A New Memetic Algorithm for the Asymmetric Traveling Salesman Problem

This paper introduces a new memetic algorithm specialized for the asymmetric instances of the traveling salesman problem (ATSP). The method incorporates a new local search engine and many other features that contribute to its effectiveness, such as: (i) the topological organization of the population as a complete ternary tree with thirteen nodes; (ii) the hierarchical organization of the population in overlapping clusters leading to the special selection scheme; (iii) efficient data structures. Computational experiments are conducted on all ATSP instances available in the TSPLIB, and on a set of larger asymmetric instances with known optimal solutions. The comparisons show that the results obtained by our method compare favorably with those obtained by several other algorithms recently proposed for the ATSP.     

Digital image correlation and biaxial test on composite material for anisotropic damage law identification

The purpose of the work is to extend the use of non-conventional tests and full field measurements to the identification of an anisotropic damage law. A Digital Image Correlation technique based on a finite element discretization is used to extract planar displacement fields. The reconditioned Equilibrium Gap Method is then used to retrieve a damage law that accounts for shear softening, a specific form suited to the present application. The identification is shown to reduce to a linear system. The example of a biaxial shear test performed on a cruciform specimen is considered. The approach is first qualified by using displacement fields resulting from a non-linear computation with a known damage law. A good agreement is observed between the prescribed and identified laws for distinct parameter settings, even when significant noise is added to the displacement fields. The reconstructed displacement fields coincide perfectly with the measurements. The complete scheme is finally tested considering images taken during an experiment performed on a carbon/carbon composite. The identified damage pattern and the corresponding damage values are similar to post-processed maps using classically identified parameters. The reconstructed displacement field accounts for 95% of the fluctuations observed in the measurements.     

Beltrami differentials and 2d (super)gravity in the chiral gauge

We consider the Beltrami parametrization of a 2-dimensional metric and work out the basic transformation laws of the constituting fields. These results are then applied to investigate the geometric structure of 2-dimensional gravity in Polyakov's light-cone gauge. Subsequently, we elaborate on the supersymmetric generalization of this theory. The general relation to the superconformai gauge is presented in detail and the corresponding change of coordinates is shown to satisfy simple super Beltrami equations.     

The adhesion molecule Necl-3/SynCAM-2 localizes to myelinated axons,binds to oligodendrocytes and promotes cell adhesion

Background  

Cell adhesion molecules are plasma membrane proteins specialized in cell-cell recognition and adhesion. Two related adhesion molecules, Necl-1 and Necl-2/SynCAM, were recently described and shown to fulfill important functions in the central nervous system. The purpose of the work was to investigate the distribution, and the properties of Necl-3/SynCAM-2, a previously uncharacterized member of the Necl family with which it shares a conserved modular organization and extensive sequence homology.     

Self‐association in {2‐[3,4‐alkylenedioxy‐5‐(3‐pyridyl)]‐thienyl}alkanols: an NMR,IR, and single‐crystal X‐ray study

syn‐2,2,4,4‐Tetramethyl‐3‐{2‐[3,4‐alkylenedioxy‐5‐(3‐pyridyl)]thienyl}pentan‐3‐ols self‐associate both in the solid state and in solution. Single‐crystal X‐ray diffraction study of the 3,4‐ethylenedioxythiophene (EDOT) derivative shows that it exists as a centrosymmetric head‐to‐tail, syn dimer in the solid state. The IR spectra of the solids display only a broad OH absorption around 3300 cm^?1, corresponding to a hydrogen‐bonded species. ¹H Nuclear Overhauser Effect Spectroscopy (NOESY) NMR experiments in benzene reveal interactions between the tert‐butyl groups and the H2 and H6 protons of the pyridyl group. Two approaches have been used to determine association constants of the EDOT derivative by NMR titration, based on the concentration dependence of (i) the syn/anti ratio and (ii) the OH proton shift of the syn rotamer. Reasonably concordant results are obtained from 298 to 323 K (3.6 and 3.9 M^?1, respectively, at 298 K). Similar values are obtained from the syn OH proton shift variation for the 3,4‐methylenedioxythiophene (MDOT) derivative. Concentration‐dependent variation of the anti OH proton shift in the latter suggests that the anti isomer associates in the form of an open, singly hydrogen‐bonded dimer, with a much smaller association constant than the syn rotamer. Self‐association constants for 3‐pyridyl‐EDOT‐alkanols with smaller substituents vary by a factor of 4 from (i‐Pr)₂ up to (CD₃)₂, while the hetero‐association constants for the same compounds with pyridine vary slightly less. Copyright © 2007 John Wiley & Sons, Ltd.     

A modal cutoff approach to the study of buried channel waveguide couplers

We investigate the higher-order supermodes of symmetric buried channel waveguide (BCW) couplers with cores of square, rectangular, and trapezoidal geometries. We show how the cutoff wavelengths of these supermodes can be used to interpret the spectral response of a practical single-mode BCW coupler. Our results highlight the design constraints imposed by second-order supermodes. We also compare the behaviour of these couplers with that of circular-core couplers to illustrate how the geometry of each core affects the coupler cutoff characteristics.     

An enthalpic scale of hydrogen-bond basicity. 3. Ammonia, primary, secondary, and tertiary amines

A reliable enthalpic scale of hydrogen-bond acceptor strength (basicity) is built for aliphatic amines by means of a new infrared method, from the temperature variation of hydrogen-bond equilibrium constants. Enthalpies of hydrogen bonding to a reference hydrogen-bond acceptor, 4-fluorophenol, have been determined in CCl4 and/or C2Cl4 for ammonia and 68 primary, secondary, and tertiary amines. The scale spans from -23.8 kJ mol(-1) for i-Pr2NCH(Et)2 to -39.4 kJ mol(-1) for Et3N. This large variation is mainly explained by the basicity-enhancing electronic effects of alkyl groups, which can be overcompensated by dramatic basicity-decreasing steric effects. Relationships between DeltaH degrees and the change in electronic energy or the infrared shift of the OH stretching upon hydrogen bonding are studied and found useful in the prediction of the hydrogen bond enthalpies of amines with several hydrogen-bond acceptor sites. A careful statistical analysis of the enthalpy-entropy relationship shows an isoentropic tendency. The entropies of 65% of hydrogen-bonding reactions between aliphatic amines and 4-fluorophenol have a mean value of -55.1 +/- 4.2 J K(-1) mol(-1). Amines excluded from the isoentropic set are mainly severely hindered ones. The hydrogen-bond enthalpic scale can be useful in measuring the electrostatic character of Lewis bases.     

Universal solid supports for the synthesis of oligonucleotides via a transesterification of H-phosphonate diester linkage

[Structure: see text]. Three universal solid supports exhibiting an hydroxyl function were prepared. The introduction of a first H-phosphonate diester linkage which was kept throughout the elongation allowed the release of 3'-hydroxyl oligonucleotides by a transesterification mechanism. The transesterification was performed in a few minutes with either amino alcohols or K2CO3/methanol. Starting from a hydroxyl solid support, tandem oligonucleotides were synthesized and the solid support was easily recyclable. This strategy was extended to the release of an oligonucleotide from the solid support by a nonbasic treatment opening the way to the synthesis of base-sensitive oligonucleotides thanks to the selective deprotection of a hydroxyl in beta of the H-phosphonate diester linkage.     

Study of a nanocomposite based on a conducting polymer: polyaniline

A simple way to obtain a conducting nanocomposite is described, and the conducting particles are characterized. Core-shell particles [polystyrene-polyaniline (PANI)] have been obtained by the dispersion process from three types of polystyrene latexes: a no-cross-linked core stabilized by a nonylphenolethoxylate (NP40) and two cross-linked cores stabilized by NP40 and a mixture NP40/Surfamid (a surfactant bearing an amide group). The surface of these particles has been extensively characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and scanning electron microscopy. A maximum coverage of 94% was obtained for the high PANI content as revealed by XPS analysis. A better coverage was obtained for the cross-linked polystyrene latex stabilized by the Surfamid. The amide group of this surfactant allows the H-bonding formation with the PANI backbone and, thus, improves the conductivity. It was shown that a uniform coverage of the core particles was not required to ensure a good conductivity.