66 research outputs found
Copolymerisation as a way to enhance the electrochromic properties of an alkylthiophene oligomer and a pyrrole derivative: copolymer of 3,3'" dihexyl-2,2':5',2":5",2'"-quaterthiophene with (R)-(-)-3-(1-pyrrolyl)propyl-N-(3,5-dinitrobenzoyl)-α-phenylglycinate
The copolymerisation of 3,3'" Dihexyl-2,2':5',2":5",2'"-quaterthiophene (DHQT) and (R)-(-)-3-(1-pyrrolyl)propyl-N-(3,5-dinitrobenzoyl)-α-phenylglycinate (DNBP) was successfully performed electrochemically in acetonitrile (CH3CN) containing tetrabutylammonium tetrafluoroborate ((C4H9)4NBF4) by direct oxidation of monomer mixtures in different feed ratios. Copolymerisation improved the properties of the films of both polymers PDHQT and PDNBP, in respect to the adhesion of PDHQT onto ITO/glass surface and the chromatic contrast of these electrochromic materials. PDHQT, PDNBP and P(DHQT-co-DNBP) films were characterised by FTIR spectroscopy, fluorescence spectroscopy, Scanning Electron Microscopy (SEM) and spectroelectrochemical techniques. Solutions of PDHQT and its copolymers with DNBP (independently of the feed ratio) in N-methylpyrrolidone are fluorescent with emission bands at 555 and 585 nm when excited at 375 nm. Reversible changes in the hue and saturation occur in all the copolymer films from yellow or orange in the reduced state to green or blue in the oxidised state, but were dependent on the proportion of the comonomers used to prepare the copolymers. These changes are more significant for P(DHQT-co-DNBP) films deposited onto ITO/glass with 1:5 feed ratio, as shown by the track of the CIE 1931 xy chromaticity coordinates and by the electrochromic parameters in which this film (thickness 0.8±0.2 ÎŒm) presented chromatic contrast (Î%T) at 660 nm of 62%, coloration efficiency (η) of 266 cm2 C-1 and stability to redox cycling (Î%T=17% at the 1000th cycle). Therefore, these copolymers are potentially applicable in displays and optoelectronic devices as electrochromic and fluorescent materials
Highâschool Students' Conceptual Difficulties and Attempts at Conceptual Change: The case of basic quantum chemical concepts
Gendered representations in Hawaiâiâs anti-GMO activism
The aim of this article is to analyse some of the representations of intersectional gender that materialise in activism against genetically modified organisms (GMOs). It uses the case of Hawaiâi as a key node in global transgenic seed production and hotspot for food, land and farming controversies. Based on ethnographic work conducted since 2012, the article suggests some of the ways that gender is represented within movements against GMOs by analysing activist media representations. The article shows how gender, understood intersectionally, informs possibilities for movement-identification, exploring how themes of motherhood, warrior masculinities and sexualised femininities are represented within these movements. The article suggests that some activist representations of gender invoke what could be considered as normative framings of gender similar to those seen in other environmental, food and anti-GMO movements. It is suggested that these gendered representations may influence and limit how different subjects engage with Hawai'i anti-GMO movements. At the same time, contextual, intersectional readings demonstrate the complex histories behind what appear to be gender normative activist representations. Taken together, this emphasis on relative norms of femininities and masculinities may provide anti-GMO organising with familiar social frames that counterbalance otherwise threatening campaigns against (agri)business in the settler state. Understood within these histories, the work that gender does within anti-GMO organising may offer generative examples for thinking through the relationships between gendered representations and situated, indigenous-centred, food and land-based resistances
Observations on the superficial sediment temperatures of some lakes in the southeastern United States*
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