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Publisher: Springer-Verlag   (Total: 2341 journals)

 Applied Magnetic Resonance   [SJR: 0.358]   [H-I: 34]   [3 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1613-7507 - ISSN (Online) 0937-9347    Published by Springer-Verlag  [2341 journals]
• MRI Study of Liesegang Patterns: Mass Transport and Banded Inorganic
Phase Formation in Gel
• Abstract: Abstract A new non-optic method for the study of Liesegang patterns was tested. Liesegang patterns are periodically banded precipitates produced by the reaction–diffusion process, mostly occurring in geology. The Liesegang experiment (5.5 M NH4OH, gelatin matrix with 0.4 M MgSO4) was monitored using a 9.4 T magnetic resonance imaging (MRI) system, allowing the acquisition of sample images in any location and orientation without interfering with the process studied. The development of patterns in a gel matrix was observed for 7 days after starting the reaction. Qualitative data (T 2- and T 2*-weighted images) and quantitative T 2 maps were acquired. Preliminary experiments show that MRI is able to distinguish the regions between the precipitated bands and the structural changes in the gel matrix during the reaction. A damaged gel matrix was measured to reveal the effect of the initial reagent-gel contact area. MRI study of Liesegang patterns provides empirical data which can be used in theoretical model testing.
PubDate: 2017-04-20

• Erratum to: Force-detected ESR Measurements in a Terahertz Range up to
0.5 THz and Application to Hemin
• PubDate: 2017-04-18

• Quantitative Susceptibility Mapping of the Substantia Nigra in
Parkinson’s Disease
• Authors: Xinxin Zhao; Hedi An; Tian Liu; Nan Shen; Binshi Bo; Zhuwei Zhang; Pengfei Weng; Meining Chen; Mengchao Pei; Yi Wang; Dongya Huang; Jianqi Li
Abstract: Abstract The purpose of this study was to evaluate the sensitivities of quantitative susceptibility mapping (QSM) and R2* mapping in clinical diagnoses of Parkinson’s disease (PD). QSM images and R2* maps from 29 patients with PD and 25 healthy controls were obtained on a clinical 3T magnetic resonance imaging (MRI) system using a three-dimensional multi-echo gradient-echo sequence. Two-tailed t tests and receiver operating characteristic curves analyses were applied to the mean values of QSM and R2* of the two groups. In the PD group, a two-tailed Pearson correlation analysis was used to investigate the correlations between MRI measures (susceptibility and R2* values) and the Unified Parkinson’s Disease Rating Scale-III (UPDRS-III) score. In the substantia nigra (SN), a significant difference between patients with PD and healthy controls was found on QSM (154.80 ± 43.36 vs. 127.50 ± 21.05 ppb, P = 0.006) but not on R2* mapping. The receiver operating characteristic curves showed that QSM was more sensitive than R2* mapping to distinguish PD patients from healthy controls, with areas under the curve equal to 0.68 and 0.51, respectively. The UPDRS-III motor scores did not correlate with mean susceptibility or R2* values in the PD group. In conclusion, QSM is a more accurate and sensitive method than R2* mapping to detect the pathologic changes in the SN of patients with PD.
PubDate: 2017-04-06
DOI: 10.1007/s00723-017-0877-x

• Floquet Hamiltonian and Entanglement in Spin Systems in Periodic Magnetic
Fields
• Authors: E. B. Fel’dman; D. E. Feldman; E. I. Kuznetsova
Abstract: Abstract We investigate entanglement in a two-spin system with the dipole–dipole interaction in the multi-pulse spin locking nuclear magnetic resonance (NMR) experiment. We discover a conflict between an exact solution and the standard approximation employing a time-independent effective Floquet Hamiltonian. While the exact solution shows nonzero entanglement in the system, the perturbative Floquet approach predicts that entanglement is absent. The failure of the Floquet method is explained by the multivaluedness of the Floquet Hamiltonian. Correct results can only be obtained with a proper choice of the branch of the Hamiltonian. The same issue is present in other applications of the Floquet theorem in the perturbation theory beyond NMR.
PubDate: 2017-04-05
DOI: 10.1007/s00723-017-0879-8

• Design and Demonstration of Four-Channel Received Coil Arrays for
Vertical-Field MRI
• Authors: Qiaoyan Chen; Yajie Xu; Yan Chang; Xiaodong Yang
Abstract: Abstract The layout of radio-frequency received coils is related to signal-to-noise ratio (SNR) in magnetic resonance imaging (MRI). In this paper, different structures of four-channel received coil arrays for vertical-field MRI are constructed and optimized by establishing the relationship between coil geometry and SNR to achieve a high SNR and a uniform SNR distribution in the region of interest (ROI). Then, the SNR distributions of three optimized configurations, including rectangular loops, non-definite shape surface coils, and solenoid loops as the main unit, are simulated and compared. The four-channel coil of solenoid loops as the main unit has been found to have the best performance with the highest mean SNR in the ROI when imaging without acceleration. In addition, g-factor and 2D SENSE SNR in yoz-plane are simply analyzed, which show a sharp decrease in SNR for all the coils. Finally, all the coils are manufactured and operated at a 0.5 T permanent magnet MRI system with phantom and joint imaging experiments. Using pixel-by-pixel manner to evaluate SNR map, the experimental results are consistent with the simulation results, while parallel imaging experiment results show that the major consideration in low field MRI is the improvement of SNR value and uniformity rather than that of the imaging speed. As different constructions of four-channel received coils are investigated, we have found the most effective configuration with high and uniform SNR for vertical-field MRI.
PubDate: 2017-04-03
DOI: 10.1007/s00723-017-0878-9

• Singular Value Decomposition Using Jacobi Algorithm in pMRI and CS
• Authors: Sohaib A. Qazi; Abeera Saeed; Saima Nasir; Hammad Omer
Abstract: Abstract Parallel magnetic resonance imaging (pMRI) and compressed sensing (CS) have been recently used to accelerate data acquisition process in MRI. Matrix inversion (for rectangular matrices) is required to reconstruct images from the acquired under-sampled data in various pMRI algorithms (e.g., SENSE, GRAPPA) and CS. Singular value decomposition (SVD) provides a mechanism to accurately estimate pseudo-inverse of a rectangular matrix. This work proposes the use of Jacobi SVD algorithm to reconstruct MR images from the acquired under-sampled data both in pMRI and in CS. The use of Jacobi SVD algorithm is proposed in advance MRI reconstruction algorithms, including SENSE, GRAPPA, and low-rank matrix estimation in L + S model for matrix inversion and estimation of singular values. Experiments are performed on 1.5T human head MRI data and 3T cardiac perfusion MRI data for different acceleration factors. The reconstructed images are analyzed using artifact power and central line profiles. The results show that the Jacobi SVD algorithm successfully reconstructs the images in SENSE, GRAPPA, and L + S algorithms. The benefit of using Jacobi SVD algorithm for MRI image reconstruction is its suitability for parallel computation on GPUs, which may be a great help in reducing the image reconstruction time.
PubDate: 2017-03-30
DOI: 10.1007/s00723-017-0874-0

• Examining Magnetic Models and Anisotropies in β -Cu 2 V 2 O 7 by
High-Frequency ESR
• Authors: M. Y. Ruan; Z. W. Ouyang; Y. C. Sun; Z. C. Xia; G. H. Rao; H. S. Chen
Abstract: Abstract High-frequency electron spin resonance (ESR) measurements were carried out on a single crystal β-Cu2V2O7, where Cu–O edge-sharing chains are connected by non-magnetic VO4 tetrahedrons. Due to sizable anisotropies, analyses of bulk magnetic properties alone have not yielded any definite conclusion and the modeling of the magnetic lattice is controversial. By means of high-frequency ESR with operating frequencies of 135–405 GHz and at a temperature range of 4.2–50 K, the large g value anisotropy is determined, which removes the ambiguity of susceptibility fitting. Moreover, non-negligible exchange anisotropy is evaluated by analyzing high-field magnetization and antiferromagnetic resonance in antiferromagnetic state appearing below T N = 26 K. Based on these microscopic information, we found that alternating-chain model is the most reasonable candidate for explaining properties of the crystal. The present study shows the importance of combining macroscopic and microscopic probes in analyzing magnetic network of complex magnetic materials.
PubDate: 2017-03-29
DOI: 10.1007/s00723-017-0871-3

• Studies of Nanosized Iron-Doped TiO 2 Photocatalysts by Spectroscopic
Methods
• Authors: A. I. Kokorin; R. Amal; W. Y. Teoh; A. I. Kulak
Abstract: Abstract Iron-doped TiO2 nanoparticles with iron content in the range of 0.005 < Fe/Ti < 0.3 were prepared using the flame spray pyrolysis method and investigated with CW X-band electron paramagnetic resonance (EPR), X-ray diffraction, and Fourier transform infrared spectroscopy. This allowed for the clarification of the internal organization of Fe–TiO2 nanoparticles. Different types of Fe(III) centers were distinguished in the samples: isolated high-spin paramagnetic Fe(III) ions (S = 5/2) in rhombic ligand fields state at 0.005 < Fe/Ti < 0.05, and Fe(III) ferromagnetic clusters at Fe/Ti < 0.1. All Fe-doped samples had rather high activity for the photocatalytic mineralization of oxalic acid under visible light illumination (λ > 400 nm) at 25 °C. Correlations were made between EPR and photocatalytic activity results. The specific surface area [S] data allowed us to deduce that the isolated Fe(III) centers were responsible for the photomineralisation of oxalic acid, while the Fe(III) ferromagnetic aggregates decreased the total efficiency of the system.
PubDate: 2017-03-27
DOI: 10.1007/s00723-017-0873-1

• Comparison of the Effects of Different 19 F π Pulses on the Sensitivity
and Phaseability of the 19 F- 13 C HSQC
• Authors: Alexander A. Marchione; Breanna Conklin
Abstract: Abstract The 19F-13C heteronuclear single quantum coherence (HSQC) experiment is vital for the structural elucidation of polyfluorinated organic species, yet its sensitivity and phaseability are limited by difficulties in uniform excitation of the widely disperse 19F spectral window. Adiabatic pulses of different types have previously been employed to generate effective π pulses for inversion and refocussing, but a systematic comparison of various adiabatic and other inversion pulses has not been published. In this work, it was observed that the use of a broadband inversion pulse (BIP) during the t 1 evolution period resulted in properly phaseable spectra for experiments optimized to detect 1 J CF, in contrast to CHIRP or WURST adiabatic pulses. For the INEPT and reverse-INEPT transfer segments of the HSQC, optimal sensitivity for resonances distant from the transmitter frequency was afforded by optimized universal rotation (BURBOP) or CHIRP pulses. In HSQC experiments with delays optimized for two-bond correlations, only the use of BURBOP pulses in INEPT and reverse-INEPT sequences afforded spectra cleanly phaseable across the F 2 and F 1 spectral windows. This observation is supported by off-resonance pulsed field gradient spin-echo experiments.
PubDate: 2017-03-25
DOI: 10.1007/s00723-017-0876-y

• Dynamic Polarization and Relaxation of 75 As Nuclei in Silicon at High
Magnetic Field and Low Temperature
• Authors: J. Järvinen; J. Ahokas; S. Sheludiakov; O. Vainio; D. Zvezdov; L. Lehtonen; L. Vlasenko; S. Vasiliev
Abstract: Abstract We present the results of experiments on dynamic nuclear polarization and relaxation of 75As in silicon crystals. Experiments are performed in strong magnetic fields of 4.6 T and temperatures below 1 K. At these conditions donor electron spins are fully polarized, and the allowed and forbidden electron spin resonance transitions are well resolved. We demonstrate effective nuclear polarization of 75As nuclei via the Overhauser effect on the time scale of several hundred seconds. Excitation of the forbidden transitions leads to a polarization through the solid effect. The relaxation rate of donor nuclei has strong temperature dependence characteristic of Orbach process.
PubDate: 2017-03-25
DOI: 10.1007/s00723-017-0875-z

• Force-detected ESR Measurements in a Terahertz Range up to 0.5 THz and
Application to Hemin
• Authors: Tsubasa Okamoto; Hideyuki Takahashi; Eiji Ohmichi; Hitoshi Ohta
Abstract: Abstract We report a novel force-detected high-frequency electron spin resonance (HFESR) technique using a microcantilever in the terahertz region. In this technique, we attach a tiny sample on the microcantilever end and the ESR signal is detected as the cantilever bending. The bending is sensitively detected by fiber-optic Fabry–Perot interferometry. We applied this technique to a tiny amount (~16 ng) of metalloporphyrin, a model substance of hemoproteins, and successfully observed ESR signals at multiple frequencies up to 0.5 THz. This result indicates that the sample volume needed in multi-frequency HFESR can be greatly reduced by several orders of magnitude, and our novel technique would be a promising tool for HFESR studies of metalloproteins in the future.
PubDate: 2017-03-24
DOI: 10.1007/s00723-017-0872-2

• Magnetic Resonance Study of Fe-Implanted TiO 2 Rutile
• Authors: C. Okay; I. R. Vakhitov; V. F. Valeev; R. I. Khaibullin; B. Rameev
Abstract: Abstract Single-crystal (100) and (001) TiO2 rutile substrates have been implanted with 40 keV Fe+ at room temperature with high doses in the range of (0.5–1.5) × 1017 ions/cm2. A ferromagnetic resonance (FMR) signal has been observed for all samples with the intensity and the out-of-plane anisotropy increasing with the implantation dose. The FMR signal has been related to the formation of a percolated metal layer consisting of close-packed iron nanoparticles in the implanted region of TiO2 substrate. Electron spin resonance (ESR) signal of paramagnetic Fe3+ ions substituting Ti4+ positions in the TiO2 rutile structure has been also observed. The dependences of FMR resonance fields on the DC magnetic field orientation reveal a strong in-plane anisotropy for both (100) and (001) substrate planes. An origin of the in-plane anisotropy of FMR signal is attributed to the textured growth of the iron nanoparticles. As result of the nanoparticle growth aligned with respect to the structure of the rutile host, the in-plane magnetic anisotropy of the samples reflects the symmetry of the crystal structure of the TiO2 substrates. Crystallographic directions of the preferential growth of iron nanoparticles have been determined by computer modeling of anisotropic ESR signal of substitutional Fe3+ ions.
PubDate: 2017-03-20
DOI: 10.1007/s00723-017-0868-y

• Influence of Defects on Photoconductivity and Photocatalytic Activity of
Nitrogen-Doped Titania
• Authors: A. A. Minnekhanov; N. T. Le; E. A. Konstantinova; P. K. Kashkarov
Abstract: Abstract Samples of nitrogen-doped titanium dioxide (anatase, 0.2 ≤ N ≤ 1.0 wt%) prepared by the sol–gel method were investigated using X-band electron paramagnetic resonance spectroscopy, photoconductivity, and photocatalysis measurements. N· and NO· paramagnetic defects in N-TiO2 have been observed; their concentrations and spin-Hamiltonian parameters were calculated. An increase both in the rate of the generation of free charge carriers and in the rate of photocatalysis was found in N-TiO2 in contrast with non-doped titania under visible light. The correlation of the density of the observed radicals with the photoconductivity and photocatalysis data is discussed.
PubDate: 2017-03-10
DOI: 10.1007/s00723-017-0870-4

• T 1 – T 2 Correlation and Biopolymer Diffusion Within Human
Osteoarthritic Cartilage Measured with Nuclear Magnetic Resonance
• Authors: Sarah E. Mailhiot; Nathan H. Williamson; Jennifer R. Brown; Joseph D. Seymour; Sarah L. Codd; Ronald K. June
Abstract: Abstract Cartilage is a load-bearing tissue that provides smooth articulation during motion of human joints like the knee and hip. Cartilage deterioration in the form of osteoarthritis (OA) causes painful joint motion in more than 100 million patients worldwide, and thus there is great interest in improving our understanding of cartilage to further clinical treatment. Previous studies have examined many aspects of cartilage mechanics, including the flow of interstitial water and repulsion of neighboring glycosaminoglycan chains. However, the contributions of specific molecules to overall tissue properties remain unclear. In this study, we use nuclear magnetic resonance (NMR) diffusometry and relaxometry to examine the molecular dynamics of water and cartilage polymers in OA human articular cartilage. To our knowledge, this is the first identification of two macromolecular populations corresponding to collagen and proteoglycan in human cartilage through their diffusive properties. Further, we performed NMR T 1–T 2 correlation studies on human cartilage and observed two populations of water distinguished by differing NMR relaxation corresponding to a solid-like component and a liquid-like component. These results provide fundamental insight on the water behavior and polymeric interactions that drive the functional mechanics of cartilage. This study provides a basis to both expand our understanding of basic cartilage mechanics and provide molecular dynamics data for design of novel biomaterials to improve joint health.
PubDate: 2017-03-10
DOI: 10.1007/s00723-017-0869-x

• β-Phosphorus Hyperfine Coupling Constant in Nitroxides: Conformational
Effects in 6-Membered Ring Nitroxides
• Authors: Lionel Bosco; Teddy Butscher; Sylvain R. A. Marque
Abstract: Abstract Recently, we reported a significant solvent effect on the phosphorus hyperfine coupling constant a P in β-phosphorylated 6-membered ring nitroxides (∆a P = 24 G in Org. Biomol. Chem. 2015). Thus, it led us to investigate the effect of solvent for several 6-membered ring nitroxides. Although smaller than mentioned above, a change of 5–7 G in a P with the polarity of solvent was still observed for these nitroxides. As for other β-phosphorylated nitroxides, a N increases with the polarity/polarizability π* and the Hydrogen Bond Donating α properties of the solvent whereas a P exhibits the reverse trends. The change of a P with the solvent depends a lot on a subtle interplay between the destabilizing steric hindrance due to the bulkiness of the substituents and the stabilizing hyperconjugation interactions SOMO → σ*C–P between the anti-bonding orbitals of the C–P bond and the SOMO.
PubDate: 2017-03-10
DOI: 10.1007/s00723-017-0867-z

• Accelerated 3D Coronary Vessel Wall MR Imaging Based on Compressed Sensing
with a Block-Weighted Total Variation Regularization
• Authors: Zhongzhou Chen; Xiaoyong Zhang; Caiyun Shi; Shi Su; Zhaoyang Fan; Jim X. Ji; Guoxi Xie; Xin Liu
Abstract: Abstract Coronary vessel wall magnetic resonance (MR) imaging is important for heart disease diagnosis but often suffers long scan time. Compressed sensing (CS) has been previously used to accelerate MR imaging by reconstructing an MR image from undersampled k-space data using a regularization framework. However, the widely used regularizations in the current CS methods often lead to smoothing effects and thus are unable to reconstruct the coronary vessel walls with sufficient resolution. To address this issue, a novel block-weighted total variation regularization is presented to accelerate the coronary vessel wall MR imaging. The proposed regularization divides the image into two parts: a region-of-interest (ROI) which contains the coronary vessel wall, and the other region with less concerned features. Different penalty weights are given to the two regions. As a result, the small details within ROI do not suffer from over-smoothing while the noise outside the ROI can be significantly suppressed. Results with both numerical simulations and in vivo experiments demonstrated that the proposed method can reconstruct the coronary vessel wall from undersampled k-space data with higher qualities than the conventional CS with the total variation or the edge-preserved total variation.
PubDate: 2017-03-01
DOI: 10.1007/s00723-017-0866-0

• Influence of Pressure on the Intramolecular Spin Exchange in a Short
• Authors: Boryana Mladenova-Kattnig; Günter Grampp; Alexander I. Kokorin
Abstract: Abstract A short-chain imidazoline-type nitroxide biradical R 5 NO –CH=N–N=C(CH3)–R 5 N , B2, with nitroxide rings R 5 N and R 5 NO as 1-oxyl-2,2,5,5-tetramethyl-3-imidazoline and 1-oxyl-2,2,5,5-tetramethyl-3-N-oxide imidazoline, respectively, has been studied using X-band electron paramagnetic resonance (EPR) spectroscopy in CH3CN solutions at variable temperature T and pressure P. Changes of the solution viscosity on the intramolecular electron spin exchange in B2 is characterized by calculating the value of the exchange integral J/a , where a denotes the 14N hyperfine splitting (hfs) constant. It is revealed that the intramolecular dynamics in B2 do not follow the Debye–Stokes–Einstein law, while the Arrhenius dependence is fulfilled. Probable reasons of such behavior are discussed.
PubDate: 2017-02-15
DOI: 10.1007/s00723-017-0865-1

• Validation of MRI-Based Fiber-Tracking Results
• Authors: K. A. Il’yasov; L. V. Konopleva; O. V. Nedopekin
Abstract: Abstract A new approach to estimating the probability of the fiber-track existence has been developed and validated on the basis of digital phantoms and diffusion-weighted magnetic resonance imaging measurements on human brain. The proposed approach includes two parameters—the local probability of the tract direction and the Shannon entropy. The local probability of the tract direction characterizes how well tracts “fit” the direction information in a voxel. The Shannon entropy characterizes the shape of diffusivity in the voxel. Calculations on digital phantoms and in vivo data showed that the combination of these parameters makes it possible to verify fiber-tracking results.
PubDate: 2017-02-10
DOI: 10.1007/s00723-017-0859-z

• Structural Phase Transition of Perovskite-Type N(CH 3 ) 4 CdBr 3 Studied
by MAS NMR and Static NMR
• Authors: Ae Ran Lim
Abstract: Abstract The structural geometry change in the perovskite-type N(CH3)4CdBr3 single crystal near the phase transition temperature of T C = 390 K was investigated using magic angle spinning nuclear magnetic resonance techniques. For 1H and 13C nuclei, the temperature dependences of their chemical shift, spectral intensity, and spin–lattice relaxation time (T 1ρ) in the rotating frame were obtained and analyzed. While the chemical shift and T 1ρ of 1H showed change near T C, those of 13C did not. In addition, the 113Cd spin–lattice relaxation time T 1 in the laboratory frame near T C show no evidence of anomalous change near the phase transition temperature, which coincides with the measured changes in the 1H T 1ρ. The driving force for this phase transition was connected to the 1H in the CH3 groups.
PubDate: 2017-02-01
DOI: 10.1007/s00723-017-0861-5

• Mimicking the Electromagnetic Distribution in the Human Brain: A
• Authors: Ana L. Neves; Lisa Leroi; Nicolas Cochinaire; Redha Abdeddaim; Pierre Sabouroux; Alexandre Vignaud
Abstract: Abstract The purpose of this study was to fabricate and test a multi-frequency human brain-mimicking phantom for magnetic resonance imaging (MRI) assessment purposes. An anatomically realistic human head phantom was elaborated, for different Larmor frequencies, which allows rapid quantification of $${\text{B}}_{1}^{ + }$$ . It is a simple alternative solution in time and cost as compared to numerical simulations to validate simulation when the coil geometry and components cannot be known as a unique solution. The permittivity $$\varepsilon^{{\prime }}$$ and conductivity $$\sigma$$ of sucrose/salt/agar aqueous solutions of varying concentrations were determined; a solution with these components and having the adequate concentration to obtain the brain’s dielectric properties at 3, 7 and 11.7T was manufactured. An anthropomorphic polymeric skull was filled with this mixture. To check the behavior of this phantom in a MRI configuration, both numerical and experimental validations were done: a $${\text{B}}_{1}^{ + }$$ field distribution inside the phantom was calculated with CST Microwave Studio inside a birdcage coil at 7T; the same mapping was assessed in a 7T MRI. The feasibility of a multi-MRI static field phantom was demonstrated. A solution composed by 54.7 wt% of sucrose, 3.1 wt% of salt and 3.1 wt% of agar was fabricated with good permittivity and conductivity matching for 3, 7 and 11.7T. The results were confirmed by both numerical simulation and MRI acquisition. This work has shown the possibility of manufacturing a head phantom with accessible and cheap components for MRI evaluation, having an adequate $${\text{B}}_{1}^{ + }$$ field distribution and the dielectric properties of the human brain.
PubDate: 2017-01-19
DOI: 10.1007/s00723-017-0862-4

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