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Applied Magnetic Resonance

Xinqiang Yan, Zhipeng Cao, Xiaoliang Zhang
Transmit/receive L/C loop arrays with the induced current elimination (ICE) or magnetic wall decoupling method has shown high signal-to-noise (SNR) and excellent parallel imaging ability for MR imaging at ultrahigh fields, e.g., 7 T. In this study, we aim to numerically analyze the performance of an eight-channel ICE-decoupled loop array at 7 T. Three dimensional (3-D) electromagnetic (EM) and radiofrequency (RF) circuit co-simulation approach was employed. The values of all capacitors were obtained by optimizing the S-parameters of all coil elements...
April 2016: Applied Magnetic Resonance
M Paczwa, A A Sapiga, M Olszewski, N A Sergeev, A V Sapiga
The (1)H nuclear magnetic resonance (NMR) spectra and the dipolar spin-lattice relaxation time T 1D for (1)H in the natural natrolite (Na2Al2Si3O10·2H2O) have been measured in the temperature range of 190-390 K. From the temperature transformations of (1)H NMR spectra, it follows that at T > 300 K, the diffusion of water molecules along the nano-channels is observed. From experimental T 1D data, it follows that the 180° flip motion of the water molecules takes place in natrolite. At low temperature (T < 250 K), the dipolar interaction with paramagnetic impurities as a relaxation mechanism of (1)H nuclei becomes significant...
2016: Applied Magnetic Resonance
Faezeh Nami, Peter Gast, Edgar J J Groenen
Rapid freeze-quench (RFQ) in combination with electron paramagnetic resonance (EPR) spectroscopy at X-band is a proven technique to trap and characterize paramagnetic intermediates of biochemical reactions. Preparation of suitable samples is still cumbersome, despite many attempts to remedy this problem, and limits the wide applicability of RFQ EPR. We present a method, which improves the collection of freeze-quench particles from isopentane and their packing in an EPR tube. The method is based on sucking the particle suspension into an EPR tube with a filter at the bottom...
2016: Applied Magnetic Resonance
A Woźniak-Braszak, K Jurga, M Baranowski
In the present work, a new method for measuring motional parameters using the off-resonance technique was described. The Lipari-Szabo model-free formalism was used to analyze molecular dynamics in a heteronuclear system [1, 2]. Cross-relaxation solid state nuclear magnetic resonance off-resonance experiments were performed on a homebuilt pulse spectrometer operating at the frequency of 30.2 MHz for protons at temperature 173 K. The proton spins were spin-locked in the effective field [Formula: see text] while (19)F spins were continuously saturated for a long time...
2016: Applied Magnetic Resonance
L Pel, P A J Donkers, K Kopinga, J J Noijen
A set-up especially designed for semi-simultaneous measurements of (1)H, (23)Na and (35)Cl in ordinary cementitious materials using nuclear magnetic resonance was built. This setup makes use of the main field of a whole body magnetic resonance imaging system (Philips Intera), which has allowed us to combine two measurement setups into one, i.e., a (23)Na/(35)Cl and a (1)H insert. This 1.5 T field was chosen as a compromise between the signal-to-noise ratio of the spin-echo signal, which increases at higher frequencies, and the line broadening due to the presence of magnetic impurities of these materials, which leads to a decrease of the resolution at higher magnetic fields...
2016: Applied Magnetic Resonance
Yves Gossuin, Zeinab Serhan, Lydia Sandiford, Daniel Henrard, Thorsten Marquardsen, Rafael T M de Rosales, Dimitrios Sakellariou, Fabien Ferrage
Nuclear magnetic relaxation dispersion (NMRD) profiles are essential tools to evaluate the efficiency and investigate the properties of magnetic compounds used as contrast agents for magnetic resonance imaging (MRI), namely gadolinium chelates and superparamagnetic iron oxide particles. These curves represent the evolution of proton relaxation rates with the magnetic field. NMRD profiles are unparalleled to probe extensively the spectral density function involved in the relaxation of water in the presence of the paramagnetic ion or the magnetic nanoparticles...
2016: Applied Magnetic Resonance
Xinqiang Yan, Rong Xue, Xiaoliang Zhang
Radiofrequency (RF) coil arrays with high count of elements, e.g., closely-spaced multi-row arrays, exhibit superior parallel imaging performance in MRI. However, it is technically challenging and time-consuming to build multi-row arrays due to complex coupling issues. This paper presents a novel and simple method for closely-spaced multi-row RF array designs. Induced current elimination (ICE) decoupling method has shown the capability of reducing coupling between microstrip elements from different rows. In this study, its capability for decoupling array elements from the same row was investigated and validated by bench tests, with an isolation improvement from -8...
November 2015: Applied Magnetic Resonance
Laxman Mainali, Jeannette Vasquez-Vivar, James S Hyde, Witold K Subczynski
This study validated the use of small unilamellar vesicles (SUVs) made of 1-palmitoyl-2-oleoylphosphatidylcholine with 1 mol% spin label of 1-palmitoyl-2-(16-doxylstearoyl)phosphatidylcholine (16-PC) as an oxygen sensitive analyte to study cellular respiration. In the analyte the hydrocarbon environment surrounds the nitroxide moiety of 16-PC. This ensures high oxygen concentration and oxygen diffusion at the location of the nitroxide as well as isolation of the nitroxide moiety from cellular reductants and paramagnetic ions that might interfere with spin-label oximetry measurements...
August 1, 2015: Applied Magnetic Resonance
Xinqiang Yan, Long Wei, Rong Xue, Xiaoliang Zhang
The monopole coil and loop coil have orthogonal radiofrequency (RF) fields and thus are intrinsically decoupled electromagnetically if they are laid out appropriately. In this study, we proposed a hybrid monopole/loop technique which could combine the advantages of both loop arrays and monopole arrays. To investigate this technique, a hybrid RF coil array containing 4 monopole channels and 4 loop channels was developed for human head MR imaging at 7T. In vivo MR imaging and g-factor results using monopole-only channels, loop-only channels and all channels of the hybrid array were acquired and evaluated...
May 1, 2015: Applied Magnetic Resonance
S M Kaczmarek, H Fuks, M Berkowski, M Głowacki, B Bojanowski
Single crystals of NdVO4 were grown by the Czochralski method under ambient pressure in a nitrogen atmosphere. Obtained crystals were transparent with strong violet coloring. Temperature and angular dependences of electron paramagnetic resonance (EPR) spectra of the samples in the 3-103 K temperature range were analyzed applying Dyson like lineshape typically used for concentrated magnetic system. EPR-NMR program was used to find local symmetry and spin-Hamiltonian parameters of neodymium ions.
2015: Applied Magnetic Resonance
Balagopalakrishna Chavali, Thierry Masquelin, Mark J Nilges, David E Timm, Stephanie L Stout, William F Matter, Najia Jin, Prabhakar K Jadhav, Gary G Deng
As an early visitor to the injured loci, neutrophil-derived human Myeloperoxidase (hMPO) offers an attractive protein target to modulate the inflammation of the host tissue through suitable inhibitors. We describe a novel methodology of using low temperature ESR spectroscopy (6 K) and FAST™ technology to screen a diverse series of small molecules that inhibit the peroxidase function through reversible binding to the native state of MPO. Our initial efforts to profile molecules on the inhibition of MPO-initiated nitration of the Apo-A1 peptide (AEYHAKATEHL) assay showed several potent (with sub-micro molar IC50s) but spurious inhibitors that either do not bind to the heme pocket in the enzyme or retain high (>50 %) anti oxidant potential...
2015: Applied Magnetic Resonance
Yoshito Nakashima
Non-invasive in vivo marbling quantification helps owners to choose the optimum nutritional management for growing cattle and buyers to more precisely evaluate grown cattle at auctions. When using time-domain proton nuclear magnetic resonance (NMR) relaxometry, it is possible to quantify muscle and fat separately by taking advantage of the difference in the spin-spin relaxation time (T2) between water molecules in muscles and fat molecules, which would contribute to the non-invasive and objective determination of marbling scores...
2015: Applied Magnetic Resonance
Enrico Salvadori, Mei Wai Fung, Markus Hoffmann, Harry L Anderson, Christopher W M Kay
Pulsed electron paramagnetic resonance (EPR) spectroscopy using microwaves at two frequencies can be employed to measure distances between pairs of paramagnets separated by up to 10 nm. The method, combined with site-directed mutagenesis, has become increasingly popular in structural biology for both its selectivity and capability of providing information not accessible through more standard methods such as nuclear magnetic resonance and X-ray crystallography. Despite these advantages, EPR distance measurements suffer from poor sensitivity...
2015: Applied Magnetic Resonance
Jadwiga A Jarzyna, Paulina I Krakowska, Edyta Puskarczyk, Roman Semyrka
Combination of laboratory measurements res ults of various properties, i.e. porosity, density, permeability and mineral composition, was done to get additional factors useful in fluid flow description in the Miocene sandy-shaly formation. Special computer processing of nuclear magnetic resonance outcomes and mercury injection porosimetry results turned out to be useful in the estimation of the relationships facilitating the reservoir characterization and defining new helpful factors. Determination of the relationships between groups of quantities describing pore space of rock formation was presented as the basis for permeability prediction and for relationships extrapolation into interesting areas...
2015: Applied Magnetic Resonance
Laxman Mainali, Jason W Sidabras, Theodore G Camenisch, Joseph J Ratke, Marija Raguz, James S Hyde, Witold K Subczynski
Spin-label W-band (94 GHz) EPR with a five-loop-four-gap resonator (LGR) was successfully applied to study membrane properties (L. Mainali, J.S. Hyde, W.K. Subczynski, Using spin-label W-band EPR to study membrane fluidity in samples of small volume, J. Magn. Reson. 226 (2013) 35-44). In that study, samples were equilibrated with the selected gas mixture outside the resonator in a sample volume ~100 times larger than the sensitive volume of the LGR and transferred to the resonator in a quartz capillary. A seven-loop-six-gap W-band resonator has been developed...
December 2014: Applied Magnetic Resonance
Wataru Takahashi, Andrey A Bobko, Ilirian Dhimitruka, Hiroshi Hirata, Jay L Zweier, Alexandre Samouilov, Valery V Khramtsov
Variable Radio Frequency Proton-Electron Double-Resonance Imaging (VRF PEDRI) enables extracting a functional map from a limited number of images acquired at pre-selected EPR frequencies using specifically designed paramagnetic probes with high quality spatial resolution and short acquisition times. In this work we explored potential of VRF PEDRI for pH mapping of aqueous samples using recently synthesized pH-sensitive phosphonated trityl radical, pTR. The ratio of Overhauser enhancements measured at each pixel at two different excitation frequencies corresponding to the resonances of protonated and deprotonated forms of pTR probe allows for a pH map extraction...
September 1, 2014: Applied Magnetic Resonance
Mark Tseitlin, Gareth R Eaton, Sandra S Eaton
Rapid-scan EPR has been shown to improve the signal-to-noise ratio relative to conventional continuous wave spectroscopy. Equations are derived for the steady-state solution to the Bloch equations as a Fourier expansion in the harmonics of the scan frequency. This simulation method is about two orders of magnitude faster than time-domain numerical integration.
December 2013: Applied Magnetic Resonance
Stanisław K Hoffmann, Janina Goslar, Stefan Lijewski
Co(2+) binding to the nicotinamide adenine dinucleotide (NAD(+)) molecule in water solution was studied by electron paramagnetic resonance (EPR) and electron spin echo at low temperatures. Cobalt is coordinated by NAD(+) when the metal is in excess only, but even in such conditions, the Co/NAD(+) complexes coexist with Co(H2O)6 complexes. EPR spin-Hamiltonian parameters of the Co/NAD(+) complex at 6 K are g z  = 2.01, g x  = 2.38, g y  = 3.06, A z  = 94 × 10(-4) cm(-1), A x  = 33 × 10(-4) cm(-1) and A y  = 71 × 10(-4) cm(-1)...
July 2013: Applied Magnetic Resonance
A Raitsimring, A V Astashkin, J H Enemark, I Kaminker, D Goldfarb, E D Walter, Y Song, T J Meade
In this work, the experimental conditions and parameters necessary to optimize the long-distance (≥ 60 Å) Double Electron-Electron Resonance (DEER) measurements of biomacromolecules labeled with Gd(III) tags are analyzed. The specific parameters discussed are the temperature, microwave band, the separation between the pumping and observation frequencies, pulse train repetition rate, pulse durations and pulse positioning in the electron paramagnetic resonance spectrum. It was found that: (i) in optimized DEER measurements, the observation pulses have to be applied at the maximum of the EPR spectrum; (ii) the optimal temperature range for Ka-band measurements is 14-17 K, while in W-band the optimal temperatures are between 6-9 K; (iii) W-band is preferable to Ka-band for DEER measurements...
June 2013: Applied Magnetic Resonance
P Kędzia, T Czechowski, M Baranowski, J Jurga, E Szcześniak
In this paper we use a simple analysis based on properties of the axial field generated by symmetrical multipoles to reveal all possible distributions of two coaxial pairs of circular windings, which result in systems featuring zero octupole and 32 pole magnetic moments (six-order systems). Homogeneity of magnetic field of selected systems is analyzed. It has been found that one of the derived systems generates homogenous magnetic field whose volume is comparable to that yielded by the eight-order system. The influence of the current distribution and the windings placement on the field homogeneity is considered...
May 2013: Applied Magnetic Resonance
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