bluuebunny/crossref_metadata_2025 huggingface dataset:
Motion‐corrected free‐breathing delayed enhancement imaging of myocardial infarction
Authors: Kellman Peter , Larson Andrew C. , Hsu Li‐Yueh , Chung Yiu‐Cho , Simonetti Orlando P. , McVeigh Elliot R. , Arai Andrew E.
Published: December 2004

Following administration of Gd‐DTPA, infarcted myocardium exhibits delayed enhancement and can be imaged using an inversion‐recovery sequence. A conventional segmented acquisition requires a number of breath‐holds to image the heart. Single‐shot phase‐sensitive inversion‐recovery (PSIR) true‐FISP may be combined with parallel imaging using SENSE to achieve high spatial resolution. SNR may be improved by averaging multiple motion‐corrected images acquired during free breathing. PSIR techniques have demonstrated a number of benefits including consistent contrast and appearance over a relatively wide range of inversion recovery times (TI), improved contrast‐to‐noise ratio, and consistent size of the enhanced region. Comparison between images acquired using segmented breath‐held turbo‐FLASH and averaged, motion‐corrected, free‐breathing true‐FISP show excellent agreement of measured CNR and infarct size. In this study, motion correction was implemented using image registration postprocessing rather than navigator correction of individual frames. Navigator techniques may be incorporated as well. Magn Reson Med 53:194–200, 2005. Published 2004 Wiley‐Liss, Inc.
Gadodiamide T1 relaxivity in brain tissue in vivo is lower than in saline
Authors: Pickup Stephen , Wood Andrew K. W. , Kundel Harold L.
Published: December 2004

In vivo measurements of gadodiamide (Gd‐DTPA‐BMA) T1 relaxivity were performed at 4.7 T in injured and normal rat brains. Cerebral lesions were induced in nine rats by a localized freezing method. T1 maps of the lesions were generated before and after injection of Gd‐DTPA‐BMA (0.1–0.6 mmol/kg). Samples of normal and necrotic brain were collected postmortem; the wet and dry weights were determined, and Gd content was measured by inductively coupled plasma mass spectroscopy. The in vivo relaxivity was determined by a linear fit of a plot of the change in relaxation rate following injection of the contrast agent as a function of Gd content. This analysis yielded a relaxivity in the injured brain of 2.8 sec−1 mmol−1 kg tissue water at 36°C. The water weight fraction was 0.90 ± SD 0.02 wt/wt in injured brain and 0.79 ± 0.02 in normal brain. Relaxivity measurements were also performed on solutions of Gd‐DTPA‐BMA (0.0–0.6 mmol) and albumin (0–30% wt/wt) in normal saline at room and physiologic temperatures. The relaxivity in the albumin/saline increased with increasing solids content with values of 4.0–4.9 sec−1 mmol−1kg at 21°C and 3.4–4.5 sec−1 mmol−1 kg at 37°C. The relaxivity of the tissues differed significantly from that of the saline solutions of comparable solids content, suggesting that the solids content of a tissue is not the only factor that determines in vivo relaxivity. Magn Reson Med 53:35–40, 2005. © 2004 Wiley‐Liss, Inc.
Statistical motor unit number estimation assuming a binomial distribution
Authors: Blok Joleen H. , Visser Gerhard H. , de Graaf Sándor , Zwarts Machiel J. , Stegeman Dick F.
Published: December 2004

The statistical method of motor unit number estimation (MUNE) uses the natural stochastic variation in a muscle's compound response to electrical stimulation to obtain an estimate of the number of recruitable motor units. The current method assumes that this variation follows a Poisson distribution. We present an alternative that instead assumes a binomial distribution. Results of computer simulations and of a pilot study on 19 healthy subjects showed that the binomial MUNE values are considerably higher than those of the Poisson method, and in better agreement with the results of other MUNE techniques. In addition, simulation results predict that the performance in patients with severe motor unit loss will be better for the binomial than Poisson method. The adapted method remains closer to physiology, because it can accommodate the increase in activation probability that results from rising stimulus intensity. It does not need recording windows as used with the Poisson method, and is therefore less user‐dependent and more objective and quicker in its operation. For these reasons, we believe that the proposed modifications may lead to significant improvements in the statistical MUNE technique. Muscle Nerve, 2005
Superficial motor units are larger than deeper motor units in human vastus lateralis muscle
Authors: Knight C. A. , Kamen G.
Published: December 2004

Previous studies have suggested that regionalization may occur for human motor units, whereby smaller motor units are located in deeper parts of the muscle and larger motor units are located in more superficial portions. We examined this possibility in the human vastus lateralis muscle using macro‐EMG (electromyography) to estimate motor unit size. The sample consisted of nine individuals from whom 114 motor units were recorded at forces ranging between 5% and 60% MVC. Peak‐to‐peak macro‐EMG amplitude was well correlated with macro area (Spearman rho = 0.96). There was a statistically significant inverse relationship between recording depth and macro peak‐to‐peak amplitude (rho = −0.402, p < 0.001). We conclude that there is a nonrandom distribution of motor units in human muscle, with larger motor units located in more superficial regions and smaller units located in deeper regions. Clinicians who monitor motor unit activity need to recognize that a representative sample of motor unit recordings should include motor units from both deeper and more superficial regions of muscle. Muscle Nerve, 2005
Enrichment of the R77C α‐sarcoglycan gene mutation in finnish LGMD2D patients
Authors: Hackman P. , Juvonen V. , Sarparanta J. , Penttinen M. , Äärimaa T. , Uusitalo M. , Auranen M. , Pihko H. , Alén R. , Junes M. , Lönnqvist T. , Kalimo H. , Udd B.
Published: December 2004

Limb‐girdle muscular dystrophy 2D (LGMD2D) is caused by mutations in the α‐sarcoglycan gene (SGCA). The most frequently reported mutation, 229CGC>TGC (R77C) in exon 3 of SGCA, results in the substitution of arginine by cysteine. We present here the clinical, immunohistochemical, and genetic data of 11 Finnish patients with LGMD2D caused by mutations in SGCA. Mutational analysis showed 10 patients homozygous and 1 compound heterozygous for R77C. A wide spectrum of SGCA mutations has been reported previously. Our results show an enrichment of R77C in Finland, further underlined by the observed carrier frequency of 1 per 150. According to the annual birth rate of ∼60.000 in Finland, one LGMD2D patient with a homozygous mutation is expected to be born every 1 or 2 years on average. The presence of an ancient founder mutation is indicated by the fact that all patients shared a short common haplotype extending ≥790 kilibases. Our results emphasize the need to include the SGCA gene R77C mutation test in routine DNA analyses of severe dystrophinopathy‐like muscular dystrophies in Finland, and suggest that the applicability of this test in other populations should be studied as well. Muscle Nerve, 2005
Impact of different sized catheters on pressure‐flow studies in women with lower urinary tract symptoms
Authors: Costantini Elisabetta , Mearini Luigi , Biscotto Sauro , Giannantoni Antonella , Bini Vittorio , Porena Massimo
Published: December 2004

Aims

This study assessed the impact of two catheters on urinary flow in women undergoing a pressure/flow (P/F) study for lower urinary tract symptoms (LUTS).

Materials and Methods

Women who agreed to undergo urodynamic testing were assigned prospectively to a 7 or 9 Fr catheter in P/F study according to a balanced randomized block design. Exclusion criteria: urinary tract infection, bladder stone or tumor, neuropathy, complete urinary retention, inability to void with catheter in place, free flowmetry volume below 150 ml, and urine volume varying by more than 20% on both free and P/F studies. We compared free flowmetry and P/F flowmetry with a 9 Fr catheter in 126/239 patients (Group A) and with a 7 Fr catheter in 113/239 (Group B). We determined the differences in the P/F results in terms of pre‐voided bladder volume, clinical and urodynamic categories, and age groups in the two groups. We compared the diagnosis of obstruction based on Qmax during the P/F study and on Qmax in free uroflowmetry.

Results

In Groups A and B, the Qmax rate was significantly less (P < 0.001) in P/F studies. Catheter size did not impact significantly. In patients with cystocele, post‐void residue or obstruction flow was reduced more than in the other categories. Qmax diminished with age, by about 15% in women aged 50–60 and by 21% in women over 70 years old.

Conclusions

Qmax in P/F studies is always reduced independently of catheter size, volume of urine, age, and clinical or urodynamic category. This may have clinical implications when interpreting P/F results and in accurately diagnosing obstruction. © 2004 Wiley‐Liss, Inc.
Modification of the lie‐algebraic scheme and approximation error estimations
Authors: Bihun Oksana , Prytula Mykola
Published: December 2004

A new modification of the the Lie‐algebraic scheme for solving partial differential equations with initial and boundary conditions based on constructing quasirepresentations of the Heisenberg‐Weyl algebra operators involving boundary conditions is proposed. Approximation errors for the modified scheme are evaluated. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fetal cardiac anomalies and genetic syndromes
Authors: Pajkrt Eva , Weisz Boaz , Firth Helen V. , Chitty Lyn S.
Published: December 2004

Cardiac anomalies may occur in isolation or can be part of a genetic syndrome. In this article, we describe some of the genetic syndromes commonly associated with cardiac anomalies where there are other sonographic features that may aid accurate prenatal diagnosis. Copyright © 2004 John Wiley & Sons, Ltd.
Application of partial least squares discriminant analysis to two‐dimensional difference gel studies in expression proteomics
Authors: Karp Natasha A. , Griffin Julian L. , Lilley Kathryn S.
Published: December 2004

Two‐dimensional difference gel electrophoresis (DIGE) is a tool for measuring changes in protein expression between samples involving pre‐electrophoretic labeling with cyanine dyes. In multi‐gel experiments, univariate statistical tests have been used to identify differential expression between sample types by looking for significant changes in spot volume. Multivariate statistical tests, which look for correlated changes between sample types, provide an alternate approach for identifying spots with differential expression. Partial least squares‐discriminant analysis (PLS‐DA), a multivariate statistical approach, was combined with an iterative threshold process to identify which protein spots had the greatest contribution to the model, and compared to univariate tests for three datasets. This included one dataset where no biological difference was expected. The novel multivariate approach, detailed here, represents a method to complement the univariate approach in identification of differentially expressed protein spots. This new approach has the advantages of reduced risk of false‐positives and the identification of spots that are significantly altered in terms of correlated expression rather than absolute expression values.
Structure conservation in cytochromes P450
Authors: Mestres Jordi
Published: December 2004

The recent availability of crystal structures for several diverse cytochromes P450 (CYPs) offers the possibility to perform an up‐to‐date comparative analysis to identify the degree of structure conservation among this superfamily of enzymes specially relevant for their involvement in drug metabolism and toxicity. A set of 9 CYPs sharing between 10% and 27% sequence identity was selected, including 7 class I (CYP 101, 107, 108, 119, 121, 51, and 55) and two class II (CYP 102, and 2C5) structures. After obtaining a multiprotein structure superimposition, a structure‐based sequence alignment was derived. Mapping the level of three‐dimensional structural conservation onto the sequence alignment revealed that over 28% of the alignment positions have the Cαcarbons of their residues within a root‐mean‐square deviation (RMSD) of 2 Å. This degree of structure conservation is found to be generally preserved, even when the structure undergoes dramatic conformational changes. Performing the analysis on 4 members of the CYP2 family (CYP 2B4, 2C5, 2C8, and 2C9), the percentage of alignment positions within 2 Å RMSD amounted to 73%, increasing to over 85% when only structures in a closed conformation are considered. The present findings suggest that it should be plausible to derive models of overall good quality for the major CYP2 metabolizing forms (CYP 2A6, 2C19, 2D6, and 2E1), whereas high levels of uncertainty are still likely to be expected in models for the remaining 2 major P450 metabolizing forms (CYP 1A2 and 3A4), with the corresponding implications for their potential applicability in drug design activities. Proteins 2005. © 2004 Wiley‐Liss, Inc.
Long‐range interactions between atoms and molecules
Authors: Dalgarno A. , Morrison I. H. , Pengelly R. M.
Published: December 2004

The refractive index data for various gases are fitted to analytical formulae from which may be calculated the coefficient of the leading term of the long‐range two‐body interactions and the coefficient of the leading term of the long‐range non‐additive three‐body interactions. Coefficients are obtained for mixtures of the gases He, Ne, A, Kr, Xe, H2, N2 and CH4, the probable error being 5%.
Influence of madelung (interatomic Coulomb) energy on Wolfsberg–Helmholz calculations
Authors: Jørgensen Chr. Klixbüll , Horner Sally M. , Hatfield William E. , Tyree S. Y.
Published: December 2004

A model is presented for the estimation of ionicities in molecules and complex ions. The model uses the minimization of total energy by the method of differential ionization energies. The effect of Madelung corrections to the energies is considered, and the model is refined by evaluating the covalent‐bond energies.

Wolfsberg–Helmholz calculations have been applied to the same type of model, also incorporating Madelung corrections. The Madelung corrections make the metal ionization energy curves less steep, and the ligand ionization energies are nearly invariant with charge. This creates a situation which has previously been artificially imposed by selecting the ligand ionization energies to give desirable terms in the Wolfsberg–Helmholz secular determinant. The effect of Madelung energy is shown to be the primary influence in describing the ionicity and total energy of a chromophore; covalent bonding effects are shown to be secondary when the ligands and the central atom have fairly different electronegativities.
Localized impurity states in the Hartree‐Fock, LCAO approximation II. The F Center in KCI
Authors: Martino F.
Published: December 2004

We apply the techniques of a previous paper (I) to the F center in KCl. Our purpose is to place the application of Hartree‐Fock methods to the F center on a firm theoretical basis by calculating in a consistent manner the magnitude and effect of approximations commonly made in less complete treatments. It is shown that the familiar point‐ion approximations and crystal‐field approximations with partial consideration of exchange effects are special cases of our results. We compute wave functions and energies step by step for each of the various levels of approximation possible with our model. It is found that the functions resulting from the point‐ion model are not good approximations to the final wave functions. Our results show that exchange effects with at least the first two shells of nearest neighbors should be considered since they are of the same order of magnitude as terms in the point‐ion model. Overlaps of the F‐center function with ion functions out to sixth neighbors are considered. The absorption energy for the F center is calculated to be 0.1619 Ry as compared with the experimentally observed energy of 0.170 Ry. The magnetic hyperfine structure contact terms are calculated for the first two shells of nearest neighbor ions, using approximate orthogonalized functions, and found to be 29.7 Mc/h for the nearest neighbor K+ ions and 10.9 Mc/h for the next nearest neighbor Cl− ions. The experimentally observed values are 21.6 and 7.0, respectively. Given these differences and the excessively low values of the one‐electron energies, it is concluded that electronic and ionic polarization effects in the ionized crystal states must be considered to calculate accurate F‐center wave functions and absolute energy levels.
The first excited triplet states of the nucleotide bases calculated with different semiempirical SCF schemes
Authors: Packer J. C. , Avery J. S. , Ladik J. , Biczó G.
Published: December 2004

The π‐electron distributions, spin densities, and energies of the first triplets of the nucleotide bases, uracil, thymine, cytosine, adenine, and guanine, were investigated in various semiempirical approximations. Results are presented for calculations using the semiempirical form of the closed‐shell SCF configuration interaction method, of the different orbitals for different spins (unrestricted Hartree–Fock) treatment, with and without spin projection, and of the Roothaan's open‐shell procedure.
Compact natural orbital expansions for the helium ground state
Authors: Cressy Norman , Miller K. R. , Ruedenberg Klaus
Published: December 2004

Using the natural orbital representation and optimizing the exponents in the Slater‐type orbital basis, configuration interaction type wave functions for the helium atom are given which combine compactness and high accuracy.
On the convergence properties of the Rayleigh–Schrödinger and the Hirschfelder–Silbey perturbation expansions for molecular interaction energies
Authors: Chałasiński Grzegorz , Jeziorski Bogumił , Szalewicz Krzysztof
Published: December 2004

The Rayleigh–Schrödinger polarization and the Hirschfelder–Silbey (HS) perturbation theories are applied, through the 38th order, to the interaction of a ground‐state hydrogen atom with a proton. The calculations were made with high precision using a large basis set of orbitals expressed in the confocal elliptic coordinates. The results obtained show that for small internuclear separations R the polarization series converges slowly in an oscillatory way to the energy of the ground 1sσg state of the H molecule. At large R, however, the polarization expansion reproduces only the Coulomb part of the interaction energy effectively. When the value of the Coulomb energy is reached, the rate of convergence deteriorates drastically so that the exchange energy is not reproduced practically. The HS method converges fast when applied to both the 1sσg and the 2pσu states, the rate of convergence being roughly independent of the internuclear distance. If the finite basis set employed to solve the perturbation equations is stable under the symmetry operations, the HS expansion is shown to converge to the energy obtained by minimizing the Rayleigh–Ritz functional within the space spanned by the functions used in the perturbation theory calculations.
Computation of the electronic density of states distributions of stereoregular polymers
Authors: Delhalle J. , Delhalle S.
Published: December 2004

A new algorithm for the computation of the density of states distributions of stereoregular polymers is presented. It is related to the Gilat–Raubenheimer technique for three dimensional systems. Its application to polyethylene is briefly described.
Environmental effects on hydrogen bonded systems: A quantum chemical study of proton relay model systems
Authors: Tapia O. , Poulain E.
Published: December 2004

In this paper an application of a reaction field theory of solvent effects has been made to study proton transfer mechanisms in hydrogen bonded systems coupled to an environment. The latter is simulated with reaction fields having variable strength and direction (defined with respect to the supermolecule's total dipole moment direction), together with superposed uniform external electric fields. Changes in proton potential curves and some other properties of a model water dimer and a water trimer are reported. The results are discussed in relation to relevant phenomena in biology and biochemistry, namely proton relay systems in enzymatic catalysis.
The MTXαR method. The determination and use of “molecular” α values in molecular multiple scattering Xα calculations
Authors: Rosenkrantz Marcy E. , Konowalow Daniel D.
Published: December 2004

A semiempirical approach is used to fix the α value for use in the extraatomic regions in multiple‐scattering (MSXα) calculations which retain the muffin‐tin treatment of the potential. Such a “molecular” α value for an atom is determined by requiring the corresponding homonuclear diatomic molecule to have its minimum at the experimentally determined equilibrium separation; hence they are called αR. Molecular αR values are determined for the ground state Li2 and F2 molecules and are tested in a calculation of the ground state LiF potential curve. We find a binding energy at the calculated equilibrium separation to be within 1% of the experimental value. The LiF curve based entirely on the ordinary atomic α values is substantially inferior. The present MTXαR approach appears to be competitive with others which are intended to improve the muffin‐tin version of MSXα calculations.
Selected valence electron SCF MO calculations on alkali metal diatomics
Authors: Mohammad S. Noor
Published: December 2004

The selected valence electron closed‐shell MO theory of Pohl, Rein, and Appel has been modified with a view to accurately determining the potential energy curves and related spectroscopic quantities of alkali metal diatomics. Binding energies −De equilibrium internuclear distances re, vibrational force constants ke, and dipole moments μbond have been calculated by this method. For the determination of ke, however, use has been made of three different formulas. The calculated potential energy curves have been fitted to a semiempirical potential function constructed in terms of De, re, and ke and then following the Woolley and Dunham method, the harmonic force constants le, me, ne, and oe, the vibrational‐rotational coupling constants αe, the vibrational anharmonicity constants wexe, and two other second order spectroscopic constants, viz., βe and γe, have been calculated with the potential function. The computed results have been compared with experiments wherever the latter are available and it has been observed that these results are in very good agreement with experiment.
Breit‐type three‐electron equation in the Pauli approximation
Authors: Rai D. K. , Ladik J.
Published: December 2004

We have reduced the Breit‐type equation written down for 3 electrons to the 8 large components of the wave function in the (v/c)2 (Pauli) approximation. This procedure required appropriate handling of the 64 scalar equations which result in this instance. According to the results obtained within the accuracy of (v/c)2 all the terms are the same as those obtained by summing up the terms of the reduced 2‐electron Breit's equation to 3 electrons. This statement is no longer valid, however, if during the reduction procedure we would go beyond the (v/c)2 approximation. Finally there is a discussion about how to begin developing a relativistic many‐electron theory valid for the inner shell electrons of heavy atoms within the accuracy of the fine structure constant.
A comparative analysis of pair equations for the H2 molecule
Authors: Adamowicz Ludwik
Published: December 2004

The perturbation contributions to the correlation energy of the H2 molecule are analyzed. This analysis is based on the computer solutions of several two‐electron equations in the Gaussian geminal basis set. The pair equations differ by the choice of the two‐electron interaction potential which may result from distinct infinite summations of correlation diagrams in Rayleigh–Schrödinger perturbation theory.
On the use of symmetry in first‐order perturbed Hartree–Fock theory
Authors: Lazzeretti Paolo
Published: December 2004

A method for the determination of the symmetry of first‐order vectors in Hartree–Fock perturbation theory is developed. This leads to the definition of symmetry‐adapted basis vectors to be employed at first order in the perturbation. It is shown that computer time can be saved, to some extent, in the calculation of second‐order properties, by exploiting molecular symmetry. Specific examples are given for methane, ammonia, and water.
London potential‐energy surfaces for symmetrical alkali trimers
Authors: Mohammad S. Noor
Published: December 2004

Semiempirical valence bond calculations have been performed on the symmetrical alkali trimers in order to obtain their potential‐energy surface, binding energy, and equilibrium geometry. For these calculations original and generalized Rosen–Morse potentials for the ground state and two similar types of new potentials for the triplet state of alkali dimers have been used. At small internuclear distances the potential surfaces show a shallow well which extends into the entrance and exit valleys without an energy barrier. The trimers are found to be stable both in linear and bent configurations, but the most stable configuration in each case is linear and symmetric. The force constants corresponding to stretching and bending deformations of the trimers have been calculated for this configuration. It has been observed that unlike the stretching, the bending deformation does not sensitively affect the energy variation of the ground state of the trimers.
On the use of spatial symmetry in atomic‐integral calculations: An efficient permutational approach
Authors: Le Rouzo H.
Published: December 2004

The minimal number of independent nonzero atomic integrals that occur over arbitrarily oriented basis orbitals of the form ℛ(r) · Ylm(Ω) is theoretically derived. The corresponding method can be easily applied to any point group, including the molecular continuous groups C∞v and D∞h. On the basis of this (theoretical) lower bound, the efficiency of the permutational approach in generating sets of independent integrals is discussed. It is proved that lobe orbitals are always more efficient than the familiar Cartesian Gaussians, in the sense that GLOs provide the shortest integral lists. Moreover, it appears that the new axial GLOs often lead to a number of integrals, which is the theoretical lower bound previously defined. With AGLOs, the numbers of two‐electron integrals to be computed, stored, and processed are divided by factors 2.9 (NH3), 4.2 (C5H5), and 3.6 (C6H6) with reference to the corresponding CGTOs calculations. Remembering that in the permutational approach, atomic integrals are directly computed without any four‐indice transformation, it appears that its utilization in connection with AGLOs provides one of the most powerful tools for treating symmetrical species.
PCILO Calculations on “true” van der Waals complexes
Authors: Lochmann R. , Hobza P.
Published: December 2004

The PCILO method was applied to complexes where dispersion energy forms the dominant attractive contribution of the intermolecular interaction energy. With alkane dimers, especially with dimers of higher alkanes (C4H10)2, (C5H12)2, etc., and the ethylene dimer PCILO was successful as to stabilization energy, equilibrium distance, optimal dimer structure, and energy composition. The dispersion energy part is always underestimated, however. With (X2)2 dimers (X = N, F, Cl) PCILO failed, which might be explained by the presence of lone pairs in the subsystems.
Quantum chemistry by random walk: H4 square
Authors: Anderson James B.
Published: December 2004

The random‐walk method of solving the Schrödinger equation is applied to the 1B1g and 1B2g states of the H4 square with side length 2.4 a.u. The results provide an independent check of the accuracy of prior variational calculations for these states. With node structures for the 1B1g state taken from a variational calculation with a single‐zeta basis set and taken in the simplest form meeting symmetry requirements, the calculated energies are lower than the expectation value of the energy for the single‐zeta basis set but not as low as the expectation value for an optimized‐exponent double‐zeta basis set with polarization terms. Comparisons of results give no suggestion of a barrier height lower than ∼120 kcal/mol for passage through the square configuration in the exchange reaction H2 + D2 → 2HD. For the 1B2g state with node structure in the simplest form meeting symmetry requirements the calculated energy is ∼65 kcal/mol lower than the expectation value of the energy for variational calculations with a double‐zeta basis set.
Neon L‐shell photoabsorption cross sections from moment theory and finite basis pseudospectra
Authors: Faegri K.
Published: December 2004

Pseudospectra from Gaussian basis set calculations within a frozen‐core approximation have been used in a moment analysis to obtain Tchebychev profiles for the photoabsorption process in the valence shell of Ne. The profiles show good agreement with cross sections obtained in equivalent calculations using numerical atomic wave functions and continuum orbitals, particularly when the dipole‐velocity form is employed. Variation of the basis sets shows that it is possible to obtain meaningful photoabsorption profiles using 13–15 virtual orbitals to describe the outgoing electron.
On the use of symmetry in first‐order perturbed HF theory. II
Authors: Lazzeretti Paolo , Zanasi Riccardo
Published: December 2004

A method is described whereby molecular symmetry is employed to reduce the number of two‐electron integrals in perturbed Hartree–Fock calculations of second‐order properties. The method is a generalization of the Dacre–Elder procedure. First‐ and second‐rank perturbing tensor operators are examined in the coupled HF approach to electric dipole polarizabilities, magnetic susceptibilities, quadrupole polarizabilities, and spin‐dopolar contributions to spin–spin coupling constants. The procedure sketched here permits a large saving of computer efforts, which is shown by some illustrative examples.
Power moments of hydrogenic Green's functions and Green's functions of the second kind
Authors: Laurenzi Bernard J.
Published: December 2004

Power moments for all of the reduced hydrogenic Green's functions have been computed. These moments have the same form as the corresponding moments of the free‐particle Green's functions. Green's functions of the second kind are defined, and uses for these objects in model potential theory and the theory of many‐body Green's functions are pointed out. In the case of the ground state of the hydrogenic atom, the Green's function of the second kind has been given.
Study of the muffin‐tin approximation in the multiple‐scattering method
Authors: Ferreira Luiz G. , Fazzio Adalberto , Closs Huberto , Brescansin Luiz M.
Published: December 2004

We consider the effects of a non‐muffin‐tin charge density in the multiple‐scattering method. The study is carried out by means of a parametrized electronic density, which is used in a variational expression for the energy of the molecular system. We show that, at least in two situations, the parametrized density reproduces the true density very well. In a numerical study of the electronic configuration of the CH4 molecule, we show that the non‐muffin‐tin density may shift the one‐electron energies by as much as 1 eV and the total energy by as much as 1 Ry.
Toward a microscopic description of molecular electronic systems
Authors: Pucci Renato , Baldo Marcello , Grassi Antonio , Tomasello Pasquale
Published: December 2004

The many‐body perturbation theory is reformulated within the dielectric function method presented in the preceding paper [12]. The self‐energy effects are explicitly considered. These corrections turn out to be important and are calculated to the same level of approximation as the corresponding local‐field terms. The method is at the moment applicable to π‐electron systems within the zero differential overlap approximation. Explicit calculations of the excitation energies for the benzene molecule, using different parametrizations, are presented. Comparison is made with the results obtained in the random phase approximation (RPA) and other schemes.
Perturbation calculation of transition moments in the ArH+ system
Authors: Chambaud G. , Levy B. , Millié Ph.
Published: December 2004

The matrix elements of the transition dipolar momentum IR have been computed between the low‐lying states associated to the Lyman–α transition. The orthogonalization of the involved electronic states (obtained by the CIPSI method) has been performed and led to a better value for the asymptotic behavior of the {Ar(3p5, 4s) + H+} configuration. Position of the satellites in the red and blue wing of the line are deduced from the potential‐energy curves in the frame of the quasistatic theory.
Spin–orbit coupling for the motion of a particle in a ring‐shaped potential
Authors: Hartmann Hermann , Schuch Dieter
Published: December 2004

As is known, the Schrödinger equation for a particle in the ring‐shaped potential V(r,v) = ησ2(2a0/r−a/r2 sin2v)ε0, defined in the whole space, has been solved exactly. Here the eigenfunctions are represented in a form which is advantageous for concrete evaluations. The spin–orbit interaction energy ELS in quasirelativistic approximation is determined analytically, for the first time with a nonspherically symmetric potential. The influence of spin–orbit interaction on the eigenvalues of the spin‐free problem and on the selection rules for electrical dipole transitions are investigated as well as the dependence of ELS on the position and depth of the potential minimum. The model can be useful for investigations of axial symmetric subjects like the benzene molecule or related problems and may be easily extended to a many‐electron theory.
Potential‐energy surfaces of low‐lying states of HNO
Authors: Nomura Okio
Published: December 2004

Global features of potential‐energy curves are drawn using minimal basis SCF–CI method. Potential‐energy surfaces are drawn at points of interest. The mechanism of the chemiluminescence is discussed along with the measurement of a rate constant exploiting the phenomena.
Molecular calculations with the nonempirical ab initioMODPOT, VRDDO, and MODPOT/VRDDO procedures. XI. Theoretical study of the [C6H5OH ⃛OC6H5]− molecular complex: Ab initioMODPOT/VRDDO calculations and electrostatic molecular potential contour maps
Authors: Sokalski W. A. , Hariharan P. C. , Popkie Herbert E. , Kaufman Joyce J. , Petrongolo Carlo
Published: December 2004

The transport of C6H5O− (or similarly charged moieties) through a lipoidal membrane may possibly be facilitated by forming complexes with the neutral compound. Thus, theoretical studies were performed on the model [C6H5OH ⃛OC6H5]− molecular complex to obtain some information concerning the possible molecular and electronic structure of such complexes. Ab initio MODPOT/VRDDO SCF calculations were carried out on the neutral‐anion dimer [C6H5OH ⃛OC6H5] to optimize the equilibrium geometry. Electrostatic molecular potential contour maps have been generated from the ab initio MODPOT/VRDDO results in the molecular plane and in the plane perpendicular to the molecular plane and intersecting the hydrogen bond O ⃛HO. Difference maps have also been generated showing the change of potential on complex formation. There is a decrease of electrostatic interactions of the phenoxide anion upon complex formation with the neutral phenol. Counterpoise corrections for basis set size could not be made since calculation of the phenoxide anions in the basis set of the phenol plus the phenoxide anion led to an excited state for the phenoxide anion. This behavior is somewhat similar to that occurring in the stabilization method for excited states of negative ions as the size of the basis set is increased.
Evaluation of multicenter integrals over Slater‐type atomic orbitals by expansion in terms of complete sets
Authors: Steinborn E. Otto , Filter Eckhard
Published: December 2004

Multicenter integrals over Slater‐type orbitals can be expanded in series with known coefficients if they are considered as elements of appropriate Hilbert spaces. Some test calculations for the three‐center nuclear attraction integrals are given.
Calculations of XPS spectra for oxyanions and related compounds by the discrete variational‐Xα method
Authors: Sasaki Teikichi , Adachi Hirohiko
Published: December 2004

Calculations of molecular‐orbital energies and x‐ray photoelectron spectra have been carried out for the third‐row oxyanions, transition‐metal oxyanions, SiO2 and TiO2, by the discrete variational‐Xα cluster method. The calculated orbital energies are consistent with those determined from the XPS experiments. Theoretical XPS line shapes with Gaussian are generally in good agreement with the observed spectra. However, underestimation has been found for the photopeak intensities in the low‐binding‐energy region of TiO2. The discrepancy is partially attributed to the use of inaccurate photoionization cross‐section for the Ti3d orbital.
Laser‐induced fluorescence of Cs2 and role of kinetic energy in the Franck–Condon principle
Authors: Katô Hajime
Published: December 2004

Quantum‐mechanical calculation of spectral intensity is done for the transitions from a particular vibrational level of the excited state E 1∏u to the discrete vibrational levels and dissociative continuum of the ground state X1Σ of the Cs2 molecule. The results are compared with the observed spectra by referring to the conservation of nuclear kinetic energy during the electronic transition.
Excimer and monomer emission of pyrene crystals associated with the phase transition
Authors: Uchida Kenji , Takahashi Yoshihiro
Published: December 2004

Emission spectra and decay times of the fluorescence under the excitation of various energies were measured in pyrene crystals. At liquid nitrogen temperature, a new excimer emission was found under 390 nm excitation, and its peak shifts a little to the high energy in comparison with that of the familiar excimer. The decay time of the former emission abruptly changes around 125°K, which seems to be due to the phase transition in pyrene crystals. Also, when the crystals were rapidly cooled below 125°K, the monomer emission in the crystals was observed, and its decay time was about 600 nsec.
Nonadditive effects in metal clusters and chemisorption. Pseudopotential study of palladium clusters
Authors: García‐Prieto J. , Novaro O.
Published: December 2004

The analysis of nonadditive effects in small palladium clusters via LCAO‐MO‐SCF calculations using the nonempirical pseudopotential model is presented. The results are tentatively correlated with previous studies on various metal clusters (Li, Be, Mg, etc.) for which a good knowledge of multibody terms has provided a valuable guide for understanding the cluster stabilities and their chemisorption capacity.
Local behavior of hückel parameters
Authors: Brüggemann R. , Voitländer J.
Published: December 2004

Properties of Hückel parameters are investigated by using a mapping concept. The mapping is constructed by means of the Linderberg relation. No efforts are made to get a numerically correct description of the Hückel parameters.
Uracil and the tautomer 4‐hydroxyuracil: An ab initio study with geometry optimization
Authors: Zielinski Theresa Julia , Shibata Masayuki , Rein Robert
Published: December 2004

Ab initio STO‐3G geometries and relative energies for uracil (U) and the tautomer 4‐hydroxyuracil (U*) were obtained with the HONDO program utilizing the rapidly convergent method of Murtaugh and Sargent for geometry optimization. ΔE for U⇄U* is 6.61 kcal/mole. The reaction field continuum model for solvent effect indicates a preferential stabilization of U* by 1.0 kcal/mole. The calculated gas phase Kt and solution Kt for U⇄U* are 1.44×10−5 and 1.3×10−4, respectively.
Calculation of isoelectronic energy differences using perturbation theory
Authors: Sontum Stephen F. , Ingraham Lloyd L. , Fink William H.
Published: December 2004

Energy difference formulas for isoelectronic processes are derived using a perturbation series. The perturbed Hamiltonian is written as a function of a perturbation parameter that changes linearly from zero to one between the limits of the isoelectronic process. The perturbation series is based on a zero order wave function obtained when the perturbation parameter has a value of ½. For the description of changes of electronic energy with internuclear geometry, this zero order wave function will correspond to the solution of a Hamiltonian which contains atoms from both internuclear geometries, but with half their normal nuclear charge. Energy differences calculated with this formalism for the stretching of simple diatomic molecules hydrogen fluoride, fluorine, and carbon monoxide and the rotational barrier in ethane are compared with results from restricted Hartree–Fock and integral‐Hellmann–Feynman theorem energies.
Nodeless wave functions and spiky potentials
Authors: Hunter Geoffrey
Published: December 2004

The exact (nonadiabatic) nuclear and electronic factors of a molecular wave function are expanded in the basis of eigenfunctions of the electronic Hamiltonian according to the Rayleigh–Schrödinger perturbation theory of Born and Huang. Thus it is shown that, with rare exceptions, the exact nuclear factor (a marginal amplitude) is a nodeless function. The nodes in vibrationally excited nuclear wave functions within the Born–Oppenheimer approximation become node‐avoiding minima in the exact nuclear wave function. Corresponding to each node‐avoiding minimum in the nuclear wave function the exact (nonadiabatic) effective potential for the nuclear motion has a spiky barrier superimposed upon the Born–Oppenheimer (adiabatic) eigenenergy of the electronic Hamiltonian. These barriers are the result of nonadiabatic coupling between electronic states, which is strongest in the vicinity of the nodes in the Born–Oppenheimer‐approximation nuclear (vibrational) wave function.
Bond–antibond analysis of internal rotation barriers in glyoxal and related molecules: Where INDO fails
Authors: Tyrrell J. , Weinstock R. B. , Weinhold F.
Published: December 2004

Ab initio and INDO LCBO–MO calculations are carried out on glyoxal, 1,3‐butadiene, and acrolein in order to analyze the qualitative failure of INDO‐like methods to describe conformation energies in these molecules. Following the method of Brunck and Weinhold for ethanelike systems we identify the principal bond–antibond interactions contributing to the glyoxal barrier, their dependence on dihedral angle and substituent, and their relative magnitudes as calculated by ab initio and INDO SCF–MO theory. We find a gross disparity in the INDO representation of π* interactions which leads to a grossly exaggerated estimate of the stability of gauche conformers in these molecules. These findings appear to have serious implications for the applicability of INDO‐like theories to conformational problems in π‐bonded molecules, including those of biological interest.
An einstein relativistic atomic and molecular model based on the Horwitz–Piron–Reuse theory
Authors: Grelland Hans H.
Published: December 2004

The Einsteinian quantum mechanics proposed by Horwitz, Piron, and Reuse is formulated in a way appropriate for atomic and molecular calculations. In this theory each particle is described by a four‐coordinate xμ = (ct, x), and the existence of a common Lorenz invariant time ordering parameter τ is postulated. For spin‐½ particles there exists in addition a superselection rule n defined by the Stern–Gerlach experiment. The description of an atom/molecule in the external approximation is given. We then formulate a method (the self‐consistent energy method) by which conventional calculation procedures can be applied within the theory. The calculation of the expectation value of a singular term which is the analog of the conventional Darwin term, is demonstrated by calculating the energy of an electron in a Coulomb field to the order α4. This calculation also demonstrates the validity of the Pauli approximation within the theory.
Use of iterative natural orbital method for calculating energy barrier to predissociation of the first excited states of NH3 (3s1,3A″2)
Authors: Müller Jiri
Published: December 2004

The barrier to predissociation of the first excited states of NH3 (3s1,3 A) is computed from a truncated first‐order wave function using the iterative natural orbital method. The results show that the barrier is lower than when calculated with RHF and the CI wave functions, where single and double replacements to a truncated virtual space are carried out. These findings are used to interpret experimental data.
Mode of action and quantitative structure–activity relationship of sulfonamides in biological systems of different complexity (enzymes, bacteria, rat, and human)
Authors: Seydel J. K.
Published: December 2004

The mode of action of sulfonamides is evaluated and described and the structural dependency of the inhibitory effect of sulfonamides against isolated enzymes as well as against whole cell bacteria is quantitatively described as a function of the variation of electronic and steric influences of the various substituents. In addition the structural dependence of various pharmacokinetic properties as rate of absorption, distribution, metabolism, and excretion on structural changes in the sulfonamide molecules is quantitatively derived. In contrast to the preconditions for inhibitory activity, changes in lipophilicity play the dominant role in pharmacokinetics of sulfonamides.
Explicit expression of the franck–condon factors in terms of the potentials of the two states
Authors: Kobeissi Hafez , Dagher Mounzer , Alameddine Mohamad Adel
Published: December 2004

The calculus of the overlap integral for two states represented by the vibrational wave functions ψ and ψ is reduced to that of the Franck–Condon integral ℒ(0, x) = ∫ ψψ (t) dt. It is proved that for “numerical potentials” (as well as for a Dunham potential), this integral is given on each interval by a simple analytic expression in terms of the two potentials. The Franck–Condon factors are well determined by “coupling constants” related uniquely to the coordinates of the turning points of the potentials. An application to the band system BIIXΣ of Nα2 is compared with the usual numerical methods.
Treatment of excited states in the CASSCF method: Application to BO
Authors: Almlöf J. , Nemukhin A. V. , Heiberg A.
Published: December 2004

The CASSCF method has been applied to some excited states of the BO molecule. Only portions of the full potential curves could be obtained with the help of the usual two‐step procedure. It was possible to complete the curves and to consider other excited states by using an averaged field technique. In this approach the energies were computed with orbitals that were self‐consistently determined with first‐ and second‐order density matrices averaged over several states.
Complex coordinate rotation calculation of branching ratios
Authors: Bačić Zlatko , Simons Jack
Published: December 2004

It is shown how branching ratios can be obtained from complex coordinate rotation calculations. The procedure is applied to a rotational Feshbach resonance in a model atom‐diatom van der Waals complex which has two open channels present, and to a simple two‐channel model potential problem which has been treated by other workers.
Calculation in K space of integrals arising in the theory of Van Der Waals forces
Authors: Malinowski P. , Tanner A. C. , Lee K. F. , Linder B.
Published: December 2004

We derive basic integrals needed for calculation of matrix elements of the Fourier transformed Coulomb operator and the Fourier transformed square of the Coulomb operator between 1s Slater functions. These integrals arise, for example, in the momentum space (k space) susceptibility formulation of van der Waals forces. The advantages of integration in k space (rather than r space) are that in k space there is a drastic reduction in the number of integration variables, and contour integration can be used. The derivation is completely analytic and the auxiliary integrals are all obtained in closed form.