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The 'detective' power of stable isotopes for processes that occurred in the past, and for elucidating mechanisms at the molecular level, has impressed researchers over the past 100 years, since the time when isotopes of elements were first discovered. While most are interested in the normalized abundance ratios of two isotopes of an element, further power was unleashed when researchers investigated the relationship of three or more isotopes of the same element, e.g. 16O, 17O, and 18O for oxygen. This Element focuses on the history of discovery of triple isotope effects, the conceptual framework behind these effects, and major lines of development in the past few years of triple oxygen isotope research.

Oxygen. --- Isotopes.

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Tracking initial ocean (de)oxygenation is critical to better constrain the coevolution of life and environment. Development of thallium isotopes has provided evidence to track the global manganese oxide burial which responds to early (de)oxygenation for short-term climate events. Modern oxic seawater thallium isotope values are recorded in organic-rich sediments deposited below an anoxic water column. An expansion of reducing conditions decrease manganese oxide burial and shifts the seawater thallium isotope composition more positive. Recent work documents that thallium isotopes are perturbed prior to carbon isotope excursions, suggesting ocean deoxygenation is a precursor for increased organic carbon burial. This Element provides an introduction to the application of thallium isotopes, case studies, and future directions.

Chemical oceanography. --- Oxygen.

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Phototoxicity is defined as a toxic response is elicited by topically or systemically administered photoreactive chemicals after the exposure of the body to environmental light. Several classes of photoreactive chemicals could cause phototoxic reactions when activated by light at otherwise non-toxic doses. Phototoxicity can be categorized as photoirritation, photoallergy, and photogenotoxicity. The purpose of this test is to measure the phototoxicity of a chemical. The main event in any phototoxic reaction is the absorption of photons of a wavelength that induces the excitation of the chromophore. Excitation energy is often transferred to oxygen molecules, followed by the generation of ROS (reactive Oxygen Species). Measurements are performed using a spectrometer. The determination of the ROS generation from irradiated chemicals with simulated sunlight is indicative of phototoxic potential.

Active oxygen --- Photochemistry. --- Physiological effect.

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Gallium Oxide: Technology, Devices and Applications discusses the wide bandgap semiconductor and its promising applications in power electronics, solar blind UV detectors, and in extreme environment electronics. It also covers the fundamental science of gallium oxide, providing an in-depth look at the most relevant properties of this materials system. High quality bulk Ga2O3 is now commercially available from several sources and n-type epi structures are also coming onto the market. As researchers are focused on creating new complex structures, the book addresses the latest processing and synthesis methods. Chapters are designed to give readers a complete picture of the Ga2O3 field and the area of devices based on Ga2O3, from their theoretical simulation, to fabrication and application.

Gallium compounds. --- Oxides. --- Chalcogenides --- Oxygen compounds --- Chemicals

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La phototoxicité est définie comme une réaction toxique causée par des produits chimiques photoréactifs administrés par voie topique ou systémique, après exposition du corps à la lumière ambiante. Plusieurs classes de produits chimiques photoréactifs peuvent provoquer des réactions phototoxiques lorsqu'ils sont activés par la lumière, à des doses ne présentant pas d'autres effets toxiques. La phototoxicité peut être subdivisée en photo-irritation, photoallergie et photogénotoxicité. Le but de cet essai est de mesurer la phototoxicité d'un produit chimique. L'événement principal dans toute réaction phototoxique est l'absorption des photons d'une longueur d'onde qui induit l'excitation du chromophore. L'énergie d'excitation est souvent transférée aux molécules d'oxygène, suivies par la génération de ROS (Reactive Oxygene Species). Les mesures sont effectuées à l'aide d'un spectromètre. La détermination de la génération ROS à partir de produits chimiques irradiés avec la lumière du soleil simulée est révélateur d'un potentiel phototoxique.

Active oxygen --- Photochemistry. --- Toxicity testing. --- Physiological effect.