A Theoretical Study on Circular Wire and Flat Strip Conductor Inductance for Magnetic Resonance-Shielded Phased-Array Circular Coils Abstract Phased-array radiofrequency (RF) coils are commonly used for signal reception in magnetic resonance for their large spatial coverage, typical of volume coils, and for their high signal-to-noise ratio, usually associated with surface coils. The simplest design of phased-array coils is an array of circular loops whose conductor can be constituted by flat strip or circular wire cross-sectional geometry, often partially enclosed in an RF shield for minimizing electromagnetic interference. This paper proposes a method for the analytical calculation of the mutual inductance between two circular loops constituting a dual-element phased-array coil by taking into account the conductor’s geometry and the effect of an eventual RF shield.

Oxyethylated Isononylphenols in Carbon Tetrachloride Abstract Translational diffusion coefficients of ethoxylated isononylphenol molecules C9H19C6H4O(C2H4O)nH in carbon tetrachloride were measured by nuclear magnetic resonance diffusometry. The hydrodynamic radii of the molecules were determined within the framework of the Stokes–Einstein relation. We showed that ethoxylated isononylphenols in carbon tetrachloride do not form micelles, and the dependence of the diffusion coefficients and, accordingly, the hydrodynamic radii of the nonionic surfactants on the number of oxyethylene groups have a kink in the region n = 6–8.

Study on the Structure of C-S-H Gels of Slag–Cement Hardened Paste by 29 Si, 27 Al MAS NMR Abstract In this paper, the 29Si and 27Al MAS NMR techniques were utilized to investigate the structure of C-S-H gels of slag cement-hardened paste. The results show that in the hardened paste of Portland cement, the silicate tetrahedron [SiO4]4− exists in the Q0, Q1 and Q2 states, and the C-S-H gel mainly exists as the dimer (Q1). After hydration for 3 days, Al3+ replaces some of the Si4+ in the tetrahedra and generates an aluminum-containing C-A-S-H gel. As the hydration proceeds, the content of C-A-S-H gel increases gradually. With an increase in the replacement of cement with slag, the content of Q2 (1 Al) in the C-A-S-H gel increases significantly, and the mean chain length of the C-(A)-S-H gel increases. For the slag–cement blend with 50% slag replacement, the mean chain length reaches 4.3, and the Al/Si ratio reaches 0.11. Throughout the hydration stage, three coordination states (AlO4, AlO5, and AlO6) exist in the hardened paste of the slag–cement blends.

Metabolomics Data Analysis Improvement by Use of the Filter Diagonalization Method Abstract The filter diagonalization method (FDM) was implemented and used instead of fast Fourier transform (FFT) to obtain the nuclear magnetic resonance (NMR) spectra from the free induction decay (FID) signals. The areas obtained by the FDM, from selected absorption lines, were used as input for a multidimensional method of data analysis. This procedure was applied in a NMR-based metabolomics investigation. In FDM, instead of spectra, the absorption peaks’ specification, such as central frequency, line width, amplitude and relative phases, are estimated and the spectra are built using this information. Therefore, one can select the lines by width and intensity to exclude the broad lines such as baseline, solvent line and albumin peak. Also lines with small amplitude such as noise can be excluded from the spectra. Moreover, the spectra do not suffer from aliasing or baseline problems. These characteristics are fundamental in the metabolomics investigations. To show the superiority of our method over the standard FFT to obtain the spectra, we reconstructed the spectra from simulated FID by both methods. As an example, this new approach is used to analyze the non-small cell lung cancer A549 exposed to different treatments and principal component analysis is used to compare the performance of both methods.

51 V and 25 Mg NMR Study of the Kagome Staircase Compound Mg 3 V 2 O 8 Abstract The 51V and 25Mg nuclear magnetic resonance (NMR) spectra have been obtained and magnetic susceptibility has been measured in polycrystalline Mg3V2O8. The analysis of 51V NMR spectra has shown that the line shift, δ(51V) = − 555 ppm, does not depend on temperature. It has been established that vanadium ions V5+ have a zero magnetic moment in this structure. The 25Mg NMR spectrum consists of two lines corresponding to two crystallographically nonequivalent positions of magnesium ions in the Kagome structure: Mg(1) are « spine » and Mg(2) are « cross tie » . Quadrupole frequencies and asymmetry parameters of 25Mg and 51V NMR spectra have been determined. The magnetic susceptibility is turn out to be zero (within the error) and remains constant over at a whole temperature range.

Exchange Interactions in Heteronuclear Clusters Containing Dysprosium Ions: EPR Spectroscopy Possibility Abstract The exchange interaction in two isostructural compounds [M2Dy2 (μ3–OH)2(L)2(O2CPh–Me–p)6] (M = Al, Cr) is studied by electron paramagnetic resonance (EPR). Studies have been performed on polycrystalline samples in different frequency ranges. The features of the shape of the spectra of clusters containing dysprosium ions are analyzed and experimental spectra are described using calculated spectra for tetranuclear clusters. The value Jzz = − 0.86 cm−1 of the spin–spin interaction of the Ising form JzzS1zS2z between dysprosium ions in the Al2Dy2 cluster, which exhibits single-molecule magnet properties, was experimentally determined. The study of the heteronuclear Cr2Dy2 cluster has demonstrated a number of features of the EPR spectra due to the Cr–Dy interaction. It is shown that this interaction has a predominantly Ising form with the parameter JCrDyzz = − 1 cm−1. However, the Cr–Dy pair fragment does not have a center of symmetry, and this suggests the presence of an antisymmetric term in the spin–spin interaction tensor, the manifestation of which is observed in the X-band EPR spectrum.

Efficient Referencing of FSLG CPMAS HETCOR Spectra Using 2D 1 H– 1 H MAS FSLG Abstract FSLG CPMAS HETCOR is a 2D solid-state NMR experiment which provides structural information and conformational correlation between a 1H and an X-nucleus. However, practical application of the experiment suffers from the chemical shift referencing problem on the indirect 1H dimension. In our paper, we present a novel 1H–1H MAS FSLG-based approach and its application to reference the FSLG CPMAS HETCOR which overcomes the 1H referencing in the 2D 1H-X HETCOR experiment. This approach works excellently irrespective of the sample type over a wide range of temperature.

Investigations on Magnetization and Electron Magnetic Resonance Properties of Nd 0.65 Ca 0.35 Mn 1–x Zn x O 3 ( x  = 0, 0.1, 0.3) Nanomanganite Abstract Zinc substitution effects on the magnetic ordering of nanosized Nd0.65Ca0.35MnO3 particles prepared by sol–gel method have been investigated by electron magnetic resonance (EMR) technique complimented by magnetization measurements. Bulk Nd0.65Ca0.35 MnO3 exhibits a charge ordering transition at 240 K and an antiferromagnetic transition at 150 K followed by a transition to a ferromagnetic (FM) phase below 50 K. In contrast, the nano Nd0.65Ca0.35MnO3 exhibits only a single transition from paramagnetic to ferromagnetic phase at 102 K which supports the general phenomenon of vanishing phase complexities in nano materials. In this paper, we discuss the effect of 10% and 30% zinc doping on the nano sized Nd0.65Ca0.35Mn1–x ZnxO3. Magnetization and EMR studies confirm the existence of ferromagnetism in all the samples which weakens with increasing doping of zinc. Though magnetization measurements do not show the charge order fluctuations and short range antiferromagnetic (AFM) order in the zinc-doped samples, EMR measurements evidence it. Electron magnetic resonance line width increases with zinc doping over a wide range of temperature due to the destruction of motional narrowing.

Investigation of Multiple-Quantum NMR Coherence Growth and Intensity Profile in Silsesquioxanes Abstract Multiple-quantum (MQ) nuclear magnetic resonance (NMR) was used to characterize the proton distribution in methyltrimethoxysilane gel (MS gel, [CH3SiO3/2]n) and octavinylsilsesquioxane (OVS, [CH2=CHSiO3/2]8). The Gaussian model of distribution of MQ coherence intensities was used to determine the effective 1H spin-cluster size (N). The growth rate was described by the exponents α in the scaling law of the form N ~ τα. The obtained values of α were 1.65 for MS gel and 1.78 for OVS. The magnitudes of the growth exponents were compared to the previously obtained values for hybrid organic–inorganic gels. The influence of the dipolar coupling strength and the arrangement of spins in these systems on the growth of MQ NMR coherences is discussed. The shape of MQ NMR coherence profiles was investigated. It was found that the intensity profiles of MQ NMR coherences at different excitation times in the investigated hybrid silica gels are similar and may be well approximated by a stretched exponential function.

NMR 63.65 Cu in a Local Field and Relaxation of Nuclear Spins in a CuFeS 2 Magnetic Semiconductor Abstract The results of the study of the spectral and relaxation parameters of 63.65Cu nuclear magnetic resonance (NMR) in a local field in natural samples of the semiconductor mineral chalcopyrite (CuFeS2), which is characterized by a strong interplay of magnetic and electronic properties, are presented. The main attention was paid to the determination of the mechanism of nuclear spin–lattice relaxation. The well-resolved quadrupole structure of the 63.65Cu NMR spectrum allowed us to investigate the kinetics of nuclear magnetization recovery for both Cu isotopes. The magnetic mechanism of the spin–lattice relaxation of the nuclear spins of copper isotopes 63.65Cu in CuFeS2, due to fluctuations of the dipole local fields created by the electron spins of magnetic Fe3+ ions, has been determined.