874 research outputs found
Evolution in Economic Geography: Institutions, Regional Adaptation and Political Economy
Economic geography has, over the last decade or so, drawn upon ideas from
evolutionary economics in trying to understand processes of regional growth and
change, with the concept of path dependence assuming particular prominence.
Recently, some prominent researchers have sought to delimit and develop an
evolutionary economic geography (EEG) as a distinct approach, aiming to create a
more coherent and systematic theoretical framework for research. This paper
contributes to debates on the nature and development of EEG. It has two main aims.
First, we seek to restore a broader conception of social institutions and agency to
EEG, informed by the recent writings of institutional economists like Geoffrey
Hodgson. Second, we link evolutionary concepts to political economy approaches,
arguing that the evolution of the economic landscape must be related to the broader
dynamics of capital accumulation, centred upon the creation, realisation and
geographical transfer of value. As such, we favour the utilisation of evolutionary and
institutional concepts within a geographical political economy approach rather than
the construction of a separate and theoretically ‘pure’ EEG; evolution in economic
geography, not an evolutionary economic geography
Aromatic transformations facilitated by η6–ruthenium complexes
The chemistry of η6-arene metal complexes has been explored for over 60 years and the ability to activate arenes through this complexation has been used extensively in organic synthesis. As a result of binding to the metal, the complexed arene becomes more susceptible to nucleophilic attack and deprotonation of the aromatic and benzylic protons is made more facile. Additionally, binding a metal centre to one face of the arene subsequently has a steric effect on the reactivity, wherein the bound face is blocked from reagents and directs attack to the free face. Over the last 15 years, this area of organometallic chemistry has seen a resurgence of interest due to the catalytic capabilities of these complexes. Through an arene exchange mechanism, arenes can participate in reactions when bound to the metal catalyst, and can then exchange for another equivalent of starting material to facilitate catalytic turnover. This thesis will describe a number of projects that have been developed over three years that uses this methodology to perform transformations which are of significant interest to the scientific community.
Firstly, a trifluoromethylation protocol is described, which uses a [RuCp]+ binding unit to activate a range of electron-deficient arenes towards the nucleophilic attack of commercially available Me3SiCF3 (Ruppert’s Reagent). A library of complexes exhibit reaction, and a mixture of products are formed via SNAr and ortho-addition mechanisms. Following trifluoromethylation, the unbound arenes can be collected in quantitative yield using photolysis and chemical oxidation.
Secondly, a C–H activation and arylation protocol is described, where the same [RuCp]+ binding unit is used to enhance aromatic acidity of a η6-arene complexes. Through a concerted metalation deprotonation mechanism, a library of complexes can be activated by silver, and consequentially arylated using catalytic palladium chemistry. Following arylation, the bi-aryl arene can be liberated from ruthenium by UV irradiation.
The largest chapter of this thesis describes the catalytic radical hydrodeiodination of aryl iodides via an arene exchange mechanism. This reaction uses commercially available materials to achieve deiodination for iodoarenes in high yields and with excellent functional group tolerance and chemoselectivity.
Lastly, the early findings towards tether assisted arene exchange is described. The rates of arene exchange are studied for a library of tethered Cp ruthenium complexes, which show potential for enhanced arene exchange in catalytic reactions
Development of ultrafast laser inscribed astrophotonic components
The rapid development of astronomical instrumentation has been aided by many
innovative new photonic designs, which offer improvements in stability, precision, size
and cost, scalability, etc. ─ the field of astrophotonics. A powerful technique enabling
many of these astrophotonic devices, ultrafast laser inscription (ULI), creates highly
localised and controlled refractive index modification, which guides the path of light in
a very efficient manner. This thesis discusses three separate astrophotonic devices, each
with a specific application, to demonstrate the versatility of ULI.
Firstly, a reformatting device based on a photonic lantern and 3D ULI waveguide
reformatting component, transforms a multimode telescope PSF to a diffraction-limited
pseudo-slit. When used to feed a spectrograph, a significant reduction in modal noise ─
a limiting factor in high-resolution multimode fibre-fed spectrographs ─ is
demonstrated, with the potential for improved near-infrared radial velocity observations.
Secondly, a similar ULI reformatting device for an integral field unit, based on
multicore fibre with affixed microlenses, may enable the direct imaging of exoplanets
and characterisation of their atmospheres. Thirdly, a two-telescope K-band beam
combiner based on ULI directional couplers with an achromatic 3dB splitting ratio is
presented. Such a device will upgrade the stellar interferometry capabilities of the
CHARA array
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