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Coulomb Energies (coulomb + energy)
Selected AbstractsThe virtual interaction panel: an easy control tool in augmented reality systemsCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 3-4 2004M. L. Yuan Abstract In this paper, we propose and develop an easy control tool called Virtual Interaction Panel (VirIP) for Augmented Reality (AR) systems, which can be used to control AR systems. This tool is composed of two parts: the design of the VirIPs and the tracking of an interaction pen using a Restricted Coulomb Energy (RCE) neural network. The VirIP is composed of some virtual buttons, which have meaningful information that can be activated by an interaction pen during the augmentation process. The interaction pen is a general pen-like object with a certain color distribution. It is tracked using a RCE network in real-time and used to trigger the VirIPs for AR systems. In our system, only one camera is used for capturing the real world. Therefore, 2D information is used to trigger the virtual buttons to control the AR systems. The proposed method is real-time because the RCE-based image segmentation for a small region is fast. It can be used to control AR systems quite easily without any annoying sensors attached to entangling cables. This proposed method has good potential in many AR applications in manufacturing, such as assembly without the need for object recognition, collaborative product design, system control, etc. Copyright © 2004 John Wiley & Sons, Ltd. [source] The Effects of Fluorine and Chlorine Substituents across the Fjords of Bifluorenylidenes: Overcrowding and StereochemistryEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2006Sergey Pogodin Abstract The bistricyclic aromatic enes (BAEs) (E)- and (Z)-1,1,-difluorobifluorenylidene, 1,8,1,,8,-tetrafluorobifluorenylidene, (E)- and (Z)-3,3,-difluorobifluorenylidene, 3,6,3,,6,-tetrafluorobifluorenylidene, and their chlorinated analogues were subjected to a DFT study of overcrowding in their fjord regions. The B3LYP hybrid functional was employed to calculate energies and geometries of the twisted conformations of these BAEs. The diastereomers E11,F2 and Z11,F2 have identical twist angles (, = 37.1°) and similar degrees of overcrowding, but differ in the degree and mode of pyramidalization, ,. In E11,F2, ,(C9) = +,(C9,) = 7.0° (syn -pyramidalization), while in Z11,F2, ,(C9) = ,,(C9,) = 1.0° (anti -pyramidalization). By contrast, in E11,Cl2 and Z11,Cl2, , = 40.6° and 42.7°, respectively. Introducing four halogen substituents results in higher twist angles: , = 40.3° in 181,8,F4 and 52.6° in 181,8,Cl4. Surprisingly, Z11,F2 is more stable than E11,F2 (,H298 = ,1.9 kJ/mol), whereas Z11,Cl2 is less stable than E11,Cl2 (,H298 = 2.2 kJ/mol). Both results are consistent with the experimental relative stabilities of these diastereomers. The unexpected stability of Z11,F2 is explained by a combination of steric and electronic effects. Calculations of Coulomb energies for point charge systems of atoms C, F, and H in the fjord regions shows stabilization of the (Z) diastereomer by ,45.5 kJ/mol. The dipole,dipole interactions in the fjord region destabilize Z11,F2 by 6.4 kJ/mol relative to E11,F2. Careful examination of the NMR spectra of E11,F2 and Z11,F2 shows, in the latter, evidence of long-range fluorine,fluorine coupling over seven bonds (11.4 Hz) and carbon,fluorine coupling over six bonds (4.8 Hz).(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] HF,CC model for atoms and molecules,INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4-5 2002E. Clementi Abstract The Hartree,Fock,Clementi,Corongiu method (HF,CC) is revisited, aiming at an unified formulation for post-HF energy computations in atomic and molecular systems. For atomic systems new parameterizations of the HF,CC functional are proposed for the computation of atoms. The previous HF,CC molecular functional (Clementi, E.; Corongiu, G. Theochem 2001, 543, 39), revisited and recalibrated with a new optimization of the parameters, is tested with a sample of 131 molecules, including radicals, H-bond, and van der Waals systems. The atomization energy is decomposed into "HF classic" energy (the sum of the HF nuclear electron, HF kinetic, and HF Coulomb energies), "HF exchange" energy, and correlation energy; the latter is computed with a scaling functional with atomic, covalent, ionic, and van der Waals contributions. For the sample of 131 molecules, the computed HF,CC atomization energies have an average standard deviation of 1.89 kcal/mol. The atomic and molecular components of the correlation energy are decomposed into nuclear electron, kinetic, Coulomb, and exchange contributions; these decompositions characterize the HF,CC model and are used to explain the origin of the chemical bond. Computations on van der Waals systems show the validity of the HF,CC method also for long-range weak interactions. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 [source] Computational screening of biomolecular adsorption and self-assembly on nanoscale surfacesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 7 2010Hendrik Heinz Abstract The quantification of binding properties of ions, surfactants, biopolymers, and other macromolecules to nanometer-scale surfaces is often difficult experimentally and a recurring challenge in molecular simulation. A simple and computationally efficient method is introduced to compute quantitatively the energy of adsorption of solute molecules on a given surface. Highly accurate summation of Coulomb energies as well as precise control of temperature and pressure is required to extract the small energy differences in complex environments characterized by a large total energy. The method involves the simulation of four systems, the surface-solute,solvent system, the solute,solvent system, the solvent system, and the surface-solvent system under consideration of equal molecular volumes of each component under NVT conditions using standard molecular dynamics or Monte Carlo algorithms. Particularly in chemically detailed systems including thousands of explicit solvent molecules and specific concentrations of ions and organic solutes, the method takes into account the effect of complex nonbond interactions and rotational isomeric states on the adsorption behavior on surfaces. As a numerical example, the adsorption of a dodecapeptide on the Au {111} and mica {001} surfaces is described in aqueous solution. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] Thinking inside the box: Novel linear scaling algorithm for Coulomb potential evaluationINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4 2006David C. Thompson Abstract Beginning with the Poisson equation, and expanding the electronic potential in terms of sine functions, the natural orbitals for describing the particle-in-a-box problem, we find that simple analytic forms can be found for the evaluation of the Coulomb energy for both the interacting and non-interacting system of N -electrons in a box. This method is reminiscent of fast-Fourier transform and scales linearly. To improve the usefulness of this result, we generalize the idea by considering a molecular system, embedded in a box, within which we determine the electrostatic potential, in the same manner as that described for our model systems. Within this general formalism, we consider both periodic and aperiodic recipes with specific application to systems described using Gaussian orbitals; although in principle the method is seen to be completely general. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Free energy determinants of tertiary structure and the evaluation of protein modelsPROTEIN SCIENCE, Issue 11 2000Donald Petrey Abstract We develop a protocol for estimating the free energy difference between different conformations of the same polypeptide chain. The conformational free energy evaluation combines the CHARMM force field with a continuum treatment of the solvent. In almost all cases studied, experimentally determined structures are predicted to be more stable than misfolded "decoys." This is due in part to the fact that the Coulomb energy of the native protein is consistently lower than that of the decoys. The solvation free energy generally favors the decoys, although the total electrostatic free energy (sum of Coulomb and solvation terms) favors the native structure. The behavior of the solvation free energy is somewhat counterintuitive and, surprisingly, is not correlated with differences in the burial of polar area between native structures and decoys. Rather, the effect is due to a more favorable charge distribution in the native protein, which, as is discussed, will tend to decrease its interaction with the solvent. Our results thus suggest, in keeping with a number of recent studies, that electrostatic interactions may play an important role in determining the native topology of a folded protein. On this basis, a simplified scoring function is derived that combines a Coulomb term with a hydrophobic contact term. This function performs as well as the more complete free energy evaluation in distinguishing the native structure from misfolded decoys. Its computational efficiency suggests that it can be used in protein structure prediction applications, and that it provides a physically well-defined alternative to statistically derived scoring functions. [source] | ||||||||||