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71.
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A Durable Alternative for Proton‐Exchange Membranes: Sulfonated Poly(Benzoxazole Thioether Sulfone)s
Dan Zhao Jinhuan Li Min‐Kyu Song Baolian Yi Huamin Zhang Meilin Liu 《Liver Transplantation》2011,1(2):203-211
To develop a durable proton‐exchange membrane (PEM) for fuel‐cell applications, a series of sulfonated poly(benzoxazole thioether sulfone)s ( SPTESBOs) are designed and synthesized, with anticipated good dimensional stability (via acid–base cross linking), improved oxidative stability against free radicals (via incorporation of thioether groups), and enhanced inherent stability (via elimination of unstable end groups) of the backbone. The structures and the degree of sulfonation of the copolymers are characterized using Fourier‐transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy (1H NMR and 19F NMR). The electrochemical stabilities of the monomers are examined using cyclic voltammetry in a typical three‐electrode cell configuration. The physicochemical properties of the membranes vital to fuel‐cell performance are also carefully evaluated under conditions relevant to fuel‐cell operation, including chemical and thermal stability, proton conductivity, solubility in different solvents, water uptake, and swelling ratio. The new membranes exhibit low dimensional change at 25°C to 90°C and excellent thermal stability up to 250°C. Upon elimination of unstable end groups, the co‐polymers display enhanced chemical resistance and oxidative stability in Fenton's test. Further, the SPTESBO‐HFB‐60 (HFB‐60=hexafluorobenzene, 60 mol% sulfone) membrane displays comparable fuel‐cell performance to that of an NRE 212 membrane at 80°C under fully humidified condition, suggesting that the new membranes have the potential to be more durable but less expensive for fuel‐cell applications. 相似文献
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Thomas P. Brennan Pendar Ardalan Han‐Bo‐Ram Lee Jonathan R. Bakke I‐Kang Ding Michael D. McGehee Stacey F. Bent 《Liver Transplantation》2011,1(6):1169-1175
Functioning quantum dot (QD) sensitized solar cells have been fabricated using the vacuum deposition technique atomic layer deposition (ALD). Utilizing the incubation period of CdS growth by ALD on TiO2, we are able to grow QDs of adjustable size which act as sensitizers for solid‐state QD‐sensitized solar cells (ssQDSSC). The size of QDs, studied with transmission electron microscopy (TEM), varied with the number of ALD cycles from 1‐10 nm. Photovoltaic devices with the QDs were fabricated and characterized using a ssQDSSC device architecture with 2,2',7,7'‐tetrakis‐(N,N‐di‐p methoxyphenylamine) 9,9'‐spirobifluorene (spiro‐OMeTAD) as the solid‐state hole conductor. The ALD approach described here can be applied to fabrication of quantum‐confined structures for a variety of applications, including solar electricity and solar fuels. Because ALD provides the ability to deposit many materials in very high aspect ratio substrates, this work introduces a strategy by which material and optical properties of QD sensitizers may be adjusted not only by the size of the particles but also in the future by the composition. 相似文献
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Organic Solar Cells: Following the Morphology Formation In Situ in Printed Active Layers for Organic Solar Cells (Adv. Energy Mater. 1/2016) 下载免费PDF全文
79.
Zhenwen Cui Zhihong Zhong Yong Yang Baofeng Wang Yuhao Sun Qingfang Sun Guo‐yuan Yang Liuguan Bian 《Journal of biochemical and molecular toxicology》2016,30(8):396-403
Free radical damage caused by ferrous iron is involved in the pathogenesis of secondary brain injury after intracerebral hemorrhage (ICH). NF‐E2‐related factor 2 (Nrf2), a major phase II gene regulator that binds to antioxidant response element, represents an important cellular cytoprotective mechanism against oxidative damage. We hypothesized that Nrf2 might protect astrocytes from damage by Fe2+. Therefore, we examined cytotoxicity in primary astrocytes induced by iron overload and evaluated the effects of Fe2+ on Nrf2 expression. The results demonstrated that 24‐h Fe2+ exposure exerted time‐ and concentration‐dependent cytotoxicity in astrocytes. Furthermore, Fe2+ exposure in astrocytes resulted in time‐ and concentration‐dependent increases in Nrf2 expression, which preceded Fe2+ toxicity. Nrf2‐specific siRNA further knocked down Nrf2 levels, resulting in greater Fe2+‐induced astrocyte cytotoxicity. These data indicate that induction of Nrf2 expression could serve as an adaptive self‐defense mechanism, although it is insufficient to completely protect primary astrocytes from Fe2+‐induced neurotoxicity. 相似文献
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Characterization of phytoplankton assemblages in a tropical coastal environment using Kohonen self‐organizing map 下载免费PDF全文
Isimemen Osemwegie Julie E. Niamien‐Ebrottié Mathieu Y. J. Koné Allassane Ouattara Jean Biemi Barbara Reichert 《African Journal of Ecology》2017,55(4):487-499
This study was aimed at understanding the main abiotic environmental factors controlling the distribution patterns of abundance and composition of phytoplankton (size less than 10 μm) assemblages in the coastal waters of south‐eastern Côte d'Ivoire. Data were collected during two cruises, in January (low‐water period) and October (high‐water period) of 2014. A total of 67 species were identified and assigned to Bacillariophyceae (49%), Cyanophyceae (21%), Chlorophyceae (13%), Euglenophyceae (10%), Dinophyceae (4%) and Chrysophyceae (3%). Three biotic zones (I, IIA and IIB) were distinguishable on a Kohonen self‐organizing map after an unsupervised learning process. The diatom genera Eunotia sp., Navicula sp. and Actinoptychus senarius are significantly associated with I, IIA and IIB biotic zones, respectively. A clear seasonal cum salinity trend was apparent in phytoplankton distribution patterns. Turbidity and nitrate levels were the main abiotic factors controlling phytoplankton distribution in I, the upland tidal regions of the lagoon. In regions along the lagoon–sea continuum, phosphate and turbidity exert the most control during the low‐water season (IIA), while total dissolved solids control phytoplankton distribution during the high‐water season (IIB). These are climate‐sensitive parameters whose concentrations depend on prevailing hydroclimatic processes. Therefore, seasonality can have important consequences on phytoplankton community and inadvertently the productivity of these systems. 相似文献