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Marine mammals possess impressive breath-holding capabilities made possible by physiological adjustments during dives. Studying marine mammals in their natural environment unravels vital information about these physiological adjustments particularly when we can monitor altered dive behavior in response to stressful situations such as human-induced oceanic disturbances, presence of predators and altered prey distributions. An important indicator of physiological status during submergence is the change in oxygen saturation in the muscles and blood of these mammals. In this work, we aim to investigate oxygen storage and consumption in the muscles of free-diving elephant seals when exposed to disturbances such as sonar or predator sounds while they are at sea. Optical oxygen sensors are a mature technology with multiple medical applications that provide a way to measure oxygenation changes in biological tissues in a minimally invasive manner. While these sensors are well calibrated and readily available for humans, they are still inadequate for marine mammals primarily due to a very small number of test candidates and therefore little data is available for validation and calibration. We propose a probe geometry and associated mathematical model for measuring muscle oxygenation in seals based on near infrared diffuse transport with no need for calibration. A prototype based on this concept has been designed and tested on humans and rats. We use the test results to discuss the advantages and limitations of the approach. We also detail the constraints on size, sensor location, electronics, light source properties and detector characteristics posed by the unique biology of seals. 

Abstract Although most class (b) transition metals have been studied in regard to CH₄activation, divalent silver (Ag^II), possibly owing to its reactive nature, is the only class (b) high‐valent transition metal center that is not yet reported to exhibit reactivities towards CH₄activation. We now report that electrochemically generated Ag^IImetalloradical readily functionalizes CH₄into methyl bisulfate (CH₃OSO₃H) at ambient conditions in 98 % H₂SO₄. Mechanistic investigation experimentally unveils a low activation energy of 13.1 kcal mol⁻¹, a high pseudo‐first‐order rate constant of CH₄activation up to 2.8×10³ h⁻¹at room temperature and a CH₄pressure of 85 psi, and two competing reaction pathways preferable towards CH₄activation over solvent oxidation. Reaction kinetic data suggest a Faradaic efficiency exceeding 99 % beyond 180 psi CH₄at room temperature for potential chemical production from widely distributed natural gas resources with minimal infrastructure reliance.