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It has been claimed that longitudinal field muon spin relaxation (LF-μSR) experiments on the organic semiconductor (OSC) tris-(8-hydroxyquinoline)aluminum(III) (Alq3) have measured electron hopping rates of ∼ 1 0 12 s − 1 , while density functional theory (DFT) calculations suggest that electron hopping between a muoniated radical and a neighboring molecule is energetically unfavorable and that the LF-μSR experiments were probing muoniated radicals with localized spin density. We have performed avoided level crossing muon spin resonance (ALC-μSR) and transverse field muon spin rotation (TF-μSR) measurements on Alq3 and 8-hydroxyquinoline (8hq), which is meant to model the muoniated radicals present in Alq3 when they are not in an OSC. These are supplemented by benchmarked DFT calculations. The ALC-μSR and TF-μSR spectra of 8hq and Alq3 are best explained by Mu adding to all six secondary carbons of the quinolate rings with roughly equal yields and localized spin density. There is no evidence in the TF-μSR spectrum of Alq3 for the formation of radicals with muon hyperfine coupling constants of 23 or 91 MHz as reported earlier by others. Our measurements support the view that there is localized spin density on the molecule to which Mu is covalently bound and the muon is not a passive probe in organic systems as it can be incorporated into radicals that have different electronic structures to the parent compounds. The muoniated radicals in Alq3 are more short-lived than in 8hq, which could be due to interactions with mobile electrons in the OSC, but with electron spin flip rates on the order of ∼ 1 0 7 s − 1 . [ABSTRACT FROM AUTHOR]

The measurement results for the muon hyperfine coupling constant (hfc) of the light hydrogen isotope mounium (Mu) in aqueous methanol, NaCl, and KCl solutions with varying concentrations, in deuterated water, and in deuterated methanol is reported. The decrease of the moun hfc and Mu in the electrolyte solution is attributed to the amount of spin density transferred from Mu to its surrounding which is dependent on the average orientation of the water molecules in the primary solvation shell.

The methylene proton and muon hfcs of the cyclohexadienyl radical are measured in neat solvents and mixtures of various polarities between octadecane and water. It is found that these polarities are directly proportional to the concentration of the dipole moments and the magnitude of the dipole moment.

Avoided level-crossing muon spin resonance (ALC-μSR) has been used to study the dynamics and local environment of spin probes formed by muonium (Mu) addition to 2-phenylethanol (PEA) and limonene (1-methyl-4-(1-methylethenyl)-cyclohexene) in an aqueous dispersion of the nonionic surfactant C12E4 (tetra(ethylene glycol) n-dodecyl ether). The spin probes derived from both cosurfactants reside within the micelles in the L1 phase and the bilayers in the Lα phase rather than in the aqueous region. The local polarity measured by the different isomers of the Mu adducts of PEA suggests there is a water gradient within the micelles and bilayers. Slow rotation of the micelles broadened the Δ1 resonances with increasing temperature in the L1 phase while narrower Δ1 resonances were observed in the Lα phase due to the rapid rotation of the spin probes around a preferred axis, which was wobbling within a cone. [ABSTRACT FROM AUTHOR]

The muon hyperfinecoupling constant (Aμ) of the muoniatedcyclohexadienyl radical (C6H6Mu) has been directlymeasured in a 5 mM solution of benzene in waterby the radio-frequency muon spin resonance (RF-μSR) technique.The relative shift of Aμin aqueoussolution compared with the value in neat benzene (ΔAμ/Aμ= +0.98(5)%at 293 K) can now be compared directly with theoretical predictions.Application of the RF-μSR method to other dilute systems willprovide extremely important information on understanding solvent effects. [ABSTRACT FROM AUTHOR]

Muoniated radicals were produced by the addition of muonium(Mu)to the aromatic compound p-xylene (1) in the solid and liquid states and to the strained aromatic compound[2.2]paracyclophane (2) in the solid state. The radicalswere characterized by avoided level crossing muon spin resonance spectroscopyand identified by comparing the experimentally determined muon hyperfinecoupling constants with values obtained from DFT calculations. Muwas observed to add to both the secondary and tertiary carbons of 1, with the relative yield of the Mu adduct of the tertiarycarbons estimated to be ∼10% in the liquid phase. The relativeyield of the tertiary adduct is much higher in the solid state althoughthis cannot be calculated exactly due to the overlap of resonancesand the apparent nonuniform distribution of the radical orientations.There are three possible addition sites in 2due to thelower symmetry of the six-membered ring compared with 1. Mu can add to the secondary carbons either from the outside of 2, generating the “exo” adduct, or from theinside, generating the “endo” adduct. The relative yieldsof the exo, endo, and tertiary carbon adducts are 67.1(1), 21.8(1),and 11.1(1)%, respectively. The barriers to Mu addition at the differentsites of isolated molecules were determined from DFT calculations.The barriers for Mu addition to 2are lower than thebarriers for Mu addition to 1, except for addition tothe “endo” position, where the unfavorable steric interactionswith the second ring of 2raise the addition barrierconsiderably. The measured relative yields do not reflect the distributionof products calculated using the activation energies obtained fromthe DFT calculations due to strong steric interactions with neighboringmolecules. [ABSTRACT FROM AUTHOR]

Background: Serological assays designed to detect SARS-CoV-2 antibodies are being used in serological surveys and other specialized applications. As a result, and to ensure that the outcomes of serological testing meet high quality standards, evaluations are required to assess the performance of these assays and the proficiency of laboratories performing them., Methods: A panel of 60 plasma/serum samples from blood donors who had reverse transcriptase-polymerase chain reaction (RT-PCR) confirmed SARS-CoV-2 infections and 21 SARS-CoV-2 negative samples were secured and distributed to interested laboratories within Canada ( n = 30) and the United States ( n = 1). Participating laboratories were asked to provide details on the diagnostic assays used, the platforms the assays were performed on, and the results obtained for each panel sample. Laboratories were blinded with respect to the expected outcomes., Results: The performance of the different assays evaluated was excellent, with the high-throughput platforms of Roche, Ortho, and Siemens demonstrating 100% sensitivity. Most other high-throughput platforms had sensitivities of >93%, with the exception of the IgG assay using the Abbott ARCHITECT which had an average sensitivity of only 87%. The majority of the high-throughput platforms also demonstrated very good specificities (>97%)., Conclusion: This proficiency study demonstrates that most of the SARS-CoV-2 serological assays utilized by provincial public health or hospital laboratories in Canada have acceptable sensitivity and excellent specificity., (Copyright © 2022, Association of Medical Microbiology and Infectious Disease Canada (AMMI Canada).)

It has been claimed that longitudinal field muon spin relaxation (LF-μSR) experiments on the organic semiconductor (OSC) tris-(8-hydroxyquinoline)aluminum(III) (Alq 3 ) have measured electron hopping rates of ∼10 12 s -1 , while density functional theory (DFT) calculations suggest that electron hopping between a muoniated radical and a neighboring molecule is energetically unfavorable and that the LF-μSR experiments were probing muoniated radicals with localized spin density. We have performed avoided level crossing muon spin resonance (ALC-μSR) and transverse field muon spin rotation (TF-μSR) measurements on Alq 3 and 8-hydroxyquinoline (8hq), which is meant to model the muoniated radicals present in Alq 3 when they are not in an OSC. These are supplemented by benchmarked DFT calculations. The ALC-μSR and TF-μSR spectra of 8hq and Alq 3 are best explained by Mu adding to all six secondary carbons of the quinolate rings with roughly equal yields and localized spin density. There is no evidence in the TF-μSR spectrum of Alq 3 for the formation of radicals with muon hyperfine coupling constants of 23 or 91 MHz as reported earlier by others. Our measurements support the view that there is localized spin density on the molecule to which Mu is covalently bound and the muon is not a passive probe in organic systems as it can be incorporated into radicals that have different electronic structures to the parent compounds. The muoniated radicals in Alq 3 are more short-lived than in 8hq, which could be due to interactions with mobile electrons in the OSC, but with electron spin flip rates on the order of ∼10 7 s -1 .

Ordering of solvent molecules in the vicinity of a dipolar free radical affects its hyperfine coupling constants (hfcs). Specifically, it is demonstrated how the variation of the experimental methylene proton and muon hfcs of the muoniated cyclohexadienyl radical in several solvents and solvent mixtures of varying polarity can be accounted for by a dipole-dipole reaction field model that is based on the model of Reddoch and Konishi (J. Chem. Phys. 1979, 70, 2121) which was developed to explain the solvent dependence of the 14N hfc in the di-tert-butyl-nitroxide radical. Ab initio calculations were carried out with the cyclohexadienyl radical in an electric field to model the electric field arising from the electric dipole moments of the surrounding solvent molecules. An extension of the model that includes the dipole-quadrupole interaction can account for the larger hfc in benzene compared with that in octadecane, and it is predicted that the hfc will be proportional to the concentration of quadrupole moments to the 4/3 power. The influence of hydrogen bonding between the radicals' pi electrons and the OH groups of the solvent on the hfcs is also discussed. Comparison with gas-phase data permits a separation of vibrational effects and reveals that approximately 28% of the temperature dependence in water is due to increasing solvent disorder.