Synthesis and Electrohydrodimerization of meta-Substituted Thiocinnamic Acid S-Esters

The synthesis of the novel m-substituted S-methyl thiocinnamates 1 – 4 is described. Cathodic reductions of S-esters 1 – 3 , carried out at constant potentials corresponding to their first voltammetric E_pc, in a polar aprotic solvent, led exclusively to the racemic `all-trans'-configured 2,3-diaryl-5-oxocyclopentane-1-carbothioates, as shown by assignments of ¹H-NMR coupling constants.     

Radical chain monoalkylation of pyridines

The monoalkylation of N-methoxypyridinium salts with alkyl radicals generated from alkenes (via hydroboration with catecholborane), alkyl iodides (via iodine atom transfer) and xanthates is reported. The reaction proceeds under neutral conditions since no acid is needed to activate the heterocycle and no external oxidant is required. A rate constant for the addition of a primary radical to N-methoxylepidinium >10⁷ M⁻¹ s⁻¹ was experimentally determined. This rate constant is more than one order of magnitude larger than the one measured for the addition of primary alkyl radicals to protonated lepidine demonstrating the remarkable reactivity of methoxypyridinium salts towards radicals. The reaction has been used for the preparation of unique pyridinylated terpenoids and was extended to a three-component carbopyridinylation of electron-rich alkenes including enol esters, enol ethers and enamides.

N-Methoxypyridinium salts are exceptionally reactive radical traps that can be used in efficient radical chain reactions with organoboranes.     

Core extensions for non-balanced TU-games

A family of core extensions for cooperative TU-games is introduced. These solution concepts are non-empty when applied to non-balanced games yet coincide with the core whenever the core is non-empty. The extensions suggest how an exogenous regulator can sustain a stable and efficient outcome, financing a subsidy via individual taxes. Economic and geometric properties of the solution concepts are studied. When taxes are proportional, the proportional prenucleolus is proposed as a single-valued selection device. An application of these concepts to the decentralization of a public goods economy is discussed. We wish to thank the editor, a referee, an anonymous reviewer, Beth Allen, Marc Dudey, Yakar Kannai, Herve Moulin, Marcel Richter, Luis Sánchez-Mier, and the participants in the Microeconomic Theory Workshop at Rice University for their helpful comments.     

Variational multiscale approximation of the one‐dimensional forced Burgers equation: The role of orthogonal subgrid scales in turbulence modeling

A numerical approximation for the one‐dimensional Burgers equation is proposed by means of the orthogonal subgrid scales–variational multiscale (OSGS‐VMS) method. We evaluate the role of the variational subscales in describing the Burgers “turbulence” phenomena. Particularly, we seek to clarify the interaction between the subscales and the resolved scales when the former are defined to be orthogonal to the finite‐dimensional space. Direct numerical simulation is used to evaluate the resulting OSGS‐VMS energy spectra. The comparison against a large eddy simulation model is presented for numerical discretizations in which the grid is not capable of solving the small scales. An accurate approximation to the phenomena of turbulence is obtained with the addition of the purely dissipative numerical terms given by the OSGS‐VMS method without any modification of the continuous problem.     

Impedimetric evaluation of hybrid cationic porphyrin/quantum dot multilayer assemblies: a biocompatible interface for calf thymus DNA immobilization

Journal of Solid State Electrochemistry - In this work, a cationic porphyrin, ascribed as [Ttolyl(P-(C6H5)3)4]4+, where Ttolyl = 5,10,15,20 tetrakistolylporphyrin, was...     

1.25–2.5 Gb/s Simple Nyquist Transmitters for Coherent UDWDM-PON with Enhanced Spectral Efficiency

We present a coherent ultra-dense wavelength division multiplexing passive optical network (UDWDM-PON) with enhanced spectral efficiency. The benefit of using Gaussian or Nyquist pulse-shaping filters at the transmitter is evaluated through numerical simulations and experiments. The transmitters consist of directly phase modulated distributed feedback (DFB) lasers through beat signals whose duty-cycle and amplitude are digitally adjusted. The results show that transmitting a Nyquist-shaped signal achieves a 25% spectral saving allowing to place 2.5 Gb/s/user data in 6.25 GHz channels. Furthermore, the proposed transmitter tolerates differential link-losses of 15 dB at Rx sensitivity of ?44 dBm at BER=10^?3 with intradyne detection.     

Dispersion and orientation of single-walled carbon nanotubes in a chromonic liquid crystal

A post-synthesis alignment of individual single-walled carbon nanotubes (SWCNTs) is desirable for translating their unique anisotropic properties to a macroscopic scale. Here, we demonstrate excellent dispersion, orientation and concomitant-polarised photoluminescence of SWCNTs in a nematic chromonic liquid crystal. The methods to obtain stable suspension are described, and order parameters of the liquid crystal matrix and of the nanotubes are measured independently.     

Group-type fractionation of petroleum and alternative fuels by column liquid chromatography

The present paper introduces an instrumental procedure based on column liquid chromatography for the total analysis of petroleum heavy ends and similar samples. The procedure avoids the precipitation of asphaltenes and asphaltols. One sequence of eluents fractionates the sample into 8 fractions: 5 non-polar (hydrocarbons), one intermediate (resins), and 2 polar fractions (asphaltenes and asphaltols). Quantitative results from gravimetric measurements and UV-Vis and FTIR spectra of fractions obtained from petroleum heavy ends are presented, as well as those from GC/MS data obtained from one fraction obtained from liquefaction of biomass. The method presented is easy to set up and operate, requires minimum operator attention, is reliable (no precipitation), reproducible, and inexpensive.