Chronic non-specific low back pain (CNSLBP) is a widespread but poorly understood condition that places a substantial burden on the sufferer, health services and the wider economy. Existing approaches to management do not demonstrate impressive levels of effectiveness. There is growing evidence that CNSLBP is associated with significant alterations in central nervous system (CNS) structure and function, suggesting a possible role for the brain in the aetiology of the condition, and presenting a case for novel therapies which aim to treat CNSLBP by affecting brain function. One such potential therapeutic approach is non-invasive brain stimulation (NIBS). Following a literature review discussing the epidemiology and management of low back pain, the evidence for altered CNS function and the potential role of brain stimulation in CNSLBP and chronic pain generally this thesis includes 3 original scientific studies: (i) A Cochrane systematic review of the effectiveness of NIBS techniques for the treatment of chronic pain; (ii) A randomised double-blind exploratory study of transcranial direct current stimulation of the motor cortex in the treatment of CNSLBP; (iii) Is blinding to the stimulation condition maintained in trials comparing 2mA tDCS with sham stimulation? A randomised cross-over study. Results: There is limited existing evidence that some forms of NIBS may have a beneficial effect on chronic pain, though caution is warranted. Exploratory data from study 2 is not suggestive that tDCS to the motor cortex is effective for treating CNSLBP. Commonly used sham controls in trials of tDCS do not ensure adequate blinding, and so introduce a potential source of bias to the existing evidence base. Conclusion: Further research is required to establish the value of NIBS as a treatment for chronic pain and CNSLBP. Future research in tDCS will need to develop and employ fully validated sham controls to ensure adequate blinding. NIBS cannot currently be recommended for the treatment of CNSLBP.

Since the late 1970s, the Chinese economic system has experienced a series of economic reforms, which include attracting foreign direct investment and the liberalisation of Chinese international trade. Due to the successful reform, China has experienced a 30 year economic growth. Previous empirical studies found the positive effect of FDI in the Chinese economic development. This study plans to investigate the factors which attract the investment to China and the impact of the inward FDI on international trade and Chinese economic development under the geographic location condition. OLI model has emphasis the location effect in motivated FDI flows. The first research question is the determinant of FDI in China with concerning the geographic effect. Different with the previous empirical paper on the FDI determinants in China, the using the geographic effect as an dummy variable in the specification, this study investigate the effect of the other determinant under different geographic background. The geographic effect has been explore in two levels: national level and regional level. On national level, there are two countries have been selected as research samples: the investment from the U.S. and the investment from Japan. These two countries have similar economic size and FDI stock in China but have different geographic relationship with China. Through the ARDL research approach, this study finds that the key drivers of inward investment are relative wages, relative capital cost, market size and net exports, although the source of these FDI flows is also found to be important especially those from the USA and Japan. The determinants of FDI from the US and Japan have different effect. International trade has negative effect of export from US to China on the US FDI stock in China, while it has positive coefficient of the exports from Japan to China on the Japanese FDI. The large market size would drive the FDI from US but reduce the FDI from Japan. The geographic effect influences the motivation of FDI (Helpman 1984, Cushman 1988). This further lead the determinants has different effect. The study on regional FDI divided the Chinese provinces in two subgroups: the eastern coastal area and the western hinterland. The eastern area has more than 80% of FDI in China. The eastern coastal has rich resource in the transportation, openness, physical and human capital. The west hinterland area has cheaper labours. However, the result shows that the competition in the sub-regions are determined by it scare resources. Cheaper wage is the key factor to attractive the investment to the east regions. While the technology, human capital and economy openness is the key factors to determine the FDI stock in the west hinterland. The second research question is the impact of FDI on international trade. Chapter 6 investigates the plausibility of FDI driving trade. The granger causality test has been applied to test the endogenity between international trade and FDI stock in China, the results does not support the causality. The further regression results show that this model is not substantiated by the data, so the maintained hypothesis that FDI is the dependent variables seems to be appropriate for China. The third contribution is to examine the effects of FDI on economic growth. In this panel data analysis the impact of FDI on the regions of the country is examined. Furthermore, the impact on the sub-regions groups has also been explored. The results show that economy of the east coastal area in China is motivated by the inward FDI stock. However, due to the limitation of the catch-up capability, FDI has negative effect on the development of the hinterland in China. The hinterland economy is driven by the international trade, although the transportation resource in the hinterland is not as rich as ones in the eastern coast.

published_or_final_version / Business Administration / Master / Master of Business Administration

The structure of direct-current microdischarges is investigated using a detailed two-dimensional multi-species continuum model. Microdischarges are directcurrent discharges that operate at a relatively high pressure of about 100 Torr and geometric dimensions in the 10-100 micrometer range. Our motivation for the study of microdischarges comes from a potential application of these devices in microthrusters for small satellite propulsion. The Micro Plasma Thruster (MPT) concept consists of a direct-current microdischarge in a geometry comprising a constant area flow section followed by a diverging exit nozzle. A detailed description of the plasma dynamics inside the MPT including power deposition, ionization, coupling of the plasma phenomena with high-speed flow, and propulsion system performance is reported in this study. A two-dimensional model is developed as part of this study. The model consists of a plasma module coupled to a flow module and is solved on a hybrid unstructured mesh framework. The plasma module provides a self-consistent, multispecies, multi-temperature description of the microdischarge phenomena while the flow module provides a description of the low Reynolds number compressible flow through the system. The plasma module solves conservation equations for plasma species continuity and electron energy, and Poisson’s equation for the self-consistent electric field. The flow module solves mass, bulk gas momentum and energy equations. The coupling of energy from the electrostatic field to the plasma species is modeled by the Joule heating term which appears in the electron and heavy species energy equations. Discretization of the Joule heating term on unstructured meshes requires special attention. We propose a new robust method for the numerical discretization of the Joule heating term on such meshes using a cell-centered, finite volume approach. A prototypical microhollow cathode discharge (MHCD) is studied to guide and validate the modeling effort for theMPT. Computational results for the impedance characteristics as well as electrodynamic and chemical features of the discharge are reported and compared to experimental results. At low current (< 0.1 mA), the plasma activity is localized inside the cylindrical hollow region of the discharge operating in the so-called “abnormal regime”. For larger currents, the discharge expands over the outer flat surface of the cathode and operates in the “normal regime”. Transient relaxation oscillations are predicted in the plasma properties for intermediate discharge currents ranging from 0.1 mA to 0.3 mA; a phenomenon that is reported in experiments. The MPT, in its present configuration, is found to operate as an electrothermal, rather than as an electrostatic thruster. A significant increase in specific impulse, compared to the cold gas micronozzle, is obtained from the power deposition into the expanding gas. For a discharge voltage of 750 V, a power input of 650 mW, and an argon mass flow rate of 5 sccm, the specific impulse of the device is increased by a factor of 1.5 to a value of 74 s. The microdischarge remains mostly confined inside the micronozzle and operates in an abnormal regime. Gas heating, primarily due to ion Joule heating, is found to have a strong influence on the overall discharge behavior. The study provides crucial understanding to aid in the design of direct-current microdischarge based thrusters. / text

The primary purpose of this study is to model the water vapor flow produced by a comet impact on the Moon using the Direct Simulation Monte Carlo (DSMC) method. Toward that end, our DSMC solver was modified in order to model the cometary water from the time of impact until it is either destroyed due to escape or photodestruction processes or captured inside one of the lunar polar cold traps. In order to model the complex flow induced by a comet impact, a 3D spherical parallel version of the DSMC method was implemented. The DSMC solver was also modified to take as input the solution from the SOVA hydrocode for the impact event at a fixed interface. An unsteady multi-domain approach and a collision limiting scheme were also added to the previous implementation in order to follow the water from the continuum regions near the point of impact to the much later rarefied atmospheric flow around the Moon. The present implementation was tested on a simple unsteady hemispherical expansion flow into a vacuum. For these simulations, the data at the interface were provided by a 1D analytical model instead of the SOVA solution. Good results were obtained downstream of the interface for density, temperature and radial velocity. Freezing of the vibrational modes was also observed in the transitional regime as the flow became collisionless. The 45° oblique impact of a 1 km radius ice sphere at 30 km/s was simulated up to several months after impact. Most of the water crosses the interface under 5 s moving mostly directly downstream of the interface. Most of the water escapes the gravity well of the Moon within the first few hours after impact. For such a comet impact, only ~3% of the comet mass remains on the Moon after impact. As the Moon rotates, the molecules begin to migrate until they are destroyed or captured in a cold trap. Of the 3% of the water remaining on the Moon after impact, only a small fraction, ~0.14% of the comet mass, actually reaches the cold traps; nearly all of the rest is photo-destroyed. Based on the surface area of the cold traps used in the present simulations, ~1 mm of ice would have accumulated in the polar cold traps after such an impact. Estimates for the total mass of water accumulated in the polar cold traps over one billion years are consistent with recent observations. / text

An immersed boundary spectral method is used to simulate laminar boundary layer flow over a periodic array of cylindrical surface roughness elements. Direct comparisons are made with experiments by using a roughness-based Reynolds number Re[subscript k] of 216 and a diameter to spanwise spacing ratio d/[lamda] of 1/3. Near-field differences between three similar studies are presented and addressed. The shear layer developed over the roughness element produces the downstream velocity deficit region while splitting of the vortex sheet shed the trailing edge forms its lateral modes. Additional geometrical configurations are simulated for comparisons with experimental results and future analysis by linear stability theory. Total disturbance energy E[subscript rms] is fairly consistent with experimental results while spanwise energy components vary significantly. Physical relaxation of the disturbance wake is found to remain a prominent issue for this simulation technique. / text

The main goal of this work is to examine classes of finite groups in which normality, permutability and Sylow-permutability are transitive relations. These classes of groups are called T , PT and PST , respectively. The main focus is on direct products of T , PT and PST groups and the behavior of a collection of cyclic normal, permutable and Sylow-permutable subgroups under the intersection map. In general, a direct product of finitely many groups from one of these classes does not belong to the same class, unless the orders of the direct factors are relatively prime. Examples suggest that for solvable groups it is not required to have relatively prime orders to stay in the class. In addition, the concept of normal, permutable and S-permutable cyclic sensitivity is tied with that of Tc, PTc and PSTc groups, in which cyclic subnormal subgroups are normal, permutable or Sylow-permutable. In the process another way of looking at the Dedekind, Iwasawa and nilpotent groups is provided as well as possible interplay between direct products and the intersection map is observed.

Compressional and shear body waves generated by a seismic source can be analyzed using vertical seismic profiling (VSP) data-acquisition procedures. If a goal of exploration geophysics is to study the physics and exploration applications of shear waves, it is important to know how much S-wave energy a source puts into the earth. To maximize S-wave created by a source, considerable effort has been expended to create surface sources that apply horizontally directed impulses to the earth (horizontal vibrators and horizontal impacts). In my project, radial shear (SR) and transverse shear (ST) waves generated by different types of sources and recorded by multicomponent receivers in a VSP well are examined and compared. The research question is ‘can a vertical-impact source create shear wave energy equivalent to the S-wave energy produced by standard horizontal-force shear-wave sources?’ To quantify the energy of shear-wave modes produced by different kinds of seismic sources, a VSP field test program was conducted at the Devine Test Site owned by The University of Texas at Austin. In the VSP data acquisition phase, the orientation of horizontal geophones is unknown because a borehole geophone rotates as it is lowered into a well, causing the horizontal geophones at each receiver station to be oriented in different azimuths. To study body waves, it is essential that all geophones in a vertical VSP array be oriented in a consistent azimuth. I mathematically rotated multi-component VSP sensors systems to change them from the inconsistent orientation they had at the time of data recording to a user-defined consistent-azimuth coordinate system. This rotation allowed ST and SR wave modes to be identified. After geophone rotation, direct-S wavelet amplitudes were analyzed in 90-ms windows starting at the first-break times of each arriving mode. Analysis of the rotated data showed that SR energy created by a vertical-impact source, a shot-hole explosive, and an inclined-impact source differ only slightly, and that there is essentially no difference in ST energy among these sources. Also, the signal frequency of SR and ST wave modes produced by horizontal-force shear wave sources are essentially the same as the frequency of SR and ST wave modes generated by a vertical-impact source. These test data show that vertical and horizontal vibrator sources produce shear wave modes having amplitudes 1000 times stronger than the other energy sources we tested. Considering the cost of using inclined-impact sources which is relatively expensive compared to using a vertical-impact source, and the difficulty of applying inclined-impacts in some land conditions, it is possible to obtain direct-S data of the same quality by using only a vertical-impact source or a shot-hole explosive. The arguments given above demonstrate that it is not necessary to use inclined-impact sources or horizontal vibrators to produce shear-wave data. S-wave data of the same quality produced by a horizontal-force source are provided by simple vertical-impact sources and shot-hole explosives. / text

Chemistry / The efforts described in this thesis were bifurcated along two distinct projects, but generally were directed toward the development of new materials to solve outstanding issues in contemporary electrochemical applications. The first project involved the synthesis and application of redox-switchable olefin metathesis catalysts. N-heterocyclic carbenes (NHCs) bearing ferrocene and other redox-active groups were designed, synthesized, and incorporated into model iridium complexes to evaluate their intrinsic electrochemical and steric parameters. Using these complexes, the ability to switch the electron donating ability of the ligands via redox processes was quantified using a variety of electrochemical and spectroscopic techniques. The donicity was either enhanced or attenutated upon reduction or oxidation of the redox-active group, respectively. The magnitude of the change in donicity upon reduction or oxidation did not vary significantly as a function of the proximity of the redox-active group from the metal center. Thus, other factors, including synthetic considerations, sterics, and redox potential requirements, were determined to guide ligand design. Regardless, redox-active NHCs were adapted into ruthenium-based olefin metathesis catalysts and used to gain control control over various ring-opening metathesis polymerizations and ring-closing metathesis reactions. The second project was focused on the development of new basic polymers for acid/base crosslinked proton exchange membranes intended for applications in direct methanol fuel cells. Polymers containing pendant pyridinyl and pyrimidinyl groups were obtained via the post polymerization functionalization of UDEL® poly(sulfone) and then blended with sulfonated poly(ether ether ketone) (SPEEK). Fuel cells containing these blends were found to exhibit reduced methanol crossover, higher open circuit voltages, and higher maximum power densities compared to plain SPEEK. The differences in fuel cell performance were attributed to the basicity and sterics of the pendant N-heterocycles. / text

One of the most visible indicators of the increasing global integration of the world economy over the past decade or so has been the phenomenal growth of Foreign Direct Investment (FDI) flows and expansion of cross-border activities of multinational enterprises. FDI inflows are considered as channels of entrepreneurship, technology, management skills, and resources that are scarce in developing countries and Southern Africa in particular. Recent developments in growth theory highlight the importance of improvements in technology, efficiency and productivity in simulating growth. In this regard, FDI’s contribution to growth comes through its role as a conduit for transferring its advanced technology from the industrialized to the developing economies and as such FDI inflows could help in the industrialization of the host countries. For instance, Findlay (1978) postulates that FDIs increases the rate of technical progress in the host country through a “contagion” effect from the more advanced technology and management practices used by foreign firms. Since FDI is said to be the most stable source of private capital for developing and transition economies, attracting FDI is at the top of the agenda of such economies around the world as they aim to reduce poverty that is deep and widespread. The paper will look at FDI and its contributions; discuss the relationship between FDI and economic growth; explore the determinants of FDI and economic growth; consider the implications of FDI to economic growth and poverty alleviation; examine Taiwan’s experience when its development was closer to current levels in Africa and Southern Africa in particular; and explore how the Southern African region can attain economic growth through FDI and alleviate its deep and widespread poverty. In trying to assess the extent to which FDI contributes to construction of production facilities, infusion of innovative technologies, management strategies, workforce practices, new employment, and skill transfer, the paper seeks to shed light on appropriate policies to pursue in order to encourage high volumes of FDI and their likely implications for economic growth and poverty alleviation. While economic growth is not synonymous with economic development, it is at least necessary. Provided that mechanisms exist to facilitate some trickle-down of the benefits of economic growth to the impoverished, economic growth can aid in poverty reduction. The most important mechanism by which trickle-down occurs is via employment-creating economic growth. In this way, it is possible that, if FDI serves as a catalyst for economic growth, it will stimulate development and contribute to alleviating poverty (Lipsey, R., 2000). David Dollar (2001) states that Globalization has been a force for growth and poverty reduction in a diverse group of countries and defines globalization as the growing integration of economies and societies around the world as a result of flows of goods and services, capital, people, and ideas. He claims that integration accelerates development and reduces gaps between the developed and developing countries by raising productivity in the developing world. In this way globalization can be a powerful force for poverty reduction. FDI is one element that links the Southern part of Africa to the global economy and as a World Bank report (2001) shows that rapid economic growth and poverty reduction are positive aspects of globalization, the volume of FDI attracted will have an influence on whether the Southern Africa’s poor can benefit from the globalization of markets.