On the Octonionic Self Duality equations of 3-brane Instantons

We study the octonionic selfduality equations for $p=3$-branes in the light cone gauge and we construct explicitly, instanton solutions for spherical and toroidal topologies in various flat spacetime dimensions $(D=5+1,7+1,8+1,9+1)$, extending previous results for $p=2$ membranes. Assuming factorization of time we reduce the self-duality equations to integrable systems and we determine explicitly periodic, in Euclidean time, solutions in terms of the elliptic functions. These solutions describe 4d associative and non-associative calibrations in $D=7,8$ dimensions. It turns out that for spherical topology the calibration is non compact while for the toroidal topology is compact. We discuss possible applications of our results to the problem of 3-brane topology change and its implications for a non-perturbative definition of the 3-brane interactions.Comment: 15 pages, 4 figure

Star Formation in Massive Low Surface Brightness Galaxies

Massive low surface brightness galaxies have disk central surface brightnesses at least one magnitude fainter than the night sky, but total magnitudes and masses that show they are among the largest galaxies known. Like all low surface brightness (LSB) galaxies, massive LSB galaxies are often in the midst of star formation yet their stellar light has remained diffuse, raising the question of how star formation is proceeding within these galaxies. We have undertaken a multi-wavelength study to clarify the structural parameters and stellar and gas content of these enigmatic systems. The results of these studies, which include HI, CO, optical, near UV, and far UV images of the galaxies will provide the most in depth study done to date of how, when, and where star formation proceeds within this unique subset of the galaxy population.Comment: to be published in proceeding of IAU 244 - Dark Galaxies and Lost Baryons IAU Symposiu

Estimating Health Care Costs Among Fragile and Conflict Affected States: an Elastic Net-Risk Measures Approach

Fragile and conflict affected states (FCAS) are those in which the government lacks the political will and/or capacity to provide the basic functions necessary for poverty reduction, economic development, and the security of human rights of their populations.Until recent history, unfortunately, the majority of research conducted and universal health care debates have been centered around middle income and emerging economies. As a result, FCAS have been neglected from many global discussions and decisions. Due to this neglect, many FCAS do not have proper vaccinations and antibiotics. Seemingly, well estimated health care costs are a necessary stepping stone in improving the health of citizens among FCAS. Fortunately, developments in statistical learning theory combined with data obtained by the WBG and Transparency International make it possible to accurately model health care cost among FCAS. The data used in this paper consisted of 35 countries and 89 variables. Of these 89 variables, health care expenditure (HCE) was the only response variable. With 88 predictor variables, there was expected to be multicollinearity, which occurs when multiple variables share relatively large absolute correlation. Since multicollinearity is expected and the number of variables is far greater than the number of observations, this paper adopts Zou and Hastie\u27s method of regularization via elastic net (ENET). In order to accurately estimate the maximum and expected maximum HCE among FCAS, well-known risk measures, such as Value at Risk and Conditional Value at Risk, and related quantities were obtained via Monte Carlo simulations. This paper obtained risk measures at 95 security level

MARGINAL ABATEMENT COSTS OF REDUCING GROUNDWATER-N POLLUTION WITH INTENSIVE AND EXTENSIVE FARM MANAGEMENT CHOICES

Cost-effectiveness is an important consideration in evaluating choices for meeting environmental quality objectives. Estimated crop yield response functions and the associated groundwater-nitrate pollution production functions were used to evaluate the optimal N fertilization and on-farm abatement costs for alternative cropping systems, with management choices at both the intensive and extensive margins. The cost-effective corn production system, which meets the Health Canada standard for nitrates with the highest returns ($278 ha-1) and lowest on-farm abatement cost ($248 ha-1), was a four-year corn-corn-soybean-wheat rotation under conventional tillage. At contaminant limits above the Health Canada standard, the cost-effective wheat cropping system shifted from a soybean-wheat rotation under no-tillage to a corn-soybean-wheat rotation under no-tillage.Environmental Economics and Policy, Farm Management,

Computation of Madelung Energies for Ionic Crystals of Variable Stoichiometries and Mixed Valencies and their application in Lithium-ion battery voltage modelling

Electrostatic energy (Madelung energy) is a major constituent of the cohesive energy of ionic crystals. Several physicochemical properties of these materials depend on the response of their electrostatic energy to a variety of applied thermal, electrical and mechanical stresses. In the present study, a method has been developed based on Ewalds technique, to compute the electrostatic energy arising from ion-ion interactions in ionic crystals like LixMn2O4 with variable stoichiometries and mixed valencies. An interesting application of this method in computing the voltages of lithium ion batteries employing spinel cathodes is presented for the first time. The advantages of the present method of computation over existing methods are also discussed.Comment: 15 page

AN ECONOMETRIC ANALYSIS OF THE CAUSES OF TROPICAL DEFORESTATION: GHANA

Deforestation is modeled in two stages, as an interaction of interlinked key sectors in the Ghanaian economy (including forest products exports, fuelwood energy consumption, cocoa production, and food crop production), which compete for forest landuse or forest products. The effects of the different first- and second-level causes of deforestation analyzed are discussed.Two-stage regression, elasticity of deforestation, forest policy/management, Resource /Energy Economics and Policy, C320, Q230,