bluuebunny/crossref_metadata_2025_split huggingface dataset:
The electronic correlation problem and loge localization
Authors: Ludeña E. V. 
Published: December 2004

AbstractThe model of complete loge localization is employed here to develop a practical method for handling correlation effects in atomic and molecular many electron systems. Intraloge correlation is dealt with by an independent variational treatment of pair functions which are continuous and vanish outside a given loge. It is shown that in the context of the model it is possible to compute pair correlation energies for localized single and double bonds in molecules by evaluating only modified atomic integrals. We bypass in this manner the evaluation of multicenter integrals necessary in other formalisms. In addition, the corrections to the model are discussed and in particular it is shown that part of the interloge correlation effects are already described by the loge localized wave function.
A theory for the construction of the irreducible representations of finite groups
Authors: Blokker Esko 
Published: December 2004

AbstractIt is shown how the irreducible representations of a finite group can be calculated from the irreducible characters (the latter can be calculated exactly by using Dixon's method). All elements of the matrix, representing a group element, lie in the rational field of polynomials of ξ = exp (2πi/e), where e is the exponent of the group.
Stability conditions for the solutions of the hartree‐fock equations. VII. Stability of some closed‐shell nonalternant systems
Authors: Laidlaw W. G. 
Published: December 2004

AbstractThe instabilities of the solutions to the Hartree‐Fock equations for the nonalternants in the pentalene, heptalene, etc., series and in the azulene, etc., series are examined. The systems are found to have symmetry‐adapted solutions which are unstable for values of the core integral β close to the standard (spectroscopic) value; for example, the pentalene solution is unstable with β equal to 75% of its standard value. The “broken” symmetry solutions although exhibiting only a very slightly lower energy (0.01 eV) may exhibit dramatically different values for other properties, e.g., 30% changes in bond orders. The off‐diagonal charge‐density wave (CDW) appearing in the “broken” symmetry solutions at the onset of instability is amplified as the cooperative phenomena dominate, until in the “fully correlated” limit, the linked‐ethylenic (bond alternating) structure is obtained.
A theory for the construction of the irreducible representations of finite groups. II
Authors: Blokker Esko 
Published: December 2004

AbstractThe restriction on a method for computing irreducible representations of finite groups, requiring that in the irreducible representation to be constructed, at least one group element has at least one nondegenerate eigenvalue, is removed. The method is thus shown to be applicable to an arbitrary finite group and constitutes a practical algorithm for handling groups of order less than 400.
The loge theory as a starting point for variational calculations. I. General formalism
Authors: Aslangul C. , Constanciel R. , Daudel R. , Esnault L. , Ludeña E. V. 
Published: December 2004

AbstractIt is shown that any expectation value of any observable associated with a molecule is the sum of loge contributions and of loge pair contributions. This result provides a rigorous theoretical basis for the study of additive properties of molecules.It is demonstrated that molecular wave functions (exact or approximate) can be expressed as a sum of functions corresponding to the various electronic events. Furthermore any of these event functions can be expressed in terms of correlated loge functions. This expression suggests many kinds of variational procedures of calculating wave functions (known methods and new ones).The case in which noncorrelated completely localized loge functions are used is discussed. If continuous functions are used the variational equation reduces to a sum of independent variational equations, each one corresponding to a particular electronic event. This is not so when discontinuous functions are used or when a delocalized function is added to replace the correlation interloge function.The noncorrelated completely localized loge model is analyzed in more detail. It is seen that local spin operators can be introduced and that each event density operator is the product of the loge density operators. Therefore that model is an independent loge model. The corresponding generalized self‐consistent field equations are derived. This treatment helps us to understand how a localized state of a molecule can produce an ion containing a delocalized region, a phenomenon which is sometimes at the origin of some misunderstanding in photoelectron spectroscopy. Finally it is seen how virtual loge functions can be introduced to describe excited states.
Theoretical investigation of the π ‐electronic structure and spectra of protonated aromatic carbonyl compounds
Authors: Kiss A. I. , Joó F. 
Published: December 2004

AbstractThe π‐electronic structure and spectra of the protonated aromatic carboxylic acids, aldehydes and ketones have been calculated by the Pariser–Parr–Pople method. An essential modification was that the positive charge has been considered as delocalized within the substituent group. The best agreement for the cation of benzoic acid was obtained using a symmetric carboxy model with equal charges on both oxygen atoms. This model gave equally good results for the protonated fluoro‐, chloro‐ and methylbenzoic acids, as well. The delocalized charge model was successfully applied in the calculation of aromatic aldehydes and ketones. The methyl group was treated both as a one‐ and as a two‐centre substituent.
First‐Order perturbation treatment of the short‐range repulsion in a system of many closed‐shell atoms or molecules
Authors: Jeziorski Bogumił , Bulski Marek , Piela Lucjan 
Published: December 2004

AbstractAssuming a determinantal form for the wave‐functions of free molecules, explicit formula for the first‐order interaction energy of many closed‐shell molecules has been derived. Provided that the determinants describing the free molecules are constructed from the Hartree‐Fock orbitals, the two‐, three‐, and four‐body effects predicted by the first‐order perturbation theory are closely related to those which one obtains in the framework of the Löwdin LCAO MO‐type approach. The results are illustrated by numerical calculations for the system of three ground‐state helium atoms.
Best optimized one‐electron wave‐functions. IV. Ionization energies of atoms
Authors: Jakubowski P. 
Published: December 2004

AbstractOn the basis of the previously described method for optimization of one‐electron wave‐functions, a simple procedure has been developed to determine the ionization energies in atomic cases. The procedure gives all the ionization energies at once with relatively high accuracy. This is possible due to optimal distribution of the total electron charge between the individual spin‐orbitals.
A comparison of orthogonalized plane wave and augmented plane wave methods for calculating photodetachment cross‐sections
Authors: Mohraz Manijeh , Lohr Lawrence L. 
Published: December 2004

AbstractThe orthogonalized plane wave (OPW) method of calculating electronic continuum wave‐functions is tested by the computation of photodetachment cross‐sections and angular distributions for gaseous halide anions. The results are compared to those obtained by a related augmented plane wave (APW) method involving the exact solution of a single‐particle Schrödinger equation containing a piecewise Coulombic potential energy. These comparisons, as well as other involving experimental and theoretical cross‐sections from the literature, indicate that OPW cross‐sections are, at best, only semi‐quantitatively reliable for describing photodetachment even at low photon energies, and that OPW cross‐sections should be calculated using the dipole length operator rather than the dipole velocity operator.
Incompletely symmetric non‐bloch electron states in perfect cubic crystals. III. Density of dynamical observables in the FCC lattice
Authors: Kunert A. 
Published: December 2004

AbstractThe operators of dynamical observables of the crystal electron (velocity vector components. reciprocal mass tensor components and their functions) commute with the energy operator; hence, the averages of these observables can be adequately approximated by the eigenfunctions for the energy operator. Calculations of the averages were based on the LCAO eigenfunctions classified according to incompletely symmetric irreducible representations of the point group of the cubic crystal, and a similar classification was made for the averages.
Model quantum chemical studies of the electronic structure and aspects of reactivity of diol epoxides of aromatic hydrocarbons
Authors: Lavery Richard , Pullman Bernard 
Published: December 2004

AbstractThis paper offers a unified presentation of the main ring conformers of the diol expoxides, triol carbonium ions, and tetrols related to the “bay‐region” benzo ring of carcinogenic metabolites of PAH and brings forward quantitative information through ab initio SCF computations about their relative energies. It substantiates and evaluates the energy of the syn epoxide‐OH4 hydrogen bond and, on the contrary, refutes the significance of an O ⃛HO or an O− ⃛HO bond in the triol carbonium ions. It provides an explanation for the similar rates of acid‐catalyzed hydrolysis of the syn and anti diol expoxides. It evaluates the stabilization of the triol carbonium ions due to the presence of a neighboring double bond and accounts for the spontaneous opening of protonated epoxides. Finally it accounts for cis hydrolysis of the syn diol epoxide and trans hydrolysis of the anit diol epoxide under acid conditions.
Modified bielectronic potential method for correlation energy
Authors: Ruelle Jean‐Louis 
Published: December 2004

AbstractLöwdin's correlation potential formalism has been used to define a modified bielectronic potential, allowing one to calculate the exact electronic energy, given the Hartree–Fock wave function. This modified potential is in principle peculiar to each electronic system, and is defined by a correlation factor depending on the interelectronic distance r2. The explicit calculation of the correlation factor has been performed for some two‐electron atoms, in the 11S and 23S states, and for the beryllium atom. Examination of the results so obtained leads us to conclude in favor of the nonexistence of a universal modified bielectronic potential.
Ab initio study of a purine nucleoside: Adenosine
Authors: Kwiatkowski J. S. , Pullman B. 
Published: December 2004

AbstractThe ab initio SCF LCAO‐MO method is used to compute the main electronic properties of a purine nucleoside, adenosine, in two specific conformational arrangements (3′‐endo conformation of the ribose, gt orientation of the extracyclic CH2OH group, anti orientation of the base with respect to the sugar and 3′‐endo conformation of the ribose, gg orientation of the extra‐cyclic CH2OH group, syn orientation of the base with respect to the sugar). The results are compared with those performed for the isolated component fragments, adenine and 3′‐endo riboses.
Natural orbital analysis of nonadiabatic H2+ wave functions
Authors: Bishop David M. , Cheung Lap M. 
Published: December 2004

AbstractPreviously determined nonadiabatic wave functions for H2+ (containing several hundred terms) are analyzed by using natural orbitals. This is the first time that the natural orbital concept has been applied to other than purely electronic wave functions. We find that the natural orbital expansion converges rapidly and that five or six terms are sufficient to reproduce the exact expectation values. Several plots are given of the orbitals so found and these allow a visualization of the somewhat abstract nonadiabatic wave function in a format more reminiscent of everyday quantum‐mechanical pictures.
Efficacy of Percutaneous Electrical Nerve Stimulation for the Treatment of Chronic Low Back Pain in Older Adults
Authors: Weiner Debra K. , Rudy Thomas E. , Glick Ronald M. , Boston J. Robert , Lieber Susan J. , Morrow Lisa A. , Taylor Stephen 
Published: December 2004

OBJECTIVES: To determine the efficacy of a complementary analgesic modality, percutaneous electrical nerve stimulation (PENS), for the treatment of chronic low back pain (CLBP) in community‐dwelling older adults.DESIGN: Randomized, controlled clinical trial.SETTING: University of Pittsburgh Pain Evaluation and Treatment Institute.PARTICIPANTS: Thirty‐four English speaking, community‐dwelling adults aged 65 and older with CLBP of at least moderate intensity experienced every day or almost every day.INTERVENTION: Subjects were randomized to receive twice‐weekly PENS and physical therapy (PT) or sham PENS and physical therapy for 6 weeks.MEASUREMENTS: At baseline, immediately after the 6‐week intervention period, and 3 months later, the primary outcome measures pain intensity and pain‐related disability were assessed. The secondary outcome measures physical performance (timed chair rise, functional reach, gait speed, static and isoinertial lifting), psychosocial factors (mood, sleep, and life control), and cognitive function (measures of attention, concentration, and mental flexibility) were also collected.RESULTS: Subjects randomized to PENS plus PT displayed significant reductions in pain intensity measures from pre‐ to posttreatment (P < .001), but the sham PENS plus PT group did not (P = .94). These pain reduction effects were maintained at 3‐month follow‐up. Similarly, significant reductions in pain‐related disability were observed at posttreatment (P = .002) for the PENS plus PT group and were maintained at follow‐up, but the sham PENS plus PT group did not show reductions in pain‐related disability (P = .81). Of the secondary outcome measures, psychosocial function, timed chair rise, and isoinertial lifting endurance also improved significantly at posttreatment for the PENS plus PT group, and their improvement was sustained at 3‐month follow‐up, but the sham PENS plus PT did not display significant changes on these measures after treatment.CONCLUSION: This preliminary study suggests that PENS may be a promising treatment modality for community‐dwelling older adults with CLBP, as demonstrated by reduction in pain intensity and self‐reported disability, and improvement in mood, life control, and physical performance. Larger studies with longer duration of follow‐up are needed to validate these findings and support the use of PENS in clinical practice.
Resource depression by a trophic generalist in an acid stream
Authors: Ledger Mark E. , Hildrew Alan G. 
Published: December 2004

The occurrence and impact of algal grazing by invertebrates is widespread and well known in circumneutral streams but poorly understood in acidified streams, where specialist grazing taxa are absent. We examined the ability of the generalist stonefly, Nemurella pictetii
(Plecoptera: Nemouridae), maintained at different densities using
in‐stream experimental enclosures, to depress the biofilm resources
coating substrata in an acid stream. Nymphs were reared on the epilithic
biofilm coating cobbles in clear aquaria in Lone Oak at 0, 0.5, 1 and 4
times ambient density and their growth rate compared. The biomass and
algal taxonomic composition of the biofilm was also compared among
treatments and contrasted with stones from the stream.
After 23 d, biofilm resources, evidenced by descriptors such as diatom
abundance, chlorophyll, carbohydrate and protein content, had been
depressed by the nymphs. The acidobiontic diatom Eunotia exigua
was harvested more efficiently than other algal taxa when nymphal
densities were high. Growth of N. pictetii nymphs in the
experimental channels was density dependent and the decline in growth of
the nymphs with increasing density was probably due to food limitation.
The ability of N. pictetii, often classed as a shredder of leafy detritus, to affect the biomass and composition of epilithic biofilm suggests that this abundant species is an important consumer of algae in acidified systems, where specialist herbivores are often absent. Grazing can clearly be important in acidified streams.
Economic globalization and oral health
Authors: Hobdell MH 
Published: December 2004

OBJECTIVES: To briefly review the origins of economic globalization and examine the evidence available concerning its possible impact on oral health.DESIGN: Based on Medline searches 1966–1999 and review of Health Wrights:Politics of Healthdatabase.SPECIFIC ORAL DISEASES: Dental caries, destructive periodontal diseases, cancrum oris and oral cancer.CONCLUSIONS: The reported growing disparity between rich and poor populations, both internationally and nationally, is arguably being exacerbated by economic globalization. Increasing levels of the above specific oral diseases might be attributed, in part, to this economic phenomenon.
Community organization and species richness of ants (Hymenoptera/Formicidae) in Mongolia along an ecological gradient from steppe to Gobi desert
Authors: Pfeiffer Martin , Chimedregzen Losol , Ulykpan Kaman 
Published: December 2004

AbstractAim Ants (Hymenoptera/Formicidae) have strong influences on ecosystems especially in arid regions. However, little is known about ants of the vast steppe and desert regions of Central Asia. Here we provide the first comprehensive study of ant communities in Mongolia, conducted along a north‐to‐south gradient in climate. We examined ants’ distribution patterns, assessed the impact of climatic parameters on community structure and species diversity and investigated the influence of the corresponding communities of plants.Location Mongolia (Central Asia).Methods We observed 31,956 ants at seed baits at 11 study sites along a transect from steppe to Gobi desert for which we attained meteorological data (mean yearly precipitation: 197 to 84 mm). Extra sampling was conducted at sugar and protein baits and by the inspection of different microhabitats. Vegetation patterns of each plot were recorded. Statistical evaluation comprised ordination and correlation.Results We observed 15 species of ants at seed baits. Three faunal complexes of ants could be distinguished by detrended correspondence analysis (DCA): (1) in steppe baits were dominated byFormica‐ andMyrmica‐species, (2) in semi desert we found mostly species ofTetramorium,Myrmica,Proformica,Plagiolepis, andLeptothorax, and (3) in desertCataglyphis aenescensandMessor aciculatusdominated, andLasiuswas exclusively found there. Another 11 rare ant species were sampled by hand and at sugar baits. Altogether five ant species were new to the Mongolian fauna:Cardiocondyla koshewnikovi,Myrmica koreana,Myrmica pisarskii,Polyergus nigerrimus, andProformica kaszabi. Assignment of taxa to functional groups showed that in steppe cold climate specialists dominated, in semi desert we found mainly opportunists, and in desert hot climate specialists. Several functional groups know from arid zones in other parts of the world were missing. In desert certain species were highly dominant. First DCA scores of ant‐ and plant‐communities were highly correlated with each other and with climatic parameters. While plant species diversity was positively correlated with increasing northern latitude, ant diversity and ant species richness were not correlated with latitude and responded neither to precipitation, nor to any other climatic parameter. Semi desert was a transition zone between steppe and desert, with high species richness. Ant genus composition of the ecotone overlapped with both other regions. However, beta diversity between pairs of plots within this zone was low, indicating a small‐scale mosaic pattern.Main conclusions The ant communities in the Mongolian steppe and desert zones were strongly influenced by low temperatures and differed in many aspects from the ant fauna in other arid ecosystems, especially in terms of species richness, diversity of feeding guilds, and richness of functional groups.
Management of chronic illness: voices of rural women
Authors: Sullivan Therese , Weinert Clarann , Cudney Shirley 
Published: December 2004

Background.  The prevalence and cost of chronic illness globally and in the United States of America continue to escalate and the day‐to‐day management of these conditions presents a major challenge. The burden of chronic illness disproportionately affects vulnerable populations such as women and those living in rural areas.Aim.  To add to the knowledge base of illness management by chronically ill rural women through examining their individual perceptions of the illness experience.Method.  The Women to Women project provided a nursing research‐based computer intervention model for conducting support groups, providing health education, and fostering self‐care, via personal computers and evaluated its effect on the women's psychosocial health.Findings.  Fatigue and pain were the major physical symptoms that impacted the women's quality of life, with depression and stress being the primary emotions they experienced. The characteristics of humour, hope, and courage were key in their successful adaptation to living with chronic illness.Conclusions.  The women's voices relate how they manage their illness responses and adaptation mechanisms. The data provide nurses with information to heighten their sensitivity to clients’ day‐to‐day needs and experiences. It will assist them in their designing and planning of interventions that will enable clients to adapt and to have the best quality of life possible within the limitations of their chronic illnesses. The data are also important to nurses involved in rural research and theory development concerning self‐management and adaptation to chronic illnesses.
Hysterectomy: a case study of one woman's experience
Authors: Fleming Valerie 
Published: December 2004

Background. There are many published qualitative studies in the large volume of literature about hysterectomy documenting themes common to the majority of participants, such as social support, feelings of illness and wellness, pain and resumption of normal life rather than events which were unique or exceptional.Aim. This study explores the meaning of the experience of abdominal hysterectomy for one woman.Methods. Single client case study method was used. An overview of case study is presented and the rationale for its selection as an appropriate methodology for this study given. The participant and her ‘significant others’ are introduced.Findings. Four major themes relating to the participant's experience were identified: doubts and justifications, pain, embodiment and sense of betterness. These are discussed in relation to the participant, the research literature and nursing and medical practice.Conclusion. Highlighting the case of one woman and analysing her experience as a single case study has produced a depth of material not previously available in other studies. The findings should be of use to staff working in gynaecological nursing, but could also be used in the education of nursing and midwifery students.