Risk and Growth: Theoretical Relationships and Preliminary Estimates for South Africa

In the recent literature on economic growth there is disagreement over the relationship between growth and volatility and their relative benefits and costs in welfare terms. An analytical resolution of this issue, which has serious implications for domestic and international development policies, has been seen to be contingent upon how relative risk aversion and intertemporal substitutability are related in frameworks characterizing utility maximization of representative agents. It is commonly assumed that these aspects of preferences are rigidly linked, casting doubt on the expected utility maximizing paradigm as an appropriate modeling methodology for analyzing this important issue. In this paper it is first shown that these concerns are only relevant for special functional forms that enforce a unitary consumption elasticity of wealth. Next, a theoretical approach is employed to specify a more general relationship between risk aversion and intertemporal substitutability. The theoretical model is developed in the context of a two country representative agent model where risk affects domestic and direct foreign investment in both countries. The two country orientation is also capable of interpretation of the relationship between one country and the rest of the world. In a preliminary empirical application of the methodology to South African data, we attempt estimation of the parameters of generalized functions for preferences and technology which are capable of distinguishing between risk aversion and intertemporal substitutability.

Optimisation of Organic Materials for Laser Applications

This project sets out to investigate the variations of the optical properties of organic conjugated polymers with a view towards understanding the transition from isolated molecule (solution) to the solid state. The polymer poly9p-phenylene vinylene-co-2,5-dioctyloxy-m-phenylene vinylene) (PmPV) is chosen as it is of interest for both light emitting and nanotube composite applications. As a model compound, 2,5-dioctoxy-p-distrylbenzene, termed the trimer, is employed for comparison. The objective are to characterize the effect of the environment, using solvent and concentration dependent studies, on the optical properties of the polymer and to compare the results for the more complex polymeric system to the more definable molecular trimer. Low concentration UV/vis absorption and fluorescence studies indicate that the trimer well represents the electronic properties of the polymer. Solvent dependent studies of the trimer indicate that although the absorption and fluorescence spectra are relatively solvent independent, the relative fluorescence yield is strongly dependent on the solvent environment of the trimer. The variation does not correlate with traditional solvatochromic parameters, but rather can be correlated with the integrated overlap of the Raman spectra of the trimer and the solvent. The variation of the fluorescence lifetime with solvent is similarly related to this vibrational overlap parameter. This indicates that the primary effect of the changing environment is on the vibrational coupling and thus the nonradiative decay mechanisms. No such clear correlation is seen for they polymer. However, it is seen that the fluorescence lifetime of the trimer and to a greater extent the polymer is strongly dependant on concentration, implying aggregation effects. The absorption and fluorescence spectra of the polymer are seen to be strongly concentration dependant, and the results indicate that the polymer has a strong tendency to aggregate. Moreover, the degree of concentration dependence is seen to be different for polymers made by different routes. Raman studies of the trimer made via the Wittig condensation and the Horner Emmons condensation routes in both toluene and DMF, indicated that different reaction schemes produce different degrees of isomerisation along the conjugated backbone. The cis/trans ration was quantified by comparison to known mixture of cis/trans stilbene characterized by H1-NMR. The variation was seen to yield a 5:1 ratio of Trans to Cis ratio for the trimer. The variation of the cis/trans ratio was also investigated utilizing Raman spectroscopy, for the trimer the synthetic route proved massively important in the degree of isomerisation. Cis/trans ratio ranging from 17 -51%. Similar variations in degree of isomerisation in the polymer were observed and quantified. The % Cis in the polymer varied between 8-55%, depending on synthetic route. As the Wittig DMF polymer is that in which the strongest aggregation is seen, the degree of aggregation can be correlated with the cis content of the backbone. The effect of the cis isomeriation on the backbone conformation can be visualized using Hyper Chem. Whereas the all trans backbone forms a regular helix due to the meta linkage, the introduction of cis linkages disrupts this regular coiling. IN the tightly coiled trans form the п electrons of the successive coils can interact giving a well defined intramolecular. Disruption of the coiling opens up the п backbone to intermolecular interactions which can have considerable effect on the optical properties. It is concluded that engineering the intramolecular interactions in this fashion may be a route towards controlling and limiting the detrimental effect of the less definable intermolecular interactions

For Want Of: A Punk Rock Short Film

In light of the specific challenges of assessing a thesis film—a project which contains artistic and academic components—the author examines his own short film For Want Of as a prototype for future work in film and as an opportunity for introspective investigation into the nature of filmmaking and personal artistic process. Reference is made to specific episodes during the film’s conception and production, as well as higher-level insight gained from following the film through an 18-month production cycle

For Want Of: A Punk Rock Short Film

In light of the specific challenges of assessing a thesis film—a project which contains artistic and academic components—the author examines his own short film For Want Of as a prototype for future work in film and as an opportunity for introspective investigation into the nature of filmmaking and personal artistic process. Reference is made to specific episodes during the film’s conception and production, as well as higher-level insight gained from following the film through an 18-month production cycle

High quality electron beam generation in a proton-driven hollow plasma wakefield accelerator

Simulations of proton-driven plasma wakefield accelerators have demonstrated substantially higher accelerating gradients compared to conventional accelerators and the viability of accelerating electrons to the energy frontier in a single plasma stage. However, due to the strong intrinsic transverse fields varying both radially and in time, the witness beam quality is still far from suitable for practical application in future colliders. Here we demonstrate efficient acceleration of electrons in proton-driven wakefields in a hollow plasma channel. In this regime, the witness bunch is positioned in the region with a strong accelerating field, free from plasma electrons and ions. We show that the electron beam carrying the charge of about 10% of 1 TeV proton driver charge can be accelerated to 0.6 TeV with preserved normalized emittance in a single channel of 700 m. This high quality and high charge beam may pave the way for the development of future plasma-based energy frontier colliders.Comment: 10 pages, 7 figure

Leiomyosarcoma of the Cephalic Vein

A 78-year-old man presented with a mass on his right forearm. A 5 x 4 x 3 cm3 mass was excised en bloc with extensions along the course of the cephalic vein and its tributaries. Histological analysis revealed the mass to be a high-grade leiomyosarcoma arising within the cephalic vein. The tumour was controlled locally and distally until the patient died 10 months later, from an unrelated illness. This is the first reported case of a venous leiomyosarcoma of the cephalic vein

Coastal vulnerability to typhoon inundation in the Bay of Bangkok, Thailand? Evidence from carbonate boulder deposits on Ko Larn island

© 2015 Elsevier Ltd. At the head of the Gulf of Thailand, the subsiding Chao Phraya delta and adjacent low-lying coastlines surrounding the Bay of Bangkok are at risk of coastal flooding. Although a significant marine inundation event has not been experienced in historical times, this work identifies coastal depositional evidence for high-energy waves in the past. On Ko Larn island in eastern Bay of Bangkok, numerous coastal carbonate boulders (CCBs) were discovered at elevations up to 4+ m above sea level, the largest weighing over 1.3 tonnes. For the majority of CCBs, their karstified appearance bears testimony to long periods of immobility since original deposition, whilst their geomorphic settings on coastal slopes of coarse blocky talus is helpful in recognising lifting (saltation) as the probable mode of wave transport. In the absence of local tsunamigenic potential, these CCBs are considered to be prehistoric typhoon deposits, presumably sourced from fringing coral reefs by high-energy wave action. Application of existing hydrodynamic flow transport equations reveals that 4.7 m/s and 7.1 m/s are the minimum flow velocities required to transport 50% and 100% of the measured CCBs, respectively. Such values are consistent with cyclone-impacted coastlines studied elsewhere in the tropical Asia-Pacific region. Overall, the evidence of elevated carbonate boulder deposits on Ko Larn implies that typhoons before the modern record may have entered the Bay of Bangkok. The recurrence of a similar event in future would have the potential to cause damaging marine inundation on surrounding low-lying coastlines