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Journal of Magnetic Resonance

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https://www.readbyqxmd.com/read/28646695/pre-polarization-fields-for-earth-s-field-nmr-fast-discharge-for-use-with-short-t1-and-large-coils
#1
Mark S Conradi, Stephen A Altobelli, Nicholas J Sowko, Susan H Conradi, Eiichi Fukushima
The sensitivity of earth's field NMR is greatly increased by the use of a pre-polarizing field Bp. When used with short T1 samples, the field must be decreased rapidly to avoid loss of the pre-polarized magnetization by relaxation. Such a rapid decrease in the field requires rapid discharge (∼10ms) of a large stored magnetic field energy (∼700J). In addition, in order that the full pre-polarized magnetization be available for the subsequent pulse sequence, the field discharge should be adiabatic. This requirement is difficult to fulfill in cases where Bp is not everywhere parallel to the earth's field, such as with a large surface coil...
June 21, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28651245/high-resolution-hyperpolarized-in-vivo-metabolic-13-c-spectroscopy-at-low-magnetic-field-48-7mt-following-murine-tail-vein-injection
#2
Aaron M Coffey, Matthew A Feldman, Roman V Shchepin, Danila A Barskiy, Milton L Truong, Wellington Pham, Eduard Y Chekmenev
High-resolution (13)C NMR spectroscopy of hyperpolarized succinate-1-(13)C-2,3-d2 is reported in vitro and in vivo using a clinical-scale, biplanar (80cm-gap) 48.7mT permanent magnet with a high homogeneity magnetic field. Non-localized (13)C NMR spectra were recorded at 0.52MHz resonance frequency over the torso of a tumor-bearing mouse every 2s. Hyperpolarized (13)C NMR signals with linewidths of ∼3Hz (corresponding to ∼6ppm) were recorded in vitro (2mL in a syringe) and in vivo (over a mouse torso). Comparison of the full width at half maximum (FWHM) for (13)C NMR spectra acquired at 48...
June 15, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28618387/two-pulse-recoupling
#3
Navin Khaneja, Ashutosh Kumar
The paper describes a family of novel recoupling pulse sequences in magic angle spinning (MAS) solid state NMR, called two pulse recoupling. These pulse sequences can be employed for both homonuclear and heteronuclear recoupling experiments and are robust to dispersion in chemical shifts and rf-inhomogeneity. The homonuclear pulse sequence consists of a building block (π)ϕ(π)-ϕ where ϕ=π4n, and n is number of blocks in a rotor period. The recoupling block is made robust to rf-inhomogeneity by extending it to (π)ϕ(π)-ϕ(π)π+ϕ(π)π-ϕ...
June 12, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28628907/whispering-gallery-mode-esr-spectroscopy-and-parameters-measurement-in-single-crystal-srlaalo4-at-millikelvin-temperature
#4
M A Hosain, J-M Le Floch, J Krupka, M E Tobar
A cylindrical single crystal SrLaAlO4 Whispering Gallery mode dielectric resonator was cooled to millikelvin temperature using a dilution refrigerator. By controlling a DC-magnetic field, impurity ions' spins were coupled to a variety of modes allowing the measurement of hybrid spin-photon systems. This Electron Spin Resonance mapping technique allowed us to detect Cu(2+),Fe(3+) and Mn(4+) impurity ions (at the level of parts per million (ppm) to parts per billion (ppb)), verified by the measurement of the spin parameters along with their site symmetry...
June 11, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28628908/design-of-a-shielded-coil-element-of-a-matrix-gradient-coil
#5
Feng Jia, Sebastian Littin, Kelvin J Layton, Stefan Kroboth, Huijun Yu, Maxim Zaitsev
The increasing interest in spatial encoding with non-linear magnetic fields has intensified the need for coils that generates such fields. Matrix coils consisting of multiple coil elements appear to offer a high flexibility in generating customized encoding fields and are particularly promising for localized high resolution imaging applications. However, coil elements of existing matrix coils were primarily designed and constructed for better shimming and therefore are not expected to achieve an optimal performance for local spatial encoding...
June 9, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28646694/elimination-of-signals-tilting-caused-by-b0-field-inhomogeneity-using-2d-lineshape-reference-deconvolution
#6
Kirill F Sheberstov, Dmitry O Sinitsyn, Dmitry A Cheshkov, Damien Jeannerat
An efficient approach for reference deconvolution of two-dimensional spectra aiming at the correction of static field inhomogeneity was established. In comparison to known techniques, a great improvement was achieved using the cross-section along the diagonal of the reference peak instead of its full 2D line shape. The method is termed pseudo-2D diagonal deconvolution. The approach developed allows suppressing the two-dimensional peaks tilting caused by the magnetic field inhomogeneity, while keeping the signal-to-noise ratio constant...
June 8, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28628906/quadrupolar-nutation-nmr-to-discriminate-central-and-satellite-transitions-spectral-assignments-for-a-ziegler-natta-catalyst
#7
E S Merijn Blaakmeer, Wouter M J Franssen, Arno P M Kentgens
In this contribution we used solid state (35)Cl (I=3/2) quadrupolar NMR to study a MgCl2/2,2-dimethyl-1,3-dimethoxypropane (DMDOMe) adduct that serves as a model system for Ziegler-Natta catalysis. Employing large Radio-Frequency (RF) field strengths we observe three spectral features with strongly varying line widths. The assignment of the spectra is complicated because of the large difference in quadrupolar interactions experienced by the different sites in the system. The satellite transitions (ST) of relatively well-defined bulk Cl sites are partially excited and may overlap with the central transition (CT) resonances of more distorted surface sites...
June 7, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28622656/a-combined-experimental-setup-for-op-and-odnmr
#8
Erika L Sesti, Matthew M Willmering, Zayd L Ma, Dustin D Wheeler, Mark S Conradi, Sophia E Hayes
Instrumentation for optically-pumped and optically-detected nuclear magnetic resonance (OPNMR and ODNMR) has been developed and implemented as a single experimental apparatus to study semiconductors such as GaAs and CdTe. These two measurement schemes use many of the same components for experiments. Here we describe, in two parts, the apparatus that can record such measurements and give examples of representative data. In Part 1, the radio-frequency probe and low-temperature cryostat are described, including single-channel and two-channel static cryogenic probes that both incorporate a modified solenoid coil that permits better optical access...
June 7, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28595121/magnetization-transfer-in-a-partly-deuterated-lyotropic-liquid-crystal-by-single-and-dual-frequency-rf-irradiations
#9
Jae-Seung Lee, Ravinder R Regatte, Alexej Jerschow
The mechanism of magnetization transfer (MT) in a lyotropic liquid crystal made of sodium dodecyl sulfate, decanol, and water molecules is investigated by using deuterated molecules and single- and dual-frequency RF irradiations. The resulting Z-spectra suggest that the decanol molecules are mainly responsible for the MT effects in this system, through proton exchange to water. This is further confirmed by monitoring the relaxation of dipolar order, which allows one to estimate the transfer rate of magnetization from decanol to water...
May 31, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28595119/optimized-fast-mixing-device-for-real-time-nmr-applications
#10
Rémi Franco, Adrien Favier, Paul Schanda, Bernhard Brutscher
We present an improved fast mixing device based on the rapid mixing of two solutions inside the NMR probe, as originally proposed by Hore and coworkers (J. Am. Chem. Soc. 125 (2003) 12484-12492). Such a device is important for off-equilibrium studies of molecular kinetics by multidimensional real-time NMR spectrsocopy. The novelty of this device is that it allows removing the injector from the NMR detection volume after mixing, and thus provides good magnetic field homogeneity independently of the initial sample volume placed in the NMR probe...
May 31, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28586738/fast-minmax-energy-based-phase-correction-method-for-nmr-spectra-with-linear-phase-distortion
#11
Tomasz P Zieliński, Krzysztof Duda, Katarzyna Ostrowska
This paper addresses the problem of phase correction of dense NMR spectra on the example of the etoxy derivative of the fused heterocyclic system 5,6,10b-triazaacephenanthrylene (TAAP-OEt). A new estimation method for the linear phase correction coefficients is proposed that successfully extends the min-max (minimization of maximum errors) approach of Siegel (1981). Distinctive to the Siegel method, the smallest values of the real part of the discrete Fourier transform (DFT) spectrum are maximized, not for the whole spectrum but only for DFT bins near the peaks selected by anew energy-based criterion...
May 30, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28623744/obtaining-sparse-distributions-in-2d-inverse-problems
#12
A Reci, A J Sederman, L F Gladden
The mathematics of inverse problems has relevance across numerous estimation problems in science and engineering. L1 regularization has attracted recent attention in reconstructing the system properties in the case of sparse inverse problems; i.e., when the true property sought is not adequately described by a continuous distribution, in particular in Compressed Sensing image reconstruction. In this work, we focus on the application of L1 regularization to a class of inverse problems; relaxation-relaxation, T1-T2, and diffusion-relaxation, D-T2, correlation experiments in NMR, which have found widespread applications in a number of areas including probing surface interactions in catalysis and characterizing fluid composition and pore structures in rocks...
May 25, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28578162/rapid-convergence-of-optimal-control-in-nmr-using-numerically-constructed-toggling-frames
#13
Paul Coote, Clemens Anklin, Walter Massefski, Gerhard Wagner, Haribabu Arthanari
We present a numerical method for rapidly solving the Bloch equation for an arbitrary time-varying spin-1/2 Hamiltonian. The method relies on fast, vectorized computations such as summation and quaternion multiplication, rather than slow computations such as matrix exponentiation. A toggling frame is constructed in which the Hamiltonian is time-invariant, and therefore has a simple analytical solution. The key insight is that constructing this frame is faster than solving the system dynamics in the original frame...
May 25, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28603039/improvements-extensions-and-practical-aspects-of-rapid-asap-hsqc-and-alsofast-hsqc-pulse-sequences-for-studying-small-molecules-at-natural-abundance
#14
David Schulze-Sünninghausen, Johanna Becker, Martin R M Koos, Burkhard Luy
Previously we introduced two novel NMR experiments for small molecules, the so-called ASAP-HSQC and ALSOFAST-HSQC (Schulze-Sünninghausen et al., 2014), which allow the detection of heteronuclear one-bond correlations in less than 30s at natural abundance. We propose an improved symmetrized pulse scheme of the basic experiment to minimize artifact intensities and the combination with non-uniform sampling to enable the acquisition of conventional HSQC spectra in as short as a couple of seconds and extremely (13)C-resolved spectra in less than ten minutes...
May 24, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28586739/a-method-for-longitudinal-relaxation-time-measurement-in-inhomogeneous-fields
#15
Hao Chen, Shuhui Cai, Zhong Chen
The spin-lattice relaxation time (T1) plays a crucial role in the study of spin dynamics, signal optimization and data quantification. However, the measurement of chemical shift-specific T1 constants is hampered by the magnetic field inhomogeneity due to poorly shimmed external magnetic fields or intrinsic magnetic susceptibility heterogeneity in samples. In this study, we present a new protocol to determine chemical shift-specific T1 constants in inhomogeneous fields. Based on intermolecular double-quantum coherences, the new method can resolve overlapped peaks in inhomogeneous fields...
May 24, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28558274/active-control-of-the-spatial-mri-phase-distribution-with-optimal-control-theory
#16
Pauline M Lefebvre, Eric Van Reeth, Hélène Ratiney, Olivier Beuf, Elisabeth Brusseau, Simon A Lambert, Steffen J Glaser, Dominique Sugny, Denis Grenier, Kevin Tse Ve Koon
This paper investigates the use of Optimal Control (OC) theory to design Radio-Frequency (RF) pulses that actively control the spatial distribution of the MRI magnetization phase. The RF pulses are generated through the application of the Pontryagin Maximum Principle and optimized so that the resulting transverse magnetization reproduces various non-trivial and spatial phase patterns. Two different phase patterns are defined and the resulting optimal pulses are tested both numerically with the ODIN MRI simulator and experimentally with an agar gel phantom on a 4...
May 22, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28558273/evolution-of-multiple-quantum-coherences-with-scaled-dipolar-hamiltonian
#17
Claudia M Sánchez, Lisandro Buljubasich, Horacio M Pastawski, Ana K Chattah
In this article, we introduce a pulse sequence which allows the monitoring of multiple quantum coherences distribution of correlated spin states developed with scaled dipolar Hamiltonian. The pulse sequence is a modification of our previous Proportionally Refocused Loschmidt echo (PRL echo) with phase increment, in order to verify the accuracy of the weighted coherent quantum dynamics. The experiments were carried out with different scaling factors to analyze the evolution of the total magnetization, the time dependence of the multiple quantum coherence orders, and the development of correlated spins clusters...
May 20, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28550818/blochsolver-a-gpu-optimized-fast-3d-mri-simulator-for-experimentally-compatible-pulse-sequences
#18
Ryoichi Kose, Katsumi Kose
A magnetic resonance imaging (MRI) simulator, which reproduces MRI experiments using computers, has been developed using two graphic-processor-unit (GPU) boards (GTX 1080). The MRI simulator was developed to run according to pulse sequences used in experiments. Experiments and simulations were performed to demonstrate the usefulness of the MRI simulator for three types of pulse sequences, namely, three-dimensional (3D) gradient-echo, 3D radio-frequency spoiled gradient-echo, and gradient-echo multislice with practical matrix sizes...
May 20, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28551586/analysis-of-2d-nmr-relaxation-data-using-chisholm-approximations
#19
S Huber, A Haase, B Gleich
To analyze 2D NMR relaxation data based on a discrete delta-like relaxation map we extended the Padé-Laplace method to two dimensions. We approximate the forward Laplace image of the time domain signal by a Chisholm approximation, i.e. a rational polynomial in two dimensions. The poles and residues of this approximation correspond to the relaxation rates and weighting factors of the underlying relaxation map. In this work we explain the principle ideas of our algorithm and demonstrate its applicability. Therefore we compare the inversion results of the Chisholm approximation and Tikhonov regularization method as a function of SNR when the investigated signal is based on a given discrete relaxation map...
May 19, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28549338/fast-backprojection-based-reconstruction-of-spectral-spatial-epr-images-from-projections-with-the-constant-sweep-of-a-magnetic-field
#20
Denis A Komarov, Hiroshi Hirata
In this paper, we introduce a procedure for the reconstruction of spectral-spatial EPR images using projections acquired with the constant sweep of a magnetic field. The application of a constant field-sweep and a predetermined data sampling rate simplifies the requirements for EPR imaging instrumentation and facilitates the backprojection-based reconstruction of spectral-spatial images. The proposed approach was applied to the reconstruction of a four-dimensional numerical phantom and to actual spectral-spatial EPR measurements...
May 17, 2017: Journal of Magnetic Resonance
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