Search results for "basis"
showing 10 items of 760 documents
Novel second-order nonlinear optical polymer materials containing indandione derivativatives as a chromophore
2006
Second order non linear optical (NLO) properties of sPMMA based host-guest systems containing eight dimethylaminobenzylidene -1, 3 - indandione (DMABI) related chromophores have been investigated by means of quantum chemical calculations and SHG experimental characterization. Ab initio calculations with basis set 6-31G were used for molecular geometry determination as well as in the calculations of molecular hyperpolarizability by FF approach. Influence of the chromophore concentration on the host-guest film NLO performance was obtained by SHG Maker fringe experiments. The highest value of d53233 =80 pm/V (frequency corrected value d033 =12 pm/V) at chromophore concentration 15 %wt have bee…
Principal part of multi-parameter displacement functions
2012
This paper deals with a perturbation problem from a period annulus, for an analytic Hamiltonian system [J.-P. Françoise, Ergodic Theory Dynam. Systems 16 (1996), no. 1, 87–96 ; L. Gavrilov, Ann. Fac. Sci. Toulouse Math. (6) 14(2005), no. 4, 663–682. The authors consider the planar polynomial multi-parameter deformations and determine the coefficients in the expansion of the displacement function generated on a transversal section to the period annulus. Their first result gives a generalization to the Françoise algorithm for a one-parameter family, following [J.-P. Françoise and M. Pelletier, J. Dyn. Control Syst. 12 (2006), no. 3, 357–369. The second result expresses the principal terms in …
Catalan Morphology and Low-level Patterns in a Network Model
2005
The fact that more specific or low-level morphological patterns may coexist with the most general or abstract ones is a characteristic insight of Cognitive Morphology. According to the bottom-up approach of the model, it is even to be expected that low-level patterns may have a more relevant role than the most inclusive and abstract ones. On the basis of the analysis of an aspect of Catalan inflection (velar verbs of the second conjugation) and one aspect of Catalan word-formation (complex words with the prefixoid radio-), we will show the advantages of incorporating to the model salient low-level patterns and the local paradigmatic relations in which they are based. info:eu-repo/semantics/…
On Discovering Low Order Models in Biochemical Reaction Kinetics
2007
We develop a method by which a large number of differential equations representing biochemical reaction kinetics may be represented by a smaller number of differential equations. The basis of our technique is a conjecture that the high dimension equations of biochemical kinetics, which involve reaction terms of specific forms, are actually implementing a low dimension system whose behavior requires right hand sides that can not be biochemically implemented. For systems that satisfy this conjecture, we develop a simple approximation scheme based on multilinear algebra that extracts the low dimensional system from simulations of the high dimension system. We demonstrate this technique on a st…
Nuclear Quadrupole Moment of 119Sn
2008
Second-order scalar-relativistic Douglas-Kroll-Hess density functional calculations of the electric field gradient, including an analytic correction of the picture change error, were performed for 34 tin compounds of which molecular structures and Sn-119 Mossbauer spectroscopy parameters are experimentally known. The components of the diagonalized electric field gradient tensor, V-xx,V-yy, V-zz, were used to determine the quantity V, which is proportional to the nuclear quadrupole splitting parameter Delta E. The slope of the linear correlation plot of the experimentally determined Delta E parameter versus the corresponding calculated V data allowed us to obtain an absolute value of the nuc…
Method and basis set dependence of the NICS indexes of aromaticity for benzene
2018
The role of theory level in prediction of benzene magnetic indexes of aromaticity is analysed and compared with calculated nuclear magnetic shieldings of 3 He used as NMR probe. Three closely related nucleus-independent chemical shift (NICS) based indexes were calculated for benzene at SCF-HF, MP2, and DFT levels of theory and the impact of basis set on these quantities was studied. The changes of benzene NICS(0), NICS(1), and NICS(1)zz parameters calculated using SCF-HF, MP2 and several density functionals were within 1 to 3 ppm. Similar deviations between magnetic indexes of aromaticity were observed for values calculated with selected basis sets. Only very small effect of polar solvent o…
Electron Correlation or Basis Set Quality: How to Obtain Converged and Accurate NMR Shieldings for the Third-Row Elements?
2022
The quality of theoretical NMR shieldings calculated at the quantum-chemical level depends on various theoretical aspects, of which the basis set type and size are among the most important factors. Nevertheless, not much information is available on the basis set effect on theoretical shieldings of the NMR-active nuclei of the third row. Here, we report on the importance of proper basis set selection to obtain accurate and reliable NMR shielding parameters for nuclei from the third row of the periodic table. All calculations were performed on a set of eleven compounds containing the elements Na, Mg, Al, Si, P, S, or Cl. NMR shielding tensors were calculated using the SCF-HF, DFT-B3LYP, and C…
Structure Validation of Natural Products by Quantum-Mechanical GIAO Calculations of 13C NMR Chemical Shifts GIAO=gauge including atomic orbitals.
2002
Geometry optimization and GIAO (gauge including atomic orbitals) 1 3 C NMR chemical shift calculations at Hartree-Fock level, using the 6-31G(d) basis set, are proposed as a tool to be applied in the structural characterization of new organic compounds, thus providing useful support in the interpretation of experimental NMR data. Parameters related to linear correlation plots of computed versus experimental 1 3 C NMR chemical shifts for fourteen low-polar natural products, containing 10-20 carbon atoms, were employed to assess the reliability of the proposed structures. A comparison with the hybrid B3LYP method was carried out to evaluate electron correlation contributions to the calculatio…
The evolution of COVID-19: A discontinuous approach.
2021
The evolution of the COVID-19 disease is monitored on the basis of the daily number of infected patients and the daily number of deaths provided from national health agencies. The variation of such parameters with time parallels that described for the growth/decay of historic transportation systems revealing the appearance of discontinuities. The evolution of the pandemic disease is represented in terms of two nominally equivalent formulations: a logistic model with sharp changes in its rate parameters, and in topological terms resulting in 2nd order phase transitions in the infected patients/time space.
Learning to Approach a Moving Ball with a Simulated Two-Wheeled Robot
2006
We show how a two-wheeled robot can learn to approach a moving ball using Reinforcement Learning. The robot is controlled by setting the velocities of its two wheels. It has to reach the ball under certain conditions to be able to kick it towards a given target. In order to kick, the ball has to be in front of the robot. The robot also has to reach the ball at a certain angle in relation to the target, because the ball is always kicked in the direction from the center of the robot to the ball. The robot learns which velocity differences should be applied to the wheels: one of the wheels is set to the maximum velocity, the other one according to this difference. We apply a REINFORCE algorith…