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Protecting Effect (protecting + effect)
Selected AbstractsHigh-Performance All-Polymer White-Light-Emitting Diodes Using Polyfluorene Containing Phosphonate Groups as an Efficient Electron-Injection LayerADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Baohua Zhang Abstract We report an efficient non-doped all-polymer polymer white-light-emitting diode (PWLED) with a fluorescent three-color, white single polymer as an emissive layer, an ethanol-soluble phosphonate-functionalized polyfluorene (PF-EP) as an electron-injection/electron-transport layer, and LiF/Al as a cathode, respectively. The all-polymer PWLED achieves a peak external quantum efficiency of 6.7%, a forward viewing luminous efficiency of 15.4 cd A,1 and a power efficiency of 11.4 lm W,1, respectively, at a brightness of 347 cd m,2 with Commission Internationale d'Eclairage coordinates of (0.37, 0.42) and color rendering index of 85, which is the best results among the non-doped PWLEDs. Moreover, this kind of PWLED not only shows excellent color stability, but also achieves high brightness at low voltages. The brightness reaches 1000, 10000, and 46830 cd m,2 at voltages of 4.5, 5.4, and 7.5 V, respectively. The significant enhancement of white-single-polymer-based PWLEDs with PF-EP/LiF/Al to replace for the commonly used Ca/Al cathode is attributed to the more efficient electron injection at PF-EP/LiF/Al interfaces, and the coordinated protecting effect of PF-EP from diffusion of Al atoms into the emissive layer and exciton-quenching near cathode interfaces. The developed highly efficient non-doped all-polymer PWLEDs are well suitable for solution-processing technology and provide a huge potential of low-cost large-area manufacturing for PWLEDs. [source] Importance of soil surface characteristics on water erosion in a small grazed Sahelian catchmentHYDROLOGICAL PROCESSES, Issue 8 2003H. Karambiri Abstract This study concerns the problem of water erosion in the Sahel. Surface water and sediment yields (suspended matter and bedload) were monitored for 3 years (1998,2000) at the outlet of a small grazed catchment (1·4 ha) in the northern part of Burkina Faso. The catchment consists of about 64% sandy deposits (DRY soil surface type), which support most of the vegetation, and about 34% of crusted bare soils (ERO soil surface type). The annual solid-matter export is more than 90% suspended sediment, varying between 4·0 and 8·4 t ha,1. The bedload represents less than 10% of soil losses. In a single flood event (10 year return period), the sediment yield can reach 4·2 t ha,1. During the period studied, a small proportion (20 to 32%) of the floods was thus responsible for a large proportion (80%) of the solid transport. Seasonal variation of the suspended-matter content was also observed: high mean values (9 g l,1) in June, decreasing in July and stabilizing in August (between 2 and 4 g l,1). This behaviour may be a consequence of a reorganization of the soil surfaces that have been destroyed by trampling animals during the previous long dry season, vegetation growth (increase in the protecting effect of the herbaceous cover) and, to a lesser extent, particle-supply limitation (exhaustion of dust deposits during July). The particle-size distribution in the suspended matter collected at the catchment outlet is 60% made up of clay: fraction ,2 µ m. The contribution of this clay is maximum when the water rises and its kaolinite/quartz ratio is then close to that of the ERO-type surfaces. This indicates that these surfaces are the main source of clay within the catchment. Copyright © 2003 John Wiley & Sons, Ltd. [source] Comparative study of the hydrolytic degradation of glycolide/L -lactide/,-caprolactone terpolymers initiated by zirconium(IV) acetylacetonate or stannous octoateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Janusz Kasperczyk Abstract A series of copolymers have been synthesized by the ring-opening polymerization of glycolide, L -lactide, and ,-caprolactone with zirconium(IV) acetylacetonate [Zr(Acac)4] or stannous octoate [Sn(Oct)2] as the catalyst. The resulting terpolymers have been characterized by analytical techniques such as proton nuclear magnetic resonance, size exclusion chromatography, and differential scanning calorimetry. Data have confirmed that Sn(Oct)2 leads to less transesterification of polymer chains than Zr(Acac)4 under similar conditions. The various copolymers have been compression-molded and allowed to degrade in a pH 7.4 phosphate buffer at 37°C. The results show that the degradation rate depends not only on the copolymer composition but also on the chain microstructure, the Sn(Oct)2 -initiated copolymers degrading less rapidly than Zr(Acac)4 -initiated ones with more random chain structures. The caproyl component appears the most resistant to degradation as its content increases in almost all cases. Moreover, caproyl units exhibit a protecting effect on neighboring lactyl or glycolyl units. The glycolyl content exhibits different features: it decreases because of faster degradation of glycolyl units, which are more hydrophilic than caproyl and lactyl ones, remains stable in the case of abundant CGC sequences, which are very resistant to degradation, or even increases because of the formation of polyglycolide crystallites. Terpolymers can crystallize during degradation if the block length of one of the components is sufficiently long, even though they are amorphous initially. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Effect of dimethyl-,-cyclodextrin concentrations on the pulmonary delivery of recombinant human growth hormone dry powder in ratsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2008Monireh Jalalipour Abstract The aim of this article is to prepare and characterize inhalable dry powders of recombinant human growth hormone (rhGH), and assess their efficacy for systemic delivery of the protein in rats. The powders were prepared by spray drying using dimethyl-,-cyclodextrin (DM,CD) at different molar ratios in the initial feeds. Size exclusive chromatography was performed in order to determine protecting effect of DM,CD on the rhGH aggregation during spray drying. By increasing the concentration of DM,CD, rhGH aggregation was decreased from 9.67 (in the absence of DM,CD) to 0.84% (using DM,CD at 1000 molar ratio in the spray solution). The aerosol performance of the spray dried (SD) powders was evaluated using Andersen cascade impactor. Fine particle fraction values of 53.49%, 33.40%, and 23.23% were obtained using DM,CD at 10, 100, and 1000 molar ratio, respectively. In vivo studies showed the absolute bioavailability of 25.38%, 76.52%, and 63.97% after intratracheal insufflation of the powders produced after spray drying of the solutions containing DM,CD at 10, 100, and 1000 molar ratio, respectively in rat. In conclusion, appropriate cyclodextrin concentration was achieved considering the protein aggregation and aerosol performance of the SD powders and the systemic absorption following administration through the rat lung. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:5176,5185, 2008 [source] Improvement of light fastness of natural dyes.COLORATION TECHNOLOGY, Issue 5 2001Part 2: Effect of functional phenyl esters on the photofading of carthamin in polymeric substrate The photofading behaviour of carthamin in cellulose acetate film was investigated. A contribution from singlet oxygen to that fading was suggested. Phenyl esters containing nickel sulphonate quenching groups were prepared and the protecting effect of these compounds towards the photofading of carthamin was examined in cellulose acetate film. It is proposed that nickel sulphonate derivatives of phenyl esters can be applied as effective stabilisers against the fading of natural dyes. [source] | |||||||||||||