Quantitative Susceptibility Mapping of the Basal Ganglia and Thalamus at 9.4 Tesla

The thalamus (Th) and basal ganglia (BG) are central subcortical connectivity hubs of the human brain, whose functional anatomy is still under intense investigation. Nevertheless, both substructures contain a robust and reproducible functional anatomy. The quantitative susceptibility mapping (QSM) at ultra-high field may facilitate an improved characterization of the underlying functional anatomy in vivo. We acquired high-resolution QSM data at 9.4 Tesla in 21 subjects, and analyzed the thalamic and BG by using a prior defined functional parcellation. We found a more substantial contribution of paramagnetic susceptibility sources such as iron in the pallidum in contrast to the caudate, putamen, and Th in descending order. The diamagnetic susceptibility sources such as myelin and calcium revealed significant contributions in the Th parcels compared with the BG. This study presents a detailed nuclei-specific delineation of QSM-provided diamagnetic and paramagnetic susceptibility sources pronounced in the BG and the Th. We also found a reasonable interindividual variability as well as slight hemispheric differences. The results presented here contribute to the microstructural knowledge of the Th and the BG. In specific, the study illustrates QSM values (myelin, calcium, and iron) in functionally similar subregions of the Th and the BG.

Контроль якості хромонікелевих сталей за парамагнітним станом аустеніту

The subject matter of the article is the processes of monitoring and assessing the quality of austenitic chromium-nickel steels. The quality of steels and products made from them depends on the combination of physical, chemical and technological properties that are formed as a result of the phase-chemical composition and various types of processing (temperature, deformation, laser, radiation, etc.). Determination of a methodology that will supplement or replace multiple tests by measuring one parameter is highly relevant. The goal is to find a methodology for a comprehensive assessment of mechanical and corrosion properties in one parameter, which is sensitive to external factors. It is proposed to use the specific paramagnetic susceptibility of austenite c0 as an integral characteristic of the influence of various factors (chemical composition, melting conditions, deformation, temperature, etc.). Parameter c0 is a characteristic of the atomic-magnetic state of austenite and a sensitive quantity to the influence of external factors. The tasks to be solved are: to formalize the correlation between the specific paramagnetic susceptibility c0 of austenite and mechanical, corrosion properties (tensile strength sв, conditional yield stress s0.2, elongation d, corrosion rate K). The methods used are: a highly sensitive magnetometric method for determining the specific magnetic susceptibility X and the low content of the ferromagnetic phase of the samples of the studied steels in the initial state (before mechanical and corrosion tests). Mechanical indicators were determined in accordance with GOST 1497-84, the value of corrosion losses in chloride-containing solutions - in accordance with GOST 9.912-89. The following results were obtained. It has been experimentally established that the tendency of changes in the mechanical and corrosion properties of steels of the AISI 321 and AISI 304 types correlates with the magnetic nature of the paramagnetic austenite matrix, which is determined by the sum of the magnetic moments of atoms per unit mass (specific magnetization). Conclusions. It is shown that the specific paramagnetic susceptibility of austenite can be used to determine the behavior (increase or decrease in mechanical and corrosion properties). It is shown that a low content of d-ferrite can also be a measure (indicator) of the behavior of these properties.

On the incorporation of nickel into hexagonal barium titanate: magnetic properties and electron paramagnetic resonance (EPR)

Systematic measurements of the magnetic moment of hexagonal 6H-BaTiO3 + 0.04 BaO + x NiO (0.005 ≤ x ≤ 0.02) ceramics were performed to study the influence of Ni ions on the magnetic properties. By temperature-dependent measurements of the paramagnetic susceptibility at 90 kOe, the Ni2+ ion was identified as the majority defect in air-sintered Ni-doped hexagonal barium titanate. Q-band EPR investigations of a 2.0 mol% Ni-doped single crystal revealed three different Ni centers located at Ti sites: first, Ni3+ ions at Ti sites in intact oxygen octahedra, second, Ni3+ associated with an oxygen vacancy and third, the presence of Ni2+ centers leading to a forbidden transition. The Ni3+—VO associate characterized by a vacancy in the face-sharing oxygen plane of the oxygen octahedra can be ruled out. The crystal field parameters of the Ni2+ defect were estimated by a combined fitting of the paramagnetic susceptibility and the EPR fine structure parameter D to $$B_{0}^{4}$$ B 0 4 ≈ −17,300 cm−1, $$\left| {B_{0}^{2} } \right|$$ B 0 2 ≈ 2500 cm−1 and $$B_{3}^{4}$$ B 3 4 ≈ 19,000 cm−1.

Paramagpy: Software for Fitting Magnetic Susceptibility Tensors Using Paramagnetic Effects Measured in NMR Spectra

Paramagpy is a python module for calculating paramagnetic effects in NMR spectra of proteins. This currently includes fitting of paramagnetic susceptibility tensors to experimental data associated with pseudocontact shifts (PCS) residual dipolar couplings (RDC), paramagnetic relaxation enhancements (PRE) and cross-correlated relaxation (CCR). A GUI allows easy viewing of data and seamless transition between PCS/RDC/PRE/CCR calculations.<br><br>

Paramagpy: Software for Fitting Magnetic Susceptibility Tensors Using Paramagnetic Effects Measured in NMR Spectra

Paramagpy is a python module for calculating paramagnetic effects in NMR spectra of proteins. This currently includes fitting of paramagnetic susceptibility tensors to experimental data associated with pseudocontact shifts (PCS) residual dipolar couplings (RDC), paramagnetic relaxation enhancements (PRE) and cross-correlated relaxation (CCR). A GUI allows easy viewing of data and seamless transition between PCS/RDC/PRE/CCR calculations.<br><br>