A Terminal Fe^(III)-Oxo in a Tetranuclear Cluster: Effects of Distal Metal Centers on Structure and Reactivity

Tetranuclear Fe clusters have been synthesized bearing a terminal Fe^(III)–oxo center stabilized by hydrogen-bonding interactions from pendant (tert-butylamino)pyrazolate ligands. This motif was supported in multiple Fe oxidation states, ranging from [Fe^(II)_2Fe^(III)_2] to [Fe^(III)_4]; two oxidation states were structurally characterized by single-crystal X-ray diffraction. The reactivity of the Fe^(III)–oxo center in proton-coupled electron transfer with X–H (X = C, O) bonds of various strengths was studied in conjunction with analysis of thermodynamic square schemes of the cluster oxidation states. These results demonstrate the important role of distal metal centers in modulating the reactivity of a terminal metal–oxo

Quantum Layers over Surfaces Ruled Outside a Compact Set

In this paper, we proved the quantum layer over a surface which is ruled outside a compact set, asymptotically flat but not totally geodesic admits ground states

Endomorphisms and automorphisms of locally covariant quantum field theories

In the framework of locally covariant quantum field theory, a theory is described as a functor from a category of spacetimes to a category of *-algebras. It is proposed that the global gauge group of such a theory can be identified as the group of automorphisms of the defining functor. Consequently, multiplets of fields may be identified at the functorial level. It is shown that locally covariant theories that obey standard assumptions in Minkowski space, including energy compactness, have no proper endomorphisms (i.e., all endomorphisms are automorphisms) and have a compact automorphism group. Further, it is shown how the endomorphisms and automorphisms of a locally covariant theory may, in principle, be classified in any single spacetime. As an example, the endomorphisms and automorphisms of a system of finitely many free scalar fields are completely classified.Comment: v2 45pp, expanded to include additional results; presentation improved and an error corrected. To appear in Rev Math Phy

Probability distributions of smeared quantum stress tensors

We obtain in closed form the probability distribution for individual measurements of the stress-energy tensor of two-dimensional conformal field theory in the vacuum state, smeared in time against a Gaussian test function. The result is a shifted Gamma distribution with the shift given by the previously known optimal quantum inequality bound. For small values of the central charge it is overwhelmingly likely that individual measurements of the sampled energy density in the vacuum give negative results. For the case of a single massless scalar field, the probability of finding a negative value is 84%. We also report on computations for four-dimensional massless scalar fields showing that the probability distribution of the smeared square field is also a shifted Gamma distribution, but that the distribution of the energy density is not.Comment: 9 pages, 1 figure. Minor edits implemente

Commons: Governance of Shared Assets [PDF Version]

Abstract & Contents The idea for this book came slowly following a gradual collection of blog posts on the CCRI website in recent years. The posts centred around the general theme of how we manage shared assets and what alternative approaches there might be, informed by research and practice in the governance of commons resources. The whole area of commons and management of common pool resources has become more topical over the last 6 years following the award of the Nobel Prize for Economics to Elinor Ostrom, for her work on commons. Commons has long been an element of research within CCRI, particularly in relation to Common Land and Town and village Greens in England and Wales. Chris Short organised annual conferences on common land management from 1999-2010 which attracted over 1,500 delegates and sponsorship from the Countryside Agency, Defra, Natural England and the Countryside Council for Wales. This book is no more than a set of ‘musings’ or collected thoughts about a range of issues which we have addressed in our professional activities. It does not claim to address all aspects of an issue, or to present a balanced view of research findings. The aim is simply to present some of our ideas about management and governance of a range of resources that can be perceived in some way as ‘shared assets’. The resources addressed range from the local to the global, and encompass what have been termed traditional commons (such as fisheries, pasture, water) and ‘new’ commons such as the internet and urban areas. Our purpose in producing this book is to raise awareness of the principles of commons governance. Our aim is to encourage thinking about the ways in which application of these principles might open up alternative solutions to achieving long-term and sustainable management of the many assets that we share in common. Contents • COP21 - ‘Gentlemen’s Agreement’ or new approach? • Cities and the concept of ‘urban commons’ • Designing the urban commons • Urban commons - the view from beneath • What value street art? • Marine fisheries • What future for Lowland commons? • Peatlands • Climbing the wall • The Internet is not a commons? • Final thought

Zirconium complexes supported by a ferrocene-based ligand as redox switches for hydroamination reactions

The synthesis of (thiolfan*)Zr(Net_2)_2 (thiolfan* = 1,1′-bis(2,4-di-tert-butyl-6-thiophenoxy)ferrocene) and its catalytic activity for intramolecular hydroamination are reported. In situ oxidation and reduction of the metal complex results in reactivity towards different substrates. The reduced form of (thiolfan*)Zr(Net_2)_2 catalyzes hydroamination reactions of primary aminoalkenes, whereas the oxidized form catalyzes hydroamination reactions of secondary aminoalkenes

Thermodynamics of Proton and Electron Transfer in Tetranuclear Clusters with Mn–OH_2/OH Motifs Relevant to H_2O Activation by the Oxygen Evolving Complex in Photosystem II

We report the synthesis of site-differentiated heterometallic clusters with three Fe centers and a single Mn site that binds water and hydroxide in multiple cluster oxidation states. Deprotonation of Fe^(III/II)_3Mn^(II)–OH_2 clusters leads to internal reorganization resulting in formal oxidation at Mn to generate Fe^(III/II)_3Mn^(III)–OH. ^(57)Fe Mössbauer spectroscopy reveals that oxidation state changes (three for Fe^(III/II)_3Mn–OH_2 and four for Fe^(III/II)_3Mn–OH clusters) occur exclusively at the Fe centers; the Mn center is formally Mn^(II) when water is bound and Mn^(III) when hydroxide is bound. Experimentally determined pK_a (17.4) of the [Fe^(III)_2Fe^(II)Mn^(II)–OH_2] cluster and the reduction potentials of the [Fe_3Mn–OH_2] and [Fe_3Mn–OH] clusters were used to analyze the O–H bond dissociation enthalpies (BDE_(O–H)) for multiple cluster oxidation states. BDE_(O–H) increases from 69 to 78 and 85 kcal/mol for the [Fe^(III)Fe^(II)_2Mn^(II)–OH_2], [Fe^(III)_2Fe^(II)Mn^(II)–OH_2], and [Fe^(III)_3Mn^(II)–OH_2] clusters, respectively. Further insight of the proton and electron transfer thermodynamics of the [Fe_3Mn–OH_x] system was obtained by constructing a potential–pK_a diagram; the shift in reduction potentials of the [Fe_3Mn–OH_x] clusters in the presence of different bases supports the BDE_(O–H) values reported for the [Fe_3Mn–OH_2] clusters. A lower limit of the pK_a for the hydroxide ligand of the [Fe_3Mn–OH] clusters was estimated for two oxidation states. These data suggest BDE_(O–H) values for the [Fe^(III)_2Fe^(II)Mn^(III)–OH] and [Fe^(III)_3Mn^(III)–OH] clusters are greater than 93 and 103 kcal/mol, which hints to the high reactivity expected of the resulting [Fe_3Mn═O] in this and related multinuclear systems

A Terminal Fe^(III)-Oxo in a Tetranuclear Cluster: Effects of Distal Metal Centers on Structure and Reactivity

Tetranuclear Fe clusters have been synthesized bearing a terminal Fe^(III)–oxo center stabilized by hydrogen-bonding interactions from pendant (tert-butylamino)pyrazolate ligands. This motif was supported in multiple Fe oxidation states, ranging from [Fe^(II)_2Fe^(III)_2] to [Fe^(III)_4]; two oxidation states were structurally characterized by single-crystal X-ray diffraction. The reactivity of the Fe^(III)–oxo center in proton-coupled electron transfer with X–H (X = C, O) bonds of various strengths was studied in conjunction with analysis of thermodynamic square schemes of the cluster oxidation states. These results demonstrate the important role of distal metal centers in modulating the reactivity of a terminal metal–oxo

How Racist Violence Becomes a Virtue: An Application of Discourse Analysis

This discourse analytic study examines how violence can be constructed as an honourable course of action, using the example of a leaflet circulated in the loyalist Donegall Pass area of Belfast urging the removal of the minority Chinese population. Starting from the assumptions that racism is an ideological practice that naturalises social categories and devalues members of some of them so that their subjugation and exclusion is legitimised (Miles and Brown 2003; Billig 2002), and that violence is a human activity imbued with meaning through discourse, we applied guidelines set out by Parker (1992) to consider language as a social practice that achieves specific discursive effects by constructing its objects in a particular way. Two interrelated discourses were identified: a community-focused discourse construed the Chinese immigrants as morally and culturally bereft and negated their worth, while a martial discourse focused on defending the locality against foreign invasion. An examination of themes in loyalist culture revealed ways in which the text reconstructed resonant fears, and we argue that the way the in-group constructs its character defines the racist construction of the other