Scaling analyses for hyperpolarization transfer across a spin-diffusion barrier and into bulk solid media

2021 ◽  
Author(s):  
Nathan A. Prisco ◽  
Arthur C. Pinon ◽  
Lyndon Emsley ◽  
Bradley F. Chmelka
Keyword(s):  
Diffusion Barrier ◽  
Spin Diffusion ◽  
Energy Transport ◽  
Bulk Solid ◽  
Solid Media ◽  
Scaling Analyses ◽  
Rate Limiting

Quantitative scaling analyses based on mass and energy transport analogies enable rate-limiting processes to be established in hyperpolarization transfer phenomena.

scholarly journals Three-spin solid effect and the spin diffusion barrier in amorphous solids

2019 ◽  
Vol 5 (7) ◽  
pp. eaax2743 ◽  
Author(s):  
Kong Ooi Tan ◽  
Michael Mardini ◽  
Chen Yang ◽  
Jan Henrik Ardenkjær-Larsen ◽  
Robert G. Griffin
Keyword(s):  
Diffusion Barrier ◽  
Nuclear Polarization ◽  
Spin Diffusion ◽  
Amorphous Solids ◽  
Second Step ◽  
Intimate Contact ◽  
Glycerol Water ◽  
Water Matrix ◽  
Solid Effect ◽  
Trityl Radical

Dynamic nuclear polarization (DNP) has evolved as the method of choice to enhance NMR signal intensities and to address a variety of otherwise inaccessible chemical, biological and physical questions. Despite its success, there is no detailed understanding of how the large electron polarization is transferred to the surrounding nuclei or where these nuclei are located relative to the polarizing agent. To address these questions we perform an analysis of the three-spin solid effect, and show that it is exquisitely sensitive to the electron-nuclear distances. We exploit this feature and determine that the size of the spin diffusion barrier surrounding the trityl radical in a glassy glycerol–water matrix is <6 Å, and that the protons involved in the initial transfer step are on the trityl molecule. 1H ENDOR experiments indicate that polarization is then transferred in a second step to glycerol molecules in intimate contact with the trityl.

Electron-driven spin diffusion supports crossing the diffusion barrier in MAS DNP

2018 ◽  
Vol 20 (16) ◽  
pp. 11418-11429 ◽  
Author(s):  
Johannes J. Wittmann ◽  
Michael Eckardt ◽  
Wolfgang Harneit ◽  
Björn Corzilius
Keyword(s):  
Dynamic Nuclear Polarization ◽  
Diffusion Barrier ◽  
Nuclear Polarization ◽  
Spin Diffusion ◽  
Hyperfine Interactions ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Diffusion Rates ◽  
Angle Spinning

Hyperfine interactions can quench homonuclear spin-diffusion in the direct vicinity of a polarizing agent in dynamic nuclear polarization (DNP). However, under magic-angle spinning (MAS), the same interactions may also enhance the spin-diffusion rates through an electron-driven spin diffusion (EDSD) mechanism introduced here.

scholarly journals Direct observation of hyperpolarization breaking through the spin diffusion barrier

2021 ◽  
Vol 7 (18) ◽  
pp. eabf5735
Author(s):  
Quentin Stern ◽  
Samuel François Cousin ◽  
Frédéric Mentink-Vigier ◽  
Arthur César Pinon ◽  
Stuart James Elliott ◽  
...  
Keyword(s):  
Diffusion Barrier ◽  
Nuclear Polarization ◽  
Spin Diffusion ◽  
Magic Angle Spinning ◽  
Resonance Spectroscopy ◽  
Magic Angle ◽  
Paramagnetic Centers ◽  
Static Mode ◽  
Angle Spinning ◽  
Marked Dependence

Dynamic nuclear polarization (DNP) is a widely used tool for overcoming the low intrinsic sensitivity of nuclear magnetic resonance spectroscopy and imaging. Its practical applicability is typically bounded, however, by the so-called “spin diffusion barrier,” which relates to the poor efficiency of polarization transfer from highly polarized nuclei close to paramagnetic centers to bulk nuclei. A quantitative assessment of this barrier has been hindered so far by the lack of general methods for studying nuclear polarization flow in the vicinity of paramagnetic centers. Here, we fill this gap and introduce a general set of experiments based on microwave gating that are readily implemented. We demonstrate the versatility of our approach in experiments conducted between 1.2 and 4.2 K in static mode and at 100 K under magic angle spinning (MAS)—conditions typical for dissolution DNP and MAS-DNP—and directly observe the marked dependence of polarization flow on temperature.

Destruction of the Spin Diffusion Barrier near Paramagnetic Impurities in Pure NQR

2002 ◽  
Vol 57 (6-7) ◽  
pp. 307-314 ◽  
Author(s):  
G. B. Furman ◽  
S. D. Goren
Keyword(s):  
Diffusion Process ◽  
Diffusion Barrier ◽  
Spin Diffusion ◽  
Double Resonance ◽  
Paramagnetic Impurities ◽  
Resonance Process

The double resonance process between nuclei inside and outside the spin diffusion barrier is considered. By applying two radiofrequency fields, both of the same amplitude, one rotating at the frequency ωS for nuclei inside of the diffusion barrier and one rotating at the frequency ωI for nuclei outside of the diffusion barrier, the Hartmann-Hahn condition will be reached, which results in conservation of the quadrupole energy in the spin diffusion process and destruction of the spin diffusion barrier. This technique can be used to detect NQR signals from nuclei near paramagnetic impurities.

Energy, transport, and consumption in the Industrial Revolution

2019 ◽  
Vol 42 ◽  
Author(s):  
Joseph A. Tainter ◽  
Temis G. Taylor
Keyword(s):  
Mass Production ◽  
Industrial Revolution ◽  
Energy Transport ◽  
Underlying Assumption

Abstract We question Baumard's underlying assumption that humans have a propensity to innovate. Affordable transportation and energy underpinned the Industrial Revolution, making mass production/consumption possible. Although we cannot accept Baumard's thesis on the Industrial Revolution, it may help explain why complexity and innovation increase rapidly in the context of abundant energy.

Ultrastructure and Morphology of the Neurospora Crassa Cell Wall Mutants, Slime And Slime X, Using Tem and Sem

1976 ◽  
Vol 34 ◽  
pp. 54-55
Author(s):  
Karen S. Howard ◽  
H. D. Braymer ◽  
M. D. Socolofsky ◽  
S. A. Milligan
Keyword(s):  
Cell Wall ◽  
Neurospora Crassa ◽  
Wild Type ◽  
Morphological Comparison ◽  
Small Areas ◽  
Solid Media ◽  
Thin Sectioning ◽  
X Cells ◽  
Mutant Cells ◽  
Isolated Cell

The recently isolated cell wall mutant slime X of Neurospora crassa was prepared for ultrastructural and morphological comparison with the cell wall mutant slime. The purpose of this article is to discuss the methods of preparation for TEM and SEM observations, as well as to make a preliminary comparison of the two mutants.TEM: Cells of the slime mutant were prepared for thin sectioning by the method of Bigger, et al. Slime X cells were prepared in the same manner with the following two exceptions: the cells were embedded in 3% agar prior to fixation and the buffered solutions contained 5% sucrose throughout the procedure.SEM: Two methods were used to prepare mutant and wild type Neurospora for the SEM. First, single colonies of mutant cells and small areas of wild type hyphae were cut from solid media and fixed with OSO4 vapors similar to the procedure used by Harris, et al. with one alteration. The cell-containing agar blocks were dehydrated by immersion in 2,2-dimethoxypropane (DMP).

TEM processing procedure for a bacillus organism grown on solid media

1990 ◽  
Vol 48 (3) ◽  
pp. 624-625
Author(s):  
Jane Payne ◽  
Philip Coudron
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Fume Hood ◽  
Vacuum Aspiration ◽  
Solid Media ◽  
Transmission Electron ◽  
Solid Agar ◽  
Processing Procedure ◽  
Agar Media ◽  
Rat Bone

This transmission electron microscopy (TEM) procedure was designed to examine a gram positive spore-forming bacillus in colony on various solid agar media with minimal artifact. Cellular morphology and organization of colonies embedded in Poly/Bed 812 resin (P/B) were studied. It is a modification of procedures used for undecalcified rat bone and Stomatococcus mucilaginosus.Cultures were fixed and processed at room temperature (RT) under a fume hood. Solutions were added with a Pasteur pipet and removed by gentle vacuum aspiration. Other equipment used is shown in Figure 3. Cultures were fixed for 17-18 h in 10-20 ml of RT 2% phosphate buffered glutaraldehyde (422 mosm/KgH2O) within 5 m after removal from the incubator. After 3 (30 m) changes in 0.15 M phosphate buffer (PB = 209-213 mosm/KgH2O, pH 7.39-7.41), colony cut-outs (CCO) were made with a scalpel.

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