Photophysics,electrochemical properties,and electroluminescence of poly(p‐phenylenevinylene) derivatives with 1,3,5‐triphenylbenzene or 2,4,6‐triphenylpyridine segments along the backbone

The steady‐state and time‐resolved photoluminescence (PL), electrochemical behavior, and electroluminescence (EL) of didodecyloxy poly(p‐phenylenevinylene)‐based polymers that contained along the backbone structure 1,3,5‐triphenylbenzene (PC) or 2,4,6‐triphenylpyridine (PN) were studied. An intensive green PL broad‐band emission with maxima at 516 and 527 nm was observed from thin films of PC and PN polymers, respectively, redshifted in comparison with the PL emission spectra measured in tetrahydrofuran solutions. The PL decay dynamics revealed the existence of more than one excited species, and the decay curves were best described by three‐term exponential functions with a dominant lifetime of about 1 ns. The results of time‐resolved PL and steady‐state PL studies indicated excimer or aggregate formation. Both polymers oxidized irreversibly. A quasireversible reduction was observed in the PN polymer, whereas the PC polymer reduced irreversibly. For PC, slightly higher values of the ionization potential (E_IP) and electron affinity (E_A) were found (E_IP = 5.52 eV, E_A = 2.85 eV) than those for PN (E_IP = 5.37 eV, E_A = 2.77 eV). Light‐emitting devices with indium tin oxide hole‐injecting and aluminum electron‐injecting electrodes were prepared and studied. They emitted green light, and their EL spectra were similar to those of PL thin films. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 524–533, 2006     

On the Identification and Quantification of Ergothioneine and Lovastatin in Various Mushroom Species: Assets and Challenges of Different Analytical Approaches

In recent years, mushrooms have drawn the attention of agro-industries and food-industries as they were considered to be valuable natural sources of health promoting compounds such as β-glucans, ergothioneine, and lovastatin. The detection and quantification of such compounds by implementing reliable analytical approaches is of the utmost importance in order to adjust mushrooms’ cultivation conditions and maximize the production in different species. Toward this direction, the current study focuses on the comparison of ultraviolet–visible (UV–Vis) spectrometry and liquid chromatography–mass spectrometry (LC–MS) methods (a) by evaluating the content of ergothioneine and lovastatin in mushrooms and (b) by highlighting any possible substrate-based interferences that hinder the accurate determination of these two compounds in order to propose the technique-of-choice for a standardized bioactive compounds monitoring. For this purpose, mushrooms produced by three species (i.e., Agaricus bisporus, Pleurotus ostreatus, and P. citrinopileatus) on various cultivation substrates, namely wheat straw (WS), winery (grape marc (GM)), and olive oil (OL) by-products, were examined. Among the two applied techniques, the developed and validated LC–MS methods, exhibiting relatively short analysis time and higher resolution, emerge as the methods-of-choice for detecting ergothioneine and lovastatin in mushrooms. On the contrary, UV–Vis methods were hindered due to co-absorbance of different constituents, resulting in invalid results. Among the studied mushrooms, P. citrinopileatus contained the highest amount of ergothioneine (822.1 ± 20.6 mg kg⁻¹ dry sample), whereas A. bisporus contained the highest amounts of lovastatin (1.39 ± 0.014 mg kg⁻¹ dry sample). Regarding the effect of different cultivation substrates, mushrooms produced on OL and WS contained the highest amount of ergothioneine, while mushrooms deriving from GM-based substrates contained the highest amount of lovastatin.     

A General Method for Obtaining Degenerate Solutions to the Dirac and Weyl Equations and a Discussion on the Experimental Detection of Degenerate States

In this work, a general method is described for obtaining degenerate solutions of the Dirac equation, corresponding to an infinite number of electromagnetic 4-potentials and fields, which are explicitly calculated. More specifically, using four arbitrary real functions, one can automatically construct a spinor that satisfies the Dirac equation for an infinite number of electromagnetic 4-potentials, defined by those functions. An interesting characteristic of these solutions is that, in the case of Dirac particles with nonzero mass, the degenerate spinors should be localized, both in space and time. The method is also extended to the cases of massless Dirac and Weyl particles, where the localization of the spinors is no longer required. Finally, two experimental methods are proposed for detecting the presence of degenerate states.     

Symmetry groups and similarity solutions for a free convective boundary-layer problem

The free convective boundary-layer problem due to the motion of an elastic surface into an electrically conducting fluid is studied with group-theoretical methods. The symmetry groups admitted by the corresponding boundary value problem are obtained. Particular attention is paid on the group of scaling which provides the similarity solution of the problem. Also, the admissible form of the data, in order to be conformed to the obtained symmetries, is provided. Finally, with the use of the entailed similarity solution the problem is transformed into a boundary value problem of ODEs and is solved numerically.     

Efficient spectral and pseudospectral algorithms for 3D simulations of whistler-mode waves in a plasma

Efficient spectral and pseudospectral algorithms for simulation of linear and nonlinear 3D whistler waves in a cold electron plasma are developed. These algorithms are applied to the simulation of whistler waves generated by loop antennas and spheromak-like stationary waves of considerable amplitude. The algorithms are linearly stable and show good stability properties for computations of nonlinear waves over tens of thousands of time steps. Additional speedups by factors of 10–20 (comparing single core CPU and one GPU) are achieved by using graphics processors (GPUs), which enable efficient numerical simulation of the wave propagation on relatively high resolution meshes (tens of millions nodes) in personal computing environment. Comparisons of the numerical results with analytical solutions and experiments show good agreement. The limitations of the codes and the performance of the GPU computing are discussed.     

Carbon nanotubes decorated with terpyridine‐ruthenium complexes

Surface functionalization of CNTs (SWCNTs or MWCNTs) with dendronized alkoxy terpyridine‐Ru(II)‐terpyridine complexes has been accomplished using either the “grafting to” or the “grafting from” approaches. Different sets of easily processable hybrid metallo‐CNTs composites have been efficiently synthesized bearing either monomeric or polymeric side chain tpy‐Ru(II)‐tpy dicomplexes. Their characterization through TGA, UV‐Vis, and Raman techniques revealed various modification degrees depending on the methodology employed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2551–2559, 2009     

Modified polyisophthalamides bearing pendent benzoylamino and/or (phenylamino)carbonyl groups

A series of modified polyisophthalamides were prepared from 5-(phenylamino)carbonyl-1,3-phenylenediamine and 5-benzoylamino-isophthalic acid. The polymers were characterized by FT-IR, ¹H-NMR, inherent viscosity, water absorption measurements, x-ray, DTA, TGA, and isothermal gravimetric analysis. The modified polyamides were amorphous and softened at 210–245°C. They showed higher hydrophilicity and better solubility in certain solvents such as DMF, DMSO, CCl₃COOH, cyclohexanone, and m-cresol than the corresponding unmodified polyamide. They started to lose weight at 329–344°C in N₂ or air, whereas the degradation of unmodified polyamide started at 320°C in N₂ and 308°C in air. © 1996 John Wiley & Sons, Inc.     

Statistical copolymers of norbornene and 5‐vinyl‐2‐norbornene by a ditungsten complex mediated ring‐opening metathesis Polymerization: Synthesis,thermal properties,and kinetics of thermal decomposition

Statistical copolymers of norbornene (NBE) with 5‐vinyl‐2‐norbornene (VNBE) were prepared by ring‐opening metathesis polymerization, employing the triply bonded ditungsten complex Na[W₂(μ‐Cl)₃Cl₄(THF)₂].(THF)₃. NMR measurements revealed that the side vinyl groups of the VNBE monomer remain intact during the copolymerization reaction. The reactivity ratios were estimated using the Finemann–Ross (FR), the inverted FR, and the Kelen–Tüdos graphical methods. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions, which were derived using the monomer reactivity ratios. The glass transition temperatures, T_g, of the copolymers were measured by differential scanning calorimetry measurements and were examined in the frame of several theoretical equations allowing the prediction of these T_g values. The best fit was obtained using methods that take into account the monomer sequence distribution of the copolymers. Finally, the kinetics of the thermal decomposition of the copolymers was studied by thermogravimetric analysis in the frame of the Ozawa–Flynn–Wall and Kissinger methods. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4835–4844