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Journal articles on the topic 'Lanczos potentials'

Author: Grafiati

Published: 4 June 2021

Last updated: 18 February 2022

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1

Mena, Filipe C., and Paul Tod. "Lanczos potentials for linearly perturbed FLRW spacetimes." Journal of Physics: Conference Series 66 (May 1, 2007): 012019. http://dx.doi.org/10.1088/1742-6596/66/1/012019.

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2

Pommaret, J. F. "Airy, Beltrami, Maxwell, Einstein and Lanczos Potentials Revisited." Journal of Modern Physics 07, no. 07 (2016): 699–728. http://dx.doi.org/10.4236/jmp.2016.77068.

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3

CHEN, MIN, and HUA ZHU. "POTENTIAL ENERGY SURFACE, MICROWAVE AND INFRARED SPECTRA OF THE Xe–CO2 COMPLEX FROM AB INITIO CALCULATIONS." Journal of Theoretical and Computational Chemistry 11, no. 03 (June 2012): 537–46. http://dx.doi.org/10.1142/s0219633612500332.

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We present a new three-dimensional potential energy surface for Xe–CO2 including the Q3 normal mode for the υ3 antisymmetric stretching vibration of the CO2 molecule. Two vibrationally adiabatic potentials with CO2 in both the ground (υ3 = 0) and the first excited (υ3 = 1) states are generated by the integration of this potential over the Q3 coordinate. Each potential is found to have a T-shaped global minimum. The radial DVR/angular FBR method and the Lanczos algorithm are employed to calculate the rovibrational energy levels. The calculated band origin shifts, microwave and infrared spectra based on the two averaged potentials are in good agreement with the available experimental data.

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4

Andersson, Fredrik, and S. Brian Edgar. "Existence of Lanczos potentials and superpotentials for the Weyl spinor/tensor." Classical and Quantum Gravity 18, no. 12 (June 6, 2001): 2297–304. http://dx.doi.org/10.1088/0264-9381/18/12/304.

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5

DOLAN, P., and B. MURATORI. "GRAVITATIONAL POTENTIALS AND THE EXISTENCE OF GRAVITATIONAL GREEN'S TENSORS." Modern Physics Letters A 13, no. 29 (September 21, 1998): 2347–53. http://dx.doi.org/10.1142/s0217732398002497.

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The non-local part of the gravitational field Cabcd can be generated by the 16-component Lanczos tensor potential Labc. When six gauge conditions are imposed, Labe;e=0, its ten degrees of freedom match those of the Weyl tensor. The Penrose wave equation for Cabcd can be independently derived from that for Labc. The consistency between Labc and Cabcd is also shown by the compatibility of their algebraic classifications. An unexpected insight into the relationship of Labc and Cabcd is found in "Euclidean gravity" which in turn leads to the introduction of a gravitational Green's tensor [Formula: see text] corresponding to the potential Labc.

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6

Andersson, F., and S. Brian Edgar. "Curvature-free asymmetric metric connections and Lanczos potentials in Kerr–Schild spacetimes." Journal of Mathematical Physics 39, no. 5 (May 1998): 2859–61. http://dx.doi.org/10.1063/1.532425.

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7

Chen, Rong, and Xiao Ling Luo. "Vibrationally Averaged Potential Energy Surfaces and Microwave Spectra for Isotopic Ne-CO₂ Complexes." Applied Mechanics and Materials 670-671 (October 2014): 235–39. http://dx.doi.org/10.4028/www.scientific.net/amm.670-671.235.

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Averaged potential energy surfaces for isotopic Ne–CO2complexes (20Ne–18O13C16O,20Ne–17O12C16O and22Ne–17O12C16O) are presented. According to the latestab initiopotential of20Ne–12C16O2(R. Chen, H. Zhu, D. Q. Xie, J. Chem. Phys, 133, 2010, 104302,) which incorporates its dependence on theQ3normal mode for the antisymmetric stretching vibration of the CO2molecule, we obtain the averaged potentials for20Ne–18O13C16O,20Ne–17O12C16O and22Ne–17O12C16O complexes by integrating the potential energy surface overQ3normal mode. Each averaged potential surfaces are found to have a T-shaped global minimum and two equivalent linear local minima. The radial DVR/angular FBR method and the Lanczos algorithm are applied to calculate the rovibrational energy levels. Comparison with the available experimental values showed an overall excellent agreement for all spectroscopic parameters and the microwave spectra.

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8

Wang, Xiao-Gang, and Tucker Carrington,. "Theoretical study of the rovibrational spectrum of He2–OCS." Canadian Journal of Chemistry 88, no. 8 (August 2010): 779–86. http://dx.doi.org/10.1139/v10-030.

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We report calculated microwave and infrared rovibrational transitions of the van der Waals complex He2–OCS. The calculations were done using a product basis, a Lanczos eigensolver, and potentials built from He–OCS, and He–He potential functions taken from the literature. All five of the large amplitude coordinates are treated exactly and calculations are done for J values up to five. All rovibrational levels are converged to 0.001 cm–1 by using basis sets with as many as 87 million funcions. Good agreement is found with previously reported experimental results. Although we assume that the dipole moment is along the OCS axis, we find transitions with appreciable intensity between different torsion states.

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9

CHANG, S. L., and C. S. CHIEN. "NUMERICAL CONTINUATION FOR NONLINEAR SCHRÖDINGER EQUATIONS." International Journal of Bifurcation and Chaos 17, no. 02 (February 2007): 641–56. http://dx.doi.org/10.1142/s0218127407017501.

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We discuss numerical methods for studying numerical solutions of N-coupled nonlinear Schrödin-ger equations (NCNLS), N = 2, 3. First, we discretize the equations by centered difference approximations. The chemical potentials and the coupling coefficient are treated as continuation parameters. We show how the predictor–corrector continuation method can be exploited to trace solution curves and surfaces of the NCNLS, where the preconditioned Lanczos method with iterative refinement is used as the linear solver. When the chemical potential is large enough, we obtain peak solutions of the NCNLS for certain values of the coupling coefficient. The contours of the peak solutions resemble those of the experimental results of Anglin and Ketterle [2002], and Anderson et al. [1995].

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10

Mena, Filipe C., and Paul Tod. "Lanczos potentials and a definition of gravitational entropy for perturbed Friedman–Lemaitre–Robertson–Walker spacetimes." Classical and Quantum Gravity 24, no. 7 (March 13, 2007): 1733–45. http://dx.doi.org/10.1088/0264-9381/24/7/004.

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11

DELILLO, THOMAS, TOMASZ HRYCAK, and VICTOR ISAKOV. "THEORY AND BOUNDARY ELEMENT METHODS FOR NEAR-FIELD ACOUSTIC HOLOGRAPHY." Journal of Computational Acoustics 13, no. 01 (March 2005): 163–85. http://dx.doi.org/10.1142/s0218396x05002554.

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We consider the problem of recovering surface vibrations from acoustic pressure measurements taken in the interior or the exterior of a region. We give two formulations of the problem. One is based on a representation of the pressure as layer potentials and the other is based on approximation by a class of specific solutions to the Helmholtz equation. Boundary element methods are developed to approximate the integral operators. A conjugate gradient algorithm based on Lanczos bidiagonalization is applied to compute regularized solutions to the ill-conditioned equations in the presence of measurement errors. Numerical examples which compare the two formulations are presented.

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12

CUI, YALI, HONG RAN, and DAIQIAN XIE. "VIBRATIONALLY AVERAGED POTENTIAL ENERGY SURFACES AND PREDICTED INFRARED SPECTRA OF THE He–18O13C18O AND He–16O13C16O COMPLEXES." Journal of Theoretical and Computational Chemistry 07, no. 04 (August 2008): 707–17. http://dx.doi.org/10.1142/s0219633608004076.

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Vibrationally averaged potential energy surfaces for isotopic He–CO 2 complexes ( He –18 O 13 C 18 O and He –16 O 13 C 16 O ) are presented. Based on the latest ab initio potential of He –16 O 12 C 16 O (Ran H, Xie D, J Chem Phys128:124323, 2008.) including the Q3 normal mode for the v3 antisymmetric stretching vibration of the CO 2 molecule, the averaged potentials for both He –18 O 13 C 18 O and He –16 O 13 C 16 O are obtained by integrating the potential energy surfaces over the Q3 normal mode. The averaged potentials have T-shaped global minima and two equivalent linear local minima. The radial discrete variable representation/angular finite basis representation method and Lanczos algorithm are employed to calculate the related rovibrational energy levels. The calculated band origin shifts of He –18 O 13 C 18 O and He –16 O 13 C 16 O are 0.1066 and 0.0914 cm-1, respectively, which agree very well with the observed values of 0.1123 and 0.0929 cm-1. The calculated rovibrational transitions of He –18 O 13 C 18 O and He –16 O 13 C 16 O are also in very good agreement with the available experimental spectra.

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13

CHEN, RONG, and HUA ZHU. "POTENTIAL ENERGY SURFACES AND MICROWAVE SPECTRA FOR 20Ne–13C16O2, 22Ne–12C16O2 and 22Ne–13C16O2 COMPLEXES." Journal of Theoretical and Computational Chemistry 11, no. 06 (December 2012): 1175–82. http://dx.doi.org/10.1142/s0219633612500782.

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We report averaged potential energy surfaces for isotopic Ne–CO2 complexes (20 Ne –13 C 16 O 2, 22 Ne –12 C 16 O 2 and 22 Ne –13 C 16 O 2). According to the latest ab initio potential of 20 Ne –12 C 16 O 2 (Chen R, Jiao EQ, Zhu H, Xie DQ, J Chem Phys133:104302, 2010) including the Q3 normal mode for the υ3 antisymmetric stretching vibration of the CO2 molecule. We obtain the averaged potentials for 20 Ne –13 C 16 O 2, 22 Ne –12 C 16 O 2 and 22 Ne –13 C 16 O 2 by the integration of the three-dimensional potential over the Q3 coordinate. The averaged potential surfaces are found to have a T-shaped global minimum and two equivalent linear local minima. The radial DVR/angular FBR method and the Lanczos algorithm are applied to calculate the rovibrational energy levels. Comparison with the available observed values showed an overall excellent agreement for all spectroscopic parameters and the microwave spectra.

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14

Karlsson, Hans O. "Stability of the complex symmetric Lanczos algorithm for computing photodissociation cross sections using smooth exterior scaling or absorbing potentials." Journal of Physics B: Atomic, Molecular and Optical Physics 42, no. 12 (June 1, 2009): 125205. http://dx.doi.org/10.1088/0953-4075/42/12/125205.

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15

Ares de Parga, Gonzálo, Oscar Chavoya A., and José L. López Bonilla. "Lanczos potential." Journal of Mathematical Physics 30, no. 6 (June 1989): 1294–95. http://dx.doi.org/10.1063/1.528306.

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16

Lam-Estrada, P., J. López-Bonilla, and H. E. Caicedo-Ortiz. "Gödel spacetime and Lanczos potential." Journal de Ciencia e Ingeniería 12, no. 1 (August 31, 2020): 124–26. http://dx.doi.org/10.46571/jci.2020.1.11.

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17

Roberts, Mark D. "The Lanczos potential and Chern–Simons theory." International Journal of Modern Physics A 35, no. 01 (January 10, 2020): 2050006. http://dx.doi.org/10.1142/s0217751x20500062.

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In electromagnetism, the Faraday tensor [Formula: see text] can be constructed from the vector potential [Formula: see text], it is possible to add term to the Lagrangian depending on [Formula: see text] but not its derivatives called Chern–Simons terms. In gravitation, the Weyl tensor [Formula: see text] can be constructed from the Lanczos potential [Formula: see text], I pursue the analogy to see if terms of Chern–Simons form can be added to the Lagrangian. A new tensor [Formula: see text] is introduced which is constructed from the Lanczos potential and is of the same form as that of the Weyl tensor [Formula: see text] expressed in terms of the Lanczos potential except that covariant differentiation is replaced by transvection with a vector [Formula: see text]. The new tensor has associated invariants [Formula: see text] and [Formula: see text], the first of these can be interpreted as a Chern–Simons term for Weyl [Formula: see text] gravity. Both invariants allow various tensors to be constructed and some of their properties are investigated by using exact examples.

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18

Bergqvist, Göran. "A Lanczos potential in Kerr geometry." Journal of Mathematical Physics 38, no. 6 (June 1997): 3142–54. http://dx.doi.org/10.1063/1.532040.

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19

Ahsan, Z., J. H. Caltenco, and J. López-Bonilla. "Lanczos potential for the Gödel spacetime." Annalen der Physik 16, no. 4 (April 3, 2007): 311–13. http://dx.doi.org/10.1002/andp.200610234.

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20

Ahsan, Zafar, and Mohd Bilal. "Lanczos Potential and Perfect Fluid Spacetimes." International Journal of Theoretical Physics 50, no. 6 (January 28, 2011): 1752–68. http://dx.doi.org/10.1007/s10773-011-0684-3.

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21

ROBERTS, M. D. "DIMENSIONAL REDUCTION AND THE LANCZOS TENSOR." Modern Physics Letters A 04, no. 28 (December 30, 1989): 2739–46. http://dx.doi.org/10.1142/s0217732389003063.

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The Lanczos tensor Hαβγ is a potential for the Weyl tensor. Given the symmetries of these tensors it would be expected that the identification Hαβ5=Fαβ would give a reduction of the five dimensional vacuum field equations into equations related to the Einstein Maxwell equation, it is shown that this does not happen; furthermore it is shown that there is no dimensional reduction scheme involving the Lanczos tensor which agrees with the one devised by Kaluza and Klein in the weak field limit. The covariant derivative of the Weyl tensor can be expressed as a type of non-linear wave equation in the Lanczos tensor, the literature contains two incorrect expressions for this equation, here the correct expression is given for the first time. The expression for the Lanczos tensor in the case of weak fields is generalized. Some remarks are made on other approaches to include electro-magnetic theory into the theory of the Lanczos tensor.

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22

Ozaki, Taisuke. "Bond-order potential based on the Lanczos basis." Physical Review B 59, no. 24 (June 15, 1999): 16061–64. http://dx.doi.org/10.1103/physrevb.59.16061.

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23

Torres del Castillo, G. F. "Lanczos potential for some type D space–times." Journal of Mathematical Physics 36, no. 1 (January 1995): 195–200. http://dx.doi.org/10.1063/1.531300.

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24

Illge, Reinhard. "Some general ansätze for the Lanczos potential spinor." Mathematische Nachrichten 278, no. 14 (November 2005): 1681–88. http://dx.doi.org/10.1002/mana.200310333.

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25

Novello, M., and A. L. Velloso. "The connection between general observers and Lanczos potential." General Relativity and Gravitation 19, no. 12 (December 1987): 1251–65. http://dx.doi.org/10.1007/bf00759104.

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26

Ahsan, Zafar, and Mohd Bilal. "Lanczos Potential for Arbitrary Petrov Type II Spacetimes." International Journal of Theoretical Physics 52, no. 12 (July 27, 2013): 4275–82. http://dx.doi.org/10.1007/s10773-013-1741-x.

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27

Mora, César, and Rubén Sánchez. "Lanczos Potential for the van Stockung Space-Time." International Journal of Theoretical Physics 48, no. 5 (November 27, 2008): 1357–68. http://dx.doi.org/10.1007/s10773-008-9907-7.

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28

Dolan, P., and B. D. Muratori. "The Lanczos potential for vacuum space–times with an Ernst potential." Journal of Mathematical Physics 39, no. 10 (October 1998): 5406–20. http://dx.doi.org/10.1063/1.532580.

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29

BRIAN EDGAR, S. "THE WAVE EQUATIONS FOR THE LANCZOS TENSOR/SPINOR, AND A NEW TENSOR IDENTITY." Modern Physics Letters A 09, no. 06 (February 28, 1994): 479–82. http://dx.doi.org/10.1142/s0217732394003701.

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The apparent discrepancy between the vacuum wave equations obtained for the Lanczos potential respectively by spinor and tensor methods is explained; it is shown that the additional expression in the tensor version is actually identically zero in four dimensions.

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30

Lopez-Bonilla, J. L., J. Morales, and G. Ovando. "Letter: A Potential for the Lanczos Spintensor in Kerr Geometry." General Relativity and Gravitation 31, no. 3 (March 1999): 413–15. http://dx.doi.org/10.1023/a:1026653030033.

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31

Sun, Din-Kow. "ALPS: An adaptive Lanczos—Padé spectral solution of mixed-potential integral equation." Computer Methods in Applied Mechanics and Engineering 169, no. 3-4 (February 1999): 425–32. http://dx.doi.org/10.1016/s0045-7825(98)00167-4.

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32

Edgar, S. Brian, and A. Höglund. "The Lanczos Potential for Weyl-Candidate Tensors Exists Only in Four Dimensions." General Relativity and Gravitation 32, no. 12 (December 2000): 2307–18. http://dx.doi.org/10.1023/a:1001951609641.

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33

Edgar, S. Brian. "Nonexistence of the Lanczos potential for the Riemann tensor in higher dimensions." General Relativity and Gravitation 26, no. 3 (March 1994): 329–32. http://dx.doi.org/10.1007/bf02108015.

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34

ZHANG, H., and S. C. SMITH. "CALCULATION OF HO2 DENSITY OF STATES ON THREE POTENTIAL ENERGY SURFACES." Journal of Theoretical and Computational Chemistry 09, no. 03 (June 2010): 653–65. http://dx.doi.org/10.1142/s0219633610005918.

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Density of states (DOS) in both bound and unimolecular dissociation regime for HO2 system have been calculated quantum mechanically by Lanczos homogeneous filter diagonalization (LHFD) method. Three potential energy surfaces are explored and the results are contrasted for the total angular momentum J = 0 density of states. While two ab initio potential energy surfaces (PESs) (TU PES, J Chem Phys, 115:3621 and XXZLG PES, J Chem Phys122:244) produce the DOSs which are in fairly good agreement, the semi-empirical double many-body expansion (DMBE) IV PES (J Phys Chem94:8073) generates the much higher DOSs in higher energy range. The quantum mechanical DOSs are also compared with Troe et al.'s results from harmonic density, semiclassical density and their early density of states on the same TU ab initio surface.

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35

Edgar, S. B., and A. Höglund. "The Lanczos potential for the Weyl curvature tensor: existence, wave equation and algorithms." Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences 453, no. 1959 (April 8, 1997): 835–51. http://dx.doi.org/10.1098/rspa.1997.0046.

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36

ANDERSSON, F. "AN ALGORITHM FOR THE ALGEBRAIC CLASSIFICATION OF THE SYMMETRIC (3,1)-SPINOR." International Journal of Modern Physics D 07, no. 06 (December 1998): 943–56. http://dx.doi.org/10.1142/s0218271898000620.

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We present a detailed classification of the symmetric (3,1)-spinor according to its factorization properties, analogously with the Petrov classification of the (4,0)-spinor, and present an efficient algorithm, suitable for implementation on a computer, for performing such a classification. One application would be for the classification of spacetimes with torsion, since the symmetric part of the torsion spinor is a symmetric (3,1)-spinor. This algorithm can also be applied to the Lanczos spinor potential of the Weyl curvature spinor.

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37

Paoletti, Valeria, Per Christian Hansen, Mads Friis Hansen, and Maurizio Fedi. "A computationally efficient tool for assessing the depth resolution in large-scale potential-field inversion." GEOPHYSICS 79, no. 4 (July 1, 2014): A33—A38. http://dx.doi.org/10.1190/geo2014-0017.1.

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In potential-field inversion, careful management of singular value decomposition components is crucial for obtaining information about the source distribution with respect to depth. In principle, the depth-resolution plot provides a convenient visual tool for this analysis, but its computational complexity has hitherto prevented application to large-scale problems. To analyze depth resolution in such problems, we developed a variant ApproxDRP, which is based on an iterative algorithm and therefore suited for large-scale problems because we avoid matrix factorizations and the associated demands on memory and computing time. We used the ApproxDRP to study retrievable depth resolution in inversion of the gravity field of the Neapolitan Volcanic Area. Our main contribution is the combined use of the Lanczos bidiagonalization algorithm, established in the scientific computing community, and the depth-resolution plot defined in the geoscience community.

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38

XU, DINGGUO, HUA GUO, and DAIQIAN XIE. "THEORETICAL STUDIES OF $\tilde{A}{}^1 A^{\prime\prime}\to\tilde{X}{}^1 A^\prime$ RESONANCE EMISSION SPECTRA OF HCN/DCN USING SINGLE LANCZOS PROPAGATION METHOD." Journal of Theoretical and Computational Chemistry 02, no. 04 (December 2003): 639–48. http://dx.doi.org/10.1142/s0219633603000707.

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Using an efficient single Lanczos propagation method, we report the [Formula: see text] resonance emission spectra of HCN and DCN from a number of low-lying vibrational levels of the Ã-state manifold. Our calculations represent the first such undertaking in which a high-quality ab initio based potential energy surface of the excited (Ã1 A″) state and a [Formula: see text] transition dipole surface were used. The results show a significant improvement over previous theoretical work in reproducing experimental stimulated emission pumping spectra of HCN. The improved theory-experiment agreement is attributed to the accurate Ã-state potential energy surface, while the impact of the transition dipole function was found to be relatively minor.

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39

Iserles, Arieh, Karolina Kropielnicka, and Pranav Singh. "Magnus--Lanczos Methods with Simplified Commutators for the Schrödinger Equation with a Time-Dependent Potential." SIAM Journal on Numerical Analysis 56, no. 3 (January 2018): 1547–69. http://dx.doi.org/10.1137/17m1149833.

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40

Li, Anyang, Sen Lin, and Daiqian Xie. "Ab Initio Potential Energy Surfaces for Both the Ground (X̃1A′) and Excited (A∼1A′′) Electronic States of HSiBr and the Absorption and Emission Spectra of HSiBr/DSiBr." Advances in Physical Chemistry 2012 (October 13, 2012): 1–20. http://dx.doi.org/10.1155/2012/572148.

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Ab initio potential energy surfaces for the ground (X̃1A′) and excited (A˜A′′1) electronic states of HSiBr were obtained by using the single and double excitation coupled-cluster theory with a noniterative perturbation treatment of triple excitations and the multireference configuration interaction with Davidson correction, respectively, employing an augmented correlation-consistent polarized valence quadruple zeta basis set. The calculated vibrational energy levels of HSiBr and DSiBr of the ground and excited electronic states are in excellent agreement with the available experimental band origins. In addition, the absorption and emission spectra of HSiBr and DSiBr were calculated using an efficient single Lanczos propagation method and are in good agreement with the available experimental observations.

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41

LAVERTY, RICHARD R., and GEORGE A. GAZONAS. "AN IMPROVEMENT TO THE FOURIER SERIES METHOD FOR INVERSION OF LAPLACE TRANSFORMS APPLIED TO ELASTIC AND VISCOELASTIC WAVES." International Journal of Computational Methods 03, no. 01 (March 2006): 57–69. http://dx.doi.org/10.1142/s0219876206000849.

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A parametric study of composite strips leads to systems of partial differential equations, coupled through interface conditions, that are naturally solved in Laplace transform space. Because of the complexity of the solutions in transform space and the potential variations due to geometry and materials, a systematic approach to inversion is necessarily numerical. The Dubner-Abate-Crump (DAC) algorithm is the standard in such problems and is implemented. The presence of discontinuous wavefronts in the problems considered leads to Gibbs phenomenon; which, in turn, overestimates the values of maximum stress. These errors are mitigated by use of Lanczos' σ-factors, which combine naturally with the DAC algorithm.

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42

Rashev, Svetoslav, and David Moule. "Variational calculations on the vibrational level structure of S0 HDCO." Open Chemistry 11, no. 1 (January 1, 2013): 1–7. http://dx.doi.org/10.2478/s11532-012-0127-x.

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AbstractWe perform converged high precision variational calculations to determine the frequencies of the vibrational levels in S0 HDCO, extending up to 5000 cm−1 of vibrational excitation energy. For these calculations we use our specific vibrational method (recently employed for studies on H2CO and D2CO), consisting of a combination of a search/selection algorithm and a Lanczos iteration procedure and based on the Martin, Lee, Taylor potential energy surface for formaldehyde. The calculated level structure is compared to the recently measured frequencies by Ellsworth et al. in order to improve their assignments and further clarify the vibrational mixing pattern and vibrational resonances in HDCO that are very different from the other more symmetric formaldehyde species H2CO and D2CO studied recently.

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43

Edgar, S. Brian, and A. Höglund. "Letter: The Non-Existence of a Lanczos Potential for the Weyl Curvature Tensor in Dimensions n ≥ 7." General Relativity and Gravitation 34, no. 12 (December 2002): 2149–53. http://dx.doi.org/10.1023/a:1021143703760.

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44

Anderson, Douglas A. "Liability for Publishing Syndicated and Free-Lance Material." Newspaper Research Journal 10, no. 3 (March 1989): 75–89. http://dx.doi.org/10.1177/073953298901000308.

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Since before Drew Pearson, whose syndicated column elicited more titan 100 libel suits, editors have feared libel suits prompted by copy produced by outside writers. The courts have given prudent editors some breathing space, however, shielding publications in most instances from potential recklessness of free-lancers.

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45

Došlić, Nadja, and O. Kühn. "The Intramolecular Hydrogen-Bond in Malonaldehyde as Seen by Infrared Spectroscopy. A Four-Dimensional Model Study." Zeitschrift für Physikalische Chemie 217, no. 12 (December 1, 2003): 1507–24. http://dx.doi.org/10.1524/zpch.217.12.1507.20477.

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AbstractThe infrared spectrum of the O–H–O fragment of malonaldehyde is studied using a four-dimensional model. This comprises the OH stretching and the two OH bending vibrations as well an O–O ring deformation mode under the assumption of overall Cs symmetry. The full anharmonic potential energy and dipole moment surfaces are calculated using density functional theory and the respective vibrational eigenvalue problem is solved by an iterative Lanczos method. Fundamental and combination transitions are discussed for the normal species and the symmetrically deuterated isotopomer. Special emphasis is paid to the OH/OD stretching region which reveals the signatures of strong mode mixing what renders a simple assignment in terms of fundamental transitions difficult. In addition results for hot transitions are presented which show a rather different OH/OD band due to the topology of the potential energy surface. The influence of H atom tunneling on the spectrum is briefly addressed employing an alternative three-dimensional model which takes into account the in-plane H atom motion as well as the O–O distance.

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Reddy, Shabashini, Andrew Gibbs, Elizabeth Spooner, Noluthando Ngomane, Tarylee Reddy, Nozipho |Luthuli, Gita Ramjee, Anna Coutsoudis, and Photini Kiepiela. "Assessment of the Impact of Rapid Point-of-Care CD4 Testing in Primary Healthcare Clinic Settings: A Survey Study of Client and Provider Perspectives." Diagnostics 10, no. 2 (February 1, 2020): 81. http://dx.doi.org/10.3390/diagnostics10020081.

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Background: The high burden of disease in South Africa presents challenges to public health services. Point-of-care (POC) technologies have the potential to address these gaps and improve healthcare systems. This study ascertained the acceptability and impact of POC CD4 testing on patients’ health and clinical management. Methods: We conducted a qualitative survey study with patients (n = 642) and healthcare providers (n = 13) at the Lancers Road (experienced POC) and Chesterville (non-experienced POC) primary healthcare (PHC) clinics from September 2015 to June 2016. Results: Patients (99%) at Lancers and Chesterville PHCs were positive about POC CD4 testing, identifying benefits: No loss/delay of test results (6.4%), cost/time saving (19.5%), and no anxiety (5.1%), and 58.2% were ready to initiate treatment. Significantly more patients at Chesterville than Lancers Road PHC felt POC would provide rapid clinical decision making (64.7% vs. 48.1%; p < 0.0001) and better clinic accessibility (40.4% vs. 24.7%; p < 0.0001) respectively. Healthcare providers thought same-day CD4 results would impact: Clinical management (46.2%), patient readiness (46.2%), and adherence (23.0%), and would reduce follow-up visits (7.7%), while 38.5% were concerned that further tests and training (15.4%) were required before antiretroviral therapy (ART) initiation. Conclusion: The high acceptability of POC CD4 testing and the immediate health, structural, and clinical management benefits necessitates POC implementation studies.

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Rashev, Svetoslav, and David Moule. "Vibrational calculations in formaldehyde: the CH stretch system." Open Chemistry 9, no. 4 (August 1, 2011): 549–56. http://dx.doi.org/10.2478/s11532-011-0042-6.

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AbstractAn alternative procedure for the calculation of highly excited vibrational levels in S0 formaldehyde was developed to apply to larger molecules. It is based on a new set of symmetrized vibrational valence coordinates. The fully symmetrized vibrational kinetic energy operator is derived in these coordinates using the Handy expression [Molec. Phys. 61, 207 (1987)]. The potential energy surface is expressed as a fully symmetrized quartic expansion in the coordinates. We have performed ab initio electronic computations using GAMESS to obtain all force constants of the S0 formaldehyde quartic force field. Our large scale vibrational calculations are based on a fully symmetrized vibrational basis set, in product form. The vibrational levels are calculated one by one using an artificial intelligence search/selection procedure and subsequent Lanczos iteration, providing access to extremely high vibrational energies. In this work special attention has been given to the CH stretch system by calculating the energies up to the fifth CH stretch overtone at ∼16000 cm−1, but the method has also been tested on two highly excited combination levels including other lower frequency modes.

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Arguez, Anthony, Mark A. Bourassa, and James J. O’Brien. "Detection of the MJO Signal from QuikSCAT." Journal of Atmospheric and Oceanic Technology 22, no. 12 (December 1, 2005): 1885–94. http://dx.doi.org/10.1175/jtech1822.1.

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Abstract Wind data from the SeaWinds instrument on NASA’s Quick Scatterometer (QuikSCAT) satellite are investigated to ascertain how well the surface manifestation of the Madden–Julian oscillation (MJO) can be resolved. The MJO signal is detected in nonfiltered gridded data using extended EOF analysis of the zonal wind field, overshadowed by annual, semiannual, and monsoon-related modes. After bandpass filtering with Lanczos weights, MJO signals are clearly detected in several kinematic quantities, including the zonal wind speed, the zonal pseudostress, and the velocity potential. Extraction of the MJO using QuikSCAT winds compares favorably with extraction using NCEP Reanalysis 2, except that the QuikSCAT signal appears to be more robust. In addition, an alternative bandpass-filtering technique using variable filter weights near time series endpoints is presented. The method uses least squares minimization to match newly created frequency response functions in edge zones as closely as possible to the predetermined frequency response function of interior points. This method stands in contrast to the common practice of simply discarding those endpoints where a convolution cannot be computed.

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YU, HUA-GEN, and JAMES T. MUCKERMAN. "THEORETICAL DETERMINATION OF ROVIBRATIONAL ENERGIES AND ANOMALOUS ISOTOPIC EFFECT OF WEAKLY BOUND CLUSTER HXeOH." Journal of Theoretical and Computational Chemistry 02, no. 04 (December 2003): 573–81. http://dx.doi.org/10.1142/s0219633603000744.

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The rovibrational energy levels of HXeOH and its isotopomers have been calculated using a two-layer Lanczos algorithm in Radau-diatom-Jacobi coordinates based on a high level ab initio potential energy surface. The surface is obtained by fitting to 1229 RCCSD(T)/SDB-cc-pVQZ energy points. The equilibrium geometry of HXeOH is determined to have a trans configuration with a nearly collinear HXeO bond angle of 177.32 degrees. The well depth of this minimum is only 0.6123 eV with respect to the OH + Xe + H dissociation limit. The results show that the H–Xe stretching frequency of HXeOH and HXeOD has an anomalous isotopic shift upon 18 O isotope substitution, whereas the D–Xe stretch in DXeOH and DXeOD displays a normal isotopic shift. This trend is consistent with the experimental observations in a Xe solid matrix. The present results predict a lower frequency for the H–Xe stretch than was observed in the solid matrix experiment. Either these results are too low or there is a strong blue shift due to the matrix in the experimental values.

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Wang, Xiao-Gang, and Tucker Carrington. "Using experimental data and a contracted basis Lanczos method to determine an accurate methane potential energy surface from a least squares optimization." Journal of Chemical Physics 141, no. 15 (October 21, 2014): 154106. http://dx.doi.org/10.1063/1.4896569.

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