New copolymers with thieno[3,2‐b]thiophene or dithieno[3,2‐b:2′,3′‐d]thiophene units possessing electron‐withdrawing 4‐cyanophenyl groups: Synthesis and photophysical,electrochemical, and electroluminescent properties

New monomers containing 4‐cyanophenyl (–PhCN) groups attached to a thieno[3,2‐b]thiophene (TT) or dithieno[3,2‐b:2′,3′‐d]thiophene (DTT) structure were synthesized and characterized as 4‐(2,5‐dibromothieno[3,2‐b]thiophen‐3‐yl)benzonitrile (Br–TT–PhCN) or 4,4′‐(2,6‐dibromodithieno[3,2‐b:2′,3′‐d]thiophene‐3,5‐diyl)dibenzonitrile (Br–DTT–PhCN). The Suzuki coupling of 9,9‐dioctylfluorene‐2,7‐diboronic acid bis(1,3‐propanediol)ester and the Br–TT–PhCN or Br–DTT–PhCN monomer was utilized for the syntheses of novel copolymers poly{9,9‐dioctylfluorene‐2,7‐diyl‐alt‐3‐(4′‐cyanophenyl)thieno[3,2‐b]thiophene‐2,5‐diyl} (PFTT–PhCN) and poly{9,9‐dioctylfluorene‐2,7‐diyl‐alt‐3,5‐bis(4′‐cyanophenyl)dithieno[3,2‐b:2′,3′‐d]thiophene‐2,6‐diyl} (PFDTT–PhCN), respectively. The photophysical, electrochemical, and electroluminescent (EL) properties of these novel copolymers were studied. Their photoluminescence (PL) exhibited the same emission maximum for both copolymers in solution. Red‐shifted PL emissions were observed in the thin films. The PL emission maximum of PFTT–PhCN was more significantly redshifted than that of PFDTT–PhCN, indicating more pronounced excimer or aggregate formation in PFTT–PhCN. The ionization potential (HOMO level) and electron affinity (LUMO level) values were 5.54 and 2.81 eV, respectively, for PFTT–PhCN and were 5.57 and 2.92 eV, respectively, for PFDTT–PhCN. Polymer light‐emitting diodes (LEDs) with copolymer active layers were fabricated and studied. Anomalous behavior and memory effects were observed from the current–voltage characteristics of the LEDs for both copolymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2629–2638     

Catalysis and reaction mechanisms of N-formylation of amines using Fe(III)-exchanged sepiolite

This study presents a rapid, economical and “green” N-formylation of anilines with formic acid (FA) using Fe(III)-exchanged sepiolite (IES) as a catalyst. The IES exhibited excellent catalytic properties and the reactions were complete within 20.90 min to afford products with high yields. The adsorption mechanism of FA on the IES sample was studied by infrared (IR) spectroscopy at a temperature range of 120–400°C. The thermal desorption of pyridine was detected by the IR technique to estimate the acidity of IES. Lewis acid-bound pyridine bands at 1618–1631 cm^-1 and 1443–1445 cm^-1 were observed even after the IES sample was heated above 400°C.     

An EPR study on cytosine irradiated

In this study, paramagnetic centers over the cytosine were formed by photolysis then these centers were investigated using EPR method. EPR signals were not recorded from non‐irradiated the cytosine, but irradiated polycrystalline exhibited complex EPR spectra. For obtaining of cytosine polycrystalline, novel crystallization method was performed on powder cytosine. Effective crystallization conditions were achieved by adjustment of the concentration of the metal ions, chemical solutions, NaCl, KCl, glacial asetic acid, nitric oxide, percloric acid, glutamic acid, and pH of buffer. Cytosine (C₄H₅N₂O) polycrystalline obtained were irradiated with ⁶⁰Co – rays at room temperature for 24 and 72 h. At the sample irradiated for 72 h, the paramagnetic centers were determined between 120 and 450 K by X‐band EPR spectrometer. The spectra were found to be dependent slightly on temperature. Two cation radicals were determined in the structure and these were called Radicals I and II. The g and hyperfine constants were found to be a_H2a = 61 G, a_N2 = 9.39 G, a_N1 = 7.15 G, and g₁=2.0026 for the Radical I; a_H3 = 10.57 G, a_H1 = 3 G, a_N3 = 6.72 G, a_N1 = 5.36 G for, and g₂=2.0034 the Radical II. Copyright © 2010 John Wiley & Sons, Ltd.     

A Comparative Study of Receptor-Targeted Magnetosome and HSA-Coated Iron Oxide Nanoparticles as MRI Contrast-Enhancing Agent in Animal Cancer Model

Magnetosomes are specialized organelles arranged in intracellular chains in magnetotactic bacteria. The superparamagnetic property of these magnetite crystals provides potential applications as contrast-enhancing agents for magnetic resonance imaging. In this study, we compared two different nanoparticles that are bacterial magnetosome and HSA-coated iron oxide nanoparticles for targeting breast cancer. Both magnetosomes and HSA-coated iron oxide nanoparticles were chemically conjugated to fluorescent-labeled anti-EGFR antibodies. Antibody-conjugated nanoparticles were able to bind the MDA-MB-231 cell line, as assessed by flow cytometry. To compare the cytotoxic effect of nanoparticles, MTT assay was used, and according to the results, HSA-coated iron oxide nanoparticles were less cytotoxic to breast cancer cells than magnetosomes. Magnetosomes were bound with higher rate to breast cancer cells than HSA-coated iron oxide nanoparticles. While 250 μg/ml of magnetosomes was bound 92 ± 0.2%, 250 μg/ml of HSA-coated iron oxide nanoparticles was bound with a rate of 65 ± 5%. In vivo efficiencies of these nanoparticles on breast cancer generated in nude mice were assessed by MRI imaging. Anti-EGFR-modified nanoparticles provide higher resolution images than unmodified nanoparticles. Also, magnetosome with anti-EGFR produced darker image of the tumor tissue in T2-weighted MRI than HSA-coated iron oxide nanoparticles with anti-EGFR. In vivo MR imaging in a mouse breast cancer model shows effective intratumoral distribution of both nanoparticles in the tumor tissue. However, magnetosome demonstrated higher distribution than HSA-coated iron oxide nanoparticles according to fluorescence microscopy evaluation. According to the results of in vitro and in vivo study results, magnetosomes are promising for targeting and therapy applications of the breast cancer cells.     

Modeling of particle–resin suspension impregnation in compression resin transfer molding of particle-filled,continuous fiber reinforced composites

A particle–resin suspension impregnation model is used for analyzing the mold filling process in compression resin transfer molding (CRTM) of particle-filled, continuous fiber composites. The model is based on Darcy flow coupled with particle filtration and is applicable to two-dimensional impregnation through isotropic/anisotropic fiber preforms. Comparisons with simple analytical solutions and experimental results from the literature were made to validate the numerical solution. Simulations showed that CRTM was advantageous over resin transfer molding (RTM) for smaller non-homogeneity in composite microstructure, when particle filtration was high. Limits on certain process parameters were observed beyond which molding pressures in CRTM became comparable with those in RTM. The preform anisotropy was effective in the particle distribution profile. The choice of inlet gate configuration in CRTM was found influential in the particle distribution homogeneity and molding pressures. The developed modeling tool can be extended to analyze any composite liquid molding process involving particle fillers.     

5-Benzyl-5-phenyl­[1,3]­di­thiolo­[4,5-d][1,3]­di­thiole-2-thione

In the title compound, C₁₇H₁₂S₅, the di­thiole ring bearing the aryl substituents assumes an envelope conformation with the maximum deviation from planarity being −0.053 Å. The phenyl and benzyl rings are twisted by 33.0 (1) and 31.1 (1)°, respectively, out of the di­thiole plane. The crystal packing is governed by short S⃛S interactions, with the shortest being 3.550 (2) Å.     

A numerically efficient method for the MAP/D/1/K queue via rational approximations

The Markovian Arrival Process (MAP), which contains the Markov Modulated Poisson Process (MMPP) and the Phase-Type (PH) renewal processes as special cases, is a convenient traffic model for use in the performance analysis of Asynchronous Transfer Mode (ATM) networks. In ATM networks, packets are of fixed length and the buffering memory in switching nodes is limited to a finite numberK of cells. These motivate us to study the MAP/D/1/K queue. We present an algorithm to compute the stationary virtual waiting time distribution for the MAP/D/1/K queue via rational approximations for the deterministic service time distribution in transform domain. These approximations include the well-known Erlang distributions and the Padé approximations that we propose. Using these approximations, the solution for the queueing system is shown to reduce to the solution of a linear differential equation with suitable boundary conditions. The proposed algorithm has a computational complexity independent of the queue storage capacityK. We show through numerical examples that, the idea of using Padé approximations for the MAP/D/1/K queue can yield very high accuracy with tractable computational load even in the case of large queue capacities.This work was done when the author was with the Bilkent University, Ankara, Turkey and the research was supported by TÜBITAK under Grant No. EEEAG-93.     

Fixed point theorems in new generalized metric spaces

The aim of our paper is to present new fixed point theorems under very general contractive conditions in generalized metric spaces which were recently introduced by Jleli and Samet in [Fixed Point Theory Appl. 2015 (2015), doi: 10.1186/s13663-015-0312-7]. Although these spaces are not endowed with a triangle inequality, these spaces extend some well known abstract metric spaces (for example, b-metric spaces, Hitzler–Seda metric spaces, modular spaces with the Fatou property, etc.). We handle several types of contractive conditions. The main theorems we present involve a reflexive and transitive binary relation that is not necessarily a partial order. We give a counterexample to a recent fixed point result of Jleli and Samet. Our results extend and unify recent results in the context of partially ordered abstract metric spaces.     

A note on “Some results on multi-valued weakly Jungck mappings in b-metric space”

The proofs of Theorems 2.1, 2.2 and 2.3 from [Olatinwo M.O., Some results on multi-valued weakly jungck mappings in b-metric space, Cent. Eur. J. Math., 2008, 6(4), 610–621] base on faulty evaluations. We give here correct but weaker versions of these theorems.