Intervalence (Charge-Resonance) Transitions in Organic Mixed-Valence Systems. Through-Space versus Through-Bond Electron Transfer between Bridged Aromatic (Redox) Centers

Intervalence absorption bands appearing in the diagnostic near-IR region are consistently observed in the electronic spectra of mixed-valence systems containing a pair of aromatic redox centers (Ar•+/Ar) that are connected by two basically different types of molecular bridges. The through-space pathway for intramolecular electron transfer is dictated by an o-xylylene bridge in the mixed-valence cation radical 3•+ with Ar = 2,5-dimethoxy-p-tolyl (T), in which conformational mobility allows the proximal syn disposition of planar T•+/T redox centers. Four independent experimental probes indicate the large through-space electronic interaction between such cofacial Ar•+/Ar redox centers from the measurements of (a) sizable potential splitting in the cyclic voltammogram, (b) quinonoidal distortion of T•+/T centers by X-ray crystallography, (c) “doubling” of the ESR hyperfine splittings, and (d) a pronounced intervalence charge-resonance band. The through (br)-bond pathway for intramolecular electron transfer is enforced in the mixed-valence cation radical 2a•+ by the p-phenylene bridge which provides the structurally inflexible and linear connection between Ar•+/Ar redox centers. The direct comparison of intramolecular rates of electron transfer (kET) between identical T•+/T centers in 3•+ and 2a•+indicates that through-space and through-bond mechanisms are equally effective, despite widely different separations between their redox centers. The same picture obtains for 3•+ and 2a•+from theoretical computations of the first-order rate constants for intramolecular electron transfer from Marcus−Hush theory using the electronic coupling elements evaluated from the diagnostic intervalence (charge-transfer) transitions. Such a strong coherence between theory and experiment also applies to the mixed-valence cation radical 7•+, in which the aromatic redox S center is sterically encumbered by annulation

THE DISTANCE CENTRALITY: MEASURING STRUCTURAL DISRUPTION OF A NETWORK

This research provides an innovative approach to identifying the influence of vertices on the topology of a graph by introducing and exploring the neighbor matrix and distance centrality. The neighbor matrix depicts the “distance profile” of each vertex, identifying the number of vertices at each shortest path length from the given vertex. From the neighbor matrix, we can derive 11 oft-used graph invariants. Distance centrality uses the neighbor matrix to identify how much influence a given vertex has over graph structure by calculating the amount of neighbor matrix change resulting from vertex removal. We explore the distance centrality in the context of three synthetic graphs and three graphs representing actual social networks. Regression analysis enables the determination that the distance centrality contains different information than four current centrality measures (betweenness, closeness, degree, and eigenvector). The distance centrality proved to be more robust against small changes in graphs through analysis of graphs under edge swapping, deletion, and addition paradigms than betweenness and eigenvector centrality, though less so than degree and closeness centralities. We find that the neighbor matrix and the distance centrality reliably enable the identification of vertices that are significant in different and important contexts than current measures.http://archive.org/details/thedistancecentr1094559576Lieutenant Colonel, United States ArmyApproved for public release; distribution is unlimited

Respuestas del ciclo del carbono del suelo al cambio global y su predicción mediante la modelización de vínculos entre procesos bióticos y abióticos clave en los ecosistemas terrestres

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Ecología. Fecha de lectura: 19-05-202

Representing the Fate of Springtime Arctic Clouds.

Observations and modeling results have shown the high latitudes’ environment changing in a warmer climate. The research presented focuses on the parameterizations used to simulate Arctic Mixed-Phase Stratocumulus (AMPS) clouds and the sensitivity of the AMPS to changing environmental conditions. A Large Eddy Simulation (LES) is used to reproduce an idealized AMPS during the intensive observation period, Indirect and Semi-Direct Aerosol Campaign (ISDAC). The level of complexity needed to simulate this cloud is investigated with two microphysics routines and two subgrid scale turbulent closure models. It was found that both the microphysics routines accurately produced macrophysical properties of the observed cloud, and that the less computationally expensive microphysics parameterization could be used to reproduce the AMPS. When the subgrid scale turbulent closure models were evaluated with the microphysics routines, it was found the choice of turbulent closure model had more of an effect on the cloud properties than the choice of microphysics. Knowledge of the parameterizations needed for representing the AMPS were applied to a parameter-space-filling uncertainty quantification technique to understand the sensitivity of the mixed-phase cloud to changes in its environment. The LES model was connected to the uncertainty quantification toolkit, Design Analysis Kit for Optimization and Terascale Applications (DAKOTA), which produced parameter ranges from which the LES model tried to produce a boundary layer mixed-phase cloud. The environmental variables that were changed were the cloud ice and aerosol concentration, surface sensible and latent heat fluxes, and large scale temperature, water vapor, and vertical motion. Four characteristic behaviors were used to classify the fates of the AMPS: stability, growth, decay, and dissipation. It was found the longevity and spatial extent of the AMPS were most sensitive to changes in large-scale temperature, water vapor, and vertical motion in the variable ranges that were investigated. It was also found the AMPS did not form unconditionally, and that environmental thresholds existed which made mixed-phase cloud formation conducive.PHDAtmospheric and Space ScienceUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/95934/1/eroesler_1.pd

Consciousness as a State of Matter

We examine the hypothesis that consciousness can be understood as a state of matter, "perceptronium", with distinctive information processing abilities. We explore five basic principles that may distinguish conscious matter from other physical systems such as solids, liquids and gases: the information, integration, independence, dynamics and utility principles. If such principles can identify conscious entities, then they can help solve the quantum factorization problem: why do conscious observers like us perceive the particular Hilbert space factorization corresponding to classical space (rather than Fourier space, say), and more generally, why do we perceive the world around us as a dynamic hierarchy of objects that are strongly integrated and relatively independent? Tensor factorization of matrices is found to play a central role, and our technical results include a theorem about Hamiltonian separability (defined using Hilbert-Schmidt superoperators) being maximized in the energy eigenbasis. Our approach generalizes Giulio Tononi's integrated information framework for neural-network-based consciousness to arbitrary quantum systems, and we find interesting links to error-correcting codes, condensed matter criticality, and the Quantum Darwinism program, as well as an interesting connection between the emergence of consciousness and the emergence of time.Comment: Replaced to match accepted CSF version; discussion improved, typos corrected. 36 pages, 15 fig

A Geocritical Approach to Coloniality and Aesthetics: Mapping the Spatial Narratives of the Amazon Basin

Coloniality, or the living legacies and practices of the 500 years of European colonization, has produced racial, political, and cultural hierarchies around the colonial difference dividing East from West, center from periphery, civilization from the Global South. This dissertation examines a particular strand of coloniality in the Western narration and aesthetics of the Amazon basin, particularly the consequences of travel writing, science fiction and cinema of Amazon’s tropicality and its enduring effects on spatial cartography. In addressing Western representations of the jungle terrain, this paper focuses on the dichotomous relationship between the metropolitan center and the colonial outer-periphery exemplified by the Amazon basin. I take an alternative approach to understanding spatiality by applying what I call the coloniality of aesthetics to the spatial analysis of tropicality, illuminating the naturalized tendencies that articulate the Amazon as simultaneously a modern physical fantasy perpetually on the verge of colonial conquest and a mythological agent of horror that resists colonial conquest by its continued deferral of meaning production between the antagonism of nature and of civilization. The coloniality of aesthetics elucidates the West’s failure to figuratively conquer the land of the Amazon and suggests that such failures are crafted intentionally to preserve the aesthetics of conquest itself. This paper argues that the ontology of tropicality can be reestablished through a radical territorialization, one that centers the protagonism of the Amazon basin through the revelation of aesthetic modes that focus on the generative qualities of the South American rainforest. In doing so, I hope to expand the role of literary geocriticism through an exercise of spatial decolonization, one that prioritizes the often ignored terrain of the Amazon jungle

Projective Ribbon Permutation Statistics: a Remnant of non-Abelian Braiding in Higher Dimensions

In a recent paper, Teo and Kane proposed a 3D model in which the defects support Majorana fermion zero modes. They argued that exchanging and twisting these defects would implement a set R of unitary transformations on the zero mode Hilbert space which is a 'ghostly' recollection of the action of the braid group on Ising anyons in 2D. In this paper, we find the group T_{2n} which governs the statistics of these defects by analyzing the topology of the space K_{2n} of configurations of 2n defects in a slowly spatially-varying gapped free fermion Hamiltonian: T_{2n}\equiv {\pi_1}(K_{2n})$. We find that the group T_{2n}= Z \times T^r_{2n}, where the 'ribbon permutation group' T^r_{2n} is a mild enhancement of the permutation group S_{2n}: T^r_{2n} \equiv \Z_2 \times E((Z_2)^{2n}\rtimes S_{2n}). Here, E((Z_2)^{2n}\rtimes S_{2n}) is the 'even part' of (Z_2)^{2n} \rtimes S_{2n}, namely those elements for which the total parity of the element in (Z_2)^{2n} added to the parity of the permutation is even. Surprisingly, R is only a projective representation of T_{2n}, a possibility proposed by Wilczek. Thus, Teo and Kane's defects realize `Projective Ribbon Permutation Statistics', which we show to be consistent with locality. We extend this phenomenon to other dimensions, co-dimensions, and symmetry classes. Since it is an essential input for our calculation, we review the topological classification of gapped free fermion systems and its relation to Bott periodicity.Comment: Missing figures added. Fixed some typos. Added a paragraph to the conclusio