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Journal of Magnetic Resonance

Roberta Frass-Kriegl, Elmar Laistler, Sajad Hosseinnezhadian, Albrecht Ingo Schmid, Ewald Moser, Marie Poirier-Quinot, Luc Darrasse, Jean-Christophe Ginefri
A novel design scheme for monolithic transmission line resonators (TLRs) is presented - the multi-turn multi-gap TLR (MTMG-TLR) design. The MTMG-TLR design enables the construction of TLRs with multiple turns and multiple gaps. This presents an additional degree of freedom in tuning self-resonant TLRs, as their resonance frequency is fully determined by the coil geometry (e.g. diameter, number of turns, conductor width, etc.). The novel design is evaluated at 4.7T and 7T by simulations and experiments, where it is demonstrated that MTMG-TLRs can be used for MRI, and that the B1 distribution of MTMG-TLRs strongly depends on the number and distribution of turns...
October 11, 2016: Journal of Magnetic Resonance
Michael J Knight, Risto A Kauppinen
No abstract text is available yet for this article.
October 11, 2016: Journal of Magnetic Resonance
Jinhyeok Choi, Hyeonjin Kim
To improve the efficacy of undersampled MRI, a method of designing adaptive sampling functions is proposed that is simple to implement on an MR scanner and yet effectively improves the performance of the sampling functions. An approximation of the energy distribution of an image (E-map) is estimated from highly undersampled k-space data acquired in a prescan and efficiently recycled in the main scan. An adaptive probability density function (PDF) is generated by combining the E-map with a modeled PDF. A set of candidate sampling functions are then prepared from the adaptive PDF, among which the one with maximum energy is selected as the final sampling function...
October 10, 2016: Journal of Magnetic Resonance
Chang-Hoon Choi, YongHyun Ha, Pandichelvam Veeraiah, Jörg Felder, Klaus Möllenhoff, N Jon Shah
Non-proton MRI has recently garnered gathering interest with the increased availability of ultra high-field MRI system. Assuming the availability of a broadband RF amplifier, performing multinuclear MR experiments essentially requires additional hardware, such as an RF resonator and a T/R switch for each nucleus. A double- or triple-resonant RF probe is typically constructed using traps or PIN-diode circuits, but this approach degrades the signal-to-noise ratio (SNR) and image quality compared to a single-resonant coil and this is a limiting factor...
October 10, 2016: Journal of Magnetic Resonance
Andrey N Pravdivtsev, Alexey S Kiryutin, Alexandra V Yurkovskaya, Hans-Martin Vieth, Konstantin L Ivanov
We propose a robust and highly efficient NMR technique to create singlet spin order from longitudinal spin magnetization in coupled spin-½ pairs and to perform backward conversion (singlet order)→magnetization. In this method we exploit adiabatic ramping of an RF-field in order to drive transitions between the singlet state and the T± triplet states of a spin pair under study. We demonstrate that the method works perfectly for both strongly and weakly coupled spin pairs, providing a conversion efficiency between the singlet spin order and magnetization, which is equal to the theoretical maximum...
October 6, 2016: Journal of Magnetic Resonance
Lucio Frydman
No abstract text is available yet for this article.
October 6, 2016: Journal of Magnetic Resonance
Bernhard Blümich
No abstract text is available yet for this article.
October 6, 2016: Journal of Magnetic Resonance
Jonas Fredriksson, Viviane S de Paula, Ana Paula Valente, Fabio C L Almeida, Martin Billeter
We demonstrate for the first time a complete small protein characterization with the projection-decomposition approach, including full assignments as well as determination of the 3D fold. In TOCSY- and NOESY-type 4D experiments, pairing of signals from hydrogens and from their respective heavy atoms in decompositions represents a new problem. An approach, referred to as "DIADECOMP" (diagonal decomposition), is introduced to solve this problem; it consists of two separate decompositions of the input projections, differing in a 45° rotation of the spectral axes...
October 3, 2016: Journal of Magnetic Resonance
Derek Marsh
Cross relaxation, and mI-dependence of the intrinsic electron spin-lattice relaxation rate We, are incorporated explicitly into the rate equations for the electron-spin population differences that govern the saturation behaviour of (14)N- and (15)N-nitroxide spin labels. Both prove important in spin-label EPR and ELDOR, particularly for saturation recovery studies. Neither for saturation recovery, nor for CW-saturation EPR and CW-ELDOR, can cross relaxation be described simply by increasing the value of We, the intrinsic spin-lattice relaxation rate...
October 3, 2016: Journal of Magnetic Resonance
Dustin D Wheeler, Matthew M Willmering, Erika L Sesti, Xingyuan Pan, Dipta Saha, Christopher J Stanton, Sophia E Hayes
We have modified the model for optically-pumped NMR (OPNMR) to incorporate a revised expression for the expectation value of the z-projection of the electron spin, 〈Sz〉 and apply this model to both bulk GaAs and a new material, InP. This expression includes the photon energy dependence of the electron polarization when optically pumping direct-gap semiconductors in excess of the bandgap energy, Eg. Rather than using a fixed value arising from coefficients (the matrix elements) for the optical transitions at the k=0 bandedge, we define a new parameter, Sopt(Eph)...
September 29, 2016: Journal of Magnetic Resonance
W M J Franssen, Y L A Rezus, A P M Kentgens
Owing to the introduction of microcoils, high RF field strength nutation NMR is a viable candidate for the study of quadrupolar nuclei with strong quadrupolar couplings, not accessible using contemporary NMR techniques. We show powder (23)Na nutation spectra on sodium nitrite for RF field strengths of up to 1170kHz, that conform to theoretical predictions. For lanthanum fluoride powder, (139)La nutation spectra taken at elevated RF field amplitudes show clear discrepancies when compared to the theory. These errors are shown to be mainly caused by pulse transients at the end of the pulse, which proved to be detrimental to the shape of the nutation spectra...
September 28, 2016: Journal of Magnetic Resonance
V S Manu, Gianluigi Veglia
Identity operation in the form of π pulses is widely used in NMR spectroscopy. For an isolated single spin system, a sequence of even number of π pulses performs an identity operation, leaving the spin state essentially unaltered. For multi-spin systems, trains of π pulses with appropriate phases and time delays modulate the spin Hamiltonian to perform operations such as decoupling and recoupling. However, experimental imperfections often jeopardize the outcome, leading to severe losses in sensitivity. Here, we demonstrate that a newly designed Genetic Algorithm (GA) is able to optimize a train of π pulses, resulting in a robust identity operation...
September 27, 2016: Journal of Magnetic Resonance
Navin Khaneja, Ashutosh Kumar
The paper describes a family of novel recoupling pulse sequences in magic angle spinning (MAS) solid state NMR, called four 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 π20°3π2ϕ°π2180°+ϕ°3π2180° where ϕ=πnϕ°=180°n, and n is number of blocks in a two rotor period. The heteronuclear recoupling pulse sequence consists of a building block [Formula: see text] and [Formula: see text] on channel I and S, where ϕ1=3π2n,ϕ2=π2n and n is number of blocks in a two rotor period...
September 26, 2016: Journal of Magnetic Resonance
Ronja M Malinowski, Kasper W Lipsø, Mathilde H Lerche, Jan H Ardenkjær-Larsen
Signal enhancement by hyperpolarization is a way of overcoming the low sensitivity in magnetic resonance; MRI in particular. One of the most well-known methods, dissolution Dynamic Nuclear Polarization, has been used clinically in cancer patients. One way of ensuring a low bioburden of the hyperpolarized product is by use of a closed fluid path that constitutes a barrier to contamination. The fluid path can be filled with the pharmaceuticals, i.e. imaging agent and solvents, in a clean room, and then stored or immediately used at the polarizer...
September 22, 2016: Journal of Magnetic Resonance
Katharina Keller, Andrin Doll, Mian Qi, Adelheid Godt, Gunnar Jeschke, Maxim Yulikov
The presence of artefacts due to Electron Spin Echo Envelope Modulation (ESEEM) complicates the analysis of dipolar evolution data in Relaxation Induced Dipolar Modulation Enhancement (RIDME) experiments. Here we demonstrate that averaging over the two delay times in the refocused RIDME experiment allows for nearly quantitative removal of the ESEEM artefacts, resulting in potentially much better performance than the so far used methods. The analytical equations are presented and analyzed for the case of electron and nuclear spins S=1/2,I=1/2...
September 22, 2016: Journal of Magnetic Resonance
Evgeny Nimerovsky, Andrew J Ilott, Alexej Jerschow
Triple Quantum Filters (TQFs) are frequently used for the selection of bi-exponentially relaxing spin 3/2 nuclei (in particular (23)Na) in ordered environments, such as biological tissues. These methods provide an excellent selection of slow-motion spins, but their sensitivity is generally low, and coherence selection requirements may lead to long experiments when applied in vivo. Alternative methods, such as 2P DIM, have demonstrated that the sensitivities of the signals from bi-exponentially relaxing sodium can be significantly increased using strategies other than TQFs...
September 17, 2016: Journal of Magnetic Resonance
Harri Koskela, Ilkka Kilpeläinen, Sami Heikkinen
ME-CAGEBIRD(r,X)-CPMG-HSMBC pulse sequence is a phase sensitive, carbon multiplicity edited 2D-experiment for detecting heteronuclear correlations originating from long-range (1)H, (13)C-couplings, (n)JCH. The presented method allows measurement of (n)JCH-values as well as is capable of separating different carbon types in subspectra ((13)C/(13)CH2 and (13)CH/(13)CH3) with minimal amount of cross talk i.e. cross peaks from wrong carbon multiplicity. Pure lineshapes and clean subspectra are achieved by utilizing CPMG in polarization transfer period, CRISIS-approach in multiplicity editing period and zero-quantum filtration...
September 17, 2016: Journal of Magnetic Resonance
Janez Stepišnik, Ioan Ardelean
Internal magnetic field gradients, arising within the porous media due to susceptibility differences at the interfaces of solid and liquid as well as due to the contained magnetic impurities, can be employed by the method of modulated gradient spin echo to get insight into the velocity autocorrelation spectrum of liquid confined in the porous structure. New theoretical treatment of spin interaction with the radio-frequency field and the simultaneously applied static non-uniform magnetic field provides the formula that match well with the measurement of restricted diffusion of water in pores of cement paste...
September 17, 2016: Journal of Magnetic Resonance
Neil MacKinnon, Peter T While, Jan G Korvink
Complex mixture analysis is routinely encountered in NMR-based investigations. With the aim of component identification, spectral complexity may be addressed chromatographically or spectroscopically, the latter being favored to reduce sample handling requirements. An attractive experiment is selective total correlation spectroscopy (sel-TOCSY), which is capable of providing tremendous spectral simplification and thereby enhancing assignment capability. Unfortunately, isolating a well resolved resonance is increasingly difficult as the complexity of the mixture increases and the assumption of single spin system excitation is no longer robust...
September 16, 2016: Journal of Magnetic Resonance
Stuart J Elliott, Lynda J Brown, Jean-Nicolas Dumez, Malcolm H Levitt
Although monodeuterated methyl groups support proton long-lived states, hindering of the methyl rotation limits the singlet relaxation time. We demonstrate an experimental case in which the rapid rotation of the CH2D group extends the singlet lifetime but does not quench the chemical shift difference between the CH2D protons, induced by the chiral environment. Proton singlet order is accessed using Spin-Lock Induced Crossing (SLIC) experiments, showing that the singlet relaxation time TS is over 2min, exceeding the longitudinal relaxation time T1 by a factor of more than 10...
September 16, 2016: Journal of Magnetic Resonance
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