Five-fold-symmetric macrocyclic aromatic pentamers: high-affinity cation recognition, ion-pair-induced columnar stacking, and nanofibrillation

Described in this study is a conceptually new class of five-fold-symmetric cavity-containing planar pentameric macrocycles with their interior decorated by five convergently aligned, properly spaced carbonyl oxygen atoms. These cation-binding oxygens enclose a hydrophilic lumen of 2.85 ? in radius and thus display high-affinity binding toward alkali metal cations, and possibly many other cations, too. Arising from their high-affinity recognition of metal ions, these planar macrocycles form cation- or ion-pair-induced one-dimensional columnar aggregates, and subsequently fascinating fibrillation results.     

Photoreactive gold(I) macrocycles with diphosphine and trans,trans-muconate ligands

A pair of trans,trans-muconate ligands have been successfully aligned in two novel Au(I) macrocycles by design from phosphino metal precursors that undergo photochemical cycloaddition reactions quantitatively, resulting in the formation of cyclooctadiene derivatives.     

Transition from anodic titania nanotubes to nanowires: arising from nanotube growth to application in dye-sensitized solar cells

Anodic formation of titania nanowires has been interpreted using a bamboo-splitting model; however, a number of phenomena are difficult to explain with this model. Herein, transition from nanotubes to nanowires is investigated by varying the anodizing conditions. The results indicate that the transition requires a large number of hydrogen ions to reduce the passivated area of tube walls, and therefore can be observed only in an intermediate chemical dissolution environment. Accordingly, a model in terms of stretching and splitting is proposed to interpret the transition process. The model provides a basis to suppress the nanowires with surface treatments before anodization and to clear the nanowires with an ultrasonication process after anodization. The nanotube-nanowire transition also arises when the tubes are directly used in dye-sensitized solar cells. Treatment with titanium tetrachloride solution for about 10 h is found to be effective in suppressing the nanowires, and thus improving the photovoltaic properties of the solar cells.     

Choosing best alliance partners and allocating optimal alliance resources using the fuzzy multi-objective dummy programming model

Synergy effects are the motives to enter into strategic alliances; however due to lack of adequate preparation or planning, these alliances often fail. It is of no doubt that a successful strategic alliance depends on choosing the correct alliance partners and appropriate resource allocation. In this paper, the fuzzy multi-objective dummy programming model is proposed to overcome the above-mentioned problems. Two types of strategic alliances, joint ventures and mergers and acquisitions (M&A), are demonstrated to choose the best alliance partners and allocate the optimal alliance resources in a numerical example. Based on the results, our method can provide the optimal alliance cluster and satisfaction in strategic alliances.     

Synthesis and properties of new soluble triphenylamine‐based aromatic poly(amine amide)s derived from N,N′‐bis(4‐carboxyphenyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine

A new triphenylamine‐containing aromatic dicarboxylic acid, N,N′‐bis(4‐carboxyphenyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine, was synthesized by the condensation of N,N′‐diphenyl‐1,4‐phenylenediamine with 4‐fluorobenzonitrile, followed by the alkaline hydrolysis of the intermediate dinitrile compound. A series of novel triphenylamine‐based aromatic poly(amine amide)s with inherent viscosities of 0.50–1.02 dL/g were prepared from the diacid and various aromatic diamines by direct phosphorylation polycondensation. All the poly(amine amide)s were amorphous in nature, as evidenced by X‐ray diffractograms. Most of the poly(amine amide)s were quite soluble in a variety of organic solvents and could be solution‐cast into transparent, tough, and flexible films with good mechanical properties. They had useful levels of thermal stability associated with glass‐transition temperatures up to 280 °C, 10% weight‐loss temperatures in excess of 575 °C, and char yields at 800 °C in nitrogen higher than 60%. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 94–105, 2003     

Frequency pulling and heterodyning observed in voltage spectrum of the Fröhlich conductor NbSe3

The voltage power spectrum of NbSe₃ has been studied in the upper charge-density wave (CDW) state where only one CDW exists. In the non-Ohmic regime sharp spikes appear in the spectrum. The frequency of these spikes increases monotonically with current as in the lower CDW state. We study the “fine structure” of the spectrum and find evidence for “frequency pulling” between the modes. A linear coupled-mode treatment is used to model this effect. There is also evidence of heterodyning of an intrinsic (current independent) 2MHz mode. We briefly discuss these phenomena in terms of Fröhlich sliding conductivity. Difficulties with the simple two-fluid model as well as models based on solid state turbulence are pointed out.     

Dependence of viscosity of polystyrene solutions on molecular weight and concentration

Viscosities of solutions of polystyrene in toluene were measured for concentrations up to 400 kg m^?3 at 298 K. Polymers of molecular weights ranging from 8.7 × 10³ to 2.4 × 10⁶ were used. It is observed that viscosity of the polymer solution increases with increasing concentration and molecular weight; the rate of increase is greater at higher values of the two parameters. A master curve for the system is constructed by using the experimental data for viscosity, concentration and molecular weight of the polymer. Regions of various polymer interactions in solution are identified.     

Curvature and mechanics

Classical or Newtonian Mechanics is put in the setting of Riemannian Geometry as a simple mechanical system (M, K, V), where M is a manifold which represents a configuration space, K and V are the kinetic and potential energies respectively of the system. To study the geometry of a simple mechanical system, we study the curvatures of the mechanical manifold (M_h, g_h) relative to a total energy value h, where M_h is an admissible configuration space and g_h the Jacobi metric relative to the energy value h. We call these curvatures h-mechanical curvatures of the simple mechanical system.Results are obtained on the signs of h-mechanical curvature for a general simple mechanical system in a neighborhood of the boundary ?M_h = {xεM: V(x) = h} and in a neighborhood of a critical point of the potential function V. Also we construct $\text{m = (}\text{n}\text{2}\text{) (n =}\text{dim}\text{M)}$ functions defined globally on M_h, called curvature functions which characterize the sign of the h-mechanical curvature. Applications are made to the Kepler problem and the three-body problem.     

Polarization phase shifting shearography for optical metrological applications

We present here a different and modified configuration in order to obtain the curvature fringes by incorporating phase shifting and image processing techniques. Optical fibers are used for obtaining shear fringes in which we have used Wollaston prism as the shear element.