The very-low-pressure study of the kinetics and equilibrium: Cl + CH4 ⇄ CH3 + HCl at 298 K. The heat of formation of the CH3 radical

The bimolecular rate constant for the direct reaction of chlorine atoms with methane was measured at 25°C by using the very-low-pressure-pyrolysis technique. The rate constant was found to be In addition, the ratio k₁/k_?1 was observed with about 25% accuracy: K₁₍₂₉₈₎ = 1.3 ± 0.3. This gives a heat of formation of the methyl radical ΔH° _{f 298}(CH₃) = 35.1 ± 0.15 kcal/mol. A bond dissociation energy BDE (CH₃ ? H) = 105.1 ± 0.15 kcal/mol in good agreement with literature values was obtained.     

(Schiff base) divalent group 14 element species: manganese and iron complexes (Salen)M=Mn(Co)2(eta 5-C5H5) (M14 = Ge, Sn, Pb) and (Salen)Sn=Fe(CO)4

Syntheses of the (divalent group 14 species)dicarbonyl(cyclopentadienyl)manganese (Salen)M=Mn(CO)2(eta 5-C5H5) [M = Ge (1), Sn (2), Pb (3)] and [(Salen)tin(II)]tetracarbonyliron (Salen)Sn=Fe(CO)4 (4) are reported. The structures of 2 and 4 were determined by X-ray crystallography. The observed Sn-Mn bond length, 2.4428(7) A, is the shortest distance observed for this type of bond and corresponds to considerable multiple bonding between these atoms. In complex 4, the iron atom has a slightly distorted trigonal-bipyramidal coordination sphere; the (Salen)tin(II) ligand occupies an axial site, indicating that it functions in this complex as a strong sigma-donor and weak pi-acceptor ligand. Crystal data for 2: orthorhombic, P2(1)2(1)2(1), a = 6.972(1) A, b = 15.678(2) A, c = 19.032(2) A, alpha = beta = gamma = 90 degrees, V = 2080.3(5) A3, T = 173(2) K, Z = 4. Crystal data for 4: triclinic, P1, a = 8.465(2) A, b = 9.795(3) A, c = 13.213(4) A, alpha = 105.55(3) degrees, beta = 105.15(3) degrees, gamma = 100.84(3) degrees, V = 978.7(5) A3, T = 173(2) K, Z = 2.     

Plasmon Mediated Near-Field Energy Transfer From Solid-State,Electrically Injected Excitons to Solution Phase Chromophores

An organic diode is demonstrated that near-field energy transfers to molecules in solution via surface plasmon polaritons, in contrast to typical far-field excitation via absorption of traveling photons. Electrically generated excitons couple to surface plasmon modes in the cathode; the plasmons subsequently excite chromophore molecules on top of the cathode. External quantum efficiency and time resolved photoluminescence measurements are used to characterize the diode and the near-field energy transfer process. In addition, it is shown that excited chromophores can charge-transfer to quencher molecules, illustrating the potential of this device to be used for photochemical applications.     

A Holistic Solution to Icing by Acoustic Waves: De-Icing,Active Anti-Icing,Sensing with Piezoelectric Crystals,and Synergy with Thin Film Passive Anti-Icing Solutions

Icing has become a hot topic both in academia and in the industry given its implications in transport, wind turbines, photovoltaics, and telecommunications. Recently proposed de-icing solutions involving the propagation of acoustic waves (AWs) at suitable substrates may open the path for a sustainable alternative to standard de-icing or anti-icing procedures. Herein, the fundamental interactions are unraveled that contribute to the de-icing and/or hinder the icing on AW-activated substrates. The response toward icing of a reliable model system consisting of a piezoelectric plate activated by extended electrodes is characterized at a laboratory scale and in an icing wind tunnel under realistic conditions. Experiments show that surface modification with anti-icing functionalities provides a synergistic response when activated with AWs. A thoughtful analysis of the resonance frequency dependence on experimental variables such as temperature, ice formation, or wind velocity demonstrates the application of AW devices for real-time monitoring of icing processes.     

A survey of the parallel performance and accuracy of Poisson solvers for electronic structure calculations

We present an analysis of different methods to calculate the classical electrostatic Hartree potential created by charge distributions. Our goal is to provide the reader with an estimation on the performance—in terms of both numerical complexity and accuracy—of popular Poisson solvers, and to give an intuitive idea on the way these solvers operate. Highly parallelizable routines have been implemented in a first‐principle simulation code (Octopus ) to be used in our tests, so that reliable conclusions about the capability of methods to tackle large systems in cluster computing can be obtained from our work. © 2013 Wiley Periodicals, Inc.     

Bifunctional electrocatalysis in pt-ru nanoparticle systems

Pt-Ru alloys are prominent electrocatalysts in fuel cell anodes as they feature a very high activity for the oxidation of reformate and methanol. The improved CO tolerance of these alloys has been discussed in relation to the so-called ligand and bifunctional mechanisms. Although these effects have been known for many years, they are still not completely understood. A new approach that bridges the gap between single crystals and practical catalysts is presented in this paper. Nanoparticulate model systems attached to an oxidized glassy carbon electrode were prepared by combining both ligand-stabilized and spontaneously deposited Pt and Ru nanoparticles. These electrodes showed very different voltammetric responses for CO and methanol oxidation. The cyclic voltammograms were deconvoluted into contributions attributed to Pt, Ru, and Pt-Ru contact regions to quantify the contribution of the latter to the bifunctional mechanism. Scanning transmission electron microscopy confirmed the proximity of Pt and Ru nanoparticles in the different samples.     

Social and Content Hybrid Image Recommender System for Mobile Social Networks

One of the advantages of social networks is the possibility to socialize and personalize the content created or shared by the users. In mobile social networks, where the devices have limited capabilities in terms of screen size and computing power, Multimedia Recommender Systems help to present the most relevant content to the users, depending on their tastes, relationships and profile. Previous recommender systems are not able to cope with the uncertainty of automated tagging and are knowledge domain dependant. In addition, the instantiation of a recommender in this domain should cope with problems arising from the collaborative filtering inherent nature (cold start, banana problem, large number of users to run, etc.). The solution presented in this paper addresses the abovementioned problems by proposing a hybrid image recommender system, which combines collaborative filtering (social techniques) with content-based techniques, leaving the user the liberty to give these processes a personal weight. It takes into account aesthetics and the formal characteristics of the images to overcome the problems of current techniques, improving the performance of existing systems to create a mobile social networks recommender with a high degree of adaptation to any kind of user.     

Investigation of the asymmetric Birch reduction-alkylation of a chiral 5-arylbenzamide containing a carbamate group

The synthesis and asymmetric Birch reduction-alkylation of chiral benzamide 17 are described. Birch reductive alkylation of benzamide 17 was optimized to give the corresponding cyclohexa-1,4-diene products in 66-78% isolated yield and with high diastereoselectivity (dr: >98:2). The effects of performing the reduction in the presence and in the absence of tert-butyl alcohol are discussed.     

Synthesis of metal nanoparticles stabilized by metal-carbon bonds

A new method for the preparation of metal nanoparticles in organic media is proposed. This is based on the formation of metal-carbon bonds after reduction of the corresponding diazonium derivative of the capping ligand. The particles are very stable due to the strong metal-ligand covalent bond, and the proposed method appears to be an alternative for the preparation of monolayer-protected metal nanoparticles when the formation of metal-sulfur or metal-nitrogen bonds needs to be avoided.