Second generation wave-function thermostat for ab-initio molecular dynamics

A rigorous two-thermostat formulation for ab-initio molecular dynamics using the fictitious Lagrangian approach is presented. It integrates the concepts of mass renormalization and temperature control for the wave functions. The new thermostat adapts to the instantaneous kinetic energy of the nuclei and thus minimizes its influence on the dynamics. Deviations from the canonical ensemble, which are possible in the previous two-thermostat formulation, are avoided. The method uses a model for the effective mass of the wave functions, which is open to systematic improvement.Comment: 9 pages, 2 figures, submitted to Physical Review

Have We Need of Invoking Postmodernity? Identity and Difference in Theological Discourse

While the term postmodernity remains vague or equivocal, theologians increasingly concede that it is one which they can not avoid trying to understand and deal with. One definition of the term proceeds by way of sharp contrast with specific features of modernity, thus clearly distinguishing postmodernity from even late modernity. The key to this distinction seems to be a particular conception of difference which is worked out rigorously in Heidegger\u27s, The Principle of Identity. Proceeding from Heidegger\u27s claim to think difference anterior to identity, postmodernity is then presented here as the source of considerable difficulty to a theology which would seem committed to basic identification with Christ. Clarification of these difficulties and the dangers they harbor for a theology which would speak according to the postmodern condition illumines the general contours of a theology which instead speaks about it or in discussion with it. Some implications in the fields of pastoral and speculative theology are highlighted

Modelling molecule-surface interactions-an automated quantum-classical approach using a genetic algorithm

We present an automated and efficient method to develop force fields for molecule-surface interactions. A genetic algorithm (GA) is used to parameterise a classical force field so that the classical adsorption energy landscape of a molecule on a surface matches the corresponding landscape from density functional theory (DFT) calculations. The procedure performs a sophisticated search in the parameter phase space and converges very quickly. The method is capable of fitting a significant number of structures and corresponding adsorption energies. Water on a ZnO(0001) surface was chosen as a benchmark system but the method is implemented in a flexible way and can be applied to any system of interest. In the present case, pairwise Lennard Jones (LJ) and Coulomb potentials are used to describe the molecule-surface interactions. In the course of the fitting procedure, the LJ parameters are refined in order to reproduce the adsorption energy landscape. The classical model is capable of describing a wide range of energies, which is essential for a realistic description of a fluid-solid interface

Ab initio modeling of oxygen impurity atom incorporation into uranium mononitride surface and subsurface vacancies

The incorporation of oxygen atoms has been simulated into either nitrogen or uranium vacancy at the UN(001) surface, sub-surface or central layers. For calculations on the corresponding slab models both the relativistic pseudopotentials and the method of projector augmented-waves (PAW) as implemented in the VASP computer code have been used. The energies of O atom incorporation and solution within the defective UN surface have been calculated and discussed. For different configurations of oxygen ions at vacancies within the UN(001) slab, the calculated density of states and electronic charge re-distribution was analyzed. Considerable energetic preference of O atom incorporation into the N-vacancy as compared to U-vacancy indicates that the observed oxidation of UN is determined mainly by the interaction of oxygen atoms with the surface and sub-surface N vacancies resulting in their capture by the vacancies and formation of O-U bonds with the nearest uranium atoms. Keywords: Density functional calculations, uranium mononitride, surface, defects, N and U vacancie

Sugar and Rice Trade between the United States and Cuba Trade Potential and Welfare Analysis

After the resignation of President Fidel Castro and forty-five years of the U.S.-trade embargo, the political environment between Cuba and the United States is expected to change. With the Trade Sanction Reform and Export Enhancement Act in 2000, trade sanctions were eased for a while. Future trade between both countries would increase the welfare in both countries. This Thesis has the approach to look at the impacts on the commodities of rice and sugar, and the trade sanctions between the United States and Cuba. Cuba is a net importer of its food supply; therefore, agriculture and food trade is an interesting business for states closely located to Cuba. Cuba also has a high consumption of rice, and the US is a net exporter of rice; the gains from trade are obvious. On the other hand, Cuba has an enormous potential in sugar cane production. Cuba was once the world\u27s largest sugar producer with over 8 million metric tons (USDA, 2008). With increasing demand in the United States, sugar cane from Cuba could supply the United States market. The trade analysis from the United States International Trade Commission shows that the agriculture trade between the United States and Cuba could increase by $661 million. Without an embargo, US rice producers and Cuban sugar could benefit from trade. Welfare analysis shows that the protection policy harms producers and consumers on both sides. Given its proximity to the U.S., Cuba could benefit similarly as Mexico and Canada under the North American Free Trade Agreement (NAFTA). These countries show that free trade increases investments, imports, and exports. It is also proven that the overall welfare increases with the removal of protectionism (Stern, 2001). It is time to open the trade embargo between the United States and Cuba on behalf of the welfare of the people in both countries

A Method for Comparing Real and Simulated Airborne Hyperspectral Imagery

This thesis proposes a method for comparing real and simulated hyperspectral imagery by examining the characteristics of simulated imagery in comparison to real imagery acquired with multiple sensors hosted on an airborne platform. The dataset includes aerial multi- and hyperspectral imagery with spatial resolutions of one meter or less. The multispectral imagery includes data from an airborne sensor with three-band visible color and calibrated radiance imagery in the long-, mid-, and short-wave infrared. The airborne hyperspectral imagery includes 360 bands of calibrated radiance and reflectance data spanning 400 to 2450 nm in wavelength. Collected in September 2012, the imagery is of a park in Avon, NY, and includes a dirt track and areas of grass, gravel, forest, and agricultural fields. A number of artificial targets were deployed in the scene prior to collection for purposes of target detection, subpixel detection, spectral unmixing, and 3D object recognition. A synthetic reconstruction of the collection site was created in DIRSIG, an image generation and modeling tool developed by the Rochester Institute of Technology, based on ground-measured reflectance data, ground photography, and previous airborne imagery. Simulated airborne images were generated using the scene model, time of observation, atmospheric conditions, and knowledge of the sensor characteristics. The thesis provides a comparison between the empirical and simulated images, including a comparison of achieved performance for classification, detection and unmixing applications. It was found that several differences exist due to the way the image is generated, including finite sampling and incomplete knowledge of atmospheric conditions and sensor characteristics. The lessons learned from these differences can be used to refine the modeling tool and its use as part of ongoing efforts to increase the realism of the simulated data

Penalized Splines, Mixed Models and the Wiener-Kolmogorov Filter

Penalized splines are widespread tools for the estimation of trend and cycle, since they allow a data driven estimation of the penalization parameter by the incorporation into a linear mixed model. Based on the equivalence of penalized splines and the Hodrick-Prescott filter, this paper connects the mixed model framework of penalized splines to the Wiener- Kolmogorov filter. In the case that trend and cycle are described by ARIMA-processes, this filter yields the mean squarred error minimizing estimations of both components. It is shown that for certain settings of the parameters, a penalized spline within the mixed model framework is equal to the Wiener-Kolmogorov filter for a second fold integrated random walk as the trend and a stationary ARMA-process as the cyclical component