We report on a novel method for sensing oxygen that is based on the use of a perylene diimide dye (1) which is electrochemically reduced to its nonfluorescent dianion form (1(2-)). In the presence of oxygen, the dianion is oxidized to its initial form via an electron-transfer reaction with oxygen upon which fluorescence is recovered. As a result, the fluorescence intensity of the dianion solution increases upon the addition of oxygen gas. Results demonstrate that high sensitivity is obtained, and the emission intensity shows a linear correlation with oxygen content (0.0-4.0% v/v) at ambient barometric pressure. In addition, using electrochemical reduction, oxygen determination becomes regenerative, and no significant degradation is observed over several turnovers. The limit of detection is 0.4% oxygen in argon gas.
Two-component amphiphiles based on hydrogen-bonded complexes between terephthaloylbisalanine (H(2)TBA) and dodecylamine (DA) are able to self-assemble into nano- and microsized superstructures in an aqueous solvent. It is possible to modulate the morphology of these self-assembled superstructures by modifying the composition of the complexes, which can be achieved by changing the molar ratio of the two components or by changing the chirality of H(2)TBA. For example, right-handed microhelical ribbon structures were formed with L-TBA(1.0)DA(2.0), whereas in the case of rac-TBA(1.0)DA(2.0), flat ribbonlike structures were observed. Although L-TBA(1.0)DA(1.0) exhibited entangled fibrous structures, rac-TBA(1.0)DA(1.0) exhibited wire structures. Different ratios of H(2)TBA and DA were self-assembled into fiber-, wire-, and tubulelike superstructures, as well as monoclinic, columnar, and lamellar aggregation patterns. The self-assembled superstructures of TBA(x)DA(y) were significantly changed by adding metal ions. Transition metal (Cd(II), Co(II), and Zn(II)) complexes with L-TBA(x)DA(y) self-assembled into rod-, tubule-, wire-, and platelike superstructures. Metal-ion complexes with rac-TBA(x)DA(y) exhibited different superstructures. Our work suggests that it is possible to fabricate a wide variety of nano- and microsized superstructures by using two- and three-component amphiphiles.
This study introduces a threat level assessment model adapting Fuzzy theories in order to help make decisions for better covering quantitative factors and qualitative ones together. The threat is classified into three major categoriesone resulting from navigational condition, another from target vessel specification and the other from external decision environment. The threat levels by each category are examined by a fuzzy inference, and its corresponding weights are assigned via fuzzy measures. Finally the high level threat measures become integrated via a Choquet Fuzzy Integral method into ultimate threat level indicators.
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