bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ontogeny of eyeblink conditioning in the rat: Auditory frequency and discrimination learning effects
Authors: Andrews Steven J. , Freeman John H. , Carter Christy S. , Stanton Mark E. 
Published: January 2005

AbstractThe present study sought to determine whether acoustic properties of the auditory conditioned stimulus (CS) or the use of a discrimination learning procedure would alter the emergence of eyeblink conditioning between postnatal Days 17 and 24 (Days 17–24) in the rat. In Experiment 1, we employed a 3 × 2 × 2 factorial design, involving pitch of the auditory CS (2.8, 5.0, and 9.0 kHz), training condition (paired vs. unpaired), and age (Days 17 or 24). Associative learning was evident at all tone frequencies on Day 24, but increased across frequencies on Day 17, although large age differences in conditioning remained at all tone frequencies. In Experiment 2, rat pups were trained to discriminate 2.8 versus 9.0‐kHz tones on Day 17 or Day 24. Eyeblink conditioning increased with tone frequency on Day 24 but discriminative conditioning failed to appear on Day 17. These findings are discussed in relation to the role of auditory system maturation in the ontogeny of eyeblink conditioning. © 1995 Johnv Wiley & Sons, Inc.
Augmented prenatal visual stimulation alters postnatal auditory and visual responsiveness in bobwhite quail chicks
Authors: Sleigh Merry J. , Lickliter Robert 
Published: January 2005

AbstractThis study examined whether previously reported effects of altered prenatal sensory experience on subsequent acceleration of intersensory development in precocial birds are mediated by mechanisms sensitive to the overall amount of stimulation provided. Results revealed that bobwhite quail chicks exposed to substantially augmented amounts of prenatal visual stimulation show altered patterns of species‐typical perceptual development. Specifically, chicks continued to respond to maternal auditory cues into later stages of postnatal development and failed to demonstrate responsiveness to maternal visual cues. Embryos also failed to demonstrate prenatal auditory learning of an individual maternal call, a behavior reliably seen in unmanipulated embryos. These findings suggest that substantially increased amounts of prenatal sensory stimulation can interfere with the emergence of species‐typical patterns of postnatal intersensory functioning and lend support to the notion that sensory stimulation that falls within some optimal range maintains or facilitates normal patterns of perceptual development, whereas stimulation beyond the range of the species norm can result in intersensory interference. © 1995 John Wiley & Sons, Inc.
Contributions of experience to the development of musical processing in infancy
Authors: Lynch Michael P. , Short Lori B. , Chua Rosario 
Published: January 2005

AbstractFull‐term infants' performance in detection of melodic alterations appeared to be influenced by perceptual experience from 6 months to 1 year of age, and an experiment with infants born prematurely supported the hypothesis that experience affects music processing in infancy. These findings suggest parallel developmental tendencies in the perception of music and speech that may reflect general acquisition of perceptual abilities for processing of complex auditory patterns. This acquisition may contribute to the cultural enfranchisement of infants through perceptual experience. © 1995 Johnv Wiley & Sons, Inc.
Stability and change in cortisol and behavioral response to stress during the first 18 months of life
Authors: Lewis Michael , Ramsay Douglas S. 
Published: January 2005

AbstractObservation of cortisol and behavioral responses to routine inoculation was conducted at 18 months for infants in a longitudinal sample whose stress responses had been observed at 2, 4, and 6 months of age. At 18 months, infants showed an increase in cortisol level over base to the perturbation. The magnitude of this response did not differ from the 6‐month response. Moreover, level of cortisol response at 18 months was related to level of cortisol response at 6 months, but not at 2 or 4 months of age. In light of previous findings for a decline in cortisol response between 2 and 6 months and for the emergence of consistent individual differences in cortisol response by 4 to 6 months, the present findings indicate that a developmental shift in adrenocortical functioning has occurred by 6 months of age. © 1995 John Wiley & Sons, Inc.
A theoretical approach to substituent effects. Interactions between directly bonded groups in the neutrals XNH2, XOH, and XF and the anions XNH− and XO−
Authors: Hinde Alan L. , Pross Addy , Radom Leo 
Published: January 2005

AbstractAb initio molecular orbital calculations have been carried out for the neutrals XNH2, XOH, and XF and the anions XNH− and XO− with substituents X = Li, BeH, BH2, CH3, NH2, OH, and F. All structures have been fully optimized with the 4‐31G basis set which is found to perform considerably better than the minimal STO‐3G basis in predicting the lengths of strongly polar bonds. A quantitative analysis of interactions between the directly bonded groups, utilizing energy changes in hydrogenation reactions, is presented and rationalized with the aid of perturbation molecular orbital theory. Favorable interactions occur when electron‐donor groups bond to electron‐acceptor groups. This applies to both σ and π interactions, the relative importance of which depends on the particular substituents.
Applications of molecular mechanics calculations in carbohydrate chemistry. I. Conformational and constitutional equilibria of tetraoxabicyclo[4.4.0]‐ and ‐[5.3.0] decanes, bicyclic diacetals of alditols
Authors: Burkert Ulrich 
Published: January 2005

AbstractThe energies of various conformations have been calculated by molecular mechanics for cis and trans isomers of 2,4,7,9‐tetraoxabicyclo[4.4.0] decane and 3,5,8,10‐tetraoxabicyclo[5.3.0]decane and their methyl derivatives. These molecules are models for reaction products from formaldehyde and the tetrols, pentitols, and hexitols. The conformational equilibria were analyzed for the cis‐bicyclo [4.4.0] and cis‐bicyclo[5.3.0] systems and compared with available experimental data. The thermodynamic stability of bicyclo[4.4.0] products was found to be higher than that of bicyclo[5.3.0] derivatives in the gas phase in every case studied. Discrepancies with experimental data that exist in a few cases can be ascribed to solvent effects.
An analysis of the molecular packing of maleic hydrazide
Authors: Hall David , Headford Christine E. L. 
Published: January 2005

AbstractA molecular packing analysis of the hydrogen‐bonded layer structure of maleic hydrazide shows that even in such a structure, the van der Waals energy is the dominant component of the lattice energy. The hydrogen‐bond energy of the observed structure is greater than that for alternative structures based on a different mode of hydrogen bonding, and this makes the observed more stable.
Small elemental clusters. I. The structures of Be2, Be3, Be4, and Be5
Authors: Whiteside Robert A. , Krishnan Raghavachari , Pople John A. , Krogh‐Jespersen Mary‐Beth , Von Ragúe Schleyer Paul , Wenke Gottfried 
Published: January 2005

AbstractThe geometries and energies of beryllium clusters up to Be5 are examined using ab initio molecular orbital theory. Allowances are made for electron correlation with Møller—Plesset perturbation theory to fourth order. Correlation is found to have a dramatic effect on the relative energies of the several structures examined for Be4 and Be5. Furthermore, the effect of d‐type basis functions on the correlation energy results in an increased binding energy for the clusters. Be2 is only weakly bound. For Be3, the best estimate of the binding energy is 6 kcal/mole for the singlet equilateral triangle. Be4 is tetrahedral in its ground state and the estimated binding is 56 kcal/mole. The best structure for Be5 is a singlet trigonal bipyramid, and the binding energy is 88 kcal/mole at the highest level of theory used.
The remarkably invariant interaction energies of lithium first‐row compounds with water and with ammonia
Authors: Kaufmann Elmar , Tidor Bruce , Schleyer Paul Von Ragué 
Published: January 2005

AbstractSolvation energies of lithium first‐row compounds LiX (X  H, Li, BeH, BH2, CH3, NH2, OH, F) and of the lithium cation with the model solvents, water and ammonia, have been calculated ab inito (MP2/6‐31 + G*//6‐31G* with zero‐point vibrational energy corrections at 3‐21G//3‐21G). The solvation energies are found to be remarkably constant: −18.0 ± 1.2 and −21.5 ± 1.3 kcal/mol for the hydrates and ammonia solvates, respectively. This independence on the nature of X is due largely to the ionic character of the LiX compounds (dipole moments 4.7–6.6 debye). The unexpectedly high solvation energies of the lithium molecule (−14.3 and −17.8 kcal/mol, respectively) are due to the polarizability of Li2. At the same level, the lithium cation has interaction energies with H2O and NH3 of −34.1 and −39.7 kcal/mol, respectively. For the hydrates of LiOH and LiF cyclic structures with hydrogen bonds and somewhat increased solvation energies also are described.
The evaluation of molecular electron affinities
Authors: Baker Jon , Nobes Ross H. , Radom Leo 
Published: January 2005

AbstractThe performance of a variety of levels of theory in evaluating molecular electron affinities (EAs) has been systematically examined. Calculations have been carried out for six different basis sets and for nine theoretical procedures including unrestricted (UHF) and restricted (RHF) Hartree‐Fock theory, Møler‐Plesset perturbation theory (UMP2, UMP3, UMP4), configuration interaction (UCISD, RCISD, RCISD(Q)) and equations‐of‐motion (EOM) approaches. Electron affinities were evaluated for CH3, NH2, OH, F, C2H, CN, BO, N3, OCN, and NO2. Very poor results are generally obtained unless diffuse functions are included in the basis set and electron correlation is incorporated. Even with the largest basis set used in the present study (6‐311 + + G(2d, 2p)), there are still residual errors greater than 0.2 eV (UMP4) or 0.6 eV (CISD) in the absolute EAs. However, better results are obtained under certain circumstances for relative EAs. The results appear to be significantly affected by spin contamination in the UHF wave‐functions. For those systems for which spin contamination is small, best absolute values of the EAs generally come from the EOM and UMP2 calculations, whereas the most constant errors (thereby allowing systematic correction) are found at the UMP4, CISD, and RCISD(Q) levels. For the systems for which spin contamination is larger, best results are obtained with the CI‐based procedures (CISD and RCISD(Q)). The errors in calculated EAs for the molecules with differing electronic characteristics can vary quite widely. Caution must therefore be exercised before applying schemes which rely on a constancy of errors to estimate electron affinities. The UMP procedures appear particularly suspect in this regard if spin contamination is significant. The RCISD(Q) approach is recommended under such circumstances.
An algorithm for the location of transition states
Authors: Baker Jon 
Published: January 2005

AbstractAn algorithm for locating transition states designed for use in the ab initio program package GAUSSIAN 82 is presented. It is capable of locating transition states even if started in the wrong region of the energy surface, and, by incorporating the ideas on hessian mode following due to Cerjan and Miller, can locate transition states for alternative rearrangement/dissociation reactions from the same initial starting point. It can also be used to locate minima.
Theoretical Investigations on Fluorine‐Substituted Ethylene Dications C2HnF4‐n2+(n = 0–4)
Authors: Frenking Gernot , Koch Wolfram , Schwarz Helmut 
Published: January 2005

AbstractThe optimized geometries and energies of fluorine‐substituted ethylene dications C2HnF4‐n 2+ (n = 0–4) have been investigated by means of ab initio methods. At the MP3/6‐31G**//6‐31G* + zero‐point energy level of theory, the results predict that C2F42+ and C2HF32+ are planar, while C2H42+, C2H3F2+ and 1,1—C2H2F22+ prefer a perpendicular geometry. For 1,2—C2H2F22+ an energy difference of only 0.3 kcal/mol is found between the (trans) planar and perpendicular structure. The stabilizations attributed to hyperconjugation, fluorine lone‐pair donation, and (CF) double‐bond conjugation are discussed. A comparison is made for the CC and CF stretching frequencies determined at 6‐31G*//6‐31G* between the neutral and dicationic species. The theoretically determined ionization energies for the vertical process N+ → N2+ at the MP3/6‐31G*//3‐21G level are compared with experimental Qmin values.
A New Method for Molecular Mechanics
Authors: Saunders Martin , Jarret Ronald M. 
Published: January 2005

AbstractA promising new method for optimizing molecular structures is described. In place of the terms involving bond angles and torsion angles, used in the force fields of conventional molecular mechanics, two‐body central forces between atoms are used exclusively, resulting in a considerable computational advantage. The program STRFIT, using this method has been tested by comparing geometries obtained with those found using the popular molecular mechanics program MM2 (Allinger) for a variety of cyclic and acyclic molecules. For unstrained molecules, the difference in steric energy between geometries refined by STRFIT and MM2 is only a few tenths of a kilocalorie and up to about a kilocalorie for strained molecules. Geometry optimization with STRFIT, to a structure that is slightly higher in energy than the structure arrived at by MM2 starting from the same initial starting geometry, is three to eight times faster. A complete new package of programs for conveniently and rapidly doing molecular mechanics calculations is described. It includes a convenient algorithm for the input of approximate molecular structures, a rapid structure‐optimizing module using a pure Central force‐field approach, and a drawing program designed for use with a dot‐matrix printer or a laser printer.
Optimized Structures and Relative Stabilities of the Carboranes from Ab Initio Calculations
Authors: Ott Jane J. , Gimarc Benjamin M. 
Published: January 2005

AbstractAb initio calculations at the STO‐3G level were performed on almost all of the possible isomers for the entire series of closo‐carboranes, C2Bn‐2Hn, 5 ⩽ n ⩽ 12. Geometry optimizations using the gradient method were also included in all calculations. We report here the relative energies obtained for the various isomers as well as the optimized structures. These calculations confirm our previous predictions of relative stabilities obtained from topological charge stabilization. Comparisons of our structures with those from experimental data provide us with a measure of reliability for bond distances obtained using ab initio SCF MO calculations at the STO‐3G level. Results from the geometry optimization substantiated the experimentally known fluxional behavior of the 8 and 11 atom polyhedra.
Calculations of first‐ and second‐order nonlinear molecular hyperpolarizabilities by perturbation methods: I. An efficient method for evaluating time‐independent hyperpolarizabilities
Authors: Fripiat J. G. , Barbier C. , Bodart V. P. , André J. M. 
Published: January 2005

AbstractFrom a suitable reorganisation of the sum‐over‐states (SOS) equations of the usual time‐independent perturbation theory, recurrent expressions for static polarizability (α) and second‐ (beta;) and third‐(γ) order hyperpolarizabilities are obtained. These expressions are given in a well‐adapted way for computer implementation and lead to an efficient algorithm reducing the computing time by a factor of 50 with respect to a “brute‐force” translation of the standard SOS equations.
Molecular modeling of polymers: I. Correct and efficient enumeration of intrachain conformational energetics
Authors: Orchard B. J. , Tripathy S. K. , Pearlstein R. A. , Hopfinger A. J. 
Published: January 2005

AbstractPolymer conformational analyses can require being able to model the intramolecular energetics of a very long (infinite) chain employing calculations carried out on a relatively short chain sequence. A method to meet this need, based upon symmetry considerations and molecular mechanics energetics, has been developed. Given N equivalent degrees of freedom in a linear polymer chain, N unique molecular groups are determined within the chain. A molecular unit is defined as a group of atoms containing backbone rotational degrees of conformational freedom on each of its ends. The interaction of these N molecular groups, each with a finite number of nearest neighbors, properly describe the intramolecular energetics of a long (infinite) polymer chain. Thus, conformational energetics arising from arbitrarily distant neighbor interactions can be included in the estimation of statistical and thermodynamic properties of a linear polymeric system. This approach is called the polymer reduced interaction matrix method (PRIMM) and the results of applying it to isotactic polystyrene (I‐PS) are presented by way of example.
Coupled equations approach to multiphoton molecular processes
Authors: Bandrauk André D. , Gélinas Nadia 
Published: January 2005

AbstractUsing the dressed molecule picture of molecule radiation interactions (A.D. Bandrauk et al., J. Chem. Phys., 79, 3256; 80, 4926; 83, 2840) one can deduce multiphoton processes (absorption, scattering, nonlinear optical properties, etc.) amplitudes from coupled second‐order differential equations with electronic surfaces and transition moments as input data obtainable from quantum chemical calculations. The present approach enables one to include in the calculation bound and continuum states simultaneously by the use of appropriate boundary conditions for the numerical solutions of these coupled equations. In the case of weak radiative couplings, one recovers the usual Fermi‐Golden rule expressions for electronic absorption, raman scattering, etc. The method is thus quite general, bridging the weak field (traditional photochemistry) and the strong field (laser chemistry) regimes which are attainable with today's lasers. The numerical solutions of the coupled equations give us the stationary states of the molecule + radiation system, called dressed molecule. Preparation of the initial state can be mimicked in the coupled equations by an artificial channel method for processes involving a final‐state dissociation. Examples of such calculations will be presented in the diatomic Cl2 for which several ab initio electronic states and transition moments were available.
Simulation studies of branched polymer molecules
Authors: Lipson J. E. G. 
Published: January 2005

AbstractMonte Carlo simulation results are presented for lattice models of uniform stars (one branch point of functionality f = 3), combs (two branch points, ƒ = 3,3) and brushes (two branch points ƒ = 3,4 and ƒ = 3,5). We estimate the critical exponent γ(ƒ), the ratio g(ƒ) = 〈S(ƒ)〉/〈S(1)〉 (where 〈S(ƒ)〉 is the mean‐square radius of gyration of a structure having ƒ branches and N monomers), and the meansquare end‐to‐end branch lengths, as a function of the number and arrangement of branches. Comparisons with theoretical predictions and experimental data are made where possible, leading to a test of some predictions, and a suggestion concerning future experiments.
Computational aspects of master equation transformation in terms of moments
Authors: Gidiotis Grigorios , Forst Wendell 
Published: January 2005

AbstractThe master equation describing the temporal evolution of a gaseous system in contact with a heat bath can be transformed into a system of linear, constant‐coefficient, first‐order differential equations of moments of the population distribution. While it has the advantage that populations are obtained directly from observables (moments), this system of equations is not too well‐conditioned and unless precautions are taken, unsurmountable numerical problems appear. These are principally associated with manipulations (inversion and taking the exponential of a matrix) involving slightly modified Vandermonde matrices whose elements span a very wide range of orders of magnitude. This article discusses ways to avoid these pitfalls which consist principally of a suitable matrix normalization.
Open‐shell coupled‐cluster method: Electron affinities of Li and Na
Authors: Kaldor Uzi 
Published: January 2005

AbstractThe open‐shell coupled‐cluster method and the diagrams needed for its implementation are described. The method is applied to the electron affinities of Li and Na, which are calculated in two ways: as the ionization potential of the anions or as the energy of adding the second electron to the cations. The two schemes give essentially the same results, in very good agreement (<0.02 eV) with experiment. Three‐body effects are negligible.
Molecular dynamics simulation of the 1:1 enzyme‐ligand complex between porcine pancreatic elastase and acetyl‐alanine‐proline‐alanine
Authors: Fujita T. , Meyer E. F. 
Published: January 2005

AbstractA 31.5 picosecond (ps) MD calculation has been completed for the 1:1 enzyme‐ligand complex between porcine pancreatic elastase (PPE) and acetyl‐alanine‐proline‐alanine (APA). The 1:2 complex studied crystallographically at product saturation conditions precludes the study of a 1:1 complex (PPE and APA1); this objective has been achieved by computational methods described here. The acetyl group of the ligand was found to occupy two neighboring sites, one within the primary specificity site and the other out into solution. The primary change of the ligand structure is ψ1 torsion angle being 171.5°. Supported by an interactive graphic display, the dynamical fluctuations of a smaller ligand compared with the width of the active site as PPE were observed by the MD simulation, although the complex has not been detected by any spectroscopic method.
Fast matrix multiplication
Authors: Bunge Carlos F. , Cisneros Gerardo 
Published: January 2005

AbstractSeveral implementations of matrix multiplication (MMUL) in Fortran and VAX assembly language are discussed. On a VAX‐11/780 computer, the most efficient MMUL is achieved through vector‐scalar‐multiply‐and‐add (VSMA) operations, rather than by means of dot products. We also discuss optimal MMUL algorithms for use in virtual memory machines when the data overflow the working set.
Gaussian basis sets for the fifth row elements, Mo‐Cd, and the sixth row elements W‐RN
Authors: Gropen Odd 
Published: January 2005

AbstractGaussian basis sets, consisting of 17 s‐type, 12 p‐type, and 8 d‐type functions, for the fifth row elements, MoCd, and 19 s‐type, 14 p‐type (16 p‐type), 10 d‐type and 5 f‐type functions for the sixth row elements, WRn, are presented. The basis sets are of double zeta quality, and are optimized to .002 a.u. in the energy. The energies are compared with D.Z. STO basis sets.
Benzene‐benzene (phenyl‐phenyl) interactions in MM2/MMP2 molecular mechanics calculations
Authors: Pettersson Ingrid , Liljefors Tommy 
Published: January 2005

AbstractThe MM2/MMP2 force‐field gives an incorrect description of benzene‐benzene interactions. This deficiency may be overcome by the addition of electrostatic interactions. Using point charges of −0.15 on carbon and +0.15 on hydrogen, a good agreement between benzene dimer potentials calculated by MMP2 and ab initio SCF CI potentials is obtained. The influence of the addition of point charges on calculated structures and conformational energies has been studied. Examples are given in which the addition of electrostatic interactions between phenyl groups substantially improves calculated conformational energies.