Financial transactions tax : panacea, threat, or damp squib ?

Attempts to raise a significant percentage of gross domestic product in revenue from a broad-based financial transactions tax are likely to fail both by raising much less revenue than expected and by generating far-reaching changes in economic behavior. Although the side-effects would include a sizable restructuring of financial sector activity, this would not occur in ways corrective of the particular forms of financial overtrading that were most conspicuous in contributing to the crisis.Debt Markets,Emerging Markets,Taxation&Subsidies,Banks&Banking Reform,Economic Theory&Research

Atomic absorption and fluorescence spectrometry at wavelengths below 200 nm

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Estimates of elastic plate thicknesses beneath large volcanos on Venus

Megellan radar imaging and topography data are now available for a number of volcanos on Venus greater than 100 km in radius. These data can be examined to reveal evidence of the flexural response of the lithosphere to the volcanic load. On Earth, flexure beneath large hotspot volcanos results in an annual topographic moat that is partially to completely filled in by sedimentation and mass wasting from the volcano's flanks. On Venus, erosion and sediment deposition are considered to be negligible at the resolution of Magellan images. Thus, it may be possible to observe evidence of flexure by the ponding of recent volcanic flows in the moat. We also might expect to find topographic signals from unfilled moats surrounding large volcanos on Venus, although these signals may be partially obscured by regional topography. Also, in the absence of sedimentation, tectonic evidence of deformation around large volcanos should be evident except where buried by very young flows. We use analytic solutions in axisymmetric geometry for deflections and stresses resulting from loading of a plate overlying an inviscid fluid. Solutions for a set of disk loads are superimposed to obtain a solution for a conical volcano. The deflection of the lithosphere produces an annular depression or moat, the extent of which can be estimated by measuring the distance from the volcano's edge to the first zero crossing or to the peak of the flexural arch. Magellan altimetry data records (ARCDRs) from data cycle 1 are processed using the GMT mapping and graphics software to produce topographic contour maps of the volcanos. We then take topographic profiles that cut across the annular and ponded flows seen on the radar images. By comparing the locations of these flows to the predicted moat locations from a range of models, we estimate the elastic plate thickness that best fits the observations, together with the uncertainty in that estimate

The mechanisms involved in the scanning of bone using technetium labelled EHDP : its application in the healing of fractures

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Solar Electric Propulsion Triple-Satellite-Aided Capture With Mars Flyby

Triple-Satellite-aided-capture sequences use gravity-assists at three of Jupiter\u27s four massive Galilean moons to reduce the DeltaV required to enter into Jupiter orbit. A triple-satellite-aided capture at Callisto, Ganymede, and Io is proposed to capture a SEP spacecraft into Jupiter orbit from an interplanetary Earth-Jupiter trajectory that employs low-thrust maneuvers. The principal advantage of this method is that it combines the ISP efficiency of ion propulsion with nearly impulsive but propellant-free gravity assists.;For this thesis, two main chapters are devoted to the exploration of low-thrust triple-flyby capture trajectories. Specifically, the design and optimization of these trajectories are explored heavily. The first chapter explores the design of two solar electric propulsion (SEP), low-thrust trajectories developed using the JPL\u27s MALTO software. The two trajectories combined represent a full Earth to Jupiter capture split into a heliocentric Earth to Jupiter Sphere of Influence (SOI) trajectory and a Joviocentric capture trajectory. The Joviocentric trajectory makes use of gravity assist flybys of Callisto, Ganymede, and Io to capture into Jupiter orbit with a period of 106.3 days.;Following this, in chapter two, three more SEP low-thrust trajectories were developed based upon those in chapter one. These trajectories, devised using the high-fidelity Mystic software, also developed by JPL, improve upon the original trajectories developed in chapter one. Here, the developed trajectories are each three separate, full Earth to Jupiter capture orbits. As in chapter one, a Mars gravity assist is used to augment the heliocentric trajectories. Gravity-assist flybys of Callisto, Ganymede, and Io or Europa are used to capture into Jupiter Orbit. With between 89.8 and 137.2-day periods, the orbits developed in chapters one and two are shorter than most Jupiter capture orbits achieved using low-thrust propulsion techniques.;Finally, chapter 3 presents an original trajectory design for a Very-Long-Baseline Interferometry (VLBI) satellite constellation. The design was created for the 8th Global Trajectory Optimization Competition (GTOC8) in which participants are tasked with creating and optimizing low-thrust trajectories to place a series of three space craft into formation to map given radio sources

A computational model of cortical-striatal mediation of speed-accuracy tradeoff and habit formation emerging from anatomical gradients in dopamine physiology and reinforcement learning

Decision making – committing to a single action from a plethora of viable alternatives – is a necessity for all motile creatures, each moving a single body to many possible destinations. Some decisions are better than others. For example, to a rat deciding between one path that will bring it to a piece of cheese and another that will bring it to the jaws of a cat, there is a clear reason for the rat to prefer one choice over the other. Two criteria for adjusting decision making for optimal outcome are to make decisions as accurately as possible – choose the course of action most likely to result in the preferred outcome – but also to decide as fast as possible. Because these criteria often conflict, decision making has an inherent “speed-accuracy tradeoff”. Presented here is a computational neural model of decision making, which incorporates neurobiological design principles that optimize this tradeoff via reward-guided transfers of control between two sensory processing systems with different speed/accuracy characteristics. This model incorporates anatomical and physiological evidence that dopamine, the key neurotransmitter in reinforcement learning, has varying effects in different sub-regions of the basal ganglia, a subcortical structure that interfaces with the neocortex to control behavior. Based on the observed differences between these sub-regions, the model proposes that gradual adaptations of synaptic links by reinforcement learning signals lead to rapid changes in the speed and accuracy of decision making, by assigning control of behavior to alternative cortical representations. Chapter one draws conceptual links from experimental data to the design of the proposed model. Chapter two applies the model to speed-accuracy tradeoffs and habit formation by simulating forced-choice paradigms. Several robust behavioral phenomena are replicated. By isolating reinforcement learning factors that control the speed and depth of habit formation, the model can help explain why all substances that strongly and synergistically affect such factors share a high potential for habit formation, or habit abatement. To illustrate such potential applications of the current model, chapter three investigates effects of varying model parameters in accord with the known neurochemical effects of some major habit-forming substances, such as cocaine and ethanol

XMM-Newton view of the N 206 superbubble in the Large Magellanic Cloud

We perform an analysis of the X-ray superbubble in the N 206 HII region in the Large Magellanic Cloud using current generation facilities to gain a better understanding of the physical processes at work in the superbubble and to improve our knowledge of superbubble evolution. We used XMM-Newton observations of the N 206 region to produce images and extract spectra of the superbubble diffuse emission. Morphological comparisons with Halpha images from the Magellanic Cloud Emission Line Survey were performed, and spectral analysis of the diffuse X-ray emission was carried out. We derived the physical properties of the hot gas in the superbubble based on the results of the spectral analysis. We also determined the total energy stored in the superbubble and compared this to the expected energy input from the stellar population to assess the superbubble growth rate discrepancy for N 206. We find that the brightest region of diffuse X-ray emission is confined by a Halpha shell, consistent with the superbubble model. In addition, faint emission extending beyond the Halpha shell was found, which we attribute to a blowout region. The spectral analysis of both emission regions points to a hot shocked gas as the likely origin of the emission. We determine the total energy stored in the bubble and the expected energy input by the stellar population. However, due to limited data on the stellar population, the input energy is poorly constrained and, consequently, no definitive indication of a growth rate discrepancy is seen. Using the high-sensitivity X-ray data from XMM-Newton and optical data from the Magellanic Cloud Emission Line Survey has allowed us to better understand the physical properties of the N 206 superbubble and address some key questions of superbubble evolution.Comment: 12 pages, 7 figures. Accepted for publication in A&

Eunotosaurus africanus and the Gondwanan ancestry of anapsid reptiles

Phylogenetic analyses confirm that the turtle-like Late Permian reptile Eunotosaurus africanus is a parareptile (sensu deBraga & Reisz 1996) and identify it as the sister taxon of Procolophonomorpha. The tree topology for anapsid reptiles suggests that a distribution in Gondwanan Pangaea is ancestral for anapsids (sensu Gauthier, Kluge & Rowe 1988). Minimum divergence times (MDTs) determined from stratigraphic calibration of anapsid phylogeny suggest that anapsids were diversifying in Early Permian Gondwana as early as the Sakmarian. MDTs also support the idea that a preservational bias was operating on terrestrial vertebrates in Gondwana prior to the onset of continental sedimentation in the Late Permian.THE COUNCIL’S RESEARCH COMMITTEE, UNIVERSITY OF THE WITWATERSRAND; NATIONAL RESEARCH FOUNDATION (NRF)