Ground- and excited-state properties of [Ru(tpy)(2)](2+), [Ru(tpy)(ttpy)](2+), and [Ru(ttpy)(2)](2+) (where tpy = 2,2':6',2″-terpyridine and ttpy = 4'-(4-methylphenyl)-2,2':6',2″-terpyridine) in room temperature acetonitrile have been investigated using linear absorption, electrochemical, and ultrafast transient pump-probe techniques. Spectroelectrochemistry was used to assign features observed in the transient spectra while single wavelength kinetics collected at a variety of probe wavelengths were used to monitor temporal evolution of the MLCT excited state. From these data, the excited-state lifetime of each complex was recovered and the rate limiting decay step was identified. In the bis-heteroleptic complex [Ru(tpy)(ttpy)](2+), photoexcitation to the (1)MLCT manifold generates both tpy-localized and ttpy-localized excited states. Accordingly, interligand electron transfer (ILET) from tpy-localized to the ttpy-localized (3)MLCT excited states is observable and the time scale has been measured to be 3 ps. For the homoleptic complex [Ru(tpy)(2)](2+), evidence for equilibration of the (3)MLCT excited-state population with the (3)MC has been observed and the time scale is reported at 2 ps.

Three new photoinduced electron donor-acceptor (D-A) systems are reported which juxtapose a Ru(II) excited-state donor with a bipyridinium acceptor via a conformationally active asymmetric aryl-substituted bipyridine ligand participating in the bridge between D and A. Across the series of complexes 1-3, steric bulk is sequentially added to tune the inter-ring dihedral angle theta between the bipyridine and the aryl substituent. Driving forces for photoinduced electron transfer (DeltaG(ET)) and back electron transfer (DeltaG(BET)) are reported based on electrochemical measurements of 1-3 as well as Franck-Condon analysis of emission spectra collected for three new donor model complexes 1'-3'. These preserve the substitution patterns on the aryl substituent in their respective D-A complexes but remove the bipyridinium acceptor. Both DeltaG(ET) and DeltaG(BET) are invariant to within 0.02 eV across the series. Upon visible photoexcitation of each of the D-A systems with approximately 100 fs laser pulses at 500 +/- 10 nm, an electron-transfer (ET) photoproduct is observed to form with a time constant of tau(ET) = 29 ps (1), 37 ps (2), and 57 ps (3). That ET remains relatively rapid throughout this series, even as steric bulk significantly increases the inter-ring dihedral angle theta, is attributed to the effects of ligand-based torsional dynamics driven by intraligand electron delocalization in the D*-A excited state manifold prior to ET. The lifetimes of the charge-separated states (tau(BET)) are also reported with tau(BET) = 98 ps (1), 217 ps (2), and 789 ps (3), representing a more than 8-fold increase across the series. This is attributed to reverse conformational dynamics in D(+)-A(-) driven by steric repulsions, which serves to minimize electronic coupling to the ground state. Steric control of ligand geometry and the range over which theta changes during conformational dynamics provides a new strategy to facilitate the formation and storage of charge-separated excited states.

Increasingly, drone-based photogrammetry has been used to measure size and body condition changes in marine megafauna. A broad range of platforms, sensors, and altimeters are being applied for these purposes, but there is no unified way to predict photogrammetric uncertainty across this methodological spectrum. As such, it is difficult to make robust comparisons across studies, disrupting collaborations amongst researchers using platforms with varying levels of measurement accuracy. Here we built off previous studies quantifying uncertainty and used an experimental approach to train a Bayesian statistical model using a known-sized object floating at the water’s surface to quantify how measurement error scales with altitude for several different drones equipped with different cameras, focal length lenses, and altimeters. We then applied the fitted model to predict the length distributions and estimate age classes of unknown-sized humpback whales Megaptera novaeangliae, as well as to predict the population-level morphological relationship between rostrum to blowhole distance and total body length of Antarctic minke whales Balaenoptera bonaerensis. This statistical framework jointly estimates errors from altitude and length measurements from multiple observations and accounts for altitudes measured with both barometers and laser altimeters while incorporating errors specific to each. This Bayesian model outputs a posterior predictive distribution of measurement uncertainty around length measurements and allows for the construction of highest posterior density intervals to define measurement uncertainty, which allows one to make probabilistic statements and stronger inferences pertaining to morphometric features critical for understanding life history patterns and potential impacts from anthropogenically altered habitats.

Photophysics of the MLCT excited-state of [Ru(bpy)(tpy)(OH2)](2+) (1) and [Ru(bpy)(tpy)(OD2)](2+) (2) (bpy = 2,2'-bipyridine and tpy = 2,2':6',2″-terpyridine) have been investigated in room-temperature H2O and D2O using ultrafast transient pump-probe spectroscopy. An inverse isotope effect is observed in the ground-state recovery for the two complexes. These data indicate control of excited-state lifetime via a pre-equilibrium between the (3)MLCT state that initiates H-bond dynamics with the solvent and the (3)MC state that serves as the principal pathway for nonradiative decay.

Quantifying the cumulative effects of stressors on individuals and populations can inform the development of effective management and conservation strategies. We developed a Bayesian state–space model to assess the effects of multiple stressors on individual survival and reproduction. In the model, stressor effects on vital rates are mediated by changes in underlying health, allowing for the comparison of effect sizes while accounting for intrinsic factors that might affect an individual's vulnerability and resilience. We applied the model to a 50‐year dataset of sightings, calving events and stressor exposure of critically endangered North Atlantic right whales Eubalaena glacialis. The viability of this population is threatened by a complex set of stressors, including vessel strikes, entanglement in fishing gear and fluctuating prey availability. We estimated that blunt and deep vessel strike injuries and severe entanglement injuries had the largest effect on the health of exposed individuals, reinforcing the urgent need for mitigation measures. Prey abundance had a smaller but protracted effect on health across individuals, and estimated long‐term trends in survival and reproduction followed the trend of the prey index, highlighting that long‐term ecosystem‐based management strategies are also required. Our approach can be applied to quantify the effects of multiple stressors on any long‐lived species where suitable indicators of health and long‐term monitoring data are available.