Communication: stabilization of radical anions with weakly bound electron in condensed media: a case study of diacetonyl radical anion

The radical anion resulting from electron capture by diacetonyl molecule has been characterized by EPR and optical absorption spectroscopy in glassy ether matrices at 77 K. In non-polar alkane glasses this species was not observed under the same conditions, which confirms the crucial role of matrix interactions in stabilizing this species. Calculations at the MP2 level show the vertical detachment energy to increase gradually from roughly zero for a bare anion to ～1 eV for the complex involving six ether molecules.     

Barr’s embedding theorem for enriched categories

We generalize Barr’s embedding theorem for regular categories to the context of enriched categories.     

Synthesis and study of redox-active acyclic triazenes: toward electrochromic applications

Coupling of various 4-substituted phenyl azides with two distinct quinone-containing N-heterocyclic carbenes (NHCs) afforded the respective mono- and ditopic 1,3-disubstituted acyclic triazenes in moderate to excellent yields (38-92%). Depending on their pendant substituents (derived from the azides), the acyclic triazenes exhibited intense absorptions in the visible spectrum (359-428 nm), which were bathochromically shifted by up to Δλ=68 nm upon reduction of the quinone moiety on the component derived from the NHC. Cyclic voltammetry confirmed that the aforementioned redox processes were reversible, and a related set of UV-vis spectroelectrochemical experiments revealed that bulk electrolysis may also be used to switch reversibly the colors exhibited by these triazenes.     

On the formation of gap solitons in nonlinear electromagnetic metamaterials

A nonlinear (Kerr‐type) electromagnetic metamaterial, characterized by a double‐Lorentz model of its frequency‐dependent linear effective dielectric permittivity and magnetic permeability, is considered. The formation of gap solitons in the low‐ and high‐frequency band gaps of this metamaterial is investigated analytically. Evolution equations governing the gap solitons, of the form of a nonlinear Klein‐Gordon and a nonlinear Schrödinger equation, are obtained, and the structure of their solutions is discussed.     

The role of guaiacyl moiety in free radical scavenging by 3,5-dihydroxy-4-methoxybenzyl alcohol: thermodynamics of 3H+/3e− mechanisms

ABSTRACT

Participation of guaiacyl moiety of 3,5-dihydroxy-4-methoxybenzyl alcohol (DHMBA) in inactivation of free radicals was investigated using the DFT method. The thermodynamics of triple (3H⁺/3e^?) free radical scavenging mechanisms was investigated. The Gibbs free energies of reactions of inactivation of selected 10 free radicals indicate DHMBA as a potent scavenger. Obtained results allow us to suggest that the contribution of guaiacyl moiety to antioxidant activity of phenolic compounds should be taken into account, what has been scarcely considered until now.     

Spectroscopic and Theoretical Study of Cyanidin–Aluminum (III) Complexes

Complexation of aluminum (III) with cyanidin, a natural anthocyanidin molecule, has been investigated in methanol and buffered solutions of pH 3.0 and 4.0. Electronic absorption spectroscopy was performed to characterize the stoichiometry and stability of the complexes formed. In investigated solvents, aluminum bonded moderately to cyanidin requiring large mole ratios of the components (up to 200) for the access of complexation. Molar ratio plots showed the formation of only one complex with stoichiometry aluminum (III):cyanidin of 1∶1 in both investigated media. Semiempirical calculations, performed in the Austin Model 1 parameterization, enabled the determination of the structural features of free compounds as well as complex structural modifications caused by chelation of Al(III).     

On the Spatial Distribution of Temporal Complexity in Resting State and Task Functional MRI

Measuring the temporal complexity of functional MRI (fMRI) time series is one approach to assess how brain activity changes over time. In fact, hemodynamic response of the brain is known to exhibit critical behaviour at the edge between order and disorder. In this study, we aimed to revisit the spatial distribution of temporal complexity in resting state and task fMRI of 100 unrelated subjects from the Human Connectome Project (HCP). First, we compared two common choices of complexity measures, i.e., Hurst exponent and multiscale entropy, and observed a high spatial similarity between them. Second, we considered four tasks in the HCP dataset (Language, Motor, Social, and Working Memory) and found high task-specific complexity, even when the task design was regressed out. For the significance thresholding of brain complexity maps, we used a statistical framework based on graph signal processing that incorporates the structural connectome to develop the null distributions of fMRI complexity. The results suggest that the frontoparietal, dorsal attention, visual, and default mode networks represent stronger complex behaviour than the rest of the brain, irrespective of the task engagement. In sum, the findings support the hypothesis of fMRI temporal complexity as a marker of cognition.     

Almost simple groups of Suzuki type acting on polytopes

Let , with an odd power of two. For each almost simple group such that , we prove that is not a C-group and therefore is not the automorphism group of an abstract regular polytope. For , we show that there is always at least one abstract regular polytope such that . Moreover, if is an abstract regular polytope such that , then is a polyhedron.