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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.

We report a combined experimental and computational study of carbon dioxide activation at gas-phase Ho+ and HoO+ centres. Infrared action spectra of Ho(CO2)n+ and [HoO(CO2)n]+ ion–molecule complexes have been recorded in the spectral region 1700–2400 cm−1 and assigned by comparison with simulated spectra of energetically low-lying structures determined by density functional theory. Little by way of activation is observed in Ho(CO2)n+ complexes with CO2 binding end-on to the Ho+ ion. By contrast, all [HoO(CO2)n]+ complexes n ≥ 3 show unambiguous evidence for formation of a carbonate radical anion moiety,. The signature of this structure, a new vibrational band observed around 1840 cm−1 for n = 3, continues to red-shift monotonically with each successive CO2 ligand binding with net charge transfer from the ligand rather than the metal centre. [ABSTRACT FROM AUTHOR]

Over the past few decades, extrinsic tracking devices (e.g., radio transmitters, GPS loggers, satellite transmitters, geolocators) have been widely used to study wildlife movement and other demographic parameters. Remote tracking and monitoring technology is continually advancing, and its use by researchers is becoming more widespread. Minimizing any potential impacts of tracking devices on focal species is of upmost importance in order to ensure and promote animal welfare and reliable scientific information. Many researchers aim to understand any potential short- or long-term impacts of remote tracking, and to develop methods that support the responsible and safe tagging of birds (e.g., Geen et al. 2019). As tracking projects become more mainstream, it is critical that banders and researchers stay up to date and contribute to current base of knowledge on the topic. This review summarizes available research demonstrating the impacts of attaching a variety of tracking devices to birds in order to guide and promote minimally invasive methods of deploying tracking devices, and to highlight the need for continued study of the effects of devices and attachment methods on bird welfare. [ABSTRACT FROM AUTHOR]

The application of evanescent wave cavity ring-down spectroscopy (EW-CRDS) in monitoring electrogenerated species within a thin-layer electrochemical cell is demonstrated. In the proof-of-concept experiments described, ferricyanide, Fe[(CN).sub.6.sup.3-], was produced by the transport-limited oxidation of ferrocyanide, Fe[(CN).sub.6.sup.4-], in a thin-layer solution cell (25-250 [micro]m) formed between an electrode and the hypotenuse of a fused-silica prism. The prism constituted one element of a high-finesse optical cavity arranged in a triangular ring geometry with light being totally internally reflected at the silica/solution interface. The cavity was pumped with the output (~417 nm) of a single-mode external cavity diode laser, which was continuously scanned across the cavity modes. The presence of electrogenerated ferricyanide within the resulting evanescent field, beyond the optical interface, was detected by the enhanced loss of light trapped within the cavity, as measured by the characteristic cavity ring down. In this way, the EW-CRDS technique is sensitive to absorption in only the first few hundred nanometers of solution above the silica surface. The cavity ring-down response accompanying both cyclic voltammetric and step potential chronoamperometry experiments at a variety of electrode-surface distances is presented, and the results are shown to be well reproduced in modeling by finite element methods. The studies herein thus provide a foundation for further applications of EW-CRDS combined with electrochemistry.

Even though the interaction of a <1 mT magnetic field with an electron spin is less than a millionth of the thermal energy at room temperature (kBT), it still can have a profound effect on the quantum yields of radical pair reactions. We present a study of the effects of sub-millitesla magnetic fields on the photoreaction of flavin mononucleotide with ascorbic acid. Direct control of the reaction pathway is achieved by varying the rate of electron transfer from ascorbic acid to the photo-excited flavin. At pH 7.0, we verify the theoretical prediction that, apart from a sign change, the form of the magnetic field effect is independent of the initial spin configuration of the radical pair. The data agree well with model calculations based on a Green's function approach that allows multinuclear spin systems to be treated including the diffusive motion of the radicals, their spin-selective recombination reactions, and the effects of the inter-radical exchange interaction. The protonation states of the radicals are uniquely determined from the form of the magnetic field-dependence. At pH 3.0, the effects of two chemically distinct radical pair complexes combine to produce a pronounced response to ~500 μT magnetic fields. These findings are relevant to the magnetic responses of cryptochromes (flavin-containing proteins proposed as magnetoreceptors in birds) and may aid the evaluation of effects of weak magnetic fields on other biologically relevant electron transfer processes. [ABSTRACT FROM AUTHOR]

The near ultraviolet photodissociation dynamics of silver atom-rare gas dimers have been studied by velocity map imaging. Ag-RG (RG = Ar, Kr, Xe) species generated by laser ablation are excited in the region of the C ((²Σ+)←X (²Σ+) continuum leading to direct, near-threshold dissociation generating Ag* (²P3/2) + RG¹S0) products. Images recorded at excitation wavelengths throughout the C (²Σ+)←X (²Σ+) continuum, coupled with known atomic energy levels, permit determination of the ground X (²Σ+) state dissociation energies of 85.9 ± 23.4 cm-1 (Ag-Ar), 149.3 ± 22.4 cm-1 (Ag-Kr), and 256.3 ± 16.0 cm-1 (Ag-Xe). Three additional photolysis processes, each yielding Ag atom photoproducts, are observed in the same spectral region. Two of these are markedly enhanced in intensity upon seeding the molecular beam with nitrous oxide, and are assigned to photodissociation of AgO at the two-photon level. These features yield an improved ground state dissociation energy for AgO of 15 965 ± 81 cm-1, which is in good agreement with high level calculations. The third process results in Ag atom fragments whose kinetic energy shows anomalously weak photon energy dependence and is assigned tentatively to dissociative ionization of the silver dimer Ag2. [ABSTRACT FROM AUTHOR]

A new giant sauropod, Australotitan cooperensis gen. et sp. nov., represents the first record of dinosaurs from the southern-central Winton Formation of the Eromanga Basin, Australia. We estimate the type locality to be 270-300 m from the base of the Winton Formation and compare this to the semi-contemporaneous sauropod taxa, Diamantinasaurus matildae Hocknull et al., 2009, Wintonotitan wattsi Hocknull et al., 2009 and Savannasaurus elliottorum Poropat et al., 2016. The new titanosaurian is the largest dinosaur from Australia as represented by osteological remains and based on limb-size comparisons it reached a size similar to that of the giant titanosaurians from South America. Using 3-D surface scan models we compare features of the appendicular skeleton that differentiate Australotitan cooperensis gen. et sp. nov. as a new taxon. A key limitation to the study of sauropods is the inability to easily and directly compare specimens. Therefore, 3-D cybertypes have become a more standard way to undertake direct comparative assessments. Uncoloured, low resolution, and uncharacterized 3-D surface models can lead to misinterpretations, in particular identification of pre-, syn- and post-depositional distortion. We propose a method for identifying, documenting and illustrating these distortions directly onto the 3-D geometric surface of the models using a colour reference scheme. This new method is repeatable for researchers when observing and documenting specimens including taphonomic alterations and geometric differences. A detailed comparative and preliminary computational phylogenetic assessment supports a shared ancestry for all four Winton Formation taxa, albeit with limited statistical support. Palaeobiogeographical interpretations from these resultant phylogenetic hypotheses remain equivocal due to contrary Asian and South American relationships with the Australian taxa. Temporal and palaeoenvironmental differences between the northern and southern-central sauropod locations are considered to explain the taxonomic and morphological diversity of sauropods from the Winton Formation. Interpretations for this diversity are explored, including an eco-morphocline and/or chronocline across newly developed terrestrial environments as the basin fills. [ABSTRACT FROM AUTHOR]