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Journal of Magnetic Resonance

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https://www.readbyqxmd.com/read/27916509/singlet-order-conversion-and-parahydrogen-induced-hyperpolarization-of-13-c-nuclei-in-near-equivalent-spin-systems
#1
James Eills, Gabriele Stevanato, Christian Bengs, Stefan Glöggler, Stuart J Elliott, Javier Alonso-Valdesueiro, Giuseppe Pileio, Malcolm H Levitt
We have demonstrated two radiofrequency pulse methods which convert the nuclear singlet order of proton spin pairs into the magnetisation of nearby (13)C nuclei. These irradiation schemes work well in the near-equivalence regime of the three-spin system, which applies when the difference in the two (1)H-(13)C couplings is much smaller than the (1)H-(1)H coupling. We use pulse sequences to generate thermally polarized singlet states in a reproducible manner, and study the singlet-to-magnetisation transfer step...
December 1, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27918897/saturation-inversion-recovery-a-method-for-t1-measurement
#2
Hongzhi Wang, Ming Zhao, Jerome L Ackerman, Yiqiao Song
Spin-lattice relaxation (T1) has always been measured by inversion-recovery (IR), saturation-recovery (SR), or related methods. These existing methods share a common behavior in that the function describing T1 sensitivity is the exponential, e.g., exp(-τ/T1), where τ is the recovery time. In this paper, we describe a saturation-inversion-recovery (SIR) sequence for T1 measurement with considerably sharper T1-dependence than those of the IR and SR sequences, and demonstrate it experimentally. The SIR method could be useful in improving the contrast between regions of differing T1 in T1-weighted MRI...
November 27, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27915179/axially-uniform-magnetic-field-modulation-excitation-for-electron-paramagnetic-resonance-in-rectangular-and-cylindrical-cavities-by-slot-cutting
#3
Jason W Sidabras, James E Richie, James S Hyde
In continuous-wave (CW) Electron Paramagnetic Resonance (EPR) a low-frequency time-harmonic magnetic field, called field modulation, is applied parallel to the static magnetic field and incident on the sample. Varying amplitude of the field modulation incident on the sample has consequences on spectral line-shape and line-height over the axis of the sample. Here we present a method of coupling magnetic field into the cavity using slots perpendicular to the sample axis where the slot depths are designed in such a way to produce an axially uniform magnetic field along the sample...
November 25, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27918896/the-physical-mechanism-of-inhomogeneous-magnetization-transfer-mri
#4
Alan P Manning, Kimberley L Chang, Alex L MacKay, Carl A Michal
Inhomogeneous MT (ihMT) is a new magnetic resonance imaging technique that shows promise for myelin selectivity. Materials with a high proportion of lipids, such as white matter tissue, show a reduced intensity in magnetic resonance images acquired with selective prepulses at positive and negative offsets simultaneously compared to images with a single positive or negative offset prepulse of the same power. This effect was initially explained on the basis of hole-burning in inhomogeneously broadened lines of the lipid proton spin system...
November 24, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27894014/a-fast-approach-to-3d-hsqc-based-spectroscopy-based-on-a-fourier-phase-encoding-of-pre-targeted-resonances
#5
Yulan Lin, Pieter E S Smith, Zhiyong Zhang, Lucio Frydman
Multidimensional Nuclear Magnetic Resonance (NMR) provides a unique window into structure and dynamics at an atomic level. Traditionally, given the scan-by-scan time modulation involved in these experiments, the duration of nD NMR increases exponentially with spectral dimensionality. In addition, acquisition times increase as the number of spectral elements being sought in each indirect domain - given by the ratio between the spectral bandwidth being targeted and the resolution desired. These long sampling times can be substantially reduced by exploiting information that is often available from lower-dimensionality acquisitions...
November 21, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27889651/effect-of-rabi-splitting-on-the-low-temperature-electron-paramagnetic-resonance-signal-of-anthracite
#6
Ryhor Fedaruk, Roman Strzelczyk, Krzysztof Tadyszak, Siarhei A Markevich, Maria Aldona Augustyniak-Jabłokow
Specific distortions of the EPR signal of bulk anthracite are observed at low temperatures. They are accompanied by variations in the microwave oscillator frequency and are explained by the manifestation of the Rabi splitting due to the strong coupling between electron spins and the cavity, combined with the use of an automatic frequency-control (AFC) system. EPR signals are recorded at negligible saturation in the temperature range of 4-300K with use of the AFC system to keep the oscillator frequency locked to the resonant frequency of the TM110 cylinder cavity loaded with the sample...
November 19, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27889653/remote-detected-low-field-mri-using-an-optically-pumped-atomic-magnetometer-combined-with-a-liquid-cooled-pre-polarization-coil
#7
Ingo Hilschenz, Yosuke Ito, Hiroaki Natsukawa, Takenori Oida, Tetsuya Yamamoto, Tetsuo Kobayashi
Superconducting quantum interference devices are widely used in basic and clinical biomagnetic measurements such as low-field magnetic resonance imaging and magnetoencephalography primarily because they exhibit high sensitivity at low frequencies and have a wide bandwidth. The main disadvantage of these devices is that they require cryogenic coolants, which are rather expensive and not easily available. Meanwhile, with the advances in laser technology in the past few years, optically pumped atomic magnetometers (OPAMs) have been shown to be a good alternative as they can have adequate noise levels and are several millimeters in size, which makes them significantly easier to use...
November 18, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27889650/large-dose-hyperpolarized-water-with-dissolution-dnp-at-high-magnetic-field
#8
Kasper Wigh Lipsø, Sean Bowen, Oleksandr Rybalko, Jan Henrik Ardenkjær-Larsen
We demonstrate a method for the preparation of hyperpolarized water by dissolution Dynamic Nuclear Polarization at high magnetic field. Protons were polarized at 6.7T and 1.1K to >70% with frequency modulated microwave irradiation at 188GHz. 97.2±0.7% of the radical was extracted from the sample in the dissolution in a two-phase system. 16±1mL of 5.0M (1)H in D2O with a polarization of 13.0±0.9% in the liquid state was obtained, corresponding to an enhancement factor of 4000±300 compared to the thermal equilibrium at 9...
November 18, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27889652/cloud-gpu-based-simulations-for-squaremr
#9
George Kantasis, Christos G Xanthis, Kostas Haris, Einar Heiberg, Anthony H Aletras
Quantitative Magnetic Resonance Imaging (MRI) is a research tool, used more and more in clinical practice, as it provides objective information with respect to the tissues being imaged. Pixel-wise T1 quantification (T1 mapping) of the myocardium is one such application with diagnostic significance. A number of mapping sequences have been developed for myocardial T1 mapping with a wide range in terms of measurement accuracy and precision. Furthermore, measurement results obtained with these pulse sequences are affected by errors introduced by the particular acquisition parameters used...
November 17, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27875798/parsimony-and-goodness-of-fit-in-multi-dimensional-nmr-inversion
#10
Petro Babak, Sergey Kryuchkov, Apostolos Kantzas
Multi-dimensional nuclear magnetic resonance (NMR) experiments are often used for study of molecular structure and dynamics of matter in core analysis and reservoir evaluation. Industrial applications of multi-dimensional NMR involve a high-dimensional measurement dataset with complicated correlation structure and require rapid and stable inversion algorithms from the time domain to the relaxation rate and/or diffusion domains. In practice, applying existing inverse algorithms with a large number of parameter values leads to an infinite number of solutions with a reasonable fit to the NMR data...
November 16, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27898299/pfg-nmr-and-bayesian-analysis-to-characterise-non-newtonian-fluids
#11
Thomas W Blythe, Andrew J Sederman, E Hugh Stitt, Andrew P E York, Lynn F Gladden
Many industrial flow processes are sensitive to changes in the rheological behaviour of process fluids, and there therefore exists a need for methods that provide online, or inline, rheological characterisation necessary for process control and optimisation over timescales of minutes or less. Nuclear magnetic resonance (NMR) offers a non-invasive technique for this application, without limitation on optical opacity. We present a Bayesian analysis approach using pulsed field gradient (PFG) NMR to enable estimation of the rheological parameters of Herschel-Bulkley fluids in a pipe flow geometry, characterised by a flow behaviour index n, yield stress τ0, and consistency factor k, by analysis of the signal in q-space...
November 10, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27886558/optimization-of-sparse-phase-encodings-for-variable-repetition-delay-turbo-spin-echo-tse-t1-measurements-for-preclinical-applications
#12
DongKyu Lee, Sohyun Han, HyungJoon Cho
A variable repetition-delay (TR) spin echo sequence with repeated refocusing pulses, i.e., a variable TR turbo-spin echo (TSE), provides an attractive means of acquiring an accurate T1 map information that is free from gradient echo based artifacts such as magnetic field inhomogeneities particularly for ultra-high field (at 7T and above) preclinical applications. However, the applicability of multi-slice TSE sequences is often limited by signal distortion from T2 relaxation due to echo-train acquisitions for short T2 tissues, inter-slice cross talks and magnetization transfer (MT) from repetitive slice-selective 180° pulse, and extended scan times with multiple TR excitations...
November 10, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27842257/artifacts-correction-for-t1rho-imaging-with-constant-amplitude-spin-lock
#13
Weitian Chen
T1rho imaging with constant amplitude spin-lock is prone to artifacts in the presence of B1 RF and B0 field inhomogeneity. Despite significant technological progress, improvements on the robustness of constant amplitude spin-lock are necessary in order to use it for routine clinical practice. This work proposes methods to simultaneously correct for B1 RF and B0 field inhomogeneity in constant amplitude spin-lock. By setting the maximum B1 amplitude of the excitation adiabatic pulses equal to the expected constant amplitude spin-lock frequency, the spins become aligned along the effective field throughout the spin-lock process...
November 5, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27842258/a-combined-epr-and-md-simulation-study-of-a-nitroxyl-spin-label-with-restricted-internal-mobility-sensitive-to-protein-dynamics
#14
Vasily S Oganesyan, Fatima Chami, Gaye F White, Andrew J Thomson
EPR studies combined with fully atomistic Molecular Dynamics (MD) simulations and an MD-EPR simulation method provide evidence for intrinsic low rotameric mobility of a nitroxyl spin label, Rn, compared to the more widely employed label MTSL (R1). Both experimental and modelling results using two structurally different sites of attachment to Myoglobin show that the EPR spectra of Rn are more sensitive to the local protein environment than that of MTSL. This study reveals the potential of using the Rn spin label as a reporter of protein motions...
November 4, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27835747/magic-angle-turning-with-double-acquisition
#15
Tatsuya Matsunaga, K Takegoshi
The double-acquisition scheme for efficient data collection of hypercomplex data (the States method) of a two-dimensional experiment is adopted to magic-angle hopping (MAH) and magic-angle turning (MAT) experiments, which are powerful methods to measure the principal values of the chemical shift anisotropy (CSA) in a powder sample. It is shown that the double acquisition MAT (DAMAT) sequence realizes the S/N ratio comparable to or better than those of other variants of the MAH/MAT sequences. In addition, we show that DAMAT has preferable features that there are no spinning sidebands in the indirect dimension, and no spectral shearing is necessary...
November 1, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27821291/development-of-ultrafast-ute-imaging-for-granular-systems
#16
Hilary T Fabich, Andrew J Sederman, Daniel J Holland
Ultrashort echo time (UTE) imaging is commonly used in medical MRI to image 'solid' types of tissue; to date it has not been widely used in engineering or materials science, in part due to the relatively long imaging times required. Here we show how the acquisition time for UTE can be reduced to enable a preliminary study of a fluidized bed, a type of reactor commonly used throughout industry containing short T2(∗) material and requiring fast imaging. We demonstrate UTE imaging of particles with a T2(∗) of only 185μs, and an image acquisition time of only 25ms...
October 29, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27866072/general-expressions-for-r1%C3%AF-relaxation-for-n-site-chemical-exchange-and-the-special-case-of-linear-chains
#17
Hans Koss, Mark Rance, Arthur G Palmer
Exploration of dynamic processes in proteins and nucleic acids by spin-locking NMR experiments has been facilitated by the development of theoretical expressions for the R1ρ relaxation rate constant covering a variety of kinetic situations. Herein, we present a generalized approximation to the chemical exchange, Rex, component of R1ρ for arbitrary kinetic schemes, assuming the presence of a dominant major site population, derived from the negative reciprocal trace of the inverse Bloch-McConnell evolution matrix...
October 27, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27894879/alternating-delays-achieve-polarization-transfer-adapt-to-heteronuclei-in-phip-experiments
#18
Gabriele Stevanato
A new methodology for producing hyperpolarized (13)C nuclei in small organic systems via parahydrogen induced polarization (PHIP) is proposed: ADAPT (Alternating Delays Achieve Polarization Transfer). The theoretical foundation of the process is investigated in some detail and experimental examples demonstrating the viability of the approach are provided as well. The number of adjustable parameters is fewer than most of other conversion schemes. The achieved theoretical heteronuclear polarization is close to unity for any examined magnetic equivalence regime...
October 26, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27835748/selective-excitation-for-spectral-editing-and-assignment-in-separated-local-field-experiments-of-oriented-membrane-proteins
#19
Sophie N Koroloff, Alexander A Nevzorov
Spectroscopic assignment of NMR spectra for oriented uniformly labeled membrane proteins embedded in their native-like bilayer environment is essential for their structure determination. However, sequence-specific assignment in oriented-sample (OS) NMR is often complicated by insufficient resolution and spectral crowding. Therefore, the assignment process is usually done by a laborious and expensive "shotgun" method involving multiple selective labeling of amino acid residues. Presented here is a strategy to overcome poor spectral resolution in crowded regions of 2D spectra by selecting resolved "seed" residues via soft Gaussian pulses inserted into spin-exchange separated local-field experiments...
October 24, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27794269/spin-dephasing-in-a-magnetic-dipole-field-around-large-capillaries-approximative-and-exact-results
#20
F T Kurz, L R Buschle, T Kampf, K Zhang, H P Schlemmer, S Heiland, M Bendszus, C H Ziener
We present an analytical solution of the Bloch-Torrey equation for local spin dephasing in the magnetic dipole field around a capillary and for ensembles of capillaries, and adapt this solution for the study of spin dephasing around large capillaries. In addition, we provide a rigorous mathematical derivation of the slow diffusion approximation for the spin-bearing particles that is used in this regime. We further show that, in analogy to the local magnetization, the transverse magnetization of one MR imaging voxel in the regime of static dephasing (where diffusion effects are not considered) is merely the first term of a series expansion that constitutes the signal in the slow diffusion approximation...
October 19, 2016: Journal of Magnetic Resonance
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