Adaptive anti-synchronization of nuclear spin generator (NSG) systems with fully uncertain parameters

This article addresses control for the chaos anti-synchronization of a high frequency oscillator nuclear spin generator (NSG), which generates and controls the oscillations of the motion of a nuclear magnetization vector in a magnetic field. Based on the Lyapunov stability theory, an adaptive control law is derived to make the states of two identical (NSG) asymptotically anti-synchronized with uncertain parameters. Finally, a numerical simulation is presented to show the effectiveness of the proposed chaos anti-synchronization scheme .

Towards Large-Scale Steady-State Enhanced Nuclear Magnetization with In Situ Detection

<div>Signal Amplification By Reversible Exchange (SABRE) boosts NMR signals of various nuclei enabling new applications spanning from magnetic resonance imaging to analytical chemistry and fundamental physics. SABRE is especially well positioned for continuous generation of enhanced magnetization on a large scale, however, several challenges need to be addressed for accomplishing this goal. Specifically, SABRE requires (i) a specialized catalyst capable of reversible H₂ activation and (ii) physical transfer of the sample from the point of magnetization generation to the point of detection (e.g., a high-field or a benchtop NMR spectrometer). Moreover, (iii) continuous parahydrogen bubbling accelerates solvent (e.g., methanol) evaporation, thereby limiting the experimental window to tens of minutes per sample.</div><div>In this work, we demonstrate a strategy to rapidly generate the best-to-date precatalyst (a compound that is chemically modified in the course of the reaction to yield the catalyst) for SABRE, [Ir(IMes)(COD)Cl] (IMes = 1,3-bis-(2,4,6-trimethylphenyl)-imidazol-2-ylidene, COD = cyclooctadiene) via a highly accessible synthesis. Second, we measure hyperpolarized samples using a home-built zero-field NMR spectrometer and study the field dependence of hyperpolarization directly in the detection apparatus, eliminating the need to physically move the sample during the experiment. Finally, we prolong the measurement time and reduce evaporation by presaturating parahydrogen with the solvent vapor before bubbling into the sample. These advancements extend opportunities for exploring SABRE hyperpolarization by researchers from various fields and pave the way to producing large quantities of hyperpolarized material for long-lasting detection of SABRE-derived nuclear magnetization.</div>

Towards Large-Scale Steady-State Enhanced Nuclear Magnetization with In Situ Detection

<div>Signal Amplification By Reversible Exchange (SABRE) boosts NMR signals of various nuclei enabling new applications spanning from magnetic resonance imaging to analytical chemistry and fundamental physics. SABRE is especially well positioned for continuous generation of enhanced magnetization on a large scale, however, several challenges need to be addressed for accomplishing this goal. Specifically, SABRE requires (i) a specialized catalyst capable of reversible H₂ activation and (ii) physical transfer of the sample from the point of magnetization generation to the point of detection (e.g., a high-field or a benchtop NMR spectrometer). Moreover, (iii) continuous parahydrogen bubbling accelerates solvent (e.g., methanol) evaporation, thereby limiting the experimental window to tens of minutes per sample.</div><div>In this work, we demonstrate a strategy to rapidly generate the best-to-date precatalyst (a compound that is chemically modified in the course of the reaction to yield the catalyst) for SABRE, [Ir(IMes)(COD)Cl] (IMes = 1,3-bis-(2,4,6-trimethylphenyl)-imidazol-2-ylidene, COD = cyclooctadiene) via a highly accessible synthesis. Second, we measure hyperpolarized samples using a home-built zero-field NMR spectrometer and study the field dependence of hyperpolarization directly in the detection apparatus, eliminating the need to physically move the sample during the experiment. Finally, we prolong the measurement time and reduce evaporation by presaturating parahydrogen with the solvent vapor before bubbling into the sample. These advancements extend opportunities for exploring SABRE hyperpolarization by researchers from various fields and pave the way to producing large quantities of hyperpolarized material for long-lasting detection of SABRE-derived nuclear magnetization.</div>

New Aspects of Fractional Bloch Model Associated with Composite Fractional Derivative

This paper studies a fractional Bloch equation pertaining to Hilfer fractional operator. Bloch equation is broadly applied in physics, chemistry, nuclear magnetic resonance (NMR), magnetic resonance imaging (MRI) and many more. The sumudu transform technique is applied to obtain the analytic solutions for nuclear magnetization . The general solution of nuclear magnetization is shown in the terms of Mittag-Leffler (ML) type function. The influence of order and type of Hilfer fractional operator on nuclear magnetization is demonstrated in graphical form. The study of Bloch equation with composite fractional derivative reveals the new features of Bloch equation. The discussed fractional Bloch model provides crucial and applicable results to introduce novel information in scientific and technological fields.

Revisiting paramagnetic relaxation enhancements in slowly rotating systems: how long is the long range?

Cross relaxation terms in paramagnetic systems that reorient rigidly with slow tumbling times can increase the effective longitudinal relaxation rates of protons of more than one order of magnitude. This is evaluated by simulating the time evolution of the nuclear magnetization using a complete relaxation matrix approach. The calculations show that the Solomon dependence of the relaxation rates on the metal-proton distance (as r−6) can be incorrect for protons farther than 15 Å from the metal, and thus can originate sizable errors in R1-derived distance restraints used, for instance, for protein structure determination. Furthermore, the chemical exchange of these protons with bulk water protons can enhance the relaxation rate of the solvent protons by far more than expected from the Solomon equation. Therefore, it may contribute significantly to the water proton relaxation rates measured at MRI magnetic fields in the presence of slow-rotating nanoparticles containing paramagnetic ions and a large number of exchangeable surface protons.