bluuebunny/crossref_metadata_2025_split huggingface dataset:
Full configuration interaction for the benzyl radical
Authors: Kuprievich V. A. , Kruglyak Yuri A. , Mozdor E. V. 
Published: December 2004

AbstractThe electronic structure of the benzyl radical in its ground state has been computed using a model Hamiltonian due to Pariser–Parr with full configuration interaction as well as with different truncated configurational sets built on SCF open‐shell orbitals. The correlation energy corresponding to this model was found to be equal to –0.929722 eV. With the singly excited configurations only 18% of this energy is taken into account. By extending the basis to include the doubly excited configurations one can account for 94% of the correlation energy. An analysis of the accuracy of the proton hyperfine splitting calculation caused by inaccurate computation of the wave function is given. If only singly and even doubly excited configurations are taken into account one cannot hope to obtain splittings with an accuracy of more than 0.5 g. Inclusion of triply excited configurations lowers this error by one order. In addition, the use of the simple McConnell relation may lead to an error in splitting calculations of no less than 1.5 g.
Small, simultaneous adjustments of orbital exponents in LCAO–MO–SCF calculations using self‐consistent perturbation theory
Authors: Vladimiroff T. 
Published: December 2004

AbstractSelf‐consistent perturbation theory is introduced to facilitate making small, simultaneous variations in orbital exponents. This is accomplished by interpreting these variations as perturbations on the quantum mechanical system. The minimum‐energy condition yields a set of linear equations for the desired exponential corrections.
Ab initio calculations, using a small Gaussian basis set, of the electronic structure of the sulphate ion
Authors: Hillier I. H. , Saunders V. R. 
Published: December 2004

AbstractAb initio molecular orbital calculations of the electronic structure of the sulphate ion have been performed in which three Gaussian‐type functions are used to simulate each member of a minimal basis of Slater‐type orbitals. Comparative calculations on H2S show that such a basis excellently reproduces the properties of the valence electrons given by calculations in a Slater basis. The expansion of the basis by the addition of sulphur 3d orbitals results in a large decrease in the molecular energy (1 a.u.) and has a pronounced effect on the ordering and energy of the molecular orbitals. The results of a number of semiempirical schemes are discussed in the light of these results.
The generalized separated electron pair model. 1. An application to NH3
Authors: Robb M. A. , Csizmadia I. G. 
Published: December 2004

AbstractThe utility of the separated electron pair (SEP) model (strongly orthogonal geminals) is examined quantitatively, for pyramidal and planar nuclear configurations of the NH3 molecule. The best SEP wave function computed for each species is capable of recovering about half of the correlation energy obtained by a fairly accurate configuration interaction (CI) calculation, (corresponding to roughly 25% of the total molecular correlation energy). It is illustrated that the model can be systematically extended with only a modest effort to yield more accurate results (about 40% of the total correlation energy). The fact that the corrections to the SEP model have a simple physical interpretation suggests that this model may be a useful starting point for “brute force” CI calculations on larger chemical systems.
Le Couplage Vibronique dans une Chaine Linéaire de Molecules Etudié par une Méthode Auto‐Cohérente
Authors: Tallet A. , Garcia‐Sucre M. , Lefebvre Et R. 
Published: December 2004

AbstractWe describe the correlation diagram of a linear crystal, in the traditional framework of the vibronic coupling. All lattice normal modes, except the symmetrical mode, are coupled to the excitation transfer. We therefore propose an iterative method, where every mode “sees” an effective coupling arising from the interaction of the other modes with the electronic excitation. This method is applied to a simple case (the pentamer) and the results are compared with the exact solution. In the weak coupling case this procedure gives the vibronic band structure and in the strong coupling case, the electronic band accompanied by vibrational excitations. These results show that the method employed represents an interpolation approach.
On energy bounds derived from the conjugate eigenvalue problem
Authors: Robinson Peter D. , Epstein Saul T. 
Published: December 2004

AbstractAn upper bound for E0, which has been derived from the conjugate eigenvalue problem by Hall, is discussed. It is emphasized that the bound is only guaranteed when V is negative‐definite. An alternative bound is presented which is free from this restriction, and the underlying iterative procedure is given. Hall's result is generalized to admit internuclear distances, and the theory is illustrated by a one‐dimensional system with delta‐function potentials. Some disadvantages of the approach are mentioned.
A study of dynamic quadrupolar and octupolar excitations and calculations on excited d and f states of atom and ions: He‐sequence
Authors: Moitra R. K. , Mukherjee P. K. , Sengupta S. 
Published: December 2004

AbstractThe quadrupolar and octupolar distortion of the ions in the He‐sequence caused by an external electro–magnetic field has been studied by a variation–perturbation method in the Hartree–Fock scheme. For certain frequencies singularities appear in the response of the system to the perturbation. Approximate representations for the excited d and f states have been obtained from a study of these resonances. Such a perturbation calculation has the advantage that representations of the different excited states are obtained independently. The orthogonality to all the lower lying levels of the same symmetry is not required. The only source of inaccuracy implicit in the procedure lies in the improper consideration of the inter‐electronic interaction. This is corrected for by an independent calculation, which is again formulated in terms of a perturbation treatment. The resulting wave functions for the excited states are accurate in the Hartree–Fock model. Expectation values of several operators have been calculated with these corrected wave functions.
Critical point, singularities and extrapolations in the helium iso‐electronic sequence
Authors: Brändas E. , Goscinski O. 
Published: December 2004

AbstractThe Z‐expansion of two‐electron systems is analyzed with the Padé technique with emphasis on establishing analytical properties of the function E(Z) formally associated with the power series expansion. The concept of critical point in this connection is stressed. For this sequence it occurs at Zc = 0.911246 with E(Zc) = −0.415184. The structure of E(Z) for Z < Zc is investigated.The use of Padé approximants to extrapolate values of electron affinities is emphasized.
Theoretical study of a 1 : 1 complex between quinone and hydroquinone
Authors: Sundaram K. , Purcell William P. 
Published: December 2004

AbstractThe Variable Electronegativity Pariser–Parr–Pople method has been successfully applied to calculate the potential energy curve for the formation of a 1: 1 complex between quinone and hydroquinone. A consistent evaluation of core and electronic repulsion integrals is important to obtain a meaningful curve. A computationally simple procedure has been suggested for separating interactions due to electron exchange between the components from other intermolecular interactions. In agreement with experimental deductions the preferred configuration for the quinone‐hydroquinone complex is found to be one in which the molecules are in parallel planes with their C—O bonds parallel. The equilibrium separation between the molecular planes is found to be 2.3 Å and the stabilization energy in this position is 1.2 eV. In this equilibrium position forces due to electron exchange constitute the major contributing factor to the stability of the complex.
Calculation of excited states of H2O and NH3 by the one‐center expansion approximation
Authors: Hatano Yasuyo , Nomura Tsutomu , Tanaka Kiyoshi 
Published: December 2004

AbstractThe potential energy curves with respect to the bond angle are calculated for some excited and ionized states of the H2O and NH3 molecules by the use of the one‐center expansion SCF MO and the improved virtual orbital approximations. The calculated equilibrium bond angles and force constants of bending motion are in good agreement with the experimental results.
CNDO calculation of polarizabilities including polarization functions in the basis set
Authors: Svendsen E. Nørby , Stroyer‐Hansen T. 
Published: December 2004

AbstractElectric polarizabilities are calculated by solving the first‐ and second‐order perturbation equations through a variational procedure. Satisfactory numerical results are obtained for a number of molecules using the CNDO approximation with an extended basis set.
Method of recurrent construction of Löwdin spin‐adapted wave functions. III. Löwdin basis and its permutation symmetry: Evaluation of overlap integrals
Authors: Panin A. I. 
Published: December 2004

AbstractThe Löwdin basis functions are introduced and their permutation symmetry is studied in detail. A simple relation between the Löwdin basis and the orthogonal basis constructed by means of Young–Yamanouchi units is established. Both analytical and recurrence formulas for the overlap integrals of the Löwdin and some relevant auxiliary functions are derived. The symmetry of the overlap matrix of the Löwdin basis functions is briefly discussed.
Ab initio studies of hydrogen bond formation in methyl cyanide or methyl isocyanide and methanol systems
Authors: Tang Ting‐Hua , Fu Xiao‐Yuan 
Published: December 2004

AbstractCH3CN ⃛ HOCH3 and CH3NC ⃛ HOCH3 hydrogen‐bonded systems have been studied theoretically by ab initio MO methods using a 4–31 G basis set at their equilibrium geometries. The stabilization energies of these hydrogen bonds are 5.4 and 5.9 kcal/mol, respectively. The nature of these hydrogen bonds is discussed in the light of frontier orbital theory and the topological properties of the charge density of the chemical bond.
A theoretical study of C4H5N isomers: Comparison of cyano and isocyano as substituents
Authors: Lien Min H. , Hopkinson Alan C. 
Published: December 2004

AbstractAb initio molecular orbital calculations using a 3‐21G basis set have been used to optimize geometries for pyrrole, CH3(X)CCH2, CH3(H)CCHX (both cis and trans), c‐C3H5X, and CH2CHCH2X, where X is CN and NC. In all the alkenyl derivatives methyl groups are found to adopt the conformation in which the methyl hydrogen eclipses the double bond. 6‐31G*∥3‐21G level calculations show the alkenyl cyanides to be of similar energy to pyrrole, but the isocyanides are ∼20 kcal mol−1 higher in energy. For both substituents the cyclopropyl derivatives are higher in energy by ∼10 kcal mol−1. At the 6‐31G* level ring strain is 27.7 kcal mol−1 for the cyanide and 30.6 kcal mol−1 for the isocyanide. Data on the relative energies of RCN and RNC are compared when R is (i) a saturated hydrocarbon, (ii) an unsaturated hydrocarbon, (iii) an α‐carbenium ion, (iv) an allyl cation, and (v) an α‐carbanion.
Efficient method for computation of representation matrices of the unitary group generators
Authors: Duch W. 
Published: December 2004

AbstractThe representation matrices of the unitary group generators Ek1 are equivalent to the representation matrices of cyclic permutations (k, k ± l, …, l ∓ 1, l). A method is presented for simultaneous computation of matrices corresponding to all different generators at a cost of less than one multiplication per nonzero element. The number of operations necessary for calculation of individual matrices for single generators or for products of two generators is at most proportional to the number of matrix elements of the final matrix. This approach eliminates the need to store the representation matrices in CI calculations.
Diagrammatic analysis and application of the coupled cluster response approach to ground‐state expectation values
Authors: Nooijen Marcel , Snijders Jaap G. 
Published: December 2004

AbstractThe response approach to couple cluster (CC) expectation values devised by Monkhorst and the normal coupled cluster method (NCCM) discussed by Arponen and Bishop are considered from a diagrammatic point of view. The perturbative diagrammatic content of the operator that parametrizes the NCCM bra state is discussed in detail. The method is applied to the calculation of the one‐particle reduced density matrix of the Be atom and the HF molecule for different values of the internuclear distance. Various contributions to the total energy obtained in the NCCM framework are compared to results from accurate multireference configuration interaction calculations. Such a comparison is shown to provide a much more stringent test on the accuracy of the CC formalism than will a comparison of total energy alone. © 1993 John Wiley & Sons, Inc.
Localized functions on a circle
Authors: Rees D. , Hall G. G. 
Published: December 2004

AbstractThe derivation of hybrids as localized equivalent functions in the plane is discussed using the simultaneous eigenfunctions of the x and y position operators, as represented in a finite basis. It proves helpful, initially, to use complex exponentials as basis functions, but the transformation to a real basis is made later. The introduction of alias functions to produce commuting matrices is described. Full results are obtained for any number of functions in the plane. © 1995 John Wiley & Sons, Inc.
Helicobacter pylori and Campylobacter rectus share a common antigen
Authors: Tanabe S. , Hinode D. , Yokoyama M. , Fukui M. , Nakamura R. , Yoshioka M. , Grenier D. , Mayrand D. 
Published: December 2004

Aim:  The aim of this study was to investigate the presence of antigens with immunological cross‐reactivity in periodontopathogenic bacteria and Helicobacter pylori, the pathogen associated with gastritis and peptic ulcers in human.Materials and methods/Results:  Among the putative periodontopathogens tested (Actinobacillus actinomycetemcomitans, Campylobacter rectus, Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia and Treponema denticola), cross‐reactive bands were only detected in C. rectus by SDS–PAGE/Western immunoblotting analysis using a polyclonal antibody directed to H. pylori cells. One of these cross‐reactive antigens, a 64‐kDa band antigen, also reacted with a monoclonal antibody directed to the human heat shock protein (HSP) 60. The N‐terminal amino acid sequence of this C. rectus protein revealed a high degree of homology with corresponding regions of other HSPs belonging to the HSP60 family, indicating that the 64‐kDa antigen was a GroEL protein. The nucleotide sequence of the C. rectus GroEL protein coded for a 547 amino acid protein with a predicted size of 57.8 kDa. Comparison of the alignment of the deduced amino acid sequence of the GroEL protein of C. rectus with that of H. pylori showed a high degree of similarity throughout its length (76.8%). GroEL protein from C. rectus possessed the ability to stimulate production of IL‐6 by a confluent monolayer of human gingival epithelial cells and was cytotoxic when used at a high concentration.Conclusions:  This study reveals an immunological relationship between H. pylori and C. rectus, and clearly indicates that one of the shared antigens is a GroEL protein possessing a biological activity that might play a role in the initiation and progression of periodontal disease.
Molecular fingerprinting of TGFß‐treated embryonic maxillary mesenchymal cells
Authors: Pisano M.M. , Mukhopadhyay P. , Greene R.M. 
Published: December 2004

AbstractThe transforming growth factor‐ß (TGFß) family represents a class of signaling molecules that plays a central role in normal embryonic development, specifically in development of the craniofacial region. Members of this family are vital to development of the secondary palate where they regulate maxillary and palate mesenchymal cell proliferation and extracellular matrix synthesis. The function of this growth factor family is particularly critical in that perturbation of either process results in a cleft of the palate. While the cellular and phenotypic effects of TGFß on embryonic craniofacial tissue have been extensively cataloged, the specific genes that function as downstream mediators of TGFß in maxillary/palatal development are poorly defined. Gene expression arrays offer the ability to conduct a rapid, simultaneous assessment of hundreds to thousands of differentially expressed genes in a single study. Inasmuch as the downstream sequelae of TGFß action are only partially defined, a complementary DNA (cDNA) expression array technology (Clontech's AtlasTM Mouse cDNA Expression Arrays), was utilized to delineate a profile of differentially expressed genes from TGFß‐treated primary cultures of murine embryonic maxillary mesenchymal cells. Hybridization of a membrane‐based cDNA array (1178 genes) was performed with 32P‐labeled cDNA probes synthesized from RNA isolated from either TGFß‐treated or vehicle‐treated embryonic maxillary mesenchymal cells. Resultant phosphorimages were subject to AtlasImageTM analysis in order to determine differences in gene expression between control and TGFß‐treated maxillary mesenchymal cells. Of the 1178 arrayed genes, 552 (47%) demonstrated detectable levels of expression. Steady state levels of 22 genes were up‐regulated, while those of 8 other genes were down‐regulated, by a factor of twofold or greater in response to TGFß. Affected genes could be grouped into three general functional categories: transcription factors and general DNA‐binding proteins; growth factors/signaling molecules; and extracellular matrix and related proteins. The extent of hybridization of each gene was evaluated by comparison with the abundant, constitutively expressed mRNAs: ubiquitin, glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH), ornithine decarboxylase (ODC), cytoplasmic beta‐actin and 40S ribosomal protein. No detectable changes were observed in the expression levels of these genes in response to TGFß treatment. Gene expression profiling results were verified by Real‐Time quantitative polymerase chain reaction. Utilization of cDNA microarray technology has enabled us to delineate a preliminary transcriptional map of TGFß responsiveness in embryonic maxillary mesenchymal cells. The profile of differentially expressed genes offers revealing insights into potential molecular regulatory mechanisms employed by TGFß in orchestrating craniofacial ontogeny.
Ant predation and the cost of egg carrying in the golden egg bug: experiments in the field
Authors: Kaitala Arja , Espadaler Xavier , Lehtonen Risto 
Published: December 2004

Golden egg bug (Phyllomorpha laciniata) females lay eggs on the
backs of both female and male conspecifics. Bugs receive eggs voluntarily
and involuntarily, and even when males carry eggs, many eggs are not
fertilised by the carrier. Carrying the eggs of another individual is
unexpected, particularly if egg carrying bears a cost in survival.
We examined the predation risk associated with egg carrying
experimentally in the field. P. laciniata individuals were
enclosed with workers of one of two ant species, Pheidole pallidula
or Cataglyphis piliscapus, which co‐occur with the bug in the
wild. Pheidole pallidula workers preyed on golden egg bugs and their
eggs, but Cataglyphis piliscapus workers did not. In P.
pallidula enclosures, golden egg bugs carrying larger egg loads were eaten first.  These results suggest that golden egg bugs experience high predation pressure and that egg carrying increases the risk of predation. Due to the direct survival costs associated with egg carrying and the lack of relatedness between the eggs and the carrier, we suggest the golden egg bug as the first known intraspecific parasite in which parasitism is not related to active parental care.
Interaction between leucocytes and human spermatozoa influencing reactive oxygen intermediates release
Authors: Frączek Monika , Sanocka Dorota , Kurpisz Maciej 
Published: December 2004

SummaryThe relationship between the presence of white blood cells (WBCs) and the fertilizing potential of human semen is still an open question. It is well known that the presence of leucocytes in human semen can be related to the production of reactive oxygen intermediates (ROI). Semen samples were obtained from 15 normozoospermic men and leucocytes were isolated from heparinized blood drawn from 15 volunteers. Lucigenin and luminol‐mediated chemiluminescence assays were used to determine reactive oxygen species (ROS) generation by non‐activated or activated leucocytes through 12‐myristate‐13‐acetate or N‐formyl‐methionyl‐leucyl‐phenyalanine (FMLP) before the addition of spermatozoa isolated by swim‐up or Percoll procedures. All spermatozoal fractions used in this study were characterized by defining their motility, morphology and viability. The levels of ROS formation by non‐activated as well as stimulated leucocytes were significantly decreased after addition of swim‐up separated spermatozoa (p < 0.01). The ability to inhibit the basal chemiluminescence was of lower degree for spermatozoa isolated from 90% Percoll fractions than for swim‐up sperm. However, addition of sperm cells from 47% Percoll fraction was found to increase both lucigenin and luminol signals. Moreover, the determined ROI levels changed depending on the type of inducing factor used for oxidative burst. Then, spermatozoa selected by swim‐up procedure although with only slightly higher viability and morphology than sperm obtained from 90% Percoll fraction clearly exhibited much higher capacity to inhibit ROI secretion by receptor‐stimulated leucocytes (FMLP‐activation) than Percoll fractionated sperm. Such results may indicate that within normal semen may exist sperm subpopulations with different biochemical mechanisms controlling the interaction between spermatozoa and contaminating leucocytes. When ROI levels contained in normozoospermic semen are dependent on the WBCs activation, it seems that spermatozoa with preserved normal functional competence are able to defend themselves against leucocytes‐derived ROI. Also for normozoospermic ejaculates, swim‐up sperm may improve semen antioxidant characteristics when comparing with Percoll (90%) separated sperm. It may help for optimal sperm preparation when assisting to infertility treatment.
In situ expression of Granzyme B and Fas‐ligand in the liver of viral hepatitis
Authors: Ibuki Naohisa , Yamamoto Kazuhide , Yabushita Kazuhisa , Okano Nobuaki , Okamoto Ryoichi , Shimada Noriaki , Hakoda Tomomi , Mizuno Motowo , Higashi Toshihiro , Tsuji Takao 
Published: December 2004

Abstract:  Background/Aims: The molecular mechanism involved in hepatocellular injury in viral hepatitis remains to be clarified.Methods: We investigated the in situ expression of effector molecules of cytotoxic T lymphocytes such as Fas‐ligand (Fas‐L), perforin and Granzyme B (Gr‐B) immunohistochemically in liver tissues from 20 patients with chronic hepatitis B (CHB) and C (CHC). The degree of cell infiltration was analysed semi‐quantitatively and compared with the histological activity index (HAI). Fas‐L was expressed in both CD4 and CD8 T‐cells in the portal tract as well as in the parenchyma.Results: Immunostaining of serial sections demonstrated that mononuclear cells at interface hepatitis and focal necrosis were mainly Fas‐L positive CD8 T‐cells. On the other hand, the expression of perforin or Gr‐B was limited to a few mononuclear cells in the portal tract and parenchyma. Semi‐quantitative analysis showed a positive correlation between HAI and the grade of infiltration of CD8 T‐cells or Fas‐L‐positive cells, while the correlation was not apparent between HAI and the number of Gr‐B positive cells. The expression of these molecules was not different between types of viruses.Conclusions: These results suggest that Fas‐L‐positive CD8 T‐cells play a major role in the pathogenesis of liver cell injury in chronic hepatitis.