Morphological study of an intrinsically stretchable photovoltaic bulk heterojunction

Thin‐film polymer solar cell consisting of [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC₇₁BM) and poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl]] (PTB7) demonstrates elastic stretchability with the aid of a high boiling point additive, 1,8‐diiodooctane (DIO). The usage of DIO not only helps to form uniformly distributed nanocrystalline grains, but may also create free volumes between the nano‐grains that allow for relative sliding between the nano‐grains. The relative sliding can accommodate large external deformation. Large dichroic ratios of the optical absorption of both PC₇₁BM and PTB7 were observed under large‐strain deformation, indicating reorientation of the nanocrystalline PC₇₁BM and PTB7 polymer chains along stretching direction. The dichroic ratio decreases to nearly 1.0 as the blend was relaxed to 0% strain. Therefore, the nanometer‐size grain blending morphology provides an approach to impart stretchability to organic semiconductors that are otherwise un‐stretchable. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 814–820     

Chitosan/Ce(IV) redox polymerization‐based amplification for detection of DNA point mutation

Polymerization‐based signal amplification, a technique developed for use in rapid diagnostic tests, hinges on the ability to localize initiators as a function of interfacial binding events. We report here a new DNA detection method in which polymer growth in redox‐polymerization is used as a means to amplify detection signals. The introduction of biotin‐labeled chitosan (biotin‐CS) with highly dense amino groups into the polymerization amplification as macromolecular reducing agent, beneficially simplifies amplification operation, as well as, provides a large amount of initiation points to improve the sensitivity of detection. DNA hybridization, SA and biotin binding reactions led to the attachment of CS on a solid surface where specific DNA sequences were located. With the addition of the mixture containing monomer AM, crosslinker PEGDA and oxidant CAN onto the CS location, the growth of polymer films was triggered to render the corresponding spots readily distinguishable to the naked eye. Direct visualization of 0.21 fmol target DNA molecules of interest was demonstrated. Non‐small cell lung cancer p53 sequence was further selected as a proof‐of‐principle to detect DNA point mutation. The proposed method exhibited an efficient amplification performance for molecule detection, and paved a new way for visual diagnosis of biomolecules. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1929–1937     

The formation of dead zones in nonisothermal porous catalyst with temperature-dependent diffusion coefficient

This paper considers the formation of dead zones in the porous catalyst pellets due to the chemical reaction and diffusion. We established and investigated the model with nonisothermal reaction of fractional order and activated temperature-dependent diffusivity. The effects of process parameters, catalyst shape, and reaction and diffusion parameters on the formation of the dead zone are studied numerically and characterized by the critical Thiele modulus. The lower bounds for the critical Thiele modulus are derived analytically in terms of process parameters for exothermic and endothermic reactions and verified numerically. The critical Thiele modulus increases with increasing Arrhenius number for diffusion and decreasing Arrhenius number for reaction in the case of exothermic reactions, whereas the opposite trends hold for the endothermic reactions. The critical Thiele modulus also increases with increasing fractional reaction order as well as with decreasing energy generation function, and increasing Biot numbers for heat and mass transfer. Moreover, the critical Thiele modulus is the highest for spherical pellets and the lowest for pellets with planar shape.     

Chain transfer agents in cationic photopolymerization of a bis‐cycloaliphatic epoxide monomer: Kinetic and physical property effects

The effects of chain transfer agents (CTA) on cationic ring‐opening polymerization of 3,4‐epoxycyclohexylmethyl‐3′,4′‐epoxycyclohexane carboxylate (EEC) were explored. EEC was polymerized in the presence of various CTAs, and epoxide conversions monitored via Raman spectroscopy. Polymer films were prepared and analyzed by dynamic mechanical analysis. Many of the organic alcohols studied greatly enhanced epoxide polymerization rates and conversion levels. The gel fraction of polymer specimens decreased rapidly with increasing amounts of octanol (gel fraction >90% up to 0.3 equiv OH) but remained high with increasing amounts of 1,2‐propanediol (gel fraction >90% up to 0.6 equiv OH). Increasing the size of primary alcohols had little effect on the polymerization rates and conversions. The polymerization rate decreased with increasing alcohol substitution (1°>2°>3°). Acidic alcohols had very low impact on conversion and polymerization rates relative to the neat epoxy resin. The glass transition temperature was inversely related to the size and amount of CTA. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Elastic Organic Crystals Based on Barbituric Derivative: Multi-faceted Bending and Flexible Optical Waveguide

Elastic organic single crystals with light-emitting and multi-faceted bending properties are extremely rare. They have potential application in optical materials and have attracted the extensive attention of researchers. In this paper, we reported a structurally simple barbituric derivative DBDT , which was easily crystallized and gained long needle-like crystals (centimeter-scale) in DCM/CH₃OH (v/v=2/8). Upon applying or removing the mechanical force, both the (100) and (040) faces of the needle-like crystal showed reversible bending behaviour, showing the nature of multi-faceted bending. The average hardness (H) and elastic modulus (E) were 0.28±0.01 GPa and 4.56±0.03 GPa for the (040) plane, respectively. Through the analysis of the single crystal data, it could be seen that the van der waals (C−H⋅⋅⋅π and C−H⋅⋅⋅C), H-bond (C−H⋅⋅⋅O) and π⋅⋅⋅π interactions between molecules were responsible for the generation of the crystal elasticity. Interestingly, elastic crystals exhibited optical waveguide characteristics in straight or bent state. The optical loss coefficients measured at 627 nm were 0.7 dBmm⁻¹ (straight state) and 0.9 dBmm⁻¹ (bent state), while the optical loss coefficient (α) were 1.5 dBmm⁻¹ (straight state) and 1.8 dBmm⁻¹ (bent state) at 567 nm. Notably, the elastic organic molecular crystal based on barbituric derivative could be used as the candidate for flexible optical devices.     

Treatment by serum up-conversion nanoparticles in the fluoride matrix changes the mechanism of cell death and the elasticity of the membrane

Nanoparticles are increasingly being used for treatment and diagnostic purposes, but their effects on cells is not fully understood. Here, the interaction of fluorescent up-conversion nanoparticles (UpC-NPs) with neutrophils was investigated by imaging and measurement of membrane-cytosceletal elasticity by atomic force microscopy. It was found that UpC-NPs induce the death of neutrophils mainly by necrosis, and to a smaller extent by a novel process called ‘mummification'. Necrosis occurs by gradual loss of intracellular contents and nuclei, 45–110 min after exposure to UpC-NPs. Mummification is apparent as an increase in the rigidity of the neutrophils' membrane and acquisition of a characteristic bumpy shape with numerous protrusions; this structure does not change during atomic force microscopy scanning. Coating UpC-NPs with protein by incubation with serum leads to (1) formation of nanoparticle aggregates in the nm and μm size range, (2) a reduction in toxicity, (3) reduced mummification of neutrophils, and (4) no significant reduction of the elasticity of the membrane-cytoskeletal complex of neutrophils 30 min after exposure to coated UpC-NPs. The study shows that serum proteins greatly curb the toxicity of nanoparticles and reveals mummification as a novel mechanism of UpC-NP-induced cell death.     

Approximation by walsh-kaczmarz-fejér means on the hardy space

The main aim of this paper is to find necessary and sufficient conditions for the convergence of Walsh-Kaczmarz-Fejér means in the terms of the modulus of continuity on the Hardy spaces H_p, when 0<p≤ 1/2.     

Quantitation of memantine hydrochloride bulk drug and its tablet formulation using proton nuclear magnetic resonance spectrometry

The use of quantitative nuclear magnetic resonance spectrometry for the determination of non‐UV active memantine hydrochloride with relative simplicity and precision has been demonstrated in this study. The method was developed on a 500 MHz NMR instrument and was applied to determination of the drug in a tablet formulation. The analysis was performed by taking caffeine as an internal standard and D₂O as the NMR solvent. The signal of methyl protons of memantine hydrochloride appeared at 0.75 ppm (singlet) relative to the signal of caffeine (internal standard) at 3.13 ppm (singlet). The method was found to be linear (r² = 0.9989) in the drug concentration range of 0.025 to 0.80 mg/ml. The maximum relative standard deviation for accuracy and precision was <2. The limits of detection and quantification were 0.04 and 0.11 mg/ml, respectively. The robustness of the method was revealed by changing nine different parameters. The deviation for each parameter was also within the acceptable limits. The study highlighted possibility of direct determination of memantine hydrochloride in pure form and in its marketed tablet formulation by the use of quantitative NMR, without the need of derivatization, as is the requirement in HPLC studies. Copyright © 2016 John Wiley & Sons, Ltd.     

On an Inequality of Pual Turan Concerning Polynomials-Ⅱ

Let P(z) be a polynomial of degree n and for any complex number α, let D_αP(z) = nP(z)+(α- z) P′(z) denote the polar derivative of the polynomial P(z) with respect to α. In this paper, we obtain inequalities for the polar derivative of a polynomial having all zeros inside a circle. Our results shall generalize and sharpen some well-known results of Turan, Govil, Dewan et al. and others.     

The construction and approximation of feedforward neural network with hyp erb olic tangent function

In this paper, we discuss some analytic properties of hyperbolic tangent function and estimate some approximation errors of neural network operators with the hyperbolic tangent activation functionFirstly, an equation of partitions of unity for the hyperbolic tangent function is givenThen, two kinds of quasi-interpolation type neural network operators are constructed to approximate univariate and bivariate functions, respectivelyAlso, the errors of the approximation are estimated by means of the modulus of continuity of functionMoreover, for approximated functions with high order derivatives, the approximation errors of the constructed operators are estimated.