Journal of Magnetic Resonance

Publisher: Elsevier

Current impact factor: 2.51

Impact Factor Rankings

2016 Impact Factor Available summer 2017
2014 / 2015 Impact Factor 2.51
2013 Impact Factor 2.315
2012 Impact Factor 2.3
2011 Impact Factor 2.138
2010 Impact Factor 2.333
2009 Impact Factor 2.531
2008 Impact Factor 2.438
2007 Impact Factor 2.253
2006 Impact Factor 2.076
2005 Impact Factor 2.418
2004 Impact Factor 2.461
2003 Impact Factor 2.084
2002 Impact Factor 2.387
2001 Impact Factor 2.332
2000 Impact Factor 2.15
1999 Impact Factor 2.106
1998 Impact Factor 2.257
1994 Impact Factor 3.271

Impact factor over time

Impact factor
Year

Additional details

5-year impact 2.42
Cited half-life >10.0
Immediacy index 0.70
Eigenfactor 0.02
Article influence 0.83
Other titles Journal of magnetic resonance (San Diego, Calif.: 1997: Online), Journal of magnetic resonance, JMR
ISSN 1096-0856
OCLC 37013322
Material type Document, Periodical, Internet resource
Document type Internet Resource, Computer File, Journal / Magazine / Newspaper

Publisher details

Elsevier

  • Pre-print
    • Author can archive a pre-print version
  • Post-print
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  • Conditions
    • Authors pre-print on any website, including arXiv and RePEC
    • Author's post-print on author's personal website immediately
    • Author's post-print on open access repository after an embargo period of between 12 months and 48 months
    • Permitted deposit due to Funding Body, Institutional and Governmental policy or mandate, may be required to comply with embargo periods of 12 months to 48 months
    • Author's post-print may be used to update arXiv and RepEC
    • Publisher's version/PDF cannot be used
    • Must link to publisher version with DOI
    • Author's post-print must be released with a Creative Commons Attribution Non-Commercial No Derivatives License
    • Publisher last reviewed on 03/06/2015
  • Classification
    green

Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: Spin-spin and spin-lattice relaxations in liquid or gas entrapped in nanosized ellipsoidal cavities with different orientation ordering are theoretically investigated. The model is flexible in order to be applied to explain experimental results in cavities with various forms, from very prolate up to oblate ones, and different degree of ordering of nanocavities. In the framework of the considered model, the dipole-dipole interaction is determined by a single coupling constant, which depends on the form, size, and orientation of the cavity and number of nuclear spins in the cavity. It was shown that the transverse and longitudinal relaxation rates differently depend on the angle between the external magnetic field and cavity main axis. The calculation results for the local dipolar field, transverse and longitudinal relaxation times explain the angular dependencies observed in MRI experiments with biological objects: cartilage and tendon. Microstructure of these tissues can be characterized by the standard deviation of the Gaussian distribution of fibril orientations. The comparison of the theoretical and experimental results shows that the value of the standard deviation obtained at the matching of the calculation to experimental results can be used as a parameter characterizing the disorder in the biological sample.
    No preview · Article · Feb 2016 · Journal of Magnetic Resonance
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    ABSTRACT: For direct NMR detection and imaging of compounds with very short coherence life times the dead time between radio-frequency (RF) pulse and reception of the free induction decay (FID) is a major limiting factor. It is typically dominated by the transient and recovery times of currently available transmit-receive (T/R) switches and amplification chains. A novel PIN diode-based T/R switch topology is introduced allowing for fast switching by high bias transient currents but nevertheless producing a very low video leakage signal and insertion loss (0.5dB). The low transient spike level in conjunction with the high isolation (75dB) prevent saturation of the preamplifier entirely which consequently does not require time for recovery. Switching between transmission and reception is demonstrated within less than 1μs in bench tests as well as in acquisitions of FIDs and zero echo time (ZTE) images with bandwidths up to 500kHz at 7T. Thereby the 2kW switch exhibited a rise-time of 350ns (10-99%) producing however a total video leakage of below 20mV peak-to-peak and less than -89dBm in-band. The achieved switching time renders the RF pulse itself the dominant contribution to the dead time in which a coherence cannot be observed, thus making pulsed NMR experiments almost time-optimal even for compounds with very short signal life times.
    No preview · Article · Feb 2016 · Journal of Magnetic Resonance
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    ABSTRACT: The uniformity of the static magnetic field B0 is of prime importance for an MRI system. The passive shimming technique is usually applied to improve the uniformity of the static field by optimizing the layout of a series of steel shims. The steel pieces are fixed in the drawers in the inner bore of the superconducting magnet, and produce a magnetizing field in the imaging region to compensate for the inhomogeneity of the B0 field. In practice, the total mass of steel used for shimming should be minimized, in addition to the field uniformity requirement. This is because the presence of steel shims may introduce a thermal stability problem. The passive shimming procedure is typically realized using the linear programming (LP) method. The LP approach however, is generally slow and also has difficulty balancing the field quality and the total amount of steel for shimming. In this paper, we have developed a new algorithm that is better able to balance the dual constraints of field uniformity and the total mass of the shims. The least square method is used to minimize the magnetic field inhomogeneity over the imaging surface with the total mass of steel being controlled by an L1-norm based constraint. The proposed algorithm has been tested with practical field data, and the results show that, with similar computational cost and mass of shim material, the new algorithm achieves superior field uniformity (43% better for the test case) compared with the conventional linear programming approach.
    No preview · Article · Feb 2016 · Journal of Magnetic Resonance
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    ABSTRACT: The longitudinal magnetization of hyperpolarized media, such as hyperpolarized 129Xe, 3He, etc., is nonrenewable. When the MRI data acquisition begins at the k-domain center, a constant flip angle (CFA) results in an image of high signal-to-noise ratio (SNR) but sacrifices the accuracy of spatial information. On the other hand, a variable flip angle (VFA) strategy results in high accuracy but suffers from a low SNR. In this paper, we propose a novel scheme to optimize both the SNR and accuracy, called constant-variable flip angles (CVFA). The proposed scheme suggests that hyperpolarized magnetic resonance signals are firstly acquired through a train of n∗ CFA excitation pulses, followed by a train of N–n∗ VFA excitation pulses. We simulate and optimize the flip angle used in the CFA section, the number of CFA excitation pulses, the number of VFA excitation pulses, and the initial and final variable flip angles adopted in the VFA section. Phantom and in vivo experiments demonstrate the good performance of the CVFA designs and their ability to maintain both high SNR and spatial resolution.
    No preview · Article · Feb 2016 · Journal of Magnetic Resonance
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    ABSTRACT: A software package, MD2NOE, is presented which calculates nuclear Overhauser effect (NOE) build-up curves directly from molecular dynamics (MD) trajectories. It differs from traditional approaches in that it calculates correlation functions directly from the trajectory instead of extracting inverse sixth power distance terms as an intermediate step in calculating NOEs. This is particularly important for molecules that sample conformational states on a timescale similar to molecular reorientation. The package is tested on sucrose and results are shown to differ in small but significant ways from those calculated using an inverse sixth power assumption. Results are also compared to experiment and found to be in reasonable agreement despite an expected underestimation of water viscosity by the water model selected.
    No preview · Article · Jan 2016 · Journal of Magnetic Resonance
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    ABSTRACT: By acquiring the FID signal in two-dimensional TD-NMR spectroscopy, it is possible to characterize mixtures or complex samples composed of solid and liquid phases. We have developed a new sequence for this purpose, called IR-FID-CPMG, making it possible to correlate spin-lattice T1 and spin-spin T2 relaxation times, including both liquid and solid phases in samples. We demonstrate here the potential of a new algorithm for the 2D inverse Laplace transformation of IR-FID-CPMG data based on an adapted reconstruction of the maximum entropy method, combining the standard decreasing exponential decay function with an additional term drawn from Abragam’s FID function. The results show that the proposed IR-FID-CPMG sequence and its related inversion model allow accurate characterization and quantification of both solid and liquid phases in multiphasic and compartmentalized systems. Moreover, it permits to distinguish between solid phases having different T1 relaxation times or to highlight cross-relaxation phenomena.
    No preview · Article · Jan 2016 · Journal of Magnetic Resonance
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    ABSTRACT: RF pulse design via optimal control is typically based on gradient and quasi-Newton approaches and therefore suffers from slow convergence. We present a flexible and highly efficient method that uses exact second-order information within a globally convergent trust-region CG-Newton method to yield an improved convergence rate. The approach is applied to the design of RF pulses for single- and simultaneous multi-slice (SMS) excitation and validated using phantom and in vivo experiments on a 3T scanner using a modified gradient echo sequence.
    No preview · Article · Jan 2016 · Journal of Magnetic Resonance
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    ABSTRACT: Frequency-swept chirp pulses, created with arbitrary waveform generators (AWGs), can achieve inversion over a range of several hundreds of MHz. Such passage pulses provide defined flip angles and increase sensitivity. The fact that spectra are not excited at once, but single transitions are passed one after another, can cause new effects in established pulse EPR sequences. We developed a MATLAB library for simulation of pulse EPR, which is especially suited for modeling spin dynamics in ultra-wideband (UWB) EPR experiments, but can also be used for other experiments and NMR. At present the command line controlled SPin DYnamics ANalysis (SPIDYAN) package supports one-spin and two-spin systems with arbitrary spin quantum numbers. By providing the program with appropriate spin operators and Hamiltonian matrices any spin system is accessible, with limits set only by available memory and computation time. Any pulse sequence using rectangular and linearly or variable-rate frequency-swept chirp pulses, including phase cycling can be quickly created. To keep track of spin evolution the user can choose from a vast variety of detection operators, including transition selective operators. If relaxation effects can be neglected, the program solves the Liouville-von Neumann equation and propagates spin density matrices. In the other cases SPIDYAN uses the quantum mechanical master equation and Liouvillians for propagation. In order to consider the resonator response function, which on the scale of UWB excitation limits bandwidth, the program includes a simple RLC circuit model. Another subroutine can compute waveforms that, for a given resonator, maintain a constant critical adiabaticity factor over the excitation band. Computational efficiency is enhanced by precomputing propagator lookup tables for the whole set of AWG output levels. The features of the software library are discussed and demonstrated with spin-echo and population transfer simulations.
    No preview · Article · Jan 2016 · Journal of Magnetic Resonance
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    ABSTRACT: Flow systems, either stopped or continuous, have long been at the core of kinetic studies of chemical reactions. Such flow systems need to be coupled with appropriate spectroscopic or otherwise techniques for the detection of the chemical species studied. If paramagnetic species are formed or consumed during the investigated reaction, electron paramagnetic resonance (EPR) with its nanomolar sensitivity can be the spectroscopic method of choice. However, not much literature is available on the application of EPR to quantitatively study kinetics of chemical reactions in the liquid state. Herein, we report the characterisation of the commercially available mixing resonator ER 4117 MX from Bruker using the TEMPO-dithionite reaction as a standard. Furthermore, this setup was used to study the kinetics of the Fenton-like system of TiCl3/H2O2 and ethanol forming the -hydroxyethyl radical. Potential contributions of reactions with O2, H2O2, Ti3+/4+, and self-recombination in the decay of the -hydroxyethyl radical were investigated and the bimolecular decay was shown to be the dominant decay pathway, with a decay rate constant of M-1 s-1. This study shows the effectiveness and capabilities of EPR as a direct, sensitive and in-situ method in kinetic studies.
    No preview · Article · Jan 2016 · Journal of Magnetic Resonance
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    ABSTRACT: Dynamic Nuclear Polarization (DNP) has become a key element in nuclear magnetic resonance (NMR). Recently, we developed a novel approach to DNP enhanced liquid-state NMR based on rapid melting of a solid hyperpolarized sample followed by ’in situ’ liquid-state NMR detection. This method allows H detection with fast cycling options for signal averaging. In nonpolar solvents, doped with BDPA radicals, proton enhancement factors were achieved of up to 400. A short recycling delay of about 5 seconds allows for a fast determination of the hyper-polarization dynamics as function of the microwave frequency and power. Here, we use the rapid melt dnp method to study the mechanisms for DNP in the solid phase in more detail. Solid Effect, Cross Effect, Solid Overhauser and Liquid-state (supercritical) Overhauser DNP enhancement can be observed in the same setup. In this paper, we concentrate on Solid Effect DNP observed with both homogeneous narrow line radicals such as BDPA and with wide line anisotropic nitroxide radicals such as TEMPOL. We find indications that BDPA protons play an important role in Solid Effect DNP with this radical. A simplified spin diffusion model for BDPA can give a semi-quantitative description of the enhancements as function of the microwave power and as function of the proton concentration in the solid solution. For aqueous frozen samples we observe a similar Solid Effect DNP enhancement, which is analysed within the simplified spin diffusion model.
    No preview · Article · Jan 2016 · Journal of Magnetic Resonance
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    ABSTRACT: Complexes of the Gd(III) ion are currently being established as spin labels for distance determination in biomolecules by pulse dipolar spectroscopy. Because Gd(III) is an f ion, one expects electron spin density to be localized on the Gd(III) ion – an important feature for the mentioned application. Most of the complex ligands have nitrogens as Gd(III) coordinating atoms. As a consequence, measurements of the 14N hyperfine coupling gives access to information on the localization of the electron spin on the Gd(III). We carried out W-band, 1D and 2D 14N and 1H ENDOR measurements on the Gd(III) complexes Gd-DOTA, Gd-538, Gd-595, and Gd-PyMTA that serve as spin labels for Gd-Gd distance measurements. The obtained 14N spectra are particularly well resolved, revealing both the hyperfine and nuclear quadrupole splittings, which were assigned using 2D Mims ENDOR experiments. Additionally, the spectral contributions of the two different types of nitrogen atoms of Gd-PyMTA, the aliphatic N atom and the pyridine N atom, were distinguishable. The 14N hyperfine interaction was found to have a very small isotropic hyperfine component of -0.25 to -0.37 MHz. Furthermore, all anisotropic hyperfine interactions – both the one with the 14N nuclei and the one with the non-exchangeable protons of the ligands – are well described by the point-dipole approximation using distances derived from the crystal structures. We therefore conclude that the spin density is fully localized on the Gd(III) ion and that the spin density distribution over the nuclei of the ligands is rightfully ignored when analyzing distance measurements.
    No preview · Article · Jan 2016 · Journal of Magnetic Resonance
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    ABSTRACT: Magnetic field B0 gradients are essential in modern Nuclear Magnetic Resonance spectroscopy and imaging. Although RF/B1 gradients can be used to fulfill a similar role, this is not used in common practice because of practical limitations in the design of B1 gradient coils. Here we present a new method to create B1 gradients using stripline RF coils. The conductor-width of a stripline NMR chip and the strength of its radiofrequency field are correlated, so a stripline chip can be tapered to produce any arbitrary shaped B1 field gradient. Here we show the characterization of this tapered stripline configuration and demonstrate three applications: magnetic resonance imaging on samples with nL - μL volumes, reaction monitoring of fast chemical reactions (10-2 – 101 s) and the compensation of B0 field gradients to obtain high-resolution spectra in inhomogeneous magnetic fields.
    No preview · Article · Jan 2016 · Journal of Magnetic Resonance
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    ABSTRACT: Use of high-temperature superconducting (HTS) inner coils in combination with conventional low-temperature superconducting (LTS) outer coils for an NMR magnet, i.e. a LTS/HTS NMR magnet, is a suitable option to realize a high-resolution NMR spectrometer with operating frequency >1GHz. From the standpoint of creating a compact magnet, (RE: Rare earth) Ba2Cu3O7-x (REBCO) HTS inner coils which can tolerate a strong hoop stress caused by a Lorentz force are preferred. However, in our previous work on a first-generation 400MHz LTS/REBCO NMR magnet, the NMR resolution and sensitivity were about ten times worse than that of a conventional LTS NMR magnet. The result was caused by a large field inhomogeneity in the REBCO coil itself and the shielding effect of a screening current induced in that coil. In the present paper, we describe the operation of a modified 400MHz LTS/REBCO NMR magnet with an advanced field compensation technology using a combination of novel ferromagnetic shimming and an appropriate procedure for NMR spectrum line shape optimization. We succeeded in obtaining a good NMR line shape and 2D NOESY spectrum for a lysozyme aqueous sample. We believe that this technology is indispensable for the realization of a compact super-high-field high-resolution NMR.
    No preview · Article · Jan 2016 · Journal of Magnetic Resonance
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    ABSTRACT: The use of the magnetic field associated with Maxwell displacement current in a capacitor is proposed for the detection of Electron Spin Resonance. A probe based on this concept is realized and successfully tested with CW radio-frequency in the band going from 200 MHz to 1 GHz with a DPPH sample. A significant increase of Signal to Noise Ratio is observed while increasing the frequency.
    No preview · Article · Jan 2016 · Journal of Magnetic Resonance
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    ABSTRACT: In this paper we demonstrate long-lived states involving a pair of chemically equivalent protons, with lifetimes ∼30 times T1 up to a total lifetime of ∼117 s at high field (8.45 T). This is demonstrated on trans-ethylene-d2 in solution, where magnetic inequivalence gives access to the long-lived states. It is shown that the remaining J-coupling between the two quadrupolar deuterium spins, JQQ, splits the conditions for optimally generating proton singlet states. Detailed simulations of the spin evolution are performed, shedding light on the coherent evolution during singlet–triplet conversion as well as on the incoherent evolution that causes relaxation. Subsequently, the simulations are compared with experimental results validating the theoretical insights. Possible applications include storage of hyperpolarization in the proton long-lived state. Of particular interest may be utilization of parahydrogen induced polarization to directly induce the examined long-lived states.
    No preview · Article · Jan 2016 · Journal of Magnetic Resonance
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    ABSTRACT: In the field of sodium magnetic resonance imaging (MRI), inversion recovery (IR) is a convenient and popular method to select sodium in different environments. For the knee joint, IR has been used to suppress the signal from synovial fluids, which improves the correlation between the sodium signal and the concentration of glycosaminoglycans (GAGs) in cartilage tissues. For the better inversion of the magnetization vector under the spatial variations of the B0 and B1 fields, the IR sequence usually employ adiabatic pulses as the inversion pulse. On the other hand, it has been shown that RF shapes robust against the variations of the B0 and B1 fields can be generated by numerical optimization based on optimal control theory. In this work, we compare the performance of fluid-suppressed sodium MRI on the knee joint in vivo, between one implemented with an adiabatic pulse in the IR sequence and the other with the adiabatic pulse replaced by an optimal-control shaped pulse. While the optimal-control pulse reduces the RF power deposited to the body by 58%, the quality of fluid suppression and the signal level of sodium within cartilage are similar between two implementations.
    No preview · Article · Dec 2015 · Journal of Magnetic Resonance
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    ABSTRACT: We describe high resolution MAS solid-state NMR experiments that utilize (1)H detection with 60kHz magic angle spinning; simultaneous cross-polarization from (1)H to (15)N and (13)C nuclei; bidirectional cross-polarization between (13)C and (15)N nuclei; detection of both amide nitrogen and aliphatic carbon (1)H; and measurement of both (13)C and (15)N chemical shifts through multi-dimensional correlation experiments. Three-dimensional experiments correlate amide (1)H and alpha (1)H selectively with (13)C or (15)N nuclei in a polypeptide chain. Two separate three-dimensional spectra correlating (1)Hα/(13)Cα/(1)H(N) and (1)H(N)/(15)N/(1)Hα are recorded simultaneously in a single experiment, demonstrating that a twofold savings in experimental time is potentially achievable. Spectral editing using bidirectional coherence transfer pathways enables simultaneous magnetization transfers between (15)N, (13)Cα(()(i)()) and (13)C'(()(i)(-1)), facilitating intra- and inter-residue correlations for sequential resonance assignment. Non-uniform sampling is integrated into the experiments, further reducing the length of experimental time.
    No preview · Article · Dec 2015 · Journal of Magnetic Resonance
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    ABSTRACT: In a liquid saturated porous sample the spatial inhomogeneous internal magnetic field in general depends on the strength of the static magnetic field, the differences in magnetic susceptibilities, but also on the geometry of the porous network. To thoroughly investigate how the internal field can be used to determine various properties of the porous structure, we present a novel multi-dimensional NMR experiment that enables us to measure several dynamic correlations in one experiment, and where all of the correlations involve the internal magnetic field and its dependence on the geometry of the porous network. (Correlations: internal gradient - pore size, internal gradient - magnetic susceptibility difference, internal gradient - longitudinal relaxation, longitudinal relaxation - magnetic susceptibility difference.) It is always a spatial average of the internal magnetic field, or one of the related properties, that is measured, which is important to take into consideration when analyzing the obtained results. We demonstrate how these correlations can be an indicator for pore structure heterogeneity, and focus in particular on how the effect from spatial averaging can be evaluated and taken into account in the different cases.
    No preview · Article · Dec 2015 · Journal of Magnetic Resonance