Diving into the vertical dimension of elasmobranch movement ecology

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements

The Scientific Foundations of Forecasting Magnetospheric Space Weather

The magnetosphere is the lens through which solar space weather phenomena are focused and directed towards the Earth. In particular, the non-linear interaction of the solar wind with the Earth's magnetic field leads to the formation of highly inhomogenous electrical currents in the ionosphere which can ultimately result in damage to and problems with the operation of power distribution networks. Since electric power is the fundamental cornerstone of modern life, the interruption of power is the primary pathway by which space weather has impact on human activity and technology. Consequently, in the context of space weather, it is the ability to predict geomagnetic activity that is of key importance. This is usually stated in terms of geomagnetic storms, but we argue that in fact it is the substorm phenomenon which contains the crucial physics, and therefore prediction of substorm occurrence, severity and duration, either within the context of a longer-lasting geomagnetic storm, but potentially also as an isolated event, is of critical importance. Here we review the physics of the magnetosphere in the frame of space weather forecasting, focusing on recent results, current understanding, and an assessment of probable future developments.Peer reviewe

Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

Evidence for side-chain π-delocalization in a planar substituted benzene: an experimental and theoretical charge density study on 2,5-dimethoxybenzaldehyde thiosemicarbazone

The charge density in 2,5-dimethoxybenzaldehyde thiosemicarbazone (1) has been studied experimentally using Mo-K(α) X-ray diffraction at 100 K, and by theory using DFT calculations at the B3LYP/6-311++G(2d,2p) level. The quantum theory of atoms in molecules (QTAIM) was used to investigate the extent of π-delocalization in the thioamide side-chain, which is virtually coplanar with the benzene ring. The experimental and theoretical ellipticity profiles along the bond paths were in excellent agreement, and showed that some of the formal single bonds in the side-chain have significant π-bond character. This view was supported by the magnitudes of the topological bond orders and by the delocalization indices δ(Ω(A), Ω(B)). An orbital decomposition of δ(Ω(A), Ω(B)) demonstrated that there was significant π-character in all the interchain non-H chemical bonds. On the other hand, the source function referenced at the interchain bond critical points could not provide any evidence for π-delocalization, showing instead only limited σ-delocalization between nearest neighbors. Overall, the topological evidence and the atomic graphs of the oxygen atoms did not provide convincing evidence for π-delocalization involving the methoxy substituents

On the unusual weak intramolecular C...C interactions in Ru₃(CO)₁₂: a case of bond path artefacts introduced by the multipole model?

In a recent publication in this journal, an experimental charge density analysis on the triruthenium cluster Ru<sub>3</sub>(CO)<sub>12</sub> showed unusual C...C bond paths linking the axial carbonyl ligands [Gervasio, G.; Marabello, D.; Bianchi, R.; Forni, A. J. Phys. Chem. A 2010, 114, 9368, hereafter GMBF]. These were also observed in one theoretical DFT calculation, and are associated with very low values of ρ(<b>r</b><sub>b</sub>) and <sup>2</sup>ρ(<b>r</b><sub>b</sub>). Our independent experimental charge density analysis on Ru<sub>3</sub>(CO)<sub>12</sub> is entirely consistent with GMBF and confirms the presence of these apparent weak interactions in the multipole model density. However, we conclusively demonstrate that these unusual C...C bond paths between the axial carbonyl ligands are in fact artifacts arising from the Hansen-Coppens multipole model, which is used to analyze the experimental data. Numerous relativistic and nonrelativistic gas-phase DFT calculations, using very extensive basis sets and with corrections for dispersion effects, uniformly fail to reproduce these intramolecular features in the QTAIM topology of the electron density. Moreover, multipole fitting of theoretical static structure factors computed from these quantum electron densities results in the reappearance of the C...C bond paths between the axial carbonyl ligands in the derived molecular graphs. On the other hand, using the experimental structure factors to generate “experimental” X-ray constrained DFT wave functions once again yields molecular graphs which do not show these secondary C...C bond paths. The evidence therefore strongly implicates the multipole model as the source of these spurious features and in turn suggests that great caution should be applied in the interpretation of bond paths where the values of ρ(<b>r</b><sub>b</sub>) and <sup>2</sup>ρ(<b>r</b><sub>b</sub>) are very low

Metal−metal and metal−ligand bonding at a QTAIM catastrophe: a combined experimental and theoretical charge density study on the alkylidyne cluster Fe₃(μ-H)(μ-COMe)(CO)₁₀

The charge density in the tri-iron methoxymethylidyne cluster Fe<sub>3</sub>(μ-H)(μ-COMe)(CO)<sub>10</sub>(1) has been studied experimentally at 100 K and by DFT calculations on the isolated molecule using the Quantum Theory of Atoms in Molecules (QTAIM). The COMe ligand acts as a nearly symmetric bridge toward two of the Fe atoms (Fe−C = 1.8554(4), 1.8608(4) Å) but with a much longer interaction to the third Fe atom, Fe−C = 2.6762(4) Å. Complex 1 provides a classic example where topological QTAIM catastrophes render an exact structure description ambiguous. While all experimental and theoretical studies agree in finding no direct metal−metal interaction for the doubly bridged Fe−Fe vector, the chemical bonding between the Fe(CO)<sub>4</sub> unit and the Fe<sub>2</sub>(μ-H)(μ-COMe)(CO)<sub>6</sub> moiety in terms of conventional QTAIM descriptors is much less clear. Bond paths implying direct Fe−Fe interactions and a weak interaction between the COMe ligand and the Fe(CO)<sub>4</sub> center are observed, depending on the experimental or theoretical density model examined. Theoretical studies using the Electron Localizability Indicator (ELI-D) suggest the metal−metal bonding is more significant, while the delocalization indices imply that both Fe−Fe bonding and Fe···C<sub>alkylidyne</sub> bonding are equally important. The source functions at various interfragment reference points are similar and highly delocalized. The potential-energy surface (PES) for the migration of the alkylidyne group from a μ<sub>2</sub> to a semi-μ<sub>3</sub> coordination mode has been explored by DFT calculations on 1 and the model complexes M<sub>3</sub>(μ-H)(μ-CH)(CO)<sub>10</sub> (M = Fe, 2; Ru, 3; and Os, 4). These calculations confirm a semi-μ<sub>3</sub> bridging mode for the alkylidyne ligand as the minimum-energy geometry for compounds 2−4 and demonstrate that, for 1, both Fe−Fe and Fe···C<sub>alkylidyne</sub> interactions are important in the cluster bonding. The PES between μ<sub>2</sub> and semi-μ<sub>3</sub> alkylidyne coordination for 1 is extremely soft, and the interconversion between several topological isomers is predicted to occur with almost no energy cost. Analysis of the density ρ(r) and the Laplacian of the density <sup>∇2</sup>ρ(r<sub>b</sub>) in the methoxymethylidyne ligand is consistent with a partial π-bond character of the C−O bond, associated with an sp<sup>2</sup> hybridization for these atoms

Bond orders in metal–metal interactions through electron density analysis

The metal–metal bond is central in the chemistry of polymetallic complexes. Many structural investigations, both experimental and theoretical, have been carried out with the purpose of understanding this interaction in more detail and of being able to predict the stereochemistry of these molecules. Among these studies, increasing importance is given to electron density analysis. Originally, only deformation densities were analysed, but it became clear that more sophisticated theories were necessary to appreciate the subtleties of these elusive chemical bonds. Thus, the quantum theory of atoms in molecules, electron delocalisation indices, the electron localisation function and the domain averaged Fermi hole density are nowadays used to characterise metal–metal bonds. The major results reported in the literature in the past few years are carefully reviewed in this chapter