24 research outputs found

    Donor-acceptor dyads and triads employing core-substituted naphthalene diimides:a synthetic and spectro (electrochemical) study

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    Donor-acceptor dyads and triads comprising core-substituted naphthalene diimide (NDI) chromophores and either phenothiazine or phenoxazine donors are described. Synthesis combined with electrochemical and spectroelectrochemical investigations facilitates characterisation of the various redox states of these molecules, confirming the ability to combine arrays of electron donating and accepting moieties into single species that retain the redox properties of these individual moieties

    Mid‐IR supercontinuum noise reduction using a short piece of normal dispersion fiber ‐ a general mechanism

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    Mid-infrared (IR) supercontinuum (SC) lasers are important in applications such as pollution detection, stand-off detection, and non-destructive testing. The performance in many applications is limited by the noise level of the supercontinuum laser. High noise typically results in low sensitivities or a need for long integration times. In this paper, a simple technique to reduce the noise of high noise soliton-based SC sources is introduced by adding a short piece of normal dispersion fiber to force the spectrally distributed solitons to spectrally broaden through self-phase modulation and thereby overlap to average out the noise. The noise reduction is demonstrated experimentally and numerically using a ZBLAN fiber based mid-IR SC source and adding a short piece of highly nonlinear arsenic-sulfide fiber. However, the method is generally applicable to any soliton-based near-IR or mid-IR SC source. Its efficiency is underlined by experimentally comparing it to SC generation in fibers in which a second zero-dispersion wavelength provides the spectral alignment noise reduction mechanism

    Thermal Stress and Coral Cover as Drivers of Coral Disease Outbreaks

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    Very little is known about how environmental changes such as increasing temperature affect disease dynamics in the ocean, especially at large spatial scales. We asked whether the frequency of warm temperature anomalies is positively related to the frequency of coral disease across 1,500 km of Australia's Great Barrier Reef. We used a new high-resolution satellite dataset of ocean temperature and 6 y of coral disease and coral cover data from annual surveys of 48 reefs to answer this question. We found a highly significant relationship between the frequencies of warm temperature anomalies and of white syndrome, an emergent disease, or potentially, a group of diseases, of Pacific reef-building corals. The effect of temperature was highly dependent on coral cover because white syndrome outbreaks followed warm years, but only on high (>50%) cover reefs, suggesting an important role of host density as a threshold for outbreaks. Our results indicate that the frequency of temperature anomalies, which is predicted to increase in most tropical oceans, can increase the susceptibility of corals to disease, leading to outbreaks where corals are abundant

    Photoinduced radical formation in hydrogen-bonded organic frameworks

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    Hydrogen-bonded organic frameworks (HOFs) constructed from naphthalene-diimide bearing tectons undergo photochromic changes whilst forming radical bearing species within the framework structure
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