bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unrestricted Hartree‐Fock calculations of spin densities with orthogonalized atomic orbitals: Proton and 13C hyperfine splittings in some pi hydrocarbon radicals
Authors: Nanda D. N. , Narasimhan P. T. 
Published: December 2004

AbstractThe spin density distribution in a few hydrocarbon radicals has been calculated using orthogonalized atomic orbitals in the Unrestricted Hartree‐Fock formalism of Amos and Snyder and including certain more important two‐electron hybrid and exchange integrals and all the core‐resonance integrals. Our calculated spin densities for the cation and anion radicals of alternant hydrocarbons, which are now different due to the breakdown of the pairing theorem, are, in general, of the right relative order so that even the simple McConnell type of relation can account partly for the observed differences in the proton splittings between cations and anions. The proton splittings for position 2 of naphthalene and anthracene radical ions are correctly predicted, thus clearing up the well‐known cation‐anion anomaly for this position. Comparative calculations have been made to show that the spin density results are worsened with the neglect of the integrals of the type mentioned before. An empirical analysis correlating the observed 13C splittings and the spin density results over a non‐orthogonal basis set shows that the available 13C splittings in alternant hydrocarbon radical ions can be explained with a set of sigma‐pi parameters which are consistent with the theory. It is shown that even though the spin densities in cations and anions may be different, these can lead to similar 13C splittings.
Molecular‐orbital calculations on transition metal complexes, charge‐transfer spectra and the sequence of metal and ligand orbitals
Authors: Van Der Lugt W. Th. A. M. 
Published: December 2004

AbstractAn outline is given of a semi‐empirical scheme for molecular‐orbital calculations on transition‐metal complexes according to a revised INDO procedure. To judge the reliability of the results of the calculations, the charge‐transfer transitions of a number of complexes have been calculated and compared with experimental data. Both for the excitation energies and for the oscillator strengths the agreement is very satisfactory. With respect to the sequence of occupied metal and ligand orbitals it was found that for closed‐shell d6 and d8 systems the molecular orbitals which are mainly composed of metal d orbitals have a lower energy than the orbitals built up from ligand p orbitals. Calculations by the extended Hückel method and other similar schemes give the d orbitals as the highest occupied ones as a result of a bad approximation of the diagonal elements of the Fock matrix. The consequences for the interpretation of photo‐electron spectra of transition‐metal complexes are discussed.
A floating one centre perturbation treatment for H‐like molecules
Authors: Ali M. K. , Meath W. J. 
Published: December 2004

AbstractClosed form one centre partial wave perturbation results are obtained through second order in the energy for H‐like molecules with arbitrary nuclear charges. The expansion centre for the method is taken at an arbitrary point along the internuclear axis and the zeroth‐order wave function is a screened “1s” function centred at the expansion point. Various fixed one centre calculations of other workers for the lsσ states of H and HeH++ and for the 2pσ state of HeH++ are generated as limiting cases of this more general treatment. The floating one centre perturbation results for the 1sσ states of H2+ and HeH++ are used as models for discussing the usefulness of allowing the expansion centre in the one centre method to be a function of nuclear configuration.
Localized orbital calculations of the bonding in SO, SO2F2, ClO3F and SOCL2
Authors: Guest M. F. , Hillier I. H. 
Published: December 2004

AbstractLocalized valence molecular orbitals have been obtained for SO, SO2F2, ClO3F and SOCl2 by the method due to Boys and Foster. The bonding in these molecules, in which the second row atom is exhibiting an excess valency, is discussed in terms of the form of these localized orbitals. The bonding of the second row atom to an oxygen atom is described by three bent bond orbitals, whilst bonding to a halogen atom is described by a single bond orbital. The participation of 3d functions in the various bonding and nonbonding orbitals is analysed in this localized orbital framework.
An alternative formalism for the method of intermediate Hamiltonians
Authors: Sack R. A. 
Published: December 2004

AbstractThe methods of intermediate Hamiltonians and of inner projections for the determination of lower bounds of eigenvalues of a Hermitian operator H are analysed and reformulated as linear matrix problems. Submatrices T which are only defined implicitly through the product TTd̊ are best represented in triangular form. If the subspace complementary to the subspace determining the inner projection can be subdivided with different lower bounds for H, the bounds for the eigenvalues can be further improved. The new formalism is applied to obtain crude lower bounds for the ground state of the helium atom, using only 2 × 2 and 3 × 3 matrices.
Determination of one‐centre core integrals from the average energies of atomic configurations
Authors: Karlsson Göran , Zerner Michael C. 
Published: December 2004

AbstractOne‐center core integrals for valence orbitals are determined from the experimental average energies of neutral atomic configurations from Li through Zn. These values are compared with those estimated from CNDO/1, “INDO/1”, CNDO/2, “INDO/2” and with theoretical values calculated from a pseudo‐potential method. The agreement is good between values obtained from neutral atoms and from the psuedo‐potential calculation except for the 3d orbitals of the transition elements where the theoretically calculated integrals over single ξ functions are not realistic. These two methods reproduce both term and average configuration energies for the first two rows of atoms; the semiempirical method reliably reproduces them for the third row. The CNDO/1 and INDO/1 methods underestimate atomic energies, while the CNDO/2 and INDO/2 procedures fail rather poorly.The propriety of using core integrals estimated semiempirically in molecular orbital calculations is discussed.
A floating spherical gaussian orbital model of molecular structure. XII. Analysis of energy terms affecting the geometry of the water molecule
Authors: Afzal M. , Frost A. A. 
Published: December 2004

AbstractThe energy terms arising in the water calculation by the FSGO method are analyzed as a function of the bond angle in order to gain insight into the reasons for the particular equilibrium configuration. The analysis is made in terms of symmetrically orthogonalized orbitals so as to exclude three‐ and four‐orbital electron repulsion terms.
Spin‐free wave functions in many‐electron perturbation theory. I. Closed‐shell systems
Authors: Shibuya Tai‐Ichi , Sinanoğlu Oktay 
Published: December 2004

AbstractThe Schrödinger equation of an N‐electron closed‐shell system is reduced to that for the spatial wave function Ψ by the aid of the theory of the symmetric (permutation) group SN. The first‐order perturbation equation based on the Hartree–Fock‐SCF model as the zero‐order solution is then solved by decomposing it into a set of soluble 1/2(N/2)[(N/2) + 1] equations for the pair‐correlation (first‐order) spatial wave functions. These spatial functions give the spatial parts of the pair functions in the spin orbital basis formulation, reducing also the number of independent pairs needed in the first order.
Spin‐free wave functions in many‐electron perturbation theory. II. Systems with one nonclosed shell
Authors: Shibuya Tai‐Ichi , Sinanoğlu Oktay 
Published: December 2004

AbstractThe formulation developed in Paper I for a closed shell system is extended for a system with one nonclosed shell. Roothaan's restricted Hartree–Fock (RHF) open‐shell wave function is taken as the zero‐order solution. The first‐order Schrödinger equation is then solved for the spatial part of the wave function by reducing it to a set of one‐ and two‐electron equations, using the properties of the symmetric group SN.
Ab initio Hartree‐Fock calculations of electronic wave functions for the c3πu state of H2
Authors: Truhlar Donald G. 
Published: December 2004

AbstractTheoretical electronic wave functions, potential curves, and expectation values of some one‐electron properties are given for the c3IIu state of the hydrogen molecule. The calculations are carried out by the matrix Hartree‐Fock method and use a 2‐center basis of Slater‐type orbitals. A total energy of −0.7292 a.u. is obtained in the best calculation. Our potential curve is reasonably consistent with that calculated by Browne, but we have examined the region of small internuclear distances (those at and below Re for the ground state) more extensively than any previous calculation. At R ≦ 1.6 a.u. our calculated potential curve is in excellent agreement with experiment.
Applications of Padé approximants of type II in partitioning technique
Authors: Røeggen I. 
Published: December 2004

AbstractPadé approximants of type II have been applied to solve equations of the type F(z) = 0. The method is compared with the first‐order iteration procedure, the Aitken‐Samuelson formula, and the Newton‐Raphson tangential method. As a test example the partitioning technique in its most simple form is applied to the Hamiltonian of a rigid symmetric‐top molecule in a static electric field. The proposed algorithm is found to be superior to the first‐order procedure and the Aitken‐Samuleson formula, and at least as effective as the Newton‐Raphson method.
Møller–Plesset theory for atomic ground state energies
Authors: Binkley J. S. , Pople J. A. 
Published: December 2004

AbstractMø–Plesset theory, in which electron correlation energy is calculated by perturbation techniques, is used in second order to calculate energies of the ground states of atoms up to neon. The unrestricted Hartree–Fock (UHF) Hamiltonian is used as the unperturbed system and the technique is then described as unrestricted Mø–Plesset to second order (UMP2). Use of large Gaussian basis sets suggests that the limiting UMP2 energies with a complete basis of s, p, and d functions account for 75–84% of the correlation energy. Preliminary estimates of the contributions of basis functions with higher angular quantum numbers indicate that full UMP2 limits give even more accurate total energies.
A correlation study of Li ground state by the MCHF procedure
Authors: Fischer Charlotte Froese 
Published: December 2004

AbstractResults are reported for multiconfiguration Hartree–Fock studies of correlation in the lithium ground state, which maintain orthogonality of orbitals within a configuration.It is shown that when the 1s‐ and 2s‐orbitals are fixed at their Hartree–Fock value, configurations for which Brillouin's theorem holds may be important, particularly for atomic properties other than energy. The Fermi contact term is considered as an example.
A finite‐difference solution of the Hartree–Fock equations for diatomic molecules
Authors: Fimple W. R. , White S. P. 
Published: December 2004

AbstractA more general application of the self‐consistent field iteration is coupled with a finite‐difference Newton–Raphson algorithm to solve the set of coupled second‐order integro‐differential equations with split boundary conditions which constitutes the Hartree–Fock problem for diatomic molecules. The N orbitals are assumed to be of the form ψα = Lα(λ) Mα (μ)eimαϕ (2π)−1/2, (α = 1, …︁, N), where λ, μ, and ϕ are the usual confocal elliptical coordinates. Requiring the expectation value of the electronic Hamiltonian to be stationary with respect to independent variations of the functions Lα and Mα, subject to constraints of orthonormality, leads to a set of coupled one‐dimensional differential equations for the functions Lα and Mα. In the new method a corresponding set of finite‐difference equations including the split boundary conditions for each function, as well as the Lagrange multipliers and associated constraints on normalization and orthogonality, are incorporated into a large system of nonlinear algebraic equations which is solved by means of a coupled self‐consistent field‐generalized Newton–Raphson iteration. As examples, calculations of the (1)2 1Σ and (1) (2pσu) 3Σ states of H2 are presented. The calculated energy for the 1Σ state of H2 is 99.985% of the three‐dimensional Hartree–Fock limit. The discrepancy is due to the assumed factored form of the orbitals ψα, and a generalization of the finite‐difference method is suggested to improve the results.
Lattice dynamics with second neighbor interactions. II. Green's formula
Authors: McIntosh Harold V. , Hehenberger Michael , Reyes‐Sanchez Rodolfo 
Published: December 2004

AbstractA satisfactory definition of spectral density for the normal modes of lattice dynamics problems requires the study of singular recurrence relations which is carried out in detail for one‐dimensional chains with pth neighbor interactions. The relationship of transfer matrices to the dynamical matrix is explored in order to obtain Green's formula. By using Green's formula, a mapping is defined between Vn, whose basis is formed from the normal modes of vibration of an n‐particle chain, and V2p, which is the space of boundary conditions for the recurrsion equations. Most of the properties of this mapping may be deduced from a symplectic bilinear form in V2p which is associated with the Hermitean inner product in Vn. This symplectic form defines a geometry which is invariant under the recursion relation, as well as canonical initial and boundary conditions, and a maximal isotropic subspace which may be used to determine square summability of the normal modes and the spectral density in the limit as the number of particles becomes infinite.
Valence‐Electron theory using the thomas–fermi–dirac model: Application to the K atom and the K− ion
Authors: Goodisman Jerry 
Published: December 2004

AbstractIt is proposed to calculate electronic structure of atoms and molecules by combining the Thomas‐Fermi‐Dirac (TFD) theory and a correct quantum mechanical treatment. The potential generated from the TFD treatment of the positively charged cores contains no adjustable parameters and requires no modification for proper asymptotic behavior. To take the exclusion principle into account, the valence electron wave‐function is constructed from the n + 1st, n + 2nd, etc. solutions to the one‐electron Schrödinger equation using the core potential, where n is the number of core electrons. For the potassium atom, the simple calculations give excellent agreement with experiment for ionization potential, transition frequencies and intensities, magnetic susceptibility, and electric polarizability. From a two‐electron configuration interaction wave‐function for K−, a value for the electron affinity of K is obtained which agrees with experimental values.
Many‐electron theory in the Waller–Hartree spin‐free method
Authors: Lim T. K. 
Published: December 2004

AbstractA many‐electron theory is developed for the determination of pure spin state wave‐functions and energies to avoid the difficulties in doing integration. The Waller–Hartree pure spin state wave‐functions are very convenient for this purpose. The required explicit formulas for the values of the Waller–Hartree wave‐functions Y(S, M) and ℋ︁Y(S, M) at some physical points are produced, where local orthonormal orbitals are used to simplify the calculation of ℋ︁Y(S, M). A method for the construction of these orbitals is given, and a transformation formula is also given to show the interchangability between the local energy expression and the conventional expectation energy integral.
An investigation into the relationship between water beetle (Coleoptera) distribution and land cover in Scotland and northeast England
Authors: Eyre M. D. , Foster G. N. , Luff M. L. , Staley J. R. 
Published: December 2004

AbstractAims  To determine the relationship between satellite‐derived land cover data and distribution patterns of water beetle species pools.Location  A total of 687 British national grid 10 km squares in Scotland and 588 1 km grid squares in 99 10 km grid squares in northeast England.Methods  Multivariate classification and constrained ordination analyses were used with water beetle species and land cover data.Results  The major variation in both the Scotland and northeast England 10 km species pools was from squares with upland acid water habitats to squares with lowland fens and ponds whilst for the 1 km northeast England data it was from squares dominated by fast‐flowing streams and rivers to those with fens and ponds. The secondary variations in the 10 and 1 km analyses were the primary ones juxtaposed. Constrained ordination of the Scottish 10 km data showed upland land cover types to be most influential in determining species pool distribution whilst lowland covers were more important with both the 10 and 1 km northeast England pools. The three analyses showed that coastal cover had a relatively high influence on species pool distribution but no species pool group was dominated by coastal species.Main conclusions  There were strong relationships between water beetle species pool distributions and the satellite‐derived land cover types dominating upland and lowland areas. The major variation in the northeast England species pool data differed at the two scales analysed. Results indicated that there is considerable potential for the synthesis of water beetle distribution and land cover data for use in environmental and conservation monitoring at both the regional and national scales.
Classifying general and specialist children's nursing competencies
Authors: Gibson Faith , Fletcher Margaret , Casey Anne 
Published: December 2004

Background.  Whilst there is evidence in the literature to support the continuation of a children's nursing qualification, the distinction between generalist and specialist nursing is insufficiently comprehensive to distinguish children's nursing from other branches of nursing.Aim.  To develop a definition of children's nursing and specialist children's nursing in terms of competencies as the basis for differentiating them from other forms of nursing.Design.  A multi‐method comparative design incorporating a case study approach was used. This included a nominal group technique, focus groups, Delphi survey and semi‐structured interviews. Two arms of data collection were undertaken concurrently (during 1998–2000) with children's nurses (n = 146) and specialist children's nurses (children's cancer nurses, n = 37) from a number of centres in the United Kingdom (UK).Findings.  The holistic competencies developed from the data exposed characteristics of knowledge, skills, abilities, values and qualities displayed in the context of professional work for both groups of nurses. A classification of competencies was developed inductively from the data by two independent researchers through the labelling, defining and ordering of competencies. The resulting hierarchy of competencies and sub‐competencies illustrates relationships between children's nurses and specialist children's nurses and provides a detailed definition of children's nursing and specialist children's nursing.Conclusion.  There is a significant common element in these two areas of nursing practice, and generalist preparation in children's nursing is the foundation of specialist children's nursing practice. Generalist knowledge and skills are expanded in specialist practice and there is also evidence of specialist practice that is beyond the scope of general nursing practice.
Torsion of undescended testis in a man with Down's syndrome
Authors: PAPATSORIS ATHANASIOS G , MPADRA FILITSA , KARAMOUZIS MICHALIS , LIKAKI‐KARATZA ELENI , KARATZAS THEODOROS 
Published: December 2004

AbstractUndescended testis is one of the most common disorders in Down's syndrome. We present an extremely rare case of torsion of an inguinal undescended testis in a 35‐year‐old patient with Down's syndrome. Surgical exploration revealed a rotated gangrenous testis, radical orchiectomy was performed, and pathological examination confirmed the diagnosis of testicular torsion.
Intratesticular varicocele: Report of two cases
Authors: POURBAGHER MIR ALI , GUVEL SEZGIN , POURBAGHER AYSIN , KILINC FERHAT 
Published: December 2004

AbstractIntratesticular varicocele is a rare entity and describes dilated intratesticular veins radiating from the mediastinum testis into the testicular parenchyma. Scrotal ultrasonography of two patients who presented to our urology clinic due to left scrotal pain revealed multiple tubular structures in the testes with diameters of more than 2 mm. Duplex spectral analysis showed a reversed flow response to Valsalva's maneuver. Apropos of two cases, intratesticular varicocele is reviewed.
Sufficient prophylactic efficacy with minor adverse effects by intravesical instillation of low‐dose bacillus Calmette‐Guérin for superficial bladder cancer recurrence
Authors: IRIE AKIRA , UCHIDA TOYOAKI , YAMASHITA HIDEYUKI , MATSUMOTO KAZUMASA , SATOH TAKEFUMI , KOH HIDESHIGE , SHIMURA SATORU , IWAMURA MASATSUGU , BABA SHIRO 
Published: December 2004

AbstractBackground: Intravesical instillation of bacillus Calmette‐Guérin (BCG) is the most efficient strategy for prophylaxis of superficial bladder cancer recurrence. Adverse effects of BCG are major obstacles, but the reduction of BCG dose could minimize these effects. The efficacy and adverse effects of half‐dose (40 mg) BCG, Tokyo 172 strain, were prospectively evaluated.Methods: A total of 93 patients with superficial bladder cancer (pTa or pT1) were sequentially assigned to receive either 40 or 80 mg of BCG after transurethral resection. BCG was administered weekly for 6 weeks postoperatively. Eighty patients observed longer than 12 months after BCG therapy (41, 40 mg group; 39, 80 mg group) were analyzed.Results: BCG therapy course was completed in 71 patients. Tumor recurrence was recognized in 11 of 40 patients in the 40 mg group and in 5 of 31 patients in the 80 mg group. There was no significant difference in tumor recurrence rate between the two groups (P = 0.547). BCG therapy was withdrawn in 1 patient in the 40 mg group and in 8 patients in the 80 mg‐group because of BCG‐related adverse effects. The morbidity of BCG‐related toxicity was significantly higher in the 80 mg group.Conclusion: Half‐dose of BCG Tokyo 172 strain had a similar efficacy and its toxicity was signi­ficantly lower compared to the standard dose. Thus, half‐dose of this strain might be suitable, at least for initial BCG therapy, for the prophylaxis of bladder cancer recurrence. Further study would be necessary to clarify the efficacy of low‐dose instillation in high‐risk patients.
Centaur database: an information system for aphid surveys and pest control
Authors: Zintzaras E. , Tsitsipis J. A. 
Published: December 2004

Abstract:The development and the use of an information system (Centaur) including aphid trapping data from suction and yellow traps are described. Centaur is a client‐server database on an NT server and the interface is in Windows. The system allows users to enter and retrieve data of aphid captures and to produce summaries of data at various time levels (daily, weekly, yearly) for specific sites. The data can be illustrated graphically and they can be exported or printed. In addition, the system allows the incorporation of biological data and morphological images, and maps which estimate the spatial distribution of aphids. The information retrieval is fast and user‐friendly. The system can be of considerable value for research, community ecology, plant protection, public and private authorities, plant protection specialists, agronomists, agrochemical companies, farmers and the agricultural industry as it can be used for decision support. The data can be used to make forecasts for risk and/or to give advice for timely interventions. The system is currently operated in Greece and includes data from 1993 but it can be applied to other European countries and can be used for other insect pests.