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Cryptochrome 4a (Cry4a) has been proposed as the sensor at the heart of the magnetic compass in migratory songbirds. Blue-light excitation of this protein produces magnetically sensitive flavin–tryptophan radical pairs whose properties suggest that Cry4a could indeed be suitable as a magnetoreceptor. Here, we use cavity ring-down spectroscopy to measure magnetic field effects on the kinetics of these radical pairs in modified Cry4a proteins from the migratory European robin and from nonmigratory pigeon and chicken. B1/2, a parameter that characterizes the magnetic field-dependence of the reactions, was found to be larger than expected on the basis of hyperfine interactions and to increase with the delay between pump and probe laser pulses. Semiclassical spin dynamics simulations show that this behavior is consistent with a singlet–triplet dephasing (STD) relaxation mechanism. Analysis of the experimental data gives dephasing rate constants, rSTD, in the range 3–6 × 107 s−1. A simple "toy" model due to Maeda, Miura, and Arai [Mol. Phys. 104, 1779–1788 (2006)] is used to shed light on the origin of the time-dependence and the nature of the STD mechanism. Under the conditions of the experiments, STD results in an exponential approach to spin equilibrium at a rate considerably slower than rSTD. We attribute the loss of singlet–triplet coherence to electron hopping between the second and third tryptophans of the electron transfer chain and comment on whether this process could explain differences in the magnetic sensitivity of robin, chicken, and pigeon Cry4a's. [ABSTRACT FROM AUTHOR]

Global migrations of diverse animal species often converge along the same routes, bringing together seasonal assemblages of animals that may compete, prey on each other, and share information or pathogens. These interspecific interactions, when energetic demands are high and the time to complete journeys is short, may influence survival, migratory success, stopover ecology, and migratory routes. Numerous accounts suggest that interspecific co-migrations are globally distributed in aerial, aquatic, and terrestrial systems, although the study of migration to date has rarely investigated species interactions among migrating animals. Here, we test the hypothesis that migrating animals are communities engaged in networks of ecological interactions. We leverage over half a million records of 50 bird species from five bird banding sites collected over 8 to 23 y to test for species associations using social network analyses. We find strong support for persistent species relationships across sites and between spring and fall migration. These relationships may be ecologically meaningful: They are often stronger among phylogenetically related species with similar foraging behaviors and nonbreeding ranges even after accounting for the nonsocial contributions to associations, including overlap in migration timing and habitat use. While interspecific interactions could result in costly competition or beneficial information exchange, we find that relationships are largely positive, suggesting limited competitive exclusion at the scale of a banding station during migratory stopovers. Our findings support an understanding of animal migrations that consist of networked communities rather than random assemblages of independently migrating species, encouraging future studies of the nature and consequences of co-migrant interactions. [ABSTRACT FROM AUTHOR]

Isolated mixed-ligand complexes provide tractable model systems in which to study competitive and cooperative binding effects as well as controlled energy flow. Here, we report spectroscopic and isotopologue-selective infrared photofragmentation dynamics of mixed gas-phase Au(12/13CO)n(N2O)m+ complexes. The rich infrared action spectra, which are reproduced well using simulations of calculated lowest energy structures, clarify previous ambiguities in the assignment of vibrational bands, especially accidental coincidence of CO and N2O bands. The fragmentation dynamics exhibit the same unexpected behaviour as reported previously in which, once CO loss channels are energetically accessible, these dominate the fragmentation branching ratios, despite the much lower binding energy of N2O. We have investigated the dynamics computationally by considering anharmonic couplings between a relevant subset of normal modes involving both ligand stretch and intermolecular modes. Discrepancies between correlated and uncorrelated model fit to the ab initio potential energy curves are quantified using a Boltzmann sampled root mean squared deviation providing insight into efficiency of vibrational energy transfer between high frequency ligand stretches and the softer intermolecular modes which break during fragmentation. [ABSTRACT FROM AUTHOR]

Prolonged bed rest impairs standing balance but the underlying mechanisms are uncertain. Previous research suggests strength loss is not the cause, leaving impaired sensorimotor control as an alternative. Here we examine vestibular control of posture in 18 male volunteers before and after 60 days of bed rest. Stochastic vestibular stimulation (SVS) was used to evoke sway responses before, 1 and 6 days after bed rest under different head yaw orientations. The directional accuracy and precision of these responses were calculated from ground reaction force vectors. Bed rest caused up to 63% increases in spontaneous standing sway and 31% reductions in leg strength, changes which were uncorrelated. The increase in sway was exacerbated when the eyes were closed. Mean directions of SVS‐evoked sway responses were unaffected, being directed towards the anodal ear and rotating in line with head orientation in the same way before and after bed rest. However, individual trial analysis revealed 25%–30% increases in directional variability, which were significantly correlated with the increase in spontaneous sway (r = 0.48–0.71; P ≤ 0.044) and were still elevated on day 6 post‐bed rest. This reveals that individual sway responses may be inappropriately oriented, a finding masked by the averaging process. Our results confirm that impaired balance following prolonged bedrest is not related to loss of strength. Rather, they demonstrate that the sensorimotor transformation process which converts vestibular feedback into appropriately directed balance responses is impaired. Key points: Prolonged inactivity impairs balance but previous research suggests this is not caused by loss of strength.Here we investigated vestibular control of balance before and after 60 days of bed rest using electrical vestibular stimulation (EVS) to evoke sway responses.Spontaneous sway significantly increased and muscle strength reduced following bed rest, but, in keeping with previous research, these two effects were not correlated.While the overall accuracy of EVS‐evoked sway responses was unaffected, their directional variability significantly increased following bed rest, and this was correlated with the increases in spontaneous sway.We have shown that the ability to transform head‐centred vestibular feedback into an appropriately directed body sway response is negatively affected by prolonged inactivity; this may contribute to the impaired balance commonly observed following bed rest. [ABSTRACT FROM AUTHOR]

The article focuses on the discussion of scattering phenomena involving larger molecules, specifically addressing questions related to the phenylethynyl radical in the interstellar medium. Topics include the challenges in detecting the phenylethynyl radical due to its complex spectrum, potential formation mechanisms in space, and the role of experimental and computational methods in predicting its presence.

The article focuses on a general discussion of scattering phenomena at condensed-phase surfaces, particularly in relation to the challenges and techniques involved in measuring angular distributions of evaporating atoms. Topics include the difficulties of measuring angular distributions from cylindrical jets versus flat jets, the prediction of helium atom evaporation patterns, and the observation of surfactant segregation in microjets.

The article focuses on a general discussion about the scattering of larger molecules, particularly examining the differences in potential energy surfaces (PES) between HDO, H2O, and D2O. Topics include the reason for stronger back scattering in HDO compared to H2O and D2O, the role of symmetry and potential terms in scattering phenomena, and specific insights into the n10 term affecting back-scattering.