bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conformational analysis of some mannose‐containing and milk oligosaccharides: Correlation of their shape with inhibitory properties in antigen/antibody interactions
Authors: Biswas Margaret , Rao V. S. R. 
Published: December 2004

AbstractPossible conformations of two mannotetraoses and several milk oligosaccharides have been studied by an energy minimization procedure using semi‐empirical potential functions. Changes in the terminal residue at the reducing end (cyclic to acyclic form) of these molecules do not affect the favored conformations of the remaining oligosaccharide moiety. However, differences in the overall shape of the native and reduced forms of the mannotetraose, mannose α(1–3) mannose α(1–2) mannose α(1–2) mannose are much less marked than between the native and reduced forms of lacto‐N‐tetraose. These differences are related to the effectiveness of the native forms as inhibitors of antibodies produced using synthetic antigens. Changes in the linkage of the residues at the nonreducing end of these molecules affect significantly the overall shape of these molecules. These differences also are related to their effectiveness as inhibitors. In the fucose‐containing milk oligosaccharides the additional fucose residues only restrict the orientation of the backbone tetrasaccharide and do not push it into a totally new conformation. The fucose residues come on a surface of the molecule which is away from the region which may be important for binding. The present studies show that it is the overall shape of the molecule which is important in determining its inhibitory properties and give information as to how best to use the immune method for identification of unknown oligosaccharide sequences by specially prepared antibodies.
Estimation of binding sites from the adsorption profile of complexed DNA
Authors: Ghosh Subhendu , Mookerjee Anjali 
Published: December 2004

AbstractThe adsorption profiles of free and Daunomycin bound DNA at an alumina–H2O interface have been studied. Proper experimental conditions were maintained to considerably reduce intercalation and to make electrostatic binding predominant in the DNA–Daunomycin complex. For both free and complexed DNA, Langmuir plots gave straight lines. Adsorption of drug bound DNA was less than that of free DNA. This has been explained from the viewpoint of electrostatic interactions between adsorbate and adsorbent. A Langmuir‐type model for adsorption of polymers combined with Scatchard equation have been used to estimate the average value of percent of phosphates in DNA stacked with Daunomycin.
Impact of lone pairs on the conformation and configuration statistics of poly(lactic acid) chains
Authors: Prasad C. V. , Sundaram K. 
Published: December 2004

AbstractNonbonded interaction energies have been calculated for various conformations of the diester giving explicit consideration to the lone‐pair electrons. As suspected from an earlier calculation on the dipeptide, such inclusion of the lone‐pair effect leads to significant differences in the conformational potential energy map. The diester is shown to be more constrained than the dipeptide. The impact of this constrained geometry and the possible occurrence of cis residues on configuration statistics of poly(lactic acid) chains have been studied. Contrary to expectation the inclusion of cis isomers does not explain the paradoxical high negative temperature coefficient of ln C∞.
Intermolecular interactions in porphin dimers: A quantum mechanical study
Authors: Sudhindra B. S. , Fuhrhop J.‐H. 
Published: December 2004

AbstractBoth short‐range and long‐range intermolecular interaction energies between two prophin molecules, both in their ground state, separated by a range of interplanar distances from 3 to 4.5 Å, are estimated using the standard perturbation theory. The results indicate that a 60° rotated sandwich structure is the most stable conformation for the dimer. Certain translated as well as the perfect sandwich forms are other favoured structures. The stability of the dimer is mainly due to the van der Waals interactions with no significant contribution from the charge‐transfer interactions. Biochemical implications of these findings are discussed.
Explicitly correlated configuration interaction studies using spherical Gaussians. II. Exploratory studies on LiH
Authors: Karunakaran K. M. , Christoffersen Ralph E. 
Published: December 2004

AbstractAb initio self‐consistent‐field and configuration interaction studies have been carried out on the ground state of the LiH molecule at its equilibrium distance. Floating spherical Gaussian basis orbitals (FSGO) were employed, along with spherical Gaussian correlation factors, using the procedure described in the preceding paper. A near‐Hartree–Fock function was found using only 13 FSGO. Exploratory configuration interaction studies recovered approximately 73% of the inner shell correlation energy and approximately 56% of the total correlation energy with five configurations plus the Hartree–Fock configuration. These studies indicate that, by using spherical Gaussian correlation factors, direct introduction of interelectronic coordinates into trial wave functions can be accomplished for molecular systems. It was also shown that correlating configurations need not utilize the full Hartree–Fock basis, but may use substantially smaller bases and still recover correlation energy effectively. Finally, the results indicate that, in spite of their improper cusp behavior, FSGOS and spherical Gaussian correlation factors can be used for construction of high accuracy wave functions.
Quantum fluid dynamics of many‐electron systems in three‐dimensional space
Authors: Ghosh S. K. , Deb B. M. 
Published: December 2004

AbstractIn presence of external electric and magnetic fields, the Schrödinger equation for many‐electron systems is transformed into a continuity equation and an Euler‐type equation of motion in configuration space. Then, using the natural‐orbital Hamiltonian, as defined by Adams, the two fluid‐dynamical equations are derived in the three‐dimensional space. This generates a “classical” view of such quantum systems, corresponding to an MCSCF wave function: The many‐electron Schrödinger fluid consists of individual fluid components, each corresponding to a natural orbital and having its own charge density and current density. The local observables, viz., the net charge density and net current density, are obtained by merely summing over the natural orbitals, with the occupation numbers as weight factors; but, the net velocity field cannot be so obtained. Further, although each fluid component moves irrotationally in the absence of a magnetic field, the net velocity field is not irrotaional. The irrotational character of each velocity component is destroyed by rotation of the nuclear framework of the system while electron spin introduces an additional term, the spin magnetization moment, into each component current density. The physical significance of the fluid‐dynamical equations as well as their advantages and disadvantages are discussed.
Electronic structure and bonding of the pentasulfur hexanitride (S5N6) molecule
Authors: Trsic Milan , Wagstaff Kim , Laidlaw William G. 
Published: December 2004

AbstractAn ab initio version of the Hartree–Fock–Slater method is applied to obtain molecular orbitals and eigenvalues for S5N6. The electronic structure, bonding, stability, and electronic spectrum are discussed.
Diamagnetic shielding constants of first‐row atoms: Studies with a piecewise exponentially decaying electron density function
Authors: Kaur Livjeet 
Published: December 2004

AbstractThe piecewise exponentially decaying electron density model of Wang and Parr is used to calculate the diagmagnetic shielding constants of first‐row atoms. Numerical results are presented for all first‐row atoms and comparisons are made with the results obtained from the one‐zone (i.e., single exponential) model. Results obtained from the two‐zone (i.e., piecewise exponential) model are in better agreement with the Hartree–Fock results.
Spontaneous symmetry breaking in large scale nervous activity
Authors: Cowan Jack D. 
Published: December 2004

AbstractA theory is outlined of the nature and origin of drug‐induced visual hallucination patterns. It is shown that such patterns correspond to blobs or stripes of visual neo‐cortical activity. A neuronal circuit is described that generates such patterns whenever its homogeneous resting state becomes unstable. Such a process is shown to be an example of spontaneous symmetry‐breaking, similar to that occurring in electro‐weak interactions, and in fluid convection. It is suggested that the neuronal instability is produced by the action of hallucinogens on monoamine secreting brain‐stem neurons.
Ab initio calculation of magnetic susceptibilities and screening constants using gauge invariant Gaussian orbitals
Authors: Boucekkine‐Yaker G. , Boucekkine A. , Zaucer M. , Berthier G. 
Published: December 2004

AbstractThe magnetic susceptibility and screening constant tensors are calculated using an ab initio finite perturbation SCF method, with gauge invariant Gaussian orbitals. The isoelectronic BH BeH−, and CH+ molecules have been studied. The calculated values for BH are relatively different from those obtained by other methods. The CH+ molecule seems to exhibit a stronger temperature independent paramagnetism than BH, while the BeH− molecule would be diamagnetic. The screening constants of the heavy atom of these molecules present a similar variation.
Force in SCF Theories. First and second derivatives of the potential energy hypersurface of chemical reaction systems
Authors: Nakatsuji H. , Hada M. , Kanda K. , Yonezawa T. 
Published: December 2004

AbstractAccurate Hellmann–Feynman force method for the first and second derivatives of energy has been applied to the studies of the chemical reaction systems. We have studied (1) the electronic origins of the structure‐reactivity correlations in the reactions CH3 + H → CH4 and CH3 + CH3 → C2H6 and (2) the geometries and force constants in the reaction intermediate and the transition state of the reactions F− + HF → [FHF]− → FH + F− and H− + CH4 → CH4 + H−, respectively. An intuitive simplicity of the underlying concepts of the first and second derivatives of the present approach is shown in the analysis.
Finite‐field calculations of molecular polarizabilities using field‐induced polarization functions. II. Second‐ and third‐order perturbation correlation corrections to the coupled Hartree–Fock polarizability of HF
Authors: Mukherjee Prasanta K. , Minato Tsutomu , Chong Delano P. 
Published: December 2004

AbstractCorrelation corrections to coupled Hartree–Fock (CHF) static dipole polarizabilities and dipole moment of the HF molecule are calculated using third‐order Rayleigh–Schrödinger perturbation theory with Møller–Plesset partitioning (RSMP) in a finite‐field procedure. Computations are also made for the dipole moment and polarizability derivatives at the equilibrium internuclear separation. Three different basis sets using contracted Gaussian orbitals augmented by field‐induced diffuse polarization functions have been employed to investigate the nature of variation of the properties under study, and the importance of field‐induced diffuse polarization functions is discussed. [2/1] Padé approximants are used to accelerate the convergence of the properties. The correlated dipole moment and polarizability values are in excellent agreement with the existing theoretical and experimental values. The dipole moment derivative is in perfect agreement with the existing correlated value. However, the polarizability derivatives at SCF and correlated levels differ appreciably from the existing SCF values and represent as improvement.
Symmetry broken self‐consistent field approximation for coupled oscillators
Authors: Lefebvre R. 
Published: December 2004

AbstractA self‐consistent field approximation allowing for a change of coordinates is applied to a model of two coupled oscillators considered by Davis and Heller [J. Chem. Phys. 75, 246 (1981)]. The model accounts well for the unsymmetrical nonstationary states involved in the quantum dynamical tunneling phenomenon.
Translation factors in atomic collisions
Authors: Piacentini R. D. 
Published: December 2004

AbstractDifferent methods proposed for taking into account the momentum transfer in electron capture collisions are reviewed. Exact one‐electron two‐Coulomb‐center molecular wave functions are considered for studying fully stripped ions–hydrogen atom collisions. The semiclassical impact parameter treatment is used, since it is well adapted to the keV/amu energy range investigated.
Heats of atomization of some conjugated molecules containing nitrogen or oxygen by a novel semiempirical method
Authors: Živković Tomislav P. 
Published: December 2004

AbstractHeats of atomization for a range of conjugated molecules containing nitrogen or oxygen are calculated by a semiempirical method that combines some features of both the MO and VB theories. The π ground state of each conjugated molecule is represented as a linear combination of Kekulé structures. Unlike in the VB theory, each Kekulé structure is a determinant containing bond orbitals. Here experimental heats of atomization are reproduced approximately as well as by the more sophisticated SCF–MO approach. The use of this method is, however, much simpler since it amounts to a single diagonalization of a matrix of the order equal to the number of Kekulé structures only.
Unusually large electrostatic field effect of the buried aspartate in serine proteinases: Source of catalytic power
Authors: Náray‐Szabó Gábor 
Published: December 2004

AbstractCalculating the electrostatic potential around the Ser–His–Asp catalytic triad in serine proteinases the very important substituent effect of the buried aspartate is revealed. It is found that the strong Coulomb field of this distant but charged side chain considerably enhances the nucleophilicity of the active serine hydroxyl group. The interpretation of the vital importance of aspartate may replace the “charge–relay” hypothesis which seems to be disproved in the light of recent experiments.
Electronic structure of small copper clusters
Authors: Miyoshi Eisaku , Tatewaki Hiroshi , Nakamura Takashi 
Published: December 2004

AbstractAn all‐electron ab initio LCAO‐MO SCF calculation has been carried out for the electronic structure of small copper clusters (Cun, n = 2–6). The basis set superposition error occurring in the calculation, the equilibrium configuration of Cu3, the bond energy in the clusters, and the localized d‐hole in excited and ionized states of Cu2 are closely examined.
Energy‐band structure and charge distribution for BaC6
Authors: Holzwarth N. A. W. , Divincenzo D. P. , Tatar R. C. , Rabii S. 
Published: December 2004

AbstractAn ab initio self‐consistent calculation has been carried out for the electronic properties of BaC6. Energy bands and charge densities are presented for BaC6 and compared with those of LiC6. The results show that the band originating from Ba states has a mixture of s and d character and the d component hybridizes appreciably with the π bands of graphite. The Fermi level intersects this band as well as the graphite π bands, giving rise to a complicated Fermi surface with several types of carriers. Depending on the type of volumetric partitioning, the charge transfer from Ba to graphite layers is determined to be between 0.7 and 1.0 electron per Ba atom. The calculated results are consistent with available transport and optical measurements.
Perturbation theoretical investigation of electron correlation effects in infinite metallic and semiconducting polymers
Authors: Suhai Sándor 
Published: December 2004

AbstractMøller–Plesset‐type perturbation theory is applied to calculate electron correlation effects in infinite, periodic, metallic, and semiconducting polymers. Different possible choices of the zeroth‐order Hamiltonian (symmetry adapted Hartree–Fock, spin‐, and charge‐density waves), the influence of the size of the atomic basis sets, lattice and conduction band sums are investigated. In the case of semiconducting systems a very efficient version of the method using optimally localized Wannier functions has been worked out. Applications include model calculations for infinite atomic hydrogen chains, the investigation of the role of correlation effects in the bond alternation and metal‐insulator phase transition in polyene, different one‐and many‐particle effects contributing to the single‐particle gap in polyene, and the calculation of correlated quasiparticle band structures using the electronic polaron model.
Electrostatics and gating of excitable membranes
Authors: Lundström Ingemar , Nylander Claes 
Published: December 2004

AbstractTwo electrostatic models for ion permeability of membranes are considered. In the first model ions pass hydrated through the membrane and in the second model ions pass unhydrated through a channel lined with polar groups. In both cases it is found that it is not necessary to assume a high macroscopic dielectric constant of the membrane or channel to provide a low enough potential energy of the ion in the membrane. Gating of excitable membranes is considered a special case of electrostatic interaction in membranes. A simple physical model which fits with Hodgkin and Huxley's empirical relation is derived. Finally, we have speculated upon other membrane bound biological phenomena where electrostatic effects may be important.
INDO Studies on the electronic structure of lanthanoid compounds
Authors: Le‐min Li , Jing‐Qing Ren , Guang‐Xian Xu , Xiu‐Zhen Wang 
Published: December 2004

AbstractExpressions needed in INDO calculations for compounds containing 4f elements were derived and an INDO program suitable for lanthanoid compounds was written and tested. Electronic structure of LnF3 and paramagnetic shift of NMR spectra of LnF were studied.
Electronic structure of model chlorophyll systems
Authors: Edwards W. Daniel , Zerner Michael C. 
Published: December 2004

AbstractAn examination of the ground and excited states of magnesium porphine and pheoporphine and their positive and negative ions using the intermediate neglect of differential overlap/spectroscopic method is reported. It is found that rather large changes in the Mg out‐of‐plane coordinate can be attained at very little cost in energy. These geometric changes alone can be used to explain the large range of spectroscopic shifts observed in the visible band of chlorophyll that are site dependent. These calculations also show a porphyrin to Mg charge transfer excitation at about 20,000 cm−1, which, if populated and allowed to relax, becomes the lowest excited singlet. This suggests that the initial photochemical event in photosynthesis may be excitation to the visible Q band followed by internal conversion to the charge transfer state accompanied by movement of the Mg atom out of the plane of the ring. This movement could result in intermolecular charge transfer, and relaxation of the Mg atom back to the plane of the ring. The nature of the positive and negative ions of these model chlorophylls is discussed in light of their role as the electron donor and their potential role as initial electron acceptor in photosynthesis.
Irreversibility, time, and fluctuations in quantum statistical theory of dissipative molecular systems. II. Application to fluorescence spectroscopy
Authors: Chatzidimitriou‐Dreismann C. A. 
Published: December 2004

AbstractSome basic concepts of the Prigogine quantum statistical theory of irreversible processes are discussed in connection with a previous paper by Chatzidimitriou‐Dreismann and Lippert. The removal of the “dual role” that the Hamiltonian plays within conventional quantum theory corresponds to the introduction of a star‐unitary operator 𝒯 called “intrinsic time.” The formalism of the previous paper is extended to systems that interact with external fields. A formal specification of 𝒯, furthermore, follows from the Lt invariance of the basic equations of motion and its connection with the intrinsic time. As an application to fluorescence spectroscopy, a photon counting experiment is presented. It allows us to detect certain predicted “dynamical” fluctuations in emission spectra. Some current experimental results are reported concerning the resolution of the broad fluorescence band of fluoranthene (dissolved in ethanol) through detection of the underlying finer vibrational structure.
Brisk Walking Speed in Older Adults Who Walk for Exercise
Authors: Parise Carol , Sternfeld Barbara , Samuels Steven , Tager Ira B. 
Published: December 2004

Objectives: To determine the self‐selected exercise intensity of older adults who report that they walk briskly for exercise. An additional aim of the study was to assess the contribution of self‐reported physical activity to self‐selected exercise intensity.Design: Observational.Setting: Community walking path.Participants: Subjects consisted of 212 participants in the Study of Physical Performance and Age‐Related Changes in Sonomans who stated in a detailed home interview that they walked briskly for exercise.Measurements: Observed brisk walking speed was measured as the time it took participants to walk half a mile at “normal brisk walking speed.” Self‐reported physical activity was categorized as metabolic equivalent of the task (MET) in minutes of exercise reported in the previous 7 days. Physiological measures and body composition were obtained through laboratory evaluation.Results: Men walked at an average speed±standard deviation of 5.72±0.69 km/h and women walked at an average speed of 5.54±0.64 km/ h. Self‐reported physical activity was not associated with brisk walking speed when adjusted for age and ratio of lean to fat mass.Conclusion: This study found that older adults who report that they walk briskly for exercise do so at a pace considered moderate or greater in absolute intensity as indicated by their walking speed (4.83 km/h). Ninety‐eight percent of men (93/95) and 97% of women (113/117) hadanobservedwalking speed equivalent to 3 or more METs based on their calculated walking speed.
Predator hunting behaviour and prey vulnerability
Authors: Quinn J. L. , Cresswell Will 
Published: December 2004

SummaryGame theoretic models of how animals manage predation risk have begun to describe predator responses to prey behaviour relatively recently. This is partly because our understanding of how terrestrial predators select vertebrate prey is often limited to numerical and functional responses to measures of prey abundance. Prey vulnerability, however, may improve our understanding of predation because predators could maximize foraging success by selecting prey on this basis.We tested the hypothesis that sparrowhawks (Accipiter nisusL.), a typical generalist predator, hunt redshanks (Tringa totanusL.), a favoured prey species on coastal shores, primarily on the basis of their vulnerability rather than their abundance.Five direct measures or indicators of redshank behaviour predicted sparrowhawk attack success in a multipredictor statistical model and therefore serve as measures of redshank vulnerability.These and other vulnerability measures influenced whether sparrowhawks decided to hunt redshanks on saltmarsh habitat. A model that included most of these measures predicted correctly whether sparrowhawks hunted redshanks (attack decision) 90% of the time and accounted for up to 75% of variation. Prey abundance accounted for no additional variation.Thus the hunting behaviour of some predators can only be predicted well by several highly dynamic and interacting factors related to prey vulnerability. These results mean that, theoretically at least, the management of prey populations may sometimes be achieved best by manipulating prey vulnerability, rather than by culling their predators.