Pyrenylamine‐functionalized aromatic polyamides as efficient blue‐emitters and multicolored electrochromic materials

A series of novel aromatic polyamides with pyrenylamine in the backbone were prepared from a newly synthesized dicarboxylic acid monomer, N,N‐di(4‐carboxyphenyl)‐1‐aminopyrene, and various aromatic diamines via the phosphorylation polyamidation technique. These polyamides were readily soluble in many organic solvents and could be solution‐cast into tough and amorphous films. They had useful levels of thermal stability with glass‐transition temperatures in the range of 276–342 °C and 10% weight loss temperatures in excess of 500 °C. The dilute N‐methyl‐2‐pyrrolidone (NMP) solutions of these polymers exhibited fluorescence maxima around 455–540 nm with quantum yields up to 56.9%. The polyamides also showed remarkable solvatochromism of the emission spectra. Their films showed reversible electrochemical oxidation and reduction accompanied by strong color changes from colorless neutral state to purple oxidized state and to yellow reduced state. The polyamide 4g containing the pyrenylamine units in both diacid and diamine sides exhibited easily accessible p‐ and n‐doped states, together with multicolored electrochromic behaviors. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Effect of oxygen addition on the hydrogen production from ethanol steam reforming in a Pd–Ag membrane reactor

In this communication, a porous stainless steel (PSS) tube was electrolessly plated into Pd–Ag membrane reactor which was used for separating hydrogen produced in an ethanol steam reforming reaction with the addition of oxygen, which has not been reported before. Palladium and silver were deposited on porous stainless steel tube via the sequential electroless plating procedure with an overall film thickness of 20 μm and Pd/Ag weight ratio of 78/22. Ethanol–water mixture (n_water/n_ethanol = 1 or 3) and oxygen (n_oxygen/n_ethanol = 0.2 or 0.7) were fed concurrently into the membrane reactor packed with MDC-3. The reaction temperatures were set at 593–723 K and the pressures 3–10 atm. The effect of oxygen addition plays a vital role on the ethanol steam reforming reaction, especially for the Pd–Ag membrane reactor in which a higher flux of hydrogen is required. If oxygen in the feed is not sufficient, it would be possible that steam reforming reaction prevails. Inversely, high O₂ addition will shift the reaction scenario to be partial oxidation dominating, and selectivity of CO₂ increases with increasing oxygen feed. At high pressure, autothermal reaction of ethanol would be easily reached.     

Enumeration in Convex Geometries and Associated Polytopal Subdivisions of Spheres

We construct CW spheres from the lattices that arise as the closed sets of a convex closure, the meet-distributive lattices. These spheres are nearly polytopal, in the sense that their barycentric subdivisions are simplicial polytopes. The complete information on the numbers of faces and chains of faces in these spheres can be obtained from the defining lattices in a manner analogous to the relation between arrangements of hyperplanes and their underlying geometric intersection lattices.     

A dynamic approach to the Shapley value based on associated games

We propose a dynamic process leading to the Shapley value of TU games or any solution satisfying Inessential Game (IG) and Continuity (CONT), based on a modified version of Hamiache's notion of an associated game. The authors are very grateful to William Thomson and two anonymous referees for valuable comments which much improve the paper. They provide better statements and proofs of several major results than the original ones.     

Influence of non-reactive solvent on optical performance, photopolymerization kinetics and morphology of nanoporous polymer gratings

A study of nanoporous polymer gratings, with controllable nanostructured porosity, as a function of grating performance, photopolymerization kinetics and morphology is presented. Modifying the standard holographic polymer dispersed liquid crystal (H-PDLC) system, by including a non-reactive solvent, results in a layered, nanoporous morphology and produces reflective optical elements with excellent optical performance of broadband reflection. The addition of the non-reactive solvent in the pre-polymer mixture results in a morphology typified by void/polymer layer-by-layer structures if sufficient optical energy is used during the holographic writing process. The duration and intensity of optical exposure necessary to form well-aligned nanoporous structures can only be obtained in the modified system by (a) illumination under longer time of holographic interference patterning (30 min) or (b) illumination under very short time of holographic interference patterning (30 s) and followed by post-curing using homogeneous optical exposure for 60 min. Comparatively, a typical H-PDLC is formed in less than 1 min. To further understand the differences in the formation of these two analogous materials, the temporal dynamics of the photoinitiation and polymerization (propagation) kinetics were examined. It is shown herein that the writing exposure gives a cross-linked polymer network that is denser in the bright regions. With 60% (or even 45%) acrylate conversion, almost no free monomer would be left after the writing. Continued exposure serves primarily to add cross-links. This has the tendency to collapse the network, especially the less dense portions, which in effect get glued down to the more dense parts. To the extent that the solvent increases the mobility of the polymer network, this process will be aided. Equally important, the size of the periodic nanopores can be varied from 10 to 50 nm by controlling either the LC concentration in the pre-polymer mixture or by controlling the time of the homogeneous post-cure.     

High temperature characteristics of ZnO-based MOS-FETs with a photochemical vapor deposition SiO2 gate dielectric

The authors report the fabrication of ZnO-based metal-oxide-semiconductor field effect transistors (MOSFETs) with a high quality SiO₂ gate dielectric by photochemical vapor deposition (photo-CVD) on a sapphire substrate. Compared with ZnO-based metal-semiconductor FETs (MESFETs), it was found that the gate leakage current was decreased to more than two orders of magnitude by inserting the photo-CVD SiO₂ gate dielectric between ZnO and gate metal. Besides, it was also found that the fabricated ZnO MOSFETs can achieve normal operation of FET, even operated at 150 °C. This could be attributed to the high quality of photo-CVD SiO₂ layer. With a 2 μm gate length, the saturated I_ds and maximum transconductance (G_m) were 61.1 mA/mm and 10.2 mS/mm for ZnO-based MOSFETs measured at room temperature, while 45.7 mA/mm and 7.67 mS/mm for that measured at 150 °C, respectively.     

Numerical inversion of laplace transform via wavelet in partial differential equations

This article presents a rational Haar wavelet operational method for solving the inverse Laplace transform problem and improves inherent errors from irrational Haar wavelet. The approach is thus straightforward, rather simple and suitable for computer programming. We define that P is the operational matrix for integration of the orthogonal Haar wavelet. Simultaneously, simplify the formulae of listing table (Chen et al., Journal of The Franklin Institute 303 (1977), 267–284) to a minimum expression and obtain the optimal operation speed. The local property of Haar wavelet is fully applied to shorten the calculation process in the task. The operational method presented in this article owns the advantages of simpler computation as well as broad application. We still can obtain satisfying solution even under large matrix. Moreover, we do not have numerically unstable problems. © 2013 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 30: 536–549, 2014     

Predicting melting temperature directly from protein sequences

Proteins of both hyperthermophilic and mesophilic microorganisms generally constitute from the same 20 amino acids; however, the extent of thermal tolerance of any given protein is an inherent property of its amino acid sequence. The present study is the first to report a rapid method for predicting Tm (melting temperature), the temperature at which 50% of the protein is unfolded, directly from protein sequences (the Tm Index program is available at http://tm.life.nthu.edu.tw/). We examined 75 complete microbial genomes using the Tm Index, and the analysis clearly differentiated hyperthermophilic from mesophilic microorganisms on this global genomic basis. These results are consistent with the previous hypothesis that hyperthermophiles express a greater number of high Tm proteins compared with mesophiles. The Tm Index will be valuable for modifying existing proteins (enzymes, protein drugs and vaccines) or designing novel proteins having a desired melting temperature.