Synthesis of a Bis(thiophenolate)pyridine Ligand and Its Titanium, Zirconium, and Tantalum Complexes

A precursor to a new tridentate LX_2 type ligand, bis(thiophenol)pyridine ((SNS)H_2 = (2-C_6H_4SH)_2-2,6-C_5H_3N), was prepared. Bis(thiophenolate)pyridine complexes of Ti, Zr, and Ta having dialkylamido coligands were synthesized and structurally characterized. The zirconium complex (SNS)Zr(NMe_2)_2 (4) displays C_2 symmetry in the solid state, unlike a related bis(phenolate)pyridine compound, C_s-symmetric (ONO)Ti(NMe_2)_2. This change is likely the result of strain about the sulfur atom in the six-membered chelate with longer metal–sulfur and carbon–sulfur bonds. Solid-state structures of tantalum complexes (SNS)Ta(NMe_2)_3 (5) and (SNS)TaCl(NEt_2)_2 (6) also display pronounced C_2 twisting of the SNS ligand. 1D and 2D NMR experiments show that 5 is fluxional, with rotation about the Ta–N(amide) bonds occurring on the NMR time scale that interchange the equatorial amide methyl groups (ΔG^‡_(393) = 25.0(3) kcal/mol). The fluxional behavior of 6 in solution was also studied by variable-temperature ^1H NMR. Observation of separate signals for the diastereotopic protons of the methylene unit of the diethylamide indicates that the complex remains locked on the NMR time scale in one diastereomeric conformation at temperatures below −50 °C, fast rotation about the equatorial amide Ta–N bonds occurs at higher temperature (ΔG^‡_(393) = 13.4(3) kcal/mol), and exchange of diastereomeric methylene protons occurs via inversion at Ta that interconverts antipodes (ΔG^‡_(393) ≈ 14(1) kcal/mol)

Formation of Trivalent Zirconocene Complexes from ansa-Zirconocene-Based Olefin-Polymerization Precatalysts: An EPR- and NMR-Spectroscopic Study

Reduction of Zr(IV) metallocenium cations with sodium amalgam (NaHg) produces EPR signals assignable to Zr(III) metallocene complexes. The chloro-bridged heterodinuclear ansa-zirconocenium cation [(SBI)Zr(μ-Cl)_2AlMe_2]^+ (SBI = rac-dimethylsilylbis(1-indenyl)), present in toluene solution as its B(C_6F_5)_4^– salt, thus gives rise to an EPR signal assignable to the complex (SBI)Zr^(III)(μ-Cl)_2AlMe_2, while (SBI)ZrIII-Me and (SBI)Zr^(III)(μ-H)_2Al^(i)Bu_2 are formed by reduction of [(SBI)Zr(μ-Me)_2AlMe_2]^+ B(C_6F_5)_4– and [(SBI)Zr(μ-H)_3(AliBu_2)_2]^+ B(C_6F_5)_4^–, respectively. These products can also be accessed, along with (SBI)ZrIII-iBu and [(SBI)ZrIII]^+ AlR_4^–, when (SBI)ZrMe_2 is allowed to react with HAl^(i)Bu_2, eliminating isobutane en route to the Zr(III) complex. Further studies concern interconversion reactions between these and other (SBI)Zr(III) complexes and reaction mechanisms involved in their formation

Evidence and morality in harm-reduction debates: can we use value-neutral arguments to achieve value-driven goals?

It is common to argue that politicians make selective use of evidence to tacitly reinforce their moral positions, but all stakeholders combine facts and values to produce and use research for policy. The drug policy debate has largely been framed in terms of an opposition between evidence and politics. Focusing on harm reduction provides useful ground to discuss a further opposition proposed by evidence advocates, that between evidence and morality. Can evidence sway individuals from their existing moral positions, so as to “neutralise” morality? And if not, then should evidence advocates change the way in which they frame their arguments? To address these questions, analysis of N=27 interviews with stakeholders involved in drug policy and harm reduction research, advocacy, lobbying, implementation and decision-making in England, UK and New South Wales, Australia, was conducted. Participants’ accounts suggest that although evidence can help focus discussions away from values and principles, exposure to evidence does not necessarily change deeply held views. Whether stakeholders decide to go with the evidence or not seems contingent on whether they embrace a view of evidence as secular faith; a view that is shaped by experience, politics, training, and role. And yet, morality, values, and emotions underpin all stakeholders’ views, motivating their commitment to drug policy and harm reduction. Evidence advocates might thus benefit from morally and emotionally engaging audiences. This paper aims to develop better tools for analysing the role of morality in decision-making, starting with moral foundations theory. Using tools from disciplines such as moral psychology is relevant to the study of the politics of evidence-based policymaking

Emergent constraint on equilibrium climate sensitivity from global temperature variability

Equilibrium climate sensitivity (ECS) remains one of the most important unknowns in climate change science. ECS is defined as the global mean warming that would occur if the atmospheric carbon dioxide (CO2) concentration were instantly doubled and the climate were then brought to equilibrium with that new level of CO2. Despite its rather idealized definition, ECS has continuing relevance for international climate change agreements, which are often framed in terms of stabilization of global warming relative to the pre-industrial climate. However, the ‘likely’ range of ECS as stated by the Intergovernmental Panel on Climate Change (IPCC) has remained at 1.5–4.5 degrees Celsius for more than 25 years1. The possibility of a value of ECS towards the upper end of this range reduces the feasibility of avoiding 2 degrees Celsius of global warming, as required by the Paris Agreement. Here we present a new emergent constraint on ECS that yields a central estimate of 2.8 degrees Celsius with 66 per cent confidence limits (equivalent to the IPCC ‘likely’ range) of 2.2–3.4 degrees Celsius. Our approach is to focus on the variability of temperature about long-term historical warming, rather than on the warming trend itself. We use an ensemble of climate models to define an emergent relationship2 between ECS and a theoretically informed metric of global temperature variability. This metric of variability can also be calculated from observational records of global warming3, which enables tighter constraints to be placed on ECS, reducing the probability of ECS being less than 1.5 degrees Celsius to less than 3 per cent, and the probability of ECS exceeding 4.5 degrees Celsius to less than 1 per cent

Beyond forcing scenarios: predicting climate change through response operators in a coupled general circulation model

Global Climate Models are key tools for predicting the future response of the climate system to a variety of natural and anthropogenic forcings. Here we show how to use statistical mechanics to construct operators able to flexibly predict climate change for a variety of climatic variables of interest. We perform our study on a fully coupled model - MPI-ESM v.1.2 - and for the first time we prove the effectiveness of response theory in predicting future climate response to CO2 increase on a vast range of temporal scales, from inter-annual to centennial, and for very diverse climatic quantities. We investigate within a unified perspective the transient climate response and the equilibrium climate sensitivity and assess the role of fast and slow processes. The prediction of the ocean heat uptake highlights the very slow relaxation to a newly established steady state. The change in the Atlantic Meridional Overturning Circulation (AMOC) and of the Antarctic Circumpolar Current (ACC) is accurately predicted. The AMOC strength is initially reduced and then undergoes a slow and only partial recovery. The ACC strength initially increases as a result of changes in the wind stress, then undergoes a slowdown, followed by a recovery leading to a overshoot with respect to the initial value. Finally, we are able to predict accurately the temperature change in the Northern Atlantic

Scaling Effects and Spatio-Temporal Multilevel Dynamics in Epileptic Seizures

Epileptic seizures are one of the most well-known dysfunctions of the nervous system. During a seizure, a highly synchronized behavior of neural activity is observed that can cause symptoms ranging from mild sensual malfunctions to the complete loss of body control. In this paper, we aim to contribute towards a better understanding of the dynamical systems phenomena that cause seizures. Based on data analysis and modelling, seizure dynamics can be identified to possess multiple spatial scales and on each spatial scale also multiple time scales. At each scale, we reach several novel insights. On the smallest spatial scale we consider single model neurons and investigate early-warning signs of spiking. This introduces the theory of critical transitions to excitable systems. For clusters of neurons (or neuronal regions) we use patient data and find oscillatory behavior and new scaling laws near the seizure onset. These scalings lead to substantiate the conjecture obtained from mean-field models that a Hopf bifurcation could be involved near seizure onset. On the largest spatial scale we introduce a measure based on phase-locking intervals and wavelets into seizure modelling. It is used to resolve synchronization between different regions in the brain and identifies time-shifted scaling laws at different wavelet scales. We also compare our wavelet-based multiscale approach with maximum linear cross-correlation and mean-phase coherence measures

Ocean Acidification at High Latitudes: Potential Effects on Functioning of the Antarctic Bivalve Laternula elliptica

Ocean acidification is a well recognised threat to marine ecosystems. High latitude regions are predicted to be particularly affected due to cold waters and naturally low carbonate saturation levels. This is of concern for organisms utilising calcium carbonate (CaCO3) to generate shells or skeletons. Studies of potential effects of future levels of pCO2 on high latitude calcifiers are at present limited, and there is little understanding of their potential to acclimate to these changes. We describe a laboratory experiment to compare physiological and metabolic responses of a key benthic bivalve, Laternula elliptica, at pCO2 levels of their natural environment (430 µatm, pH 7.99; based on field measurements) with those predicted for 2100 (735 µatm, pH 7.78) and glacial levels (187 µatm, pH 8.32). Adult L. elliptica basal metabolism (oxygen consumption rates) and heat shock protein HSP70 gene expression levels increased in response both to lowering and elevation of pH. Expression of chitin synthase (CHS), a key enzyme involved in synthesis of bivalve shells, was significantly up-regulated in individuals at pH 7.78, indicating L. elliptica were working harder to calcify in seawater undersaturated in aragonite (ΩAr = 0.71), the CaCO3 polymorph of which their shells are comprised. The different response variables were influenced by pH in differing ways, highlighting the importance of assessing a variety of factors to determine the likely impact of pH change. In combination, the results indicate a negative effect of ocean acidification on whole-organism functioning of L. elliptica over relatively short terms (weeks-months) that may be energetically difficult to maintain over longer time periods. Importantly, however, the observed changes in L. elliptica CHS gene expression provides evidence for biological control over the shell formation process, which may enable some degree of adaptation or acclimation to future ocean acidification scenarios

Allowable CO2 emissions based on regional and impact-related climate targets

This paper was accepted for publication in the journal Nature and the definitive published version is available at http://dx.doi.org/10.1038/nature16542© 2016 Macmillan Publishers Limited. All rights reserved. Global temperature targets, such as the widely accepted limit of an increase above pre-industrial temperatures of two degrees Celsius, may fail to communicate the urgency of reducing carbon dioxide (CO2) emissions. The translation of CO2 emissions into regional- and impact-related climate targets could be more powerful because such targets are more directly aligned with individual national interests. We illustrate this approach using regional changes in extreme temperatures and precipitation. These scale robustly with global temperature across scenarios, and thus with cumulative CO2 emissions. This is particularly relevant for changes in regional extreme temperatures on land, which are much greater than changes in the associated global mean

Proceedings of the Thirteenth International Society of Sports Nutrition (ISSN) Conference and Expo

Meeting Abstracts: Proceedings of the Thirteenth International Society of Sports Nutrition (ISSN) Conference and Expo Clearwater Beach, FL, USA. 9-11 June 201