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 Applied Magnetic Resonance   [SJR: 0.358]   [H-I: 34]   [4 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1613-7507 - ISSN (Online) 0937-9347    Published by Springer-Verlag  [2355 journals]
Acetylene Groups: ENDOR and DFT Investigation
• Authors: A. I. Kokorin; R. B. Zaripov; O. I. Gromov; K. Hideg; T. Kálai
Pages: 137 - 149
Abstract: A specially synthesized nitroxide biradical R5-C≡13C-(p-C6H4)2-13C≡C-R5 (B4) and two radicals, R5-C≡13CH (RCC) and R5-C≡13C-C6H5 (RCCPh), where R5 is 1-oxyl-2,2,5,5-tetramethyl-pyrroline group, have been studied by X- and W-band electron paramagnetic resonance (EPR) spectroscopy, and by W-band electron-nuclear double resonance (ENDOR). Spin density distribution and hyperfine splitting (hfs) constants on 13C atoms were experimentally determined and also calculated using ORCA 3.0.3 program package. The biradical and radicals geometries were optimized on UKS/B3LYP/cc-pVDZ level. Hfs constants were calculated using density functional theory (DFT) with PBE0 functional and N07D, and were compared with the experimental value of the hfs constant on 13C atoms, measured from ENDOR spectra. It is concluded that at small values of the exchange integral as J ≤ a/2 ≈ 7–8 G, the current quantum chemical approaches do not allow determining precise values of the hfs constants on the 13C atoms in the bridge connecting two paramagnetic nitroxide rings of the biradical.
PubDate: 2018-02-01
DOI: 10.1007/s00723-017-0942-5
Issue No: Vol. 49, No. 2 (2018)

• Optimizing Image Reconstruction in SENSE Using GPU
• Authors: Sohaib A. Qazi; Saima Nasir; Abeera Saeed; Hammad Omer
Pages: 151 - 164
Abstract: Parallel magnetic resonance imaging (MRI) (pMRI) uses multiple receiver coils to reduce the MRI scan time. To accelerate the data acquisition process in MRI, less amount of data is acquired from the scanner which leads to artifacts in the reconstructed images. SENSitivity Encoding (SENSE) is a reconstruction algorithm in pMRI to remove aliasing artifacts from the undersampled multi coil data and recovers fully sampled images. The main limitation of SENSE is computing inverse of the encoding matrix. This work proposes the inversion of encoding matrix using Jacobi singular value decomposition (SVD) algorithm for image reconstruction on GPUs to accelerate the reconstruction process. The performance of Jacobi SVD is compared with Gauss–Jordan algorithm. The simulations are performed on two datasets (brain and cardiac) with acceleration factors 2, 4, 6 and 8. The results show that the graphics processing unit (GPU) provides a speed up to 21.6 times as compared to CPU reconstruction. Jacobi SVD algorithm performs better in terms of acceleration in reconstructions on GPUs as compared to Gauss–Jordan method. The proposed algorithm is suitable for any number of coils and acceleration factors for SENSE reconstruction on real time processing systems.
PubDate: 2018-02-01
DOI: 10.1007/s00723-017-0951-4
Issue No: Vol. 49, No. 2 (2018)

• Encoding Textual Information in Magnetic Resonance Imaging
• Authors: Nikolay V. Anisimov; Olga S. Pavlova
Pages: 165 - 174
Abstract: The data of magnetic resonance imaging (MRI) studies include not only grayscale images, but also textual information associated with them —personal data about the patient, parameters of scanning and data processing, etc. This information is stored separately from graphic images. Therefore, the possibility for its correction and loss cannot be excluded. In this paper, the method of generation of marker information on diagnostic images is described. The marker information, as a textual analogue, is entered on the image during an MRI scan and becomes an integral part of the diagnostic material along with the images of anatomical structures. The method is realized by using the selective radiofrequency presaturation of non-scanable slices oriented perpendicularly to the scanned slices. It leads to the formation of bands of reduced signal in the areas of intersections of these slices on images. In this case, the band thicknesses are equal to the thicknesses of non-scanable slices. Different combinations of these bands (marker lines) are formed directly on images and can contain information about MRI studies. This information is determined not only by positions and angle orientations of bands, but also by their thickness, total brightness and brightness distribution in the transverse direction of these bands. The examples of introducing and positioning the marker information in conventional MRI studies are presented.
PubDate: 2018-02-01
DOI: 10.1007/s00723-017-0944-3
Issue No: Vol. 49, No. 2 (2018)

• FMR Studies of Ultra-Thin Epitaxial Pd 0.92 Fe 0.08 Film
• Authors: A. Esmaeili; I. R. Vakhitov; I. V. Yanilkin; A. I. Gumarov; B. M. Khaliulin; B. F. Gabbasov; M. N. Aliyev; R. V. Yusupov; L. R. Tagirov
Pages: 175 - 183
Abstract: Magnetic anisotropies of 20 nm epitaxial film of palladium–iron alloy Pd0.92Fe0.08 grown on the (001) MgO substrate were studied. Ferromagnetic resonance (FMR) spectroscopy and vibrating sample magnetometry (VSM) were exploited to determine magnetic parameters of the film. It was found that the synthesized film reveals cubic anisotropy with tetragonal distortion. The simulated magnetic hysteresis loops, obtained utilizing the magnetic anisotropy constants taken from the FMR spectra analysis, agree well with those measured by VSM.
PubDate: 2018-02-01
DOI: 10.1007/s00723-017-0946-1
Issue No: Vol. 49, No. 2 (2018)

• Determination of Carbon Chain Lengths of Fatty Acid Mixtures by Time
Domain NMR
• Authors: E. Nikolskaya; Y. Hiltunen
Pages: 185 - 193
Abstract: 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 R 2 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. The correlation coefficient between the known and measured values was equal to 0.994. Based on the relaxation theory, a linear-like dependence between the relaxation rate and carbon chain length was briefly shown, which endorses the experimental results. The developed methodology for determining carbon chain lengths offers robustness and rapidity, which are significant advantages when it comes to online use of the method in real industrial environments.
PubDate: 2018-02-01
DOI: 10.1007/s00723-017-0953-2
Issue No: Vol. 49, No. 2 (2018)

• Towards Determination of Distances Between Nanoparticles and Grafted
Paramagnetic Ions by NMR Relaxation
• Authors: A. M. Panich; N. A. Sergeev
Pages: 195 - 208
Abstract: 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. The nuclear magnetic resonance data data are compared with the results of electron paramagnetic resonance measurements and density functional theory calculations.
PubDate: 2018-02-01
DOI: 10.1007/s00723-017-0952-3
Issue No: Vol. 49, No. 2 (2018)

• Assessment of Combined Therapy of Histochrome and Nebivalol as
Angioprotectors on the Background of Experimental Hypertension by Magnetic
Resonance Angiography
• Authors: Irina G. Agafonova; Vladimir N. Kotelnikov; Boris I. Geltser; Natalya G. Kolosova; Valentin A. Stonik
Pages: 217 - 225
Abstract: The renovascular model of arterial hypertension (AH) was induced in Wistar and OXYS strains. The model of AH was verified by magnetic resonance angiography. It was shown that histochrome enhances the vasodilatory effect of selective beta1 blocker, nebivalol, against cerebral and renal arteries using a combined therapy in this model. Monotherapy with histochrome had no significant effect on blood pressure. The angioprotective effect of histochrome in the combined therapy was significantly more expressed in hypertensive OXYS rats compared to hypertensive Wistar rats as shown by magnetic resonance imaging (MRI) morphometry. These differences were more observable in the intrarenal part of renal arteries. The degree of regional discirculation of arteries was calculated by the Cerebro-Renal Vascular Index, which confirms the therapeutic advantage of combined therapy with histochrome and nebivalol in the background of AH. Thus, comparative MRI angiography and MRI morphometry of the cerebral and renal arteries in hypertensive Wistar and OXYS strain rats showed that histochrome expands the therapeutic potential of nebivalol due to angioprotective effects in the vascular region of the target organs.
PubDate: 2018-02-01
DOI: 10.1007/s00723-017-0960-3
Issue No: Vol. 49, No. 2 (2018)

• Dipolar Relaxation of Multiple Quantum NMR Coherences as a Model of
Decoherence of Many-Qubit Coherent Clusters
• Authors: G. A. Bochkin; E. B. Fel’dman; S. G. Vasil’ev; V. I. Volkov
Pages: 25 - 34
Abstract: Dipolar relaxation of multiple quantum (MQ) nuclear magnetic resonance (NMR) coherence is investigated on the evolution period of the MQ NMR experiment in chains of 19F nuclei in a single crystal of calcium fluorapatite. The dependence of the relaxation time of the MQ coherence of the second order on the size of the coherent spin cluster formed on the preparation period is obtained. The dipolar relaxation of MQ NMR coherences is considered as a model for the investigation of decoherence of quantum states of many-qubit spin clusters.
PubDate: 2018-01-01
DOI: 10.1007/s00723-017-0925-6
Issue No: Vol. 49, No. 1 (2018)

• Features of Exchange Interaction Between Cr 3+ Ions in Compounds [Fe(phen)
3 ][Cr 2 (OH)(Ac)(nta) 2 ]·6,25H 2 O and [Fe(bpy) 3 ][Cr 2 (OH)(Ac)(nta)
2 ]·8H 2 O
• Authors: L. V. Mingalieva; R. T. Galeev; A. A. Sukhanov; V. K. Voronkova; I. K. Budnikova; G. Novitchi
Pages: 61 - 69
Abstract: Dimers of Cr3+ ions in compounds [Fe(phen)3][Cr2(OH)(Ac)(nta)2]·6,25H2O (I) and [Fe(bpy)3][Cr2(OH)(Ac)(nta)2]·8H2O (II), temperature dependences of the electron paramagnetic resonance (EPR) spectra of which in the range of 300–12 К are characteristic for dimers with strong antiferromagnetic exchange interaction are studied by the EPR method in the X-band. The anisotropy of the spin–spin interaction is estimated from fitting spectra corresponding to the multiplet with S = 2 to model spectra. It is shown that the tensor of the anisotropic spin–spin interaction considerably differs from that of the dipole–dipole contribution. Signals from the multiplet with S = 1 were also separated for the compound II that made it possible to estimate the fine structure parameter of the Cr3+ ion. Features of the variation of the integral intensity of EPR spectra are observed at temperatures below 6 К for I and 7 К for II, which are explained by the decrease in the value of the isotropic exchange between chromium ions in dimers. Only the intensity of spectrum changes and its shape is completely preserved.
PubDate: 2018-01-01
DOI: 10.1007/s00723-017-0937-2
Issue No: Vol. 49, No. 1 (2018)

• 31 P NMR Manifestation of Metabolic Changes in Blood of Spinal Cord
Injured Rats
• Authors: S. V. Yurtaeva; M. Yu. Volkov; G. G. Yafarova; D. I. Silantyeva; E. I. Yamalitdinova
Abstract: The 31P nuclear magnetic resonance spectroscopy technique was applied to study the blood of rats with a 3-day spinal cord injury and control rats. Phosphorus-containing blood metabolites: 2,3-diphosphoglycerates, inorganic phosphates, phospholipids, ATP and adenosine monophosphates were detected and quantitatively evaluated. It was found that the amount of 2,3-diphosphoglycerates, inorganic phosphates, phospholipids and adenosine monophosphates increase, and pH of the blood decreases after spinal cord injury. The results demonstrate increased hypoxia in injured rats.
PubDate: 2018-02-06
DOI: 10.1007/s00723-018-0982-5

• A Variable Temperature X- and W-Band EPR Study of Fe-Doped SiCN Ceramics
Annealed at 1000, 1100, and 1285 °C: Dangling Bonds, Ferromagnetism and
Superparamagnetism
• Authors: S. I. Andronenko; A. A. Rodionov; S. K. Misra
Abstract: Polymer-derived SiCN ceramics, annealed (also referred to as pyrolyzed) at 1000, 1100, and 1285 °C, and doped with Fe(III) acetylacetonate, are investigated by electron paramagnetic resonance (EPR) from 4 to 120 K at X-band (9.425 GHz). In addition, the SiCN ceramic, annealed at 1100 °C, was studied by EPR at 300 K at W-band (93.96 GHz). There was observed a significant increase in EPR linewidth due to dangling bonds (g = 2.001) below 20 K at X-band. The low-field X-band FMR line (g ≈ 12) indicated the presence of ferromagnetic Fe5Si3 crystallites. There were found two EPR lines due to carbon-related dangling bonds: (1) those present as defects on the surface of the free-carbon phase (as sp2 carbon-related dangling bonds with g = 2.0011) and (2) those present within the bulk of carbon phase (as sp3 carbon-related dangling bonds with g = 2.0033). On the other hand, the intense low-field EPR signal observed at X-band was not observed at W-band. As well, there was observed splitting of the single broad EPR signal observed at g = 2.05 at X-band into two signals at W-band at g = 1.99 and g = 2.06, due to two different Fe-containing superparamagnetic nanocrystallites. Two new EPR signals, not observed at X-band, were observed at W-band, namely at g = 2.28 and g = 3.00, which are also due to g∥ of these superparamagnetic nanocrystallites.
PubDate: 2018-02-01
DOI: 10.1007/s00723-017-0973-y

• ViP-CSI: Virtual Phantom Chemical Shift Imaging
• Authors: Jie Liu; Ahmad Karfoul; Longyu Jiang; Huazhong Shu; Hervé Saint-Jalmes; Giulio Gambarota
Abstract: To apply the Virtual Phantom (ViP) method for generating reference signals, to the chemical shift imaging (CSI) technique. The ViP method, previously used for generating reference images in magnetic resonance imaging (MRI), was here extended to generate reference peaks in the MR spectra acquired with a 2D-CSI sequence. Theoretical analysis was carried out to design the ViP signal. ViP-2D-CSI experiments were performed on a 4.7 Tesla MR scanner. Data analysis was carried out with the jMRUI software to fit the ViP peaks to determine their amplitude and frequency. Based on the theoretical analysis, it was found that the ViP peak could be generated by transmitting the ViP signal only in one repetition time of the 2D-CSI sequence. The amplitude and frequency of the ViP peak could be precisely adjusted and fine-tuned. The ViP peak was uniform over all CSI voxels, both in amplitude and in frequency. Furthermore, a good stability of the ViP reference amplitude and frequency was observed. The ViP method provides a means to generate a reference MR peak in 2D-CSI experiments. This could be of interest for signal quantification in CSI experiments.
PubDate: 2018-01-20
DOI: 10.1007/s00723-018-0981-6

• FMR Investigation of the Magnetic Anisotropy in Films Synthesized by Co +
Implantation into Si
• Authors: V. V. Chirkov; G. G. Gumarov; V. Yu. Petukhov; M. M. Bakirov; V. I. Nuzhdin; V. F. Valeev
Abstract: Thin ferromagnetic films with the uniaxial magnetic anisotropy were synthesized by Co+ implantation into single-crystal silicon in the magnetic field. It was concluded that the formation of the induced magnetic anisotropy is due to the directional atomic pair ordering (Neel–Taniguchi model). The synthesized films were studied by the ferromagnetic resonance (FMR) method in the temperature range from 100 to 300 K. The FMR linewidth is almost independent of temperature, which is in agreement with the Raikher model describing the magnetic resonance of uniaxial magnetic particles. It is found that the temperature dependence of the anisotropy constant is linear. This dependence can be associated with the difference in the coefficients of thermal expansion of the Si (111) substrate and the ion-beam-synthesized cobalt silicide films.
PubDate: 2018-01-20
DOI: 10.1007/s00723-018-0980-7

• Influential Factors of Internal Magnetic Field Gradient in Reservoir Rock
and Its Effects on NMR Response
• Authors: Dong-hui Xing; Yi-ren Fan; Shao-gui Deng; Xin-min Ge; Jian-yu Liu; Fei Wu
Abstract: Nuclear magnetic resonance (NMR) plays a significant role in porous media analysis and petroleum exploration, but its response is significantly influenced by the internal magnetic field gradient in fluid saturated porous medium, which obviously limits the accuracy of rock core analysis and logging interpretation. The influential factors of the internal magnetic field gradient in formation and its influences on NMR response are studied in this paper, based on NMR mechanism through one- and two-dimensional core NMR experiments. The results indicate that the internal magnetic field gradient is positively correlated with the static magnetic field strength and the magnetic susceptibility difference between pore fluid and solid grains, while it presents negative correlation with pore radius. The internal magnetic field gradient produces an additional diffusion relaxation in hydrogen relaxation system and accelerates the attenuation of magnetization vector. As a result, T2 spectrum shifts to the left and NMR porosity and diffusion coefficient of the fluid could be inaccurate. This research sets a foundation for the NMR porosity correction and fluid distribution on T2-G maps based on the internal magnetic field gradient correction.
PubDate: 2018-01-15
DOI: 10.1007/s00723-018-0979-0

• Viscosity Correlations with Nuclear (Proton) Magnetic Resonance Relaxation
in Oil Disperse Systems
• Authors: R. S. Kashaev
Abstract: Using nuclear (proton) magnetic resonance relaxometry (NMRR) was studied oil disperse systems. Dependences of NMR–relaxation parameters—spin–lattice T1i, spin–spin T2i relaxation times, proton populations P1i and P2i, and petrophysical correlations were received for light and heavy oils. Experimental results are interpreted on the base of structure-dynamical ordering of oil molecules with structure unit formation.
PubDate: 2018-01-15
DOI: 10.1007/s00723-018-0977-2

• Trigonal Distortions of the Cr 3+ Octahedral Centers in Cr 3+ -Doped ABO 3
(A = Sc, In, Lu) Crystals Obtained by Analyzing EPR Data
• Authors: R. M. Peng; Y. Mei; H. G. Liu; W. C. Zheng
Abstract: The spin-Hamiltonian parameters (g factors g//, g⊥ and zero-field splitting D) of the trigonal Cr3+ centers in Cr3+-doped ABO3 (A = Sc, In, Lu) borate crystals are computed from both the complete diagonalization (of energy matrix) method and also the perturbation method based on the two-spin–orbit-parameter model, where the contributions to spin-Hamiltonian parameters due to both the spin–orbit parameter of central d n ion and that of ligands via covalence effect are considered. The calculated results are compatible with those available in experiments. The defect structures of the trigonal (CrO6)9− octahedral centers are also evaluated from the calculations. It is found that the trigonal (MO6)9− octahedra change from the elongation in the host crystals to the compression in the impurity centers because of the large size and nature mismatch substitution in these Cr3+-doped ABO3 crystals. The results are discussed.
PubDate: 2018-01-13
DOI: 10.1007/s00723-017-0976-8

• Translational Mobility of Components and Structure of Water–Ethanol
Solutions
• Authors: V. A. Sevryugin; N. M. Azancheev; G. N. Kosova
Abstract: The concentration dependences of self-diffusion coefficients of water and ethanol molecules in water–ethanol solutions are obtained by the method of nuclear magnetic resonance spectroscopy with the pulse magnetic field gradient. On the basis of the ideas of hydration of ethanol molecules, the obtained dependences are interpreted and assumptions are made about the structural organization of water–ethanol solutions in the region of diluted and concentrated solutions.
PubDate: 2018-01-12
DOI: 10.1007/s00723-017-0974-x

• Theoretical Investigations of the Spin Hamiltonian Parameters for the
Mononuclear Square Pyramidal [CuO 5 ] Groups in Two Paddle Wheel Copper
Complexes
• Authors: Li-Na Wu; Shao-Yi Wu; Min-Quan Kuang; Li-Juan Zhang; Li Peng
Abstract: The spin Hamiltonian parameters (SHPs) (g factors and hyperfine structure constants) for the mononuclear square pyramidal [CuO5] groups in two paddle wheel copper complexes {Cu2(μ2–O2CCH3)4}(OCNH2CH3) and $${}_{\infty }^{3} [{\text{Cu}}_{ 2}^{\text{I}} {\text{Cu}}_{ 2}^{\text{II}} ( {\text{H}}_{ 2} {\text{O)}}_{ 2} {\text{L}}_{ 2} {\text{Cl}}_{ 2} ]$$ are theoretically investigated from the perturbation calculations of these parameters for a rhombically elongated octahedral 3d 9 group. The slightly larger anisotropy Δg (≈ g // − g⊥) of complex 1 than complex 2 is attributed to the slightly bigger deviations of the polar angles related to the ideal value 90° and relative differences between the axial and basal Cu–O distances in the former. The axiality of the EPR signals for both systems can be illustrated as the fact that the perpendicular anisotropic contributions to X and Y components of the SHPs arising from the four basal ligands with slightly distinct bond lengths and bond angles may roughly cancel one another. The signs of hyperfine structure constants are also theoretically determined for both complexes.
PubDate: 2017-12-21
DOI: 10.1007/s00723-017-0971-0

• Editor’s Preface
• Authors: Kev M. Salikhov
PubDate: 2017-12-18
DOI: 10.1007/s00723-017-0969-7

• Multiple Parallel Round Leg Design for Quadrature Birdcage Coil in
Ultrahigh-Field MRI
• Authors: Yongfeng Xu; Qingqing Wen; Hongyi Yang; Kai Zhong
Abstract: Copper foil has been widely employed in conventional radio frequency (RF) birdcage coils for magnetic resonance imaging (MRI). However, for ultrahigh-field (UHF) MRI, current density distribution on the copper foil is concentrated on the surface and the edge due to proximity effect. This increases the effective resistance and distorts the circumferential sinusoidal current distribution on the birdcage coils, resulting in low signal-to-noise ratio (SNR) and inhomogeneous distribution of RF magnetic (B1) field. In this context, multiple parallel round wires were proposed as legs of a birdcage coil to optimize current density distribution and to improve the SNR and the B1 field homogeneity. The design was compared with three conventional birdcage coils with different width flat strip surface legs for a 9.4 T (T) MRI system, e.g., narrow-leg birdcage coil (NL), medium-leg birdcage coil (ML), broad-leg birdcage coil (BL) and the multiple parallel round wire-leg birdcage coil (WL). Studies were carried out in in vitro saline phantom as well as in vivo mouse brain. WL showed higher coil quality factor Q and more homogeneous B1 field distribution compared to the other three conventional birdcage coils. Furthermore, WL showed 12, 10 and 13% SNR increase, respectively, compared to NL, ML and BL. It was proposed that conductor’s shape optimization could be an effective approach to improve RF coil performance for UHF MRI.
PubDate: 2017-12-11
DOI: 10.1007/s00723-017-0963-0

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