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Applied Magnetic Resonance

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https://www.readbyqxmd.com/read/29391666/towards-determination-of-distances-between-nanoparticles-and-grafted-paramagnetic-ions-by-nmr-relaxation
#1
A M Panich, N A Sergeev
We developed an approach for determining distances between carbon nanoparticles and grafted paramagnetic ions and molecules by means of nuclear spin-lattice relaxation data. The approach was applied to copper-, cobalt- and gadolinium-grafted nanodiamonds, iron-grafted graphenes, manganese-grafted graphene oxide and activated carbon fibers that adsorb paramagnetic oxygen molecules. Our findings show that the aforementioned distances vary in the range of 2.7-5.4 Å and that the fixation of paramagnetic ions to nanoparticles is most likely implemented by means of the surface functional groups...
2018: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/29391665/determination-of-carbon-chain-lengths-of-fatty-acid-mixtures-by-time-domain-nmr
#2
E Nikolskaya, Y Hiltunen
Average carbon chain length is a key parameter that defines the quality of liquid biofuels. In this paper, a method for the determination of carbon chain lengths of fatty acid mixtures is presented. The approach is based on proton relaxation rates measured by time domain nuclear magnetic resonance. The spin-spin relaxation rates R2 were used for the estimation of the carbon chain lengths. The method was examined for the set of samples with different mean lengths of the main linear carbon chain. Samples were prepared using four different fatty acids and mixtures of two, three or four of these fatty acids...
2018: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/29367808/spin-label-order-parameter-calibrations-for-slow-motion
#3
Derek Marsh
Calibrations are given to extract orientation order parameters from pseudo-powder electron paramagnetic resonance line shapes of 14N-nitroxide spin labels undergoing slow rotational diffusion. The nitroxide z-axis is assumed parallel to the long molecular axis. Stochastic-Liouville simulations of slow-motion 9.4-GHz spectra for molecular ordering with a Maier-Saupe orientation potential reveal a linear dependence of the splittings, [Formula: see text] and [Formula: see text], of the outer and inner peaks on order parameter [Formula: see text] that depends on the diffusion coefficient [Formula: see text] which characterizes fluctuations of the long molecular axis...
2018: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/29391664/resonators-for-in-vivo-imaging-practical-experience
#4
George A Rinard, Richard W Quine, Laura A Buchanan, Sandra S Eaton, Gareth R Eaton, Boris Epel, Subramanian V Sundramoorthy, Howard J Halpern
Resonators for preclinical electron paramagnetic resonance imaging have been designed primarily for rodents and rabbits and have internal diameters between 16 and 51 mm. Lumped circuit resonators include loop-gap, Alderman-Grant, and saddle coil topologies and surface coils. Bimodal resonators are useful for isolating the detected signal from incident power and reducing dead time in pulse experiments. Resonators for continuous wave, rapid scan, and pulse experiments are described. Experience at the University of Chicago and University of Denver in design of resonators for in vivo imaging is summarized...
December 2017: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/29332998/high-pressure-epr-spectroscopy-studies-of-the-e-coli-lipopolysaccharide-transport-proteins-lpta-and-lptc
#5
Kathryn M Schultz, Candice S Klug
The use of pressure is an advantageous approach to the study of protein structure and dynamics because it can shift the equilibrium populations of protein conformations toward higher energy states that are not of sufficient population to be observable at atmospheric pressure. Recently, the Hubbell group at the University of California, Los Angeles, reintroduced the application of high pressure to the study of proteins by electron paramagnetic resonance (EPR) spectroscopy. This methodology is possible using X-band EPR spectroscopy due to advances in pressure intensifiers, sample cells, and resonators...
December 2017: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/29332997/epr-uniform-field-signal-enhancement-by-dielectric-tubes-in-cavities
#6
James S Hyde, Richard R Mett
The dielectric tube resonator (DTR) for EPR spectroscopy is introduced. It is defined as a metallic cylindrical TE011 microwave cavity that contains a dielectric tube centered on the axis of the cylinder. Contour plots of dimensions of the metallic cylinder to achieve resonance at 9.5 GHz are shown for quartz, sapphire, and rutile tubes as a function of wall thickness and average radius. These contour plots were developed using analytical equations and confirmed by finite element modeling. They can be used in two ways: design of the metallic cylinder for use at 9...
December 2017: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/29276341/an-x-band-crossed-loop-epr-resonator
#7
George A Rinard, Richard W Quine, Joseph McPeak, Laura Buchanan, Sandra S Eaton, Gareth R Eaton
A copper X-band (9.22 GHz) cross loop resonator has been constructed for use with 4 mm sample tubes. The Q for the two resonators are 380 and 350, respectively. The resonator efficiency is about 1 G per square root of watt. Operation has been demonstrated with measurement of T1 by saturation recovery for samples of coal and an immobilized nitroxide radical.
December 2017: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/29151678/a-pulse-epr-25-mt-magnetometer-with-10ppm-resolution
#8
Subramanian V Sundramoorthy, Boris Epel, Howard J Halpern
A magnetometer designed for permanent magnet manufacturing and operated around 25 mT with 10ppm absolute accuracy is described. The magnetometer uses pulse electron paramagnetic resonance (EPR) methodology. The use of a pulsed broadband acquisition allowed reliable measurements in the presence of the magnetic field gradient and in relatively inhomogeneous magnetic fields of un-shimmed magnets.
August 2017: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/28894349/epr-line-shifts-and-line-shape-changes-due-to-spin-exchange-between-nitroxide-free-radicals-in-liquids-10-spin-exchange-frequencies-of-the-order-of-the-nitrogen-hyperfine-interaction-a-hypothesis
#9
Barney L Bales, Miroslav Peric
The behavior of Electron paramagnetic resonance spectra due to (15)N and (14)N nitroxide free radicals undergoing spin exchange in liquids at high frequencies ωex , of the same order of magnitude as the nitrogen hyperfine coupling constant A0 is investigated. The well known features are reconfirmed: (1) at low values of ωex where the lines broaden, shift toward the center of the spectrum, and change shape due to the introduction of a resonance of the form of a dispersion component; (2) at values of ωex comparable to A0, the line merge into one; and (3) at values much larger than A0, the merged line narrows...
February 2017: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/29151677/uniform-field-re-entrant-cylindrical-te-formula-see-text-cavity-for-pulse-electron-paramagnetic-resonance-spectroscopy-at-q-band
#10
Jason W Sidabras, Edward J Reijerse, Wolfgang Lubitz
Uniform field (UF) resonators create a region-of-interest, where the sample volume receives a homogeneous microwave magnetic field ([Formula: see text]) excitation. However, as the region-of-interest is increased, resonator efficiency is reduced. In this work, a new class of uniform field resonators is introduced: the uniform field re-entrant cylindrical TE[Formula: see text] cavity. Here, a UF cylindrical TE[Formula: see text] cavity is designed with re-entrant fins to increase the overall resonator efficiency to match the resonator efficiency maximum of a typical cylindrical TE[Formula: see text] cavity...
2017: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/29151676/jim-hyde-and-the-endor-connection-a-personal-account
#11
Klaus Möbius, Wolfgang Lubitz, Anton Savitsky
In this minireview, we report on our year-long EPR work, such as electron-nuclear double resonance (ENDOR), pulse electron double resonance (PELDOR) and ELDOR-detected NMR (EDNMR) at X-band and W-band microwave frequencies and magnetic fields. This report is dedicated to James S. Hyde and honors his pioneering contributions to the measurement of spin interactions in large (bio)molecules. From these interactions, detailed information is revealed on structure and dynamics of macromolecules embedded in liquid-solution or solid-state environments...
2017: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/28179750/-23-na-and-27-al-nmr-study-of-structure-and-dynamics-in-mordenite
#12
N A Sergeev, M Paczwa, M Olszewski, A M Panich
Temperature dependencies of (27)Al and (23)Na nuclear magnetic resonance spectra and spin-lattice relaxations in mordenite have been studied in static and magic angle spinning regimes. Our data show that the spin-lattice relaxations of the (23)Na and (27)Al nuclei are mainly governed by interaction of nuclear quadrupole moments with electric field gradients of the crystal, modulated by translational motion of water molecules in the mordenite channels. At temperatures below 200 K, the dipolar interaction of nuclear spins with paramagnetic impurities becomes an important relaxation mechanism of the (23)Na and (27)Al nuclei...
2017: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/28111499/nmr-techniques-in-metabolomic-studies-a-quick-overview-on-examples-of-utilization
#13
REVIEW
Joanna Kruk, Marek Doskocz, Elżbieta Jodłowska, Anna Zacharzewska, Joanna Łakomiec, Kornelia Czaja, Jacek Kujawski
Metabolomics is a rapidly developing branch of science that concentrates on identifying biologically active molecules with potential biomarker properties. To define the best biomarkers for diseases, metabolomics uses both models (in vitro, animals) and human, as well as, various techniques such as mass spectroscopy, gas chromatography, liquid chromatography, infrared and UV-VIS spectroscopy and nuclear magnetic resonance. The last one takes advantage of the magnetic properties of certain nuclei, such as (1)H, (13)C, (31)P, (19)F, especially their ability to absorb and emit energy, what is crucial for analyzing samples...
2017: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/29033501/eight-channel-monopole-array-using-ice-decoupling-for-human-head-mr-imaging-at-7-t
#14
Xinqiang Yan, Long Wei, Suoda Chu, Rong Xue, Xiaoliang Zhang
Due to the unique structure of radiative coil elements, traditional decoupling methods face technical challenges in reducing the electromagnetic coupling of the radiative arrays. In this study, we aim to investigate the possibility of using the recently introduced induced current elimination (ICE) decoupling technique for cylindrical shaped radiative coil array designs. To evaluate the method, an eight-channel transmit/receive monopole array with the ICE decoupling, suitable for human head imaging at 7 T, was built and comparatively investigated...
May 2016: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/27034578/simulation-verification-of-snr-and-parallel-imaging-improvements-by-ice-decoupled-loop-array-in-mri
#15
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
https://www.readbyqxmd.com/read/27881902/temperature-dependent-oxygen-effect-on-nmr-d-formula-see-text-relaxation-diffusion-correlation-of-n-alkanes
#16
Igor Shikhov, Christoph H Arns
Nuclear magnetic resonance (NMR) diffusion-relaxation correlation experiments (D-[Formula: see text]) are widely used for the petrophysical characterisation of rocks saturated with petroleum fluids both in situ and for laboratory analyses. The encoding for both diffusion and relaxation offers increased fluid typing contrast by discriminating fluids based on their self-diffusion coefficients, while relaxation times provide information about the interaction of solid and fluid phases and associated confinement geometry (if NMR responses of pure fluids at particular temperature and pressure are known)...
2016: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/27818577/parameter-estimation-error-dependency-on-the-acquisition-protocol-in-diffusion-kurtosis-imaging
#17
Nima Gilani, Paul N Malcolm, Glyn Johnson
Mono-exponential kurtosis model is routinely fitted on diffusion weighted, magnetic resonance imaging data to describe non-Gaussian diffusion. Here, the purpose was to optimize acquisitions for this model to minimize the errors in estimating diffusion coefficient and kurtosis. Similar to a previous study, covariance matrix calculations were used, and coefficients of variation in estimating each parameter of this model were calculated. The acquisition parameter, b values, varied in discrete grids to find the optimum ones that minimize the coefficient of variation in estimating the two non-Gaussian parameters...
2016: Applied Magnetic Resonance
https://www.readbyqxmd.com/read/27489405/proton-dipolar-spin-lattice-relaxation-in-nano-channels-of-natrolite
#18
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
https://www.readbyqxmd.com/read/27340337/rapid-freeze-quench-epr-spectroscopy-improved-collection-of-frozen-particles
#19
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
https://www.readbyqxmd.com/read/27340336/the-lipari-szabo-model-free-analysis-as-a-method-for-study-of-molecular-motion-in-solid-state-heteronuclear-systems-using-nmr-off-resonance
#20
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
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