Read by QxMD icon Read

Applied Magnetic Resonance

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
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
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
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
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
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
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
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
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
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
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
Robert J Usselman, Shefah Qazi, Priyanka Aggarwal, Sandra S Eaton, Gareth R Eaton, Stephen Russek, Trevor Douglas
Polymeric nanohybrid P22 virus capsids were used as templates for high density Gd(3+) loading to explore magnetic field-dependent (0.5-7.0 T) proton relaxivity. The field-dependence of relaxivity by the spatially constrained Gd(3+) in the capsids was similar when either the loading of the capsids or the concentration of capsids was varied. The ionic longitudinal relaxivity, r1, decreased from 25-32 mM(-1) s(-1) at 0.5 T to 6-10 mM(-1) s(-1) at 7 T. The ionic transverse relaxivity, r2, increased from 28-37 mM(-1) s(-1) at 0...
March 2015: Applied Magnetic Resonance
Xinqiang Yan, Xiaoliang Zhang, Long Wei, Rong Xue
Radio-frequency coil arrays using dipole antenna technique have been recently applied for ultrahigh field magnetic resonance (MR) imaging to obtain the better signal-noise-ratio (SNR) gain at the deep area of human tissues. However, the unique structure of dipole antennas makes it challenging to achieve sufficient electromagnetic decoupling among the dipole antenna elements. Currently, there is no decoupling methods proposed for dipole antenna arrays in MR imaging. The recently developed magnetic wall (MW) or induced current elimination decoupling technique has demonstrated its feasibility and robustness in designing microstrip transmission line arrays, L/C loop arrays and monopole arrays...
January 2015: Applied Magnetic Resonance
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"