bluuebunny/crossref_metadata_2025_split huggingface dataset:
Four‐dimensional density and energy density functional
Authors: Kryachko Eugene S. 
Published: December 2004

AbstractThe relations based on an external one‐electron operator V(r) are examined from two view‐points, i.e., from the Hohenberg–Kohn approach and the four‐dimensional density concept introduced by Wilson and Frost, and extensively studied by Parr and Politzer. The object being to obtain, with the help of the Hellmann–Feynman theorem, new formulas for the energy of atoms and molecules, and to discuss the construction of the universal energy density functional on the basis of the four‐dimensional density.
Bonding in alkali metal homonuclear diatomics
Authors: Pelissier Michel , Davidson Ernest R. 
Published: December 2004

AbstractAn analysis of the factors that contribute to the stability of the bond between alkali metal atoms is made by using nonorthogonal configuration interaction. Beyond the orbital size, the overlap of the valence orbitals of one atom with the core orbitals of the other accounts for most of the difference between the hydrogen molecule and the alkali metal diatomics. It is shown that the valence bond description does not provide a satisfactory description in any case except for the hydrogen molecule, and valence electron correlation using the p‐type valence orbitals is essential.
Calculation of bound‐state energies from a variational functional method
Authors: Fernández Francisco M. , Arteca Gustavo A. , Castro Eduardo A. 
Published: December 2004

AbstractA variational functional method is improved and generalized in order to obtain approximate bound‐state energies of a wide variety of quantum‐mechanical systems. Calculations on the discrete spectrum of the hydrogen atom in a magnetic field and the bounded harmonic oscillator show that the procedure is very promising.
A modified PCILO framework using the CNDO/Boyd–Whitehead parametrization
Authors: Lochmann R. , Weller Th. , Köhler H.‐J. 
Published: December 2004

AbstractThe CNDO/BW modification of the CNDO/2 approximation was used within the PCILO framework. It was shown on some significant examples that all the good results of the original PCILO‐CNDO/2 method can be reproduced by the modified version PCILO‐CNDO/BW at least. Thus, preserving the quality of its results a computer‐expense‐reduced PCILO method is proposed for calculations on large molecular systems.
Hydration of GABA and of the GABA·ZN2+ complex: A Monte Carlo simulation study
Authors: Leś Andrzej , Grabowski Sławomir 
Published: December 2004

AbstractWith empirical and theoretical atom–atom potentials the GABA·nH2O, n = 25, 192 and GABA·Zn2+ · nH2O, n = 25, 50, 100 complexes are simulated at 298.15 K by the Monte Carlo technique. The results show that the carboxyl group of GABA coordinates six water molecules. Two geometries of the GABA·Zn2+ complex, corresponding to the “direct” and “through‐water” interaction of Zn2+ with the carboxyl group of GABA were found. For the latter interaction a GABA·Zn2+ · 6H2O complex was found whereas the hydration of the former interaction leads to a GABA·Zn2+ · 5H2O complex. Here the carboxyl group of GABA displaces only one water molecule in the first hydration shell of Zn2+. Energetically the “direct” and “through‐water” geometries seem to be competitive, the former being slightly favored.
Iterative degenerate perturbation theory
Authors: Golovko V. F. 
Published: December 2004

AbstractA fairly general degenerate perturbation theory has been considered which involves two versions, i.e., the Rayleigh‐Schrodinger and Brillouin‐Wigner treatments. The simple recursive formulas have been found for effective Hamiltonians which allow one to split the degenerate energy levels in any orders of this theory.
Charge distributions and chemical effects. XXXIV. Concepts involved in an approximate, but accurate, description of bond energies
Authors: Fliszár Sándor 
Published: December 2004

AbstractThe concepts underlying the definition of bond energies in terms of potentials at the nuclei are outlined. The theory is rooted, first, in a definition of the energy, Ei, of “atom” i in the molecule in terms of the potential energy, V(i, mol), of nucleus Zi in the field of all the electrons and nuclei of the molecule: Ei = K V(i, mol). The K parameter, which is not required to be a constant in the derivation of the energy expression describing the contribution of an ij bond, turns out to be virtually constant for each atomic species—a situation which is exploited in numerical applications. Second, the Hellmann—Feynman theorem is applied in the calculation of the derivative, δΔE/δZi, of the atomization energy, ΔE, using (i) the exact quantum‐chemical definition of ΔE and (ii) the view that ΔE is the sum of bond energy contributions, εij, plus a small interaction between nonbonded atoms. The individual bond energies derived in this manner necessarily depend on local charges at the bond‐forming atoms. Numerical applications illustrate how this new bond‐energy formula provides a simple link between typical saturated, olefinic, acetylenic, and aromatic hydrocarbons.
Preliminary results of a theoretical ab initio model study of adsorption on ionic crystals
Authors: Bourg M. 
Published: December 2004

AbstractThe adsorption of metals on ionic surfaces takes place on preferential sites and is affected by the presence of defects. In order to provide some theoretical indication concerning electronic energy changes connected with these effects, we have extended previous work [A. Julg and M. Bourg, J. Phys. Lett. 43, L243 (1982)] where Lin clusters embedded in a matrix simulated by point charges had been studied by STO‐6G (G‐70) calculations. We have treated an Li2 molecule in the presence of an fcc lattice of positive and negative point charges placed at the distances characteristic of an LiF crystal: The perfect surface as well as steps and point defects have been thus simulated. In this article we briefly describe the results obtained.
A model of the primary process in photosynthesis
Authors: Avery John 
Published: December 2004

AbstractThe arrangement of membrane‐bound pigments, proteins, and lipids in the thylakoids of higher plants is described, and the role of the membrane in preventing the back‐reaction is discussed. The photosynthetic bacterium halobacterium halobium is also described. A simplified quantum‐mechanical picture of the primary process in photosynthesis is presented, and the mechanism of electron‐hole separation in this picture is compared with the corresponding mechanism in a silicon solar cell. An appendix discusses the application of Frenkel exciton theory to the antenna effect.
Similarity transformation of the ab initio density matrix
Authors: Singh O. P. , Yadav J. S. 
Published: December 2004

AbstractBond orders and hybrid populations have been calculated from the density matrix localized in molecular space using similarity transformation for some fluorobenzene with the minimal basis set using Gaussian series of program. The ab initio bond orders and hybrid populations have been compared with the semiempirical calculations on this set of molecules. Also, these bond orders have been used in Coulson's bond order‐bond length relationship to estimate bond lengths. The present calculations suggest that the qualitative predictions of molecular geometries are possible from these bond orders.
The pseudopotential‐CI study of the interaction between ethylene and metal atoms, metal Oxides, and their cations (Me = Be, Mg, and Zn)
Authors: Witko Malgorzata , BonačIć‐Koutecký Vlasta 
Published: December 2004

AbstractPotential energy curves for the lowest singlet and triplet states of Me + C2H4, Me+ + C2H4, MeO, MeO + C2H4, and (MeO + C2H4)+ systems for Me = Be, Mg, and Zn have been determined employing PP‐MRD‐CI or an all electron MRD‐CI procedure. A binding interaction in the ground state has been found for oxides, all cation systems, and the BeO + C2H4 system. In the cases of MgO + C2H4 and ZnO + C2H4, only low lying excited states exhibit attractive interactions. Among three oxides considered, BeO is less pronounced biradically than MgO and ZnO. In order to obtain a binding interaction between an oxide and the olefin in the ground state, the p orbital of the metal must be sufficiently involved in binding.
High spatial resolution Auger linescans across heterogeneous chemical edges by Monte Carlo calculation
Authors: Tuppen C. G. , Davies G. J. 
Published: December 2004

AbstractPrevious calculations have shown that Auger yields increase at chemical edge/free space interfaces. In this paper we consider the edge formed by a well defined thin film on a substrate of different chemical composition. Two systems have been investigated: Au and Si and Al on Si. Linescans are presented for a number of different electron beam configurations and show significant features attributable to an edge effect. These effects are explained in terms of the different layer materials and their corresponding backscatter coefficients.
Chemical synapses, particle arrays, pseudo‐gap junctions and gap junctions of neurons and glia in the buccal ganglion of Helisoma
Authors: Berdan R. C. , Shivers R. R. , Bulloch A. G. M. 
Published: December 2004

AbstractThe nervous system of the snail, Helisoma trivolvis, has been utilized for a wide range of studies of neuronal plasticity; however, the ultrastructural features of this tissue were perviously unknown. The present study examined the nature of synaptic interactions of neurons and glia and considered several plasma membrane specializations of these cells. The symmetrical pair of buccal ganglia consisted of a ring of unipolar neurons surrounding a central neuropil. The neurons were separated by two morphologically distinct types of glia: type I were most numerous and possessed an electron‐dense homogenous cytoplasm, whereas type II glia were of lower electron density, possessed a heterogenous cytoplasm, and appeared to be phagocytic. Gap junctions were abundant between glia and were occasionally found between neuronal processes, including those of neurons 19 injected with horseradish peroxidase (HRP). Comparison of neuron and glial gap junction widths (16.4 and 17.6 nm, respectively) in thin sections and their intramembrane particle diameters (13.1 and 13.7 nm, respectively) by freeze fracture, did not elucidate significant differences. A heterogenous population of putative chemical synapses, similar to those reported in other molluscs, was also observed between axonal collaterals in the neuropil. Additionally, examination of freeze‐fractured neuropil revealed rhombic arrays of particles localized on neuronal membranes; these arrays do not appear to form intercellular junctions but may represent postsynaptic receptor sites. Freeze fracture also revealed small, square arrays consisting of 7–9 nm diameter particles on glial membranes which may correspond to pentalaminar membrane contact (pseudo‐gap junctions) seen in thin sections between glia situated around dilated extracellular spaces (lacunae).
Transplantation of cultured human adrenal chromaffin cells into 6‐hydroxydopamine‐lesioned rat brain
Authors: Kamo Hisaki , Kim Seung U. , McGeer Patrick L. , Tago Hisao , Shin Doo H. 
Published: December 2004

AbstractAdult young rats were subjected to a unilateral 6‐hydroxydopamine lesion of the nigrostriatal dopamine pathway and then given intrastriatal grafts of human fetal adrenal chromaffin cell cultures. Amphetamine‐induced ipsiversive turning behavior in the lesioned rats was largely reversed in four of eight rats given such transplants when tested at 1.5 and 4.5 months post‐transplantation. Two rats showed a transient recovery at 1.5 months followed by deterioration at 4.5 months, while two other rats showed continuous deterioration. Six rats given sciatic nerve grafts as controls all showed deterioration from the pretransplantation levels. Catecholamine fluorescent and immunohistochemical examination of chromaffin‐cell‐transplanted brains demonstrated neurons and neuronal processes positive for catecholamines or tyrosine hydroxylase in the transplanted area. This transplantation of cultured human fetal cells to an animal model may provide the necessary basic experimental system for assessing the possible utility of human neuronal transplants.
Neonatal deafferentation prevents normal expression of synaptic vesicle antigens in the developing rat superior cervical ganglion
Authors: Greif Karen F. , Trenchard Holly 
Published: December 2004

AbstractThe effect of neonatal deafferentation of the rat superior cervical ganglion (SCG) on the expression of two synaptic vesicle proteins was studied to assess the role of transsynaptic influences in the regulation of these neural antigens in the SCG. The two proteins studied were a 65 kilodalton integral membrane protein of synapatic vesicles (SV), and synapsin‐1 (S‐1), a synaptic vesicle phosphoprotein. Antigen levels were quantified by radioimmunoassay using antibodies directed against the proteins. Distribution of SV in control, deafferented and reinnervated ganglia from 30‐day‐old rats was visualized by immunohistochemical labeling. Levels of both antigens were reduced following deafferentation of the SCG on postnatal days 1–3. The reduction in S‐1 levels at 30 days was less than that observed for SV. The amount of S‐1 remaining in deafferented ganglia was consistent with estimates of the postsynaptic pool in the SCG reported previously. SV levels, in contrast, were reduced to 24% of control levels, suggesting that SV synthesis in principal ganglionic neurons might be affected. The time course of postnatal development of S‐1 in the SCG differed from previous studies of SV expression, with significant increases occurring after the second week after birth. The differences in response to deafferentation may reflect functional differences of the two vesicle‐associated proteins. These studies demonstrate that transsynaptic regulation of antigens other than those directly associated with neurotransmitters occurs in the SCG.
Physiological and morphological characterization of striatal neurons transplanted into the striatum of adult rats
Authors: Walsh John P. , Zhou Feng C. , Hull Chester D. , Fisher Robin S. , Levine Michael S. , Buchwald Nathaniel A. 
Published: December 2004

AbstractPhysiological and morphological properties of transplanted striatal neurons (TSNs) were examined in an in vitro slice preparation. Fetal striatal tissue (E13‐14) was implanted as a dissociated cellular suspension into the striatum of adult rats. Intracellular records were obtained from TSNs 2–6 weeks after transplantation. TSNs exhibited biophysical, morphological, and synaptic properties characteristic of normal striatal neurons, despite the disruption involved in processing of the fetal tissue. Differences were observed, however, between the TSNs and host striatal neurons. TSNs consistently had higher input resistance values than host striatal neurons as determined by neuronal responses to intracellular current injection. Stimulation of adjacent host striatum elicited both excitatory and inhibitory postsynaptic potentials in TSNs. By contrast, the same stimuli elicited only excitatory responses in host striatal neurons. Morphologically, TSNs resembled host medium‐size spiny neurons as demonstrated by intracellular injection of lucifer yellow. However, the complexity of dendritic branching and the density of spines on the dendrites were less than that observed for host striatal neurons. It was concluded that during the posttransplantation period studied, TSNs possess neuronal properties expected of developmentally immature striatal neurons.
Purification and characterization of PCPP‐260: A Purkinje cell‐enriched cyclic amp‐regulated membrane phosphoprotein of Mr 260,000
Authors: Weeks Gerald , Picciotto Marina , Nairn Angus C. , Walaas S. Ivar , Greengard Paul 
Published: December 2004

AbstractPCPP‐260 (Purkinje cell phosphoprotein of Mr 260,000), a substrate for cAMP‐dependent protein kinase, appears to be an integral membrane protein highly enriched in Purkinje cells of the mammalian cerebellum (Walaas et al.: J. Neurosci., 3:291–301, 1983; Walaas et al.: J. Neurosci., 6:954–961, 1986). PCPP‐260 has now been purified from a crude particulate fraction of bovine cerebellum, using the ionic detergent N‐lauryl sarcosine (NLS) as solubilizing agent, and monitoring the purification by silver stain and autoradiography of 32P‐phosphorylated samples, after separation by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. Concanavalin A was found to bind to PCPP‐260, suggesting that it is a glycoprotein. PCPP‐260 was therefore extracted, retained on a column of concanavalin A‐agarose, and eluted by α‐methyl mannoside. Further chromatography on Sephacryl S‐400 yielded a preparation that was purified approximately 250‐fold relative to the initial particulate fraction and that was at least 95% pure. The protein was estimated to represent approximately 0.4% of total membrane protein in the cerebellum. Peptide mapping and phosphoamino acid analysis following phosphorylation of the protein by cAMP‐dependent protein kinase showed one major tryptic phosphopeptide containing phosphoserine. A similar, less prominent protein was also found in membranes from other brain regions but could not be detected in liver membranes. The availability of highly purified PCPP‐260 should facilitate the investigation of its possible functional roles in the nervous system.
Neurophysiological maturation of cat substantia nigra neurons: Evidence from in vitro studies
Authors: Walsh John P. , Cepeda Carlos , Buchwald Nathaniel A. , Levine Michael S. 
Published: December 2004

AbstractThe membrane properties and synaptic physiology of developing cat substantia nigra (SN) neurons were studied in in vitro slice preparations. Stable intracellular recording were obtained from 46 neurons in 20 kittens ranging in age from fetal day (F) 51 to postnatal day (P) 120. Only two of these properties changed with development. The percentage of cells displaying inward rectification and the percentage of cells that generated low‐threshold Ca++ spikes increased with age. Properties that did not change included resting membrane potentials, action potential amplitudes and durations, and input resistances. At all ages locally evoked synaptic responses consisted of sequences of excitatory postsynaptic potentials followed by inhibitory postsynaptic potentials. Most of the cells recorded had the electrophysiological properties which have been attributed to SN dopamine‐containing neurons. To identify neurons morphologically, and verify the recording site, cells were filled with Lucifer yellow at the end of each experiment. Somatic shapes varied widely from oval to fusiform to triangular. Somatic diameters and dendritic length increased with development. Filopodial processes and growth cones were present up to the first postnatal month. Dye‐coupling occurred only in the fetal group. These results indicate that cat SN neurons have many mature physiological properties during late fetal and early postnatal development. This contrasts with the significant maturation that occurs in cat caudate neurons during the same developmental period (Cepeda et al., Synapse, 7:278–290, 1991).
High affinity histamine binding site is the H3 receptor: Characterization and autoradiographic localization in rat brain
Authors: Cumming Paul , Shaw Christopher , Vincent Steven R. 
Published: December 2004

AbstractThe binding of the histamine autoreceptor (H3) agonist [3H]‐Nα‐methyl‐histamine ([3H]‐N‐MeHA) was examined in 25 μm thick rat forebrain sections. The specific binding was saturable and of high affinity: Scatchard analysis indicated a Kd of 2 nM and a Bmax of 25 ± 3 fmol/section. Under similar conditions, [3H]‐histamine ([3H]‐HA) bound with a Kd of 8 nM and a Bmax of 20 ± 2 fmol/section. Competition studies indicated that both ligands bound an identical site which had the pharmacological characteristics of the H3 binding site. The high affinity binding of [3H]‐N‐MeHA was sensitive to the presence of 5′ ‐guanylyl‐imidodiphosphate, indicating that the binding site is likely coupled to a G‐protein. Autoradiographic studies indicated the [3H]‐N‐MeHA binding to be greatest in the nucleus accumbens, striatum, substantia nigra pars reticulata, and certain cortical areas. Striatal quinolinic acid lesions greatly reduced binding in both the striatum and ipsilateral substantia nigra, while 6‐hydroxydopamine lesions of the nigrostriatal dopamine system were without effect on binding. Therefore, most of the H3 binding sites in the basal ganglia are on striatonigral projection neurons. Cortical quinolinic acid lesions greatly reduced H3 binding in cortex, indicating that the binding in cortex, as in striatum, is largely on intrinsic neurons, rather than on afferents such as histamine nerve terminals.
Morphological and electrophysiological study of distal motor nerve fiber degeneration and sprouting after irreversible cholinesterase inhibition
Authors: Kawabuchi Masaru , Cintra Wagner M. , Deshpande Sharad S. , Albuquerque Edson X. 
Published: December 2004

AbstractA single subcutaneous injection of a sublelthal dose of the irreversible organophosphate sarin (0.08 mg/kg) in rat induced a non‐Wallerian‐type axonal degeneratin of the neuromuscular synapse in the slow twitch, soleus muscle. These alterations of the endplate region were more obvious in the soleus than in the fast extensor digitorum longus muscle and were slowly reversible, complete recovery requiring about 10 days. Silver‐cholinesterase staining and electrophysiological techniques were used to define the spatiotemporal evolution of prejunctional abnormalities. The non‐Wallerian‐type axonal degeneration of the neuromuscular synapse was characterized by bead or balloon‐like varicosities of the focal, dista, and terminal nerve fibers and a retraction of terminal axons. Axonal degeneration was accompanied by junctional and extrajunctional membran depolarization and was followed by nerve sprouting at focal, distal, and terminal nerve fibers. Transients similar to miniature endplate potentials were recorded along the muscle fiber at distances of 800–2500 μm away from the parent endplate. New ectopic endings, originating fromthe same endplate, were discovered adjacent to the terminal axon and also distant from the parent endplate. Very elaborate terminal arborization and occasional multibranching arose from a progressive growth sprout. The new sprouting may have served to compensate for the loss of synaptic contact caused by sarin. Thus the present study demonstrates a direct cytotoxic effect of sarin and indicates that this organophosphate agent may be an important neurotoxicological tool to understand the mechanisms involved in nerve sprouting.