1 constitutes a rare structural motif for discrete TiIV4 oxo-clusters. High-resolution ESI-MS studies of 1 in methyl alcohol revealed the presence of isotopic distribution patterns which can be attributed to the tetranuclear clusters containing the inorganic core {Ti4(μ-O)2}. Solid-state IR spectroscopy of 1 showed the presence of an intense band at ~800 cm−1 which is absent in the spectrum of the H2dihybe and was attributed to the high-energy ν(Ti2–μ-O) stretching mode. The ν(C=O) in 1 is red-shifted by ~10 cm−1, while the ν(N-O) is blue-shifted by ~20 cm−1 in comparison to H2dihybe. Density Functional Theory (DFT) calculations reveal that in the experimental and theoretically predicted IR absorbance spectra of the ligand and Ti-complex, the main bands observed in the experimental spectra are also present in the calculated spectra supporting the proposed structural model. 1H and 13C NMR solution (CD3OD) studies of 1 reveal that it retains its integrity in CD3OD. The observed NMR changes upon addition of base to a CD3OD solution of 1, are due to an acid–base equilibrium and not a change in the TiIV coordination environment while the decrease in the complex’s lability is due to the improved electron-donating properties which arise from the ligand deprotonation. Luminescence spectroscopic studies of 1 in solution reveal a dual narrow luminescence at different excitation wavelengths. The TOC 1 exhibits a band-gap of 1.98 eV which renders it a promising candidate for photocatalytic investigations.

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Prammer, M. G., J. Bouton, E. D. Drack, M. N. Miller, and R. N. Chandler. "A New Multiband Generation of NMR Logging Tools." SPE Reservoir Evaluation & Engineering 4, no. 01 (February 1, 2001): 59–63. http://dx.doi.org/10.2118/69670-pa.

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Summary This paper describes the hardware and operation of a new generation of nuclear magnetic resonance (NMR) logging tools. In the past, NMR required the logging engineer to consider the T1 relaxation times of the reservoir fluids likely to be encountered. Actual, or simply assumed, long T1's translated into slow logging speeds. The new tool generation overcomes this limitation. The key feature is that nine sensitive volumes are polarized in parallel and are read out in rapid sequence. A new sonde design speeds up the polarization process by a factor of 2. Each volume contributes equally to the result and can support identical measurements for rapid stacking and fast logging, and each can be used for individual, simultaneous measurements. Laboratory data and field-test results are presented to demonstrate both the relative simplicity of operation and the improvement in data quality. Logging speeds typically can be upgraded by a factor of 4, while data for total porosity determination and fluid typing are acquired in a single logging pass. Background Over the past few years, log analysts have become familiar with the potential and the limitations of NMR logging. Basically, an NMR tool reports the total number of hydrogen atoms that are in the liquid or gaseous state. As such, NMR is a lithology-independent porosity tool as long as the hydrogen index of the fluids can be estimated. The commercial use of modern pulsed-NMR tools (NUMAR's MRIL1,***, and Schlumberger's CMR,2,**** brought two surprises:The near-borehole zone, which was assumed to be flushed, can contain substantial amounts of native hydrocarbons, both oil and gas.The T1 relaxation times of hydrocarbons (connate fluids and filtrate from oil-based muds) under reservoir conditions are substantially longer than previously assumed. The consequence of these findings was that NMR began to be used as a hydrocarbon-detection and reservoir-quantification tool, at the expense of logging speed and wellsite efficiency.3,4 From the theory of nuclear spin relaxation in liquids by Bloembergen, Purcell, and Pound5 follows the proportionality of bulk relaxation time and self-diffusion coefficient: T1~D. The Stokes relationship between viscosity and correlation time stipulates that D~T/µ; therefore, we can expect that T1~T/µ over a certain range of temperatures. We conducted measurements of T1 and T2 in the 30 to 150°C range on oils used for oil-based mud synthesis.***** Some of our results are listed in Table 1. These oils are typically type C16/C18, with hydrogen indices close to that of water. The absence of longer chains or aromatics suggests short correlation times and long T1 relaxation times for Larmor frequencies in the low-MHz range. For all samples investigated, T1=T2. In general, our data confirm the expected temperature dependency of T1. Certain oils, however, including Oil B and Oil C in Table 1, show a sharp discontinuity at some point between 110 and 150°C. We have confirmed that no chemical change takes place in the oil because the original T1 can be restored by cooling the sample to room temperature and exposing it to the atmosphere. The most likely explanation is dissolved oxygen that becomes volatile above 110°C. Paramagnetic oxygen is a potent relaxation agent even at low concentrations, and its disappearance at high temperatures causes an additional increase in T1. The surface interaction, which is responsible for rapid relaxation/polarization in the water phase, is inefficient for oil, even in cases where rock analysis would classify the rock as oil-wet. Gas is another example of high T1's (4-5 sec and more) caused by weak internal relaxation and nonexistent interaction with the rock surface. T 1 affects data acquisition and logging speed in a direct fashion:The hydrogen atoms must be exposed to the polarizing magnetic field for a multiple of T1. A factor of 3 is considered minimum. Fig. 1 illustrates exponential polarization curves for T1's of 1 sec, 2 sec, and 4 sec. Note that 95% polarization is reached only after 12 sec for fluids with T1=4 sec.The measurement itself is contaminated by thermal noise and must be repeated a few times to bring the influence of this noise down to acceptable levels. After each measurement, a full wait time (tw) of at least 3× T1 is required. Assuming 8 repeats and T1=4 sec, we find that the wait times required for a single measurement add up to 8×4×3=96 sec. If a vertical resolution of 3 ft is acceptable, the NMR tool cannot move faster than 3×60/96˜2 ft/min. A speed limit of 120 ft/hr makes it impractical to deploy NMR on a routine basis over large openhole intervals. An undesirable option is to forego full polarization. This mode is faster but results in data that are substantially harder to interpret in a quantitative fashion. Furthermore, this mode defeats the unique capability of NMR to detect hydrocarbons independent of resistivity contrast. It is highly desirable to use an NMR tool that is virtually free of T1 effects. Current NMR applications such as total and effective porosities, pore-size distribution, permeability modeling, hydrocarbon typing, and gas detection require that all hydrogen components are equally visible; i.e., even the slowest T1 component should be fully polarized. Furthermore, these applications should run at logging speeds of 1,000-1,500 ft/hr. Lastly, a higher level of automation should reduce the amount of job planning and setup procedures required today. These requirements are met by the newest generation of MRIL tools, MRIL-Prime. The T1 problem is solved by using a large number of measurement volumes in parallel and by employing a new prepolarization scheme. New Tool Features The key feature of the new MRIL tool is the ability to rapidly polarize and to read out many identical measurement volumes. The scheme is illustrated in Fig. 2. There are nine tightly packed cylindrical shells, each 24 in. tall and each containing on average 750 mL. The tool electronics can rapidly switch back and forth between volumes by changing the operating frequency over a wide range. The magnetic field gradient translates lower operating frequencies into resonance conditions that occur farther away from the tool. The gradient is circularly symmetric, resulting in resonance shells around the tool. These shells are labeled A (innermost, diameter 14 in.) to J (outermost, diameter 16.5 in.). In an 8-in. borehole, these diameters correspond to a depth of investigation between 3 and 4 in. The individual volumes are completely separated such that concurrent measurements do not influence each other. The approximate field strength, resonance frequency, and magnetic field gradient for each measurement volume is listed in Table 2.

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Pech-Puch, Dawrin, Jaime Rodríguez, Bastien Cautain, Carlos Alfredo Sandoval-Castro, and Carlos Jiménez. "Cytotoxic Furanoditerpenes from the Sponge Spongia tubulifera Collected in the Mexican Caribbean." Marine Drugs 17, no. 7 (July 16, 2019): 416. http://dx.doi.org/10.3390/md17070416.

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Two new spongian furanoditerpenes, 3β-hydroxyspongia-13(16),14-dien-2-one (1) and 19-dehydroxy-spongian diterpene 17 (2), along with five known terpenes, the spongian furanoditerpenes 9-nor-3-hydroxyspongia-3,13(16),14-trien-2-one (3), 3β,19 dihydroxyspongia-13(16),14-dien-2-one (epispongiadiol) (4) and spongian diterpene 17 (5), the furanoditerpene ambliol C (6), and the sesterterpene scalarin (7), were isolated from the methanolic extract of the sponge Spongia tubulifera, collected in the Mexican Caribbean. The planar structures of the new compounds were elucidated by 1D/2D NMR and IR spectroscopic analysis, high resolution electrospray mass spectrometry (HRESIMS), and comparison of their spectral data with those reported in the literature. Absolute configurations were determined by comparison of the experimental electronic circular dichroism (ECD) spectrum with those calculated by time-dependent density functional theory (TDDFT). Compounds 1, 4, and 6 displayed weak cytotoxic activity against different human tumour cell lines.

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Li, Yang, Hannah M. Rhoda, Anthony M. Wertish, and Victor N. Nemykin. "Organometallic pyrene-containing porphyrins: Synthesis, characterization, and non-covalent interactions with C60 fullerenes." Journal of Porphyrins and Phthalocyanines 20, no. 08n11 (August 2016): 1098–113. http://dx.doi.org/10.1142/s1088424616500735.

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A reaction between 5,10,15,20-tetra(4-hydroxyphenyl)porphyrin and 1-bromopyrene resulted in the formation of 5,10,15,20-tetra[4-(4-(pyrenyl-1)butoxy)phenyl]porphyrin (1), while cross-condensation between 4-(4-(pyrenyl-1)butoxy)benzaldehyde, ferrocenecaboxaldehyde, and pyrrole resulted in the formation of 5-ferrocenyl-10,15,20-tri[4-(4-(pyrenyl-1)butoxy)phenyl]porphyrin (2), 5,10-diferrocenyl-15,20-di[4-(4-(pyrenyl-1)butoxy)phenyl]porphyrin (3), and 5,15-diferrocenyl-10,20-di[4-(4-(pyrenyl-1)butoxy)phenyl]porphyrin (4). All pyrene-containing porphyrins were characterized by 1H NMR, UV-vis, MCD, and high-resolution ESI methods, while their electronic structures and the nature of the excited states were elucidated using density functional theory (DFT) and time-dependent DFT (TDDFT) calculations. The molecular structure of 1 and its fluorescence quenching upon the addition of C[Formula: see text] fullerene was also investigated using X-ray crystallography and steady-state fluorescence approaches.

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Gómez, Jennifer S., Andrew G. M. Rankin, Julien Trébosc, Frédérique Pourpoint, Yu Tsutsumi, Hiroki Nagashima, Olivier Lafon, and Jean-Paul Amoureux. "Improved NMR transfer of magnetization from protons to half-integer spin quadrupolar nuclei at moderate and high magic-angle spinning frequencies." Magnetic Resonance 2, no. 1 (June 17, 2021): 447–64. http://dx.doi.org/10.5194/mr-2-447-2021.

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Abstract. Half-integer spin quadrupolar nuclei are the only magnetic isotopes for the majority of the chemical elements. Therefore, the transfer of polarization from protons to these isotopes under magic-angle spinning (MAS) can provide precious insights into the interatomic proximities in hydrogen-containing solids, including organic, hybrid, nanostructured and biological solids. This transfer has recently been combined with dynamic nuclear polarization (DNP) in order to enhance the NMR signal of half-integer quadrupolar isotopes. However, the cross-polarization transfer lacks robustness in the case of quadrupolar nuclei, and we have recently introduced as an alternative technique a D-RINEPT (through-space refocused insensitive nuclei enhancement by polarization transfer) scheme combining a heteronuclear dipolar recoupling built from adiabatic pulses and a continuous-wave decoupling. This technique has been demonstrated at 9.4 T with moderate MAS frequencies, νR≈10–15 kHz, in order to transfer the DNP-enhanced 1H polarization to quadrupolar nuclei. Nevertheless, polarization transfers from protons to quadrupolar nuclei are also required at higher MAS frequencies in order to improve the 1H resolution. We investigate here how this transfer can be achieved at νR≈20 and 60 kHz. We demonstrate that the D-RINEPT sequence using adiabatic pulses still produces efficient and robust transfers but requires large radio-frequency (rf) fields, which may not be compatible with the specifications of most MAS probes. As an alternative, we introduce robust and efficient variants of the D-RINEPT and PRESTO (phase-shifted recoupling effects a smooth transfer of order) sequences using symmetry-based recoupling schemes built from single and composite π pulses. Their performances are compared using the average Hamiltonian theory and experiments at B0=18.8 T on γ-alumina and isopropylamine-templated microporous aluminophosphate (AlPO4-14), featuring low and significant 1H–1H dipolar interactions, respectively. These experiments demonstrate that the 1H magnetization can be efficiently transferred to 27Al nuclei using D-RINEPT with SR412(270090180) recoupling and using PRESTO with R2227(1800) or R1676(270090180) schemes at νR=20 or 62.5 kHz, respectively. The D-RINEPT and PRESTO recoupling schemes complement each other since the latter is affected by dipolar truncation, whereas the former is not. We also analyze the losses during these recoupling schemes, and we show how these magnetization transfers can be used at νR=62.5 kHz to acquire in 72 min 2D HETCOR (heteronuclear correlation) spectra between 1H and quadrupolar nuclei, with a non-uniform sampling (NUS).

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22

Horii, Fumitaka. "High-resolution NMR: Solid-state NMR." Kobunshi 39, no. 12 (1990): 888–91. http://dx.doi.org/10.1295/kobunshi.39.888.

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23

Chaves, Otávio Augusto, Vitor Sueth-Santiago, Douglas Chaves de Alcântara Pinto, José Carlos Netto-Ferreira, Debora Decote-Ricardo, and Marco Edilson Freire de Lima. "2-Chloro-4,6-bis{(E)-3-methoxy-4-[(4-methoxybenzyl)oxy]styryl}pyrimidine: Synthesis, Spectroscopic and Computational Evaluation." Molbank 2021, no. 3 (September 7, 2021): M1276. http://dx.doi.org/10.3390/m1276.

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A novel curcumin analog namely 2-chloro-4,6-bis{(E)-3-methoxy-4-[(4-methoxybenzyl)oxy]-styryl}pyrimidine (compound 7) was synthesized by three-step reaction. The condensation reaction of protected vanillin with 2-chloro-4,6-dimethylpyrimidine (6) was the most efficient step, resulting in a total yield of 72%. The characterization of compound 7 was performed by 1H and 13C nuclear magnetic resonance (NMR), as well as high-resolution mass spectrometry. The experimental spectrometric data were compared with the theoretical spectra obtained by the density functional theory (DFT) method, showing a perfect match between them. UV-visible spectroscopy and steady-state fluorescence emission studies were performed for compound 7 in solvents of different polarities and the results were correlated with DFT calculations. Compound 7 showed a solvatochromism effect presenting higher molar extinction coefficient (log ε = 4.57) and fluorescence quantum yield (ϕ = 0.38) in toluene than in acetonitrile or methanol. The simulation of both frontier molecular orbitals (FMOs) and molecular electrostatic potential (MEP) suggested that the experimental spectra profile in toluene was not interfered by a possible charge transfer. These results are an indication of a low probability of compound 7 in reacting with unsaturated phospholipids in future applications as a fluorescent dye in biological systems.

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24

Saarinen, Timothy R., and Charles S. Johnson. "High-resolution electrophoretic NMR." Journal of the American Chemical Society 110, no. 10 (May 1988): 3332–33. http://dx.doi.org/10.1021/ja00218a071.

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25

Allerhand, Adam, and Steven R. Maple. "Ultra-high resolution NMR." Analytical Chemistry 59, no. 6 (March 15, 1987): 441A—452A. http://dx.doi.org/10.1021/ac00133a001.

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26

Diehl, Bernd W. K. "High resolution NMR spectroscopy." European Journal of Lipid Science and Technology 103, no. 12 (December 2001): 830–34. http://dx.doi.org/10.1002/1438-9312(200112)103:12<830::aid-ejlt830>3.0.co;2-8.

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27

Yamada, Hiroaki. "High-Pressure, High-Resolution NMR." REVIEW OF HIGH PRESSURE SCIENCE AND TECHNOLOGY 2, no. 2 (1993): 132–38. http://dx.doi.org/10.4131/jshpreview.2.132.

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28

Teigen, Knut, Vidar R. Jensen, and Aurora Martinez. "The Reaction Mechanism of Phenylalanine Hydroxylase. – A Question of Coordination." Pteridines 16, no. 1 (February 2005): 27–34. http://dx.doi.org/10.1515/pteridines.2005.16.1.27.

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Abstract Phenylalanine hydroxylase (PAH) is a non-heme iron and tetrahydrobiopterin-dependent enzyme that catalyzes the hydroxylation of L-phenylalanine to L-tyrosine using dioxygen as additional substrate. The cofactor tetrahydrobiopterin accepts one of the oxygen atoms of dioxygen during catalysis and also seems to be involved in prereduction of the active site iron from the ferric to the activated ferrous form. Structures of the truncated form of PAH in complex with substrate and cofactor are available, but the oxygen binding site and the actual mechanism of electron transfer are uncertain. It is believed that dioxygen binds directly to the metal, where it is activated, and several reaction mechanisms involving end-on binding of 0 2 have been proposed based on both experimental studies and quantum mechanical calculations. However, in this work we aimed to investigate the possibility of side-on binding of dioxygen to the iron. Furthermore, NMR and recent high-resolution crystallographic studies also place the cofactor in closer proximity to the iron, challenging the mechanistic conclusions from earlier crystallographic and computational studies. In this paper we report preliminary results from a density functional theory (DFT) study of the coordination of dioxygen to a structural model of PAH based on a recent crystallographic structure. These results are compared with existing computational and experimental data and their implications for the mechanism of the PAH-reaction are discussed. Particular attention is paid to the binding-mode of dioxygen and the iron-cofactor distance.

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29

Jelinski, Lynn W., and Michael T. Melchior. "High-Resolution NMR of Solids." Applied Spectroscopy Reviews 35, no. 1-2 (May 24, 2004): 25–93. http://dx.doi.org/10.1081/asr-100101220.

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30

SAITÔ, HAZIME. "High-resolution Solid-state NMR." Sen'i Gakkaishi 44, no. 6 (1988): P219—P223. http://dx.doi.org/10.2115/fiber.44.6_p219.

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31

Freeman, Ray. "Pioneers of high-resolution NMR." Concepts in Magnetic Resonance 11, no. 2 (1999): 61–70. http://dx.doi.org/10.1002/(sici)1099-0534(1999)11:2<61::aid-cmr1>3.0.co;2-7.

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32

Shulman, Robert G. "High resolution NMR in vivo." Trends in Biochemical Sciences 13, no. 2 (February 1988): 37–39. http://dx.doi.org/10.1016/0968-0004(88)90022-9.

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33

Goel, Sahil, Harsh Yadav, Nidhi Sinha, Budhendra Singh, Igor Bdikin, Devarapalli Chenna Rao, Kovuru Gopalaiah, and Binay Kumar. "An insight into the synthesis, crystal structure, geometrical modelling of crystal morphology, Hirshfeld surface analysis and characterization ofN-(4-methylbenzyl)benzamide single crystals." Journal of Applied Crystallography 50, no. 5 (September 28, 2017): 1498–511. http://dx.doi.org/10.1107/s1600576717012316.

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A versatile approach for the synthesis ofN-(4-methylbenzyl)benzamide, C15H15NO, using CuI as catalyst has been reported. Single crystals of the synthesized compound were grown using the slow evaporation solution technique. The crystal structure of theN-(4-methylbenzyl)benzamide crystals has been determined by single-crystal X-ray diffraction. The compound crystallizes in an orthorhombic lattice, noncentrosymmetric space groupPna21. The crystal structure is stabilized by intermolecular N—H...O hydrogen bonds and weak C—H...π interactions to form layers parallel to theaaxis. A user-friendly approach based on centre of mass propagation vector theory was used to predict the crystal morphology. The framework developed here utilizes the concept of intermolecular bond strength to discern the crystal morphology. Fourier transform IR, NMR and high-resolution mass spectrometry analytical techniques were used for the identification of functional groups and confirmation of the structure of the title compound. All of the intermolecular interactions present in the crystal structure, including the C—H...π, C—H...O and N—H...O interactions, were investigated and confirmed by molecular Hirshfeld surface analysis. From linear optical spectroscopy, the transmittance, optical band gap and UV cutoff wavelength were determined. The photoluminescence emission spectrum was recorded for a grown crystal. Dielectric measurements were performed at room temperature for various frequencies. The mechanical strength of the (001) plane of the title compound was measured using the Vickers micro-hardness technique. A piezo-coefficient of 15 pC N−1was found along the (001) plane of the title crystals. The thermal stability and melting point were also investigated. In addition, density functional theory simulations were used to calculate the optimized molecular geometry and the UV–vis spectrum, and to determine the highest occupied molecular orbital/lowest unoccupied molecular orbital energy gap. The results show thatN-(4-methylbenzyl)benzamide is a potential candidate for multifunctional optical and piezoelectric crystals.

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34

Dědeček, Jiří, Stepan Sklenak, Chengbin Li, Fei Gao, Jiří Brus, Qingjun Zhu, and Takashi Tatsumi. "Effect of Al/Si Substitutions and Silanol Nests on the Local Geometry of Si and Al Framework Sites in Silicone-Rich Zeolites: A Combined High Resolution 27Al and 29Si NMR and Density Functional Theory/Molecular Mechanics Study." Journal of Physical Chemistry C 113, no. 32 (July 15, 2009): 14454–66. http://dx.doi.org/10.1021/jp9042232.

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35

Barbera, Vincenzina, Luigi Brambilla, Alberto Milani, Alberto Palazzolo, Chiara Castiglioni, Alessandra Vitale, Roberta Bongiovanni, and Maurizio Galimberti. "Domino Reaction for the Sustainable Functionalization of Few-Layer Graphene." Nanomaterials 9, no. 1 (December 30, 2018): 44. http://dx.doi.org/10.3390/nano9010044.

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The mechanism for the functionalization of graphene layers with pyrrole compounds was investigated. Liquid 1,2,5-trimethylpyrrole (TMP) was heated in air in the presence of a high surface area nanosized graphite (HSAG), at temperatures between 80 °C and 180 °C. After the thermal treatments solid and liquid samples, separated by centrifugation, were analysed by means of Raman, Fourier Transform Infrared (FT-IR) spectroscopy, X-Rays Photoelectron Spectroscopy (XPS) and 1H-Nuclear Magnetic Resonance (1H NMR) spectroscopy and High Resolution Transmission Electron Microscopy (HRTEM). FT-IR spectra were interpreted with the support of Density Functional Theory (DFT) quantum chemical modelling. Raman findings suggested that the bulk structure of HSAG remained substantially unaltered, without intercalation products. FT-IR and XPS spectra showed the presence of oxidized TMP derivatives on the solid adducts, in a much larger amount than in the liquid. For thermal treatments at T ≥ 150 °C, IR spectral features revealed not only the presence of oxidized products but also the reaction of intra-annular double bond of TMP with HSAG. XPS spectroscopy showed the increase of the ratio between C(sp2)N bonds involved in the aromatic system and C(sp3)N bonds, resulting from reaction of the pyrrole moiety, observed while increasing the temperature from 130 °C to 180 °C. All these findings, supported by modeling, led to hypothesize a cascade reaction involving a carbocatalyzed oxidation of the pyrrole compound followed by Diels-Alder cycloaddition. Graphene layers play a twofold role: at the early stages of the reaction, they behave as a catalyst for the oxidation of TMP and then they become the substrate for the cycloaddition reaction. Such sustainable functionalization, which does not produce by-products, allows us to use the pyrrole compounds for decorating sp2 carbon allotropes without altering their bulk structure and smooths the path for their wider application.

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36

Jonas, J., P. Koziol, X. Peng, C. Reiner, and D. M. Campbell. "High-Resolution NMR Spectroscopy at High Pressures." Journal of Magnetic Resonance, Series B 102, no. 3 (December 1993): 299–309. http://dx.doi.org/10.1006/jmrb.1993.1099.

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37

McDowell, Lynda M., and Jacob Schaefer. "High-resolution NMR of biological solids." Current Opinion in Structural Biology 6, no. 5 (October 1996): 624–29. http://dx.doi.org/10.1016/s0959-440x(96)80028-5.

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38

Grimmer, Arnd-Rüdiger, Dirk Müller, and Jochen Neels. "Solid-state high-resolution NMR K2PO3F·KF." Journal of Fluorine Chemistry 29, no. 1-2 (August 1985): 60. http://dx.doi.org/10.1016/s0022-1139(00)83295-9.

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39

Freeman, Ray. "High resolution NMR using selective excitation." Journal of Molecular Structure 266 (March 1992): 39–51. http://dx.doi.org/10.1016/0022-2860(92)80048-m.

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40

Balbach, John J., Mark S. Conradi, D. P. Cistola, Changguo Tang, Joel R. Garbow, and W. C. Hutton. "High-resolution NMR in inhomogeneous fields." Chemical Physics Letters 277, no. 4 (October 1997): 367–74. http://dx.doi.org/10.1016/s0009-2614(97)00858-0.

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41

Freeman, Ray. "Selective excitation in high-resolution NMR." Chemical Reviews 91, no. 7 (November 1991): 1397–412. http://dx.doi.org/10.1021/cr00007a006.

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42

Kupce, E., and R. Freeman. ""Template Excitation" in High-Resolution NMR." Journal of Magnetic Resonance, Series A 106, no. 1 (January 1994): 135–39. http://dx.doi.org/10.1006/jmra.1994.1016.

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43

Luy, Burkhard. "Towards Portable High-Resolution NMR Spectroscopy." Angewandte Chemie International Edition 50, no. 2 (December 10, 2010): 354–56. http://dx.doi.org/10.1002/anie.201005976.

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44

Grechishkin, V. S., R. V. Grechishkina, G. S. Kuprianova, J. N. Latosińska, and B. Nogaj. "High-resolution NMR studies of nifedipine." Applied Magnetic Resonance 17, no. 1 (May 1999): 113–18. http://dx.doi.org/10.1007/bf03162074.

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45

Emid, S., and J. H. N. Creyghton. "High resolution NMR imaging in solids." Physica B+C 128, no. 1 (January 1985): 81–83. http://dx.doi.org/10.1016/0378-4363(85)90087-7.

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46

Rachdi, F., J. Reichenbach, L. Firlej, P. Bernier, M. Ribet, R. Aznar, G. Zimmer, M. Helmle, and M. Mehring. "High resolution 13C NMR of K6C60." Solid State Communications 87, no. 6 (August 1993): 547–50. http://dx.doi.org/10.1016/0038-1098(93)90593-c.

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47

Ribó, Josep M., Joaquim Crusats, Zoubir El-Hachemi, Miguel Feliz, Paloma Sanchez-Bel, and Félix Romojaro. "High-resolution NMR of irradiated almonds." Journal of the American Oil Chemists' Society 81, no. 11 (November 2004): 1029–33. http://dx.doi.org/10.1007/s11746-004-1017-1.

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48

Eccles, C. D., and P. T. Callaghan. "High-resolution imaging. The NMR microscope." Journal of Magnetic Resonance (1969) 68, no. 2 (June 1986): 393–98. http://dx.doi.org/10.1016/0022-2364(86)90261-1.

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49

Nishihara, H., I. Fujii, T. Hattori, H. Yoshida, and T. Nakaoki. "NMR of11B in glasses with combined techniques of field-swept NMR and high-resolution NMR." Czechoslovak Journal of Physics 46, S4 (April 1996): 2177–78. http://dx.doi.org/10.1007/bf02571080.

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50

Jonas, J., L. Ballard, and D. Nash. "High-Resolution, High-Pressure NMR Studies of Proteins." Biophysical Journal 75, no. 1 (July 1998): 445–52. http://dx.doi.org/10.1016/s0006-3495(98)77532-0.

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Journal articles on the topic 'NMR theory][High resolution NMR'

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