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  • 2000-2004
  • 1980-1984  (400)
  • 1980  (400)
  • Atomic, Molecular and Optical Physics  (277)
  • Ultrastructure  (122)
  • Nuclear reactions
Material
Years
  • 2000-2004
  • 1980-1984  (400)
Year
  • 101
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 206 (1980), S. 211-223 
    ISSN: 1432-0878
    Keywords: Enameloid ; Lophius ; Ultrastructure ; X-ray analysis ; Electron diffraction ; Electron microprobe analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé La microscopie électronique à transmission, la microscopie électronique à balayage, la diffraction X, la diffraction électronique et l'analyse par microsonde ont prouvé l'existence d'un émailoïde, ultrastructuralement et chimiquement différent de la dentine, chez la baudroie. La microscopie électronique à balayage et la microscopie électronique à transmission ont mis en évidence un chapeau d'émailoïde, d'environ 50 μm d'épaisseur, et une couche fine (1 μm) d'émailoïde du collet. L'émailoïde du collet, dont l'ultrastructure différente de celle de la dentine a été mise en évidence en microscopie électronique à transmission et en microscopie électronique à balayage, apparaît, après analyse par microsonde, moins minéralisé que le chapeau. Le chapeau d'émailoïde diffère de la dentine par (i) sa densité aux électrons en microscopie électronique à transmission; (ii) sa structure perpendiculaire à celle de la dentine sous-jacente, visible en microscopie électronique à transmission et en microscopie électronique à balayage et confirmée par la diffraction électronique, qui montre une orientation préférentielle des cristaux; (iii) son contenu en fluor plus élevé, qui diminue progressivement de l'apex à la jonction avec la dentine et chute brutalement au-dessous de cette jonction; (iv) sa teneur plus basse en magnésium. Les auteurs proposent que soit établie une classification des émailoïdes analogue à celle des dentines et dans laquelle l'émailoïde de Sélaciens constituerait un standard de référence.
    Notes: Summary The ultrastructural and chemical differences between mature enameloid and dentine in the teleost fish Lophius were demonstrated using transmission (TEM) and scanning (SEM) electron microscopy, X-ray diffraction analysis, electron diffraction analysis and electron microprobe analysis. An enameloid cap (about 50 μm thick) and a thin layer (1 μm thick) of collar enameloid were revealed in the scanning (SEM) and transmission (TEM) electron microscopes. Collar enameloid, structurally different from dentine both in SEM and TEM, proved to be less mineralized than the cap as revealed by electron microprobe analysis. The enameloid cap was seen to differ from dentine by (i) its electron density in TEM; (ii) the structural arrangement perpendicular to the underlying dentine, observed in SEM and TEM and corroborated by electron diffraction data, which showed a preferred orientation of enameloid crystallites; (iii) its higher F content decreasing gradually from the apex of the tooth to the junction with dentine and falling suddenly below this junction; and (iv) its lower Mg content. Establishment of a classification of enameloids is proposed, similar to that for dentines, in which selachian enameloid would be a reference standard.
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  • 102
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 206 (1980), S. 291-302 
    ISSN: 1432-0878
    Keywords: Neurohypophysis ; Perivascular space ; Pericytes ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The vascular and perivascular regions of the human neurohypophysis were studied electron microscopically. The abluminal basement membrane, perivascular space, luminal basement membrane and endothelium are interposed between the neural parenchyma and the blood stream. The capillaries are fenestrated, with pores measuring 30 to 50 nm in diameter. The perivascular and intercellular spaces form prominent networks that penetrate between rows of neurohypophysial parenchymal cells. The perivascular space contains pericytes, histiocytes, fibroblasts and mast cells, with ultrastructural features typical of each cell type. No transitional forms between histiocytes and pericytes were observed. A schema for the extracellular flow of neurohypophysial hormones through the sinusoidal and perivascular spaces is proposed, suggesting an important role for the pituicytes and their intercellular junctions in the control of hormone release.
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  • 103
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    Springer
    Cell & tissue research 206 (1980), S. 417-430 
    ISSN: 1432-0878
    Keywords: Pinealocyte ; Fetus ; Mole ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of the pinealocytes in the fetal mole (Talpa europaea) was examined and compared with that in the adult mole. The parenchyma of the fetal pineal gland consists primarily of pinealocytes with very few dispersed “glial” cells. Three different morphological types of pinealocytes (I, II and III) were observed. Pinealocytes of types I and II, homologous to the rudimentary photoreceptor cells of lacertilians and birds, were commonly found, especially around the pineal lumen, which is still present in the fetus. These results support the concept of the phylogenetic origin of mammalian pinealocytes from the pineal photoreceptor cells of the non-mammalian vertebrates. Considering their synthetic/secretory activity, the pinealocytes of the mole fetus are characterized by the presence of accumulations of proteinaceous material (APM) in the cisternae of the granular endoplasmic reticulum (GER). Two types of APM were also found. One type shows a paracrystalline organization as described in the adult mole. In the fetus, however, the paracrystalline-organized APM occur only infrequently. A progressive transformation, via an increase in size or fusion of vacuoles containing material originating from the cisternae of the GER in APM, free of a paracrystalline structure, has been observed. Granular vesicles (GV) originating from the Golgi saccules were rarely observed. Sometimes GV and APM were found to be present in the same cell.
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  • 104
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    Springer
    Cell & tissue research 206 (1980), S. 441-449 
    ISSN: 1432-0878
    Keywords: Protonephridium ; Planarian ; Configuration of flame cell ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The protonephridial flame cell of the freshwater planarian Bdellocephala brunnea was studied by electron microscopy. This basketlike cell with luminal cilia and fenestrae is known as a cyrtocyte. Careful examination revealed the actual continuity of the fenestrae over the surface of the cell and the microvillous nature of thin cytoplasmic rods composing the fenestrae. On the basis of these findings, a new interpretation was given for the threedimensional configuration of a single cell: this cell is essentially stellate in shape, with several irregular cytoplasmic processes adjoining one another, thus bearing a basic resemblance to the podocyte of a mammalian renal corpuscle. The cytoplasmic features strongly suggest its great capability of reabsorbing substances from the filtrate and of carrying out intracellular digestion. Some additional structural specialization of the fenestra, serving for enlargement of the filtration surface, was observed.
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  • 105
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    Cell & tissue research 206 (1980), S. 451-458 
    ISSN: 1432-0878
    Keywords: Protonephridium ; Planarian ; Regional differentiation of tubules ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A systematic electron microscopic investigation was undertaken to elucidate the regional differentiation of the protonephridial tubules of the freshwater planarian Bdellocephala brunnea. The excretory system consists of many independent protonephridia, each made up of the repeatedly branching “proximal tubules,” and highly tortuous “distal tubule.” The proximal tubules are composed of a simple ciliated epithelium except in the trunk which lacks ciliation. The cytoplasmic features of the ciliated cell closely resemble those of the flame cell, indicating highly active protein reabsorption by pinocytosis. Pinocytosis seems also active in the trunk of the proximal tubules and in the distal tubule, resulting in cytoplasmic vesicles of typical appearance. Salient features of the distal tubule cell are the increased density of the cytoplasmic matrix and the presence of many basal compartments of cytoplasm with mitochondria, a pattern common to many epithelia with osmoregulatory function. The morphology and possible functions of the planarian protonephridium are discussed in comparison with the vertebrate nephron.
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  • 106
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    Cell & tissue research 206 (1980), S. 505-508 
    ISSN: 1432-0878
    Keywords: Ticks ; Ultrastructure ; Synapses ; Muscles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Peripheral nerve axons synapse with somatic muscle fibres in the tropical bont tick Amblyomma variegatum. Each fibre is innervated by numerous terminals; some of the axons synapse more than once. The nerve terminals on coxal muscle fibres contain agranular electron lucent vesicles 50 to 58 nm in size and have the specialised synaptic membranes characteristic of chemically transmitting nerve-muscle junctions. Some of the terminals on trochanteral muscle fibres additionally contain larger vesicles (90 nm) with electron dense cores, suggesting that these junctions operate with a different kind of neurotransmitter.
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  • 107
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    Springer
    Cell & tissue research 209 (1980), S. 329-343 
    ISSN: 1432-0878
    Keywords: Stomach ; Innervation ; Myenteric plexus ; Guinea-pig ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of the vesicle-containing axon profiles in the myenteric ganglia of the guinea-pig stomach was studied in specimens fixed by vascular perfusion and in specimens fixed by immersion in cold fixative after incubation in 5-hydroxydopamine. Three major types of vesicle-containing axon profile were identified in the ganglia: 1. Profiles containing numerous small, mainly spherical vesicles and only limited numbers of large dense-cored vesicles. In perfusion-fixed specimens, the small vesicles in these profiles were all clear. In specimens fixed by immersion after incubation in 5-hydroxydopamine, the profiles could be divided into three types: a) profiles containing small clear vesicles; b) profiles containing small dense-cored vesicles; c) profiles in which the small vesicles contained a peripheral rim of dense material. In these profiles, large vesicles which contained dense cores were rare. The mean diameter of the vesicles in the profiles was also significantly higher than in the profiles containing small clear vesicles. 5. Profiles containing flattened membrane-bounded structures. Reconstructions prepared from serial sections suggested that these structures represented sections through networks of smooth endoplasmic reticulum-like tubules rather than flattened vesicles. 6. Profiles containing many large dense-cored vesicles and few small clear vesicles. In perfusion-fixed specimens, the diameter of the dense-cored vesicles in these profiles was significantly higher than in the type 1 profiles. Type 1 a and type 1 c profiles were much more numerous than either type 2 or type 3 profiles, and type 1 b profiles were few. Synaptic junctions were found in association only with type 1 a profiles. Type 1 a and type 1 b profiles resembled cholinergic and adrenergic axon terminals. The remaining profiles may represent the terminals of different forms of peptidergic axon or of other as yet unidentified types of axon.
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  • 108
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    Cell & tissue research 213 (1980), S. 475-482 
    ISSN: 1432-0878
    Keywords: Vaginal epithelium ; Prenatal estrogen treatment ; Mucification ; Ultrastructure ; Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary After transplacental treatment of mice with estrogens, a heavy mucification was found in the fornices of the vaginae of the offsping. The resulting mucified stratified epithelium is described by light and electron microscopy. It consists of two different cell types: cells forming mucus on top of cells forming tonofilaments. Mucus formation is usually attributed to treatment with progestagens, or with with estrogens combined with vitamin A. Estrogen treatment per se has been shown to be responsible for tonofilament formation. Our unexpected findings are discussed against the background of different theories of development of vaginal epithelium as well as their possible interpretation as beginning of adenosis.
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  • 109
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    Cell & tissue research 205 (1980), S. 273-287 
    ISSN: 1432-0878
    Keywords: Human neurohypophysis ; Ultrastructure ; Pituicytes ; Ependyma ; Choristoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pars nervosa of the neurohypophysis from 12 patients undergoing hypophysectomy for palliative treatment of advanced carcinoma was studied electron microscopically. Special attention was given to the cellular elements, the pituicytes. Five different classes of pituicytes, with various transitional forms, were elucidated based on their ultrastructural characteristics: (1) The most common type, referred to as “major pituicytes”, is reminiscent of astrocytes. (2) “Dark pituicytes” are thought to represent different functional stages of the “major pituicytes”. (3) “Ependymal pituicytes” are believed to provide ultrastructural evidence that human pituicytes are phylogenetically derived from ependymal cells. (4) “Oncocytic pituicytes” were observed in all cases and are of unknown significance. (5) The ultrastructural features of “granular pituicytes” suggest the existence of an active uptake and catabolism of extracellular material by pituicytes, probably through “ultraphagocytosis” or “endocytosis”. These five classes of pituicytes are considered to represent different functional forms of one cell line that originates phylogenetically from the ependyma.
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  • 110
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    Cell & tissue research 205 (1980), S. 361-370 
    ISSN: 1432-0878
    Keywords: Enamel organ ; Human foetus ; Tooth germ ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of external enamel epithelium, stellate reticulum and stratum intermedium in primary tooth germs (bell stage) from four human foetuses was investigated. Characteristically, the cells of the differentiated external enamel epithelium, stellate reticulum and stratum intermedium exhibit many free ribosomes, few rough endoplasmic reticulum cisterns, well-developed Golgi complexes, many coated and smooth vesicles, often in relation to the cell membranes, and many bundles of tonofilaments. The cells are connected by numerous desmosomes and gap junctions. A parallel differentiation of stratum intermedium — external enamel epithelium, and the ameloblast layer is demonstrated. The morphology of the cells of the three layers indicates that these have secretory, transport and supporting functions.
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  • 111
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    Cell & tissue research 206 (1980), S. 95-114 
    ISSN: 1432-0878
    Keywords: Lateral eyes ; Scorpion ; Ultrastructure ; Retina ; Arhabdomeric cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The dioptric apparatus of the lateral eyes of the scorpion, Androctonus austrails, consists of a cuticular lens, but lacks a vitreous body. The retina is formed by (1) retinula cells displaying a contiguous network of rhabdoms; (2) arhabdomeric cells bearing a distal dendrite that contacts retinula cells via numerous projections and ends before the rhabdomere of the retinula cells; (3) pigment cells that ensheath retinula and arhabdomeric cells with the exception of the contact regions; and (4) neurosecretory fibres possibly originating in the supraesophageal ganglion. The ratio of the number of retinula to arhabdomeric cells is determined to be close to 2 ∶ 1 in the three larger anterolateral eyes, in contrast to the median eyes where the ratio is 5 ∶ 1. The construction of the dioptric apparatus as well as the anatomy of the retina imply that in the lateral eyes of Androctonus australis visual acuity is reduced. A certain degree of spatial discrimination, however, may be retained by the presence of a relatively high number of arhabdomeric cells. It is suggested that the lateral eyes of A. australis mainly function as light detectors, e.g., for Zeitgeber stimuli.
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  • 112
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    Cell & tissue research 206 (1980), S. 123-138 
    ISSN: 1432-0878
    Keywords: Ultrastructure ; Sense organs ; Compound eyes ; Interfacetal mechanoreceptor ; Coleoptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The structure of the compound eyes of adult Cicindela tranquebarica Herbst was examined by use of light, scanning, and transmission electron microscopy. Each ommatidium of these photopic eyes is eucone and has a “subcorneal layer” situated between the corneal lens and crystalline cone. A distal rhabdomere consisting only of microvilli from retinula cell seven, a more proximal, rectangular, fused rhabdom formed from six retinula cells, and a basal, eighth retinula cell with a spherical rhabdomere comprise the light sensitive portions of the ommatidium. The “subcorneal layer” consists of lamellae of endocuticular microfibrils and, in surface view, shows 11 concave polygons. Proximal extensions of the crystalline thread form inter-retinular fibres containing microtubules between retinula cells 1/2, 3/4, 5/6, and 7/1. The primary pigment cells are devoid of pigment granules, but are rich in rough endoplasmic reticulum. Proximal to each retinula cell nucleus are two basal bodies, one perpendicular to the other. The more proximal basal body extends two fibrillar feet proximally which fuse to form a horizontally-banded ciliary rootlet extending the length of the retinula peripheral to the rhabdom. Each ommatidium is surrounded by 16 secondary pigment cells. Interfacetal mechanoreceptors between some adjacent lenses each have a single bipolar neuron, with a dendritic sheath, tubular body, cilium, outer and inner sheath cells, and an axon surrounded by a neurilemma sheath cell.
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  • 113
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    Cell & tissue research 210 (1980), S. 85-94 
    ISSN: 1432-0878
    Keywords: Hypothalamus ; Domestic fowl ; Preoptic area ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Numerous secretory parvocellular perikarya were found in the preoptic region of the domestic fowl (Gallus gallus). The dense-core secretory vesicles belong to two categories: vesicles with a diameter of (i)80–90 nm and (ii) 110–140nm. Scattered magnocellular elements display larger dense-core granules. The parvocellular neurons form unit-like clusters, showing also zones of direct apposition of neuronal membranes. The surrounding neuropil is rich in synaptic structures, formed by at least three types of axon terminals, distinguishable on the basis of vesicular morphology. These observations confirm the findings in other avian species. The hypothetical function of this system of peptidergic neurons in the rostral hypothalamus of birds is discussed.
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  • 114
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    Cell & tissue research 210 (1980), S. 257-267 
    ISSN: 1432-0878
    Keywords: Ultrastructure ; Smooth muscle ; Connective tissue ; Portal vein ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The smooth muscle of rabbit portal vein was studied by electron microscopy with particular emphasis on the mechanical linkage between the muscle cells and on the distribution of connective tissue. The media of this vein is composed of inner circular and outer longitudinal muscle layers which are orientated almost perpendicularly to each other. The muscle of the inner circular layer shows very irregular contours with much branching and anastomosing of the cytoplasmic processes, which often make membrane contacts with neighbouring cells to form an extensive network of cytoplasmic processes. The muscle cells of the outer longitudinal layer are arranged in densely packed bundles and are spindle-shaped, with no branching processes. Opposing dense areas from neighbouring cells, with variable gap distances (30–100 nm) and close membrane contacts (intermediate junctions) with a gap of 11 nm were observed in both circular and longitudinal muscle layers. In the terminal regions of muscle cells in both circular and longitudinal layers a specialized anchoring structure was present which was closely related to extracellular elastic tissue. Muscle cells in the longitudinal layer showed the most elaborate structure, the tapering end of the muscle cell showing a honeycomb-like structure penetrated by columns of connective tissue compounds. The functional implications of these structures are discussed.
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  • 115
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    Cell & tissue research 210 (1980), S. 339-347 
    ISSN: 1432-0878
    Keywords: Seasonal breeding ; Leydig cells ; Ultrastructure ; Bat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Leydig cells of the bat, Myotis adversus, have been examined by electron microscopy throughout fourteen months. During the breeding season the Leydig cells become hypertrophied and are characterised by prominent areas of agranular endoplasmic reticulum and numerous small, membrane-bound granules. Microperoxisomes are also observed. During the period of testicular regression. Leydig cell size and the number of membrane-bound granules are greatly reduced. Lipid droplets and dense bodies are more numerous.
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  • 116
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    Cell & tissue research 210 (1980), S. 417-433 
    ISSN: 1432-0878
    Keywords: Pinealocytes ; Ultrastructure ; Malaysian rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé Les pinéalocytes d'un Rat de Malaisie (Rattus sabanus), un animal vivant près de l'équateur donc dans une zone où les variations annuelles de la longueur des jours sont minimes, examinés au microscope électronique ont été comparés à ceux d'autres Mammifères. Une seule population de pinéalocytes a été observée. La présence d'un grand nombre de vésicules granulaires et de rubans circonscrits par des vésicules est la caractéristique premi`ere des pinéalocytes de cette espèce. Les rubans circonscrits par des vésicules ont été plus spécialement observés dans les terminaisons des prolongements des pinéalocytes où ils sont nombreux et la plus souvent en contact directe avec l'espace périvasculaire. L'importance physiologique de ces rubans circonscrits par des vésicules et des vésicules granulaires est discuté.
    Notes: Summary The ultrastructure of the pinealocytes of the Malaysian rat (Rattus sabanus), a mammal inhabiting a zone near the equator where the annual variations of daylength are inconspicuous, was examined and compared with that of pinealocytes of other mammals. On the basis of the presence of granular vesicles, only one population of pinealocytes was found. A large number of granular vesicles and vesicle-crowned rodlets is characteristic of the pinealocytes of this equatorial species. Vesicle-crowned rodlets are especially numerous in the endings of the pinealocyte processes and; they most often found in direct topographical connection with the perivascular spaces. The physiological significance of the presence of such large amounts of vesicle-crowned rodlets and of the secretory process characterized by the formation of granular vesicles is discussed.
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  • 117
    ISSN: 1432-0878
    Keywords: Ultrastructure ; Fluorescence histochemistry ; Prevertebral ganglia ; Ageing ; 5-hydroxydopamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Sympathetic post-ganglionic neurones in the coeliac-superior mesenteric ganglion (CSMG) complex of aged (24 month) rats have been studied by glyoxylic acid-induced fluorescence and electron microscopy. Comparisons have been made with the CSMG of young adult (4 month) rats. In the aged rats the noradrenaline fluorescence of the majority of neuronal perikarya was very low or absent and few intraganglionic fluorescent varicosities were seen. Lipofuscin pigment was very prominent at the nuclear pole region of neurones and also in dendrites and axonal processes. Ultrastructural studies revealed large accumulations of residual bodies at the nuclear poles and in axons and dendritic profiles. Within the perikarya many mitochondria were distorted or swollen, the rough endoplasmic reticulum was disarranged and much dilated as were Golgi cisternae. Primary lysosomes were encountered throughout the neurone perikaryon and its axonal or dendritic processes. In contrast to the young adult CSMG, no evidence for loading of transmitter storage vesicles with an identical dose level of 5-hydroxydopamine was detected in any part of the neurones of aged rats. This might reflect an impairment of the uptake mechanisms and/or storage of noradrenaline in aged sympathetic neurones and their axonal and dendritic processes.
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  • 118
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    Cell & tissue research 208 (1980), S. 123-133 
    ISSN: 1432-0878
    Keywords: Lesioned axons ; Ultrastructure ; Crayfish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distal stumps of severed medial giant axons (MGAs) and of non-giant axons (NGAs) in the CNS of the crayfish Procambarus clarkii show long-term (5–9 months) survival associated with disorientation of mitochondria and thickening of the glial sheath. However, the morphological responses of the two axonal types differ in that neither the proximal nor the distal stump of severed MGAs ever fills with mitochondria as is observed in some severed NGAs. Furthermore, the adaxonal glial layer never completely encircles portions of MGA axoplasm as occurs in many severed NGAs; in fact, ultrastructural changes in the adaxonal layer around severed MGAs are often difficult to detect. No multiple axonal profiles are ever seen within the glial sheath of the proximal or distal stumps of severed MGAs whereas these structures are easily located within severed NGAs.
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  • 119
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    Cell & tissue research 208 (1980), S. 183-196 
    ISSN: 1432-0878
    Keywords: Sinus node ; Atrium ; Ultrastructure ; Caveolae ; Freeze fracture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Caveolae or membrane vesicles are commonly observed in smooth and skeletal muscle as well as in working heart muscle. Using sections of fixed tissue and replicas of freeze-cleaved material, we show in this study that caveolae are also very numerous in sinus node cells of the rabbit, and to a lesser degree, in the atrial cells. Caveolae increase the plasma membrane surface area by 115% in the leading sinus node, and by 56% in the atrial cells. In these two cell types, the membrane of the caveolae contains four times fewer intramembranous particles than the rest of the plasma membrane, and this difference applies to both PF and EF faces. The role of the caveolae is still unclear, but it does not seem that they have a pinocytotic function.
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  • 120
    ISSN: 1432-0878
    Keywords: Stannius bodies ; Secretory cell types ; Teleosts (Fundulus, Carassius) ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The Stannius bodies of killifish and goldfish were ultrastructurally investigated after exposure of the fish to media of different osmolality and calcium content. In both species two structurally different secretory cell types are found. Type-1 cells predominate. They contain an extensive granular endoplasmic reticulum, some large Golgi areas, and secretory granules with a mean diameter of about 0.4 μm. These cells are activated by transfer of freshwater fish to seawater, but not by transfer to low-calcium seawater. Type-2 cells often contain cytoplasmic processes that penetrate between the type-1 cells and are ending on the basal lamina. In this contact area granule release takes place. Type-2 cells contain some strands of granular endoplasmic reticulum, several small Golgi areas, and secretory granules with a mean diameter between 0.15 and 0.20 μm. Type-2 cells are not activated after transfer of fish to seawater. In killifish seawater exposure leads to a reduction of type-2 cells. The differences between the reactions of both cell types to different media point to functional differences between their secretory products. Type-1 cells may produce a hypocalcemic factor. It is concluded that type-2 cells are typical for freshwater fish or euryhaline fish spending part of their life cycle in freshwater. The proper function of these cells is unclear.
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  • 121
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    Cell & tissue research 212 (1980), S. 307-314 
    ISSN: 1432-0878
    Keywords: Thymus (Mammalia) ; Erythropoiesis ; Macrocytes ; Anaemia ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The thymus of wild young and adult bank voles (Clethrionomys glareolus) was examined by histological methods for the presence of developing erythroid cells. Nucleated erythroid cells were observed in 26% of the glands examined by light microscopy and in 69% of the glands examined by electron microscopy. The largest number of developing erythroid cells was observed in the thymus of pregnant females, also showing raised reticulocyte counts (3.1–10.2%). However, erythropoiesis could also be found in breeding and non-breeding, first year and older animals. Erythroid cells were mainly located in the cortex, sometimes in small groups interspersed between lymphoid cells, and also randomly scattered in the cortex. Occasionally, macrocytic erythroid cells were also present. Pyknotic cells were commonly present, and granulopoiesis was frequently observed.
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  • 122
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    Cell & tissue research 213 (1980), S. 149-157 
    ISSN: 1432-0878
    Keywords: Trophic chamber ; Nutritive cord ; Ultrastructure ; Homoptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Each ovariole of the coccidian Aspidiotus hederae contains a single oocyte connected by means of a nutritive cord to the trophic chamber. The trophic chamber consists of three nurse cells characterized by an enlarged, ramified nucleus with a prominent nucleolus. The perinuclear cytoplasm contains nuage material, large amounts of free ribosomes, and scattered mitochondria. Occasional cisternae of the rough endoplasmic reticulum and bacteroids are found in trophocyte cytoplasm. The nutritive cord contains many microtubules in parallel array interspersed with numerous free ribosomes and a few mitochondria. The nutritive cord is strengthened by trophocyte projections which surround it. Microtubules in the projections are oriented perpendicular to the long axis of the cord.
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  • 123
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    Cell & tissue research 213 (1980), S. 221-235 
    ISSN: 1432-0878
    Keywords: Peripheral blood lymphocyte ; Density separation ; T cell depleted rabbits ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Density separation of purified peripheral blood leucocytes from T-cell depleted rabbits on a linear Ficoll-metrizoate gradient has been applied to obtain different leucocyte fractions. Two lymphocyte fractions separated on density seem to have different characteristics, both morphologically and immunologically. In this study these two fractions have been characterized ultrastructurally by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and a relationship has been established between the surface architecture (SEM), the cell size (SEM/TEM) and surface-Ig/C3-receptors (LM, light microscopy). Finally three types of lymphocytes have been described in the two lymphocyte fractions separated on density. Morphometric information such as cell size, cell shape, eu-/heterochromatin ratio in the nucleus and the nucleus-/cell ratio have been correlated to the stage of activation of the B lymphocyte in a representative density separation.
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  • 124
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The results of calculations of the transition energies and polarization in nucleotide bases performed by the CNDO/S CI method are compared with experimental data for long-wavelength and vacuumabsorption bands. The calculations and the analysis of experimental data testify to the existence of n - π* transitions in the first absorption bands of the bases. The study of double-stranded polynucleotides and DNA hypochromism based on the theoretical electronic characteristics of the bases and perturbation theory is performed. The role of stacking and complementary interactions within the hypochromic effect is cleared up. Two mechanisms for the shift of the fluorescence band maximum are investigated: two-proton transfer along H bonds and excimer formation. The study of H-bond potential curves shows the disadvantage of two-proton phototautomerism in the nucleotide base pairs in contrast to model systems. The possibility of excimer state formation in stacked homo- and heterodimers of nucleotide bases is shown within the extended-Hückel treatment. The nature of excimer minimum for the excited-state potential curve is analyzed.
    Additional Material: 4 Ill.
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  • 125
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    International Journal of Quantum Chemistry 17 (1980) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 126
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies concerning the effect of 2-alkyl pyridine N-oxides with different substituents on electron transfer, phosphorylation, and light-dependent proton transport in photosynthesizing membranes of chloroplasts were conducted. It is determined that 2-alkyl pyridine N-oxides with short alkyl chains stimulate the Hill reaction and light-dependent proton transport inside chloroplasts. Compounds having alkyl residues with 6-10 carbon atoms in the chain inhibit electron transport, ADP phosphorylation, and reduction of ferrocyanide in thylakoids. A conclusion is drawn on the presence of the hydrophobic “pocket,” which is of importance for organization of the electron-transport chain of chloroplasts, near photosystem II.
    Additional Material: 4 Ill.
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  • 127
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper summarizes our findings on the effects of protons and neutral salt ions on intermolecular interactions and the self-organization of nucleotide systems in aqueous media, both at monomer and polymer levels. To gain quantitative information about these processes, methods were developed to determine the thermodynamic parameters of monomer association from the data obtained by various experimental techniques (NMR, UV spectroscopy, and spin labeling) and to estimate the individual contributions of base stacking and H-bonding in ordered structures of polynucleotides and their complexes. The main results obtained using these methods are as follows. (i) A difference was discovered in the effects of positive and negative charges on the stacking interaction between ionized and neutral molecules of nucleic heterocycles. Protonation strongly decreases the heterocycle ability to form ordered stacks whereas deprotonation slightly affects stacking. (ii) Base-phosphate interaction, which has not yet really been investigated, was studied. This interaction, along with base stacking, governs nucleotide association in water media. It appears upon protonation of the base moiety and increases with decreasing ionic strength. (iii) Base stacking was found to become stronger under the action of salt anions stabilizing the water structure and it became weaker under the action of destabilizing salt anions, both in monomer and polymer systems, which is indicative of an indirect mechanism of the anionic effects. It is essential that small salt ion additives acting by such a “distance” mechanism can affect the formation of ordered structures in nucleotide systems as strong as the direct interaction of the bases with protons. (iv) The results obtained suggest that an increase in solvent entropy upon the self-organization of nucleotide systems in aqueous media may be an important factor promoting these processes. (v) As follows from our data, specific weakening or strengthening of intermolecular interactions by protons and salt ions at small, physiological-range changes in pH or solvent salt composition seems to be an effective regulatory mechanism for the functioning of nucleotide systems.
    Additional Material: 8 Ill.
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  • 128
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    International Journal of Quantum Chemistry 17 (1980), S. 399-413 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An attempt is made to refine the physical background underlying qualitative quantum-chemical concepts that are an essential component of the modern theory of chemical reactivity. The energy of electron delocalization in a transition state (stabilization energy, SE) is used as a measure of chemical reactivity. Using Coulson's integral representation for bond order matrix enables one to present the Woodward-Hoffmann rules and the effects of conjugated substitutents as theorems for a Hückel SE in alternant systems. A part of the results are extended to heteroatomic systems. The validity of the present treatment is discussed in terms of the SCF PPP theory.
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  • 129
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    International Journal of Quantum Chemistry 17 (1980), S. 415-428 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Fock generating function method is employed for the separation of spin variables into two-particle transition density matrices. Their spatial components introduced by McWeeny are expressed through Schrödinger's coordinate wave functions. Some nontrivial integral relations between these components and the charge and transition spin density matrices are obtained. The interrelation between the mentioned spatial components and the Matsen-Poshusta symmetrized density matrices of an arbitrary spatial function is found.
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  • 130
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper investigates the polarization effects associated with functional processes in photosynthetic membranes.
    Additional Material: 6 Ill.
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  • 131
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We use a previously proposed variation-perturbation method to calculate the electric polarizabilities and the electric dipole moment at equilibrium nuclear distance of the BH molecule. We obtain 3.56 × 10-24 cm3 for the perpendicular polarizability αxx and 3.22 × 10-24 cm3 for the parallel polarizability αzz. Our result for the electric dipole moment μ0 is 1.734 debye units; there is no reliable experimental result to compare it with.
    Additional Material: 3 Tab.
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  • 132
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    International Journal of Quantum Chemistry 17 (1980), S. 485-500 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for direct configuration-interaction (CI) calculations with a multiconfigurational reference function is described. The reference state can contain several closed-shell electronic configurations and the CI expansion comprises all single and double replacements out of all these configurations. The resulting secular problem is solved using a variation-perturbation method. A number of examples are given showing the efficiency of the method. The largest CI expansion used in calculations with this program so far contains 76,471 spin- and space-symmetrized configurations.
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  • 133
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    International Journal of Quantum Chemistry 17 (1980), S. 737-745 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A temperature correction to the Thomas-Fermi (TF) model of a neutral compressed atom has been given by Marshak and Bethe. The aim of the present work is to point out that, by formulating a variational principle, one may obtain approximate analytical solutions of the temperature-perturbed TF equation. As a test of the proposed theory, the total energy of a Ne atom, confined to a spherical container, has been calculated as a function of the container radius at T = 0°K. Comparison of the data obtained with energy values calculated by Ludeña, using a self-consistent-field Hartree-Fock approach, shows reasonable agreement. It is, therefore, concluded that the variational approach suggested in this paper is a sound one.
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  • 134
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    International Journal of Quantum Chemistry 17 (1980), S. 1042-1042 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 135
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    International Journal of Quantum Chemistry 17 (1980), S. 983-993 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A mathematical model to relate order and rotational motion in lipid hydrocarbon chains in biological membranes is proposed. Schrödinger equations with suitable potential functions for C—C rotations in lipid hydrocarbons chains have been solved to obtain wave functions characterizing these motions. For a free chain a threefold potential function has been assumed. The effect of collisions between neighboring chains in a membrane is considered by including another term (δ function) in the potential function.
    Additional Material: 4 Ill.
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  • 136
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    International Journal of Quantum Chemistry 17 (1980), S. 1007-1029 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monte Carlo simulation results are reported for clusters consisting of 250 water molecules surrounding serine, both in the neutral form and in two zwitterionic conformers (in order to gain some insight into conformational effects). Calculations were carried out at 300 K and using two-body potentials obtained by means of quantum-mechanical calculations. The spatial dependence of the average interaction energies was investigated. The solvation structure was investigated by means of radial distribution functions and probability density maps, which showed a few water molecules directly solvating the hydrophilic groups and, beyond them, a more or less rich and complex hydrogen-bonded network of solvent molecules.
    Additional Material: 16 Ill.
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  • 137
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    International Journal of Quantum Chemistry 17 (1980) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 138
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: La méthode d'analyse de la densité de paire est appliquée à l'étude de fonctions d'onde CNDO/2 de la molécule d'eau dans différentes configurations. Une attention particulière a été accordée aux modifications introduites par la prise en considération des effects d'environnement. On discute la validité de l'approximation des paires séparées et on donne une analyse détaillée des fonctions de groupe.
    Abstract: Wellenfunktionen von CNDO/2-Typ für das Wassermolekül in verschiedenen Konfigurationen sind mittels der Paardichtemethode analysiert worden. Im besonderen wurden die Veränderungen beachtet, die mit den Umgebungseffekten zusammenhängen. Die Gültigkeit der Separierten-Paar-Näherung wird diskutiert, und eine detaillierte Analyse der Gruppenfunktionen wird gegeben.
    Notes: The pair-density-analysis method is applied to the study of CNDO/2 wave functions of the water molecule in various configurations. Particular attention is devoted to the modifications introduced by the consideration of environmental effects. The validity of the separated pair approximation is discussed and a detailed analysis of group functions is given.
    Additional Material: 10 Ill.
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  • 139
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    International Journal of Quantum Chemistry 17 (1980), S. 1125-1141 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: L'approximation HF présentée dans la partie I a été testée par rapport à plusieurs propriétés moléculaires. Trois niveaux d'aproximation différents a, b, et c sont considérés. Des résultats satisfaisants - en comparaison avec des calculs HF “exacts” - sont obtenus avec la base STO-3G et le niveau a. A ce niveau-ci l'erreur dans l'énergie de liaison est de 0.001-0.025 a.u. pour toutes les molécules considérées, qui contiennent jusqu'à six atomes de la première ligne comme par exemple le cyclopentanone (C5OH8). L'erreur dans les énergies de réaction traitées ici est d'environ 4 kcal/mol (l'erreur maximale est de 9 kcal/mol). Les énergies orbitalaires, les moments dipolaires, les charges brutes, les géométries d'équilibres et les barrières de rotation interne sont bien reproduits par notre méthode à tous les trois niveaux.
    Abstract: Die HF-Näherungsmethode, welche im Teil I vorgestellt wurde, wird an einigen Moleküleigenschaften getestet. Drei Näherungsstufen a, b, und c werden untersucht. Zufriedenstellende Ergebnisse - verglichen mit entsprechenden “exakten” HF-Rechnungen - erhält man mit der STO-3G Basis und der Näherungsstufe a. Bei dieser Näherung ist der Fehler in der Bindungsenergie 0.001-0.025 a.u. für alle untersuchten Moleküle, welche bis zu 6 Atome der 1. Reihe enthalten, wie z.B. Cyclopentanon (C5OH8). Der Fehler in den hier behandelten Reaktionsenergien beträgt etwa 4 kcal/mol (der maximale Fehler beträgt 9 kcal/mol). Orbitalenergien, Diplolmomente, Bruttoladungen, Gleichgewichtsgeometrien und Rotationsbarrieren werden durch die Näherungsmethode bei allen Näherungsstufen gut wiedergegeben.
    Notes: The HF approximation method that was outlined in Paper I is tested with respect to several molecular properties. Three different levels of approximation a, b, and c are considered. Satisfactory results - compared to corresponding “exact” HF calculations - are obtained with the STO-3G basis and the approximation level a. At this level the error in the binding energy is 0.001-0.025 a.u. for all considered molecules which contain up to six first-row atoms as, e.g., cyclopentanone (C5OH8). The error in the reaction energies considered here is about 4 kcal/mol (the maximal error is 9 kcal/mol). Orbital energies, dipole moments, gross charges, equilibrium geometries, and barriers to internal rotation are well reproduced by the approximation method at all three levels.
    Additional Material: 5 Ill.
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  • 140
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    International Journal of Quantum Chemistry 17 (1980), S. 1185-1189 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Une measure pour comparer deux structures moléculaires basée sur des fonctions de densité est décrite. Quelques exemples reliés à l'activité d'un phéromone d'alarme sont donnés; les résultats sont encourageants en ce qui concerne l'utilisation possible de notions de densité semblables dans la technologie moléculaire.
    Abstract: Ein auf Dichtefunktionen basierendes Vergleichsmass zwischen zwei Molekülstrukturen wird beschrieben. Einige mit der Aktivität eines Alarmpheromons verbundene Beispiele werden gegeben; die Ergebnisse ermutigen die mögliche Anwendung ähnlicher Dichtebegriffe in der Molekültechnologie.
    Notes: A matching measure between two molecular structures based on density functions is described. Some examples related with an alarm pheromone activity are given; the results encourage the possible use of similarity density concepts in molecular engineering.
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  • 141
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    International Journal of Quantum Chemistry 17 (1980), S. 1221-1227 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 142
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    International Journal of Quantum Chemistry 17 (1980), S. 1191-1200 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Dans le present article on considére un nouveau modèle pour le transport moléculaire à travers des membranes, qui a été introduit antérieurement par Hosur. Dans ce modèle, la membrane est assimilée à une barrière de potentiel, en déterminant le flux matériel à travers de la měme partant dès le coefficient de transmission de la barrière, en supposant l'existence d'une différence d'énergie parmi les molécules qui appartiennent à les fluides d'une et d'autre cǒté de la membrane. On obtient ainsi, une expression pour le flux dans le cas de pétites différences d'énergie, qui a été particularisée au cas ou la difference d'énergie est due à un gradient de température, un gradient de concentration ou à tous les deux gradients agissant ensemble. Dans tous les cas, sous certaines conditions, on obtient des equations qui sont formellement identiques à celles obtenues par la thermodynamique des processus irréversibles.
    Abstract: In vorliegendem Artikel wird ein von Hosur eingeführtes Modell für Transport durch Membranen untersucht. In diesem Modell wird die Membran mit einer Potentialschwelle assimiliert, und der Materialfluss durch die Membran wird vom Transmissionskoeffizient der Schwelle bestimmt, wobei es wird angenommen, dass ein Energieunterschied unter den Molekülen an den beiden Seiten der Membran existiert. Für den Fall wo dieser Energieunterschied klein ist wird eine Gleichung für den Transport erhalten. Diese wird spezialisiert zu den Fallen wo der Energieunterschied von einem Temperatur-oder Konzentrationsgradient oder beiden zusammen verursacht wird. In allen Fallen werden-mit gewissen Begrenzungen-Gleichungen erhalten, die mit denen der Thermodynamik irreversibler Prozesse formal identisch sind.
    Notes: In the present paper a new model for the transport through membranes, introduced previously by Hosur, is considered. In this model, the membrane is assimilated to a potential barrier, and the material flow through the membrane is determined from the transmission coefficient of the barrier, assuming the existence of an energy difference among the molecules placed at both sides of the membrane. An equation for the transport, in the case of small energy differences, is obtained, which is particularized to the cases that the energy difference is caused by a temperature gradient, a concentration gradient, and both gradients acting together. In all cases, under certain limitations, formally identical equations to those of the thermodynamics of irreversible processes are obtained.
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  • 143
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nonrigid molecule symmetry group for methylamine is determined as a set of permutations and permutation inversions for two situations. In the first case the internal rotations of the methyl group and NH2 group are included and the second case the transition of a hydrogen atom from the methyl group to NH2 group is also included. In both cases the energy level splitting of the rigid model of the methylamine is found, nuclear statistical weights of the split levels are calculated, and sections rules for the allowed dipole transitions are given.
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  • 144
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    International Journal of Quantum Chemistry 17 (1980), S. 1111-1123 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Une méthode est proposée, qui réduit considérablement le travail numérique dans un calcul HF en réduisant le nombre d'intégrales à deux électrons qui doivent ětre calculées. Les procédés suivants sont utilisés: (i) la densité électronique est approximée par un petit nombre de fonctions pour la partie de Coulomb de la matrice HF; (ii) cette densité approchée est modifiée pour améliorer son potentiel; (iii) dans la partie d'échange une fonction de base χ est remplacée par une fonction \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \chi $\end{document} avec un nombre moindre de lobes gaussines; (iv) l'érreur causée par ce remplacement-ci est réduite par une modification des densités \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \chi _i \tilde \chi _j $\end{document} dans les intégrales d'échange. Le temps de calcul pour les intégrales est réduit par un facteur 6 pour des molécules contenant cinq atomes de la première ligne comme par exemple CF4, si l'on utilise une base 7S/3P contractée à (5, 1, 1/3). Le temps augmente approximativement avec n3, si n est le nombre de lobes gaussiens.
    Abstract: Eine Methode wird vorgeschlagen, welche den numerischen Aufwand von Hartree-Foch Rechnungen dadurch verringert, indem die Zahl der zu berechnenden Zweielektronenintegrale reduziert wird. Dabei werden folgende Konzepte verwendet: (i) Zur Berechnung des Coulombanteils der HF Matrix wird die Elektronendichte durch wenig Funktionen approximiert. (ii) Die approximierte Dichte wird so modifiziert, daß ihr Potential verbessert wird. (iii) Zur Berechnung des Austauschanteils wird eine Basisfunktion χ durch eine Funktion \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \chi $\end{document} ersetzt, welche weniger Gauss-lobes enthält. (iv) Der dadurch hervorgerufene Fehler wird durch eine Änderung der in den Austauschintegralen vorkommenden Dichten \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \chi _i \tilde \chi _j $\end{document} reduziert. Für Moleküle, welche 5 Atome der 1. Reihe enthalten, wie z.B. CF4, wird die Rechenzeit für den Integralteil um den Faktor 6 reduziert, wenn eine 7S/3P Basis kontrahiert zu (5, 1, 1/3) verwendet wird. Die Integralzeit nimmt etwa mit der 3. Potenz der Zahl der Gauss-lobes zu.
    Notes: A method is proposed that reduces the computational effort of HF calculations considerably by reducing the number of two-electron integrals that have to be calculated. The following concepts are used: (i) approximation of the electron density by only few functions for the Coulomb part of the HF matrix; (ii) modification of this approximate density, to improve its Coulomb field; (iii) in the exchange part, a basis function χ is replaced by a function \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \chi $\end{document} consisting of fewer Gaussian lobes; (iv) the error caused by this replacement is reduced by a modification of the densities \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \chi _i \tilde \chi _j $\end{document} in the exchange integrals. The computation time of the integral part is reduced by a factor 6 for molecules containing five first-row atoms as, e.g., CF4, if one uses a 7S/3P basis set contracted to (5, 1, 1/3). The integral time increases roughly with n3, if n is the number of Gaussian lobes.
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  • 145
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    International Journal of Quantum Chemistry 17 (1980), S. 1179-1184 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Un simple potentiel analytique avec deux paramètres et ajusté pour reproduire les niveaux expérimentaux est utilisé pour engendrer des fonctions d'onde pour l'état fondamental et quelques états excités de l'atome de lithium. Avec ces fonctions d'onde, l'approximation de Born et le schema de couplage LS de Russell-Saunders nous calculons les forces d'oscillateur optiques pour un nombre d'excitations à partier de l'état fondamental 1s22s(2S1/2). Les résultats sont comparés aux valeurs expérimentales et à ceux obtenus d'autres calculs.
    Abstract: Ein einfaches analytisches Zweiparameterpotential, angepasst um die experimentellen Energieniveaus zu reproduzieren, wird für die Erzeugung von Wellenfunktionen für den Grundzustand und einige angeregten Zustände des Lithiumatoms angewandt. Mit diesen Wellenfunktionen, der Bornapproximation und dem Russell-Saunders'schen LS-Kopplungsschema werden die optischen Oszillatorenstärken für verschiedene Anregungen vom Grundzustand 1s22s(2S1/2) berechnet. Die Resultate werden mit Experimentalwerten und Resultaten anderer Berechnungen verglichen.
    Notes: A simple two-parameter analytic potential adjusted so as to reproduce the experimental energy levels is used to generate wave functions for the ground and excited states of the lithium atom. Using these wave functions in conjunction with the Born approximation and the Russell-Saunders LS-coupling scheme, we calculate the optical oscillator strengths for various excitations from the 1s22s(2S1/2) ground state. The results are compared to experiment and other calculations.
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  • 146
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    International Journal of Quantum Chemistry 18 (1980), S. 263-273 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 147
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    International Journal of Quantum Chemistry 18 (1980), S. 275-280 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binding energy spectra for the valence orbitals of hydrogen chloride have been obtained using the binary (e,2e) method at 1200 eV. The strength of the innermost valence orbital (4σ) is severely split among several ion states in the energy range 25 to 41 eV. The measured cross sections are compared with results of calculations using contracted Gaussian basis sets of double-zeta quality, and with a one-particle Green's function calculation.
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  • 148
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    International Journal of Quantum Chemistry 18 (1980), S. 307-310 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The charge exchange process in the intervalence (mixed-valence) system is interpreted in terms of the nonstationary state mechanism which is a well-known approach for rationalizing the molecular tautomerism process. The two kinds of processes are viewed in a close analogy in the sense that both involve a pair of near-degenerate levels in a double-well potential. However, a comparison is made between the two cases to demonstrate that an electron moves not only faster but also farther in distance than a nucleus does.
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  • 149
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Traditionally, the calculation of the vibrational spectra of molecules involves at one point or another a numerical differentiation procedure. Such a method has some serious drawbacks both in efficiency and in accuracy. In this paper, an alternative method based on linear response theory is presented. The second derivative of the ground-state energy is expressed in terms of the electron density response matrix by means of perturbation theory. The unperturbed wave functions are obtained from the Hartree-Fock equation. First-order perturbation theory applied to this equation leads to the Hartree-Fock linear response. As an illustration of this method the vibrational frequency of a H2 molecule is calculated. The result is 1.348 × 1014 Hz as compared to the experimental value of 1.319 × 1014 Hz. This method is also applicable in the calculation of the phonon dispersion curves of solids.
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  • 150
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    International Journal of Quantum Chemistry 18 (1980), S. 331-338 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new approach to evaluate the determinant of the adjacency matrix is presented in this paper.
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  • 151
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
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    Topics: Chemistry and Pharmacology
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  • 152
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    International Journal of Quantum Chemistry 18 (1980), S. 369-380 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Graph- and information-theoretical indices were recently developed as quantitative structural characteristics of molecules. In this paper they are found to correlate well with a number of molecular properties of alkylbenzenes: heats of formation, combustion (both in liquid and gas phase) and vaporization, molecular volume, boiling point, and parachor. The topological information index and the number of carbon atoms are taken as variables. The correlation coefficient was found to be equal or close to 1. In three cases the mean relative error is less than 0.1%, in another three cases it is within the range 0.2-0.4%, and for boiling points only it is 1.25%. The proposed approach is compared with the additive scheme of Tatevskii.
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  • 153
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    International Journal of Quantum Chemistry 18 (1980), S. 403-408 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new parameterization for the first transition metal has been proposed in the framework of CNDO/2 method. We carried out CNDO/2 calculation of hexamine complexes [M(NH3)6]2+ and hexa-aquo complexes [M(OH2)6]2+ in the high spin state where M = Mn, Fe, Co, Ni, and Cu, using new parameters. It is shown that the calculated order of binding energy is Mn—L 〈 Fe—L 〈 Co—L 〈 Ni—L ≈ Cu—L (where L means the ligand), and is in good agreement with experiment. We discussed how the orbital nodes affect the nature of bonding between metal and ligand.
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  • 154
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    International Journal of Quantum Chemistry 18 (1980), S. 293-300 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Effects of incident photon field coherence on resonant light scattering have been investigated. In order to obtain the scattering intensity and the photon counting rate, an expression for the reduced density matrix for the scattered field has been derived. The expression involves the first-order correlation function of the incident field. The relation between the line shape of the scattered light and the bandwidth of the incident field has been clarified. Model calculations of the photon counting rate have been performed in the case of an incident field without first-order coherence. In our treatment, the transverse and longitudinal relaxation constants have been taken into account by using the impact approximation.
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  • 155
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    International Journal of Quantum Chemistry 18 (1980), S. 317-321 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The vibrational properties of a quantum system are determined by the density response matrix. In linear response theory this quantity is connected to the polarizability matrix, which can be expressed in terms of a double summation over one-particle energies and wave functions. In has been shown that this expression is not useful in the calculation of vibrational frequencies because of the very slow convergence of the summation in terms of the unoccupied states. In this paper, a different but equivalent expression is presented using a continued fraction. The resulting expression contains only one summation over the occupied states, solving in this way all the problems connected with the sum-over-states expression of the polarizability matrix. The elimination of all the unoccupied states via the use of the moment formula turns out to be a crucial step in the solution of the problem of the first-principles calculation of the vibrational spectra of molecules and solids.
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  • 156
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    International Journal of Quantum Chemistry 18 (1980), S. 323-329 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Normal-mode vibrational frequencies were obtained for uracil and 4-hydroxyuracil with the MINDO/3 SCF method. MINDO/3 vibrational frequencies and the moments of inertia for STO-3G optimized geometries yielded a ΔST0 for U ⇄ U* of 1.06 e.u./mol by standard statistical thermodynamic equations. ΔGT0 is then 6.29 kcal/mol in the gas phase for U ⇄ U*. The reaction field continuum model of solvent effect lowers ΔGT0 to 5.3 kcal/mol in aqueous solution. The tautomeric equilibrium constant in solution is then 1.3 × 10-4, in good agreement with experimental values.
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  • 157
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    International Journal of Quantum Chemistry 18 (1980), S. 515-519 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potential-energy curves for the movement of proton along the hydrogen-bond direction were calculated for the parent and cations produced from the β- decay of pyridine-pyrrole labeled by tritium (3H) or carbon-14(14C). For all cations the double minimum potential is predicted to be formed, and the activation energy for the proton transfer from one well to the other is about 10.0 kcal/mol, which is much lower than that in the (NH2—H—NH2)+ ion. A positional effect of nuclear transformation is scarcely expected in 3H β- decay, whereas a slight positional effect may be expected in 14C β- decay.
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  • 158
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    International Journal of Quantum Chemistry 18 (1980), S. 393-396 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A brief account of a quantum chemistry literature data base (QCLDB) is described, which contains the key information of about 2000 papers of ab initio calculations of atoms and molecules published in 1977-1979. The QCLDB is stored in a computer and can be sorted and rearranged into author and substance indices. Selection of the items for each paper in a computer-readable data base is discussed.
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    International Journal of Quantum Chemistry 18 (1980), S. 641-644 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Neutron scattering spectra from methane molecules adsorbed on a surface of graphite were observed by Newbery et al. They found four inelastic peaks in the temperature range lower than 30°K and assigned them to transitions between rotational tunneling states of methane molecules. This system was investigated by introducing both the interaction between methane molecules and that between a methane molecule and carbon atoms of graphite in order to explain the observed spectrum. It is shown that the system can be analyzed in terms of an effective field with tetrahedral symmetry.
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  • 160
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    Topics: Chemistry and Pharmacology
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  • 161
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    International Journal of Quantum Chemistry 18 (1980), S. 695-708 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method has been proposed for calculating the Gaussian matrix elements of the interaction operator represented by an arbitrary degree of interelectron distance X12ρ. The method is based on the expansion of two-electron integrals as the sum of one-electron integrals which in turn admit compact operator representation in terms of confluent hypergeometric functions. The generating differential operator has been shown to be related to the modified Hermitian polynomials. The standard structure of the special functions encountered in this approach is useful in studying the analytical behavior of the integrals and makes it possible to obtain for these integrals recurrence relations, direct algebraic expressions in the forms of finite sum of confluent hypergeometric functions, integral representations, and asymptotic properties. Unlike the usual methods based on integral transformation of the interaction operator, the proposed approach has a wider field of application, and in addition, leads to compact and convenient analytical expressions. The idea of using differential properties of integrals to simplify the integrand structure gives the proposed approach a certain resemblance to that suggested by Boys but not developed in detail in his pioneer work.
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  • 162
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    International Journal of Quantum Chemistry 18 (1980), S. 775-782 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Properties of Hückel parameters are investigated by using a mapping concept. The mapping is constructed by means of the Linderberg relation. No efforts are made to get a numerically correct description of the Hückel parameters.
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  • 163
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    International Journal of Quantum Chemistry 18 (1980), S. 797-810 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The performance of the MINDO/3 method has been evaluated in simple heteroatomic molecules that are representative of several important biological systems. Molecular geometries are accurate to within 0.04 Å for bond lengths, and 3° for most bond angles. Dipole moments and charge distributions are estimated satisfactorily, and ionization potentials are predicted to an accuracy of 0.5 eV. The method is less accurate in estimating the ionization of some upper level σ orbitals. The overall evaluation shows that MINDO/3 provides a good description of the geometries and electronic properties of the molecules studied. The results of MINDO/3 calculations in several other chemical systems are also reviewed.
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  • 164
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    International Journal of Quantum Chemistry 18 (1980), S. 439-448 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to elucidate further details of RNA conformations we have studied base stacking in dinucleoside monophosphates (DNP's) using UV difference spectra and the hypochromic effect. SCF CI MO calculations according to PPP and MIM approximations were carried out for six pyrimidine-containing DNP's in each of several stacking geometries. The calculated and plotted difference spectra were fitted to the experimental spectra. Different DNP's showed distinct geometries in the range of the helix angle of 35°. From our results we conclude that there is a microstructure in the helix. This would imply an additional content of information in this macromolecule, a higher precision in nucleic acid interactions, and make possible the prediction of the conformation of polynucleotides.
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  • 165
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    International Journal of Quantum Chemistry 18 (1980), S. 463-468 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction mechanism of photoisomerization of isoxazoles to oxazoles through azirine intermediates is investigated theoretically by means of ab initio MO CI calculations. Azirine intermediates in S1 state [(n →*) state of the carbonyl chromophore] cause the C—N bond rupture of azirine ring and transform to isoxazoles via intersystem crossing to T1 state. On the other hand, azirine intermediates in S2 state [(n →*) state of the ketimine chromophore] lead to the C—C bond rupture of azirine ring and convert to oxazoles via intersystem crossing to T1 state.
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  • 166
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    International Journal of Quantum Chemistry 18 (1980), S. 481-492 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The optical spectrum of a model oxyheme complex has been calculated using a new intermediate neglect of differential overlap (INDO-SCF-CI) method that allows for the inclusion of configuration interaction and transition metals. In addition to the porphyrin π→π* transitions common to all heme proteins, four weak x,y polarized transitions observed only in oxyheme complexes have been calculated and assigned to excitations involving the lowest-empty highly delocalized (Oπ, dπ) orbital. Two broad z-polarized bands observed in the single-crystal polarized absorption spectra of oxymyoglobin and hemoglobin have also been calculated. Controversy exists over the assignment of these transitions and, in particular, over the extent of involvement of the oxygen ligand. Our calculations assign the weaker near-IR visible band mainly to the d σ dπ→ dπ* excitations and the more intense UV band mainly to a2u → dσ* excitations. While significant participation (25%) of the highly delocalized (Oπ, dπ) virtual orbital is also found, these z-polarized transitions need not be totally unique to oxyheme complexes, in keeping with experimental observation.
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    International Journal of Quantum Chemistry 18 (1980), S. 1473-1477 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ground state and the first few excited states of an MnO69- cluster are calculated in the unrestricted Hartree-Fock model. The state ordering is 5B1 g, 5A1 g, 5B2 g, and 5Eg as can be expected from simpler models. Consistent with the results by the same method for copper complexes, we obtain d-d transition energies about one half or less of the experimental energies. The charge transfer spectrum is subject to a large spin polarization in the sense that the lowest charge transfer state (5Eu) has five unpaired spins on Mn.
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  • 168
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    International Journal of Quantum Chemistry 18 (1980), S. 1157-1163 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transformation of two-electron integrals from an atomic orbital basis to a symmetry orbital basis is a straightforward procedure, but becomes a time-consuming process when the system has high symmetry. In the conventional transformation algorithm, the number of multiplications is proportional to the fifth power of the basis size. To reduce the computer time, a new transformation algorithm is proposed. In this method, the number of multiplications for the transformation is proportional to the fourth power of the number of atomic orbitals in an equivalent orbital group. A new transformation program has been completed and tested against the conventional n5 method. The present method may be regarded as extension of Almlöf's method to any molecular point group. The program cuts the CPU time for the transformation to one-third in calculations for C4H8 and NiF6. This reduction is quite significant for large systems having high symmetry.
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  • 169
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    International Journal of Quantum Chemistry 18 (1980), S. 1271-1278 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio Hartree-Fock and multiple-scattering wave functions are calculated for linear CuF2. These wave functions are used to calculate the spin-orbit coupling in a new way where the neglect of two- and many-center terms is avoided and where experimental or calculated spin-orbit coupling constants for the atomic ions are used. The calculated value of g is too small by the MSXα method and too large by the ab initio method, indicating too much 3d-L interaction in the MSXα case and too little in the ab initio case.
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    International Journal of Quantum Chemistry 18 (1980), S. 1339-1359 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The intermediate and complete neglect of differential overlap (INDO and CNDO/2) molecular-orbital theories are developed for molecules with f block elements in both the open- and closed-shell configurations.
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  • 171
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    International Journal of Quantum Chemistry 18 (1980), S. 1371-1391 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Geometries have been optimized using molecular-orbital calculations (a) with a 4-31G Gaussian basis set for carbanions CH2X- where X = H, CH3, NH2, OH, F, C≡CH, CH≡CH2, CHO, COCH3, CN, and NO2; and (b) with an STO-3G basis set for methyl acetate and acetyl deprotonated methyl acetate. All the carbanions containing unsaturated substituents are planar, with a considerable shortening of the C—X bond. Carbanions containing saturated substituents are pyramidal with the out-of-plane angle α increasing with the electronegativity of the substituent. Double-zeta basis set calculations give proton affinities over the range 449 (for CH3CH2-) to 355 kcal/mol (for CH2NO2-), with all unsaturated anions having smaller affinities than saturated anions. The correlation of proton affinities with 1s binding energies, and with charges on both the carbon of the anion and on the acidic proton of the neutral molecule are examined.
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    International Journal of Quantum Chemistry 18 (1980), S. 1483-1484 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    International Journal of Quantum Chemistry 18 (1980), S. 1491-1503 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A certain type of classical nonlinear field theory of chemical bonding has been proposed. The interaction between two neighboring atoms is assumed to be nonlinear. The coupled field equations are decoupled applying the methods of parametrization. The field energy associated with the coupled field has been determined perturbation theoretically. The chemical bonding energy equivalent to the change of field energy due to the coupling has been expressed in a closed form. The bonding energies of the molecules Li2, Na2, and K2 are evaluated.
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    International Journal of Quantum Chemistry 17 (1980) 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    International Journal of Quantum Chemistry 17 (1980), S. 37-40 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    International Journal of Quantum Chemistry 17 (1980), S. 25-35 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The salient features of generalized second-quantization representations for nonrelativistic systems of composite particles are reviewed and their application to a reformulation of the quantum theory of reactive collisions is discussed. Such representations allow the properties of the bound composite states to be built explicitly into the algebra of states and observables. A single unperturbed Hamiltonian simultaneously describes the free propagation of the various species of bound composites as well as of their unbound constituents, while the interaction Hamiltonian describes only true scattering and reaction processes. The inclusion of the binding of all composites in the unperturbed Hamiltonian cures the divergences in the Born series arising from bound-state poles. Unstable composites can be included in a natural way, leading to an explicit representation for the kinematics and dynamics of their decay and their contribution to collision phenomena.
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  • 177
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    International Journal of Quantum Chemistry 17 (1980), S. 107-120 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper contains the skeleton of one lecture, and of two raporteur's interventions, made at the Sanibel Symposium in February-March, 1979. The task asked of this lecturer was to present an outline of the program of nonequilibrium statistical mechanics, and to indicate some of the recent developments in our understanding of this program. Section I lists a few of the principal physical ingredients of the theory. The possible implementation of certain aspects of the program is demonstrated in Sec. II with the help of three exactly soluble models. Finally in Sec. III we extrapolate from these particular examples in two directions: the stochastic aspect of statistical mechanics, and some remarks on the theory of the quantum measurement process. The presence, at the Symposium, of several distinguished lecturers who presented their own original, and most interesting, contributions hopefully made appear less outrageous - at least at the time - the severe omissions due to the personal choices this particular speaker had to make to keep within the time limitations inherent to such a gathering. It is now hoped that, even when taken out of the full context of the Symposium, the rearranged text which follows might nevertheless help focusing attention on some of the important problems remaining to be solved. It is a pleasure to acknowledge here the stimulating hospitality of the Symposium Scientific Director, Professor P.-O. Löwdin.
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  • 178
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    International Journal of Quantum Chemistry 17 (1980), S. 211-233 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A complete development of the PCILO method is presented for the INDO approximation. The introduction of exchange terms in the theoretical treatment is discussed and a detailed analysis of the successive contributions to the total energy is given. The method is applied to various conformational problems (geometry optimization, rotation, and inversion barriers). Its ability to deal with biological systems is tested on the acetylcholine neurotransmitter. Inversion barriers are highly improved with respect to the corresponding CNDO algorithm. A better account of σ-π exchange phenomena can be expected with the presented PCILO-INDO development.
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  • 179
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    International Journal of Quantum Chemistry 17 (1980), S. 255-263 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In agreement with previous calculations by the authors, three definite resonances in the elastic electron-SF6 molecule scattering in the energy range 5-40 eV have been obtained with a multiple scattering method, elaborated originally for molecular bound states and modified here for scattering states. Results with various more-reliable one-electron potentials have been compared with previous calculations and available experimental data.
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  • 180
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: While regarding the elementary biological function as a series of elementary acts resulting in either chemical bond formation (breakage) or a changed molecular subsystem state, we would like to focus attention on some of the most essential and general features of this process in terms of the Von Neumann theory of self-reproducing automata.
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  • 181
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron mechanism of the nonequilibrium vibration excitation is considered in multiatom molecules with the condition that the bottleneck effect takes place. The quantum-statistical theory states that if the simplest enzyme reaction is proposed on the basis of the vibrational energy recuperation idea, the vibrons emitted in producing the free product and enzyme activate the first stage of the formation of the Michaelis-Menten complex and the multiphonon feedback mechanism is realized. Resulting solutions are applied to explain some biochemical and genetic effects.
    Additional Material: 3 Ill.
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  • 182
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We suggest the explicit transformation of the parametrized atomic φ-basis semiempirical Hamiltonian to the Löwdin λ basis. A nontrivial problem then arises concerning the transformation of the four-index electron interaction matrix Γ, for which parametrization is given in the φ basis, whereas the NDO approximation is introduced in the λ basis. The main result is that under the CNDO assumption the two-index Coulomb matrix can be transformed independently of other integrals of Γ. The explicit form of the transformation between the Coulomb matrix γ of parameters given in the φ basis and the Coulomb matrix λγ in the λ basis is found. The λγ calculated by this method differs only slightly from the result of the exact complicated four-index transformation. On the other hand the elements of γ and λγ may differ by several eV when overlap is significant.
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  • 183
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: First- and second-order perturbation theory in a polarization approximation was employed to calculate interaction energies of planar xanthine-xanthine pairs in stable configurations. Electrostatic energy was obtained in the atomic-dipole approximation. The results provided a basis for formulation of a four-stranded model of poly(xanthylic acid) that allows two hydrogen bonds per base. The model accounts satisfactorily for the unusual thermal stability and the observed pH transition of the polymer. The latter is due to the gradual dissociation of the N3 protons accompanying by disrupture of the weak N3—H ··· O6 hydrogen bonds. However, the structure is only moderately weakened since the configuration of the coplanar bases remains stabilized by four N1—H ··· O2 hydrogen bonds.
    Additional Material: 3 Ill.
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  • 184
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio calculations within the minimal basis set of STO-4LGTO have been carried out on molecules of type H3MX (M = Si, C; X = H, NH2, OH, F). The influence of the MH3-group inversion on the electronic structure of these compounds has been investigated and illustrated by MO electron density maps. The ability of the central atom to form an additional bond has been estimated with the help of calculations on the complexes of these molecules with the hydrogen negative ion. The complexes of type [H4SiX]- have been found to be more stable than their unbonded components. The [H4CX]- complex formation has not proved to be advantageous.
    Additional Material: 5 Ill.
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  • 185
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    International Journal of Quantum Chemistry 18 (1980) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 186
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    International Journal of Quantum Chemistry 18 (1980), S. 921-935 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is suggested that simple electronic shielding effects induced by wave function antisymmetrization tend to govern the energy ordering of singlet and triplet terms within a two-electron atomic configuration. This approach gives rise to the following alternating rule: For the term of greatest orbital angular momentum within a configuration, the triplet lies below the singlet. The energy ordering reverses for the term of next highest angular momentum, and continues to alternate with each change of one unit in the orbital angular momentum until the term of lowest angular momentum is reached. In an examination of over 600 energy levels of the elements and their ions, the alternating rule reliably orders singlet-triplet energy levels in some 90% of the cases.
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  • 187
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    International Journal of Quantum Chemistry 18 (1980), S. 995-1003 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple self consistent variation perturbation method in the coupled Hartree-Fock scheme has been proposed to calculate 1s2s 1S state of the He atom. The present paper deals with an 1s2s 1S wave function in which all the relevant orthogonality conditions are imposed in successive stages. The resulting wave functions together with some interesting features are discussed.
    Additional Material: 3 Ill.
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  • 188
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    International Journal of Quantum Chemistry 18 (1980), S. 1005-1027 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Paths of length two and three appear to dominate variations in isomers of alkanes when various physical and chemical molecular properties are compared. The regularities previously observed for octanes have been fully examined for the set of 35 nonane isomers C9H20. Such examinations are facilitated by construction of appropriate grid graphs with paths of length two and three, respectively, representing molecules and connecting such points along the grid axes. By ordering structures in the two-dimensional coordinate plane, various trends and regular changes in the relative magnitudes for the selected thermodynamic properties have been traced to molecular connectivity and topology.
    Additional Material: 5 Ill.
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  • 189
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    International Journal of Quantum Chemistry 18 (1980), S. 1057-1069 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present a simple model for the calculation of some properties of disordered one-dimensional organic conductors. We focus our attention on two points: the decrease of the insulator-to-metal transition temperature and the increase of the highest electrical conductivity temperature that both occur when the amount of disorder is increased. We give an explanation that brings a new insight to the still little understood zone around the insulator-to-metal transition. The model enters the general framework of the alternant molecular orbital method and seems to be a priori restricted to systems such as NMP-TCNQ. We discuss its possible application to more complicated systems such as TTF-TCNQ.
    Additional Material: 1 Tab.
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  • 190
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    International Journal of Quantum Chemistry 18 (1980), S. 1101-1108 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that the Löwdin orthogonalization gives the unique minimum for the functional φ measuring the least squares distance between the given orbitals and the orthogonalized orbitals. Furthermore a much stronger result is obtained, namely that φ has only one local minimum, which is attained at the Löwdin orthogonalization and which is global. This justifies certain computer programs that compute Löwdin orthogonalization via minimization procedures. Finally there is a discussion of replacing the least squares metric by other metrics. The Löwdin orthogonalization turns out to be optimal with respect to all the commonly encountered norms.
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  • 191
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    International Journal of Quantum Chemistry 18 (1980) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 192
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    International Journal of Quantum Chemistry 18 (1980), S. 1143-1155 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper an attempt is made to define charge transfer trying also other ways than Mulliken's population analysis. To illustrate this the amount of transferred charge (q) in the complexes HCONH2 + OHC - CHO in two relative geometrical positions, H2O + H2O and H2O + Li+ has been calculated with the help of Mulliken's population analysis using the wave function of the complex on the one hand and in the framework of different methods to subdivide the total space of the complex into subspaces for the acceptor and donor molecule, respectively, on the other hand. The results obtained show that Mulliken's population analysis gives a qualitatively correct description of the charge transfer process but to obtain the finer details most probably the use of a single number (q) is not sufficient. Further, the change in the total energy with respect to an effective charge transfer of a water dimer and of a solvent-cation complex has been investigated using the new mutually consistent field method. In this way the amount of transferred charge as well as the charge transfer interaction energy have been obtained in one step. These results have been compared with calculations applying second-order perturbation theory including overlap and the supermolecule method.
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  • 193
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    International Journal of Quantum Chemistry 18 (1980), S. 1207-1221 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Average procedures of SCF methods are discussed. Although average operators are known from early Hartree-Fock times, some remarks against indiscriminate use of such operator forms may still be useful. In general, unless a very particular set of average structures is chosen, a dependence of final results on the SCF starting vectors is a troublesome fact. Consequently, energies, populations and molecular parameters in general may show unpredictable behavior under various trial vectors. It is shown that variationally coherent operator forms are given by state parameters with equal values for all the active MO's used in the construction of Coulomb and exchange terms throughout the SCF cycles.
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  • 194
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    International Journal of Quantum Chemistry 18 (1980), S. 1279-1307 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A decomposition of an N-particle operator as a sum of N + 1 components is defined such that, in the case of a model system employing a finite one-particle basis set, the decomposition is invariant under unitary transformations of the basis set. Applied to a two-particle Hamiltonian, this decomposition gives rise to the distinction between the independent-particle energy and the coupling energy defined in previous papers. Applied to the reduced density operator for a quantum state, the decomposition corresponds to partitioning the density into irreducible components. This partitioning is illustrated by graphs of electron density for the water molecule.
    Additional Material: 4 Ill.
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  • 195
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    International Journal of Quantum Chemistry 18 (1980), S. 1361-1370 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The modified PCILO method, for which the use of the Rayleigh-Schrödinger many-body perturbation theory with the Møller-Plesset type of Hamiltonian partitioning is characteristic, has been extended to energy calculations of transition metal compounds. On the CNDO/2 level of the Hamiltonian approximation the energy and geometry of the ions CuX42-, MCl42- and the molecules CuX (X = F, Cl, Br; M = Mn, Fe, Co, Ni, Cu) have been calculated. The comparison with MO—LCAO—SCF calculations (CNDO/2-UHF) shows that the localized bonding model used here can be regarded as a good zeroth-order approximation describing the bonding situation in complexes of this type. The perturbation theory also provides an improvement of the harmonic force constants of the CuX molecules with respect to the SCF level of approximation.
    Additional Material: 4 Tab.
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  • 196
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    International Journal of Quantum Chemistry 18 (1980), S. 1449-1463 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of saturated XnHm (X being either C or Si) molecules is studied using the MINDO/3 and MNDO quantum-chemistry procedures. We find that the proximity of H atoms tends to shorten X—X bonds, and that this effect is (especially for MINDO/3) much larger than a similar trend in experimental values. The connection between this and hybridization values calculated from localized orbitals is investigated. It is found that the hybridization model works well for X—H bonds, whereas for X—X bonds non-σ-bond effects also play a significant role. It is shown that the changes in electronic structure may be directly connected to differences in X and H atomic levels, so that similar bond length differences may be expected in other molecular orbital calculations.
    Additional Material: 3 Ill.
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  • 197
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    International Journal of Quantum Chemistry 18 (1980), S. 1479-1482 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The quantum-mechanical methods (EHT and CNDO/2) have been applied to the homoallylic cation. Both methods successfully predict that the ion need not be represented as a nonclassical structure.
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  • 198
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    International Journal of Quantum Chemistry 18 (1980), S. 1489-1489 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 199
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A nonlinear dynamical equation for the electronic collective motion is presented by employing the traditional time-dependent procedure. The equation is applied to the model π-electron system of ethylene, and the effects of nonlinear interactions are investigated using its several states as reference states. It is shown that the nonlinear correlation plays an important role in describing the change of the lower excited states.
    Additional Material: 2 Ill.
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  • 200
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Double-helical polynucleotide conformations, poly(dA)·poly(dT), poly(d(A-T))·poly(d(T-A))·poly(dG)·poly(dC), and poly(d(G-C))·poly(d(C-G)) are analyzed by the atom-atom potential method. The energy optimization is carried out in the space of eight independent geometric parameters using analytical procedures for the constraints, taking into account the flexibility of the β-D-deoxyribose rings. At the first stage, the full screening of atomic partial charges was assumed. The structures of the calculated B and the A forms of DNA are characterized by low energy and absence of short contacts; the dihedral angles are near the average values in the monomers. With the typical energy difference of 3-5 kcal/mol nucleotide pairs in all cases, the B form is more preferable as compared to the A form. At the final step the effect of the Coulomb term is evaluated for poly(dA)·poly(dT) using various values of the effective dielectric constant (ε = 28, 24, 20, 18, 14, 12, 10, 8, 6, 4, and 1). If ε ≤24, the energy optimization leads A to B. We discuss the stereochemical details of the intermediate conformations on the A-B path and hypothesize the nature of stability of the A and the B forms and the mechanism of the A-B transition.
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