Polarization of electronic transitions in aromatic hydorcarbon molecules and their mono- and di-valent ions

An overview of predictive chemical kinetics is presented, with an application to the simulation and design of homogeneous charge compression ignition (HCCI) engines. The engine simulations are sensitive to the details of hydroperoxyalkyl (QOOH) radical chemistry, which are only partially understood, and there is a significant discrepancy between the simulations and experiment that limits the usefulness of the simulations. One possible explanation is that QOOH decomposes by other channels not considered in existing combustion chemistry models. Rate constants for one of these neglected channels, the intramolecular radical attack on the QOOH peroxide linkage to form hydroxyalkoxyl (HOQO) radicals, are predicted using quantum chemistry (CBS-QB3), to test whether or not this proposed channel can explain the observed discrepancies in the engine simulations. Although this channel has a significant rate, the competing attack on the other O atom in the peroxide to form a cyclic ether+OH is computed to be an order of magnitude faster, so the HOQO channel does not appear to be fast enough to explain the discrepancy. Definitive judgement on the importance of this reaction channel will require a careful reconsideration of all the coupled chemically activated QOOH reaction channels using modern predictive chemical kinetics software.     

Unitarity in “Quantization Commutes with Reduction”

Let M be a compact Kähler manifold equipped with a Hamiltonian action of a compact Lie group G. In this paper, we study the geometric quantization of the symplectic quotient M // G. Guillemin and Sternberg [Invent. Math. 67, 515–538 (1982)] have shown, under suitable regularity assumptions, that there is a natural invertible map between the quantum Hilbert space over M //G and the G-invariant subspace of the quantum Hilbert space over M.Reproducing other recent results in the literature, we prove that in general the natural map of Guillemin and Sternberg is not unitary, even to leading order in Planck’s constant. We then modify the quantization procedure by the “metaplectic correction” and show that in this setting there is still a natural invertible map between the Hilbert space over M // G and the G-invariant subspace of the Hilbert space over M. We then prove that this modified Guillemin–Sternberg map is asymptotically unitary to leading order in Planck’s constant. The analysis also shows a good asymptotic relationship between Toeplitz operators on M and on M // G.     

Comparison of simulations and data from a seismo-acoustic tank experiment

A tank experiment was carried out to investigate underwater sound propagation over an elastic bottom in flat and sloping configurations. The purpose of the experiment was to evaluate range-dependent propagation models with high-quality experimental data. The sea floor was modeled as an elastic medium by a polyvinyl chloride slab. The relatively high rigidity of the slab requires accounting for shear waves in this environment. Acoustic measurements were obtained along virtual arrays in the water column using a robotic apparatus. Elastic parabolic equation solutions are in excellent agreement with data.     

Photocatalytic properties of Ta-doped TiO2

Ionics - This work reports the effect of tantalum (0.1–1 at.% Ta) on the photocatalytic performance of TiO2 annealed at 1373 and 1673 K in air. It was shown that addition of...     

Thiolated poly(ε-caprolactone) macroligand with vacant coordination sites on gold substrate: Synthesis and surface characterization

Surface-confined telechelic poly(ε-caprolactone) macroligand with two distinct functional groups per polymeric chain has been synthesized and characterized. The molecular microstructure of the macroligand with regard to the properties of the end-capped functionalities and with those on surface substrate has been studied by solution and surface analytical methods (i.e., X-ray photoelectron spectroscopy (XPS), grazing angle reflectance-Fourier transform IR spectroscopy (GA-FTIR), water contact angle measurements, and atomic force microscopy (AFM)) to elucidate the structure and properties of such multifunctional polymer on gold (1 1 1) substrate.     

The effect of sound level on perception of reproduced soundscapes

The aim of this work was to investigate the perception of soundscape reproduced by an ambisonic reproduction system on a horizontal plane, how the experience of space affected the perception of soundscape reproduction, and how the sound level adjustment on soundscape reproduction affected the perception of soundscape compared with actual conditions. There were three experiments conducted: a soundwalk in situ in Manchester (United Kingdom) city centre, listening tests in Salford (United Kingdom), and listening tests in Bandung (Indonesia). The listening tests used material recorded from four locations on the soundwalk route in Manchester. The Salford listening tests were performed at the in-situ measured sound level, and the participants were asked to adjust the sound level to the level that represents actual locations. The listening test in Bandung was conducted to understand the effect of participants who never come to the actual location to the perception of soundscape and the sound level adjustment. The listening tests in Bandung were conducted at the in situ sound level, at 9.5 dB below the in situ sound level (based on the preference sound level from the experiment in Salford), and the participants were also requested to adjust the sound level to the level that represents the actual space (to examine the consistency with the experiment in Salford). In each case, soundscape perception was measured on 19 semantic differential scales. Analysis of the semantic differential results showed that the ambisonic reproduction produced a similar subjective experience to the in situ soundwalk when the reproduction sound level was 9.5 dB lower than the actual sound level in situ. Reproduction at the actual sound level in situ produced a different dimensional space. The study shows that the sound level adjustment of soundscape reproduction in laboratory experiment produces more ecologically valid results compared to the reproduction at the actual sound level in situ.     

Engineered pixels using active plasmonic holograms with liquid crystals

Digital holography requires arrays of small reconfigurable elements to achieve complex reconstruction of the hologram with common systems based on pixels utilizing liquid crystal on silicon (LCoS) technology. The backplane of a typical pixel element is potentially underutilized and thus relatively large physical areas exist in which information can be stored and exploited to give additional functionality to pixel elements. Polarisation and wavelength dependent optical properties can be achieved in small areas using the plasmonic effects of optical antennae. The integration of LCs with optical antennae‐based plasmonic holograms allows active modulation of the far field pattern. The work here demonstrates the concept that conventional LCoS pixel elements can be greatly enhanced with the integration of plasmonic holograms, composed of optical antennae patterned on the surface, giving rise to new levels of modulation capability for holographic pixel elements. Using LCs, polarisation dependent effects in plasmonic holograms can be switched. ‘Engineered pixels', with sub‐wavelength multiplexing over both polarisation and wavelength, can increase the channel capacity of a typical LC display device. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Hinge peptide combinatorial libraries for inhilbitors of botulinum neurotoxins and saxitoxin: Deconvolution strategy

Combinatorial library screening offers a rapid process for identifying potential therapies to toxins. Hinge peptide libraries, which rely on conformational diversity rather than traditional molecular diversity, reduce the need for huge numbers of syntheses and screening steps and greatly expedite the discovery process of active molecules. Hinge peptide libraries having the structures: Acetyl-X₁–X₂–hinge–X₃–X₄–NH₂ (capped) and X₁–hinge–X₂–X₃ (uncapped), where X₁ through X₄ are near-equimolar mixtures of twelve L-amino acids and hinge = 4-aminobutyric acid, were screened for inhibitory activity in bioassays for botulinum neurotoxins A and B (BoNT/A, BoNT/B) and saxitoxin. The zinc protease activity of the reduced light chains of BoNT/A and /B was assayed by measuring the cleavage of synthetic substrates. Saxitoxin activity was measured by the restoration of the viability of neuroblastoma cells treated with ouabain and veratridine. Deconvolution of libraries was accomplished by fixing one position at a time beginning with the C-terminus. Primary library subsets in which position 4 was fixed showed moderate levels of inhibition for BoNT/A. Secondary library subsets showed stronger inhibition in the bioassays. In each of the bioassays, inhibitory potency was stronger when the second position to be fixed was on the opposite side of the hinge, rather than on the same side with respect to the C-terminus, suggesting that the hinge facilitates the interaction of side chains. Inhibitors for all three of the toxins studied were discovered within library subsets, although not necessarily in primary subsets. These studies demonstrate that (1) the best strategy for deconvoluting hinge peptide libraries is by fixing residues alternately on each side of the hinge moiety, and (2) it is essential to investigate secondary subsets even when primary subsets are inactive. The present findings support the concept that the increased flexibility imposed by the inclusion of a central hinge residue in small peptides increases the opportunity for side chain interactions, providing a distinct advantage for hinge peptide libraries over conventional peptide libraries. Hinge peptide libraries are a rich source of novel ligands for modulation of biomechanisms. The library subsets uncovered in this study may possess peptides that will lead to effective therapies to neurotoxin poisoning.     

A power-law distribution for tenure lengths of sports managers

We show that the tenure lengths for managers of sport teams follow a power law distribution with an exponent between 2 and 3. We develop a simple theoretical model which replicates this result. The model demonstrates that the empirical phenomenon can be understood as the macroscopic outcome of pairwise interactions among managers in a league, threshold effects in managerial performance evaluation, competitive market forces, and luck at the microscopic level.