In memoriam Afäwärq Täkle (1932–2012)

  Obituary  

In memoriam Stanislaw Chojnacki (1951-2010)

Obituary

Innovation and Misoneism during the Reign of Emperor Yoḥannǝs IV (1872–1889)

The article attempts to examine the character and extent of innovation and misoneism during the reign of Yoḥannǝs, i.e. the period between the largely frustrated aspirations of Tewodros and of more substantial achievements of Mǝnilǝk. The study suggests that the reign of Yoḥannǝs in fact witnessed changes in many fields of life. These included improvements in communication between Ethiopia and the outside world; the advent of new imports; changes in land tenure and class relations; the strengthening of church land-holding; attempted action against slavery and the slave trade; increasing diffusion of fire-arms; the forced conversion of Muslims, and prohibition of foreign missionaries; the banning of tobacco; the depletion of wild-life; the introduction of a national flag, the appointment of a foreign consul abroad, and the building of a church in Jerusalem

Two Unpublished 19th Century Ethiopian Letters: From Emperor Tewodros to Sir Robert Napier, and from Däǧǧazmač Nǝguśe to Naib Hasän Bey

The two letters here published supplement those in Sven Rubenson’s invaluable compilation “Tewodros and his Contemporaries”. The first letter throws intriguing light on Emperor Tewodros’s remarkably amical attitude to the British in the run-up to his military confrontation with them at Mäqdäla. The second letter, the background to which has still to be established, may be regarded as a contribution to our knowledge of däǧǧazmač Nǝguśe’s rule in Tǝgray

Ethiopia and the Great Transformation

The article considers Karl Polanyi’s thesis that 19th century Western capitalism was unique in basing itself on the principle of gain, as expressed by the  self-regulating market system. Polanyi’s argument is examined in the light of Ethiopian historical experience, with special reference to land and labour (including slavery), agricultural production, control over trade and prices, and traditional institutions which curtail or serve as an alternative to market factors. These include church holidays, compulsory hospitality, state banquets, alms giving, and, more generally, asceticism and resignation to the Will of God

Uoldelul Chelati Dirar, Alessandro Gori, and Irma Taddia: Lettere tigrine. I documenti etiopici del Fondo Ellero

Revie

Complexes of Schiff-base macrocycles and donor-expanded dipyrrins for catalysis and uranyl reduction

The modern world faces a number of challenges related to energy and the environment. Atmospheric levels of carbon dioxide have now surpassed the 400 ppm mark due to the burning of fossil fuels, yet despite its abundance and potential use as a C1 feedstock for value-added products, there are both thermodynamic and kinetic barriers associated with the strong carbon-oxygen bonds that preclude its widespread deployment in industry. Nuclear energy is an alternative power source that reduces carbon emissions by billions of tonnes each year, but there are widespread concerns regarding the treatment of the radioactive waste that it accrues (of which the main component is uranyl, [UO2]2+). Most of the work presented in this thesis concerns the synthesis of transition-metal complexes, with the aim of directing catalytic reactivity to convert CO2 to useful products. Part of this thesis also concerns the synthesis of uranyl complexes and the study of uranyl reduction chemistry, which is relevant to uranyl remediation and nuclear waste treatment at a fundamental level. Making use of Earth-abundant metals to carry out hydrocarbon oxidation catalysis is a further focus of this work, as the efficient production of oxygenated compounds under mild conditions is of importance to the fine-chemical industry. Chapter 1 reviews important complexes reported in the literature that successfully convert CO2 to useful products through molecular, homogenous electro-catalysis and ring-opening copolymerisation catalysis. Reactions that exemplify a two-electron reduction of uranyl (i.e. uranium(VI) to uranium(IV)) are reviewed, along with uranyl complexes that undergo ligand-centred redox to give ligand-based radicals. The state of the literature on hydrocarbon oxidation catalysis is reviewed in the introduction. The development of multinuclear, macrocyclic complexes and the reactivity of dinuclear Pacman complexes are also presented. Chapter 2 reports the synthesis and characterisation of a new set of Schiff-base macrocycles and acyclic dipyrrin ligands. A number of attempted synthetic routes towards incorporating a dipyrrin coordination compartment in a macro-cyclic setting are discussed. Differences in electronic structures between dipyrromethanes and dipyrromethenes are also examined by theoretical and experimental methods. Chapter 3 introduces the coordination chemistry of these new macrocycles with zinc(II), where the isolation of dinuclear and tetranuclear complexes is demonstrated using different zinc(II) precursors. Tetranuclear zinc-alkyl complexes presented here are shown to be resistant to insertion chemistry with small molecules, but readily form zinc-oxo, -hydroxyl and -alkoxide clusters upon protonolysis with water and alcohols. These molecular clusters display reactivity towards CO2: a zinc-hydroxyl complex precipitates ZnCO3 at high temperature; and zinc-alkoxide complexes have been used to catalyse the copolymerisation reaction between CO2 and cyclohexene oxide to form polycarbonates. Chapter 4 describes the synthesis of late-transition-metal complexes of macrocyclic ligands and dipyrrins, and explores the relationship between macrocycle geometry and electronic structure. Their reactivities towards CO2 are assessed here, using cyclic voltammetry to assess the electro-catalytic activity of a number of the complexes. Chapter 5 reports the oxidation chemistry of hydrocarbon substrates catalysed by copper(II) complexes. High-temperature catalysis occurs with bimetallic copper(II) complexes, and this chapter describes how added FeCl3 acts as a co-catalyst, leading to greater catalyst stability and allowing the catalytic reaction to occur at room temperature. A range of analytical methods have been used to deduce the catalytically active species, and chemical kinetic measurements have been used to deduce a possible reaction mechanism. Chapter 6 reports the synthesis of a uranyl(VI) dipyrrin complex and details characterisation of its electronic structure by theoretical and experimental methods. Theoretical modelling has indicated that the observed two-electron reduction of uranium(VI) to uranium(IV) is facilitated by the dipyrrin ligand, representing a novel uranyl reduction mechanism

Safety Implications of High-Field MRI: Actuation of Endogenous Magnetic Iron Oxides in the Human Body

Background: Magnetic Resonance Imaging scanners have become ubiquitous in hospitals and high-field systems (greater than 3 Tesla) are becoming increasingly common. In light of recent European Union moves to limit high-field exposure for those working with MRI scanners, we have evaluated the potential for detrimental cellular effects via nanomagnetic actuation of endogenous iron oxides in the body.Methodology: Theoretical models and experimental data on the composition and magnetic properties of endogenous iron oxides in human tissue were used to analyze the forces on iron oxide particles.Principal Finding and Conclusions: Results show that, even at 9.4 Tesla, forces on these particles are unlikely to disrupt normal cellular function via nanomagnetic actuation