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In this paper, we introduce a class of predator-prey system with general functional response, whose harvesting policy is modeled by a discontinuous function. Based on the differential inclusions theory, topological degree theory in set-valued analysis and generalized Lyapunov approach, we analyze the existence, uniqueness and global asymptotic stability of positive periodic solution. In particular, a series of useful criteria on existence, uniqueness and global asymptotic stability of the positive equilibrium point are established for the autonomous system corresponding to the non-autonomous biological and mathematical model with a discontinuous right-hand side. Moreover, some new sufficient conditions are provided to guarantee the global convergence in measure of harvesting solution and convergence in finite time of any positive solution for the autonomous discontinuous biological system. The obtained results, which improve and generalize previous works on dynamical behavior in the literature, are of interest for understanding and designing biological system with not only continuous or even Lipschitz continuous but also discontinuous harvesting function. Finally, we give three examples with numerical simulations to show the applicability and effectiveness of our main results. [ABSTRACT FROM AUTHOR]

Abstract: To gain ideal conjugated polymers with a low band-gap (E g) and a deep HOMO (highest occupied molecular orbital) energy level for photovoltaic application, both strong and weak electron withdrawing units were introduced into polymer backbone. A series of –(D–A1–D–A2) n – type diketopyrrolopyrrole (DPP) containing polymers P1–P7 were designed and synthesized. The resulting copolymers exhibited both low E g of 1.27–1.48 eV and deep HOMO energy levels of −5.25to −5.44 eV. Preliminary photovoltaic properties of the copolymers blended with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) were investigated. All photovoltaic devices featured high open circuit voltages (V oc, 0.72–0.91 V). Among the seven copolymers, P5 exhibited the best performance with a V oc of 0.80 V, a short circuit current density (I sc) of 3.48 mA/cm2, a fill factor (FF) of 43.2%, and a power conversion efficiency (PCE) of 1.33%. [Copyright &y& Elsevier]

Conjugated polymers having good electrochemical and thermal stability are highly desired in optoelectronics. We report a new polythiophene consisting of alternating 4,4′-didodecyl-2,2′-bithiophene and terthiophene units (HPL1) synthesized via Stille coupling reaction. The optical band gap of HPL1 (1.92 eV) is similar to that of regioregular poly(3-hexylthiophene) (rr-P3HT, 1.89 eV). In comparison to rr-P3HT, the HPL1 when subjected to the cyclic voltammetry as thin film shows much superior electrochemical stability and a lower highest occupied molecular orbital energy level (−4.87 eV for rr-P3HT and −4.95 eV for HPL1). The transient photoluminescence study of HPL1 and rr-P3HT shows that both materials have two exciton decay processes, and the excitons of rr-P3HT are quenched more quickly. The onset decomposition, Td for rr-P3HT (465°C) is 4°C lower than HPL1 (469°C). Preliminary photovoltaic study disclosed that the polymer solar cell based on HPL1:[6,6]-phenyl-C61-butyric acid methyl ester blend showed a power conversion efficiency of 0.63%, with a Voc of 0.6 V, and a short circuit current ( Jsc) of 2.79 mA cm−2 under AM 1.5 illumination (100 mW cm−2). The whole study provided an important example to design new electrochemically and thermally stable polymers with longer exciton life time for application in bulk heterojunction polymer solar cells. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012 [ABSTRACT FROM AUTHOR]

We developed a film-forming processing method for morphology control and organic solar cells (OSCs) optimization. In this protocol, the processing solvent inside a wet active layer is removed by dripping a soaking solvent that is selectively soluble for the processing solvents onto the wet active layer film. By this method, OSCs based on diketopyrrolopyrrole containing copolymers: [6,6]-phenyl-C61-butyric acid methyl ester blend were fabricated. Devices processed by this treatment show a significantly increased efficiency by a factor of 3 compared to devices fabricated by the traditional spin-coating method (from 1.03% to 3.2%), which is mainly attributed to morphology improvements. [ABSTRACT FROM AUTHOR]

Abstract: A series of conjugated polymers were designed and synthesized via the alternating copolymerization of the electron-donating monomer 2,7-carbazole and electron-accepting monomers of naphthalene diimide (NDI), dithienyl-naphthalene diimide (DTNDI), perylene diimide (PDI) and dithienyl-perylene diimide (DTPDI), respectively. The obtained four copolymers showed good thermal stability as well as broad absorptions in visible region and narrow optical band gaps (1.86–1.59eV). Through cyclic voltammetry (CV) measuremnts, it was found that all copolymers were n-type semiconductive materials. The copolymers'' photovoltaic properties were evaluated when the blends of poly(3-hexyl thiophene) (P3HT) and copolymers were used as the active layers of polymer solar cells (PSCs): among four copolymers, the copolymer alternating 2,7-carbazole and DTPDI units (PCDTPDI) exhibited the best photovoltaic performance with an open-circuit voltage (V oc) of 0.48V, a short circuit current density (J sc ) of 3.40mA/cm2, fill factor (FF) of 0.42, and a power conversion efficiency (PCE) of 0.68%. [Copyright &y& Elsevier]

A simple epoxidation of E-2-(arylmethylidene)-2,3-dihydro-1H-pyrrolizin-1-ones was accomplished using cyclohexylidenebishydroperoxide as the oxygen source. A number of 3-arylspiro[oxirane-2,2'-pyrrolizin]-1'(3'H)-ones were obtained in moderate to good yields. [ABSTRACT FROM AUTHOR]

The interaction between novel spiro[cyclopropane-pyrrolizin] (NSCP) and bovine serum albumin (BSA) was analyzed by fluorescence and ultraviolet–visible (UV–Vis) spectroscopy at 298 K, 304 K and 310 K under simulative physiological conditions. The results showed that NSCP can effectively quench the intrinsic fluorescence of BSA via static quenching. The binding constants, binding sites of NSCP with BSA were calculated. Hydrogen binds and van der Waals force played a major role in stabilizing the complex and the binding reaction were spontaneous. According to the Förster non-radiation energy transfer theory, the average binding distances between NSCP and BSA were obtained. What is more, the synchronous fluorescence spectra indicated that the conformation of BSA has been changed. [ABSTRACT FROM AUTHOR]

In this study, laboratory experiments were conducted to compare the efficacy of several H2O2-based advanced oxidation processes (AOPs): UV-Fenton, UV-H2O2, and Fenton reagent, to treat landfill leachate with the objective of removing COD and improving the leachate's overall biodegradability (evaluated in terms of BOD5/COD ratio). The results indicated that, at optimized experimental conditions of 25 degrees C, pH 4.0, 4000 mg L(-1) H2O2, 30 mg L(-1) Fe(II) (for UV-Fenton and Fenton) and 60 min reaction time, the UV-Fenton system showed the highest COD removal. The COD removal rate in the H2O2-based AOPs was strongly dependent on the concentration of H2O2 and the pH value. Temperature had little effect on overall COD removal rate in the Fenton and Fenton-like systems. All three systems would result in a significant increase in the ratio of BOD5/COD, from 0.17 to about 0.60, at the applied H2O2 dosage of 4000 mg L(-1). The increase in biodegradability of the AOP leachate indicates that these AOPs would be beneficial for the subsequent biological treatment process. The UV-Fenton process was found to be the most effective approach of these H2O2-based AOPs to enhance the biodegradability and eliminate the colour of the leachate.