bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solvolyse von 3,17‐Dioxo‐19‐mesyloxy‐Δ4‐androsten. Über Steroide, 216. Mitteilung
Authors: Wieland P. , Anner G. 
Published: December 2004

Abstract3,17‐Dioxo‐19‐mesyloxy‐Δ4‐androstene was reacted with lithiumchloride in isopropanol. In addition to the mainly formed 3,17‐dioxo‐19‐chloro‐Δ4‐androstene two side products were isolated and identified as 6ß‐methylestrone and 3,17‐dioxo‐B‐homo‐Δ4,6‐19‐norandrostadiene.
Sur les carbonates basiques de fer (III): III. Préparation, radiocristallographie et spectres IR. du (NH4)4Fe2(OH)4(CO3)3·3H2O
Authors: Dvořák V. , Feitknecht W. 
Published: December 2004

AbstractThe obtention of the crystalline basic carbonate of iron (III) and ammonium, (NH4)4Fe2(OH)4(CO3)3 · 3 H2O, is described, and its formula is established by chemical analysis and infrared spectroscopy. The compound is probably monoclinic, but it was not possible to index with certainty all X‐ray reflections. The compound is similar to (NH4)2Fe2(OH)4(CO3)2 · H2O and its infrared spectrum leads to the assumption that in both the CO group is linked in the same fashion.
Contribution à l'étude du dosage de traces d'acide borique par luminescence
Authors: Marcantonatos M. , Gamba G. , Monnier D. 
Published: December 2004

AbstractA highly sensitive luminescent reaction is proposed for the determination of submicrotraces of boric acid by complexation with dibenzoylmethane in ether‐concentrated sulfuric acid. The optimal conditions of complex formation between boric acid and dibenzoylmethane are investigated, luminescence spectral caracteristics of the solutions of the complex are described, and the phosphorescence mean lifetime of the dibenzoylmethane‐boric acid system is evaluated. Analytical curves, established by fluorimetry and phosphorimetry, are satisfactory. 0.0005 μg B/ml is the minimum detectable concentration.
Cuprous complexes and dioxygen, VII. Competition between one‐ and two‐electron reduction of O2 in the autoxidation of Cu(1‐methyl‐2‐hydroxymethyl‐imidazole)2+
Authors: Zuberbühler Andreas D. 
Published: December 2004

AbstractThe complexation of 1‐methyl‐2‐hydroxymethyl‐imidazole (L) with Cu(I) and Cu(II) has been studied in aqueous acetonitrile (AN). Cu(I) forms three complexes, Cu(AN)L+, CuL2+, and Cu(AN)H−1L, with stability constants logK(Cu(AN)+ + L ⇌ Cu(AN)L+) = 4.60 ± 0.02, logβ2 = 11.31 ± 0.04, and logK(Cu(AN)H−1L+H+ ⇌ Cu(AN)L+) = 10.43 ± 0.08 in 0.15M AN. The main species for Cu(II) are CuL2+, CuH−1L+, CuH−1L2+, and CuH−2L2.The autoxidation of CuL2+ was followed with an oxygen sensor and spectrophotometrically. Competition between the formation of superoxide in a one‐electron reduction of O2 and a path leading to H2O2 via binuclear (CuL2)2O was inferred from the rate law

with ka = (2.31 ± 0.12) · 104M−2S−1, kb = (1.0 ± 0.2) · 103M−1, kc = (2.85 ± 0.07) · 102M−2S−1, kd = 3.89 ± 0.14M−1S−1, ke = 0.112 ± 0.004, kf = (2.06 ± 0.24) · 10−10M S−1, kg = (1.35 ± 0.07) · 10−7 S−1, and kh = (6.8 ± 1.4) · 10−7M−1 S−1.
Structural Studies of 1,8‐Disubstituted Naphthalenes as Probes for nucleophile‐electrophile interactions
Authors: Schweizer W. Bernd , Procter Garry , Kaftory Menahem , Dunitz Jack D. 
Published: December 2004

AbstractResults of crystal structure analyses of seven 1, 8‐disubstituted naphthalenes (2a, 8‐(N,N‐dimethylamino)‐1‐naphthyl methyl ketone; 2b, 8‐(N, N‐dimethylamino)naphthalene‐1‐carboxylic acid; 2c, methyl 8‐(N, N‐dimethylamino)naphthalene‐1‐carboxylate; 2d, 8‐methoxy‐1‐naphthyl methyl ketone; 2e, 8‐methoxynaphthalene‐1‐carboxylic acid; 2f, N, N‐dimethyl‐8‐methoxynaphthalene 1‐carboxamide; 2g, N, N‐dimethyl‐8‐hydroxynaphthalene‐1‐carboxamide) with a nucleophilic centre (N(CH3)2, OCH3, OH) at one of the peri positions and an electrophilic centre (carbonyl C) at the other are described. All seven molecules show a characteristic distortion pattern: the exocyclic bond to the electrophilic centre is splayed outward, and the one to the nucleophilic centre is splayed inward; the carbonyl C is displaced from the plane of its three bonded atoms towards the nucleophile. This distortion pattern differs from that found in other 1,8‐disubstituted naphthalenes and is interpreted as an expression of incipient nucleophilic addition to a carbonyl group. The crystal structure of 2b contains an ordered arrangement of equal numbers of amino acid and zwitterionic molecules.
Persistent inward currents in motoneuron dendrites: Implications for motor output
Authors: Heckman C. J. , Gorassini Monica A. , Bennett David J. 
Published: December 2004

AbstractThe dendrites of motoneurons are not, as once thought, passive conduits for synaptic inputs. Instead they have voltage‐dependent channels that provide the capacity to generate a very strong persistent inward current (PIC). The amplitude of the PIC is proportional to the level of neuromodulatory input from the brainstem, which is mediated primarily by the monoamines serotonin and norepinephrine. During normal motor behavior, monoaminergic drive is likely to be moderately strong and the dendritic PIC generates many of the characteristic features of motor unit firing patterns. Most of the PIC activates at or below recruitment threshold and thus motor unit firing patterns exhibit a linear increase just above recruitment. The dendritic PIC allows motor unit derecruitment to occur at a lower input level than recruitment, thus providing sustained tonic firing with little or no synaptic input, especially in low‐threshold units. However the dendritic PIC can be readily deactivated by synaptic inhibition. The overall amplification due to the dendritic PIC and other effects of monoamines on motoneurons greatly increases the input–output gain of the motor pool. Thus the brainstem neuromodulatory input provides a mechanism by which the excitability of motoneurons can be varied for different motor behaviors. This control system is lost in spinal cord injury but PICs nonetheless recover near‐normal amplitudes in the months following the initial injury. The relationship of these findings to the cause of the spasticity syndrome developing after spinal cord injury is discussed. Muscle Nerve, 2005
Symmetry properties of natural orbitals and geminals I. Construction of spin‐ and symmetry‐adapted functions
Authors: McWeeny R. , Kutzelnigg W. 
Published: December 2004

AbstractNatural spin‐orbitals (NSO), natural spin‐geminals (NSG) and their spinless counterparts are not always adapted to the symmetry group of the Hamiltonian. Alternative orbitals and geminals that are always symmetry adapted and as close as possible to the NSO and NSG are defined and their properties are discussed. The expansion of the one‐ and two‐ particle density matrices ρ1 and ρ2 in irreducible tensor components is considered and the relations between the tensor components of ρ2 and the spin coupling functions introduced previously are established. The totally symmetric components ρ and ρ of ρ1 and ρ2 are of particular interest, because their eigenfunctions are the required symmetry‐adapted NSO'S and NSG'S, respectively.
Semiempirical molecular‐orbital calculations of the basicities of pyrazole, imidazole, and methyl‐substituted pyrazoles and imidazoles: Inductive model of electron release
Authors: Vaughan John D. , Fullerton David C. , Chang Chin‐An 
Published: December 2004

AbstractThis work is concerned with the interpretation of the relative base strengths of pyrazole, imidazole, and some of their methyl derivatives. The LACO‐SCF method of Pariser, Parr, and Pople was used to calculate the π energies of protonation of the bases. We found that the usual treatments of the core attraction integrals failed to order the basicities of pyrazole and imidazole, but this failing could be corrected by using a scaling factor with the core penetration integrals. The electronic effect of the methyl substituents was assumed to be wholly inductive, and the inductive modification of the core integrals αp was found to be highly sensitive to the scaling parameter for the core penetration integrals. A good correlation was obtained between the pKa values and the π protonation energies of seven diazoles, but this correlation could not be extended quantitatively to triazoles.
Etudes en methode de Hartree–Fock avec projection. I. Fonctions propres de S2. Evaluation de l'energie
Authors: Lefebvre R. , Prat R. F. 
Published: December 2004

AbstractThe rotational projection operator previously introduced [12] serves here to build up an explicit formula for the non‐relativistic energy associated with a spin‐projected determinant. Corresponding orbitals are used throughout, and interchange of configuration space and Euler angles integrations provides rapidly an energy expression previously obtained either by use of Löwdin's projector (via first‐ and second‐order density matrices (8)) or by mixed space and spin permutation operator (GF method (9)).
Lattice dynamics with second‐neighbor interactions. III. Green's matrix
Authors: McIntosh Harold V. , Hehenberger Michael , Reyes‐Sanchez Rodolfo 
Published: December 2004

AbstractThe theory of pth‐order singular differential equations is adaptable to the study of the system of recurrence relations occurring in the problem of a one‐dimensional chain with pth‐neighbor interactions. By using Green's formula, a mapping is defined between the space Vn of eigenvectors to the dynamical matrix and the symplectic space V2p of boundary conditions for the recurrence equations. The properties of the resolvent are obtained from an analysis of the solutions of a system of inhomogeneous equations and Green's matrix is constructed for the case of standard Sturm–Liouvilletype boundary conditions. The Weyl surface is discussed and its properties used for the construction of square summable sequences which in turn can be employed in expansion formulas. The generalization of Weyl's m‐function in the second‐order case (p = 1) becomes for p ≥ 2 a p × p matrix M(λ), where λ is a complex parameter. The imaginary part Im {M(λ)} is related to the spectral properties and serves as basis for the discussion of different concepts of spectral density for the normal modes of lattice dynamical problems. An important practical result is the equation M = −ΨΦa valid in the limit point case, generalizing the corresponding second‐order formula.
MO‐LCAO‐Calculations on polymethines. V. PPP‐type calculations and configuration analyses of simple prototype dyes in terms of molecular subsystems
Authors: Fabian J. , Tröger‐Naake G. 
Published: December 2004

AbstractIn order to elucidate certain controversies in interpreting the π‐electronic structure of some simple quinone and indigo dyes the Pariser–Parr–Pople SCβ,γ‐wave‐functions have been subjected to configuration analyses. Whereas 2,5‐diamino‐quinone (1) can be excellently represented by coupling of two trimethine‐merocyanine chains, the analogous consideration is less appropriate with bispyrrolindigo (2). In this case the results of the configuration analyses indicate clearly the limited applicability of the Longuet/Higgins–Murrell–method.
The interference in the decay of two ½ spins in a molecular medium, studied by the Nakajima–Zwanzig technique
Authors: Hardisson A. , Lefebvre R. , Mauricio F. , Velasco S. 
Published: December 2004

AbstractThis paper studies the decay, due to the spin‐lattice coupling, of two ½ spins with slightly different Zeeman energies when the lattice is thermally excited. The analysis is based on obtaining, by means of the Nakajima–Zwanzig projection operator technique, an equation for the evolution of the reduced density operator of the spin system which manifests the influence of one spin on the relaxation process of the other. The zero‐order solutions obtained for the evolution of the expectation values of the spin dynamics operators are essentially equivalent to the Bloch equations; higher order solutions are also obtained.
Clebsch–Gordan coefficients for chains of groups of interest in quantum chemistry. II. The chain SU(2) ⊃ D′∞ ⊃ D′4 ⊃ D′2
Authors: Kibler M. R. , Grenet G. 
Published: December 2004

AbstractThe formalism described in the first paper of this series is applied to the chain SU(2) ⊃ D′∞ ⊃ D′4 ⊃ D′2, the covering of SO(3) ⊃ D∞ ⊃ D4 ⊃ D2. The state vectors (|αJaΓγ) adapted to each link of the chain under consideration and the corresponding coupling coefficients \documentclass{article}\pagestyle{empty}\begin{document}$ f\left( {\begin{array}{*{20}c} {J_1 } & {J_2 } & J \\ {a_1 \Gamma _1 \gamma _1 } & {a_2 \Gamma _2 \gamma _2 } & {a\Gamma \gamma } \\ \end{array}} \right) $\end{document} are given in analytical form. The material reported here is very convenient for a quantum‐mechanical description of molecular and nuclear systems with linear, tetragonal, or orthorhombic symmetry. In this respect, we present an outline for its applications to the electronic and vibrational–rotational spectroscopy of molecular aggregates and to the rotational spectroscopy of molecules or nuclei. In addition, we briefly show how the material may simplify the second–order non‐Lie subgroup type approach to the representation theory of SU(2).
The symmetric groups and the Waller–Hartree spin‐free method
Authors: Lim T. K. 
Published: December 2004

AbstractThe relations between the Waller–Hartree spin‐free method and the symmetric group theory are given. It is shown that the Gallup method is a special case of ours with S = M. Furthermore, all the irreducible representation matrices and other matrices needed are written explicitly in terms of Sanibel coefficients which makes the method more useful. However, it was shown that the cases with S ≠ M for the spin‐free pure spin states might be beyond the power of the symmetric group theory.
The floating spherical gaussian orbital model and shape of B2H5 ion
Authors: Rastogi R. C. , Ray N. K. 
Published: December 2004

AbstractThe FSGO model has been used to make ab initio calculations of the geometry of B2H ion. The results indicate that the acetylenic structure has the lowest energy (−43.881 a.u.) and the planar structure has the highest energy (−43.838 a.u.). The energy of the non‐symmetric structure is only slightly higher (−43.879 a.u.) than that of the acetylenic one. Results of CNDO/2 calculations reported here also predict the acetylenic structure to be the most stable one.
The energetic effects of p, d, and f Gaussian polarization functions on closed‐shell AHn oxygen and sulfur hydrides
Authors: Kari Roy , Csizmadia Imre G. 
Published: December 2004

AbstractA series of LCAO‐MO‐SCF calculations, using various basis sets of Gaussian‐type functions, has been made in order to study the effects of p, d, and f polarization functions for a 10‐electron isoelectronic series of oxygen hydrides and for an 18‐electron isoelectronic series of sulfur hydrides. Conclusions from these results suggest that meaningful proton affinities cannot be calculated without the inclusion of a d function on the heavy atom and a p function on the hydrogen atoms.
Conformational energy map for a pair of peptide units using the bond polarisability method
Authors: Sundaram Srinivasan K. A. R. 
Published: December 2004

AbstractA method recently developed for the calculation of intramolecular nonbonded interactions based on experimental bond polarisabilities and atomic charges and transition π‐charges obtained from MO calculations has been applied to the alanyl dipeptide. The potential energy contours in the ϕ, ψ plane obtained by this method compare favourably with those derived from the frequency of occurrence of conformations in globular proteins. An analysis of the various components of the nonbonded interaction energy indicates that the fairly frequent occurrence of conformations around ϕ = −80°, ψ=0° is presumably due to a favourable interaction of the π‐polarisation.
A weakly bound, quantum‐mechanical buridan's ass
Authors: Moiseyev N. , Katriel J. , Trindle C. 
Published: December 2004

AbstractThe spherical limit of a single particle in the field of three nuclei is shown to exhibit a variety of phenomena associated with the stability of the various extrema involved. Some consequences with respect to the general problem of detecting broken symmetry solutions of variational problems are pointed out.
On convergence in many‐shell SCF theory
Authors: Firsht D. , Pickup B. T. 
Published: December 2004

AbstractThe effect of damping factors on convergence to general stationary solutions in many‐shell SCF theory is discussed using a first order perturbation analysis. Their bearing on the maximum overlap criterion is examined and a comparison made with Hartree damping. Examples are drawn from numerical experience with hole state and transition operator calculations, some of which lead to saddle point stationary conditions. The method of Hsu et al. is reviewed in the light of the foregoing arguments.
Exact calculations of Franck–Condon overlaps and of matrix elements of some potentials by means of the coherent state representation
Authors: Nishikawa Kiyoshi 
Published: December 2004

AbstractFranck–Condon overlaps are described as the matrix elements of unitary operators related to the spatial displacement and the frequency shift. They are calculated exactly by means of the coherent state representation. Furthermore, the generalized matrix elements of xj, e−αx, and e−βx2 between two states with different equilibrium coordinates and frequency are evaluated in the same way.
Angular dependence of Gaussian‐Lobe orbitals. II. Set of axial Gaussian‐Lobe orbitals
Authors: Le Rouzo H. , Silvi B. 
Published: December 2004

AbstractThe topological properties of real spherical harmonic representations on the unit sphere have been found to provide a convenient tool to infer the lobe edifices which mimic these orbitals. The prohibitive number of lobes required in such an approach for l > 2, can be avoided in using only axial Gaussian‐lobe orbitals (AGLO). It is proved that 2l + 1 independent Ylo‐like functions correctly span the relevant Ylm (m = −l,l) subspace. The multipolar component analysis of any spatial arrangement of lobes is derived, and allows the optimization of the angular dependence of AGLOS. The cases of d‐ and f‐orbitals are studied in detail and accurate optimized functions are proposed. This method can be easily extended to obtain the atomic orbitals of any azimuthal quantum number l‐subspace.
An ab initio molecular orbital study of the deprotonation of amines
Authors: Hopkinson Alan C. , Lien Min H. 
Published: December 2004

AbstractThe geometries of the amines NH2X and amido anions NHX−, where X = H, CH3, NH2, OH, F, C2H, CHO, and CN have been optimized using ab initio molecular orbital calculations with a 4‐31G basis set. The profiles to rotation about the NX bonds in CH3NH−, NH2NH−, and HONH− are very similar to those for the isoprotic and isoelectronic neutral compounds CH3OH, NH2OH, and HOOH. The amines with unsaturated bonds adjacent to the nitrogen atoms undergo considerable skeletal rearrangement on deprotonation such that most of the negative charge of the anion is on the substituent. The computed order of acidity for the amines NH2X is X = CN > HCO > F ≈ C2H > OH > NH2 > CH3 > H and for the reaction NHX− + H+ → NH2X the computed energies vary over the range 373–438 kcal/mol.
Extended virial theorem applied to predissociation phenomena. Interpretation of the nearly degenerate G1Π ∼ I1Π energy spectra in SiO
Authors: Brändas Erkki , Elander Nils , Froelich Piotr 
Published: December 2004

AbstractThe extended virial theorem, obtained from a Fourier–Laplace transformation of equations of motion, is applied to the phenomenon of predissociation. The underlying resonance energy model rigorously defined by means of the theory of dilation analytic operators prescribes in detail the balance between the various energy contributions in a way analogous to the situation prevailing in a stationary system. The extended virial theorem is applied to predissociation, particularly in connection with the interpretation of the nearly degenerate G 1Π ∼︁ I 1Π energy spectrum in SiO. It was previously found for the rovibronic spectra assigned to G 1Π – X 1Σ+ and I1Π – X1 Σ+, that every G – X band is accompanied by a I – X band. Whereas the I 1Π state does not seem to undergo predissociation, the G state shows increasing predissociation with increasing vibrational quantum number. We show that the virial theorem generalized to include continuum phenomena offers an interpretation of the nearly degenerate spectra of SiO as well as of the concomitant isotope shift of SiO16 and SiO18 with respect to both resonance positions and widths.
Time dependence, complex scaling, and the calculation of resonances in many‐electron systems
Authors: Nicolaides Cleanthes A. , Beck Donald R. 
Published: December 2004

AbstractThe theory of this paper deals with certain aspects of the formal properties of atomic and molecular highly excited nonstationary states and the problem of calculating their wave functions, energies, and widths. The conceptual framework is a decay theory based on the consistent definition and calculation of the t = 0 localized state, |Ψ. Given this framework, the following topics are treated: (a) The variational calculation of Ψ0 and E0 using a previously published theory that generalized the projection operator approach to many‐electron systems. (b) The exact definition of the resonance energy. (c) The possibility of bound states in the continuum. (d) The relation of Ψ0 to the resonance (Gamow) function Ψ and of the Hamiltonian to the rotated Hamiltonian H(θ) based on the notion of perturbation of boundary conditions in the asymptotic region. (e) The variational calculation of real and complex energies employing matrix elements of H and H2 with square‐integrable and resonance functions. (f) The mathematical structure of the time evolution of |Ψ0〉 and the possibility of observing nonexponential decays in certain autoionizing states that are very close to the ionization threshold. (g) A many‐body theory of atomic and molecular resonances that employs the coordinate rotation method.
Use of the overlap multipole expansion for approximating molecular electrostatic potentials
Authors: Goldblum A. , Perahia D. , Pullman A. 
Published: December 2004

AbstractThe molecular electrostatic potentials computed by the overlap‐multipole‐expansion procedure (OMTP) are compared to exact electrostatic potentials computed with the same Gaussian basis set, for different molecular species. It is shown that at distances of the molecule larger than 2.2 Å, the OMTP values compared to those of the exact ones are within an error of 0.5 kcal/mol. This error decreases with increasing distance. For distances below this limit the OMTP potentials may be used as a first indication of the trends of the molecule, provided the values to compare are not too close.
Contributions from inner and outer shell electron energies to reaction heats for C1, C2, and C3 hydrocarbons
Authors: George P. , Bock C. W. , Trachtman M. 
Published: December 2004

AbstractThe expectation energy values EK, Vee, Vnn, Ven, and ET have been calculated for H2 and the C1, C2, and C3 hydrocarbons using a (9,5) basis set and the experimental geometries. Treating the theoretical reaction heat, ΔET, as the resultant of the nuclear repulsion term, ΔVnn, and the net electron energy term, ΔEelec = ΔEK + ΔVee + ΔVen, the contribution of inner and outer shell electron energies to ΔEelec, and hence to ΔET, has been calculated for a large number of hydrocarbon reactions by evaluating the Coulson–Neilson energies ηi, where Σηi = Eelec. For the vast majority of reactions, 67/84, the change in inner shell electron energy, (Σηi)inner, accounts for more than 10% of ΔEelec, in many cases being as high as 20–35%. Furthermore, in addition to these cases in which the change in inner shell electron energy serves to augment (significantly) the change in outer shell electron energy, there are other cases in which the change in inner shell electron energy either exceeds in magnitude the change in outer shell energy, or is even opposite in sign, indicative of inner and outer shell electrons acting contrariwise. Inner shell electron energies contribute to the reaction heats because they are structure dependent, like the more familiar orbital energies ε, but the dependence is of a different kind.